COMMUNICATION | doi:10.20944/preprints202212.0295.v1
Subject: Physical Sciences, Applied Physics Keywords: Metasurface; Materials characterization; Sensing; Microwave sensors; Powders; Materials science; Millimeter wave devices
Online: 16 December 2022 (05:45:54 CET)
A novel technique using a W-band metasurface for the purpose of transmissive fine powder layer sensing is presented. The proposed technique may allow for the detection, identification, and characterization of inhomogeneous ultrafine powder layers which are effectively hundreds of times thinner than the incident wavelengths used to sense them. Such a technique may be useful during personnel screening processes (i.e., at an airport) and in industrial manufacturing environments where early detection and quantization of harmful airborne particulates can be a matter of security or safety. To our knowledge, the requisite science involved in such a novel W-band metasurface sensing technique has not been fully explored.
ARTICLE | doi:10.20944/preprints201902.0126.v1
Subject: Engineering, Electrical And Electronic Engineering Keywords: microwave technique; transmittance; soil moisture; microstrip patch antennas; rhizobox; roots; plant phenotyping
Online: 13 February 2019 (16:49:06 CET)
Interactions of soil moisture with plant root systems are very important for plant growth. For non-invasive determination of volumetric soil moisture in a rhizobox, a microwave system based on transmittance of electromagnetic waves in the microwave frequency range was developed using microstrip patch antennas. Vector Network Analyzers (VNAs) were used to measure the S-parameters at frequency ranges close to 5 GHz. A transmission system with microstrip patch antennas was developed. The result of this attenuation is in the frequency domain. The antennae were designed as resonant microstrip antennae. The antennae were placed on both sides of a rhizobox, which allowed non-invasive measuring soil moisture in the box. The attenuation (S21(dB)) was used to measure the effect of temperature, and different types of soil; as well as sensitivity, reproducibility and repeatability of the system. In this work we present quantitative results of soil moisture in rhizobox. The microwave technique, using microstrip patch antennas, is a reliable and accurate system, and showed very promising potential applications for rhizobox-based investigations of root performance.
ARTICLE | doi:10.20944/preprints202206.0102.v1
Subject: Medicine And Pharmacology, Other Keywords: endoscopes; medical diagnostic imaging; microwave antenna arrays; microwave imaging; colorectal cancer
Online: 7 June 2022 (09:55:21 CEST)
This study assesses the efficacy of a microwave colonoscopy algorithm to detect colorectal cancer precursors or polyps in an ex-vivo human colon model. The algorithm works with a device composed of a cylindrical ring-shaped switchable antenna array, which can be attached to the tip of a conventional colonoscope as an accessory. The accessory is connected to an external processing unit that generates an acoustic signal when a polyp is detected. Nowadays, 22% of polyps go undetected with conventional colonoscopy and the risk of cancer after a negative colonoscopy can be up to 7.9%. Fifteen ex-vivo freshly excised human colons with cancer (n=12) or polyps (n=3) were examined with the microwave-assisted colonoscopy system simulating a real colonoscopy exploration. Successive measurements of the colon were taken with the microwave-based colonoscopy device and processed with a microwave imaging algorithm. After the experiment, the dielectric properties of the specimens were measured with a coaxial probe and finally the samples underwent a pathology analysis. The results show that all the neoplasms were detected with a sensitivity of 100% and specificity of 87.4%.
ARTICLE | doi:10.20944/preprints202202.0152.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: microwave; green chemistry; benzimidazoles
Online: 10 February 2022 (12:10:52 CET)
A microwave assisted method for synthesis of 2-substituted benzimidazoles has been developed. The combination of molar ratio N-phenyl-o-phenylenediamine:benzaldehyde (1:1) using microwave irradiation and only 1% mol of Er(OTf)3 provide an efficient, environmental and mild access to a diversity of benzimidazoles under solvent-free conditions.
ARTICLE | doi:10.20944/preprints202305.1685.v1
Subject: Chemistry And Materials Science, Analytical Chemistry Keywords: LIBS; microwave; isotope; plasma; emission
Online: 24 May 2023 (04:17:21 CEST)
Isotope detection and identification is paramount in many fields of science and industry, such as in the fusion and fission energy sector, in medicine and material science, and in archeology. The isotopic information provides fundamental insight on the research questions related to these fields as well as insight on product quality and operational safety. However, isotope identification with the established mass-spectrometric methods is laborious and requires laboratory conditions. In this work, Microwave-Assisted Laser-Induced Breakdown Spectroscopy (MW-LIBS) is introduced for isotope detection and identification utilizing radical and molecular emission. The approach is demonstrated with stable B and Cl isotopes in solids and H isotopes in liquid using emission from BO and BO2, CaCl, and OH molecules, respectively. MW-LIBS utilizes the extended emissive plasma lifetime and molecular emission signal integration times up to 900 s to enable use of low ~4 mJ ablation energy without compromising signal intensity and, consequently, sensitivity. On the other hand, long plasma lifetime gives time for molecular formation. Increase in the signal intensity towards the late microwave-assisted plasma was prominent in BO2 and OH emission intensities. As MW-LIBS is online-capable and requires minimal sample preparation, it is an interesting option for isotope detection in various applications.
REVIEW | doi:10.20944/preprints202207.0124.v1
Subject: Medicine And Pharmacology, Oncology And Oncogenics Keywords: microwave radiometry; postmenopausal; cancer biomarker
Online: 7 July 2022 (09:46:43 CEST)
Ovarian cancer is the third most common female genital cancer. Therefore, the timely diagnosis and comprehensive treatment of postmenopausal patients with benign ovarian tumors remains crucial in the field of gynecology. The significance of ovarian tumors depends on their frequency and their effects on the quality of life of a woman, as well as the possible development of ovarian cancer. Most ovarian cancers are diagnosed late and as a result are difficult to treat and often carry a poor prognosis. Currently there is no clear algorithm available for examining and accurately diagnosing patients with postmenopausal ovarian tumors; moreover, reliable criteria allowing dynamic observation and determining surgical access and optimal surgical intervention measures in postmenopausal patients is lacking.
REVIEW | doi:10.20944/preprints202009.0597.v1
Subject: Engineering, Automotive Engineering Keywords: microcombs; RF; microwave signal processing
Online: 25 September 2020 (07:46:28 CEST)
Integrated Kerr micro-combs, a powerful source of many wavelengths for photonic RF and microwave signal processing, are particularly useful for transversal filter systems. They have many advantages including a compact footprint, high versatility, large numbers of wavelengths, and wide bandwidths. We review recent progress on photonic RF and microwave high bandwidth temporal signal processing based on Kerr micro-combs with spacings from 49-200GHz. We cover integral and fractional Hilbert transforms, differentiators as well as integrators. The potential of optical micro-combs for RF photonic applications in functionality and ability to realize integrated solutions is also discussed.
Subject: Engineering, Electrical And Electronic Engineering Keywords: nonlinear optics; microwave; waveform generator; microcombs
Online: 15 May 2020 (09:57:38 CEST)
We report a photonic-based radio frequency (RF) arbitrary waveform generator (AWG) using a soliton crystal micro-comb source with a free spectral range (FSR) of 48.9 GHz. The comb source provides over 80 wavelengths, or channels, that we use to successfully achieve arbitrary waveform shapes including square waveforms with a tunable duty ratio ranging from 10% to 90%, sawtooth waveforms with a tunable slope ratio of 0.2 to 1, and a symmetric concave quadratic chirp waveform with an instantaneous frequency of sub GHz. We achieve good agreement between theory and experiment, validating the effectiveness of this approach towards realizing high-performance, broad bandwidth, nearly user-defined RF waveform generation.
ARTICLE | doi:10.20944/preprints201802.0153.v1
Subject: Engineering, Electrical And Electronic Engineering Keywords: microwave filters; vibration sensitivity; acoustic noise
Online: 26 February 2018 (07:56:14 CET)
A novel characterization method for discrete saw filters vibrational sensitivity is presented. The proposed approach allows the characterization of filters under vibrations and the extraction of a behavioural model. Filters are assumed to be transducers so that external induced vibrational energy is partially transformed in a undesired simultaneous amplitude and phase modulation of the input RF signal. When the filter is mechanically excited with vibrations, it introduces spurious amplitude and phase modulation to the input signal that can potentially affect the link quality.
ARTICLE | doi:10.20944/preprints201702.0044.v2
Subject: Engineering, Energy And Fuel Technology Keywords: dielectric properties; microwave; zinc sulfide concentrate
Online: 14 February 2017 (07:45:08 CET)
Microwave technology has a potential application in the extraction of zinc from sulphide ores, knowledge of the dielectric properties of these ores plays a major role in the microwave design and simulation for any process. The dielectric properties of zinc sulfide concentrate for two different apparent densities—1.54 and 1.63 g/cm3—have been measured by using the resonance cavity perturbation technique at 915 and 2450 MHz during the roasting process for the temperature ranging from room temperature to 850 °C. The variations of dielectric constant, the dielectric loss factor, the dielectric loss tangent and the penetration depth with the temperature, frequency and apparent density have been investigated numerically. The results indicate that the dielectric constant increases as the temperature increases and temperature has a pivotal effect on the dielectric constant, while the dielectric loss factor has a complicated change and all of the temperature, frequency and apparent density have a significant impact to dielectric loss factor. Zinc sulfide concentrate is high loss material from 450 to 800 °C on the basis of theoretical analyses of dielectric loss tangent and penetration depth, its ability of absorbing microwave energy would be enhanced by increasing the apparent density as well. The experimental results also have proved that zinc sulfide concentrate is easy to be heated by microwave energy from 450 to 800 °C. In addition, the experimental date of dielectric constant and loss factor can be fitted perfectly by Boltzmann model and Gauss model, respectively.
REVIEW | doi:10.20944/preprints202210.0109.v1
Subject: Engineering, Other Keywords: addressed fiber Bragg structure; fiber Bragg grating; fiber-optic sensor; microwave photonics; microwave-photonic sensor systems
Online: 9 October 2022 (08:10:39 CEST)
Five years ago, the concept of addressed fiber Bragg structures (AFBS) was proposed, which simultaneously perform the functions of a two-frequency radiation shaper, the difference frequency of which is the AFBS address, and a sensitive element, since the value of the difference frequency is invariant to measured physical fields, and the set of difference frequencies, moreover, is orthogonal in the array of such sensors, enabling their address multiplexing. In this article, we provide an overview of the theory and technology of AFBS, including the structures with three or more spectral components with various combinations of difference frequencies, symmetrical and asymmetric, performing the functions of the address and converting information signals to the low-frequency range at the same time, along with other functions. The subjects of interrogation of these structures, their fabrication and calibration are discussed as well. We also consider a wide range of applications in which AFBS can be used, covering such areas as oil and gas production, power engineering, transport, medicine, etc. In addition, the prospects of AFBS further development are proposed.
ARTICLE | doi:10.20944/preprints202303.0556.v1
Subject: Physical Sciences, Optics And Photonics Keywords: Microwave photonics; optical microcombs; optical signal processing
Online: 31 March 2023 (15:55:34 CEST)
Microwave photonic (MWP) transversal signal processors offer a compelling solution for realizing versatile high-speed information processing by combining the advantages of reconfigurable electrical digital signal processing and high-bandwidth photonic processing. With the capability of generating a number of discrete wavelengths from micro-scale resonators, optical microcombs are powerful multi-wavelength sources for implementing MWP transversal signal processors with significantly reduced size, power consumption, and complexity. By using microcomb-based MWP transversal signal processors, a diverse range of signal processing functions have been demonstrated recently. In this paper, we provide a detailed analysis for the processing inaccuracy that are induced by the imperfect response of experimental components. First, we investigate the errors arising from different sources including imperfections in the microcombs, the chirp of electro-optic modulators, chromatic dispersion of the dispersive module, shaping errors of the optical spectral shapers, and noise of the photodetector. Next, we provide a global picture quantifying the impact of different error sources on the overall system performance. Finally, we introduce feedback control to compensate the errors caused by experimental imperfections and achieve significantly improved accuracy. These results provide a guide for optimizing the accuracy of microcomb-based MWP transversal signal processors.
ARTICLE | doi:10.20944/preprints202204.0135.v1
Subject: Engineering, Electrical And Electronic Engineering Keywords: Bandpass filters; microwave; EHF; wideband transistor stages
Online: 14 April 2022 (12:20:33 CEST)
The article shows that active RC- and RLC- filters based on the simplest wideband SiGe transistor stages are quite promising for RF and microwave frequency ranges. The results of computer simulation of the RC- and RLC-filters proposed by the authors of this article, which are oriented for use in communication and telecommunications devices, incl. with tunable and adaptive parameters.
ARTICLE | doi:10.20944/preprints202101.0529.v1
Subject: Engineering, Automotive Engineering Keywords: radio frequency; microwave; spectrum analyzer; integrated; photonic
Online: 26 January 2021 (09:57:01 CET)
We report an all-optical radio-frequency (RF) spectrum analyzer with a bandwidth greater than 5 terahertz (THz), based on a 50-cm long spiral waveguide in a CMOS-compatible high-index doped silica platform. By carefully mapping out the dispersion profile of the waveguides for different thicknesses, we identify the optimal design to achieve near zero dispersion in the C-band. To demonstrate the capability of the RF spectrum analyzer, we measure the optical output of a femtosecond fiber laser with an ultrafast optical RF spectrum in the terahertz regime.
Subject: Engineering, Energy And Fuel Technology Keywords: heterogenous catalyst; biodiesel; agrowaste; microwave; optimization; transesterification
Online: 30 November 2019 (12:10:38 CET)
Application of solid catalysts synthesized from agricultural wastes provides an environmentally benign and low-cost process route to the synthesis of biodiesel. An ash containing equal mixture of cocoa pod husk, plantain peel and kola nut pod husk ashes (CPK) which was obtained by open combustion of each biomass in air and calcined at 500 oC for 4 h. The calcined CPK ash was characterized to determine its catalytic potential. Two-level transesterification technique was used to synthesize biodiesel using the developed catalyst. The process parameters involved were optimized for the microwave-aided transesterification of a blend of honne, rubber seed and neem oils in volumetric ratio 20:20:60, respectively. The study showed that ash derived from combination of various biomass wastes provides a catalyst which consists all necessary catalytic ingredients in their relative abundance. The calcined CPK consists of 47.67% of potassium, 5.56% calcium and 4.21% magnesium attesting to its heterogenous status. The physisorption isotherms reveals that it was dominantly mesoporous in structure made up of nanoparticles. Maximum of 98.45 wt.% biodiesel was obtained through MeOH:oil blend of 12:1, CPK concentration of 1.158 wt.% and reaction time of 6 min under microwave irradiation. Quality of the synthesized biodiesel satisfied the requirements stipulated by standard specifications. Thus, this work demonstrates that blend of agrowastes and mixture of non-edible oils could be used to synthesize quality and sustainable biodiesel that can replace fossil diesel.
ARTICLE | doi:10.20944/preprints202201.0052.v1
Subject: Chemistry And Materials Science, Metals, Alloys And Metallurgy Keywords: metal-ceramic; microwave sintering; susceptor; phase modulation; nanostructures
Online: 6 January 2022 (09:42:02 CET)
This study provides a novel method to prepare metal-ceramic composites from magnetically selected iron ore using microwave heating. By introducing three different microwave susceptors (Activated Carbon, SiC, and a mixture of Activated Carbon and SiC) during the microwave process, effective control of the ratio of metallic and ceramic phases has been achieved easily. The effects of the three susceptors on the microstructure of the metal-ceramics and the related reaction mechanisms were also investigated in detail. The results show that the metal phase (Fe) and ceramic phase (Fe2SiO4, FeAl2O4) can be maintained, but the metal phase to ceramic phase changed significantly. In particular, the microstructures appeared as well-distributed nanosheet structures with diameters of ~400 nm and thicknesses of ~20 nm when SiC was used as the microwave susceptor.
ARTICLE | doi:10.20944/preprints202112.0004.v1
Subject: Environmental And Earth Sciences, Environmental Science Keywords: hydrological changes; wetlands; Arctic; Subarctic; microwave remote sensing
Online: 1 December 2021 (10:32:31 CET)
Specific emissivity features of swamps and wetlands of Western Siberia were studied for changing seasonal conditions with the use of daily data of satellite microwave sounding. The research technique involved the analysis of brightness temperatures of the underlying surface at the test sites. Variations in seasonal dynamics of brightness temperatures were mainly caused by different rates of seasonal freezing of the upper waterlogged layer of the underlying surface and dielectric characteristics of water containing natural media (water body, soil, vegetation). We analyzed long-term trends in seasonal and annual dynamics of brightness temperatures of the underlying surface and estimated hydrological changes in the Arctic and Subarctic. The findings open up new possibilities for using satellite data in the microwave range for studying natural seasonal dynamic processes and predicting hazardous hydrological phenomena.
ARTICLE | doi:10.20944/preprints202106.0563.v1
Subject: Engineering, Automotive Engineering Keywords: Radar imaging; target detection; experimental measurements; Microwave imaging.
Online: 23 June 2021 (10:25:26 CEST)
In microwave imaging it is often of interest to inspect electrically large spatial regions. In these cases, data must be collected over a great deal of measurement points which entails long measurement time and/or costly, and often unfeasible, measurement configurations. In order to counteract such drawbacks, we have recently introduced a microwave imaging algorithm which looks for the scattering targets in terms of equivalent surface currents supported over a given reference plane. While this method is suited to detect shallowly buried targets, it allows to independently process each frequency data, hence the source and the receivers do not need to be synchronized. Moreover, spatial data can be reduced at large extent, without incurring in aliasing artefacts, by properly combining single-frequency reconstructions. In this paper, we validate such an approach by experimental measurements. In particular, the experimental test site consists of a sand box in open air where metallic plate targets are shallowly buried (few cm) under the air/soil interface. The investigated region is illuminated by a fixed transmitting horn antenna whereas the scattered field is collected over a planar measurement aperture at a fixed height from the air-sand interface. The transmitter and the receiver share only the working frequency information. Experimental results confirm the feasibility of the method.
Subject: Chemistry And Materials Science, Analytical Chemistry Keywords: Microwave hearting; CO2 conversion; Semi-coke; Boudouard reaction
Online: 1 February 2021 (15:26:34 CET)
The conversion of CO2 into more synthetically flexible CO is an effective and potential method for CO2 remediation, utilization and carbon emission reduction. In this paper, the reaction of carbon-carbon dioxide (Boudouard reaction) was performed in a microwave fixed bed reactor using semi-coke (SC) as both the microwave absorber and reactant and was systematically compared with that heated in a conventional thermal field. The effects of the heating source, SC particle size, CO2 flow rate and additives on CO2 conversion and CO output were investigated. By microwave heating (MWH), CO2 conversion reached more than 99 %, while by conventional heating (CH), the maximum conversion of CO2 was approximately 29% at 900 °C. Meanwhile, for the reaction with 5 wt% Barium Carbonate added as a promoter, the reaction temperature was significantly reduced to 750 °C with almost quantitative conversion of CO2. Further kinetic calculations showed that the apparent activation energy of the reaction under microwave heating was 46.3 kJ/mol, which was only one-third of that observed under conventional heating. The microwave-assisted Boudouard reaction with catalytic barium carbonate is a promising method for carbon dioxide utilization.
REVIEW | doi:10.20944/preprints202101.0617.v1
Subject: Chemistry And Materials Science, Biomaterials Keywords: zeolite T; offretite; erionite; hydrothermal; microwave; secondary growth
Online: 29 January 2021 (12:34:58 CET)
Synthesis of zeolite T with a variety of desired characteristics necessitate extensive work in the formulation and practical experiments either by conventional hydrothermal methods or aided with different approaches and synthesis techniques such as secondary growth or microwave irradiation. The objectives of this review are to adduce the potential work in zeolite T (Offretite-Erionite) synthesis evaluating determining factors affecting the synthesis and quality of the zeolite T crystals. Attention is given to the extensive studies that interconnect with other significant findings.
ARTICLE | doi:10.20944/preprints202007.0234.v1
Subject: Chemistry And Materials Science, Applied Chemistry Keywords: cannabis; THC; CBD; microwave assisted extraction; continuous flow
Online: 11 July 2020 (09:04:17 CEST)
Cannabis is a flowering plant that has long been used for medicinal, therapeutic, and recreational purposes. Cannabis contains more than 500 different compounds, including a unique class of terpeno-phenolic compounds known as cannabinoids; Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD) are the most prevalent cannabinoids and have been associated with the therapeutic and medicinal properties of the cannabis plant. In this paper, continuous flow microwave assisted extraction (MAE) is presented and compared with other methods for commercial cannabis extraction. The practical issues of each extraction method are discussed. The main advantages of MAE are: continuous-flow method which allows for higher volumes of biomass to be processed in less time than existing extraction methods, improved extraction efficiency leading to increased final product yields, improved extract consistency and quality because the process does not require stopping and restarting material flows, and ease of scale-up to industrial scale without the use of pressurised batch vessels. Moreover, due to the flexibility of changing the operation conditions, MAE eliminates additional steps required in most extraction methods, such as biomass decarboxylation, winterisation, which typically adds at least a half day to the extraction process. Another factor that sets MAE apart is the ability to achieve high extraction efficiency even at the industrial scale. Whereas the typical recovery of active compounds using supercritical CO¬2 remains around 70-80%, via MAE up to 95% of the active compounds from cannabis biomass can be recovered at the industrial scale.
Subject: Engineering, Electrical And Electronic Engineering Keywords: microwave photonic; signal channelization; integrated optical frequency comb
Online: 26 March 2020 (02:19:45 CET)
We report a broadband radio frequency (RF) channelizer with up to 92 channels using a coherent microcomb source. A soliton crystal microcomb, generated by a 49 GHz micro-ring resonator (MRR), is used as a multi-wavelength source. Due to its ultra-low comb spacing, up to 92 wavelengths are available in the C band, yielding a broad operation bandwidth. Another high-Q MRR is employed as a passive optical periodic filter to slice the RF spectrum with a high resolution of 121.4 MHz. We experimentally achieve an instantaneous RF operation bandwidth of 8.08 GHz and verify RF channelization up to 17.55 GHz via thermal tuning. Our approach is a significant step towards the monolithically integrated photonic RF receivers with reduced complexity, size, and unprecedented performance, which is important for wide RF applications ranging from broadband analog signal processing to digital-compatible signal detection.
ARTICLE | doi:10.20944/preprints201901.0147.v1
Subject: Chemistry And Materials Science, Nanotechnology Keywords: MSQ aerogel; mesoporous structure; sol-gel; microwave drying
Online: 15 January 2019 (09:30:09 CET)
Methylsilsesquioxane aerogels with uniform mesopores have been facilely prepared via a sol–gel process followed by microwave drying with methyltrimethoxysilane (MTMS) as precursor, hydrochloric acid (HCl) as catalyst, water and methanol as solvents, hexadecyltrimethylammonium chloride (CTAC) as surfactant and template and propylene oxide (PO) as gelation agent. The microstructure, chemical composition and pore structures of the resultant MSQ aerogels were investigated in detail to achieve controllable preparation of MSQ aerogels, and the thermal stability of MSQ aerogels was also analyzed. The gelation agent, catalyst, solvent and microwave power have important roles on pore structures of MSQ aerogels. Meanwhile, microwave drying method is found to not only have a remarkable effect on improving production efficiency, but also be conducive to avoid the collapse of pore structure especially micropores during drying. The resulting MSQ aerogel microwave-dried at 500 W possesses a specific surface area up to 821 m2/g and a mesopore size of 20 nm, and displays good thermal stability.
ARTICLE | doi:10.20944/preprints201809.0505.v1
Subject: Engineering, Electrical And Electronic Engineering Keywords: renewable energy, microwave, free fatty acid, crude oil
Online: 26 September 2018 (10:31:20 CEST)
A novel method proposed in the production of Calophyllum inophyllum biodiesel has been investigated experimentally. In this study, we report the results of biodiesel processing with electromagnetic induction technology. The method used is to compare the results of Calophyllum inophyllum biodiesel processing between conventional, microwave and electromagnetic induction. The degumming, transesterification, and esterification process of the 3 methods are measured by stopwatch to obtain time comparison data. Characteristics of viscosity, density, and Fatty Acid Metil Ester (FAME) were obtained from testing of a Gas Chromatography-mass Spectrometry (GCMS) at the Polytechnic Chemistry Laboratory of the State of Malang. The results show that the biodiesel produced by this method satisfies the biodiesel standards and their characteristics are better than the biodiesel produced by conventional and microwave methods. The electromagnetic induction method also offers a fast and easy route to produce biodiesel with the advantage of increasing the reaction rate and improving the separation process compared to other methods. This advanced technology has the potential to significantly increase biodiesel production with considerable potential to reduce production time and costs.
ARTICLE | doi:10.20944/preprints201809.0018.v1
Subject: Chemistry And Materials Science, Other Keywords: SSPCM, Vacuum Drying, Microwave Acid Treatment, Solar Applications
Online: 3 September 2018 (09:57:39 CEST)
Today with enhancement in technology, sciences, there is also an increase in global heating rate. There is an urgent need of any alternate efficient source to reduce the wastage of energy and to utilize it efficiently. The advanced preparation of Expanded graphite ,lauric acid, stearic acid as shape stabilized phase change material deals with different energy harvesting applications. The main reason behind the need for synthesis of this matrix is to prepare a material that can be used in low temperature energy storage applications. Mixture of lauric acid , stearic acid impregnated in expanded graphite through vacuum impregnation followed by Vacuum Drying and Microwave acid treatment serves as novel shape stabilized phase change material of its type. The microwave acid treatment was done in order to increase the removal of moisture from the sample thus initiating proper bonding of its constituents. The mixture was produced in 1:1:1 ratio where all expanded graphite, lauric acid , stearic acid has one proportions of each other. The product obtained after microwave acid treatment was subjected to SEM, DSC analysis
ARTICLE | doi:10.20944/preprints201807.0600.v1
Subject: Environmental And Earth Sciences, Atmospheric Science And Meteorology Keywords: Remote Sensing; Climate Data Record; Passive Microwave; Hydrology
Online: 30 July 2018 (22:11:39 CEST)
Passive microwave measurements have been available on satellites dating back to the 1970s on research satellites flown by the National Aeronautics and Space Administration (NASA). Since then, several other sensors have been flown to retrieve hydrological products for both operational weather applications (e.g., the Special Sensor Microwave/Imager–SSM/I; the Advanced Microwave Sounding Unit–AMSU) and climate applications (e.g., the Advanced Microwave Scanning Radiometer–AMSR; the Tropical Rainfall Measurement Mission Microwave Imager–TMI; the Global Precipitation Mission Microwave Imager–GMI). Here the focus is on measurements from the AMSU-A, AMSU-B and Microwave Humidity Sounder (MHS). These sensors have been in operation since 1998 with the launch of NOAA-15, and are also on board NOAA-16, -17, -18, -19 and the MetOp-A and -B satellites. A data set called the “Hydrological Bundle” is a Climate Data Record (CDR) that utilizes brightness temperatures from Fundamental CDRs to generate Thematic CDRs (TCDR). The TCDR’s include: Total Precipitable Water (TPW), Cloud Liquid Water (CLW), Sea-Ice concentration (SIC), Land surface temperature (LST), Land surface emissivity (LSE) for 23, 31, 50 GHz, rain rate (RR), snow cover (SC), ice water path (IWP), and snow water equivalent (SWE). The TCDR’s are shown to be in general good agreement with similar products from other sources such as the Global Precipitation Climatology Project (GPCP) and the Modern-Era Retrospective Analysis for Research and Applications (MERRA-2). Because of the careful intercalibration of the FCDR’s, little bias is found among the different TCDR’s produced from individual NOAA and MetOp satellites, except for normal diurnal cycle differences.
ARTICLE | doi:10.20944/preprints201804.0243.v1
Subject: Chemistry And Materials Science, Polymers And Plastics Keywords: acrylamide; microwave assistance; intrinsic viscosity; flocculant; phenol removal
Online: 18 April 2018 (15:48:27 CEST)
A composite flocculant P(AM–DMDAAC) was synthesized by the copolymerization of acrylamide (AM) and dimethyl diallyl ammonium chloride (DMDAAC). Using microwave (MV) assistance with ammonium persulfate as initiator, the synthesis provided short reaction time and better solubility product. Nuclear magnetic resonance spectroscopy (1H NMR and 13C NMR), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and differential thermal analysis-thermo gravimetric analyzer (DTA-TGA) were used to determine the structure and morphology of P(AM–DMDAAC). Parameters affecting the intrinsic viscosity ([η]) of P(AM–DMDAAC), such as microwave time, mass ratio of DMDAAC to AM, initiator ammonium persulfatedosage, sodium benzoate dosage, bath time, reaction temperature and pH value were examined. Results showed that the optimum synthesis conditions were microwave time 1.5 min, m(DMDAAC): m(AM) is 4:16, 0.5 wt‰ initiator, 0.4 wt‰ EDTA, 0.3 wt‰ sodium benzoate, 2 wt‰ urea, 4 h bath time, 4.0h reaction time and pH 2. To study the removal of phenol by P(AM–DMDAAC), the influence of flocculant dose, pH value and the stirring speed were investigated, with optimization providing 99.8 % removal.
ARTICLE | doi:10.20944/preprints201710.0148.v1
Subject: Environmental And Earth Sciences, Geophysics And Geology Keywords: ground penetrating radar; microwave tomography; time-reversal technique
Online: 23 October 2017 (11:08:34 CEST)
This paper provides a comparative study between microwave tomography and synthetic time-reversal imaging techniques as applied to ground penetrating radar (GPR) surveys. The comparison is carried out by processing experimental data collected at a controlled test site, with various types of buried targets at given subsurface depths and representative soil conditions. It is shown that the two techniques allow us to obtain complementary information about position, depth and size of the targets from a single GPR survey.
ARTICLE | doi:10.20944/preprints202207.0114.v1
Subject: Physical Sciences, Particle And Field Physics Keywords: Quantum Non-Locality; Cosmic Microwave Background; Ether Drift Experiments
Online: 7 July 2022 (07:44:37 CEST)
“Non-Locality is most naturally incorporated into a theory in which there is a special frame of reference. One possible candidate for this special frame of reference is the one in which the Cosmic Microwave Background (CMB) is isotropic. However, other than the fact that a realistic interpretation of quantum mechanics requires a preferred frame and the CMB provides us with one, there is no readily apparent reason why the two should be linked” (L. Hardy). Starting from this remark we first argue that, given the present view of the vacuum, the basic tenets of Quantum Field Theory cannot guarantee that Einstein Special Relativity, with no preferred frame, is the physically realized version of relativity. Then, to try to understand the nature of the hypothetical preferred Σ−frame, we consider the so called ether-drift experiments, those precise optical measurements that try to detect in laboratory a small angular dependence of the two-way velocity of light and then to correlate this angular dependence with the direct CMB observations with satellites in space. By considering all experiments performed so far, from Michelson-Morley to the present experiments with optical resonators, and analyzing the small observed residuals in a modern theoretical framework, the long sought Σ− frame tight to the CMB naturally emerges. Finally, if quantum non-locality reflects some effect propagating at vastly superluminal speed vQI→∞, its ultimate origin could be hidden somewhere in the infinite speed cs→∞ of vacuum density fluctuations.
ARTICLE | doi:10.20944/preprints202109.0477.v1
Subject: Environmental And Earth Sciences, Atmospheric Science And Meteorology Keywords: rain cells; atmospheric attenuation; microwave radar; Ka-band; altimetry
Online: 28 September 2021 (21:32:59 CEST)
The impact of large atmospheric attenuation events on data quality and availability is a critical aspect for future altimetry missions based on Ka-band altimetry. The SARAL/AltiKa mission and its Ka-band nadir altimeter offer a unique opportunity to assess this impact. Previous publications (Tournadre et al. 2009, 2015) already analyzed the impact of rain on the waveforms at Ka-band and proposed a definition of an elaborate rain flag. This notion tends to give a simpler black and white view of the atmospheric attenuation when the effect on the altimeter measurement is intense. But in practice, there is continuum of measurements that may be partially distorted or corrupted by rain events. The present study proposes a wider point of view , the ACECAL approach providing statistics on rain cells occurrences as well as their amplitude and their size, as guidelines for future Ka-band missions concerning the impact of the atmosphere. At global scale, 1 % of the measurements are affected by an attenuation larger than 23 dB and 10 % of the atmospheric attenuation events have a size larger than 40 km. This study demonstrates that the data quality and availability over some regions of particular interest for oceanography as Gulf Stream, North Pacific and Brazil currents could be affected compared to global statistics. It also opens some perspectives on the benefits that the community could be drawn from the systematic distribution of the rain cells parameters as secondary products of altimetry missions.
Subject: Engineering, Automotive Engineering Keywords: microcombs; microwave photonics; micro-ring resonators; RF sideband generation
Online: 10 November 2020 (11:52:59 CET)
We review recent work on narrowband orthogonally polarized optical RF single sideband generators as well as dual-channel equalization, both based on high-Q integrated ring resonators. The devices operate in the optical telecommunications C-band and enable RF operation over a range of either fixed or thermally tuneable frequencies. They operate via TE/TM mode birefringence in the resonator. We achieve a very large dynamic tuning range of over 55 dB for both the optical carrier-to-sideband ratio and the dual-channel RF equalization for both the fixed and tunable devices.
ARTICLE | doi:10.20944/preprints202305.1141.v1
Subject: Engineering, Electrical And Electronic Engineering Keywords: Phase shifter; Circular polarizer; High-power microwave (HPM); Waveguide component
Online: 16 May 2023 (09:38:27 CEST)
This paper presents a novel high-power rotary waveguide phase shifter based on circular polarizers specifically engineered for high-power microwave (HPM) applications. The phase shifter is capable of performing a precise 360° linear phase shift through rotation and consists of three parts: a linear polarized to left-handed circular polarized (LP-LHCP) mode converter, a left-handed to right-handed circular polarized (LH-RHCP) mode converter, and a linear polarized to right-handed circular polarized (LP-RHCP) mode converter. The paper analyzes the phase shifting principle, optimizes the three parts of the X-band rotary waveguide phase shifter, and conducts simulation studies on the entire phase shifter made of aluminum. The results show that the reflection is less than -20dB and the transmission efficiency is over 95% within 9.5GHz to 10.2GHz. The phase shift has a linear relationship with the rotation angle by a factor of two within this frequency range. Specifically, the phase shifter can achieve a linear phase shift of 360° when rotated from 0° to 180°, with a maximum deviation of less than 1.2°. Moreover, the power-handling capacity of the phase shifter in vacuum exceeds 242mW.
ARTICLE | doi:10.20944/preprints202212.0545.v1
Subject: Physical Sciences, Astronomy And Astrophysics Keywords: Flatness problem; horizon problem; cosmic microwave background anisotropy; isothermization; thermalization
Online: 28 December 2022 (12:46:45 CET)
The cosmological model presented here rests on the postulate that the universe can be described as an interacting attraction (exerted by matter) and repulsion (exerted by the excitation energy of the quantum vacuum) system in virial equilibrium. The basic parameters of the model, the matter density and the excitation energy of the quantum vacuum are determined by observations and are not adjusted to the model. The model requires only a few assumptions that can be deduced from the laws of conventional physics and from the rules of quantum field theory. Existing problems in standard cosmology, such as the flatness and the horizon problems, among others, can be resolved in a straightforward way without inflation and without recourse to dark matter and dark energy.
ARTICLE | doi:10.20944/preprints202212.0484.v1
Subject: Engineering, Electrical And Electronic Engineering Keywords: Doppler frequency shift; Angle of arrival; Microwave photonics; Sagnac loop.
Online: 26 December 2022 (10:49:47 CET)
A novel scheme that can simultaneously measure the Doppler frequency shift (DFS) and angle of arrival (AOA) of microwave signals is proposed. At the signal receiving unit (SRU), two echo signals and the reference signal are modulated by a Sagnac loop structure and sent to the central station (CS) for processing. At the CS, two low-frequency electrical signals are generated after polarization control and photoelectric conversion. The DFS without direction ambiguity and wide AOA measurement can be real-time acquired by monitoring the frequency and power of the two low-frequency electrical signals. In the simulation, an unambiguous DFS measurement with errors of ±3×10-3 Hz and a -90° to 90° AOA measurement range with errors of less than ±0.5° are realized. The safety and robustness of the system to environmental disturbance are improved, and it is more suitable for the modern electronic warfare system.
ARTICLE | doi:10.20944/preprints202210.0266.v1
Subject: Medicine And Pharmacology, Oncology And Oncogenics Keywords: Breast cancer; early diagnostics; passive microwave radiometry (MWR); MicroRNA (miRNA)
Online: 19 October 2022 (04:11:29 CEST)
Breast cancer prevention is very important for a woman's health worldwide. We have demonstrated a correlation between mammography and ultrasound with diagnoses using passive microwave radiometry (MWR) and a miRNA oncopanel. While mammography screening dynamics could be completed in 3-6 months, MWR will provide us with a prediction in a matter of weeks or even days with the potential for complementary miRNA diagnostics. An early breast cancer diagnosis may be accomplished using either one of these novel techniques alone or in conjunction with more established techniques
ARTICLE | doi:10.20944/preprints202011.0180.v1
Subject: Physical Sciences, Optics And Photonics Keywords: microwave photonics; RF channelizer; micro-ring resonators; Kerr micro-combs
Online: 4 November 2020 (09:25:43 CET)
We report a 92 channel RF channelizer based on a 48.9 GHz integrated micro-comb that operates via soliton crystals, together with a passive high-Q ring resonator that acts as a periodic filter with an optical 3dB bandwidth of 121.4 MHz. We obtain an instant RF bandwidth of 8.08 GHz and 17.55 GHz achieved through temperature tuning. These results represent a major advance to achieving fully integrated photonic RF spectrum channelizers with reduced low complexity, size, and high performance for digital-compatible signal detection and broadband analog signal processing.
ARTICLE | doi:10.20944/preprints201911.0238.v1
Subject: Environmental And Earth Sciences, Environmental Science Keywords: land surface temperature; all-weather; infrared; microwave; surface energy balance
Online: 20 November 2019 (11:12:02 CET)
An all-weather land surface temperature (LST) product derived at the Satellite Application Facility on Land Surface Analysis (LSA-SAF) is presented. The product is based on clear-sky LST retrieved from MSG/SEVIRI infrared (IR) measurements, complemented by LST estimated with a land surface energy balance (EB) model to fill gaps caused by clouds. The EB model solves the surface energy balance mostly using products derived at LSA-SAF. The new product is compared with in situ observations made at 3 dedicated validation stations, and with a Microwave (MW) based LST product derived from AMSR-E measurements. The validation against in-situ LST indicates an accuracy of the new product between -0.8 K and 1.1 K and a precision between 1.0 K and 1.4 K, generally showing a better performance than the MW product. The EB model shows some limitations concerning the representation of the LST diurnal cycle. Comparisons with MW LST generally show higher LST of the new product over desert areas, and lower LST over tropical regions. Several other imagers provide suitable measurements for implementing the proposed methodology, which offers the potential to obtain a global, nearly gap-free LST product.
ARTICLE | doi:10.20944/preprints201709.0142.v1
Subject: Engineering, Civil Engineering Keywords: soil moisture; AMSR2; remote sensing; downscale; SCAN-NRCS; passive microwave
Online: 28 September 2017 (03:37:51 CEST)
A continuous spatio-temporal database of accurate soil moisture (SM) measurements is an important asset for agricultural activities, hydrologic studies, and environmental monitoring. The Advanced Microwave Scanning Radiometer 2 (AMSR2), launched in May 2012, has been providing SM data globally with a revisit period of two days. It is imperative to assess the quality of this data before performing any application. Since resources of accurate SM measurements are very limited in Puerto Rico, this research will assess the quality of the AMSR2 data by comparing with ground-based measurements and perform a downscaling technique to provide a better description of how the sensor perceives the surface soil moisture as it passes over the island. The comparison consisted of the evaluation of the mean error, root mean squared error, and the correlation coefficient. Two downscaling techniques were used and their performances were studied. The results revealed that AMSR2 products tend to underestimate. This is due to the extreme heterogeneous distributions of elevations, vegetation densities, soil types, and weather events on the island. This research provides a comprehensive study on the accuracy and potential of the AMSR2 products over Puerto Rico. Further studies are recommended to improve the AMSR2 products.
ARTICLE | doi:10.20944/preprints201609.0112.v1
Subject: Chemistry And Materials Science, Surfaces, Coatings And Films Keywords: carbonyl iron; composites film; external magnetic field; microwave absorption properties
Online: 28 September 2016 (10:32:52 CEST)
The carbonyl iron particles were dispersed in a polychloroprene rubber (CR) matrix under an external magnetic field for practical application as microwave absorption composites film. The film prepared under external magnetic field with a thickness of only 0.54 mm showed least reflection loss of -15.98 dB and the reflection loss value less than -10.0 dB over the frequency range of 11.4~14.8 GHz. In comparison with the microwave absorption properties of calculation by transmission line theory based on the tested relative complex permittivity and permeability and film prepared by general route without external magnetic field, the film made with external magnetic field exhibited more excellent microwave absorption properties, strongly depending on the increment of anisotropy and rearrangement of magnetic particles. The results indicated the composite film made under external magnetic field have excellent microwave absorption properties, which suggest that the composites thin film could be used as a thinner and lighter microwave absorber.
ARTICLE | doi:10.20944/preprints202209.0374.v1
Subject: Physical Sciences, Applied Physics Keywords: Commercial microwave links; Power level; SNMP protocol; Acquisition system; Rainfall estimation
Online: 26 September 2022 (02:05:11 CEST)
Since the 1990s, mobile telecommunication networks have gradually become denser around the world. Nowadays, large parts of their backhaul network consist of commercial microwave links (CMLs). Since CML signals are attenuated by rainfall the exploitation of records of this attenua-tion for precipitation monitoring purposes is an innovative and inexpensive solution. Performance data from mobile operators' networks is crucial for the implementation of this technology. And, moreover for near real-time quantification. To meet this requirement, a real-time system for col-lecting and storing CML power levels from the cellular phone operator "Telecel Faso" in Burkina Faso was implemented. This new acquisition system, which uses the Simple Network Manage-ment Protocol (SNMP) can simultaneously record the transmitted and received power levels from all the CML to which it has access, with a time resolution of one minute. Installed at “Laboratoire des Matériaux et Environnement de l’Université Joseph KI-ZERBO (Burkina Faso)”, this acquisi-tion system is dynamic and has gradually grown from eight to more than 1000 radio links Tele-cel Faso CML links between 2019 and 2021. The system covers the capital Ouagadougou and the main cities of Burkina Faso (Bobo Dioulasso, Ouahigouya, Koudougou and Kaya) as well as the axes connecting Ouagadougou to these cities.
REVIEW | doi:10.20944/preprints202111.0461.v1
Subject: Medicine And Pharmacology, Pediatrics, Perinatology And Child Health Keywords: juvenile idiopathic arthritis; X-Ray; ultrasound; MRI; passive microwave radiometry (MWR).
Online: 24 November 2021 (16:11:24 CET)
Juvenile idiopathic arthritis (JIA) is a disease with unknown causes within all forms of arthritis in children under 16 years of age. The diagnosis is made when another joint pathology is excluded. Difficulties in early and differential diagnosis lead to the rapid disability of patients and an unfavourable life prognosis. Therefore, timely diagnosis is necessary to prevent irreversible damage to the joints and preserve their function. Due to the widespread use of new technologies, modern multimodal imaging has gained recognition, which includes X-ray, ultrasound, and MRI. The combination of methods plays a key role in confirming the diagnosis, monitoring disease activity, prognosis during the course, and outcome in children with JIA. Each method has its own advantages and disadvantages. The introduction of the method of passive microwave radiometry (MWR), in combination with other imaging methods, makes it possible to expand the possibilities of screening the disease in the preclinical and early clinical phases.
ARTICLE | doi:10.20944/preprints202111.0425.v1
Subject: Physical Sciences, Atomic And Molecular Physics Keywords: chirality; microwave spectroscopy; electroweak force; precision measurement; differential spectroscopy; parity violation
Online: 23 November 2021 (14:37:44 CET)
Observation of parity-violating effects in chiral molecules is a long-standing challenge of the molecular spectroscopy community. In the microwave regime, the difference in transition frequencies between enantiomers is predicted to be below the mHz level, which is considerably beyond current experimental capabilities. The most promising future efforts combine vibrational spectroscopy, buffer gas cooling, and carefully chosen molecular candidates with large predicted parity-violating shifts. Here, we demonstrate for the first time high-precision differential microwave spectroscopy, achieving sub-Hz precision by coupling a cryogenic buffer gas cell with a tunable microwave Fabry-Perot cavity. We report statistically limited sub-Hz precision of (0.08±0.72) Hz, observed between enantiopure samples of (R)-1,2-propanediol and (S)-1,2-propanediol at frequencies near 15 GHz. We confirm highly repeatable spectroscopic measurements compared to traditional pulsed-jet methods, opening up new capabilities in probing subtle molecular structural effects at the 10−10 level and providing a platform for exploring sources of systematic error in parity-violation searches. We discuss dominant systematic effects at this level and propose possible extensions of the technique for higher precision.
ARTICLE | doi:10.20944/preprints202110.0350.v1
Subject: Engineering, Industrial And Manufacturing Engineering Keywords: microwave heating; cavity; reflector; double-waveguide; uniform heating; high heating efficiency
Online: 25 October 2021 (12:51:39 CEST)
To reduce the carbon emissions during heating in the manufacturing process, microwaves have attracted significant attention. Microwave has a lot of advantages rather than traditional heating method such as rapid heating, lower thermal damage and eco-friendly process. In order to apply microwaves to manufacturing process, uniform and efficient heating is required. We have analyzed the effect of various design parameters such as cavity heights, the application of the reflector, and the number and positions of waveguides for uniform and efficient heating by numerical simulation and verified that by experiment. The results showed that a slight change in the cavity height altered the electromagnetic field distribution and heating parameters, such as the coefficient of variance and power absorption efficiency. With reflectors installed, uniform heating was achieved and power absorption was improved, with the spherical reflector showing the maximum efficiency. The use of double waveguides heated the target material in a uniform manner. An increase in the power supply also led to uniform heating. This large-scale analysis will be helpful in applying microwaves to actual industrial sites.
Subject: Physical Sciences, Optics And Photonics Keywords: Kerr micro-combs; microwave photonics; signal channelization; integrated optical frequency combs
Online: 12 November 2020 (08:53:59 CET)
We review recent work on broadband RF channelizers based on integrated optical frequency Kerr micro-combs combined with passive micro-ring resonator filters, with microcombs having channel spacings of 200GHz and 49GHz. This approach to realizing RF channelizers offers reduced complexity, size, and potential cost for a wide range of applications to microwave signal detection.
ARTICLE | doi:10.20944/preprints202003.0041.v1
Subject: Engineering, Industrial And Manufacturing Engineering Keywords: ultrasonic wave; microwave; instant green tea; extraction rate; active components; aroma
Online: 3 March 2020 (11:38:20 CET)
The production of instant green tea requires hot-water extraction, which is time consuming and contributes to losses in aromatic compounds. In this study, an ultrasonic-assisted technology was used to improve the extraction efficiency of green tea, thereby shortening extraction time from 45 to 15 min. In pure water, the dissolution of caffeine and theanine did not change significantly, but total catechin dissolution increased by 0.23 mg/mL and total tea polyphenol dissolution decreased by 3.2 mg/mL. In 76.2% ethanol, the dissolution of caffeine and theanine did not change significantly, but total catechin dissolution increased by 1.57mg/mL and total tea polyphenol dissolution decreased by 1.5 mg/mL. Additionally, we used microwave-assisted technology to further improve the extraction efficiency of green tea, which shortened the extraction time to 2 min. However, the extraction rate remained unchanged. In pure water, the dissolution of caffeine and theanine did not change significantly, but the dissolution of total catechins increased by 0.41 mg/mL and the dissolution of tea polyphenols decreased by 2.9 mg/mL. Ultrasonic treatment increased the proportion of 3-hydroxybutan-2-one, (5S)-5-(hydroxymethyl)oxolan-2-one and 2-phenylethanol, which were the main aroma compounds in tea. Microwave treatment changed the aroma compounds in tea, causing losses in aroma compounds with low boiling point and maintaining (5S)-5-(hydroxymethyl)oxolan-2-one. The taste and aroma of instant green tea improved based on sensory evaluation results.
ARTICLE | doi:10.20944/preprints201809.0458.v2
Subject: Chemistry And Materials Science, Applied Chemistry Keywords: Suzuki coupling reaction; Layered double hydroxides; Solid base catalyst; Microwave irradiation
Online: 8 January 2019 (15:13:46 CET)
Suzuki cross-coupling reaction has developed one of the furthermost effectual approaches for the synthesis of biaryls or substituted aromatic moieties from aryl halides and arylboronic acids with a palladium-catalyst in the past two era’s. Herein, Pd-free layered double hydroxide containing nickel catalysts were prepared by co-precipitation method under ultrasonic irradiation and N2 atmosphere with different molar ratios of Ni: Mg: Al and coded as (1NiLDHs-Dr), (1.5NiLDHs-Dr) and (2NiLDHs-Dr). A series of reduced catalysts under 5%H2/N2 at different temperatures were coded as 1NiLDHs-R200, 1.5NiLDHs-R200 and 2NiLDHs-R200. As-synthesized 2NiLDHs-Dr was the superlative catalyst when coupling different aryl halides with different boronic acids derivatives. Deep investigation of all catalysts was done using different techniques such as inductively coupled plasma optical emission spectroscopy (ICP-OES), x-ray photoelectron spectroscopy (XPS), powder x-ray diffraction (XRD), thermogravimetric analyses (TGA), Fourier transfer infrared (FTIR), scanning electron microscope (SEM) connected with energy dispersive x-ray (EDX) and N2-physisorption at -196 ℃. The results attained verified that ɑ-Ni(OH)2 was fashioned for 2NiLDHs-Dr catalyst and the enclosure of nickel ions in the cationic sheet of layered structure were responsible for the fascinating catalytic efficacy rather than the basic nature of material. The Ni-containing LDHs catalysts encourage forthcoming studies in Pd-free catalyzed C-C coupling reactions.
REVIEW | doi:10.20944/preprints201810.0012.v1
Subject: Medicine And Pharmacology, Other Keywords: noninvasive glucose measurement; IR spectroscopy; Raman spectroscopy; photoacoustic spectroscopy; microwave sensing
Online: 1 October 2018 (14:04:05 CEST)
Diabetic patients need long-term and frequent glucose monitoring to assist in insulin intake. The current finger-prick devices are painful and costly which make noninvasive glucose sensors highly demanded. In this review paper, we discuss several advanced electromagnetic (EM) wave based technologies for noninvasive glucose measurement, including infrared (IR) spectroscopy, photoacoustic (PA) spectroscopy, Raman spectroscopy, fluorescence, optical coherent tomography (OCT) and microwave sensing. Development and progress of each method are discussed regarding fundamental principle, system setup and experimental results. Despite the promising achievements reported previously, there is no established product to obtain FDA approval or survive marketing test. Limitations and prospects of these techniques are discussed at the end of this review.
ARTICLE | doi:10.20944/preprints201807.0604.v1
Subject: Environmental And Earth Sciences, Environmental Science Keywords: backscattering; L-band; SAR polarimetry; microwave; Chapman-Richards model; tropical forest
Online: 31 July 2018 (05:02:29 CEST)
Secondary forests (SF) are important carbon sinks, removing CO2 from the atmosphere through the photosynthesis process and storing photosynthates in their aboveground live biomass (AGB). This process occurring at large-scales partially counteracts C emissions from land-use change, playing, hence, an important role in the global carbon cycle. The absorption rates of carbon in these forests depend on forest physiology, controlled by environmental and climatic conditions as well as on the past land use, which is rarely considered for retrieving AGB from remotely sensed data. In this context, the main goal of this study is to evaluate the potential of full polarimetric ALOS-2 PALSAR-2 data for estimating AGB by taking into account the past-land use of SF areas in the Brazilian Amazon. We surveyed a chronosequence of 42 SF plots (20 ha) near the Tapajós National Forest in Pará state to quantifying AGB growth rates. We explored the full polarimetric data testing three regression models including non-linear (NL), multiple linear regressions models (MLR), and the semi-empirical extended water cloud model (EWCM). The results showed that the intensity of previous use has affected the structure of SF by reducing the AGB accumulation and being noticeable by several polarimetric attributes. The combination of multiple prediction variables with MLR improved the AGB estimation by 70% comparing amongst other models (R² adj. = 0.51; RMSE = 13.2 Mg ha-1) bias = 2.1 ± 37.9 Mg ha-1. The error propagation of the MLR model was estimated to be 15%.
ARTICLE | doi:10.20944/preprints202211.0388.v1
Subject: Biology And Life Sciences, Immunology And Microbiology Keywords: microwave assisted extraction (MAE); canolol; sinapine; high temperature; de-oiled canola; processing
Online: 21 November 2022 (11:45:34 CET)
Canola is the major oilseed crop of Canada. The de-oiled material is an important by-product due to its rich phenolic profile and high protein content. This co-processing stream from canola is primarily utilized as animal feed but represents an invaluable source of nutraceuticals. Microwave-assisted solvent extraction (MAE), as a green extraction method, has received considerable attention in recent times. The ease of use and application of many solvents at the same time makes the MAE one of the best methods for studying multiple solvents at the same time. The formation of canolol, from sinapine and sinapic acid, is primarily dependant on temperature which favors the decarboxylation reaction. Hence, MAE using green extractants can be used to enhance the yield of canolol. This study examined the effects of different pre-treatment temperature-time combinations of 140, 150, 160, and 170℃ for 5, 10, 15, 20 and 30 minutes on the extraction of canolol and other canola endogenous phenolic compounds. Three antioxidant assays assessed the antioxidant activity of the different extracts obtained by MAE confirming the microwave as a novel and versatile instrument for enhancing the yield of canolol. Improvements in the antioxidant activity of the different extracts further established the efficacy of the current method for isolating important natural phenolic derivatives for utilization by the nutraceutical industry.
Subject: Chemistry And Materials Science, Food Chemistry Keywords: dried Chinese sausage; fat replacement; mango peel pectin; microwave-assisted extraction technique
Online: 11 March 2020 (03:07:13 CET)
In this research, low-fat dried Chinese sausage was formulated with mango peel pectin (MPP) extracted by microwave assisted extraction (MAE) (0%, 5%, 10% and 15% (w/w). The extractable yield of pectin attained from peel of Nam Dok Mai variety was achieved at 13.85% using 700-watt power. The extracted MPP were of high equivalent weight (1,485.78 mg/mol), degree esterification (77.19%) and methoxyl content (19.33%) with the structure of more porosity as compared to that of the conventional method. Spectrum scans by Fourier transform infrared spectrophotometer (FT-IR) advised that the extracted MPP gave the similar wave number profiles as the commercial pectin. Quality attributes of the Chinese sausages were accessed and compared with the control formula (CTRL). At higher concentrations of MPP, the product had positively increased colour intensity. The texture profile of the sausage illustrated that only the hardness value was comparable with the CTRL, while springiness, cohesiveness, gumminess and chewiness were statistically lower (p < 0.05). Furthermore, the sensory evaluation by experienced panellists (n=12) indicated that 5% MPP similarly represented overall acceptability with the CTRL. Consequently, MPP can be effectively applied at low level as fat replacement in Chinese sausage allowing colour improvement and product of healthier option.
ARTICLE | doi:10.20944/preprints201908.0188.v1
Subject: Chemistry And Materials Science, Biomaterials Keywords: porous silicon nitride ceramics; microwave sintering technology; agglomeration process; law of influence
Online: 18 August 2019 (02:30:04 CEST)
In this paper, the preparation methods of porous silicon nitride materials with controllable dielectric constant and pore structure were systematically studied. By using microwave sintering technology, porous silicon nitride materials with high closed pore ratio were prepared by adjusting the content of sintering additives and sintering process parameters, and controlling the grain boundary phase and pore structure and size. The effects of sintering conditions on the total porosity, closed porosity, pore structure and dielectric properties of materials were systematically studied.
ARTICLE | doi:10.20944/preprints201902.0046.v1
Subject: Environmental And Earth Sciences, Remote Sensing Keywords: Soil Moisture; Remote Sensing; Landsat; SMAP; Random Forest; Machine Learning; Downscaling; Microwave
Online: 5 February 2019 (08:01:58 CET)
If given the correct remotely sensed information, machine learning can accurately describe soil moisture conditions in a heterogeneous region at the large scale based on soil moisture readings at the small scale through rule transference across scale. This paper reviews an approach to increase soil moisture resolution over a sample region over Australia using the Soil Moisture Active Passive (SMAP) sensor and Landsat 8 only and a validation experiment using Sentinal-2 and the Advanced Microwave Scanning Radiometer (AMSR-E) over Nevada. This approach uses an inductive localized approach, replacing the need to obtain a deterministic model in favor of a learning model. This model is adaptable to heterogeneous conditions within a single scene unlike traditional polynomial fitting models and has fixed variables unlike most learning models. For the purposes of this analysis, the SMAP 36 km soil moisture product is considered fully valid and accurate. Landsat bands coinciding in collection date with a SMAP capture are down sampled to match the resolution of the SMAP product. A series of indices describing the Soil-Vegetation-Atmosphere Triangle (SVAT) relationship are then produced, including two novel variables, using the down sampled Landsat bands. These indices are then related to the local coincident SMAP values to identify a series of rules or trees to identify the local rules defining the relationship between soil moisture and the indices. The defined rules are then applied to the Landsat image in the native Landsat resolution to determine local soil moisture. Ground truth comparison is done via a series of grids using point soil moisture samples and air-borne L-band Multibeam Radiometer (PLMR) observations done under the SMAPEx-5 campaign. This paper uses a random forest due to its highly accurate learning against local ground truth data yet easily understandable rules. The predictive power of the inferred learning soil moisture algorithm did well with a mean absolute error of 0.054 over an airborne L-band retrieved surface over the same region.
ARTICLE | doi:10.20944/preprints201809.0577.v1
Subject: Chemistry And Materials Science, Polymers And Plastics Keywords: waste tire recycling; bitumen plasticization; microwave treatment; synergistic effects; structure-property relationships
Online: 29 September 2018 (04:50:58 CEST)
In this paper, ground tire rubber (GTR) was mechano-chemically modified with road bitumen 160/220 and subsequently treated using a microwave radiation. The combined impact of bitumen 160/220 content and microwave treatment on short-term devulcanization of GTR were studied by thermal camera, wavelength dispersive X-ray fluorescence spectrometry (WD-XRF), static headspace and gas chromatography-mass spectrometry (SHS-GC-MS), thermogravimetric analysis combined with Fourier transform infrared spectroscopy (TGA-FTIR), oscillating disc rheometer and static mechanical properties measurements. The obtained results showed that bitumen plasticizer prevent oxidation of GTR during microwave treatment and simultaneously improves processing and thermal stability of obtained reclaimed rubber.
REVIEW | doi:10.20944/preprints202301.0016.v1
Subject: Physical Sciences, Optics And Photonics Keywords: Integrated photonics; microcombs; microwave photonics; optical communications; precision measurements; neuromorphic computing; quantum optics
Online: 3 January 2023 (08:00:03 CET)
Optical microcombs represent a new paradigm for generating laser frequency combs based on compact chip-scale devices, which have underpinned many modern technological advances for both fundamental science and industrial applications. Along with the surge in activity related to optical micro-combs in the past decade, their applications have also experienced rapid progress ‒ not only in traditional fields such as frequency synthesis, signal processing, and optical communications, but also in new interdisciplinary fields spanning the frontiers of light detection and ranging (LiDAR), astronomical detection, neuromorphic computing, and quantum optics. This paper reviews the applications of optical microcombs. First, an overview of the devices and methods for generating optical microcombs is provided, which are categorized into material platforms, device architectures, soliton classes, and driving mechanisms. Second, the broad applications of optical microcombs are systematically reviewed, which are categorized into microwave photonics, optical communications, precision measurements, neuromorphic computing, and quantum optics. Finally, the current challenges and future perspectives are discussed.
ARTICLE | doi:10.20944/preprints202205.0090.v1
Subject: Physical Sciences, Applied Physics Keywords: machine learning/artificial intelligence; precipitation type classification; passive microwave; precipitation radar; retrieval algorithm
Online: 7 May 2022 (03:46:06 CEST)
Precipitation type is a key parameter used for better retrieval of precipitation characteristics as well as to understand the cloud-convection-precipitation coupling processes. Ice crystals and water droplets inherently exhibit different characteristics in different precipitation regimes (e.g., convection, stratiform), which reflect on satellite remote sensing measurements that help us distinguish them. The Global Precipitation Measurement (GPM) Core Observatory’s Microwave Imager (GMI) and Dual-Frequency Precipitation Radar (DPR) together provide ample information on global precipitation characteristics. As an active sensor, DPR provides an accurate precipitation type assignment, while passive sensors like GMI are traditionally only used for empirical understanding of precipitation regimes. Using collocated precipitation type flags from DPR as the “truth”, this paper employs machine learning (ML) models to train and test the predictability and accuracy of using passive GMI-only observations together with ancillary information from reanalysis and GMI surface emissivity retrieval products. Out of six ML models, four simple ones (Support Vector Machine, Neural Network, Random Forest, and Gradient Boosting) and the 1-D convolutional neural network (CNN) model are identified to produce 90% - 94% prediction accuracy globally for 5 types of precipitation (convective, stratiform, mixture, no precipitation, and other precipitation), which is much more robust than previous similar effort. One novelty of this work is to introduce data augmentation (subsampling and bootstrapping) to handle extremely unbalanced samples in each category. Careful evaluation of Impact matrices demonstrate that polarization difference (PD) and surface emissivity at high-frequency channels dominate the decision process, which are consistent with the physical understanding of polarized microwave radiative transfer over different surface types, as well as in snow and liquid clouds with different microphysical properties. Furthermore, the view-angle dependency artifact that DPR precipitation flag bears with does not propagate into the conical-viewing GMI retrievals. This work provides a new and promising way for future physics-based ML retrieval algorithm development.
ARTICLE | doi:10.20944/preprints202105.0250.v1
Subject: Chemistry And Materials Science, Analytical Chemistry Keywords: acid dissolution; neodymium magnet; open system; microwave sample preparation system; ICP-MS analysis
Online: 11 May 2021 (15:06:50 CEST)
The separation of rare earth metals (REM) from a neodymium magnet has been widely studied in the last year. We have shown that the waste of computer hard disk contains 25.41 % neodymium, 64.09 % iron, and <<1 % boron. To further isolate rare-earth metals, the magnet was acidically dissolved in open and closed systems. In both methods of dissolution was used concentrated nitric acid. The difference between these methods are the conditions of dissolution of magnet. The magnet was dissolved in a microwave sample preparation system at different temperatures and pressures in a closed system. In the open system, the acid dissolution of the magnet conducted at room temperature. 0.2 g of the neodymium magnet sample was taken under two conditions, and the dissolution process in the closed system lasted 1 hour, and in the open system-30-40 minutes. The open system is a non-laborious, simple and cheap method of dissolving the magnet by comparing both systems. Therefore, an open sample preparation system is used for further work. To remove the iron in the magnet, oxalic acid was used and precipitated as oxalates under both conditions. According to the result of the ICP-MS method, it is shown that the neodymium and iron contents in the precipitate are 24.66 % and 0.06 %, respectively. This shows that the iron has almost completely passed to the filtrate. Thus, it is possible to remove the iron from the sample.
ARTICLE | doi:10.20944/preprints202012.0627.v1
Subject: Physical Sciences, Acoustics Keywords: Fiber Bragg Structure; microwave photonics; vibration; fiber optic sensor; Address Fiber Bragg Grating
Online: 24 December 2020 (13:56:51 CET)
The paper presents the results of a study of the concept of address fiber Bragg structures in the problem of vibration control. The mathematical model of measuring transformation is presented; the experimental study of a vibration diagnostics system based on Address Fiber Bragg Gratings is carried out; the quantitative and qualitative comparative assessment with electronic accelerometers is made; the gain by an order of magnitude in some parameters is shown.
ARTICLE | doi:10.20944/preprints201812.0068.v1
Subject: Environmental And Earth Sciences, Environmental Science Keywords: Soil moisture; Fengyun-3C; Passive microwave; Chinese Automatic Soil Moisture Observation Stations; NDVI
Online: 5 December 2018 (14:05:35 CET)
Soil moisture (SM) products derived from passive satellite missions are playing an increasingly important role in agricultural applications, especially in crop monitoring and disaster warning. Evaluating the dependability of those products before they can be used on a large scale is crucial. In this study, we assessed the level 2 (L2) SM product from the Chinese Fengyun-3C (FY-3C) radiometer against in situ measurements collected from the Chinese Automatic Soil Moisture Observation Stations (CASMOS) during a one-year period from January 1 to December 31, 2016 in Henan, which is an agricultural province in China. Four statistical parameters were used to evaluate the products’ reliability: mean difference, root-mean-square error (RMSE), unbiased RMSE (ubRMSE), and the correlation coefficient. These statistical indicators revealed that the FY-3C L2 SM product generally did not agree with the in situ SM data from CASMOS. The time-series analysis further indicated that the correlations and estimated error were highly related to the growing periods of the crops in our study area. FY-3C L2 SM data tended to overestimate soil moisture during May, August, and September, when the crops reach their maximum vegetation density, and tended to underestimate the soil moisture content during the rest of the year. The averaged correlation coefficient between FY-3C SM and the Moderate Resolution Imaging Spectroradiometer (MODIS) normalized difference vegetation index was 0.55, which demonstrates that the vegetation water content of the crops considerably influences the SM product. To improve the accuracy of the FY-3C SM product, an improved algorithm that can filter out the influences of the crops should be applied in the future.
ARTICLE | doi:10.20944/preprints201810.0120.v1
Subject: Physical Sciences, Optics And Photonics Keywords: NDIR; methane; sensor; infrared; thin film; III-V; heterostructure; bandpass; microwave; sputter; MBE
Online: 7 October 2018 (10:52:34 CEST)
In this work performance improvements are described of a low power consumption non-dispersive infrared (NDIR) methane (CH4) gas sensor using customised optical thin film bandpass filters (BPF). BPF’s shape the spectral characteristic of the combined mid infrared III-V based light emitting diode (LED)/ photodiode (PD) light source/detector optopair, enhancing NDIR CH4 sensor performance. The BPF, deposited using a novel microwave plasma assisted pulsed DC sputter deposition process, is deposited at room temperature directly onto the temperature sensitive PD heterostructure. BPF’s comprise germanium (Ge) and niobium pentoxide (Nb2O5) alternating high and low refractive index layers respectively. Two different optical filter designs are progressed; with BPF bandwidths (BWs) of 160 nm and 300 nm. Comparison of modelled and measured NDIR sensor performance is described, highlighting maximized signal to noise ratio (SNR) and minimized cross talk performance benefits. BPF spectral stability for various environmental temperature and humidity conditions is demonstrated.
ARTICLE | doi:10.20944/preprints202106.0544.v1
Subject: Environmental And Earth Sciences, Atmospheric Science And Meteorology Keywords: Snowfall Retrieval; Snow Water Equivalent; Cloud Liquid Water; Emissivity; Brightness Temperature; Passive Microwave; GPM
Online: 22 June 2021 (14:22:16 CEST)
Falling snow alters its own microwave signatures when it begins to accumulate on the ground, making retrieval of snowfall challenging. This paper investigates the effects of snow-cover depth and cloud liquid water content on microwave signatures of terrestrial snowfall using reanalysis data and multi-annual observations by the Global Precipitation Measurement (GPM) core satellite with particular emphasis on the 89 and 166 GHz channels. It is found that over shallow snow cover (snow water equivalent (SWE) ≤ 100 kg m-2) and low values of cloud liquid water path (LWP 100–150 g m-2), the scattering of light snowfall (intensities ≤ 0.5 mm h−1) is detectable only at frequency 166 GHz, while for higher snowfall rates, the signal can also be detected at 89 GHz. However, when SWE exceeds 200 kg m-2 and the LWP is greater than 100–150 g m-2, the emission from the increased liquid water content in snowing clouds becomes the only surrogate microwave signal of snowfall that is stronger at frequency 89 than 166 GHz. The results also reveal that over high latitudes above 60°N where the SWE is greater than 200 kg m-2 and LWP is lower than 100–150 g m-2, the snowfall microwave signal could not be detected with GPM without considering a priori data about SWE and LWP. Our findings provide quantitative insights for improving retrieval of snowfall in particular over snow-covered terrain.
Subject: Physical Sciences, Astronomy And Astrophysics Keywords: cosmic microwave background; cosmological parameters; cosmology: observations; cosmology: redshift; cosmology: theory; large-scale structure
Online: 14 June 2020 (16:16:26 CEST)
The notion that dust might have formed the cosmic microwave background (CMB) has been strongly refuted on the strength of four decades of observation and analysis, in favour of recombination at a redshift z ~ 1080. But tension with the data is growing in several other areas, including measurements of the Hubble constant H(z) and the BAO scale, which directly or indirectly impact the physics at the surface of last scattering (LSS). The R_h=ct universe resolves at least some of this tension. We show in this paper that---if the BAO scale is in fact equal to the acoustic horizon---the redshift of the LSS in this cosmology is z_cmb ~ 16, placing it within the era of Pop III star formation, prior to the epoch of reionization at 15 > z > 6. Quite remarkably, the measured values of z_cmb and H_0 = H(0) in this model are sufficient to argue that the CMB temperature today ought to be ~ 3 K, so H_0 and the baryon to photon ratio are not independent free parameters. This scenario might have resulted from rethermalization of the CMB photons by dust, presumably supplied to the interstellar medium by the ejecta of Pop III stars. Dust rethermalization may therefore yet resurface as a relevant ingredient in the R_h=ct universe. Upcoming high sensitivity instruments should be able to readily distinguish between the recombination and dust scenarios by either (i) detecting recombination lines at z ~ 1080, or (ii) establishing a robust frequency-dependent variation of the CMB power spectrum at the level of ~ 2-4% across the sampled frequency range.
Subject: Physical Sciences, Mathematical Physics Keywords: dark energy; dark matter; cosmic microwave background; large numbers hypothesis; varying fundamental constants; symmetry
Online: 14 June 2019 (09:53:08 CEST)
Recent observations of the dark energy density have demonstrated the fine-tuning problem, and the challenges faced by theoretical modeling. In this study, we apply the self-similar symmetry (SSS) model, describing the hierarchical structure of the universe based on the Dirac large numbers hypothesis, to Einstein's cosmological term. We introduce a new similarity dimension, DB, in the SSS model. Using the DB SSS model, the cosmological constant Λ is simply expressed as a function of the cosmic microwave background (CMB) temperature. The result shows that both the gravitational constant G and Λ are coupled with the CMB temperature, which simplifies the solution of Einstein's field equations for the variable Λ-G model.
ARTICLE | doi:10.20944/preprints202110.0388.v1
Subject: Physical Sciences, Astronomy And Astrophysics Keywords: cosmic microwave background; cosmic infrared background; cosmic background detector; Planck Surveyor; Baryon Oscillation Spectroscopic Survey
Online: 26 October 2021 (13:53:29 CEST)
In this research, the other reasonable explanations for the cosmic microwave background radiation is revealed. Due to the microwave resolution, it very roughly shows the image of galaxies in the universe. Moreover, the intensity measurement on each pixel of the image is the sum of the incident microwaves from different directions, so the microwave image cannot represent the microwave sources clearly far away from the Earth. Hence, we propose a simulation after removing several strongest microwave sources, the remaining microwave radiation sources can establish a very uniform intensity distribution over a range of several ten light years. On the other hand, Sloan Digital Sky Survey reveals 200 million galaxies in the universe and, in fact, only to eliminate the contributions of all galaxies from the microwave image is impossible. The way to further obtain the fine-scale structure by only removing the few strongest microwave sources as the foreground effect will keep the other contributions from all the rest galaxies and stars. Therefore, the Cosmic Microwave Background cannot be uniquely explained the radiation which was left after the initial formation of the universe. Moreover, it is the mainly residual radiation from the un-calculated galaxies and inaccurate estimation of the microwave source strength.
ARTICLE | doi:10.20944/preprints202109.0414.v1
Subject: Engineering, Electrical And Electronic Engineering Keywords: Fiber optics sensors; Microwave photonics; Interferometry; Distributed acoustic sensing (DAS); optical frequency domain reflectometry (OFDR)
Online: 23 September 2021 (17:22:27 CEST)
A microwave-photonics method has been developed for measuring distributed acoustic signals. This method uses microwave-modulated low coherence light as a probe to interrogate distributed in-fiber interferometers, which are used to measure acoustic-induced strain. By sweeping the microwave frequency at a constant rate, the acoustic signals are encoded into the complex microwave spectrum. The microwave spectrum is transformed into the joint time-frequency domain and further processed to obtain the distributed acoustic signals. The method is first evaluated using an intrinsic Fabry Perot interferometer (IFPI). Acoustic signals of frequency up to 15.6 kHz were detected. The method was further demonstrated using an array of in-fiber weak reflectors and an external Michelson interferometer. Two piezo-ceramic cylinders (PCCs) driven at frequencies of 1700 Hz and 3430 Hz were used as acoustic sources. The experiment results show that the sensing system can locate multiple acoustic sources. The system resolves 20 nε when the spatial resolution is 5 cm. The recovered acoustic signals match the excitation signals in frequency, amplitude, and phase, indicating an excellent potential for distributed acoustic sensing (DAS).
ARTICLE | doi:10.20944/preprints202106.0120.v1
Subject: Environmental And Earth Sciences, Atmospheric Science And Meteorology Keywords: IMERG; Stage IV; Infrared; Passive microwave; Snow; Ice; Precipitation; GPM; Wet-bulb temperature; AMSR-2
Online: 3 June 2021 (14:59:21 CEST)
Various products of the Integrated Multisatellite Retrievals for GPM (IMERG) and passive mi-crowave (PMW) sensors are assessed with respect to near-surface wet-bulb temperature (Tw), precipitation intensity, and surface type (i.e., with and without snow and ice on the surface) over the CONUS and using Stage-IV product as reference precipitation. IMERG products include precipitation estimates from infrared (IR), combined PMW, and their combination. PMW products generally have higher skills than IR over snow- and ice-free surfaces. Over snow- and ice-covered surfaces (1) PMW products (except AMSR-2) show a higher correlation coefficient than IR, (2) IR and PMW precipitation products tend to overestimate precipitation, but at colder temperatures (e.g., Tw<-10oC) PMW products tend to underestimate and IR product continues to show large overestimations, and (3) PMW sensors show higher overall skill in detecting precipitation oc-currence, but not necessarily at very cold Tw. The results suggest that the current approach of IMERG (i.e., replacing PMW with IR precipitation estimates over snow- and ice-surfaces) may need to be revised.
ARTICLE | doi:10.20944/preprints202304.0936.v1
Subject: Engineering, Electrical And Electronic Engineering Keywords: planar microwave sensor; humidity sensor; microstrip technology; detection of sweat; detection of urine leakage; enuresis; hyperhidrosis
Online: 26 April 2023 (03:20:36 CEST)
A planar microwave sensor devoted to the detection of humidity in underwear and clothes in general is proposed. The ultimate goal of the sensor is to detect the presence of liquids in fabrics, of interest to aid patients that suffer from certain pathologies, such as hyperhidrosis and enuresis. The main target in the design of the sensor, considering the envisaged application, is simplicity. Thus, the sensor operates at a single frequency, and the working principle is the variation in the mag-nitude of the transmission coefficient of a matched line loaded with an open-ended quar-ter-wavelength sensing stub resonator. The stub, which must be in contact with the so-called fabric under test (FUT), generates a notch in the transmission coefficient with a resonance frequency that depends on the humidity level of the fabric. By designing the stub with a moderately high quality factor, the variation in the resonance frequency causes a significant change in the magnitude level at the operating frequency, the resonance frequency when the sensing stub is loaded with the dry fabric, and the presence of liquid can be detected by means of an amplitude detector. A prototype device is proposed and experimentally validated.
ARTICLE | doi:10.20944/preprints202106.0540.v1
Subject: Business, Economics And Management, Accounting And Taxation Keywords: food processing; packaging; UHT; high-pressure; pulsed-electric fields; pasteurization; microwave; consumer research; farm-to-fork
Online: 22 June 2021 (12:06:04 CEST)
Given the increasing public interest in how ingredients are processed and the growing demand for organic food products, it is critical to understand consumers’ expectations about the process-related quality of organic products. In the minds of consumers, organic food is a concept related to either natural or less processed food, which leads them to prefer products obtained with careful processes. The main objective of this paper is to propose a working definition of "careful processing" for organic products and test its consistency while being used in scoring different processing methods by consumers. Results show that the proposed definition allows to consistently rate alternative processing methods. Consumers tend to score novel processing methods such as pulsed electric fields and microwave as less careful, supporting the idea that organic consumers want the least man-made interference with their food products. Results show that a simple but effective definition of careful processing may help consumers to distinguish further organic food products from conventional ones, no matter which communication scheme is used.
ARTICLE | doi:10.20944/preprints202103.0707.v1
Subject: Chemistry And Materials Science, Analytical Chemistry Keywords: Grape processing waste; Polyphenols; Green extraction; Microwave-hydrodiffusion and gravity, Enocyanin; Resveratrol; Flavonoids; Anthocyanins; Wine pomace
Online: 29 March 2021 (16:06:18 CEST)
The extraction of grape processing waste (wine pomace) via microwave-hydrodiffusion and gravity (MHG) from three different cultivars grown in Sicily (Syrah, Perricone and Nero d’Avola) rapidly affords aqueous extracts highly concentrated in valued biophenols including flavonoids, anthocyanins and phenolic acids. The method does not employ organic solvent, acid or base and does not require grinding or freeze drying of the wine pomace nor separation of the grape skins from seeds and stem. All the extracts have a pronounced stability as shown by their red-violet color fully retained after storage for more than a year (15 months) in freezer under air. Concentrations of phenolics up to 2000 ppm were detected in the aged extracts of Sicily’s local cultivar Perricone, which also has the highest content of flavonoids. These findings provide a simple and economically viable extraction route to biophenol-rich red extracts that can be used as food colorants as well as to formulate nutraceutical, cosmetic and personal care products starting from an agricultural by-product available in >10 million tonne yearly amount.
ARTICLE | doi:10.20944/preprints202009.0017.v1
Subject: Engineering, Control And Systems Engineering Keywords: microwave photonic sensor system; numerical simulation; addressed fiber Bragg structures; load sensing bearings; vehicle dynamics control
Online: 1 September 2020 (12:11:45 CEST)
The work presents an approach to instrument the load sensing bearings for automotive applications for estimation of the loads acting on the wheels. The system comprises fiber-optic sensors based on addressed fiber Bragg structures (AFBS) with two symmetrical phase shifts. A mathematical model for load-deformation relation is presented, and the AFBS interrogation principle is described. The simulation includes (i) modeling of vehicle dynamics in a split-mu braking test, during which the longitudinal wheel loads are obtained, (ii) the subsequent estimation of bearing outer ring deformation using a beam model with simply supported boundary conditions, (iii) the conversion of strain into central wavelength shift of AFBS, and (iv) modeling of the beating signal at the photodetector. The simulation results show that the estimation error of the longitudinal wheel force from the strain data acquired from a single measurement point was 5.44% with root-mean-square error of 113.64 N. A prototype load sensing bearing was instrumented with a single AFBS sensor and mounted in a front right wheel hub of an experimental vehicle. The experimental setup demonstrated comparable results with the simulation during the braking test. The proposed system with load-sensing bearings is aimed at estimation of the loads acting on the wheels, which serve as input parameters for active safety systems, such as automatic braking, adaptive cruise control, or fully automated driving, in order to enhance their effectiveness and safety of the vehicle.
ARTICLE | doi:10.20944/preprints201909.0290.v1
Subject: Biology And Life Sciences, Immunology And Microbiology Keywords: microbial antioxidants; bioactive compounds; microwave extract; aspergillus flavus; rice, antioxidant compounds; free radical; phenolic compounds; temperatures
Online: 26 September 2019 (03:39:00 CEST)
The current study aims to study the optimal fermentation conditions for producing microbial bioactive compounds. The microwave parameters consist on 2450 MHz, and 500-watt for 20, 30, and 40 seconds. The solubility of solvents was tested for the extraction of antioxidant compounds from fermented rice (Koji) by A. flavus, Ethyl acetate was the best solvent used for extraction purposes. Antioxidant properties were differentiated by blocking the oxidation of the linoleic acid with an inhibition rate of 73.13% at a concentration of 200 mg/mL, in addition to increasing its effectiveness for free radical extraction and reduction strength by increasing concentrations gradually. The bond ability to irons was lower compared to the EDTA-2Na, in addition to the obtained total content corresponding to phenolic compounds in the ethyl acetate extract of fermented rice (Koji) by A. flavus was 232.11 mg, on the basis of galic acid/mg. The stability of the antioxidant compounds of the ethyl acetate extract of fermented rice (Koji) by A. flavus was also studied; showing stability under neutral conditions, as well as at high temperatures (185 °C during two hours). However, no stability was obtained under acidic and alkaline conditions.
ARTICLE | doi:10.20944/preprints202105.0756.v1
Subject: Engineering, Automotive Engineering Keywords: microwave devices; telecommunication systems; polarizer; differential phase shift; crosspolar isolation; axial ratio; satellite information systems; antenna systems
Online: 31 May 2021 (11:56:05 CEST)
This research presents the design and characteristics of new wideband polarizer based on the square waveguide with irises. Matching and polarization characteristics of the polarizer have been simulated and optimized. Frequency dependences of the characteristics are presented. Developed polarizer can be applied in satellite information systems.
ARTICLE | doi:10.20944/preprints202304.0971.v1
Subject: Medicine And Pharmacology, Pulmonary And Respiratory Medicine Keywords: 2019-nCoV; COVID-19; RT-PCR; SARS-CoV-2; Community-acquired pneumonia; Chest CT; microwave radiometry; temperature measurement
Online: 26 April 2023 (08:02:32 CEST)
Background. Chest CT is widely regarded as a dependable imaging technique for detecting pneumonia in COVID-19 patients, but there is growing interest in microwave radiometry (MWR) of the lungs as a possible substitute for diagnosing lung involvement. Aim. The aim of the study is to examine the utility of the MWR approach as a screening tool for diagnosing pneumonia with complications in patients with COVID-19. Methods. Our study involved two groups of participants. The control group consisted of 50 individuals (24 male and 26 female) between the ages of 20 to 70 years who underwent clinical evaluations and had no known medical conditions. The main group included 142 participants (67 men and 75 women) between the ages of 20 to 87 years who were diagnosed with COVID-19 complicated by pneumonia and were admitted to the emergency department between June 2020 to June 2021. Skin and lung temperatures were measured at 14 points, including 2 additional reference points, using a previously established method. Lung temperature data were obtained with the MWR2020 (RTM-01-RES) (MMWR LTD, Edinburgh, UK), a CE Class I device. All participants underwent clinical evaluations, laboratory tests, chest CT scans, MWR of the lungs, and reverse transcriptase polymerase chain reaction (RT-PCR) testing for SARS-CoV-2. Results. The MWR exhibits a high predictive capacity as demonstrated by its sensitivity of 98.6% and specificity of 84.0%. Conclusions. MWR of the lungs can be a valuable substitute for chest CT in diagnosing pneumonia in patients with COVID-19, especially in situations where chest CT is unavailable or impractical.
ARTICLE | doi:10.20944/preprints202103.0267.v2
Subject: Medicine And Pharmacology, Immunology And Allergy Keywords: Scanning acoustic microscopy; speed of sound; attenuation of sound; anticancer drugs; tannic acid; acetic acid; microwave; Computer Imaging
Online: 11 March 2021 (11:25:34 CET)
Cells receive external stimuli to incur structural and functional damages. On scanning acoustic microscopy (SAM), speed-of-sound (SOS), attenuation-of-sound (AOS), and thickness values are plotted on the screen to create cellular images, which are related to stiffness, viscosity, and cell size, respectively. The obtained digital data compared using statistical analysis. We aimed to investigate the effects of anticancer drugs, acidic fluids, and heat effects on the cells by using SAM. Anticancer drug cisplatin induced cancer cell apoptosis/necrosis and regeneration in culture, causing elevated SOS, reduced AOS, and thickness. During a more prolonged incubation, the SAM values fluctuated differently between the cisplatin-treated and untreated cells. The tannic and acetic acid and microwave stimuli induced SOS and AOS elevations. These stimuli altered the cell size, number, differentiation, viscosity, and stiffness, which corresponded well to the fluctuation of the SOS and AOS values after incubation. Different anticancer drugs interacted with cancer cells to induce the characteristic alterations of the SAM values. These structural and mechanical alterations induced in cells was difficult to observe on light microscopy. Cellular damages were statistically compared between different stimuli and time-lapse cellular changes were observed using a SAM analysis. SAM is a useful modality to evaluate cellular damage.
ARTICLE | doi:10.20944/preprints201807.0053.v1
Subject: Engineering, Electrical And Electronic Engineering Keywords: Intra-body communication; path loss; microwave probes; channel characterization; fat tissue; ex-vivo; phantom; dielectric properties; topology optimization.
Online: 3 July 2018 (15:08:56 CEST)
In this paper, we investigate the use of fat tissue as a communication channel between in-body, implanted devices at R-band frequencies (1.7–2.6 GHz). The proposed fat channel is based on an anatomical model of the human body. We propose a novel probe that is optimized to efficiently radiate the R-band frequencies into the fat tissue. We use our probe to evaluate the path loss of the fat channel by studying the channel transmission coefficient over the R-band frequencies. We conduct extensive simulation studies and validate our results by experimentation on phantom and ex-vivo porcine tissue, with good agreement between simulations and experiments. We demonstrate a performance comparison between the fat channel and similar waveguide structures. Our characterization of the fat channel reveals propagation path loss of 1.4 dB and 3.8 dB per 20 mm for phantom and ex-vivo porcine tissue, respectively. These results demonstrate that fat tissue can be used as a communication channel for high data rate intra-body networks.
ARTICLE | doi:10.20944/preprints202207.0370.v1
Subject: Medicine And Pharmacology, Oncology And Oncogenics Keywords: breast cancer; passive microwave radiometry (MWR); cascaded correlation neural network (CCNN); weight agnostic neural network (WANN); CMA-ES algorithm.
Online: 25 July 2022 (10:04:03 CEST)
Abstract Background and Objective: Medical Microwave Radiometry (MWR) is used to capture the thermal properties of internal tissues and has usages in breast cancer detection. Our goal in this paper is to improve classification performance and investigate automated neural architecture search methods. Methods: We investigate optimizing the weights of a weight agnostic neural network using bi-population covariance matrix adaptation evolution strategy (BIPOP-CMA-ES) once the topology is found. We compare it against a weight agnostic and cascade correlation neural network. Results: The experiments are conducted on a breast cancer dataset of 4912 patients. Our proposed weight agnostic BIPOP-CMA-ES model achieved the best performance. It obtained an F1-score of 0.9225, accuracy of 0.9219, precision of 0.9228, recall of 0.9217 and topology of 153 connections. Conclusions: The results are an indication of the potential of MWR utilizing a neural network-based diagnostic tool for cancer detection. By separating the tasks of topology search and weight training, we are able to improve the overall performance.
ARTICLE | doi:10.20944/preprints201908.0048.v1
Subject: Physical Sciences, Space Science Keywords: coordinate and time transformation; kinematics; universal frame of reference; one-way speed of light; anisotropy of cosmic microwave background
Online: 5 August 2019 (05:18:01 CEST)
The article presents formal proof that the Special Theory of Relativity is wrong, that is, the interpretation of the mathematics on which STR is based, proposed by Einstein is incorrect. The article shows that there are infinitely many kinematics in which one-way speed of light is always equal to c. The kinematics of Special Theory of Relativity (STR) is only one of those infinitely many kinematics. It presents that mathematics on which STR kinematics is based can be interpreted differently and this leads to other conclusions on the properties of this kinematics. In this article, the whole class of linear transformations of time and coordinate was derived. Transformations were derived on the assumption that conclusions from Michelson-Morley’s and Kennedy-Thorndikea’s experiments are met for the observer from each inertial frame of reference, i.e. that the mean velocity of light in the vacuum flowing along the way back and forth is constant. It was also assumed that there is at least one inertial frame of reference, in which the velocity of light in a vacuum in each direction has the same value c, and the space is isotropic for observers from this distinguished inertial frame of reference (universal frame of reference). Derived transformations allow for building many different kinematics according to Michelson-Morley’s and Kennedy-Thorndikea’s experiments. The class of transformations derived in the study is a generalization of transformations derived in the paper , which consists in enabling non-zero values of parameter e(v). The idea of such a generalization derives from the person, who gave me this extended transformations class for analysis and publication.
ARTICLE | doi:10.20944/preprints202207.0399.v10
Subject: Physical Sciences, Quantum Science And Technology Keywords: relativity; spacetime; cosmology; cosmic microwave background; Hubble’s law; Hubble constant; dark energy; wave–particle duality; quantum entanglement; Theory of Everything
Online: 7 October 2022 (08:29:57 CEST)
Today’s concepts of space and time trace back to Albert Einstein’s theories of relativity. In special relativity, he derives relations of how a “moving observer” experiences space and time with respect to an “observer at rest”. In general relativity, he derives relations of how mass and energy are affecting space and time. Both theories have been very successful, but fail to solve fundamental mysteries such as competing values of the Hubble constant, dark energy, the wave–particle duality, and quantum entanglement. Here we show that this failure is due to prioritizing a “system at rest”: In Einstein’s relativity, there is no superordinate reference frame that would treat objects at rest and moving objects alike. We replace Minkowski spacetime with Euclidean spacetime (ES) and claim that reality is formed by projecting ES to 3D space. Alternative models of Euclidean relativity run into geometric paradoxes as they claim reality to be in ES. Our theory profits from two new concepts: “distance” (space and time in one) and “wavematter” (electromagnetic wave packet and matter in one). In Cartesian ES coordinates, it is not predefined for all objects alike which axial distance relates to time. Time is a subordinate quantity: covered distance divided by the speed of light. Wavematter is a generalized concept of energy: Each object is wave from an external view, but matter from its internal view. Length contraction, time dilation, acceleration, and gravitation are geometric effects. We even derive a Theory of Everything in ES. Matching the symmetry simplifies physics.
Subject: Physical Sciences, Acoustics Keywords: electromagnetic waves, microwave frequency range, biological medium, wave propagation, reflection, refraction, surface wave, creeping wave, multilayered biological medium, body area networks
Online: 5 May 2021 (12:13:48 CEST)
Propagation of electromagnetic (EM) waves inside and on the surface of the human body is the subject of active research in area of biomedical applications. This research area is the basis for wireless monitoring of biological object parameters and characteristics. Much attention has been paid to radio-frequency identification systems, which are intended for biomedical applications. Solutions to the following problems are crucial to achieve the stated goals in the area of wireless monitoring: EM wave propagation inside regular and multilayer biological media, through the interface between different media, and on-body surface wave propagation. The biological object monitoring is based on a consideration of the followingprocesses: a) propagation of the EM wave in a biological medium considered as the dielectric with a high dielectric permittivity and substantial conductivity; b) penetration of the EM wave through the biological medium–air interface (wave reflection and refraction); c) propagation of the EM wave in a multi-layer biological medium; d) propagation of the EM wave along the plane or curved surface of biological objects.
REVIEW | doi:10.20944/preprints202104.0272.v1
Subject: Chemistry And Materials Science, Biomaterials Keywords: carbon materials synthesis and functionalization; energy; graphene; gas separation; hydrothermal and solvothermal carbonization; microwave-assisted synthesis; nanocomposite membranes; sensing; water treatment
Online: 12 April 2021 (09:32:49 CEST)
There is great importance and need of improving existing carbon materials fabrication methods. As such, this work proposes to discuss, interrogate, and propose viable hydrothermal, solvothermal, and other advanced carbon materials synthetic methods. The advanced carbon materials to be interrogated will include the synthesis of carbon dots, carbon nanotubes, nitrogen/titania-doped carbons, graphene quantum dots, and their nanocomposites with solid/polymeric/metal oxide supports. This will be done with special mind to microwave-assisted solvothermal and hydrothermal synthesis due to their favourable properties such as rapidity, low cost, and green/environmentally-friendliness. Thus, these methods are important during the current and future synthesis and modification of advanced carbon materials for application in energy, gas separation, sensing, and water treatment. Simultaneously, the work will pay special cognizance to methods reducing the fabrication costs and environmental impact while enhancing the properties as a direct result of the synthesis methods. As a direct result, the expectation is to impart a significant contribution to the scientific body of work regarding the improvement of the said fabrication methods.
ARTICLE | doi:10.20944/preprints202007.0717.v1
Subject: Environmental And Earth Sciences, Environmental Science Keywords: soil moisture; scattering albedo; tau-omega model; allometry; vegetation fraction; vegetation water content; passive microwave remote sensing; SMOS; SMAP; AMSR-E
Online: 30 July 2020 (10:58:24 CEST)
An accurate radiative transfer model (RTM) is essential for the retrieval of soil moisture (SM) from microwave remote sensing data, such as the passive microwave measurements from the Soil Moisture Active Passive (SMAP) mission. This mission delivers soil moisture products based upon L-band brightness temperature data, via retrieval algorithms for surface and root-zone soil moisture, the latter is retrieved using data assimilation and model support. We found that the RTM based on the tau-omega (?-ω) model, can suffer from significant errors over croplands (in average between -9.4K and + 12.0K for Single Channel Algorithm SCA; -8K and + 9.7K for Dual-Channel Algorithm DCA) if the vegetation scattering albedo (omega) is treated as a constant and the temporal variations are not accounted. In order to reduce this uncertainty, we propose a time-varying parameterization of omega for the widely established zeroth order radiative transfer ?-ω model. The main assumption is that omega can be expressed by a functional relationship between vegetation optical depth (tau) and the Green Vegetation Fraction (GVF). The validation was performed from 14 May to 13 December 2015 over 61 Climate Reference Network sites (SCRN) classified as croplands. The application of the proposed time-varying vegetation scattering albedo results in a consistent improvement for the unbiased root mean square error of 16% for SCA and 15% for DCA. The reduction for positive and negative biases was 45% and 5% for SCA and 26% and 12% for DCA, respectively. This indicates that vegetation dynamics on croplands are better represented by a time-dynamic single scattering albedo.
ARTICLE | doi:10.20944/preprints201904.0105.v1
Subject: Physical Sciences, Astronomy And Astrophysics Keywords: galaxies; supernovae; GRB; distances and redshifts; cosmic microwave background radiation; distance scale; cosmology theory; cosmological constant; Hubble constant; general relativity; TMT
Online: 9 April 2019 (11:38:12 CEST)
Many models have been proposed to explain the intergalactic redshift using different observational data and different criteria for the goodness-of-fit of a model to the data. The purpose of this paper is to examine several suggested models using the same supernovae Ia data and gamma-ray burst (GRB) data with the same goodness-of-fit criterion and weigh them against the standard CDM model. We have used the redshift – distance modulus ( ) data for 580 supernovae Ia with to determine the parameters for each model, and then use these model parameter to see how each model fits the sole SNe Ia data at and the GRB data up to . For the goodness-of-fit criterion, we have used the chi-square probability determined from the weighted least square sum through non-linear regression fit to the data relative to the values predicted by each model. We find that the standard ΛCDM model gives the highest chi-square probability in all cases albeit with a rather small margin over the next best model - the recently introduced nonadiabatic Einstein de Sitter model. We have made ( ) projections up to for the best four models. The best two models differ in only by 0.328 at , a tiny fraction of the measurement errors that are in the high redshift datasets.
REVIEW | doi:10.20944/preprints201609.0096.v2
Subject: Physical Sciences, Astronomy And Astrophysics Keywords: big bang; planck scale Hubble parameter; quantum cosmology; Mach’s principle; holographic principle; observational cosmology; super luminal expansion speed; super luminal rotation speed; dark energy; cosmic rotational kinetic energy; cosmic microwave back
Online: 8 October 2016 (10:26:06 CEST)
With reference to Planck scale Hubble parameter, super luminal expansion speeds, super luminal rotation speeds, Mach’s principle and Holographic principle, we review the current cosmological observations with eight simple assumptions. By understanding Yuri N. Obukhov and V.A. Korotky proposed cosmic rotational effects of polarization of radiation due to massive bodies, to some extent cosmic rotation can be deep-rooted in an observational approach and the ratio of current angular velocity and Hubble parameter can be estimated. It is possible to show that, at H0 =70 km/sec/Mpc, current cosmic temperature, age, radius, mass, mass density are 2.721 K, 4.41x1017 sec, 90 billion light years, 1.14654x1054 kg, 0.0482 times the current critical density respectively. Clearly speaking, current universe seems to constitute 267 Hubble spheres. Important point to be noted is that, current rotational kinetic energy is 0.6667 times the current critical energy. Based on the estimated current mass density and current rotational kinetic energy, current cosmic dark matter density can be shown to be 0.2851 times the current critical density. These numerical coincidences cast serious doubt on the on the real existence of currently believed ‘dark energy’. Initial and current expansion speeds are 3x108 m/sec and 3.56x109 m/sec respectively. With increasing cosmic age and increasing cosmic expansion speed, current universe is expanding with a speed of 11.885c. By knowing the time to time future cosmic temperatures, future Hubble parameters and corresponding future cosmic expansion speeds can be estimated and thus future expansion speed can be understood. Starting from ‘speed of light’, our model assumes a continuous increase in expansion speed and attains a current radius of 90 billion light years (without inflationary concepts) and casts a serious doubt on the actuality of currently believed ‘inflation’.