REVIEW | doi:10.20944/preprints202310.0480.v1
Subject: Medicine And Pharmacology, Orthopedics And Sports Medicine Keywords: ceramic-on- metal; hip replacement; hard-on-hard bearings
Online: 9 October 2023 (07:40:43 CEST)
Hip replacement has significantly improved the quality of life of patients with symptomatic hip osteoarthritis. Metal-on-metal (MoM) bearings have been used with conventional total hip re-placement (THR) for several decades with promising results from early applications. Wear and corrosion of these implants may lead to a release of metal products into surrounding tissue and body fluids. From the 1980s onwards, the search for increasingly better coupling materials with low levels of wear led to the rise of hard-on-hard couplings such as ceramic-on-ceramic (CoC). The latter is currently the coupling with the longest known duration and with a wear rate close to zero. MoM coupling has been for a long time the most significative alternative, but systemic and local complications linked to the release of chromium and cobalt ions, determine the withdrawn from the market. One other alternative proposed over the time has been Ceramic-on-Metal (CoM) bearing. Preliminary results have been described as favourable, but due to the failures of metal on metal it has been withdrawn from the market, without causing significant clinical complications. In this narrative review, we analysed risks and benefits associated with the implantation of hybrid hard-on-hard bearings, such as CoM.
CASE REPORT | doi:10.20944/preprints202308.1742.v1
Subject: Medicine And Pharmacology, Dentistry And Oral Surgery Keywords: Oral; Hard palate; Verrucous; Carcinoma; Histological examination
Online: 24 August 2023 (10:21:15 CEST)
This paper presents the case of a 75-year-old female with an extensive lesion located in the hard palate. Intraoral examination revealed an exophytic white lesion that extended from the entire left maxillary alveolar ridge to the palate beyond the midline. A thorough clinical, radiological, and histopathological examination confirmed the diagnosis of oral verrucous carcinoma.
Subject: Physical Sciences, Condensed Matter Physics Keywords: equation of state; hard hyperspheres; fluid mixtures
Online: 25 March 2020 (08:47:08 CET)
New proposals for the equation of state of four- and five-dimensional hard-hypersphere mixtures in terms of the equation of state of the corresponding monocomponent hard-hypersphere fluid are introduced. Such proposals (which are constructed in such a way so as to yield the exact third virial coefficient) extend, on the one hand, recent similar formulations for hard-disk and (three-dimensional) hard-sphere mixtures and, on the other hand, two of our previous proposals also linking the mixture equation of state and the one of the monocomponent fluid but unable to reproduce the exact third virial coefficient. The old and new proposals are tested by comparison with published molecular dynamics and Monte Carlo simulation results and their relative merit is evaluated.
ARTICLE | doi:10.20944/preprints201807.0049.v1
Subject: Physical Sciences, Condensed Matter Physics Keywords: residual multiparticle entropy; hard spheres; fractal dimension
Online: 3 July 2018 (13:07:09 CEST)
The residual multiparticle entropy (RMPE) of a fluid is defined as the difference, Δs, between the excess entropy per particle (relative to an ideal gas with the same temperature and density), sex, and the pair-correlation contribution, s2. Thus, the RMPE represents the net contribution to sex due to spatial correlations involving three, four, or more particles. A heuristic “ordering” criterion identifies the vanishing of the RMPE as an underlying signature of an impending structural or thermodynamic transition of the system from a less ordered to a more spatially organized condition (freezing is a typical example). Regardless of this, the knowledge of the RMPE is important to assess the impact of non-pair multiparticle correlations on the entropy of the fluid. Recently, an accurate and simple proposal for the thermodynamic and structural properties of a hard-sphere fluid in fractional dimension 1 < d < 3 has been proposed [Santos, A.; López de Haro, M. Phys. Rev. E 2016, 93, 062126]. The aim of this work is to use this approach to evaluate the RMPE as a function of both d and the packing fraction ϕ. It is observed that, for any given dimensionality d, the RMPE takes negative values for small densities, reaches a negative minimum Δsmin at a packing fraction ϕmin, and then rapidly increases, becoming positive beyond a certain packing fraction ϕ0. Interestingly, while both ϕmin and ϕ0 monotonically decrease as dimensionality increases, the value of Δsmin exhibits a nonmonotonic behavior, reaching an absolute minimum at a fractional dimensionality d ≃ 2.38. A plot of the scaled RMPE Δs/|Δsmin| shows a quasiuniversal behavior in the region −0.14 ≲ ϕ − ϕ0 ≲ 0.02.
ARTICLE | doi:10.20944/preprints202306.0419.v1
Subject: Biology And Life Sciences, Food Science And Technology Keywords: chalky rice; xylanase activity; cellulase activity; hard water; hardness
Online: 6 June 2023 (08:40:23 CEST)
Global warming has led to the increase in chalky grains of rice, which has also caused the deteriorations of physicochemical and cooking qualities of rice grains. These chalky rice grains are characterized by high α-amylase activity, high protease activity, and low apparent amylose contents, low degree of hardness and stickiness of boiled rice than those of the whole rice grains. In the present paper, we evaluated 14 Japonica unpolished rice grains harvested in Japan in 2021, and these samples (original grains) were divided to two groups (whole grain group and chalky grain one). We found that the chalky rice grains showed higher values of xylanase activity than those of the whole rice grains, while cellulase activity were lower than that of whole rice grains. Using rice grains blended with 30 % of chalky grains as material, we compared sugar and mineral contents and textural properties of the boiled rice grains soaked and boiled in the ordinary water or in the hard water, such as Evian or Contrex. It was shown that the hard water is useful for the prevention of the texture deterioration of the boiled rice grains due to the inhibition of the reduction of endogenous hydrolytic enzymes, such as amylase, proteinase, and xylanase. Furthermore, we found that hard water is useful for the increase of calcium and magnesium intake through the meal with the boiled rice grains soaked and cooked using hard water.
REVIEW | doi:10.20944/preprints202102.0084.v1
Subject: Business, Economics And Management, Accounting And Taxation Keywords: soft energy; hard energy; decentralization; centralization; sustainable systems; developing world
Online: 2 February 2021 (11:14:25 CET)
A reliable and affordable energy supply is a fundamental prerequisite for reducing poverty, promoting investment, and boosting economic growth in the developing world. Among the different challenges that developing countries face, chronic energy crises are harrowing. The crises result from the unsatisfactory state of the central grid, a misguided energy mix, and ill-informed policies, among other things. The possibility of solving energy crises through a variety of alternative solutions is worth exploring. This review discusses two paths of energy development side by side: a traditional “hard” path of energy development (i.e., central grid extension powered by fossil fuels and nuclear energy expansion) and a relatively recent “soft” path of energy development, which is based on energy conservation and the deployment of renewable energy resources. This paper focuses on one central axis of the discussion: centralization vs. decentralization. This discussion, in turn, has technological, economic/business, and political dimensions. Finally, the paper discusses the significance of the debate from meeting the developing world’s energy demands. The paper intends not to prefer one or another path of energy development, nor it gives recommendations on diffusing or adopting those development paths. Instead, it explores the literature’s central arguments that might help frame the questions for further research. While this debate could be used to ask interesting questions that might help solve the energy crisis in the developing world, the discussion informs countries to advance policies specific to their circumstances under the umbrella of a sound and thoughtful energy productivity policy framework.
ARTICLE | doi:10.20944/preprints201904.0056.v1
Subject: Chemistry And Materials Science, Electrochemistry Keywords: Co-B/SiC composite coatings; electrodeposition; hard coatings; wear volume
Online: 4 April 2019 (12:52:34 CEST)
In the present paper, Co-B/SiC composite coatings were obtained via electrodeposition from colloidal suspensions with different concentrations of SiC particles and subsequent heat treatments at 350 °C. The composition, morphology and structure of the Co-B/SiC composite coatings were analyzed using glow discharge spectrometry (GDS), scanning electron microscopy (SEM) coupled with energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD). Hardness and tribological properties were also studied. The results showed that an increase in the SiC concentration in the colloidal suspensions resulted in both an increase in the SiC content and a decrease in the B content in the obtained Co-B/SiC coatings. The Co-B/SiC coatings were adherent, glossy and soft and exhibited a homogeneous composition in all thicknesses. By contrast, an increase in the SiC particle content of the Co-B/SiC composite coating from 0 to 2.56 at.% SiC reduced the hardness of the film from 680 to 360 HV and decreased the wear volume values from 1180 to 23 mm3 N-1 m-1, respectively (that is, the wear resistance increased). Moreover, when the Co-B/SiC coatings with SiC content ranging from 0 to 2.56 at.% SiC were subjected to a heat treatment process, the obtained coating hardness values were in the range of 1200 to 1500 HV and the wear volume values were in the range of 382 to 19 mm3 N-1 m-1.
ARTICLE | doi:10.20944/preprints202212.0532.v1
Subject: Computer Science And Mathematics, Computer Science Keywords: lung nodule segmentation; 3D segmentation; dual-encoder-based CNN; hard attention
Online: 28 December 2022 (09:03:49 CET)
Measuring pulmonary nodules accurately can help with early diagnosis of lung cancer, which can improve a patient’s chances of survival. Many methods for segmenting nodules have been developed, but they all rely on input from radiologists in the form of a 3D volume of interest (VOI) or use a constant region of interest (ROI) and only consider the presence of nodule within the given VOI. These approaches limit the networks’ ability to detect nodules outside the given VOI and can also include unnecessary structures in the VOI, leading to potentially inaccurate segmentation. In this work, we propose a novel approach for 3D lung nodule segmentation by using 2D region of interest (ROI) inputted from radiologist or computer-aided detection (CADe) system. Particularly, we design a dual-encoder-based hard attention network (DEHA-Net) which incorporates the full slice of thoracic computed tomography scan along with the ROI mask to produce an accurate segmentation mask of lung nodule in the given slice. The proposed architecture exploits the adaptive region of interest (A-ROI) algorithm to automatically investigates the penetration of lung nodule into surrounding slices while eliminating the need to drawing separate ROIs in each slice. Further, the framework performs the multi-view analysis, i.e., in sagittal and coronal views, to improve the segmentation performance. The proposed scheme has been rigorously evaluated on the lung image database consortium and image database resource initiative (LIDC/IDRI) dataset and an extensive analysis of results have been performed. The quantitative analysis shows that the proposed method not only improves the existing state-of-the-art in term of dice score but also, significantly robust against the different types, shape and dimensions of lung nodules.
ARTICLE | doi:10.20944/preprints201711.0184.v2
Subject: Chemistry And Materials Science, Food Chemistry Keywords: Cistus incanus; Strandja; antioxidants; polyphenols; flavonoids; seasonality; buds; hard-coated seeds
Online: 2 January 2018 (11:21:12 CET)
The purpose of the present study is survey of extraction conditions and exploring antioxidant potential of the non-traditional for the Bulgarian ethno-medicine wild herb Cistus incanus widespread in Strandja Mountain. The influence of the extraction time (0–500 min) and solvent composition (0–50% ethanol in water) on the polyphenols, flavonoids yields and on antioxidant capacity of the extracts of leaves, stalks (wood parts) and buds mixture were studied. The antioxidant capacity (AOC) was evaluated by use of scavenging assays of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals. Total polyphenol and flavonoid contents were quantified using UV–vis spectrometry. Optimal yield of desired components has been obtained with 30% ethanol in water solvent at 390th min extraction time. In addition, the influence of the seasonality (winter and summer Cistus incanus), and of the different areal parts - hard-coated seeds; buds, and mixture of leaves and stalks of the wild plant on the presence of polyphenols, flavonoids and AOC were investigated. Present work revealed the high values of the polyphenols, flavonoids, the high AOC not only in the summer leaves, but also found in the winter leaves, hard-coated seeds, buds and stalks. Based on the obtained results the Cistus incanus from Strandja mountain could be a new excellent source of natural antioxidants in food and pharmaceutical industries.
REVIEW | doi:10.20944/preprints202309.1834.v1
Subject: Engineering, Energy And Fuel Technology Keywords: hydrogen combustion; hydrogen blends; power generation; gas turbines; hard-to-abate industry
Online: 27 September 2023 (08:15:14 CEST)
The aim of this article is to review hydrogen combustion applications within the energy transition framework. Hydrogen blends are also included, from the well known hydrogen enriched natural gas (HENG) to the hydrogen and ammonia blends whose chemical kinetics is still not clearly defined. Hydrogen and hydrogen blends combustion characteristics will be firstly summarized, in terms of standard properties like the laminar flame speed and the adiabatic flame temperature, but also evidencing the critical role of hydrogen preferential diffusion in burning rate enhancement and the drastic reduction in radiative emission with respect to natural gas flames. Then, combustion applications in both thermo-electric power generation (based on internal combustion engines, i.e., gas turbines and piston engines) and hard-to-abate industry (requiring high temperature kilns and furnaces) sectors will be considered, highlighting the main issues due to hydrogen addition related to safety, pollutant emissions, and potentially negative effects on industrial products (e.g., glass, cement and ceramic).
ARTICLE | doi:10.20944/preprints202307.1419.v1
Subject: Engineering, Industrial And Manufacturing Engineering Keywords: hydrogen; hard-to-abate sectors; energy transition; electrolysis; blended combustion; steel industry
Online: 20 July 2023 (11:09:46 CEST)
This paper offers a set of comprehensive guidelines aimed at facilitating the widespread adoption of hydrogen in the industrial hard-to-abate sectors. The authors begin by conducting a detailed analysis of these sectors, providing an overview of their unique characteristics and challenges. The paper delves into specific elements related to hydrogen technologies, shedding light on their potential applications and discussing feasible implementation strategies. By exploring the strengths and limitations of each technology, the paper offers valuable insights into its suitability for specific applications. Finally, through a particular analysis focused on the steel sector, the authors provide in-depth information on the potential benefits and challenges associated with hydrogen adoption in this particular context. By emphasizing the steel sector as a focal point, the authors contribute to a more nuanced understanding of hydrogen's role in decarbonizing industrial processes and inspire further exploration of its applications in other challenging sectors.
REVIEW | doi:10.20944/preprints202305.0832.v1
Subject: Chemistry And Materials Science, Biomaterials Keywords: biomaterials; coatings; calcium phosphates; hydroxyapatite; bone implant; biocompatibility; bioactivity; hard tissue repair
Online: 11 May 2023 (09:03:34 CEST)
This review article deals with the design of bioactive calcium phosphate coatings deposited on metallic substrates to produce bone implants. The bioceramic coating properties are used to create a strong bonding between the bone implants and the surrounding bone tissue. They provide a fast response after implantation and increase the lifespan of the implant in the body environment. The first part of the article describes the different compounds belonging to the calcium phosphate family and their main properties for applications in biomaterials science. The calcium to phosphorus atomic ratio (Ca/P)at. and the solubility (Ks) of these compounds define their behavior in a physiological environment. Hydroxyapatite is the gold standard among calcium phosphate materials, but other chemical compositions/stoichiometries have also been studied for their interesting properties. The second part reviews the most usual deposition processes to produce bioactive calcium phosphate coatings for bone implant applications. Plasma spraying is the main industrial process, but magnetron sputtering, pulsed laser deposition, electrospray deposition, electrophoretic deposition, and electrodeposition are also widely studied in academic and industrial research. The last part describes the main physicochemical properties of calcium phosphate coatings and their impact on the bioactivity of bone implants in a physiological environment.
REVIEW | doi:10.20944/preprints202310.1233.v1
Subject: Engineering, Marine Engineering Keywords: coasts monitoring; climate change; sea level rise; coastal erosion; hard engineering; soft engineering
Online: 20 October 2023 (08:12:18 CEST)
Coasts are characterized by high biological and ecological productivities, and are theatre of strategic economic activities, including tourism, fishing and aquaculture. Both anthropic and natural hazards can thus affect coasts, causing their deterioration. The monitoring of coasts in terms of evolution, adaptation, contamination and resilience, is a pivotal point composed of both classic measurement approaches, and innovative approaches as remote sensing and the use of unmanned aerial vehicles. In the last years, climate change is increasing its effects all over the world and coasts are a delicate system suffering these effects particularly. Climate change has important impacts on coasts, with a serious consequence represented by sea level rise. The latter causes coastal erosion, leading to ecological and economic issues and with consequences for human health. The Mediterranean Basin, which has always represented an important crossroads of different civilizations and economic and cultural exchanges, is now threatened by the consequences of climate change. This area is decribed as an example of coastal system of strategic importance and subjected to serious challenges. Engineering interventions are countermeasures to cope with coastal erosion and coastal degradation. These countermeasures are aimed at protecting the coasts and the populations living on the coasts. The types of intervention can be defined of hard engineering, as in the case of fixed structures in concrete, and of soft engineering, with structures of protection builted according to the principles of nature. Engineering procedures provide coastal benefits, although they can cause further coastal damage. It is thus necessary to protect the coasts and the same time actions aimed at mitigating climate change must be implemented, according to the rules of sustainability.
ARTICLE | doi:10.20944/preprints202307.0027.v1
Subject: Engineering, Other Keywords: Hard bottom layer; Surface profile features; Local roughness; Unmanned farms; Smart farming machines
Online: 4 July 2023 (02:07:02 CEST)
The hard bottom layer of paddy field has a great influence on the driving stability and operation quality and efficiency of intelligent farm machinery, and the continuous improvement of unmanned precision operation accuracy and operation efficiency of paddy field operation machin-ery is the support to realize unmanned rice farm. In this paper, in view of the complicated hard bottom layer situation of unmanned operation farm machinery driving is difficult to realize to quantify the local characteristics of hard bottom layer of paddy field, the unmanned rice direct seeding machine chassis is used to operate the operation field and collect the hard bottom layer information simultaneously, and the data processing method of automatic calibration of sensor installation error, abnormal value rejection and 3D sample curve denoising of contour trajectory is designed; a hard bottom layer surface profile evaluation method based on the local sliding surface roughness is proposed. The local characteristics of the hard bottom layer were quantified, and the quantified results of the local characteristics of the hard bottom layer in the test plots showed that the mean value of the local roughness was 0.0065, 68.27% was distributed in the variation range of 0.0042~0.0087, and 99.73% was distributed in the variation range of 0~0.0133. Based on the test field data, the surface roughness features are verified to describe the variability of representative working conditions such as transport, downfield, operation and trapping of unmanned operation of intelligent farm machinery. The method of quantifying the hard-bottom local features of farm machinery driving can provide feedback on the local environmental features of intelligent farm machinery driving at the current position, and provide a reference basis for the design optimization of unmanned system for improving the quality of intelligent farm machinery operation.
ARTICLE | doi:10.20944/preprints202107.0556.v1
Subject: Physical Sciences, Acoustics Keywords: solid-state detectors; position detectors; radiation hard detector; hydrogenated amorphous silicon; 3D detector
Online: 26 July 2021 (09:46:02 CEST)
Hydrogenated amorphous silicon (a-Si:H) can be produced by plasma-enhanced chemical vapour deposition (PECVD) of SiH4 (Silane) mixed with Hydrogen. The resulting material shows outstanding radiation resistance properties and can be deposited on a wide variety of different substrates. These devices have been used to detect many different kinds of radiation namely: MIPs, x-rays, neutrons and ions as well as low energy protons and alphas. However, MIP detection using planar diodes has always been difficult due to the unsatisfactory S/N ratio arising from a combination of high leakage current, high capacitance and a limited charge collection efficiency (50% at best for a 30 µm planar diode). To overcome these limitations the 3D-SiAm collaboration proposes to use a 3D detector geometry. The use of vertical electrodes allows for a small collection distance to be maintained while conserving a large detector thickness for charge generation. The depletion voltage in this configuration can be kept below 400 V with consequent reduction in the leakage current. In this paper, following a detailed description of the fabrication process, the results of the tests performed on the planar p-i-n structures made with ion implantation of the dopants and with carrier selective contacts will be illustrated.
Subject: Chemistry And Materials Science, Surfaces, Coatings And Films Keywords: fundamental science; atomic nature; hard coating; expansion and contraction; force-energy behavior; surface and interface
Online: 2 April 2019 (12:41:20 CEST)
Coating of suitable materials having thickness of few atoms to several microns on a substrate is of great interest to the scientific community. Hard coatings develop under the significant composition of suitable-natured atoms where their force-energy behaviors when in certain transition state favour binding. In the binding mechanism of suitable atoms, electron belonging to outer ring filled state of gas-atom undertakes another clamp of energy knot belonging to outer ring unfilled state of solid-atom. Set process conditions develop the binding of different-natured atoms when processing their suitable composition in a system. Atoms of different nature develop structure in the form of hard coating by locating their ground points between the original ones. Here, gas-natured atoms increase the potential energy under decreasing levitational force of electrons, whereas, solid-natured atoms decrease the potential energy under decreasing gravitational force of electrons. In TiN coating, Ti–Ti atoms bind under the difference of expansion of their lattices, called nets of energy knots, where one atom just lands on the already landed atom. An adhered N-atom to a Ti-atom forms its position among four Ti-atoms where N-atom occupies the interstitial site of Ti-atoms. Two oppositely working force-energy behavior atoms deposit in the form of coating at substrate surface as per set conditions of the process. The rate of ejecting (or dissociating) solid-natured atoms depend on the nature of their source (target), process parameters and processing technique. In random arc-based vapor deposition system, depositing differently natured atoms at substrate surface depends on the input power. In addition to intrinsic nature of atoms, different properties and characteristics of coatings emerge as per engaged forces under their involved energy. The present study sets new trends in the field of coatings involving the diversified class of materials and their counterparts.
COMMUNICATION | doi:10.20944/preprints202108.0045.v1
Subject: Engineering, Automotive Engineering Keywords: Magnetic Instruments; Digital compass; Soft and Hard iron compensation; Helmholtz coil; Towed hydrophone array
Online: 2 August 2021 (13:32:53 CEST)
Usually, towed hydrophone arrays are instrumented with a set of compasses. Data from these sensors are utilized while beamforming the acoustic signal for target bearing estimation. However, elements of the hydrophone array mounted in the neighborhood of a compass can affect the Earth’s magnetic field detection. The effects depend upon the kind of elements present in the platform hosting the compass. If the disturbances are constant in time, they can be compensated for by means of a magnetic calibration. This process is commonly known as soft and hard iron compensation. In this paper, a solution is presented to carry out the magnetic calibration of a COTS (Commercial Off The Shelf) digital compass without unattainable sensor motion. This approach is particularly suited in applications where a physical rotation of the platform that hosts the sensor is unfeasible. In our case, the platform consists in an assembled and operational towed hydrophone array. A standard calibration process relies on physical rotation of the platform and thus on the use of the geomagnetic field as a reference during the compensation. As a variation on this approach, we provide to the sensor an artificial reference magnetic field to simulate the unfeasible physical rotation. We obtain this by using a tri-axial Helmholtz coil, which enables programmability of the reference magnetic field and assures the required field uniformity. In our work, the simulated geomagnetic field is characterized in terms of its uncertainty. The analysis indicates that our method and experimental set-up represent a suitably accurate approach for the soft and hard iron compensation of the compasses equipped in the hydrophone array under test.
ARTICLE | doi:10.20944/preprints202308.0165.v1
Subject: Computer Science And Mathematics, Computer Science Keywords: Canonical Huffman Coding (CHC); 2D Discrete Wavelet Transform (2D DWT); hard thresholding; Lossy Image Compression
Online: 2 August 2023 (07:35:21 CEST)
Image compression is a top priority today due to the need for faster encoding and decoding. To achieve this, the present study has proposed the use of Canonical Huffman Coding (CHC) as an entropy coder, which has a lower decoding time complexity than binary Huffman codes. For image compression, combining of the Discrete Wavelet Transform (DWT) and CHC with Principal Component Analysis (PCA) has been recommended. The lossy method has been introduced by using PCA, followed by DWT and CHC to enhance compression efficiency. By using DWT and CHC instead of PCA alone, the reconstructed image has been found to have a better peak signal-to-noise ratio (PSNR) value. This study has developed a hybrid compression model combining the advantages of DWT, CHC and PCA. With the increasing use of image data, better image compression techniques are necessary for efficient use of storage space. The proposed technique has achieved up to 60% compression while maintaining high visual quality. This method has also outperformed the currently available techniques in terms of both PSNR (in dB) and bit-per-pixel (bpp) scores. This approach has been tested on various color images, including Peppers 512×512 and Couple 256×256, showing improvement by 17 dB and 22 dB, respectively, while reducing bpp by 0.56 and 0.10, respectively. For grayscale images, i.e., Lena 512×512 and Boat 256×256, the proposed method has shown an improvement by 5 dB and 8 dB, respectively, with a decrease of 0.02 bpp in both cases.
ARTICLE | doi:10.20944/preprints201804.0149.v1
Subject: Engineering, Energy And Fuel Technology Keywords: multi-layer hard roof; failure of overlying strata; ground pressure behaviour; longwall top coal caving
Online: 11 April 2018 (12:51:34 CEST)
In the extra-thick coal seams and multi-layered hard roofs, the longwall hydraulic support yielding, coal face spalling, strong deformations of goaf-side entry, and severe ground pressure dynamic events typically occur at the longwall top coal caving longwall faces. Based on the Key strata theory an overburden caving model is proposed here to predict the multilayered hard strata behaviour. The proposed model together with the measured stress changes in coal seam and underground observations in Tongxin coal mine provides a new idea to analyse stress changes in coal and help to minimise rock bursts in the multi-layered hard rock ground. Using the proposed primary Key and the sub-Key strata units the model predicts the formation and instability of the overlying strata that leads to abrupt dynamic changes to the surrounding rock stress. The data obtained from the vertical stress monitoring in the 38 m wide coal pillar located adjacent to the longwall face indicates that the Key strata layers have a significant influence on ground behaviour. Sudden dynamically driven unloading of strata was caused by the first caving of the sub-Key strata while reloading of the vertical stress occurred when the goaf overhang of the sub-Key strata failed. Based on this findings several measures were recommended to minimise the undesirable dynamic occurrences including pre-split of the hard Key strata by blasting and using the energy consumption yielding reinforcement to support the damage prone gate road areas. Use of the numerical modelling simulations was suggested to improve the key theory accuracy.
ARTICLE | doi:10.20944/preprints202306.1155.v1
Subject: Business, Economics And Management, Business And Management Keywords: Problem solving; Wicked problem; Hard OR; Soft OR; Problem Structuring Methods; Decision-Making; Subdivision-based PSM
Online: 15 June 2023 (14:06:11 CEST)
Because of hyper complexity, difficulty to define, multiple stakeholders with conflicting perspectives, and lack of clear-cut solutions, wicked problems necessitate innovative and adaptive strategies. Operations Research has been a valuable tool for managers to make informed decisions for years. However, as we face increasingly complex and messy problems, it has become apparent that relying solely on either hard or soft OR approaches is no longer sufficient. We need to explore more innovative methodologies to address these wicked problems effectively. This study has bridged the research gap by proposing a structured process encompassing a subdivision-based problem structuring method for defining the wicked problem, a multi-attribute decision-making (MADM) for prioritizing sub-problems, and a hard OR technique, data envelopment analysis (DEA) for tackling one of the most critical sub-divisions. The proposed methodology, implemented in a case study, focuses on a higher education institution experiencing a decline in student admissions and involves five steps. First, a diverse group of stakeholders is formed to ensure comprehensive consideration of perspectives. Second, the wicked problem is defined, considering long-term consequences, multiple stakeholders, and qualitative stakeholder opinions. Third, a hierarchical structure is created to break down the wicked problem into manageable sub-problems. Fourth, a multi-criteria decision-making (MCDM) method prioritizes sub-problems. Finally, the sub-problems are addressed one by one using a combination of soft and hard OR tools. The findings highlight the benefits of integrating hard and soft OR approaches. The article concludes with reflections on the implications of using a combined OR approach to tackle wicked problems in higher education and beyond.
ARTICLE | doi:10.20944/preprints201712.0179.v1
Subject: Engineering, Electrical And Electronic Engineering Keywords: cognitive radio; cognitive vehicular networks; spectrum sensing; sensing/reporting channel; correlated rayleigh fading channel; hard fusion
Online: 25 December 2017 (10:42:53 CET)
An explosive growth in vehicular wireless services and applications gives rise to spectrum resource starvation. Cognitive radio has been used to vehicular networks to mitigate the impending spectrum starvation problem by allowing vehicles to fully exploit spectrum opportunities unoccupied by licensed users. Efficient and effective detection of licensed user is a critical issue to realize cognitive radio applications. However, spectrum sensing in vehicular environments is a very challenging task due to vehicles mobility. For instance, vehicle mobility has a large effect on the wireless channel, thereby impacting the detection performance of spectrum sensing. Thus, gargantuan efforts have been made in order to analyze the fading properties of mobile radio channel in vehicular environments. Indeed, numerous studies have demonstrated that the wireless channel in vehicular environments can be characterized by a temporally correlated Rayleigh fading. In this paper, we focus on energy detection for spectrum sensing and a counting rule for cooperative sensing based on Neyman-Pearson criteria. Further, we go into the effect of the sensing and reporting channels condition on spectrum sensing performance under temporally correlated Rayleigh sensing channel. For local and cooperative sensing, we derive some alternative expressions for average probability of miss detection. The pertinent numerical and simulating results are provided to further validate our theoretical analyses under a variety of scenarios.
ARTICLE | doi:10.20944/preprints202310.1875.v1
Subject: Public Health And Healthcare, Public Health And Health Services Keywords: quality of life; ozone therapy; local hyperbaric oxygen therapy; venous leg ulcers; treatment; hard to heal wounds
Online: 30 October 2023 (09:08:39 CET)
Venous leg ulcers still pose a significant medical problem worldwide. The complexity of the problem determines the need for further interdisciplinary activities that will improve the quality of life of treated patients. The study compared the quality of life of patients with venous leg ulcers who received local hyperbaric oxygen therapy or local ozone therapy procedures as a part of comprehensive treatment. The study included 129 patients (62 men and 57 women) with venous leg ulcers. Group I underwent local hyperbaric oxygen therapy (HBOT), group II - local ozone therapy (OZONE). In both groups, the patients' quality of life was assessed before the start of treatment cycle, as well as 10 weeks and 6 months after the completion of the treatment, by using the EQ-5D-5L questionnaire and the Polish shortened version of the SF-36 scale. After completing the respective therapeutic cycle, both groups showed a statistically significant (p<0.001) improvement the quality of life according to the EQ-5D-5L questionnaire and the SF-36 scale. Differences were noted between 1st examination (before treatment) and 2nd examination (10 weeks after treatment), as well as 3 examination (6 months after treatment). In the EQ-5D-5L assessment of anxiety and depression, self-care and activities of daily living 6 months after the end of treatment, better results were found in the group of patients treated with local hyperbaric oxygen therapy (p<0.001). In this group, 6 months after the end of the treatment, a statistically significantly higher result on the EQ-VAS scale was also obtained (73.09±19.8 points vs. 68.03±17.37 points, p=0.043). However, in the SF-36 assessment 6 months after the end of treatment better results - a statistically significantly lower value of the quality of life index - were recorded in the group of patients treated with local ozone therapy (103.13±15.76 points vs. 109.89±15.42 points, p<0.015). Hyperbaric oxygen therapy and local ozone therapy procedures have a beneficial effect on improving the quality of life of patients with venous leg ulcers.
ARTICLE | doi:10.20944/preprints202105.0716.v1
Subject: Engineering, Civil Engineering Keywords: hard rock mine; cemented rock fill (CRF); backfilling step scenario; major principal stress; stress concentration factor (SCF); displacement
Online: 31 May 2021 (08:43:52 CEST)
Cemented rock fill (CRF) is commonly used in cut-and-fill stoping operation in underground mining. This allows for the maximum recovery of ore. Backfilling can improve stope stability in underground workings, and then improve ground stability of the whole mine site. Backfilling step scenarios vary from site to site. This paper presents the investigation of five different backfilling step scenarios and their impacts on the stability of stopes at four different mining levels. A comprehensive comparison of displacements, major principal stress and stress concentration factor (SCF) was conducted. The results show that different backfilling step scenarios have little influence on the final displacement for displacement in the stopes. Among the five backfilling scenarios, the major principal stress and stress concentration factor (SCF) have almost the same final results. The backfilling scenario SCN-1 is the optimum option among these five backfilling scenarios. It can immediately prevent the increase of the displacement and reduce the sidewall stress concentration, thereby preventing possible failures. Using the same strength of CRF can achieve same effects among the four mining levels. Applying backfilling CRF of the same strength at different mining depths is acceptable and feasible to improve the stability of the stopes.
ARTICLE | doi:10.20944/preprints202104.0353.v1
Subject: Computer Science And Mathematics, Artificial Intelligence And Machine Learning Keywords: WEAK Clampdown Effect, STRONG Clampdown Effect, KARDASHEV Scale, ERROR Processing, EXTRAVAGENT Curiosity, SOFT Singularity, HARD Singularity, ERROR Approximation
Online: 13 April 2021 (12:58:00 CEST)
There exists an implicit potential limitation in every physical discoveries that has been implemented and understood. However, the limitations can be bounded within a safe limit to prevent any constructing theory to be free from errors. As, it’s the inert nature of the humans, to go far beyond the scope of experimental findings in order to pursue any studies with the sole help of logical reasoning and mathematics, the argument can be prevailed in the form of WEAK Clampdown Effect & STRONG Clampdown Effect. More, the theories are constructed out of physical nature, more the theory gets hypothetical without any finding evidence, but that does or doesn’t actually justify the phenomenon, that too with the more increment of KARDASHEV Scale, more moderate ways of experimentation got developed curbing down the limitations within the human limit of ‘ERRORS’, that does can be neglected by approximation. Relationship being cross-judgmental on the basis of the computational limits and calculation accuracy, leading to a soft singularity, as a warning, that if computer powers cannot be checked on the basis of error approximations, then this may lead to the hitting of a hard singularity, that in phase with the forbidden gap (or after the optimum limit that arises at the core constraints of nature) to prevent the computation being carried off with respect to super-intelligence machines that are cognitive capability oriented future computers responsible for self growth & reproduction with more improvement algorithm, restricting all forms of humanity & constraints the human growth by virtue of limiting capacities of the humans as compared to computers.
Subject: Chemistry And Materials Science, Polymers And Plastics Keywords: drying; materials processing; vacuum oven; small-scale; lab equipment; air-powered; open hard-ware; open source; digital manufacturing; dehydration
Online: 22 April 2021 (09:16:02 CEST)
Vacuum drying can dehydrate materials further than dry heat methods while protecting sensitive materials from thermal degradation. Many industries have shifted to vacuum drying as cost- or time-saving measures. Small-scale vacuum drying, however, has been limited by high costs of specialty scientific tools. To make vacuum drying more accessible, this study provides design and performance information for a small-scale open source vacuum oven, which can be fabricated from off-the-shelf and 3-D printed components. The oven is tested for drying speed and effective-ness on both waste plastic polyethylene terephthalate (PET) and a consortium of bacteria developed for bioprocessing of terephthalate wastes to assist in distributed recycling of PET for both additive manufacturing as well as potential food. Both materials can be damaged when exposed to high temperatures, making vacuum drying a desirable solution. The results showed the open source vacuum oven was effective at drying both plastic and biomaterials, drying at a higher rate than a hot-air dryer for small samples or for low volumes of water. The system can be constructed for less than 20% of commercial vacuum dryer costs for several laboratory-scale applications including dehydration of bio-organisms, drying plastic for distributed recycling and additive manufacturing, and chemical processing.
REVIEW | doi:10.20944/preprints201801.0166.v1
Subject: Chemistry And Materials Science, Materials Science And Technology Keywords: carbon clathrates; hybrid carbon-silicon clathrates; hybrid carbon-nitrogen clathrates; electrode materials; hydrogen storage materials; energy storage materials; hard materials
Online: 18 January 2018 (05:08:03 CET)
Hybrid carbon-silicon, carbon-nitrogen, and carbon-boron clathrates are new classes of Type I carbon-based clathrates that have been identified by first-principles computational methods by substituting atoms on the carbon clathrate framework with Si, N, and/or B atoms. The hybrid framework is further stabilized by embedding appropriate guest atoms within the cavities of the cage structure. Series of hybrid carbon-silicon, carbon-boron, carbon-nitrogen, and carbon-silicon-nitrogen clathrates have been shown to exhibit small positive values of the energy of formation, indicating that they may be metastable compounds and amenable to fabrication. In this overview article, the energy of formation, elastic properties, and electronic properties of selected hybrid carbon-based clathrates are summarized. Theoretical calculations that explore the potential applications of hybrid carbon-based clathrates as energy storage materials, electronic materials, or hard materials are presented. The computational results identify compositions of hybrid carbon-silicon and carbon-nitrogen clathrates that may be considered candidate materials for use as either electrode materials for Li-ion batteries or as hydrogen storage materials. Prior processing routes for fabricating selected hybrid carbon-based clathrates are highlighted and difficulties encountered are discussed.
ARTICLE | doi:10.20944/preprints202106.0175.v1
Subject: Physical Sciences, Acoustics Keywords: Ornstein-Zernike equation; coupling-parameter expansion; thermodynamic perturbation theory; adhesive hard-sphere model; liquid-vapor phase transition; generalized Lennard-Jonnes potential.
Online: 7 June 2021 (12:42:22 CEST)
The objective of this paper is to investigate the convergence of coupling-parameter expansion-based solutions to Ornstein-Zernike equation in liquid state theory. The analytically solved Baxter's adhesive hard sphere model is analyzed first using coupling-parameter expansion. It is found that the expansion provides accurate approximations to solutions - including the liquid-vapor phase diagram - in most parts of the phase plane. However, it fails to converge in the region where the model has only complex solutions. Similar analysis and results are, then, obtained using analytical solutions within the mean spherical approximation for the hard-core Yukawa potential. Next, convergence of the expansion is analyzed for the Lennard-Jonnes potential using an accurate density-dependent bridge function in the closure relation. Numerical results are presented which show convergence of correlation functions, compressibility versus density profiles, etc., in the single as well as two phase regions. Computed liquid-vapor phase diagrams, using two independent schemes employing the converged profiles, compare excellently with simulation data. Results obtained for the generalized Lennard-Jonnes potential, with varying repulsive exponent, also compare well with simulation data. All these results together establish the coupling-parameter expansion as a practical tool for studying single component fluid phases modeled via general pair-potentials.
ARTICLE | doi:10.20944/preprints201611.0033.v1
Subject: Computer Science And Mathematics, Information Systems Keywords: genetic algorithms; parallel computation; computational complexity; algorithms; optimization techniques; traveling salesman problem; NP-Hard problems; Berlin-52 data set; machine learning; linear regression
Online: 7 November 2016 (04:57:46 CET)
This paper examines the correlation between numbers of computer cores in parallel genetic algorithms. The objective to determine the linear polynomial complementary equation in order represent the relation between number of parallel processing and optimum solutions. Model this relation as optimization function (f(x)) which able to produce many simulation results. F(x) performance is outperform genetic algorithms. Compression results between genetic algorithm and optimization function is done. Also the optimization function give model to speed up genetic algorithm. Optimization function is a complementary transformation which maps a TSP given to linear without changing the roots of the polynomials.
ARTICLE | doi:10.20944/preprints202209.0170.v1
Subject: Physical Sciences, Atomic And Molecular Physics Keywords: n/a; Hard Sphere; Crystallization; Entropy-driven phenomena; packing, polymer, molecular simulation, phase transition, face centered-cubic, hexagonal close packed; random walk; colloids; crystal perfection
Online: 13 September 2022 (10:16:17 CEST)
We present results on the spontaneous crystallization of freely-jointed polymers of hard spheres obtained in an unprecedentedly long Monte Carlo (MC) simulation on a system of 54 chains of 1000 monomers. Starting from a purely amorphous configuration and after a transitory dominance of the hexagonal closed packed (HCP) polymorph, the system crystallizes in a final, stable, face centered cubic (FCC) crystal of very high perfection. Through refined metrics we gauge the degree of ordering and identify the regions of the phase transition and the corresponding morphologies. An analysis of chain conformational characteristics, of the spatial distribution of monomers and of the volume accessible to them shows that the phase transition is caused by an increase in translational entropy that is larger than the loss of conformational entropy of the chains in the crystal compared to the amorphous state. Polymer chains in the crystal adopt ideal random walk statistics as their great length renders local conformational details, imposed by the geometry of the FCC crystal, irrelevant.
ARTICLE | doi:10.20944/preprints201706.0106.v1
Subject: Chemistry And Materials Science, Biomaterials Keywords: Tricalcium phosphate putty scaffold; bioactive ceramics; bone formation, osteogenesis, osteogenic markers, hard tissue histology; immunohistochemical analysis; split-mouth design; sinus floor augmentation; bone grafting materials
Online: 22 June 2017 (18:33:01 CEST)
This study examines the effect of a hyaluronic acid (HyAc) containing tricalcium phosphate putty scaffold material (TCP-P) and of a particulate tricalcium phosphate (TCP-G) graft on bone formation, volume stability and osteogenic marker expression in biopsies sampled 6 months after bilateral sinus floor augmentation (SFA) in 7 patients applying a split-mouth design. Biopsies were processed for immunohistochemical analysis of resin embedded sections. Sections were stained for collagen type I (Col I), alkaline phosphatase (ALP), osteocalcin (OC) and bone sialoprotein (BSP). Furthermore, the bone area and particle area fraction were determined histomorphometrically. Cone-beam CT data recorded after SFA and 6 month later were used for calculating the graft volume at these two time points. TCP-P displayed more advantageous surgical handling properties and a significantly greater bone area fraction and smaller particle area fraction. This was accompanied by significantly greater expression of Col I and BSP and in osteoblasts and osteoid and a less pronounced reduction in grafting volume with TCP-P. SFA using both types of materials resulted in formation of sufficient bone volume for facilitating stable dental implant placement with all dental implants having been in function without any complications for 6 years. Since TCP-P displayed superior surgical handling properties and greater bone formation than TCP-G, without the Hyac hydrogel matrix having any adverse effect on bone formation or graft volume stability, TCP-P can be regarded as excellent grafting material for SFA in a clinical setting.
ARTICLE | doi:10.20944/preprints202203.0332.v1
Subject: Biology And Life Sciences, Biochemistry And Molecular Biology Keywords: protein determination; soft protein corona; hard protein corona; covalent immobilization; supernatant method; gold nanoparticles; latex polymer particles; gold sodium chloride method; amino acid analysis; aromatic amino acid analysis; AAAA; acid hydrolysis
Online: 24 March 2022 (14:32:48 CET)
Protein immobilization for the functionalization of particles is used in various applications, including biosensors, lateral-flow immunoassays (LFIA), bead-based assays, and others. Common methods for the quantification of bound protein are measuring protein in the supernatant before and after coating and calculating the difference. This popular approach has the potential for a significant overestimation of the amount of immobilized protein since layers not directly bound to the surface (soft protein corona) are usually lost during washing and handling. Only the layer directly bound to the surface (hard corona) can be used in subsequent assays. A simplified amino acid analysis method based on acidic hydrolysis and RP-HPLC-FLD of tyrosine and phenylalanine (aromatic amino acid analysis, AAAA) is proposed to directly quantify protein bound to the surface of gold nano- and latex microparticles. The results are compared with indirect methods such as colorimetric protein assays, such as Bradford, bicinchoninic acid (BCA), as well as AAAA of the supernatant. For both particle types, these indirect quantification techniques show a protein overestimation of up to 1700% compared to the direct AAAA measurements. In addition, protein coating on latex particles was performed both passively through adsorption and covalently through EDC/sulfo-NHS chemistry. Our results showed no difference between the immobilization methodologies. This finding suggests that usual protein determination methods are no unambiguous proof of a covalent conjugation on particles or beads.
ARTICLE | doi:10.20944/preprints202301.0026.v1
Subject: Chemistry And Materials Science, Polymers And Plastics Keywords: semi-flexible polymers; hard sphere; athermal chain; Monte Carlo; molecular simulation; crystallization; packing; phase transition; order parameter; liquid crystal; nematic order; oblate mesogen; prolate mesogen; face centered cubic; hexagonal close packed; bending angle; freely-jointed model
Online: 3 January 2023 (09:30:22 CET)
The local and global order in dense packings of linear, semi-flexible polymers of tangent hard spheres are studied by employing extensive Monte Carlo simulations at increasing volume fractions. Chain stiffness is controlled by a tunable harmonic potential for the bending angle whose intensity dictates the rigidity of the polymer backbone as a function of the bending constant and equilibrium angle. The studied angles range from acute to obtuse ones, reaching the limit of rod-like polymers. We analyze how packing density and chain stiffness affect the ability of chains to self-organize at the local and global levels. The former corresponds to crystallinity as quantified by the Characteristic Crystallographic Element (CCE) norm descriptor, while the latter is computed through the scalar orientational order parameter. In all cases, we identify the critical volume fraction for the phase transition and gauge the established crystal morphologies, developing a complete phase diagram as a function of packing density and equilibrium bending angle. A plethora of structures is obtained, ranging from random hexagonal closed packed morphologies of mixed character and almost perfect face centered cubic (FCC) and hexagonal close-packed (HCP) crystals at the level of monomers, to nematic mesophases, with prolate and oblate mesogens at the level of chains. For rod-like chains, hysteresis is observed between the establishment of long-range nematic order and crystallization, while for right-angle chains both transitions are synchronized. A comparison is also provided against the analogous packings of monomeric and fully flexible chains of hard spheres.
ARTICLE | doi:10.20944/preprints202010.0294.v1
Subject: Physical Sciences, Condensed Matter Physics Keywords: crystallization; crystal, hexagonal close packed, face center cubic, body center cubic, hexagonal crystal, square lattice, honeycomb lattice, trigonal lattice, Monte Carlo, crystallography, crystallographic elements, symmetry, entropy, hard sphere, polymer, square well, local structure, dense packing, thin film
Online: 14 October 2020 (10:05:22 CEST)
In the present work we revise and extend the Characteristic Crystallographic Element (CCE) norm, an algorithm used to simultaneously detect radial and orientational similarity of computer-generated structures with respect to specific reference crystals and local symmetries. Based on the identification of point group symmetry elements, the CCE descriptor is able to gauge local structure with high precision and finely distinguish between competing morphologies. As test cases we use computer-generated monomeric and polymer systems of spherical particles interacting with the hard-sphere and square-well attractive potentials. We demonstrate that the CCE norm is able to detect and differentiate, between others, among: hexagonal close packed (HCP), face centered cubic (FCC), hexagonal (HEX) and body centered cubic (BCC) crystals as well as non-crystallographic fivefold (FIV) local symmetry in bulk 3-D systems; triangular (TRI), square (SQU) and honeycomb (HON) crystals, as well as pentagonal (PEN) local symmetry in thin films of one-layer thickness (2-D systems). The descriptor is general and can be applied to identify the symmetry elements of any point group for arbitrary atomic or particulate system in two or three dimensions, in the bulk or under confinement.