ARTICLE | doi:10.20944/preprints201710.0089.v1
Subject: Physical Sciences, Acoustics Keywords: ultrasonic; cure monitoring; resonant ultrasonic spectroscopy
Online: 13 October 2017 (10:37:45 CEST)
With an ever broadening use of composite materials manufacturers are in high demand of efficient curing cycles to reduce costs and speed up production cycles. One method to to archive this goal is active cure monitoring to determine the exact time of curing needed. This article provides a novel method to measure the cure inside of closed tools by using ultrasonic spectroscopy. For this a simple experiment is used to show the change of the ultrasonic spectrum during the cure of an epoxy. The results clearly show a direct correlation of amplitude and state of cure where the amplitude reaches a global minimum at the glass point.
ARTICLE | doi:10.20944/preprints201808.0351.v1
Subject: Engineering, Biomedical & Chemical Engineering Keywords: transient response; phononic crystal sensors; resonant sensors
Online: 20 August 2018 (10:51:35 CEST)
Phononic crystals are periodic composite structures with specific resonant features that are gaining strength in the field as liquid sensors. The introduction of a structural defect in an otherwise periodic regular arrangement can generate a resonant mode, also called defect mode, inside the characteristic band gaps of phononic crystals. The morphology, as well as the frequency in which these defect modes appear, can give useful information on the composition and properties of an analyte. Currently, only gain, and frequency measurements are performed using phononic crystal sensors. Other measurements like the transient response have been implemented in resonant sensors such as quartz microbalances showing great results and proving to be a great complimentary measure to the gain and frequency measurements. In the present paper, a study of the feasibility of using the transient response as a measure to acquire additional information about the analyte is presented. Theoretical studies using the transmission line model were realized to show the impact of variations in the concentration of an analyte, in this case, lithium carbonate solutions, in the transient time of the system. Experimental realizations were also performed showing that the proposed measurement scheme presents significant changes in the resulting data, indicating the potential use of this measure in phononic crystal sensors. This proposed measure could be implemented as a stand-alone measure or as a compliment to current sensing modalities.
Subject: Physical Sciences, Condensed Matter Physics Keywords: X-ray resonant diffraction; forbidden reflections; X-ray spectroscopy
Online: 14 July 2020 (03:37:08 CEST)
Examining forbidden reflections provides valuable information on electronic states and the local environment of resonant atoms in crystals. Experimental studies of two forbidden reflections 002 and 100 in TeO2 single crystals were performed at photon energies close to the L1 tellurium absorption edge. It was found that the spectral form corresponding to these two reflections looks almost identical, which is completely unexpected for a highly anisotropic material. Theoretical consideration shows that only one component fxy of the tensor describing dipole-dipole resonance scattering contributes to the 002 reflection, while two components fxy and fxz correspond to the 100 reflection. Numerical calculations show that the latter tensor component is comparable to the first one, but the combination of several geometric factors leads to the fact that its contribution to the spectrum is negligible. This explains the experimentally observed results. The finding shows a way for targeted investigation of single tensor components and makes it possible to compare different spectra and use them the study the physical phenomena in functional materials.
ARTICLE | doi:10.20944/preprints202003.0179.v1
Subject: Engineering, Mechanical Engineering Keywords: fast tool servo; voice coil motor; flexure mechanism; resonant controller
Online: 11 March 2020 (04:04:49 CET)
In this paper, a voice coil motor (VCM) actuated fast tool servo (FTS) system is developed for diamond turning. To guide motions of the VCM actuator, a crossed double parallelogram flexure mechanism is selected featuring totally symmetric structure with high lateral stiffness. To facilitate the determination of the multi-physical parameters, analytical models of both electromagnetic and mechanical systems are developed. The designed FTS with balanced stroke and natural frequency is then verified through the finite element analysis. Finally, the prototype of the VCM actuated FTS is fabricated and experimentally demonstrated to have a stroke of ±59.02 μm and a first natural frequency of 253 Hz. By constructing a closed-loop control using PID controller with the internal-model based resonant controller, the error for tracking a harmonic trajectory with ±10 μm amplitude and 120 Hz frequency is obtained to be ±0.2 μm, demonstrating the capability of the FTS for high accuracy trajectory tracking.
ARTICLE | doi:10.20944/preprints201911.0075.v1
Subject: Materials Science, Polymers & Plastics Keywords: ITO-free polymer solar cells; resonant microcavity; ultrathin Cu film
Online: 7 November 2019 (09:51:49 CET)
Here we report highly efficient, indium tin oxide (ITO)-free polymer solar cells (PSCs) with an ultrathin copper (Cu) film(~10 nm) coated with a thin layer of poly[(9,9-bis(3‘-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN) as transparent electrode. Despite of its lower far-field transmittance of the electrode, the obtained ITO-free device based on the ultrathin Cu film can delivery higher absorption efficiency than that of the device based on ITO substrate in the long wavelength region, which can be attributed to the formation of metal resonant microcavity between the opaque back metal mirror (MoO3/Al electrode) and the transparent Cu film with high reflectance. As a result, polymer solar cells based on poly[[2,6'-4,8-di(5-ethylhexylthienyl)benzo[1,2-b;3,3-b]dithiophene][3-fluoro-2[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]] (PTB7-Th) and [6,6]-phenyl C71-butyric acid methyl ester (PC71BM) blend show a high power conversion efficiency (PCE) of 8.21 %, comparable to that of the control device based on ITO electrode (with a PCE of 9.60% ). The results demonstrate that thermally evaporated Cu thin film electrode can be promising candidate to replace ITO for highly efficient PSCs, thus may open up the possibility for massive production of PSCs with low cost.
ARTICLE | doi:10.20944/preprints201705.0042.v1
Subject: Engineering, Mechanical Engineering Keywords: drop test; impact analysis; reliability; haptic actuator; linear resonant actuator (LRA)
Online: 4 May 2017 (11:39:49 CEST)
Impact characterization of linear resonant actuator (LRA) is studied experimentally by newly developed drop tester, which can control various experimental uncertainty such as rotational moment, air resistance, secondary impact and so on. The feasibility of this test apparatus was verified by comparison with free fall test. By utilizing a high-speed camera and measuring the vibrational displacement of spring material, the impact behavior was captured and the damping ratio of the system was defined. Based on the above processes, the finite element model was established and the experimental and analytical results were successfully correlated. Finally, the damage of the system from impact loading can be expected by developed model and as a result, this research can improve the impact reliability of LRA.
ARTICLE | doi:10.20944/preprints201906.0131.v1
Subject: Engineering, Electrical & Electronic Engineering Keywords: phase-shifted full-bridge; resonant converter; photovoltaics; zero voltage switching; power loss
Online: 14 June 2019 (10:01:32 CEST)
This paper presents the design of a high frequency zero voltage switching (ZVS) full-bridge converter with a phase-shifted driving signal for photovoltaic applications. The resonant power converter can provide high-power capacity under high-frequency operation. The proposed power converter can also reduce the size of the transformer under the same power rating. The high-frequency transformer was developed by using the resonant and switching frequencies of the power converter to reduce the switching loss and to improve the system efficiency. Phase-shifted modulation was selected to drive the switches of a full-bridge power converter based on the switching loss minimization method. The desired output voltage was controlled using a closed-loop controller under a loop gain stability margin. The simulation results showed that the output voltage can be controlled to the desired constant when the input voltage changes from 30 VDC to 60 VDC. The desired output voltage of power converter is constant at 400 VDC. The power converter can transfer the DC supply to a 220 VAC household via grid-connected inverter. Therefore, the proposed study showed the effectiveness of the phase-shift ZVS full-bridge power converter with high-frequency transformer. This power converter can control the operation of the desired voltage system and has a small sizing of power converter system, low switching loss, and high system efficiency.
ARTICLE | doi:10.20944/preprints202207.0352.v1
Subject: Engineering, Civil Engineering Keywords: Calcareous sand; Microbially induced calcite precipitation; Dynamic shear modulus; Resonant column test; Reference shear strain
Online: 25 July 2022 (05:56:36 CEST)
Calcareous sand deposits are widely distributed along the shoreline in ropical and subtropical regions. Microbially induced calcite precipitation treatment (MICP) is a relatively new method to improve the stiffness and strength of the soil. Little is known about the small-strain shear modulus and damping ratio of MICP-treated calcareous sand, which are two crucial parameters for the prediction of the dynamic behavior of soil. A series of resonant column tests are performed to investigate the dynamic performance of MICP-treated calcareous sand, with special attention paid to the influence of treatment duration and confining stress on the stiffness and damping characteristics. The relationship between the initial dynamic shear modulus and unconfined compressive strength is analyzed. Additionally, the empirical equations of the reference shear strain between treatment duration and confining stress are given. The G/G0 of MICP-cemented calcareous sand presents a higher strain sensitivity than that of untreated sand, and its attenuation pattern can be described by Hardin-Drnevich model. The σc has an apparent effect on the degradation characteristics of the dynamic shear modulus of MICP-treated calcareous sand with a low cementation level, however, its effect decreases with the increasing treatment duration. The relationship between the reference shear strain and the treatment duration and confining stress can be described by a power and a linear formula, respectively.
ARTICLE | doi:10.20944/preprints201811.0632.v1
Subject: Engineering, Electrical & Electronic Engineering Keywords: fault line detection; data fusion; non-artificial setting; sound distance; fault distance; resonant grounding system
Online: 30 November 2018 (10:38:18 CET)
Fault line detection timely and accurately when single-phase-to-earth fault occurs in resonant grounding system is still a focus of research. This paper presents a new approach for fault detection based on data fusion and it has non-artificial setting. Firstly, the fault criterion for interphase difference energy ratio and time-frequency correlation coefficient of each line is proposed. Subsequently, the paper establish a coordinate system with the interphase difference energy ratio as X axis and the time-frequency correlation coefficient as Y axis, and it uses the Euclidean distance algorithm to get the characteristic distance of each line by fusing two-dimensional information. Finally, comparing the sound distance and the fault distance of each line to discriminate the fault line. Electromagnetic Transients Program (EMTP) simulation results and adaptability analysis have confirmed the effectiveness and reliability of the proposed scheme.
ARTICLE | doi:10.20944/preprints201710.0008.v1
Subject: Engineering, Electrical & Electronic Engineering Keywords: : microstrip antenna, vertical slots , adaptive network-based fuzzy Inference system , resonant frequency, artificial neural networks
Online: 2 October 2017 (09:16:02 CEST)
This paper attempts at applying adaptive network-based fuzzy inference system (ANFIS) for analysis of the resonant frequency of a microstrip rectangular patch antenna with two equal size slots which are placed on the patch vertically. The resonant frequency is calculated as the position of slots is shifted to the right and left sides on the patch. As a result , the antenna resonates at more than one frequency . Commonly, machine algorithms based on artificial neural networks are employed to recognize the whole resonant frequencies. However ,they fail to estimate the resonant frequencies correctly as in some cases variations are not very sensible and the resonant frequencies overlap each other . It can be concluded that artificial neural networks could be replaced in such designs by the adaptive network-based fuzzy Inference system due to its high approximation capability and much faster convergence rate.
Subject: Earth Sciences, Geophysics Keywords: mineral physics; ultrasonic interferometry; resonant ultrasound spectroscopy; law of corresponding states; equations-of-state; Columbia University; American Geophysical Union
Online: 29 March 2019 (07:54:57 CET)
From 1964 to the early 1970s, Orson Anderson led a research program at the Lamont Geological Observatory in the newly-emerging field of “mineral physics”. In collaboration with colleagues Edward Schreiber and Naohiro Soga, Orson exploited the techniques of physical acoustics to study the behavior of the sound velocities of minerals at elevated pressures and temperatures. This research program also included semi-empirical studies of relationships between the bulk modulus and the molar volume of solids and the use of lattice dynamics to calculate the elastic moduli of cubic structures as a function of pressure to predict instabilities, as well as theoretical investigations of the Lagrangian vs. Eulerian formulations of finite strain equations of state.
ARTICLE | doi:10.20944/preprints201811.0345.v1
Subject: Physical Sciences, Fluids & Plasmas Keywords: Landau damping; resonant transfer; anharmonic lattice; nonlinear waves; collective modes; gravity waves; Stokes flow; Basset drag force; surfactant approximation; fractional derivative; anharmonic
Online: 15 November 2018 (05:43:52 CET)
The Landau damping effect was observed in collisionless plasma, as a microscopic resonant mechanism between electromagnetic radiation and the collective modes. In this paper we demonstrate the occurrence of the Landau damping at macroscopic scale in the interaction between water waves and anharmonic lattice of magnetic buoys. By coupling the Navier-Stokes equations for incompressible fluid with the nonlinear dynamics of an anharmonic magnetic lattice we obtain a resonant transfer of momentum and energy between the two systems. The velocity of the flow is obtained in the Stokes approximation with Basset type of drag force. The dynamics of the buoys is calculated in the surfactant approximation for a specific frequency, then we use Fourier analysis to obtain the general time variable interaction. After involving an integral Dirichlet transform we obtain the time dependent expression of the drag force, the interaction waves-lattice with a new term in the form of a Caputo fractional derivative. We compare the results of the model with experiments performed in a wave tank with free floating magnetic buoys under the action of small amplitude gravitational waves. This configuration can be applied in studies for the attenuation with resonant damping of rogue waves, storms or tsunamis.
ARTICLE | doi:10.20944/preprints201802.0058.v1
Subject: Engineering, Electrical & Electronic Engineering Keywords: brushless doubly fed induction generator; direct control; stand-alone; sliding-mode; resonant; reduced-order generalized integrator; variable-speed constant-frequency; wind energy conversion systems
Online: 7 February 2018 (08:39:56 CET)
In this paper, a novel voltage control strategy of stand-alone operation brushless doubly fed induction generator for variable speed constant frequency wind energy conversion systems was presented and discussed particularly. Based on the model of the generator power system, the proposed direct flux control strategy employs a nonlinear reduced-order generalized integrator based resonant sliding-mode control scheme to directly calculate and regulated the output value of converter which control winding stator required so as to eliminate the instantaneous errors of power winding stator flux, and no involving any synchronous rotating coordinate transformations. The stability, robustness and convergence capability of the proposed control strategy were described and analyzed. Owing to no extra current control loops involved, therefore simplifying the system configuration design and enhancing the transient performance. Constant converter switching frequency was achieved by using space vector pulse width modulation, which reduce the harmonic of generator terminal voltage. In addition, experimental results prove the feasibility and validity of the proposed scheme, and excellent steady and dynamic state performance is achieved.