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Periodic polymers with increasing repetition unit: Energy structure and carrier transfer
摘要： We study the energy structure and the transfer of an extra electron or hole along periodic polymers made of N monomers, with a repetition unit made of P monomers, using a tight-binding wire model, where a site is a monomer (e.g., in DNA, a base pair), for P even, and deal with two categories of such polymers: made of the same monomer (GC …, GGCC …, etc.) and made of different monomers (GA …, GGAA …, etc.). We calculate the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) eigenspectra, density of states, and HOMO-LUMO gap and find some limiting properties these categories possess, as P increases. We further examine the properties of the mean over time probability to find the carrier at each monomer. We introduce the weighted mean frequency of each monomer and the total weighted mean frequency of the whole polymer, as a measure of the overall transfer frequency content. We study the pure mean transfer rates. These rates can be increased by many orders of magnitude with appropriate sequence choice. Generally, homopolymers display the most efficient charge transfer. Finally, we compare the pure mean transfer rates with experimental transfer rates obtained by time-resolved spectroscopy.
关键词： LUMO,periodic polymers,weighted mean frequency,pure mean transfer rates,energy structure,carrier transfer,HOMO,density of states,HOMO-LUMO gap,tight-binding wire model
更新于2025-09-04 15:30:14
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Analytical Analysis and Experimental Validation of a Multi-parameter Mach-Zehnder Fiber Optic Interferometric Sensor
摘要： Here we report a simple analytical technique to model a Mach–Zehnder fiber optic interferometric sensors that allow us to predict and calculate via computer simulations parameters that are not easily obtained experimentally. This model was calibrated and compared with experimental data using a 120 mm sensor for measurements of temperature, refractive index and water level. For instance, we were able to calculate the effects on the cladding index caused by the variation of those physical effective parameters. Moreover, this analysis could further our understanding of such sensors and allow us to make predictions about their use in different applications and even their behavior with different sensing lengths.
关键词： optical fiber devices,analytical model,Optical fiber interference,optical fiber applications,optical interferometry
更新于2025-09-04 15:30:14
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[IEEE 2017 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC) - Atlanta, GA, USA (2017.10.21-2017.10.28)] 2017 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC) - Detector response function of a HPGe detector to photon energies between 200 keV and 1.5 MeV for Gamma-ray nondestructive assay instrument
摘要： A semi-empirical detector response function (DRF) model of HPGe detector was proposed to fit gamma-ray nondestructive assay transmission spectra. The model for each single peak contained a step function, a Gaussian function, and an exponential tail function. The Gaussian standard deviation obtained by electronic noise and Fano factor, so our DRF only had 4 parameters and they were obtained by the weighted nonlinear least-squares fitting method. In the application, 152Eu spectra were obtained by using the 30%, 50%, 70% HPGe detector, and fitted by the established DRF model. Reduced chi- square values were at the interval of 0.039-0.202. Its validity that the model had good versatility, can be applicable to different detection efficiency of HPGe detectors.
关键词： gamma-ray nondestructive assay,HPGe detector,semi-empirical model,detector response function
更新于2025-09-04 15:30:14
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Dependence of Modulation Transfer Function on Electric Field Intensity of Photo conductor and Mobility-lifetime Product of Carriers in Polycrystalline Mercuric Iodide Based Flat Panel X-Ray Detectors: A Quantitative Approach and Error Analysis
摘要： In this Paper, a simplified mathematical model for Modulation Transfer Function (MTF) of Polycrystalline Mercuric Iodide based flat panel x-ray detector is applied on three different published prototypes of Polycrystalline Mercuric Iodide. Our aim was to fit the curves generated by simulation of MTF model with the curves acquired from experimental data. The mobility-lifetime product for the best curve fitting was examined for each prototype. Percentage of fitting error has been estimated for each prototype. Finally, average absolute error has been calculated for all the incorporated prototypes. This study can be further extended to develop a generic empirical model for the Modulation Transfer Function of polycrystalline mercuric iodide based flat panel x-ray detectors.
关键词： Modulation Transfer Function,Mobility-Lifetime Product,Average Absolute Error,Error Analysis,Empirical Model,Electric Field Intensity
更新于2025-09-04 15:30:14
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Model Development for Threshold Voltage Stability Dependent on High Temperature Operations in Wide-Bandgap GaN-Based HEMT Power Devices
摘要： Temperature-dependent threshold voltage (Vth) stability is a significant issue in the practical application of semi-conductor power devices, especially when they are undergoing a repeated high-temperature operation condition. The Vth analytical model and its stability are dependent on high-temperature operations in wide-bandgap gallium nitride (GaN)-based high electron mobility transistor (HEMT) devices that were investigated in this work. The temperature effects on the physical parameters—such as barrier height, conduction band, and polarization charge—were analysed to understand the mechanism of Vth stability. The Vth analytical model under high-temperature operation was then proposed and developed to study the measurement temperatures and repeated rounds dependent on Vth stability. The validity of the model was verified by comparing the theoretical calculation data with the experimental measurement and technology computer-aided design (TCAD) simulation results. This work provides an effective theoretical reference on the Vth stability of power devices in practical, high-temperature applications.
关键词： high-temperature operation,gallium nitride (GaN),analytical model,high electron mobility transistors (HEMTs),threshold voltage (Vth) stability
更新于2025-09-04 15:30:14
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Polarimetric remote sensing in oxygen A and B bands: sensitivity study and information content analysis for vertical profile of aerosols
摘要： Theoretical analysis is conducted to reveal the information content of aerosol vertical profile in space-borne measurements of the backscattered radiance and degree of linear polarization (DOLP) in oxygen (O2) A and B bands. Assuming a quasi-Gaussian shape for aerosol vertical profile characterized by peak height H and half width γ (at half maximum), the Unified Linearized Vector Radiative Transfer Model (UNL-VRTM) is used to simulate the Stokes four-vector elements of upwelling radiation at the top of atmosphere (TOA) and their Jacobians with respect to H and γ. Calculations for different aerosol types and different combinations of H and γ values show that the wide range of gas absorption optical depth in O2 A and B band enables the sensitivity of backscattered DOLP and radiance at TOA to the aerosol layer at different altitudes. Quantitatively, DOLP in O2 A and B bands is found to be more sensitive to H and γ than radiance, especially over the bright surfaces (with large visible reflectance). In many O2 absorption wavelengths, the degree of freedom of signal (DFS) for retrieving H (or γ) generally increases with H (and γ) and can be close to unity in many cases, assuming that the composite uncertainty from surface and aerosol scattering properties as well as measurements is less than 5 %. Further analysis demonstrates that DFS needed for simultaneous retrieval of H and γ can be obtained from a combined use of DOLP measurements at ～ 10–100 O2 A and B absorption wavelengths (or channels), depending on the specific values of H. The higher the aerosol layer, the fewer number of channels for DOLP measurements in O2 A and B bands are needed for characterizing H and γ. Future hyperspectral measurements of DOLP in O2 A and B bands are needed to continue studying their potential and their combination with radiance and DOLP in atmospheric window channels for retrieving the vertical profiles of aerosols, especially highly scattering aerosols, over land.
关键词： oxygen A and B bands,radiative transfer model,aerosol vertical profile,polarimetric remote sensing,degree of linear polarization
更新于2025-09-04 15:30:14
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Coupling of Human Rhodopsin to a Yeast Signaling Pathway Enables Characterization of Mutations Associated with Retinal Disease
摘要： G protein-coupled receptors (GPCRs) are crucial sensors of extracellular signals in eukaryotes, with multiple GPCR mutations linked to human diseases. With the growing number of sequenced human genomes, determining the pathogenicity of a mutation is challenging, but can be aided by a direct measurement of GPCR-mediated signaling. This is particularly difficult for the visual pigment rhodopsin, a GPCR activated by light, for which hundreds of mutations have been linked to inherited degenerative retinal diseases such as retinitis pigmentosa (RP). In this study, we successfully engineered, for the first time, activation by human rhodopsin of the yeast mating pathway, resulting in signaling via a fluorescent reporter. We combine this novel assay for rhodopsin light-dependent activation with studies of subcellular localization, and the upregulation of the unfolded protein response (UPR) in response to misfolded rhodopsin protein. We use these assays to characterize a panel of rhodopsin mutations with known molecular phenotypes, finding that rhodopsin maintains a similar molecular phenotype in yeast, with some interesting differences. Furthermore, we compare our assays in yeast with clinical phenotypes from patients with novel disease-linked mutations. We demonstrate that our engineered yeast strain can be useful in rhodopsin mutant classification, and in helping to determine the molecular mechanisms underlying their pathogenicity. This approach may also be applied to better understand the clinical relevance of other human GPCR mutations, furthering the use of yeast as a tool for investigating molecular mechanisms relevant to human disease.
关键词： disease model,G protein-coupled receptor,rhodopsin,Visual degenerative disease,retinitis pigmentosa
更新于2025-09-04 15:30:14
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3D ICs-power Analysis Using Cylindrical and Co-axial Through Silicon Via (TSV)
摘要： In this study, analytical model and electrical equivalent circuit of Through Silicon Via (TSV) is analyzed. Through silicon Vias form an integral component of the 3-D IC technology by enabling vertical interconnections in 3-D ICs. Among various types, the performances of the simplified lumped TSV model of cylindrical and co-axial type were studied. The performance analyses of these structures were presented by introducing these structures between the tiers of digital circuits. The power consumption of the transistor level digital circuits for single tier without TSV and multiple tiers with cylindrical TSV and Co-axial TSV was simulated using Virtuoso Schematic Editor of Cadence. The comparison for cylindrical and co-axial TSV model with different level tiers were tabulated and performed.
关键词： Three-dimensional ICs,Through Silicon Via (TSV),TSV lumped RLC model
更新于2025-09-04 15:30:14
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Can a Channelized Hotelling Observer assess image quality in acquired mammographic images of an anthropomorphic breast phantom including image processing?
摘要： Purpose: To study the feasibility of a channelized Hotelling observer (CHO) to predict human observer performance in detecting calcification-like signals in mammography images of an anthropomorphic breast phantom, as part of a quality control (QC) framework. Methods: A prototype anthropomorphic breast phantom with inserted gold discs of 0.25 mm diameter was imaged with two different digital mammography x-ray systems at four different dose levels. Regions of interest (ROIs) were extracted from the acquired processed and unprocessed images, signal-present and signal-absent. The ROIs were evaluated by a CHO using four different formulations of the difference-of-Gaussian (DoG) channel sets. Three human observers scored the ROIs in a two-alternative forced-choice experiment. We compared the human and the CHO performance on the simple task to detect calcification-like discs in ROIs with and without post-processing. The proportion of correct responses of the human reader (PCH) and the CHO (PCCHO) was calculated and the correlation between the two was analyzed using a mixed-effect regression model. To address the signal location uncertainty, the impact of shifting the DoG channel sets in all directions up to two pixels was evaluated. Correlation results including the goodness of fit (r2) of PCH and PCCHO for all different parameters were evaluated. Results: Sub-analysis by system yielded strong correlations between PCH and PCCHO, with r2 between PCH and PCCHO was found to be between 0.926 and 0.958 for the unshifted and between 0.759 and 0.938 for the shifted channel sets, respectively. However, the linear fit suggested a slight system dependence. PCCHO with shifted channel sets increased CHO performance but the correlation with humans was decreased. These correlations were not considerably affected by of the DoG channel set used. Conclusions: There is potential for the CHO to be used in QC for the evaluation of detectability of calcification-like signals. The CHO can predict the PC of humans in images of calcification-like signals of two different systems. However, a global model to be used for all systems requires further investigation.
关键词： Image quality,mammography,model observers,anthropomorphic breast phantom,human observers
更新于2025-09-04 15:30:14
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Hyperelastic material modeling of graphene based on density functional calculations
摘要： A new parameter set for the graphene material model of [1] is obtained. The material model is anisotropic hyperelastic and calibrated by a trial dataset generated by density functional theory (DFT). The DFT experiments are one pure dilatation test and two uniaxial stretch tests along the armchair and zigzag directions. The strain energy is computed from ab-initio simulations and used to calibrate the parameters of the hyperelastic model. The strain energy and stresses from the new parameter set are calculated and verified with the results of [1].
关键词： density functional theory,hyperelastic material model,DFT,anisotropic,strain energy,graphene
更新于2025-09-04 15:30:14