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[IEEE 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) - Xiamen, China (2019.12.17-2019.12.20)] 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) - A 220 GHz GaN HEMT Power Amplifier
摘要： Evolutions of Geant4 code have affected the simulation of electron backscattering with respect to previously published results. Their effects are quantified by analyzing the compatibility of the simulated electron backscattering fraction with a large collection of experimental data for a wide set of physics configuration options available in Geant4. Special emphasis is placed on two electron scattering implementations first released in Geant4 version 10.2: the Goudsmit-Saunderson multiple scattering model and a single Coulomb scattering model based on Mott cross section calculation. The new Goudsmit-Saunderson multiple scattering model appears to perform equally or less accurately than the model implemented in previous Geant4 versions, depending on the electron energy. The new Coulomb scattering model was flawed from a physics point of view, but computationally fast in Geant4 version 10.2; the physics correction released in Geant4 version 10.2p01 severely degrades its computational performance. Problems observed in electron backscattering simulation in previous publications have been addressed by evolutions in the Geant4 geometry domain.
关键词： Electrons,Monte Carlo,simulation,Geant4
更新于2025-09-23 15:19:57
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Exper?±mental and Numer?±cal Analysis of the Effect of Components on a Double-Sided PCB on LED Junction Temperature and Light Output Using CFD
摘要： In today’s lighting industry, with developing technology and a widened usage area, LEDs have become very popular due to their higher energy efficiency and longer life. In the present study, the effect of electronic components on printed circuits and the radiation level on light output was studied. The performed analysis was validated with an experimental method. For the finite volume method, FloEFD 2019, commercial software, was used. The ambient temperature was assumed to be 23 °C. The value of solar irradiance was taken as 1009 W/cm2. LEDs on a PCB were driven at 70 mA at first and then at 50 mA, and, by exerting power on all electronic components, analyses were performed. Both sides of the PCB were examined, and, in order to achieve efficient heat conduction, the power and distribution of the electronic components on the back side of the LEDs were optimized. With a new electronic circuit design, analyses were performed at 50, 55, 60, 65, and 70 mA. It was determined that the highest light output was achieved at 65 mA and that the distribution of electronic components on a PCB indirectly affects light output through junction temperature (T j).
关键词： Laminar natural convection,Junction temperature,Monte Carlo radiation,LED automotive lamp,Computational fluid dynamics (CFD)
更新于2025-09-23 15:19:57
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Rays via Single-Shot Laser-Electron Interaction
摘要： Generation of circularly polarized (CP) and linearly polarized (LP) γ rays via the single-shot interaction of an ultraintense laser pulse with a spin-polarized counterpropagating ultrarelativistic electron beam has been investigated in nonlinear Compton scattering in the quantum radiation-dominated regime. For the process simulation, a Monte Carlo method is developed which employs the electron-spin-resolved probabilities for polarized photon emissions. We show efficient ways for the transfer of the electron polarization to the high-energy photon polarization. In particular, multi-GeV CP (LP) γ rays with polarization of up to about 95% can be generated by a longitudinally (transversely) spin-polarized electron beam, with a photon flux meeting the requirements of recent proposals for the vacuum birefringence measurement in ultrastrong laser fields. Such high-energy, high-brilliance, high-polarization γ rays are also beneficial for other applications in high-energy physics, and laboratory astrophysics.
关键词： nonlinear Compton scattering,electron-spin-resolved probabilities,high-energy physics,Monte Carlo method,circularly polarized γ rays,vacuum birefringence,quantum radiation-dominated regime,laboratory astrophysics,linearly polarized γ rays
更新于2025-09-23 15:19:57
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Development of a coupled aerosol lidar data quality assurance and control scheme with Monte Carlo analysis and bilateral filtering
摘要： Mie-scatter lidar can capture the vertical distribution of aerosols, and a high degree of quantification of lidar data would be capable of coupling with a chemical transport model (CTM). Thus, we develop a data quality assurance and control scheme for aerosol lidar (TRANSFER) that mainly includes a Monte Carlo uncertainty analysis (MCA) and bilateral filtering (BF). The AErosol RObotic NETwork (AERONET) aerosol optical depth (AOD) is utilized as the ground truth to evaluate the validity of TRANSFER, and the result exhibits a sharp 41% (0.36) decrease in root mean square error (RMSE), elucidating an acceptable overall performance of TRANSFER. The maximum removal of uncertainties appears in MCA with an RMSE of 0.08 km-1, followed by denoising (DN) with 50% of MCA in RMSE. BF can smooth interior data without destroying the edge of the structure. The most noteworthy correction occurs in summer with an RMSE of 0.15 km-1 and Pearson correlation coefficient of 0.8, and the least correction occurs in winter with values of 0.07 km-1 and 0.93, respectively. Overestimations of raw data are mostly identified, and representative values occur with weak southerly winds, low visibility, high relative humidity (RH) and high concentrations of both ground fine particulate matter (PM2.5) and ozone. Apart from long-term variations, the intuitional variation in a typical overestimated pollution episode, especially represented by vertical profiles, shows a favorable performance of TRANSFER during stages of transport and local accumulation, as verified by backward trajectories. Few underestimation cases are mainly attributed to BF smoothing data with a sudden decrease. The main limitation of TRANSFER is the zigzag profiles found in a few cases with very small extinction coefficients. As a supplement to the research community of aerosol lidar and an exploration under complicated pollution in China, TRANSFER can aid in the preprocessing of lidar data-powered applications.
关键词： Aerosol Lidar,Bilateral filtering,North China Plain,Monte Carlo,data quality control
更新于2025-09-23 15:19:57
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Remote Spatio-Temporal Focusing over Multimode Fiber Enabled by Single-Ended Channel Estimation
摘要： Interest in deep probabilistic graphical models has increased in recent years, due to their state-of-the-art performance on many machine learning applications. Such models are typically trained with the stochastic gradient method, which can take a significant number of iterations to converge. Since the computational cost of gradient estimation is prohibitive even for modestly sized models, training becomes slow and practically usable models are kept small. In this paper we propose a new, largely tuning-free algorithm to address this problem. Our approach derives novel majorization bounds based on the Schatten- norm. Intriguingly, the minimizers of these bounds can be interpreted as gradient methods in a non-Euclidean space. We thus propose using a stochastic gradient method in non-Euclidean space. We both provide simple conditions under which our algorithm is guaranteed to converge, and demonstrate empirically that our algorithm leads to dramatically faster training and improved predictive ability compared to stochastic gradient descent for both directed and undirected graphical models.
关键词： Monte Carlo simulation methods,graphical models,Boltzmann distributions,Gradient methods,maximum likelihood estimation
更新于2025-09-23 15:19:57
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An AMOLED Pixel Circuit Based on LTPS Thin-film Transistors with Mono-Type Scanning Driving
摘要： Using low-temperature poly-silicon thin-film transistors (LTPS TFTs) as a basis, a pixel circuit for an active matrix organic light-emitting diode (AMOLED) with narrow bezel displays was developed. The pixel circuit features mono-type scanning signals, elimination of static power lines, and pixel-integrated emitting control functions. Therefore, gate driver circuits of the display bezel can be simplified efficiently. In addition, the pixel circuit has a high-resolution design due to an increase of the pulse width of the scan signal to extend the threshold voltage and internal–resistance drop (IR drop) detection period. Further, regarding the influences of process–voltage–temperature (PVT) variation in the pixel circuit, comparison investigations were carried out with the proposed circuit and other pixel circuits with mono-type scanning signals using Monte Carlo analysis. The feasibility of the proposed pixel circuit is well demonstrated, as the current variations can be reduced to 2.1% for the supplied power reduced from 5 V to 3 V due to IR drop, and the current variation is as low as 10.6% with operating temperatures from –40 degrees to 85 degrees.
关键词： pixel circuit,AMOLED,IR drop,Monte Carlo,LTPS TFT
更新于2025-09-23 15:19:57
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Experimentally Calibrated Kinetic Monte Carlo Model Reproduces Organic Solar Cell Currenta??Voltage Curve
摘要： Kinetic Monte Carlo simulations are used to describe the current-voltage characteristics of an organic bulk heterojunction solar cell. Excellent agreement between model and experiment is obtained by calibrating the injection barriers, the blend morphology and the charge transfer recombination rate with data from independent measurement techniques.
关键词： organic photovoltaics,charge recombination,Kinetic Monte Carlo simulations,morphology,charge injection
更新于2025-09-23 15:19:57
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RBS/C, XRR, and XRD Studies of Damage Buildup in Er‐Implanted ZnO
摘要： Accumulation and transformation of defects formed in bulk ZnO crystals at room temperature upon 300 keV Er ions bombardment have been thoroughly examined using complementary techniques: Rutherford Backscattering Spectrometry in ion Channeling mode (RBS/C), X-Ray Reflectivity (XRR), and X-Ray Diffraction (XRD). Evaluation of RBS/C spectra has been performed using Monte Carlo (MC) simulations (McChasy software). Two defect types have been indicated: point defects (randomly displaced atoms, RDA) and extended ones (edge dislocations, DIS). Depth-distributions of RDA and DIS turned out to be shifted toward deeper regions of ZnO crystals (relative to Er-ions range) while DIS are localized even deeper than RDA. The MC simulations reveal three regions of defects accumulation separated by two regions of rapid defects transformation occurring at a certain critical Er fluence. Strain, suggested to be a driving force of defect transformation, has been determined using simulations of the XRD profiles based on the dynamical theory of X-ray diffraction (MROX software). The presented research can help to better understand the interaction between impurity Er ions and ZnO target atoms during the implantation process. Hence, implantation conditions, for example, for luminescence purpose may now be more efficiently chosen based on the results discussed.
关键词： Monte Carlo simulations,defects analysis,X-ray reflectivity,ion channeling,dynamical theory of X-ray diffraction
更新于2025-09-23 15:19:57
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Reconstruction of X-rays spectra of clinical linear accelerators from transmission data with generalized simulated annealing
摘要： The spectral distribution of megavoltage X-rays used in radiotherapy departments is a fundamental quantity from which, in principle, all relevant information required for radiotherapy treatments can be determined. The direct measurement is di?cult to achieve clinically and analyzing the transmission is a clinically viable indirect method for determining clinical linear accelerators photon spectra. In this method, transmission signals are acquired after the beam passes through di?erent thicknesses of attenuators. The objective of this work was the establishment and application of an indirect method that used a spectral model based on generalized simulated annealing algorithm to determine the spectrum of clinical linear accelerators photons based on the transmission curve. Analysis of the spectra was made by analytical determination of dosimetric quantities and related parameters.
关键词： Spectrometry,Photons,Radiotherapy,Monte Carlo,Generalized simulated annealing
更新于2025-09-23 15:19:57
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Implementation and validation of time-of-flight PET image reconstruction module for listmode and sinogram projection data in the STIR library
摘要： In this paper, we describe the implementation of support for Time-of-Flight (TOF) Positron Emission Tomography (PET) for both listmode and sinogram data in the open source Software for Tomographic Image Reconstruction (STIR). We provide validation and performance characterization using simulated data from the open source GATE Monte Carlo toolbox, with TOF configurations spanning from 81.2 to 209.6 ps. The coincidence detector resolution was corrected for the timing resolution deterioration due to the contribution of the crystal length. Comparison between the reconstruction of listmode and sinogram data demonstrated good agreement in both TOF and non-TOF cases in terms of relative absolute error. To reduce the reconstruction time, we assessed the truncation of the TOF kernel along Lines-of-Response (LOR). Rejection of LOR elements beyond four times the TOF standard deviation provides significant acceleration of ≈ 45% without compromising the image quality. Further narrowing of the kernel can provide extra time reduction but with the gradual introduction of error in the reconstructed images. As expected, TOF reconstruction performs better than non-TOF in terms of both Contrast-Recovery-Coefficient (CRC) and Signal-to-Noise ratio (SNR). CRC achieves convergence faster with TOF, at lower noise levels. SNR with TOF was superior for early iterations, but with quick deterioration. Higher timing resolution further improved reconstruction performance, while TOF bin mashing was shown to have only a small impact on reconstructed images.
关键词： Medical Imaging,Open-Source Software,Positron Emission Tomography,Monte Carlo,Computer Simulations,Time-of-Flight
更新于2025-09-23 15:19:57