- 标题
- 摘要
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- 实验方案
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Theoretical and Experimental Features of Nano-Crystals Rochelle Salt: Piezoelectric Resonance and Phase Transition
摘要： A new methodology based on Three-Electrode System (TES) technique was used to measure both, elastic (C44) and piezoelectric (d14) constants of Rochelle salt (RS) crystal. This technique was also used to observe the phase transitions at ?18 °C and 24 °C, manifested as an increase of the output signal at these temperatures. Mechanical wave attenuation coefficient (α) into the crystal was found. Also, first principle methodology in the framework of the density functional theory was utilized to confirm the electronic structure of Rochelle Salt. The results present high accuracy theoretical/experimental as well as a complete agreement with those known in the literature done by different methodologies.
关键词： Phase Transitions,Rochelle Salt Crystal,Piezoelectric Device,Ab Initio Simulation
更新于2025-09-23 15:22:29
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Terahertz Differential Computed Tomography: a Relevant Nondestructive Inspection Application
摘要： In recent years, tremendous advances have been made in the choice of materials used in the industry. With weight reduction as the goal, composite and polymer materials are more and more popular but they are almost transparent to X-ray. Because of this, interest has grown in other wavelengths like terahertz (THz). Due to a difference in how X-ray and THz propagate, X-ray CT algorithms cannot be directly used. For example, THz induces refraction making the reconstruction problem nonlinear. In this paper, we present a new algorithm which complies with beam profile intensities, refraction, and reflection. It is based on linearizing the reconstruction process around a computer-aided design (CAD) model of the object to be reconstructed. The method we propose computes the deviation between the object and this model.
关键词： Terahertz computed tomography,Inverse problem,Nondestructive testing,Modeling,Monte Carlo,Refraction,Nonlinear problem,Projection simulation
更新于2025-09-23 15:22:29
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Modeling the threshold voltage variation induced by channel random dopant fluctuation in fully depleted silicon-on-insulator MOSFETs
摘要： In nanoscale fully depleted silicon-on-insulator (FD-SOI) MOSFETs, the standard deviation of threshold voltage (σVth) caused by random dopant fluctuation (RDF) is an important parameter to predict the performance of transistors and circuits. In this paper, an analytic model of σVth considering both the dopant 'number' and dopant 'position' fluctuation in channels is proposed. A new model of σVth,num caused by 'number' is given and the method of obtaining the 'position' influence ratio Rp is discussed in this paper. Moreover, the simulation methods are analyzed in detail. The calculated σVth values in FD-SOI MOSFETs are compared with the Sentaurus TCAD simulation results at different channel lengths, channel doping concentrations, SOI film thicknesses, front gate oxide thicknesses, and buried-oxide thicknesses. The comparison shows that the proposed model matches well with the obtained numerical simulation results.
关键词： threshold voltage variation,analytical model,fully depleted silicon-on-insulator MOSFETs,Sentaurus TCAD simulation,random dopant fluctuation
更新于2025-09-23 15:22:29
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In vivo measurement of blood clot mechanics from computational fluid dynamics based on intravital microscopy images
摘要： Ischemia which leads to heart attacks and strokes is one of the major causes of death in the world. Whether an occlusion occurs or not depends on the ability of a growing thrombus to resist flow forces exerted on its structure. This manuscript provides the first known in vivo measurement of how much stress a clot can withstand, before yielding to the surrounding blood flow. Namely, Lattice-Boltzmann Method flow simulations are performed based on 3D clot geometries, which are estimated from intravital microscopy images of laser-induced injuries in cremaster microvasculature of live mice. In addition to reporting the blood clot yield stresses, we also show that the thrombus 'core' does not experience significant deformation, while its 'shell' does. This indicates that the shell is more prone to embolization. Therefore, drugs should be designed to target the shell selectively, while leaving the core intact to minimize excessive bleeding. Finally, we laid down a foundation for a nondimensionalization procedure which unraveled a relationship between clot mechanics and biology. Hence, the proposed framework could ultimately lead to a unified theory of thrombogenesis, capable of explaining all clotting events. Thus, the findings presented herein will be beneficial to the understanding and treatment of heart attacks, strokes and hemophilia.
关键词： Yielding,Blood,Simulation,Microscopy,Thrombus,Lattice Boltzmann Method
更新于2025-09-23 15:22:29
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Strain control of GaN grown on Si substrates using an AlGaN interlayer
摘要： To suppress wafer bowing and crack generation of GaN on Si substrates, we investigated the effects of the Al content and thickness of the AlGaN interlayer on the compressive strain in the overlying GaN layer theoretically and experimentally. In the simulation, AlGaN relaxes gradually over the critical thickness. Therefore, the relaxation ratio of AlGaN at the top surface can be defined as a function of Al content and thickness. Too high Al content or too thick AlGaN interlayer induced too large initial strain in the upper GaN layer, which caused rapid and succeeding gradual relaxation, i.e., decrease of strain, of the GaN layer during growth because of generation of threading dislocations. Conversely, low Al content or thin AlGaN interlayer could induce constant but only small strain in the GaN layer. Therefore, the ideal relaxation ratio of the AlGaN surface exists to apply the maximal constant compressive strain in the GaN layer. The relaxation ratios of AlGaN interlayers determined in experiments were much smaller than those calculated in the simulation. Although the measured compressive strain in the GaN layer was smaller than expected, its decrease rate was small when grown on AlGaN interlayers with an almost ideal relaxation ratio.
关键词： Computer simulation,Characterization,Metalorganic vapor phase epitaxy,Stresses,Growth models,Nitrides
更新于2025-09-23 15:22:29
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Study of energy and timing characteristics of 38.1mm?×?38.1mm CeBr3 scintillator detectors
摘要： We report the results of measurements and GEANT4 simulation for the performance of two 38.1mm × 38.1mm CeBr3 detectors. The linearity and energy resolution of both the detectors have been measured using low energy gamma sources in the range from 121.8 keV to 4.44 MeV. Maintaining the energy linearity condition, the best time resolution value of 423 ± 14 ps was measured for 1173–1332 keV photon pair from a 60Co source. A GEANT4 simulation was performed to reproduce the measured experimental spectrum and to estimate the absolute photopeak efficiencies at several energies up to 4.44 MeV.
关键词： Time resolution,GEANT4 simulation,Energy resolution,Scintillator,CeBr3
更新于2025-09-23 15:22:29
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The influence of Marangoni effect on the growth quality of multi-crystalline silicon during the vacuum directional solidification process
摘要： A multi-field coupling model of heat-flow-thermal stress was established to investigate the influence of Marangoni effect on the growth quality of multi-crystalline silicon (mc-Si) during the vacuum directional solidification (VDS) process. The simulation results showed that the Marangoni effect has a significant effect on the distribution of temperature and thermal stress as well during the VDS process due to the increased velocity of melts. The enhanced flow incurred more homogeneous temperature distribution of silicon melts and reduced radial temperature gradient, which then leads to the flatter solid/liquid (s/l) interface. However, as temperature gradient of the crystal increased, thermal stress of the silicon ingot was strengthened as a result. The growth quality of crystal was more desirable when adopting a pulling-down rate of 10 μm/s, in which case the (111) surface was advantageous throughout the entire crystal growth process by XRD detection. Finally, the reliability of the numerical simulation result was verified by the experiment.
关键词： Multi-crystalline,Melt flow,Vacuum directional solidification,Numerical simulation,Marangoni effect
更新于2025-09-23 15:22:29
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Perforating Freestanding Molybdenum Disulfide Monolayers with Highly Charged Ions
摘要： Porous single layer molybdenum disulfide (MoS2) is a promising material for applications such as DNA sequencing and water desalination. In this work, we introduce irradiation with highly charged ions (HCIs) as a new technique to fabricate well-defined pores in MoS2. Surprisingly, we find a linear increase of the pore creation efficiency over a broad range of potential energies. Comparison to atomistic simulations reveals the critical role of energy deposition from the ion to the material through electronic excitation in the defect creation process, and suggests an enrichment in molybdenum in the vicinity of the pore edges at least for ions with low potential energies. Analysis of the irradiated samples with atomic resolution scanning transmission electron microscopy reveals a clear dependence of the pore size on the potential energy of the projectiles, establishing irradiation with highly charged ions as an effective method to create pores with narrow size distributions and radii between ca. 0.3 and 3 nm.
关键词： 2D material,perforation,ion irradiation,MD simulation,molybdenum disulfide,highly charged ions,STEM
更新于2025-09-23 15:22:29
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Simulation of digital pixel readout chip architectures with the RD53 SystemVerilog-UVM verification environment using Monte Carlo physics data
摘要： The simulation and verification framework developed by the RD53 collaboration is a powerful tool for global architecture optimization and design verification of next generation hybrid pixel readout chips. In this paper the framework is used for studying digital pixel chip architectures at behavioral level. This is carried out by simulating a dedicated, highly parameterized pixel chip description, which makes it possible to investigate different grouping strategies between pixels and different latency buffering and arbitration schemes. The pixel hit information used as simulation input can be either generated internally in the framework or imported from external Monte Carlo detector simulation data. The latter have been provided by both the CMS and ATLAS experiments, featuring HL-LHC operating conditions and the specifications related to the Phase 2 upgrade. Pixel regions and double columns were simulated using such Monte Carlo data as inputs: the performance of different latency buffering architectures was compared and the compliance of different link speeds with the expected column data rate was verified.
关键词： Front-end electronics for detector readout,Simulation methods and programs,Pixelated detectors and associated VLSI electronics
更新于2025-09-23 15:22:29
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[IEEE 2018 IEEE International Ultrasonics Symposium (IUS) - Kobe, Japan (2018.10.22-2018.10.25)] 2018 IEEE International Ultrasonics Symposium (IUS) - Hierarchical Cascading in FEM Simulations of SAW Devices
摘要： Application of the finite element method (FEM) for the simulation of SAW devices has traditionally been constrained by the large number of degrees-of-freedom required, resulting in large memory usage and long computation times, and limiting the accuracy of the simulation. In this paper we review the recently introduced hierarchical cascading method, which offers drastically reduced memory consumption and simulation times in 2D simulations. In 3D, the advantages of hierarchical cascading are diminished due to the high number of cross-sectional degrees-of-freedom. As a partial solution to this problem, an iterative hierarchical cascading method is proposed, with reduced number of effective degrees-of-freedom. Examples of simulations of finite devices in 2D and of a periodic array in 3D are provided.
关键词： FEM,SAW simulation,SAW
更新于2025-09-23 15:22:29