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Analysis of Secondary Photons Emergent from Combined Material Slab as a Function of Slab Thickness
摘要： Material science is very important for developing the linear accelerator. Determination and understanding of material behavior face to X-rays is a basic study for photon beam modifiers improvements. In this study, the 6 MV photon beams produced by Varian Clinac 2100 was modelled by Monte Carlo simulation using BEAMnrc code and thereafter the flattening filter was replaced by a slab of aluminum and copper separately and by slab of both materials combined together with different thickness of 2.5, 5, 7.5, and 10 mm. The purpose of this study is to investigate the scattered photons with thickness of combined material slab as a function of off-axis distance. The scattered photons increased with thickness of copper alone slab, combined aluminum-copper slab and copper-aluminum slab, but for aluminum alone slab they decreased with slab thickness. The stacking order of these two materials affects the characterization of scattered photons emergent from material slab with thickness. The combination of materials and the manner that the stacking was done affects the scattered photons production. The material combination could improve the radiotherapy efficiency in beam modifier development using more than two materials.
关键词： Monte Carlo simulation,BEAMnrc code,scattered photons,copper slab,aluminum slab,BEAMDP code
更新于2025-09-04 15:30:14
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Finite Element Simulation of Temperature and Stress Field for Laser Cladded Nickel-Based Amorphous Composite Coatings
摘要： In this paper, a nickel-based amorphous composite coating was obtained on the carbon steel surface by the laser cladding process. The thermal ?eld and stress distribution were simulated by using ANSYS ?nite element software where the moving heat source and powder feeding were modelled by the “Element birth and death” method. The simulation results were veri?ed by comparing the cross-sectional pro?le of fusion lines and X-ray stress measurements, respectively. The results on thermal ?eld showed that the cooling rate of the coating could reach up to 10389.15 K/s and it gradually decreased from the outside surface to the interior, which promoted the formation of amorphous phase. The simulated stress ?eld showed that the coating was in the state of tensile stress after cladding and the longitudinal stress was larger than the transverse stress. The coating was experienced with tensile plastic deformation along the laser scanning direction, which resulted in longitudinal residual stress. A higher stress concentration was occurred between the coating layer and substrate, which increased the susceptibility of crack formation. The test results on transverse residual stress were generally consistent with the simulation. On the contrary, the measured longitudinal stress was nearly close to zero, which was not in agreement with the model due to the formation of cracks.
关键词： stress ?eld,temperature ?eld,laser cladding,amorphous,numerical simulation
更新于2025-09-04 15:30:14
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Enhanced etching of tin-doped indium oxide due to surface modification by hydrogen ion injection
摘要： It is known that the etching yield (i.e., sputtering yield) of tin-doped indium oxide (ITO) by hydrocarbon ions (CHx+) is higher than its corresponding physical sputtering yield [H. Li et al., J. Vac. Sci. Technol. A 33, 060606 (2015)]. In this study, the effects of hydrogen in the incident hydrocarbon ion beam on the etching yield of ITO have been examined experimentally and theoretically with the use of a mass-selected ion beam system and by first-principles quantum mechanical (QM) simulation. As in the case of ZnO [H. Li et al., J. Vac. Sci. Technol. A 35, 05C303 (2017)], mass-selected ion beam experiments have shown that the physical sputtering yield of ITO by chemically inert Ne ions increases after a pretreatment of the ITO film by energetic hydrogen ion injection. First-principles QM simulation of the interaction of In2O3 with hydrogen atoms shows that hydrogen atoms embedded in In2O3 readily form hydroxyl (OH) groups and weaken or break In–O bonds around the hydrogen atoms, making the In2O3 film less resistant to physical sputtering. This is consistent with experimental observation of the enhanced etching yields of ITO by CHx+ ions, considering the fact that hydrogen atoms of the incident CHx+ ions are embedded into ITO during the etching process.
关键词： quantum mechanical simulation,sputtering yield,tin-doped indium oxide,hydrogen ion injection,physical sputtering,ITO,etching yield,In2O3,hydrocarbon ions,hydroxyl groups
更新于2025-09-04 15:30:14
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Performance of resonant tunneling diodes based on the nonpolar-oriented AlGaN/GaN heterostructures
摘要： The performance of resonant tunneling diodes (RTDs) based on nonpolar-oriented AlGaN/GaN heterostructures has been theoretically investigated by numerical simulation. Simulation results show that the RTDs grown along the nonpolar orientation can yield the current–voltage (I–V ) characteristics with the peak current, the peak-to-valley ratio (PVCR), and the peak voltage of about 3.5 times and 1.5 times higher and 1.1 times lower than those of RTDs grown along the conventional polar orientation, respectively. The results also show excellent symmetry, high reproducibility of I–V characteristics, and high intrinsic response frequency.
关键词： current–voltage characteristics,resonant tunneling diodes,numerical simulation,AlGaN/GaN heterostructures,nonpolar orientation
更新于2025-09-04 15:30:14
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Effect of elastomer characteristics on fiber optic force sensing performance in biomedical robotics applications
摘要： Miniaturized and “smart” sensors are required for research in biology, physiology, and biomechanics, and they have extremely important clinical applications for diagnostics and minimally invasive surgery. Fiber optic sensors have been proven to provide advantages compared to conventional sensors and high potential for biomechanical and biomedical applications. They are small, easy to operate, minimally invasive with low risk, more accurate, and inexpensive. This paper reports the design and modeling of a fiber optic force sensor that is capable of measuring compliance for a contact force of up to 1 N. The main objective of this study is to design and model a fiber optic sensor capable of measuring the total force applied on an object. A polydimethylsiloxane (PDMS) elastomer film with a thickness of 1.2 mm is placed between an optical fiber tip and an object, and it is used for measuring the force applied on a rigid element. The compliance of the fiber optic force sensor is measured by recording the response of PDMS elastomer films under different load conditions. We use finite element modeling results as a basis for comparing experimental data. The agreement between theoretical predictions and experimental data is reasonable and within an acceptable range.
关键词： Force sensor,FEM analysis,Optical fiber,Elastomer,MATLAB analysis,LabVIEW,ANSYS simulation,Biomedical robotics
更新于2025-09-04 15:30:14
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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Low-Cost Multi-Objective Optimization of Antennas By Means Of Generalized Pareto Ranking Bisection Algorithm
摘要： This paper introduces a generalized Pareto ranking bisection algorithm for low-cost multi-objective design optimization of antenna structures. The algorithm allows for identifying a set of Pareto optimal sets of parameters (that represent the best trade-offs between considered objectives) by iterative partitioning of the intervals connecting previously found designs and executing a Pareto-ranking-based poll search. The initial approximation of the Pareto front found using the bisection procedure is subsequently refined to the level of the high-fidelity EM model of the antenna at hand using local optimization. A serious limitation of the original bisection algorithm was that only two objectives could be considered. The generalized version proposed here allows for handling any number of design goals. An improved poll search procedure has also been developed and incorporated. Our algorithm has been demonstrated using an example of a UWB monopole antenna with three figures of interest taken into account: structure size, reflection response, and gain variability.
关键词： Antenna design,simulation-driven design,variable-fidelity simulations,generalized bisection algorithm,multi-objective optimization,Pareto ranking
更新于2025-09-04 15:30:14
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[IEEE 2018 - 3DTV-Conference: The True Vision - Capture, Transmission and Display of 3D Video (3DTV-CON) - Helsinki (2018.6.3-2018.6.5)] 2018 - 3DTV-Conference: The True Vision - Capture, Transmission and Display of 3D Video (3DTV-CON) - VIEWING SIMULATION OF INTEGRAL IMAGING DISPLAY BASED ON WAVE OPTICS
摘要： We present an accurate model of integral imaging display based on wave optics. The model enables accurate characterization of the display through simulated perceived images by the human visual system. Thus, it is useful to investigate the capabilities of the display in terms of various quality factors such as depth of field and resolution, as well as delivering visual cues such as focus. Furthermore, due to the adopted wave optics formalism, simulation and analysis of more advanced techniques such as wavefront coding for increased depth of field are also possible.
关键词： point spread function,wave optics,Integral imaging,simulation
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE 14th International Conference on Automation Science and Engineering (CASE) - Munich, Germany (2018.8.20-2018.8.24)] 2018 IEEE 14th International Conference on Automation Science and Engineering (CASE) - Simulation-based Performance Assessment of Tool Requalification Strategies in Wafer Fabs
摘要： In this paper, we discuss requalification strategies for stepper tools in semiconductor wafer fabrication facilities (wafer fabs). Before processing lots on steppers, the steppers have to be qualified. A mathematical programming formulation is used periodically to determine appropriate qualification plans. These plans will be implemented at the shop-floor. Dur-ing consecutive planning epochs, certain already established qualifications of steppers can be canceled, for instance, due to stepper breakdowns. We study the performance of several re-qualification strategies in this situation. Therefore, we use a discrete-event simulation framework that allows for applying the mathematical programming formulation in a rolling hori-zon manner and for performing the requalification strategies while the production is executed in the simulation. We demon-strate by designed simulation experiments that some of the pro-posed strategies perform well with respect to throughput and cycle time while requiring only a low additional qualification effort.
关键词： semiconductor wafer fabrication,mathematical programming,discrete-event simulation,requalification strategies,stepper tools
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE International Conference on Imaging Systems and Techniques (IST) - Krakow, Poland (2018.10.16-2018.10.18)] 2018 IEEE International Conference on Imaging Systems and Techniques (IST) - Measurement of External-Solids Circulation Flux in a Circulating Fluidized Bed by Electrical Capacitance Tomography and Microwave Doppler Radar
摘要： In a gas-solids circulating fluidized bed (CFB), the external-solids circulating flux (Gs) has important effect on the mass and heat transfer inside the CFB system. To improve the process operation efficiency and reduce the emission of pollution, it is important to accurately measure Gs. In this paper, the authors proposed a new approach to measuring Gs using electrical capacitance tomography (ECT) and microwave Doppler radar (MDR) velocity meter based on a lab-scale CFB system with multi-cyclone separators. The ECT sensor is used to get the solids volume fraction in the cross section of the standpipe and MDR is used to measure the averaged solids velocity along the standpipes. Based on those two values, Gs can be addressed. Meanwhile, computation particle fluid dynamic (CPFD) is used to investigated the gas-solids flow hydrodynamic characteristics and verified the measurement results.
关键词： CPFD simulation,Microwave Doppler radar,External-Solids Circulating flux,Electrical capacitance tomography
更新于2025-09-04 15:30:14
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Modification of the Optical and Electronic Properties of TiO2 By N Anion-Doping for Augmentation of the Visible Light Assisted Photocatalytic Performance
摘要： In this work, a nitrogen-doped anatase TiO2 nanocrystal is prepared by a modified sol-gel preparation method using the nonionic surfactant (polyoxyethylene sorbitan monooleate) as a structural controller and a soft template. The as-prepared samples are characterized by X-ray diffraction, Raman spectroscopy, UV-Vis diffuse reflectance spectroscopy, and X-ray photoelectron spectroscopy techniques. Then the photocatalytic activity of these samples is assessed by the photocatalytic oxidation of phenol under visible light irradiation. The phenol concentration is measured using a UV-Vis spectrometer. Experimental results show that N-doping leads to an excellent visible light photocatalytic activity of the TiO2 nanocatalyst. Furthermore, the formation energy and electronic structure of pure and N-doped anatase TiO2 are described by density functional theory (DFT) calculations. It is found that N-doping narrowed the band gap of bare TiO2, which leads to an excellent visible light photocatalytic activity of N–TiO2 nanocatalysts. Therefore, the prepared N–TiO2 photocatalyst is expected to find the use in organic pollutant degradation under solar light illumination.
关键词： nitrogen doping,DFT simulation,photocatalysis,titania
更新于2025-09-04 15:30:14