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[IEEE 2018 IEEE Asia-Pacific Conference on Antennas and Propagation (APCAP) - Auckland, New Zealand (2018.8.5-2018.8.8)] 2018 IEEE Asia-Pacific Conference on Antennas and Propagation (APCAP) - Wideband Metamaterial Antenna Design
摘要： This paper presents the design of composite right/left handed (CRLH TL) wideband metamaterial antenna. The bandwidth enhancement was achieved by replacing horizontal ohm’s shape slot with series horizontal slot. A comprehensive parametric analysis using Computer Simulation Technology CST software is carried out by varying the position of the slot Ln to determine the effectiveness of the concept and find the right position of the slot for obtaining the wideband. From the simulation work, it was found that the impedance bandwidth covered from 2.2 GHz to 4.6 GHz which is equivalent to 75% fractional bandwidth. The antenna has a compact size of 30 by 16.80 mm2. It has three different resonating bands at 2.6 GHz, 3.4 GHz and 4.5 GHz within the range with realised peak gain of 2.39 dBi, 2.41 dBi, and 3.22 dBi respectively and average efficiency of 95%.
关键词： wideband,metamaterial,composite right hand left hand transmission line,computer simulation technology (CST),bandwidth
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 (2017.10.21-2017.10.28)] 2017 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC) - Monte Carlo Simulation and Collimator optimization for Tomographic Gamma Scanning
摘要： We present the design and optimization of a Tomographic Gamma Scanning (TGS) collimator using Monte Carlo methods. In these simulations, an accurate TGS model was built and the radius, depth and shape of the TGS collimator were optimized. The simulation results reveal that the optimal collimator aperture radius and depth for this system are 3.1 cm and 18.6 cm, respectively, achieved when the full width at half-maximum (FWHM) is 26.7 cm. Also, a rotated 30° hexagon is found to be the optimal shape. Our TGS design shows significantly improved performance.
关键词： collimator optimization,Monte Carlo simulation,sensitivity,spatial resolution,Tomographic Gamma Scanning
更新于2025-09-04 15:30:14
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Research on Beam Emission Spectroscopy Combined HL-2A Tokamak Real Experimental Data With Spectra Simulation Code
摘要： A beam emission spectroscopy (BES) diagnostic system has been developed on HL-2A tokomak. Combined with motional Stark effect (MSE) diagnostics, the BES could assess the radial electric ?eld Er and the safety factor q, which play an important role in plasma control and impurity transport processes. A simulation of spectra (SOS) code has been developed for spectra simulations based on various tokamak devices’ real situations. It can be used for designing visible spectral diagnostics systems and predicting their performance. In this paper, based on the HL-2A real experimental running parameters, we used the SOS code to simulate BES and MSE spectra. These spectra were consistent with experimental data ?tting results. The SOS code was also able to get the safety factor q and other parameters. The results reveal that the SOS code could be used to design similar diagnostic systems for ITER in the future.
关键词： neutral beam injection (NBI) diagnostics,motional Stark effect (MSE),simulation of spectra (SOS),Beam emission spectroscopy (BES)
更新于2025-09-04 15:30:14
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Survey of Markov Chain Monte Carlo Methods in Light Transport Simulation
摘要： Two decades have passed since the introduction of Markov chain Monte Carlo (MCMC) into light transport simulation by Veach and Guibas, and numerous follow-up works have been published since then. However, up until now no survey has attempted to cover the majority of these methods. The aim of this paper is therefore to offer a first comprehensive survey of MCMC algorithms for light transport simulation. The methods presented in this paper are categorized by their objectives and properties, while we point out their strengths and weaknesses. We discuss how the methods handle the main issues of MCMC and how they could be combined or improved in the near future. To make the paper suitable for readers unacquainted with MCMC methods, we include an introduction to general MCMC and its demonstration on a simple example.
关键词： Light Transport Simulation,Markov Chain Monte Carlo,Metropolis-Hastings,STAR,Metropolis Light Transport
更新于2025-09-04 15:30:14
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[IEEE 2018 13th European Microwave Integrated Circuits Conference (EuMIC) - Madrid, Spain (2018.9.23-2018.9.25)] 2018 13th European Microwave Integrated Circuits Conference (EuMIC) - Design and Implementation of an Encapsulated GaN X-Band Power Amplifier Family
摘要： This paper describes the design and verification results of two wideband class AB High Power Amplifiers (PA), encapsulated in commercial packages. Both amplifiers designed on WIN Semiconductors’ 0.25 μm GaN on SiC technology. The selected GaN process features compact common-source (CS) transistor layouts with individual source grounding vias. The family spans the whole X-band frequency with the first design tuned between 7-11 GHz and the second design tuned between 10-12 GHz. Both designs have saturated power output greater than 25 W throughout the whole bandwidth with peak power added efficiency at 30%. A multistage power combining matching strategy to achieve a tradeoff in wideband performance and power output is given. In depth discussion of the MMIC design of the PAs is supported by a discussion of the thermal management of the packages, including the PCB design and active cooling methodology, in order to present a fully functional PA family.
关键词： pseudomorphic high electron mobility transistor (pHEMT),X-Band,wideband amplifiers,high efficiency,Power Amplifier (PA),thermal analysis,EM simulation,monolithic microwave integrated circuit (MMIC)
更新于2025-09-04 15:30:14
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NONLINEAR CHARACTERISTICS OF P-I-N DIODE CIRCUITS ANALYZED BY A PHYSICALLY BASED SIMULATION METHOD
摘要： Nonlinear characteristics of semiconductor devices play a key role in the performances of circuits, but their modelling is still a big challenge in circuit simulations nowadays. This paper explores modelling nonlinear characteristics of circuits containing semiconductor devices by presenting a modified physically based simulation method. A p-i-n diode microstrip circuit is taken as a sample, and its nonlinear characteristics, such as the power limiting, bistability, and forward recovery characteristics, are simulated and analysed. The applied method demonstrates its good capability and accuracy of modelling the nonlinear characteristics in the simulation, and moreover clarifies the underlying physical mechanisms. In contrast, the Advanced Design System (ADS) software, a popular circuit simulation program based on the equivalent circuit model, fails to reveal some of those nonlinear characteristics.
关键词： Nonlinear characteristics,microstrip circuit,p-i-n diode,semiconductor devices,physically based simulation method
更新于2025-09-04 15:30:14
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Numerical simulation of light propagation in metal-coated SNOM tips
摘要： Presented are the results of numerical simulations accomplished to investigate the propagation of electromagnetic excitations in certain types of metal-coated tapered tips terminating SiO2 multimode optical fibres with a subwavelength output aperture. The numerical simulations were initiated in order to enable better interpretation of previously reported experimental results concerning some features of the mesoscopic effect of spectral modulation observed for a broadband light transmitted by such tips. This effect occurs due to the interference between a small number of waveguide modes exiting a metal-coated tip, and the experimental results indicate a possible mode-selective photon-plasmon coupling in the studied tips. To match the experimental conditions, the tips were modelled for the light wavelength of 800 nm as three-layer systems (with the intermediate adhesion Cr layer and the outer layer of Al or Au). However, due to computational restrictions the end of a tip, only 18 μm long (most significant), was modelled. Numerical simulations yielded the dependences of propagation and attenuation constants on the fibre core radius for the most intensive (both photonic and plasmonic) output modes. The pairs of modes most probably contributing to the observed spectral modulation were identified. Although the simulations did not reveal any explicit mode coupling, the imperfections of real tips can cause mode transformations implying possible involvement of more than two modes. The thin (20 nm) Cr layer plays the main role for plasmonic modes generated on its SiO2 interface, which explains the small outer metal layer influence on the observed modal dispersion.
关键词： numerical simulation,multimode optical fibre,optics,spectral modulation,SNOM tip,plasmonics,photonics
更新于2025-09-04 15:30:14
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Variant Construction from Theoretical Foundation to Applications || Synchronous Property—Key Fact on Quantum Interferences
摘要： Double-slit experiment plays a key role in Quantum Theory to distinct particle and wave interactions according to Feynman’s claims. In this chapter, double path model and variant logic principle are applied to establish a simulation system for exhaustive testing targets. Using Einstein quanta interaction, different measure quaternion structures are investigated. Under Symmetry/Anti-symmetry and Synchronous/Asynchronous interaction conditions, eight groups of statistical results are generated as eight histograms to show their distributions. From this set of simulation results, it can be recognized that the synchronous condition is the key fact to generate quantum wave interference patterns and, in addition, the asynchronous condition is the key fact to make classic particle distributions. Sample results are illustrated and explanations are discussed.
关键词： Probability,Interaction,Double path,Simulation,Statistics
更新于2025-09-04 15:30:14
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[Springer Theses] Electrical Properties of Indium Arsenide Nanowires and Their Field-Effect Transistors || Influence of Different Growth Methods on the Electrical Properties of InAs Nanowires
摘要： In this chapter, we have studied the similarity and difference between the electrical properties of InAs nanowires grown by two commonly used material growth systems, MBE and MOCVD. Bases on the statistical data of more than 70 InAs nanowires back-gated FETs whose diameter range from 16 nm to more than 100 nm, we ?nd that when the diameter of InAs nanowires is relatively small, most of the MOCVD-grown InAs nanowires have similar electron mobility, threshold voltage, ON-state current, and OFF-state current with MBE-grown InAs nanowires. However, the dispersion of these electrical properties within the MOCVD-grown InAs nanowires is much larger than that within the MBE-grown nanowires. On the other hand, when the diameter of InAs nanowires is relatively large, the ON-state properties of MBE- and MOCVD-grown nanowires does not show obvious difference, but their OFF-state properties have apparently different features. The MOCVD-grown nanowires have smaller OFF-state resistance than the MBE-grown nanowires, and some of the large-diameter nanowires even show metallic behavior. By simulating the distribution of electrons under ON-state and OFF-state in the nanowires with various doping levels through the ?nite element model, we attribute the background carbon doping induced by the organic sources used in the growing procedures of MOCVD to be the main cause for the above differences. Our work has deepened the understanding of the relation between nanowire growth and device performance, and may be instructive for controlling the growth of InAs nanowires.
关键词： OFF-state current,Growth methods,Simulation of the distribution of electrons,Background carbon doping,ON-state current
更新于2025-09-04 15:30:14
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Molecular Modeling of CO2 and n-Octane in Solubility Process and α-Quartz Nanoslit
摘要： After primary and secondary oil recovery, CO2-enhanced oil recovery (EOR) has become one of the most mentioned technologies in tertiary oil recovery. Since the oil is confined in an unconventional reservoir, the interfacial properties of CO2 and oil are different from in conventional reservoirs, and play a key role in CO2 EOR. In this study, molecular dynamics simulations are performed to investigate the interfacial properties, such as interfacial tension, minimum miscibility pressure (MMP), and CO2 solubility. The vanishing interfacial tension method is used to get the MMP (~10.8 MPa at 343.15 K) which is in agreement with the reported experimental data, quantitatively. Meanwhile, the diffusion coefficients of CO2 and n-octane under different pressures are calculated to show that the diffusion is mainly improved at the interface. Furthermore, the displacement efficiency and molecular orientation in α-quartz nanoslit under different CO2 injection ratios have been evaluated. After CO2 injection, the adsorbed n-octane molecules are found to be displaced from surface by the injected CO2 and, then, the orientation of n-octane becomes more random, which indicates that and CO2 can enhance the oil recovery and weaken the interaction between n-octane and α-quartz surface. The injection ratio of CO2 to n-octane is around 3:1, which could achieve the optimal displacement efficiency.
关键词： molecular dynamics simulation,CO2-enhanced oil recovery,minimum miscibility pressure,α-quartz pore,n-octane
更新于2025-09-04 15:30:14