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61.
An approach to control the spurious currents in a multiphase lattice Boltzmann method and to improve the implementation of initial condition
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Sébastien Leclaire Nicolas Pellerin Marcelo Reggio Jean‐Yves Trépanier 《国际流体数值方法杂志》2015,77(12):732-746
Multiphase lattice Boltzmann methods are known to generate spurious or parasitic currents at the fluid–fluid interfaces. This nonphysical phenomenon has to be avoided, or at least controlled, in order to achieve reliable solutions. In this article, a method to control these fictitious velocities via lattice refinement is proposed, which is based on interface thickness control for which both the spurious currents and the physical fluid–fluid interface thickness vanishes as the spatial resolution increases. It has been found that a proper interface thickness adjustment is required as the lattice refinement is applied, or an increase in spurious currents, instead of a reduction, can occur. By combining the new method with an appropriate multiphase flow initialization, the overall stability for high density O(1000) and viscosity O(100) ratios is greatly improved. Although this research has been conducted with a Rothman and Keller type lattice Boltzmann model, it is believed that other types of multiphase lattice Boltzmann models could benefit from the basic ideas underlying this research. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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该次试验的目的是为了开发出85℃3000小时这种新的系列的焊片式铝电解电容器。为此,对该系列选取了最小电压200V的小容量和大容量,及最大电压450V的小容量和大容量的产品分别进行了设计和开发。开发过程中对阳极箔,阴极箔,电解纸,电解液等原材料进行了分析比较,并将四种设计分别做成产品并测试最薄弱的环节85℃3000小时的纹波电流试验,结果表明该系列的设计能很好地满足电性能要求。 相似文献
63.
Wideband LC balun transformer using coupled LC resonators embedded into organic substrate 总被引:1,自引:0,他引:1
Jong Cheol Park 《Microelectronics Journal》2009,40(11):1555-1560
In this paper, wideband LC balun using coupled LC resonator has been newly designed, simulated, and fabricated. The proposed balun has a novel scheme which consists of two pairs of coupled embedded LC resonators which share one resonator with each other. The coupled resonators are applied to provide a precise phase difference of 180° and an identical magnitude between two balanced ports and DC isolation characteristic with impedance transformation. Furthermore, proposed resonators have relatively small inductance values which can be easily embedded into the organic package substrate. In order to reduce the size of embedded capacitors, BTO composite high dielectric film was applied to increase their capacitance densities. The measured results of fabricated wideband balun exhibited an insertion loss of 1.8 dB, a return loss of 10 dB, a phase imbalance of 0.5°, and magnitude imbalance of 0.7 dB at frequency bandwidth of 700 MHz ranged from 1.8 to 2.5 GHz, respectively. They agreed well with the simulated ones. The fabricated balun has a relatively small volume of 2 mm×3.5 mm×0.66 mm (height). 相似文献
64.
关于电容器及电容教学思考 总被引:1,自引:0,他引:1
电容器及电容是"工程电磁场原理"学习静电场和恒定电场时遇到的一个知识点,教材通常先给出电容器的定义,然后直接给出电容表达式,没有推算过程及对结果的分析.本文通过场分布推导电容表达式,并举例对结果进行讨论,实践证明教学效果有所改善. 相似文献
65.
B. Goldstein 《辐射效应与固体损伤》2013,168(3-4):229-237
Single crystal silicon, both with and without oxygen, has been diffused with lithium to concentrations ~1017/cm2, irradiated with 1 to 1.5 MeV electrons, and the ensuing defects studies by EPR measurements. The presence of oxygen strongly affects the properties of these defects. Measurements have indicated the presence of two new defects which involve Li-one in O-containing material and one in O-free material. The defects are observed in their electron-filled state, and indicate a net electron spinof ½. The defect spectra disappear (with time) at room temperature, and can be explained by the formation of other Li-involved defects which lie deeper in the energy bandgap and are not visible by EPR. Electron irradiation at 40 °K followed by annealing at higher temperatures show that both EPR defects described above begin to form at about 200 °K and begin to decrease at about 275 °K-just as does the 250 °K reverse annealing observed generally for n-type Si. Based on these data, and the work of others, it is suggested that both defects form as a result of the motion of Si interstitials which produce a (Li-O-interstitial) complex in O-containing Si, and a (Li-interstitial) complex in O-free Si. 相似文献
66.
Richard Hahnkee KimSeok Ju Kang Insung BaeYeon Sik Choi Youn Jung ParkCheolmin Park 《Organic Electronics》2012,13(3):491-497
In this study, we investigated the molecular and microstructures of thin poly(vinylidene fluoride-chlorotrifluoro ethylene) (PVDF-CTFE) copolymer films with three different CTFE compositions of 10, 15, 20 wt% with respect to PVDF in relation with their ferroelectric properties. All PVDF-CTFE annealed at 130 °C showed consecutive TTTT trans conformation with β type crystals while films molten and re-crystallized from a temperature above their melting points exhibited α type crystals with characteristic TGTG conformation. Microstructures of the films treated with the two different thermal histories also supported the formation of β and α type crystals with hundreds of nanometer scale sphere caps and micron level spherulites, respectively. Interestingly, PVDF-CTFE films with both α and β type crystals gave rise to relatively high remnant polarization of approximately 4 μC/cm2 in metal/ferroelectric/metal capacitors regardless of the composition of CTFE. The ferroelectric polarization of a PVDF-CTFE film independent of thermal processing history allowed a wide processing window and easy fabrication protocol, resulting in a non-volatile ferroelectric field effect transistor memory which exhibited saturated hysteresis loops with the current ON/OFF ratio of approximately 103 at ±60 V sweep and reliable data retention. 相似文献
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69.
Stelios A. Mitilineos Anna E. Andreoudi Christos N. Capsalis 《Wireless Personal Communications》2006,38(4):421-433
Switched Parasitic Arrays (SPAs) are proposed as an attractive alternative to fully adaptive arrays, due to their compact size and significantly lower cost of development. The main concept of SPAs is the deployment of switches on parasitic elements, which can be properly adjusted, in order to effectively control the radiation pattern of one active element. Conventional SPAs consist of circular arrays of vertically polarized dipoles and parasitic elements. In this paper, a novel SPA design is proposed, which is based on multiple switches employed on the body of horizontally polarized elements (one active and two parasitics). Design considerations are discussed and numerical results are illustrated. Furthermore, a simple diversity scheme is proposed, based on the novel SPA design. Superior performance of the proposed array, relative to simple non-diversity reception schemes, is indicated by simulation results.
Stelios A. Mitilineos was born in Athens, Greece, in 1977. He received the Diploma in electrical and computer engineering from the National Technical University of Athens (NTUA), Greece, in October 2001. He is currently working towards his Ph.D. degree in electrical engineering at the same university. His research interests include antennas and propagation, smart antennas and mobile communications, channel estimation and location detection algorithms, MIMO systems and microwave components.
Anna E. Andreoudi was born in Thessalonica, Greece, in 1977. She received the Diploma in electrical and computer engineering from the National Technical University of Athens, in 2004. Her research interests include electromagnetic waves propagation and scattering, antenna design and adaptive arrays, wireless communications and wireless mobile networks.
Christos N. Capsalis was born in Nafplion, Greece in 1956. He received the Diploma in electrical and mechanical engineering from the National Technical University of Athens in 1979 and the B.S. degree in economics from the University of Athens in 1983. He obtained the Ph.D. degree in electrical engineering from NTUA in 1985. He is currently a Professor at the department of Electrical and Computer Engineering in NTUA. His current scientific activity concerns satellite and mobile communications, antenna theory and design, and electromagnetic compatibility. 相似文献
70.
提出了由AT89C51单片机控制增益和截至频率的低通滤波器设计方案.采用测量放大器和开关电容滤波器构成功能部件,重点讨论了基于开关电容滤波芯片和非易失性数字电位器实现截止频率和增益多档位调节的新方法。 相似文献