随机耦合对人为反向耦合的影响

采用密度矩阵方法描述了两模反向耦合.在两模反向耦合情况下,用随机畸变的功率耦合系数(即模混合系数)对密度矩阵运动方程作了修正,并获得了修正后方程的精确解析解的表达式.     

非保守耦合系统的耦合损耗因子

研究利用子结构的导纳计算非保守耦合系统的耦合损耗因子的方法。首先,利用经典保守耦合系统统计能量分析能量平衡方程的形式,推导了非保守耦合系统中耦合损耗因子与结构振动能量比的关系;然后,给出了利用子结构的导纳计算结构振动能量比的方法;最后,实验测量了非保守耦合系统的耦会损耗因子,并与理论预测值比较。结果表明,理论预测和实验测量结果的一致性很好。     

从LS耦合到jj耦合的过渡

以两个光学电子的原子的ｓｐ和ｐ＾２组态为例,分析了由于电子自旋－轨道磁相互作用相对于静电相互作用的增强而导致原子状态的角动量从ＬＳ耦合过渡到ｊｊ耦合。     

基于通用型耦合方法蒙特卡罗核热耦合

在自主堆用蒙卡程序RMC内部开发的热工水力子通道功能模块 RMC-TH以及蒙特卡罗几何栅元计数器的基础上,研究并开发了通用型内耦合接口。与传统依赖文件传递信息的外耦合相比,该耦合方式对两种物理过程使用统一的输入文件,利用重复结构热工反馈栅元展开技术,可以实现物理-热工大规模几何模型的快速内部对应,突破了以往核热耦合程序通用性的限制；截面更新方面,采用在线多普勒展宽法（OTF）实现温度对中子截面的反馈作用。该方法只需加载0 K的截面库,可以降低对计算机内存的需求,提高计算效率。以单棒及典型压水堆PWR1717组件为例,对核热耦合过程进行了稳态模拟分析,结果证明了内耦合方法的可行性、正确性及高效性。     

电荷耦合器件

应广大读者的要求，我们组织了光电接收器件专集，分两期刊登．为适应各类读者的需要，本专集介绍了各种光电接收器件的原理、性能、使用体会和注意事项，并附有部分国内外资料．有些光电接收器件已比较成熟，但至今仍在各个领域内广泛地应用，对此，我刊也将以一定篇幅加以介绍．本期刊登的集成光电接收器件是一个比较新的专题，以后将刊登光电倍增管、热电接收器件、各种分立半导体接收器件等专题．     

间接耦合机械结构之间的耦合损耗因子

本文利用双端口法推导了强耦合或相互处于振动波近场范围内的机械结构中间接耦合结构之间的耦合损耗因子的计算公式。用考虑了间接耦合损耗因子的修正统计能量分析的能量平衡方程预测了转动机械结构响应，预测结果与实验测量结果之间的一致性优于用经典统计能量分析法预测的振动响应。     

耦合团方法

无论液体还是固体.无论原子、分子还是原子核,都是相互作用的多体系统,即使一个核子也可以看成一个多体系统,因为它们是由通过胶子作用的三个夸克所组成的,而且量子场论中还可能存在真空态产生多粒子虚激发.表1列出了一些多粒子系统.许多这种系统都存在某些我们不能直接根据其组分和粒子间相互作用导出的性质,例如固体中的超导、核聚变等.需要有一些新观念才能理解这些现象.多体物理是理论物理的一个分支,它主要研究多体系统中基本成分间的相互作用所产生的新现象,并提供对这些新性质进行计算的新方法. 量子力学建立不久.狄喇克和海森伯关于…     

非线性耦合对线性耦合同步的调制研究

基于李亚普诺夫稳定性理论,构造了指数型的李亚普诺夫函数,以四变量的Chen超混沌系统为例,解析地证明了线性耦合实现同步的可靠性．进一步研究了非线性耦合对线性耦合同步的调制作用．基于无量纲化的动力学方程定义一个统计函数来估算控制器的消耗功率,确定了线性耦合与非线性耦合实现同步对应的参数范围,数值计算结果验证了理论结果的可靠性．     

ΔπN耦合以及πNN耦合的计算

通过相对论夸克模型并结合介子云的贡献 ,计算了ΔπN耦合常数以及πNN耦合常数 .计算结果表明了介子云对Δ( 1 2 3 2 )共振态的性质的重要作用 .由此可以明显地看出介子云在低能区的效应     

ΔπN耦合以及πNN耦合的计算

通过相对论夸克模型并结合介子云的贡献,计算了ΔπN耦合常数以及πNN耦合常数.计算结果表明了介子云对Δ(1232)共振态的性质的重要作用.由此可以明显地看出介子云在低能区的效应.     

CFD modeling of a biogas fuelled SOFC

Mathematical modeling of transport and electrochemical phenomena within SOFCs can lead to improved understanding of the involved physical, electrical, and chemical processes and represents a powerful tool for their development. In this context, the present work illustrates a three-dimensional CFD simulation of a planar SOFC unit cell fuelled by modeled biogas/steam mixtures. The simulations estimate the distribution of gas species, the current densities and the potentials, as well as the temperature gradients and confirm that equimolar CH₄/CO₂ biogas leads to improved performance, while minimal steam addition can prevent carbon deposition.     

Electrochemical open circuit voltage (OCV) characterization of SOFC materials

In this paper, we are reporting an extensive characterization, by means of open circuit voltage measurements, of Ce_0.8Gd_0.2O₂, La_0.9Sr_0.1Ga_0.8Mg_0.2O₃, and La₂Mo_0.6W_1.4O₉ oxide-ions and BaCe_0.8Y_0.2O₃ and BaCe_0.55Zr_0.3Y_0.15O₃ proton-conducting electrolyte materials for solid oxide fuel cell (SOFC) applications. This simple and common technique, well known for a long time in the electrochemical study of solid oxide fuel cells, has been here proposed for the electrical characterization of these ceramic materials, in order to define their ionic transport numbers, the maximum voltage performances, the thermal and chemical stability, and also to suggest the ideal temperature range for different applications, as in the electrochemical devices, sensors, and SOFC field. In the paper, controlled and reproducible working conditions have been applied in a wide range of temperature, by means of ultrapure gas (H₂ and O₂), under operational conditions found in real SOFC devices and, mainly, without the usual problems related to the chemical compatibility, the depolarization efficiency, and the high current density required to the electrode materials in the design of a more efficient SOFC device.     

The study on two-dimensional analytical model for gate stack fully depleted strained Si on silicon-germanium-on-insulator MOSFETs

Based on the exact resultant solution of two-dimensional Poisson’s equation in strained Si and Si1-X GeX layer, a simple and accurate two-dimensional analytical model including surface channel potential, surface channel electric field, threshold voltage and subthreshold swing for fully depleted gate stack strained Si on silicon-germanium-on-insulator (SGOI) MOSFETs has been developed. The results show that this novel structure can suppress the short channel effects (SCE), the drain-induced barrier-lowering (DIBL) and improve the subthreshold performance in nanoelectronics application. The model is verified by numerical simulation. The model provides the basic designing guidance of gate stack strained Si on SGOI MOSFETs.     

基于多物理场模拟的阳极支撑微管燃料电池的结构优化设计

High volumetric power density (VPD) is the basis for the commercial success of micro-tubular solid oxide fuel cells (mtSOFCs). To find maximal VPD (MVPD) for anode-supported mtSOFC (as-mtSOFC), the effects of geometric parameters on VPD are analyzed and the anode thickness, t_an, and the cathode length, l_ca, are identified as the key design parameters. Thermo-fluid electrochemical models were built to examine the dependence of the electrical output on the cell parameters. The multiphysics model is validated by reproducing the experimental I-V curves with no adjustable parameters. The optimal l_ca and the corresponding MVPDs are then determined by the multiphysics model for 20 combinations of r_in, the inner tube radius, and t_an. And all these optimization are made at 1073.15 K. The results show that:(i) significant performance improvement may be achieved by geometry optimization, (ii) the seemingly high MVPD of 11 and 14 W/cm³ can be easily realized for as-mtSOFC with single-and double-terminal anode current collection, respectively. Moreover, the variation of the area specific power density with l_ca2(2 mm, 40 mm) is determined for three representative (r_in, t_an) combinations. Besides, it is demonstrated that the current output of mtSOFC with proper geometric parameters is comparable to that of planar SOFC.     

High oxide ion conductivity in Fe and Mg doped LaGaO3 as the electrolyte of solid oxide fuel cells

La(Sr)Ga(Fe,Mg)O₃ exhibited the high oxide ion conductivity and the electrical power generating property of SOFC single cell using La_0.7Sr_0.3Ga_0.7Fe_0.2Mg_0.1O_3-δ (LSGFM) electrolyte was investigated in this study. The transport number of oxide ion is almost 0.8 in LSGFM and so open circuit potential (OCV) is as low as 0.8 V. OCV was strongly affected by anode materials and the highest OCV was achieved on Ni–Fe bimetallic anode. The extremely high power density was achieved by using LSGFM for electrolyte of SOFC. The maximum power densities of the cells can be elevated by coating with oxide ion conductor film at anode side. The maximum power density increased in the following order for coating film: LSGM > SDC > YSZ. The maximum power density of 197 and 100 mW/cm² can be achieved at 873 and 773 K, respectively, when LSGM film deposited on the anode side of LSGFM. Therefore, LSGFM can be used as electrolyte of SOFC operating at intermediate temperature.     

Modeling light trapping and electronic transport of waffle-shaped crystalline thin-film Si solar cells

Monocrystalline Si films from the novel perforated-Si process are candidates for the fabrication of thin-film solar cells because their waffle shape enhances the optical absorption and hence permits the use of films with a thickness of only a few microns. We study the optics of waffle cells by three-dimensional Monte Carlo ray-tracing. A high photogeneration of 38 mA/cm² from a film of thickness W_f=4 μm is possible due to a detached Al-back surface reflector that has an effective reflectance of 99.7% at 1250 nm. Our analytical model for light trapping in thin films explains this high reflectance. Two-dimensional numerical transport modeling reveals the existence of an optimum texture period p≈2W_f that originates from a carrier collection efficiency that increases with texture period while the photogeneration decreases with period. For well-passivated cells the optimum thickness W_f is at least one fifth of the diffusion length L. Efficiencies of 17% to 18% are feasible with waffle films of 1 to 3 μm in thickness. We introduce an analytic model for the minority carrier transport that agrees with two-dimensional numerical modeling to within 10% and reduces the computation time by orders of magnitude. This analytic model is also applicable to conformal thin-film geometries differing from the waffle geometry. Received: 1 March 1999 / Accepted: 28 March 1999 / Published online: 24 June 1999     

Al2O3钝化及其在晶硅太阳电池中的应用

介绍了Al₂O₃的材料性质及其原子层沉积制备方法, 详细阐述了该材料的钝化机制(化学钝化和场效应钝化), 并从薄膜厚度、热稳定性及叠层钝化等角度阐释其优化方案. 概述了Al₂O₃钝化在晶体硅太阳电池中的应用, 主要包括钝化发射极及背面局部扩散电池和钝化发射极及背表面电池. 最后, 对Al₂O₃钝化工艺的未来研究方向和大规模的工业应用进行了展望.     

Remarks on optimized predictions for the Drell-Yan process

We discuss the optimization of the Drell-Yan pair production cross section calculated atO(α _s ) and compare it with theO(α _s ² ) results of van Neerven et al. It is shown that the optimized predictions do agree analytically with the latter calculation near the phase space boundary. They also provide a good numerical approximation wherever the stability equations have a solution.     

Validation of a lattice Boltzmann model for gas–solid reactions with experiments

A lattice Boltzmann method is used to model gas–solid reactions where the composition of both the gas and solid phase changes with time, while the boundary between phases remains fixed. The flow of the bulk gas phase is treated using a multiple relaxation time MRT D3Q19 model; the dilute reactant is treated as a passive scalar using a single relaxation time BGK D3Q7 model with distinct inter- and intraparticle diffusivities. A first-order reaction is incorporated by modifying the method of Sullivan et al. [13] to include the conversion of a solid reactant. The detailed computational model is able to capture the multiscale physics encountered in reactor systems. Specifically, the model reproduced steady state analytical solutions for the reaction of a porous catalyst sphere (pore scale) and empirical solutions for mass transfer to the surface of a sphere at Re = 10 (particle scale). Excellent quantitative agreement between the model and experiments for the transient reduction of a single, porous sphere of Fe₂O₃ to Fe₃O₄ in CO at 1023 K and 10⁵ Pa is demonstrated. Model solutions for the reduction of a packed bed of Fe₂O₃ (reactor scale) at identical conditions approached those of experiments after 25 s, but required prohibitively long processor times. The presented lattice Boltzmann model resolved successfully mass transport at the pore, particle and reactor scales and highlights the relevance of LB methods for modelling convection, diffusion and reaction physics.     

Material transport and degradation behavior of SOFC interconnects

The SOFC interconnect materials, both lanthanum chromite based oxides and Fe–Cr ferritic alloys, are discussed from the viewpoint of material transport which causes the degradation in conductivity or chemical stability. The controlling factors, such as effect of oxygen chemical potential gradient, interaction with other cell components, and surrounding gaseous atmospheres are evaluated. The role grain boundary is important in the transport of metal components in oxide materials such as lanthanum chromites, or oxide scales on alloy. The diffusivity of metal components in alloy is much faster, which causes the interdiffusion on nickel and chromium between alloy and anode current collector. The reaction of alloy and sealing materials would be more significant, since the chromium component in alloy easily reacts with alkaline earth components in sealing materials. The slight amount of water vapor in air may greatly enhance the chromium vaporization rate from chromium oxide (Cr₂O₃).