紧凑等离子体环整体加速过程的数值计算

紧凑等离子体环（CT）应用广泛,可以作为聚变驱动源和脉冲X射线源等,对CT加速过程的研究是其应用方面研究的基础．描述了CT加速的基本原理,基于整体加速模型导出数值模拟方程组,采用四阶龙格-库塔法数值求解此方程组．根据Phillips实验室MARADUER的参数和SHIVA—STAR电容器组参数,对CT在同轴加速器内的加速过程进行了数值模拟,定量地分析了影响加速效率的各种因素．计算结果表明：CT的质量越大、加速器越长,加速效率越高,但加速效率存在饱和趋势;电感和电阻越小,加速效率越高;对于一定的电容器初始储能,电容值较小时加速效率越高．     

Protein stability for single substitution mutants and the extent of local compactness in the denatured state

The stability changes caused by single amino acid substitutionsare studied by a simple, empirical method which takes accountof the free energy change in the compact denatured state aswell as in the native state. The conformational free energyis estimated from effective inter-residue contact energies,as evaluated in our previous study. When this method is applied,with a simple assumption about the compactness of the denaturedstate, for single amino acid replacements at Glu49 of the tryptophansynthase subunit and at Ile3 of bacteriophage T4 lysozyme,the estimates of the unfolding Gibbs free energy changes correlatewell with observed values, especially for hydrophobic aminoacids, and it also yields the same magnitudes of energy as theobserved values for both proteins. When it is also applied foramino acid replacements at various positions to estimate theaverage number of contacts at each position in the denaturedstate from the observed value of unfolding free energy change,those values for replacements with Gly and Ala at the same residueposition in staphylococcal nuclease correlate well with eachother. The estimated numbers of contacts indicate that the proteinis not fully expanded in the denatured state and also that thecompact denatured state may have a substantially native-liketopology, like the molten globule state, in that there is aweak correlation between the estimated average number of contactsat each residue position in the denatured state and the numberof contacts in the native structure. These results provide somefurther evidence that the inter-residue contact energies asapplied here (i) properly reflect actual inter-residue interactionsand (ii) can be considered to be a pairwise hydrophobicity scale.Also, the results indicate that characterization of the denaturedstate is critical to understanding the folding process.     

碳纳米管场效应晶体管紧凑模型研究进展

随着摩尔定律逼近极限,碳纳米管场效应晶体管(CNTFET)被认为是5 nm以下CMOS晶体管的有力替代者。CNTFET具有准一维结构,栅极可有效控制导电沟道的导通/关断;同时,载流子在沟道内可实现近弹道输运,具有极高的迁移率。因此,CNTFET在低电压环境下,可提供较大的电流传输能力,为实现纳米级超大规模模拟/逻辑电路提供了解决方案。文章综述了CNTFET紧凑模型的发展现状,分析了现阶段面临的漏极电流精确模型、隧穿效应、寄生效应、多纳米管模型等存在的问题,重点探讨了针对这些问题的解决方案。最后对该紧凑模型未来的应用前景进行了讨论。     

宽阻带小型化双频带通滤波器

文中提出了一种具有宽阻带的紧凑型双频带通滤波器,它采用了折叠短路枝节负载谐振器、紧凑型微 带单元谐振器(CMRC)和阶跃阻抗谐振器结构。由于多个谐振器产生了五个可控传输零点(TZ),该滤波器实现了两个 通带之间的良好隔离度以及宽阻带特性。制作并测试了尺寸紧凑的双频带通滤波器实验样品,测试结果显示,第一通 带和第二通带的中心频率/ 插入损耗分别为0. 66 GHz/0. 8 dB 和1. 73 GHz/0. 7 dB,阻带频率高达10. 5 GHz,抑制水平 超过15 dB。     

宽频带圆极化缝隙螺旋天线的设计

研究了一种宽阻抗带宽和宽圆极化轴比带宽的缝隙螺旋天线。天线印制在由FR4 介质基板构建的 方形柱状结构的内外表面,两组长短不同的缝隙螺旋臂印制在介质基板外表面并延伸至天线顶部;一条弯折的微带 线作为馈电网络印制在介质基板内表面,通过对各缝隙耦合馈电,实现天线宽阻抗带宽和轴比带宽。实测结果表 明:天线尺寸为0. 111λ0 ×0. 111λ0 ×0. 221λ0(λ0 为北斗B2 中心频率1. 207 GHz 对应的自由空间波长),S11 ≤ -10 dB 的阻抗带宽为1. 158~1. 778 GHz,轴比≤3 dB 的圆极化带宽为1. 133~1. 918 GHz。该天线采用缝隙螺旋结构,通过 简易的馈电网络实现天线小型化和宽频带特性,在卫星导航系统中具有较好的应用前景。     

基于小户型住宅的一体式橱柜设计

目的研究在小户型住房空间下能满足人们需求的厨房橱柜。方法分析小户型居住人群需求特点、现代人生活的行为模式以及现代厨房所需的设备,运用家居产品的弹性设计理念和橱柜设计原则得出设计要素,在现有一体式橱柜的基础上进行外观、功能、结构等的改良、整合和再设计。结果一体式橱柜的概念设计集烹饪、清洗、储存一体化的系统设计于一体,紧凑的空间利用能适应小户型用户的使用需求,外观上需融入现代家装风格使其符合现代人的审美需求。结论小户型住宅的一体式橱柜相当于一个独立完整的厨房操作系统,在厨房有限的面积得到最大化利用的条件下,应给予该领域产品更多外观设计和概念化设计,为中国橱柜设计的发展提供参考。     

求解变系数对流扩散反应方程的指数型高精度紧致差分方法

本文给出了一种数值求解变系数对流扩散反应方程的指数型高精度紧致差分方法.我们首先将模型方程变形,借助常系数对流扩散方程的指数型高精度紧致差分格式,采用残量修正法得到变系数对流扩散反应方程的指数型高精度紧致差分格式;并从理论上分析了当Pelect数很大时,本文格式达到四阶计算精度时网格步长的限制条件;离散得到的代数方程组可采用追赶法直接求解.数值实验结果与理论分析完全吻合,表明了本文格式对于边界层问题或大梯度变化的物理量求解问题具有的高精度和鲁棒性的优点.     

社会网络中紧密度模型分析

针对社会网络中节点的复杂性,以及节点间关系的不确定性,本文采用中心性和凝聚子群对社会网络进行建模分析,并通过MATLAB进行仿真实验验证,从而在复杂的网络中选择出有效的中心节点。通过对节点的管理和利用,实现对整个社会网络管理的科学性,严谨性。通过模型的理论分析,我们可以设想该方法将对社会网络知识的传播,有效信息的发布,社会网络的稳定等起到有的放矢的作用。因而此研究具有良好的实践价值。     

A Compact Fourth-Order Finite Difference Scheme for Unsteady Viscous Incompressible Flows

In this paper, we extend a previous work on a compact scheme for the steady Navier–Stokes equations [Li, Tang, and Fornberg (1995), Int. J. Numer. Methods Fluids, 20, 1137–1151] to the unsteady case. By exploiting the coupling relation between the streamfunction and vorticity equations, the Navier–Stokes equations are discretized in space within a 3×3 stencil such that a fourth order accuracy is achieved. The time derivatives are discretized in such a way as to maintain the compactness of the stencil. We explore several known time-stepping approaches including second-order BDF method, fourth-order BDF method and the Crank–Nicolson method. Numerical solutions are obtained for the driven cavity problem and are compared with solutions available in the literature. For large values of the Reynolds number, it is found that high-order time discretizations outperform the low-order ones.     

A new coupled high-order compact method for the three-dimensional nonlinear biharmonic equations

This paper presents a new family of fourth- compact finite difference schemes for the numerical solution of three-dimensional nonlinear biharmonic equations using coupled approach. The numerical solutions of unknown variable and its first- derivatives as well as v(=Δ u) are obtained not only in the interior but also at the boundary. A prominent contribution of this work is that the boundary conditions for the variable v are approximated more accurately, which plays an important role for the efficiency of calculation. Finally, numerical experiments are conducted to verify the feasibility of this new method and the high accuracy of these schemes, including the steady Navier–Stokes equation in terms of vorticity-stream function formulation.