GaAs功率MESFET输出线性度的改进

为了提高GaAs功率MESFET的输出线性度,器件有源层掺杂分布的改进是一种 有效的手段。本文探索了有源层掺杂分布与器件输出线性度之间的关系,提出了非均匀有源层掺杂分布模型。该模型将有源层划分成A,B两层,分别用N_dA(y)和N_dB(y)函数描述A,B层的掺杂分布,分布函数表示为: 结合GaAs FET分析模型,完成了有源层理论分布的计算、器件直流I—V特性的计算以及器件其它参数的计算,以便实现最佳的有源层掺杂分布。结果表明:双层尖峰型有源层掺杂分布是制造高输出线性度GaAs功率MESFET理想的掺杂分布。根据分析结果,在器件制造中用VPE生长方法获得了这种掺杂分布的外延材料,并设计制造了总栅宽为1200μm的GaAs功率FET。器件的直流I—V特性与理论分析结果相吻合,与均匀掺杂分布的器件相比较,实验器件的输出线性度得到了明显的改善,获得了良好的微波性能。微波性能测试结果为:     

无锡国际马拉松赛电视转播方案

本文简述了无锡国际马拉松赛的背景资料.重点就本次马拉松赛的电视转播方案进行了阐述.其中涉及到转播方案的模块组成、各模块之间的连接方式以及分别承担的作用.并就转播中的一些实际感受谈了谈自己的想法.主要涉及前期赛道准备的意义、EFP系统核心设备的选择及在该次转播中的使用方法,并对大型转播中各种传输方式的选择以及注意点阐述了自己的观点.     

Resonance in Defect Turbulence under Periodic External Force

The periodically forced spatially extended Brusselator is investigated in the chaotic regime. We explore resonant or non-resonant patterns generated under various forcing frequencies and forcing amplitudes. Resonant spatially uniform oscillation and irregular structures are found. Furthermore two types of regular spatial patterns are generated under appropriate parameters. Our results of numerical simulations demonstrate that periodic force can give rise to resonant patterns in forced systems of spatiotemporal chaos similar to the situation of forced systems of regular oscillations.     

粗糙核算子的加权弱(1,1)有界性

本文得到了Bochner-Ries:平均，R.} Fefferman型奇异积分，粗橄极大算子关于权}r卜的加权弱(1.1)有界性.     

测定核间距的不对称2D NOESY方法Ⅲ.从不对称2D NOESY重叠峰强度求取完整混合系数矩阵

建立了包括重叠峰在内的不对称2D NOESY峰强度来求取完整混合系数矩阵的方法。并应用数值模拟方法验证了其正确性。该方法充分利用了不对称2D NOESY重叠峰强度来求解完整混合系数矩阵,这对大分子体系中核间距的准确计算是有价值的。     

现代核磁共振方法测定核间距的新进展

现代核磁共振方法是目前研究和测定溶液中分子特别是生物大分子的三维空间结构的主要手段，而ＮＯＥ实验特别是二维ＮＯＥ实验测定分子中核间距则是其中最为关键的步骤。本文对二维ＮＯＥ实验测定核间距的基本原理、计算方法以及实验过程和这方面最新进展作了详细介绍。     

Noise effect in metabolic networks

Constraint-based models such as flux balance analysis (FBA) are a powerful tool to study biological metabolic networks. Under the hypothesis that cells operate at an optimal growth rate as the result of evolution and natural selection, this model successfully predicts most cellular behaviours in growth rate. However, the model ignores the fact that cells can change their cellular metabolic states during evolution, leaving optimal metabolic states unstable. Here, we consider all the cellular processes that change metabolic states into a single term `noise', and assume that cells change metabolic states by randomly walking in feasible solution space. By simulating a state of a cell randomly walking in the constrained solution space of metabolic networks, we found that in a noisy environment cells in optimal states tend to travel away from these points. On considering the competition between the noise effect and the growth effect in cell evolution, we found that there exists a trade-off between these two effects. As a result, the population of the cells contains different cellular metabolic states, and the population growth rate is at suboptimal states.     

Stochastic resonance in a financial model

We report on our model study of stochastic resonance in the stock market using numerical simulation and analysis,In the model,we take the interest rate as the external signal,the randomness of traders‘ behaviour as the noise,and the stock price as the output,With computer simulations.we find that the system demonstrates a characteristic of stochastic resonance as noise intensity varies,An analytical explanation is proposed.     

Social influence in small—world networks

We report on our numerical studies of the Axelrod model for social influence in small-world networks.Our simulation results show that the topology of the network has a crucial effect on the evolution of cultures .As the randomness of the network increases,the system undergoes a transition from a highly fragmented phase to a uniform phase.we also find that the power-law distribution at the transition point,reported by castellano et al,is not a critical phenomenon;it exists not only at the onset of transition but also for almost any control parameters,All these power-law distributions are stable against pertubations.A mean-field theory is developed to explain these phenomena.     

体贴入微的TEAC至尊数码影院TSP—1

TEAC作为我们熟知的东洋音响名家,其很多Hi-Fi产品为国内发烧友所称道,跟着市场大趋势,TEAC也出家庭影院套餐了,这就是本次的主角TSP—1至尊数码影院系统,她由DV-3100VK DVD机、AG—D9260NAV放大器与LS—F300主音箱、LS—S30环绕音箱以及LS—C30中置音箱构成,不仅配置完善、功能先进、效果出色,而且设计时尚,为一套不可多得的数码家庭影院系统。