能量包线随机平均法在双线性迟滞系统随机响应分析中的应用

 本文将能量包线随机平均法应用于分析单自由度双线性迟滞系统对白噪声激励的随机响应,详细分析了位移、速度及总能量的平稳响应各统计量随系统粘性阻尼、次斜率及激励强度的变化。解析结果与数字模拟结果比较表明,该方法优于迄今为止用于双线性迟滞系统随机响应分析的其他近似方法。     

Effects of the position of the solar wind termination shock and the heliopause on the heliospheric modulation of cosmic rays

The effects of changing the position of the solar wind termination shock and the position of the heliopause, and therefore the extent of the heliosheath, on the modulation of cosmic ray protons are illustrated. An improved numerical model with diffusive termination shock acceleration, a heliosheath and drifts is used. The modulation is computed in the equatorial plane and at 35 heliolatitude using recently derived diffusion coefficients applicable to a number of cosmic ray species during both magnetic polarity cycles of the Sun. It was found that qualitatively the modulation results for the different heliopause positions are similar although they differ quantitatively, e.g., clearly different radial gradients are predicted for the regions beyond the termination shock compared to inside the shock. The difference between the modulation for the two solar polarity cycles are less significant at a heliolatitude of 35° than in the equatorial plane. We found that moving the termination shock from 90 to 100 AU, with the heliopause fixed at 120 AU, caused only quantitative differences so that the exact position of the TS in the outer heliosphere seems not crucially important to global modulation. Moving the heliopause outwards, to represent the modulation in the tail region of the heliosphere, causes overall decreases in the cosmic ray intensities but not linearly as a function of energy, e.g., at 1 GeV the effect is insignificant. We conclude from this modelling that the modulation of protons in the heliospheric nose and tail regions are qualitatively similar although, clear quantitative and interesting differences occur.     

三能级原子和两个压缩态光场多光子相互作用中的量子效应

本文研究了具有A型跃迁结构的三能级原子与两个压缩态光场多光子相互作用过程中的一些量子效应。通过数值计算得到不同参数条件下原子能级布居数反转的时间特性,光场平均光子数及其统计性质的时间演化,并讨论了多光子过程对加深光场压缩状态的影响。计算结果表明,多光子相互作用使系统的基本Rabi振荡频率增大,崩坍—复原持续期缩短,Mandel参数的改变加剧,光场的压缩增强。     

New results on planetary lightning

We present the latest observations from spacecraft and ground-based instruments in search for lightning activity in the atmospheres of planets in the solar system, and put them in context of previous research. Since the comprehensive book on planetary atmospheric electricity compiled by Leblanc et al. (2008), advances in remote sensing technology and telescopic optics enable detection of additional and new electromagnetic and optical emissions, respectively. Orbiting spacecraft such as Mars Express, Venus Express and Cassini yield new results, and we highlight the giant storm on Saturn of 2010/2011 that was probably the single most powerful thunderstorm ever observed in the solar system. We also describe theoretical models, laboratory spark experiments simulating conditions in planetary mixtures and map open issues.     

The Iapetus’s ridge: Possible explanations of its origin

Images from the Cassini mission show the existence of a long ridge on Iapetus. It extends at least 1400 km along the great circle defined by the equator. We discuss the possibility that the ridge is a result of extensional forces acting above an ascending current of solid-state convection. A two-cell pattern of convection is a reasonable explanation of the observed feature. Three scenarios of the ridge formation are proposed: spin–orbit resonance scenario, convection in low viscosity-interior scenario, and impact generating flow scenario.     

汉语语音识别的平滑声韵基元HMM算法

汉语语音识别的基本单元一般为音素、音节以及声韵母.以声韵母为基元的识别系统由于HMM模型较少,计算量小,适合于实时实现.但是由于模型比较孤立,对语音信号的声学特性描述得不够精确,因而识别率一般比音节基元的系统低.而以音节、音素(tri-phone、di-phone)为基元的系统则有HMM模型数量多、训练和识别过程中计算量大的缺点,影响到系统的实时性.本文提出了一种折衷的方案,系统基元仍选择声韵母,而在HMM训练阶段,对整个音节序列的参数进行运算,使声韵过渡段的状态得到平滑,同时计算并保存每个音节声韵之间的转移概率,识别时动态组装为完整的音节HMM.该方法在保持少量HMM个数的同时,能够降低误试率,适合于以DSP为核心的实时连接词语音识别系统.      

一种基于Web的工作流系统的设计与实现

工作流技术和应用软件系统的结合是计算机应用领域的一个研究方向.分析了当前基于Web的工作流技术的研发现状,提出了一种基于脚本解释、同应用数据类型无关的基于Web的工作流系统WebWFS,采用对象化的引擎结构、基于脚本语言的描述语言和IIS过滤器方式实现的引擎和Web应用之间的接口.为验证系统的实用性,以某大型应用系统中的计划管理为例,分析了系统的应用过程并对通过对比验证了系统的重用性和灵活性.      

支持企业过程动态优化的集成环境研究

简要介绍企业过程的优化原理与方法,并开发出企业过程动态优化的集成环境IEDOEP(Integrated Environment for Dynamic Optimizing Enterprise Process).它通过决策支持系统DSS (Decision Supporting System)将过程的定义工具PDT(Process Defining Tool)和过程模拟工具PST (Process Simulating Tool)以及过程优化工具POT(Process Optimizing Tool)等构件有机集成为一个整体,对其构架和其各个构件功能进行了详细介绍.IEDOEP对企业优化业务过程、实施BPR(Business Process Reengineering)、进行ERP(Enterprise Resource Planning)管理有很大的指导意义.      

系统工程内涵、过程及框架探讨

旨在探讨系统工程内涵、过程及框架,初步思考航天器系统工程的建设内容。首先在对数个典型系统工程定义的分析基础上,概括了系统工程内涵及特点;然后分析了系统工程全寿命周期过程及系统研制阶段;最后提出了具有三层次结构的系统工程框架,分析了系统工程组成要素,并初步探讨了航天器系统工程建设思路。