基于Internet交互系统引入微分环的多媒体同步方法

针对交互系统多媒体同步中存在的问题，提出了引入预测环节的多媒体同步方法，采用控制论方法，将交互系统的多媒体信息传输与回放过程作为一个系统进行分析，得出发送缓冲和接收缓冲是惯性环节，网络传输是迟滞环节，各环节都存在一定的相角滞后，媒体信息预测是一个微分环节，可引入一定的相角超前，将这种预测环节引入到多媒体同步系统中，对系统进行超前校正，可改善系统的实时性能，减小网络延迟抖动对多媒体同步的影响，仿真结果证明了预测环节在克服网络延迟抖动的影响，提高交互系统的实时性，改善媒体间同步效果等方面的有效性。     

优先级倒置问题的集成资源管理技术

提出一种集成的实时资源管理和实时服务器技术,它对进程间通信和同步机制进行有效地管理;同时在两种技术的基础之上,构造了一个比较高效的优先级倒置问题的控制算法,克服了传统的用优先级继承方法来解决优先级倒置问题在最坏情况下延迟很大,而用优先级冲顶方法会引起低优先级进程阻塞的缺点。通过这种机制,既可以使系统避免多重优先级倒置现象的发生,又可以使系统的行为具有可分析性和可预测性。     

分布式交互虚拟仿真飞行训练平台的设计与实现

虚拟仿真训练已成为飞行训练的重要手段之一。利用HLA分布式仿真技术,基于COM组件与PLUGIN设计了分布式交互飞行虚拟仿真训练平台,综合运用数据池、回调函数、C/S组播等方法,通过一种面向交互状态的主动触发和筛选机制,实现了通用平台下单舱、单机前后舱以及多机协同训练中实时交互和设备状态的同步。该平台适用于桌面级仿真训练软件和中小型飞行训练器的快速开发。     

安全的分散式多播密钥管理方案

为解决集中式多播密钥管理方案中服务器端的可靠性、安全性和可用性问题,提出了一种新的安全分散式多播的密钥管理方案.基于分散式控制和门限秘密共享的思想,将单个密钥服务器扩展为具有(t,m)门限控制结构的服务器组.多播组密钥的产生、分发和更新由多个服务器结点协作完成.提供了确保服务器成员只知道组密钥的影子密钥而不知道所产生的组密钥的安全机制,这种机制使得某些服务器成员被攻击导致信息泄漏也不会影响系统安全.此外,分散式管理结构和门限控制机制可有效避免单点失效和性能瓶颈问题,还可提高了密钥服务器的可靠性和抗毁性能.     

分布式虚拟海战场仿真关键技术研究

在分布式虚拟环境下进行大规模军事战场仿真是目前仿真领域的研究热点。作为虚拟战场仿真的重要组成部分,分布式虚拟海战场仿真主要是解决大面积海浪视景实时生成和网络数据量太大引发的网络延迟这两个关键性问题。本文以海浪统计学模型为基础,采用视点相关的LOD模型实现了海面多细节层次建模,有效提高了大面积海浪视景仿真的实时性和逼真度;并基于Winsock 的TCP/IP协议,采用多播技术和推算定位技术,大大减少了分布式虚拟海战场仿真中的网络数据流量,实现了多通道视景同步,取得了较好的效果。     

空战实时仿真系统研究

为了评估空中作战对抗效能,建立了虚拟空战实时对抗网络仿真系统,给出了系统设计的思路、框架和功能,详细介绍了视景仿真系统的实现方法和关键技术,采用最小二乘拟合算法解决了仿真实体的轨迹不连贯,画面有抖动等现象;基于Vega仿真软件环境开发了战场中的各种复杂场景特效,解决了非视觉物理量的可视化问题,可在不同的场景环境下,动态演示导弹对相应目标的打击过程,包含特效、声音等各类仿真信息,画面流畅、系统稳定,具有良好的交互能力;利用Visual C 开发了视景仿真程序,解决了视景驱动和自动视点切换等具体问题。仿真结果表明视景系统可以实时逼真地演示虚拟空战作战过程,并给出了作战效能的直观评估。     

基于VRML的交互式虚拟产品展示技术

研究了构建交互式产品展示系统的方法和关键技术，包括VRML建模技术和实时交互控制技术等．进而，利用CAD软件和VRML语言构建了虚拟产品的静态模型及其交互环境，结合脚本语言JavaScript，实现了用户对虚拟产品展示的实时交互控制．     

基于三维地形的虚拟仪表仿真技术研究与实现

虚拟仪表仿真技术研究一直是航空仿真领域中热门研究课题。文章研究了某型飞机虚拟仪表在Creator/Vega开发环境下利用DOF技术的快捷实现方法,讨论仪表的数据驱动技术,应用多线程编程技术实现仪表的实时仿真功能。仿真结果表明该系统具有开销小、延迟低特点,平均帧率达到30 fps以上,满足实时交互需求。     

交互虚拟装配仿真过程中物体间间隙动态计算方法

提出一种支持实时交互虚拟装配操作中物体间最小间隙的快速计算方法,该方法使用基于层次包围盒模型的最小距离计算快速定位场景中模型间距离最小的一个或一组包围盒,进而确定模型距离最近的目标多边形组群,最终计算最小间隙数值和位置.该方法优点为能够借助虚拟装配系统中动态碰撞检测功能以及并行计算体系完成最小间隙计算.随后将该计算方法集成到DPVAE（Distributed Parallel Virtual Assembly Environment）虚拟装配软件系统,并以某型轿车的底盘装配中间隙动态计算和显示为例进行应用验证.结果表明,该方法能够支持交互虚拟装配仿真中的间隙动态测量与显示.     

基于RTCP反馈的TCP友好的实时流媒体拥塞控制机制

提出了一种端到端的、基于RTCP反馈的、改进了的TFRC拥塞控制机制,即a-TFRC(amelioratedTFRC);主要针对实时流媒体要求低延迟和低抖动的特点,修改了TFRC的慢启动阶段,使得TFRC流开始的发送速率不至于太低而使得接收端在开始有较大的延迟和抖动·仿真结果验证了此机制在实现对TCP流友好性的同时提高了实时流媒体的QoS     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

An affordable accurate evaluation of the binding conformations predicted by molecular docking studies in bio-system

Franck-Condon factors bridge the gap between theoretical modeling and experimental observations for molecular electronic spectroscopy and electron transfer.Under the displaced harmonic oscillator approximation,multidimensional Franck-Condon factors are decomposed into a product of many one-dimensional(1D)Franck-Condon(FC)factors,and each 1D-FC factor is associated with one Huang-Rhys factor that determines the leading contribution of     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

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