Economics Analysis for Information Flow of the Leader Dynamic Management in Virtual Enterprise

The virtual enterprise will play a more and more im po rtant role in economy development. The virtual enterprise leader raises market a daptability and group cooperation ability through its dynamic management. Thus t he validity and efficiency of leader’s dynamic management determines the efficie ncy of the virtual enterprise operation, and the validity of the information flo w is one of the main factors. In this paper, the validity of the information flo w in the course of the leader’s dynamic management in the virtual enterprise is analyzed by using the economic searching theory and the information theory, and the possible ways to improve the validity and efficiency of leader’s dynamic man agement are indicated. Firstly, the basic concepts such as leader’s dynamic management, virtual enterpr ise, and its leader are defined. The dynamic management procedure for the virtua l enterprise leader is analyzed with the dynamic theory raised by Mowshowitz. Secondly, the model for the dynamic management of the virtual enterprise leader is constructed using multi-goal selection. The information flow validity for th e leader during the stages of the identification and the establishment is analyz ed with the economic searching theory and the information theory. Meanwhile, the value of the dynamic management policy is discussed with the information va lue theory. Finally, two ways to improve the validity of the information flow are obtained. The first way is to process the various kinds of information of the existing mem bers in the virtual enterprise for the future cooperative usage and to extend th e selective objects for the leader, and to make the detailed and clear mechanism of the object evaluation and selection (the market chance and the cooperative partner). The other way is to build the system of the effective transfer and process of the feedback information flow during the operation of the virtual ent erprise based on the information technology.

从Immersion到Flow experience:“沉浸式传播”的再认识

虚拟现实技术的进步使沉浸式传播成为新的研究焦点,“沉浸”对应着Immersion和Flow experience两个英文术语,术语混用体现着两种研究取向,也意味着一种新的研究趋势。图景构建带来的感官沉浸是沉浸传播的初级阶段,而基于各种媒介手段实现的意识沉浸则是沉浸传播的发展方向,对沉浸问题的研究最终会在用户认知研究形成新的跨学科研究交点。媒介世界与真实世界之间的边界问题是沉浸式传播需要解决的关键问题,虚拟现实技术和注意力强化是消除边界的两大方式。艺术手法、拟像技术、综合互动、意义内爆是沉浸传播形成的前提,构建泛在网络、运用交互叙事手法、积极探索受众差异、合理地使用虚拟现实技术进行传播,是实现沉浸式传播的重要方法。

基于OpenFlow的软件定义网络虚拟化方案

软件定义网络(SDN)可以将网络控制平面与数据平面分离开来,为网络虚拟化提供了良好的平台。为了解决SDN中多租户下的虚拟化,提出了一种基于OpenFlow的网络虚拟化方案。通过一个中间代理来转换并匹配物理MAC地址与虚拟MAC地址,以及物理流表项和虚拟流表项,以此实现流量空间的虚拟化。其中,根据实际数据包的惰性计算,使用前缀或通配符来精确匹配流表项。另外,为了保障物理OpenFlow网络上不同租户之间的隔离,将单个虚拟MAC-通配符流表项映射为多个具有精确MAC地址的物理流表项。实验结果表明,该方案成功地实现了网络虚拟化,且虚拟化开销较小,具有可行性。

基于预测缓存的OpenFlow虚拟流表高效查找方法

OpenFlow支持通配符查找,会造成严重的流表查找性能瓶颈。为此,基于网络流量局部性,提出一种OpenFlow虚拟流表查找方法。通过缓存在数据包流中近期频繁出现的连接和对应的掩码,对大部分数据包直接定位其掩码,进而查找流表,无需逐个探测掩码数组。理论分析和实验结果表明,相比于目前主流虚拟交换机中的流表查找方法OFT-OVS,该方法的平均查找长度较小,可有效提升OpenFlow虚拟交换机的数据转发性能。

一种抗恶意攻击的OpenFlow虚拟流表高性能查找方法

针对恶意攻击给OpenFlow虚拟流表查找带来的破坏性影响,构建了一种抗恶意攻击的OpenFlow虚拟流表高性能查找方法。该方法基于近似成员关系查询理论,采用布鲁姆过滤器预测元组查找失败结果,以绕过绝大多数元组失败查找操作,提高OpenFlow虚拟流表查找效率;进一步,设计了一种可扩展计数型布鲁姆过滤器,根据元组规模的动态变化进行适应性伸缩,从而始终以高准确率判定元组查找失败结果;最后,采用实际网络流量样本和模拟恶意攻击方式,评估所提OpenFlow虚拟流表查找方法的性能。实验结果表明:当攻击包与正常包分别按1:2和2:1比例混合时,所提方法的假阳性错误率始终保持在6%以下,比计数型布鲁姆过滤器降低了93%,而平均查找长度降低了90%。

基于OpenFlow的虚拟网实现研究

软件定义网络是一种数据和控制平面分离、软件可编程的新型网络架构及技术,控制平面使用以Open Flow为代表的协议对转发平面进行集中式控制。SDN架构的这些特点能很好地满足了云计算对虚拟网络的集中化、标准化、自动化的配置管理要求。针对传统虚拟网络技术支持云计算平台的不足,提出基于Open Flow的SDN技术设计虚拟网络的思路,论述了几种虚拟网络实现的原理与处理流程,并给出了模块化的软件设计及部分关键代码功能描述。

3D Visual Plant Models in Computational Fluid Dynamics Simulation of Ambient Wind Flow around an Isolated Tree

Plants can reduce the velocity of wind and wind erosion and prevent the movement of sand.But it may be extremely difficult to measure directly the aerodynamic characteristics of the airflow near the real vegetation in field experiments on account of restriction by many objective factors.Therefore,numerous investigations have been carried out to study the efficiency of windbreaks by conducting wind tunnel experiments on simulated models or using computational fluid dynamics(CFD) simulation instead of field measurements.Plant models are simplified at some level to be used for numerical simulation in existing literatures.It is a little distortion of leaves in details if the tree canopy is regarded as a whole region which can have a certain influence on the CFD simulation.Hence,one modeling approach that combines Visual Basic for applications(VBA) and computer aided design(CAD) technology is proposed to design 3D virtual plant models.The tree models used for numerical simulation of wind flow around trees are more lifelike.In addition,this method can be applied for creating a 3D virtual vegetation library.It is also more convenient to get the diversified biological indicators by digital plants in computer.

Three-Dimensional Instability of Flow Around Two Circular Cylinders in Tandem Arrangement

The spatial evolution of vortices and transition to three-dimensionality in the wake of two circular cylinders in tandem arrangement have been numerically studied. An improved virtual body method developed from the virtual boundary method is used here. A Reynolds number range between 220 and 270 has been considered, and the spacing between two cylinders is selected as L/D=3 and L/D=3.5. When L/D=3, the secondary vortices of Mode-A are seen to appear at Re=240 and persist over the range of the Reynolds number of 240～270. When L/D=3.5, the similar critical Reynolds number has been found at Re=250. No obvious discontinuity has been found in the Strouhal-Reynolds number relationship, and this is different from three-dimensional flow around a single cylinder at the critical Reynolds number. The spanwise wavelength is about four times the diameter of the cylinder, and it is the characteristic wavelength for Mode-A instability. This paper can give some foremost insight into the three-dimensional instability of flow by complicated geometrical configuration.

双层虚拟垂线时差法流量计算模型实证研究

为提高天然河道河流流量在线监测精度,基于超声波时差法多层测流技术,提出并构建了双层虚拟垂线时差法流量计算模型,对江苏省秦淮新河水利枢纽泄洪期进行了计算,并与同期开展的走航ADCP流量比测结果进行对比分析。结果表明,该双层虚拟垂线时差法流量计算方法在一定程度上克服了由于天然河道水情条件复杂而导致率定期长的难题,河道流量测验精度高,计算的泄洪期河道流量与走航ADCP测量数据基本一致,相关系数为0.999,相对误差均在15%以内,在一定程度上能够满足洪水期河道流量测验精度要求。

一种基于物质点法的熔冰仿真方法

为了解决拉格朗日法模拟熔冰时产生的穿模现象,提出一种基于物质点法的熔冰仿真方法。首先,将欧拉空间中的每个拉格朗日粒子视为固-液双相耦合的集合体,实现固相到液相的平稳过渡;其次,在物质点法背景网格上计算热能,采用预处理共轭梯度法求解相变过程的温度线性系统;最后,对潜热现象进行处理,引入虚拟水模型,通过限制虚拟水的移动来实现对冰块外部水流现象的仿真。实验结果表明,该方法不仅能够利用物质点法处理自碰撞的优势解决穿模现象,而且能模拟出真实的潜热过程的水流现象。

旅游虚拟社区用户心流体验对价值共创的影响研究

旅游虚拟社区是用户实现分享旅游经历、获取旅游资讯和寻找出游同伴等功能的重要平台,也是企业实现精准营销的重要手段。企业和用户在虚拟社区共同投入、共同产出价值的过程称为价值共创。心流体验作为完全投入和集中注意力的积极心理状态,会影响用户与企业的契合程度,进而影响企业与用户之间的价值共创。文章通过对旅游虚拟社区用户数据进行采集与实证分析,揭示了用户心流体验对价值共创的影响机制。结果表明:内部动机和外部动机对用户产生的积极心理状态有显著正向影响;用户的积极心理状态及其与企业的契合程度对价值共创均有积极影响,且顾客与企业的契合程度在心流体验和价值共创过程中起部分中介作用。据此,文章提出了旅游虚拟社区企业可以通过提升用户参与动机,激发用户积极心理状态,强化顾客与企业之间密切关系,推动价值共创持续发展,实现引流交易和精准营销等管理启示。

闸坝控制感潮河道洪水位预报方法探讨

针对闸坝控制感潮河道洪水位预报,应用雨洪定律的计算方法,从雨洪期间各时段降水量开始,按时序演算转化为入河虚拟断面流量,并建立水位-虚拟流量关系,由涨水之初水位及虚拟流量反推洪水位及涨水过程。研究方法简单便捷,预报快速高效,在闸坝控制感潮河道洪水位预报中具有一定的应用意义。

基于虚拟实验数据库的流式细胞术线上教学应用研究

目的探讨线上教学在流式细胞术及其应用课程实验课教学中的应用效果。方法研究时间为2022年3月至2023年12月。选取首都医科大学2019级和2021级选修流式细胞术及其应用课程的37名硕士研究生为对照组,2022级和2023级选修流式细胞术及其应用课程的31名硕士研究生为试验组。对照组接受实验课线下教学,试验组接受实验课线上和线下混合教学模式教学。对试验组实验课线上教学模式满意度进行调查和评价,比较两组流式数据分析成绩和实验操作成绩。结果调查显示,试验组线上教学模式提升流式数据分析能力和线上教学模式满意度最高(96.7%),线上教学模式提升科研能力满意度最低(83.9%)。试验组流式数据分析成绩和实验操作成绩均高于对照组(P<0.05)。结论基于虚拟实验数据库的流式细胞术线上教学可提高研究生流式细胞术数据分析及实验操作能力。

Development of a Synchronization Method for Fluid-Thermal Study of Hypersonic Flow

A synchronization method is developed for the fluid-thermal study of hypersonic flow.Different from conventional loosely/tightly coupled methods which separately deal with the flow field and the structure temperature field,the presented method expresses the governing equations in a unified framework so that the two fields can be calculated simultaneously.For efficiently solving the unified equations,the finite volume method together with the dual-time stepping approach is employed.Like in the flow field,the local time step is also used in the temperature field,which is determined from thermal conductivity spectral radii.In order to treat the fluid-structure interface more conveniently,an expanded virtual boundary is introduced.For validation,several fluid-thermal hypersonic flow problems are simulated.The computed results are compared with those obtained from the coupled methods and the experiment.In the continuous heating problems,the stagnation temperatures predicted by both the coupled and synchronization methods are in good agreements with the experimental data.In the unsteady flowthermal hypersonic flows,the stagnation heat fluxes predicted by the presented method and tightly coupled method are basically the same,which agree better with the experimental data than those predicted by the loosely coupled method.In terms of prediction of the stagnation temperature,the synchronization method shows better accuracy than the tightly coupled method.

基于万维引擎自主开发虚拟仿真实验——以流体阻力实验为例

化工类实验具有危险且复杂多变的特点。文章以流体阻力实验为例,阐述了基于万维引擎的网页版虚拟仿真实验的自主开发过程,包括实验设备建模和渲染、教学模块设计、软件功能开发、逐项功能测试等内容。所开发的虚拟仿真实验实现了虚拟实验与现场实验从设备到内容的紧密关联,契合真实的实验教学过程,为国内外学生提供了在线学习与操作练习的机会,同时也是开展线上线下混合式实验教学的重要基础。

面向钣金混流生产线的仿真优化研究

文章以某电梯钣金加工公司的钣金混流生产线为背景,通过虚拟仿真方法对钣金生产环节中的投产序列和瓶颈问题进行优化。首先,根据某电梯门板生产线的实际生产状况,建立生产线的仿真模型,以工件完工时间、设备空闲时间和设备总切换时间为目标,基于遗传算法,优化钣金混流生产线的投产序列;其次,通过分析缓存区添加位置和容量对钣金生产线产量的影响,解决生产线堵塞、利用率不平衡等问题。结果表明,对生产线的优化有效,经优化后的投产序列相比原始投产序列整体时间缩短约15%,通过适宜的缓存区设置,各工位设备平均利用率提高了9.6%,产量提高了14.15%。

沉浸式场景理论视域下VR皮影展陈应用设计研究

基于场景理论和沉浸理论,设计交互式的VR皮影展陈,探索皮影艺术保护和发展的新方式。首先研究了VR皮影展陈的发展意义,然后根据沉浸理论和场景理论,介绍了虚拟空间中沉浸式场景理论的内容,接着提出了沉浸式场景理论视域下VR虚拟展陈的设计策略。完成了交互式VR皮影展陈的设计实践,设计了沉浸式的展陈场景、互动方法和社群生态,实现了皮影文化的创新式发展。为皮影文化的传播和发展提供了新思路。

基于Web的凝汽器热力特性虚拟实验设计

基于Web的凝汽器热力特性虚拟实验,以某660 MW超超临界机组的凝汽器系统为原型,采用两相流仿真模型作为虚拟实验底层计算模型,准确模拟凝汽器系统的参数变化和热力过程的动态特性,直观形象地展示了凝汽器的特性曲线,填补了学生脱离实物设备无法实验的空白。该虚拟实验改变了实验教学方式,改善了教学效果;培养了学生对凝汽器系统的认识和理解能力,提高了学生的工程实践能力以及创新能力。

基于气固两相流数值模拟的下鼻甲切除虚拟手术效果评价研究

运用数值模拟的方法探讨不同的下鼻甲切除虚拟手术方案的效果。为一位患慢性肥厚性鼻炎的患者重建了真实鼻腔模型A,采用虚拟手术的方法修改模型A的几何结构,分别根据双侧下鼻甲下缘水平切除术、下鼻甲后端切除术以及下鼻甲下缘及后端切除术得到了鼻腔模型B、模型C和模型D。并在上述四个模型内分别展开数值模拟,对比分析其流场分布和颗粒物的沉积比与沉积形式。模型A中左侧鼻腔的气流速度较快,左右鼻腔的气流分布差异也较大,模型B和模型D的最大气速和左右鼻腔的流速差异均有减小。在不同流量条件下,模型B和模型D的鼻腔进出口压降与模型A相比均降低。较大粒径的颗粒在鼻腔模型内的沉积比显著降低,8μm时模型B和模型D的沉积比分别比模型A降低了14.5%和14.8%,10μm时分别降低了14%和14.5%。模型C的流场分布和颗粒物的沉积特性与模型A相差不大。模型B和模型D可以更好地降低鼻阻力,减轻左右鼻腔流场差异引起的不舒适感,降低颗粒物在鼻腔内的沉积比,尤其减少了鼻中隔、鼻咽和咽喉区域的颗粒物沉积。

三维流场的虚拟现实技术开发与教学应用

开发了一种动态展示三维精细流场结构的虚拟现实系统。该系统包括:流场生成模块,用于通过数值模拟计算目标场景的瞬时流场,并进行可视化,得到目标场景的三维流场模型;存储模块,用于存储目标场景的三维流场模型;显示模块,根据按键指令调用并播放三维流场模型。通过虚拟现实技术实现多种模型的三维瞬时流场动态展示,实现了在流体力学教育与研究领域还原复杂流场中三维结构的功能,极大地激发了学生的求知欲与探索精神。