Optimal selection of annulus radius ratio to enhance heat transfer with minimum entropy generation in developing laminar forced convection of water-Al2O3 nanofluid flow

Heat transfer and entropy generation of developing laminar forced convection flow of water-Al_2O_3 nanofluid in a concentric annulus with constant heat flux on the walls is investigated numerically. In order to determine entropy generation of fully developed flow, two approaches are employed and it is shown that only one of these methods can provide appropriate results for flow inside annuli. The effects of concentration of nanoparticles, Reynolds number and thermal boundaries on heat transfer enhancement and entropy generation of developing laminar flow inside annuli with different radius ratios and same cross sectional areas are studied. The results show that radius ratio is a very important decision parameter of an annular heat exchanger such that in each Re, there is an optimum radius ratio to maximize Nu and minimize entropy generation. Moreover, the effect of nanoparticles concentration on heat transfer enhancement and minimizing entropy generation is stronger at higher Reynolds.

Entropy generation analysis of thermally developing forced convection in fluid-saturated porous medium

Entropy generation for thermally developing forced convection in a porous medium bounded by two isothermal parallel plates is investigated analytically on the basis of the Darcy flow model where the viscous dissipation effects had also been taken into account. A parametric study showed that decreasing the group parameter and the Peclet number increases the entropy generation while for the Brinkman number the converse is true. Heatline visualization technique is applied with an emphasis on the Br 〈 0 case where there is somewhere that heat transfer changes direction at some streamwise location to the wall instead of its original direction, i.e., from the wall.

Effect of preload force on heat generation of fatigue crack in ultrasonic infrared thermography

The heat generation behaviors of fatigue crack are deeply investigated under different preload forces combing numerical simulation and experiment.Firstly,a multi-contact simulation model is applied to stimulate the crack surfaces contact and the horn-sample contact under ultrasonic excitation for calculating the temperature fields.Then,the ultrasonic infrared thermography testing and the microscope testing are carried out for the heat generation and the plastic deformation behaviors of crack region under different preload forces.On this basis,an indirect observation method based on dots distribution is proposed to estimate the plastic deformation on crack contact surfaces.The obtained results show that the temperature rise of crack region increases with the increase of preload force when the preload force is less than 250 N,while the temperature rise rapidly declines due to the plastic deformation on crack contact surfaces and the inhibition effect when the preload force is 280 N.Moreover,the plastic deformation does not lead to the crack propagation,but reduces the detection repeatability of fatigue crack.This work provides an effective method for optimizing testing conditions in practical testing processes,which will be helpful to the establishment of testing standards for batches of test objects in ultrasonic infrared thermography testing.

Optical pulse shaper with integrated slab waveguide for arbitrary waveform generation using optical gradient force

Integrated optical pulse shaper opens up possibilities for realizing the ultra high-speed and ultra wide-band linear signal processing with compact size and low power consumption. We propose a silicon monolithic integrated optical pulse shaper using optical gradient force, which is based on the eight-path finite impulse response. A cantilever structure is fabricated in one arm of the Mach–Zehnder interferometer（MZI） to act as an amplitude modulator. The phase shift feature of waveguide is analyzed with the optical pump power, and five typical waveforms are demonstrated with the manipulation of optical force. Unlike other pulse shaper schemes based on thermo–optic effect or electro–optic effect, our scheme is based on a new degree of freedom manipulation, i.e., optical force, so no microelectrodes are required on the silicon chip,which can reduce the complexity of fabrication. Besides, the chip structure is suitable for commercial silicon on an insulator（SOI） wafer, which has a top silicon layer of about 220 nm in thickness.

VR-Forces计算机兵力生成程序分析与设计

计算机生成兵力程序的开发环境一般是基于外军环境与武器模型进行构建,为了适应具体的需求,用户必须进行仿真功能的自定义和扩展。以VR-Forces为计算机生成兵力开发环境,对VR-Forces程序结构、类层次结构、类工厂机制和API接口进行分析,利用VisualC++开发环境和VR-Forces提供的应用编程接口(Application Programming Interface),对VR-Forces提供的源程序重新进行编程与编译,建立一个自定义的、实现了功能扩展的计算机兵力生成程序,试验数据表明,新的仿真系统功能得到扩展,运行正确,具有较好的适用性。

基于VR-Force的协同空战效能评估研究

在空战对抗中,通过综合参战实体各项战技指标,从理论上拟合单个实体对对方的杀伤概率。基于VR-Force开发环境,进行协同空战任务分配研究。根据任务分配方案,对每个参战实体制定对应的作战计划,按此方案制作作战想定,进行战场推演,实现效能评估。实验仿真结果与理论推导说明了科学合理的任务分配方案在协同空战中的作用和意义。

基于VR-Force的计算机兵力生成过程研究

计算机生成兵力能在虚拟环境中与其它真实的、虚拟的或其它计算机生成的实体交互。在VR-Force开发环境下,CGF能够以较小的代价提供真实而丰富的战场环境,从而达到提高训练训练效果、检验训练成果的目的。

基于VR-Forces的水面舰艇防空作战仿真

作战模拟是水面舰艇对空防御研究的有效手段之一,VR-Forces为此提供了有力的支持。首先建立了基于VR-Forces的舰空对抗仿真系统,分析了基于VR-Forces组件式作战兵力实体结构特点,提出了基于功能组件的实体结构元模型;在电子对抗模型的基础上,以雷达告警仿真为例建立了基于VR-Forces的水面舰艇对空防御仿真组件开发过程,对组件及组件间的数据流程进行详细说明。所提出的开发方法已经成功运用于多型作战模拟训练系统中,实现了电磁环境下的舰空对抗训练。

VR-Forces中发射与毁伤仿真机制

VR-Forces是当前较为成熟的计算机生成兵力仿真平台,使用该平台实现仿真实体间对抗及毁伤是关键技术之一。针对该平台中发射与毁伤仿真机制,分析了对象参数数据库组织结构、发射武器配置方法、弹药选择列表构成和命中概率表的原理,阐述了毁伤机制、毁伤概率表组成以及毁伤执行器的配置方法。结合某飞机发射反舰导弹对敌方舰船突防的作战仿真实验案例,实现了红蓝双方的突防和防空仿真对抗。研究成果对基于VRForces的作战仿真开发和开发类似系统有一定的技术参考价值。

Effect of Preload Force on Heat Generation of Li(Ni_(0.8)Co_(0.1)Mn_(0.1))O_(2)/SiO_(x)-C System Batteries:The Discharge Process

Lithium-ion batteries(LIBs)undergo various degradation phenomena such as material decomposition,structural change and uneven lithium ion distribution during long-term cycles,which would affect their performance and safety.In order to improve the performance of the LIBs during their life cycle,preload force is preset when the batteries are assembled.Different preload forces will in turn affect the cycle life and heat generation of the battery.In order to address this issue,this work carries out charge/discharge cycle tests on a NCM811 battery under different preload forces.Isothermal calorimetry tests are performed to investigate the battery heat generation under different states of health(SOHs)and preload forces.Based on the test results,an empirical prediction model for heat generation power as a function of SOH is established.Results show that when the preload force is 5 N·m,the battery capacity decreases in the slowest rate and the average heat generation power is the lowest.Changes in peaks of the incremental capacity curve can be used to characterize the loss of lithium at the electrode,which in turn characterizes the change of heat generation power of the battery.The average heat generation power is mainly affected by the SOH,going through a period of trough with the decrease of the SOH and continuing to increase after crossing the critical point.In general,these findings emphasize the relationship between preload force,SOH and heat generation power,which is helpful for the judgment of optimal preload to improve the efficiency of LIBs.

Second Law Analysis of Forced Convective Cooling in a Channel with a Heated Wall Mounted Obstacle

The present work details a numerical simulation of forced convective laminar flow in a channel with a heated obstacle attached to one wall. The second law analysis is employed to investigate the distribution of entropy generation in the flow domain to demonstrate the rate of irreversibilities in thermal system. The conjugate problem including the convection heat transfer in the fluid flow and conduction one inside the obstacle is solved numerically to obtain the velocity and temperature fields in both gas and solid phases. To reach this goal, the set of governing equations including momentum and energy equations for the gas phase and conduction equation for the obstacle are solved by CFD technique to determine the hydrodynamic and thermal behaviors of the fluid flow around the obstacle and the temperature distribution in the solid element. An attempt is made to detail the local Nusselt number distribution and mean Nusselt number and also the local entropy generation distribution for the individual exposed obstacle faces. A good consistency is found between the present numerical results with experiment.

有限状态机在CGF行为建模中的应用

对有限状态机在CGF系统中的应用作了比较全面的论述，首先对有限状态机的数学模型进行介绍，然后分析了利用有限状态机建立CGF行为模型的原理，最后详细介绍了有限状态机建模方法在ModSAF中的应用。

CGF中的协同行为建模技术

协同行为建模技术是计算机生成兵力的重要研究内容,也是作战仿真中人类行为表示是否准确、仿真结果是否可信的关键所在。根据国内外研究现状和需求分析,针对现有协同行为模型的不足,提出了具有协同行为能力的CGF Agent认知体系结构,设计了协同行为建模框架,重点阐述了各子模块间的相互关系及其关键实现技术。文章最后讨论了协同行为建模技术的发展趋势和应用前景。

任务型CGF组织本体建模

针对作战模拟对人类行为表示的准确性要求,建立真实反映战场行为的组织模型是非常重要的。根据需求分析和已有研究的不足,提出了基于本体论的组织建模方法,阐述了该组织本体的构建原则,并从组织静态结构和动态行为两个方面定义了相关概念及概念间的关系。在此基础上采用一阶谓词逻辑描述了该组织本体的形式化过程。实验结果表明,该方法能够准确地建立起用于实体的组织模型,使得实体行为可以反映实际战场行为,且能够保证组织本体的通用性。

基于Agent的电子战CGF建模研究

计算机生成兵力(CGF)是一个具有自主性、智能性的复杂系统。传统的建模方法难以精确的描述其模型。Agent技术作为面向对象技术的延伸,为解决这类复杂系统的建模与仿真问题提供了有效手段。应用基于Agent建模技术,建立了电子战CGF的层次模型,并解决了个体Agent模型设计中的感知、动作、决策及实现方法上的问题,最后讨论了用于设计聚合级实体的多Agent系统的组织结构、通信语言、通信机制及协作模式。

CGF的目标探测控制

ＣＧＦ系统必须频繁地检测它所控制的实体之间以及这些实体与ＤＩＳ环境中的其他实体之间的通视性和可探测性，这种检测是ＣＧＦ中较为耗时的过程。本文讨论采用探测启发式来控制ＣＧＦ系统的目标探测，合理减少ＣＧＦ的目标探测次数，从而节省目标探测所占用的计算时间。这种方法节省探测计算时间最多可达到５０％，而对ＣＧＦ实体自治行为的逼真性的影响很小。

CGF实体战场感知行为建模研究

计算机生成兵力(CGF)系统中,通常认为CGF实体具有完全的战场感知能力,但这与实战过程中信息获取的不确定性相互矛盾。为了解决上述问题,在研究感知行为机理的基础上,对其产生过程进行形式化描述,并进一步分析了影响证据可信度的客观因素和主观因素,并结合实际战场环境和装备性能完成客观因素的量化工作,运用模糊逻辑量化了主观因素。最后利用证据理论合成法则将直接证据、间接证据以及先验态势进行合并,建立了可计算的CGF实体战场感知行为模型。通过仿真实例验证了模型的可用性。

基于AGENT的防空作战CGF行为建模研究

介绍了防空作战CGF系统的组成结构,对防空作战CGF系统的特征和防空作战CGF实体对象的行为特征进行了分析,提出了基于Agent的实体行为建模方法,以防空作战单元CGF系统为例,构建了搜索指挥Agent的行为模型,对多Agent的行为规划和Agent主体交互问题进行探讨,为防空作战CGF系统建模提供了有效的方法和途径。

城市作战仿真中CGF Agent战术路径规划

在城市作战仿真中,提出一种单CGF Agent战术路径规划方法。分析Agent路径规划过程中需要考虑的战术任务要求,建立距离代价与战术代价相结合的综合路径评价模型,设计基于改进概率路标图的战术路径规划方法。实验结果表明,该方法进行100次实验的平均规划时间为72.94 ms,最大和最小规划时间分别为110 ms和15 ms。

FSM在海军作战仿真CGF中的应用

计算机兵力生成(CGF)是现代作战模拟仿真中的一项重要内容,特别是在对抗条件下,CGF还必须具有战术决策能力,知道如何根据当前的战场态势,按照己方的作战原则,动态更新自身的行为。文章结合海军对海突击作战的特点,将有限状态自动机(FSM)与行为规则相结合来实现对抗条件下CGF的行为仿真,该方法已运用到对海突击作战仿真软件中,应用表明:该方法可以较真实地仿真红蓝方的行为,具有相当的战术决策能力,取得了良好的效果,也为该系统后期基于Agent的行为仿真提供了一种行为规则表示方法。