复杂地形环境中电磁波多径传输建模与仿真

分析各种环境效应的产生原理及其计算方法,在此基础上设计一个通用的雷达及雷达对抗电磁波多径传输仿真系统,用于仿真各种环境效应引起的雷达及雷达对抗电磁波的衰减,该仿真系统具有良好的人机交互界面,通过不同的仿真设置可以满足不同的试验需求,从而可以更灵活地支持雷达及雷达对抗仿真试验。     

大型浮吊控制系统可靠性分析与仿真

根据系统的结构组成,以及现场收集的数据,建立了浮吊控制系统的故障树（FTA）;运用蒙特卡罗随机模拟方法,在Matlab环境下对系统进行了可靠性指标的计算与仿真,得出了系统的可靠度曲线,掌握了现有装置可靠性水平及影响可靠性的薄弱环节,同时,仿真结果为浮吊控制系统的维护和检修提供了依据。     

Transport for older people: Characteristics and solutions

Entering the 21st century, one of the most significant demographic changes in developed countries is the aging of the population. Travel is an important aspect of older people's economic well-being, so with the aging of the population, improving transport for older people is increasingly important. This article presents the results of a study of older people's travel behaviour based largely but not exclusively on LATS (London Area Travel Survey) 2001 data. The focus is on older people's trip chaining behaviour, including trip chain complexity, trip purpose sequence and mode choice in a chain. After identifying the policy implications it looks at the role of Special Transport Services in improving the supply of transport for older people, taking the London Borough of Camden as a case study.     

公路工程单价合同中变更单价的确定方法

随着政府对基建项目尤其是国家重点工程的监督力度加大,工程变更问题已成为项目审计的核心问题之一,科学、合理、规范地确定变更工程的单价具有深远的意义,值得深入研究.     

顶置凸轮轴配气机构多体运动学分析与应用

基于多体系统运动学数值原理,对顶置凸轮轴配气机构多体运动学正解计算问题进行了研究;探讨了利用气门升程数据和由各种不同生产检测方法测得的测头位移数据确定凸轮型线的逆解途径;提出了顶置凸轮轴配气机构多体运动学的正-逆联解方法,实现从原理上精确反求凸轮型线。所述研究较好地解决了顶置凸轮轴配气机构在设计、制造和检测过程中产生和派生出来的各种运动学关系问题。     

船体平面分段智能制造流水线工艺装备技术

针对船厂对船体平面分段结构优质、高效制造的技术需求,以船体平面分段中间产品加工为功能对象,进行船体平面分段智能制造流水线装备的研发制造,突破流水线总体设计、智能化焊接、系统集成控制等关键技术,形成一条包含拼板装焊、纵骨装焊、中组立制造等多工位的智能化流水生产线.通过工程应用实现船体平面分段由传统生产模式向以智能装备为标...     

强夯法加固饱和粉土地基的效果

该文通过一工程实例,介绍通过合理确定施工参数,并采用严格的工艺控制,强夯法在饱和粉土地基处理中取得了良好的加固效果。     

Dynamic Simulation and Performance Investigation of No-Frost Refrigerator： Part Ⅱ System Simulation and Performance Analysis

The methodology for modeling no-frost refrigerator is described based on the component models developed in Part I, and then, system simulation is applied to a BCD-235W refrigerator-freezer (RF). Experiments are carried out to study “pull-down” and steady-state performance of the RF, and to determine how the experiment and simulation temperature stack up against each other. Good match is found between simulated and measured results for the “pull-down” period. For the steady-state period, the simulation results are also found to agree well with experiment ones except for the temperature profiles of the refrigerator compartment (RC) and freezer compartment (FC). The average temperature and the energy consumption errors between measurement and simulation are less than 10%. Although the model can not reflect the non-uniform air temperature fields in the RC and FC, the variation range and periodicities of the temperature correlate well between the simulation and experiment. We conclude that such a model is valid for investigating the performance of no-frost refrigerator.      

Dynamic simulation and performance investigation of no-frost refrigerator: Part I mathematical model

A dynamic approach for the modeling, simulation and analysis of no-frost Refrigerator (RF) is discussed. In Part I, the complex interactions among the components in the cooling system are analyzed in detail, based on which the modeling simplifications are proposed. Then, the mathematical models for the evaporator, cabinet and duct-fan are presented. The whole system is divided into two subsystems—refrigerant cycling system and air cycling system. In order to simplify the model, two closed-loop systems are broken into the compressor component and the evaporator component, respectively. A general distributed parameter model is employed for evaporator with homogeneous flow to simplify the two-phase evaporating flow region. The z-transfer function model is used to describe the cabinet load. Computational fluid dynamics (CFD) method is employed to obtain the pressure drop and flow rate curve of the duct-fan model.

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旋涡影响下的振动翼水动力性能

Fish are able to make good use of vortices. In a complex flow field, many fish continue to maintain both efficient cruising and maneuverability. Traditional man-made propulsion systems perform poorly in complex flow fields. With fish-like propulsion systems, it is important to pay more attention to complex flow fields. In this paper, the influence of vortices on the hydrodynamic performance of 2-D flapping-foils was investigated. The flapping-foil heaved and pitched under the influence of inflow vortices generated by an oscillating D-section cylinder. A numerical simulation was run based the finite volume method, using the computational fluid dynamics (CFD) software FLUENT with Reynolds-averaged Navier-Stokes (RANS) equations applied. In addition, dynamic mesh technology and post processing systems were also fully used. The calculations showed four modes of interaction. The hydrodynamic performance of flapping-foils was analyzed and the results compared with experimental data. This validated the numerical simulation, confirming that flapping-foils can increase efficiency by absorbing energy from inflow vortices.