基于随机模糊参数的导弹武器系统可用度分析

针对复杂战场条件的导弹武器系统可用度评估,各时间参数分布不完全服从指数分布,且不能用马尔可夫过程来分析的缺点,假定部件的寿命服从指数分布,修理时间和保障延误时间均服从任意分布,并且修理设备服务期服从指数分布,其更换时间服从任意分布的情况下,利用马尔可夫更新过程理论和拉普拉斯变换工具,建立考虑技术阵地设备部分战损情况下和具有保障延误的串联可修导弹武器系统可用度模型。同时考虑分布参数的不确定性和区间模糊性,将随机模糊理论引入可用度分析领域,采用三角模糊数量化模糊信息,并给出算例进行验证。算例结果与前期仿真结果吻合,验证了模型的可行性和有效性。该方法能综合考虑各种可用度的影响因素及其模糊性,为非马尔可夫型系统的可用度分析提供了有效的方法。     

水下耐压壳体结构可靠性的设计方法

在水下耐压壳体的环肋圆柱壳结构设计中,为了保证结构的强度和稳定性,几何参数的确定必须要满足规范所要求的五个约束条件.完工后的几何尺度与设计几何尺度存在着一定的误差,可将这些误差分布密度函数认为服从正态分布,利用其约束条件结合可靠性理论建立环肋圆柱壳耐压壳体可靠性分析方法,以实际测量中统计得到的数据为已知条件给出了可靠度计算方法.     

子母弹对轻装甲舰艇目标毁伤分析

随着导弹艇等轻装甲舰艇在现代海战中发挥着越来越重要的作用,对其打击也随之成为难点.在假定子母弹母弹散布误差和子弹在落点区域服从特定散布的假设下,对子弹典型的落点分布形态进行了分析.在此基础上,选取导弹艇作为研究目标,通过建立毁伤计算模型,分析了某型子母弹对导弹艇的的毁伤效果.结果表明,该型子母弹对于轻装甲的导弹艇目标具有较好的毁伤效果.     

基于最小化振速重构误差的等效源分布优化方法研究

针对波叠加法计算声场存在的预报精度受等效源分布位置及计算频率影响的问题,研究了使用预报的声压逆向求解结构边界法向振速时存在振速重构误差的问题,推导了声压预报误差与振速重构误差之间的解析关系,研究发现减小振速重构误差能够降低声场预报误差.为提高波叠加法的声场计算精度,提出了一种基于最小化振速重构误差优化确定等效源位置分布的方法,并设计了一种频率阈值准则来确定一定数量等效源所适用的计算频率范围.通过数值仿真和试验对所提方法进行了验证,结果表明所提方法能够有效降低声场预报误差,可用于实际声场计算.     

移动通信衰落信道的仿真分析

介绍了无线信道的基本概念和特性,对幅度服从莱斯分布和瑞利分布的衰落信道的概率密度函数进行仿真。建立了多径衰落信道模型,详细分析了BFSK信号在多种衰落信道中误比特率与信噪比的关系,并进行了性能比较。仿真的结果表明,瑞利衰落信道的误比特性能较高斯白噪声信道和莱斯信道的误比特性能更差,且所建立的仿真方法可以作为多径衰落信道的分析方法。     

不完全测量情形下非线性离散时滞系统的模糊H∞滤波

针对非线性离散时滞模糊系统,研究其不完全测量情形下的H∞滤波问题.假设非线性项满足扇形条件,并利用服从Bernoulli分布的随机变量来描述不完全测量.目的是设计H∞滤波器,使得滤波误差系统均方指数稳定且满足给定的干扰抑制水平.首先,基于模糊Lyapunov泛函得到了滤波误差系统均方指数稳定的时滞依赖充分条件.然后,给...     

轴向荷载作用下K型管节点焊缝周围应力分布的参数公式

应用分区产生网格的方法产生了K型节点的有限元模型,计算了在轴向荷载作用下K型节点焊缝周围的热点应力分布情况,并与相关试验结果进行对比分析,验证了所提出的有限元模型的可行性和准确性。通过对1152个K节点模型分析,研究了几何参数对K型节点焊缝周围热点应力分布的影响,发现在几何参数取不同值时热点应力的分布随几何参数的变化发生改变,而且热点应力的位置也随着几何参数的变化在冠点和鞍点之间移动。并在此几何参数分析的基础上,提出了K型节点焊缝周围应力集中系数分布的参数公式,并对参数公式进行了误差分析。对于绝大多数K节点模型,拟合得到的参数公式所计算的焊缝周围应力分布结果是精确可靠的,所以提出的参数公式为工程中K节点疲劳设计和分析提供了参考方法。     

在随机载荷作用下用断裂力学法估算潜艇耐压壳体的疲劳寿命和裂纹尺寸

潜艇在上浮下潜的过程中承受着反复作用的由外部水压力所产生的随机载荷,耐压壳体面临着疲劳破坏。本文引入了潜艇的疲劳载荷谱,模拟了潜艇随机载荷历程,并对一次载荷历程估算了疲劳寿命;同时模拟了100次载荷历程,分别对疲劳寿命和裂纹尺寸进行了统计,结果表明裂纹的疲劳寿命符合威布尔分布,裂纹扩展尺寸服从对数正态分布。该结论与目前疲劳可靠性分析中使用的对数正态分布模型和威布尔分布模型相一致。     

直立墙上不规则波波浪力试验和统计分析

为确定波谷作用下波浪荷载的概率分布和统计参数,进行了不规则波浪对直立墙作用的室内试验,并对测得的波浪力进行统计分析;通过长期波浪最大荷载与短期波浪荷载的统计关系,得到50 a设计基准期内波浪荷载的概率分布和统计参数。研究结果表明,波谷作用下短期波浪荷载服从Weibull分布,50 a设计基准期内最大波浪荷载服从极值I型分布。     

蒙特卡罗仿真用于多种失效分布底事件的故障树分析

考虑部件寿命服从多种分布的实际情况,利用蒙特卡罗方法进行故障树可靠性仿真建模,根据故障树所表示的系统模型的特点,绘制故障树法仿真的算法框图,并根据框图编写FORTRAN程序,通过分析和计算,得到系统的可靠度、平均寿命以及各底事件的重要度和模式重要度等.     

噪声对高速ADC的动态性能影响分析

针对目前数据采集过程中存在很多不准确和抗干扰性差等缺点,提出了一种新的ADC动态测试方法,设计了基于高速ADC动态测试的测试平台,介绍了其测试的方法和基本原理;验证噪声信号对ADC测试影响较大,提出可以利用噪声信号有效提高ADC转换性能。通过对ADI公司的AD6645-105进行测试与分析,结果表明该测试方法不仅具有安全可靠、准确等特点,且可以有效提高ADC转换性能,改善转换的转换精度,提高ADC的抗干扰性。     

Uncertainties estimates of hull girder still water loads of bulk and dry cargo ships through Monte Carlo simulations

This paper deals with the estimate of uncertainties affecting still water hull girder loads of bulk and dry cargo ships. In strength assessment of ships, two main categories of acting loads are considered: still water loads and wave induced ones. While the latter are generally defined bearing in mind their stochastic nature, this is not the case for still water loads, which are basically deterministically considered. The underlying assumption is that there is an overall control of the operational profile during the service of a ship. However, this is not the case in actual fact, especially for general dry cargo ships and bulk carriers, since the loading/unloading process cannot be fully controlled by the crew, often resulting into loading conditions rather different from those planned by the designer. Based on an earlier work, where loading conditions of the above-mentioned ship types were statistically analyzed, in the present paper Monte Carlo simulations are used to estimate the uncertainties affecting the hull girder still water loads of ships in service, showing that their allowable values can be exceeded due to inaccuracies in ship and cargo management.     

On the importance of mooring system parametrisation for accurate floating structure designs

This paper analyses the importance of mooring design parametrisation on the dynamic behaviour of mooring loads. An exhaustive sensitivity analysis is performed to evaluate the variability of mooring loads because of inaccuracies in the definition of model inputs, including physical and numerical parameters. Results show a relevant dependence on the length and significance in other parameters, such as the weight together with the hydrodynamic equivalent diameter and the drag forces. An inaccuracy below 1% in the mooring reference length can generate loads of up to twice the design, and an incorrect definition of the weight or the drag coefficient in the mooring design can lead to a design load variability of up to 30%. Stiffness plays a crucial role in snap events, reaching load differences of 19% depending on the stiffness selected.This research is based on a set of numerical models capable of predicting the mooring system response. A dynamic numerical model with two schemes of resolution is implemented and calibrated according to an experimental test campaign. Other sources of results provided by a quasi-static model and commercial software, Sesam (DNV-GL), are incorporated. In general, the dynamic numerical models show a good accuracy with an experimental database composed by a set of 2D prescribed movement tests at the fairlead of the mooring system.     

Challenges in the application of spatial computable general equilibrium models for transport appraisal

The use of spatial computable general equilibrium (SCGE) models for assessing the economic impacts of transport projects is one of the key items on the research agenda for project appraisal in the Netherlands. These models are particularly suitable for analysing indirect effects of transport projects through linkages between the transport sector and the wider economy. Potentially, according to the literature, indirect effects that are additional to first-order direct cost reductions can turn out to be up to almost 80% in magnitude of the direct impacts. Given the relevance of these models for policy appraisal, experiences with this new modelling approach are important to report. After two years of development and application of SCGE models for transport appraisal, we found that the translation of theory behind the spatial equilibrium models into practical model specifications and empirical applications is a challenging task, and may lead to problems in project appraisal in terms of inaccuracies in the assessment of impacts. This paper discusses some key challenges we encountered with the specification of the Dutch SCGE model RAEM. This chapter is especially useful for researchers developing SCGE applications for use in transport appraisal and those who want to get a better understanding of differences between theoretical and computable SCGE modelling.     

浅析仿真系统的概念模型

概念模型是仿真系统开发的“蓝图”，也是仿真模型确认和验证的依据所在。正如国内外仿真领域有关专家所指出的，概念模型的重要性已经被充分的认识到，但是，对概念模型的认识却不统一^[1]。有关概念模型的开发要求和理论研究也非常的匮乏。对仿真系统的概念模型开发和表达进行了初步探索，界定了概念模型的表达范围，研究了相应的表达方法。     

虚拟仪器激光轨迹跟踪仪的设计与实现

为了实现非合作目标的跟踪定位,在Labview平台下引用虚拟仪器技术,以硬件为基础,软件为核心,采用基于事件结构状态机的编程方法,设计并开发虚拟仪器激光轨迹跟踪仪,实现非合作目标轨迹、航向及速度的测量.激光轨迹跟踪仪界面友好,操作简单,并已经应用于实际的测量、测试实验中,可为目标特性的测量提供有力的数据参考信息.     

基于FPGA的网络传输信道加密系统

介绍了一种基于现场可编程门阵列(FPGA)的网络传输信道加密系统。通过对硬件加密中的序列密码加密算法的改进，不仅提高了安全性，而且提高了纠错能力。由于该系统具有硬件实现容易、处理速度快、实时性好、扩展能力强等优点，使得该系统在网络安全中具有广泛的应用前景。     

Analysis of the economic and social parameters of the Three-Wheeler Taxi service in Sri Lanka

Sri Lanka has an extensive Three-Wheeler Taxi service comprised of around 300,000 vehicles. These vehicles, which first made an entry to Sri Lanka’s roads in the early 1980s, account for around 15% of the active motor vehicle fleet at present. Three-Wheelers Taxis also account for around 6% of the passenger kilometres. These vehicles are mostly individually operated with some owned by the operator and others hired on a monthly or daily basis. The industry is unregulated with vehicle registration and driving licenses being the only instruments of regulation. Fares are unregulated. However, most operators belong to associations which are loose collections of operators found in a given locality. These associations impose a degree of self regulation with respect to fares. They also tend to demonstrate oligapolistic behaviour.The paper is based on a survey of 200 operators and 100 passengers from a Divisional Secretariat area in Colombo District. The survey covered a number of details pertaining to ownership, management and fare structures, as well as opinions on the service attributes by users. The survey also covered perceptions of operators to determine the social, economic and transport implications of the services provided. Details were also obtained on the profiles of the operators and their expectations.The paper provides the results of the analysis of this data and draws a number of conclusions on the economics of the industry as well as the social aspects associated with it. It also discusses the characteristics of the users of these three wheelers as well as their typical use. The analysis also investigates complementarily of service provision between three wheelers as an access mode to buses and railways. This analysis has been used to develop an understanding of the manner in which the industry has grown over the last two decades and how it is being operated today. It also identifies areas wherein the industry has become inefficient and assesses the degree of over pricing that exists due to this. The data also helps to determine the relationship between unemployment and provision of self-employed transport services.The paper concludes with a synopsis of the profile of the industry and its role within the wider transport sector and with respect to ownership. It also discusses the positive and negative impacts of the lack of regulation on the industry.     

基于模糊AHP综合评价方法的航运公司综合实力评价

提出了—种基于模糊AHP的综合评价方法,从客户的角度对航运公司的综合实力进行了综合评价、排序。经过分析计算,结论基本合理,且本方法简单实用。不但为企业选择优良的航运企业提供了理论依据,同时也为航运公司在航运市场中的位置定位提供了帮助,为其弥补不足提升综合实力提供参考。两种评价方法单独使用各有自己的缺陷,将其相结合,弥补各自的缺陷,形成一个综合评价方法。     

公路边坡挡土墙注浆加固技术探讨

随着高速公路运营时间增长,边坡结构物病害也不断显现。通过某工程实例,说明对部分岩体或砂性土边坡挡土墙开裂、外倾等病害用压力注水泥浆体进行维修加固具有较好的效果。在加固边坡挡土墙等结构物的同时对后方土体也具有一定的改良复合作用,能有效提高坡脚抗压能力,消除坡脚应力集中的影响。