GB/T 16675.1～16675.2-1996《技术制图简化表示法》实施浅探

一、标准颁布实施的重要意义GB/T16675.1～16675.2—1996《技术制图简化表示法》,1996年12月18日发布,1997年7月1日实施,是我国制定的第一个简化制图方面的系列标准。它是在密切注意国际标准的制定动向,结合我国具体情况,参考GB/T4458.1—1984《机械制图图样画法》和GB/T4458.4—1984《机械制图尺寸注法》两项标准相关部分的基础上,等同采用国际标准和国外发达国家先进标准的有关章节而制定的。自发布实施以来,大大推动了工程技术界、图学界及教育界的发展,取得了十分明显的经济效益和社会效益。《技术制图简化表示法》是与正规投影绘图…     

I-DEAS的三维几何建模

Ｉ－ＤＥＡＳ几何建模有两种方法。一是通过对基本体素进行布尔集合运算而构成复杂表体,称作体素拼接法;一是通过面扫描及点、线和面之间的运算操作构成三维实体,称作边界表示法。本文还介绍了Ｉ－ＤＥＡＳ几何建模的数据结构。     

无源雷达的二维定位精度分析和图形描述

为了分析无源雷达三站时差定位技术的定位精度,综合考虑了目标水平面位置和高度以及测量站站址对定位精度的影响,在三维空间直角坐标系下建立定位精度模型,通过计算机仿真分别采用相对定位误差和椭圆概率误差表示法描述定位误差分布.仿真结果表明,所建模型正确、有效,两种表示法能从不同角度描述定位误差的空间分布,两者反映出的分布信息可...     

基于知识的模型表示研究

基于知识的模型表示是信息管理系统,特别是决策支持系统(DSS)的基础。根据模型管理和模型建立动态性原则的要求,提出了模型知识化的框架表示法,并给出了应用实例。     

计算机局部地区网络的若干问题

计算机局部地区网络是通信技术与计算机技术相结合的产物。在英文的文献中,常见到LAN这样的称呼(代表Local Area Network)。也常见到LCN或LACN的表示法(这里C代表Computer)。预计今后“LAN”的表示法将和用“CPU”表示中央处理机一样,广泛为人们所采用。LAN有时简称为局部网络。这当然不如“计算机局部地区网络”意义明确,但大多数技术人员是清楚“局部网络”的含义的。在本文中,将尽量采用简便的称呼     

《技术制图 简化表示法》浅谈

对宣贯学习 GB/T 16675.1～16675.2—1996《技术制图简化表示法》过程中的体会、认识、具体作法谈了自己的几点意见,旨在探讨如何深入细致地更好宣贯该标准,以期收到更好的效果。     

流体力学中的一种简单张量表示法

本文介绍张量表示法在流体力学中的应用,采用最简单的记号分析流体的流动现象,使得许多复杂的公式推导及方程的变换大为简化。     

基于案例的推理在舰船维修费预测中的应用

针对市场经济条件下舰船维修费预测不确定性越来越大的问题,提出了一种基于案例推理的舰船维修费预测模型。首先,利用修船厂的历史数据,采用特征向量表示法构建舰船维修费案例库;其次,为提高案例检索效率,采用组合模糊聚类算法建立舰船维修费案例的分类索引结构,并提出基于最近邻法的两步检索策略检索相似案例;最后,采用加权平均法对相似案例进行修改以获取预测值,同时采用主动学习策略保存当前案例并更新案例库。实例仿真结果表明:与传统舰船维修费预测模型相比,基于案例的推理模型具有更高的预测精度,所提模型是有效的。     

M468——雷特最新特种用途枪弹卡宾枪

M468特种用途枪弹卡宾枪,是以0.50口径步枪而著名于世的美国巴雷特火器制造公司的最新力作。该枪型号采用组合表示法,4表示该卡宾枪研制于2004年,68是指口径为6．8mm。     

面向对象的战略战役指挥训练模拟系统数据建模

大型的战略战役指挥训练模拟系统需要内容复杂、数量庞大的数据作为支撑,而结构清晰、容易理解的数据模型是系统成功开发和应用的前提。采用面向对象的基本方法,给出了系统数据建模的概念定义并采用UM L表示法进行了建模方法分析,最后讨论了OO数据模型在系统工程化的数据准备以及运行时和事后分析等应用中所具有的特点。     

基于约束的交互式电气线路故障诊断

给出了器件的约束表示,实现了电气线路的约束网络化.分析了电气线路约束网络的特点,找出了故障树的剪节方法,提出了基于约束故障诊断的方法和步骤.     

Coating processes towards selective laser sintering of energetic material composites

This research aims to contribute to the safe methodology for additive manufacturing (AM) of energetic materials. Coating formulation processes were investigated and evaluated to find a suitable method that may enable selective laser sintering (SLS) as the safe method for fabrication of high explosive (HE) compositions. For safety and convenience reasons, the concept demonstration was conducted using inert explosive simulants with properties quasi-similar to the real HE. Coating processes for simulant RDX-based microparticles by means of PCL and 3,4,5-trimethoxybenzaldehyde (as TNT simulant) are reported. These processes were evaluated for uniformity of coating the HE inert simulant particles with binder materials to facilitate the SLS as the adequate binding and fabrication method. Suspension system and single emulsion methods gave required particle near spherical morphology, size and uniform coating. The suspension process appears to be suitable for the SLS of HE mocks and potential formulation methods for active HE composites. The density is estimated to be comparable with the current HE compositions and plastic bonded explosives (PBXs) such as C4 and PE4, produced from traditional methods. The formulation method developed and understanding of the science behind the processes paves the way toward safe SLS of the active HE compositions and may open avenues for further research and development of munitions of the future.     

A linear-programming-based method for determining whether or not n demand points are on a hemisphere

Whenever n demand points are located on a hemisphere, spherical location problems can be solved easily using geometrical methods or mathematical programming. A method based on a linear programming formulation with four constraints is presented to determine whether n demand points are on a hemisphere. The formulation is derived from a modified minimax spherical location problem whose Karush-Kuhn-Tucker conditions are the constraints of the linear program. © 1993 John Wiley & Sons, Inc.     

A mathematical formulation and efficient heuristics for the dynamic container relocation problem

The container relocation problem (CRP) is concerned with emptying a single yard‐bay which contains J containers each following a given pickup order so as to minimize the total number of relocations made during their retrieval process. The CRP can be modeled as a binary integer programming (IP) problem and is known to be NP‐hard. In this work, we focus on an extension of the CRP to the case where containers are both received and retrieved from a single yard‐bay, and call it the dynamic container relocation problem. The arrival (departure) sequences of containers to (from) the yard‐bay is assumed to be known a priori. A binary IP formulation is presented for the problem. Then, we propose three types of heuristic methods: index based heuristics, heuristics using the binary IP formulation, and a beam search heuristic. Computational experiments are performed on an extensive set of randomly generated test instances. Our results show that beam search heuristic is very efficient and performs better than the other heuristic methods.Copyright © 2014 Wiley Periodicals, Inc. Naval Research Logistics 61: 101–118, 2014     

基于迭代结构滤波器的SAR图像去噪方法研究

通过比较各种合成孔径雷达 (SAR)图像的滤波方法 ,指出他们存在的不足。然后提出基于模拟退火的迭代滤波器的SAR图像滤波方法。这种方法通过引入相关邻域模型 ,描述图像的局部特性。首先建立一系列反映方向信息的模板 ,每一个模板代表了一种邻域结构。然后在SAR图像的统计性质基础上 ,对于每个邻域结构 ,利用Bayes方法 ,根据图像的观测值 ,获得强度真实值的最大后验概率 (MAP)估计。然后运用模拟退火算法 ,根据每个结构的概率随机选取一个邻域结构作为最适合结构 ,它所对应的估计值作为图像真实强度的估计。模拟退火保证随着温度逐步趋向于 0 ,算法可以获得估计的全局最优解     

材料随机梁的有限元分析

提出一种以柔度为基础的具有随机刚度弯曲梁的有限元公式。在计算过程中 ,用与刚度均值有关的内力近似表示未知内力值。通过蒙特卡罗模拟可示出刚度的一维可靠性密度函数和相关函数 ,可用来估算柔度的均值和协方差函数。最后根据新的公式计算出随机梁的均值和协方差。     

Optimizing the allocation of components to kits in small-lot,multiechelon assembly systems

The kitting problem in multiechelon assembly systems is to allocate on-hand stock and anticipated future deliveries to kits so that cost is minimized. This article structures the kitting problem and describes several preprocessing methods that are effective in refining the formulation. The model is resolved using an optimizing approach based on Lagrangian relaxation, which yields a separable problem that decomposes into a subproblem for each job. The resulting subproblems are resolved using a specialized dynamic programming algorithm, and computational efficiency is enhanced by dominance properties devised for that purpose. The Lagrangian problem is resolved effectively using subgradient optimization and a specialized branching method incorporated in the branch-and-bound procedure. Computational experience demonstrates that the specialized approach outperforms the general-purpose optimizer OSL. The new solution approach facilitates time-managed flow control, prescribing kitting decisions that promote cost-effective performance to schedule. © 1994 John Wiley & Sons. Inc.     

单站纯方位目标跟踪系统可观测性分析

针对单站纯方位目标跟踪系统的可观测性,在研究国内外有关状况的基础上,给出了单站纯方位目标运动分析的问题描述,综述了国内外的研究和发展情况,给出了由观测可观测性的一些结论和证明.其中对某些经典的结论给出了简单、明了的证明方法,这些有助于该问题的深入理解和研究.     

Developing an optimal repair-replacement strategy for pallets

A Markovian model is presented for the development of an optimal repair-replacement policy for the situation requiring a decision only at failure. The problem is characterized by the presence of growth which is integrated into the formulation. The model is applied to an actual problem, with data analysis and results given. Substantial savings are indicated.     

One-person games of economic survival

This paper discusses the one-person economic survival game model with a discrete probability distribution for the contribution to surplus variable. The general game model and strategies in these games are examined, and necessary conditions which an undominated, stationary strategy must satisfy are obtained. For a special class of these games a mathematical formulation of the value of the game is given, and examples and theorems which relate to undominated strategies in this class are presented. This paper, in some sense, is a sequel to a portion of a paper by Shubik and Thompson [7] which appeared in this journal.