ATM TraP:异步传输模式通信量与性能测量工具

我们经常用理论通信量模式来进行ATM网络通信量控制算法的分析与开发。根据这些模型已经提出了用于通信量成形、管理、流量控制和交换结构的算法。当模型帮助我们获得初步的解决办法时,提出的这种算法的成功和有效将会成为一种假模想模型与真实通信量模型程度相似的一种功能。 本文介绍的ATMTraP,即异步传输模型通信量和性能测试工具,是一个试验性样机,它能够用来表征构成ATM网络的信息源和部件。ATMTraP已经用于Nectar千兆位试验台,用来收集来自各信息源,诸如Cray C-90巨型计算机、Sun工作站、iWARP systolic阵列等的初步通信量统计数据。     

复杂形状薄壁零件加工的综合质量控制

首先分析了加工时零件表面热量场和加工参数、余量场之间的关系;利用数字扫描及滤波的方法建立起复杂形面零件的数学模型;以此为基础,在加工过程中,对零件的几何质量和表面层质量进行了综合控制。研究表明,该方法是提高飞行器发动机中高负载复杂形状薄壁零件可靠性和寿命的有效新途径。     

分布式多媒体系统的操作系统支持结构

分布式多媒体系统应用在系统的各层次——从网络协议、操作系统到操作应用支持平台——引起了新的设计挑战。本文介绍了一种将网络服务与操作系统综合起来用以支持分布式多媒体系统的面向对象体系结构。该结构称为动态对象结构(DOA),基于开放分布式处理(DOP),是基于分布式系统的客户服务器结构国际标准。DOA利用面向对象技术解决分布式多媒体系统的各项要求,诸如连续媒体、自然同步、服务动态质量(QoS)和分组通信等。该结构还提供一种途径,即应用成熟的工业标准来开发新的应用领域,同时保持与旧的应用领域的兼容性。     

最优滤波的综合方法

与用于现代最优滤波理论中的解析方法相反,本文介绍一种综合方法。由计算机模拟或者实际实验产生的信号的传感器数据,通过训练一个递推多层感知机(RMLP)而综合到一个滤波器中,其中多层感知机至少具有一个隐蔽层,其神经元完全或部分内连,有或者没有输出反馈。 经过适当训练后的递推多层感知机,对于给定的结构是一个递推的最优滤波器,在每一个时刻,包含最优条件统计量的延滞反馈。最重要地是,随着隐蔽层神经元数的增加,它收敛于最小方差滤波器。我们称这种RMLP为神经滤波器。 模拟结果表明:只有少数隐蔽神经元的神经滤波器,对于所研究的简单非线性信号/传感器系统,它始终胜过广义卡尔曼滤波器,甚至迭代的广义卡尔曼滤波器(IEKF)。     

直接立体显示装置

直接立体显示装置(DVDD)直接在空间生成图象,支援生理和心理深度线索,要使其具有商业生命力,DVDD需要更多的色彩和更多的三维象素。     

黑海的秘密(连载之一)

1991年7月,北大西洋,距阿果尔群岛以西约300英里处,美国航空母舰“罗斯福”号在开始演习以前已完成一系列长时间训练…     

论柔性化后勤装备维修外包合同管理

柔性管理是21世纪管理学发展的新方向,目前被广泛应用于现代企业管理包括合同管理实践中。以具有柔性的外包合同应对外包环境的不确定性,已成为提高外包绩效的有效途径。当前,后勤领域应积极顺应这一大方向,努力在制定后勤装备维修外包合同管理规章、设计外包柔性合同、研制外包合同柔性管理信息系统、培养外包合同柔性管理人才等方面,开拓新思路,迎接新挑战,取得新进展。     

Noise and vibration measurements in a Viking military vehicle

Noise and whole-body vibration measurements were made in a Viking military vehicle to determine the variation that should be expected during repeat measures, the effect of speed (up to 60 km/h in 5 km/h increments), and during travel over different types of terrain (comprising concrete road, gravel track and rough cross-country). Measurements were made at various crew positions (including the driver and commander) in both the front and the rear cabs in the vehicles. Three translational axes of vibration were measured in each seat. Two speeds were investigated over road (35 km/h and 55–60 km/h) and gravel (20 km/h and 35 km/h) surfaces. The effect of varying speed of the vehicle on the measured noise and vibration magnitudes was also investigated. The highest sound pressure level (L_Aeq) of 104 dB(A) was measured at the commander’s standing position during travel over concrete road at 55 km/h. Higher noise levels occurred for a standing commander compared with when sitting on the seat. A maximum single axis frequency-weighted vibration magnitude of 1.0 m/s² r.m.s. was measured on the driver’s seat during travel over track at 35 km/h. Higher vibration magnitudes occurred during travel over track compared with travel over road. Both noise and vibration exposure of crew within the Viking vehicle increased with increasing speed of the vehicle.     

Critical interfaces in body armour systems

The ballistic performance, and behaviour, of an armour system is governed by two major sets of variables, geometrical and material. Of these, the consistency of performance, especially against small arms ammunition, will depend upon the consistency of the properties of the constituent materials. In a body armour system for example, fibre diameter, areal density of woven fabric, and bulk density of ceramic are examples of critical parameters and monitoring such parameters will form the backbone of associated quality control procedures. What is often overlooked, because it can fall into the User’s domain, are the interfaces that exist between the various products; the carrier, the Soft Armour Insert (SAI), and the one or two hard armour plates (HAP1 and HAP2). This is especially true if the various products are sourced from different suppliers.There are between 30 and 150 individual layers within a typical body armour system, and each of the interfaces between each of those layers will, in some way or another, contribute to the ballistic performance of the system. For example, consider the following interfaces/interlayers: (i) the frictional, sliding, inter-ply surfaces within a soft armour pack, and also between the pack and the carrier, (ii) the air-gaps that may develop within the soft armour pack, (iii) the interconnecting space between the soft armour pack and the hard armour plate, (iv) the nature of the interfaces between adjacent plies of a multiplied backing laminate, even in a highly compressed Ultra High Molecular Weight Polyethylene (UHMWPE) variant, (v) the interlayer between the ceramic and its substrate, within a HAP, and (vi) the geometrical fit between two hard armour plates within a stacked body armour system. This paper will provide a User-friendly overview of all such interfaces and provide unique guidance as to their criticality and influence.