超燃冲压模型发动机实验设备与实验技术

超燃冲压发动机是高超声速飞行器的先进的动力系统,在基础研究和工程应用方面都具有重大意义.其实验设备的建设与实验技术的积累是一个国家在航空航天领域综合实力的体现.本文综述了国外超燃冲压发动机地面实验设备的发展情况,介绍了我国用于超燃冲压模型发动机实验的高超声速推进实验装置及其关键组成部分的设计思想、研制方法和调试结果.马赫数5.8,总压5\,MPa,总温2\,000\,K,总流量4.5\,kg/s的设备运行参数为超燃冲压模型发动机的研究提供了必要的实验条件.      

Approximating connected facility location with buy-at-bulk edge costs via random sampling

In the connected facility location problem with buy-at-bulk edge costs we are given a set of clients with positive demands and a set of potential facilities with opening costs in an undirected graph with edge lengths obeying the triangle inequality. Moreover, we are given a set of access cable types, each with a cost per unit length and a capacity such that the cost per capacity decreases from small to large cables, and a core cable type of infinite capacity. The task is to open some facilities and to connect them by a Steiner tree using core cables, and to build a forest network using access cables such that the edge capacities suffice to simultaneously route all client demands unsplit to the open facilities. The objective is to minimize the total cost of opening facilities, building the core Steiner tree, and installing the access cables. In this paper, we devise a constant-factor approximation algorithm for this problem based on a random sampling technique.     

山西省农村水利设施发展的因子分析

以市域农村为单位,用因子分析法对山西省农村水利设施现状进行了研究,按照因子分析结果,把山西省市域农村水利设施发展现状分为三类:水利设施较发达地区、欠发达地区和落后地区,并给出了各市域农村水利设施建设和投资的建议.     

On a connection between facility location and perfect graphs

We characterize the graphs for which a linear relaxation of a facility location problem defines a polytope with all integral extreme points. We use a transformation to a stable set problem in perfect graphs. Based on this transformation, these graphs can be recognized in polynomial time.     

Estimating diverter valve corrections

A new method has been developed for estimating the corrections to be made to the measured time interval for diverter valves used in primary liquid flow measurement facilities. The model relates the mass flowrate, m, to the measured mass of liquid collected and the effective collection time. The effective collection time is the sum of the measured time interval and the diverter valve correction, τ, to be estimated. The diverter valve correction is the adjustment made to the collection time to account for the non-instaneous diversion of the flow between the collection vessel and the reservoir of the flow loop. An auxiliary flow measurement device in the flow pipeline is used to estimate m and an iterative process is used in the estimation of τ. This method gives statistical information on the variability of the performance of the system as indicated by the individual estimates of τ. Experimental data for two diverters used in the US National Bureau of Standards Primary Liquid Flow Measurement Facility are used to illustrate the calculation procedure     

Mathematical Modeling,Control, Computer Simulation and Laboratory Experiments of a Spatial Servopneumatic Parallel Robot

In this paper (Part I), the special construction of a controlled parallel structure, called spatial servopneumatic multi-axles test facility (MAP), will be theoretically and numerically investigated and controlled. The investigations include the following steps: (i) design of mathematical models of different complexity of both, the test facility mechanics in terms of DAEs and ODEs (a multi-body system which contains 13 rigid bodies under spatial motion, connected by joints), and the servopneumatic actuators; (ii) construction of different linear and nonlinear (model based) control algorithms; (iii) development of a computer simulation program of the MAP; and (iv) evaluation of various computer simulation runs, obtained by applying different control algorithms and spatial command-input signals. The results show that the efficiency of the control algorithms is closely related to their complexity and cost. In order to check the closeness to reality of the computer simulation results and their benefit for industrial applications, laboratory experiments must be formed with the same MAP, the same control algorithms, and applying the same command-input signals which have been used in the computer simulations. These experimental investigations will be presented in Part II of the paper.     

On the compression process in a free-piston shock-tunnel

Preliminary results in the Marseille free-piston shock-tunnel facility are presented. The compression of the driver gas by the piston is studied experimentally for two different geometries of the end of the compression tube. Peak pressures obtained with the end of the compression tube closed, and with bursting of the diaphragm separating the high pressure from the low pressure chamber, are compared with calculated values in the cases of N₂ and He as driver gases. A phenomenon of accoustic resonance has been uncovered, generating strong pressure oscillations which, if not properly dealt with, could impair the quality of the useful flow in such a facility.This article was processed using Springer-Verlag T_EX Shock Waves macro package 1.0 and the AMS fonts, developed by the American Mathematical Society.     

Apparatus for Testing Concrete under Multiaxial Compression at Elevated Temperature (mac2T)

This paper describes a new test facility for determining material mechanical properties of structural concrete. The novel facility subjects 100 mm cubic concrete specimens to true multiaxial compression (σ₁ ≠ σ₂ ≠ σ₃) up to 400 MPa at temperatures of up to 300°C. Forces are delivered through three independent loading frames equipped with servo-controlled hydraulic actuators creating uniform displacement boundary conditions via rigid platens. Specimen deformation is calculated from displacements measured to an accuracy of 10⁻⁶ m using a system of six laser interferometers. The combination of stiff loading frames, rigid platens, an accurate and reliable strain measurement system and a fast control system enables investigation of the material response in the post-peak range. The in-house developed control software allows complex multi-stage experiments involving (i) load and temperature cycling, (ii) small stress probes and (iii) arbitrary (pre-defined) loading paths. The program also enables experiments in which the values of the control parameters and the execution of the test sequences depend on the response of the specimen during the test. The capabilities of the facility are illustrated in this paper by experiments determining the effects of different heat-load regimes on the strength and stiffness of the material and tests identifying the tangent stiffness matrix of the material and the associated changes in the acoustic tensor under multiaxial compression.     

一种以TATB/HMX为基的高聚物粘结炸药的短脉冲冲击起爆特性

利用金属箔电爆炸驱动聚酯薄膜飞片产生短脉冲冲击波的加载技术（电炮），依据DRM（Delayed Robbins-Monro）试验程序，研究了以TATB/HMX为基的高聚物粘结炸药的短脉冲冲击起爆特性，获得了其50%起爆概率条件下的冲击起爆阈值和100%起爆的最小起爆阈值。利用光纤探针/光电转换器/示波器接收技术，研究了冲击起爆压力幅值和脉宽对该炸药到爆轰距离的影响，得到了相应的Pop关系。     

随机容错设施选址问题的原始-对偶近似算法

研究两阶段随机容错设施选址问题,其中需要服务的顾客在第二阶段出现（在第一阶段不知道）．两个阶段中每个设施的开设费用可以不同,设施的开设依赖于阶段和需要服务的顾客集合（称为场景）．并且在出现的场景里的每个顾客都有相同的连接需求,即每个顾客需要由r个不同的设施服务．给定所有可能的场景及相应的概率,目标是在两个阶段分别选取开设的设施集合,将出现场景的顾客连接到r个不同的开设设施上,使得包括设施费用和连接费用的总平均费用最小．根据问题的特定结构,给出了原始。对偶（组合）3-近似算法．