AA5083铝合金的搅拌摩擦焊接工艺参数对搅拌头受力和热输入的影响(英文)

采用系统实验设计方法研究AA5083铝合金搅拌摩擦焊接工艺参数对搅拌头受力和热量输入的影响,得到了用来设计搅拌摩擦焊搅拌头和焊机的经验模型。当采用计算机来控制搅拌摩擦焊接时,这些模型可用来确定AA5083这类铝合金的摩擦焊接工艺参数、编制焊接程序及工艺参数控制。结果表明:影响轴向力和热量输入的重要参数是搅拌头转速、焊接速度和搅拌头轴肩直径,而影响纵向应力的重要参数是焊接速度和探头直径。     

Detection of milk fat adulteration with admixture of foreign oils and fats using a fractionation technique and the apparent solidification time test

A fractionation technique followed by the apparent solidification time (AST) test was adopted for detecting the admixture of foreign oils and fats in milk fat. The AST values of the solid fraction obtained at 20°C, and solid and liquid fractions obtained at 18°C for pure cow milk fat, were 2 min 30 s, and 3 min 21 s and 3 min 31 s, while for buffalo milk fat they were 1 min 58 s, and 2 min 47 s and 3 min 10 s respectively. This new approach can detect some mixtures of foreign oils and fats in cow milk fat but not in buffalo milk fat.     

Fuzzy clustering of mechanisms

During the course of development of Mechanical Engineering, a large number of mechanisms (that is, linkages to perform various types of tasks) have been conceived and developed. Quite a few atlases and catalogues were prepared by the designers of machines and mechanical systems. However, often it is felt that a clustering technique for handling the list of large number of mechanisms can be very useful, if it is developed based on a scientific principle. In this paper, it has been shown that the concept of fuzzy sets can be conveniently used for this purpose, if an adequate number of properly chosen attributes (also called characteristics) are identified. Using two clustering techniques, the mechanisms have been classified in the present work and in future, it may be extended to develop an expert system, which can automate type synthesis phase of mechanical design. To the best of the authors?? knowledge, this type of clustering of mechanisms has not been attempted before. Thus, this is the first attempt to cluster the mechanisms based on some quantitative measures. It may help the engineers to carry out type synthesis of the mechanisms.     

Time delayed control of classically damped structural systems

The effects of time delays on collocated as well as non-collocated point control of classically damped discrete dynamic systems have been examined. Controllers of PID type nave been considered. Analytical estimates of time delays to maintain/obtain stability for small gains have been given. Several new results dealing with the effect of time delays on collocated and non-collocated control designs are obtained. It is shown that undamped structural systems cannot be stabilized with pure velocity (or integral) feedback without time delays while using a controller that is not collocated with the sensor, when the mass matrix is diagonal. However, with the appropriate choice of time delays, for certain classes of commonly occurring structural systems, stable non-collocated control can be achieved. Analytical results providing the upper bound on the controller's gain necessary for stability have been presented. The theoretical results obtained are illustrated and verified with numerical examples.     

A method for finding minimal bottle-neck cells for grouping part-machine families†

The selection of parts and machines poses an important problem in the design and planning phases of cellular manufacturing and flexible manufacturing systems. In most real-life situations, this grouping invariably leads to 'bottleneck’ parts and machines. This paper discusses a method of identifying the minimal number of bottle-neck cells (machines or parts) which, when dealt with through either duplication of machines or subcontracting of parts, will result in perfect part-machine groupings with no overlap. The polynomially bounded algorithms used in the analysis are oriented towards finding minimal cut-nodes in either partition of the bipartite part-machine graph.

     

Deductive efficiency,belief revision and acting

Abstract

The SNePS inference engine is optimized for deductive efficiency, i.e. all beliefs acquired via inference are added to the agent's beliefs so that future queries may be answered by a retrieval rather than rederivation. An assumption-based truth maintenance system keeps track of the derivation histories of derived beliefs. We show how such an architecture simplifies the ontology of prepositional representations of plans; acts; preconditions, and effects of actions. In addition, the deductive efficiency of the basic system automatically extends itself to efficient search of plans, and hierarchical plan decompositions.     

Structural and mechanical behaviour of 5% Al2O3-reinforced Fe metal matrix composites (MMCs) produced by powder metallurgy (P/M) route

The aim of this paper is to investigate the effect of sintering temperature and time on the properties of Fe–Al₂O₃ composite (5 wt% Al₂O₃; 95 wt% Fe) prepared by powder metallurgy process. X-ray diffraction, microstructure, density, hardness and compressive strength of prepared samples have been investigated. XRD studies show the presence of Fe and Al₂O₃ along with iron aluminate phase. Iron aluminate is formed as a result of reactive sintering between iron and alumina particles. Microstructural examination of the specimen showed a dense structure with nanosize dispersion of the reinforcement of ceramic phase. Density as well as hardness of specimens depend on the formation of iron aluminate phase, which in turn depends on sintering temperature and time.     

Cold test of cylindrical open resonator for 42 GHz, 200 kW gyrotron

This paper presents experimental results for cold testing of a gyrotron open resonator. Experiments were carried out to measure resonant frequency and their particular quality factor for TE mode at the frequency 42 GHz. The perturbation technique was used to determine the axial, radial and azimuthal electric field profile for identification of TE₀₃₁ mode at operating frequency 42 GHz. The good agreement between experimental results and theoretical studies was found. The results verify the design and fabrication of the specific gyrotron cavity.     

System dynamics simulation of Hopfield neural networks

Hopfield networks are a class of neural network models where non-linear graded response neurons organized into networks with effectively symmetric synaptic connections are able to implement interesting algorithms, thereby introducing the concept of information storage in the stable states of dynamical systems. In addition to opening up the possibility of using system dynamics as a vehicle to gain potentially useful insights into the behaviour of such networks, especially in the field or nonelectrical engineering, we study the dynamics of the state-space trajectory as well as time domain evolution of sensitivities of the states with respect to circuit parameters.