Microstructure,mechanical properties and wear resistance of an Al–Mg–Si alloy produced by equal channel angular pressing

Microstructure, mechanical properties and wear resistance in an ultrafine-grained Al–Mg–Si alloy fabricated utilizing a combination of equal channel angular pressing (ECAP) and dynamic aging were investigated in this paper. The results indicated that the grain size of the ECAP alloy was significantly refined, i.e., to ~239 nm after three ECAP passes. Meanwhile, the yield and tensile strength of the ECAPed material reached 340 MPa and 445 MPa, respectively, while maintaining a significant uniform elongation of 14%. Wear resistance results demonstrated that the wear rate, wear depth and width of the ECAPed material decreased in comparison with the solution-treated (SST) and peak-aged (T6) conditions under a load range of 5–25 N. The adhesive wear that occurs in the undeformed specimens at 10 N does not appear in the ECAPed specimen at the same load, indicating that the ECAPed specimen delay the appearance of more serious wear mechanisms under certain loads. The cooperative interaction of high density nano-scale β" precipitates and dislocations resulted in a combination of super-high strength and good work hardening ability which suppressed the extension of cracks between the friction layer and the plastic deformation zone. As a consequence, the combination of ECAP and dynamic aging brings a significant improvement for antifriction performance of the 6061 aluminum alloy.     

考虑引入渠道竞争的双渠道信号传递策略

在一个存在高低两种类型制造商的供应链中,通过对制造商向零售商进行信号传递策略的研究,把制造商引入渠道竞争的动机解释为"渠道竞争"及"信息非对称"两种效应.把零售商努力纳入需求函数,建模分析了不完全信息条件下单(双)渠道供应链中制造商通过调整入场费和批发价进行信号传递的决策.并在此基础上通过两种渠道模式下供应链成员决策参数的对比,重点分析了渠道入侵对信号传递策略两种效应的综合影响.研究发现:两种模式下,制造商都需要通过向上扭曲批发价、降低支付给零售商的入场费来进行信号传递,同时零售商会减少附加值服务的提供;但当满足一定条件时,制造商可以通过引入线上直销渠道降低批发价向上扭曲的概率(即更容易实现自然分离),并减少信号传递成本;产品需求波动性、需求对零售商提供附加服务的敏感性以及渠道间竞争强度都将在一定程度上影响引入渠道竞争的效果.     

A neural network versus Black–Scholes: a comparison of pricing and hedging performances

An Erratum has been published for this article in Journal of Forecasting 22(6‐7) 2003, 551 The Black–Scholes formula is a well‐known model for pricing and hedging derivative securities. It relies, however, on several highly questionable assumptions. This paper examines whether a neural network (MLP) can be used to find a call option pricing formula better corresponding to market prices and the properties of the underlying asset than the Black–Scholes formula. The neural network method is applied to the out‐of‐sample pricing and delta‐hedging of daily Swedish stock index call options from 1997 to 1999. The relevance of a hedge‐analysis is stressed further in this paper. As benchmarks, the Black–Scholes model with historical and implied volatility estimates are used. Comparisons reveal that the neural network models outperform the benchmarks both in pricing and hedging performances. A moving block bootstrap is used to test the statistical significance of the results. Although the neural networks are superior, the results are sometimes insignificant at the 5% level. Copyright © 2003 John Wiley & Sons, Ltd.     

保密通信新介质--人工神经网络

根据人工神经网络的结构特点和信息传输与处理特征，提出了利用物理神经网络作为通信信道的观点．在分析了现有通信信道物理模型之后，具体讨论了作为通信信道的神经网络的可能拓朴结构、神经网络学习要点、允许传输信号的模式特征，研究了神经网络信道的传输延时、通信带宽及信噪比，分析了神经网络信道处理多媒体信号的计算潜力，并着重剖析了神经网络信道固有的保密通信特征．最后给出了一个具体的神经网络信道设计实例．     

对西方数学直观的评析

本文从数学方法论的角度,具体论述和评析了西方数学直观随数学发展的不同阶段所表现出的特点和演变方式。     

电视接收机图像中频的探讨

依据电视接收机图像中频选择原则，论述了我国电视接收机两次改变图像中的必要性。     

蒙版浅议

介绍了蒙版在图像处理中的应用，详细阐述了快速蒙版、Alpha通道蒙版、图层蒙版的特点及示例操作。     

大兴井田4#煤层砂岩砾岩体特征及成因分析

运用沉积学理论,通过对铁法煤田大兴井田4#煤层中发育的砂岩、砾岩体的研究,指出它们均为河道沉积产物,并从中识别出了聚煤早期河道正常沉积、聚煤期后河道水携物与坍塌物混积和河道泥石流沉积三种成因类型,论述了它们各自的岩相和空间发育特征,这将有益于揭示其平面分布规律,为进一步指导采场的科学设计和修订提供了基础.     

两段绞接式联合收割机输送槽的设计研究

本文介绍一种适宜配置在悬挂式联合收割机上的两段铰接式输送槽设计,这种输送槽后段固定,前段与割台连接并与后输送槽铰接,该铰接点为前悬挂割台的支点,借助液压油缸升降,文中对该铰接点位置的确定,以及两段输送槽铰接处的圆弧过渡板设计进行了分析研究,提供了设计方法.     

基于符号定向图(SDG)深层知识模型的定性仿真

定性仿真是系统仿真技术中的重要研究和应用方向，同时也是人工智能技术的一个重要方面。近年来，随着现代计算机技术的日新月异，使得基于符号定向图(SDG)深层知识模型的定性仿真研究和应用取得了显著进展。SDG模型能够表达复杂的因果关系，具有包容大规模潜在信息的能力，因此特别适合于过程系统危险评价(PHA)、危险识别与故障诊断。SDG模型结构简单，易于建立和修改。然而高质量的SDG模型必须采用经验数据和定量动态仿真检验和校正。采用SDG模型进行定性仿真的关键技术是高效双向推理“引擎”，由计算机软件自动完成。目前，在计算机辅助过程系统危险评价方面，SDG是最有效的方法；在过程系统故障诊断方面，其完备性较好，但诊断分辨率尚待提高。今后的研究应解决：定性仿真和定量仿真相结合；SDG自动建模；通用推理软件平台；大系统高分辨率故障诊断等问题。