埋地管道施工过程中受力分析及强度计算

文章分析埋地管道使用介质、工作状况、开孔位置在开孔施工过程中以及日后运行过程中的安全性能,说明合理开孔位置、了解开孔处埋地管道的受力情况及其载荷分布、合理计算埋地管道的强度,对于管道开孔工程的安全保证有着极其重要的意义。     

装配状态下的后螺旋弹簧强度计算

文章通过对圆柱螺旋压缩弹簧的设计公式的描述,指出其在五连杆后悬架螺旋弹簧设计中的局限性,提出一种基于有限元方法的计算后悬架螺旋弹簧强度的分析方法。该方法在螺旋弹簧垂直压缩工况下,通过验证有限元计算的结果后再用后悬架总成的方法分析后螺旋弹簧在装配状态下的强度结果,从而保证了分析结果的可靠性。该方法弥补了传统方法中基于经验公式计算弹簧强度的不足,增加了一种验证螺旋弹簧强度的方法。     

板翅式换热器芯体主要零件的强度计算

绝大多数板翅式换热器由铝合金制成,其它类型紧凑式换热器也不局限只用钢材制造。从原则上讲,由铝合金制成的受压构件的强度完全可以采用钢制压力容器规范上所规定的方法来计算或校核。     

隔爆外壳的强度刚度验证计算

目前隔爆外壳大多采用经验法或类比法进行隔爆外壳设计,这种设计模式不仅耽误生产周期,还会造成较大的经济损失.本文以某型号矿用隔爆兼本质安全型电控箱为研究对象,通过对其进行理论强度刚度计算,指出其薄弱之处,提出了改进措施.为隔爆外壳结构设计,尤其是加强筋布置、箱体壁厚选择等提出了一种优化改进设计方法.     

某蓄电池车体有限元计算及静强度试验研究

针对公司设计生产的蓄电池工程车车体,利用有限元分析手段对车体结构进行仿真计算,并对其按照相关标准进行静强度试验。仿真计算结果与静强度试验结果表明：车架垂向静载刚度都小于标准值,纵向拉伸、压缩工况下,最大应力均小于材料许用应力,刚度、强度满足相关标准要求。通过对比分析,同一测试位置,其仿真计算的应力值与试验得到的应力值偏差较小。试验说明有限元仿真结果值可信,仿真过程边界条件加载及约束与实际需求一致,为以后的车体结构设计及优化提供了有效依据。     

大型汽轮发电机汽端联轴器刚强度计算

本文对大型汽轮发电机的汽端联轴器整体装配进行了非线性有限元分析,针对其不同的计算工况,对热套圆键连接结构的联轴器进行刚强度的分析计算。经过计算,通过对计算结果的分析和评判,保证机组能够满足正常运行工况、过速工况以及短路工况的强度要求,同时联轴器位置的变形也不能超过使用要求。     

四方位接触轴承的承载能力和寿命

本文简略介绍了四方位接触轴承的静载荷承载能力,动载荷承载能力和寿命计算。     

起重机箱形伸缩式起重臂强度计算浅析

本文使用两种不同的计算方法对箱形伸缩式随车起重机起重臂强度进行计算,通过对各节起重臂危险截面的应力值进行对比,分析不同计算方法下各节起重臂应力值大小,总结出起重臂强度计算过程中采用哪种计算方法能够得到比较准确的起重臂强度计算结果,从而指导起重臂过程中设计值与理论要求值较优匹配。     

A contingent theory of supplier management initiatives: Effects of competitive intensity and product life cycle

Direct investments in supplier development and close relationship building are the two major collaborative supplier management strategies for developing and accessing superior supplier capability. The impact of these two strategies, however, has not been uniform across firms, calling for a deeper examination of their relative effectiveness. Utilizing multiple theoretical frameworks, this study examines the relevance and effectiveness of the two collaborative strategies across the growth and maturity stages of the product life cycle (PLC). Specifically, the study analyzes the influence of competitive intensity as an antecedent to supplier development and relational initiatives, and the role of product life cycle as a moderator of the inter-relationships among competitive intensity, supplier development, relational initiatives, and supplier capability. Based on primary survey data, and discussion with practicing managers, the study finds that the individual and integrative effectiveness of supplier development investments (SDI) and relational orientation (RO) can be influenced differently by competitive intensity and PLC stage. In particular, RO can have a foundational role in motivating SDI for superior supplier capability, as also in safeguarding against supplier opportunism in the standardized product market context of the maturity stage. The managerial and theoretical implications of varied emphasis on the two collaborative supplier management strategies across the PLC stages are discussed.     

熊市下我国开放式证券投资基金业绩特点研究

采用平均收益率、詹森指数和Fama-French三因素詹森指数对我国开放式证券投资基金在熊市下的业绩特点进行了实证研究。研究结果表明:大多数基金业绩基本上与市场指数持平;基金从总体上看偏好于对大公司及成长型公司的投资。     

管道泵出口段断裂原因分析

根据管道泵管路安装布置情况,进行受力状态分析及计算,提出管道泵装置时的合理安装方式的建议。     

横轴掘进机减速器斜齿轮副弯曲疲劳寿命分析

齿轮弯曲疲劳强度是齿轮设计的基本准则之一。由于缺乏有效的方法,传统的斜齿轮弯曲疲劳强度分析通常采用当量直齿轮近似计算。本文针对横轴掘进机减速器斜齿轮副的弯曲疲劳寿命研究了一种经典ANSYS与ANSYS Workbench相接合的方法进行精确分析。利用ANSYS的瞬态分析功能精确求取齿根的最大弯曲应力和对应的最恶啮合位置,然后利用ANSYS Workbench的疲劳分析功能对斜齿轮副的疲劳寿命进行精确分析。仿真结果表明,该方法可以精确求取斜齿轮副的弯曲疲劳寿命和安全系数,为横轴掘进机减速器的设计与优化提供可靠保证。     

Unfolding intensity function of a Poisson process in models with approximately specified folding operator

Quasi-maximum likelihood histogram sieve estimators of the intensity function of an indirectly observed Poisson process are studied. The setup differs from the standard one in that the exact form of the folding operator may not be known. Instead, approximate knowledge on its discretized version is available. Conditions for strong L ²-consistency are given and admissible discretization rates are studied. In non-folding problems, the number of histogram bins may essentially increase at the usual maximal rate while folding reduces the allowed discretization rates. It is shown that, even in moderately ill-posed problems, the discretization effects may be critical for the strong L ²-convergence and that there is an essential need both for further regularization and for imposing stronger conditions on the estimated function. Not surprisingly, the most restrictive factor is the low approximation power of piecewise constant functions. A regularization method is proposed which suitably modifies the discrete approximation of the folding operator and ensures the strong consistency. Since no penalty term is being introduced, the EM algorithm can be used in its factorized, efficient form. Convergence rates are obtained in terms of the discrete problem. Received: July 1999     

The dynamics of innovation and horizontal differentiation

We study innovation in a dynamic stochastic discrete-time duopoly with endogenous horizontal differentiation. Innovation takes the form of a quality ladder; horizontal differentiation is Hotelling competition. We compute Markov-perfect equilibria and study the effects on long-run innovation of changes in taste heterogeneity (transport costs) and firms' costs of relocating products. Innovation rises as the industry's long-run position moves toward products that are permanently co-located in the space of horizontal tastes. A large enough fall in taste heterogeneity will raise long-run innovation, while more costly product relocation lowers innovation if taste heterogeneity is high, and raises it otherwise.     

Estimation of the intensity of a Poisson point process by means of nearest neighbor distances

A new unbiased consistent asymptotically normal estimator U _k of the intensity λ of a stationary multivariate Poisson point process is exhibited. This estimate is based on a combination of the j -th nearest neighbor (possibly non Euclidean) distances ( j =1, ..., k ) to a single fixed site x . A simple closed form containing logarithmic terms is obtained for E ( U ^l _k )(0< l < k ).     

熊市下我国开放式证券投资基金业绩持续性研究

采用基于回归分析的多期基金业绩持续性评价模型,对56只中国的各类开放式证券投资基金在熊市下的业绩持续性进行了实证研究。结果表明:在短期内,各类基金的业绩不存在持续性,基金业绩往往具有反转性。不同的基金超额业绩的计算方法有时会对评价结果影响很大。     

利用城市流强度划分中心城市规模等级体系--以江西省为例

利用计算城市流强度的方法来划分江西省中心城市规模等级体系,得出江西省中心城市规模等级体系中的四个层次的城市,通过计算对划分结果的分析,证实利用城市流强度来划分城市规模等级体系是一种切实有效的科学方法.     

基于Pro/E的微型电机转子冲片模具设计

文章分析了微型电动机转子冲片冲压成形工艺方案,并进行了综合比较,选取精密复合模作为最终方案。确定了模具总体结构,利用Pro/E建立了模具的三维实体模型,检查了零件间的干涉情况,验证了装配结构的正确性。