基于局部模型网络的超声波浓度测量和在线校正

在很多情况下 ,液体浓度是其声速的函数 ,而且在不同的温度点上 ,这种函数关系是不同的 .针对浓度、声速和温度关系的这种特点 ,本文提出了基于局部模型网络的浓度和声速、温度关系的拟合和校正方法 .这种方法比普通的多项式拟合具有更多的灵活性和适用性 ,易于在线进行 .     

An effect of strength of railway axle steels on fatigue resistance under press fit

High-cycle fatigue tests with an evaluation of fatigue limit were carried out on large model components of bars with press fitted hubs of diameter 63/59 mm. Bars were made of three railway axle steels EA1N, EA4T and 34CrNiMo6 with considerable different strength from 586 MPa to 1041 MPa, respectively. Detection and measurement of crack growth under hubs by ultrasonic method was performed during the tests. In spite of the differences in strength and alloying of tested bars, differences in mean value of fatigue limit were not significant. This result was connected with specific damage mechanism and microcracks initiation under hubs with fretting effects. Short fatigue crack growth under hubs occurred at stress intensity factor range ΔK considerably bellow threshold value ΔK_th of long cracks. Simultaneous growth of main cracks from more than one point of surface circumferential area under hub was quite frequently observed.     

精轧机出口带钢头部浪形分析及应对措施

针对精轧机组出口板坯头部浪形不达标的问题,采用实测轧机弹跳曲线的方法找出了轧机的机械推上系统间隙无法有效消除是产生浪形不达标的主要原因。根据实际情况提出改造方案,结果表明其有效性。     

渣罐耳轴的液氮冷装工艺

在装配大过盈量零件时,热装工艺有时无法完成,需采用液氮冷装工艺才能较好的完成设计要求。文章对渣罐耳轴的具体装配过程进行了详细的介绍,并用一些具体的数据、图像进行了工艺分析。     

基于动态Copula的风光联合出力建模及动态相关性分析

准确描述风力发电和光伏发电的动态相关性及联合出力的波动性,对风光互补系统的出力预测和经济调度具有重要意义。针对现行静态相关系数无法准确描述风光出力相依关系的问题,研究了风光出力的动态相关性,提出了基于动态Copula函数的风光联合出力模型构建方法。结合实测数据建立了8组动态与静态的风光联合出力Copula模型,用动态相关系数描述风光出力的相关性。运用拟合优度检验方法验证了动态Copula模型对比其静态模型的优越性,选出最优模型。最后将该模型应用在数据驱动的风光联合系统中,验证了其合理性与正确性。     

Evaluating model fit for growth curve models: Integration of fit indices from SEM and MLM frameworks.

Evaluating overall model fit for growth curve models involves 3 challenging issues. (a) Three types of longitudinal data with different implications for model fit may be distinguished: balanced on time with complete data, balanced on time with data missing at random, and unbalanced on time. (b) Traditional work on fit from the structural equation modeling (SEM) perspective has focused only on the covariance structure, but growth curve models have four potential sources of misspecification: within-individual covariance matrix, between-individuals covariance matrix, marginal mean structure, and conditional mean structure. (c) Growth curve models can be estimated in both the SEM and multilevel modeling (MLM) frameworks; these have different emphases for the evaluation of model fit. In this article, the authors discuss the challenges presented by these 3 issues in the calculation and interpretation of SEM- and MLM-based fit indices for growth curve models and conclude by identifying some lines for future research. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

基于有限元分析的压机用螺纹的比较

通过有限元软件对压机用锯齿形螺纹和潘克螺纹的齿面应力和齿根应力进行分析比较,阐明了潘克螺纹较锯齿形螺纹具有明显的优势,表现为应力在每一牙上分布的均匀程度高,齿根应力高应力分布范围窄。锯齿形螺纹已经阻碍了现代压机的技术进步,急需一种新型螺纹来代替。期望本文对压机用螺纹技术进步起到积极的推进作用。     

零件固定联接新方法的研究

通过理论分析与计算,提出了一种代替键、销、螺钉等零件固定联接的新方法,简化了制造工艺,降低了成本,保证了联接的可靠性。     

GPS和水准测量相结合在工程中的应用

文章结合某工程,详细论述了GPS和水准测量相结合的基本原理及工作方法,并得出了有益的结论.