球墨铸铁曲轴的气体软氮化

柴油机的珠墨铸铁曲轴系重要零件,气体软氮化应用到球墨铸铁领域还是一种新工艺,而且比中频淬火效果好,提高了曲轴的抗疲劳和抗磨损的能力。本文对气体软氮化的基本原理、设备、工艺参数的选择和催渗方法进行了探讨,对软氮化后曲轴的尺寸形状误差、光洁度和机械性能的提高等进行了较详细的试验、分析和比较,结果,经气体软氮化后的曲轴不但尺寸形站误差符合图纸要求外,而且抛去轻微氧化层后光洁度还略有提高,曲轴安全系数由1.3～1.6提高到1.70～1.77,并且一般不再发生疲劳断(?),使用寿命比原来寿命增加3.32倍以上。     

船艏泵喷射侧向推力水动力计算

给出了船艏泵喷射侧向推力的水动力计算，并对两种泵的出口段形状作了比较，从而得出较好的出口段，并选择合适的水泵，为改善船舶操纵性能提供一种可行的方法．     

Non-parametric Regression with Dependent Censored Data

Abstract.  Let ( X _i , Y _i ) ( i = 1 ,…, n ) be n replications of a random vector ( X , Y  ), where Y is supposed to be subject to random right censoring. The data ( X _i , Y _i ) are assumed to come from a stationary α -mixing process. We consider the problem of estimating the function m ( x ) = E ( φ ( Y ) |  X = x ), for some known transformation φ . This problem is approached in the following way: first, we introduce a transformed variable     , that is not subject to censoring and satisfies the relation     , and then we estimate m ( x ) by applying local linear regression techniques. As a by-product, we obtain a general result on the uniform rate of convergence of kernel type estimators of functionals of an unknown distribution function, under strong mixing assumptions.     

Asymptotic Results of a Nonparametric Conditional Quantile Estimator for Functional Time Series

We consider the estimation of the conditional quantile function when the covariates take values in some abstract function space. The main goal of this article is to establish the almost complete convergence and the asymptotic normality of the kernel estimator of the conditional quantile under the α-mixing assumption and on the concentration properties on small balls of the probability measure of the functional regressors. Some applications and particular cases are studied. This approach can be applied in time series analysis to the prediction and building of confidence bands. We illustrate our methodology with El Niño data.     

A plug-in technique in nonparametric regression with dependence

The problem addressed is that of smoothing parameter selection in kernel nonparametric regression in the fixed design regression model with dependent noise. An asymptotic expression of the optimum bandwidth parameter has been obtained in recent studies, where this takes the form h = C ₀ n ^?1/5. This paper proposes to use a plug-in methodology, in order to obtain an optimum estimation of the bandwidth parameter, through preliminary estimation of the unknown value of C ₀.     

水下高围压射流模拟装置的工程设计及测试分析

设计了水下高围压射流模拟装置的主体部分和辅助部分。结合对模拟装置的理论模型分析。实验测试了水下高围压射流模拟装置伴随射流时内部的压力变化过程,并验证了理论模型。     

Convergence de I estimateur a noyau de derivees de Radon-Nikodym generales dans le cas melangeant

In many situations, nonparametric inference in point-process theory consists in estimating a Radon-Nikodym derivative of a nonnegative measure p with respect to another nonnegative measure v, where p and v are intensities of point processes. We consider the case of a mixing andstrictly stationary sequence of point processes and establish convergence results for the kernel estimator.     

Bias-corrected confidence bands in nonparametric regression

Bias-corrected confidence bands for general nonparametric regression models are considered. We use local polynomial fitting to construct the confidence bands and combine the cross-validation method and the plug-in method to select the bandwidths. Related asymptotic results are obtained. Our simulations show that confidence bands constructed by local polynomial fitting have much better coverage than those constructed by using the Nadaraya–Watson estimator. The results are also applicable to nonparametric autoregressive time series models.     

水泥土桩复合地基承载力取值方法探讨

水泥土桩复合地基承载力的确定,目前常用的方法是现场载荷试验,并被公认为是比较可靠的方法。结合工程实测资料,讨论了用该法确定水泥土极复合地基承载力的取值问题,提出用相对变形S认的取值是合理的。同时通过一定数量的水泥土单桩静载荷试验、单极复合地基载荷试验和多桩复合地基载荷试验对比分析,说明用一组极和桩间土所组成的单元作进行承载力试验,更接近实际复合地基的受力性状和承载机理。     

对一例桩基事故的处理及分析

对一工程实例钻孔灌注桩基事故的概况进行介绍,对事故原因进行分析;列举了多种处理该事故的方案,并对此进行了优化方案的比较。对优化方案进行了设计,构造处理。提出进行施工时注意的问题。同时提出了几点建议。