焊接接头热影响区表面裂纹疲劳扩展速率

给出了数据处理的方法，通过对试验数据的分析，给出了裂纹扩展速率与ΔK的关系，为油田的安全生产提供了依据。     

T0-spaces and pointwise convergence

The purpose of this paper is to give several different characterizations of those T₀-spaces E with the property that if F:X × E → Y is separately continuous, then it is jointly continuous. One such is that the lattice 0(E) of open sets of E be a hypercontinuous lattice (i.e. the interval topology on 0(E) is Hausdorff). If E is a sober space, then E must be a quasicontinuous poset endowed with the Scott topology.     

Implementation of an algorithm for detecting patterns in defocused scenes using binary joint transform correlation

An original method to detect images in defocused scenes by means of a binary joint transform correlation is presented. Defocused images are described in frequency domain as the product between the Fourier transform of the in-focus scene by the optical transfer function of the imaging lens. This function, which presents positive and negative values, introduces sign errors in the joint power spectrum. The goal of this study is to detect the sign of the optical transfer function starting from the defocused image by means of a digital algorithm. Information provided by the algorithm allows to compensate the sign errors in the binary joint power spectrum and to obtain invariant correlations with respect to defocusing. Theoretical analysis and digital experiments to test the procedure are provided.     

On the use of linear graph theory in multibody system dynamics

Multibody dynamics involves the generation and solution of the equations of motion for a system of connected material bodies. The subject of this paper is the use of graph-theoretical methods to represent multibody system topologies and to formulate the desired set of motion equations; a discussion of the methods available for solving these differential-algebraic equations is beyond the scope of this work. After a brief introduction to the topic, a review of linear graphs and their associated topological arrays is presented, followed in turn by the use of these matrices in generating various graph-theoretic equations. The appearance of linear graph theory in a number of existing multibody formulations is then discussed, distinguishing between approaches that use absolute (Cartesian) coordinates and those that employ relative (joint) coordinates. These formulations are then contrasted with formal graph-theoretic approaches, in which both the kinematic and dynamic equations are automatically generated from a single linear graph representation of the system. The paper concludes with a summary of results and suggestions for further research on the graph-theoretical modelling of mechanical systems.     

Contrast-improved joint transform correlator using spatial light modulators

When real time optical pattern recognition is carried out by means of spatial light modulators, a practical situation may arise in which the size of the Fourier transform and the intensity of the light source are fixed. Then, provided the input scene and the size of the spatial light modulator allow it, an interesting possibility for improving the overall intensity in the Fourier plane is the replication of the scene, either along a regular lattice structure or a random replication. In this work we analyse the usefulness of these methods, both to obtain diffraction images or cross-correlation between images in a joint transform correlator.     

焊接接头和U型试样中的氢分布

本文作者利用自行研制的激光测氢装置,测量了焊接接头和U型试样中的氢分布,并且推导了U型试样弯曲部分(塑性变形区)的应变、残余应力计算公式。结果表明:在焊接接头中,1.沿熔深方向上,氢分布是不均匀的。最高氢含量在熔合线附近;2.氢的具体分布情况,取决于焊缝金属和母材原始含氧量,以及金相组织。在U型试样中,1.计算应变的公式和应力公式可以用来计算无明显反弹的U型试样弯曲部分的应变量和残余应力值。1Cr18Ni9Ti(C.R.)钢的F=990MPa、n=0.146;2.氢分布明显受应力和应变的影响。应力、应变值愈大,含氢量愈高。     

任意相位差条纹信号细分方法的研究

为消除传统细分方法中由于两路条纹信号不正交引入的细分误差，提出了一种可对任意相位差条纹信号直接细分的新方法。根据两路条纹信号的极性和幅值大小，把一个信号周期分成8个区段。高速采集两路条纹信号，通过判断信号采样点所处的区段是否跳变对信号幅值交点进行动态跟踪。对不足一个周期的条纹移动，当测量出起点与终点的幅值，计算出其所在的区段及位置后，结合两路信号的交点，可实现对任意相位差条纹信号的细分。实验结果表明，该方法突破了传统细分方法必须信号正交的限制，可对任意相位差信号进行准确地细分，降低了条纹测量中器件安装与调试的难度，具有更强的环境适应性和抗干扰能力。     

Impact dynamics of multibody systems with frictional contact using joint coordinates and canonical equations of motion

This paper presents a methodology in computational dynamics for the analysis of mechanical systems that undergo intermittent motion. A canonical form of the equations of motion is derived with a minimal set of coordinates. These equations are used in a procedure for balancing the momenta of the system over the period of impact, calculating the jump in the body momentum, velocity discontinuities and rebounds. The effect of dry friction is discussed and a contact law is proposed. The present formulation is extended to open and closed-loop mechanical systems where the jumps in the constraints' momenta are also solved. The application of this methodology is illustrated with the study of impact of open-loop and closed-loop examples.     

On the limiting behavior of randomly weighted partial sums

We study the almost sure limiting behavior and convergence in probability of weighted partial sums of the form where {W_nj, 1jn, n1} and {X_nj, 1jn, n1} are triangular arrays of random variables. The results obtain irrespective of the joint distributions of the random variables within each array. Applications concerning the Efron bootstrap and queueing theory are discussed.     

Properties of fourth-order strong mixing rates and its application to random set theory

We shall define the concept of fourth-order strong mixing rates and study their properties. Results are useful for establishing a condition of the form (*) Σ_a,b,c |cum(X_o, X_a, X_b, X_c)| < ∞ or ∫|cum(X_o, X_a, X_b, X_c)| da db dc < ∞ for dependent random variables {X_a}. As an application we shall consider an evaluation of a fourth-order strong mixing rate for a random closed set Z (in the sense of Matheron) and derive the condition (*) for {X_a}, X_a being an outcome of a local measurement upon Z. The result is also applicable to point processes which admit clustering representations.