A two-step basis vector extraction strategy for multiset variable correlation analysis

In the present work, multiple data spaces, in which the same variables are measured on different sources of objects, are related with each other by a two-step analysis strategy, which focuses on finding their common structure in variable correlations. Common basis vectors, which are closely related with each other over sets, are extracted and deemed to enclose the cross-set similar correlations. Therefore, two different subspaces are separated from each other in each dataset. One is the common subspace driven by the common bases, in which, variable correlations are deemed to be consistent over sets; and the residual is the specific subspace, in which, variable correlations are unique to each definite data table. This is achieved by solving a mathematical optimization problem, in which, theoretical support is framed and the related statistical characteristics are analyzed. Its feasibility and performance are illustrated with the laboratory experiment data from the literatures. The proposed approach provides an insight into the inherent variable correlations of multiple-set data with further application potential.     

Performance of locality-aware topologies for peer-to-peer live streaming

This study is concerned with the effect of overlay network topology on the performance of live streaming peer-to-peer systems. The study focuses on the evaluation of topologies which are aware of the delays experienced between different peers on the network. Metrics are defined which assess the topologies in terms of delay, bandwidth usage and resilience to peer drop-out. Several topology creation algorithms are tested and the metrics are measured in a simple simulation testbed. This gives an assessment of the type of gains, which might be expected from locality awareness in peer-to-peer networks.     

Setting Up a Databank on the Properties of Substances and Materials: A Task Undertaken by the State Reference Data Service

Research results are reported for a databank on the thermophysical properties of substances and materials, which covers researches in the Soviet Union and Russia between 1950 and 2000. An archive of 3475 documents has been set up, which provides bibliographic information on the publications containing the original experimental data and which has been implemented in the Lotus Notes environment. The database organization and retrieval in it are considered.     

烧结钕铁硼永磁体矫顽力理论及其影响

综述了建立在不同缺陷模型基础上的烧结钕铁硼永磁体矫顽力的成核理论、热激活理论、钉扎理论和发动场理论等;简述了添加合金元素对钕铁硼磁体矫顽力的影响,通常少量多加合金元素有利于其整体性能的提高;详述了钕铁硼磁体的生产工艺,如熔炼、制粉、成型、烧结回火等对其矫顽力的影响;提出了提高烧结钕铁硼永磁矫顽力的有效途径和未来其生产研究的主要方向.     

Efficient numerical modelling of hydrogen diffusion with trapping

In view of the growing interest both in numerical solutions of the McNabb and Foster model for hydrogen diffusion with trapping, and the computational scheme proposed by Caskey and Pillinger, a more efficient, simpler scheme is presented which more closely replaces this model. Further techniques are presented which reduce the cost of the computations yet increase the accuracy of the results. Using a formulation better adapted to analysis, and with readily comprehensible variables, bounds are given on the numerical mesh sizes which ensure the stability of the scheme. For cases where these bounds are overly restrictive, alternative numerical tests are suggested. Finally, driving equations are given on which an approximation to the McNabb and Foster model in which the concentration of traps varies with time may be validly based.     

Elastodynamic scattering by fluid-filled nonplanar cracks

A recent modification of the null field approach is adapted to the study of scattering of elastic waves by fluid-filled nonplanar cracks. The fluid-filled crack is modeled as a surface over which friction-free boundary conditions apply. A closed surface is formed by adding a fictitious surface, on which latter surface boundary conditions of welded contact are applied. The surface fields on the closed surface are expanded in vector spherical harmonics in a manner which takes the edge conditions into account. Some numerical results on farfield quantities, such as scattering cross sections and backscattering amplitudes (both in the frequency and time domains), are presented for rotationally symmetric cracks.     

Computing what the public wants: some issues in road safety cost-benefit analysis

In road safety, as in other fields, cost–benefit analysis (CBA) is used to justify the investment of public money and to establish priority between projects. It amounts to a computation by which ‘few’ – the CB analysts – aim to determine what the ‘many’ – those on behalf of which the choice is to be made – would choose. The question is whether there are grounds to believe that the tool fits the aim. I argue that the CBA tool is deficient. First, because estimates of the value of statistical life and injury on which the CBA computation rests are all over the place, inconsistent with the value of time estimates, and government guidance on the matter appears to be arbitrary. Second, because the premises of New Welfare Economics on which the CBA is founded apply only in circumstances which, in road safety, are rare. Third, because the CBA requires the computation of present values which must be questioned when the discounting is of future lives and of time. Because time savings are valued too highly when compared to life and because discounting tends to unjustifiably diminish the value of lives saved in the future, the CBA tends to bias decisions against investment in road safety.     

Magnetomechanical effects in the Rayleigh region

A brief résumé of basic magnetism is followed by a consideration of the magnetization process in the absence of applied mechanical stress, in which the importance of internal stresses and inclusions is emphasized and which leads to the introduction of Néel's disperse field theory. The Rayleigh laws are interpreted in terms of "Preisach loops." Early work on the influence of stress on the magnetization process is discussed, leading on to a detailed consideration of this phenomenon in terms of three mechanisms which, for simplicity, are taken to be essentially distinct. These are, first, the alteration of the pressure on 90° domain walls by the application of stress; second, the alteration in the opposition term, which must clearly be in balance with this pressure for domain-wall equilibrium, and, finally, large-scale alterations in the overall domain structure. Existing experimental observations, on both magnetically soft and hard materials, are interpreted in terms of these three mechanisms.     

Some improvements of the finite element solution for one-dimensional problems

New algorithms which improve the finite element solution on a fixed mesh of the domain are developed. For this, objective functions which depend on a positive parameter to be determined are proposed. These functions lead to criteria which combine in several ways the residual of the solution, the approximation in the Euclidean norm of the value of the solution at the nodes, and the approximations in the energy and H^k norms. Some aspects of optimality are studied and, finally, numerical results are given.     

Stability and accuracy of finite element methods for flow acoustics. II: Two‐dimensional effects

This is the second of two articles that focus on the dispersion properties of finite element models for acoustic propagation on mean flows. We consider finite element methods based on linear potential theory in which the acoustic disturbance is modelled by the convected Helmholtz equation, and also those based on a mixed Galbrun formulation in which acoustic pressure and Lagrangian displacement are used as discrete variables. The current paper focuses on the effects of numerical anisotropy which are associated with the orientation of the propagating wave to the mean flow and to the grid axes. Conditions which produce aliasing error in the Helmholtz formulation are of particular interest. The 9‐noded Lagrangian element is shown to be superior to the more commonly used 8‐noded serendipity element. In the case of the Galbrun elements, the current analysis indicates that isotropic meshes generally reduce numerical error of triangular elements and that higher order mixed quadrilaterals are generally less effective than an equivalent mesh of lower order triangles. Copyright © 2005 John Wiley & Sons, Ltd.     

UNEP assesment of the Montreal protocol: Refrigeration within the framework of the technology review

In order to provide a scientific and technological basis for adjustments and amendments to the Montreal Protocol (which was conceived and adopted in 1987), a large number of reports were made by international experts in 1989. These reports are used in the assessment procedure which takes place in the period June 1989–June 1990, after which period final decisions will be made by the Contracting Parties in the so-called ‘Second Meeting of the Parties’. In this contribution the assessment process and the time schedule of the whole procedure is described. One of the Panel Reports centres on a Review of the Technology; conclusions from this report are presented. In its turn, information in this report is based on sector reports, one of which is the Options Report ‘Refrigeration, AC and Heat Pumps’. Specific topics dealt with in this sector report are presented here. Some concluding remarks on the findings presented in the reports and on possible future reassessments are given.     

Einfluss der Beschichtungen beim stoffschlüssigen Lichtbogenfügen von Stahl mit Aluminium

Influence of the coating by bonded arc joining of steel to aluminium The firmly bonded joint between steel and aluminium has, so far, not been achieved successfully in joining technology. The problems of joining these metals thermally are caused by the low up to non‐existing solid solubility of the metals and by the development of brittle intermetallic phases. The quality of the joints depends on many influential factors which are, sometimes, also interacting. One of those influential factors is the coating of the steel sheets. Using the example of coatings which are common and others which are unusual in automotive engineering it has been tried to demonstrate the influence on the wetting length and wetting angle of those factors with, otherwise, constant boundary parameters. The results are part of a test series which is currently carried out at the Joining and Welding Institute, Aachen.     

Steels for bearings

A casual metallurgist might be forgiven in believing that there are but a few basic types of steels used in the manufacture of some of the most technologically important engineering components, the rolling bearings. First the famous 1C-1.5Cr steel from which the majority of bearings are made. Its structure is apparently well-understood and the focus is on purity in order to avoid inclusions which initiate fatigue during rolling contact. Then there is the M50 steel and its variants, from which bearings which serve at slightly higher temperatures in aeroengines are manufactured, based on secondary-hardened martensite.The casual metallurgist would be wrong; there is a richness in the subject which inspires deep study. There are phenomena which are little understood, apparently incommensurate observations, some significant developments and other areas where convincing conclusions are difficult to reach. The subject seemed ready for a critical assessment; hence, this review. The structure and properties of bearing steels prior to the point of service are first assessed and described in the context of steelmaking, manufacturing and engineering requirements. This is followed by a thorough critique of the damage mechanisms that operate during service and in accelerated tests.     

Preconditioning techniques for non-symmetric matrices with application to temperature calculations of cooled concrete

Preconditioning techniques based on incomplete LU-decomposition are described for large, sparse, non-symmetric matrix systems in which the largest part of the coefficient matrix is a symmetric M-matrix with a very regular sparsity pattern. Some methods are described in which a small part of the matrix with an irregular sparsity pattern is treated very efficiently. The methods are combined with CGSTAB and tested on a non-stationary diffusion problem in three dimensions. For this type of problems the modified incomplete decomposition as suggested by Gustafsson performs significantly better than the standard incomplete factorization. Also some methods are described to construct preconditioners for large, sparse, non-symmetric matrices with arbitrary sparsity patterns. Methods in which the sparsity pattern of the preconditioning matrix is based on a drop tolerance are very effective and relatively cheap.     

可更换耗能连接力学机理及变形性能研究

提出一种安装于装配式混凝土梁柱连接部位的可更换耗能连接组件,可以诱导结构的损伤集中在连接区域,保证结构主要构件在强震下处于弹性状态,增强结构的可修复性。利用MTS力学试验机开展3个组件的试验分析,研究组件的滞回性能、耗能能力和低周疲劳性能。试验结果表明,可更换耗能连接组件的滞回性能稳定,展现出了优良的延性和低周疲劳性能。基于ABAQUS开展的组件参数化分析主要针对核心耗能部件的厚度及核心耗能部件与约束部件之间的间隙。结果表明：增加核心耗能部件的厚度会减轻结构的高阶屈曲波数,优化构件长度方向的应变分布均匀性;核心耗能部件与约束部件之间的间隙也会影响核心耗能部件的应变分布。该文分析结果表明,该可更换耗能连接可以应用于对结构延性和可恢复性要求比较高的高震区框架结构中。     

Multiattribute utility functions,partial information on coefficients,and efficient choice

Summary The expected utility analysis of decision under risk needs information on the alternatives and on the decision maker's preferences which in many practical situations are difficult to obtain. This paper presents a procedure for choosing between multiattribute risky alternatives when the probabilities of outcomes are known, the utility function is general multilinear (i.e., can be decomposed into sums and products of univariate utility functions), and there is some partial information on univariate utilities (viz. increasingness) and arbitrary partial information on the scaling coefficients. Pairwise comparisons in the set of alternatives yield a subset which is efficient under the given partial information. Additive and multiplicative utility functions are special cases of the multilinear one. The paper gives particular attention to linear partial information (LPI) on coefficients, which is obtained by standard assessment procedures. The approach can be combined with dominance procedures which use other partial information as LPI on probabilities.     

Predicting the number of accidents at a road junction

We consider a model, within a Bayesian framework, which can be used to predict the number of accidents occurring at a road junction in a given period of time. The predictions are based on measurements of the traffic flows as well as on covariates which describe important features of the junctions. Various approximate and estimative methods, which use Gibbs sampling, posterior normality and Laplace approximations, are considered and compared. Procedures to assess the importance of the different covariates through the use of the Kullback-Leibler measure of divergence are also developed.     

Targets of high vapor pressure elements

The high vapor pressure of some elements requires target preparation methods in which these elements are converted into chemical compounds. These compounds must have low enough vapor pressures in order to withstand the elevated temperatures which are on these targets during ion bombardment. A method is described in which the conversion is directly done on the target foil. In this way even compounds can act as targets which decompose before reaching the temperature necessary for an evaporation process. The reaction partner for the high vapor pressure element is a suitable low vapor pressure metal, of which a freshly evaporated film is inserted into a small autoclave. In this autoclave the compound is formed at a temperature up to 500 K and at a pressure of 0.1 to 1 Pa of the high vapor pressure element. The compounds are formed as homogeneous films, which can be selfsupporting targets or targets on carbon backings.