硼酸铝晶须氮化特性研究

针对硼酸铝晶须增强铝基复合材料的界面反应问题,经热力学预测,首次提出对硼酸铝晶须进行氮化处理这一新工艺。采用Ｘ射线光电子能谱（ＸＰＳ）研究了硼酸铝晶须的氮化特性。实验结果表明：硼酸铝晶须中已渗入氮元素;同时,硼酸铝晶须中硼元素向ＢＮ转变。硼酸铝晶须的氮化反应受扩散控制,为一热激活过程,其反应活化能为３０６．３４ｋＪ／ｍｏｌ。     

Informetric studies using databases: Opportunities and challenges

Since their arrival in the 1960s, electronic databases have been an invaluable tool for informetricians. Databases and their delivery mechanism have provided both the source of raw data, as well as the analytical tools for many informetric studies. In particular, the citation databases produced by the Institute for Scientific Information have been the key source of data for a whole range of citation-based research. However, there are also many problems and challenges associated with the use of online databases. Most of the problems arise because databases are designed primarily for information retrieval purposes, and informetric studies represent only a secondary use of the systems. The sorts of problems encountered by informetricians include: errors or inconsistency in the data itself; problems with the coverage, overlap and changeability of the databases; as well as problems and limitations in the tools provided by the database hosts such as DIALOG. For some informetric studies, the only viable solution to these problems is to download the data and perform offline correction and data analysis. This revised version was published online in June 2006 with corrections to the Cover Date.     

SSRF储存环预研制铝合金真空室的机械加工

上海同步辐射装置（SSRF）储存环铝合金超高真空室已研制成功，该机加真空室的尺寸大、尺寸精度、形位公差及粗糙度要求极高，不同于常规的大型超高真空室。在预研件加工中，成功地解决了一系列问题，如光洁度提高困难，加工成型后变形大；加工尺寸和精度受环境温度影响较大等。本文详细阐述了储存环真空室材料和热处理状态的选择依据，为了保证尺寸精度和形位公差所采取的工艺措施，分析了粗糙度的形成机理和影响因素，从刀具材料、几何角度、切削参数、冷却液选型等多方面提出了解决办法。     

A hybrid,auto-adaptive and rule-based multi-agent approach using evolutionary algorithms for improved searching

Selecting the most appropriate heuristic for solving a specific problem is not easy, for many reasons. This article focuses on one of these reasons: traditionally, the solution search process has operated in a given manner regardless of the specific problem being solved, and the process has been the same regardless of the size, complexity and domain of the problem. To cope with this situation, search processes should mould the search into areas of the search space that are meaningful for the problem. This article builds on previous work in the development of a multi-agent paradigm using techniques derived from knowledge discovery (data-mining techniques) on databases of so-far visited solutions. The aim is to improve the search mechanisms, increase computational efficiency and use rules to enrich the formulation of optimization problems, while reducing the search space and catering to realistic problems.     

A Global Optimization Approach to Classification

We reduce the classification problem to solving a global optimization problem and a method based on a combination of the cutting angle method and a local search is applied to the solution of this problem. The proposed method allows to solve classification problems for databases with an arbitrary number of classes. Numerical experiments have been carried out with databases of small to medium size. We present their results and provide comparisons of these results with those obtained by 29 different classification algorithms. The best performance overall was achieved with the global optimization method.     

The PE2D package for transient eddy current analysis

The PE2D package is a suite of programs for solving, by the finite element method, the electro-magnetic and electrostatic problems which are described by the Laplace, Poisson, Helmholtz or diffusion equation in two dimensions. This paper describes the package and illustrates its use in solving transient eddy-current problems.     

An Evidence‐Based Strategy for Problem Solving

Over 150 published basic strategies for problem solving are documented and compared. “Nested” strategies are described. Research is summarized of the cognitive and attitudinal processing used when we solve problems. The connection between past problems that have been solved successfully, the subject knowledge, the current problem to be solved, and the problem solving process is described. “Problems” are distinguished from “exercises.” Based on the research evidence, eleven criteria are posed for the creation of an evidence‐based strategy. A resulting strategy is described. Suggestions are given about how to overcome the propensity to use the strategy as a series of linear, sequential steps. Evidence is summarized of the use and effectiveness of the proposed evidence‐based strategy. Most successful problem solvers use a “strategy.” In this paper, we survey published strategies, consider the research evidence about the appropriateness of using and teaching via strategies, summarize pertinent research evidence about the problem solving process and apply criteria to devise an evidence‐based strategy for problem solving.     

Validating crash locations for quantitative spatial analysis: a GIS-based approach

In this paper, the spatial variables of the crash database in Hong Kong from 1993 to 2004 are validated. The proposed spatial data validation system makes use of three databases (the crash, road network and district board databases) and relies on GIS to carry out most of the validation steps so that the human resource required for manually checking the accuracy of the spatial data can be enormously reduced. With the GIS-based spatial data validation system, it was found that about 65-80% of the police crash records from 1993 to 2004 had correct road names and district board information. In 2004, the police crash database contained about 12.7% mistakes for road names and 9.7% mistakes for district boards. The situation was broadly comparable to the United Kingdom. However, the results also suggest that safety researchers should carefully validate spatial data in the crash database before scientific analysis.     

The method of approximate fundamental solutions (MAFS) for Stefan problems

The paper presents a new meshless numerical technique for solving one and two-dimensional Stefan problems. The technique presented is based on the use of the delta-shaped functions and the method of approximate fundamental solutions (MAFS) first suggested for solving elliptic problems and heat equations in domains with fixed boundaries. The one-dimensional problems in the plane and cylindrical geometries are considered. The numerical examples are presented and the results are compared with the analytical solutions. The comparison shows that the method presented provides a very high precision in determining the position of the moving boundary even for degenerate and singular problems when a region initially has zero thickness. The same technique was developed for 2D Stefan problems with completely or partially unknown boundary.     

Numeric Databases for Chemical Analysis

Databases for use with analytical chemistry instrumental techniques are surveyed, with attention to existing databases and collection efforts now underway, as well as needs for new data-bases. Collections of spectra for use in NMR, infrared spectroscopy, and mass spectroscopy are described. Using mass spectral databases as an example, a critique is presented of automated quality control procedures used to evaluate individual spectra in large collections; the kinds of problems which have been en-countered in using these procedures are discussed. Finally, a brief critical review is presented covering the application of computers to the identification of unknown compounds using spectral data-bases; again, algorithms used with mass spectrometry are taken as the example. Ongoing work at NIST with the NIST/EPA/MSDC Mass Spectral Database is concerned with many of these problems; recent developments are described.     

Pitfalls and modelling inconsistencies in computational radiation dosimetry: lessons learnt from the QUADOS intercomparison. Part II: Photons, electrons and protons

'QUADOS', a concerted action of the European Commission, has promoted an intercomparison aimed at evaluating the use of computational codes for dosimetry in radiation protection and medical physics. This intercomparison was open to all users of radiation transport codes. Eight problems were selected for their relevance to the radiation dosimetry community, five of which involved photon and proton transport. This paper focuses on a discussion of lessons learned from the participation in solving the photon and charged particle problems. The lessons learned from the participation in solving the neutron problems are presented in a companion paper (in this issue).     

硼酸铝晶须增强6061 铝复合材料的界面改性

采用溶胶凝胶C₂Al₂O₃ 涂层涂覆硼酸铝晶须方法来改善硼酸铝晶须增强6061Al 复合材料的界面性能。结果表明: 试验采用的涂覆工艺可以在硼酸铝晶须表面获得40 nm 厚的氧化铝涂层。硼酸铝晶须与铝合金基体在压铸过程中生成的几乎连续的脆性尖晶石产物使晶须连续性结构损伤严重。C₂Al₂O₃ 涂层虽然不能完全阻止界面反应的发生, 但是却有效地抑制了尖晶石界面反应, 保持了硼酸铝晶须的结构完整性。     

Al18B4O33W/Mg复合材料制备方法及其对材料性能及界面的影响

综述了硼酸铝晶须增强镁基复合材料的研究概况,着重介绍了该复合材料的制备方法、性能、界面行为以及制备工艺对其影响,并对硼酸铝晶须增强镁基复合材料当前研究当中存在的一些问题以及某些需要深入研究的方向进行了探讨.     

TWO SIMPLE FAST INTEGRATION METHODS FOR LARGE-SCALE DYNAMIC PROBLEMS IN ENGINEERING

A new simple explicit two-step method and a new family of predictor–corrector integration algorithms are developed for use in the solution of numerical responses of dynamic problems. The proposed integration methods avoid solving simultaneous linear algebraic equations in each time step, which is valid for arbitrary damping matrix and diagonal mass matrix frequently encountered in practical engineering dynamic systems. Accordingly, computational speeds of the new methods applied to large system analysis can be far higher than those of other popular methods. Accuracy, stability and numerical dissipation are investigated. Linear and nonlinear examples for verification and applications of the new methods to large-scale dynamic problems in railway engineering are given. The proposed methods can be used as fast and economical calculation tools for solving large-scale nonlinear dynamic problems in engineering.     

The use of finite element analysis techniques for solving rail gunproblems

The use of commercial electromagnetic finite-element programs for solving railgun problems such as inductance calculations, force evaluations, and current-density distributions is described. The first code considered, PE2D, is a program for solving the electromagnetic and electrostatic problems described by the Laplace, Poisson, Helmholz or diffusion equations in two dimensions. PE2D is limited in that only 2-D problems can be solved, and that current distributions through rail-armature configurations are not readily calculable. Hence, a three-dimensional code called MEGA is being developed. This program, has been used to calculate the 2-D current-density distributions through rails and armatures; however, it is expected that it will be used to calculate full three-dimensional problems     

Cyrillic databases of former Soviet Union countries

The article considers different search options using patent databases (DB), which belong to the former Soviet Union (SU) countries and where the Cyrillic alphabet and Russian language are used. The main emphasis is on the databases where there is the possibility of using an English interface. In the cases when it is not possible to receive information in English advice is given on what kind of machine translation is preferable. Advice is given for English- and Russian-speaking users for making the search more efficient.     

偶联剂对硼酸铝晶须/双马来酰亚胺性能的影响

应用自行合成的一类新型硼酸酯偶联剂及硅烷偶联剂等对硼酸铝晶须进行表面处理,考察了硼酸铝晶须对双马来酰亚胺树脂体系性能的影响.结果表明,硼酸酯处理后的晶须对材料的改性作用较硅烷更加显著;硼酸铝晶须添加到双马来酰亚胺树脂中后,材料的弯曲强度在晶须含量为5%时达到最大值,而后随晶须含量的增大稍有下降;随晶须添加量的增大材料的弯曲模量和耐热性逐渐提高;经硼酸酯处理的晶须与树脂基体具有更好的界面粘接.     

Using state-space models for solving elastodynamic problems discretized by the MLPG method

One of the popular methods for solving ordinary differential equations is the state-space approach. In this paper, the use of the state-space method to analyze elastodynamic problems, discretized by the MLPG method, is proposed. Two methods commonly used in solving such problems, namely, the central difference method and the Newmark method, are compared with the proposed method. To examine the accuracy and the computational time of the new method, an example is studied. The results of the implementation of these methods are compared with a finite element solution. The results show that the state-space method saves substantial computational time for a given accuracy.     

无水三氯化铝的制备方法及研究进展

无水三氯化铝是一种重要的工业原料,其制备方法受到广泛关注。评述了国内外无水三氯化铝的制备方法,分析了铝锭法、氧化铝法、含铝资源氯化法、结晶六水氯化铝高温气氛保护脱水法和结晶六水氯化铝有机盐脱水法等制备方法的特点,阐述了无水三氯化铝的制备进展。目前粉煤灰制备无水三氯化铝是研究的热点,开发操作简单、经济合理的工艺和配套的工业化生产设备将是今后研究的难点和重点。     

A similarity coefficient measure and machine-parts grouping in cellular manufacturing systems

For more than three decades, similarity coefficient measures one of the important tools for solving group technology problems have gained the attention of the research community in cellular manufacturing systems. A new similarity coefficient measure that uses a set of important characteristic properties for grouping is developed here for use as an intermediate tool to form cohesive cells. A mathematical model that uses this similarity coefficient for optimally solving the cell-formation problems in cellular manufacturing is developed. A heuristic procedure that improves the optimal methodology in term of solution capability of the large instances is devised for an efficient solution. Both the optimal methodology and the heuristic are applied to some well-known problems from literature to compare the grouping efficiencies. The similarity coefficient and the solution methodologies developed are able to solve the cell formation problems efficiently.