Correction to: A note on the three methods of item analysis

Behaviormetrika - In the original publication of the article, Appendix A was published incorrectly.     

A note on the validity and reliability of ergonomics methods

The view that, by analogy, ergonomics methods should be subject to the same requirements of validity and reliability as are demanded of psychometric tests is shown to be an oversimplification. Two broad classes of method are distinguished. Analytic methods aim to produce a better understanding of the processes affecting complex human-machine systems, whilst evaluative methods are limited to the measurement of specific variables. The analogy with psychometrics applies to the latter type but is less appropriate to the former. Analytic methods depend heavily on the application of currently accepted theories of performance. Empirical data may be variable, but the expertise of the analyst may be more to blame than the method as such.     

Integration of three visualization methods based on co-word analysis

Visualization of subject structure based on co-word analysis is used to explore the concept network and developmental tendency in certain field. There are many visualization methods for co-word analysis. However, integration of results by different methods is rarely reported. This article addresses the knowledge gap in this field of study. We compare three visualization methods: Cluster tree, strategy diagram and social network maps, and integrate different results together to one result through co-word analysis of medical informatics. The three visualization methods have their own character: cluster trees show the subject structure, strategic diagrams reveal the importance of topic themes in the structure, and social network maps interpret the internal relationship among themes. Integration of different visualization results to one more readable map complements each other. And it is helpful for researchers to get the concept network and developmental tendency in a certain field.     

A note on one of the methods of solution of the diffusion equation

An account is given of one of the methods of solution of the equation which describes the variation of the radius of a water droplet whose temperature has become established.     

三种方法检测水中总大肠菌群的比较探讨

采用多管发酵法、滤膜法及酶底物法三种方法同时检测水中总大肠菌群,并对结果进行比较分析,结果表明三种方法各有优劣,我们在实际检测工作中,应根据需要,采用不同的检测方法,使结果更加准确可靠。     

A note on data checking for large framework analysis

Sources of data errors in the analysis of large frameworks are listed. Outputs of various forms for error detection are discussed; emphasis is given to the advantages of graphical output. For further error detection, a few procedures that can be included in computer programs are listed.     

A note on upper bound formulations in limit analysis

In this paper, we study some recent formulations for the computation of upper bounds in limit analysis. We show that a previous formulation presented by the authors does not guarantee the strictness of the upper bound, nor does it provide a velocity field that satisfies the normality rule everywhere. We show that these deficiencies are related to the quadrature employed for the evaluation of the dissipation power. We derive a formulation that furnishes a strict upper bound of the load factor, which in fact coincides with a formulation reported in the literature. From the analysis of these formulations, we propose a post‐process, which consists in computing exactly the dissipation power for the optimum upper bound velocity field. This post‐process may further reduce the strict upper bound of the load factor in particular situations. Finally, we also determine the quadratures that must be used in the elemental and edge gap contributions, so that they are always positive and their addition equals the global bound gap. Copyright © 2012 John Wiley & Sons, Ltd.     

A note on true desingularisation of boundary integral methods for three-dimensional potential problems

A desingularized boundary element formulation for the three-dimensional potential problem will be presented. It is based on integral identities for the fundamental solution. The shown approach has the advantage that the singular terms on both influence matrices can be directly calculated by replacing it with a special summation of the other off-diagonal elements. It is an extension of the so-called 4π rule in which the strongest singularity is removed by replacing the terms of one of the influence matrices by 4π minus the sum of the off-diagonal terms of the same row. It is shown here that a similar method can also be applied to the weakest singularity, thereby completely desingularizing the method. Both integral equations and their corresponding matrix–vector notation will be presented.     

A note on concrete creep analysis under static temperature fields

The analysis of concrete structures in the presence of sustained temperature fields is discussed, and, in particular, the variation of strain compliance with position in the structure as a result of the temperature variation. A form of the constitutive relationship for linear creep is proposed. By means of the use of a fictitious time, it is invariable in form; that is, the equations depend on duration since loading and not on the age at loading. Thus, it is possible to perform analyses using viscoelastic methods; in iterative schemes, considerable saving of computation effort is achieved. Direct solutions are also possible in some cases. The method reduces to the familiar rate of creep method if the reversible creep is ignored.

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Résumé Lorsque les ouvrages en béton sont soumis à des gradients thermiques, il peut en résulter de grandes déformations et une importante redistribution des contraintes. La principale raison en est l'effet de la température sur la vitesse de fluage, quoiqu'on ait aussi constaté une variation du module élastique avec la température. Cet article analyse deux formes de l'adaptation du fluage pour les déformations du béton; la première repose sur l'application de fonctions de variation de température, tandis que la seconde est essentiellement une formulation de la vitesse de fluage. Il faut souligner que l'utilisation des fonctions de variation de température (pour des matériaux thermo-rhéologiquement simples) en analyse structurelle est quelque peu restreinte, car on doit tenir compte de l'effet de l'age du chargement tant sur ses fonctions que sur la courbe de fluage de référence. D'autre part, on montre que la méthode de la vitesse de fluage, qui est d'application beaucoup plus simple, peut être étendue jusqu'à inclure le fluage réversible. Le fluage irréversible est pris en compte exactement et l'analyse du fluage réversible se fait avec une certaine approximation; étant donné que le fluage réversible n'atteint pas 30% du fluage total, les approximations introduites sont peu importantes. On montre que les solutions disponibles en régime permanent de contrainte sont indépendantes du fluage réversible. La solution proposée peut s'exprimer sous une forme visco-élastique et peut par conséquent servir à obtenir des solutions directes; en outre, la tache est simplifiée lorsqu'on a à effectuer des calculs itératifs.

     

A note on the porous-wavemaker problem

Summary A complete analytical solution is obtained, by using an integral transform method, for the porous-wavemaker problem, when the effect of surface tension is taken into account on the free surface of water of finite-depth in which surface waves are produced by small horizontal oscillations of a porous vertical plate. The final results are expressed in the form of convergent integrals as well as series and known results are reproduced when surface tension is neglected.     

A note on the wall-jet problem

Summary The wall-jet problem is considered with, in turn, the effects of blowing and suction through the wall and the wall moving. In both cases it is assumed that the effect has the appropriate power-law variation so as to maintain the similarity form. It is shown that the resulting ordinary differential equation has no acceptable solution satisfying the required boundary conditions. The wall jet problem in which the original momentum condition is retained, but allowing for both transpiration velocity and the wall velocity is derived and it is shown that this implies that a solution is possible only for suction. A solution to this problem is then obtained for the appropriate power-law variations to keep the similarity form.     

A note on stress

Summary Consider an arbitrary stress system at a pointP in a continuum. AtP there exists at least one circle of directions of the unit vectorn for which the corresponding traction vectorst(_n) lie on a circle.