A comment on the article “inspection and maintenance optimization methods” by K.M. Mjelde

In this note we point out the fact that the ‘incremental method’ used by Mjelde (1984) in his article “Inspection and maintenance optimization methods” is nothing more than an application of the well known greedy heuristic. It is also shown that the adaptation of this heuristic to the problem considered in Section 4 of Mjelde's paper is questionable since the problem is a pure transportation problem. Furthermore we point out that one of the theorems is badly stated and that the proof is incorrect.     

Comment on: “Fundamental flows with nonlinear slip conditions: exact solutions”, by R. Ellahi, T. Hayat, F. M. Mahomed and A. Zeeshan, Z. Angew. Math. Phys. 61 (2010) 877–888

In their article (Fundamental flows with nonlinear slip conditions: exact solutions, R. Ellahi, T. Hayat, F. M. Mahomed and A. Zeeshan, Z. Angew. Math. Phys. 61 (2010) 877–888.), the authors considered three simple cases of the steady flow of a third grade fluid between parallel plates with slip conditions; namely, Couette flow, Poiseuille flow, and generalized Couette flow. They obtained exact solutions, which were utilized in a way that did not lead to useful results. Their conclusion that the Couette flow cannot be obtained from the generalized Couette flow, by dropping the pressure gradient, is incorrect. Meaningful results based on their solution are herein presented.     

Comment on: “Fundamental flows with nonlinear slip conditions: exact solutions”, by R. Ellahi,T. Hayat,F. M. Mahomed and A. Zeeshan,Z. Angew. Math. Phys. 61 (2010) 877–888

In their article (Fundamental flows with nonlinear slip conditions: exact solutions, R. Ellahi, T. Hayat, F. M. Mahomed and A. Zeeshan, Z. Angew. Math. Phys. 61 (2010) 877–888.), the authors considered three simple cases of the steady flow of a third grade fluid between parallel plates with slip conditions; namely, Couette flow, Poiseuille flow, and generalized Couette flow. They obtained exact solutions, which were utilized in a way that did not lead to useful results. Their conclusion that the Couette flow cannot be obtained from the generalized Couette flow, by dropping the pressure gradient, is incorrect. Meaningful results based on their solution are herein presented.     

Contribution à un problème de M. M. Picone

Résumé Par une méthode fonctionnelle développée ailleurs (cf. la bibliographie), on apporte dans cet article une contribution à un problème posé parM. M. Picone. On montre que, sur des ouverts dont la frontière est suffisamment régulière, le problème deM. M. Picone (et même un type plus général de problèmes aux limites) admet une solution unique, les conditions aux limites étant prises ? en moyenne ? (cf. N^o 6 pour les définitions précises).     

评B.M.伯拉基斯著:“中学数学教学法”

自从我们有教学法文献以来,试图讨论中学数学教学法中的一般问题,这还是第一本著作。试图把各个分科教学法汇集在一本书里讲述,这也还是第一次。本书(1949年版)的优点方面,在勃拉哥维申斯基的论文中已有讨论(见苏联“数学教学”杂志1951年第3期)。我们认为有必要来谈一下在勃拉哥维申斯基评论中所没有指出的缺点。消除这些缺点将会大大提高本书的价值。