The methodology of modelling and of qualitative analysis of large rotating systems with gear and bearing couplings is presented. The emphasis is laid on the modelling of nonlinear gear and bearing couplings and on their influence on the dynamic system response to the internal kinematic excitation in gearing and to parametric excitation caused by the time-varying meshing stiffness. The aim is to introduce a method of investigation the beahviour of the rotating system influenced by the mentioned excitation and to examine the influence of chosen operational parameters. The methodology of modelling and of qualitative dynamic behaviour analysis is tested on a two-stage gearbox. and Obsahuje seznam literatury
The paper presented deals with a met,hod of calculation of Qualitative Behaviours Sirnilarity Measure. At the beginning, the measure of the qualitative distance of qualitative States in a given time-point is defined. Then the páper solves practical problems of landmark sets unification. Cornpared qualitative behaviours are each described by a different set of landmarks and distinguished time-points. All work is surnmarised in a rneasure of the similarity definition and the algorithm of similarity calculation.
Non linear and multidimensional models of an interdisciplinary nature are needed to study a broad spectrum of tasks related to design of mechanical engineering systems. Oversimplified and therefore inapplicable results are frequently obtained as the final result of model development. A human way of making decisions is not based on numbers but on common-sense reasoning. Qualitative modeling brings additional options in the modeling of complex systems. Qualitative variables are quantified using three values only - positive (increasing), zero (constant) and negative (decreasing). The classical quantitative tools cannot deal with such variables. Typical areas suitable for qualitative modeling are design related tasks with a large number of variables. A presented case study an optimization of a solar collector, is given in details. and Obsahuje seznam literatury
Some recent results concerning properties of solutions of the half-linear second order differential equation (∗) (r(t)Φ(x' ))' + c(t)Φ(x)=0, Φ(x) := |x| p−2x, p > 1, are presented. A particular attention is paid to the oscillation theory of (∗). Related problems are also discussed.
The aim of this study was to evaluate macroscopically, histologically and immunohistochemically the quality of newly formed tissue in iatrogenic defects of articular cartilage of the femur condyle in miniature pigs treated with the clinically used method of microfractures in comparison with the transplantation of a combination of a composite scaffold with allogeneic mesenchymal stem cells (MSCs) or the composite scaffold alone. The newly formed cartilaginous tissue filling the defects of articular cartilage after transplantation of the scaffold with MSCs (Group A) had in 60 % of cases a macroscopically smooth surface. In all lesions after the transplantation of the scaffold alone (Group B) or after the method of microfractures (Group C), erosions/fissures or osteophytes were found on the surface. The results of histological and immunohistochemical examination using the modified scoring system according to O’Driscoll were as follows: 14.7±3.82 points after transplantations of the scaffold with MSCs (Group A); 5.3±2.88 points after transplantations of the scaffold alone (Group B); and 5.2±0.64 points after treatment with microfractures (Group C). The O’Driscoll score in animals of Group A was significantly higher than in animals of Group B or Group C (p<0.0005 both). No significant difference was found in the O’Driscoll score between Groups B and C. The treatment of iatrogenic lesions of the articular cartilage surface on the condyles of femur in miniature pigs using transplantation of MSCs in the composite scaffold led to the filling of defects by a tissue of the appearance of hyaline cartilage. Lesions treated by implantation of the scaffold alone or by the method of microfractures were filled with fibrous cartilage with worse macroscopic, histological and immunohistochemial indicators., A. Nečas ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy
Quametopia gen. n. is established on the basis of recent phylogenetic analysis of taxa formerly assembled under the genus Mumetopia Melander, 1913 to include M. terminalis (Loew, 1863) and two new closely related Nearctic species of Anthomyzidae. The new genus is diagnosed and its phylogenetic relationships discussed. Quametopia terminalis (Loew, 1863) comb. n. is transferred from Mumetopia and redescribed based on revision of the type material (lectotypes of Anthophilina terminalis Loew, 1863 and its synonym Mumetopia nitens Melander, 1913 are designated) and other extensive material. Quametopia clintonia sp. n. and Q. amplistylus sp. n. (both from Canada, USA) are described and relationships of all three Quametopia species discussed. Immature stages of Q. terminalis and Q. clintonia sp. n. obtained by means of adult-to-adult rearing are described (1st- and 2nd-instar larvae for the first time in the family Anthomyzidae) and illustrated. Keys to adults, eggs, larvae and puparia of Quametopia species are presented. Biology (habitat and host-plant associations, life history) of Q. terminalis and Q. clintonia sp. n. are studied in detail and their ecological separation demonstrated. Distribution of all Quametopia species is reviewed. and Jindřich Roháček, Kevin N. Barber.