Technical University of Ostrava

About: Technical University of Ostrava is a education organization based out in Ostrava, Czechia. It is known for research contribution in the topics: Artificial neural network & Evolutionary algorithm. The organization has 4186 authors who have published 8936 publications receiving 65393 citations. The organization is also known as: Vysoká škola báňská – Technická univerzita Ostrava & VŠB – Technical University of Ostrava.

Minimizing quadratic functions over non-negative cone with the rate of convergence and finite termination

Abstract: A new active set based algorithm is proposed that uses the conjugate gradient method to explore the face of the feasible region defined by the current iterate and the reduced gradient projection with the fixed steplength to expand the active set The precision of approximate solutions of the auxiliary unconstrained problems is controlled by the norm of violation of the Karush-Kuhn-Tucker conditions at active constraints and the scalar product of the reduced gradient and the reduced gradient projection The modifications were exploited to find the rate of convergence in terms of the spectral condition number of the Hessian matrix, to preserve its finite termination property even for problems whose solution does not satisfy the strict complementarity condition, and to avoid any backtracking at the cost of evaluation of an upper bound for the spectral radius of the Hessian matrix The performance of the algorithm is illustrated on solution of the inner obstacle problems The result is an important ingredient in development of scalable algorithms for numerical solution of elliptic variational inequalities AMS classification: Primary 65K05; Secondary 90C20

Understanding of resilience in the context of regional development using Composite index approach: the case of European Union NUTS-2 regions

Abstract: Economies have always been prone to different kinds of exogenous shocks, which can destabilize the path and pattern of regional economic growth. Regional economy perturbed by a shock may move onto ...

Investigation of the taper of kerfs cut in steels by AWJ

Abstract: The abrasive water jet (AWJ) taper inside the cut material is one of the characteristic phenomena of the AWJ cutting. The taper, together with a retardation of the jet inside the kerf, causes deformation of workpieces, especially in corners and curvatures. Some deviations of the side walls from the plains perpendicular to the material surface can be observed and measured even in the straight line parts of trajectories. This paper is aimed at experimental research of this phenomenon on steels because precision cutting of stainless and hard steels with thicknesses over 10 mm is a serious problem in practice, and the AWJ cutting can solve this problem quite well. The experiments were performed on three sets of steel plates with thicknesses close to 30 mm. The steels of the first and the second set were identical (1.2379, 1.3343, 1.4307, 1.4404 and 1.4845). The steels of the first set were cut in their normal states, and the steels of the second set were subjected to cooling in the liquid nitrogen prior to cutting (marked 1.abcd/N). The third set of samples consisted of steels with very different composition and brittle/ductile behaviour cut in their normal states (1.0036, 1.2767, 1.3379, 1.7225 and 1.7733). The model for calculation of the limit traverse speed from both the jet parameters and material properties has been used for determination of the proper traverse speed scale. The widths of the cuts were measured both on the top and on the bottom of the slots. The difference between these widths has been used for evaluation of the inclination angle, i.e. the wall deviation from the plane perpendicular to the material surface, referred also as the taper. This angle can be used for determination of the tilting angle for compensation of the negative influence on workpiece. The influence of brittle/ductile behaviour and the influence of cooling in liquid nitrogen have been tried to find out. The results were also compared with the theoretical relationship between traverse speed and inclination angle (the taper) on steels presented as a result of previous investigations in scientific articles. The difference between the inlet and the outlet width of kerf made by AWJ in tested steels ranges from 5.2 to 35.4 % for the traverse speed of 5 mm min−1 and from 25.5 to 44.9 % for the traverse speed of 50 mm min−1.