Suchergebnisse

The paper deals with the design of swinging self-clean screen bars and the assessment of pressure losses in the combined sewer overflow chamber (HOBAS CSO Chamber), sold by the company HOBAS. The HOBAS CSO Chamber ensures a safe transfer of rainwater during a major rain event. The main goal of the research was to determine the pressure losses of the overflow chamber under various conditions - without self-clean screen bars; with screen bars without impurities and with screen bars partially or fully clogged with various impurities. The measurements were performed on a 1 : 5 scale physical model of CSO using 4 probes for measuring level heights. From the measured values, the coefficients of local losses were calculated, which were then entered into the currently used design table of flow capacities of the CSO HOBAC Chamber.
At the same time, the optimal shape of individual rods of swinging self-clean bars was investigated, so that the oscillation of the free ends of the rods supports the separation and self-cleaning function during their operation. The research was conducted on a 1 : 1 scale model, so that impurities present in the CSO during the overflow (i.e. textile, cosmetic handkerchiefs, feminine hygiene products, condoms and others) could be used directly in the measurement. At the end of the experiments, the variants of the rods of screen bars that were the most effective in the separation and self-cleaning function were selected. The self-cleaning effect, which occurs at the end of the rain event and ensures that the CSOis free of impurities and ready for further use, was subsequently tested with the selected variant of the rods.

Valuation of the insurance portfolio is one of the essential actuarial tasks. Life insurance valuation is usually based on a projection of cash flows for each policy which is demanding computation time. Furthermore, modern financial management requires multiple valuations under different scenarios or input parameters. A method to reduce computation time while preserving as much accuracy as possible based on cluster analysis is presented. The basic idea of the method is to replace the original portfolio by a smaller representative portfolio based on clusters with some weights that would ensure the similarity of the valuation results to the original portfolio. Valuation is then significantly faster but requires initial time for clustering and the results are only approximate – different from the original results. The difference is studied for a different number of clusters and the trade-off between the approximation error and calculation time is evaluated.

Cutting tools have long been coated with an AlCrN hard coating system that has good mechanical and tribological qualities. Boron (B) and vanadium (V) additions to AlCrN coatings were studied for their mechanical and tribological properties. Cathodic multi-arc evaporation was used to successfully manufacture the AlCrBN and AlCrVN coatings. These multicomponent coatings were applied to the untreated and plasma-nitrided surfaces of HS6-5-2 and H13 steels, respectively. Nanoindentation and Vickers micro-hardness tests were used to assess the mechanical properties of the materials. Ball-on-flat wear tests with WC-Co balls as counterparts were used to assess the friction-wear capabilities. Nanoindentation tests demonstrated that AlCrBN coating has a higher hardness (HIT 40.9 GPa) than AlCrVN coating (39.3 GPa). Steels' wear resistance was significantly increased by a hybrid treatment that included plasma nitriding and hard coatings. The wear volume was 3% better for the AlCrBN coating than for the AlCrVN coating on H13 nitrided steel, decreasing by 89% compared to the untreated material. For HS6-5-2 steel, the wear volume was almost the same for both coatings but decreased by 77% compared to the untreated material. Boron addition significantly improved the mechanical, tribological, and adhesive capabilities of the AlCrN coating. © 2021 by the authors. Licensee MDPI, Basel, Switzerland. ; Department of Mechanical Engineering, University of Defence in Brno [SV20-216]; Project for the Development of the Organization "DZRO Military autonomous and robotic systems"; Slovak Research and Development AgencySlovak Research and Development Agency [APVV-15-0710] ; Agentúra na Podporu Výskumu a Vývoja, APVV: APVV-15-0710