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Shcherba Viktor Evgen’yevich,Shalai Viktor Vladimirovich,Tegzhanov Ablay-Khan Savitovich,Bolshtyanskiy Aleksandr Pavlovich,Nosov Evgeniy Yur’yevich 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.12
A generalized analysis of crosshead and crosshead-free piston hybrid power machine (PHPM) is conducted in this research. A comparison of these machines was carried out experimentally by using two created experimental samples for comparison with practically the same working volumes of the compressor and pump sections, crosshead, and crossheadfree piston hybrid power machines. The comparison was performed within the framework of the following units: thermodynamic unit, dynamic unit, comparison unit for weight and size indicators, comparison unit for reliability and durability, comparison unit for the manufacturing technology, and the provision of gaps in the cylinder-piston group. Results of the experimental data were compared in the thermodynamic comparison unit in terms of cooling the compressor section, flow coefficient and its components, volumetric efficiency of the pump section, and cavitation margin. Comparison results show that the temperature of the cylinder-piston group and, in particular, the temperature of the valve body and of the suction gas of the crossheadfree PHPM is lower than those of the crosshead PHPM; the indicator isothermal efficiency of the crosshead-free PHPM is higher than that of the crosshead PHPM; and the volumetric efficiency for a cross-head-free PHPM is 5 %-10 % higher than that for a crosshead PHPM. The comparison of the acting forces and torques of the crosshead and crosshead-free PHPM established that the crosshead PHPM has better dynamic characteristics in terms of maximum effective force and torque unevenness. Moreover, the PHPM crosshead-free scheme has better overall characteristics.
Chitosan hemostatic dressing for control of hemorrhage from femoral arterial puncture site in dogs
Viktor Szatmári 대한수의학회 2015 Journal of Veterinary Science Vol.16 No.4
Removal of an introducer-sheath from a femoral artery after completing transarterial embolization of a patent ductus arteriosus can cause life-threatening hemorrhage in dogs. In the present study, the effectiveness of chitosan acetate dressing in 10 experimental dogs was tested. Under general anesthesia, an introducer-sheath was placed into the femoral artery with percutaneous puncture using Seldinger’s technique. The outer diameter of the introducer-sheaths varied from 3.0 to 4.0 mm with an introducer/artery ratio of 80 to 123%. The artery’s diameter was measured using ultrasonography. Following removal of the introducer-sheath, a chitosan acetate dressing was applied to the wound and held in place with manual compression for 10 min. Successful hemostasis was reached on 12 arteries. However, on two arteries, hemorrhage was uncontrollable and led to a hypovolemic shock during 10 min of manual compression. Possible causes of the negative outcome in two dogs were their old age and an introducer-sheath with a too large diameter. The chitosan acetate dressing was easy to use and the artery remained patent. Dogs could walk directly after recovery from anesthesia and their femoral arteries were saved. In conclusion, the outer diameter of the introducer-sheath should not exceed 3 mm or the inner diameter of the artery.
INVESTIGATION OF CAVITATION PROCESS IN MONOTUBE SHOCK ABSORBER
Viktor Skrickij,Dzmitry Savitski,Valentin Ivanov,Paulius Skačkauskas 한국자동차공학회 2018 International journal of automotive technology Vol.19 No.5
The paper investigates cavitation effect which negatively influences the performance of a monotube shock absorber of road vehicle (passenger car). For better understanding of this phenomena, three physical models of shim stack valves are analyzed. Validation results allowed selecting the most appropriate valve model in presence of cavitation processes. A mathematical model of monotube damper with consideration of fluid compressibility and cavitation phenomena is developed. Simulation results are validated by experimental data obtained on hydraulic test rig. Based on the selected approach, a simplified method suitable for assessment of cavitation processes in automotive monotube shock absorbers is proposed. After investigation it is found that damping force when cavitation occurs mainly depends on the initial pressure and absorber inner diameter.
Dark Conductivity in Semi-Insulating Crystals of CdTe:Sn
Viktor P. Makhniy,Sklyarchuk Valeriy Mykhailovyc,Yuri Vorobiev,Paul Horley 대한전자공학회 2015 Journal of semiconductor technology and science Vol.15 No.2
We prepared semi-insulating CdTe for radiation detectors by isothermal annealing of single crystals grown by Bridgeman technique in a sealed quartz container filled with Sn vapor. The resistivity of CdTe:Sn samples thus obtained was of order of 10<SUP>10</SUP> Ohm·cm at room temperature with electrons lifetime of 2´10<SUP>-8</SUP> s, which is appropriate for the applications desired. Analysis of electric transport characteristics depending on temperature, sample thickness and voltage applied revealed the presence of traps with concentration of about (4-5)´10<SUP>12</SUP> cm<SUP>-3</SUP> with the corresponding energy level at 0.8 ? 0.9 eV counted from the bottom of conduction band. The conductivity was determined by electron injection from electrodes in space charge limited current mode.
Viktor Gribniak,Aleksandr K. Arnautov,Arvydas Rimkus 한국CDE학회 2021 Journal of computational design and engineering Vol.8 No.2
The elegant stress-ribbon systems are efficient in pedestrian bridges and long-span roofs. Numerous studies defined corrosion of the steel ribbons as the main drawback of these structures. Unidirectional carbon fiber-reinforced polymer (CFRP) is a promising alternative to steel because of lightweight, high strength, and excellent corrosion and fatigue resistance. However, the application of CFRP materials faced severe problems due to the construction of the anchorage joints, which must resist tremendous axial forces acting in the stress-ribbons. Conventional techniques, suitable for the typical design of the strips made from anisotropic material such as steel, are not useful for СFRP strips. The anisotropy of СFRP makes it vulnerable to loading in a direction perpendicular to the fibers, shear failure of the matrix, and local stress concentrations. This manuscript proposes a new design methodology of the gripping system suitable for the anchorage of flat strips made from fiber-reinforced polymers. The natural shape of a logarithmic spiral Nautilus shell describes the geometry of the contact surface. The continuous smoothly increasing bond stresses due to friction between the anchorage block and the CFRP strip surface enable the gripping system to avoid stress concentrations. The 3D-printed polymeric prototype mechanical tests proved the proposed frictional anchorage system efficiency and validated the developed analytical model.
Swedish Language to Immigrants (SFI): Some Reflections on Motivation
Viktor Sundgren 한국 스칸디나비아학회 2016 스칸디나비아 연구 Vol.18 No.-
This paper looks at the recent debate regarding teaching the Swedish language to immigrants (SFI) in Sweden, reviewing recent articles in this area. Teaching Swedish to immigrants is seen as a key to integration and it is therefore important that it is effective and achieves its goal. However, there has been widespread criticism in terms of the results it achieves. Especially, many students interrupt their studies before they complete the highest course level. In 2010, a performance-based financial compensation system was introduced in order to make the students complete the courses quicker. As seen in many evaluation reports, this way of aiming at increasing the students’ instrumental motivation has been inefficient, and the compensation system was eventually abolished. Although many factors for improvements are present in the discourse, when reviewing a number of articles it is striking that the most important factor for learning – integrative motivation – receives little attention. In order to improve SFI and the immigrants’ language learning, there needs to be more research on the individuals’ needs and their integrative motivation.