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Search Results: 1 - 10 of 205 matches for " Dmytro Kevorkov "
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Experimental study of the Ca–Mg–Zn system using diffusion couples and key alloys
Yi-Nan Zhang, Dmytro Kevorkov, Florent Bridier and Mamoun Medraj
Science and Technology of Advanced Materials , 2011,
Abstract: Nine diffusion couples and 32 key samples were prepared to map the phase diagram of the Ca–Mg–Zn system. Phase relations and solubility limits were determined for binary and ternary compounds using scanning electron microscopy, electron probe microanalysis and x-ray diffraction (XRD). The crystal structure of the ternary compounds was studied by XRD and electron backscatter diffraction. Four ternary intermetallic (IM) compounds were identified in this system: Ca3MgxZn15 x (4.6≤x≤12 at 335 °C, IM1), Ca14.5Mg15.8Zn69.7 (IM2), Ca2Mg5Zn13 (IM3) and Ca1.5Mg55.3Zn43.2 (IM4). Three binary compounds were found to have extended solid solubility into ternary systems: CaZn11, CaZn13 and Mg2Ca form substitutional solid solutions where Mg substitutes for Zn atoms in the first two compounds, and Zn substitutes for both Ca and Mg atoms in Mg2Ca. The isothermal section of the Ca–Mg–Zn phase diagram at 335 °C was constructed on the basis of the obtained experimental results. The morphologies of the diffusion couples in the Ca–Mg–Zn phase diagram at 335 °C were studied. Depending on the terminal compositions of the diffusion couples, the two-phase regions in the diffusion zone have either a tooth-like morphology or contain a matrix phase with isolated and/or dendritic precipitates.
Experimental Investigation of the Phase Equilibria in the Al-Mn-Zn System at 400°C
Tian Wang,Dmytro Kevorkov,Ahmad Mostafa,Mamoun Medraj
Journal of Materials , 2014, DOI: 10.1155/2014/451587
Abstract: Al-Mn-Zn ternary system is experimentally investigated at 400°C using diffusion couples and key alloys. Phase relationships and homogeneity ranges are determined for binary and ternary compounds using EPMA, SEM/EDS, and XRD. Reported ternary compound T3 (Al11Mn3Zn2) is confirmed in this study and is denoted as τ2 in this paper. Two new ternary compounds (τ1 and τ3) are observed in this system at 400°C. τ1 is determined as a stoichiometric compound with the composition of Al31Mn8Zn11. τ3 has been found to have homogeneity range of AlxMnyZnz ( ?at%; ?at%; ?at%). The binary compounds Al4Mn and Al11Mn4 exhibit limited solid solubility of around 6?at% and 4?at% Zn, respectively. Terminal solid solution Al8Mn5 is found to have maximum ternary solubility of about 10?at% Zn. In addition, ternary solubility of Al-rich β-Mn′ at 400°C is determined as 4?at% Zn. Zn-rich β-Mn′′ has a ternary solubility of 3?at% Al. The solubility of Al in Mn5Zn21 is measured as 5?at%. Based on the current experimental results, the isothermal section of Al-Mn-Zn ternary system at 400°C has been constructed. 1. Introduction Automotive industry represents one of the most important markets for aluminum alloys. The use of aluminum and its alloys offers considerable potential to reduce the weight of an automobile body or engine without compromising performance and safety [1]. Many different elements including Mg, Cu, Zn, Mn, Si, and so forth are used to improve the properties of Al alloy for specific applications. Al-Zn based alloys have high strength and hardness, improved creep, wear resistance, and low density. It is well known that a small amount of Mn added to Al alloys plays a positive role in improving the fracture toughness, recrystallization, grain refinement, and resistance to stress corrosion fatigue of these alloys [1–3]. Because the Al-Mn-Zn system is an important ternary system for the development of Al alloys, it is essential to understand the phase relationships in the system. In addition, this system is an essential subsystem for AZ, AM-series magnesium alloys, high strength steels, and for galvanizing-related alloy systems [4, 5]. The three constituent binary systems were reasonably studied. Khan and Medraj [6] reevaluated the Al-Mn system which was in good agreement with most of the experimental results [7–10]. From their work [6], thermodynamic calculation almost reproduced the EPMA results of Minamino et al. [11]. Their calculation was consistent with the observation of Okamoto [12] who suggested a smooth continuous liquidus curve between the terminal δ-phase (BCC)
Analysis of Dynamics of Boundary Shape Perturbation of a Rotating Elastoplastic Radially Inhomogeneous Plane Circular Disk: Analytical Approach  [PDF]
Dmytro М. Lila, А. А. Martynyuk
Applied Mathematics (AM) , 2012, DOI: 10.4236/am.2012.35068
Abstract: For a rotating inhomogeneous circular disk a way of calculating dynamics of boundary shape perturbation and failure of bearing capacity is proposed in terms of small parameter method. Characteristic equation of plastic zone critical radius is obtained as a first approximation. A formula of critical angular velocity is derived which determines the stability loss of the disc according to the self-balanced form. Efficiency of the proposed method is shown by an illustrative example considered in Section 7. Values of critical angular velocity of rotation are found numerically for different parameters of the disc.
Genetic aspects of endothelium dysfunction in Uzbek hypertensive patients
Gulnoza Khamidullaeva,Amayak Kevorkov,Marietta Eliseyeva
Medical and Health Science Journal , 2010,
Abstract: The objective of the study was to evaluate the prevalence of ACE/ID, AGT/M235T, AT1R/A1166C, CYP11B2/C344T, B2ВKR/+9-9, ecNOS/4a4b, GNB3/C825T, and ARB2/Gln27Glu gene polymorphisms and their association with endothelium dysfunction (ED) in Uzbek hypertensive patients. The study found an association between ED and AGT M235T gene polymorphism. Genetic models disclosed that the T-allele, MT-, and TT-genotypes of the AGT gene were associated with an increased risk of ED. However, multivariate logistic regression analysis confirmed the negative association between the MM genotype of the AGT gene and positive association between IMT and ED. An association between essential hypertension (EH) in Uzbek males with ACE/ID and GNB3/C825T gene polymorphisms has been demonstrated. There is an association of AGT/ M235T gene polymorphism and ED in Uzbek hypertensive patients.
Estudos s?bre Longicórneos Neotrópicos (Coleoptera, Cerambycidae)
Zajciw, Dmytro;
Memórias do Instituto Oswaldo Cruz , 1958, DOI: 10.1590/S0074-02761958000200014
Abstract: in this paper, based on the study of the materials of the collections belonging to dr. c. a. campos seabra and the author's own, the author gives the additional characters of the rare species volxemia dianella lam., sthelenus braconimus bates and sth. ichneumoneus buq., the redescription of the genus xenocrasis bates, the descriptions of allotypes of the males of brasilianus testaceicornis melz., xenocrasis badeni bates and oncideres castanea dill. & dill., and the key for the determination of the species colobothea serv. with 6 (8) pale spots on the elytra. all these species are from brazil.
Novos longicórneos neotrópicos: XIII. (Col., Cerambycidae, Cerambycinae)
Zajciw, Dmytro;
Memórias do Instituto Oswaldo Cruz , 1967, DOI: 10.1590/S0074-02761967000200006
Abstract: the author describes one new genus, dihammaphoroides allied to dihammaphora chevr., 1859 and tree new species: coleoxestia omega, approximate to bivittata (buq., 1852), ommata (eclipta) melzeri resembling castanea bat., 1873 and dihammaphoroides sanguinicollis, all from brazil, prov. rio de janeiro, national park itatiaia, collected by j. f. zikan.
Dmytro Myeshkov
Magister Dixit , 2012,
Abstract: The article deals with the history of the Soviet policy in manpower management in the first two post-war decades on an example of two Russian regions – Sverdlovsk region and Stavropol Krai. The purpose is to analyze the problem of provision agriculture with qualified personnel during de-Stalinization of public life of able-bodied population migration, including mass migrations of rural youth to the cities. In the 1950th – the beginning of the 1960th country leaders undertook measures for regulation of labor migrations. Thus the new methods gradually come to change to mobilization character of policy in relation to manpower reserves, urged to raise appeal of agricultural work and quality of the village life. Not only party and state authorities, but also local writers, and also local mass media were involved in this work.
Formation of a Tunnel under the Major Hepatic Vein Mouths during Removal of IVC Tumor Thrombus
Dmytro Shchukin
Case Reports in Urology , 2013, DOI: 10.1155/2013/129632
Abstract: This study describes a clinical observation of successful implementation of a new surgical maneuver: formation of a cross tunnel under the mouths of the major hepatic veins during removal of a tumor thrombus of the inferior vena cava. This surgical technique helps avoid the usage of ? “piggyback” mobilization of the liver and the complications associated with it. However, for objective evaluation of this approach, a further clinical study is required. 1. Introduction Obvious limitations of high tumor thrombus removal with the use of balloon catheters or cardiopulmonary bypass have determined the development of alternative methods making it possible to fully control subhepatic, retrohepatic, and intrapericardial segments of the inferior vena cava (IVC) [1, 2]. The most important aspect of this approach is feasibility of external digital displacement of the thrombus apex below the diaphragm [3, 4]. However, due to the weakness of caval collateral vessel development, the clamping of the IVC above the mouths of the major hepatic veins can cause serious hemodynamic changes. Therefore, the main task of a surgeon in such a situation is to further displace the thrombus downwards and clamp the IVC below the mouths of the major hepatic veins [3, 4]. This maneuver was proposed by Ciancio et al. and now is used by many surgeons worldwide. It helps maintain hepatic blood flow, which accounts for about 25% of blood flow to the inferior vena cava. The main condition for the implementation of this stage of the operation is to carry out the mobilization of the liver using the classical and “piggyback” variants. But we should be aware that due to the problems associated with the venous anatomy, “piggyback” liver mobilization is possible only in 80%–92% of cases [5, 6]. This study presents a clinical observation of removal of a high tumor thrombus of the IVC with the use of a surgical technique, which involves forming a cross tunnel under the mouths of the major hepatic veins without “piggyback” mobilization of the liver. 2. Case Presentation A 57-year-old man was admitted to the hospital with complaints of gross hematuria and general weakness. Examination revealed a left kidney tumor, 150?mm 120?mm in size, extending up to the intrapericardial segment of the inferior vena cava (Figure 1). Distant and regional metastases were not found. Ultrasonography demonstrated thrombus apex flotation, which suggested the absence of adhesions of intraluminal tumor to the vena cava endothelium. Figure 1: MSCT images of supradiaphragmatic IVC tumor thrombus ((a) frontal reconstruction
From the mass gap in O(N) to the non-Borel-summability in O(3) and O(4) sigma-models
Dmytro Volin
Physics , 2009, DOI: 10.1103/PhysRevD.81.105008
Abstract: We give an analytical derivation of the mass gap of the O(N) sigma models and investigate a large-order behavior of the weak coupling asymptotic expansion for the energy. For sufficiently large N the series is sign-oscillating, which is expected from the large N solution of the sigma model. However, for N=3 and N=4 the series are sign positive.
Development of electromagnetic calorimeter detectors and simulations for spectroscopic measurements of charmonium with PANDA
Dmytro Melnychuk
Physics , 2010,
Abstract: The subject of the thesis is the study of electromagnetic transitions in charmonium with PANDA. The possible registration of the $h_c$ state in charmonium, observed recently by the E760 and E835 Fermilab experiments, is used for demonstration of the physics performance of the PANDA detector. The measurement of the angular distribution of $\gamma$-rays from radiative transitions can be used for the verification of its $J^{PC}$ quantum numbers. The electromagnetic calorimeter of the PANDA detector is the crucial component for this studies from the point of view of signal registration and background suppression.
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