Behavior of the impurity atom in a weakly-interacting Bose gas

We studied the properties of a single impurity atom immersed in a dilute Bose condensate at low temperatures. In particular, we perturbatively obtained the momentum dependence of the impurity spectrum and damping. By means of the Brillouin-Wigner perturbation theory we also calculated the self-energy both for attractive and repulsive polaron in the long-wavelength limit. The stability problem of the impurity atom in a weakly-interacting Bose gas is also examined.Comment: 11 pages, 4 figure

Effect of Structure and Texture on Failure of Pipe Steel Sheets produced by TMCP

The method of orientation microscopy (EBSD) is used to study the structure and texture of low-carbon, low-alloy pipe steel sheets processed by controlled thermomechanical processing (TMCP). The temperatures of isothermal hot rolling varied. Samples cut from sheets showed a different fracture tendency during mechanical testing. The formation of cleavages (secondary cracks) during failure of steel is related to the presence of ferrite grains with orientation {001} <110> extended in the hot rolling direction. The formation of grains is a consequence of the isothermal hot rolling below the temperature

The effect of accelerated cooling on the structure of pipe steels for thermomechanical controlled processing

Scanning electron microscopy with orientation analysis by the electron backscatter diffraction (EBSD) method is used to study microstructures and textures formed in low-carbon low-alloy pipe steel after thermomechanical controlled processing (TMCP) and subsequent quenching with cooling rates of 50 to 700 °/s. It has been established that, in the range of industrial rates of cooling between 50 and 350 °/s from austenitic regions, the γ→α transformation starts at temperatures of 700-670 °C and proceeds by the shear mechanism. As a result, a bainite structure of different dispersity with martensitic inclusions is predominantly formed. © 2018 Author(s)

Evolution of microstructure in stainless martensitic steel for seamless tubing

Scanning electron microscopy with orientation analysis by the electron backscatter diffraction (EBSD) method is used to study microstructures and textures formed in the 0.08C-13Cr-3Ni-Mo-V-Nb steel through seamless tube production route: after hot deformation by extrusion; after quenching from various temperatures and subsequent high tempering. It is shown that the martensitic microstructure formed both after hot deformation and after quenching is characterized by the presence of deformation crystallographic texture, which is predetermined by the texture of austenite. The effect of heat treatment on texture, packet refinement, lath width, precipitation of carbides and Charpy impact energy is analyzed. © 2017 Author(s).The work was done using the equipment of the laboratory of Structural Methods of Analysis and Properties of materials and nanomaterials of the Collective Use Center affiliated to Ural Federal University. The study was supported by the program of increasing the competitiveness of the leading Russian universities, RF Government resolution No. 211, contract No. 02.А03.21.0006. We are grateful to the TMK company for their support and assistance in organizing the study

Роль математичної моделі комплексної оцінки сумісності поєднання будівельних процесів

The scientific article defines the role of mathematical modeling in the assessment of construction production regarding the admissibility of a combination of processes. Special attention is paid to the comprehensive study of the stages of construction in order to identify the main types of work and identify possible ways of combining them. In addition, the existing methods of construction organization were analyzed. Based on the conducted research, the course of model development was determined. The article examines and analyzes the complex influence of organizational and technological factors that affect construction, develops a mathematical model of the researched process in the form of systems of equations connecting the indicators of the researched process and its variable parameters, the variation of which studies the behavior of the process. The need for the use of information technologies in a construction company, the development of a mathematical model of the resource planning process and the selection of suppliers, and the requirements for the development of an information system. Based on the received relationships of qualitative and quantitative parameters, a model is developed and an algorithm for its calculation is built. In connection with the above, it is obvious that the development of such a model will allow a comprehensive assessment of the admissibility of combining construction processes. Construction of objects is a process in which implementing organizations, suppliers and consumers of material and technical resources, vehicles and other elements interact in a complex relationship. At the same time, the performance of work is affected by many different, in particular random, factors. A mathematical model is proposed for their influence, which will allow taking into account the joint influence of various factors, taking into account random factors of influence. Consider the value of mathematical modeling during the analysis of a potential combination of processes in construction. We focus on the study of construction processes, identify the main stages of work and identify methods of combination. We will analyze the construction methods used and determine their modeling methods.Наукова стаття визначає роль математичного моделювання в оцінці будівельного виробництва щодо допустимості поєднання процесів. Особлива увага звертається на комплексне дослідження етапів будівництва з метою виявлення основних видів робіт та виявлення можливих способів їх поєднання. Окрім того, проаналізовано існуючі методи організації будівництва. На основі проведеного дослідження визначено перебіг розробки моделі. В статті розглянуто та проаналізовано комплексний вплив організаційно-технологічних факторів, які впливають на будівництво, розроблено математичну модель досліджуваного процесу у вигляді систем рівнянь, що пов'язують показники досліджуваного процесу та його змінні параметри, варіюванням яких вивчається поведінка процесу. Необхідність застосування інформаційних технологій у будівельній компанії, розробка математичної моделі процесу планування ресурсів та вибору постачальників та вимоги щодо розробки інформаційної системи. На основі отриманих взаємозв'язків якісних та кількісних параметрів розробляється модель та вибудовується алгоритм її розрахунку. У зв'язку з вищесказаним очевидно, що розробка такої моделі дозволить здійснити комплексну оцінку допустимості суміщення будівельних процесів. Будівництво об'єктів є процесом, у якому організації-виконавці, постачальники та споживачі матеріально-технічних ресурсів, автотранспорт та інші елементи взаємодіють у складному взаємозв'язку. Одночасно виконання робіт впливають безліч різних, зокрема випадкових, чинників. Для їхнього впливу запропоновано математичну модель, яка дозволить враховувати спільний вплив різних чинників з урахуванням випадкових факторів впливу. Розглянемо значення математичного моделювання під час аналізу потенційного поєднання процесів у будівництві. Акцентуємо на дослідженні процесів будівництва, визначимо основні етапи робіт та виявимо способи поєднання. Зробимо аналіз використовуваних способів будівництва та визначимо їх методи моделювання

Features of shear transformation texture in seamless pipes

Microstructure and texture in seamless 0.08C-Cr-Mo-V, 0.25C-Cr-Mo-V-Nb, 0.08-13Cr-3Ni-Mo-V-Nb, and 18Cr-9Ni steel pipes are studied in the as-rolled and heat-treated states using orientation EBSD microscopy. It has been found that all types of microstructure (ferrite, martensite, and bainite) in products, both after hot rolling and after heat treatment, have well-defined axial crystallographic texture, where the direction is predominately perpendicular to the pipe surface. It is demonstrated that texture formation in heat-treated states is inherited due to the following factors important for the rules of orientation selection during the γ→α phase transformation: 1) occurrence of stable orientation of austenite grains resulted from straining; 2) special misorientation (boundaries) of austenite grains where transformation starts; 3) orientation relationships known for phase transformation; 4) thermal stresses in a product, formed during cooling. The latter can be considered as factor determining special texture in seamless steel pipes. © 2018 Author(s)

Influence of thermal oxidation on the properties of titanium alloys

In this study, the effect of thermal oxidation on the properties of the surface of titanium alloys was examined. Thermal oxidation was carried out at 750 C within 6 hours, 800 C within 5 hours, and 850 C within 4 hours. Electrical resistance of the surface after thermal oxidation was measured. Metallographic analysis, microprobe analysis and X-ray phase analysis were carried out to determine the structure, chemical and phase compound of the oxide layer on the surface of titanium alloys after thermal oxidation. The results indicate that thermal oxidation leads to increase of electrical resistance of the surface of titanium alloys. Microstructural analysis showed that thickness of the oxide layer after thermal oxidation is in the range of 25 to 100 μm. Microprobe and X-ray phase analysis showed that TiO2 and Al2O3 oxides have the best impact on electrical resistance. Two variants of possible application of the results have been presented. © Published under licence by IOP Publishing Ltd

Conditions of formation of Vikhoreva river and Ust-Vikhorevsky bay hydrochemical regime (Ust-Ilimsk reservoir)

Relevance. The necessity to control the hydrochemical regime of water bodies significantly affected by anthropogenic impacts. Aim. To study the spatial distribution of major ions and trace element concentrations and identify natural and anthropogenic formation factors of the hydrochemical composition of the Vikhoreva river and Ust-Vikhorevsky bay of the Ust-Ilimsk reservoir. Objects. Waters of the Vikhoreva river before and after inflow of wastewater from the Bratsk industrial zone, waters of the Ust-Vikhorevsky bay (Vikhorevskaya and Burdoyskaya parts) of the Ust-Ilimsk reservoir. Methods. Determination of micronutrients concentrations in water was performed by inductive coupled plasma mass spectrometry, mercury – by atomic absorption method. Cations and anions were determined using standard methods accepted in hydrochemical studies, Sorg – by titrimetric method, oxygen – by iodometric method. Results. In the Vihoreva river water after wastewater inflow from the Bratsk industrial zone, significant transformations of its hydrochemical composition were detected. Along the water area of river decrease of O2 concentrations (up to 0.3 mg O2/l) and increase of Сorg (up to 131 mg/l), SO42– (up to 262 mg/l), K+ (up to 10.6 mg/l), Cl– (up to 220 mg/l), Na+ (up to 240 mg/l), Mn (up to 248.5 mg/l), Cr (up to 7.4 mg/l), to a lesser extent Al (up to 224.1 mg/l), Co (up to 0.26 mg/l), Cu (up to 5.4 mg/l), Zn (up to 43.2 mg/l), Cd (up to 0.126 mg/l), Pb (up to 0.40 mg/l), Hg (up to 0.0032 mg/l) are observed. In surface waters of the Ust-Vikhorevsky bay concentrations of most components of the main ionic composition and trace elements decrease, as compared to the Vikhoreva river water. Maximum concentrations of Mn (511.5 mg/l), Fe (1567.2 mg/l), Co (0.80 mg/l), Pb (0.77 mg/l) were detected in bottom waters. The main ionic composition and trace element concentrations in the Vihoreva river water are determined primarily by anthropogenic factor. At the same time, the hydrochemical regime of the river is effected by natural factors. Inflow of both waters of the highly polluted and forming waters of the channel part of the Ust-Ilimsk reservoir impacts the hydrochemistry of the Ust-Vikhorevsky bay