Proceedings of the National Academy of Sciences of Belarus, Physical-Technical Series / Известия Национальной академии наук Беларуси. Серия физико-технических наук
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МАГНИТНЫЕ НАНОМАТЕРИАЛЫ И НАНОСТРУКТУРЫ. ПЕРСПЕКТИВЫ РАЗВИТИЯ
Get PDFThere are analyzed creation and development of magnetic nanomaterials and nanostructures, films with a columnar type of crystal structure, multilayer film structures, nanocomposites, granular alloys and nanowires. The methodics of obtaining, structure, magnetic and magnetoresistive properties of three types of nanowires – multilayered and granular ones and the ones of spin-valve type are discussed. It is shown that multilayer film coatings with very thin (< 1 nm) alternating magnetic and nonmagnetic layers behave like films of granular alloys. It is emphasized that the films of granular Cu–Co alloys were first obtained at the Scientific and Practical Materials Research Center of the National Academy of Sciences of Belarus by the method of electrolytic deposition without subsequent annealing, as is the case with other methods for their preparation. As prepared Cu–Co films are superparamagneties. That is, they demonstrate ferromagnetic below blocking temperature, which is dependent on the size of cobalt clusters in diamagnetic matrix of copper. The granulated nanowires, firstly obtained by us, exhibit similar behavior. Special attention is paid to the analysis of obtaining and properties of multilayered films of the spin-valve type. The trends in the development of materials science are predicted, which will allow creating new materials with a high level of quality and specified properties, what will allow expanding the area of export of such materials and products from them in the future.
ВЛИЯНИЕ СИЛ ГРАВИТАЦИИ НА ПАРАМЕТРЫ ПАРОДИНАМИЧЕСКОГО ТЕРМОСИФОНА
Get PDFThe two-phase vapordynamic thermosyphon (VDT) is an efficient heat transfer device. Closed vapordynamic evaporative-condensation heat transfer cycle is realized inside it. Vapor pressure acts as a driving force for returning the liquid phase of working fluid to the condenser. The original design of the condenser and the evaporator of the VDT allows to transfer heat flow in horizontal direction to large (10–20 meters) distance. VDT can be used in heat exchangers of heat pumps, heat and cold accumulators of alternative energy sources and secondary energy sources for utilization. This article presents results of the experimental study and shows VDT heat transfer capability depending on the conditions of its work. For this purpose following VDT parameters were determined for different values of heat load and various drops between the thermosyphon evaporator and its condenser: the operating range of heat loads, maximum allowable thermosyphon angle of inclination, dependence of thermal resistance on the transmitted heat flow. The scheme of VDT is described and the methodology of the study is presented. Experimental data allows to conclude that high heat-transfer device working efficiency is achievable with heat loads between 300 and 1500 W and with vertical inclination angles up to 85 degrees.
ИССЛЕДОВАНИЕ ВОЗМОЖНОСТИ КООРДИНАЦИИ ПРОЦЕССОВ СЪЕМКИ ПОВЕРХНОСТИ ЗЕМЛИ КОСМИЧЕСКИМИ АППАРАТАМИ VNREDSat-1 (ВЬЕТНАМ) И БКА (БЕЛАРУСЬ)
Get PDFLeading companies in the field of obtaining data from Earth remote sensing from space are building Satellite constellations to increase the frequency (multiplicity) and monitor various parts of the Earth’s surface. The Satellite constellation remote sensing equipment from Airbus (France) allows daily observation of any point on the Earth’s surface with high spatial resolution, and the grouping of DigitalGlobe (USA) – with ultra-high spatial resolution. The analysis of the mutual exploitation of the national space systems of the Socialist Republic of Vietnam and the Republic of Belarus has been carried out. There have been analyzed the joint capabilities of VNREDSat-1 (Vietnam) and BKA (Belarus) Earth Observation Systems for the monitoring of natural resources, the environment and natural disasters by comparison of their space and temporal characteristics (orbit parameters and re-visit time) as well as spectral-energetic characteristics (space, spectral and radiometric resolutions). The accepted correlation of technical parameters for solving the previously mentioned tasks having into account the different phases of the mentioned satellites has been determined. The conclusions have been reinforced by the results of live experiments with archival and instant data from both EO satellites.
ИССЛЕДОВАНИЕ СПОСОБОВ ПОСТАНОВКИ ПОМЕХ ПРИЕМНИКАМ СИСТЕМ ГЛОБАЛЬНОЙ НАВИГАЦИИ, УСТОЙЧИВЫХ К ПОДАВЛЕНИЮ СРЕДСТВАМИ КОГЕРЕНТНОЙ АВТОКОМПЕНСАЦИИ
Get PDFActive jamming of a global navigation system GNSS receiver (GPS, Galileo, GLONASS, BeiDou) is of growing significance for the missions of security, control and monitoring. GNSS facilitates organization of various tasks: transportation, protecting mobile facilities or persons, traffic control, and a lot of others. Organizing generation of effective jamming denying normal navigation represents an important applied problem. Jamming GNSS, even though formally subject to international restrictions, is nevertheless a mandatory military technical component of ensuring the defensive capability of any developed state.The experience of recent years testifies to fast development of the equipment generating jamming against GNSS, and the technologies of counteracting jamming. Effective employment of jamming against GNSS users made the arms manufacturers seriously tackle the problem of improving jamming immunity of GNSS through modern techniques. Given the certain narrow limits for this characteristic of a system (long distances to satellites, limitations imposed on the power of information signals emitted by them, feeble directivity of their transmitting antennas), the countries possessing GNSS have published a plethora of information related to having achieved a dramatic improvement of their antijamming capacity giving rise to certain doubt in objectivity of the data.The article presents the results of scientific analysis and modeling of effectiveness of jamming against users of GNSS information with the receivers outfitted with correlative automatic jamming cancellers (AJC). Proof is provided of corrupting effectiveness of jamming cancellation, based on use of essentially parametric properties of the AJCs.
МОДЕЛИРОВАНИЕ УДАРНОГО КОНТАКТА ИНДЕНТОРА С НЕЖЕСТКИМИ СТАЛЬНЫМИ КОНСТРУКЦИЯМИ ПРИ ИЗМЕРЕНИИ ТВЕРДОСТИ
Get PDFThe problems of measuring hardness of constructions with insufficient rigidity by the dynamic indentation are discussed. The disadvantages of the existing dynamic hardness testers are described, the operation of which consists in impact indentation and determination of the hardness, depending on the restitution coefficient. Finite-element models of the contact of the indenter and the pipes samples with various wall thicknesses and diameters and cantilevered plates of various thicknesses are developed. Indentation diagrams for the investigated samples of pipes and plates in the coordinate plane of force-displacement are obtained. The results of the simulation have good convergence with the experimental data. With the help of the finite element models the separation of local penetration and deflection of construction is made. It is shown the influence of steel construction deflection on the process of indenter impression into the material tested and the change of indentation parameters as restitution coefficient, contact force, penetration depth and time of the active part of the impact. The limits of possible application of dynamic hardness testers have been determined. The ways of the increasing of the hardness measurement accuracy on the base of the data obtained during impact interaction are shown. It is established that the use of dependences between hardness and the time of the active stage of impact, as well as the ratio of the contact force to the depth of penetration at the loading stage, makes it possible to evaluate the hardness for pipes with the wall thickness exceeding 5 mm and cantilevered plates at the distance from the fixed support up to 100 mm.
Исследование перестраиваемого гиротрона на конусообразном волноводе
Get PDFThe results of calculations of a nonlinear model of a tunable frequency gyrotron on a cone-shaped waveguide and the main wave TE01 are presented. It is shown that the adjustment range can reach 2.8 %. To extend this band, it is necessary to lengthen the cone-shaped part of the waveguide without changing the angle of increase in the radius of the waveguide.The wave efficiency of a waveguide expanding along the axis is 21 % at a working frequency of 10 GHz. To achieve these parameters, it is necessary to divide the gyrotron electromagnet into two parts – the main electromagnet and auxiliary one, which has a limited length and can move along the waveguide. The second magnet can be made in the form of a set of individual electromagnets of limited length the set of electromagnets must fill the entire length of the cone-shaped waveguide. The fulfillment of this condition will allow to move the resonant magnetostatic field along the waveguide by switching the current in the coils of this set of electromagnets, which will exclude the mechanical movement of the auxiliary electromagnet. At a frequency of 200 GHz, the wave efficiency is reduced to 15 %, while the ohmic losses in the walls of the waveguide are 3 % of the power of the electron beam.The dependence of the gyrotron efficiency on the initial angular spread of electron velocities was investigated. It was concluded that the initial angular spread of the electron velocities has very little effect on the efficiency of the tunable gyrotron.The wave efficiency of a waveguide narrowing in length can reach 29 % at a frequency of 200 GHz, ohmic losses in the walls of a copper waveguide amount to 4 % of the power of the electron beam. Calculations have shown that a lamp backward wave gyrotron with a waveguide narrowing along the axis is more efficient than the version of the gyrotron traveling wave tube. However, in both cases, the synchronous value of the magnetostatic field must be displaced along the axis, depending on the required operating frequency, otherwise there occurs either a rearrangement of the electron beam or a return of the energy to the high-frequency field by the electron beam.Приводятся результаты расчетов нелинейной модели перестраиваемого по частоте гиротрона на конусообразном волноводе и основной волне TE01. Показано, что диапазон перестройки может достигать 2,8 %. Чтобы расширить данную полосу, необходимо удлинить конусообразную часть волновода без изменения угла увеличения радиуса волновода.Волновой КПД расширяющегося вдоль оси волновода составляет 21 % на рабочей частоте 10 ГГц. Чтобы достичь данных показателей, необходимо электромагнит гиротрона разделить на две части – основной электромагнит и вспомогательный, который имеет ограниченную длину и может перемещаться вдоль волновода. Второй магнит можно выполнить в виде набора отдельных электромагнитов ограниченной длины. Набор электромагнитов должен заполнять всю длину конусообразного волновода. Выполнение данного условия позволит перемещать резонансное магнитостатическое поле вдоль волновода путем переключения тока в катушках указанного набора электромагнитов, что позволит исключить механическое перемещение вспомогательного электромагнита. На частоте 200 ГГц волновой КПД уменьшается до 15 %, при этом омические потери в стенках волновода составляют 3 % от мощности электронного потока.Была исследована зависимость КПД гиротрона от начального углового разброса скоростей электронов, сделан вывод о том, что начальный угловой разброс скоростей электронов очень слабо влияет на КПД перестраиваемого гиротрона.Волновой КПД сужающегося по длине волновода может достигать 29 % на частоте 200 ГГц, омические потери в стенках медного волновода составляют 4 % от мощности электронного потока. Расчеты показали, что гиротронная лампа обратной волны с сужающимся вдоль оси волноводом более эффективна, чем вариант гиротронной лампы бегущей волны. Однако в обоих вариантах синхронное значение магнитостатического поля должно смещаться вдоль оси в зависимости от требуемой рабочей частоты, иначе происходит или перегруппировка электронного потока, или обратная отдача энергии высокочастотным полем электронному потоку
РАБОЧИЙ ПРОЦЕСС ДВИГАТЕЛЯ ВНУТРЕННЕГО СГОРАНИЯ НА СМЕСИ БЕНЗИНА С ВОЗДУХОМ, ОБОГАЩЕННОЙ ВОДОРОДОМ
Get PDFThe effect of hydrogen additives on the working process of a piston-type gasoline engine is studied. The indicator diagram has been built, and the operation of the piston engine on gasoline-air mixtures enriched with hydrogen in the amount of 0…20 % of the volume of air entering the engine has been analyzed. The possibility of obtaining satisfactory parameters when the engine works on gasoline with hydrogen additives is shown. The dynamics of the engine performance is studied depending on the oxidant excess coefficient. It has been established that the oxidizer excess ratio at which the maximum indicator pressure is reached is moved to the zone of poor mixtures. When the mixture is enriched with hydrogen in the amount of 20 % of the air volume, the maximum of indicator pressure pimax = 5.3...5.8 MPa is reached at α = 1.15...1.25, while for 10 % hydrogen addition the maximum pimax = 4.9...5.2 MPa takes place at α = 1.05...1.10 against pimax = 4.7...5.1 MPa at α = 0.90...0.95 for pure gasoline. According to the indicator diagram, the dynamics of intra-cylinder parameters is studied when the mixture is enriched with hydrogen. Thus, with a 20 % hydrogen addition the mean indicator pressure decreases by 12...19 %, despite a slight increase in the maximum cycle pressure (3...18 %), compared with gasoline operation, which leads to a proportional decrease in both the engine indicator power, and the indicator efficiency
Совершенствование технологии изготовления и контроля качества зеркал-отражателей из алюминиевого сплава
Get PDFAt present, the technology of diamond blade whetting with nano-sized roughness is widely used at the manufaсturing of metal-optical products, first of all, mirror-reflectors for “transportation” of powerful laser energy flows. Optimum material for mirror-reflectors is an aluminum alloy AMg2, which surface purity, is affected by the quality of preliminary mechanical heat treatment during superfinishing treatment by diamond whetting.Preliminary machining of the surface with a carbide cutter and finishing with a diamond cutter (with a radius of curvature of the blade less than 0.05 μm) were performed on a precision lathe of the MK 6501 model with a vertical spindle position on an air bearing. Thermal treatment was carried out in the laboratory electric furnace SNOL 58/350. Various modes of preliminary heat treatment, machining with a carbide cutter and finishing with a diamond cutter of substrates (20×20×7 mm3) were tested. The surface state analysis was carried out using the PMT-3 microhardness tester, the SolverPro P47 atomic-force microscope (AFM), and the experimental probe-electrometry device. The control of the electrophysical parameters of the surface was carried out by recording the distribution of the electron work function (RWF) by the contact potential difference with the processing by the microprocessor measuring transducer of electrostatic potentials. The recorded changes in the RWF characterize the physic-chemical and mechanical parameters of the surface of mirrors and indicate the presence of a different type and nature of defects.Modified preliminary mechanical-thermal treatment allowed to improve the cleanliness of surface treatment of substrates. Finishing nanoscale diamond blade processing, including the complete removal of the surface layer that was disturbed by previous operations, bring to the greatest possible improvement in the quality of the surface in terms of the uniformity of the distribution of its electrophysical properties. As a result, according to the values and changes of the RWF, achievement of the specified performance characteristics of the product surface was monitored in order to optimize the technological processing modes in accordance with the functional designations of the devices.The methods for increasing the efficiency of nanoscale diamond blade processing and performing researches of the electrophysical properties of the surface to control defects in the manufacture of metal reflector mirrors with high reflectivity and radiation strength for operation under extreme conditions.В настоящее время технология алмазного лезвийного точения с наноразмерной шероховатостью широко используется при изготовлении металлооптических изделий, прежде всего зеркал-отражателей для «транcпортировки» мощных лазерных энергетических потоков. Оптимальным материалом для зеркал-отражателей представляется алюминиевый сплав АМг2, на чистоту поверхности которого при суперфинишной обработке алмазным точением влияет качество предварительной механо-термической обработки. Целью работы являлось улучшение оптических характеристик зеркал-отражателей с высокой лучевой прочностью путем совершенствования технологии изготовления и контроля качества.Предварительная механическая обработка поверхности твердосплавным резцом и финишная обработка алмазным резцом (с радиусом закругления лезвия менее 0,05 мкм) проводились на прецизионном токарном станке модели МК 6501 с вертикальным расположением шпинделя на воздушном подшипнике. Термическая обработка осуществлялась в лабораторной электропечи марки SNOL 58/350. Были апробированы различные режимы предварительной термической обработки, обработки твердосплавным резцом и финишной обработки алмазным резцом подложек (20×20×7 мм3). Анализ состояния поверхности проводился с использованием микротвердомера ПМТ-3, атомно-силового микроскопа (АСМ) SolverPro P47 и экспериментальной установки зондовой электрометрии. Контроль электрофизических параметров поверхности осуществлялся путем регистрации распределения работы выхода электрона (РВЭ) по контактной разности потенциалов с обработкой микропроцессорным измерительным преобразователем электростатических потенциалов. Регистрируемые изменения РВЭ характеризуют физико-химические и механические параметры поверхности зеркал и указывают на наличие различного типа и природы дефектов.Модифицированная предварительная механо-термическая обработка позволила улучшить чистоту обработки поверхности подложек. Финишная наноразмерная алмазная лезвийная обработка, включающая полное удаление нарушенного предыдущими операциями поверхностного слоя материала, приводила к максимально возможному повышению качества поверхности по параметру однородности распределения ее электрофизических свойств. В результате по значениям РВЭ и их изменениям контролировалось достижение заданных эксплуатационных характеристик поверхности изделий для оптимизации технологических режимов обработки в соответствии с функциональными назначениями формируемых приборов и устройств.Разработаны методики повышения эффективности наноразмерной алмазной лезвийной обработки и проведения исследований электрофизических свойств поверхности по контролю дефектов при изготовлении металлических зеркал-отражателей с высокой отражательной способностью и лучевой прочностью для работы в экстремальных условиях