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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ВЗАИМОСВЯЗЬ МЕЖДУ СТРУКТУРОЙ, ЭЛЕКТРИЧЕСКИМИ И ДИЭЛЕКТРИЧЕСКИМИ СВОЙСТВАМИ ИОНОПРОВОДЯЩИХ ПОЛИМЕРНЫХ КОМПОЗИТОВ НА ОСНОВЕ ЭПОКСИДНЫХ ОЛИГОМЕРОВ И СОЛИ ПЕРХЛОРАТА ЛИТИЯ
Get PDFSolid polymer electrolytes (SPE) have received a great attention to the decisive role as an ionic conductor in various electrochemical devices. Significant efforts have been devoted to the high ionic conductivity with better mechanical stability of SPE. The aim of this work is to investigate the relationship between structure, electrical and dielectric properties of the crosslinked ion-conducting polymers based on a mixture of oligomers with similar functional epoxy groups. The effect of lithium perchlorate salt content on structure and properties of the synthesized polymer systems based on aliphatic epoxy oligomer – diglycidylether of ethylene glycol DEG-1 and epoxy-diane resin ED-20, which were cured by polyethylene polyamine, has been studied by means of the Differential Scanning Calorimetry, the Wide Angle X-ray Diffraction and the Broadband Dielectric Spectroscopy. It was found that the glass transition temperature of the synthesized systems increases with increasing amount of the LiClO4 that is connected with formation of coordination complexes between lithium cations and atoms of macromolecular chains. Presence of one single diffraction maximum of the diffuse type, an angular value of which is approximately 19.6, on the wide angle X-ray diffractograms indicates that systems are amorphous and they are characterized by the short-range ordering. The real parts of permittivity and complex electrical conductivity depend on the content of lithium perchlorate salt and temperature of measurements. The maximum level of ionic conductivity and permittivity at elevated temperatures was revealed for the systems with a concentration 30 phr. of the lithium perchlorate salt.
РАБОТА ВЫХОДА ЭЛЕКТРОНА И ФИЗИКО-ХИМИЧЕСКИЕ СВОЙСТВА ПОВЕРХНОСТНЫХ СЛОЕВ ИОННО-ЛЕГИРОВАННОГО ТВЕРДОГО СПЛАВА ВК6
Get PDFThe correlation between structural-phase transformations and physical-chemical properties of surface layers of hard alloy after ion-beam nitriding (temperature range 670–870 K) was established. The distribution of electron work function on hard-alloy plate surface after ion-beam nitriding was investigated. It is shown, that wear resistance of surface layers of hard alloy after ion-beam nitriding under different temperatures is uniform and has the same intensity for the first 450 m. At later stages of testing, the intensity of wear resistance is markedly different due to the modified layer abrasion. It is shown, that hard alloy ВК6 after ion-beam nitriding in the temperature range 750–790 K has enhanced microhardness, corrosion resistance and decreased up to 3 times mass wear during friction without lubricant, which is associated with carbonitrides formation and their strength increasing due to solid-solution hardening. The high values of the electron work function are characteristic for the surface layer of a hard alloy BК6 after ion-beam nitriding under 750–790 K, which is explained by the electron concentration increase. It is suggested, that ion-beam nitriding under this temperature range increases the corrosion resistance.
АНАЛИТИЧЕСКОЕ ПРЕДСТАВЛЕНИЕ ГРАФИКА ПРОДОЛЖИТЕЛЬНОСТИ ЭЛЕКТРИЧЕСКОЙ НАГРУЗКИ ДЛЯ ОПТИМИЗАЦИОННЫХ ИССЛЕДОВАНИЙ
Get PDFA method has been developed to restore the shape of the electrical load duration curve as the main predictive information on the demand for electric energy used in long-term and medium-term optimization studies of power systems. The main feature of the proposed method is the direct use in the algorithm of the basic coefficients characterizing the given form of the expression for energy demand, as well as a number of fixed points on the desired curve that are characteristic of the particular power system under study. The decision on the choice of fixed points is done with the help of retrospective historical statistics on the operation of the power system. The analytical polynomial expressions obtained using this method allow to quickly obtain the shape of the load duration curve and to simplify the procedure for entering the initial forms of curves in optimization programs, as well as to facilitate the process of predicting them for long time periods. The accuracy of the method was verified by comparison with the curves of past years obtained from the detailed hourly electrical load of the power system of the Republic of Belarus. It was found that the error value on the main part of the curve does not exceed ±1 % and slightly increases at its edges (±4–6 %), which is assumed to be sufficient accuracy for long-term energy planning.
Принципы проектирования станов штучной периодической прокатки для предприятий машиностроения
Get PDFThe use of variable profiles in engineering is the most effective way to reduce metal consumption and improve performance, increase the lifetime, reliability of machines and mechanisms, and reduce costs for their production, repair and operation. The purpose of the present work is to systematize the blanks of machine-building industries obtained by methods of plastic deformation and to develop general principes of the con cept of creating single-stage rolling mills on the basis of analysis of their design and operation. Three main classes of profiles are distinguished, differing in the type of the initial workpiece: strip, shaped and tube periodic billets. All these types of blanks can be used as semi-finished products for the production of the main parts of suspension and chassis of cars. Strip billets are widely used for the manufacturing of elastic suspension elements, tubular – for manufacturing of hollow body parts with increased requirements for strength and rigidity, in particular, driving axle housing, semi-axles of cars and trailers, jet engine casings. Shaped periodic profiles of various shapes are used as blanks for hot volumetric stamping. Mills and automatic lines for the rolling of blanks of low-spring springs, under-springs, guide bearings of air suspension, rolling of the bars of the front axle beam, manufacturing of protective elements and semi-axes of agricultural machinery developed under the guidance or with the direct participation of the author are presented. General requirements for the deformation equipment of machine-building industries are formulated. Recommendations to use induction heating and high-temperature thermomechanical treatment are justified. It is not recommended to change the direction of movement of the workpiece in the process chain. As a power drive equipment it is better to take electromechani cal, rather than hydraulic systems. It is also advisable to choose separate drives for each working element of the equipment.Использование переменных профилей в машиностроении является наиболее эффективным способом уменьшения металлоемкости и повышения эксплуатационных характеристик, повышения ресурса, надежности машин и механизмов, позволяет снизить затраты на их производство, ремонт и эксплуатацию. Целью представленной работы является систематизация заготовок машиностроительных производств, получаемых методом пластической деформации, и разработка на основе анализа проектирования и эксплуатации общих принципов концепции создания станов штучной периодической прокатки. Выделены три основных класса профилей, отличающиеся типом исходной заготовки: полосовые, фасонные и трубные периодические заготовки. Все эти типы заготовок можно использовать в качестве полуфабрикатов для производства основных деталей подвески и ходовой части автомобилей. Полосовые заготовки широко применяются при изготовлении упругих элементов подвески, трубчатые – для производства полых корпусных деталей с повышенными требованиями к прочности и жесткости, в частности, картера ведущего моста, полуосей автомобилей и прицепов, корпусов реактивных двигателей, фасонные периодические профили различных форм – в качестве заготовок под горячую объемную штамповку. Представлены созданные под руководством или при непосредственном участии автора станы и автоматические линии для прокатки заготовок малолистовых рессор, подрессорников, направляющих опор пневмоподвески, вальцовки заготовок балки передней оси, изготовления защитных элементов и полуосей сельскохозяйственной техники. Сформулированы общие требования к деформационному оборудованию машиностроительных производств. Обосновано использование индукционного нагрева и высокотемпературной термомеханической обработки. Не рекомендуется изменять направление движения заготовки в технологической цепочке. В качестве силового привода оборудования предложено принимать электромеханические, а не гидравлические системы. Рекомендовано предпочесть отдельные приводы для каждого рабочего органа оборудования
МОДИФИЦИРОВАНИЕ ЭНЕРГОНАСЫЩЕННОГО ГЕТЕРОГЕННОГО КОМПОЗИЦИОННОГО МАТЕРИАЛА ЦИКЛИЧНЫМИ НИТРАМИНАМИ
Get PDFФормализация процесса и разработка алгоритма твердофазного смешивания компонентов гетерогенного композиционного материала
Get PDFThe article considers one of the approaches to modeling the process of mixing of polydisperse powders, which includes three main fractions of different sizes, the shape of which is close to spherical. The work is aimed at reducing material costs at the stage of development of mixing processes by reducing the number of experiments. Aiming to obtain the most uniform mixing with the minimum time of the technological process, the model is based on the target function for a certain number of iterations of mixing of the composition to obtain the required (maximum possible) density of the package of mixed solid particles.To develop a model of the mixing process, one of the heuristic algorithms – the “metal annealing method” – was used. As a representative element of the model, an elementary cell in the form of several hexagonal densely. Packed particles around one introduced into the composition of the composite material (in a small amount, from 5 to 15 %) as a modifier was adopted. The mo del is formalized with the condition of averaging the particle sizes within each fraction, as well as the morphology of their surface. The number of particle repackaging iterations is calculated by the probability of obtaining the minimum amount of voids in the representative element and the uniformity of distribution of the modifying element.Comparison of the values obtained during the simulation with the measured values of the mixing results on a specific mixer will form a scale of compliance of the simulation results with the operating modes of the process equipment. This will make it possible to predict the appropriate mixing modes at the stage of development of the technological process with the possible system of fluctuations in the characteristics of the supplied raw materials and, thereby, to create a methodological basis for the formation of quality management of manufacturing heterogeneous composite material. The model can be adapted for polydisperse powders with the content of the main fractions of more than three.Рассмотрен один из подходов к моделированию процесса смешивания полидисперсных порошков, включающих три основные фракции различных размеров, форма которых приближается к сферической. Такой подход позволяет снизить материальные издержки на стадии разработки технологических процессов смешивания благодаря уменьшению количества проводимых экспериментов. Для получения наиболее равномерного смешивания при минимальном времени технологического процесса в основу разрабатываемой модели положена целевая функция за определенное число итераций смешивания композиции получения требуемой плотности (максимально возможной) упаковки смешиваемых частиц твердой фазы.С целью разработки модели процесса смешивания использовался один из эвристических алгоритмов – метод отжига метала. В качестве представительного элемента модели принята элементарная ячейка в виде гексогонально плотно упакованных частиц вокруг одной, введенной в состав композиционного материала (в небольшом количестве, от 5 до 15 %) в качестве модификатора. Модель формализована с условием усреднения размеров частиц в пределах каждой из фракций, а также морфологии их поверхности. Количество итераций переупаковки частиц рассчитывается по вероятности получения минимального объема пустот в составе представительного элемента и равномерности распределения модифицирующего элемента.Сопоставление значений, полученных в ходе моделирования, с измеренными значениями результатов перемешивания на конкретном смесителе позволят сформировать шкалу соответствия результатов моделирования режимам работы технологического оборудования. Это обеспечит возможность прогнозирования целесообразных режимов смешивания еще на этапе разработки технологического процесса при колебаниях характеристик поставляемого сырья и тем самым создать методологические основы для формирования системы управления качеством изготовления гетерогенного композиционного материала. Модель может быть адаптирована для полидисперсных порошков с содержанием более трех основных фракций
ЛИНЕЙНОЕ СУММИРОВАНИЕ СИГНАЛОВ РАВНОЙ МОЩНОСТИ, ПЕРЕДАВАЕМЫХ ПОСРЕДСТВОМ ОБОБЩЕННОГО КАНАЛА СВЯЗИ С ЗАМИРАНИЯМИ
Get PDFWe suggest the alternative approach based on definition of the moment generating function for the average signal-to-noise ratio (SNR) at the receiver output with the purpose to analyze performance of systems with equal gain combining over Nakagami-n (Rice) and Nakagami-q (Hoyt) fading channels under consideration of land, mobile and satellite telecommunication systems. We derive the exact closed-form mathematical expressions for average symbol error probability and outage probability using the Pade rational approximation to moment generating function of the SNR at the output of the combiner. We investigate the following important receiver performance such as the average SNR at the receiver output, fading, spectral effectiveness at weak input signals. Additionally, we study the rational Pade approximation of the moment generating function applying to the average SNR at the receiver output and evaluate bit error rate and the outage probability. Additionally, we investigate a possibility of modeling a Hoyt fading channel based on presentation Nakagami-m statistical model for evaluation of error performance under the use of equal gain combining technique.
МЕТОДИКА ПАРАМЕТРИЧЕСКОГО РАСЧЕТА НОВОЙ КОМПОЗИЦИИ ЗЕРКАЛЬНОГО ПЛАНАНАСТИГМАТА
Get PDFA four-mirror planaanastigmat calculation method is presented. Design feature of new mirror composition is existence of the afoсal scheme from the first two mirrors. The first and fourth mirrors can be combined into one unit (double mirror) which frame is an objective aperture. Different variants of designs are found; parametric characteristics of various modules are given. Seidel coefficients are described and the formulas of third order aberration polynomials are obtained. The correction factors of spherical aberration, coma, astigmatism are determined. Aberration correction is carried out at the expense of an asferization of smooth surfaces. The plane – field anastigmats are discussed; сlassification analysis by type of circuit decisions is executed for the purpose of obtaining a flat image field. A model of aberrational parametric algorithm of a new mirror plane – field anastigmat composition with a double mirror is developed. The system summary graphic and design factors have been presented. The problem on protection of the image plane from the foreign light has been considered. A light-gathering system (relative aperture D/f´ 1 : 1) consisting of four mirrors with a large field of view (near 2 w = 15o ) has been developed. The system proposed provides a stable correction of aberrations in the field of view: in the setup plane, the circle of confusion is equal to 0.1 mm at the center and does not exceed 0.05 mm, with a small back-ground exceeding this limit at the edge. The image curvature is corrected and the astigmatism does not exceed 0.05 mm. The absence of chromatic aberrations, high resolving power, and acceptable conditions for disposition of receiving apparatus in the new mirror plananastigmat composition proposed allow it to be widely used. The objective proposed can be used in thermal imaging as well as optical devices operating in the infrared region of the spectrum.
РАЗРАБОТКА ТЕХНОЛОГИИ ИЗГОТОВЛЕНИЯ ЗУБОПРОТЕЗНЫХ ДИСКОВ ИЗ СПЛАВОВ ЗОЛОТА И ИССЛЕДОВАНИЕ ИХ СВОЙСТВ
Get PDFSearching of such ways of processing at which irrevocable losses of precious metal will be minimum is necessary during the work with precious metals. In this regard it is necessary to investigate the main physico-mechanical properties of precious metals: durability, hardness, elasticity, plasticity and their rust resistance; to define temperature effect of processing on mechanical characteristics of the obtained precious metal ingots. Besides it is necessary to know physical and chemical properties of the metals which are a part of alloy, their workability by methods of metal forming, and knowledge of such properties is especially important at manufacture of dentoprosthetic disks. As a result of researches it is established that when rolling a strip of gold alloy of 900 fineness from initial thickness 4 mm to 0.55 mm, there is an extraction of grains in the direction of rolling; ultimate strength of alloy of AuAgCu 900-40 increases almost twice. Further annealing at temperature of 650 °C for 3 minutes completely restores plastic properties of the alloy. При работе с драгоценными металлами необходим поиск таких способов обработки, при которых безвозвратные потери драгоценного металла будут минимальными. В связи с этим необходимо исследовать основные физико- механические свойства драгоценных металлов: прочность, твердость, упругость, пластичность и их коррозионную стойкость; определить влияние температуры обработки на механические характеристики полученных слитков драгметалла. Кроме того, необходимо знать физико-химические свойства металлов, входящих в состав сплава, возможности воздействия на них методами обработки металлов давлением, причем знание таких свойств особенно важно при изготовлении зубопротезных дисков. В результате исследований установлено, что при прокатке полосы сплава золота 900-й пробы исходной толщины от 4 до 0,55 мм происходит вытягивание зерен в направлении прокатки, предел прочности сплава ЗлСрМ 900-40 увеличивается почти в 2 раза и отжиг при температуре 650 °С в течение 3 мин полностью восстанавливает пластические свойства сплава.
МОДИФИЦИРОВАНИЕ СИЛУМИНОВ НАНОКОМПОЗИТНЫМИ ПОРОШКАМИ ИНТЕРМЕТАЛЛИД/ОКСИД, ПОЛУЧЕННЫМИ МАСВС
Get PDFThe process of silumin modifying by introducing nanodispersed powders of intermetalliсs NiAl, FeAl, and composite powders of NiAl / 15% Al2O3 and Si / Al2 O3 obtained by the method of mechanically activated self-propagating high-temperature synthesis (MASHS) with addition of 10% tungsten or copper to increase the density was studied. It is shown that the developed modifier compositions make it possible to increase mechanical properties of silumin and to obtain improved values as compared with standards. The effectiveness of introduction of nanocomposite MASHS powders is explained by their activity due to destruction of the oxide surface film and creation of nonequilibrium state in the surface region during mechanical activation. With the introduction of all modifiers, in addition to the composite powder NiAl / 15 % Al2O3 , ultimate tensile strength of silumin increases. Maximum strength, ductility and hardness are achieved with insertion of MASHS Si/Al2O3 powders and addition of tungsten or copper. The introduction of modifiers containing MASHS powders results in changing in distribution, size and amounts of primary and eutectic silicon and improves homogeneity of silumin metal matrix. The use of tungsten and copper improves assimilability of the introduced modifying powders.