On unilateral contact problems with friction for an elastic body with cracks (Analysis of inverse problems through partial differential equations and related topics)

This expository article deals with contact problems with friction for a linearized (visco) elasticity in two dimension, which are arising from a wide variety of phenomena in mechanical engineering and concerning with some inverse problems and control problems. Contact conditions for cracks are so-called non-penetration conditions defined as unilateral conditions on the displacements of bodies to exclude nonphysical phenomenon such as mutual penetration of crack faces, see [11] for the details. In the present paper, mathematical results obtained in [9] and [5] are introduced and moreover, dynamic unilateral contact problems are discussed

Determination of the Growth Time Period of Loose Zinc Deposit Using Interval Analysis Methods

Abstract: A characteristic of obtaining metal powders by direct current electrolysis is changes in the morphology of particles over the loose deposit layer thickness up to the formation of large spherulites. Deposits should be periodically removed from the cathode in order to obtain a powder with homogeneous composition. This paper justifies the choice of the parameter describing the change in loose deposit properties and proposes a method for determining the periodicity of its removal from the cathode. Loose zinc deposits were obtained at 25°C from zincate electrolyte containing 0.3 mol L–1 of ZnO and 4 mol L–1 of NaOH at a current setpoint exceeding six times the limiting diffusion current calculated using the smooth electrode. Electrode potential, deposit thickness and evolved hydrogen volume were measured directly in the process of electrolysis. Current redistribution between the metal reduction and hydrogen evolution leads to a change in the structure of loose deposit particles. It is shown that the differential current efficiency of zinc is the parameter describing the change in the loose zinc deposit density. Its value should not exceed 0.96, in order to ensure deposition of loose deposit with homogeneous properties. A further increase in current efficiency will lead to the formation of aggregates at the deposit growth front. It is proposed to determine the periodicity of loose deposit removal from the cathode using the empirical equation for the time dependency of differential current efficiency of zinc. The mathematical and statistical analysis of the data obtained in six replicates was carried out. The interval approach made it possible to significantly narrow the range of permissible differential current efficiency values and, as a consequence, to determine empirical equation coefficients with acceptable accuracy and calculate the growth time period of a deposit with homogeneous structure. The obtained approach can be used to estimate the time period of loose metal deposition accompanied by hydrogen evolution. © 2020, Allerton Press, Inc.This study was supported by the Government of the Russian Federation, regulation no. 211, state assignment no. 0836-2020-003

Statistical Analysis of the Distribution of Impurities during Copper Electrorefining

Abstract: Electrolytic copper refining allows one to obtain high-purity copper, so analyzing the main ways impurities transition into electrolysis products is a relevant problem. Solving it makes it possible to control the process when changing the composition of raw materials and, as a result, the content of impurities in the anodes. In this work, on the basis of a complex analysis and synchronization of a large array of data on impurity concentrations in various industrial environments obtained on a series of commercial cells, the directions of the flow of impurities is determined and the relationship between the content of impurities in the different products of the electrolysis (slime, electrolyte, and copper cathode) is established. It is shown that the transition of impurities from one process medium (source) to another (receiver) occurs by four main schemes: linear increase, no visible dependence, the presence of the limit concentration in the receiver, and the presence of the threshold concentration in the source. The results of a statistical analysis of the distribution of six impurities (bismuth, arsenic, lead, sulfur, nickel, and silver) belonging to different groups are presented in four main pairs of the impurity source–receiver: anode–solution, anode–slime, slime–cathode, and solution–cathode. For all dependencies of the impurity concentration in the source on the content in the receiver, the coefficients of linear regression equations are determined and their significance is estimated. The coefficients make it possible to explain the pathways of the impurity transition observed in the commercial cells and predict the quality of cathode copper and the composition of slime when the anode composition changes. Calculations show that the accumulation of impurities in the cathodes is due to the occlusion of slime particles and the incomplete removal of the solution from the surface of commercial cathodes rather than electrochemical reactions. Attempts to improve and develop the technology of copper electrorefining should be focused on finding surfactants that would prevent the adsorption of suspended slime particles on the cathode surface, as well as on more completely washing the electrolyte off of them. © 2021, Allerton Press, Inc.This work is performed in the frame of the State Assignment number 075-03-2020-582/1 dated 18.02.2020 (the theme number 0836-2020-0037)

ОСНОВНЫЕ ПРИОРИТЕТЫ РАЗВИТИЯ МЕЖРЕГИОНАЛЬНЫХ И МЕЖГОСУДАРСТВЕННЫХ ПРОДОВОЛЬСТВЕННЫХ СВЯЗЕЙ РЕГИОНОВ СИБИРИ

Methodical positions for priority development of interregional and interstate food relations are justified. They include estimation of the current state and layout of AIC industries; definition of efficiency of existing interregional and interstate food relations and their influence upon functioning of agrofood market; justification for the system of measures to improve the formed food relations subject to Russia’s membership in WTO. Stemming from the methodical positions, Siberia’s regions are determined which have the opportunity to export grain and livestock output beyond their territories. It is established that the level of interdependence of Siberia’s regions on goods exchange operations is quite high. It is revealed that at the present time there is no strategy of development of foreign-economic relations of Siberia’s regions to frontier countries. Insufficiently developed is the regulatory-legal base of interstate cooperation, there are no special programs for the development of regional export potential, personnel training and infrastructure development. The study resulted in perspective directions suggested for the development of foreign-economic activity in Siberia.Обоснованы методические положения по приоритетному развитию межрегиональных и  межгосударственных продовольственных связей. Они включают в  себя оценку современного состояния и размещения отраслей АПК; определение эффективности сложившихся межрегиональных и межгосударственных продовольственных связей и  их влияния на функционирование агропродовольственного рынка; обоснование системы мер по улучшению сложившихся продовольственных связей с учетом членства России в ВТО. Исходя из методических положений определены регионы Сибири, имеющие возможность вывозить зерно и продукты животноводства за пределы своих территорий. Установлено, что уровень взаимозависимости регионов Сибири от товарообменных операций весьма высок. Выявлено, что в настоящее время отсутствует стратегия развития внешнеэкономических связей регионов Сибири с приграничными странами. Недостаточно развита нормативно-правовая база межгосударственного сотрудничества, отсутствуют специальные программы по развитию экспортного потенциала регионов, по подготовке кадров, по развитию инфраструктуры. В  результате исследования предложены перспективные направления развития внешнеэкономической деятельности Сибири

Influence of the Tread Material on the Efficiency of Protection of Steel Structures of the Water Treatment Tract of CHP

В работе выполнена оценка влияния различных материалов на эффективность протекторной защиты баков-нейтрализаторов, изготовленных из Ст. 3, в средах водоподготовительного тракта ТЭЦ. Определен состав продуктов коррозии, измерены значения рН и электропроводности среды в процессе коррозии стали в водах бака-нейтрализатора. Показано, что наибольшую защиту по отношению к стали в водах переменного состава обеспечивают цинковые протекторы.The paper assesses the effect of various materials on the effectiveness of the sacrificial protection of neutralizing tanks made of St. 3 in the environments of the water treatment path of the CHPP. The composition of corrosion products was determined, the pH values and electrical conductivity of the medium were measured in the process of steel corrosion in the waters of the neutralizing tank. It is shown that zinc protectors provide the greatest protection against steel in waters of variable composition

Выбор условий получения электролитических порошков цинка для металлнаполненных композиций

The paper presents a method of obtaining high-dispersed zinc powders by electrolysis and comparison of the properties of zinc-rich compositions prepared using as a pigment zinc powders obtained by different methods. Measurements have shown that the electrical conductivity of zinc-rich coatings containing electrolytic zinc powder, not inferior to the conductivity of the film with powder PZHD-0 obtained by the method of evaporation-condensation, despite the significant difference in the amount of zinc pigment. On the basis of the received data we can conclude that the use of electrolytic zinc powder as a pigment will significantly save zinc.В работе представлен способ получения высокодисперсных порошков цинка электролизом и сравнение свойств цинкнаполненных композиций, приготовленных с применением в качестве пигмента цинковых порошков, полученных разными методами. Проведенные измерения показали, что удельная электропроводность цинкнаполненных покрытий, содержащих электролитический порошок цинка, не уступает по проводимости пленкам с порошком ПЦВД-0, полученного методом испарения-конденсации, несмотря на существенное различие в количестве цинкового пигмента. На основании полученных данных можно сделать вывод, что использование электролитического порошка цинка в качестве пигмента позволит значительно экономить цинк.This work was supported by RFBR, project number 11-03-00226.Работа выполнена при поддержке РФФИ, проект № 11-03-00226

Involvement of Noradrenergic Neurotransmission in the Stress- but not Cocaine-Induced Reinstatement of Extinguished Cocaine-Induced Conditioned Place Preference in Mice: Role for β-2 Adrenergic Receptors

The responsiveness of central noradrenergic systems to stressors and cocaine poses norepinephrine as a potential common mechanism through which drug re-exposure and stressful stimuli promote relapse. This study investigated the role of noradrenergic systems in the reinstatement of extinguished cocaine-induced conditioned place preference by cocaine and stress in male C57BL/6 mice. Cocaine- (15 mg/kg, i.p.) induced conditioned place preference was extinguished by repeated exposure to the apparatus in the absence of drug and reestablished by a cocaine challenge (15 mg/kg), exposure to a stressor (6-min forced swim (FS); 20–25°C water), or administration of the α-2 adrenergic receptor (AR) antagonists yohimbine (2 mg/kg, i.p.) or BRL44408 (5, 10 mg/kg, i.p.). To investigate the role of ARs, mice were administered the nonselective β-AR antagonist, propranolol (5, 10 mg/kg, i.p.), the α-1 AR antagonist, prazosin (1, 2 mg/kg, i.p.), or the α-2 AR agonist, clonidine (0.03, 0.3 mg/kg, i.p.) before reinstatement testing. Clonidine, prazosin, and propranolol failed to block cocaine-induced reinstatement. The low (0.03 mg/kg) but not high (0.3 mg/kg) clonidine dose fully blocked FS-induced reinstatement but not reinstatement by yohimbine. Propranolol, but not prazosin, blocked reinstatement by both yohimbine and FS, suggesting the involvement of β-ARs. The β-2 AR antagonist ICI-118551 (1 mg/kg, i.p.), but not the β-1 AR antagonist betaxolol (10 mg/kg, i.p.), also blocked FS-induced reinstatement. These findings suggest that stress-induced reinstatement requires noradrenergic signaling through β-2 ARs and that cocaine-induced reinstatement does not require AR activation, even though stimulation of central noradrenergic neurotransmission is sufficient to reinstate

Photochemically reduced polyoxometalate assisted generation of silver and gold nanoparticles in composite films: a single step route

A simple method to embed noble metal (Ag, Au) nanoparticles in organic–inorganic nanocomposite films by single step method is described. This is accomplished by the assistance of Keggin ions present in the composite film. The photochemically reduced composite film has served both as a reducing agent and host for the metal nanoparticles in a single process. The embedded metal nanoparticles in composites film have been characterized by UV–Visible, TEM, EDAX, XPS techniques. Particles of less than 20 nm were readily embedded using the described approach, and monodisperse nanoparticles were obtained under optimized conditions. The fluorescence experiments showed that embedded Ag and Au nanoparticles are responsible for fluorescence emissions. The described method is facile and simple, and provides a simple potential route to fabricate self-standing noble metal embedded composite films

Статистический анализ распределения примесей при электрорафинировании меди

Electrolytic copper refining makes it possible to obtain high purity metal, so the analysis of the main ways of impurity transition into electrolysis products is an actual problem. If it is solved, the process can be controlled when changing the composition of raw materials and, as a result, the content of impurities in the anodes. This paper uses the comprehensive analysis and synchronization of a large array of data on impurities concentrations in various process media (anodes, electrolyte, slime, and cathode metal) obtained on the series of commercial cells to identify the directions of impurity flows and relationship between their content in these media. It is shown that the transition of impurities from one process medium (source) to another (receiver) is implemented according to four main patterns: linear increase, no visible dependence, the presence of a limit concentration in the receiver and the presence of a threshold concentration in the source. The paper provides the results obtained in the statistical analysis of the distribution of six impurities (bismuth, arsenic, lead, sulfur, nickel and silver) belonging to different groups in four main pairs of the impurity source – receiver: anode – solution, anode – slime, slime – cathode, solution – cathode. The coefficients of linear regression equations are determined and their significance is estimated for all dependencies of the impurity concentration in the source on the content in the receiver. The coefficients obtained make it possible to explain the impurity transition paths observed in the commercial cells and predict the quality of cathode copper and the composition of slimes when the anode composition changes. The calculations showed that impurities are accumulated in cathodes due to the occlusion of slime particles and incomplete solution removal from the surface of commercial cathodes rather than due to electrochemical reactions. The copper electrorefining technology should be improved and developed so as to find surface-active additives that would prevent the adsorption of suspended slime particles on the cathode surface, as well as better wash them from the electrolyte.Электролитическое рафинирование меди позволяет получать металл высокой степени чистоты, поэтому анализ основных путей перехода примесей в продукты электролиза является актуальной проблемой, решение которой дает возможность управлять технологическим процессом при изменении состава сырья и, как следствие, содержания примесей в анодах. В настоящей работе на основе комплексного анализа и синхронизации большого массива данных по концентрации примесей в различных технологических средах (аноды, электролит, шлам и катодный металл), полученных на сериях товарных ванн, определены направления потока примесей и выявлены связи между их содержанием в этих средах. Показано, что переход примесей из одной технологической среды (источник) в другую (приемник) реализуется по четырем основным схемам: линейное увеличение, отсутствие видимой зависимости, наличие предельной концентрации в приемнике и наличие пороговой концентрации в источнике. Приведены результаты статистического анализа распределения 6 примесей (висмут, мышьяк, свинец, сера, никель и серебро), относящихся к разным группам, в четырех основных парах источник примеси – приемник: анод–раствор, анод–шлам, шлам–катод и раствор–катод. Для всех зависимостей концентрации примеси в источнике от содержания в приемнике определены коэффициенты линейных уравнений регрессии и проведена оценка их значимости. Полученные коэффициенты позволяют объяснить наблюдаемые в промышленном электролизере пути перехода примесей и прогнозировать качество катодной меди и состав шламов при изменении состава анодов. Проведенные расчеты показали, что накопление примесей в катодах происходит не столько за счет электрохимических реакций, сколько вследствие окклюзии частиц шлама и неполного удаления раствора с поверхности товарных катодов. Совершенствование и развитие технологии электролитического рафинирования меди должно быть направлено на поиск поверхностно-активных веществ, которые бы способствовали предотвращению адсорбции частиц взвешенного шлама на поверхности катодов, а также улучшению их отмывки от электролита