Theoretical backgrounds of nonlinear THz spectroscopy of semiconductor superlattices

We consider terahertz absorption and gain in a single miniband of semiconductor superlattice subject to a bichromatic electric field in the most general case of commensurate frequencies of the probe and pump fields. Using an exact solution of Boltzmann transport equation, we show that in the small-signal limit the formulas for absorption always contain two distinct terms related to the parametric and incoherent interactions of miniband electrons with the alternating pump field. It provides a theoretical background for a control of THz gain without switching to the negative differential conductivity state. For pedagogical reasons we present derivations of formulas in detail.Comment: 14 page

Physical Principles of the Amplification of Electromagnetic Radiation Due to Negative Electron Masses in a Semiconductor Superlattice

In a superlattice placed in crossed electric and magnetic fields, under certain conditions, the inversion of electron population can appear at which the average energy of electrons is above the middle of the miniband and the effective mass of the electron is negative. This is the implementation of the negative effective mass amplifier and generator (NEMAG) in the superlattice. It can result in the amplification and generation of terahertz radiation even in the absence of negative differential conductivity.Comment: 5 pages, 3 figure

Russian Troops in the Badakhshan-Mountain Autonomous Region in 1992-1997

The study is devoted to the most dramatic period of the stay of Russian troops on the territory of Badakhshan-mountain - the era of the civil war in Tajikistan (1992-1997). The authors of the work tried to overcome the schematism and descriptive nature of the historiography of the topic. For this, documents from the archives of the Badakhshan mountain Autonomous Region (BMAR), data from the regional periodical press, and previously unpublished analytical materials and photographs from the funds of the Central Border Museum of the Federal Security Service of the Russian Federation were used. As a result of studying the opposing forces, instead of confronting the faceless, monolithic and mechanically opposed “Russians” and “fighters”, a complex picture of the interaction of various actors involved in the thick of events with the unpredictable dynamics of the context is formed. The authors conclude that the armed forces of the former “Center” at some point turned out to be the only significant economic agent, security guarantor and socialization institution that prevented the development of the region according to the “Afghan” scenario

Interconnection of structural characteristics with dynamic properties of A5083 aluminum alloy

In this work, the resistance of high-strain rate deformation and fracture during shock-wave compression of aluminum alloy A5083 previously obtained in two structural states by torsion under high pressure or dynamic pressing is studied. It is shown by electron microscopy that sub-microcrystalline structures differ in the size of grain–subgrains, dislocation density, and ratio of low-angle and high-angle boundaries. It is established that, at the same grain size, the sub-microcrystalline alloy exhibits higher dynamic properties, and after dynamic pressing, it has higher spall strength

ПОДБОР ПАРАМЕТРОВ ПОЛИКАПИЛЛЯРНОЙ КОЛОНКИ ДЛЯ ПОРТАТИВНЫХ ГАЗОАНАЛИЗАТОРОВ ПО ИНДЕКСАМ КОВАЧА

Short straight multicapillary columns (MCC) allow for fast gas chromatographic separation. However, their limited efficiency makes it difficult to use them for the analysis of multicomponent mixtures. Therefore, it is important to preliminarily evaluate the possibility of separation of target substances, based on the available information about their characteristics, in particular, by retention indices (RI). The paper provides an example of the choice of MCC and chromatographic conditions for the separation of explosives in stationary phases OV-5 and SE-54. To find the correspondence of the retention indices of the target substances with their retention factors k on the studied MCCs, the retention times of C10−C19 n-alkanes were experimentally determined at different column temperatures. Then the dependences of the calculated lnk on the quantity of carbon atoms m in n-alkanes CmH2m+2  were plotted and approximated by linear functions ln k = a + bm and their coefficients a and b were found for each temperature. From where, it was easy to calculate the retention factors of the target substances by their RI, assuming that RI = m·100, as well as to estimate the MCC efficiency required to separate neighboring peaks to obtain the desired level of separation. Based on the obtained equations, the explosives retention factors for MCCs at different temperatures were calculated and their required efficiency for separating adjacent peaks was estimated. The retention factors experimentally determined for some explosives on the MCCs at 140 °C turned out to be quite close to the theoretically calculated ones. In the future, the similar approach can be used to predict the possibility of gas chromatographic separation of mixtures of dangerous substances such as narcotic drugs.Key words: fast gas chromatography, multicapillary column, chromatographic column selection, retention indices, explosivesDOI: http://dx.doi.org/10.15826/analitika.2022.26.1.003A.P. Efimenko1, I.I. Naumenko2, E.V.Kirillova3, A.A. Shorokhov31Multichrom ltd., Arbusova str. 4a,  b. 1, Novosibirsk, 630117,Russian Federation2Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyga 3, Novosibirsk, 630090,Russian Federation 3«SPO «Analitpribor», Babushkina str. 3, Smolensk, 214031, Russian FederationКороткие прямые поликапиллярные колонки (ПКК) позволяют проводить быстрые газохроматографические разделения, однако их ограниченная эффективность требует тщательного подбора ПКК при анализе многокомпонентных смесей. Поэтому при решении конкретной аналитической задачи актуально предварительно оценить возможность разделения целевых веществ, опираться на доступные сведения об их характеристиках, в частности, на индексы удерживания (RI). В настоящей работе приведен пример подбора ПКК и условий хроматографирования для разделения смесей взрывчатых веществ (ВВ) на неподвижных фазах (НФ) OV-5 и SE-54, выбранных нами из-за того, что известные индексы удерживания ВВ в основном определены на НФ подобного состава. Для нахождения соответствия индексов удерживания целевых веществ с их фактором удерживания k на исследуемых ПКК экспериментально были определены времена удерживания н-алканов С10 – С19 при различных температурах колонок, после чего построены зависимости рассчитанных ln k от числа атомов углерода m в н-алканах CmH2m+2 и аппроксимацией линейной функцией ln k = a + bm для каждой температуры найдены коэффициенты аппроксимации a и b. Откуда легко можно было вычислить факторы удерживания целевых веществ по их RI, считая, что RI = m·100, а также оценить эффективность ПКК, достаточную для разделения соседних пиков целевых веществ с необходимой степенью разделения. На основании полученных уравнений рассчитаны факторы удерживания ВВ для ПКК при разных температурах и оценена необходимая эффективность для разделения соседних пиков. Экспериментально определенные для некоторых ВВ факторы удерживания на ПКК с исследуемыми НФ при 140 оС оказались достаточно близки к теоретически рассчитанным. В дальнейшем подобный подход может быть использован для прогноза возможности газохроматографического разделения смесей опасных веществ или соединений, обращение с которыми имеет законодательные ограничения.Ключевые слова: экспрессная газовая хроматография, поликапиллярные колонки, подбор хроматографических колонок, индексы удерживания, взрывчатые веществаDOI: http://dx.doi.org/10.15826/analitika.2022.26.1.00

Suppressed absolute negative conductance and generation of high-frequency radiation in semiconductor superlattices

We show that space-charge instabilities (electric field domains) in semiconductor superlattices are the attribute of absolute negative conductance induced by small constant and large alternating electric fields. We propose the efficient method for suppression of this destructive phenomenon in order to obtain a generation at microwave and THz frequencies in devices operating at room temperature. We theoretically proved that an unbiased superlattice with a moderate doping subjected to a microwave pump field provides a strong gain at third, fifth, seventh, etc. harmonics of the pump frequency in the conditions of suppressed domains.Comment: 8 pages. Development of cond-mat/0503216 . Version 2: Final version, erratum is include

An application of microservices architecture pattern to create a modular computer numerical control system

Currently, the most common approach to Computer Numerical Control (CNC) system design is a monolithic architecture. However, the introduction of the concept of Cyber-Physical Production Systems (CPPS) requires a paradigm shift in the design of control systems. This paper suggests a new approach to developing modular industrial equipment using a microservices architecture pattern. Microservices architecture features are addressed, as well as advantages and disadvantages. A heterogeneous computer network, where nodes communicate via a message queue, is proposed as a basis for the computer numerical control system. Fault tolerance is provided by modules full autonomy and reliable messaging. Furthermore, NoSQL database, guaranteeing high data accessibility and increased data access speed, is applied. An apparatus for selective photopolymer laser curing of free-form surfaces is considered as an example. Common setup structure, as well as main hardware and software modules, are described. Moreover, a distributed network latency simulation was carried out to prove the viability of the proposed microservices architecture