ВЛИЯНИЕ АКТИВНОГО СОПРОТИВЛЕНИЯ ОБМОТОК ИМПУЛЬСНОГО ТРАНСФОРМАТОРА НА ПАРАМЕТРЫ ФОРМИРУЕМЫХ НА ЕМКОСТНОЙ НАГРУЗКЕ ИМПУЛЬСОВ НАПРЯЖЕНИЯ

Goal. Analysis of the influence of the active resistance of the primary and secondary windings of a pulse transformer on the voltage at the load capacitance based on the developed methodology for the analysis of transients caused by the discharge of the storage capacitance in the primary winding. Methodology. A model for calculating transients is developed using the Laplace transform. Transient modeling is carried out in the MATLAB software package. The results of transient calculations are compared with experimental results. Results. A method for calculating transients in test installations with pulse transformers has been developed, which allows taking into account the effect of power losses in the primary and secondary windings on the voltage at the load capacitance. The calculated relations are obtained, allowing to take into account the influence of the active resistance of the primary and secondary windings of the transformer on the voltage at the load capacitance, the currents in the primary and secondary windings of the transformer, as well as on the voltage drop on the inductance of the primary winding of the transformer. Scientific novelty. A mathematical model is developed for calculating transients in the primary and secondary windings of a pulse transformer, taking into account the influence of the active resistance of the windings when it changes over a wide range of possible values. Practical value. Using the proposed technique, it is possible to determine the parameters of the discharge circuit at which test voltage pulses are formed on the load capacitance without distorting the shape of the pulse front. Цель. Анализ влияния активного сопротивления первичной и вторичной обмоток импульсного трансформатора на напряжение на нагрузочной емкости на основании разработанной методики анализа переходных процессов, вызванных разрядом накопительной емкости в первичной обмотке. Методика. Модель для расчета переходных процессов разработана с применением преобразования Лапласа. Моделирование переходных процессов проводилось в программном пакете MATLAB. Результаты расчетов переходных процессов сравнивались с экспериментальными результатами. Результаты. Разработана методика расчета переходных процессов в испытательных установках с импульсными трансформаторами, позволяющая учитывать влияние потерь мощности в первичной и вторичной обмотках на напряжение на нагрузочной емкости. Получены расчетные соотношения, позволяющие учитывать влияние активного сопротивления первичной и вторичной обмоток трансформатора на напряжение на нагрузочной емкости, токи в первичной и вторичной обмотках трансформатора, а также на падение напряжения на индуктивности первичной обмотки трансформатора. Научная новизна. Разработана математическая модель для расчета переходных процессов в первичной и вторичной обмотках импульсного трансформатора с учетом влияния активного сопротивления обмоток при его изменении в широком диапазоне возможных значений. Практическое значение. Использование предложенной методики позволяет определять параметры разрядной цепи, при которых на нагрузочной емкости происходит формирование тестовых импульсов напряжения без искажений формы фронта импульсов.

Structural properties of hard disks in a narrow tube

Positional ordering of a two-dimensional fluid of hard disks is examined in such narrow tubes where only the nearest-neighbor interactions take place. Using the exact transfer-matrix method the transverse and longitudinal pressure components and the correlation function are determined numerically. Fluid-solid phase transition does not occur even in the widest tube, where the method just loses its exactness, but the appearance of the dramatic change in the equation of state and the longitudinal correlation function shows that the system undergoes a structural change from a fluid to a solid-like order. The pressure components show that the collisions are dominantly longitudinal at low densities, while they are transverse in the vicinity of close packing density. The transverse correlation function shows that the size of solid-like domains grows exponentially with increasing pressure and the correlation length diverges at close packing. It is managed to find an analytically solvable model by expanding the contact distance up to first order. The approximate model, which corresponds to the system of hard parallel rhombuses, behaves very similarly to the system of hard disks.Comment: Acceped in Journal of Statistical Mechanics: Theory and Experimen

Plaquette operators used in the rigorous study of ground-states of the Periodic Anderson Model in D=2D = 2 dimensions

The derivation procedure of exact ground-states for the periodic Anderson model (PAM) in restricted regions of the parameter space and D=2 dimensions using plaquette operators is presented in detail. Using this procedure, we are reporting for the first time exact ground-states for PAM in 2D and finite value of the interaction, whose presence do not require the next to nearest neighbor extension terms in the Hamiltonian. In order to do this, a completely new type of plaquette operator is introduced for PAM, based on which a new localized phase is deduced whose physical properties are analyzed in detail. The obtained results provide exact theoretical data which can be used for the understanding of system properties leading to metal-insulator transitions, strongly debated in recent publications in the frame of PAM. In the described case, the lost of the localization character is connected to the break-down of the long-range density-density correlations rather than Kondo physics.Comment: 34 pages, 5 figure

Is diversity good?

Prominent ethical and policy issues such as affirmative action and female enrollment in science and engineering revolve around the idea that diversity is good. However, even though diversity is an ambiguous concept, a precise definition is seldom provided. We show that diversity may be construed as a factual description, a craving for symmetry, an intrinsic good, an instrumental good, a symptom, or a side effect. These acceptions differ vastly in their nature and properties. The first one cannot lead to any action and the second one is mistaken. Diversity as intrinsic good is a mere opinion, which cannot be concretely applied; moreover, the most commonly invoked forms of diversity (sexual and racial) are not intrinsically good. On the other hand, diversity as instrumental good can be evaluated empirically and can give rise to policies, but these may be very weak. Finally, symptoms and side effects are not actually about diversity. We consider the example of female enrollment in science and engineering, interpreting the various arguments found in the literature in light of this polysemy. Keywords: ethics, policy, higher education, female students, minority students, affirmative actionComment: 7 page

Ferromagnetism without flat bands in thin armchair nanoribbons

Describing by a Hubbard type of model a thin armchair graphene ribbon in the armchair hexagon chain limit, one shows in exact terms, that even if the system does not have flat bands at all, at low concentration a mesoscopic sample can have ferromagnetic ground state, being metallic in the same time. The mechanism is connected to a common effect of correlations and confinement.Comment: 37 pages, 12 figures, in press at Eur. Phys. Jour.

СТАТИСТИЧНА МОДЕЛЬ КОНТРОЛЮ СТАБІЛЬНОСТІ НАПРУГИ ПРОБОЮ ІЗОЛЯЦІЇ В ПРОЦЕСІ ВИРОБНИЦТВА ЕМАЛЬПРОВОДІВ

This paper is devoted to non- destructive technological monitoring of defects of insulation of enameled wires with poliimid polymer. The authors present a statistical method for processing, comparison and analysis of outcomes of measurements of parameters of insulation of enameled wires. A mathematical model of trend for application in active technological monitoring is developed to develop recommendations for parameters of such monitoring. It is theoretically justified and the possibility of a diminution of dependence of an error on the velocity of movement of a wire for want of quantifying defects of enameled insulation using non- destructive tests by high voltage is shown. The dependence of average value of amount of defects for enameled wires with two-sheeted poliimid insulation in a range of nominal diameter 0.56 mm is experimentally determined. The technological monitoring purpose is to reduce quantifying defects of enameled insulation.Представлено результати технологічного контролю напруги пробою ізоляції емаль проводу на основі поліімідного полімеру. Розглянуто застосування статистичного аналізу результатів вимірювання показників контролю за допомогою інтервальної статистичної моделі для використання результатів в активному технологічному контролі. Запропоновано рекомендації щодо практичного використання інтервальної статистичної моделі для визначення гарантованого рівня відносної дисперсії контрольованого параметру. Представлена кількісна оцінка відносної дисперсії δ напруги пробою U впродовж тривалого технологічного циклу. Теоретично показана і вимірюваннями підтверджена можливість надійної кількісної оцінки тенденції зміни дефектності емаль ізоляції для проводу ПЭЭИДХ2 – 200 з двохшаровою поліімідною ізоляцією номінальним діаметром 0,56 мм впродовж тривалого технологічного циклу. Визначення кількісної оцінки тенденції зміни дефектності емаль ізоляції дозволяє також виділити і кількісно оцінити випадкову похибку технологічного процесу – сумарну похибку результатів технологічного контролю, яка є кількісною характеристикою випадкової складової стабільності технологічного процесу. Застосування методів інтервальної статистики дозволяє одержувати достовірні (надійна ймовірність дорівнює одиниці) числові оцінки навіть для окремої серії невеликої кількості вимірів, до яких не ставлять вимоги ні статистичної сталості, ні взаємної незалежності.

EPR and ODMR defect control in AlN bulk crystals

The results of pulse electron paramagnetic resonance (EPR), electron nuclear double resonance (ENDOR) and optically detected magnetic resonance (ODMR) are presented to show the electron structure of deep level defect color center in AlN single crystals such as a nitrogen vacancy in neutral charge state (VN 0) as well as a new type of point defect such as exchange-coupled pair of the nitrogen vacancies (VN-VN). Analyzing spin density distribution of an unpaired VN 0 electron on different ions of AlN crystalline lattice by means of high frequency ENDOR technique (94 GHz) give us a possibility to calculate hyperfine and quadrupole interactions (QI) with 27Al nuclei spins up to fourth coordinate sphere. Particularly data about quadrupole interactions allowed to estimate the fundamental parameter of AlN crystalline lattice in itself namely so called «crystalline field gradient» to be 4.9×1020V/m2 © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Evidence of exchange interaction of localized carriers and transition metals in diluted II-VI nanostructures: ODMR study

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.Optically detected magnetic resonance study of (CdMn)Te/(CdMg)Te quantum wells allowed to reveal the formation of exchange-coupled complexes consisting of Mn ions and localized holes in quantum wells with excess hole concentration and the directional electron tunneling towards wider wells in multiple quantum well structures. The existence of a distribution of Mn-hole complexes that differ in a number of Mn ions interacting with a localized hole is justified. In colloidal cobalt doped ZnO nanocrystals, several nm in diameter, the interaction between the magnetic ions and the shallow donor electron in the confined system of ZnO quantum dots has been revealed. Direct evidence of interaction of Co ions with the interstitial Li shallow donor in the ZnO nanocrystal core and hyperfine coupling with 1H in the quantum dot shell have been demonstrated

Evidence of exchange interaction of localized carriers and transition metals in diluted II-VI nanostructures: ODMR study

Copyright © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimOptically detected magnetic resonance study of (CdMn)Te/(CdMg)Te quantum wells allowed to reveal the formation of exchange-coupled complexes consisting of Mn ions and localized holes in quantum wells with excess hole concentration and the directional electron tunneling towards wider wells in multiple quantum well structures. The existence of a distribution of Mn-hole complexes that differ in a number of Mn ions interacting with a localized hole is justified. In colloidal cobalt doped ZnO nanocrystals, several nm in diameter, the interaction between the magnetic ions and the shallow donor electron in the confined system of ZnO quantum dots has been revealed. Direct evidence of interaction of Co ions with the interstitial Li shallow donor in the ZnO nanocrystal core and hyperfine coupling with 1H in the quantum dot shell have been demonstrated. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)