Charge ordering and interlayer phase coherence in quantum Hall superlattices

The possibility of the existence of states with a spontaneous interlayer phase coherence in multilayer electron systems in a high perpendicular to the layers magnetic field is investigated. It is shown that phase coherence can be established in such systems only within individual pairs of adjacent layers, while such coherence does not exist between layers of different pairs. The conditions for stability of the state with interlayer phase coherence against transition to a charge-ordered state are determined. It is shown that in the system with the number of layers N\leq 10 these conditions are satisfied at any value of the interlayer distance d. For N>10 there are two intervals of stability: at sufficiently large and at sufficiently small d. For N\to \infty the stability interval in the region of small d vanishesComment: 10 page

Forecast of potentially dangerous rock pressure manifestations in the mine roadways by using information technology and radiometric control methods

Purpose. To reduce risk of emergency and injury-risk situations while improving the methods for predicting stress-strain state of the rock mass with the help of information systems, and to detect fissure locations in the mine roadways with the help of radiometric control. Methods. Analysis and generalization of experimental data; mathematical modeling of geomechanical and filtration processes by means of the finite element method; underground investigations of changes in activity of α-radiation of certain radon-isotope in the atmosphere of the mine roadways using standard methods as well as radiometric control equipment; and statistical processing of measurement results. Findings. Ratios, determining correlation between parameters of geomechanical process (i.e. fracture porosity, inclination angles of the fracture networks and their strike) and parameters of gas- dynamic process (i.e. intensity, gas flow rates and direction of gas travel) have been obtained. A mathematical model based on the finite element method is proposed in which a reasonable assumption is made that deformation of the pore medium is equal to the varied volume of the pore and fracture area. In the context of the model, deviation part of the strain tensor determines changes in the shape of the rock mass elements during disintegration. Spherical part of the strain tensor characterizes changes in volume and permeability of the pore and fracture area; it is determined by a value of minimum principal strains of the model elements. Parameters of the pore and fracture area location, volume and permeability were substantiated in the rock mass. The mine investigations have helped determine that within the areas of geological dislocations, concentration of radon daughter decay product of alpha-radiation polonium (Po218) experiences more that 2 – 4 times increase in relation to the roadway average value. On the basis of the criterion, it is proposed to use radiation monitoring of the mine roadways to identify areas of newly formed fracture systems resulting from fracture system deformation as one of the elements of method for the integrated control of the rock mass state. Originality. For the first time, regularities of changes in the pore and fracture area shape and volume at different stages of the adjacent longwall mining have been determined basing on parameters of technogenic fracture system orientation and spherical part of the strain tensor. The method of controlling the safe state of rocks has been further developed; it differs in the use of the determined ratios between changes in fracture system parameters and changes in α-radiation activity of some radon isotopes, methane concentrations and their correlation. Practical implications. The research results have been applied for the development of analytical and experimental approach to control safety of production environment in mines.Мета. Знизити ризики виникнення аварійних і травмонебезпечних ситуацій в шахтах шляхом вдосконалення методів прогнозу напружено-деформованого стану масиву порід із використанням інформаційних систем та виявлення локацій тріщин у гірничих виробках методом радіометричного контролю. Методика. Аналіз і узагальнення експериментальних даних; математичне моделювання геомеханічних і фільтраційних процесів методом скінченних елементів; шахтні дослідження змін активності α-випромінювань окремих ізотопів радону в атмосфері гірничих виробок стандартними методами та апаратурою радіометричного контролю; статистична обробка результатів вимірювань. Результати. Отримані співвідношення, що встановлюють взаємозв’язки параметрів геомеханічного процесу (тріщиною пористістю, кутами падіння і простягання систем тріщин) з параметрами газодинамічного процесу (інтенсивністю, витратами та напрямком переміщення газів). Запропоновано математичну модель на базі методу скінченних елементів, в якій прийнято обґрунтоване припущення, що деформація пористого середовища дорівнює зміні об’ємів порово-тріщинного простору. У моделі девіаторна частина тензора деформацій визначає зміни форми елементів породного масиву в процесі руйнування. Кульова частина тензора деформацій характеризує зміни об’єму і проникності порово-трещинного простору та визначається величиною мінімальних головних деформацій елементів моделі. Обґрунтовані параметри розташування, об’ємів і проникності порово-тріщинного простору в масиві порід. Шахтними дослідженнями встановлено, що в місцях дислокації геологічних порушень концентрація дочірнього продукту розпаду радону α-випромінювання полонію (Po218) зростає більш ніж в 2 – 4 рази по відношенню до середнього по виробці значення. На базі вказаного критерію запропоновано використовувати радіометричний моніторинг гірничих виробок для виявлення локацій новоутворених в процесі деформування систем тріщин в якості одного з елементів методу комплексного контролю стану породного масиву. Наукова новизна. Вперше на базі параметрів орієнтації систем тріщин техногенного походження й кульової частини тензора деформацій встановлені закономірності змін форми та об’ємів порово-тріщинного простору на різних етапах відпрацювання суміжних лав. Подальший розвиток отримав метод контролю безпечного стану гірських порід, який відрізняється використанням встановлених взаємозв’язків між змінами параметрів систем тріщин та змінами активності α-випромінювань окремих ізотопів радону, концентрацій метану і їх співвідношень. Практична значимість. Наукові результати використані при розробці аналітико-експериментального методу контролю безпеки виробничого середовища шахт.Цель. Снизить риски возникновения аварийных и травмоопасных ситуаций в шахтах путем совершенствования методов прогноза напряженно-деформированного состояния массива пород с использованием информационных систем и выявления локаций образовавшихся трещин в горных выработках методом радиометрического контроля. Методика. Анализ и обобщение экспериментальных данных; математическое моделирование геомеханических и фильтрационных процессов методом конечных элементов; шахтные исследования изменений активности α-излучений отдельных изотопов радона в атмосфере горных выработок стандартными методами и аппаратурой радиометрического контроля; статистическая обработка результатов измерений. Результаты. Получены соотношения, устанавливающие взаимосвязи параметров геомеханического процесса (трещинной пористостью, углами падения и простирания систем трещин) с параметрами газодинамического процесса (интенсивностью, расходами и направлением перемещения газов). Предложена математическая модель на базе метода конечных элементов, в которой принято обоснованное допущение, что деформация пористой среды равна изменению объема порово-трещинного пространства. В модели девиаторная часть тензора деформаций определяет изменение формы элементов породного массива в процессе разрушения. Шаровая часть тензора деформаций характеризует изменения объема и проницаемости порово-трещинного пространства и определяется величиной минимальных главных деформаций элементов модели. Обоснованы параметры расположения, объемов и проницаемости порово-трещинного пространства в массиве пород. Шахтными исследованиями установлено, что в местах дислокации геологических нарушений концентрация дочернего продукта распада радона α-излучения полония (Po218) возрастает более чем в 2 – 4 раза по отношению к среднему по выработке значению. На базе указанного критерия предложено использовать радиометрический мониторинг горных выработок для выявления локаций вновь образовавшихся в процессе деформирования систем трещин в качестве одного из элементов метода комплексного контроля состояния породного массива. Научная новизна. Впервые на базе параметров ориентации систем трещин техногенного происхождения и шаровой части тензора деформаций установлены закономерности изменений формы и объемов порово-трещинного пространства на различных этапах отработки смежных лав. Дальнейшее развитие получил метод контроля безопасного состояния горных пород, который отличается использованием установленных взаимосвязей между изменениями параметров систем трещин и изменениями активности α-излучения отдельных изотопов радона, концентраций метана и их соотношений. Практическая значимость. Научные результаты использованы при разработке аналитико-эксперимен-тального метода контроля безопасности производственной среды шахт.The authors express their gratitude to the Director of the Institute of Geotechnical Mechanics named by N. Poljakov of National Academy of Sciences of Ukraine, Academician of the National Academy of Sciences of Ukraine, Professor A.F. Bulat for providing technical and informational support for the research

Drag of superfluid current in bilayer Bose systems

An effect of nondissipative drag of a superfluid flow in a system of two Bose gases confined in two parallel quasi two-dimensional traps is studied. Using an approach based on introduction of density and phase operators we compute the drag current at zero and finite temperatures for arbitrary ratio of densities of the particles in the adjacent layers. We demonstrate that in a system of two ring-shape traps the "drag force" influences on the drag trap in the same way as an external magnetic flux influences on a superconducting ring. It allows to use the drag effect to control persistent current states in superfluids and opens a possibility for implementing a Bose analog of the superconducting Josephson flux qubit.Comment: 12 pages, 2 figures, new section is added, refs are adde

Research of ozonation process of the biologically pre-purified municipal wastewater

The paper considers the problem of post-treatment of municipal wastewater in Odessa using ozone. A significant place is given to the effect of the breakdown of toxic substances and important carcinogens. Based on theoretical studies, it was concluded that biological wastewater treatment does not guarantee a significant effect of the neutralization of many toxicants. The authors hypothesize the significant advantage of ozonation for the disposal and disinfection of wastewater compared to other methods, for example, chlorination. An important place is occupied by the search for optimal ozone treatment parameters. In laboratory conditions, data for mathematical modeling and optimization have been obtained. It has been established that the best treatment effect is achieved for the main wastewater pollutants, especially for synthetic surface-active substances (90 %) and BOD5 (65 %). Moreover, the processing time is 15 minutes at a dose of ozone of 20–25 mg/l. The concentration of total nitrogen decreases the least (20 %). It was found that a significant effect of disinfection by E. coli during ozonation is achieved by treating wastewater for 4 min at a dose of 3 mg/l of ozone. in a mixture of wastewater and natural water, this effect is achieved in 24 hours. The author's hypothesis of the gentle action of ozonation products for the widespread aquatic culture of Chlorella pyrenoidosa is confirmed. A significant effect of destruction under the influence of ozone of carcinogens was observed. It was found that up to 82 % of benzpyrene in wastewater is destroyed within 16 minutes at a dose of 15 mg/l. The authors conclude that ozonation is a universal method for the purification of biologically treated municipal wastewater, which has a significant effect on the destruction of many toxicants and pathogenic microflora, without the presence of ozonation products that inhibit the development of natural aquatic cultures. Further research should focus on finding low cost ozone synthesis methods

Ultrasound effect on electrospark cementation process

The process of carburizing is well-studied and is one of the traditional processes of the thermochemical treatment of steel. The process has disadvantages such as high energy consumption, long exposure time, complicated processing of large products and surfaces. Electrospark deposition with a carbon electrode is proposed as an alternative process. The carburizing extent and the working layer depth can be increased when the process is used in the ultrasonic vibration field. A resonant vibration introducing circuit with a standing wave generated in the specimen tested is implemented to identify the influence of specific ultrasonic wave areas on the hardened layer formed. The highest carbon saturation of the surface layer was found in the standing ultrasonic wave oscillation node area, where cyclic stretching and compression of the medium contribute to the excess phases release. The carbon in the martensite estimated by the c/a ratio was 0.78% by weight. The highest cementite layer depth and transition zone size are in the ultrasonic wave antinode area, where the highest dynamic medium particles displacement is observed under the influence of vibrations. It is shown that the base metal structure component dispersiveness is responsible for the increased hardened layer depth. © Published under licence by IOP Publishing Ltd

Laser-controlled local magnetic field with semiconductor quantum rings

We analize theoretically the dynamics of N electrons localized in a semiconductor quantum ring under a train of phase-locked infrared laser pulses. The pulse sequence is designed to control the total angular momentum of the electrons. The quantum ring can be put in states characterized by strong currents. The local magnetic field created by these currents can be used for a selective quantum control of single spins in semiconductor systems

An approach to NLO QCD analysis of the semi-inclusive DIS data with modified Jacobi polynomial expansion method

It is proposed the modification of the Jacobi polynomial expansion method (MJEM) which is based on the application of the truncated moments instead of the full ones. This allows to reconstruct with a high precision the local quark helicity distributions even for the narrow accessible for measurement Bjorken $x$ region using as an input only four first moments extracted from the data in NLO QCD. It is also proposed the variational (extrapolation) procedure allowing to reconstruct the distributions outside the accessible Bjorken $x$ region using the distributions obtained with MJEM in the accessible region. The numerical calculations encourage one that the proposed variational (extrapolation) procedure could be applied to estimate the full first (especially important) quark moments

Investigation of Photoelectric Converters with a Base Cadmium Telluride Layer with a Decrease in Its Thickness for Tandem and Two-sided Sensitive Instrument Structures

Photovoltaic cells with a base layer of cadmium telluride with a decrease in its thickness are studied. It is known that the widespread use of photovoltaic converters is constrained by their high price in the case of highly efficient instrument structures, or low efficiency. The creation of tandem and two-sided sensitive photoelectric converters will reduce their cost while increasing their efficiency. However, to create tandem and two-sided sensitive photoelectric converters, the necessary conditions are the use of transparent contacts and a decrease in the thickness of the base layer for efficient absorption of incident radiation by the converter, which is lower. In the research process, it was found that reducing the thickness of the base layer to 1 μm allows to increase the efficiency of the photoelectric transducer during irradiation from the back. An increase in the efficiency of the photoelectric converter occurs due to a decrease in the distance from the generation region of nonequilibrium charge carriers in the region of separation. If the thickness of the base layer is less than 1 μm, then regardless of which side of the irradiation is carried out, a decrease in the efficiency of the instrument structure is observed. Increase in the efficiency of photoconverters is associated with an increase in the negative influence of recombination processes on the back contact, a decrease in the number of charge carriers generated due to incomplete absorption of incident radiation, and a decrease in the volume of the built-in field of the separating barrier when it overlaps with the depletion region of the back contact. ITO/CdS/CdTe/Cu/ITO SCs with a base layer thickness of 1 μm demonstrates degradation stability. The highest value of efficiency in the case of illumination from the front side 8.1 % and with illumination from the back side 3.8 % received after a year of operation of the photovoltaic converter