Spin-controlled Mott-Hubbard bands in LaMnO_3 probed by optical ellipsometry

Spectral ellipsometry has been used to determine the dielectric function of an untwinned crystal of LaMnO_3 in the spectral range 0.5-5.6 eV at temperatures 50 K < T < 300 K. A pronounced redistribution of spectral weight is found at the Neel temperature T_N = 140 K. The anisotropy of the spectral weight transfer matches the magnetic ordering pattern. A superexchange model quantitatively describes spectral weight transfer induced by spin correlations. This analysis implies that the lowest-energy transitions around 2 eV are intersite d-d transitions, and that LaMnO_3 is a Mott-Hubbard insulator.Comment: 4 pages, 4 figure

Raman spectra of MgB2 at high pressure and topological electronic transition

Raman spectra of the MgB2 ceramic samples were measured as a function of pressure up to 32 GPa at room temperature. The spectrum at normal conditions contains a very broad peak at ~590 cm-1 related to the E2g phonon mode. The frequency of this mode exhibits a strong linear dependence in the pressure region from 5 to 18 GPa, whereas beyond this region the slope of the pressure-induced frequency shift is reduced by about a factor of two. The pressure dependence of the phonon mode up to ~ 5GPa exhibits a change in the slope as well as a "hysteresis" effect in the frequency vs. pressure behavior. These singularities in the E2g mode behavior under pressure support the suggestion that MgB2 may undergo a pressure-induced topological electronic transition.Comment: 2 figure

Strong 3D correlations in vortex system of Bi2212:Pb

The experimental study of magnetic flux penetration under crossed magnetic fields in Bi2212:Pb single crystal performed by magnetooptic technique (MO) reveals remarkable field penetration pattern alteration (flux configuration change) and superconducting current anisotropy enhancement by the in-plane field. The anisotropy increases with the temperature rise up to $T_m = 54 \pm 2 K$. At $T = T_m$ an abrupt change in the flux behavior is found; the correlation between the in-plane magnetic field and the out-of-plane magnetic flux penetration disappears. No correlation is observed for $T > T_m$. The transition temperature $T_m$ does not depend on the magnetic field strength. The observed flux penetration anisotropy is considered as an evidence of a strong 3D - correlation between pancake vortices in different CuO planes at $T < T_m$. This enables understanding of a remarkable pinning observed in Bi2212:Pb at low temperatures.Comment: 8 pages, 9 figure

Параметрическая оптимизация системы автоматического управления мощностью энергоблоков 300 МВт в режиме переменного давления пара перед турбиной

The article deals with the problem of parametric optimization of automatic control systems for power units of 300 MW of Lukoml’skaya GRES in the mode of variable pressure of turbine inlet superheated steam. The modernization of automatic power control systems of all power units of Lukoml’skaya GRES was carried out in the nineties of XX century for the last time. At the moment, these systems no longer meet all the requirements of the new standard, which regulates the participation rates of thermal power units in the normalized primary frequency control and in automatic secondary control of frequency and active power flows. According to this standard, the time to achieve the half value of the required power change should be 10 seconds within the normal and emergency reserves; the time to achieve the full value of the required power change should be 30 seconds within the normal reserve and 2 minutes within the emergency one. The construction of the Belarusian NPP is also being completed; its first unit will be put into operation in 2019, and the second one–in 2020. After the launch of the NPP, the Lukoml’skaya GRES power units will be necessitated to operate in a wide range of load changes. It is for these reasons that it is necessary to improve the efficiency of power units in particular and of the entire power plant in general. This can be achieved with the help of the outlined method of parametric optimization of a typical system of automatic control of power units, which allows improving the quality of control of turbine inlet steam power and pressure. The results of computer simulation of transient processes in the system illustrate the technique described in this article and confirm its correctness and undoubted advantages over other methods of optimization of typical systems of automatic control of power units.Статья посвящена вопросу параметрической оптимизации систем автоматического управления мощностью энергоблоков 300 МВт Лукомльской ГРЭС в режиме переменного давления перегретого пара перед турбиной. Последний раз модернизация систем автоматического управления мощностью энергоблоков на всех энергоблоках Лукомльской ГРЭС проводилась в 90-е гг. XX в. В данный момент эти системы уже не удовлетворяют всем требованиям нового стандарта, который регулирует нормы участия энергоблоков тепловых электростанций в нормированном первичном регулировании частоты и автоматическом вторичном регулировании частоты и перетоков активной мощности. Согласно данному стандарту, время достижения половинного значения необходимого изменения мощности должно составлять 10 с в пределах нормального и аварийного резервов; время достижения полного значения необходимого изменения мощности должно составлять 30 с в пределах нормального резерва и 2 мин – в пределах аварийного. Также завершается строительство Белорусской АЭС, первый энергоблок которой будет введен в эксплуатацию в 2019 г., второй – в 2020 г. После запуска АЭС энергоблоки Лукомльской ГРЭС будут вынуждены работать в широком диапазоне изменения нагрузок. Именно по этим причинам необходимо повысить эффективность работы энергоблоков, в частности и всей станции в целом. Этого можно добиться с помощью приведенной методики параметрической оптимизации типовой системы автоматического управления мощностью энергоблоков, позволяющей повысить качество регулирования мощности и давления пара перед турбиной. Результаты компьютерного моделирования переходных процессов в системе иллюстрируют описанную в данной статье методику и подтверждают ее правильность и несомненные преимущества перед другими методами оптимизации типовых систем автоматического управления мощностью энергоблоков

Параметрическая оптимизация системы автоматического управления мощностью энергоблоков 300 МВт в режиме постоянного давления пара перед турбиной

The problem of parametric optimization of automatic control systems of power units (ACSPU) of 300 MW at the Lukoml’skaya GRES (Lukoml Condensing Power Plant) at a constant superheated steam pressure upstream of the turbine is under consideration. During 1974–1979, eight units of the Lukoml’skaya GRES implemented ACSPU with a leading boiler power control, which will be forced to work in a wide range of loads due to the planned commissioning of two power units of the Belarusian NPP: the first one – in 2019, and the second one – in 2020. The total capacity of the Belarusian Nuclear Power Plant will amount to 2400 MW. In addition, modern requirements for the regulation of the frequency and flows of active electric power in the power system have been tightened: the time to reach the half value of the required power alteration should be 10 seconds within the normal and emergency reserves; the time to reach the full value of the required power alteration should be 30 seconds within the range of the normal reserve and 2 minutes – within the range of the emergency reserve. With this regard, increasing the efficiency of the units operating in the variable part of the electric load schеdule by the use of modern methods of calculation of parameters of the dynamic adjustment of the regulating devices of ACSPU becomes an urgent problem. The methodology of parametric optimization of the typical ACSPU that make it possible to improve the quality of power regulation and the pressure of the superheated steam upstream of the turbine is presented. The described technique is illustrated by the results of computer simulation of transient processes in the system when the task and internal disturbances are worked out, which confirm the correctness of the proposed technique in comparison with the known methods of optimization of the typical ACSPU.Рассмотрен вопрос параметрической оптимизации систем автоматического управления мощностью энергоблоков (САУМБ) 300 МВт Лукомльской ГРЭС в режиме постоянного давления перегретого пара перед турбиной. В течение 1974–1979 гг. на восьми энергоблоках Лукомльской ГРЭС были внедрены САУМБ с ведущим котельным регулятором мощности, которые будут вынуждены работать в широком диапазоне изменения нагрузок в связи с планируемым вводом двух энергоблоков Белорусской АЭС: первого – в 2019 г., второго – в 2020 г. Суммарная мощность Белорусской АЭС составит 2400 МВт. Кроме того, ужесточились современные требования к регулированию частоты и перетоков активной электрической мощности в энергосистеме: время достижения половинного значения необходимого изменения мощности должно составлять 10 с в пределах нормального и аварийного резервов; время достижения полного значения необходимого изменения мощности должно составлять 30 с в пределах нормального резерва и 2 мин – в пределах аварийного. В связи с этим актуальной становится задача повышения эффективности работы энергоблоков, работающих в переменной части графика электрических нагрузок, за счет использования современных методов расчета параметров динамической настройки регулирующих устройств САУМБ. Приведена методика параметрической оптимизации типовой САУМБ, позволяющая улучшить качество регулирования мощности и давления перегретого пара перед турбиной. Описанная методика иллюстрируется результатами компьютерного моделирования переходных процессов в системе при отработке задания и внутренних возмущений, которые подтверждают правильность предлагаемой методики по сравнению с известными методами оптимизации типовых САУМБ

Innovative technologies implementation to the investment and construction industry: problems and determining factors

Construction is one of the most significant sectors of the economy both by the share of the population employed in the industry and in the share of gross value added. Simultaneously сonstruction is one of the outsiders of digital transformation processes, which are now a trend in the development of the Russian economy. However, the construction industry has significant potential and prerequisites for the introduction of digital technologies, including building information modeling (BIM). A relevant scientific and practical task is to identify and systematize the factors (groups of factors) that have a significant impact on the introduction of innovative technologies in construction. This article presents the results of such systematisation with a focus on the implementation of BIM. The object of study was the enterprises of the investment and construction sphere of various focus, carrying out the transition to innovative digital technologies, including BIM. The subject is the factors of internal and external in relation to the organization of the nature that influence on the processes under study. The result of the study is a structured system of these factors, including external and internal environmental factors that may or may not be manageable in a particular management situation

Innovation infrastructure and innovation climate: innovation development ecosystem

The fourth industrial revolution “Industry 4.0” defines a paradigm shift in technological patterns, requiring the modernization of the institutional environment in the context of the development of end-to-end technologies. This fact determines the need for analysis and subsequent development of innovation infrastructure subsystems. The system-forming elements of the innovative development of the national and regional economies are: scientific activities of educational, research, expert organizations; venture forms of entrepreneurship; innovative enterprises and clusters; regulatory and legislative regulators; attributive mechanisms of innovative development and subjects of the innovative environment. The progressive development of the elements and subsystems of the innovation infrastructure determines the need for a systematic representation of the innovation environment. The aim of the study is to analyze the innovation infrastructure and ecosystem in the Russian Federation. The article discusses the categories of “innovation infrastructure” and “innovation ecosystem”, which are becoming increasingly widespread in the scientific literature and government documents, while being used in similar semantic contexts. The key objectives of the study, described in the theoretical part of the work, are the analysis of the elements of the innovation infrastructure and the innovation climate of the territories of federal districts and regions. The study uses general scientific research methods. The information base of the study is the data of federal authorities, research and analytical centers, international consulting companies, publications of Russian and foreign experts. The results obtained are of an applied nature, since they reflect the problem areas and directions for the development of the innovation ecosystem. The main problem is the lack of a single effective approach to managing innovation processes in the Russian Federation, despite the multiplicity of infrastructure elements in the national and regional innovation systems. This aspect is debatable, but the discreteness of the process of developing the national innovation infrastructure is obvious, which does not allow for the functioning of a self-developing open innovation ecosystem

Application of electric erosion machining for the restoration of splined surfaces

© Published under licence by IOP Publishing Ltd. The paper presents an analysis of the possibility of using electric erosive machining when restoring splined surfaces on specialized equipment

LEED Holography applied to a complex superstructure: a direct view of the adatom cluster on SiC(111)-(3x3)

For the example of the SiC(111)-(3x3) reconstruction we show that a holographic interpretation of discrete Low Energy Electron Diffraction (LEED) spot intensities arising from ordered, large unit cell superstructures can give direct access to the local geometry of a cluster around an elevated atom, provided there is only one such prominent atom per surface unit cell. By comparing the holographic images obtained from experimental and calculated data we illuminate validity, current limits and possible shortcomings of the method. In particular, we show that periodic vacancies such as cornerholes may inhibit the correct detection of the atomic positions. By contrast, the extra diffraction intensity due to slight substrate reconstructions, as for example buckling, seems to have negligible influence on the images. Due to the spatial information depth of the method the stacking of the cluster can be imaged down to the fourth layer. Finally, it is demonstrated how this structural knowledge of the adcluster geometry can be used to guide the dynamical intensity analysis subsequent to the holographic reconstruction and necessary to retrieve the full unit cell structure.Comment: 11 pages RevTex, 6 figures, Phys. Rev. B in pres

Cинтез котельных регуляторов системы автоматического управления мощностью энергоблоков

The article concerns the problem of structure-and-parametric optimization of a cascade automatic control system (CACS) by an example of a boiler power controller and a fuel controller. This CACS, which is a part of automatic control systems for power units, consists of two loops, viz. of an inner loop (which purpose is stabilization of the system) and an outer loop (designed for the adjustment) and, also, of two controller, viz. an outer controller (which is a basic one) provided for stabilization of the output value of the object (in our case, of the actual power unit capacity) and of an inner controller (which is an auxiliary one) provided to regulate fuel consumption. The internal controller builds up the control action with the aid of the boiler load controller of the power unit. As compared to single-loop automatic control systems, the cascade  system provides better quality of transient control due to the higher performance of the internal loop of the system. This advantage is especially noticeable when compensating for disturbances that come through the channel of regulating impact. The article presents two methods of setting, viz. the fuel controller and the boiler power controller. The application of these methods can improve the quality of power control and reduce fuel consumption in transient modes in comparison with the setting of these controllers of a typical power unit automatic power control system. The results of computer simulation of transient processes in CACS for input step surge and internal perturbation confirm the advantages of the methods are presented in this article.Статья посвящена вопросу структурно-параметрической оптимизации каскадной системы автоматического регулирования на примере котельного регулятора мощности и регулятора топлива. Каскадная система автоматического регулирования, являющаяся составной частью системы автоматического управления мощностью энергоблоков, состоит из двух контуров: внутреннего, предназначенного для стабилизации системы, и внешнего, предназначенного для корректирования, а также из двух регуляторов: внешнего (основного), необходимого для стабилизации выходной величины объекта (в рассматриваемом случае – фактической мощности энергоблока), и внутреннего (вспомогательного), назначением которого является регулирование расхода топлива. Внутренний регулятор формирует управляющее воздействие регулятором нагрузки котла энергоблока. По сравнению с одноконтурными системами автоматического регулирования каскадная система обеспечивает лучшее качество регулирования переходного процесса из-за более высокого быстродействия внутреннего контура системы. Данное преимущество особенно заметно при компенсации возмущений, которые поступают по каналу регулирующего воздействия. Каскадная система автоматического регулирования предназначена для автоматического управления объектами с большим запаздыванием по каналу регулирующего воздействия. Предложены два метода настройки: регулятора топлива и котельного регулятора мощности. Использование этих методов позволяет повысить качество регулирования мощности и снизить расход топлива в переходных режимах по сравнению с настройкой данных регуляторов типовой системы автоматического управления мощностью энергоблоков. Результаты компьютерного моделирования переходных процессов в каскадной системе автоматического регулирования при скачке задания и внутреннем возмущении подтверждают преимущества предлагаемых методов