Spatial and Wavenumber Resolution of Doppler Reflectometry

Doppler reflectometry spatial and wavenumber resolution is analyzed within the framework of the linear Born approximation in slab plasma model. Explicit expression for its signal backscattering spectrum is obtained in terms of wavenumber and frequency spectra of turbulence which is assumed to be radially statistically inhomogeneous. Scattering efficiency for both back and forward scattering (in radial direction) is introduced and shown to be inverse proportional to the square of radial wavenumber of the probing wave at the fluctuation location thus making the spatial resolution of diagnostics sensitive to density profile. It is shown that in case of forward scattering additional localization can be provided by the antenna diagram. It is demonstrated that in case of backscattering the spatial resolution can be better if the turbulence spectrum at high radial wavenumbers is suppressed. The improvement of Doppler reflectometry data localization by probing beam focusing onto the cut-off is proposed and described. The possibility of Doppler reflectometry data interpretation based on the obtained expressions is shown.Comment: http://stacks.iop.org/0741-3335/46/114

Photoactive Heterostructures: How They Are Made and Explored

In our review we consider the results on the development and exploration of heterostructured photoactive materials with major attention focused on what are the better ways to form this type of materials and how to explore them correctly. Regardless of what type of heterostructure, metal–semiconductor or semiconductor–semiconductor, is formed, its functionality strongly depends on the quality of heterojunction. In turn, it depends on the selection of the heterostructure components (their chemical and physical properties) and on the proper choice of the synthesis method. Several examples of the different approaches such as in situ and ex situ, bottom‐up and top‐down, are reviewed. At the same time, even if the synthesis of heterostructured photoactive materials seems to be successful, strong experimental physical evidence demonstrating true heterojunction formation are required. A possibility for obtaining such evidence using different physical techniques is discussed. Particularly, it is demonstrated that the ability of optical spectroscopy to study heterostructured materials is in fact very limited. At the same time, such experimental techniques as high‐resolution transmission electron microscopy (HRTEM) and electrophysical methods (work function measurements and impedance spectroscopy) present a true signature of heterojunction formation. Therefore, whatever the purpose of heterostructure formation and studies is, the application of HRTEM and electrophysical methods is necessary to confirm that formation of the heterojunction was successful

IR Spectroscopic Study of Photostimulated Processes on the Titanium Dioxide Surface with Adsorbed CO Molecules

The photostimulated processes on the titanium dioxide surface in the presence of ad-sorbed CO molecules were studied by IR spectroscopy and volumetry methods and the main parameters of these processes were analyzed

Role of turbulence and electric fields in the formation of transport barriers and the establishment of improved confinement in tokamak plasmas through inter-machine comparison

Over the past decade new regimes of tokamak operation have been identified, whereby electrostatic and magnetic turbulence responsible for anomalous transport, can be externally suppressed, leading to improved confinement. Although turbulence measurements have been performed on many confinement devices, the insight gained from these experiments is relatively limited. To make further progress in the understanding of plasma turbulence in relation to improved confinement and transport barriers, an extensive experimental and theoretical research programme should be undertaken. The present INTAS project investigates the correlations between on the one hand the occurrence of transport barriers and improved confinement in the tokamaks TEXTOR & T-10 and Tore Supra as well as on the smaller-scale tokamaks FT-2, TUMAN-3M and CASTOR, and on the other hand electric fields, modified magnetic shear and electrostatic and magnetic turbulence using advanced diagnostics with high spatial and temporal resolution. This is done in a strongly coordinated way and exploiting the complementarity of TEXTOR and T-10 and the backup potential of the other tokamaks, which together have all the relevant experimental tools and theoretical expertise. Advanced theoretical models and numerical simulations are used to check the experimental results.За останні десять років було отримано нові режими роботи токамаків, у яких електростатична і магнітна турбулентність, відповідальна за аномальний перенос, могла заглушатися шляхом зовнішнього впливу, і тим самим досягалося поліпшене утримання. Незважаючи на те, що дослідження турбулентності проводилися на багатьох установках, розуміння цих процесів залишається досить обмеженим. Для досягнення подальшого прогресу в розумінні плазмової турбулентності з погляду поліпшеного утримання і транспортних бар'єрів необхідні інтенсивні експериментальні і теоретичні дослідження. Проект INTAS спрямовано на з'ясування кореляції між виникненням транспортних бар'єрів і поліпшеного утримання в токамаках TEXTOR, Т-10 і Tore Supra, а також у токамаках малих розмірів ФТ-2, ТУМАН-3М и CASTOR, з одного боку, і електричними полями, модифікованим магнітним широм і електростатичною і магнітною турбулентністю, з іншого боку, з використанням передових діагностичних засобів з високим просторовим і тимчасовим розділенням. Дослідження проводяться з високим ступенем координації робіт і використанням взаємодоповнюваності установок TEXTOR і Т-10, і можливостей інших токамаків, що в сукупності забезпечить необхідну експериментальну і теоретичну перевірку. Для перевірки експериментальних результатів буде використано нові теоретичні моделі і чисельне моделювання.В последние десять лет были получены новые режимы работы токамаков, в которых электростатическая и магнитная турбулентность, ответственная за аномальный перенос, могла подавляться путём внешнего воздействия, и тем самым достигалось улучшенное удержание. Несмотря на то, что исследования турбулентности проводились на многих установках, понимание этих процессов остаётся весьма ограниченным. Для достижения дальнейшего прогресса в понимании плазменной турбулентности с точки зрения улучшенного удержания и транспортных барьеров необходимы интенсивные экспериментальные и теоретические исследования. Проект INTAS направлен на выяснение корреляции между возникновением транспортных барьеров и улучшенного удержания в токамаках TEXTOR, Т-10 и Tore Supra, а также в токамаках малых размеров ФТ-2, ТУМАН-3М и CASTOR, с одной стороны, и электрическими полями, модифицированным магнитным широм и электростатической и магнитной турбулентностью, с другой стороны, с использованием передовых диагностических средств с высоким пространственным и временным разрешением. Исследования проводятся с высокой степенью координации работ и использованием взаимодополняемости установок TEXTOR и Т-10, и возможностей других токамаков, что в совокупности обеспечит необходимую экспериментальную и теоретическую проверку. Для проверки экспериментальных результатов будут использованы новые теоретические модели и численное моделирование

Role of turbulence and electric fields in the establishment of improved confinement in tokamak plasmas

An extensive (INTAS) research programme started in 2002 to investigate the correlations between on the one hand the occurrence of transport barriers and improved confinement in the medium-size tokamaks TEXTOR and T-10 and on the smaller tokamaks FT-2, TUMAN-3M and CASTOR, and on the other hand electric fields, modified magnetic shear and electrostatic and magnetic turbulence using advanced diagnostics with high spatial and temporal resolution and of various active means to externally control plasma transport . This has been done in a strongly coordinated way and exploiting the complementarity of TEXTOR and T-10 and the backup potential of the three other tokamaks, which together have all the relevant experimental tools and theoretical expertise

USE OF GAS TURBINES FOR COMBINED ENERGY PRODUCTION

Abstract. Aim. Despite the obvious expediency of their widespread implementation, gas turbine (GT) and combined cycle gas turbine (CCGT) plants were only used in limited quantities in the former USSR and CIS countries. Due to the exhaustion of possibilities to increase the fuel use efficiency and return on investment (ROI) in steam-turbine combined heat and power (CHP) plants, the development of GT and CCGT plants becomes an urgent problem. In current global practice, the primary fuel for gas turbines and combined cycle gas turbines is natural gas. However, until recently, there has been a lack of experience in the design, construction and operation of GT and CCGT plants in the CIS countries. Method. Due to the ad hoc nature of research in this area, it was necessary to systematise the results of existing studies and assess the state of research at the world level taking regional characteristics into account. Results. The article presents the main considerations and potential effectiveness of the use of gas turbines. Basic gas turbine construction schemes are investigated along with their techno-economic characteristics and an assessment of their comparative utility. Conclusion. Considering the widespread availability of natural gas, it is recommended that gas turbine and combined-cycle plants be installed as part of the process of technical re-equipment in the fuel and energy complex, industry, agriculture and municipal energy sectors as part of the design and construction of new energy sources in the light of positive world experience and the current level of development of gas turbine technologies. Ubiquitous implementation of gas turbine units in the centres supplying heat and electric loads will reduce the regional economy’s need for energy fuel and ensure an increase in energy capacity without the need to construct new complex and uneconomic steam turbine power plants

METHOD FOR MEASURING ENERGY IN HEAT SUPPLY SOURCES

Objectives. This study was aimed at determining the actual flow rate of a gaseous working fluid by the pressure drop in the constriction device with its changing parameters (speed, pressure, temperature, gas composition).Method. Since the pycnometric method provides high accuracy in determining the density and is simpler than the calorimetric method for determining the calorific value, the value of the latter can be checked using the dependence proposed in the article. In the event of a discrepancy between the calculated value of the calorific value and the experimentally obtained value of more than 0.5%, the determination of the calorific value and the density should be repeated. The relationship between the density and calorific value of a gas is subject to verification and refinement when gas from other fields is used. In all cases, a sampler should be used to accumulate an average gas sample over an appropriate period of time. The methodological error in calculating the amount of gaseous working fluid can be eliminated or reduced by using a computer as part of an automated heat supply enterprise management system.Results. It was established that the calorific value of energy fuels non-linearly depends on the hydrogen and carbon contained therein; a formula has been developed to describe this relationship. When studying the energy characteristics of fuels, a previously unknown regularity was established: hydrocarbons ethylene, benzene and annelated hydrocarbons (naphthalene, anthracene, naphthacene, etc.) form the homologous series CnH(n+6)/2  with the homological difference C4H2, while all other series of hydrocarbons have a homological difference CH2.Conclusion. The greatest difficulties consist in accounting (measuring) the amount of energy contained in the fuel used at TPPs, mainly natural gas, and the coolant, since there are no appropriate technical means for direct measuring the amount of a particular type of energy. The developed theoretical provisions make a certain contribution to the development of the scientific foundations of heat and gas supply, increase accuracy and reduce the complexity of calculating the technical and economic indicators of thermal power plants and boiler houses