Determination of air and hydrofoil pressure coefficient by laser doppler anemometry

Some results of experiments performed in water cavitation tunnel are presented. Pressure coefficient (Cp) was experimentally determined by Laser Doppler Anemometry (LDA) measurements. Two models were tested: model of airplane G4 (Super Galeb) and hydrofoil of high speed axial pump. These models are not prepared for conventional pressure measurements, so that LDA is applied for Cp determination. Numerical results were obtained using a code for average Navier-Stokes equations solutions. Comparisons between computational and experimental results prove the effectiveness of the LDA. The advantages and disadvantages of LDA application are discussed. Flow visualization was made by air bubbles

Diagnostic Systems as Basis for Technological Improvement

AbstractHereunder the ways of technical diagnostics in metal manufacturing and peculiarities of challenges which are faced in technical diagnostics are given. The matters of the ways of technical diagnostics, which are required to be solved in near future, are described in the article. Solutions of problems concerning diagnostics of condition of an edge tool, using real-time vibration analysis, are provided. The article says about affect of bearings of spindle units on three-dimensional distribution of vibration parameters. An example concerning a spindle unit that induces auto vibration, which produce a false diagnosis regarding the condition of the edge tool, is given

Identification of Fe3+-Li+ complexes in ZnO by means of high-frequency EPR/ENDOR spectroscopy

Theoretical prediction of a high Curie temperature in ZnO doped with Mn, Fe, and other transition metals has stimulated the investigation of these materials by many research groups. Although charge-compensated Fe3+ centers in ZnO:Fe have been observed by means of EPR and have been known for decades, conclusions on the chemical nature of these defects are still contradictory. Originally, these centers were treated as Fe3+-Li + complexes with both ions occupying adjacent cationic sites. Recently, however, the centers were interpreted as a substitutional Fe 3+ ion with a vacancy at an adjacent zinc or oxygen site (Fe-V Zn or Fe-VO). In order to determine the chemical nature of the impurity associated with Fe3+, electron-nuclear double resonance (ENDOR) spectroscopy was used. ENDOR measurements reveal NMR transitions corresponding to nuclei with g-factor gN = 2.171 and spin I = 3/2. This unambiguously shows presence of Li as a charge compensator and also resolves contradictions with the theoretical prediction of the Fe-VO formation energy. The electric field gradients at the 7Li nuclei (within the Fe3+-Li+ complexes) were estimated to be significantly lower than the gradient at undistorted Zn sites. © 2013 Elsevier Inc. All rights reserved

Synthesis and Optimization of Reversible Circuits - A Survey

Reversible logic circuits have been historically motivated by theoretical research in low-power electronics as well as practical improvement of bit-manipulation transforms in cryptography and computer graphics. Recently, reversible circuits have attracted interest as components of quantum algorithms, as well as in photonic and nano-computing technologies where some switching devices offer no signal gain. Research in generating reversible logic distinguishes between circuit synthesis, post-synthesis optimization, and technology mapping. In this survey, we review algorithmic paradigms --- search-based, cycle-based, transformation-based, and BDD-based --- as well as specific algorithms for reversible synthesis, both exact and heuristic. We conclude the survey by outlining key open challenges in synthesis of reversible and quantum logic, as well as most common misconceptions.Comment: 34 pages, 15 figures, 2 table

Effects of Thermal Mass, Window Size, and Night-Time Ventilation on Peak Indoor Air Temperature in the Warm-Humid Climate of Ghana

Most office buildings in the warm-humid sub-Saharan countries experience high cooling load because of the predominant use of sandcrete blocks which are of low thermal mass in construction and extensive use of glazing. Relatively, low night-time temperatures are not harnessed in cooling buildings because office openings remain closed after work hours. An optimization was performed through a sensitivity analysis-based simulation, using the Energy Plus (E+) simulation software to assess the effects of thermal mass, window size, and night ventilation on peak indoor air temperature (PIAT). An experimental system was designed based on the features of the most promising simulation model, constructed and monitored, and the experimental data used to validate the simulation model. The results show that an optimization of thermal mass and window size coupled with activation of night-time ventilation provides a synergistic effect to obtain reduced peak indoor air temperature. An expression that predicts, indoor maximum temperature has been derived for models of various thermal masses

Effect of quantum confinement and influence of extra charge on the electric field gradient in ZnO

By means of electron-nuclear double resonance (ENDOR), it is shown that the Al impurity, which acts as a shallow donor in ZnO, leads to a significant reduction of the electric field gradient in ZnO single crystals. In ZnO quantum dots, however, the gradient on the Al sites remains virtually unchanged. When the Zn 2+ ion is substituted by Mn 2+ in a ZnO single crystal, the electric field gradient slightly increases (by about 20%). Therefore, the Mn 2+ ions can be used as probes to monitor the electric field gradients in ZnO crystals. © 2012 Pleiades Publishing, Ltd

Simulating chemistry efficiently on fault-tolerant quantum computers

Quantum computers can in principle simulate quantum physics exponentially faster than their classical counterparts, but some technical hurdles remain. Here we consider methods to make proposed chemical simulation algorithms computationally fast on fault-tolerant quantum computers in the circuit model. Fault tolerance constrains the choice of available gates, so that arbitrary gates required for a simulation algorithm must be constructed from sequences of fundamental operations. We examine techniques for constructing arbitrary gates which perform substantially faster than circuits based on the conventional Solovay-Kitaev algorithm [C.M. Dawson and M.A. Nielsen, \emph{Quantum Inf. Comput.}, \textbf{6}:81, 2006]. For a given approximation error $\epsilon$, arbitrary single-qubit gates can be produced fault-tolerantly and using a limited set of gates in time which is $O(\log \epsilon)$ or $O(\log \log \epsilon)$; with sufficient parallel preparation of ancillas, constant average depth is possible using a method we call programmable ancilla rotations. Moreover, we construct and analyze efficient implementations of first- and second-quantized simulation algorithms using the fault-tolerant arbitrary gates and other techniques, such as implementing various subroutines in constant time. A specific example we analyze is the ground-state energy calculation for Lithium hydride.Comment: 33 pages, 18 figure

Определение диагностических параметров оценки технического состояния высоковольтных выключателей

Надійність роботи електричних станцій та електропідстанцій в значній мірі залежить від надійності роботи високовольтних вимикачів. Будь-які зміни в струмових колах енергетичних систем при нормальних та аварійних режимах виконують вимикачі, робота яких в більшості випадків залежить від технічного стану дугогасильної камери та привода. Для визначення технічного стану вимикача використовують методи постійного та періодичного контролю, найбільш інформативною формою представлення яких є залежності швидкості руху рухомих контактів від часу. Проте їх отримання обмежено конструктивними особливостями, а саме місцями приєднання сенсорів кутового та лінійного переміщення. Запропоновано для визначення технічного стану дугогасильної камери і привода використати метод накладання тестового високочастотного сигналу на коло, яке містить контакти камер елегазових вимикачів під час їх спрацювання. Для визначення сукупності параметрів оцінки технічного стану привода елегазових вимикачів, було проведено дослідження роботи вимикача при нормальній та ненормальній роботі привода вимикача. Запропоновано в якості діагностичного параметра, який характеризує технічний стан спряжених частин привода інтервал часу.Reliability of power plants and substations is largely dependent on the reliability of high-voltage circuit breakers. Any change in current circles of power systems under normal and emergency modes perform switches which work in most cases depends on the technical condition of arc chutes and drive. To determine the technical state of the switch using the methods of continuous and periodic monitoring of the most informative form of representation which is depending on the velocity of the moving contact times. However, they receive on-strictions design features, such as the ground connection of sensors of angular and linear movement. Proposed for determining the technical state explosion chambers and drive - tachi method using overlay test high-frequency signal in the range that contains the contact chambers hexafluoride circuit breakers during their operation. To determine the set of parameters to assess technical state drive gas-insulated switches, a study of the switch during normal operation and abnormal operation of the switch actuator. Proposed as a diagnostic parameter that describes the technical condition of conjugated units drive time interval.Надежность работы электрических станций и электроподстанций в значительной степени зависит от надежности работы высоковольтных выключателей. Любые изменения в токовых цепях энергетических систем при нормальных и аварийных режимах выполняют выключатели, работа которых в большинстве случаев зависит от технического состояния дугогасительной камеры и привода. Для определения технического состояния выключателя используют методы постоянного и периодического контроля, наиболее информативной формой представления которых есть зависимости скорости движения подвижных контактов от времени. Однако их получения ограниченное конструктивными особенностями, а именно местами присоединения сенсоров углового и линейного перемещения. Предложено для определения технического состояния дугогасительной камеры и привода использовать метод наложения тестового высокочастотного сигнала на цепь, которая содержит контакты камер элегазовых выключателей при их срабатывании. Для определения совокупности параметров оценки технического состояния привода элегазовых выключателей, было проведено исследование работы выключателя при нормальной и ненормальной работе привода выключателя. Предложено в качестве диагностического параметра, который характеризует техническое состояние сопряженных частей привода интервал времени

Identification of shallow Al donors in ZnO

A combined magnetic resonance, photoluminescence, photoconductivity, and Raman scattering study of ZnO is presented. Electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) spectroscopy identify substitutional Al as a binding core of a shallow, effective-mass-like donor in ZnO. Based on the correlation between the EPR and photoluminescence data it is shown that recombination of an exciton bound to Al gives rise to the 3360.7meV photoluminescence line (I 6). A 1s→ 2p donor transition at 316cm -1 is detected in photoconductivity and Raman spectra. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim