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991.
We have investigated the preparation of molybdenum powders by reducing the oxide compounds MoO3, MgMoO4, and CaMoO4 with magnesium vapor at residual argon pressures in the range 5–20 kPa and temperatures in the range 700–800°C. Using the MgMoO4 and CaMoO4 compounds as precursors, we have obtained molybdenum powders with specific surface areas of up to 20 m2/g. The powders have a mesoporous structure. The reduction of the molybdenum compounds under such conditions was accompanied by separation of the reaction products due to the removal of magnesium oxide from the reaction zone. 相似文献
992.
Oleg Fryazinov Pierre-Alain FayolleTurlif Vilbrandt Galina PaskoAlexander Pasko 《Computers & Graphics》2011,35(3):524-531
The automatic generation of volumes bounding the intersection of two implicit surfaces (isosurfaces of real functions of 3D point coordinates) or feature based volumes (FBV) is presented. Such FBVs are defined by constructive operations, function normalization and offsetting. By applying various offset operations to the intersection of two surfaces, we can obtain variations in the shape of an FBV. The resulting volume can be used as a boundary for blending operations applied to two corresponding volumes, and also for visualization of feature curves and modeling of surface based structures including microstructures. 相似文献
993.
Alexander Pasko Oleg Fryazinov Turlif Vilbrandt Pierre-Alain Fayolle Valery Adzhiev 《Graphical Models》2011,73(5):165-181
We propose a new approach to modelling heterogeneous objects containing internal volumetric structures with size of details orders of magnitude smaller than the overall size of the object. The proposed function-based procedural representation provides compact, precise, and arbitrarily parametrized models of coherent microstructures, which can undergo blending, deformations, and other geometric operations, and can be directly rendered and fabricated without generating any auxiliary representations (such as polygonal meshes and voxel arrays). In particular, modelling of regular lattices and cellular microstructures as well as irregular porous media is discussed and illustrated. We also present a method to estimate parameters of the given model by fitting it to microstructure data obtained with magnetic resonance imaging and other measurements of natural and artificial objects. Examples of rendering and digital fabrication of microstructure models are presented. 相似文献
994.
Vladimir Poulkov Pavlina Koleva Oleg Asenov Georgi Iliev 《Telecommunication Systems》2014,55(4):481-489
In this paper the application of Role Game Theory to Power Control (PC) and Inter-Cell Interference Control (ICIC) for Long Term Evolution (LTE) is considered. The authors propose an approach based on defining different roles of the users within a cell of the LTE network. The main idea is to apply different methods and algorithms for PC and ICIC depending on the classified by role subscriber. Such an approach will give the possibility for flexible application and combination of different PC and ICIC methods for achieving better performance. 相似文献
995.
碳热还原/氮化合成Si3N4在1 300~1 600℃下N2或N2-H2混合气中进行。反应物由非晶Si O2与C粉以1∶4.5摩尔比混合、压片。产生的CO由红外传感器监测,样品中氧、氮、碳含量由LECO元素分析仪测得,混合物各相由X射线衍射(XRD)检测。Si O2还原反应在1 300℃以下开始,速率随温度升高增大;温度高于1 570℃时,速率因反应物表面被生成物覆盖降低。由于还原产物CO平衡分压差别小,选择生成Si3N4或Si C的临界温度不明显。碳热还原/氮化法合成氮化硅的原理需进一步探讨。 相似文献
996.
Dina V. Dudina Igor S. Batraev Vladimir Yu. Ulianitsky Natalia V. Bulina Michail A. Korchagin Oleg I. Lomovsky 《Materials and Manufacturing Processes》2015,30(6):724-729
The goal of this work was to study the phase and microstructure changes involved in the process of coating formation by detonation spraying of Ti3Al, TiAl, and TiAl3 intermetallics. The O2/C2H2 ratio was varied between 1.1 and 2.0, and the explosive charge was 30–40% of the barrel volume. In most experiments air was used as a carrier gas; selected experiments were performed with argon. We found that depending on the spraying parameters, TiAl3 essentially retains in the coatings or partially decomposes forming TiAl and Ti3Al as minor phases. Detonation sprayed Ti3Al reacts with nitrogen and oxygen partially transforming into titanium nitrides TiN/Ti2N and titanium oxynitrides TiNxOy. TiAl partially decomposes forming Ti3Al, which further reacts with oxygen and nitrogen as the particle temperature and the content of oxygen in the explosive mixture increase. The in situ formed titanium nitrides and oxynitrides show a reinforcing effect increasing the hardness of the coatings. 相似文献
997.
998.
Qian D Zhuang Ezekiel A Anyebe Ana M Sanchez Mohana K Rajpalke Tim D Veal Alexander Zhukov Benjamin J Robinson Frazer Anderson Oleg Kolosov Vladimir Fal’ko 《Nanoscale research letters》2014,9(1):321
We report the self-catalysed growth of InAs nanowires (NWs) on graphite thin films using molecular beam epitaxy via a droplet-assisted technique. Through optimising metal droplets, we obtained vertically aligned InAs NWs with highly uniform diameter along their entire length. In comparison with conventional InAs NWs grown on Si (111), the graphite surface led to significant effects on the NWs geometry grown on it, i.e. larger diameter, shorter length with lower number density, which were ascribed to the absence of dangling bonds on the graphite surface. The axial growth rate of the NWs has a strong dependence on growth time, which increases quickly in the beginning then slows down after the NWs reach a length of approximately 0.8 μm. This is attributed to the combined axial growth contributions from the surface impingement and sidewall impingement together with the desorption of adatoms during the diffusion. The growth of InAs NWs on graphite was proposed following a vapour-solid mechanism. High-resolution transmission electron microscopy reveals that the NW has a mixture of pure zinc-blende and wurtzite insertions. 相似文献
999.
Omid Madani Ghahfarokhi Kambulakwao Chakanga Stefan Geissendoerfer Oleg Sergeev Karsten von Maydell Carsten Agert 《Progress in Photovoltaics: Research and Applications》2015,23(10):1340-1352
Silicon heterojunction (SHJ) solar cells are highly interesting, because of their high efficiency and low cost fabrication. So far, the most applied transparent conductive oxide (TCO) is indium tin oxide (ITO). The replacement of ITO with cheaper, more abundant and environmental friendly material with texturing capability is a promising way to reduce the production cost of the future SHJ solar cells. Here, we report on the fabrication of the SHJ solar cells with direct current‐sputtered aluminum‐doped zinc oxide (ZnO:Al) as an alternative TCO. Furthermore, we address several important differences between ITO and the ZnO:Al layers including a high Schottky barrier at the emitter/ZnO:Al interface and a high intrinsic resistivity of the ZnO:Al layers. To overcome the high Schottky barrier, we suggest employing micro‐crystalline silicon (µc‐Si:H) emitter, which also improves temperature threshold and passivation of the solar cell precursor. In addition, we report on the extensive studies of the effect of the ZnO:Al deposition parameters including layer thickness, oxygen flow, power density and temperature on the electrical properties of the fabricated SHJ solar cells. Finally, the results of our study indicate that the ZnO:Al deposition parameters significantly affect the electrical properties of the obtained solar cell. By understanding and fine‐tuning all these parameters, a high conversion efficiency of 19.2% on flat wafer (small area (5 × 5 mm2) and without any front metal grid) is achieved. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
1000.
Petr M. Solyankin Mikhail N. Esaulkov Igor A. Chernykh Ivan V. Kulikov Maxim L. Zanaveskin Andrey R. Kaul Artem M. Makarevich Dmitrii I. Sharovarov Oleg E. Kameshkov Boris A. Knyazev Alexander P. Shkurinov 《Journal of Infrared, Millimeter and Terahertz Waves》2018,39(12):1203-1210
In this paper, we propose a switchable focuser device based on a Fresnel zone plate (FZP) structure for terahertz (THz) applications. Each FZP contains seven rings, etched in thin VO2 film with the designed focal lengths of 50 and 100 mm for 3.7-THz frequency. Temperature-induced VO2 phase transition leads to the change in dielectric susceptibility of the material, which allows one to switch on and off the focusing properties of the device. The devices were tested with radiation of 3.1 and 3.7 THz emitted by quantum cascade lasers. Experimental results were compared with numerical simulations. In this article, we compare the FZP based on VO2 films with different properties and show that a thicker VO2 film reveals higher focusing efficiency, while a thinner one reveals a higher modulation ratio for the peak intensity at the focal point of FZP. We demonstrate experimentally the near-diffraction-limited size of the beam in the focal point of the device. Switching between two phase states of the VO2 films results in up to the 38-fold change of intensity in the focal point. 相似文献