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flow-field Analysis of Anti-Kidney Vortex film Cooling

Journal of Thermal Science 2012年第1期21卷 66-76页

作者： Lars Grf Leonhard Kleiser Institute of fluid Dynamics

film cooling is an important measure to enable an increase of the inlet temperature of a gas turbine and, thereby, to improve its overall efficiency. The coolant is ejected through spanwise rows of holes in the blades or endwalls to build up a film shielding the material. The holes often are inclined in the downstream direction and give rise to a kidney vortex. This is a counter-rotating vortex pair, with an upward flow direction between the two vortices, which tends to lift off the surface and to locally feed hot air towards the blade outside the pair. Reversing the rotational sense of the vortices reverses these two drawbacks into advantages. In the considered case, an anti-kidney vortex is generated using two subsequent rows of holes both inclined downstream and yawed spanwise with alternating angles. In a previous study, we performed large-eddy simulations (which focused on the fully turbulent boundary layer) of this anti-kidney vortex film-cooling and compared them to a corresponding physical experiment. The present work analyzes the simulated flow field in detail, beginning in the plenum (inside the blade or endwall) through the holes up to the mixture with the hot boundary layer. To identify the vortical structures found in the mean flow and in the instantaneous flow, we mostly use the λ 2 criterion and the line integral convolution (LIC) technique indicating sectional streamlines. The flow regions (coolant plenum, holes, and boundary layer) are studied subsequently and linked to each other. To track the anti-kidney vortex throughout the boundary layer, we propose two criteria which are based on vorticity and on LIC results. This enables us to associate the jet vortices with the cooling effectiveness at the wall, which is the key feature of film cooling.

关键词： film cooling anti-kidney vortex vortex identification trajectory tracking large-eddy simulation LES compound angle double row kidney vortex jet in cross-flow.

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Elastic, thermodynamic, electronic, and optical properties of recently discovered superconducting transition metal boride NbRuB:An ab-initio investigation

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Chinese Physics B 2017年第10期26卷 339-347页

作者： f Parvin S H Naqib Department of Physics University of Rajshahi

The elastic, thermodynamic, electronic, and optical properties of recently discovered and potentially technologically important transition metal boride NbRuB, are investigated using the density functional formalism. Both generalized gradient approximation （GGA） and local density approximation （LDA） are used for optimizing the geometry and for estimating various elastic moduli and constants. The optical properties of NbRuB are studied for the first time with different photon polarizations. The frequency （energy） dependence of various optical constants complement quite well the essential features of the electronic band structure calculations. Debye temperature of NbRuB is estimated from the thermodynamical study. All these theoretical estimates are compared with published results, where available, and discussed in detail. Both electronic band structure and optical conductivity reveal robust metallic characteristics. The NbRuB possesses significant elastic anisotropy. Electronic features, on the other hand, are almost isotropic in nature. The effects of electronic band structure and Debye temperature on the emergence of superconductivity are also analyzed.

关键词： hard materials ternary borides DfT calculations electronic band structure optical properties superconductivity

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Surface morphology and impurity distribution of electron beam recrystallized silicon films on low cost substrates for solar cell absorber

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Rare Metals 2006年第z1期25卷 195-200页

作者： GROMBALL f MüLLER J Department of Mikrosystemtechnik Technische Universitt Hamburg-Harburg Hamburg 21073 Germany

A line shaped electron beam recrystallised polycrystalline silicon film on the low cost substrate was investigated for the use of the solar cell absorber. The applied EB energy density strongly influences the surface morphology of the film system. Lower EB energy density results in droplet morphology and the rougher SiO2 capping layer due to the low fluidity. With the energy increasing, the capping layer becomes smooth and continuous and less and small pinholes form in the silicon film. Tungstendisilicide (WSi2) is formed at the interface tungsten/silicon but also at the grain boundaries of the silicon. Because of the fast melting and cooling of the silicon film, the eutectic of silicon and tungstendisilicide mainly forms at the grain boundary of the primary silicon dendrites. The SEM-EDX analysis shows that there are no chlorine and hydrogen in the area surrounding a pinhole after recrystallization because of outgassing during the solidification.

关键词： polycrystalline silicon film solar cell recrystallization energy surface morphology outgassing

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Impact of wastewater reuse on cobalt status in Egyptian environment

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Journal of Environmental Sciences 2003年第3期15卷 388-395页

作者： M.f. Abdel-Sabour Soil and Water Research Department Nuclear Research Center Atomic Energy Authority

Cobalt is used in the manufacture of alloys, catalysts in the petroleum industry, catalytic converters, and paint pigments. Thus the potential for Co releases into the environment is highly increased. Use of waste sludges and sewage effluent to fertilize and irrigate soils has also increased soil Co concentrations. Total cobalt contents of alluvial delta soil of Egypt show considerable variation ranging from 13.1 to 64.7 ppm. The impact of either wastewater irrigation or industrial activities on soil total Co was obvious due to accumulation of organic matter and solid waste in the surface soil samples. food crops and vegetables should not be grown on soil highly contaminated by Co. It is noteworthy that the delayed neutron activation analysis(DNAA) technique could be used successfully for total Co determination due to its high sensitivity. It is quit clearly that dust samples of Cairo City contains higher Co level, as compared to Suez Canal Region(Ismailia, Port Said and El-Suez cities). The high values in Cairo City may be due to the existence of industries around the city and the intensive traffic. To minimize Co environmental hazards, waste effluents should be treated on site. Thus, levels of potentially toxic Co needs to be continuously monitored and should be removed during several treatment processes before the disposal of these wastes.

关键词： cobalt environment Egypt

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Influence of Processing Parameters on the Strength of Air Brazed Alumina Joints Using Aluminium Interlayer

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Journal of Materials Science & Technology 2011年第7期27卷 641-646页

作者： A. Ibrahim f. Hasan Department of Metallurgical and Materials Engineering University of Engineering and TechnologyLahore Pakistan

Alumina specimens were joined together with thin aluminium interlayer at 750 and 900°C under different applied pressures and holding time in air. flexural strength of the joints was then measured using a standard four-point bend test method. Characterization of the interface was carried out to correlate the increase in flexural strength with the applied pressure, holding temperature and time. The study showed that the strength of joint is affected by all three parameters, i.e., processing temperature, holding time as well as applied pressure.

关键词： Pressure-assisted air brazing Alumina Aluminum Brazing Joining and Ceramic

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Numerical Modeling of the Solidification Phase Change in a Pipe and Evaluation of the Effect of Boundary Conditions

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Journal of Thermal Science 2010年第5期19卷 419-424页

作者： A.Jalali A.f.Najafi Department of Energy Engineering Power and Water University of Technology

A numerical solution to a two-dimensional model of flow and transient heat transfer involving solidification in a pipe has been *** the temperature of pipe wall is below the freezing point of fluid,phase change of flowing fluid and the influence of different boundary condition,such as pipe wall temperature,initial temperature and inlet velocity has been taken into *** it has been investigated to elicit proper non-dimensional numbers to show the solidification proceeding *** comparing the two acceptable inlet conditions,show distinctions between velocity inlet and pressure inlet boundary condition in such problems,which affect the whole freezing process.

关键词： Phase change Solidification Heat transfer

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Projective representation of D_(6)group in twisted bilayer graphene

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Chinese Physics B 2021年第7期30卷 1-4页

作者： Noah f.Q.Yuan Department of Physics Massachusetts Institute of TechnologyCambridgeMassachusetts 02139USA

Within the framework of continuum model,we study the projective representation of emergent D_(6)point group in twisted bilayer *** then construct tight-binding models of the lowest bands without and with external elec... 详细信息

关键词： twisted bilayer graphene tight-binding model projective representation

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Impacts of wastewater sludge amendments in restoring nitrogen cycle in p-nitrophenol contaminated soil

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Journal of Environmental Sciences 2011年第4期23卷 616-623页

作者： f. Olcay Topac Sagban Department of Environmental Engineering Uludag University

The possible impacts on nitrogen-cycle in a p-nitrophenol （PNP） polluted soil and the effectiveness of wastewater sludge amendments in restoring nitrification potential and urease activity were evaluated by an incubation study. The results indicated that PNP at 250 mg/kg soil inhibited urease activity, nitrification potential, arginine ammonification rate and heterotrophic bacteria counts to some extents. After exposure to PNP, the nitrification potential of the tested soil was dramatically reduced to zero over a period of 30 days. Based on the findings, nitrification potential was postulated as a simple biochemical indicator for PNP pollution in soils. Nitrogen-cycling processes in soils responded positively to the applications of wastewater sludges. A sludge application rate of 200 tons/ha was sufficient for successful biostimulation of these nitrogen processes. The microbial activities in sludge-amended, heavy PNP-polluted soils seemed to recover after 30–45 days, indicating the effectiveness of sludge as a useful soil amendment.

关键词： p-nitrophenol wastewater sludge soil pollution nitrogen-cycle biostimulation

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Antibacterial and anti-parasitic activities of Terfezia claveryi methanolic extract against some common pathogenic agents of infectious diarrhea

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Asian Pacific Journal of Tropical Biomedicine 2022年第5期12卷 216-222页

作者： Sultan f Alnomasy Department of Medical Laboratories Sciences College of Applied Medical SciencesShaqra UniversityAl-Quwayiyah 19257Saudi Arabia

Objective:To assess the antidiarrheal effects of Terfezia claveryi methanolic extract against Escherichia coli,Salmonella typhimurium,Shigella flexneri,and Giardia ***:Antibacterial effects of the Terfezia claveryi methanolic extract were carried out by determining the minimum inhibitory concentration(MIC)and minimum bactericidal concentration through micro broth dilution ***,reactive oxygen species production and protein leakage were *** evaluate the in vitro anti-giardial effects of Terfezia claveryi methanolic extract,Giardia lamblia WB(ATCC®30957)trophozoites were treated with various concentrations of Terfezia claveryi methanolic extract for 10-360 *** addition,the plasma membrane permeability of trophozoites treated with Terfezia claveryi methanolic extract was *** cytotoxicity effects of Terfezia claveryi methanolic extract against normal(HEK293T)and cancer(MCf-7)cells were also assessed using the MTT ***:The MIC and minimum bactericidal concentration of Terfezia claveryi methanolic extract against bacterial strains were in the range of 0.52-1.04 and 1.04-2.08 mg/mL,*** results revealed that reactive oxygen species production and protein leakage were significantly increased after the bacteria were treated with the Terfezia claveryi methanolic extract,especially at 1/3 and 1/2 MICs(Pfurthermore,Terfezia claveryi methanolic extract decreased the viability of Giardia lamblia trophozoites in a dose-dependent *** claveryi methanolic extract at 1,2,and 4 mg/mL resulted in 100%mortality in Giardia lamblia trophozoites after 360,240,and 120 min,***,Terfezia claveryi methanolic extract altered the permeability of plasma membrane of Giardia lamblia trophozoites by increasing the *** assay revealed that the 50%cytotoxic concentrations values for HEK293T and MCf-7 cells were 4.32 mg/mL and 6.40 mg/mL,respectively,indicating that Terfezia clavery

关键词： Terfezia claveryi Shigellosis Giardiasis Herbal medicines Infectious diarrhea Cellular mechanisms Cytotoxicity Microbiology

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An Extended Model for Coexistence of Superconductivity and Paramagnetism in High-T_c Superconductors

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Communications in Theoretical Physics 2008年第6期49卷 1631-1634页

作者： f.Inanir Department of Physics Rize UniversityRize53100Turkey

In the present work, the total magnetization in superconducting state is separated into critical state and paramagnetic components in terms of an H（x）-dependent magnetic flux density. Utilizing this model, we reproduce successfully M-H curves measured by Sandu et al. [Phys. Rev. B 74 （2006） 184511] and Sandu et al. [J. Supercond. Incorp. Novel Magn. 17 （2004） 701] for different forms of Jc.

关键词： superconductivity paramagnetism high-Tc superconductor critical-state model

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