检索结果-南通市图书馆

Journal of Rare Earths 2014年第10期32卷 965-972页

作者： M.Eshraghi P.Kameli f.Khalili M.h.Ehsani h.Salamati Department of Physics Payame Noor University Department of Physics Isfahan University of Technology Department of Physics Semnan University

Structural, magnetic and electrical properties of the La0.7Ca0.3Co1–xMnxO3（x=0, 0.7 and 1） samples prepared by a simple method were systematically studied and it was found that the crystal structure was transformed from rhombohedral for La0.7Ca0.3CoO3（LCCO） and La0.7Ca0.3Co0.3Mn0.7O3（LCCMO） samples to orthorhombic for La0.7Ca0.3MnO3（LCMO） sample. The AC magnetic susceptibility measurements showed that LCCO sample underwent a transition from paramagnetic（PM） to ferromagnetic（fM） phase at Curie temperature, TC^155 K and below Curie temperature, the glassy ferromagnetism nature was observed. In LCCMO sample,clear evidence of spin glass（SG） state was observed at low temperature. PM-fM phase transition at about TC^260 K and long range fM order at low temperatures were observed in LCMO sample. Both the LCCO and LCCMO samples exhibited insulating behavior in the whole range of measuring temperature whereas the LCMO sample underwent a clear metal-insulator（MI） transition at about TMI^263 K, corresponding to Curie temperature. Metallic region of ρ（T） curve of the LCMO sample was fitted to the model of electron-electron and electron-magnon scattering. The charge carrier transport behavior in all the samples was compared based on polaronic models.

关键词： cobaltite spin glass manganites rare earths

Influence of Turbulators in Blade Cooling Passages on film hole Discharge Coefficients

在线全文

学校读者我要写书评

暂无评论

Journal of Thermal Science 2004年第3期13卷 245-254页

作者： h.-P. SChIffER J. TAEGE f. hASELBACh Rolls-Royce Deutschland Eschenweg 11 D-15827 Dahlewitz GermanyRolls-Royce Deutschland Eschenweg 11 D-15827 Dahlewitz GermanyRolls-Royce Deutschland Eschenweg 11 D-15827 Dahlewitz Germany

This paper details the results of a joint project between Rolls-Royce Deutschland (RRD) and the Northwestern Polytechnical University of China (NWPU). The objective of the project was the determination of the influence of tabulators in turbine blade cooling passages on film hole discharge coefficients (Cd coefficients). A large-scale plexiglas model was used by the NWPU to measure the turbulator influence on Cd coefficients for a wide range of different geometrical parameters, Reynolds numbers and cooling flow off take ratios. RRD specified the comprehensive test matrix and analysed the test data. The CfD code fLUENT was used by RRD for numerical simulation of the test cases with the main objective to support the interpretation of observed trends. Both, experimental and numerical results will be presented in this paper for a selection of test configurations.

关键词： film hole discharge coefficient turbulator blade cooling.

Numerical Simulation of Vortex Engine flow field:One Phase and Two Phases

在线全文

学校读者我要写书评

暂无评论

Journal of Thermal Science 2009年第3期18卷 226-234页

作者： A.f.Najafi S.D.Saemi M.h.Saidi Department of Energy Engineering Power and Water University of Technology Department of Mechanical Engineering Sharif University of Technology

Aiming at improving efficiency in combustion systems, the study on droplet behavior and its trajectory is of crucialimportance. Vortex engine is a kind of internal combustion engine which uses swirl flow to achieve highercombustion efficiency. One of the important advantages of designing vortex engine is to reduce the temperatureof walls by confining the combustion products in the inner vortex. The scopes of this investigation are to studyvortex engine flow field as well as effective parameters on fuel droplet behavior such as droplet diameter, dropletinitial velocity and inlet velocity of the flow field. The flow field is simulated using Reynolds Stress TransportModel (RSM). The Eulerian-Lagrangian method and the one-way coupling approach are employed to simulatetwo phase flow and dispersed phase in the chamber, respectively. A new method, based on computing pressureforce exerted on the droplet surface, is introduced to determine the distinction between using one-way andtwo-way coupling approaches. The results showed that the droplets with smaller diameter are more likely to followthe flow stream lines than bigger droplets, thus evaporate completely in the chamber. Moreover, droplets withgreater initial velocity have higher evaporation rate, yielding the existence of evaporation and combustion in theinner vortex. Additionally, the higher inlet velocity of continuous phase results in higher centrifugal force, leadsdroplets in question to deviate towards the wall faster.

关键词： Vortex Engine Swirl flow Lagrangian Approach fuel Droplet

Reactive DC Magnetron Sputter Deposited Titanium-Copper-Nitrogen Nano-Composite Thin films with an Argon/Nitrogen Gas Mixture

在线全文

学校读者我要写书评

暂无评论

Plasma Science and Technology 2010年第6期12卷 681-687页

作者： A.RAhMATI h.BIDADI K.AhMADI f.hADIAN faculty of sciences Vali-e-Asr University of Rafsanjan faculty of physics University of Tabriz Department of physics Islamic Azad University of Tabriz Materials and Energy Research Centre(MERC)

A sintered Ti13Cus7 target was sputtered by reactive direct current （DC） magnetron sputtering with a gas mixture of argon/nitrogen for different sputtering powers. Titanium-coppernitrogen thin films were deposited on Si （111）, glass slide and potassium bromide （KBr） substrates. Phase analysis and structural properties of titanium-copper-nitrogen thin films were studied by X-ray diffraction （XRD）. The chemical bonding was characterized by fourier transform infrared （fTIR） spectroscopy. The results from XRD show that the observed phases are nano-crystallite cubic anti rhenium oxide （anti ReO3） structures of titanium doped Cu3N （Ti：Cu3N） and nanocrystallite face centered cubic （fcc） structures of copper. Scanning electron microscopy and energy dispersive X-ray spectroscopy （SEM/EDX） were used to determine the film morphology and atomic titanium/copper ratio, respectively. The films possess continuous and agglomerated structure with an atomic titanium/copper ratio （-0.07） below that of the original target （- 0.15）. The transmittance spectra of the composite films were measured in the range of 360 nm to 1100 nm. film thickness, refractive index and extinction coefficient were extracted from the measured transmittance using a reverse engineering method. In the visible range, the higher absorption coefficient of the films prepared at lower sputtering power indicates more nitrification in comparison to those prepared at higher sputtering power. This is consistent with the formation of larger Ti：Cu3N crystallites at lower sputtering power. The deposition rate vs. sputtering power shows an abrupt transition from metallic mode to poisoned mode. A complicated behavior of the films＇ resistivity upon sputtering power is shown.

关键词： nano-composite reactive magnetron sputtering Ti doped Cu3N

Materials databases for the computational materials scientist

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2011年第3期18卷 303-308页

作者： Marcel h.f. Sluiter Darko Simonovic Emre S. Tasci Materials Science and Engineering 3ME Delft University of Technology Materials innovation institute M2i física de la Materia Condensada Universidad del Pais Vasco

Until recently, many computational materials scientists have shown little interest in materials databases. This is now changing be-cause the amount of computational data is rapidly increasing and the potential for data mining provides unique opportunities for discovery and optimization. here, a few examples of such opportunities are discussed relating to structural analysis and classification, discovery of correlations between materials properties, and discovery of unsuspected compounds.

关键词： database systems materials data mining ab initio prediction structural analysis

A New Analytical Expression for the Relationship Between the Charpy Impact Energy and Notch Tip Position for functionally Graded Steels

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2013年第3期26卷 232-240页

作者： h.Samareh Salavati Pour f.Berto Y.Alizadeh Department of Mechanical Engineering Amirkabir University of Technology Shahid Chamran College of Kerman/Technical&Vocational University Department of Management and Engineering University of Padova

The effect of the distance between the notch tip and the position of the middle phase in the fGSs on the Charpy impact energy is investigated in the present paper. The results show that when the notch apex is close to the middle layer, the Charpy impact energy reaches its maximum value. This is due to the increment of the absorbed energy by plastic deformation ahead of the notch tip. On the other hand, when the notch tip is far from the middle layer, the Charpy impact energy strongly decreases. Another fundamental motivation of the present work is that for crack arrester configuration, no accurate mathematical or analytical modelling is available up to now. By considering the relationship between the Charpy impact energy and the plastic volume size, a new theoretical model has been developed to link the Charpy impact energy with the distance from the notch apex to the middle phase. This model is a simplified one and the effect of different shapes of the layers and the effect of microstructureon the mechanical properties and plastic region size will be considered in further investigation. The results of the new developed closed form expression show a sound agreement with some recent experimental results taken from the literature.

关键词： Charpy impact energy functionally graded steel Crack divider configu- ration Crack arrester configuration

Numerical Solutions for heat Transfer of An Unsteady Cavity with Viscous heating

在线全文

学校读者我要写书评

暂无评论

Computers, Materials & Continua 2021年第7期68卷 319-336页

作者： h.f.Wong Muhammad Sohail Z.Siri N.f.M.Noor Institute of Mathematical Sciences Faculty of ScienceUniversity of Malaya50603 Kuala LumpurMalaysia Unit of Engineering Design and Product Development Technology and Engineering DivisionMalaysian Rubber Board47000 Sungai BulohMalaysia Department of Applied Mathematics&Statistics Institute of Space Technology44000 IslamabadPakistan

The mechanism of viscous heating of a Newtonian fluid filled inside a cavity under the effect of an external applied force on the top lid is evaluated numerically in this *** investigation is carried out by assuming a two-dimensional laminar in-compressible fluid flow subject to Neumann boundary conditions throughout the numerical iterations in a transient *** the walls of the square cavity are perfectly insulated and the top moving lid produces a constant finite heat flux even though the fluid flow attains the steady-state *** objective is to examine the effects of viscous heating in the fully insulated lid-driven cavity under no-slip and free-slip Neumann boundary conditions coupled with variations in Reynolds and Prandtl *** partial differential equations of time-dependent vorticity-stream function and thermal energy are discretized and solved using a self-developed finite difference code in MATLAB®*** dependence of fluid thermodynamics is envisaged through contour and image plots.A commercial simulation software,Ansys fluent®utilizing a finite element code is employed to verify the finite difference results *** the effect of viscous heating is very minimal,Neumann no-slip and free-slip boundary conditions are able to trap the heat inside the fully insulated cavity as the heat flux is constantly supplied at the top lid.A lower Reynolds number and a greater Prandtl number with free-slip effects reduce temperature distribution in the cavity with a faster velocity than in the no-slip condition as the free-slip behaves as a lubricant.

关键词： Lid-driven viscous heating vorticity-stream function finite difference method finite element method

An empirical study on vortex-generator insert fitted in tubular heat exchangers with dilute Cu–water nanofluid flow

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Chemical Engineering 2016年第6期24卷 728-736页

作者： M. Khoshvaght-Aliabadi M.h. Akbari f. hormozi Department of Chemical Engineering Shahrood Branch Islamic Azad University Shahrood lran School of Chemical Petroleum and Gas Engineering Semnan University Semnan lran

The heat transfer enhancement(hTE) in tubular heat exchangers fitted with vortex-generator(VG) inserts is experimentally investigated. The studied four parameters and ranges are: winglets-pitch ratio(1.33, 2.67, and 4),winglets-length ratio(0.33, 0.67, and 1), winglets-width ratio(0.2, 0.4, and 0.6), and Reynolds number(5200to 12200). The testing fluids are the water and Cu–water nanofluid at the volumetric fraction of 0.2%. The results obtained on hTE, pressure drop, and performance evaluation criterion(PEC) are compared with those for water in a smooth tube. It is found that the VG inserts with lower winglets-pitch ratio and higher winglets-length/width ratios present higher values of.hTE and pressure drop. Over the range studied, the maximum PEC of 1.83 is detected with the Cu–water nanofluid inside the tube equipped with a VG insert at the winglets-width ratio of0.6 for the maximum Reynolds number, when the heat transfer rate and pressure drop are 1.24 times and 2.03 times of those in the smooth tube. Generalized regression equations of the Nusselt number, friction factor, and PEC are presented for the tubular heat exchangers with the VG inserts for both water and Cu–water *** is concluded that the main advantage of the VG inserts is their simple fabrication and considerable performance, particularly at higher Reynolds number.

关键词： heat transfer enhancementVortex-generator insertNanofluid Turbulent flowCorrelation

Endophytic fungal diversity of endemic carnivorous plant Nepenthes khasiana in Meghalaya,India

在线全文

学校读者我要写书评

暂无评论

Studies in fungi 2021年第1期6卷 138-150页

作者： Naseem f Kayang h Microbial Ecology laboratory Department of BotanyNorth Eastern Hill UniversityShillongMeghalaya-793022India

The present investigation deals with the isolation of endophytic fungi from leaf,stem,root and pitcher cup tissue segments of the endemic carnivorous plant Nepenthes khaisana collected from its natural habitat for a period of one year at monthly *** of 576 tissue segments inoculated,a total of 39 fungal endophytes along with mycelia sterilia were isolated from the host *** assess the diversity of fungal endophytes,the colonization frequency(%Cf)was first recorded using past software and MS *** fungal isolates were mainly composed of the phylum Ascomycota,followed by Zygomycota and *** highest percentage colonization frequency on an average of three replicates were recorded in pitcher cup tissues followed by root,stem and least was recorded in leaf of the host *** the isolates,Globisporangium irregulare(83.33%)showed high%Cf in leaf,Juxtiphoma eupyrena(83.33%)reported to have maximum%Cf in the stem,Talaromyces ruber(66.66%)was recorded high%Cf in root and mycelia sterilia(white)were showed the highest%Cf in the segments of *** diversity index analyses of Shannon-Weiner,Simpson’s index,species richness and species evenness of diversity showed that leaf of *** has the highest diversity than the other parts of the ***,with the help of the present finding,we conclude that the distribution of fungal endophytes and their%colonization frequencies vary within different tissues of the host plant and thus,this confirms tissue specificity nature of endophytic fungi.

关键词： Colonization frequency Diversity indices Natural habitat Pitcher plant Tissue specificity

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

梦魇中的游历——《发条橘子》

电影文学 2002年第4期 67-页

作者： f.h

库布里克于1975年把“笔触”从未来移至往昔,从太空召返人间,执导了历史巨片《巴里·林登》。该片以18世纪欧洲7年战争为背景,讲述了一个爱尔兰人混迹于上层社会,最后复归穷困潦倒的故事。导演把英国作家萨克雷的原作演绎成一部促人反... 详细信息

库布里克于1975年把“笔触”从未来移至往昔,从太空召返人间,执导了历史巨片《巴里·林登》。该片以18世纪欧洲7年战争为背景,讲述了一个爱尔兰人混迹于上层社会,最后复归穷困潦倒的故事。导演把英国作家萨克雷的原作演绎成一部促人反省启蒙运动并关注人类生存状态的影片。《巴里·林登》色彩华丽、构图精美,仿佛每格画面都出自18世纪名家的油画杰作。

关键词：库布里克《发条橘子》影片