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Journal of Central south University 2015年第3期22卷 1114-1123页

作者： M.BILAL AsHRAF t.HAYAt A.ALsAEDI s.A.sHEHZAD Department of Mathematics Comsats Institute of Information Technology Department of Mathematics Quaid-i-Azam University Nonlinear Analysis and Applied Mathematics (NAAM) Research Group Department of MathematicsFaculty of Science King Abdulaziz University

Mixed convection flow of magnetohydrodynamic(MHD) Jeffrey nanofluid over a radially stretching surface with radiative surface is studied. Radial sheet is considered to be convectively heated. Convective boundary conditions through heat and mass are employed. the governing boundary layer equations are transformed into ordinary differential equations. Convergent series solutions of the resulting problems are derived. Emphasis has been focused on studying the effects of mixed convection, thermal radiation, magnetic field and nanoparticles on the velocity, temperature and concentration fields. Numerical values of the physical parameters involved in the problem are computed for the local Nusselt and sherwood numbers are computed.

关键词： Jeffrey nanofluid mixed convection flow radially stretching surface convective boundary conditions magnetic field

Observed Impacts of Climate Variability on LULC in the Mesopotamia Region

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Computers, Materials & Continua 2021年第5期67卷 2255-2269页

作者： Muntaha Alzubade Orkan Ozcan Nebiye Musaoglu Murat türke¸s Istanbul technical University Istanbul3400Turkey Bogazici University Istanbul3400Turkey

Remote sensing analysis techniques have been investigated extensively,represented by a critical vision,and are used to advance our understanding of the impacts of climate change and variability on the *** study aims to find a means of analysis that relies on remote sensing techniques to demonstrate the effects of observed climate variability on Land Use and Land Cover(LULC)of the Mesopotamia region,defined as a historical region located in the Middle *** study employed the combined analysis of the Normalized Difference Vegetation Index(NDVI),Land surface temperature(Lst),and two statistical analysis methods(Pearson Correlation Analysis,r;Coefficient of Determination,R^(2)),which were applied using the Moderate Resolution Imaging spectroradiometer data and observed surface meteorological data from 2000 to *** resulting NDVI images show five LULC classes with NDVI values varying between−0.3 and ***,changes in the classified LULC area were compared statistically to those in NDVI values,where a positive relationship was ***,when the Lst values and temperature are more extreme,the NDVI values were found to be smaller,suggesting a decrease in the density of vegetation cover.A negative correlation was found through Pearson correlation analysis(r=∼−0.64),indicating a direct effect of increased temperatures on ***,this negative relationship between NDVI and Lst was proven using R^(2) values,where a two-dimensional scatter plot analysis showed that R^(2) ranges from 0.54 to ***,the results obtained from this study reveal changes that may have many prominent effects in the field of LULC classification,accelerating the implications of climate change and variability factors.

关键词： NDVI Lst MODIs data meteorological data Mesopotamia

Development of aluminum rheo-extrusion process using semi-solid slurry at low solid fraction

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transactions of Nonferrous Metals society of China 2010年第9期20卷 1763-1768页

作者： t.RAttANOCHAIKUL s.JANUDOM N.MEMONGKOL J.WANNAsIN Department of Mining and Materials Engineering Faculty of EngineeringPrince of Songkla University Department of Industrial Engineering Faculty of EngineeringPrince of Songkla University

An aluminum extrusion process is mainly used to fabricate long tubes, beams and rods for various applications. However, this process has a high production cost due to the need for investment of high-pressure machinery. the objective of this work is to develop a new semi-solid extrusion process using semi-solid slurry at low solid fractions. A laboratory extrusion system was used to fabricate aluminum rods with the diameter of 12 ram. the semi-solid metal process used in this study was the gas induced semi-solid （GIss） technique. to study the feasibility of the GIss extrusion process, the effects of extrusion parameters such as plunger speed and solid fi-action on the extrudability, microstructure, and mechanical properties of extruded samples were investigated. the results show that the plunger speed and solid fraction of the semi-solid metal need to be carefully controlled to produce complete extruded parts.

关键词： aluminum alloys extrusion semi-solid metal rheo-extrusion gas induced semi-solid (GIss)

Influence of alkali metal doping on surface properties and catalytic activity/selectivity of CaO catalysts in oxidative coupling of methane

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Journal of Natural Gas Chemistry 2008年第4期17卷 313-320页

作者： V.H.Rane s.t.Chaudhari V.R.Choudhary Chemical Engineering and Process Development Division National Chemical Laboratory

surface properties （viz. surface area, basicity/base strength distribution, and crystal phases） of alkali metal doped CaO （alkali metal/Ca= 0.1 and 0.4） catalysts and their catalytic activity/selectivity in oxidative coupling of methane （OCM） to higher hydrocarbons at different reaction conditions （viz. temperature, 700 and 750 ℃; CH4/O2 ratio, 4.0 and 8.0 and space velocity, 5140-20550 cm^3 ·g^-1·h^-1） have been investigated. the influence of catalyst calcination temperature on the activity/selectivity has also been investigated. the surface properties （viz. surface area, basicity/base strength distribution） and catalytic activity/selectivity of the alkali metal doped CaO catalysts are strongly influenced by the alkali metal promoter and its concentration in the alkali metal doped CaO catalysts. An addition of alkali metal promoter to CaO results in a large decrease in the surface area but a large increase in the surface basicity （strong basic sites） and the C2＋ selectivity and yield of the catalysts in the OCM process. the activity and selectivity are strongly influenced by the catalyst calcination temperature. No direct relationship between surface basicity and catalytic activity/selectivity has been observed. Among the alkali metal doped CaO catalysts, Na-CaO （Na/Ca = 0.1, before calcination） catalyst （calcined at 750 ℃）, showed best performance （C2＋ selectivity of 68.8% with 24.7% methane conversion）, whereas the poorest performance was shown by the Rb-CaO catalyst in the OCM process.

关键词： oxidative coupling of methane alkali metal doped CaO catalysts basicity/base strength distribution catalytic activity/selectivity

Entrance Effects in Microchannel Gas Flow

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Journal of thermal science 2009年第4期18卷 345-352页

作者： t.Lewandowski s.Jebauer J.Czerwinska P.Doerffer Institute of Fluid Flow Machinery Polish Academy of Science Institute of Fundamental technological Research Polish Academy of Science

Motivation of this work has its origin in the boundary layer control for aeronautics and turbomachinery. For thatpurpose boundary layer can be modified by perforated plates with holes of specific sizes. the questions whichrise in such configuration are related to the existence of optimal size of the holes and the influence of microscalephenomena on the global flow patterns. this paper concentrates on the issue of the entrance effects on the microchannelflow. It is shown that mass flow rate is only insignificantly influenced by slip effects. Global parameterssuch as pressure difference and geometrical shape in more pronounced way alter flow behavior. In this paper weconcentrate on the numerical investigation of the microchannel flow for Kn the channellength is finite. Hence, entrance and outlet effects on microchannel flow can be studied.

关键词： perforated plates microchanneis gas flow simulations

Equivalent series system to model a multiple friction pendulum system with numerous sliding interfaces for seismic analyses

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Earthquake Engineering and Engineering Vibration 2014年第1期13卷 85-99页

作者： C.s.tsai H.C.su t.C.Chiang Department of Civil Engineering Feng Chia University Department of Water Resources Engineering and Conservation Feng Chia University Earthquake Proof systems Inc.

Current structural analysis software programs offer few if any applicable device-specifi c hysteresis rules or nonlinear elements to simulate the precise mechanical behavior of a multiple friction pendulum system(MFPs) with numerous sliding *** on the concept of subsystems,an equivalent series system that adopts existing nonlinear elements with parameters systematically calculated and mathematically proven through rigorous derivations is *** aim is to simulate the characteristics of sliding motions for an MFPs isolation system with numerous concave sliding interfaces without prior knowledge of detailed information on the mobilized forces at various sliding *** MFPs with numerous concave sliding interfaces and one articulated or rigid slider located between these interfaces is divided into two subsystems: the fi rst represents the concave sliding interfaces above the slider,and the second represents those below the *** equivalent series system for the entire system is then obtained by connecting those for each subsystem in *** equivalent series system is validated by comparing numerical results for an MFPs with four sliding interfaces obtained from the proposed method with those from a previous study by Fenz and ***,these numerical results demonstrate that an MFPs isolator with numerous concave sliding interfaces,which may have any number of sliding interfaces,is a good isolation device to protect structures from earthquake damage through appropriate designs with controllable mechanisms.

关键词： seismic isolation base isolation earthquake engineering multiple friction pendulum system structural control mathematical modeling equivalent series system

Application of cold drawn lamellar microstructure for developing ultra-high strength wires

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中国有色金属学会会刊：英文版 2007年第6期17卷 1129-1138页

作者： s. Goto R. Kirchheim t . Al-Kassab C. Borchers Faculty of Engineering and Resource science Akita University Tegata Gakuencho Akita 010-8502 Japan Institute fuer Materialphysik University of Goettingen Friedrich-Hund-Platz 1 D-37077 Goettingen Germany

Composite materials having lamellar structure are known to have a good combination of high strength and ductility. they are widely used in the fields of automobiles, civil engineering and construction, machines and many other industries. An application of lamellar microstructure for developing ultra-high strength steel wires was studied and discussed. Based on the experimental results, the relationships between the strength increase and microstructure development during the cold wire drawing were studied to reveal the strengthening mechanism. As cold drawing proceeds, the wire strength extremely increases, the microstructure changes from large single crystal lamellar structure to very fine polycrystalline lamellar one which has nano-sized grains, high dislocation density and amorphous regions. From the results obtained, it is concluded that heavy cold drawing technique is an effective method for lamellar composite to get high strength wires. Furthermore, formation process of the best microstructure for producing the ultra-high strength wires was also discussed.

关键词：薄片复合物金属丝加固装置机械性质

superplasticity of fine-grained Mg-10Li alloy prepared by severe plastic deformation and understanding its deformation mechanisms

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Journal of Magnesium and Alloys 2024年第1期12卷 316-331页

作者： H.t.Jeong s.W.Lee W.J.Kim Department of Materials science and Engineering Hongik UniversityMapo-guSangsu-dong 72-1Seoul 121-791Republic of Korea

the superplastic behavior and associated deformation mechanisms of a fine-grained Mg-10.1 Li-0.8Al-0.6Zn alloy(LAZ1011)with a grain size of 3.2μm,primarily composed of the BCCβphase and a small amount of the HCPαphase,were examined in a temperature range of 473 K to 623 *** microstructural refinement of this alloy was achieved by employing high-ratio differential speed *** best superplasticity was achieved at 523 K and at strain rates of 10^(-4)-5×10^(-4)s^(-1),where tensile elongations of 550±600%were *** the heating and holding stage of the tensile samples prior to tensile loading,a significant increase in grain size was observed at temperatures above 573 ***,it was important to consider this effect when analyzing and understanding the superplastic deformation behavior and *** the investigated strain rate range,the superplastic flow at low strain rates was governed by lattice diffusion-controlled grain boundary sliding,while at high strain rates,lattice diffusion-controlled dislocation climb creep was the rate-controlling deformation *** was concluded that solute drag creep is unlikely to *** the late stages of deformation at 523 K,it was observed that grain boundary sliding led to the agglomeration of theαphase,resulting in significant strain *** mechanism maps were constructed forβ-Mg-Li alloys in the form of 2D and 3D formats as a function of strain rate,stress,temperature,and grain size,using the constitutive equations for various deformation mechanisms derived based on the data of the current tests.

关键词： Magnesium-lithium alloy superplasticity severe plastic deformation Grain size Grain growth

Origin of extension twinning-mediated static recrystallization and unique parallel alignment of(0001) poles to transverse direction in Mg-3Al-0.4Mn(mass%) alloy sheet

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Journal of Magnesium and Alloys 2023年第9期11卷 3200-3213页

作者： t.Nakata C.Xu L.Geng s.Kamado Nagaoka University of technology 1603-1KamitomiokaNagaoka 940-2188Japan school of Materials science and Engineering Harbin Institute of technology Harbin 150001China

the origin of unique parallel alignment of(0001) poles to transverse direction(tD) was investigated using Mg-3Al-0.4Mn(mass%)alloy sheets rolled with different process conditions. When rolling was performed with intermediate reheating, the alloy showed a sluggish static recrystallization(sRX) behavior during post-annealing, facilitating the nucleation and growth of statically recrystallized grains from extension twins. this resulted in the apparent texture component with the parallel alignment of the(0001) poles to the tD, and the sheet exhibited good ductility for both the rolling direction(RD) and tD. In contrast, continuous rolling without intermediate reheating led to the formation of severely deformed regions near double twins. sRX was promoted at such regions, forming a typical basal textural feature with weak RD-split of the(0001) poles. Although extension twins were formed after the continuous rolling, sRX was facilitated at the severely deformed regions with double twins, and the formation of the unique alignment of the(0001) poles to the tD was suppressed. the RD-split texture led to the large elongation to failure along the RD, while it along the tD decreased owing to the narrow distribution of the(0001)poles toward the tD, resulting in the in-plane anisotropy in ductility.

关键词： Magnesium Rolling twinning static recrystallization texture

Convective heat and mass transfer effects in three-dimensional flow of Maxwell fluid over a stretching surface with heat source

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Journal of Central south University 2015年第2期22卷 717-726页

作者： t.Hayat M.Bilal Ashraf A.Alsaedi s.A.shehzad Department of Mathematics Quaid-i-Azam University 45320Islamabad 44000 Pakistan Nonlinear Analysis and Applied Mathematics (NAAM) Research Group Department of MathematicsFaculty of Science King Abdulaziz University P.O.Box 80257 Jeddah 21589 Saudi Arabia

Heat and mass transfer effects in three-dimensional flow of Maxwell fluid over a stretching surface were *** was performed in the presence of internal heat generation/absorption. Concentration and thermal buoyancy effects were accounted. Convective boundary conditions for heat and mass transfer analysis were explored. series solutions of the resulting problem were developed. Effects of mixed convection, internal heat generation/absorption parameter and Biot numbers on the dimensionless velocity, temperature and concentration distributions were illustrated graphically. Numerical values of local Nusselt and sherwood numbers were obtained and analyzed for all the physical parameters. It is found that both thermal and concentration boundary layer thicknesses are decreasing functions of stretching ratio. Variations of mixed convection parameter and concentration buoyancy parameter on the velocity profiles and associated boundary layer thicknesses are enhanced. Velocity profiles and temperature increase in the case of internal heat generation while they reduce for heat absorption. Heat transfer Biot number increases the thermal boundary layer thickness and temperature. Also concentration and its associated boundary layer are enhanced with an increase in mass transfer Biot number. the local Nusselt and sherwood numbers have quite similar behaviors for increasing values of mixed convection parameter, concentration buoyancy parameter and Deborah number.

关键词： Maxwell fluid mixed convection convective conditions three-dimensional flow internal heat generation/absorption