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Chinese Physics B 2013年第9期22卷 480-485页

作者： Ahm.d m. megahed Departm.nt of m.them.tics Faculty of ScienceBenha University

The effects of variable fluid properties and variable heat flux on the flow and heat transfer of a non-Newtonian m.xwell fluid over an unsteady stretching sheet in the presence of slip velocity have been studied. The governing differential equations are transform.d into a set of coupled non-linear ordinary differential equations and then solved with a num.rical technique using appropriate boundary conditions for various physical param.ters. The num.rical solution for the governing non-linear boundary value problem.is based on applying the fourth-order Runge-Kutta m.thod coupled with the shooting technique over the entire range of physical param.ters. The effects of various param.ters like the viscosity param.ter, therm.l conductivity param.ter, unsteadiness param.ter, slip velocity param.ter, the Deborah num.er, and the Prandtl num.er on the flow and tem.erature profiles as well as on the local skin-friction coefficient and the local Nusselt num.er are presented and discussed. Com.arison of num.rical results is m.de with the earlier published results under lim.ting cases.

关键词： m.xwell fluid unsteady stretching sheet variable fluid properties variable heat flux

Tribological Characterization of Hybrid m.tal m.trix Com.osites Processed by Powder m.tallurgy

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Acta m.tallurgica Sinica(English Letters) 2017年第8期30卷 781-790页

作者： m. megahed m. A. Attia m. Abdelham.ed A. G. El-Shafei Departm.nt of m.chanical Design and Production Engineering Faculty of EngineeringZagazig UniversityP.O.Box 44519ZagazigEgypt

Alum.num.（Al）-based alum.num.oxide （Al2O3） and silicon carbide （SIC） particles hybrid m.tal m.trix com. posites were processed by powder m.tallurgy technique, followed by sintering at 500 ℃ and then hot extrusion. The tribological properties of these com.osites with different weight fractions of Al2O3 and SiC were investigated; extrusion process significantly reduces the extent of porosity after cold com.action and sintering processes. Hybridization of the two reinforcem.nts im.roved hardness and wear resistance of the com.osites. With an increase in SiC content, hardness was increased and consequently the wear resistance was enhanced also. Scanning electron m.croscopy observations show a better interfacial bond between m.trix and reinforcem.nts and a better distribution of the reinforcem.nts.

关键词： Hybrid m.tal m.trix com.osite Powder m.tallurgy Abrasive wear Hardness Porosity

Num.rical Study for Sim.lation the m.D Flow and Heat-Transfer Due to a Stretching Sheet on Variable Thickness and Therm.l Conductivity with Therm.l Radiation

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Applied m.them.tics 2015年第12期6卷 2045-2056页

作者： m.ham.d m. Khader m.ham.ed m. Babatin Ali Eid Ahm.d m. megahed Departm.nt of m.them.tics and Statistics College of Science Al-Imam Mohammad Ibn Saud Islamic University (IMSIU) Riyadh Saudi Arabia Departm.nt of m.them.tics Faculty of Science Benha University Benha Egypt Departm.nt of Physics College of Science Al-Imam Mohammad Ibn Saud Islamic University (IMSIU) Riyadh Saudi Arabia

The m.in aim.of this article is to introduce the approxim.te solution for m.D flow of an electrically conducting Newtonian fluid over an im.erm.able stretching sheet with a power law surface velocity and variable thickness in the presence of therm.l-radiation and internal heat generation/absorption. The flow is caused by the non-linear stretching of a sheet. Therm.l conductivity of the fluid is assum.d to vary linearly with tem.erature. The obtaining PDEs are transform.d into non-linear system.of ODEs using suitable boundary conditions for various physical param.ters. We use the Chebyshev spectral m.thod to solve num.rically the resulting system.of ODEs. We present the effects of m.re param.ters in the proposed m.del, such as the m.gnetic param.ter, the wall thickness param.ter, the radiation param.ter, the therm.l conductivity param.ter and the Prandtl num.er on the flow and tem.erature profiles are presented, m.reover, the local skin-friction and Nusselt num.ers. A com.arison of obtained num.rical results is m.de with previously published results in som. special cases, and excellent agreem.nt is noted. The obtained num.rical results confirm.that the introduced technique is powerful m.them.tical tool and it can be im.lem.nted to a wide class of non-linear system. appearing in m.re branches in science and engineering.

关键词： Newtonian Fluid Stretching Sheet Variable Therm.l Conductivity Therm.l Radiation Chebyshev Spectral m.thod

m.deling and Sim.lation of Laparoscopic Tools for Autonom.usly Positioning Laparoscope in Laparoscopic Surgery

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Engineering（科研） 2013年第10期5卷 85-89页

作者： S. m. megahed A. A. Balbola m.chanical Design & Production Engineering Departm.nt Faculty of Engineering Giza Egypt

In laparoscopic surgery, the surgeons are equipped with the suitable tools for the surgery, while the laparoscope is used to capture the operation environm.nt and displays it on a m.nitor. This paper presents the m.them.tical kinem.tic position m.deling of the laparoscopic tools used for autonom.us positioning of a laparoscope in such operations. These m.dels are obtained using Denavit-Hartenberg (D-H) Notations and Hom.genous Transform.tion m.trix (HTm.. The laparoscopic tools are considered as six degrees of freedom.(DOF) m.chanism. while the laparoscope has four DOF. The 3D loop closure equation is used to obtain the laparoscope kinem.tic position m.dels in term. of those of the laparoscopic tools. These m.dels are used to sim.late and align the laparoscope cam.ra with the surgeon’s laparoscopic Tools Center Points (TCP). The obtained results show the sm.oth positioning of the laparoscope cam.ra for better visu-alization of laparoscopic surgery environm.nts.

关键词： Laparoscopic Surgery Hom.genous Transform.tion m.trix Denavit-Hartenberg Notations

Developm.nt of Tailored Structure and Tensile Properties of Therm.m.chanical Treated m.cro Alloyed Low Carbon Dual Phase Steel

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m.terials Sciences and Applications 2020年第12期11卷 851-866页

作者： Hany Khalifa G. m. megahed Taher El-Bitar m.ham.d A. Taha Faculty of Engineering Ain-Shams University Cairo Egypt EZZ Steel Cairo Egypt Central m.tallurgical R & D Institute (Cm.DI) Helwan Cairo Egypt

Direct hot rolled dual phase steel production represents a challenging route, com.ared with cold rolled and intercritical annealing process, due to com.lex and sophisticated control of the hot strip m.ll processing param.ters. Instead, high technology com.act slab production plant offers econom.c advantages, adequate control and prom.t use of the advanced therm.m.chanical controlled rolling. The current work aim. to obtain different structures and tensile properties by physical sim.lation of direct hot rolled niobium.m.cro alloyed dual phase low carbon steel by varying the m.tallurgical tem.eratures of hot strip m.ll plant. This starts with adaptation of the chem.cal analysis of a low carbon content to fall far from.the undesired peritectic region to avoid slab cracking during casting. Therm.dynam.c and kinetics calculations by Therm.-Calc 2020 and Jm.t pro software are used to define the transform.tion’s tem.eratures Ae1 and Ae3 as well as processing tem.eratures;nam.ly of reheating, finishing rolling, step cooling and coiling tem.eratures. The results show that the increase of finishing rolling tem.erature from.780°C to 840°C or decreasing either of step cooling duration at ferrite bay from.7 to 4 seconds, enhances yield and tensile strengths, all due to m.re m.rtensite volum. fraction form.tion. The yield and tensile strengths also increase with decreasing coiling tem.erature from.330°C to 180°C, which is explained due to the increase of dislocation densities resulted from.the sudden shape change during m.rtensite form.tion at the lower coiling tem.erature in additional to the self-tem.ering of m.rtensite form.d at higher coiling tem.eratures which soften the dual phase steel.

关键词： m.cro-Alloyed Steel Dual Phase Steel Therm.m.chanical Sim.lation Therm.m.chanical Rolling Com.act Slab Production CSP Hot Strip m.ll HSm

Green retrofitting of heritage buildings based on(3Ts)fram.work:An applied case study

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Frontiers of Architectural Research 2024年第4期13卷 776-798页

作者： Alaa O.Shehata Asm.a m.Hassan m.rhan m.Shahda Naglaa A.megahed Architectural Engineering and Urban Planning Departm.nt Faculty of EngineeringPort Said UniversityPort SaidEgypt

Diverse heritage architecture characterizes Port Said in Egypt,reflecting European and Arab *** Canal heritage villas com.rise 25%of the total listed heritage buildings in the ***,it is im.ortant to retrofit them.aligning with the Sustainable Developm.nt Goals(SDGs).By reviewing the previous literature related to the green retrofitting of heritage buildings,the(3Ts)fram.work can be considered a holistic fram.work that covers the latest trends due to its three com.onents:targets,tools,and tasks,which help the success of the process through a holistic vision of supporting building inform.tion m.deling(BIm.technologies and organizing stakeholders’*** paper aim. to apply the(3Ts)fram.work to Suez Canal heritage villas in Port Said,*** applied study is based on how stakeholders perceive their input and decision-m.king,m.asuring the clim.te param.ters,proposing several green retrofits,and integrating them.into green *** of scenarios is conducted by utilizing the Design Builder sim.lation ***,the Skelion plugin calculates the photovoltaic system.s(PVs)energy *** results indicated that the total energy savings could reach approxim.tely 12%e74%and nearly 10%e73%CO₂em.ssions reduction without affecting heritage values.

关键词： Green retrofitting Heritage buildings BIm BES Suez Canal heritage villas Port Said/Egypt

Facile synthesis of sam.rium.and cerium.doped double perovskite cobaltite with enhanced dielectric response

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Journal of Rare Earths 2024年第7期42卷 1317-1327,I0005页

作者： Yasir Abbas m.Kam.an m.Anis-ur-Rehm.n Applied Therm.l Physics Laboratory Department of PhysicsCOMSATS University IslamabadIslamabad 45550Pakistan

The investigation of Sm.Ce doping on structure,conduction,and dielectric response of Bi_(2)Ca_(2-2x)Sm.(x)CexCoO_(6)(x=0.000,0.025,0.050,0.075)(BCSCCO)are *** the specim.ns were synthesized by a facile synthesis technique nam.d the co-precipitation route.X-ray diffraction(XRD)reveals that BCSCCO crystallizes into one phase with space group P21/*** crystallite size,dislocation density,lattice param.ters,lattice strain,unit cell volum.,and bulk density were determ.ned using XRD *** structural properties of Bi_(2)Ca_(2)CoO_(6)were exam.ned using calculations based on the density functional *** and experim.ntal values discrepancy is less than 1%.A scanning electron m.croscope was used for perform.ng a m.crostructural *** SEm.im.ges dem.nstrate the hom.geneous distribution of grains with a range of sizes(0.054-0.090μm..The alternating current(ac)conductivity,dielectric perm.ttivity,and tangent loss were also studied as a function of frequency(20 Hz-3 m.z)at different tem.eratures(100-500℃).All synthesized sam.les were exam.ned using non-linear Debye's function to determ.ne their spreading factor and relaxation *** specim.n with the lowest crystallite size(∼23 nm.exhibits a high dielectric perm.ttivity(∼3.80×10^(6)).The conduction m.chanism.was exam.ned in the studied sam.les with the use of Jonscher's power *** power law indicates that the BCSCCO(x=0.000,0.025)follows correlated barrier hopping,whereas the x=0.050 and 0.075 com.ositions follow non-overlapping polaron *** studied specim.n Bi_(2)Ca_(1.9)0Sm.(0.05)0Ce_(0.05)_(0)CoO_(6)with the highest density(∼5.65 g/cm.(3))displays a high electrical conductivity(∼46.1 S/cm..These findings correspond to those published for ceram.cs m.de from.calcium.cobaltite using solid-state reactions(5.0-26.0 S/cm..

关键词： Bism.th calcium.sam.rium.cerium.cobaltite (BCSCCO) Spreading factor Conduction m.chanism Rare earths

Cooperative Target Fencing of m.ltiple Vehicles for a General Target with Connectivity Preservation and Collision Avoidance

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Journal of System. Science & Com.lexity 2024年第1期37卷 136-151页

作者： PAN Zini CHEN Ben m Departm.nt of m.chanical and Autom.tion Engineering The Chinese University of Hong KongHong KongChina

In this paper,the authors study the cooperative target-fencing problem.for n-dim.nsional system. and a target with a general *** using the velocity of the vehicles,a position feedback control law is proposed to fence the general target into the convex hull form.d by the ***,the dynam.cs of each vehicle is described by a double-integrator *** potential functions are designed to guarantee connectivity preservation of the com.unication network and collision avoidance am.ng the *** proposed approach can deal with a target whose trajectory is any twice continuously differentiable function of *** effectiveness of the result is verified by a num.rical exam.le.

关键词： m.lti-agent system. networked system. target fencing

HVSR analysis of pum.ce sands for sedim.nt depth characterization:A case study for Guadalajara,m.xico

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Earthquake Engineering and Engineering Vibration 2024年第3期23卷 577-591页

作者： Hafid Salgado m. Alejandro Ram.rez-Gaytan Adolfo Preciado Christian R.Escudero Departam.nto de Ciencias Exactas Centro Universitario de la CostaUniversidad de GuadalajaraCP.48280 Puerto VallartaJaliscoMéxico Departam.nto de Ciencias Com.utacionales Centro Universitario de Ciencias Exactas e IngenieríaUniversidad de GuadalajaraCP.44430 GuadalajaraJaliscoMéxico Departam.nto del Hábitat y Desarrollo Urbano Instituto Tecnológico y de Estudios Superiores de Occidente(ITESO)CP.45604 TlaquepaqueMéxico

The horizontal to vertical spectral ratio(HVSR)m.thodology is used here to characterize pum.ce soils and to im.ge the three-dim.nsional surface geom.try of Guadalajara,*** to other Latin Am.rican cities,Guadalajara is exposed to high seism.c risk,with the particularity of being the largest urban settlem.nt in Latin Am.rica built on pum.ce *** has not yet been tested to characterize subsoil depths in pum.ce *** to the questionable use of traditional geotechnical tests for the analysis of pum.ce soils,HVSR provides an alternative for its characterization without altering its fragile and porous *** this work,resonance frequency(F0)and peak am.litude(A0)are used to constrain the depth of the m.jor im.edance contrast that represents the interface between bedrock and pum.ce *** were com.ared with borehole depths and other available geotechnical and geophysical data and show good *** of the profiles estim.ted on the riverbanks that cross the city,reveals different subsoil thickness that could have an im.act on different site responses on riverine areas to an eventual *** and academ.c efforts are com.ined in this work to characterize depth sedim.nts,an im.ortant param.ter that im.acts the regulations for construction in the city.

关键词： subsoil of Guadalajara shallow soil thickness bedrock depth pum.ce soil characterization

A high Li-ion diffusion kinetics in m.ltidim.nsional and com.act-structured electrodes via vacuum.filtration casting

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Journal of Energy Chem.stry 2024年第6期93卷 368-376,I0010页

作者： Jieqiong Li Ting Ouyang Lu Liu Shu Jiang Yongchao Huang m.-Sadeeq Balogun College of m.terials Science and Engineering Hunan Joint International Laboratory of Advanced Materials and Technology for Clean EnergyHunan UniversityChangsha 410082HunanChina Institute of Environm.ntal Research at Greater Bay Key Laboratory for Water Quality and Conservation of the Pearl River DeltaMinistry of EducationGuangzhou UniversityGuangzhou 510006GuangdongChina

m.nufacturing process,diffusion co-efficient and areal capacity are the three m.in criteria for regulating thick electrodes for lithium.ion batteries(LIBs).However,sim.ltaneously regulating these criteria for LIBs is desirable but rem.ins a significant *** this work,niobium.pentoxide(Nb_(2)O_(5))anode and lithium.iron phosphate(LiFePO_(4))cathode m.terials were chosen as the m.del m.terials and dem.nstrate that these three param.ters can be sim.ltaneously m.dulated by incorporation of m.cro-carbon fibers(m.F)and carbon nanotubes(CNT)with both Nb_(2)O_(5) and LFP via vacuum.filtration *** as-prepared m.C-20 anode and m.C-20 cathode achieves high reversible areal capacity of≈5.4 m.A h cm.(-2)@0.1 C and outstanding Li-ion diffusion coefficients of≈10~(-8)cm.2 s~(-1)in the half-cell *** assem.led m.C-20‖m.C-20 full cell LIB delivers m.xim.m.energy and power densities of244.04 W h kg^(-1)and 108.86 W kg^(-1),*** excellent electrochem.cal properties of the asprepared thick electrodes can be attributed to the highly conductive,m.chanical com.actness and m.ltidim.nsional m.tual effects of the m.F,CNT and active m.terials that facilitates rapid Li-ion diffusion ***,electrochem.cal im.edance spectroscopy(EIS),sym.etric cells analysis,and insitu Ram.n techniques clearly validates the enhanced Li-ion diffusion kinetics in the present architecture.

关键词： Thick electrodes Carbon nanotubes Li-ion diffusion co-efficient Vacuum.filtration technique High areal capacity Lithium.ion batteries