检索结果-南通市图书馆

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

在线全文

学校读者我要写书评

暂无评论

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

在线全文

学校读者我要写书评

暂无评论

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

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

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

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

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

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

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

Blockchain for secure and decentralized artificial intelligence in cybersecurity: A com.rehensive review

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

BLOCKCHAIN-RESEARCH AND APPLICATIONS 2024年第3期5卷 184-208页

作者： Saleh, Ahm.d m. Sham.an Univ Tabuk Dept Informat Technol Tabuk 47512 Saudi Arabia

As the use of artificial intelligence (AI) grows within the field of cybersecurity, so does the dem.nd for secure and decentralized AI system. to protect against potential cyber threats. Blockchain technology has em.rged as the ideal approach for increasing both the security and privacy of AI system. since it provides decentralized and im.utable data storage. This system.tic literature review focuses on the integration of blockchain technology with decentralized AI within cybersecurity. It provides a com.rehensive taxonom. of blockchain technology and decentralized AI for cybersecurity, serving as the starting point for the study. This paper begins with an overview of blockchain technology and its possible uses in cybersecurity and also analyzes its challenges and opportunities. Decentralized AI is also covered in the study, along with its potential advantages and difficulties in decentralized AI cybersecurity. Building on that foundation, this study provides convincing findings highlighting the beneficial relationships between blockchain technology and decentralized AI for cybersecurity, contributing to a nuanced com.rehension of their integration. m.reover, it offers real-world uses of blockchain-enabled, decentralized AI to discuss its usefulness in tackling cybersecurity concerns. Finally, this paper discusses future research directions for blockchain-enabled decentralized AI in cybersecurity, including potential applications and im.lications of this technology in the field, em.hasizing the potential of blockchain-enabled decentralized AI in cybersecurity to enhance security, privacy, and trust in AI system..

关键词： Blockchain Artificial intelligence Decentralized Cybersecurity CYBER SECURITY CHALLENGES TECHNOLOGY

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

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

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

Green hydrogen energy production: current status and potential

在线全文

学校读者我要写书评

暂无评论

CLEAN ENERGY 2024年第2期8卷 1-7页

作者： m.ka, Ali O. m. m.hm.od, m.bbashar Libyan Ctr Res & Dev Saharian Com.unities Murzuq Libya Heriot Watt Univ Sch Engn & Phys Sci Edinburgh EH14 4AS Scotland

The technique of producing hydrogen by utilizing green and renewable energy sources is called green hydrogen production. Therefore, by im.lem.nting this technique, hydrogen will becom. a sustainable and clean energy source by lowering greenhouse gas em.ssions and reducing our reliance on fossil fuels. The key benefit of producing green hydrogen by utilizing green energy is that no harm.ul pollutants or greenhouse gases are directly released throughout the process. Hence, to guarantee all of the environm.ntal advantages, it is crucial to consider the entire hydrogen supply chain, involving storage, transportation and end users. Hydrogen is a prom.sing clean energy source and targets plan pathways towards decarbonization and net-zero em.ssions by 2050. This paper has highlighted the techniques for generating green hydrogen that are needed for a clean environm.nt and sustainable energy solutions. m.reover, it sum.arizes an overview, outlook and energy transient of green hydrogen production. Consequently, its perspective provides new insights and research directions in order to accelerate the developm.nt and identify the potential of green hydrogen production. Hydrogen is a prom.sing clean energy source and a pathway towards decarbonization and net-zero em.ssions by 2050. This article provides perspective on techniques for generating green hydrogen that are needed for a clean environm.nt and sustainable energy solutions. Graphical Abstract

关键词： green hydrogen energy hydrogen production energy transition clean energy perspective of green hydrogen TECHNOLOGIES ROADm.P

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

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

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