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Magnetocaloric effect in La_(0.7)Sr_(0.3)MnO_(3)/Ta_(2)O_(5) composites

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Journal of Advanced Ceramics 2013年第3期2卷 213-217页

作者： mahmoud Aly HAMAD Physics Department College of ScienceAl Jouf UniversityAl JoufSkakaP.O.Box 2014Saudi Arabia Physics Department Faculty of ScienceTanta UniversityTantaEgypt

The magnetocaloric effect (MCE) achieved for La_(0.7)Sr_(0.3)MnO_(3)/Ta_(2)O_(5) composites has been investigated. The maximum value of magnetic entropy change of La_(0.7)Sr_(0.3)MnO_(3) composites is found to decrease slightly with the further increasing of Ta_(2)O_(5) concentration. It is shown that La_(0.7)Sr_(0.3)MnO_(3)/Ta_(2)O_(5) composites exhibit much more uniform magnetic entropy change than that of gadolinium. Moreover, the results indicate that the temperature range between 100 K and 400 K can be covered using the La_(0.7)Sr_(0.3)MnO_(3)/Ta_(2)O_(5) composites. Therefore, MCE makes the composites promising for room-temperature magnetic cooling applications.

关键词： magnetic materials simulation and modeling

Thermal radiation effect on flow and heat transfer of unsteady MHD micropolar fluid over vertical heated nonisothermal stretching surface using group analysis

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Applied Mathematics and Mechanics(English Edition) 2013年第6期34卷 703-720页

作者： I. A. HASSANIEN H. M. EL-HAWARY M. A. A. mahmoud R. G. abdel-RAHMAN A. S. ELFESHAWEY Department of Mathematics Faculty of Science Assuit University Department of Mathematics Faculty of Science Benha University

The aim of this paper is to study the thermal radiation effects on the flow and heat transfer of an unsteady magnetohydrodynamic （MHD） micropolar fluid over a vertical heated nonisothermal stretching surface in the presence of a strong nonuniform magnetic field. The symmetries of the governing partial differential equations are de- termined by the two-parameter group method. One of the resulting systems of reduced nonlinear ordinary differential equations are solved numerically by the Chebyshev spec- tral method. The effects of various parameters on the velocity, the angular velocity, and the temperature profiles as well as the skin-friction coefficient, the wall couple stress co- efficient, and the Nusselt number are studied.

关键词： thermal radiation micropolar fluid unsteady flow group theoretic method,Chebyshev spectral method

Shared Cache Based on Content Addressable Memory in a Multi-Core Architecture

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Computers, Materials & Continua 2023年第3期74卷 4951-4963页

作者： Allam Abumwais mahmoud Obaid Computer Systems Engineering Arab American UniversityJenin240Palestine

Modern shared-memory multi-core processors typically have shared Level 2(L2)or Level 3(L3)*** bottlenecks and replacement strategies are the main problems of such architectures,where multiple cores try to access the shared cache *** main problem in improving memory performance is the shared cache architecture and cache *** paper documents the implementation of a Dual-Port Content Addressable Memory(DPCAM)and a modified Near-Far Access Replacement Algorithm(NFRA),which was previously proposed as a shared L2 cache layer in a multi-core *** Performance Evaluation Corporation(SPEC)Central Processing Unit(CPU)2006 benchmark workloads are used to evaluate the benefit of the shared L2 cache *** show improved performance of the multicore processor’s DPCAM and NFRA algorithms,corresponding to a higher number of concurrent accesses to shared *** new architecture significantly increases system throughput and records performance improvements of up to 8.7%on various types of SPEC 2006 *** miss rate is also improved by about 13%,with some exceptions in the sphinx3 and bzip2 *** results could open a new window for solving the long-standing problems with shared cache in multi-core processors.

关键词： Multi-core processor shared cache content addressable memory dual port CAM replacement algorithm benchmark program

Microstructure and mechanical characteristics of AA6061-T6 joints produced by friction stir welding,friction stir vibration welding and tungsten inert gas welding:A comparative study

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International Journal of Minerals,Metallurgy and Materials 2021年第3期28卷 450-461页

作者： Behrouz Bagheri mahmoud Abbasi Amin Abdollahzadeh Department of Mining and Metallurgy Amirkabir University of TechnologyTehranIran Faculty of Engineering University of KashanRavandi Blvd.KashanIran Department of Materials Science and Engineering Faculty of EngineeringShahid Chamran University of AhvazAhvazIran

This study compared the microstructure and mechanical characteristics of AA6061-T6 joints produced using friction stir welding(FSW),friction stir vibration welding(FSVW),and tungsten inert gas welding(TIG).FSVW is a modified version of FSW wherein the joining specimens are vibrated normal to the welding line during *** results indicated that the weld region grains for FSVW and FSW were equiaxed and were smaller than the grains for *** addition,the weld region grains for FSVW were finer compared with those for *** also showed that the strength,hardness,and toughness values of the joints produced by FSVW were higher than those of the other joints produced by FSW and *** vibration during FSW enhanced dynamic recrystallization,which led to the development of finer *** weld efficiency of FSVW was approximately 81%,whereas those of FSW and TIG were approximately 74%and 67%,respectively.

关键词： friction stir welding vibration tungsten inert gas welding mechanical characteristics microstructure

Seismic performance of high-rise buildings in selected regions in Saudi Arabia according to different seismic codes

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Earthquake Engineering and Engineering Vibration 2021年第1期20卷 179-191页

作者： Sayed mahmoud Mohamed Alsearheed Waleed Abdallah Department of Civil and Construction Engineering College of EngineeringImam Abdulrahman Bin Faisal UniversitySaudi Arabia Department of Building Engineering College of ArchitectureImam Abdulrahman Bin Faisal UniversitySaudi Arabia Department of Civil Engineering College of Engineering at MatariaHelwan UniversityCairoEgypt

The design code for each country is revised and updated based on an expected zone’s seismic intensities,geotechnical site classifications,structural systems,construction materials and methods of construction in order to provide more realistic considerations of seismic demand,seismic response,and seismic *** on the aforementioned provisions,structures designed according to different seismic codes may yield different performances for the same level of *** study aims to investigate and compare the induced responses related to the earthquake-resistant design of reinforced concrete(RC)buildings according to the Saudi building code(SBC-301),American code(ASCE-7),uniform building code(UBC-97),and European code(EC-8).In order to account for the provision regarding the hazard specification and its effect on the induced seismic responses,four regions in the Kingdom of Saudi Arabia with different seismic levels are *** code provisions related to the specification of site classification and its effect on the induced design base shear are investigated as *** differences are observed in the induced responses with the variation in seismic design codes for the considered seismic hazards and site classifications.

关键词： high-rise building SBC-301 international seismic codes seismic zones site classifications

Theoretical investigations on electrocaloric properties of(111)-oriented PbMg_(1/3)Nb_(2)/3O_(3) single crystal

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Journal of Advanced Ceramics 2013年第4期2卷 308-312页

作者： mahmoud Aly HAMAD Physics Department Faculty of ScienceTanta UniversityTantaEgypt

The electrocaloric(EC)effect accompanied with the ferroelectric to paraelectric phase transition in(111)-oriented PbMg_(1/3)Nb_(2)/3O_(3)(PMN)is *** is shown that the largest change TDis 0.37 K in 3 kV/cm electric field shift near the Curie temperature of 221 K;that is,the cooling TDper unit field(MV/m)is 1.23×10^(-6) m·K/*** value is significantly larger,and comparable with the value of 0.254×10^(-6) m·K/V for PbZr_(0.95)Ti_(0.05)O_(3)thin film under larger electric field shift ED=30 kV/***,the EC effect of(111)PMN single crystal provides cooling solutions at low temperatures,and opens more opportunities for practical application in cooling systems.

关键词： electrocaloric(EC)effect PbMg_(1/3)Nb_(2)/3O_(3)(PMN) model polarization entropy change heat capacity change

Effect of Heat Input on the Microstructure and Properties of Dissimilar Weld Joint Between Incoloy 28 and Superaustenitic Stainless Steel

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Acta Metallurgica Sinica(English Letters) 2014年第2期27卷 259-266页

作者： M.S.abdel Rahman N.A.abdel Raheem M.R.El Koussy Department of Metallurgy Faculty of EngineeringCairo University

Abstract This work focuses on studying the effect of welding heat input within the range from 1 to 5 kJ/mm on the microstructure and the corresponding mechanical and corrosion properties of dissimilar joint between superaustenitic stainless steel （UNS S31254） and Incoloy 28 （UNS N08028）. The two materials were butt-welded with ER NiCrMo3. The metallurgical changes associated with welding of SASS and Incoloy 28 were studied using optical microscope, SEM, and EDX. The mechanical and corrosion properties were investigated using tensile test, Vickers hardness test, and pitting and crevice corrosion tests. The weld metal microstructure showed precipitates with needle-like shape at 3 and 5 kJ/mm. Also, the microstructure showed unmixed zone （UMZ） at the fusion line of both SASS and Incoloy 28 sides at all the investigated heat inputs. The Mo microsegregation within UMZ at Incoloy 28 side increased as the heat input increased from 1 to 5 k J/ram but that in SASS increased with increasing heat input from 1 to 3 kJ/mm and then decreased with increasing from 3 to 5 kJ/mm. The ultimate tensile strengths for all specimens at all the investigated heat inputs are acceptable. The average hardness noticeably changed in weld metal as the heat input increased from 1 to 5 kJ/mm. Other zones such as HAZ or UMZ did not demonstrate marked changes in the average hardness. The pitting and crevice corrosion rates of the weld joint were found significant at l and 3 kJ/mm but insignificant at 5 kJ/mm according to ASTM G48.

关键词： Superaustenitic Incoloy 28 Welding Heat input Unmixed zone Microsegregation Corrosion

A Blockchain-Based Architecture for Enabling Cybersecurity in the Internet-of-Critical Infrastructures

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Computers, Materials & Continua 2022年第7期72卷 1579-1592页

作者： mahmoud Ragab Ali Altalbe Information Technology Department Faculty of Computing and Information TechnologyKing Abdulaziz UniversityJeddah21589Saudi Arabia Center of Artificial Intelligence for Precision Medicines King Abdulaziz UniversityJeddah21589Saudi Arabia Mathematics Department Faculty of ScienceAl-Azhar UniversityNaser City11884CairoEgypt

Due to the drastic increase in the number of critical infrastructures like nuclear plants,industrial control systems(ICS),transportation,it becomes highly vulnerable to several *** become the major targets of cyberattacks due to the increase in number of interconnections with other *** research works have focused on the design of intrusion detection systems(IDS)using machine learning(ML)and deep learning(DL)*** the same time,Blockchain(BC)technology can be applied to improve the security *** order to resolve the security issues that exist in the critical infrastructures and ICS,this study designs a novel BC with deep learning empowered cyber-attack detection(BDLE-CAD)in critical infrastructures and *** proposed BDLE-CAD technique aims to identify the existence of intrusions in the *** addition,the presented enhanced chimp optimization based feature selection(ECOA-FS)technique is applied for the selection of optimal subset of ***,the optimal deep neural network(DNN)with search and rescue(SAR)optimizer is applied for the detection and classification of ***,a BC enabled integrity checking scheme(BEICS)has been presented to defend against the misrouting *** experimental result analysis of the BDLE-CAD technique takes place and the results are inspected under varying *** simulation analysis pointed out the supremacy of the BDLE-CAD technique over the recent state of art techniques with the accuy of 92.63%.

关键词： BC internet of critical infrastructure ids deep learning security deep neural network machine learning

The Rank of the 2-Class Group of Some Fields with LargeDegree

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Algebra Colloquium 2022年第2期29卷 181-188页

作者： Mohamed mahmoud Chems-Eddin Department of Mathematics Faculty of Sciences Dhar El Mahraz Sidi Mohamed Ben Abdellah UniversityFezMorocco

Let n≥3 be an integer and d an odd square-free *** compute the rank of the 2-class group of some fields of the form L_(n,d)=Q(ζ_(2^(n)),√d)when all the prime divisors of d are congruent to±3(mod 8)or 9(mod 16).

关键词： cyclotomic Z_(2)-extension 2-rank 2-class group