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Density functional theory study of structural,electronic,and thermal properties of Pt,Pd,Rh,Ir,Os and PtPdX(X=Ir,Os,and Rh)alloys

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Chinese Physics B 2016年第3期25卷 298-306页

作者： Shabbir ahmed muhammad Zafar m Shakilt m A Choudhary Simulation Laboratory Department of Physicsthe Islamia University of BahawalpurBahawalpur 63100Pakistan o Department of Physics Hafiz Hayat CampusUniversity of GujratGujrat 50700Pakistan

The structural, electronic, mechanical, and thermal properties of Pt, Pd, Rh, Ir, Os metals and their alloys PtPdX （X = Ir, Os and Rh） are studied systematically using ab initio density functional theory. The groundstate properties such as lattice constant and bulk modulus are calculated to find the equilibrium atomic position for stable alloys. The electronic band structure and density of states are calculated to study the electronic behavior of metals on making their alloys. The electronic properties substantiate the metallic behavior for all studied materials. The firstprinciples density functional perturbation theory as implemented in quasi-harmonic approximation is used for the calculations of thermal properties. We have calculated the thermal properties such as the Debye temperature, vibrational energy, entropy and constant-volume specific heat. The calculated properties are compared with the previously reported experimental and theoretical data for metals and are found to be in good agreement. Calculated results for alloys could not be compared because there is no data available in the literature with such alloy composition.

关键词： electronic structural and thermal properties platinum group metals

Assessment of clay stiffness and strength parameters using index properties

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Journal of Rock mechanics and Geotechnical Engineering 2018年第3期10卷 579-593页

作者： Sayed m.ahmed Structural Engineering Department Ain Shams University

A new approach is developed to determine the shear wave velocity in saturated soft to firm clays using measurements of the liquid limit, plastic limit, and natural water content with depth. The shear wave velocity is assessed using the site-specific variation of the natural water content with the effective mean stress. Subsequently, an iterative process is envisaged to obtain the clay stiffness and strength *** at-rest earth pressure coefficient, as well as bearing capacity factor and rigidity index related to the cone penetration test, is also acquired from the analyses. Comparisons are presented between the measured clay parameters and the results of corresponding analyses in five different case studies. It is demonstrated that the presented approach can provide acceptable estimates of saturated clay stiffness and strength parameters. One of the main privileges of the presented methodology is the site-specific procedure developed based on the relationships between clay strength and stiffness parameters, rather than adopting direct correlations. Despite of the utilized iterative processes, the presented approach can be easily implemented using a simple spreadsheet, benefiting both geotechnical researchers and practitioners.

关键词： Soft to firm clays Atterberg limits Shear wave velocity Small-strain shear modulus Constrained modulus Undrained shear strength Effective friction angle Cone penetration test

An Integrated Framework for Cloud Service Selection Based on BOm and TOPSIS

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Computers, materials & Continua 2022年第8期72卷 4125-4142页

作者： ahmed m.mostafa Computer and Systems Engineering Department Faculty of Engineering at HelwanHelwan UniversityCairo11795Egypt

many businesses have experienced difficulties in selecting a cloud service provider(CSP)due to the rapid advancement of cloud computing services and the proliferation of *** independent criteria should be considered when evaluating the services provided by different *** is a case of multi-criteria decision-making(mCDm).This paper presents an integrated mCDm cloud service selection framework for determining the most appropriate service provider based on the best only method(BOm)and technique for order of preference by similarity to ideal solution(TOPSIS).To obtain the weights of criteria and the relative importance of CSPs based on each criterion,BOm performs pairwise comparisons of criteria and also for alternatives on each criterion,and TOPSIS uses these weights to rank cloud *** evaluation and validation of the proposed framework have been carried out through a use-case model to prove its efficiency and ***,the developed framework was compared with the analytical hierarchical process(AHP),a popular mCDm approach,based on two perspectives:efficiency and *** to the research results,the proposed framework only requires 25%of the comparisons needed for the AHP ***,the proposed framework has a CR of 0%,whereas AHP has 38%.Thus,the proposed framework performs better than AHPwhen it comes to computation complexity and consistency,implying that it is more efficient and trustworthy.

关键词： Cloud computing(CC) multiple-criteria decision-making(mCDm) cloud service providers(CSPs) analytical hierarchical process(AHP) the best only method(BOm) technique for order of preference by similarity to ideal solution(TOPSIS)

mosquito autogeny in Aedes caspius （Diptera： Culicidae）： alterations of larval nourishments reservation upon bacterial infection

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Insect Science 2013年第4期20卷 472-484页

作者： Ashraf m. ahmed Zoology Department College of Science King Saud University SaudiArabia Zoology Department College of Science Minia UniversityEl-Minia Egypt

The present study recorded mosquito autogeny for the first time amongst Aedes caspius species in the Eastern region of Saudi Arabia. Laboratory rearing showed an obligatory autogenous species of Ae. caspius since it foregoes blood feeding during its first ovarian cycle, even in the presence of the hosts （CD mouse）, but produces its second egg batch only if ingested a blood meal. Both morphological and molecular identification confirmed that both autogenous and anautogenous strains belong to the same species of Ae. caspius. Data from biochemical analysis showed significant 2, 1.6, and 1.4 folds higher total carbohydrates, proteins, and lipids reserves respectively in the fourth larval instar of the autogenous strain compared to that of the anautogenous ones. In addition, exposing the fourth larval instars of autogenous strain to the infection stress by the mosquito larvicidal bacterium, Bacillus thuringiensis var kurstaki has significantly reduced total carbohydrates, proteins and lipids reserves by 29%, 35%, and 46%, respectively, at 12 h postinfection compared to those of uninfected ones. These reductions in nourishment reserves were more pronounced at 24 h postinfection in the case of proteins and lipids, but not carbohydrates. These results may indicate that bacterial infection is a health stress that significantly reduced nourishments reservation, which may interrupt the success of adult autogeny. However, the impact of infection-induced decline in larval nourishments reservation on successful adult autogeny is still to be investigated.

关键词： Aedes caspius anautogeny autogeny Bacillus thuringiensis nourishmentsreservation

Voltage imbalance mitigation in an active distribution network using decentralized current control

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Protection and Control of modern Power Systems 2023年第2期8卷 68-84页

作者： ahmed m.m.Nour ahmed A.Helal magdi m.El-Saadawi ahmed Y.Hatata Alexandria Higher Institute of Engineering and Technology(AIET) AlexandriaEgypt Department of Electrical and Control Engineering Arab Academy for Science and Technology and Maritime TransportAlexandriaEgypt Department of Electrical Engineering Faculty of EngineeringMansoura UniversityMansouraEgypt Department of Electrical Engineering College of EngineeringShaqra UniversityShaqraKingdom of Saudi Arabia

Voltage imbalance(VI)is caused by the difference in connected single-phase load or generation in a low voltage distribution network(DN).VI increase in a smart distribution grid is due to the current practice of increasing single-phase distributed generators such as photovoltaic(PV)*** paper proposes a decentralized control method to mitigate VI using distributed batteries included in smart grid interfaced residential PV *** mitigate VI using the batteries in this way,five challenges must be overcome,i.e.,equalizing all battery stress currents within the DN,mitigating VI in abnormal conditions such as signal loss among bus controllers,being immune from the distorted feedback measurements,minimizing the steady-state error at different loads,and overcoming the insufficient number or capacity of the distributed batteries at the same *** fuzzy logic controllers(FLC)are proposed at each bus to overcome these five tasks based on a decentralized control *** proposed decentralized control based on FLC is compared with centralized control based on a PI *** proposed control method is tested and verified using simulations in the mATLAB/Simulink software,and the results validate the ability of the scheme to alleviate VI on a smart distribution network under both normal and abnormal conditions.

关键词： Fuzzy controller Distributed batteries Decentralized control Voltage imbalance Distributed PV

Rotational flow of Oldroyd-B nanofluid subject to Cattaneo-Christov double diffusion theory

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Applied mathematics and mechanics(English Edition) 2020年第7期41卷 1083-1094页

作者： A.HAFEEZ m.KHAN A.ahmed J.ahmed Department of mathematics Quaid-i-Azam UniversityIslamabad 44000Pakistan Department of Basic Sciences University of Engineering and TechnologyTaxila 47050Pakistan

A nanofluid is composed of a base fluid component and nanoparticles, in which the nanoparticles are dispersed in the base fluid. The addition of nanoparticles into a base fluid can remarkably improve the thermal conductivity of the nanofluid, and such an increment of thermal conductivity can play an important role in improving the heat transfer rate of the base fluid. Further, the dynamics of non-Newtonian fluids along with nanoparticles is quite interesting with numerous industrial applications. The present predominately predictive modeling studies the flow of the viscoelastic Oldroyd-B fluid over a rotating disk in the presence of nanoparticles. A progressive amendment in the heat and concentration equations is made by exploiting the Cattaneo-Christov heat and mass flux expressions. The characteristic of the Lorentz force due to the magnetic field applied normal to the disk is studied. The Buongiorno model together with the Cattaneo-Christov theory is implemented in the Oldroyd-B nanofluid flow to investigate the heat and mass transport mechanism. This theory predicts the characteristics of the fluid thermal and solutal relaxation time on the boundary layer flow. The von K′arm′an similarity functions are utilized to convert the partial differential equations(PDEs) into ordinary differential equations(ODEs). A homotopic approach for obtaining the analytical solutions to the governing nonlinear problem is carried out. The graphical results are obtained for the velocity field, temperature, and concentration distributions. Comparisons are made for a limiting case between the numerical and analytical solutions, and the results are found in good agreement. The results reveal that the thermal and solutal relaxation time parameters diminish the temperature and concentration distributions, respectively. The axial flow decreases in the downward direction for higher values of the retardation time parameter. The impact of the thermophoresis parameter boosts the temperature di

关键词： Oldroyd-B nanofluid rotating disk magnetohydrodynamic(mHD) Cattaneo-Christov theory analytical solution

Von Kármán rotating flow of maxwell nanofluids featuring the Cattaneo-Christov theory with a Buongiorno model

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Applied mathematics and mechanics(English Edition) 2020年第8期41卷 1195-1208页

作者： A.ahmed m.KHAN J.ahmed A.HAFEEZ Department of mathematics Quaid-i-Azam UniversityIslamabad 44000Pakistan Department of Basic Sciences University of Engineering and TechnologyTaxila 47050Pakistan

This research paper analyzes the transport of thermal and solutal energy in the maxwell nanofluid flow induced above the disk which is rotating with a constant angular *** significant features of thermal and solutal relaxation times of fluids are studied with a Cattaneo-Christov double diffusion theory rather than the classical Fourier’s and Fick’s laws.A novel idea of a Buongiorno nanofluid model together with the Cattaneo-Christov theory is introduced for the first time for the maxwell fluid flow over a rotating ***,the thermal and solutal distributions are controlled with the impacts of heat source and chemical *** classical von Karman similarities are used to acquire the non-linear system of ordinary differential equations(ODEs).The analytical series solution to the governing ODEs is obtained with the well-known homotopy analysis method(HAm).The validation of results is provided with the published results by the comparison *** graphically presented outcomes for the physical problem reveal that the higher values of the stretching strength parameter enhance the radial velocity and decline the circumferential *** increasing trend is noted for the axial velocity profile in the downward direction with the higher values of the stretching strength *** higher values of the relaxation time parameters in the Cattaneo-Christov theory decrease the thermal and solutal energy transport in the flow of maxwell *** higher rate of the heat transport is observed in the case of a larger thermophoretic force.

关键词： maxwell fluid nanoparticle Cattaneo-Christov theory rotating disk homotopy analysis method(HAm)

Double compound combination synchronization among eight n-dimensional chaotic systems

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Chinese Physics B 2018年第8期27卷 150-158页

作者： Gamal m mahmoud Tarek m Abed-Elhameed ahmed A Farghaly Department of mathematics Faculty of Science Assiut University

Depending on double compound synchronization and compound combination synchronization, a new kind of syn- chronization is introduced which is the double compound combination synchronization （DCCS） of eight n-dimensional chaotic systems. This kind may be considered as a generalization of many types of synchronization. In the communica- tion, based on many of drive and response systems, the transmitted and received signals will be more secure. Using the Lyapunov stability theory and nonlinear feedback control, analytical formulas of control functions are obtained to insure our results. The corresponding analytical expression and numerical treatment are used to show the validity and feasibility of our proposed synchronization scheme. The eight memristor-based Chua oscillators are considered as an example. Other examples can be similarly investigated. The proposed synchronization technique is supported using the mATLAB simula- tion outcomes. We obtain the same results of numerical treatment of our synchronization using simulation observations of our example.

关键词： double compound synchronization compound combination synchronization chaotic system Lya-punov stability

EDSUCh:A robust ensemble data summarization method for effective medical diagnosis

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Digital Communications and Networks 2024年第1期10卷 182-189页

作者： mohiuddin ahmed A.N.m.Bazlur Rashid School of Science Edith Cowan UniversityPerthAustralia

Identifying rare patterns for medical diagnosis is a challenging task due to heterogeneity and the volume of *** summarization can create a concise version of the original data that can be used for effective *** this paper,we propose an ensemble summarization method that combines clustering and sampling to create a summary of the original data to ensure the inclusion of rare *** the best of our knowledge,there has been no such technique available to augment the performance of anomaly detection techniques and simultaneously increase the efficiency of medical *** performance of popular anomaly detection algorithms increases significantly in terms of accuracy and computational complexity when the summaries are ***,the medical diagnosis becomes more effective,and our experimental results reflect that the combination of the proposed summarization scheme and all underlying algorithms used in this paper outperforms the most popular anomaly detection techniques.

关键词： Data summarization Ensemble medical diagnosis Sampling