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Generalized Second Law of Thermodynamics in Wormhole Geometry with Logarithmic Correction

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Chinese Physics Letters 2011年第7期28卷 55-58页

作者： Faiz-ur-rahman Salahuddin M.Akbar Centre for Advanced Mathematics and Physics National University of Sciences and Technology(NUST)IslamabadPakistan

We construct various cases for validity of the generalized second law(GSL)of thermodynamics by assuming the logarithmic correction to the horizon entropy of an evolving *** is shown that the GSL is always respected fo... 详细信息

关键词： correction thermodynamics horizon

Parametric study and effect of calcination and carbonation conditions on the CO_2 capture performance of lithium orthosilicate sorbent

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Chinese Journal of Chemical Engineering 2018年第3期26卷 631-641页

作者： Nurul Azrin Zubbri Abdul rahman Mohamed Maedeh Mohammadi Low Carbon Economy (LCE) Research Group School of Chemical Engineering Engineering Campus Universiti Sains Malaysia Faculty of Chemical Engineering Babol Noushirvani University of Technology

The world is currently facing the challenges of global warming and climate change. Numerous efforts have been taken to mitigate CO2 emission, among which is the use of solid sorbents for CO2 capture. In this work, Li4SiO4 was synthesised via a sol-gel method using lithium nitrate （LiNO3） and tetraethylorthosilicate （SiC8H20O4） as precursors. A parametric study of Li：Si molar ratio （1-5）, calcination temperature （600-800℃） and calcination time （1-8 h） were conducted during sorbent synthesis. Calcination temperature （700-800℃） and carbonation temperature （500-700℃） during CO2 sorption activity were also varied to confirm the optimum operating temperature. Sorbent with the highest CO2 sorption capacity was finally introduced to several cyclic tests to study the durability of the sorbent through 10 cycles of CO2 sorption-desorption test. The results showed that the calcination temperature of 800℃ and carbonation temperature of 700℃ were the best operating temperatures, with CO2 sorption capacity of 7.95 mmol CO2·（g sorbent）^-1 （93% of the theoretical yield）. Throughout the ten cyclic processes, CO2 sorption capacity of the sorbent had dropped approximately 16.2% from the first to the tenth cycle, which was a reasonable decline. Thus, it was concluded that Li4SiO4 is a potential CO2 solid sorbent for high temperature CO2 capture activity.

关键词： CO2 capture Adsorption Carbon dioxide Lithium orthosilicate Sol-gel Sorption-desorption

Computational Study on a Squid-Like Underwater Robot with Two Undulating Side Fins

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Journal of Bionic Engineering 2011年第1期8卷 25-32页

作者： Md. Mahbubar rahman Yasuyuki Toda Hiroshi Miki Department of Naval Architecture and Ocean Engineering Graduate School of Engineering Osaka University 2-1 Yamadaoka Suita City Osaka 565-0871 Japan

The undulating fin propulsion system is an instance of the bio-inspired propulsion systems. In the current study, the swimming motion of a squid-like robot with two undulating side fins, mimicking those of a Stingray or a Cuttlefish, was investigated through flow computation around the body. We used the finite analytic method for space discretization and Euler implicit scheme for time discretization along with the PISO algorithm for velocity pressure coupling. A body-fitted moving grid was generated using the Poisson equation at each time step. Based on the computed results, we discussed the features of the flow field and hydrodynamic forces acting on the body and fin. A simple relationship among the fin＇s principal dimensions was established. Numerical computation was done for various aspect ratios, fin angles and frequencies in order to validate the proposed relationship among principal dimensions. Subsequently, the relationship was examined base on the distribution of pressure difference between upper and lower surfaces and the distribution of the thrust force. In efficiency calculations, the undulating fins showed promising results. Finally, for the fin, the open characteristics from computed data showed satisfactory conformity with the experimental results.

关键词： biomimetics squid robot undulating fin propulsion efficiency hydrodynamics CFD

Networked Control Approach for Distributed Generation Systems

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IEEE/CAA Journal of Automatica Sinica 2018年第4期5卷 836-851页

作者： Magdi S.Mahmoud Mohamed Saif Ur rahman Systems Engineering Department King Fahd University of Petroleum and MineralsP.O.Box 5067Dhahran 31261Saudi Arabia

Microgrid has emerged as an answer to growing demand for distributed generation(DG) in power systems. It contains several DG units including microalternator, photovoltaic system and wind generation. It turns out that sustained operation relies on the stability of these constituent systems. In this paper, a microgrid consisting of microalternator and photovoltaic system is modeled as a networked control system of systems(So S)subjected to packet dropouts and delays. Next, an observerbased controller is designed to stabilize the system in presence of the aforementioned communication constraints and simulation results are provided to support the control design methodology.

关键词： Microalternator microgrid systems networked control observer-based controller photovoltaic systems

Analytical Determination of Collisionless Sheath Properties for Triple Frequency Capacitively Coupled Plasma

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Plasma Science and Technology 2015年第2期17卷 141-146页

作者： M.T.rahman M.N.A.DEWAN Department of Electrical and Electronic Engineering Bangladesh University of Engineering and Technology

A triple frequency capacitively coupled plasma （TF-CCP） has been considered to investigate the behavior of the sheath parameters. A self-consistent time-independent collisionless model has been developed. The sheath width and potential are calculated using the present model and compared with those calculated using a single-frequency （SF）, a dual-frequency （DF） and a triple-frequency （TF） model for time independent collisionless cases. The sheath motion and sheath potential are found to be larger compared with those of SF and DF CCPs for an inhomogeneous sheath, and that of TF CCP for a homogeneous sheath. The effects of the source parameters, i.e., current magnitudes, frequencies and phase difference, on the sheath parameters are investigated. The sheath parameters show higher values at higher source currents whereas they decrease with the increase of excitation frequencies. It has also been found that, by the proper choice of source frequencies and phase differences, it is possible to adjust the energy of ions when they hit the electrode.

关键词： capacitively coupled plasma collisionless sheath triple frequency sheath parameters

Propagation of Ion Solitary Pulses in Dense Astrophysical Electron-Positron-Ion Magnetoplasmas

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Plasma Science and Technology 2015年第12期17卷 1000-1005页

作者： ATA-UR-rahman S.A.KHAN A.QAMAR Department of Physics Theoretical Plasma Physics GroupIslamia College Peshawar(A Public Sector University) National Centre for Physics QAU Campus Department of Physics University of Peshawar

In this paper,we theoretically investigate the existence and propagation of low amplitude nonlinear ion waves in a dense plasma under the influence of a strong magnetic *** plasma consists of ultra-relativistic and degenerate electrons and positrons and non-degenerate cold ***,the appearance of two distinct linear modes and their evolution is studied by deriving a dispersion equation with the aid of Fourier ***,the dynamics of low amplitude ion solitary structures is investigated via a Korteweg-de Vries equation derived by employing a reductive perturbation *** effects of various plasma parameters like positron concentration,strength of magnetic field,obliqueness of field,etc.,are discussed in *** the end,analytical results are supplemented through numerical analysis by using typical representative parameters consistent with degenerate and ultra-relativistic magnetoplasmas of astrophysical regimes.

关键词： degenerate relativistic perturbation solitary representative Electron appearance dense collective normalized

Continuity of Almost Harmonic Maps with the Perturbation Term in a Critical Space

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Chinese Annals of Mathematics,Series B 2022年第4期43卷 585-600页

作者： Mati ur rahman Yingshu Lü Deliang XU School of Mathematical Sciences Shanghai Jiao Tong UniversityShanghai 200240China

The authors study the continuity estimate of the solutions of almost harmonic maps with the perturbation term f in a critical integrability class(Zygmund class)L^(n/2)log^(q) L,n is the dimension with n≥*** prove that when q>n/2 the solution must be continuous and they can get continuity modulus *** a byproduct of their method,they also study boundary continuity for the almost harmonic maps in high dimension.

关键词： Harmonic maps Nonlinear elliptic PDE Boundary regularity

Modeling and Comprehensive Review of Signaling Storms in 3GPP-Based Mobile Broadband Networks:Causes,Solutions,and Countermeasures

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Computer Modeling in Engineering & Sciences 2025年第1期142卷 123-153页

作者： Muhammad Qasim Khan Fazal Malik Fahad Alturise Noor rahman Department of Computer Science Iqra National UniversityPeshawar25000Pakistan Department of Cybersecurity College of ComputerQassim UniversityBuraydah52555Saudi Arabia Department of Computer Science and Engineering Al-Fayha CollegeAl Jubayl31961Saudi Arabia

Control signaling is mandatory for the operation and management of all types of communication networks,including the Third Generation Partnership Project(3GPP)mobile broadband ***,they consume important and scarce network resources such as bandwidth and processing *** have been several reports of these control signaling turning into signaling storms halting network operations and causing the respective Telecom companies big financial *** paper draws its motivation from such real network disaster incidents attributed to signaling *** this paper,we present a thorough survey of the causes,of the signaling storm problems in 3GPP-based mobile broadband networks and discuss in detail their possible solutions and *** provide relevant analytical models to help quantify the effect of the potential causes and benefits of their corresponding *** important contribution of this paper is the comparison of the possible causes and solutions/countermeasures,concerning their effect on several important network aspects such as architecture,additional signaling,fidelity,etc.,in the form of a *** paper presents an update and an extension of our earlier conference *** our knowledge,no similar survey study exists on the subject.

关键词： Signaling storm problems control signaling load analytical modeling 3GPP networks smart devices diameter signaling mobile broadband data access data traffic mobility management signaling network architecture 5G mobile communication

DEM simulation of particle percolation in a packed bed

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Particuology 2008年第6期6卷 475-482页

作者： Mahbubur rahman Haiping Zhu Aibing Yu John Bridgwater Lab for Simulation and Modeling of Particulate Systems School of Materials Science and Engineering The University of New South Wales Sydney NSW 2052 Australia Department of Chemical Engineering University of Cambridge Cambridge CB2 3RA UK

The phenomenon of spontaneous particle percolation under gravity is investigated by means of the discrete element method. Percolation behaviors such as percolation velocity, residence time distribution and radial dispersion are examined under various conditions. It is shown that the vertical velocity of a percolating particle moving down through a packing of larger particles decreases with increasing the restitution coefficient between particles and diameter ratio of the percolating to packing particles. With the increase of the restitution coefficient, the residence time and radial dispersion of the percolating particles increase. The packing height affects the residence time and radial dispersion. But, the effect can be eliminated in the analysis of the residence time and radial dispersion when they are normalized by the average residence time and the product of the packing height and packing particle diameter, respectively. In addition, the percolation velocity is shown to be related to the vertical acceleration of the percolating particle when an extra constant vertical force is applied. Increasing the feeding rate of percolating particles decreases the dispersion coefficient.

关键词： Discrete element method Particle percolation Residence time Radial dispersion