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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

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

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

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

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

An Efficient Tide-Surge Interaction Model for the Coast of Bangladesh

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China Ocean Engineering 2020年第1期34卷 56-68页

作者： M.Mizanur rahman Gour Chandra PAUL Ashabul HOQUE Department of Mathematics Shahjalal University of Science&TechnologySylhet 3114Bangladesh Department of Mathematics University of RajshahiRajshahi-6205Bangladesh

The numerical method of lines(MOLs)in coordination with the classical fourth-order Runge Kutta(RK(4,4))method is used to solve shallow water equations(SWEs)for foreseeing water levels owing to the nonlinear interaction of tide and surge accompanying with a storm along the coast of *** SWEs are developed by extending the body forces with tide generating forces(TGFs).Spatial variables of the SWEs along with the boundary conditions are approximated by means of finite difference technique on an Arakawa C-grid to attain a system of ordinary differential equations(ODEs)of initial valued in time,which are being solved with the aid of the RK(4,4)*** grid technique is adopted to solve coastal complexities closely with least computational cost.A stable tidal solution in the region of our choice is produced by applying the tidal forcing with the major tidal constituent M2(lunar semi-diurnal)along the southern open-sea boundary of the outer *** experimentations are carried out to simulate water levels generated by the cyclonic storm AILA along the coast of *** model simulated results are found to be in a reasonable agreement with the limited available reported data and observations.

关键词： Bangladesh coast shallow water equations method of lines tide-surge interaction islands tide generating forces inverse barometer

Effects of multiple shapes for steady flow with transformer oil+Fe_(3)O_(4)+TiO_(2) between two stretchable rotating disks

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Applied Mathematics and Mechanics(English Edition) 2024年第2期45卷 373-388页

作者： M.rahman M.TURKYILMAZOGLU Z.MUSHTAQ Department of Mathematics Mirpur University of Science and TechnologyMirpur 10250Pakistan Department of Mathematics Hacettepe UniversityBeytepeAnkara 06532Turkiye

In this study,we examine the effects of various shapes of nanoparticles in a steady flow of hybrid nanofluids between two stretchable rotating *** steady flow of hybrid nanofluids with transformer oil as the base fluid and Fe_(3)O_(4)+TiO_(2)as the hybrid nanofluid is *** shapes of Fe_(3)O_(4)+TiO_(2)hybrid nanofluids,including sphere,brick,blade,cylinder,and platelet,are *** shape exists in the same volume of a *** leading equations(partial differential equations(PDEs))are transformed to the nonlinear ordinary differential equations(ODEs)with the help of similarity *** system of equations takes the form of ODEs depending on the boundary conditions,whose solutions are computed numerically by the bvp4c MATLAB *** outputs are compared with the previous findings,and an intriguing pattern is discovered,such that the tangential velocity is increased for the rotation parameter,while it is decreased by the stretching values because of the lower *** the reaction rate parameter,the concentration boundary layer becomes shorter,and the activation energy component increases the rate at which mass transfers come to the higher disk but have the opposite effect on the bottom *** ranges of various parameters taken into account are Pr=6.2,Re=2,M=1.0,φ_(1)=φ_(2)=0.03,K=0.5,S=-0.1,Br=0.3,Sc=2.0,α_(1)=0.2,γ=0.1,E_(n)=2.0,and q=1.0,and the rotation factor K is within the range of 0 to 1.

关键词： transformer oil Brinkman number skin friction coefficient double rotating disk Nusselt number Sherwood number

Efficient Algorithm for Prolonging Network Lifetime of Wireless Sensor Networks

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Tsinghua Science and Technology 2011年第6期16卷 561-568页

作者： Md Nafees rahman M A Matin Department of Electrical Engineering and Computer Science North South University

One of the fundamental design challenges in designing a Wireless Sensor Network （WSN） is to maximize the network lifetime, as each sensor node of the network is equipped with a limited power battery. To overcome this challenge, different methods were developed in the last few years using such techniques as network protocols, data fusion algorithms using low power, energy efficient routing, and locating optimal sink position. This paper focuses on finding the optimal sink position. Relay nodes are introduced in conjunction with the sensor nodes to mitigate network geometric deficiencies since in most other approaches the sensor nodes close to the sink become heavily involved in data forwarding and, thus, their batteries are quickly depleted. A Particle Swarm Optimization （PSO） based algorithm is used to locate the optimal sink position with respect to those relay nodes to make the network more energy efficient. The relay nodes communicate with the sink instead of the sensor nodes. Tests show that this approach can save at least 40% of the energy and prolong the network lifetime.

关键词： wireless sensor network lifetime sensor node relay node particle swarm optimization sink