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Electrostatic Nonplanar Positron-Acoustic shock Waves in superthermal Electron-Positron-Ion Plasmas

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Communications in Theoretical Physics 2015年第6期63卷 754-760页

作者： m.J.Uddin m.s.alam A.A.mamun Department of Physics Jahangirnagar University

The basic properties of the nonlinear propagation of the nonplanar （cylindrical and spherical） positronacoustic （PA） shock waves （sHWs） in an unmagnetized electron-positron-ion （e-p-i） plasma containing immobile positive ions, mobile cold positrons, and superthermal （kappa distributed） hot positrons and electrons are investigated both analytically and numerically. The modified Burgers equation （roBE） is derived by using the reductive perturbation method. The basic features of PA sHWs are significantly modified by the cold positron kinematic viscosity （U）, superthermal parameter of electrons （ke）, superthermal parameter of hot positrons （kp）, the ratio of the electron temperature to hot positron temperature （or）, the ratio of the electron number density to cold positron number density （μe）, and the ratio of the hot positron number density to cold positron number density （μph）. This study could be useful to identify the basic properties of nonlinear electrostatic disturbances in dissipative space and laboratory plasmas.

关键词： positron-acoustic waves superthermal particles Kappa distribution shock waves modified Burg-ers equation electron-positronion plasmas

Diversity and structural composition of species in dipterocarp forests:a study from Fasiakhali Wildlife sanctuary, Bangladesh

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Journal of Forestry Research 2018年第5期29卷 1241-1249页

作者： s.C.Das m.s.alam m.A.Hossain Institute of Forestry and Environmental sciences University of Chittagong

Fasiakhali Wildlife sanctuary is a protected area composed of tropical remnant rainforest that harbor substantial number of large,old Garjan（Dipterocarpus spp.）*** present study assessed composition,structure and diversity of the species in this protected area.A total of 32 trees species were recorded with DBH ≥ 11 cm belonging to 24 genera and 19 *** forest is low in plant diversity as represented by shannon–Wiener diversity and simpson Dominance *** turbinatus was the most dominant species with maximum relative density,frequency,dominance,and importance value *** firmum and Tectona grandis followed in terms of *** structural composition indicated higher number of individuals in the medium growth classes（41 to 〈 511 cm DBH and 16–20 m height ranges）,whereas *** was the only species that dominated most of the growth *** stem density in lower growth classes indicated meager recruitment of regeneration which may be due to lower annual precipitation,increased grazing and *** study will help to understand the patterns of tree species composition and diversity in the remnant dipterocarp forests of *** will also contribute to identifying threatened plants to undertake *** based conservation and sustainable management of the Fasiakhali Wildlife sanctuary.

关键词： species diversity structural composition Protected area Importance value index Cluster analysis

Cylindrical and spherical Electron-Acoustic shock Waves in Electron-Positron-Ion Plasmas with Nonextensive Electrons and Positrons

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Communications in Theoretical Physics 2015年第2期63卷 243-248页

作者： A.Rafat m.m.Rahman m.s.alam A.A.mamun Department of Physics Jahangirnagar University

Electron-acoustic shock waves （EAsWs） in an unmagnetized four-component plasma （containing hot elec- trons and positrons following the q-nonextensiv.e distribution, cold mobile viscous electron fluid, and immobile positive ions） are studied in nonplanar （cylindrical and spherical） geometry. With the help of the reductive perturbation method, the modified Burgers equation is derived. Analytically, the effects of nonplanar geometry, nonextensivity, relative number density and temperature ratios, and cold electron kinematic viscosity on the basic properties （viz. amplitude, width, speed, etc.） of EAsWs are discussed. It is exarmined that the EAsWs in nonplanar geometry significantly differ from those in planar geometry. The results of this investigation can be helpful in understanding the nonlinear features of EAsWs in various astrophysical plasmas.

关键词： electron-acoustic shock waves electron-positron-ion plasmas modified Burgers equation nonpla-nar geometry nonextensivity

Numerical simulations of Hydromagnetic mixed Convection Flow of Nanofluids inside a Triangular Cavity on the Basis of a Two-Component Nonhomogeneous mathematical model

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Fluid Dynamics & materials Processing 2021年第1期17卷 1-20页

作者： Khadija A.Al-Hassani m.s.alam m.m.Rahman Department of mathematics College of ScienceSultan Qaboos UniversityMuscatOman Department of mathematics Jagannath UniversityDhakaBangladesh

Nanofluids have enjoyed a widespread use in many technological applications due to their peculiar *** simulations are presented about the unsteady behavior of mixed convection of Fe_(3)O_(4)-water,Fe_(3)O_(4)-kerosene,Fe_(3)O_(4)-ethylene glycol,and Fe_(3)O_(4)-engine oil nanofluids inside a lid-driven triangular *** particular,a two-component non-homogeneous nanofluid model is *** bottom wall of the enclosure is insulated,whereas the inclined wall is kept a constant(cold)temperature and various temperature laws are assumed for the vertical wall,namely:θ=1(Case 1),θ=Yð1YÞ(Case 2),andθ=sinð2-YÞ(Case 3).A tilted magnetic field of uniform strength is also present in the fluid *** a numerical point of view,the problem is addressed using the Galerkin weighted residual finite element *** role played by different parameters is assessed,discussed critically and interpreted from a physical *** find that a higher aspect ratio can produce an increase in the average Nusselt ***,the Fe_(3)O_(4)-EO and Fe_(3)O_(4)-H2O nanofluids provide the highest and smallest rate of heat transfer,respectively,for all the considered(three variants of)thermal boundary conditions.

关键词： Nanofluid mixed convection lid-driven triangular cavity finite element method

Pre-sowing treatments for improved germination and growth of two rare native species of Bangladesh

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Journal of Forestry Research 2018年第5期29卷 1277-1282页

作者： m.A.Hossain K.s.Islam N.Rajasree m.K.Hossain m.s.alam Institute of Forestry and Environmental sciences University of Chittagong

Pre-sowing treatments are expected to increase seed *** evaluates response to pre-sowing treatments and the growth performance of two native and rare tree species,Garuga pinnata *** Vitex glabrata *** hard seed coats were treated by rubbing with sand paper,nail clipping,and immersion in water and acid（H_2sO_4）.Results indicate that *** showed a 90% germination rate and 30% germination energy when seed coats were nicked with a nail *** with sand paper was the best pre-sowing treatment for ***,resulting a 80% germination rate and 30% germination *** and *** seedlings from seeds soaked 24h in water resulted in maximum heights and collar *** were significantly higher（at p〈0.05） than those of other *** results indicate that scarification or nicking of seeds may have some negative impacts on seedling ***,it is difficult to recommend a pre-sowing treatment of seeds for achieving both maximum germination and good early seedling growth.

关键词： Germination Early seedling growth Height Native species Garuga pinnata Vitex glabrata

Economic profitability of cane based furniture enterprises of Chittagong City Corporation Area, Bangladesh

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Journal of Forestry Research 2006年第2期17卷 153-156页

作者： m.alamgir m.A.R.Bhuiyan m.Jashimuddin m.s.alam Bangladesh Forest school Chittagong Bangladesh Institute of Forestry and Environmental sciences University of ChittagongChittagong-4331Bangladesh

An exploratory survey was conducted to assess economic profitability of cane based furniture enterprises in Chittagong City Corporation area of Bangladesh. A multistage random sampling was adopted to carry out the study. Based on the total investment the enterprises were divided into large, medium and small.. most of the entrepreneurs （55%） are in the age class 40-50 years and only （18.33%）are ＞50 years. In small and medium category lowest entrepreneurs （8.33% each） are found graduate and 18.33% in large farm. most of the enterprises are in the small category （45%） and 66.67% labors are skilled whereas only 33.33% are unskilled. seven articles of sixteen different sizes were identified made from cane, which are sofa （45 cm × 45 cm, 50 cm × 50 cm and 55 cm × 55 cm）, Dinning （4ch. 1tab,and 6ch. 1tab.）, Bed （1 m × 2m, 1.3 m × 2.3 m and 1.5 m × 2.3 m）, Chair （45 cm × 45 cm and 50 cm ×50 cm）, Rocking chair （large size,medium and small size）, Dolna （Hanging and Running） and Partition. In all the three category enterprises chair （45 cm × 45 cm） was produced in highest number and the lowest production was Bed （1.5 m × 2.3 m）. The total net benefit （2089 Us$） and benefit cost ratio （1：16）was the highest for large cane enterprises. so among three categories of the cane enterprises the large enterprises are more profitable than others.

关键词： Bangladesh Cane enterprises Net benefit Benefit-cost ratio,

Oblique collisional effects of dust acoustic waves in unmagnetized dusty plasma

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Chinese Physics B 2020年第6期29卷 304-313页

作者： m.s.alam m R Talukder Department of mathematics Chittagong University of Engineering and TechnologyChittagong-4349Bangladesh Plasma science and Technology Laboratory Department of Electrical and Electronic EngineeringUniversity of RajshahiRajshahi-6205Bangladesh

Effects of oblique collisions of the dust acoustic(DA)waves in dusty plasma are studied by considering unmagnetized fully ionized *** plasma consists of inertial warm negatively charged massive dusts,positively charged dusts,superthermal kappa distributed electrons,and isothermal *** extended Poincaré–Lighthill–Kuo(e PLK)method is employed for the drivation of two-sided Korteweg–de Vries(KdV)equations(KdVEs).The Kd V soliton solutions are derived by using the hyperbolic secant *** effects of superthermality index of electrons,temperature ratio of isothermal ion to electron,and the density ratio of isothermal ions to negatively charged massive dusts on nonlinear coefficients are *** effects of oblique collision on amplitude,phase shift,and potential profile of right traveling solitons of DA waves are also *** study reveals that the new nonlinear wave structures are produced in the colliding region due to head-on collision of the two counter propagating DA *** nonlinearity is found to decrease with the increasing density ratio of ion to negative dust in the critical *** phase shifts decrease(increase)with increasing the temperature ratio of ion to electron(κe).The hump(compressive,κeshaped(rarefactive,κe>κec)solitons are produced depending on the angle(θ)of oblique collision between the two waves.

关键词： ion acoustic wave dusty plasma kappa distribution ePLK method hyperbolic secant method

Head-on collision between single-and multi-soliton heavy ion acoustic waves in multi-ion plasmas

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Plasma science and Technology 2019年第9期21卷 58-72页

作者： m.s.alam m R TALUKDER Department of mathematics Chittagong University of Engineering and Technology Chittagong-4349 Bangladesh Plasma science and Technology Lab Department of Electrical and Electronic Engineering University of Rajshahi Rajshahi-6205 Bangladesh

Head-on collisions among the single-and multi-soliton’s heavy ion acoustic waves(HIAWs) of multi-ion plasma are studied. The plasma consists of adiabatic positively charged inertial heavy ions, Boltzmann energy distributed light ions and kappa energy distributed electrons. The extended poincaré-Lighthill-Kuo(e PLK) method is applied for the derivation of two-sided Korteweg–de Vries(KdV) equations(KdVEs). The KdV single-soliton solutions(KdVsss) are determined using the hyperbolic secant method and the KdV multi-soliton solutions(KdVmss)are obtained using the Hirota method. The effects of superthermality of electrons, temperature ratios of electron to light ion and heavy ion to electron, and the density ratio of electron to heavy ion on phase shifts are investigated for the head-on collisions between two-soliton HIAWs. The effects of plasma parameters on angular frequency, phase speed, production of multi-soliton structures, and the head-on collisions among single-, double-, triple-, quadruple-, and quintuplesolitons are also studied.

关键词： HIAWs multi-soliton kappa-distribution ePLK method Hirotta's method multi-ion

Performance of m-QAm, m-DPsK and m-PsK with mRC diversity in a Nakagami-m fading channel

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Journal of Central south University 2014年第4期21卷 1347-1352页

作者： alam s.m.shamsul alam Choi Goangseog Department of Information and Communication Engineering Chosun University

The nature of a wireless communication channel is very unpredictable. To design a good communication link, it is required to know the statistical model of the channel accurately. The average symbol error probability(AsER) was analyzed for different modulation schemes. A unified analytical framework was presented to obtain closed-form solutions for calculating the AsER of m-ary differential phase-shift keying(m-DPsK), coherent m-ary phase-shift keying(m-PsK), and quadrature amplitude modulation(QAm) over single or multiple Nakagami-m fading channels. moreover, the AsER was estimated and evaluated by using the maximal ratio-combining(mRC) diversity technique. simulation results show that an error rate of the fading channel typically depends on Nakagami parameters(m), space diversity(N), and symbol rate(m). A comparison between m-PsK, m-DPsK, and m-QAm modulation schemes was shown, and the results prove that m-ary QAm(m-QAm) demonstrates better performance compared to m-DPsK and m-PsK under all fading and non-fading conditions.

关键词： m-ary differential phase-shift keying(m-DPsK) m-ary phase shift keying(m-PsK) Nakagami-m fading channel probability density function(PDF) symbol error rate(sER) m-ary quadrature amplitude modulation(m-QAm)