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Plasma Science and Technology 2017年第12期19卷 71-80页

作者： n C ROY m R TALUKDER A n chowdhury Plasma Science and Technology Laboratory Department of Applied Physics and Electronic EngineeringUniversity of RajshahiRajshahi 6205Bangladesh Bangladesh Council of Scientific and Industrial Research Laboratory Rajshahi Rajshahi 6206Bangladesh

Atmospheric pressure air/Ar/H_2O gliding arc discharge plasma is produced by a pulsed dc power supply. An optical emission spectroscopic（OES） diagnostic technique is used for the characterization of plasmas and for identifications of OH and O radicals along with other species in the plasmas. The OES diagnostic technique reveals the excitation Tx？≈？5550–9000 K, rotational Tr？≈？1350–2700 K and gas Tg？≈？850–1600 K temperatures, and electron density n？（1.1-1.9） ′101 4 cm^（-3） e under different experimental conditions. The production and destruction of OH and O radicals are investigated as functions of applied voltage and air flow rate. Relative intensities of OH and O radicals indicate that their production rates are increased with increasing Ar content in the gas mixture and applied voltage. nereveals that the higher densities of OH and O radicals are produced in the discharge due to more effective electron impact dissociation of H_2O and O_2 molecules caused by higher kinetic energies as gained by electrons from the enhanced electric field as well as by enhanced n *** productions of OH and O are decreasing with increasing air flow rate due to removal of Joule heat from the discharge region but enhanced air flow rate significantly modifies discharge maintenance properties. Besides, Tgsignificantly reduces with the enhanced air flow rate. This investigation reveals that Ar plays a significant role in the production of OH and O radicals.

关键词： reactive oxygen species(ROS) optical emission spectroscopy(OES) gliding arc discharge plasma kinetics broadening mechanism

Atmospheric pressure gliding arc discharge plasma treatments for improving germination, growth and yield of wheat

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Plasma Science and Technology 2018年第11期20卷 90-100页

作者： n C ROY m m HASAn A H KABIR m A REZA m R TALUKDER A n chowdhury Plasma Science and Technology Laboratory Department of Applied Physics and Electronic EngineeringUniversity of Rajshahi Rajshahi 6205 Bangladesh Department of Agronomy and Agricultural Extension University of Rajshahi Rajshahi 6205 Bangladesh Depatment of Botany University of Rajshahi Rajshahi 6205Bangladesh Department of Genetic Engineering and Biotechnology University of Rajshahi Rajshahi 6205Bangladesh Bangladesh Council of Scientific and Industrial Research Laboratory Rajshahi Rajshahi 6206Bangladesh

Wheat （Triticum aestivum） seeds were treated with atmospheric pressure gliding arc discharge plasmas to investigate the effects on water absorption, seed germination rate, seedling growth and yield in wheat. The surface architectures and functionalities of the seeds were found to modify due to plasma treatments. 6 rain treatment was provided 95%-100% germination rate. For the treatment duration of 3 and 9 rain the growth activity, dry matter accumulation, leaves chlorophyll contents, longest spikes, number of spikes/spikelet and total soluble protein content in shoots were improved. The grain yield of wheat was increased ,--20% by 6 min treatment with H2O/O2 plasma with respect to control.

关键词： atmospheric pressure gliding arc discharge plasmas wheat germination growth improvement total soluble protein

magnetic properties of Sn-substituted ni-Zn ferrites synthesized from nano-sized powders of niO, ZnO, Fe2O3, and SnO2

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Chinese Physics B 2017年第7期26卷 377-382页

作者： m A Ali m m Uddin m n I Khan F U Z chowdhury S m Hoque S I Liba Department of Physics Chittagong University of Engineering and Technology (CUET) materials Science Division Atomic Energy Center

A series of ni0.6-x/2Zn0.4-x/2SnxFe2O4(x = 0.0, 0.05, 0.1, 0.15, 0.2, and 0.3)(nZSFO) ferrite composities have been synthesized from nano powders using a standard solid state reaction technique. The spinel cubic structure of the investigated samples has been confirmed by x-ray diffraction(XRD). The magnetic properties such as saturation magnetization(ms),remanent magnetization(mr), coercive field(Hc), and Bohr magneton(μ) are calculated from the hysteresis loops. The value of msis found to decrease with increasing Sn content in the samples. This change is successfully explained by the variation of A-B interaction strength due to Sn substitution in different sites. The compositional stability and quality of the prepared ferrite composites have also been endorsed by the fairly constant initial permeability(μ’) over a wide range of frequency. The decreasing trend of μ’ with increasing Sn content has been observed. Curie temperature TChas been found to increase with the increase in Sn content. A wide spread frequency utility zone indicates that the nZSFO can be considered as a good candidate for use in broadband pulse transformers and wide band read-write heads for video recording. The composition of x = 0.05 shows unusual results and the possible reason is also mentioned with the established formalism.

关键词： magnetic properties saturation magnetization permeability Curie temperature

Ion-Acoustic Rogue Waves in multi-ion Plasmas

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Communications in Theoretical Physics 2019年第8期71卷 1017-1023页

作者： m.Hassan m.H.Rahman n.A.chowdhury A.mannan A.A.mamun Department of Physics Jahangirnagar University Savar Dhaka-1342 Bangladesh Wazed miah Science Research Center Jahangirnagar University Savar Dhaka-1342 Bangladesh Institut fur mathematik Martin Luther Universitat Halle-Wittenberg Halle Germany

The basic properties of nonlinear ion-acoustic(IA) waves(IAWs), particularly finite amplitude IA rogue waves(IARWs) in a plasma medium(containing pair ions, iso-thermal positrons, and non-thermal electrons) are theoretically investigated by deriving the nonlinear Schr¨odinger equation(nLSE).The criteria for the modulational instability of IAWs, and the basic features of finite amplitude IARWs are *** modulationally stable and unstable regions are determined by the sign of the ratio of the dispersive coefficient to the nonlinear coefficient of *** latter is analyzed to obtain the region for the existence of the IARWs, which corresponds to the unstable *** shape of the profile of the rogue waves depends on the non-thermal parameter α and the ratio of electron temperature to positron *** is found that the increase in the value of the non-thermal parameter enhances both the amplitude and width of IARWs, and that the enhancement of electron(positron) temperature reduces(enhances) the amplitude and width of *** is worth to mention that our present investigation may be useful for understanding the salient features of IARWs in space(viz., upper region of Titan’s atmosphere, cometary comae, and Earth’s ionosphere, etc.)and laboratory(viz., plasma processing reactor and neutral beam sources, etc.) plasmas.

关键词： pair ions modulational instability rogue waves

modulated Dust-Acoustic Wave Packets in an Opposite Polarity Dusty Plasma System

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Communications in Theoretical Physics 2019年第3期71卷 327-333页

作者： S.Jahan n.A.chowdhury A.mannan A.A.mamun Department of Physics Jahangirnagar University

The nonlinear propagation of the dust-acoustic bright and dark envelope solitons in an opposite polarity dusty plasma(OPDP) system(composed of non-extensive q-distributed electrons, iso-thermal ions, and positively as well as negatively charged warm dust) has been theoretically investigated. The reductive perturbation method(which is valid for a small, but finite amplitude limit) is employed to derive the nonlinear Schr¨odinger equation. Two types of modes, namely, fast and slow dust-acoustic(DA) modes, have been observed. The conditions for the modulational instability(mI) and its growth rate in the unstable regime of the DA waves are significantly modified by the effects of non-extensive electrons, dust mass, and temperatures of different plasma species, etc. The implications of the obtained results from our current investigation in space and laboratory OPDP medium are briefly discussed.

关键词： dust-acoustic waves opposite polarity modulational instability envelope solitons

Stokes flow before plane boundary with mixed stick-slip boundary conditions

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Applied mathematics and mechanics(English Edition) 2011年第6期32卷 795-804页

作者： n.AKHTAR G.A.H.chowdhury S.K.SEn Department of mathematics Shahjalal University of Science and Technology Research Centre for mathematical and Physical Sciences University of Chittagong

A general theorem for the Stokes flow over a plane boundary with mixed stick-slip boundary conditions is established. This is done by using a representation for the velocity and pressure fields in the three-dimensional Stokes flow in terms of a biharmonic function and a harmonic function. The earlier theorem for the Stokes flow due to fundamental singularities before a no-slip plane boundary is shown to be a special case of the present theorem. Furthermore, in terms of the Stokes stream function, a corollary of the theorem is also derived, providing a solution to the problem of the axisymmetric Stokes flow along a rigid plane with stick-slip boundary conditions. The formulae for the drag and torque exerted by the fluid on the boundary are established. An illustrative example is given.

关键词： Stokes flow Stokes stream function stick-slip boundary conditions,harmonic function biharmonic function

A new approach for accurate determination of particle sizes in microfluidic impedance cytometry

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nanotechnology and Precision Engineering 2022年第4期5卷 8-17页

作者： n.Priyadarshi Usama Ahmed Abbasi V.Kumaran P.chowdhury Department of Chemical Engineering Indian Institute of ScienceBangalore 560012India Pratimesh Laboratory Indian Institute of ScienceBangalore 560012India nanomaterials Research Laboratory Surface Engineering DivisionCSIR–National Aerospace LaboratoriesBangalore 560017India

In microfluidic impedance cytometry,the change in impedance is recorded as an individual cell passes through a channel between electrodes deposited on its walls,and the particle size is inferred from the amplitude of the impedance signal using ***,because the current density is nonuniform between electrodes of finite width,there could be an error in the particle size measurement because of uncertainty about the location of the particle in the channel cross ***,a correlation is developed relating the particle size to the signal amplitude and the velocity of the particle through the *** latter is inferred from the time interval between the two extrema in the impedance curve as the particle passes through a channel with cross-sectional dimensions of 50μm(width)×30μm(height)with two pairs of parallel facing *** change in impedance is predicted using 3D COmSOL finite-element simulations,and a theoretical correlation that is independent of particle size is formulated to correct the particle diameter for variations in the cross-sectional *** this correlation,the standard deviation in the experimental data is reduced by a factor of two to close to the standard deviation reported in the manufacturer specifications.

关键词： Impedance cytometry Lab on chip COmSOL simulation

Intelligent algorithm for optimal meter placement and bus voltage estimation in ring main distribution system

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Frontiers in Energy 2012年第1期6卷 47-56页

作者： L.RAmESH n.CHAKRABORTY S.P.chowdhury Electrical Engineering Department Jadavpur Universitykolkata 700032India Centre for Power Distribution Research Dr.MGRUniversityChermai 600095India Power Engineering Department Jadavpur Universitykolkata 700032India Electrical Engineering Department University ef Cape TownCape Town 7701South Africa

The advancement in power distribution system poses a great challenge to power engineering researchers on how to best monitor and estimate the state of the distribution network. This paper is exe,：uted in two stage processes. The first stage is to identify the optimal location for installation of monitoring instrument with minimal investment cost. The second stage is to estimate the bus voltage magnitude, where real time measurement is conducted and measured through identified meter location which is more essential for decision making in distribution supervisory control and data acquisition system （DSCADA）. The hybrid intelligent technique is applied to execute the above two algorithms. The algorithms are tested with institute of electrical and electronics engineers （IEEE） and Tamil nadu electricity board （TnEB） bench- mark systems. The simulated results proves that the swarm tuned artificial neural network （Ann） estimator is best suited for accurate estimation of voltage with different noise levels.

关键词： artificial intelligence power distribution control state estimation

A modified gas flow model in the near wellbore region below dew point pressure

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Petroleum 2021年第3期7卷 294-302页

作者： Abed Inan chowdhury md mostafijul Karim Department of Petroleum and mining Engineering Chittagong University of Engineering&TechnologyChittagongBangladesh

When pressure in gas reservoirs fall below the dew point,condensate banking occurs around the wellbore which alters the fluid flow *** state of the knowledge on this flow behavior is yet not fully-developed;which leads to severe problems in *** this study,the Al-Hussainy,Ramey,and Crawford Solution Technique has been modified to accurately resemble the real gas flow behavior for this ***,a primary investigation was conducted to observe the severity of the problem in three condensate banked *** this study involved Constant Composition Expansion tests for determining the dew point,Prode Properties software for modeling the reservoir fluid properties,Flowing material Balance(or Dynamic P/Z material Balance)for identifying the pressure distribution of the selected *** real field data along with the determined(analytical,computational,and experimental)data were incorporated to check the validity of the *** modification proposes a Dimensionless Correction Factor(CD)for any condensate banked reservoir and identifies parameters such as the Perforation Factor(Pf)and Heterogeneity Factor(n).It is found that the modified Al-Hussainy,Ramey,and Crawford Solution Technique successfully models the actual flow characteristics of the stated condition.

关键词： Condensate banking Effective permeability Gas flow modeling model fitting