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Rare Metals 2022年第4期41卷 1332-1341页

作者： Majibul Haque Babu Bidhan Chandra Dev Jiban podder Department of Physics Bangladesh University of Engineering and TechnologyDhaka 1000Bangladesh

An investigation of Fe-doping effect on SnO_(2) thin films was performed in this study using thermal spray pyrolysis(TSP) *** surface morphology and structural,optical and electrical properties were studied by field energy scanning electron microscope(FESEM),X-ray diffraction(XRD),ultraviolet-visible(UV-Vis) spectroscopy and four-point probe *** EM images demonstrate that the surface morphology of the as-deposited films varies when Fe-doping content *** studies reveal that crystallite size and preferential growth orientations of the films are dependent on Fe-doping *** grain size is found to decrease with the increase in Fe *** studies also specify that the films have tetragonal rutile-type structure with mixed secondary *** texture coefficient value of(110) plane increases with the concomitant in-plane(220) decrease in higher doping *** resistivity and the optical absorbance are found to increase with Fe *** direct optical band gap decreases from 3.94 to3.52 eV with increasing Fe content.

关键词： SnO_(2)thin film Thermal spray pyrolysis Texture coefficient Optical band gap

Fractional order prey-predator model incorporating immigration on prey:Complexity analysis and its control

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International Journal of Biomathematics 2024年第5期17卷 285-317页

作者： Md.Jasim Uddin Chandra Nath podder Departmentof Mathematics University of Dhaka Dhaka-1000Bangladesh

In this paper,the Caputo fractional derivative is assumed to be the prey-predator *** order to create Caputo fractional differential equations for the prey-predator model,a discretization process is first *** fixed points of the model are categorized *** identify requirements for the fixed points of the suggested prey-predator model's local asymptotic *** demonstrate analytically that,under specific parametric conditions,a fractional order prey-predator model supports both a Neimark-Sacker(NS)bifurcation and a Flip *** present evidence for NS and Flip bifurcations using central manifold and bifurcation *** parameter values and the initial conditions have been found to have a profound impact on the dynamical behavior of the fractional order prey-predator *** the bifurcation parameter is increased,the system displays chaotic *** simulations are shown to demonstrate chaotic behaviors like bifurcations,phase portraits,invariant closed cycles,and attractive chaotic sets in addition to validating analytical *** suggested prey-predator dynamical system's chaotic behavior will be controlled by the OGY and hybrid control methodology,which will also visualize the chaotic state for various biological parameters.

关键词： Prey-predator model Caputo fractional derivative Flip and Neimark-Sacker(NS)bifurcations immigration chaos control numerical simulation

Band gap tuning and p to n-type transition in Mn-doped CuO nanostructured thin films

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Journal of Semiconductors 2022年第1期43卷 59-68页

作者： R.Rahaman M.Sharmin J.podder Department of Physics Bangladesh University of Engineering and TechnologyDhaka 1000Bangladesh

Here we discuss the synthesis of copper(II)oxide(CuO)and manganese(Mn)-doped CuO thin films varying with 0 to 8 at%Mn using the spray pyrolysis ***-deposited film surfaces comprised of agglomerated spherical nanoparticles and a semi-spongy porous structure for 4 at%Mn *** dispersive analysis of X-rays confirmed the chemical composi-tion of the films.X-ray diffraction spectra showed a polycrystalline monoclinic structure with the predominance of the(11)*** band gap energy for direct and indirect transitions was estimated in the ranges from 2.67-2.90 eV and 0.11-1.73 eV,*** index and static dielectric constants were computed from the optical *** resistivity of CuO and Mn-doped CuO(Mn:CuO)thin films was found in the range from 10.5 to 28.6Ω·*** tiniest electron effective mass was calculated for 4 at%Mn:CuO thin films.P to n-type transition was observed for 4 at%Mn doping in CuO *** con-centration and mobility were found in the orders of 10^(17)cm^(-3)and 10^(-1)cm^(2)/(V·s),*** Hall coefficient was found to be between 9.9 and 29.8 cm^(3)/*** above results suggest the suitability of Mn:CuO thin films in optoelectronic applications.

关键词： Mn:CuO spray pyrolysis FESEM XRD band gap Hall effect

Effect of Fe-doping on the structural and optical properties of ZnO thin films prepared by spray pyrolysis

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Journal of Semiconductors 2013年第7期34卷 31-36页

作者： S.M.Salaken E.Farzana J.podder Department of Electrical and Electronic Engineering Bangladesh University of Engineering and TechnologyDhaka-1000Bangladesh Department of Physics Bangladesh University of Engineering and TechnologyDhaka-1000Bangladesh

Fe-doped ZnO thin films have been prepared by spray pyrolysis on glass substrates and the influence of Fe-doping concentration on the structural and optical properties of the films has been *** X-ray diffraction （XRD） analysis shows that Fe doping has a significant effect on crystalline quality,grain size and strain in the thin *** best crystalline structure is obtained for 3 at%Fe doping as observed from scanning electron microscopy （SEM） and ***,lower or higher Fe-doping degrades the crystalline quality in ***,UV spectroscopy demonstrates the influence of Fe-incorporation on visible range transmittance of ZnO where the best transmittance is obtained for 3 at%*** results have been illustrated simultaneously focusing previous results obtained from literature.

关键词： ZnO spray pyrolysis thin films

Dynamics of novel COVID-19 in the presence of Co-morbidity

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Infectious Disease Modelling 2022年第2期7卷 138-160页

作者： Amit Kumar Saha Chandra Nath podder Ashrafi Meher Niger Department of Mathematics University of DhakaDhaka1000Bangladesh

A novel coronavirus(COVID-19)has emerged as a global serious public health issue from December *** having a weak immune system are more susceptible to coronavirus *** is a double challenge for people of any age with certain underlying medical conditions including cardiovascular disease,diabetes,high blood pressure and cancer ***-morbidity increases the probability of COVID-19 *** this paper a deterministic compartmental model is formulated to understand the transmission dynamics of *** mathematical analysis of the model shows that it exhibits backward bifurcation phenomenon when the basic reproduction number is less than *** the case of no re-infection it is shown that having the reproduction number less than one is necessary and sufficient for the effective control of COVID-19,that is,the disease free equilibrium is globally asymptotically stable when the reproduction threshold is less than ***,in the absence of reinfection,a unique endemic equilibrium of the model exists which is globally asymptotically stable whenever the reproduction number is greater than *** simulations of the model,using data relevant to COVID-19 transmission dynamics,show that the use of efficacious face masks publicly could lead to the elimination of COVID-19 up to a satisfactory *** study also shows that in the presence of co-morbidity,the disease increases significantly.

关键词： COVID-19 Co-morbidity Face-mask

Effect of awareness,quarantine and vaccination as control strategies on COVID-19 with Co-morbidity and Re-infection

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Infectious Disease Modelling 2022年第4期7卷 660-689页

作者： Amit Kumar Saha Shikha Saha Chandra Nath podder Department of Mathematics University of DhakaDhaka1000Bangladesh Department of Mathematics Bangladesh University of Engineering and Technology(BUET)Dhaka1000Bangladesh

In this paper,a deterministic compartmental model is presented to assess the impact of vaccination and non-pharmaceutical interventions(social distance,awareness,face mask,and quarantine)on the transmission dynamics of COVID-19 with co-morbidity and *** expression for the basic reproduction number is then derived for this *** analysis shows that the model exhibits backward bifurcation phenomenon when the basic reproduction number is less than *** for the case of no reinfection,the model has a globally asymptotically stable disease-free equilibrium(DFE)when the basic reproduction number is less than ***,it is shown that in the case of no re-infection,a unique endemic equilibrium point(EEP)of the model exists which is globally asymptotically stable whenever the reproduction number is greater than *** the global sensitivity and uncertainty analysis,we have identified mask coverage,mask efficacy,vaccine coverage,vaccine efficacy,and contact rate as the most influential parameters influencing the spread of *** simulation results show that the use of effective vaccines with proper implementation of non-pharmaceutical interventions could lead to the elimination of COVID-19 from the *** simulations also suggest that the control strategy that ensures a continuous and effective mass vaccination program is the most cost-effective control *** study also shows that in the presence of any co-morbidity and with the occurrence of re-infection,the disease burden may increase.

关键词： COVID-19 Co-morbidity Face-mask Quarantine Vaccination Optimal control Re-infection

A Study on Structural, Optical, Electrical and Etching Characteristics of Pure and L-Alanine Doped Potassium Dihydrogen Phosphate Crystals

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Journal of Crystallization Process and Technology 2011年第3期1卷 55-62页

作者： Ferdousi Akhtar Jiban podder 不详

Pure potassium dihydrogen phosphate (KDP) crystals and KDP doped with L-alanine have been grown by slow evaporation technique at room temperature. Grown crystals have been characterized using powder X-ray diffraction, (XRD), Energy Dispersive X-ray spectroscopy (EDX) and Fourier Transform Infrared spectroscopy (FTIR). The presence of L-alanine into pure KDP crystal was confirmed by FTIR and EDX spectra. Crystal structure has been studied by XRD. Pure KDP and L-alanine doped KDP crystals both possessed tetragonal structure. The transparency is found to increase with the increase of doping concentrations of the grown crystals as observed by UV-Vis spectra. A.C. electrical conductivity of grown crystals along the growth axis was carried out at various temperatures ranging from 35?C - 400?C. Dielectric constant and dielectric losses are measured as a function of temperature and this study reveals the contribution of space charge polarization. Crystal defects and surface morphology are studied by dissolution solvent technique and reveals the step growth mechanism for both pure and doped crystals.

关键词： Amino Acid KDP Solution Growth FT-IR Electrical Conductivity Etch Pits

Structural, Optical, Electrical and Thermal Characterizations of Pure and L-alanine Doped Ammonium Dihydrogen Phosphate Crystals

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Journal of Crystallization Process and Technology 2011年第2期1卷 18-25页

作者： Ferdousi Akhtar Jiban podder 不详

Pure ammonium diyidrogen phosphate and L-alanine doped ammonium diyidrogen phosphate crystals were grown from aqueous solutions by natural evaporation process. The grown crystals are characterized by Fourier Transform Infrared spectroscopy, Energy Dispersive X-ray, UV-visible spectroscopy and differential thermal analysis. Crystal structure has been studied by powder X-ray diffraction. Pure and doped crystals both possessed tetragonal structure. The optical transparency is found to increase with the increase of doping concentration in the grown crystals and band gap energies of all crystals have been calculated at their cut off frequencies. It is found that the optical band gap increases with doping concentrations. *** conductivity of grown crystals along the growth axis was carried out at temperatures ranging from 35-140°C by the conventional two-probe method. The conductivity of the crystals increases with temperature and also increases with the L-alanine concentration. The decomposition temperatures and weight loss have been estimated from the Thermo Gravimetric Analysis and Differential Thermal Analysis and hardness was found from the Vicker’s microhardness measurement.

关键词： Amino Acid Solution Growth Decomposition Electrical Conductivity Optical Transmission

Optical and Electrical Properties of Nanocrystalline SnO<sub>2</sub>Thin Films Synthesized by Chemical Bath Deposition Method

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Soft Nanoscience Letters 2015年第4期5卷 55-64页

作者： Suresh Sagadevan Jiban podder Department of Physics AMET University Chennai India Department of Chemical and Biological Engineering University of Saskatchewan Saskatoon Canada

The chemical bath deposition (CBD) technique was used for the synthesis of the tin oxide (SnO2) thin films. X-ray diffraction (XRD) was employed to find the crystallite size by using Debye Scherrer’s formula. The surface morphology of SnO2 films was analyzed by the scanning electron microscopic (SEM) studies. The FT-IR spectrum exhibits the strong presence of SnO2. The optical properties of the SnO2 thin films were determined using UV-Visible spectrum. The dielectric studies were carried out at different frequencies and at different temperatures for the prepared SnO2 thin films. Further, electronic properties, such as valence electron plasma energy, average energy gap or Penn gap, Fermi energy and electronic polarizability of the SnO2 thin films, were determined. The ac conductivity of the SnO2 thin films increases with increase in temperature and frequency. The activation energy was determined by using dc electrical conductivity measurement. The Hall properties were also calculated.

关键词： SnO2 CBD XRD SEM FTIR and Dielectric Studies