Authors:Mitali Biswas, Mehnaz Sharmin, Chitra Das, Jibon Poddar, Shamima Choudhury Pages: 1 - 6 Abstract: Pure and magnesium (Mg) doped zinc oxide (ZnO) thin films were prepared onto clean glass substrate by spray pyrolysis (SP) technique at the substrate temperature of 300°C. Various optical parameters such as absorption co-efficient, band gap energy, refractive index, extinction coefficient of the thin films were studied using UV-VIS-NIR spectrophotometer in the photon wavelength range of 300-2500 nm. Optical band gap increased from 3.24 to 3.46 eV with the increase of Mg concentration from 0 to 40%. Transmittance and refractive index of the Mg doped ZnO thin films decreased due to the increase of Mg concentration. The EDX spectra confirmed the increase of Mg and consequent reduction in Zn content in the Mg doped ZnO thin films. Pure and Mg- doped ZnO films were annealed at 425°C for 1 hour. X-ray diffraction (XRD) study of the annealed films showed hexagonal type of polycry-stalline structure with the preferred orientation along (101) plane with some other peaks (100), (002), (102), (110), (103) and (112). From the XRD patterns it was found that grain size decreased from 63.45 to 36.56 nm, lattice constant _ and c remained almost constant with Mg doping concentration.Dhaka Univ. J. Sci. 64(1): 1-6, 2016 (January) PubDate: 2016-06-28 Issue No:Vol. 64, No. 1 (2016)

Authors:Onic Islam Shuvo, Md Naimul Islam Pages: 7 - 13 Abstract: One of the major problems with Electrical Impedance Tomography (EIT) is the lack of spatial sensitivity within the measured volume. In this paper, sensitivity distribution of the tetrapolar impedance measurement system was visualized considering a cylindrical phantom consisting of homogeneous and inhomogeneous medium. Previously, sensitivity distribution was analysed analytically only for the homogeneous medium considering simple geometries and the distribution was found to be complex1,2. However, for the inhomogeneous volume conductors sensitivity analysis needs to be done using finite element method (FEM). In this paper, the results of sensitivity analysis based on finite element method using COMSOL Multiphysics simulation software are presented. A cylindrical non-uniform, inhomogeneous phantom, which mimics the human upper arm, was chosen to do the experiments by varying different parameters of interest. A successful method for controlling the region of interest was found where the sensitivity was maximum. Refining the finite element mesh size and introducing multifrequency input current (up to 1 MHz) this simulation method can be further improved.Dhaka Univ. J. Sci. 64(1): 7-13, 2016 (January) PubDate: 2016-06-28 Issue No:Vol. 64, No. 1 (2016)

Authors:Molla Manjurul Islam, Naimul Islam Pages: 15 - 20 Abstract: The Hodgkin-Huxley model is the first successful mathematical model for explaining the initiation and propagation of an action potential in a neuron cell. In this paper we reinvestigated the Hodgkin-Huxley model through computer simulation and determined the threshold potentials by applying different types of stimulating input signals. To implement the work, a computer programme of the Hodgkin-Huxley model was written in MATLAB programming language. The action potentials of neuron cells were checked and the threshold potentials of the neuron cell for specific types of stimulating input signals were tabulated with an aim to utilize these values to do experiment on neuron cell in future.Dhaka Univ. J. Sci. 64(1): 15-20, 2016 (January) PubDate: 2016-06-28 Issue No:Vol. 64, No. 1 (2016)

Authors:Farzana Chowdhury, Jahida Gulshan Pages: 21 - 24 Abstract: In Bangladesh, drowning is the single leading cause of death among children aged 1 to 17 years. With a view of measuring the drowning of under 18 children in Bangladesh, this paper attempts to analyze different factors responsible for drowning by using the MICS 2006 data. Bivariate analysis is employed to examine the factors related to drowning and logistic regression model is used to determine the contribution of different significant factors to drowning. This study found that divisions, residing in flood prone area or riverbank and wealth index have significant association with drowning. Children residing in flood prone area and riverbank have greater risk of drowning as compared to their counterparts.Dhaka Univ. J. Sci. 64(1): 21-24, 2016 (January) PubDate: 2016-06-28 Issue No:Vol. 64, No. 1 (2016)

Authors:Milton C Das, Rajib Biswas, Humaiara Akter, MA Haque, PK Bakshi, AA Shaikh Pages: 25 - 30 Abstract: Electrochemical studies on the interaction of Fe(III) with proton pump inhibitors (PPIs) (omeprazole, pantoprazole, esomeprazole and rabeprazole) in acetate buffer solution were carried out at gassy carbon electrode (GCE) at various pH (3.5, 4.0 and 4.5). In presence of omeprazole (Ome), the anodic and cathodic peak current for Fe(III) decreased in comparison to solely Fe(III). However, in some cases both the peaks were almost disappeared. Moreover, anodic and cathodic peaks shifted significantly towards negative potential. This is an indication that a strong interaction occurred between Fe(III) and Ome. The maximum interaction is found at 1:2 molar ratio of Fe(III) and Ome at above mentioned pH. The electrochemical interaction of Fe(III) and other PPIs was found as identical with the behavior of Ome. The electrochemical study of the interactions between metal ions and PPIs would provide important information for the technological application of PPIs in human body.Dhaka Univ. J. Sci. 64(1): 25-30, 2016 (January) PubDate: 2016-06-28 Issue No:Vol. 64, No. 1 (2016)

Authors:Roushanara Begum, MZI Bangalee Pages: 31 - 37 Abstract: Effects of different boundary conditions at the surfaces of the extended computational domain on buoyancy driven natural convection flow in a three dimensional open cavity are studied numerically. This study is carried out for turbulent flow where Rayleigh number is greater than 108. Air is used as working fluid having properties at 25°C temperature and 1atm pressure. To capture the turbulent nature of the flow k - ε model is used. ANSYS CFX software is used to solve the governing equations subject to the corresponding boundary conditions. The methodology is verified through a satisfactory comparison with some published results. Average mass flow, temperature, stream line, contour velocity and velocity profile are studied at different height. An extended computational domain around the physical domain of the cavity at different surrounding conditions is considered to investigate the effect of its existence on the computation. Effects of different surrounding boundary conditions on the physical domain of the cavity are studied and reported.A relation among non-dimensional parameters such as Nusselt number, Rayleigh number, Prandlt number and Reynolds number is also reported.Dhaka Univ. J. Sci. 64(1): 31-37, 2016 (January) PubDate: 2016-06-28 Issue No:Vol. 64, No. 1 (2016)

Authors:Rezvi Shahariar, Abu Naser, Riham Morsed Pages: 39 - 44 Abstract: Mobile ad hoc network is a temporary wireless network consisting of mobile nodes. Frequent route breakage is a common event in Every node is equipped with battery energy. This form of energy is one of the scarce resources in MANET. This paper is focused on promiscuous mode to observe packets coming from the nodes within a direct transmission range. At the same time critical energy of a routing node is used to find the low energy node on an ongoing route. This low energy node will perform local route repairing scheme such as QLR-APM to find alternate node of low energy node which avoids route breakage in MANET. This approach prevents route breakage and the same time packet loss and retransmission of packets are reduced in MANET. Thus it is easily seen that QLR-APM incorporating this proposed approach outperforms than QLR-APM.Dhaka Univ. J. Sci. 64(1): 39-44, 2016 (January) PubDate: 2016-06-28 Issue No:Vol. 64, No. 1 (2016)

Authors:Sajal Chakroborty, M Babul Hasan Pages: 45 - 50 Abstract: In this paper, we develop a new technique for solving transportation problems (TP) and develop a computer code by using mathematical programming language AMPL. There are many existing techniques for solving TP problems in use. By these techniques one has to determine initial basic feasible solution at first then improve this solution to determine optimal solution by another method. But this process is very lengthy and time consuming. By our technique we can determine optimal solution directly without determining initial basic feasible solution and optimal solution separately and we hope that this technique will provide an easier way than that of the other methods. We use the idea of decomposition based pricing (DBP) method to develop our technique. To our knowledge, there is no other paper which used DBP to solve TP. We demonstrate our technique by solving real life models developed by collecting data from a business organization of Bangladesh.Dhaka Univ. J. Sci. 64(1): 45-50, 2016 (January) PubDate: 2016-06-28 Issue No:Vol. 64, No. 1 (2016)

Authors:M Asadujjaman, M Babul Hasan Pages: 51 - 58 Abstract: In this paper, a new method namely, objective separable method based on Linear Programming with Bounded Variables Algorithm is proposed for finding an optimal solution to a Quasi-Concave Quadratic Programming Problems with Bounded Variables in which the objective function involves the product of two indefinite factorized linear functions and the constraint functions are in the form of linear inequalities. For developing this method, we use programming language MATHEMATICA. We also illustrate numerical examples to demonstrate our method.Dhaka Univ. J. Sci. 64(1): 51-58, 2016 (January) PubDate: 2016-06-28 Issue No:Vol. 64, No. 1 (2016)

Authors:NC Roy, MN Firoza, AK Halder Pages: 59 - 64 Abstract: This paper concerns the unsteady mixed convection laminar boundary layer flow past a vertical wedge in the presence of thermal radiation. The governing equations have been solved by the straightforward finite difference method for the entire frequency range. We observe that the Richardson’s number, Ri, strongly affects the skin friction, heat transfer and mass transfer. The effect of the Schmidt number, Sc, on the mass transfer is significant, whereas the skin friction and the heat transfer are almost unaffected by it. Also the heat transfer is considerably dependent on the conduction-radiation parameter, Rd, but the influence of this parameter on the skin friction and the mass transfer is rather weak.Dhaka Univ. J. Sci. 64(1): 59-64, 2016 (January) PubDate: 2016-06-28 Issue No:Vol. 64, No. 1 (2016)

Authors:NC Roy, P Akther, AK Halder Pages: 65 - 70 Abstract: The flow an heat transfer on the unstea y laminar mixe convection boun ary layer in a micropolar flui past a vertical we ge have been stu ie taking into account the effect of magnetic fiel . We assume that the free stream velocity an surface temperature oscillate in magnitu e but not in the irection of the oncoming flow velocity. The governing equations have been solve numerically by using the straight forwar finite ifference metho . The amplitu es of skin friction an couple stress are foun to be significantly epen ent on the Richar son’s number, Ri, the magnetic parameter, M, an the vortex viscosity parameter, K. We observe that the amplitu es of skin friction an couple stress increases owing to an increase of the Richar son’s number, Ri, while these become lower for the higher value of the magnetic parameter, M, an the vortex viscosity parameter, K. Also the results emonstrate that the effects of the parameters on the amplitu es of heat transfer are rather weak. Dhaka Univ. J. Sci. 64(1): 65-70, 2016 (January) PubDate: 2016-06-28 Issue No:Vol. 64, No. 1 (2016)

Authors:Enayet Hossain, Shamima Choudhury, DK Saha, MA Hakim Pages: 71 - 75 Abstract: The effect of annealing condition on nanocrystalline amorphous FINEMET type of alloy with nominal composition Fe74Cu1.5Nb2.5Si12B10 prepared by rapid solidification method has been studied to observe the structural properties and crystallization behavior of the material. Nanocrystalline alloy with ferromagnetic bcc nanocrystals with size 15-29 nm embedded in a residual amorphous matrix was produced from amorphous precursor by appropriate annealing condition. The amorphosity of the material, primary crystallization temperature, the nanometric grain size, Si content and the lattice parameter of Fe(Si) nano-phase have been determined from XRD patterns of the samples annealed at different temperatures ranging from 475°C - 650°C with annealing time 5, 12, 20 and 30 minutes. The annealing temperature 475°C (with annealing time of 12 minutes) was determined as primary crystallization temperature with grain size 15 nm, Si content 16.25 at.% and lattice parameter 2.8431 Å. The grains were found to grow rapidly after 550°C attaining a maximum value of 29 nm at the annealing temperature of 650°C. The grain size and Si content increase whereas the lattice parameter decreases with the increase of annealing temperature and time.Dhaka Univ. J. Sci. 64(1): 71-75, 2016 (January) PubDate: 2016-06-28 Issue No:Vol. 64, No. 1 (2016)

Authors:M Alauddin, MM Islam, MK Hasan, T Bredow, MA Aziz Pages: 77 - 81 Abstract: The structural, spectroscopic (IR, NMR and UVis) UV-Vis) and optical properties of adenine (6-aminopurine, C5H5N5) are investigated theoretically using HF/DFT hybrid approach B3LYP. The calculated results are compared with available experimental data. The optimized bond distances and bond angles are converged within ±0.01 Å and ±0.8° with respect to the experimental values. The investigation of1H NMR chemical shift spectra of the aromatic C-H protons shows that the maximum deviation of the calculated chemical shift is ~ 0.53 ppm compared to the experimental data. The calculated vibrational spectra analysis shows four distinct IR active mode of vibrations which are assigned as scissoring vibration of –NH2, symmetric stretching vibration of, –NH2, free –NH vibration and anti-symmetric stretching vibration of–NH2, respectively The electronic and optical properties are calculated by Time Dependent Density Functional Theory (TD-DFT) approach. A reasonable agreement is obtained for the calculated optical absorption energy with the experimental value. Dhaka Univ. J. Sci. 64(1): 77-81, 2016 (January) PubDate: 2016-06-28 Issue No:Vol. 64, No. 1 (2016)

Authors:Nilufar Nahar, AKM Ahsan Habib, SM Mizanur Rahman, Tofail Ahmed Chowdhury Pages: 83 - 88 Abstract: Arabinogalactan and rhamnogalactglucuronan were isolated from soluble dietary fiber (SDF) of cauliflower. The isolated SDF was fractioned into neutral and acidic parts by ion-exchange column chromatography using DEAESepharose Cl-6B gel. Structure elucidation of the isolated SDF polysaccharides were determined sugar analysis, 1HNMR, H-H COSY and TOCSY spectroscopic studies. Neutral fraction of cauliflower was found to be composed of galactose, arabinose and rhamnose whereas the acidic part was found to contain rhamnose, galactose, galacturonic and glucuronic acids. The main chain of the neutral fraction was found to be a 1,4-β-galactan where terminal rhamnose and arabinose residues were attached to the main chain at the 3-position of by α-linkage.The main chain of the acidic fraction was composed of 1,4-b-linked galacturonic acid and 1,2-b-linked rhamnopyranose residues. α- Glucuronic acid and α-galactose were attached to the main chain of galacturonic acid at its 3-position.Dhaka Univ. J. Sci. 64(1): 83-88, 2016 (January) PubDate: 2016-06-28 Issue No:Vol. 64, No. 1 (2016)