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Dhaka, Bangladesh

Daffodil International University , is a co-educational private university located in Dhanmondi, Dhaka, Bangladesh, was established on 24 January 2002 under the Private University Act, 1992.DIU is the first university in Bangladesh to have signed the UN's Commitment to Sustainable Practices of Higher Education Institutions. Wikipedia.

Gronlund A.,Orebro University | Islam Y.M.,Daffodil International University
Information Technology for Development

This paper reports a project working to improve distance education in Bangladesh by means of a low-cost, large-scale interactive learning environment using video, mobile phones, SMS- based tools administered in a learning management system, and innovative pedagogy based on the student-centered learning model. The paper addresses the question of how to use existing mobile telephony technical infrastructure to create interactive learning environments which can reach a majority of the population, be able to include thousands of students, and be sustainable from a resource perspective. This question includes challenges relating to pedagogy and teaching methods, technical tools for learning and communication, and institutional arrangements. The paper addresses these challenges by the illustrative case of the Bangladesh Virtual Interactive Classroom testing the tools and ideas in course at Bangladesh Open University. We find that our tools are feasible and usable but also that sustainability requires meeting organizational and social challenges. © 2010 Commonwealth Secretariat. Source

Hossen M.R.,Daffodil International University | Mamun A.A.,Jahangirnagar University
Plasma Science and Technology

A theoretical study on the nonlinear propagation of nonplanar (cylindrical and spherical) electrostatic modified ion-acoustic (mIA) shock structures has been carried out in an unmagnetized, collisionless four component degenerate plasma system (containing degenerate electron fluids, inertial positively as well as negatively charged light ions, and positively charged static heavy ions). This investigation is valid for both non-relativistic and ultra-relativistic limits. The modified Burgers (mB) equation has been derived by employing the reductive perturbation method, and used to numerically analyze the basic features of shock structures. It has been found that the effects of degenerate pressure and number density of electron and inertial positively as well as negatively charged light ion fluids, and various charging state of positively charged static heavy ions significantly modify the basic features of mIA shock structures. The implications of our results to dense plasmas in astrophysical compact objects (e.g., non-rotating white dwarfs, neutron stars, etc.) are briefly discussed. © 2015, IOP. All rights reserved. Source

Ema S.A.,Jahangirnagar University | Hossen M.R.,Daffodil International University | Mamun A.A.,Jahangirnagar University
Contributions to Plasma Physics

The nonlinear propagation of modified electron-acoustic (mEA) shock waves in an unmagnetized, collisionless, relativistic, degenerate quantum plasma (containing non-relativistic degenerate inertial cold electrons, both nonrelativistic and ultra-relativistic degenerate hot electron and inertial positron fluids, and positively charged static ions) has been investigated theoretically. The well-known Burgers type equation has been derived for both planar and nonplanar geometry by employing the reductive perturbation method. The shock wave solution has also been obtained and numerically analyzed. It has been observed that the mEA shock waves are significantly modified due to the effects of degenerate pressure and other plasma parameters arised in this investigation. The properties of planar Burgers shocks are quite different from those of nonplanar Burgers shocks. The basic features and the underlying physics of shock waves, which are relevant to some astrophysical compact objects (viz. non-rotating white dwarfs, neutron stars, etc.), are briefly discussed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Murad M.H.,Daffodil International University
Astrophysics and Space Science

The paper presents a new class of parametric interior solutions of Einstein-Maxwell field equations in general relativity for a static spherically symmetric distribution of a charged perfect fluid with a particular form of electric field intensity. This solution gives us wide range of parameter, K (0. 69≤K≤7. 1), for which the solution is well behaved hence, suitable for modeling of superdense star. For this solution the gravitational mass of a superdense object is maximized with all degree of suitability by assuming the surface density of the star equal to the normal nuclear density ρnm=2. 5×1017kg m-3. By this model we obtain the mass of the Crab pulsar MCrab=1. 401M⊙ and the radius, RCrab=12. 98 km constraining the moment of inertia INS,38>1. 61 for the conservative estimate of Crab nebula mass 2M⊙ and MCrab=2. 0156M⊙ with radius, RCrab=14. 07 km constraining the moment of inertia INS,38>3. 04 for the newest estimate of Crab nebula mass 4. 6M⊙ which are quite well in agreement with the possible values of mass and radius of Crab pulsar. Besides this, our model yields the moments of inertia for PSR J0737-3039A and PSR J0737-3039B are IA,38=1. 4624 and IB,38=1. 2689 respectively. It has been observed that under well behaved conditions this class of parametric solution gives us the maximum gravitational mass of causal superdense object 2. 8020M⊙ with radius 14. 49 km, surface redshift zR=0. 4319, charge Q=4. 67×1020C, and central density ρc=2. 68ρnm. © 2012 Springer Science+Business Media Dordrecht. Source

Murad M.H.,Brac University | Fatema S.,Daffodil International University
European Physical Journal C

In this work some families of relativistic anisotropic charged fluid spheres have been obtained by solving the Einstein–Maxwell field equations with a preferred form of one of the metric potentials, and suitable forms of electric charge distribution and pressure anisotropy functions. The resulting equation of state (EOS) of the matter distribution has been obtained. Physical analysis shows that the relativistic stellar structure for the matter distribution considered in this work may reasonably model an electrically charged compact star whose energy density associated with the electric fields is on the same order of magnitude as the energy density of fluid matter itself (e.g., electrically charged bare strange stars). Furthermore these models permit a simple method of systematically fixing bounds on the maximum possible mass of cold compact electrically charged self-bound stars. It has been demonstrated, numerically, that the maximum compactness and mass increase in the presence of an electric field and anisotropic pressures. Based on the analytic models developed in this present work, the values of some relevant physical quantities have been calculated by assuming the estimated masses and radii of some well-known potential strange star candidates like PSR J1614-2230, PSR J1903+327, Vela X-1, and 4U 1820-30. © 2015, The Author(s). Source

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