Bangladesh University of Engineering & Technology
American International University of - Bangladesh [AIUB]
Higher rank coals, coal-tar pitches and poiynuclear aromatic compounds are characterised by their transition through a mesophase as precursor to graphitization. During mesophase, all planar aromatic molecules become aligned in a parallel array to form an optically anisotropic liquid crystal. Differential thermal analysis has been employed as a novel technique for detecting the graphitizability of the carbonaceous substances as well as the lifetime of the mesophase. An initial large endothermic process of transformation with effective activation energy of the order of 60 kcaL/mole or above has been found for graphitizing carbon. Graphitizing carbons are found relatively soft, brilliant black, high apparent density, rich in hydrogen or low in oxygen, nitrogen and sulphur and possess low micro-porosity. The recently discovered Khalaspir coal of north-western Bangladesh has been found as higher rank of medium volatile bituminous with low moisture, ash, sulphur content according to ASTM standard method. This medium volatile coal having high free swelling index 7.5 possesses mesophase transition and ultimately leading to graphitization. Mesophase transition is quantitatively observed by the differential scanning calorimetric study. The total enthalpy (AFT) involved in this mesophase transformation has been calculated from the endothermic peak area of the DSC trace. From proximate, ultimate, thermal and Vicker's microhardness studies, Khalaspir coal of northwestern Bangladesh has been identified as graphitizing carbon.
Kanazawa University, Japan
Kanazawa University, Japan
Sharp Corporation, Japan
We investigate in this paper a self-pulsating operation at room temperature for InGaN laser emitting at 395nm wavelength. The laser structure consists of a multi-quantum well InGaN active layer and a p-type InGaN single quantum well saturable absorber. Self-pulsations with a frequency range from 1.6GHz to 2.9GHz have been obtained. The results show a good agreement between measured and calculated characteristics of the self-pulsation. We have also investigated the influence of device and material parameters on the laser dynamics.
American International University-Bangladesh [AIUB]
A mathematical model has been developed to assess the radiation doses to an individual member of the public due to radiations which may be released from the primary and secondary containment barrier of a Pressurized Water Reactor (PWR) following a loss of coolant accident (LOCA). It appears that the presence of a secondary containment structure around the primary containment of a PWR is very effective in reducing radiation doses to the environment. Performance of the secondary containment has also been studied as a function of leakage rate of its contained radioactivity. It is observed that even a secondary containment which may be leaking at the rate of 100% of its contained radioactive gas per day is capable of reducing the radiation dose to the public by about 98% and 88% after one hour and ten hours of the accident respectively. Whole-body dose and thyroid dose calculated at distances between 500 m and 30 km are reported for the first ten hours of the accident.
Kanazawa University, Japan
Kanazawa University, Japan
A ness theoretical model to analyze operation and noise characteristics of semiconductor lasers under arbitrary strength of optical feedback ranging from weak to strong is presented. Influence of intrinsic fluctuations in the intensity and optical phase of the lasing field on the laser dynamics is taken into account. The results showed that the operation of semiconductor lasers is classified into continuous wave (CW), chaotic, and pulsing operations depending on the operating conditions. Under strong optical feedback, we predicted for the first time pulsing operation of lasers at injection currents well above the threshold. Counting the intrinsic fluctuations was found to reduce the OFB-induced instabilities so as to bring the laser faster to its steady state operation. The optical feedback noise is found to be as low as the quantum noise level when the laser is injected well above its threshold level.
American International University Bangladesh [AIUB]
American International University Bangladesh [AIUB]
Ad Hoc network is a collection of independent mobile nodes that are capable of communicating with each other without any requirement of wired infrastructure. In this type of network as the nodes are free to move, it is very much required to have an efficient and correct algorithm to discover as well as to maintain the path from source to destination node through intermediate nodes (if required). This article examines route discovery and path maintenance due to link breakage and movement of source and destination nodes of different source-initiated on-demand routing protocols and proposes a different approach of path maintenance using backtracking.
Engineering University Higher Secondary School, Dhaka
Bangladesh University of Engineering and Technology [BUET]
The formation constants (logK ZAL of some mixed ligand complexes of the type MAL,where M = Cu(II), Ni(II) ; A = PA; and L = oxalic acid (ox), ethylenediamine (en), glycine (gly), phenylalanine (ph-ala), tryptophane (tryp) and tyrosine (tyr), were determined by using computer programme. The ionic strength of complex solutions (II = 0.2M) and temperature (25°C) were kept constant.
American International University - Bangladesh [AIUB]
University of Dhaka
The present paper investigates the effects of temperature dependent viscosity on an unsteady flow of an incompressible electrically conducting fluid on a rotating disc in presence of uniform magnetic field. The induced magnetic field is neglected. The fluid viscosity is assumed to be an inverse linear function of temperature. The system of axisymmetric non-linear partial differential equations governing the unsteady flow and heat transfer are written in cylindrical polar coordinates, and reduced to non linear ordinary differential equations by introducing suitable similarity parameters. Numerical solutions are obtained by using Runge-Kutta and Shooting method. The nature of radial, tangential and axial velocities and the temperature profiles are shown for changing viscosity parameter and magnetic interaction parameter at different layers of the medium. The coefficients of skin frictions and the rate of heat transfer are also calculated at different viscosity parameter (s), rotational parameter R and magnetic interaction parameter M.
American International University - Bangladesh [AIUB]
We investigate many-body correlation effects and tunnel couplings on the ground state electronic structure of quasi two-dimensional square shaped quantum dot systems by employing the spin density functional theory. Three different sizes of laterally coupled quantum dots are considered to examine the size effects on electronic structures, which originate from electron-electron interaction. By varying interdot separation parameter, we examine the effects of tunnel coupling upon ground state electronic and charging properties. The ground state eigenvalues, charge densities, variation of spin configurations, additional energy spectra and chemical potential at strong, intermediate and weak coupling regimes are calculated. The calculated results are analyzed to examine role of many-body effects and single electron tunneling in coupled dot systems.
Bangladesh Agricultural University, Mymensingh
Shizuoka University, Shizuoka, Japan
American International University of - Bangladesh [AIUB]
Fullerene species are produced by the JxB arc discharge method. This method has an advantage over the conventional arc discharge method. Produced carbon soot by this method are extracted by xylene, toluene, pyridine, carbon disulfide and 1, 2, 4 trichlorobenzene (TCB). Among them TCB is better solvent for the extraction of all fullerenes.
Jahangirnagar University Savar, Dhaka
Stereo correspondence is a basic task in computer or robot vision. It is applied in numerous applications, such as the determination of three- dimensional depth information of objects for virtual reality, autonomous vehicle and robot navigation by using a pair of left and right images from a stereo camera system. These applications require a very fast estimation of dense stereo correspondence. The intensity of a pixel alone in the left image does not have sufficient discriminatory power to determine its correspondence uniquely from the right image, thus other pixels in its neighborhood comprising a window is used for more accurate estimation. In the window-based approaches, the correspondence is conventionally determined based on matching windows of pixels by using sum of square differences, sum of absolute differences, or normalized correlation techniques. From the viewpoint of reducing the computation time, a fast algorithm is proposed in this paper where it is not necessary to compute the window costs for all candidate pixels in the right image within the search range. To determine the correspondence of a pixel in the left image we just compute the window costs for candidate pixels in the right image whose intensities are different within a certain range to the intensity of the pixel in the left image. The usefulness of the proposed technique is verified with the help of standard stereo images and the results show that we can easily reduce the computation time of about 30% with no appreciable degradation of accuracy.
