American International University Bangladesh (AIUB)
Kitami Institute of Technology, Japan
The sliding mode control system is able to have a high gain, robust to external and parameter disturbances, and capable to ensure the desired motion dynamics. Since the dynamics of an induction motor can be represented by multi-input and multi-output state space energy model, a multi-input and multi-output sliding mode controller is designed to obtain high-performance speed and torque control of an induction motor based on the energy model. The stability of designed controller is confirmed by satisfying the Lyapunov stability criteria. Since all state variables are not accessible, a full-order observer, whose gains are obtained by using the Lyapunov stability criteria, is also designed to estimate the unmeasured state variables. The effectiveness of the designed controller and observer system are verified by simulation using Matlab/Simulink.
Jadavpur University, India
Jadavpur University, India
Jadavpur University, India
Jadavpur University, India
Rapid progress in the miniaturization of the semiconductor electronic devices leads towards chip features smaller than 100 nanometers in size. This revolution offers opportunities for developing a new generation of device incorporating standard microelectronics with spin-dependent effects arising from the interaction between carrier spin and the magnetic properties of materials. In this paper we attempt to exploit the versatility of burgeoning spin devices in connection with its application in advanced communication systems such as mobile communication as they are motivated by the anticipated low power consumption, higher degree of functionality, increased data processing speed and increased integration densities compared with conventional semiconductor devices. In fact, with “integration” being the buzzword in today’s electronics industry, gone are the days of bulky mobile cellular sets. However mobile communication systems still suffer from several limitations like multi path fading, interference, dependence on weather condition for good reception. Several error correction codes are used to get rid of such errors partially or fully. In the present work such attempt is made to realize a spintronics device based VLSI chips for error correction in wire less cellular communication. Three error correcting algorithms are employed and realized here using spintronic devices to make it power and space efficient.
Jagannath University, Dhaka
Jagannath University, Dhaka
A digital device is proposed herewith on the basis of autocorrelation function (ACF). Such device can measure the properties extracted from the evoked potentials (EP) of the human brain as psycho-biological responses by the concern properties of the physical stimulus around the individual. The ACF is however, a well known signal processor contains four fundamental factors for the digital devices already being used by other scientific fields. The four fundamental factors of the ACF can analyze well the acoustic and visual stimuli as well as the EPs. Evoked potentials are the electrical and electro-magnetic responses can be found by using the electrodes on the particular points of surface over the head. An outline of digital device is going to be proposed in which both the stimuli and the responses will be analyzed simultaneously by an autonomic technique. Correlation should be established between the two measures of ACF in such digital device. A series of studies should be conducted on the basis of such proposals.
American International University Bangladesh (AIUB)
Bangladesh University of Engineering and Technology (BUET)
In this work, two methods of enhancing the bandwidth of a VCSEL have been presented keeping in mind the application of such a laser in high speed data transmission. Enhancement of bandwidth of a VCSEL has been evaluated by obtaining the modulation response through computation of transfer function for different values of frequency. The resonant frequency and the bandwidth of a VCSEL have been increased by increasing the confinement factor and this has been done by increasing the number of quantum wells in the active region and simultaneously by decreasing the length of the separate confinement (SCH) region. It has been observed that by increasing the number of quantum wells from 3 to 5 the value of confinement factor increases from 0.253 to 0.4216. As a result, the resonant frequency of the laser increases from 7.28 GHz to 9.41 GHz. On the other hand, for this increased value of the confinement factor the modulation bandwidth of the laser increases from 11.28 GHz to 14.58 GHz. In condition to this due to the increase of the confinement factor the output power of the laser increases. Due to this the resonant frequency and bandwidth are also found to increase. After computations using MATLAB simulator it has been observed that a maximum output power value of 0.646 mW is observed for a 5 number of quantum wells (computing value of confinement factor = 0.4216). At this value of maximum power a maximum resonant frequency of 9.14 GHz and a maximum bandwidth of 14.16 GHz are obtained. Further computations by varying the number of quantum wells show that by increasing the number of quantum wells frequency modulation (FM) noise decreases. Increasing the linewidth enhancement factor increases the FM noise of a VCSEL.
American International University-Bangladesh (AIUB)
Center for Environmental GIS, Dhaka
Bangladesh University of Engineering and Technology (BUET)
In recent times, several studies around the globe show that climatic change is likely to impact significantly upon freshwater resources availability. Demand for water has already increased manifold over the years due to urbanization, agriculture expansion, increasing population, rapid industrialization and economic development. At present, changes in cropping pattern and land-use pattern, over-exploitation of water storage and changes in irrigation and drainage are modifying the hydrological cycle in many climate regions and river basins. This paper examines changes of water requirement due to climate change. The objective of this study was to determine the impacts of potential climate change on daily total Crop Water Requirements (CWR) of major crops in local area of Bangladesh using CROPWAT model in conjunction with the climate scenarios. The climate parameters of temperature, precipitation, relative humidity, sunshine duration and wind speed were used in CROPWAT model for calculating Evapotranspiration and to simulate the total CWR for the present and the future years. Results compared to the base climate show an increase in crop water requirements in 2050 and 2070. Under current climate conditions, the average reference evapotranspiration (ETo) is 3.26 mm /day which will rise 3.39mm/day in 2050 and 3.5 mm/day in 2070 which indicates average. ETo will be 4.17 % more in 2050 and 7.49% higher in 2050 than that of the base climate condition at present. In addition, CWR of major season growing crop will also increase about 3%-4% and 6%-8%in 2050 & 2070 respectively.
American International University - Bangladesh (AIUB)
Bangladesh University of Engineering and Technology (BUET)
In this paper, the reflecting mirrors of a Vertical Cavity Surface Emitting Laser (VSCEL) have been formed by arranging the Distributed Bragg Reflector (DBR) layers in four different ways to explore new ways of forming such lasers. Using such DBR based VCSEL the effect of external feedback is shown. Using Sampled Transfer Matrix Method (STMM), the amount of optical feedback inside a VCSEL from the external reflector has been computed. Four different arrangements of DBR mirror including traditional quarter wavelength thick HIGH and LOW refractive index DBR were used to compute the performance parameters of the VCSEL. The variations of threshold current, differential quantum efficiency and output power due to different positions of the external reflector have been computed for four of the above mentioned different VCSELs. For each case the computed results were compared with the theoretical and experimental results obtained by other researchers. Good agreements have been observed.
American International University Bangladesh (AIUB)
American International University Bangladesh (AIUB)
Bangladesh University of Engineering and Technology (BUET)
In this work, the output power of a VCSEL is calculated by solving the rate equations using MATLAB. The chirp of a VCSEL is calculated using the values of carrier density obtained after solving the rate equations. The effects of variation of injection current, differential gain and linewidth eanhancement factor on the chirp characteristics of a VCSEL are then evaluated and the obtained results are presented as plots. Values of chirp are calculated for short wavelength and long wavelength VCSELs. It has been observed that the effect of chirp is more dominant in the case of long wavelength VCSELs compare to short wavelength VCSELs.
American International University Bangladesh (AIUB)
It is people that make architecture alive. It is motion that captures our attention. Together they make our architectural environment believable. Besides portraying a friendly environment, digital people can portray the best reference for scale, time, location and character of an environment.
Representing architecture along with human figures has always been an integral aspect of architectural representation in traditional media. As we moved from traditional representation to animated 3D digital modeling, representation of people lost its spirit. Perhaps the reason for this is that a great deal of time and energy needed to be dedicated to the development of human figures. In addition, defining movements and poses for each figure requires additional skills. The aim of this paper is to explore the options of simulating people in the context of environmental design as well as to provide simplified techniques for representations of people in 3D digital animation.
American International University Bangladesh (AIUB)
Similarity solution of an unsteady MHD laminar combined convective boundary layer incompressible flow for a vertical porous plate with the effects of time dependent suction/injection velocity, viscous dissipation and variable fluid properties ( viscosity ( ) and thermal conductivity ( )) has been studied under the action of transverse applied magnetic field. The boundary layer equations have been transformed into dimensionless nonlinear ordinary differential equations by similarity transformations. The nonlinear ordinary differential equations are then solved numerically by using Range-Kutta six order integration scheme and Nachtsheim-Swigert iteration technique. The obtained numerical results are presented graphically in the form of velocity and temperature. Finally the effects of the relative temperature difference parameter on the skin friction and heat transfer coefficients are also examined.
American International University Bangladesh (AIUB)
American International University Bangladesh (AIUB)
Jahangirnagar University, Savar, Dhaka
The feasibility of U-free fuels is studied for transmuting neptunium-237 (237Np) nuclide in a light water reactor (LWR). The 237Np transmutation capability of a typical mixed oxide fuel (MOX: PuO2+UO2) fueled LWR is considered as reference. As U-free fuel, rock-like oxide (ROX: PuO2+ZrO2) and thorium oxide (TOX: PuO2+ThO2) are considered, in which corresponding 237Np isotope as oxide form are added to fuel for transmutation. The transmutation effects of 237Np on the Pu transmutation as well as on the ingestion radiotoxicity hazard indexes of spent fuels are investigated for the once-through fuel cycle scheme. It was found that the transmutation performance of 237Np is very high in a ROX+Np fueled LWRs than that in a TOX+Np or MOX+ Np fueled LWRs. Also, the net Pu transmutation of ROX+Np fueled LWR is higher than that in a TOX+Np and MOX+Np fueled LWRs. As a result, the toxicity yield of Np burning ROX spent fuel is less than that of Np burning TOX and MOX spent fuels. By considering the transmutation capability and their associated hazard in spent fuel, ROX fuel is recommenced for once through burning of 237Np in a LWR.
American International University Bangladesh (AIUB)
University of Dhaka
University of Dhaka
The density of states for binary alloys of Fe based noble metals and FeNi alloys are calculated using the tight binding linear muffin-tin orbital (TB-LMTO) method. The recursion technique is adopted to solve the LMTO equations in real space and the augmented space formalism is used for averaging over the random distribution of constituents in the alloys. The density of states of FeNi, AuFe, AgFe, and CuFe binary alloys are obtained for 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80% and 90% concentrations of Fe. The results show that the method is reasonably accurate and computationally efficient for calculating the electronic structure of metallic system and alloys based on noble metals and metallic ion.
University of Dhaka
Scanning tunneling microscopy (STM) and current imaging tunneling spectroscopy (CITS) were carried out on [2×2] Co4II Grid-Type Supramolecular metal ion nanoarchitectures to achieve topographic as well as spatially resolved electronic structural information at the single molecule level. CITS is the one of the common methods of scanning tunneling spectroscopy (STS). One- and two-dimensional arrangements as well as single molecules of the compounds were observed in STM topography, preferably at the step edges of the highly oriented pyrolytic graphite (HOPG) surfaces. The size of the individual molecules was confirmed by comparison with x-ray crystallographic data. In the CITS images of single molecules a strong tunneling current contrast at the positions of the metal ions was observed. These data can be interpreted by the fact that the bonds coordinating the metal ions are weaker than the ones of the surrounding ligands; therefore the energy levels next to the Fermi energy of the molecule should be dominated by metal ion orbitals. This interpretation is consistent with density-functional theory calculations (DFT) that predict a nearly exclusive contribution of metal 3d orbitals near the Fermi energy, i.e. in all cases the highest occupied molecular orbitals (HOMO) and the lowest unoccupied molecular orbitals (LUMO) are dominated by transition metal 3d orbitals.
American International University Bangladesh (AIUB)
American International University Bangladesh (AIUB)
A simplified analytical model for the calculation of the Signal-to-Noise Ratio (SNR) in Multi Wavelength Erbium-Doped Fiber Amplifier (EDFA) cascades is used to observe the effect of different wave length’s light sources on SNR. In this work, the wavelengths chosen for the analysis is 1330 nm and 1550 nm. It has been found that the SNR for 1550 nm is higher than 1330 nm wavelength. The effect of changing the amplifier spacing on SNR has been observed for fixed transmission length with different Gain-Loss differences ((i)) and for different transmission lengths. For a 3000 km long transmission line with gain-loss difference (i) = -0.15 dB, maximum SNR of 20.45 dB for 1550 nm wavelength and 19.8 dB for 1330 nm wavelength light sources has been found. These maximum SNRs occur for the amplifier spacing of 44.8 km. Maximum amplifier spacing to obtain a fixed SNR (15 dB) for different (i) and variable transmission lengths has also been observed for 1330 nm 1550 nm.
Rajshahi University of Engineering & Technology (RUET), Bangladesh.
This paper presents the comparison between the novel control strategies of SMES with the aid of self-tuned Fuzzy Frequency (FF) controller and Fuzzy Gain Scheduled (FGS) controllers associated with the Automatic Generation Control (AGC). The proposed self-tuning control schemes are used to implement the AGC adding to conventional control configuration for improving Load Frequency Control (LFC) of single area power system. The effects of the self-tuning configuration with FF controller in AGC on SMES control is also compared with that of PI controlled AGC. The effectiveness of the SMES control technique is investigated when frequency deviation (f) is used as the control input to SMES. The computer simulation of the single-area isolated power system shows that both self-tuning FF control scheme and FGS control scheme of AGC are very effective in damping out of the oscillations caused by load disturbances and it is also seen that the FF controlled AGC with SMES perform more effective primary frequency control compared to FGS controller on AGC with SMES.
