Rajshahi University of Engineering and Technology

Rajshahi, Bangladesh
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Razzak M.A.,Rajshahi University of Engineering and Technology
Alexandria Engineering Journal | Year: 2017

In this paper, a new noble modified iterative method is proposed to obtain the approximate solution of strongly nonlinear oscillator systems having a rational and an irrational forces. The approximate frequency and the corresponding periodic solution can easily be determined by the present proposed method. Two examples are considered to illustrate the effectiveness and convenience of this procedure. The results obtained in this paper show good agreement with the corresponding numerical solution (considered to be exact) for both small and large amplitudes of oscillation. Furthermore, the method provides better result than other existing results (those results obtained by several authors). The main advantage of the present method is its simplicity which contains up to third harmonic terms. These harmonic terms make the solution rapidly converge. The method is important and powerful for solving nonlinear oscillator systems arising in nonlinear science and engineering. © 2017 Faculty of Engineering, Alexandria University.

Basak D.,Rajshahi University of Engineering and Technology
ICECTE 2016 - 2nd International Conference on Electrical, Computer and Telecommunication Engineering | Year: 2017

Glass lasers are one type of solid state laser that uses glass as gain medium where active ions (Nd3+, Er3+ Ho3+, Tm3+ etc.) are doped. Materials for laser operation must possess sharp fluorescent lines, strong absorption bands, and reasonably high quantum efficiency for the fluorescent transition of interest. These characteristics are generally shown by solids (crystals or glass) which incorporate in small amount of elements in which optical transitions can occur between states of inner, incomplete electron shells. Thus the transition metals, the rare earth (lanthanide) series, and the actinide series are of interest in this connection. For this paper Nd:glass is of interest that shows inhomogeneous broadening. For inhomogeneous broadening central frequency is shifted due to local variation of electric field and thus gain reduces as gain is inversely to line width. But in case of homogeneous broadening each atom response in an identical fashion causes line broadening. However, this broadening is much less than inhomogeneous broadening and affect gain profile less severely. On the other hand, if the glass structure can be crystallize by external parameter like temperature, pressure etc. than local field variation will be compensated and we might reach to homogeneous broadening. © 2016 IEEE.

Islam S.,Rajshahi University of Engineering and Technology
2016 3rd International Conference on Electrical Engineering and Information and Communication Technology, iCEEiCT 2016 | Year: 2017

Wind energy is widely considered as a major source of clean energy. As such, wind turbines are becoming popular in the renewable energy world. The output of the wind turbine varies with randomly changing speed of the wind. This is a critical problem for wind turbines in general, and fixed speed wind generators in particular. However, conventional pitch controllers and governor control systems are not capable enough to keep the power system frequency to the expected stage. By using variable reference line power in pitch controller of wind turbine, frequency fluctuation can be minimized significantly. In this paper, we propose PITCHY, a novel pitch controller to minimize output frequency of wind turbines. PITCHY minimizes frequency fluctuation by generating reference power using low pass filter (LPF). We design a simulation model and evaluate PITCHY using PSCAD/EMTDC. We used a number of wind (induction) generators having varying governor control systems in our simulation. The results show that using PITCHY power system frequency fluctuation can be varied from 49.9 to 50.1 Hz. © 2016 IEEE.

Amin A.,Rajshahi University of Engineering and Technology
2016 3rd International Conference on Electrical Engineering and Information and Communication Technology, iCEEiCT 2016 | Year: 2017

Heterojunction structure CdS/CdTe solar cell has long been regarded as one auspicious choice for the development of the renewable energy sector. CdS/CdTe tandem solar cell with addition of Electron Transport-Hole Blocking Layer (ET-HBL) on the Cadmium Sulfide (CdS) window layer has been simulated using One-Dimensional Device Simulation Program for Analysis of Microelectronic and Photonic Structures (AMPS-1D) in this simulation model. The band diagram of the solar cell has been obtained at the thermodynamic equilibrium condition, & electron current & hole current density are also observed at short circuit & under AM 1.5G light illumination. The hole density of CdTe has tremendous effect on the efficiency of solar cell. The maximum efficiency of 36.908% has been achieved by varying the hole density of CdTe. The performance parameters of the CdS/CdTe solar cell with ET-HBL are compared with the without ET-HBL. © 2016 IEEE.

Mustafi N.N.,Rajshahi University of Engineering and Technology | Raine R.R.,University of Auckland | Verhelst S.,Ghent University
Fuel | Year: 2013

Among the different efforts towards the reduction in pollutant emissions from direct injection (DI) diesel engines, the use of gaseous fuels as a partial supplement for diesel fuel has been proposed by many researchers. An experimental investigation was performed to investigate the influence of dual-fuel combustion on the performance and exhaust emissions of a DI diesel engine fueled with natural gas (NG) and biogas (BG). The engine was operated at a constant speed of 1750 rpm and at two different loads: low (∼3 N m) and high (∼28 N m), which were about 10% and 85% respectively of the rated torque output of the engine at 1800 rpm. In this work, the combustion pressure and the rate of heat release were evaluated experimentally in order to analyze the combustion characteristics and their effects on exhaust emissions including particulate matter (PM) for single-fuel (diesel) and dual fuel combustion modes. In dual fuel mode, the peak cylinder pressure was found to be similar to diesel at 75% of the rated output of the engine. About 27-30% higher maximum net heat release rates were obtained for NG and biogas fueling respectively compared to diesel fueling. Longer ignition delays but shorter combustion durations were characterized for dual fueling operations. Specific NOx emissions for dual fueling was always lower than diesel fueling case. Significantly lower specific PM emissions but sharply increased unburned hydrocarbons (UHC) emissions were measured for biogas-diesel dual fuel operations as compared to diesel fueling. © 2013 Elsevier Ltd. All rights reserved.

Islam M.R.,Rajshahi University of Engineering and Technology | Parveen M.,Kitami Institute of Technology | Haniu H.,Kitami Institute of Technology
Bioresource Technology | Year: 2010

Agricultural waste in the form of sugarcane bagasse was pyrolyzed in a fixed-bed fire-tube heating reactor under different pyrolysis conditions to determine the role of final temperature, sweeping gas flow rate and feed size on the product yields. Final temperature range studied was between 375 and 575 °C and the highest liquid product yield was obtained at 475 °C. Liquid products obtained under the most suitable conditions were characterized by physical properties, elemental analysis, GCV, FT-IR, 1H NMR analysis and distillation. The empirical formula of the bio-oil with heating value of 23.5 MJ/kg was established as CH 1.68O 0.557N 0.012. Comparison with other approaches showed that the liquid product yield by this simpler reactor system was higher with better physico-chemical properties as fuel. These findings show that fixed-bed fire-tube heating pyrolysis is a good option for production of bio-oils from biomass solid wastes. © 2010 Elsevier Ltd. All rights reserved.

Hossain A.,Rajshahi University of Engineering and Technology | Yin J.-H.,Hong Kong Polytechnic University
International Journal of Geomechanics | Year: 2014

An interface between compacted soil and a structure is commonly encountered in various geotechnical engineering projects, e.g., soil nails, retaining walls, shallow foundations, pile foundations, and so on. The interface strength depends on the way the soil-structure interface is formed. A cast-in-situ interface is very common in many geotechnical projects. This kind of interface is formed by placing concrete/cement grout over the prepared soil surface. The cement part can be formed over a prepared soil surface in two ways: (1) by normal gravity grouting and (2) by pressure grouting. In this study, a series of interface direct-shear tests was performed between compacted, completely decomposed granite (CDG) soil and cement grout under saturated conditions with different grouting pressures and normal stresses. The behaviors of the shear-stress- displacement curves of the soil-cement interface are similar to those of CDG soil. Grouting pressure and normal stress have influence on the behavior of the soil-cement interface. The failure envelopes for different grouting pressures are observed to be linear. The apparent effective interface friction angles are constant for different grouting pressures. On the other hand, apparent effective adhesion intercepts increase with grouting pressure.When the shear plane is fixed, the apparent effective interface friction angles for different grouting pressures are greater than the effective friction angle of CDG soil under the same normal stresses, which implies that a compacted CDG soil-cement grout interface behaves as a rough interface. The variation in interface shear strength with grouting pressure (grouting-pressure envelope) at the same shear-plane level is approximately linear, and declivities are constant for different normal stresses. A model is proposed for interface shear strength under saturated conditions that considers grouting pressure as an independent variable. The predicted interface shear strength of the proposed model agrees fairly well with the experimental data. © 2014 American Society of Civil Engineers.

Bari M.W.,Rajshahi University of Engineering and Technology | Shahin M.A.,Curtin University Australia
Geotextiles and Geomembranes | Year: 2014

The design of soil consolidation via prefabricated vertical drains (PVDs) has been traditionally carried out deterministically and thus can be misleading due to the ignorance of the uncertainty associated with the inherent variability of soil properties. To treat such uncertainty in the course of design of soil improvement by PVDs, more rational probabilistic methods are necessary. In this paper, a simplified probabilistic method is proposed in which the inherent variability of the coefficient of consolidation, which is the most significant uncertain soil parameter that affects the consolidation process, is considered. An easy-to-use design procedure and charts are provided for routine use by practitioners. © 2013.

Hosen M.A.,Rajshahi University of Engineering and Technology
Ain Shams Engineering Journal | Year: 2014

In this paper, a modified harmonic balance method based an analytical technique has been developed to determine approximate solutions for a strongly nonlinear oscillator with a discontinuous term which is arising from the motion of rigid rod on the surface without slipping. Usually, a set of nonlinear algebraic equations is solved in this method. However, analytical solutions of these algebraic equations are not always possible, especially in the case of a large oscillation. We have been compared the solution results of this method with the numerical solution in order to validate the approach and assess the accuracy of the solutions has been demonstrated and discussed. We found that, a second order modified harmonic balance method works very well for the whole range of initial amplitudes. The advantage of the using method is its simple procedure and gives almost similar results in comparison with the exact solution. © 2014 Production and hosting by Elsevier B.V. on behalf of Ain Shams University.

Hasan M.I.,Rajshahi University of Engineering and Technology | Razzak S.M.A.,Rajshahi University of Engineering and Technology | Habib M.S.,Rajshahi University of Engineering and Technology
Journal of Lightwave Technology | Year: 2014

A residual dispersion compensating octagonal photonic crystal fiber (OPCF), with an elliptical array of circular air-holes in the fiber core region, is proposed. The full-vector finite-element method with perfectly matched layer boundary is used as the analysis tool. It is demonstrated that it is possible to obtain large average negative dispersion of-562.52 ps/(nm · km) over 240 nm and-369.10 ps/(nm · km) over 630 nm wavelength bands for the fast and the slow axis, respectively. In addition to large negative dispersion, ultra-high birefringence, high nonlinearity, and zero-dispersion wavelengths with low confinement loss are also warranted. The proposed OPCFs would be a promising candidate for residual dispersion compensation, supercontinuum generation, and other applications. © 2014 IEEE.

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