Rahman A.T.M.M.,Dhaka International University |
Alam M.S.,Dhaka University of Engineering and Technology |
Chowdhury M.K.,Bangladesh University of Engineering and Technology
International Communications in Heat and Mass Transfer | Year: 2012
In this paper, the effects of thermophoresis particle deposition on an unsteady two dimensional forced convective heat and mass transfer flow past a wedge taking into account the variation of fluid viscosity and fluid Prandtl number with temperature are studied. The local similarity equations are derived and solved numerically using Nachtsheim-Swigert shooting iteration technique along with the sixth order Runge-Kutta integration scheme. Comparisons with previously published work are performed, and the results are found to be in excellent agreement. Results for the non-dimensional velocity, temperature, concentration, Prandtl number and thermophoretic velocity are displayed graphically whereas thermophoretic deposition velocity is shown in the tabulated form for various values of the pertinent parameters. The obtained numerical results show that in modeling the thermal boundary-layer flow with a temperature-dependent viscosity, consideration of the Prandtl number as a constant within the boundary layer produces unrealistic results, and therefore, it must be treated as a variable rather than a constant within the boundary layer. The results also show that the thermophoretic particle deposition velocity decreases as the thermophoretic coefficient increases. © 2012 Elsevier Ltd.
Zaman K.,Bangladesh University of Engineering and Technology |
Dey P.R.,Dhaka University of Engineering and Technology
Structural and Multidisciplinary Optimization | Year: 2017
In this paper, we propose a new likelihood-based methodology to represent epistemic uncertainty described by sparse point and/or interval data for input variables in uncertainty analysis and design optimization problems. A worst-case maximum likelihood-based approach is developed for the representation of epistemic uncertainty, which is able to estimate the distribution parameters of a random variable described by sparse point and/or interval data. This likelihood-based approach is general and is able to estimate the parameters of any known probability distributions. The likelihood-based representation of epistemic uncertainty is then used in the existing framework for robustness-based design optimization to achieve computational efficiency. The proposed uncertainty representation and design optimization methodologies are illustrated with two numerical examples including a mathematical problem and a real engineering problem. © 2017 Springer-Verlag Berlin Heidelberg
Cosco N.G.,North Carolina State University |
Moore R.C.,North Carolina State University |
Islam M.Z.,Dhaka University of Engineering and Technology
Medicine and Science in Sports and Exercise | Year: 2010
The preschool that children attend has been shown to be a significant but variable predictor of physical activity of 3-to 5-yr-olds, whereas the time outdoors has been found to be a strong correlate of physical activity. Researchers speculate that variations in preschool physical activity may be attributed to variations in preschool policies and practices, including the form and content of outdoor physical environments. However, assessment methods linking them to physical activity are limited. Improved understanding of links between environment and activity could be used to influence childcare policy, which is highly regulated, usually at state level, to create outdoor environments more conducive to children's informal play and physical activity. The purpose of this article was to introduce behavior mapping as a direct observation method on the basis of the theories of behavior setting and affordance and to demonstrate its sensitivity to gathering physical activity and associated environmental data at a sufficiently detailed level to affect built environment design policy. Methods: Behavior mapping data, including outdoor environmental characteristics and children's physical activity levels, were obtained in two preschool centers at the Research Triangle region, NC. Results: Physical activity levels at the two centers varied across different types of behavior settings, including pathways, play structures, and open areas. The same type of setting with different attributes, such as circular versus straight pathways, and open areas with different ground surfaces, such as asphalt, compacted soil, woodchips, and sand, attracted different levels of physical activity. Conclusions: Behavior mapping provides a promising method for objectively measuring relationships between physical behavior settings and directly associated activity levels. Copyright © 2010 by the American College of Sports Medicine.
Mitra S.K.,University of Dhaka |
Chowdhury A.R.,Dhaka University of Engineering and Technology
Proceedings of the IEEE International Conference on VLSI Design | Year: 2012
Conventional circuit dissipates energy to reload missing information because of overlapped mapping between input and output vectors. Reversibility recovers energy loss and prevents bit error by including Fault Tolerant mechanism. Reversible Computing is gaining the popularity of various fields such as Quantum Computing, DNA Informatics and CMOS Technology etc. In this paper, we have proposed the fault tolerant design of Reversible Full Adder (RFT-FA) with minimum quantum cost. Also we have proposed the cost effective design of Carry Skip Adder (CSA) and Carry Look-Ahead Adder (CLA) circuits by using proposed fault tolerant full adder circuit. The regular structures of n-bit Reversible Fault Tolerant Carry Skip Adder (RFT-CSA) and Carry Look-ahead Adder (RFT-CLA) by composing several theorems. Proposed designs have been populated by merging the minimization of total gates, garbage outputs, quantum cost and critical path delay criterion and comparing with exiting designs. © 2012 IEEE.
Faruk M.S.,Dhaka University of Engineering and Technology |
Kikuchi K.,University of Tokyo
IEEE Photonics Journal | Year: 2013
We propose a novel method of compensation for imbalance between in-phase (I) and quadrature (Q) channels in the front-end circuit of digital coherent optical receivers. Adaptive finite-impulse-response (FIR) filters in the butterfly configuration, which are commonly used for signal equalization and polarization demultiplexing, are modified so as to allow for adjustment of any imbalance between the IQ channels. IQ imbalances under consideration include the gain mismatch, the phase mismatch, and the timing-delay skew. Computer simulations for the dual-polarization quadrature-amplitude-modulation (QAM) format up to an order of 256 show that such IQ imbalances can severely degrade the system performance, especially for higher order QAM; however, using the proposed scheme, we can compensate for them without any significant penalty over a wide range of imbalances. © 2009-2012 IEEE.
Chowdhury M.A.,Dhaka University of Engineering and Technology |
Nuruzzaman D.M.,Universiti Malaysia Pahang
Tribology in Industry | Year: 2013
Friction coefficient and wear rate of different steel materials are investigated and compared in this study. In order to do so, a pin on disc apparatus is designed and fabricated. Experiments are carried out when different types of disc materials such as stainless steel 314 (SS 314), stainless steel 202 (SS 202) and mild steel slide against stainless steel 314 (SS 314) pin. Experiments are conducted at normal load 10, 15 and 20 N, sliding velocity 1, 1.5 and 2 m/s and relative humidity 70%. At different normal loads and sliding velocities, variations of friction coefficient with the duration of rubbing are investigated. The obtained results show that friction coefficient varies with duration of rubbing, normal load and sliding velocity. In general, friction coefficient increases for a certain duration of rubbing and after that it remains constant for the rest of the experimental time. The obtained results reveal that friction coefficient decreases with the increase in normal load for all the tested materials. It is also found that friction coefficient increases with the increase in sliding velocity for all the materials investigated. Moreover, wear rate increases with the increase in normal load and sliding velocity for SS 314, SS 202 and mild steel. In addition, at identical operating condition, the magnitudes of friction coefficient and wear rate are different for different materials depending on sliding velocity and normal load. © 2013 Published by Faculty of Engineering.
Faruk M.S.,Dhaka University of Engineering and Technology
Optical and Quantum Electronics | Year: 2016
A novel blind equalization and carrier-phase-recovery technique based on modified constant-modulus algorithm is proposed for polarization-division multiplexed quadrature phase-shift keying (PDM-QPSK) systems. The proposed scheme is validated with computer simulations as well as transmission experiments with 40-Gbits/s PDM-QPSK signals. © 2015, Springer Science+Business Media New York.
Uddin M.N.,Dhaka University of Engineering and Technology
Indian Journal of Traditional Knowledge | Year: 2013
The Jamuna is a large scale sand bed braided river. It always changes it courses within its braid belt. Erosion is a major problem along the Jamuna river. More than thirty bank protection structures have been constructed along both banks of this river to protect bank from erosion. The response of these structures to the river is different. The people neighborhood of these structures has already gained experience-based traditional ecological knowledge. The main objectives of the present study are to investigate experience-based Traditional Ecological Knowledge (TEK) on flow and erosion around different bank protection works. Participatory Rural Appraisal (PRA) method was used to investigate the (TEK) around different bank protection works. Different tools of PRA such as: Focus Group Discussion (FGD), Key Informant Interview (KII) and Informal Group Discussion have been used around some selected bank protection works along the braided Jamuna river. Finally, comparisons are made among the experienced-based TEK, field engineer's knowledge, field measure result and result obtained from laboratory experiment. It has been found that there are similarities among the experienced-based traditional knowledge, field engineer's knowledge, field measure result and result obtained from laboratory experiment. The following Traditional Ecological Knowledge (TEK) have been investigated from the present study such as: (i) the TEK on flow and erosion processes around Sirajganj hardpoint, Betil and Enayetpur spurs, Shuvogacha spurs and around bandal structures, (ii) the experienced-based TEK on flow and erosion processes are very similar to scientific analysis from the field measured data, (iii) the causes of failure of the Sirajganj hardpoint, Betil and Enayetpur spurs and Shuvogacha, (iv) the indication of failure of bank protection works. It is clear that the local peoples experienced-based TEK can play a vital role in the management activity during emergency situation.
Anowar Hossain M.,Saga University |
Onaka Y.,Saga University |
Afroz H.M.M.,Dhaka University of Engineering and Technology |
Miyara A.,Saga University
International Journal of Refrigeration | Year: 2013
This experimental study measured and compared the heat transfer coefficients during in-tube evaporation of R1234ze(E), R32, the nearly azeotropic HFC refrigerant blend R410A and a zeotropic mixture R1234ze(E)/R32 (55/45 mass %) inside a water heated double tube heat exchanger. The experiment has been carried out under the conditions of mass flux varying from 150 to 445 kg m-2 s-1, the saturation temperatures are 5 and 10 °C, over the vapor quality range 0.0-1.0. The effect of vapor quality, mass flux and saturation temperature on heat transfer coefficients have been analyzed. It is found that the experimental heat transfer coefficients of R1234ze(E) are lower than R1234ze(E)/R32 (55/45mass%), R410A and R32 by 11%, 56% and 83%, respectively, at about 0.48 vapor quality and 300 kg m-2 s-1 mass velocity. Experimental results have been compared with some well-known correlations. © 2012 Elsevier Ltd and IIR. All rights reserved.
Faruk M.S.,Dhaka University of Engineering and Technology
8th International Conference on Electrical and Computer Engineering: Advancing Technology for a Better Tomorrow, ICECE 2014 | Year: 2015
In this paper, unconstraint adaptive frequency-domain equalizer (FDE) based on the constant-modulus algorithm (CMA) is investigated for equalization of linear transmission impairments in coherent optical receivers. With unrepeated 200-km transmission of 10-Gbaud quadrature phase-shift keying (QPSK) signal, it is verified that, compared with conventional constraint FDE, the proposed unconstraint FDE causes a very small sensitivity penalty; however, can be applied with much less computational complexity. © 2014 IEEE.