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Dombkowski A.A.,Wayne State University | Sultana K.Z.,Chittagong University of Engineering and Technology | Craig D.B.,Wayne State University
FEBS Letters | Year: 2014

Improving the stability of proteins is an important goal in many biomedical and industrial applications. A logical approach is to emulate stabilizing molecular interactions found in nature. Disulfide bonds are covalent interactions that provide substantial stability to many proteins and conform to well-defined geometric conformations, thus making them appealing candidates in protein engineering efforts. Disulfide engineering is the directed design of novel disulfide bonds into target proteins. This important biotechnological tool has achieved considerable success in a wide range of applications, yet the rules that govern the stabilizing effects of disulfide bonds are not fully characterized. Contrary to expectations, many designed disulfide bonds have resulted in decreased stability of the modified protein. We review progress in disulfide engineering, with an emphasis on the issue of stability and computational methods that facilitate engineering efforts. © 2013 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

Akter A.,Chittagong University of Engineering and Technology | Babel M.S.,Asian Institute of Technology
Journal of Hydrology | Year: 2012

Sources of pollution in river basins are increasing due to rapid changes in land uses and excessive nutrient application to crops which lead to degraded instream water quality. In this connection, the Mun River basin, one of the important and largest river basins in Thailand, has been studied. Comparative figures of nutrients in the Mun's water over a decade showed an increased total nitrogen (TN) and phosphorus (TP) ratio in the Lower Mun region (TN:TP>14). Laboratory analysis of weekly water samples showed a realistic nutrient response when daily rainfall was compared to the seasonal water quality data collected by the Pollution Control Department (PCD). The Hydrologic Simulation Program - FORTRAN (HSPF) was calibrated and used to assess the effects of different land uses on river water quality. Model parameters related to hydrology and sediment were calibrated and validated using relevant measurements by the Royal Irrigation Department (RID). With a reasonable and acceptable model performance (r 2=0.62), the highest simulated runoff was observed in urban areas. The trend of agricultural land (as a percentage of total area) - total nitrogen showed a linear relationship of a good correlation (i.e. r 2=0.85). Based on the findings, it can be concluded that this model is expected to provide vital information for developing suitable land management policies and strategies to improve river water quality. © 2012 Elsevier B.V.

Milton Md.A.A.,Chittagong University of Engineering and Technology | Khan A.A.S.,Chittagong University of Engineering and Technology
2012 International Conference on Informatics, Electronics and Vision, ICIEV 2012 | Year: 2012

A remote exploration and control system has been developed using web Application, web server, database, GSM network, and Android mobile phone. Web application is used to control remotely an Android mobile phone and electrical devices connected with the mobile phone. Firstly, command is sent from the web Application and saved in database. The Android mobile phone reads the sent command from database and performs predefined procedure to execute the command and hence, generate outcome due to execution of the command. Thus, this system can be used as an exploration and control system because remote mobile phone automatically implements command like capturing picture and upload the captured picture to the server and control electrical devices. Command is implemented to capture picture automatically of the surrounding location and upload it to server. It can also send automatically GPS location of the mobile phone to server's database. So, it can be used to detect the device's geographical location and collateral condition. Hence, it can be used in monitoring as well as in security system. Finally, command is implemented for generating DTMF tone signal on Android phone. A DTMF detection circuit, interfaced with mobile phone, can automatically detect the DTMF tone signal and generates 4 bit digital code output. This digital output code can be utilized to control any electrical device. © 2012 IEEE.

Hossen M.B.,Chittagong University of Engineering and Technology | Hossain A.K.M.A.,Bangladesh University of Engineering and Technology
Journal of Magnetism and Magnetic Materials | Year: 2015

Abstract The influence of Al substitution on the structural and electromagnetic properties of Ni0.27Cu0.10Zn0.63AlxFe2-xO4; (where x=0.0 to x=0.16 with step =0.02) prepared by the combustion technique, has been investigated. X-ray diffraction analysis confirms the presence of single phase cubic spinel structure without any secondary phase. The lattice constant, theoretical density, bulk density and average grain size decreases with increasing Al content. B-H loops have been traced for all the compositions and the various hysteresis parameters like saturation induction, coercivity, remanance, remanance ratio and power loss have been studied as a function of Al content. The saturation induction and the initial permeability increases with sintering temperature up to 1150 °C where the maximum bulk density is obtained, while for higher sintering temperature they decrease. The variation of complex initial permeability for Al substituted NiCuZn ferrites can be presented as a form of semicircle so called the Cole-Cole plot and the relaxation phenomena were explained with various shapes of the plots. The analysis of complex impedance spectra by an equivalent circuit model were used to separate the grain and grain boundary resistance of various Ni0.27Cu0.10Zn0.63AlxFe2-xO4. The impedance plot showed the first semicircle at high frequency which corresponds to grain effect and the second semicircle at lower frequency which corresponds to grain boundary (conduction phenomenon). Both grain and grain boundary resistance increases with increasing Al content and the relative increase of grain resistance is larger than the grain boundary resistance. The frequency dependent conductivity results support the double (Jonscher's modified) power law,σT(ω)=σ(o)+ A1ωn1+A2ωn2, and the results showed evidence of three types of conduction process at room temperature: (i) low frequency conductivity is due to long-range ordering (frequency independent or its tendency, region I), (ii) mid frequency conductivity may be due to the short range hopping (dispersion and frequency independent plateau, region II) and (iii) high frequency conduction is due to the localized relaxation (region III) hopping mechanism. © 2015 Elsevier B.V. All rights reserved.

Mohammad N.,Chittagong University of Engineering and Technology | Karim T.,Chittagong University of Engineering and Technology
Journal of Solar Energy Engineering, Transactions of the ASME | Year: 2013

A solar tracker is a system for orienting solar photovoltaic modules and solar thermal collectors toward the sun. This paper presents a microcontroller based energy efficient hybrid automatic solar-tracking system with a view to assess the improvement in solar conversion efficiency. The two-axis solar-tracking system is constructed with both hardware and software implementations. The proposed tracking system uses a new solar position sensor with adaptive features. A comparative analysis was performed using four systems, i.e., hybrid tracking, dual-axis, single-axis, and stationary module. The results showed that the use of the dual-axis tracking system produced 18% gain of power output, compared with a single-axis tracking system. The gain of output power with the hybrid tracking system was much higher (54%) when compared with a stationary system inclined at 23.5 deg to the horizontal. Considering the state of the art of the technology, successful strategy, robust control philosophy, and the potential added benefit of this research work can be employed on a large scale in sustainable manner. © 2013 by ASME.

Rahman M.M.,Chittagong University of Engineering and Technology
International Journal of Hydrogen Energy | Year: 2015

Aqueous-phase reforming of glycerol was investigated over a series of Ni and Cu-Ni bimetallic catalysts supported on multiwalled carbon nanotubes (MWNT). The reaction was carried out in a continuous flow fixed bed reactor (240 °C, 40 atm) with a solution of 1 wt% glycerol in DI water at a flow rate of 0.05 mL/min. Amongst the catalysts tested, bimetallic 1Cu-12Ni/MWNT catalyst gave the higher H2 selectivity (86%) and glycerol conversion (84%) than the benchmark 12Ni/MWNT catalyst. Irrespective of Cu and Ni ratio, bimetallic Cu-Ni catalysts showed higher selectivity and glycerol conversion towards H2 production than the Ni catalyst. The presence of Cu in bimetallic catalysts resulted in suppression of undesirable methanation reaction. Catalysts characterized by XRD and XPS showed a significant peak shift of Ni in bimetallic Cu-Ni catalysts than the Ni catalyst, suggesting a strong interaction between Cu and Ni. Also H2-TPR analysis showed that introducing Cu increased Ni reducibility. The bimetallic interaction is thought to be responsible for the lowered methane yield and ultimately, higher hydrogen yield observed. © 2015 Hydrogen Energy Publications, LLC.

Hafez M.G.,Chittagong University of Engineering and Technology
Alexandria Engineering Journal | Year: 2016

In this article, the exp(-Φ(ξ))-expansion method is modified for (3+1)-dimensional space-time coordinate system and successfully implemented to construct the new exact traveling wave solutions of the (3+1)-dimensional coupled Klein-Gordon-Zakharov equation. The solutions of this equation are expressed in terms of hyperbolic, trigonometric, exponential and rational functions. The results illustrate its effectiveness for solving nonlinear coupled partial differential equations arises in mathematical physics and engineering. The annihilation phenomena of the wave propagation in the x-y plane are also investigated. Furthermore, the three-dimensional surface plots due to the obtained solutions are also given to make the dynamics of the equation visible. © 2016 Faculty of Engineering, Alexandria University.

Quamruzzaman M.,Chittagong University of Engineering and Technology | Rahman K.M.,Bangladesh University of Engineering and Technology
WSEAS Transactions on Power Systems | Year: 2014

There is an inherent tracking-oscillations trade-off problem in Perturb and Observe (P&O) maximum power point tracking (MPPT) technique for photovoltaic (PV) system. Higher perturbation step-size increases the tracking speed at the cost of greater oscillations around maximum power point (MPP); whereas, smaller step-size slows down the tracking while reducing the oscillations around MPP. In this paper, a modification in P&O method is proposed to reduce this tracking-oscillations trade-off problem by setting an initial approximate perturbation value whenever irradiance changes and continuing tracking with adaptive stepsize. Detail simulation results of the modified P&O method are presented and compared with the results obtained considering different values of fixed step sizes. The P&O method with the proposed modifications clearly shows maximum tracking speed with minimum oscillations around MPP. Moreover, due to the modifications, the algorithm can track MPP efficiently in case of sudden irradiance change.

Miah M.I.,Chittagong University of Engineering and Technology
Procedia Engineering | Year: 2014

Shale volume and porosity are the most important rock properties for petrophysical analysis, formation evaluation and estimation of hydrocarbon reserve in the oil and gas fields. This research shows how to shale volume and porosity estimation of Titas gas field (T-11) using wireline log data of Bokabil Formation in Bangladesh. Shale volume has been estimated from Gamma Ray, Self-Potential logs and True resistivity method. Porosity estimated from single log method as well as from Neutron-Density and sonic logs. Lithology is mainly sand and shale where sand is the dominant fraction. In A2 sand interval of T-11, sand and shaly sand appeared as alternating units. The shales are laminated. Shale volume percentage is ranges from 3.82 to 17.52 averaging 9.23 using Gamma Ray log which is optimistic and more reliable than other two methods. The total porosity (average) percentage is 25.09 based on sonic log which is over estimated but Neutron-density combination formula with clay corrected gives better results as averaging 18.17% which is more reliable for estimation of water saturation, formation evaluation and reserve estimation and similar as core porosity. The porosity quality is good of A2 gas sand which is potential hydrocarbon reservoir. © 2014 The Authors. Published by Elsevier Ltd.

Dhar P.K.,Chittagong University of Engineering and Technology
8th International Conference on Electrical and Computer Engineering: Advancing Technology for a Better Tomorrow, ICECE 2014 | Year: 2015

This paper presents a blind audio watermarking method based on lifting wavelet transform (LWT) and QR decomposition (QRD) for audio copyright protection. In our proposed method, initially the original audio is segmented into non-overlapping frames. Watermark information is embedded into the largest element of the upper triangular matrix obtained from the low frequency LWT coefficients of each frame. A blind watermark detection technique is introduced to identify the embedded watermark under various attacks. Simulation results indicate that the proposed watermarking method is highly robust against different attacks. In addition, it has high data payload and provides good imperceptible watermarked sounds. Moreover, it shows superior performance than the state-of-theart watermarking methods reported recently. © 2014 IEEE.

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