American International University-Bangladesh (AIUB)
Kitami Institute of Technology, Japan
Kitami Institute of Technology, Japan
This paper presents a speed control strategy with efficiency optimization of space-vector pulse-width modulated (SVPWM) inverter-fed interior permanent magnet synchronous motor (IPMSM). The efficiency optimization algorithm is derived by minimizing the total controllable losses in terms of d-axis magnetizing current component. A discrete time state space multi-input and multi-output (MIMO) model from linear continuous time state space model is first developed and an augmented system for implementing the efficiency optimized algorithm with speed control is designed based on optimal regulator. Since SVPWM is the best among all the carrier based PWM techniques, SVPWM-fed inverter is used to implement the designed speed control strategy with efficiency optimization of IPMSM. The complete control system of IPMSM including the SVPWM inverter has been simulated to verify the performance of the proposed speed controller with efficiency optimization. The simulation has also been done for vector control to compare with the efficiency optimization technique. The simulation results are found to have excellent performance of speed control without any overshoot and steady state error.
American International University-Bangladesh (AIUB)
Bangladesh University of Engineering and Technology (BUET)
In this work, the performance characteristics of a GaAs-based 980 nm multiple quantum well (MQW) VCSEL have been obtained through computations considering thermal effect. The obtained characteristics have been analyzed for obtaining better performance. For achieving a superior performance, the concentrations of InGaAs QW material have been chosen using the results of other research works. The material gain of a compressively strained In0.2Ga0.8As/GaAs MQW VCSEL has been theoretically computed. Using the peak material gain obtained from this computation the performance characteristics of the designed VCSEL have been obtained. At 300K, the threshold current of the VCSEL has been obtained as 2.5 mA for a corresponding bias voltage of 3.6 volt. A maximum output power of 22.499 mW has been obtained for this designed VCSEL at 44 mA injection current. This figure of power is better compared to other similar VCSELs. Corresponding to this the modulation bandwidth has been obtained as 39 GHz which indicates superior performance of the designed VCSEL compared to the similar results of other research works.
Khulna University of Engineering & Technology (KUET), Bangladesh
Khulna University of Engineering & Technology (KUET), Bangladesh
American International University-Bangladesh (AIUB)
This paper presents performance analysis of field orientation controlled induction motor (IM) drive considering saturation in the magnetic circuit. Two different machines: one squirrel cage induction motor (SCIM) and the other wound rotor induction motor (WRIM) are used to have a more generalized approach of analysis. The magnetization characteristics are used to select magnetization levels and flux producing currents of the motors to have constant parameter models those are justified by the loss model of the motors. Linear model of IMs with constant nominal parameters and nonlinear model with saturation are considered in the analysis. Inappropriate transmission of control quantities are also taken into account for performance analysis. Performance of both the current and voltage controlled drives are presented. The effects of d-and q- axes voltage and current components on the performance of the induction motor drives are presented for steady state and transient conditions. Effects of calculation errors are also considered in the analysis. Finally, experimental results are provided to validate the simulated results.
Jagannath University, Bangladesh
North South University, Bangladesh
Jagannath University, Bangladesh
Different values of temporal perception were found as effect of the different nature of the slope of signal when the psychophysical processing was psycho-acoustical. Two types of methods were applied to determine different values of slopes of the acoustical signals which were measured by autocorrelation function. The slope means here the rise and fall-times in respect to the zero line. In one method, slopes were measured simply the time duration from the beginning to the highest level for rise-time and for fall-time that is from the highest level to the end of the signal. In another method, rise and fall-times were measured on the basis of the definition of -3dB slope from the steady level. Using white-noise signals under same sound-pressure level (SPL = 80dBA) of three slop values measured on the basis of two above methods. Acoustic signals were transmitted in an anechoic chamber. Subjective responses of perceived-temporal duration under paired-comparison test were recorded by an automatic system in response to that of the measured slopes. Cumulative frequencies of subjective responses after calculating average were plotted in the psychometric function. Results showed that the average subjective responses are found significantly different when the slope measuring methods are different.
American International University-Bangladesh (AIUB)
University Malaysia Sarawak, Malaysia
This study examined the current strength of indigenous industrial technology in garments sector of Bangladesh. This work was specially designed to focus on acquisition policy and the barriers to the adoption of locally available technology in garments manufacturing industries. Literature review and field survey by using questionnaire were the main tools of this research. The study reveals that the rate of acquisition of indigenous technology is significantly low and marginally poor due to policy barriers. It is the researchers’ view that the rate of acquisition of indigenous technology should be higher in order to reduce the investment and to increase the growth of this manufacturing industry. This paper is ended with a recommendation for adopting industrial growth policy by using and by strengthening the marketing of indigenous technology.
American International University-Bangladesh (AIUB)
In this paper the performance of the generic schedulers such as Round Robin, Max-SNR, and Proportional Fair (PF) in macrocells-only highly dense urban environments is evaluated. Since the PF scheduler provides a trade-off between throughput and fairness, the PF scheduler is considered for investigating the performance of femtocells in macro-femtocellnetwork architecture under variable user density. Then the performance of the PF scheduler betweenmacrocells-only and macro-femtocellarchitecture with the variation of user density is evaluated, and how the user density can play a major role on the viable potential deployment of femtocells in two-tier LTE-Advanced systems is investigated. A system level simulation is carried out to evaluate the performance of schedulers as well as the impact of user density on femtocells deployment in LTE-Advanced systems.
American International University-Bangladesh (AIUB)
American International University-Bangladesh (AIUB)
American International University-Bangladesh (AIUB)
American International University-Bangladesh (AIUB)
The notion of history of Bengal has undergone profound changes throughout the
20th century, and ‘the organization of history’ has become an increasingly
faceted and increasingly controversial question. Organizing history concerns the
ways we deal with the past, the present and the future; how do we construe the
role of the past, and how we construct images of past realities? A social and
philosophical disparity was created between the ruler and masses in British
colonial period- where the obvious result was the power and superiority,
building for permanence and the functional nature of architecture without much
response to the Bengal context. In time immemorial, it gradually hybridized to
develop a new language in Bengal architecture. ‘Bungalow’ is such a dwelling
unit which was regenerated from the basic living unit of Bengal hut of the
indigenous subordinate people and became popular and patronized by the colonial
ruler and later established as a kind of architectural style in European and
American continent. And ‘Zamindarbari’ is the provincial elite house represented
neo classical style derived from the aspirations of the local zamindars to
European ideas and consciously cultivated European social habits to confirm
their power and prestige.
The idea of this text is to re-narrativize and re-evaluate the privileged,
academic, institutionalized architectural history of Bangladesh through two
totally different types of edifice-‘Bungalow’ and ‘Zamindarbari’.[house for the
zamindar who were the landlord and collected taxes from peasant in British
period]
This essay tries to speak out and reclaim the identity and re-inscribe their
position [Bungalow and Zamindarbari] in Bengal history which eventually
valorizes the Bengal culture where these two are the relations of dependence and
reinscription between architecture and anthropology.
American International University-Bangladesh (AIUB)
This paper aims to identify the urban form and design issues that are concerned with the sustainable development of a new settlement. Drawing on the theoretical literature, it recognizes eight key issues to achieve a sustainable urban form which includes compact and mixed use development, high density, social wellbeing, design excellence, renewable energy sources, sustainable built environment, efficient transport network and preservation of open space and ecosystems. It explains the two most important but opposing theories to achieve a sustainable urban form: compact city and short cycle city. Then it argues that while considering the metropolitan scale, a comparatively recent development of sustainable urban form: the strategy of decentralised concentration is more appropriate for contemporary European cities. The suitability of the third strategy which is basically a combination of compact and dispersed city with an emphasis on greening will be examined through a case study. Based on a practical study of issues, opportunities and constraints the paper will try to identify the urban form that is the most sustainable and environmentally sound for Hackney wick, London which forms a significant part of the Legacy site for the Olympic Games 2012.
American International University-Bangladesh (AIUB)
Khulna University, Bangladesh
Khulna University, Bangladesh
Here an efficient lossless image compression scheme is proposed. The scheme is based on some simple arithmetic operations and uses repeat reduction and arithmetic coding to improve the results of compression. Better results have been achieved than Log-Exp based compression and Arithmetic modulo based compression. We have analyzed the complexity of our proposed scheme and other related schemes with respect to compression ratio and shown that the proposed scheme is more efficient that other related schemes. From the experimental results, it can be seen that the performance of the proposed scheme is better for all standard images. The proposed scheme is most applicable for those images where lossy compression is to be avoided. The experimental results show that our proposed method compresses data more than the existing related methods. The superiority of the image quality of our proposed method is shown using PSNR values.
American International University-Bangladesh (AIUB)
American International University-Bangladesh (AIUB)
American International University-Bangladesh (AIUB)
Security of wireless sensor network (WSN) is always considered a critical issue and has a number of considerations that separate them from traditional wireless sensor network. First, sensor devices are typically vulnerable to physical compromise. Second, they have significant power and processing constraints. Third, the most critical security issue is protecting the aggregate output of the system, even if individual nodes may be compromised. While a variety of security techniques are being developed and lots of researches are going on security fields. In this paper we have proposed a new technique to provide data authentication and privacy in faster, scalable and cost effective way.
American International University-Bangladesh (AIUB)
American International University-Bangladesh (AIUB)
American International University-Bangladesh (AIUB)
proXcrum is a proposed Hybrid Software Process Model in the Offshore Software Development (OSD) paradigm. This model intends to resolve the common problems related to offshore software development project failures of the firms with remote clients. The methodologies incorporated with this model will provide the firm with a clear picture of the system to be developed through a more concrete requirement elicitation. Moreover, this model has suggested some principles of communications and documentations which, in turn, will enhance the project management maturity, reduce the cost of maintenance efforts and produce high quality end products.
Bangladesh University of Engineering & Technology (BUET),
B.C.S.I.R. laboratory, Bangladesh
American International University-Bangladesh (AIUB)
In this study, spray pyrolysis method has been employed for the deposition of some transparent oxide thin films like ZnO, CdO and SnO2 onto glass substrate under atmospheric pressure using zinc acetate, cadmium acetate and tin chloride precursors at relatively low temperature around 200~350°C. Films of various thicknesses have been obtained by varying the deposition time and concentrations, while all other deposition parameters such as spray rate, carrier gas pressure and distance between spray nozzle to substrate were kept constant. Surface morphology, structural and optical properties of the as-deposited thin films have been studied by Scanning Electron Microscopy (SEM) attached with an EDX, XRD and UV visible spectroscopy. The elemental composition of the samples studied by EDX reveals that the as-deposited films are homogeneous and stoichiometric. The SEM micrograph shows uniform deposition and scattered nano fiber around the nucleation centers of the ZnO film and small crystallites and agglomeration of the grain particles for pure cadmium oxide and tin oxide samples. The optical band gaps of the ZnO, CdO and SnO2 thin films were found to be around 3.40 eV, 2.53 eV and 3.75 eV respectively. The obtained experimental results also discuss the suitability of these films as transparent and conducting window materials in optoelectronics applications.
American International University-Bangladesh (AIUB)
American International University-Bangladesh (AIUB)
American International University-Bangladesh (AIUB)
The effects of magnetic field and soret number on a steady three dimensional MHD convective heat and mass transfer flow due to a porous rotating disk are studied. The results of the numerical solution are presented graphically in the form of velocity, temperature and concentration profiles for different values of suction/injection parameter and magnetic interaction parameter M. The parameter (Soret number) does not enter directly into the momentum and energy equations. Thus the effect of Soret number on velocity and temperature profiles is not apparent. The variation of concentration profiles for different values of is also presented graphically. The corresponding skin friction coefficients, the Nusselt number and the Sherwood number are also calculated and displayed in tables showing the effects of various parameters on them. A good comparison between the present numerical predictions and the previously published data (Sparrow and Gregg [1], Benton [2], and Kelson and Desseaux[3] ) has been achieved.
American International University-Bangladesh (AIUB)
Garyounis University, Libya
Helicobecter pylori infection is nfluenced by socioeconomic variables through Enzyme Linked Immuno Sorbent [ELISA] concentration. The present work is aimed to study the direct and indirect effects of socioeconomic variables on H. pylori infection, where indirect effects are observed through ELISA concentration. The infection has been detected among 132 patients of non-ulcer dyspepsia and also among 360 non-patients. Analytical results show that, patients and non-patients are significantly different in respect of the characteristics under study. The significance of the difference is investigated by chi-square test. The aged and non-patients are infected more in numbers. Lower infected cases are detected among higher socioeconomic status group of both patients and non-patients. But higher educated normal individuals are likely to be exposed to infection in large number.
