Showing papers by "Chittagong University of Engineering & Technology published in 2008"

Voltage mode control of single phase boost inverter

Abstract: Boost inverter is able to generate an AC voltage whose peak value can be larger or smaller than the DC input voltage in a single stage. The boost inverter consists of two individual boost DC-DC converters. Each of the boost DC-DC converters has to be controlled in variable operating point condition. This paper proposes two voltage mode controllers. First one is conventional feedback controller based on small signal model. Second one is a simplified voltage mode controller based on feedforward pulse width modulation (FF-PWM) and simple voltage feedback loop to control the output voltage of the boost inverter. The second controller gave better result. The controller also ensures output voltage to meet IEEE Std 519 voltage harmonic limits. Unlike most previously proposed controllers, the proposed method is based only on output voltage feedback, making unnecessary the inductor current measurement. The control method is verified by means of simulations.

Mechanical and physical properties of slate from Britannia Cove, Newfoundland

Abstract: The experimental investigation described in this study was carried out to determine the physical and mechanical properties (elastic moduli, Poisson’s ratio, compressive and tensile strengths, hardn...

Security enhancement of MD5 hashed passwords by using the unused bits of TCP header

Abstract: When a password is encrypted by a hash algorithm the resultant is called hashed password. In a server client based communication system such as Yahoo Messenger, AIM, passwords of clients are hashed by MD5 and passed to the server for authentication. This type of transmission is always a subject of interception by the hackers. These hashed passwords are passed through the Internet as a data packet. TCP header is a most common part of the data packet. In a TCP header there are six reserved bits which remains always unused. In this paper we propose a new approach to enhance the security of hashed passwords by using the six reserved bits of a TCP header. Here we encrypt the hashed password by a random key using simple mathematical function. The information needed to decrypt the encrypted hashed password is carried by the six bits of TCP header.

Bangla vowel sign recognition by extracting the fuzzy features

Abstract: This paper presents a fuzzy based Bangla vowel sign recognition system. Vowel and consonant are the main criteria to express any language. Exceptionally, Bangla has some vowel sign which are used to express Bangla word. Therefore, to recognize any Bangla word, at first it is necessary to recognize which vowel sign is used to express that word. Due to its low computational requirement and very high accuracy, fuzzy logic system is probably the most efficient method available for online vowel sign recognition. The most important task for this implementation is the building of the rule base using fuzzy logic that would describe the recognized vowel sign, which is more complicated as different people write the same vowel sign in completely different ways. In this paper, we propose a system that uses automatically generated fuzzy membership value that describes the handwritten Bangla vowel sign written by different individuals.

Bangla Numeral Recognition Engine (BNRE)

Abstract: Numeral recognition is the process to classify the given character according to the predefined character class This paper proposed a methodology for recognizing Bangla handwritten numerals which are based on fuzzy logic theory due to its low computational requirement Every numeral is segmented and several features are extracted for each segment In this paper, we use unique fuzzy rule base for each numeral We have tested our engine for Bangla numerals considering various writing style and got more than 80% recognition accuracy

Developing a model of e-governance for urban and rural areas of Bangladesh

Abstract: Several developing countries including Bangladesh are realizing the role ICT (information & communication technology) can play in the governance sector, and are putting into practice innovative e-governance models that may be technologically simple but are drastically changing the way information is distributed in the society. This paper depicts and implements a model of e-governance for urban and rural areas in Bangladesh. The project deeply considered existing ICT infrastructure in Bangladesh and put effort to implement the model in a cost effective and flexible manner. A clear, comprehensive layout and network architecture for rural and city areas is given separately. We also described complementary tasks such as database implementation, system development, web related task etc. for e-governance. The main objective of the project is to implement e-governance in an easy and cost effective way to suit with existing ICT infrastructure in Bangladesh to provide better information and service delivery of government to the people.

An empirical framework for translating of Phrasal verbs of English sentence into Bangla

Abstract: Generally phrasal verbs comprise a verb followed by a preposition that is commonly occurring feature in English. Each of the phrasal verbs acquires absolutely different meanings in different contexts. Having highly context dependent meanings, phrasal verbs may be disambiguated only by devising a technique involving utilization of semantic information pertaining to the context. This paper presented a framework for translating the phrasal verbs in English sentence into its equivalent Bangla. Semantics is necessary in the field of natural language processing to detect the meaning of the individual words in the sentence. This paper also describes different types of semantic features that perform semantic based disambiguation of phrasal verbs. A translation engine works to find out the exact Bangla meaning of the phrasal verb from different English sentences. We have tested our model for different type of English sentences containing phrasal verbs that are taken from the English newspaper and English textbook. We got successful results for most of the test cases.

Berthing Problem of Ships in Chittagong Port and Proposal for its Solution

Abstract: INTRODUCTION Since 1888, Chittagong port, the main port of Bangladesh with the shore base facilities, has been playing a vital role in the economic development of the country. It has 15 general purpose jetties beside having a few additional jetties to handle oil, clinker, food grain, etc. The jetties were built about nine nautical miles inside from the shoreline of the Bay of Bengal. The ports of the world have changed significantly with the advent of containerization in trade in the seventies of the last century. The port of Chittagong, despite many constraints, continues to cope with the changing patterns of the trade. However, it has been suffering from the problems of poor operational efficiency. The traffic through the port is increasing along with the economic development of the country. It is frequently seen that a queue of arriving ships is formed and sometimes ships have to wait for a longer time. In addition to that the lack of adequate inland infrastructure to handle containers gives rise to the instances of congestion in jetties and the delays in the final delivery of goods to the importer premises with consequent increase in transportation and other costs. In this paper, the berthing problem of ships in Chittagong port is analyzed using multi-server queuing models. Data of arrivals and departures of ships from 1994 to 2000 are collected and statistical techniques are applied to find out and analyze the probability distributions and other parameters of the arrival and departure processes. It is predicted that the congestion problem at Chittagong port will take a serious turn after 2015 AD if the present import and export growth rates continue. Therefore, some proposals are made to solve the congestion problem of this important seaport.

Development of control strategy for load sharing in grid-connected PV power system

Abstract: In a power system of conventional parallel connected generators, share of real power and reactive var of an incoming generator are controlled by adjusting shaft power input and field excitation The scenario of load sharing by a grid connected PV system is however different since no prime mover or excitation source are present Due to serious power crisis, there are needs for evacuation of PV power to grid systems However, this needs intensive analysis on the load sharing phenomena In this paper, aspects of load sharing of a grid connected PV system are analyzed, and a strategy is proposed where the load sharing task can be undertaken controlling both modulation index and phase angle of the inverter It is seen that both real power and reactive var are affected upon change in index of modulation and phase angle of the PV inverter Analysis and simulation results are presented to demonstrate effectiveness of the proposed control technique

Modeling and numerical analysis of thermal treatment of granulated porous particles by induction plasma

Abstract: In this paper it is aimed to describe the modeling and numerical analysis of thermal treatment of granulated porous particles by induction plasma To investigate the heat exchange dynamics between plasma and particles during the flight of granulated porous particles through the hot plasma, a plasma-particle interactive flow model has been developed This model solves the conservation equations to predict the temperature and flow fields of plasma, under local thermal equilibrium (LTE) conditions, and then computes the injected particles trajectories, temperature and size histories, and the particle source terms to incorporate the particle loading effects It is found that the size and dose of injected particles greatly affect the particle trajectory and temperature, and hence the heat transfer to particles at higher powder feed-rate

Harmonic mitigation in transformers of twelve-pulse rectifier using active filter

Abstract: Researchers proposed several techniques to reduce the harmonics present in the input current of 12-pulse rectifier. But the transformers used in the rectifier contain more low order harmonics in their input currents. In this paper a novel active filtering method for input current wave shaping of the transformers used in a 12-pulse rectifier is proposed. With the proposed method both the rectifier and transformers are shown to draw near sinusoidal input currents from the utility. This active filtering technique uses high switching frequency PWM Boost converter that shapes the input currents by eliminating high frequency harmonic components with the aid of small size LC filters. The size of the LC filters is reduced to a considerable extent with the proposed technique. Detailed design and simulation results are presented to show the effectiveness of the proposed method.

Structural operational semantics of packages in Java

Abstract: A good understanding of programming language can be developed and understood in a machine independent manner called structural operational semantics. It is a mathematical model for specifying the meaning of a language by defining the effect of a running program in terms of its structure. The emphasis of this work is to present the structural operational semantics of several important aspects of packages in Java programming. With that we have showed how structural operational semantics is helpful for understanding the structure of packages.

Dual beam phased array antenna with wide scan angle for repeater applications

Abstract: A dual polarized, dual beam phased array antenna with wide scan angle capabilities was designed and manufactured for repeater application Two fixed feeding networks were designed and manufactured for the dual beams With the feed networks, one broadside main beam and one tilted main beam were generated The antenna achieved good isolation of -355 dB between the two main beams (broadside and tilted beam) within the frequency band of interest (25-27 GHz) The return loss for the broadside feed network port was found to be below -75 dB and return loss for the tilted beam feed network port was less than -15 dB The side lobe levels for the broadside beam and the tilted beam were -12 dB and -8 dB down, respectively The cross-polar level for the broadside beam was lower than -20 dB at the center frequency both in the elevation plane and in the azimuth plane Also, for the tilted beam the cross-polar level in elevation plane was measured to be as low as -20 dB at the centre frequency

Design of an Intelligent Remote Monitoring and Control of Bangladesh Railway Transport System Using Information and Communication Technologies (ICTs)

Abstract: In Bangladesh, transport sectors are developing rapidly to meet the increasing demand for transporting passengers and freight inside and outside the country. But there is not such development in railway transport system. The Bangladesh Railway transport system is still using an old technology to monitor and control signalling, scheduling, operations etc. This paper describes various problems in the existing systems and also solutions have been provided considering the existing railway transport systems of Bangladesh. A new system has been developed to control and monitor the total railway transport system from remote locations. While designing the system, various sensors and actuators have been introduced and also Information and Communication Technologies (ICTs) have been applied in the field of railway transport. So a Machatronics aspect of system has been designed to ensure a collision free, safe and efficient operation and management of railway transport system. This system is not only for monitoring and controlling of railway transport but also ensures efficient asset management. As a result face-to-face accidents, cross-road accidents and accidents due to railway line displacements or breakage can be avoided and there will be no loss of assets and valuable human lives.Copyright © 2008 by ASME

PIR with P-Cache: A New Private Information Retrieval Protocol With Improved Performance

Abstract: The increasing model of e-commerce infrastructure opens the door for secure transaction of information over the Net, keeping some records private as users’ choice within a few seconds. A client, while frequently retrieving his records, seldom wishes to hide the identity of the records to the database server. Private Information Retrieval (PIR) protocols allow users to retrieve information from a database while keeping their query private. Existing protocols have pros and cons in terms of communication and computational complexity. In some PIRs the computational complexity is reduced to O(1), and optimal, but still holds the high communication complexity O(Ns) as there is a huge amount of communication needed to satisfy the query. In our research a new PIR, namely PIR with P-cache, is introduced, based on the concept of database caching technology. In an average case, whenever a client requests a query in the system, there is a high probability to satisfy it from the P-cache instead of accessing the main database server that contains a huge amount of records. Our protocol outperforms the existing protocols in terms of both communication and computational complexity for queries supporting from P-cache and hence an improved performance.