http://dspace.mist.ac.bd:8080/xmlui/handle/123456789/36 Volume 2, Number 1, (2010) 2026-04-29T20:09:24Z http://dspace.mist.ac.bd:8080/xmlui/handle/123456789/538 DESIGN OF A MICROSTRIP PATCH ANTENNA IN A SILICON SUBSTRATE USING HFSS Nabila Nikhat, Shamma; Rashid, Rimi; Rayhan, Sajeeb; Saha, Pran Kanai The aim of this paper is to design a compact microstrip patch antenna for use in wireless/cellular devices. A typical cellular phone measures about 14.5 cm by 4.5 cm. Hence the antenna designed must be able to fit in such a cellular phone. A compact microstrip patch antenna has been successfully designed having a center frequency of 1.9 GHz. The ground plane dimensions for the patch antenna have been designed to be 31 mm by 40 mm and the patch dimensions are 22 mm by 31 mm. This is designed and simulated in High Frequency Structure Simulator (HFSS-9.2) of Ansoft Corporation. Shamma Nabila Nikhat (1), Rimi Rashid (1) , Sajeeb Rayhan (1) and Pran Kanai Saha (2) 1. Department of Electrical Electronic and Communication Engineering, MIST Email: nikhat038@gmail.com 2. Department of Electrical and Electronic Engineering, BUET, Email: sahapk@eee.buet.ac.bd 2010-02-01T00:00:00Z http://dspace.mist.ac.bd:8080/xmlui/handle/123456789/537 AN EXPERIMENTAL INVESTIGATION OF WIND LOAD ON TALL BUILDINGS WITH HEXAGONAL CROSS-SECTION Sultana, Kaniz Ronak; Chandra Mandal, Dr. Amalesh; Shameem Mahmood Ebna Hai, Bhuiyan An experimental investigation of surface static pressure distributions on hexagonal cylinder was conducted. The study was performed on both the single cylinder and the group consisting of two cylinders, one in the upstream and another in the downstream side. The test was conducted in an open circuit wind tunnel at a Reynolds number of 4.13 x 104 based on the face width of the cylinder across the flow direction in a uniform flow of velocity 13.2 m/s. The study was done on the single cylinder at various angles of attack from 00 to 500 at a step of 100. The surface pressure distributions were measured with the help of an inclined manometer. Then the group of two cylinders was taken into consideration for the study and the surface static pressures were measured for various inter-spacing of 1D, 2D, 3D, 4D, 6D and 8 D, D being the width of the cylinder across the flow direction. In each case the wind velocity was kept constant at 13.2 m/s. The pressure coefficients were calculated from the measured values of the surface static pressure distributions on the cylinder. Then the drag and lift coefficients were obtained from the pressure coefficients by the numerical integration method. It was observed that the drag coefficients become remarkably smaller compared to those for a sharp-edged square cylinder. It was also observed that at various angles of attack, the values of the lift coefficients were insignificant compared to those for a sharp-edged square cylinder. It can be further concluded that the hexagonal cylinder produces significantly low values of drag and lift forces and they approach to those of the cylinder with circular cross-section. Kaniz Ronak Sultana (1), Dr. Amalesh Chandra Mandal (2), Bhuiyan Shameem Mahmood Ebna Hai (3) 1. M.Sc in ME, Department of Mechanical Engineering, BUET, E-mail: kaniz.buet@engineer.com 2. Faculty of Mechanical Engineering Department, BUET, E-mail: amalesh@me.buet.ac.bd 3. Faculty of Mechanical Engineering Department, MIST, E-mail: shameem.me@mist.edu.bd 2010-02-01T00:00:00Z http://dspace.mist.ac.bd:8080/xmlui/handle/123456789/536 DERIVATIVES FOR CAPITAL MARKET EFFICIENCY Jahan, Masud; Hossain, Md. Moulude; Jaman, Md. Derivative contracts transfer risk, especially price risk, to those who are able and willing to bear it. How they transfer risk is complicated and frequently misinterpreted. Derivatives have also been associated with some spectacular financial failures and with dubious financial reporting. This paper will discuss the role of derivative products in capital flows, especially in providing a means of both reducing and enhancing market risks associated with given net flows. It will emphasize how derivatives can be used to evade risk-control or prudential regulation, circumvent capital controls, drive the dynamics of currency instabilities, and obscure true risk positions and thereby undermine the usefulness of balance of payments capital account categories. Financial derivatives (credit default swaps, options, etc) are screwing over the economy because too much money is being poured into the invisible (derivatives) market. This probably undervalues the prices of the underlying goods/assets/etc in the real market (instead, investors should just simply buy the stocks, etc and the increased demand would drive up the stock price and it would make everyone happy). All these derivatives may contribute to risk… it may encourage people to take on unreasonable risk and could lead to drastic market volatility. Masud Jahan (1), Md. Moulude Hossain (2), Md. Jaman (3) 1. Lecturer, Department of Science & Humanities, MIST, Email: masudjahan@gmail.com 2. Teaching Assistant, Department of Business Administration, IST, Email: mdmoulude@gmail.com 3. Student of BBA program, IST, Email: jamanheart510@gmail.com 2010-02-01T00:00:00Z http://dspace.mist.ac.bd:8080/xmlui/handle/123456789/535 WIMAX SECURITY ANALYSIS AND ENHANCEMENT Kowsar, Mir Md. Saki; Rahman, Muhammad Sakibur The importance of IEEE 802.16, Worldwide Interoperability for Microwave Access (WiMAX) is growing and will compete with technologies such as 3G. The acceptance and adoption of technologies also depend on security. Therefore, this article shows security vulnerabilities found in WiMAX and gives possible solutions to eliminate them. We find the initial network procedure is not effectively secured that makes man-in-the-middle attack possible. Focusing on this attack, we propose Diffie-Hellman (DH) key exchange protocol to enhance the security level during network initialization. We modify DH key exchange protocol to fit it into mobile WiMAX network as well as to eliminate existing weakness in original DH key exchange protocol. Finally we found that the proposed algorithm shows 2.5 times better performance in comparison with existing systems. Mir Md. Saki Kowsar (1), Muhammad Sakibur Rahman (2) 1. Department of Computer Science and Engineering, CUET E-mail: sakikowsar@cuet.ac.bd 2. Department of Computer Science and Engineering, CUET E-mail sakib_cse_cuet@yahoo.com 2010-02-01T00:00:00Z