Volume: 1
Number: 2
July-December 2002

To see an article directly, click its Title. To see abstract, click its [Abstract] link.

• THE EFFECT OF CONVECTIVE HEAT TRANSFER COEFFICIENTS ON THE DESIGN OF CONDENSER AND EVAPORATOR OF A REFRIGERATION SYSTEM
  A.K.M. Iqbal Hussain
  Abstract PDF
  THE EFFECT OF CONVECTIVE HEAT TRANSFER COEFFICIENTS ON THE DESIGN OF CONDENSER AND EVAPORATOR OF A REFRIGERATION SYSTEM
  A.K.M. Iqbal Hussain

  Abstract

  In this paper, some possibilities to increase the overall heat transfer coefficients for condenser and evaporator of a refrigeration system are discussed. Some important heat transfer equations have been compiled and are presented for ready reference. Condensing and boiling heat transfer coefficients for R-12, R-22 and R-717 have been calculated for a 1.0 TR cooling capacity system operating on a given refrigeration cycle, and the calculated results are discussed with reference to designs of condenser and evaporator for given heat transfer duties. Some sample calculations of heat transfer coefficients have been included in the Appendix.
• A MODIFIED DIGITAL SIGNATURE STANDARD (DSS) ALGORITHM TO IMPROVE NETWORK SECURITY
  Omer Ali Beshir, ElyasTowhid Sheik Mahmoud, Shareeful Islam
  Abstract PDF
  A MODIFIED DIGITAL SIGNATURE STANDARD (DSS) ALGORITHM TO IMPROVE NETWORK SECURITY
  Omer Ali Beshir, ElyasTowhid Sheik Mahmoud, Shareeful Islam

  Abstract

  Authentication is fundamentally a part of our lives as privacy. We use authentication throughout everyday lives; when we sign our name to some document or we move to a world where our decisions and agreements are communicate electronically, we need to have electronic techniques for providing authentication. Digital signatures are used to detect unauthorized modification to data and to authenticate the identity of the signatory. In this research paper, a digital signature algorithm is developed which is a modified version of the Digital Signature Algorithm (DSA) proposed by the National Institute of Standards and Technology (NIST).
• IMAGE TEXTURE CLASSIFICATION USING CORTEX TRANSFORM: A BLOCK PROCESSING APPROACH (BPA)
  M.K. Bashar, M.S. Islam, N. Ohnishi
  Abstract PDF
  IMAGE TEXTURE CLASSIFICATION USING CORTEX TRANSFORM: A BLOCK PROCESSING APPROACH (BPA)
  M.K. Bashar, M.S. Islam, N. Ohnishi

  Abstract

  We present a block-based multi-channel mechanism for image texture classification inspired by human vi¬sual system(HVS). The proposed approach compresses the feature space by adopting the filters within a small sliding block of data meaningful to relatively accu¬rate boundary extraction. In our efforts, 2D Gaus¬sian functions were used as bandpass cortex filters to simualte the behaviour of simple cells in HVS. A square block of data was captured and cortex filters at various directions arid radial bands were applied to fil- terout. the required frequency components. The output of the filters were used to compute average energy and magt.it.ude deviation as texture features in the block. We repeated this procedure for the subsequent blocks of data. Hence we obtained a set of feature images. The obtained feature images were then integrated with min¬imum distance classifier for supervised and k-means algorithm for unsupervised classification. We demon- trated the performance of our approach by experiments on real world scence images from camera, Drodatz’s album and satellite sensors. Comparison with Haral- ick’s gray-level co-occurencematrix(GLCM) and dis¬crete wavelet frame(DWF) based approaches show the superiority of our method.
• COMPARISON OF BUILTD-IN-STORAGE AND NATURAL FLOW TYPE SOLAR WATER HEATERS
  M.R. Alam, M.R. Rahaman, S.M.N. Shams, M.F.Ilahi, M.A.R. Akhanda
  Abstract PDF
  COMPARISON OF BUILTD-IN-STORAGE AND NATURAL FLOW TYPE SOLAR WATER HEATERS
  M.R. Alam, M.R. Rahaman, S.M.N. Shams, M.F.Ilahi, M.A.R. Akhanda

  Abstract

  This paper compares experimental results of the performance tests of a Built-in-Storage Type Solar Water Heater (BSWH) and the Natural Flow Type Solar Water Heater (NFSWH) performed at IUT campus, Dhaka, Bangladesh during the rainy season.
  Both of these solar water heaters were mainly made of wood, G.l. Sheet, steel frame, and some valves and piping. The BSWH is 114 litres in capacity, 1.265m2 of collector surface area, and 10 cm. in depth and the NFSWH has a cylindrical tank of 900 mm length and 600 mm diameter having a capacity of 150 litres, the collector has a surface area of 1.84 m2 and depth of 200 mm. The readings were taken on hourly basis starting from 8 AM to 5 PM. The BSWH can heat 114 litres of water to a maximum temperature of 56°C and 59.5°C absorbing 2510.4 Wh/m2 and 2573.1 Wh/m2 heat energy during August and September respectively, whereas the NFSWH can heat 150 litres water to a maximum temperature of 60 C and 61 °C absorbing 2355.75 Wh/m2 and 2527.45 Wh/m2 heat energy in the same day. For BSWH the daily rise of water temperature was about 12°C in August and about 14 °C in September and for NFSWH the rise was about 16°C in August and about 18°C in September. The daily average heat energy absorbed by BSWH is about 1276.2 Wh/m2 and for the NFSWH it is about 1667.14 Wh/m2. The efficiency of the BSWH varies from 36.95 to 41.9 percent and that of for NFSWH 38.24 to 46.5 percent. These differences in heat energy absorption and the efficiencies are because of the fact that loss of heat increases rapidly with the rise of water temperature and the weather conditions also affect the total performance. On a very clear bright sunny day, the maximum efficiency can be obtained with a maximum mean water temperature.