Volume: 3
Number: 1
January-June 2004

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

• PERFORMANCE COMPARISION OF BEAMFORMING TECHNIQUES
  Fakhrul Alam, Md. Zakir Hossain
  Abstract PDF
  PERFORMANCE COMPARISION OF BEAMFORMING TECHNIQUES
  Fakhrul Alam, Md. Zakir Hossain

  Abstract

  Smart antenna employing beamforming technique is one of the most promising approaches for combating Multiple Access Interference (MAI). In this paper the performances of two of the most popular criteria for beamforming namely Minimum Mean Square Error (MMSE) and the Minimum Signal to Interference and Noise Ratio (MSINR) have been verified. The effect of the number of samples on the estimation of second order statistics for beamforming is also investigated.
• PERFORMANCE ANALYSIS OF DATA TRAFFIC IN A GPRS BASED WIRELESS NETWORK USING SHARING TECHNIQUES
  Mohammad Rakibul Islam, Mohammad Nazrul Islam
  Abstract PDF
  PERFORMANCE ANALYSIS OF DATA TRAFFIC IN A GPRS BASED WIRELESS NETWORK USING SHARING TECHNIQUES
  Mohammad Rakibul Islam, Mohammad Nazrul Islam

  Abstract

  GPRS is a packet-based radio service that enables "always on" connections, eliminating repetitive and time consuming dial-up connections. It also provides real throughput in excess of 40 Kbps, about the same speed as an excellent landline analog modem connection. It greatly improves and simplifies wireless access to Packet Data Networks (PDN). An analytical model is presented in this paper to analyze the performance of different sharing techniques in the circuit switched voice and packet switched data networks. The blocking probability, throughput, average delay and utilization for these techniques are compared. Impact of data channels on these parameters is shown. In the partial sharing technique, these traffic parameters show better performance than the other sharing techniques. It is noted that in the lower traffic cases, fixed sharing is relatively better. We need to allocate dedicated data channel, which will not be shared with the voice channel. However, allocation of dedicated data channel is needed.
• BEHAVIOUR OF DIESEL COMBUSTION AND EXHAUST EMISSION WITH NEAT DIESEL FUEL AND DIESEL-BIODIESEL BLENDS
  Md. NurunNabi, Mhia Md. ZaglulShahadat
  Abstract PDF
  BEHAVIOUR OF DIESEL COMBUSTION AND EXHAUST EMISSION WITH NEAT DIESEL FUEL AND DIESEL-BIODIESEL BLENDS
  Md. NurunNabi, Mhia Md. ZaglulShahadat

  Abstract

  The diesel combustion and exhaust emissions with neat diesel fuel and diesel-bloodlessly blends are investigated. In the investigation, firstly, making of biodiesel is done by esterification and secondly, experiment is conducted with neat diesel fuel and diesel-biodiesel blends in a four stroke naturally aspirated (NA) direct injection (DI) diesel engine. The volumetric blending ratios of biodiesel with conventional diesel fuel are set at 0, 5, 10, and 20. Compared with neat diesel fuel ,diesel-biodiesel blends show lower carbon monoxide (CO), nitrogen oxides (NOx) and smoke emissions due to improved properties after esterificaton and presence of oxygen in the biodiesel. Engine noise is reduced with all diesel-biodiesel blends.
• AERODYNAMIC FORCES AROUND A TAPERED SQUARE CYLINDER
  M.F.Kader, M.F. IIahi, M.Q. Islam
  Abstract PDF
  AERODYNAMIC FORCES AROUND A TAPERED SQUARE CYLINDER
  M.F.Kader, M.F. IIahi, M.Q. Islam

  Abstract

  An experimental investigation of the pressure distribution around a tapered aquaria cylinder placed in uniform flow with three Reynolds numbers i.e.5.49 x 104, 6.88 x 104 and 1.38 x 105 is presented. Mean pressure was measured for 0 and 45 angle of attack at different planes of the tapered square cylinder in an open circuit wind tunnel. The drag co-efficient was calculated by numerical integration. The pressure co-efficient around the cylinder at different planes has been obtained by measuring the static pressure head on the surfaces of the cylinder.