Chittagong University of Engineering & Technology

About: Chittagong University of Engineering & Technology is a education organization based out in Chittagong, Bangladesh. It is known for research contribution in the topics: Computer science & Renewable energy. The organization has 1200 authors who have published 1444 publications receiving 10418 citations. The organization is also known as: Engineering College, Chittagong & Bangladesh Institute of Technology, Chittagong.

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

Effect of Annealing Temperature on the Structural and Optical Properties of CdS Thin Films Deposited by CBD

Abstract: CdS thin-films deposited by CBD offers ultrathin films along with the good structural, electrical and optical properties within a very low processing cost. CdS thin-films were deposited by CBD technique and the as deposited films were annealed at 200°C and 400°C temperature under vacuum environment. The as deposited and annealed films were characterized by X-ray diffraction and UV-Visible near infrared spectroscopy. A comparative study of crystallographic and optical properties between the as deposited and annealed films were investigated. Analysis on structural and optical properties showed that the annealed CdS thin films offer much better crystallinity and less lattice defects as compared to the as deposited films. Near about 90% transmittance is achieved for the as deposited films and the optical transmittance is quite reduced for the annealed films and at the same time, the transmittance has increased slightly in the blue region at 400°C annealing temperature. Moreover, thinner (near about 100 nm) CdS layer can be fabricated by CBD with high transmittance enhances the possibility of applying this layer as buffer layer for high performance thin-film solar cell fabrication.

Intra- and inter-wafer characterization of waveguide propagation loss and reflectivity

Abstract: In silicon photonics, due to the increasing complexity of the device designs and the increasing density of the functions integrated on a single circuit, the precise characterization of the building blocks has become essential in order to assess the quality of the fabrication outcomes. As waveguides are the fundamental building block of photonic integrated circuits, its accurate characterization is very important to evaluate the quality of all passive elements. In this paper the characterization of two very important parameters, namely waveguide propagation loss and waveguide sidewall reflectivity, are reported for waveguides utilized inside a microring-based silicon photonic network-on-chip. Using a recently proposed method based on undercoupled all-pass microring structure, the two parameters from five differently positioned chips in two different wafers are measured in order to investigate the intra- and inter-wafer variations. Precise measurements allow to define range of values and variations for these two parameters in photonic network-on-chip.

Measurement of the Activity Concentrations of the Terrestrial Radionuclides from the Samples Collected from the Northern Part of Chittagong City Corporation, Chittagong, Bangladesh

Abstract: The concentrations of natural and artificial radionuclides in soil samples collected from the different areas of Chittagong City Corporation were measured by using Gamma-ray Spectrometry of High Purity Germanium (HPGe) detector.The concentration of 238U was found to be in the range 25.66 ± 5.48 Bq/Kg to 48.87 ± 6.00 Bq/Kg with an average value of 39.11 ± 5.77 Bq/Kg, the activity concentration of 232Th was found to be in the range of 27.12 ± 7.07Bq/Kg to 64.71 ± 7.95 Bq/Kg with an average value of 45.65 ± 7.48 Bq/Kg , and the activity concentration of 40K was found to be in the range of 293.81 ± 75.36 Bq/Kg to 637.49 ± 81.88 Bq/Kg with an average value of 430.56 ± 76.79 Bq/ Kg. The level of natural radioactivity in the region has been compared with the other areas of the world and the world average. In the soil samples, the overall activity concentration of Uranium and Potasium has been found to be higher than that of the world average, and the activity concentration of Thorium has been found to be nearly of the world average and the activity concentration. The artificial radionuclide 137Cs has not been detected in the samples.

A study on the reactive power control mechanism of current source boost inverter for Photovoltaic power system

Abstract: In this paper, a study has been performed on current source DC-AC boost inverter especially for Photovoltaic (PV) applications. It presents a reactive power control strategy and its effects on the other parameters of the system. It also prescribes a range of modulation index; at which the percentage of Total Harmonic Distortion (THD) is within the suitable limit according to the IEEE standard 519. The reactive power controlling mechanism has been achieved by finding the right combination of bank capacitors placed between the inverter and the load side for different modulation index (M a ). Sine Pulse Width Modulation (SPWM) technique has adopted for generating switching signals of the Boost Inverter which controls the output parameters of the inverter. A set of parameters have been studied along with in-depth analysis and simulated which are presented to demonstrate the effectiveness of the proposed control technique.