Browsing by Author "Rahman, Tasfia"

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Design of an efficient energy harvester from ambient vibration
(BRAC University, 2012-04) Rahman, Tasfia; Rahman, Syedur; Onna, Shawzia Dewan; Rahman, Mossaddekur
The aim of this thesis was to design and an efficient energy harvester from ambient vibrations. An energy harvester is merely a device that will convert ambient energy into some usable electrical energy. In this work we designed a vibration energy harvester using electromagnetic transduction mechanism. The system consists of a fixed (movable) magnet and a movable (fixed) coil attached to a spring. When under vibration, relative motion between the fixed magnet and a moving coil or between the moving magnet and a fixed coil created a time varying flux linkage to the coil, thus inducing an electro-magnetic force. The electrical energy thus extracted from these vibrations need to be stored, using a battery charger circuit, and later on this may be used to drive electronic gadgets, self-powered micro-systems and wireless sensor network. In this work we designed the electro-mechanical energy harvesting system for optimum performance for a range of vibration energy and frequency, starting from 300-350Hz and studied the impact of difference device parameters, such as, size of the mass (510mg), stiffness of the spring, number of turns and dia of the coil. A charge controller circuit to store the generated electrical energy can be designed for implementation.
Industrial Effluent Treatment by Aeration and Filtration (Multimedia Filter)
(Department of Civil and Environmental Engineering(CEE), Islamic University of Technology(IUT), Board Bazar, Gazipur-1704, Bangladesh, 2024-06-03) Ahmed, Taki Tahmid; Rahman, Tasfia
Tannery industries produces large amount of wastewater containing huge amount of pollutants that doesn’t satisfies the standard values of ECR. It should be treated before contaminating river water. This study focuses on treating tannery wastewater without using any chemical products. The Study aimed to reach Bangladesh guideline levels for industrial wastewater of which were pH(6-9),TS (2200mg/L), EC(1200 micro siemens per centimeter), DO (6mg/l), At first aeration and sedimentation was done of the wastewater for various retention times like 1 hour, 2 hours, 3 hours and so on. After completing aeration and sedimentation finally filtration was done using a multimedia filter which contains five layers of filter materials. These filter materials can reduce turbidity, color, total suspended solids etc. The main aim of this project is reducing the chemical oxygen demand (COD) value. These three steps process (aeration + sedimentation + filtration) resulted in 80-90% reduction in COD. Pollutant removal efficiency was measured in terms of total dissolved solids, total suspended solids, color, turbidity and COD. Dissolved oxygen level of the wastewater was increased due to aeration. Most values were found to achieve standard values.