Browsing by Author "Shariful islam, Md."

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Behaviour of G. I. fiber reinforced concrete made with natural and recycled aggregates
(Department of Civil Engineering, 2014-12) Shariful islam, Md.; Siddique, Dr. Mohammad Al Amin
The use of recycled aggregates from construction and demolition waste (CDW) as the replacement of coarse aggregates has increased in recent years in order to reduce the high consumption of natural resources by civil infrastructure construction sectors. In addition, steel fiber reinforced concrete has been used in many applications such as concrete pavements, overlays, patching repair of hydraulic structures, thin shells and precast products over the past several decades. Nowadays, it is well established that the incorporation of steel fibers improves engineering performance of structural and nonstructural concrete, including better crack resistance, increase in ductility and toughness as well as enhancement in resistance to fatigue and impact. In this work an experimental investigation is carried out to observe the influence of Galvanized Iron (G.I.) fiber reinforcement on the stress-strain behavior of concrete made with brick aggregate and recycled brick aggregate. In addition, compressive strength by destructive test as well as non-destructive test, Splitting tensile strength and Young’s modulus are also determined. Two types of coarse aggregates, brick and recycled brick aggregates having the same gradation and water cement ratio (w/c=0.44) are used. Hooked end G.I. wires with 50 mm of length and aspect ratio of 55.6 are used as fiber reinforcements in a volume fraction of 0%, 0.50% and 1.00%, respectively for the both cases. The experimental results show that around 10% to 15% and 40% to 60% increase in 28 days compressive strength and tensile strength of GI fiber reinforced concrete, respectively compared to control case (0% G.I. fiber replacement) for both the aggregates. It is seen that effect of addition of 1% fiber on the concrete compressive strength is little compared to that of 0.5% G.I. fiber addition for both the aggregate types. On the other hand, concrete strain at failure of G.I. fiber reinforced concrete has increased almost 2 times compared to the control case (0% GI fiber replacement) for both the aggregate types. It is also observed that effect of fiber reinforced concrete made with 1% fiber is more than 0.5% fiber for the both cases of aggregates in the terms of maximum strain of concrete. Keywords: Brick aggregate, Recycled Brick aggregate, G.I. fiber, Compressive strength, Tensile strength, Young’s Modulus, Stress-strain behavior.
Exergy and thermo-economic study of A 412 MW natural gas-fired combined cycle power plant
(Department of Mechanical Engineering (ME), BUET, 2023-07-26) Shariful islam, Md.; Haq, Dr. Md. Zahurul
Combined cycle power plants are highly favored for their superior power output and efficiency. However, evaluating and optimizing these plants require more than just first law-based energy analysis; a combination of energy, exergy, and thermoeconomic analyses is necessary. This thesis presents such an analysis for the 412 MW Haripur combined cycle power plant, utilizing over 3.7 million real-time operational data points collected over a year. This extensive dataset allowed for the examination of seasonal impacts on performance parameters and the development of a correlation table for key metrics. The analysis found that gas turbines (GT) perform optimally at lower ambient temperatures, while steam turbines (ST) achieve their highest efficiency in hot, dry conditions. The plant’s peak efficiency was 60.19% Exergy analysis identified the combustion chamber as the primary source of irreversibility, accounting for about 70% of total exergy destruction, with an exergoeconomic factor of 3.82%. To mitigate this, it is recommended to match the compressor outlet and fuel temperatures before combustion. Although the condenser is a major source of heat loss in energy analysis, exergy analysis showed it has a high exergoeconomic factor of 95.32%, indicating minimal economic loss per unit of exergy destroyed. The thesis concludes with key observations and recommendations for optimizing the power plant under various ambient conditions.
Performance analysis of space frequency block coded OFDM free-space optical communication systems with polarization diversity over atmospheric turbulent channel
(Department of Electrical and Electronic Engineering (EEE), BUET, 2022-11-26) Shariful islam, Md.; Majumder, Dr. Satya Prasad
Free-space optical (FSO) communication system is an emerging technology for future broadband optical data communication network due to its lucrative properties like required no license, cost effective, simple hardware architecture, high data rate, full duplex communication, easy to deployment, etc.. During the last two decades, the user demand for data rate increased tremendously. To meet up the current data rate demand, FSO technology can play as a key parallel technology to enhance the capacity of the existing data communication network. However, there are some adverse weather effects like molecular absorption, scattering, beam divergence, background radiation, rain, snow, fog etc. severely limits the performance of FSO communication links. Beside these, pointing error due to earth quake, building sway and building vibration due to heavy mechanical load may occurs link failure which drastically degrades the performance of FSO communication links. Huge numbers of research works have already been published regarding how to mitigate the limitations of FSO communication system. Various methods of mitigation techniques like aperture averaging, diversity, adaptive optics, coding, modulation, relay transmission, background noise rejection, jitter isolation and rejection, hybrid RF/FSO link etc. are already employed by many of the researchers. In this dissertation, several analytical models are developed for a non-Hermitian OFDM FSO system followed by differential quadrature phase shift keying (DQPSK) modulation with polarization diversity over atmospheric turbulent channel. Firstly, an analytical model is developed to evaluate the signal to noise ratio (SNR) and bit error rate (BER) of a non-Hermitian OFDM FSO system followed by DQPSK modulation in presence of atmospheric turbulence. To perform non-Hermitian OFDM, two different laser sources are required for transmitting real and imaginary part separately. Secondly, analysis is also carried out for the same system model with polarization diversity to overcome the requirement of two laser sources and evaluated the cross polarization induced crosstalk, signal to crosstalk plus noise ratio (SCNR) and BER performance of the system in presence of all atmospheric turbulent conditions. The effect of pointing error on system BER performance is also carried out. Further analysis is also carried out to mitigate the fading due to atmospheric turbulence by applying aperture averaging technique. Thirdly, a novel analytical model is developed to evaluate the output SCNR and average BER for Space Frequency Block Coded non-Hermitian coherent-optical OFDM DQPSK FSO system with polarization diversity under turbulent atmospheric conditions. For a given BER, the SFBC coding gain is also numerically determined. Fourthly, the analysis is extended to compare the coding gain of SFBC with STBC for the same system parameters. Results are compared in terms of SCNR, BER, power penalty and receiver sensitivity. Finally, the numerically evaluated performance results for different system and channel parameters are validated by numerical simulations. Optimum system design parameters are also determined. The results of this dissertation may be used for the future development of FSO communication systems.