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Mohammad S. Rahman,Mohammad S. Islam,도정윤,김두기 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.63 No.3
This paper presents a review on getting a Weighted Multi-Objective Optimization (WMO) of Tuned Mass Damper (TMD) parameters based on Response Surface Methodology (RSM) coupled central composite design and Weighted Desirability Function (WDF) to attenuate the earthquake vibration of a jacket supported Offshore Wind Turbine (OWT). To optimize the parameters (stiffness and damping coefficient) of damper, the frequency ratio and damping ratio were considered as a design variable and the top displacement and frequency response were considered as objective functions. The optimization has been carried out under only El Centro earthquake results and after obtained the optimal parameters, more two earthquakes (California and Northridge) has been performed to investigate the performance of optimal damper. The obtained results also compared with the different conventional TMD‟s designed by Den Hartog‟s, Sadek et al.‟s and Warburton‟s method. From the results, it was found that the optimal TMD based on RSM shows better response than the conventional damper. It is concluded that the proposed response model offers an efficient approach regarding the TMD optimization.
Rahman, Mohammad S.,Islam, Mohammad S.,Do, Jeongyun,Kim, Dookie Techno-Press 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.63 No.3
This paper presents a review on getting a Weighted Multi-Objective Optimization (WMO) of Tuned Mass Damper (TMD) parameters based on Response Surface Methodology (RSM) coupled central composite design and Weighted Desirability Function (WDF) to attenuate the earthquake vibration of a jacket supported Offshore Wind Turbine (OWT). To optimize the parameters (stiffness and damping coefficient) of damper, the frequency ratio and damping ratio were considered as a design variable and the top displacement and frequency response were considered as objective functions. The optimization has been carried out under only El Centro earthquake results and after obtained the optimal parameters, more two earthquakes (California and Northridge) has been performed to investigate the performance of optimal damper. The obtained results also compared with the different conventional TMD's designed by Den Hartog's, Sadek et al.'s and Warburton's method. From the results, it was found that the optimal TMD based on RSM shows better response than the conventional damper. It is concluded that the proposed response model offers an efficient approach regarding the TMD optimization.
( Mohammad N. Islam ),( Hoi N. Yang ),( Han S. Yang ),( Keum J. Park ) 한국농업기계학회 2010 한국농업기계학회 학술발표논문집 Vol.15 No.1
This research paper focuses on a design of a feasible and efficient technique for the reuse of industrial chemical wastewater. Combination techniques of the automatic restore filter (ARF) and reverse osmosis (RO) can be one of the possible solutions for treating industrial chemical wastewater. In this study, four types ( tin wastewater, Fine chemical industry wastewater, mixed chemical wastewater and Kumho chemical industry wastewater) of industrial chemical wastewater was evaluated using combined ARF and RO pilot plant, on the basis of COD, TN and TSS removal efficiency. Experiment was carried out using continuous flow operation system. Analyzing the all samples, we obtained the highest removal efficiency of COD, TN and TSS, 98.2%, 98.9% and 90.0%, respectively from tin wastewater. Also the removal efficiencies of Fine chemical industry wastewater, mixed chemical wastewater and Kumho chemical industry wastewater for COD, TN and TSS were 99.5%, 93.2%, 62.6%; 69.9%, 77.8%,95.0% and 99.8%, 86.9%, 99.0%, respectively. The results indicate that the combination of ARF and RO is a good technique for treating industrial chemical wastewater.
Islam, Mohammad S.,Shahin, Hossain M. Techno-Press 2013 Geomechanics & engineering Vol.5 No.4
Vetiver grass (Vetiveria zizanioides) is being effectively used in many countries to protect embankment and slopes for their characteristics of having long and strong roots. In this paper, in-situ shear tests of the ground with the vetiver roots have been conducted to investigate the stabilization properties corresponding to the embankment slopes. Numerical analyses have also been performed with the finite element method using elastoplastic subloading $t_{ij}$ model, which can simulate typical soil behavior. It is revealed from field tests that the shear strength of vetiver rooted soil matrix is higher than that of the unreinforced soil. The reinforced soil with vetiver root also shows ductile behavior. The numerical analyses capture well the results of the in-situ shear tests. Effectiveness of vetiver root in geotechnical structures-strip foundation and embankment slope has been evaluated by finite element analyses. It is found that the reinforcement with vetiver root enhances the bearing capacities of the grounds and stabilizes the embankment slopes.
Mohammad S. Islam,Shahria Alam 한국콘크리트학회 2013 International Journal of Concrete Structures and M Vol.7 No.4
This study evaluates the shear strength of steel fiber reinforced concrete (SFRC) beams from a database, which consists of extensive experimental results of 222 SFRC beams having no stirrups. In order to predict the analytical shear strength of the SFRC beams more precisely, the selected beams were sorted into six different groups based on their ultimate concrete strength (low strength with fc<SUP>1</SUP><50 MPa and high strength with fc<SUP>1</SUP><50 MPa), span-depth ratio (shallow beam with a/d ≥ 2.5 and deep beam with a/d < 2.5) and steel fiber shape (plain, crimped and hooked). Principal component and multiple regression analyses were performed to determine the most feasible model in predicting the shear strength of SFRC beams. A variety of statistical analyses were conducted, and compared with those of the existing equations in estimating the shear strength of SFRC beams. The results showed that the recommended empirical equations were best suited to assess the shear strength of SFRC beams more accurately as compared to those obtained by the previously developed models.
Manufacture and Characterization of hemp-Acrodur Biocomposites: Variation of Process Parameters
Mohammad S Islam,Menghe Miao 한국섬유공학회 2022 Fibers and polymers Vol.23 No.8
In this study, hemp fibre reinforced Acrodur resin biocomposites were manufactured using nonwoven hemp fibremats by varying a range of processing parameters such as Acrodur solution to dispersion ratio, relative humidity, curing time,and temperature. Dry fibre mats using Acrodur solution to dispersion ratio of 3:1 at a temperature of 160 oC and processingtime of 20 minutes were found to be optimum condition for the manufacture of the biocomposites. These optimumparameters gave the best combination of specific tensile strength (26.4 MPa-cm3/g) and specific Young’s modulus (4.4 GPacm3/g) with a density of 0.94 g/cm3. Thermogravimetric analysis (TGA) of the optimised biocomposites showedsimilarthermal stability when compared with pristine fibres. Contact angle measurements of the optimised biocomposites showedincreased hydrophobicity of the biocomposites than those of the pristine fibres. From the water immersion test, the path ofwicking of water molecules into the biocomposites was believed to be rather straight than tortuous and A 4-week waterimmersion test of the optimised biocomposites conceded about 43.5 % loss of tensile strength and 57.1 % loss of Young’smodulus which was believed to be due to wicking of the water molecules into the fibre of the biocomposites in a straight pathrather than a tortuous path.
Islam, Mohammad S.,Do, Jeongyun,Kim, Dookie Techno-Press 2018 Smart Structures and Systems, An International Jou Vol.21 No.2
In this inquisition, a passive damper namely Stockbridge Damper (SBD) has been introduced to the field of vibration control of Offshore Wind Turbine (OWT) to reduce the earthquake excitations. The dynamic responses of the structure have been analyzed for three recorded earthquakes and the responses have been assessed. To find an optimum SBD, the parameters of damper have been optimized using Response Surface Methodology (RSM) based on Box-Behnken Design (BBD) and Particle Swarm Optimization (PSO). The influence of the design variables of SBD such as the diameter of messenger cable, the length of messenger cable and logarithmic decrement of the damping has been investigated through response variables such as maximum displacement, RMS displacement and frequency amplitude of structure under an artificially generated white noise. After that, the structure with optimized and non-optimized damper has been analyzed with under the same earthquakes. Moreover, the comparative results show that the structure with optimized damper is 11.78%, 18.71%, 11.6% and 7.77%, 7.01%, 10.23% more effective than the structure with non-optimized damper with respect to the displacement and frequency response under the earthquakes. The results show that the SBD can obviously affect the characteristics of the vibration of the OWT and RSM based on BBD and PSO approach can provide an optimum damper.
Mohammad S. Islam,Jeongyun Do,Dookie Kim 국제구조공학회 2018 Smart Structures and Systems, An International Jou Vol.21 No.2
In this inquisition, a passive damper namely Stockbridge Damper (SBD) has been introduced to the field of vibration control of Offshore Wind Turbine (OWT) to reduce the earthquake excitations. The dynamic responses of the structure have been analyzed for three recorded earthquakes and the responses have been assessed. To find an optimum SBD, the parameters of damper have been optimized using Response Surface Methodology (RSM) based on Box-Behnken Design (BBD) and Particle Swarm Optimization (PSO). The influence of the design variables of SBD such as the diameter of messenger cable, the length of messenger cable and logarithmic decrement of the damping has been investigated through response variables such as maximum displacement, RMS displacement and frequency amplitude of structure under an artificially generated white noise. After that, the structure with optimized and non-optimized damper has been analyzed with under the same earthquakes. Moreover, the comparative results show that the structure with optimized damper is 11.78%, 18.71%, 11.6% and 7.77%, 7.01%, 10.23% more effective than the structure with non-optimized damper with respect to the displacement and frequency response under the earthquakes. The results show that the SBD can obviously affect the characteristics of the vibration of the OWT and RSM based on BBD and PSO approach can provide an optimum damper.