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RISS 인기검색어
- 검색키워드
- 저자 : Mahmud Ashraf (검색결과 5 건)
- 무료
- 기관 내 무료
- 유료
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Informational and Hybrid-informational Modelling of Yielding Shear Panel Device
Md. Raquibul Hossain,Mahmud Ashraf 대한토목학회 2014 KSCE JOURNAL OF CIVIL ENGINEERING Vol.18 No.4
Yielding Shear Panel Device (YSPD) is a recently developed passive control device, which is designed to exploit the sheardeformation characteristics of a steel diaphragm plate to dissipate energy when subjected to seismic excitation. Force-displacementresponse for a wide variety of YSPDs obtained using validated Finite Element (FE) models are used in the current paper to formulatea mathematical model using Neural Network (NN) to facilitate the structural modelling of the device. The proposed NNinformational model is able to accurately represent the complex pinching hysteretic response of YSPDs. The concept is furtherextended to devise a hybrid informational model to utilise the learning ability of a NN model within a mathematical framework. Theproposed hybrid model shows good agreement in predicting the force-deformation response of YSPDs in a simplistic manner andshould facilitate the full scale modelling of building frames retrofitted with YSPD without the need for complicated and detailed FEmodelling of the device.
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Mushfika Baishakhi Upama,Matthew Wright,Naveen Kumar Elumalai,Md Arafat Mahmud,Dian Wang,Kah Howe Chan,Cheng Xu,Faiazul Haque,Ashraf Uddin 한국물리학회 2017 Current Applied Physics Vol.17 No.2
Semitransparent organic solar cells are a promising approach to smart window applications and building integration. Here, we demonstrate a high performance semitransparent organic solar cell that incorporates the low bandgap polymer, PTB7, in the photoactive layer and a simple, non-patterned Dielectric/Metal/Dielectric or D/M/D anode (MoO3/Ag/MoO3). The combination of excellent photovoltaic properties of PTB7:PC71BM based solar cell and transparency of the MoO3/Ag/MoO3 anode resulted in an impressive power conversion efficiency of 5% at 18.3% visible light transmission. By tuning the active layer and outer MoO3 layer thicknesses, devices with ~25% average visible transmission were fabricated, which is considered as a benchmark transmittance for window applications. Transfer matrix modelling (TMM) was used to optimise the active layer and electrode thickness in terms of the optical field in the active layer. Additionally, the color rendering ability was found to be dependent on the active layer thickness, as well as the electrode. Device properties were studied from the perspectives of color rendering property, photovoltaic performance and theoretical optical field distribution.
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Highly crystalline bilayer electron transport layer for efficient conjugated polymer solar cells
Cheng Xu,Matthew Wright,Naveen Kumar Elumalai,Arafat Mahmud,Dian Wang,Mushfika Baishakhi Upama,Faiazul Haque,Ashraf Uddin 한국물리학회 2018 Current Applied Physics Vol.18 No.5
Solution processed solar cells are a promising renewable energy technology due to the low fabrication costs. The most commonly used electron transport layer for solution processed organic solar cells is ZnO. However, sol-gel derived ZnO is amorphous, which limits interfacial charge transport. In this study, we demonstrate a ZnO bilayer, composed of a nanoparticle ZnO and sol-gel derived ZnO layer, as the electron transport layer in polymer solar cells incorporating the novel polymer poly [(5,6-difluoro-2,1,3-benzothiadiazol-4,7-diyl)-alt-(3,3‴-di (2-octyldodecyl)-2,2′; 5′,2″; 5″,2‴-quaterthiophen-5,5‴-diyl)] (PffBT4T-2OD). Compared with the single layer sol-gel ZnO, the bilayer displayed enhanced crystallinity. Consequently, the interfacial transport from the active layer was improved, as evidenced by dark J-V and PL spectroscopy measurements. Solar cells incorporating this bilayer ZnO layer achieved PCE values exceeding 10%, a relative improvement of 25% compared to the sol-gel ZnO devices.
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Fire performance curves for unprotected HSS steel column
M. Shahria Alam,A.H.M. Muntasir Billah,Shahriar Quayyum,Mahmud Ashraf,A.N.M. Rafi,Ahmad Rteil 국제구조공학회 2013 Steel and Composite Structures, An International J Vol.15 No.6
The behaviour of steel column at elevated temperature is significantly different than that atambient temperature due to its changes in the mechanical properties with temperature. Reported literaturesuggests that steel column may become vulnerable when exposed to fire condition, since its strength andcapacity decrease rapidly with temperature. The present study aims at investigating the lateral load resistanceof non-insulated steel columns under fire exposure through finite element analysis. The studied parametersinclude moment-rotation behaviour, lateral load-deflection behaviour, stiffness and ductility of columns atdifferent axial load levels. It was observed that when the temperature of the column was increased, there wasa significant reduction in the lateral load and moment capacity of the non-insulated steel columns. Moreover,it was noted that the stiffness and ductility of steel columns decreased sharply with the increase intemperature, especially for temperatures above 400°C. In addition, the lateral load capacity and the momentcapacity of columns were plotted against fire exposure time, which revealed that in fire conditions, thenon-insulated steel columns experience substantial reduction in lateral load resistance within 15 minutes offire exposure.
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Flexural behaviour of Steel Timber Composite (STC) beams
Ruyuan Yang,Haitao Li,Rodolfo Lorenzo,Youfu Sun,Mahmud Ashraf 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.41 No.2
Structural performance of a new type of lightweight steel-timber composite (STC) beam has been investigated by conducting four-point bending tests on 21 specimens. This paper presents key findings on its structural performance parameters such as failure modes, load-deflection response, load-slip response, load-strain response, and the ultimate bending capacity by grouping 21 specimens into 7 subgroups based on various geometric characteristics. In the proposed STC beams, glulam slabs were connected to the steel beams using high-strength bolts, and the effect of different thickness and width of glulam slabs on the structural behaviour of STC beams were carefully investigated. In addition, the effective bending stiffness, deflection, and bending capacity of the STC beams were theoretically calculated based on elastic theory and compared with experimental values. For all considered specimens, timber slabs and steel beams showed good composite action. Increasing the thickness and width of the timber slabs can effectively limit the lateral deformation of the specimens, improve the bending capacity of the specimens, and provides a secant stiffness to the STC beams. It was observed that for the whole cross section of STC beams, the plane section assumption is not applicable, but the strains on timber and steel seemed to satisfy the plane section assumption individually. γ (Gamma) method has been observed to better reflect the deformation capacity of STC beams. Analytical equations were derived to predict the elastic bending capacity of STC beams, and comparison between theoretical and experimental values showed good agreement.
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