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RISS 인기검색어
- 검색키워드
- 저자 : Moghaddas S. (검색결과 4 건)
- 무료
- 기관 내 무료
- 유료
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Transient Protection Optimization of Pipelines Using Air-chamber and Air-inlet Valves
S. Mahmood Jazayeri Moghaddas,Hossein M. V. Samani,Ali Haghighi 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.5
Air-chambers are mechanical devices capable of decreasing positive and increasing negative water-hammer pressures in pumping pipelines; however, large size air-chambers might increase the costs substantially. Also, air-inlet valves are powerful devices which can efficiently control negative pressures. Obtaining the best protection scheme where transient pressures are maintained in a safe bound while minimizing the protection cost is an optimization problem. In this research, a single objective optimization model is introduced in which the types and locations of air-inlet valves and the size of air-chamber are determined such that the total cost is minimized while all pressures along the pipeline are in the allowable range. Maximum and minimum transient pressures are considered as constraints in the optimization analysis using penalty functions. A self-adaptive real genetic algorithm is used to solve the problem. The model is applied to a real transmission pipeline with 4 m3/s flow capacity. The results indicate that the proposed model is capable to determine proper number of air-inlet valves, their locations and types so that the air-chamber size and the total cost are substantially reduced.
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Moghaddas S.,Salehi M.,Bagheri-Kazemabad S. 한국세라믹학회 2022 한국세라믹학회지 Vol.59 No.5
A facile hydrothermal route has been used to produce a SnO 2 (tin oxide)/RGO (reduced graphene oxide) nanocomposite. The microstructure and properties of the prepared nanocomposite were studied by an X-ray diffraction (XRD), fi eld emission scanning electron microscope (FE-SEM), Fourier transformed infrared (FTIR), UV–Vis analysis, and transmission electron microscope (TEM). The formation of SnO 2 phase over RGO is confirmed by the XRD and FTIR results. The absence of a distinct peak of GO in the SnO 2 /RGO nanocomposite produced hydrothermally shows the reduction of GO to RGO com- pletely. FE-SEM and TEM images show that SnO 2 nanoparticles with size about 20 nm distributed homogeneously on the graphene surface. UV–Vis analysis of the SnO 2 /RGO sample exhibits broad absorption in the visible range (400–700 nm) indicating the SnO 2 formation on the sheets of reduced graphene oxide. Moreover, the nanocomposite was employed as a photocatalyst under UV light irradiations to the removal of methylene blue (MB). The produced SnO 2 /RGO nanocomposite removes the absorption peak of MB at around 665 nm within 20 min, implying the nanocomposite possesses good photo- catalytic efficiency under UV light irradiations.
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Application of waste rubber to reduce the settlement of road embankment
Tafreshi, S.N. Moghaddas,Norouzi, A.H. Techno-Press 2015 Geomechanics & engineering Vol.9 No.2
In this paper, a series of repeated load tests were carried out on a 150 mm diameter plate simulative of vehicle passes, to demonstrate the benefits of soil-rubber shred mixture in decreasing the soil surface settlement of road embankment. The results show that the efficiency of rubber reinforcement is significantly a function of the rubber content, thickness of rubber-soil mixture and soil cap thickness over the mixture. Minimum surface settlement is provided by 2.5% of rubber in rubber-soil mixture, the thickness of mixture layer and soil cap of 0.5 times the loading surface diameter, giving values of 0.32-0.68 times those obtained in the unreinforced system for low and high values of amplitude of repeated load. In this installation, in contrast with unreinforced bed that shows unstable response, the rate of enhancement in settlement decreases significantly as the number of loading cycles increase and system behaves resiliently without undergoing plastic deformation. The findings encourage the use of rubber shreds obtained from non-reusable tires as a viable material in road works.
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Cyclic loading response of footing on multilayered rubber-soil mixtures
Tafreshi, S.N. Moghaddas,Darabi, N. Joz,Dawson, A.R. Techno-Press 2018 Geomechanics & engineering Vol.14 No.2
This paper presents a set of results of plate load tests that imposed incremental cyclic loading to a sandy soil bed containing multiple layers of granulated rubber-soil mixture (RSM) at large model scale. Loading and unloading cycles were applied with amplitudes incrementally increasing from 140 to 700 kPa in five steps. A thickness of the RSM layer of approximately 0.4 times the footing diameter was found to deliver the minimum total and residual settlements, irrespective of the level of applied cyclic load. Both the total and residual settlements decrease with increase in the number of RSM layers, regardless of the level of applied cyclic load, but the rate of reduction in both settlements reduces with increase in the number of RSM layers. When the thickness of the RSM layer is smaller, or larger, settlements increase and, at large thicknesses may even exceed those of untreated soil. Layers of the RSM reduced the vertical stress transferred through the foundation depth by distributing the load over a wider area. With the inclusion of RSM layers, the coefficient of elastic uniform compression decreases by a factor of around 3-4. A softer response was obtained when more RSM layers were included beneath the footing damping capacity improves appreciably when the sand bed incorporates RSM layers. Numerical modeling using "FLAC-3D" confirms that multiple RSM layers will improve the performance of a foundation under heavy loading.
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