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51.
Detailed R-C-L-M models of power transformers, which are based on lumped parameters, are used extensively not only for transient analysis of power transformers to determine electrical stresses in windings, but also for studying transients in power systems. Models with few elements are generally more practicable for power system studies but at the expense of accuracy. The use of artificial methods to reduce an R-C-L-M model is the main contribution of this paper. Advantages of the suggested method include: (1) a reduced loss of accuracy compared with the original model and (2) the flexibility to choose the number of model elements to achieve the desired model depending on size and accuracy. The ability of three different artificial methods, genetic algorithm, particle swarm optimization, and bacterial foraging algorithm, to model reduction is evaluated using measurements on an actual 400 kV test object and the results are compared with those obtained by common analytical formulae. 相似文献
52.
Shabnam Hasani Faramarz Doulati Ardejani Mohammad Ebrahim Olya 《Korean Journal of Chemical Engineering》2017,34(8):2265-2274
Adsorption of BR 18 dye onto nano-clay adsorbent was investigated. Nano-clay was characterized by using FTIR, SEM, TEM, XRD and BET analysis. The percent removal increased by increasing nano-clay dose, while pH and stirring speed had no significant effect on the adsorption rate. It was observed that the uptake of dye onto nano-clay initially increased rapidly, and then decreased slowly until the equilibrium was reached. The adsorption capacity rose with an increase in temperature. Moreover, the adsorption kinetics was very fast and followed a pseudo second-order. The intra-particle diffusion was observed to be the rate-controlling step. In addition, equilibrium data fitted well with the Langmuir adsorption model. This paper also presents a numerical simulation incorporating the second-order kinetic expression using COMSOL Multiphysics software. The numerical modelling results and the experimental data were in excellent agreement. 相似文献
53.
Seyed Ebrahim Moussavi Torshizi Pedram Safarpour 《Journal of Failure Analysis and Prevention》2018,18(2):322-329
A common failure in a certain type of gas turbine, observed during the first periodic inspection, is radial cracks in the tip plate of gas fuel nozzles. Here, each gas turbine has 18 nozzles. In all nozzles and in all similar units, these cracks of lengths ranging from 1 mm to a maximum of 14.5 mm are observed. As prescribed by the manufacturer, the defective part must be removed and replaced by welding and machining of a new one. But this problem is repeated and observed in the next periodic visits, and in all units. Depending on the number of nozzles in each gas turbine unit and the number of units in total, these repairs are very expensive and time-consuming. In this paper, the failure is analyzed and the causes of the cracks in the nozzles are investigated. Studies show that the main causes of nozzle failure are residual stresses caused by welding and thermal stresses caused by the start-up and shutdown processes. According to results, a solution has been proposed to release these residual and thermal stresses. After the implementation of this method in 1998, no more failure has been reported by the repair team, which proves the effectiveness of this solution. Since this paper has been prepared based on technical reports from the years between 1996 and 1998, the cited references of this paper are these technical reports. 相似文献
54.
55.
Ali Moghimi Mohammad Hosaien Saiedirad Ebrahim Ganji Moghadam 《International Journal of Food Science & Technology》2011,46(4):855-861
Viscoelastic behaviour of some commercial sweet cherry cultivars of Iran has been studied in current research. For this purpose, stress relaxation test was conducted on five cultivars of sweet cherry including Siah Mashhad, Abarde, Victoria, Dovom Ras and Tak Dane. Two common models (Generalised Maxwell model and Peleg model) were fitted to the experimental data. Both models could describe stress relaxation behaviour of cherries (R2 = 0.99), but Generalised Maxwell model had lower root mean square error (RMSE) than Peleg model. Based on analysis of stress relaxation data using models constants, Tak Dane exhibited more solid properties, while Victoria showed less elastic behaviour than other cultivars. The results revealed that relaxation ratio (R%) and the area under the stress relaxation curve could be effective alternative to models with easier mathematical procedure. 相似文献
56.
Single Molecule with Dual Function on Nanogold: Biofunctionalized Construct for In Vivo Photoacoustic Imaging and SERS Biosensing 下载免费PDF全文
U. S. Dinish Zhegang Song Chris Jun Hui Ho Ghayathri Balasundaram Amalina Binte Ebrahim Attia Xianmao Lu Ben Zhong Tang Bin Liu Malini Olivo 《Advanced functional materials》2015,25(15):2316-2325
Multimodal imaging provides complimentary information that is advantageous in studying both cellular and molecular mechanisms in vivo, which has tremendous potential in pre‐clinical research and clinical translational imaging. It is desirable to design probes for multimodal imaging that can be administered minimally but provides multifaceted information. Herein, we demonstrate the complementary dual functional ability of a nanoconstruct for molecular imaging in both photoacoustic (PA) and surface‐enhanced Raman scattering (SERS) biosensing simultaneously in tandem. To realize this, a group of NIR active organic molecules are designed and synthesized that possess both SERS and PA activity. Nanoconstructs realized by anchoring such molecules onto gold nanoparticles are demonstrated for targeting cancer biomarkers in vivo while providing complimentary information about biodistribution and targeting efficiency. In future, such nanoconstructs could play a major role in identifying surgical margins and also for disease monitoring in translational medicine. 相似文献
57.
Rahimi Ebrahim Sharifi Teshnizi Ebrahim Rastegarnia Ahmad Motamed Al-shariati Ehsan 《Bulletin of Engineering Geology and the Environment》2019,78(4):2817-2834
Bulletin of Engineering Geology and the Environment - Water seepage from dam foundations causes reservoir water loss and raises the risk of dam instability. One method of remediation for... 相似文献
58.
Mark Grigorian Abdolreza S. Moghadam Mozhgan Kamizi 《The Structural Design of Tall and Special Buildings》2019,28(7)
Performance‐based seismic design, as an alternative to conventional methods of approach, has served engineers and the public rather well during the last two decades. Neither approach guaranties catastrophic collapse prevention nor post‐earthquake realignment and repairs (PERR) due to major seismic events. As a result, most code‐compliant buildings can be regarded as relatively safe but practically disposable. The paper presents a new philosophy that leads to sustainable design of new structures and the upgrading of existing earthquake resisting moment frames. Repairability‐based design (RBD) relies on softening and control rather than strength and resistance to elevate seismic performance to economically viable, physical collapse prevention, damage control, and post‐earthquake realignment and repairs. The new approach was inspired by design led analysis (DLA), performance control (PC), and recent developments in rocking core‐moment frame design. DLA is a displacement based method of analysis with built‐in results. PC is the ability to design a structure in such a way as to expect predetermined modes of response at certain stages of loading, extents of damage, and drift ratios. This paper advocates higher performance objectives than current codes of practice do. Several demonstrative examples have been provided. 相似文献
59.
Navid Rahgozar Nima Rahgozar Abdolreza S. Moghadam 《The Structural Design of Tall and Special Buildings》2019,28(1)
Modern rocking and stepping cores have been known as the efficient self‐centering earthquake‐resisting systems (SC‐ERSs). The current article proposes an approximate equivalent linear (EL) model for rapid estimation of the SC‐ERS displacement. An equivalent damping ratio and effective stiffness are formulated for flag‐shaped hysteresis of a fully SC‐ERS. The approximate EL model is first established using secant stiffness and Jacobsen's damping model. Nonlinear response history analyses are carried out to compare exact and approximated peak displacements. Findings reveal that EL analysis of the SC‐ERS based on Jacobsen's damping leads to underestimation of the maximum inelastic displacement. Accordingly, a new optimal damping formula is proposed using a genetic algorithm and nonlinear regression analyses. The improved EL model is validated by practical examples, and the results show acceptable accuracy in design‐level displacement estimation. 相似文献
60.
Journal of Porous Materials - The aim of this study was to encapsulate 2-tert-butylhydroquinone (TBHQ), as a common synthetic antioxidant in food industries, by mesoporous silica nanoparticles... 相似文献