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A fundamental principle in the safe design of bridge piers is to estimate maximum scour depth. As such, many researchers devoted their efforts to study the phenomenon of scour around bridge piers and to present relationships to estimate maximum scour depth. In the current research, scour around circular bridge piers with two different diameters and different inclination angles toward downstream has been investigated experimentally under clear water and different discharges. The obtained results revealed that increase in the inclination angle leads to a significant decrease in the scour depth, dimensions of sediment ridge and scour hole. Moreover, by comparing the data obtained from vertical bridge pier and well-known relationships, a relationship having the most agreement with the results was selected and modified to estimate equilibrium scour depth around inclined piers. 相似文献
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Phototransients under radiation of 274 nm have been studied in anodic tantalum oxide thin films. The area under the phototransient curves, the relaxation time end the decay time are found U> decrease with the applied field. For short times ΔI αexp ( ? t/r) with τ decreasing with field, while for longer times thore is a departure from exponential behaviour. These photo transients may be due to the drift of photoexcited electrons under the action of an applied field end their subsequent retrapping. 相似文献
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MOHAMMAD H. EIKANI FERESHTEH GOLMOHAMMAD MEHDI MIRZA SOOSAN ROWSHANZAMIR 《Journal of food process engineering》2007,30(2):255-266
A comparative study of superheated water extraction (SWE) with two conventional methods including hydrodistillation and Soxhlet extraction was performed on cumin (Cuminum cyminum L.). The effect of some superheated water parameters at 20 bar pressure on the essential oil extraction from 4 g cumin seeds such as temperatures from 100 to 175C, particle size at 0.25 and 0.50 mm, and flow rates at 2 and 4 mL/min were investigated. Separation and identification of the components were carried out by gas chromatography‐flame ionization detector and gas chromatography‐mass spectrometry. The best operating conditions for the SWE of C. cyminum L. were determined to be 150C temperature, 0.50 mm mean particle size and 4 mL/min flow rate for 3‐h extraction time. The SWE method resulted in a more valuable essential oil with respect to the oxygenated components. 相似文献
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Aydin SHISHEGARAN Mohammad SHOKROLLAHI Ali MIRNOROLLAHI Arshia SHISHEGARAN Mohammadreza MOHAMMAD KHANI 《Frontiers of Structural and Civil Engineering》2020,14(6):1418
We investigate the performance of a novel vertical slot fishway by employing finite volume and surrogate models. Multiple linear regression, multiple log equation regression, gene expression programming, and combinations of these models are employed to predict the maximum turbulence, maximum velocity, resting area, and water depth of the middle pool in the fishway. The statistical parameters and error terms, including the coefficient of determination, root mean square error, normalized square error, maximum positive and negative errors, and mean absolute percentage error were employed to evaluate and compare the accuracy of the models. We also conducted a parametric study. The independent variables include the opening between baffles (OBB), the ratio of the length of the large and small baffles, the volume flow rate, and the angle of the large baffle. The results show that the key parameters of the maximum turbulence and velocity are the volume flow rate and OBB. 相似文献
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ABSTRACT This study investigates the effect of 1-Methylenaphthalene and Benzophenon as additives in cable oil used in extra high voltage paper insulated underground cable in service in Riyadh area. Samples containing different concentrations of these additives were used. Impact of variation of temperature and additive concentrations was evaluated for conduction current and burst current. Virgin samples of the dielectric paper used in this cable were impregnated in these oil samples for the investigation of power factor and breakdown voltage. The results indicate that an optimum concentration of the additives improves the performance of paper-liquid composite. 相似文献