Explicit data-driven models for prediction of pressure fluctuations occur during turbulent flows on sloping channels     

Samadi  Mehrshad  Sarkardeh  Hamed  Jabbari  Ebrahim 《Stochastic Environmental Research and Risk Assessment (SERRA)》2020,34(5):691-707

Stochastic Environmental Research and Risk Assessment - Pressure fluctuations are among the favorite topics for hydraulic engineers due to their critical role in the design and safe operation of...  相似文献   

Peak displacement patterns for the performance-based seismic design of steel eccentrically braced frames     

Fakhraddini  Ali  Hamed  Saffari  Fadaee  Mohammad Javad 《地震工程与工程振动(英文版)》2019,18(2):379-393

Performance-based seismic design(PBSD) aims to assess structures at different damage states. Since damage can be directly associated to displacements, seismic design with consideration of displacement seems to be logical. In this study, simple formulae to estimate the peak floor displacement patterns of eccentrically braced frames(EBFs) at different performance levels subjected to earthquake ground motions are proposed. These formulae are applicable in a PBSD and especially in direct displacement-based design(DDBD). Parametric study is conducted on a group of 30 EBFs under a set of 15 far field and near field accelerograms which they scaled to different amplitudes to adapt various performance levels. The results of thousands of nonlinear dynamic analyses of EBFs have been post-processed by nonlinear regression analysis in order to recognize the major parameters that influence the peak displacement pattern of these frames. Results show that suggested displacement patterns have relatively good agreement with those acquired by an exact nonlinear dynamic analysis.  相似文献   

Evaluation of a passive gap damper to control displacements in a shaking test of a seismically isolated three‐story frame          下载免费PDF全文

Hamed Zargar  Keri L. Ryan  Taylor A. Rawlinson  Justin D. Marshall 《地震工程与结构动力学》2017,46(1):51-71

Recent studies have indicated uncertainty about the performance limit states of seismically isolated buildings in very large earthquakes, especially if the isolator displacement demands exceed the seismic gap and induce pounding. Previous research has shown the benefit of providing phased supplemental damping that does not affect the isolation system response in a design event. A phased passive control device, or gap damper, was designed, fabricated, and experimentally evaluated during shake table testing of a quarter scale base‐isolated three‐story steel frame building. Identical input motions were applied to system configurations without a gap damper and with a gap damper, to directly assess the influence of the gap damper on displacement and acceleration demands. The gap damper was observed to reduce displacement demands by up to 15% relative to the isolated system without the gap damper. Superstructure floor accelerations increased substantially because of damper activation, but were limited to a peak of about 1.18 g. The gap damper reduces displacement most effectively if the ground motion contains one or more of the following characteristics: the spectral displacement increases with increasing period near the effective period of the isolation system, the motion is dominated by a single large pulse rather than multiple cycles at a consistent intensity, and the motion has a dominant component aligned with a major axis of the structure. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Impaired Functions in Nile Tilapia,Oreochromis niloticus (Linnaeus, 1757), from Polluted Waters     

Khadiga G. Adham  Sherufa S. Hamed  Hania M. Ibrahim  Ramadan A. Saleh 《洁净——土壤、空气、水》2001,29(5):278-288

Oreochromis niloticus is an endemic species in the River Nile and represents the main object of fishery in the Nile Delta Lakes of which Lake Maryût is the smallest and most polluted. Due to current pollution problems, fish production in the lake greatly declined. Besides fish biology, this study considered a wide array of water databases in selected sites along the lake. Hydrologic and biologic data were compared to that of a reference fish hatchery. Water concentrations of ammonia, manganese, nickel, cadmium, lead and mercury proved hazardous to fish, whereas chromium, copper, iron, zinc, pH, alkalinity, hardness, phosphate, nitrate, and nitrite always fell within acceptable levels. Physiologic evaluation of O. niloticus pointed out improper growth, protein inadequacy, and functional impairment in fish inhabiting polluted sites, in particular the lake main basin. These were reflected by data of specific formulae as RNA/DNA and the relative RNA content (r) in cells of the liver and gill arches as well as by the relative mobilization of serum protein fractions. It seems, however, that growth competence is additionally affected by the stress impact exerted upon fish by massive population numbers in some cramped commercial ponds.  相似文献   

Ultraviolet Spectral Evolution of V1974 Cyg Using IUE Low Resolution Spectra     

G. M. Hamed  M. R. Sanad  A. Essam  S. Yousef 《Astrophysics》2018,61(1):91-100

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