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911.
912.
Adaptive multi‐rate interface: development and experimental verification for real‐time hybrid simulation 下载免费PDF全文
Amin Maghareh Jacob P. Waldbjørn Shirley J. Dyke Arun Prakash Ali I. Ozdagli 《地震工程与结构动力学》2016,45(9):1411-1425
Real‐time hybrid simulation (RTHS) is a powerful cyber‐physical technique that is a relatively cost‐effective method to perform global/local system evaluation of structural systems. A major factor that determines the ability of an RTHS to represent true system‐level behavior is the fidelity of the numerical substructure. While the use of higher‐order models increases fidelity of the simulation, it also increases the demand for computational resources. Because RTHS is executed at real‐time, in a conventional RTHS configuration, this increase in computational resources may limit the achievable sampling frequencies and/or introduce delays that can degrade its stability and performance. In this study, the Adaptive Multi‐rate Interface rate‐transitioning and compensation technique is developed to enable the use of more complex numerical models. Such a multi‐rate RTHS is strictly executed at real‐time, although it employs different time steps in the numerical and the physical substructures while including rate‐transitioning to link the components appropriately. Typically, a higher‐order numerical substructure model is solved at larger time intervals, and is coupled with a physical substructure that is driven at smaller time intervals for actuator control purposes. Through a series of simulations, the performance of the AMRI and several existing approaches for multi‐rate RTHS is compared. It is noted that compared with existing methods, AMRI leads to a smaller error, especially at higher ratios of sampling frequency between the numerical and physical substructures and for input signals with high‐frequency content. Further, it does not induce signal chattering at the coupling frequency. The effectiveness of AMRI is also verified experimentally. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
913.
Physically based modelling of sheet erosion (detachment and deposition processes) in complex hillslopes 总被引:1,自引:0,他引:1 下载免费PDF全文
Ali Talebi Rasoul Hajiabolghasemi Mohamad Reza Hadian Nosratollah Amanian 《水文研究》2016,30(12):1968-1977
A one‐dimensional uncoupled model governed by this research is a physics‐based modelling of the rainfall‐runoff induced erosion process. The presented model is composed of three parts of a three‐dimensional (3D) hillslope geometry, a nonlinear storage (kinematic wave) model for hillslope hydrological response, and an unsteady physically based surface erosion model. The 3D hillslope geometry model allows describing of the hillslope morphology by defining their plan shape and profile curvature. By changing these two topographic parameters, nine basic hillslope types are derived. The modelling of hillslope hydrological response is based on a flow continuity equation as the relation of discharge and flow depth is passed on kinematic wave approximation. The erosion model is based on a mass conservation equation for unsteady flow. The model assumes that suspended sediment does not affect flow dynamics. The model also accounts for the effect of flow depth plus loose soil depth on soil detachment. The presented model was run for two different precipitations, slope content, and length, and results were plotted for sediment detachment/deposition rate. Based on the obtained results, in hillslopes with convex and straight profile curvatures, sediment detachment only occurred in the whole length of the hillslope. However, in concave ones, sediment detachment and deposition only occurred together in hillslope. The hillslopes with straight profiles and convergent plans have the highest rate of detachment. Also, results show that most detachment rates occur in convex profile curvatures, which are about 15 times more than in straight profiles. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
914.
Investigation into regional thermal structure of the Thrace Region, NW Turkey, from aeromagnetic and borehole data 总被引:1,自引:0,他引:1
Z. Mümtaz Hisarli M. Nuri Dolmaz Mahmut Okyar Ali Etiz Naci Orbay 《Studia Geophysica et Geodaetica》2012,56(1):269-291
The aeromagnetic values over the study region are relatively uniform except for a few anomalies in the northeastern and southwestern
areas. Analyses of aeromagnetic data were performed in NW Turkey, in order to have a look into the subsurface regional thermal
structure of the region. For this purpose, power spectra, reduced to pole (RTP), and band-pass filtered anomalies were produced
using geophysical techniques. Band-pass filtered data were produced from the RTP aeromagnetic anomalies to isolate near surface
and undesired deep effects. Based on the aeromagnetic data interpretation, the thickness of the magnetized crust, named the
Curie Point Depth (CPD), in the study area lies between 9.7 and 20.3 km. The CPD estimates in the Thrace region of Turkey
indicate two shallow CPD (SCPD1 and SCPD2) zones (the Istranca Massif and the Saros Graben area). The deep CPD are located
within the Thrace Basin with sediment thickness of about 9 km. The corresponding heat flow map prepared from the averaged
thermal conductivities and thermal gradients from the CPD reveals the existence of one low heat flow zone (75 mW/m2) over the center of Thrace Basin, and two high heat flow zones over the Istranca Masif (100–125 mW/m2) in the northern side and Saros Graben (125–135 mW/m2) areas in the southern side of the Thrace Basin. 相似文献
915.
The cumulative impacts of reclamation and dredging on the marine ecology and land-use in the Kingdom of Bahrain 总被引:1,自引:0,他引:1
Zainal K Al-Madany I Al-Sayed H Khamis A Al Shuhaby S Al Hisaby A Elhoussiny W Khalaf E 《Marine pollution bulletin》2012,64(7):1452-1458
This article assesses the ecological and economic impacts of land reclamation and dredging through consulting recent environmental impact assessment reports. Geographic features of Bahrain during 1963-2008 are produced using Geographical Information System. Extensive but inexpensive shallow coastal areas and tidal flats have been reclaimed particularly from 1997 to 2007 at a high rate of 21 km(2)/year. Formal records show the increase in the original land mass by the year 2008 to be 91 km(2). An estimated total cumulative loss of major habitats resulting from 10 reclamation projects was around 153.58 km(2). Also much larger scale impacts should be considered resulting from the borrow areas used for the extraction of sand or infill materials. A number of key habitats and species are affected in the vicinity of these projects. The study attempts to assign a monetary value to the marine ecosystem functions. There is a need for efficient coastal zone management to regulate a sustainable use of the marine resources. 相似文献
916.
Topographic,pedologic and climatic interactions influencing streamflow generation at multiple catchment scales 总被引:1,自引:0,他引:1
Dominant flow pathways (DFPs) in mesoscale watersheds are poorly characterized and understood. Here, we make use of a conservative tracer (Gran alkalinity) and detailed information about climatic conditions and physical properties to examine how temporally and spatially variable factors interact to determine DFPs in 12 catchments draining areas from 3.4 to 1829.5 km² (Cairngorms, Scotland). After end‐member mixing was applied to discriminate between near surface and deep groundwater flow pathways, variation partitioning, canonical redundancy analyses and regression models were used to resolve: (i) What is the temporal variability of DFPs in each catchment?; (ii) How do DFPs change across spatial scales and what factors control the differences in hydrological responses?; and (iii) Can a conceptual model be developed to explain the spatiotemporal variability of DFPs as a function of climatic, topographic and soil characteristics? Overall, catchment characteristics were only useful to explain the temporal variability of DFPs but not their spatial variation across scale. The temporal variability of DFPs was influenced most by prevailing hydroclimatic conditions and secondarily soil drainability. The predictability of active DFPs was better in catchments with soils supporting fast runoff generation on the basis of factors such as the cumulative precipitation from the seven previous days, mean daily air temperature and the fractional area covered by Rankers. The best regression model R2 was 0.54, thus suggesting that the catchments’ internal complexity was not fully captured by the factors included in the analysis. Nevertheless, this study highlights the utility of combining tracer studies with digital landscape analysis and multivariate statistical techniques to gain insights into the temporal (climatic) and spatial (topographic and pedologic) controls on DFPs. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
917.
The concept of equivalent linearization, in which the actual nonlinear structure is replaced by an equivalent linear single-degree-of-freedom (SDOF) system, is extended for soil-structure systems in order to consider the simultaneous effects of soil-structure interaction (SSI) and inelastic behavior of the structure on equivalent linear parameters (ELP). This is carried out by searching over a two-dimensional equivalent period–equivalent damping space for the best pair, which can predict the earthquake response of the inelastic soil-structure system with sufficient accuracy. The super-structure is modeled as an elasto-plastic SDOF system whereas the soil beneath the structure is considered as a homogeneous half-space and is replaced by a discrete model. An extensive parametric study is carried out for a wide range of soil-structure systems subjected to a suite of 59 ground motions. The effect of SSI on ELP is studied through introducing a set of non-dimensional key parameters, which define the soil-structure system. It is shown that ELP of soil-structure systems result from a trade-off between SSI effect and nonlinear behavior of the structure. The contribution of each of these two factors depends on the characteristics of the soil-structure system which, in turn, are defined by the introduced non-dimensional key parameters. Moreover, the reliability of the predicted response of soil-structure systems and its sensitivity to deviation from optimal ELP is studied in detail, which sheds light on the consequences of using improper pairs of ELP for interacting systems in the framework of performance-based design of structures. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
918.
Ulf Gräwe Eric Deleersnijder Syed Hyder Ali Muttaqi Shah Arnold Willem Heemink 《Ocean Dynamics》2012,62(4):501-514
During the last decades, the Euler scheme was the common “workhorse” in particle tracking, although it is the lowest-order approximation of the underlying stochastic
differential equation. To convince the modelling community of the need for better methods, we have constructed a new test
case that will show the shortcomings of the Euler scheme. We use an idealised shallow-water diffusivity profile that mimics the presence of a sharp pycnocline and thus a quasi-impermeable
barrier to vertical diffusion. In this context, we study the transport of passive particles with or without negative buoyancy.
A semi-analytic solutions is used to assess the performance of various numerical particle-tracking schemes (first- and second-order
accuracy), to treat the variations in the diffusivity profile properly. We show that the commonly used Euler scheme exhibits a poor performance and that widely used particle-tracking codes shall be updated to either the Milstein scheme or second-order schemes. It is further seen that the order of convergence is not the only relevant factor, the absolute
value of the error also is. 相似文献
919.
Parviz Mohammadi Shaliza Ibrahim Mohamad Suffian Mohamad Annuar Shahin Ghafari Sabaratnam Vikineswary Ali Akbar Zinatizadeh 《洁净——土壤、空气、水》2012,40(11):1297-1305
Hydrogen (H2) is one of renewable energy sources known for its non‐polluting and environmentally friendly nature, as its end combustion product is water (H2O). The biological production of H2 is a less energy intensive alternative where processes can be operated at ambient temperature and pressure. Dark fermentation by bacterial biomass is one of multitude of approaches to produce hydrogen which is known as the cleanest renewable energy and is thus receiving increasing attention worldwide. The present study briefly reviews the biohydrogen production process with special attention on the effects of several environmental and operational factors towards the process. Factors such as organic loading rate, hydraulic retention time, temperature, and pH studied in published reports were compared and their influences are discussed in this work. This review highlights the variations in examined operating ranges for the factors as well as their reported optimum values. Divergent values observed for the environmental/operational factors merit further exploration in this field. 相似文献
920.
This study aims to remove of Cu2+, Cd2+, and Pb2+ ions from solution and to investigate the adsorption isotherms, adsorption kinetics, and ion‐exchange affinities of these metals using waste activated sludge (AS) biomass. The adsorptions of the metals on biomass were optimal at an acidic pH value of 6.0 based on its monolayer capacities. Maximum monolayer capacities of AS biomass (qmax) were calculated as 0.478, 0.358, and 0.280 mmol g?1 for Cu2+, Cd2+, and Pb2+, respectively, and the adsorption equilibrium time was found as 60 min for each metal. The adsorbed amount of metal rose with increasing of initial metal ion concentration. The equilibrium adsorption capacity of AS for initial 0.25 mmol L?1 metal concentration was determined as 0.200, 0.167, and 0.155 mmol g?1 for Cu2+, Cd2+, and Pb2+ ions, respectively. These relevant values were determined as 0.420, 0.305, and 0.282 mmol g?1 for Cu2+, Cd2+, and Pb2+ ions, respectively, when initial metal concentration was 0.50 mmol L?1. In the multi‐metal sorption system, the adsorption capacity of AS biomass was observed in the order of Cu2+ > Cd2+ > Pb2+. In the presence of 100 mmol L?1 H+ ion, the order of ion‐exchange affinity with H+ was found as Cu2+ > Cd2+ > Pb2+. The adsorption kinetics were also found to be well described by the pseudo‐second‐order and intraparticle diffusion models. Two different rate constants were obtained as ki1 and ki2 and ki1 (first stage) was found to be higher than ki2 (second stage). 相似文献