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81.
The behaviour of spudcan foundations during the installation and preloading in two-layer sand sediments was investigated through large deformation finite element (LDFE) analyses. The LDFE analyses were carried out using the coupled Eulerian-Lagrangian approach, modifying Mohr-Coulomb soil model to capture hardening and subsequent softening effects of sand. Parametric analyses were undertaken varying the top layer thickness, relative density of sand and spudcan diameter. Both loose to medium dense-over-dense and dense-over-loose to medium dense sand deposits were explored. The results showed that, for the investigated relatively thin top layer thickness of ≤ 5 m, spudcan behaviour was dictated by the bottom sand layer with a minimal influence of the top layer. For assessing the penetration resistance profile in two-layer sands, the performance of the ISO, SNAME, InSafeJIP, and other existing theoretical design methods were evaluated. 相似文献
82.
The relationship between air (Ta) and water temperature (Tw) is very important because it shows how the temperature of a water body might respond to future changes in surface Ta. Mean monthly Tw records of three gauging stations (Bezdan, Bogojevo i Veliko Gradi?te) were analysed alongside mean monthly discharge (Q) for the same stations. Additionally, Ta series from two meteorological stations (Sombor and Veliko Gradi?te) were correlated with Tw variations over the period 1950–2012. Locally weighted scatter point smoothing (LOWESS) was used to investigate long‐term trends in the raw data, alongside the Mann–Kendall (MK) trend test. Trend significance was established using Yue–Pilon's pre‐whitening approaches to determine trends in climate data. Also, the rescaled adjusted partial sums (RAPS) method was used to detect dates of possible changes in the time series. Statistically significant warming trends were observed for annual and seasonal minimum and maximum Tw at all investigated sites. The strongest warming was observed at Bogojevo gauging station for seasonal maximum Tw, with +0.05 °C per year on average. RAPS established that the trend began in the 1980s. This behaviour is linked to climate patterns in the North and East Atlantic which determine the amount of heat advected onto mainland Europe. Statistically significant correlations were found for all Tw on an annual basis. Overall, the strongest correlations (p < 0.01) between Tw residuals and the North Atlantic Oscillation (NAO) were recorded for the winter period. These findings suggest possible predictability of Tw over seasonal time‐scales. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
83.
Prediction of river water temperature: a comparison between a new family of hybrid models and statistical approaches 下载免费PDF全文
Sebastiano Piccolroaz Elisa Calamita Bruno Majone Aurélien Gallice Annunziato Siviglia Marco Toffolon 《水文研究》2016,30(21):3901-3917
River water temperature is a key physical variable controlling several chemical, biological and ecological processes. Its reliable prediction is a main issue in many environmental applications, which however is hampered by data scarcity, when using data‐demanding deterministic models, and modelling limitations, when using simpler statistical models. In this work we test a suite of models belonging to air2stream family, which are characterized by a hybrid formulation that combines a physical derivation of the key equation with a stochastic calibration of parameters. The air2stream models rely solely on air temperature and streamflow, and are of similar complexity as standard statistical models. The performances of the different versions of air2stream in predicting river water temperature are compared with those of the most common statistical models typically used in the literature. To this aim, a dataset of 38 Swiss rivers is used, which includes rivers classified into four different categories according to their hydrological characteristics: low‐land natural rivers, lake outlets, snow‐fed rivers and regulated rivers. The results of the analysis provide practical indications regarding the type of model that is most suitable to simulate river water temperature across different time scales (from daily to seasonal) and for different hydrological regimes. A model intercomparison exercise suggests that the family of air2stream hybrid models generally outperforms statistical models, while cross‐validation conducted over a 30‐year period indicates that they can be suitably adopted for long‐term analyses. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
84.
Three dimensional numerical simulation of residential building on shrink–swell soils in response to climatic conditions 下载免费PDF全文
Shrink–swell soils can cause distresses in buildings, and every year, the economic loss associated with this problem is huge. This paper presents a comprehensive system for simulating the soil–foundation–building system and its response to daily weather conditions. Weather data include rainfall, solar radiation, air temperature, relative humidity, and wind speed, all of which are readily available from a local weather station or the Internet. These data are used to determine simulation flux boundary conditions. Different methods are proposed to simulate different boundary conditions: bare soil, trees, and vegetation. A coupled hydro‐mechanical stress analysis is used to simulate the volume change of shrink–swell soils due to both mechanical stress and water content variations. Coupled hydro‐mechanical stress‐jointed elements are used to simulate the interaction between the soil and the slab, and general shell elements are used to simulate structural behavior. All the models are combined into one finite element program to predict the entire system's behavior. This paper first described the theory for the simulations. A site in Arlington, Texas, is then selected to demonstrate the application of the proposed system. Simulation results are shown, and a comparison between measured and predicted movements for four footings in Arlington, Texas, over a 2‐year period is presented. Finally, a three‐dimensional simulation is made for a virtual residential building on shrink–swell soils to identify the influence of various factors. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
85.
Atmospheric Concentrations and Phase Partitioning of Polycyclic Aromatic Hydrocarbons in Izmir,Turkey 总被引:1,自引:0,他引:1
Ambient air polycyclic aromatic hydrocarbon (PAH) samples were collected at a suburban (n = 63) and at an urban site (n = 14) in Izmir, Turkey. Average gas‐phase total PAH (∑14PAH) concentrations were 23.5 ng m?3 for suburban and 109.7 ng m?3 for urban sites while average particle‐phase total PAH concentrations were 12.3 and 34.5 ng m?3 for suburban and urban sites, respectively. Higher ambient PAH concentrations were measured in the gas‐phase and ∑14PAH concentrations were dominated by lower molecular weight PAHs. Multiple linear regression analysis indicated that the meteorological parameters were effective on ambient PAH concentrations. Emission sources of particle‐phase PAHs were investigated using a diagnostic plot of fluorene (FLN)/(fluorine + pyrene; PY) versus indeno[1,2,3‐cd]PY/(indeno[1,2,3‐cd]PY + benzo[g,h,i]perylene) and several diagnostic ratios. These approaches have indicated that traffic emissions (petroleum combustion) were the dominant PAH sources at both sites for summer and winter seasons. Experimental gas–particle partition coefficients (KP) were compared to the predictions of octanol–air (KOA) and soot–air (KSA) partition coefficient models. The correlations between experimental and modeled KP values were significant (r2 = 0.79 and 0.94 for suburban and urban sites, respectively, p < 0.01). Octanol‐based absorptive partitioning model predicted lower partition coefficients especially for relatively volatile PAHs. However, overall there was a relatively good agreement between the measured KP and soot‐based model predictions. 相似文献
86.
87.
One dimensional solutions for the classic critical upward seepage gradient/quick condition and the time rate of consolidation problems are obtained using coupled routines for the finite volume method (FVM) and discrete element method (DEM), and the results compared with the analytical solutions. The two phase flow in a system composed of fluid and solid is simulated with the fluid phase modeled by solving the averaged Navier–Stokes equation using the FVM and the solid phase is modeled using the DEM. A framework is described for the coupling of two open source computer codes: YADE-OpenDEM for the discrete element method and OpenFOAM for the computational fluid dynamics. The particle–fluid interaction is quantified using a semi-empirical relationship proposed by Ergun [12]. The two classical verification problems are used to explore issues encountered when using coupled flow DEM codes, namely, the appropriate time step size for both the fluid and mechanical solution processes, the choice of the viscous damping coefficient, and the number of solid particles per finite fluid volume. 相似文献
88.
89.
大规模三维地震数据的直接体绘制,是一个计算和数据双重密集型问题.为了提高三维图像的重建效率,提出了一种基于立方体元的Shear- warp地震数据体绘制算法.该算法通过构建立方体元在相邻的体素点之间建立联系;然后根据地震数据的特征对体元进行分类,在绘制过程中通过二叉树索引,快速定位分类结果.通过索引结果,避免了对等值体... 相似文献
90.