排序方式： 共有118条查询结果，搜索用时 78 毫秒
21.
New empirical models were developed to predict the soil deformation moduli using gene expression programming (GEP). The principal soil deformation parameters formulated were secant (Es) and reloading (Er) moduli. The proposed models relate Es and Er obtained from plate load-settlement curves to the basic soil physical properties. The best GEP models were selected after developing and controlling several models with different combinations of the influencing parameters. The experimental database used for developing the models was established upon a series of plate load tests conducted on different soil types at depths of 1–24 m. To verify the applicability of the derived models, they were employed to estimate the soil moduli of a part of test results that were not included in the analysis. The external validation of the models was further verified using several statistical criteria recommended by researchers. A sensitivity analysis was carried out to determine the contributions of the parameters affecting Es and Er. The proposed models give precise estimates of the soil deformation moduli. The Es prediction model provides considerably better results in comparison with the model developed for Er. The simplified formulation for Es significantly outperforms the empirical equations found in the literature. The derived models can reliably be employed for pre-design purposes. 相似文献
22.
Seyyed Mohammad Mousavi Amir Hossein Alavi Ali Mollahasani Amir Hossein Gandomi 《Engineering Geology》2011,123(4):324
In this study, new empirical equations were developed to predict the soil deformation moduli utilizing a hybrid method coupling genetic programming and simulated annealing, called GP/SA. The proposed models relate secant (Es), unloading (Eu) and reloading (Er) moduli obtained from plate load–settlement curves to the basic soil physical properties. Several models with different combinations of the influencing parameters were developed and checked to select the best GP/SA models. The database used for developing the models was established upon a series of plate load tests (PLT) conducted on different soil types at various depths. The validity of the models was tested using parts of the test results that were not included in the analysis. The validation of the models was further verified using several statistical criteria. A traditional GP analysis was performed to benchmark the GP/SA models. The contributions of the parameters affecting Es, Eu and Er were analyzed through a sensitivity analysis. The proposed models are able to estimate the soil deformation moduli with an acceptable degree of accuracy. The Es prediction model has a remarkably better performance than the models developed for predicting Eu and Er. The simplified formulations for Es, Eu and Er provide significantly better results than the GP-based models and empirical models found in the literature. 相似文献
23.
Sakineh?Mashjoor Fatemeh?Heidary?Jamebozorgi Ehsan?KamraniEmail author 《Ocean Science Journal》2018,53(4):655-665
Ecosystem-based management is one of the most important approaches that may lead to reducing the impacts of fishing on ecosystems. In this context, we have assessed the impact of Iranian coastal fishing (using landing data of 49 exploited species) on the ecosystem of the North Sea of Oman (Sistan and Baluchestan Province), during the last decade (2002–2011), with emphasis on testing the occurrence of the “fishing down? phenomenon. The Mean Trophic Level (MTL) and Fishing-in-Balance (FiB) index are two indicators that we used for analysis. The data indicated that the increased total landings in this region might be related to the exploitation of marine fishery resources especially with regard to large pelagic fish. Over the past decade, moderate decreasing trends in MTL and an increasing trend in the FiB-index were observed. In this regard, an upward trend in the spatial expansion factor and also a downward trend in the piscivory index and in Primary Production Required (PPR) in the time period could all indicate a spatial expansion toward deep waters, the catching of the large pelagic piscivorous species, such as tuna, and a sign of fishing pressures on the ecosystem. The results suggest a range of fishery exploitation patterns throughout the food web but it seems that these patterns are not a consequence of ?fishing down?. We suggest that the monitoring research be continued in this region and these indicators should be used to make fisheries management decisions and to prevent the continuance of this trend in future. 相似文献
24.
In this paper, we study an interacting holographic dark energy model in the framework of fractal cosmology. The features of fractal cosmology could pass ultraviolet divergencies and also make a better understanding of the universe in different dimensions. We discuss a fractal FRW universe filled with the dark energy and cold dark matter interacting with each other. It is observed that the Hubble parameter embraces the recent observational range while the deceleration parameter demonstrates an accelerating universe and a behavior similar to \(\Lambda \mbox{CDM}\). Plotting the equation of state shows that it lies in phantom region for interaction mode. We use \(\mathit{Om}\)-diagnostic tool and it shows a phantom behavior of dark energy which is a condition of avoiding the formation of black holes. Finally we execute the StateFinder diagnostic pair and all the trajectories for interacting and non-interacting state of the model meet the fixed point \(\Lambda \mbox{CDM}\) at the start of the evolution. A behavior similar to Chaplygin gas also can be observed in statefinder plane. We find that new holographic dark energy model (NHDE) in fractal cosmology expressed the consistent behavior with recent observational data and can be considered as a model to avoid the formation of black holes in comparison with the main model of NHDE in the simple FRW universe. It has also been observed that for the interaction term varying with matter density, the model generates asymptotic de-Sitter solution. However, if the interaction term varies with energy density, then the model shows Big-Rip singularity. Using our modified CAMB code, we observed that the interacting model suppresses the CMB spectrum at low multipoles \(l<50\) and enhances the acoustic peaks. Based on the observational data sets used in this paper and using Metropolis-Hastings method of MCMC numerical calculation, it seems that the best value with \(1\sigma \) and \(2\sigma \) confidence interval are \(\Omega _{m0}=0.278^{+0.008~+0.010} _{-0.007~-0.009}\), \(H_{0}=69.9^{+0.95~+1.57}_{-0.95~-1.57}\), \(r_{c}=0.08^{+0.02~+0.027}_{-0.002~-0.0027}\), \(\beta =0.496^{+0.005~+0.009} _{-0.005~-0.009}\), \(c= 0.691^{+0.024~+0.039}_{-0.025~-0.037}\) and \(b^{2}=0.035\) according to which we find that the proposed model in the presence of interaction is compatible with the recent observational data. 相似文献
25.
Mountainous torrents often carry large amounts of loose materials into the rivers, thus causing strong sediment transport. Experimentally it was found for the first time that when the intensive sediment motion occurs downstream over a gentle slope, the siltation of the riverbed is induced and the sediment particles can move upstream rapidly in the form of a retrograde sand wave, resulting in a higher water level along the river. To further study the complex mechanisms of this problem, a sediment mass model in the framework of the Smoothed Particle Hydrodynamics(SPH) method was presented to simulate the riverbed evolution, sediment particle motion, and the generation and development of dynamic hydraulic jump under the condition of sufficient sediment supply over a steep slope with varying angles. Because the sediment is not a continuous medium, the marker particle tracking approach was proposed to represent a piece of sediment with a marked sediment particle. The twophase SPH model realizes the interaction between the sediment and fluid by moving the bed boundary particles up and down, so it can reasonably treat the fluid-sediment interfaces with high CPU efficiency. The critical triggering condition of sediment motion, the propagation of the hydraulic jump and the initial siltation position were all systematically studied. The experimental and numerical results revealed the extra disastrous sediment effect in a mountainous flood. The findings will be useful references to the disaster prevention and mitigation in mountainous rivers. 相似文献
26.
Superficial sediments (top Im) of the Eastern Mediterranean Basin, Sea of Marmara, Turkey accumulated rapidly (0.087 ± 0.012 g/cm2 · y) by hemipelagic sedimentation with only limited amounts of gravity flow or bottom current action under low oxygenated but not anoxic conditions. They have restricted faunas, relatively higher organic carbon (1–1.8%) and lower calcium carbonate (14–20%) contents than other Eastern Mediterranean Basin sediments. Sedimentation shows little change over the last millenium except for an increase in Cu, Zn, Pb, Cr, and P over the last few centuries. The increase was most likely caused by increased metallurgical activities since the eighteenth century but are not at sufficient levels for the area to be regarded as polluted. 相似文献
27.
Rehman Saif ur Umar Muhammad Ehsan Muhammad Irfan Munawar Muhammad Jawad Miraj Muhammad Armaghan Faisal Ullah Muhammad Fahad 《Doklady Earth Sciences》2023,507(3):S446-S456
Doklady Earth Sciences - The research work involves rock physics modeling and reservoir characterization of Suliman fold belt to sulamain fold depression. This area is a brighter zone for... 相似文献
28.
Near‐fault ground motions with forward directivity are characterized by a large pulse. This pulse‐like motion may cause a highly non‐uniform distribution of story ductility demands for code‐compliant frame structures, with maximum demands that may considerably exceed the level of code expectations. Strengthening techniques for multi‐story frame structures are explored with the objective of reducing maximum drift demands. One option is to modify the code‐based SRSS distribution of story shear strength over the height by strengthening of the lower stories of the frame. The modified distribution reduces the maximum story ductility demand, particularly for weak and flexible structures. However, this strengthening technique is less effective for stiff structures, and is almost ineffective in cases in which the maximum demand occurs in the upper stories, i.e. strong and flexible structures. As an alternative, the benefits of strengthening frames with elastic and inelastic walls are evaluated. The effects of adding walls that are either fixed or hinged at the base are investigated. It is demonstrated that strengthening with hinged walls is very effective in reducing drift demands for structures with a wide range of periods and at various performance levels. Wall inelastic behavior only slightly reduces the benefits of strengthening with hinged walls.Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
29.
Ehsan BARZGAR Iraj ABDOLLAHIE FARD Rasoul HAMIDZADEH MOGHADAM Emadoddin ABDOLLAHIE KHALILI Aboozar GARAVAND 《《地质学报》英文版》2015,89(1):105-120
A structural cross-section constructed across the Zagros Fold-Thrust Belt covering the Abadan Plain, Dezful Embayment, and Izeh Zone applied 2D and 3D seismic data, well data, surface and subsurface geological maps, satellite images and field reconnaissance. Besides validation and modification of the cross-section, restoration allows better understanding of the geology, structural style and stratigraphy of the Zagros basin. In the area of interest, the Hormuz basal decollement and the Gachsaran detachment play the most significant roles in the structural style and deformation of the Zagros belt. More complexity is associated with interval decollements such as Triassic evaporites, Albian shales and Eocene marls. A variety of lithotectonic units and detachment surfaces confound any estimation of shortening, which generally decreases with increasing depth. Deformation completely differs in the Abadan Plain, Dezful Embayment and Izeh Zone because of different sedimentation histories and tectonic evolution; gentle and young structures can be interpreted as pre-collisional structures of the Dezful Embayment before the Late Cretaceous. After the Late Cretaceous, the Mountain Front Fault is the main control of sedimentation and deformation in the Zagros Basin, and this completely characterizes fold style and geometry within the Dezful Embayment and the Izeh Zone. 相似文献
30.