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121.
The objective of this paper is to test the ability of a spatially distributed hydrologic model (WetSpa) to simulate soil moisture. The test is conducted in the Baron Fork river basin (Oklahoma, USA), where soil moisture has been recorded on a daily basis at the WEST site soil moisture monitoring station of the Oklahoma Mesonet. The model is calibrated by comparing hourly simulated and observed river flows at Eldon gaging station from October 1, 1995 to December 31, 1996. The model performance to predict hourly river flows is verified by comparing model estimates and observations from January 1, 1997 to December 31, 2000. Next, the model predictions of soil moisture are compared with observations of WEST site soil moisture monitoring station for the same validation period. The observations are well reproduced by the model with errors that are within range of the observation accuracy, although the predictions show somewhat more abrupt temporal fluctuations as the whole root zone is considered to react instantaneously to precipitation events. The good performance compared to other studies is especially attributed to the quality of the rainfall data provided by weather radars. It is concluded that the performance of the model to predict soils moisture is promising, although spatial patterns still have to be verified. 相似文献
122.
This study investigated the effect of cations and anions on the sorption and desorption of iron (Fe) and manganese (Mn) in six surface calcareous soil samples from Western Iran. Six 10 mM electrolyte background solutions were used in the study, i.e., KCl, KNO3, KH2PO4, Ca(NO3)2, NaNO3, and NH4NO3. NH4NO3 and NaNO3 increased the soil retention of Fe and Mn, whereas Ca(NO3)2 decreased the soil retention of Fe and Mn. Iron and Mn sorption was decreased by NO3 ? compared with H2PO4 ? or Cl?. The Freundlich equation adequately described Fe and Mn adsorption, with all background electrolytes. The Freundlich distribution coefficient (K F) decreased in the order H2PO4 ? > Cl? > NO3 ? for Mn and H2PO4 ? > NO3 ? > Cl? for Fe. The highest sorption reversibility was for Fe and Mn in competition with a Ca2+ background, indicating the high mobility of these two cations. A MINTEQ speciation solubility model showed that Fe and Mn speciation was considerably affected by the electrolyte background used. Saturation indices indicated that all ion background solutions were saturated with respect to siderite and vivianite at low and high Fe concentrations. All ion background solutions were saturated with respect to MnCO3(am), MnHPO4, and rhodochrosite at low and high Mn concentrations. The hysteresis indices (HI) obtained for the different ion backgrounds were regressed on soil properties indicating that silt, clay, sand, and electrical conductivity (EC) were the most important soil properties influencing Fe adsorption, while cation exchange capacity (CEC), organic matter (OM), and Mn-DTPA affected Mn adsorption in these soils. 相似文献
123.
The role of grains in evolution of accretion disc is an important issue in astrophysics. In this paper, we study the effect of vapor pressure of grains in the dead zones of protoplanetary discs. Our study is limited to some particular observed cases in which evaporation of grains would be important and their vapor gas are constrained to an approximately isolated case. Here, we use the Einstein model to investigate the thermodynamics of vapor pressure. The results show that there is a critical temperature as a function of oscillation frequency and binding energy of particles. For temperatures greater than this critical value, the system goes into unstable mode. We show that the dead zone of the disc may reach to enough conditions to condense via instability caused by vapor pressure of grains. This mechanism may play an important role in the formation of planetesimals through protoplanetary disc. 相似文献
124.
Mohsen Dhieb 《制图学和地理信息科学》2013,40(2):163-175
ABSTRACTSemiology of Graphics is a seminal work of contemporary cartography. Published in 1967 by Jacques Bertin, the book attracted as much mistrust as it did interest even if some claims seem obsolete or outdated with the advent of GIS. This article discusses some underlying perspectives regarding an Arabic translation of Sémiologie Graphique. First, one may question the usefulness and the language of translation, and what issues readers should learn or be aware of before reading the book. In the Arab world, little research has engaged graphical semiology and its paradigms are rarely encountered. Second, only a limited number of graphical procedures have been experimented or implemented by digital means. There is a gap between some theoretical statements and their practical applications. Third, many other semiological aspects remain, in substance, little known in detail. This article considers whether these should be revisited by visualization and graphical analytics. 相似文献
125.
How does DEM resolution affect microtopographic characteristics,hydrologic connectivity,and modelling of hydrologic processes? 总被引:1,自引:0,他引:1
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The resolution of a digital elevation model (DEM) is a crucial factor in watershed hydrologic and environmental modelling. DEM resolution can cause significant variability in the representation of surface topography, which further affects quantification of hydrologic connectivity and simulation of hydrologic processes. The objective of this study is to examine the effects of DEM resolution on (1) surface microtopographic characteristics, (2) hydrologic connectivity, and (3) the spatial and temporal variations of hydrologic processes. A puddle‐to‐puddle modelling system was utilized for surface delineation and modelling of the puddle‐to‐puddle overland flow dynamics, surface runoff, infiltration, and unsaturated flow for nine DEM resolution scenarios of a field plot surface. Comparisons of the nine modelling scenarios demonstrated that coarser DEM resolutions tended to eliminate topographic features, reduce surface depression storage, and strengthen hydrologic connectivity and surface runoff. We found that reduction in maximum depression storage and maximum ponding area was as high as 97.56% and 76.36%, respectively, as the DEM grid size increased from 2 to 80 cm. The paired t‐test and fractal analysis demonstrated the existence of a threshold DEM resolution (10 cm for the field plot), within which the DEM‐based hydrologic modelling was effective and acceptable. The effects of DEM resolution were further evaluated for a larger surface in the Prairie Pothole Region subjected to observed rainfall events. It was found that simulations based on coarser resolution DEMs (>10 m) tended to overestimate ponded areas and underestimate runoff discharge peaks. The simulated peak discharge from the Prairie Pothole Region surface reduced by approximately 50% as the DEM resolution changed from 2 to 90 m. Fractal analysis results elucidated scale dependency of hydrologic and topographic processes. In particular, scale analysis highlighted a unique constant–threshold–power relationship between DEM scale and topographic and hydrologic parameters/variables. Not only does this finding allow one to identify threshold DEM but also further develop functional relationships for scaling to achieve valid topographic characterization as well as effective and efficient hydrologic modelling. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
126.
In this experimental study,the effect of suspended sediment concentration on the characteristics of a submerged hydraulic jump in a rectangular channel has been investigated,based on the sediment conce... 相似文献
127.
Mohsen Shadmehri 《Monthly notices of the Royal Astronomical Society》2009,395(2):877-883
We study the effects of winds on the time evolution of isothermal, self-gravitating accretion discs by adopting a radius-dependent mass-loss rate because of the existence of the wind. Our similarity and semi-analytical solution describes time evolution of the system in the slow accretion limit. The disc structure is distinct in the inner and outer parts, irrespective of the existence of the wind. We show that the existence of wind will lead to a reduction of the surface density in the inner and outer parts of the disc in comparison to a no-wind solution. Also, the radial velocity significantly increases in the outer part of the disc, however, the accretion rate decreases due to the reduced surface density in comparison to the no-wind solution. In the inner part of the disc, mass loss due to the wind is negligible according to our solution. But the radial size of this no-wind inner region becomes smaller for stronger winds. 相似文献
128.
Mohsen Asadi Nader Shariatmadari Mehran Karimpour-Fard Ali Noorzad 《Geotechnical and Geological Engineering》2017,35(5):2003-2015
The increasing demand of engineering landfills requires that designers propose a framework for landfill design, construction, repair and maintenance. As municipal solid waste (MSW) is a major part of a landfill, the analysis should consider MSW mechanical behavior using a constitutive model. To investigate this, 18 direct shear (DS) and triaxial (TX) tests were conducted on MSW samples with different fiber contents. Different shearing mechanisms lead to understand effects of fibers on stress–strain response. Based on obtained results the hyperbolic model Duncan and Chang (J Soil Mech Found Div 96(5):1629–1653, 1970) has been employed to simulate the TX results indicating the ability of the model to predict stress–strain behavior of MSW. This model could also be employed to the DS test results with some assumptions. The model can capture DS stress–strain response well whereas for TX tests the predictions were just enough. The experimental results and two sets of proposed MSW parameters of hyperbolic model have been compared and discussed. 相似文献
129.
130.
The Haftcheshmeh porphyry Cu-Mo-Au deposit in the Arasbaran metallogenic belt(AMB) of NW Iran contains more than 185 Mt of ore, with a grade ranging from 0.3% to 0.4%. It is hosted within a porphyritic diorite to granodiorite intruded into an older gabbro-diorite intrusion. 40 Ar/39 Ar analyses of primary magmatic hornblende from the granodiorite porphyry and gabbro-diorite show plateau ages of 26.41 ± 0.59 Ma, with an inverse isochron age of 25.9 ± 1.0 Ma and a plateau age of 27.47 ± 0.17 Ma, with an inverse isochron age of 27.48 ± 0.35 Ma for these two rock types, respectively. Comparing these new age data with those from the nearby Sungun(20.69 ± 0.35 Ma) and Kighal porphyry deposits defines a northwest-southeast Cu-Mo-Au mineralization zone extending for 20 km over the time span of ~27 to 20 Ma. Geochemically, Haftcheshmeh rocks are calc-alkaline with high potassium affinities with tectonic setting in relation to volcanic arc setting. Large ion lithophile elements(LILE) such as Th, U and K show enrichment on a primitive mantle normalized diagram(specially Pb), and are depleted in high field strength elements(HFSE) such as Ti and Nb, pointing to a mantle magma source contamination with crustal materials by subducted oceanic crust. 相似文献