排序方式： 共有44条查询结果，搜索用时 15 毫秒
1.
The paper presents the 3D finite element simulation of tidal flow and Sediment transport in the estuarine region of the Haihe river. The proposed model adopts sigma-transformation of the hydrodynamic and sediment transport equations. The hydrodynamic and sediment transport models are verified in case of a simple test problem for which analytical solutions are available. Finally the models are applied to muddy Haihe river estuary of North China and it is claimed that hydrodynamic and sediment transport models give a reliable comparison with the observed field data. However, there are certain discrepancies, and some reasonable questions regarding the present state-of-art, in the modeling of three-dimensional multilevel hydrodynamics and sediment transport, which are provided below for answer. 相似文献
2.
Abstract— Detailed investigations of the microimpact phenomena on Australasian microtektites from four samples from the Central Indian Basin reveal an array of features, such as very low-velocity captured droplets, welded projectiles, angular fragments and dust, craters generated by projectiles defining an oblique trajectory, high-velocity “pitless” craters, and the conventional hypervelocity craters with well-defined central pits and radial and concentric cracks—found commonly on lunar surface materials. The microimpacts are a consequence of interparticle collisions within the ejecta plume (as suggested by their chemistry) subsequent to a major impact and, therefore, reveal processes inherent in an impact-generated plume. All the impact phenomena observed here have taken place while the targets and projectiles were in flight and are therefore secondary impacts in lunar terms. However, some of the resultant features are analogous to lunar micro-craters attributed to primary impacts by cosmic dust. Therefore, ballistic sedimentation on the Moon is likely to contain plume collisional debris as well. 相似文献
3.
4.
E.K.KRISHNA KUMAR S.ABHILASH SANKAR SYAM P.VIJAYKUMAR K.R.SANTOSH A.V.SREENATH 《大气科学进展》2023,40(4):697-710
The inverse relationship between the warm phase of the El Ni?o Southern Oscillation(ENSO) and the Indian Summer Monsoon Rainfall(ISMR) is well established. Yet, some El Ni?o events that occur in the early months of the year(boreal spring) transform into a neutral phase before the start of summer, whereas others begin in the boreal summer and persist in a positive phase throughout the summer monsoon season. This study investigates the distinct influences of an exhausted spring El Ni?o(springtime)... 相似文献
5.
The North–East Corridor(NEC) Testbed project is the 3rd of three NIST(National Institute of Standards and Technology) greenhouse gas emissions testbeds designed to advance greenhouse gas measurements capabilities. A design approach for a dense observing network combined with atmospheric inversion methodologies is described. The Advanced Research Weather Research and Forecasting Model with the Stochastic Time-Inverted Lagrangian Transport model were used to derive the sensitivity of hypothetical observations to surface greenhouse gas emissions(footprints). Unlike other network design algorithms, an iterative selection algorithm, based on a k-means clustering method, was applied to minimize the similarities between the temporal response of each site and maximize sensitivity to the urban emissions contribution. Once a network was selected, a synthetic inversion Bayesian Kalman filter was used to evaluate observing system performance. We present the performances of various measurement network configurations consisting of differing numbers of towers and tower locations. Results show that an overly spatially compact network has decreased spatial coverage, as the spatial information added per site is then suboptimal as to cover the largest possible area, whilst networks dispersed too broadly lose capabilities of constraining flux uncertainties. In addition, we explore the possibility of using a very high density network of lower cost and performance sensors characterized by larger uncertainties and temporal drift. Analysis convergence is faster with a large number of observing locations, reducing the response time of the filter. Larger uncertainties in the observations implies lower values of uncertainty reduction. On the other hand, the drift is a bias in nature, which is added to the observations and,therefore, biasing the retrieved fluxes. 相似文献
6.
7.
BY VIKRAM GUPTA RUCHIKA SHARMA MADHO PRASAD SAH 《Geografiska Annaler: Series A, Physical Geography》2009,91(3):179-188
Four rock types (quartz mica gneiss, schist, quartzite and calc-silicate) located in the Satluj and Alaknanda valleys were used to test whether a Schmidt hammer can be used to distinguish rock surfaces affected by various natural and man-induced processes like manual smoothing of rock surfaces by grindstone, surface weathering, deep weathering, fluvial polishing and blasting during road construction. Surfaces polished by fluvial process yielded the highest Schmidt hammer rebound (R-) values and the blast-affected surfaces yielded the lowest R-values for the same rock type. Variations in R-value also reflect the degree of weathering of the rock surfaces. It has been further observed that, for all the rock types, the strength of relationship between R-values for the treated surfaces (manual smoothing of rock surface by grindstone) and the unconfined compressive strength (UCS) is higher than for the fresh natural surfaces. 相似文献
8.
The interpretation of total field anomalies becomes somewhat complicated, especially when an arbitrarily magnetized spherical ore mass happens to be the causative body. Even though some attempts have been made to analyze total field anomaly maps, they are often too complicated and their underlying assumptions in respect of permanent and induced components of magnetism are far from realistic. In this note, an attempt has been made to show that vertical magnetic anomalies are capable of yielding interpretation with ease and precision as far as magnetized spheres are concerned. An empirical method has been outlined for computing the magnetization inclination in the plane of the profile using the measured distances between principal maximum, principal minimum, and zero anomaly positions on a magnetic anomaly profile. 相似文献
9.
The Edgecumbe volcanics, which range from basalt through rhyodacite,have Sr contents between 125 and 370 p.p.m., Rb contents of1 to 70 p.p.m., Ba ranging from 50–550 p.p.m. and initial87Sr/86Sr ratios between 0.70291 and 0.70404. No simple correlationexists between these components and silica. The highest 87Sr/86Srvalues occur in a group of intermediate lavas (55–60 wt.per cent SiO2) while the rhyodacites have initial ratios between0.7035 and 0.7038. With increasing silica, Sr increases to amaximum in the andesites and then steadily decreases; Ba andRb increase over the same compositional range. The highest 87Sr/86Srlavas have major and trace element concentrations which departfrom trends defined by most of the lavas. The variation in strontiumisotopic compositions suggests interaction between parentalbasaltic magma and crustal material. Attempts to model the assimilationprocess using fixed end-member assimilation and assimilation-fractionalcrystallization models have failed to produce the observed chemicaltrends. Because the parental basaltic liquid underwent littlefractionation, the variability in hybrid lavas is attributedto variation in contaminant composition. Initial melts werelow in CaO, A12O3, MgO and Sr and enriched in SiO2. K2O, Na2O,Rb and Ba. As melting progressed, melts became enriched in themore refractory components. Because hybrid strontium isotopiccomposition is a function of Sr concentration as well as isotopiccompositions, the Sr content of the assimilant strongly influencesresultant isotopic systematics. The development of the assimilantssuggests plagioclase was a residual phase during early melting.This model of crustal assimilation represents one end-memberin the spectrum of processes responsible for the generationof continental volcanic suites. 相似文献
10.
An analysis system experiment was conducted for the month of June 2008 with Gridpoint Statistical Interpolation (GSI) analysis
scheme using NCMRWF’s (National Centre for Medium Range Weather Forecasting) T254L64 model. Global analyses were carried out
for all days of the month and respective forecast runs are made up to 120-hr. These analyses and forecasts are inter-compared
with the operational T254L64 model outputs which uses Spectral Statistical Interpolation (SSI) analysis scheme. The prime
objective of this study is to assess the impact of GSI analysis scheme with special emphasis on Indian summer monsoon as compared
to SSI. 相似文献