共查询到20条相似文献，搜索用时 31 毫秒
1.
本文用有限差分法模拟研究二维空间中波的传播、散射及其与介质间断的相互作用。文章第一部分运用所模拟的纵波波源讨论了半无限空间表面台阶地形或槽形裂隙所造成的波的散射。这些间断可模拟具有波长量级的悬崖或狭谷。第二部分用差分法与扰动法结合而成的混合法处理半无限空间表面有另一种物质构成的表面浅障碍时波的传播,以模拟山脊、堑沟等地形的影响。此混合法也被用于讨论半无限空间内含有水平夹层或孔隙的问题。所得研究结果对波的传播及其与介质间断的相互作用的理论研究和地震波破坏效应的分析和隔离等应用研究有一定的意义。 相似文献
2.
Priti Maheshwari P. K. Basudhar S. Chandra 《Geotechnical and Geological Engineering》2006,24(2):313-324
The paper describes a mechanical model for estimating the flexural response of a strip footing, supporting a column (imposing
a concentrated load), resting on a compacted granular bed overlying a reinforcement layer for example, geogrids, geomats etc.
below which lies a loose soil deposit. The footing is idealized as a beam and the reinforcing element is assumed to have finite
bending stiffness and negligible frictional resistance. The upper and lower soil layers are idealized by a series of linear
and discrete springs (Winkler springs) of different stiffness values. To find the response of such a model the governing differential
equations have been derived and expressed in a nondimensional form. A closed form analytical solution of the same has been
obtained subjected to appropriate boundary conditions. Using the present approach the resulting solution for a degenerated
case of a long beam is found to be identical to the same of Hetenyi (1946, Beams on elastic foundations, University of Michigan
press, Ann Arbor, MI). Parametric studies reveal that the ratio of flexural rigidity of upper and lower beam and the ratio
of stiffness of the upper and lower soil layers affect significantly the response of the foundation. 相似文献
3.
B. P. Harlamov 《Mathematical Geology》2003,35(4):431-449
Zones of increased concentration formed by a solvent flowing from a source are considered. A matehmatical model for forming such zones is proposed. It takes into account that such a zone is composed of a set of independent particles. Hence the distribution of a substance around the source can be explained by movement of an individual particle. In the model this movement is a continuous semi-Markov process with terminal stopping at some random point in space. Parameters of the process depend on the velocity field of the flow. Forward and backward partial differential equations for the distribution density of a random stopping point of the process are derived. The forward equation is investigated for the centrally symmetric case. Solutions of the equation demonstrate either a maximum or a local minimum at the source location. In the latter case a concentric ring around the source is formed. If different substances vary in their absorption rates, they can form separable concentration zones as a family of concentric rings. 相似文献
4.
重力场定义的澄清 总被引：3，自引：1，他引：2
《朗曼现代英文词典》(LongmanModernEnglishDictionary)、《牛津高阶英汉双解词典》(OxfordAdvancedLearner’sEnglish ChineseDictionary)、《韦氏词典》(Merriam Webster’sNewCollegiateDictionary)、作为地球物理专业词汇定义源的《勘探地球物理百科词典》(EncyclopedicDictionaryofExplorationGeo physics)以及中国的一些重力教科书、专著及词典 ,把重力场定义为重力或重力作用存在的空间 ,重力效应可以测量的空间 ,即 :力或重力存在的空间。这个定义不同于国外英文地球物理教科书、专著及中、英、俄文场论教科书对重力场的定义 :空间中的重力。定义重力场为重力存在的空间 ,混淆了“场”本身及“场域”的概念 ,并不是一个标准的物理或地球物理定义 ,是一种误导。物理场是空间中存在的一种物理作用或效应 ,分布于引起它的场源体周围。两个物体之间存在着的相互作用力 ,通过每个物体引起的引力场给予另一个物体。重力场可以定义如下 :地球内部及其附近空间一点处存在的重力作用 ,或单位质量受到的重力。重力场是一种力或力场 ,存在于地球表面及其附近的空间。重力场不是空间 ,重力场的测量应当是在重力场存在的空间或场域中 ,而不是在重力场中进行。 相似文献
5.
依据松辽盆地西南部新站地区嫩江组三段孢粉和藻类化石百分含量纵向变化特征,自下而上划分7个能识别水体盐度变化的孢粉和藻类组合：Cyathidites Pinuspollenites Dinogymniopsis组合,指示缩小的微咸水湖相沉积环境;Dinogymniopsis Leiosphaeridia Pinuspollenites组合,代表水域扩大的微咸水湖相沉积环境;Cicatricosisporites Pinuspollenites Botryococcus组合,代表水域缩小的淡水-微咸水湖相沉积环境;Dinogymniopsis Chlamydophorella Taxodiaceaepollenites组合,反映淡水与微咸水频繁交互变化的浅湖相沉积环境;Cicatricosisporites Pinuspollenites Pediastrum组合,代表水域缩小的淡水湖相沉积环境;Nenjiangella Balmula Cyathidites组合,代表水域范围较大的淡水湖相沉积环境;Cyathidites Trilobosporites Botryococcus组合,指示水域缩小的微咸水湖相沉积环境。 相似文献
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7.
汤山温泉是中国四大著名温泉疗养胜地之一,阐明其成因模式对于该温泉区的进一步开发和热水资源的可持续利用具有一定意义。基于硅-焓图解法和水文地球化学方法对其进行了系统研究,结果表明该区热储温度为90℃,岩溶热水与岩溶冷水、孔隙潜水和地表水之间在水化学和同位素组成上存在明显差异,地热井深度越大,冷水混入相对较少,地热水温度相对较高。经分析,该地热系统成因上属于中低温对流型。其补给区主要来自汤山山体(宁镇山区)及句容盆地东侧茅山山脉,循环深度为2.6~2.9 km,地热水通过汤山-东昌街断裂在浅部与区内NW向断裂、NE向断裂交汇形成温泉水。 相似文献
8.
9.
A numerical investigation to illustrate the consequences of hydraulic connections between granular and fractured-rock aquifers 总被引：1，自引：1，他引：0
Natural or artificial hydraulic connections between a granular aquifer in contact with a fractured-rock aquifer can have significant physical and chemical impacts at both a local and a regional scale. In this study, numerical simulations are conducted in order to illustrate the hydrogeological consequences of such hydraulic relationships. The numerical investigation, based on a conceptual model, focuses on the effects of the hydraulic connections when conducting a pumping test in a well that is set into a granular confined aquifer overlying a fractured-rock aquifer which presents a few fractures directly connected to the granular aquifer. It is illustrated that when interpreting the pumping test with the conventional methods consisting of plotting the drawdown versus time, a bias is introduced on the estimation of the transmissivity of the granular aquifer due to groundwater flowing from the fractured-rock aquifer via connecting fractures. However, it is underlined that plotting drawdown log-derivative versus time helps to diagnose the existence of these hydraulic relationships and therefore avoids committing a bias on the transmissivity estimation of the granular aquifer. Numerical simulation results also illustrate that hydraulic connections between the two aquifers can have significant impacts on the hydrogeochemical signature of the granular aquifer under investigation. 相似文献
10.
Inclusion trails in 58 garnet porphyroblasts in a single sample from the Cram Hill Formation in southeast Vermont were imaged using high-resolution X-ray computed tomography. Texturally the porphyroblasts have a large core with a sub-vertical foliation that has a well defined geometry with a mean orientation of 113/72E for a 95% confidence cone semi-angle of 5.3°. This steep foliation curves into a sub-horizontal foliation. The foliation intersection/inflection axes (FIAs) defined by hinge lines for this curvature are tightly clustered with a mean plunge of 11° towards 201° with a 95% confidence cone semi-angle of 4.1°. Eigenvalue analysis indicates that the clustered distribution of the foliation and FIA data are unlikely to be the result of a random event. There is evidence in the specimen for multiple foliation-forming events subsequent to garnet nucleation, and the preservation of these clustered distributions in their wake strongly suggests that the porphyroblasts have not rotated with respect to a geographic reference frame. FIAs represent a measurable structural element that can provide information on tectonic events at the time the porphyroblasts grew. A comparison of FIA data collected using high-resolution X-ray computed tomography with data collected using the asymmetry method demonstrates that the asymmetry method is a valid technique for defining the mean FIA orientations in a sample. 相似文献
11.
承压含水层非完整反滤回灌井的稳定流计算 总被引：2，自引：0，他引：2
反滤回灌井是地下水库中一种有效的回灌设施,它由回灌井和井口反滤层组成。非完整反滤回灌井井流运动由砂反滤层的竖向流和非完整回灌井井流组合而成。文中提出了承压含水层非完整反滤回灌井稳定流的计算方法,分析了反滤层、井损和回灌堵塞等因素对回灌量的影响,并结合实例证明了反滤回灌井回灌量大大低于普通回灌井的回灌量。 相似文献
12.
We consider the interaction of interstellar dust grains with a galactic shock in the gaseous component. Typical parameters of dust grains and spiral density waves imply that the formation of large-scale dust lanes at the front of a galactic shock is possible only in models taking into account a self-focusing phenomenon. In the case of an isothermal flow of interstellar gas through a spiral arm in a model with a gaseous disk of variable thickness, dust lanes can be projected onto the region of increased gas density, although this is not associated with a galactic shock. The dust density peak derived from the classical model of a galactic shock (isothermal flow and a constant thickness of the gaseous disk) is appreciably shifted downstream of the gas flow, so that it does not outline the gas density maximum. 相似文献
13.
Compacted bentonite has been considered as a candidate buffer material in the underground repository for the disposal of high-level radioactive waste. An erosion of bentonite particles caused by a groundwater flow at the interface of a compacted bentonite and a fractured granite was studied experimentally under various geochemical conditions. The experimental results showed that bentonite particles could be eroded from a compacted bentonite buffer by a flowing groundwater depending upon the contact time, the flow rate of the groundwater, and the geochemical parameters of the groundwater such as the pH and ionic strength.
A gel formation of the bentonite was observed to be a dominant process in the erosion of bentonite particles although an intrusion of bentonite into a rock fracture also contributed to the erosion. The concentration of the eroded bentonite particles eroded by a flowing groundwater was increased with an increasing flow rate of the groundwater. It was observed from the experiments that the erosion of the bentonite particles was considerably affected by the ionic strength of a groundwater although the effect of the pH was not great within the studied pH range from 7 to 10. An erosion of the bentonite particles in a natural groundwater was also observed to be considerable and the eroded bentonite particles are expected to be stable at the given groundwater condition.
The erosion of the bentonite particles by a flowing groundwater did not significantly reduce the physical stability and thus the performance of a compacted bentonite buffer. However, it is expected that an erosion of the bentonite particles due to a groundwater flow will generate bentonite particles in a given groundwater condition, which can serve as a source of the colloids facilitating radionuclide migration through rock fractures. 相似文献
14.
Listric versus planar normal fault geometry: an example from the Eisenstadt-Sopron Basin (E Austria) 总被引：1，自引：0，他引：1
Darko Spahić Ulrike Exner Michael Behm Bernhard Grasemann Alexander Haring Herbert Pretsch 《International Journal of Earth Sciences》2011,100(7):1685-1695
In a gravel pit at the eastern margin of the Eisenstadt-Sopron Basin, a satellite of Vienna Basin (Austria), Neogene sediments
are exposed in the hanging wall of a major normal fault. The anticlinal structure and associated conjugated secondary normal
faults were previously interpreted as a rollover anticline above a listric normal fault. The spatial orientation and distribution
of sedimentary horizons and crosscutting faults were mapped in detail on a laser scan of the outcrop wall. Subsequently, in
order to assess the 3D distribution and geometry of this fault system, a series of parallel ground penetrating radar (GPR)
profiles were recorded behind the outcrop wall. Both outcrop and GPR data were compiled in a 3D structural model, providing
the basis for a kinematic reconstruction of the fault plane using balanced cross-section techniques. However, the kinematic
reconstruction results in a geologically meaningless normal fault cutting down- and up-section. Additionally, no evidence
for a weak layer serving as ductile detachment horizon (i.e. salt or clay horizon) can be identified in stratigraphic profiles.
Instead, the observed deflection of stratigraphic horizons may be caused by a displacement gradient along a planar master
fault, with a maximum displacement in the fault centre, decreasing towards the fault tips. Accordingly, the observed deflection
of markers in the hanging wall—and in a nearby location in the footwall of the normal fault—is interpreted as large-scale
fault drag along a planar fault that records a displacement gradient, instead of a rollover anticline related to a listric
fault. 相似文献
15.
16.
A time sequence of airborne infrared imagery provides a unique view of phenomena associated with a turbulent tidal intrusion
into a stratified bay. During flood tide, cooler water from the Strait of Juan de Fuca is observed to penetrate Sequim Bay
(Washington, U.S.V.) as a turbulent jet. After separating from the shoreline, the jet collapses into the stratified middle
part of the bay, forming a mushroom-shaped head consisting of a semicircular plunge front and areas of recirculating flow.
As the plunge front advances into the estuary, a set of nonlinear internal waves emerges and propagates toward the relatively
stagnant southern part of the bay, where they are a potential source of vertical mixing. This range of phenomena is expected
based on laboratory studies, but has not been seen previously in a natural setting. 相似文献
17.
Myers developed a matrix form of the cokriging equations, but one that entails the solution of a large system of linear equations.
Large systems are troublesome because of memory requirements and a general increase in the matrix condition number. We transform
Myers’s system into a set of smaller systems, whose solution gives the classical kriging results, and provides simultaneously
a nested set of lower dimensional cokriging results. In the course of developing the new formulation we make an interesting
link to the Cauchy-Schwarz condition for the invertibility of a system, and another to a simple situation of coregionalization.
In addition, we proceed from these new equations to a linear approximation to the cokriging results in the event that the
crossvariograms are small, allowing one to take advantage of a recent results of Xie and others which proceeds by diagonalizing
the variogram matrix function over the lag classes. 相似文献
18.
We have computed the ejection of a massive envelope by a star during a type II supernova explosion in the presence of a compact
remnant (a neutron star or black hole). This problem is of interest because of the possible presence of a compact remnant
following the SN 1987A explosion. The computations demonstrate that a fairly large amount of matter is left in the neighborhood
of the compact gravitating body. We present computations of the accretion rate onto the surface of the compact remnant. The
estimated luminosity exceeds that observed for SN 1987A in various frequency ranges by several orders of magnitude. 相似文献
19.
V.R. Livshits 《Russian Geology and Geophysics》2010,51(2):159-162
The distribution of hydrocarbon accumulations in a basin is modeled as a nonstationary Poisson field of points with the average density of accumulations as a function of distance from the basin margin. The model, in which this distance is a unique parameter to define the intensity function, is suitable, in a first approximation, for Monte-Carlo simulation of the real pattern of accumulations. The Poisson random field of points is described with a power function, where the power is a fractal dimension used as an integral numerical parameter of the distribution. 相似文献
20.
博斯腾湖碳酸盐和同位素组成的全新世古环境演变高分辨记录及与冰川活动的响应 总被引：5，自引：0，他引：5
本文通过对在新疆南部塔里木盆地北缘博斯腾湖采集的一根953cm的岩心进行了早全新世以来的古气候重建。对BSTC2000岩心进行了碳酸盐矿物组成、Ca/1000Sr,有机质TOC,C/N和C/S分析,并结合BSTC2000岩心附近的一个沉积物剖面的孢粉资料,利用多指标重建了8500aBP以来的古气候变化特征。在2个平行岩心中对保存的植物叶片、草籽,以及全有机质进行了9个AMS14C年代测定。8500～8100aBP气候冷湿,钻孔位置为河流-滨湖相环境,沉积物中有3层泥炭层。从8100～6400aBP,气温升高,湖泊扩张,气候暖湿,湖泊可能为最高湖面时期。而从6400～5100aBP湖泊稍微下降,气候变冷。在中全新世晚期从5100～3100aBP气候变得高温干旱,但其间的4400～3800aBP有短暂的气候变冷,早期大量的冰雪融水补给博斯腾湖,使得湖泊水位上升。湖泊的第二个高湖面期是5200～3800aBP。在3100～2200aBP气候冷湿,由于蒸发减弱而湖泊有所扩张,湖泊在3100至2800aBP期间是最后一次短暂的高湖面期。这次短期高湖面后,湖泊由于较长时期的低温而引起的供水减少,湖泊收缩。从2200～1200aBP,气候变得干热,湖泊收缩。尽管从1200aBP以来,温度有所下降,气候变得暖干,湖泊又开始有所上升,但是没有达到博斯腾湖出水口孔雀河的海拔高度。 相似文献