A transient model to predict the weekly temperatures of the ventilation air in a partially wetted airway     

J. Cheung 《Geotechnical and Geological Engineering》1988,6(4):343-352

Summary Most theoretical methods for the prediction of strata heat flow in an underground airway assume that the air temperature remains constant or that only small changes take place over the ventilated age of the airway. This assumption is clearly not correct; air temperature (especially those measured in British coal mines) display variation of up to 5° C during any one week at any one point. These variations are periodic in nature and relate to both the daily and weekly production cycle. In order to predict the transient heat flow from strata the Duhamel Theorem is used. Details of the theorem incorporating the air temperature history to calculate the surface temperature of a partially wetted airway are derived. An algorithm is presented for the calculation of surface temperatures and hence the heat flux from the rock. The algorithm is used in the computation of heat and moisture transfer rates from the rock to the ventilating air in the airway. Finally, the air temperatures at the end of the airway are predicted due to the heat flows from the strata and they are compared to the measured data supplied by British Coal, United Kingdom.  相似文献   

瞬变电磁测深法          下载免费PDF全文

张木生 《地震地质》1989,11(1):77-83

瞬变电磁测深法是一种人工源的电磁方法,适用于寻找火山岩覆盖区以及逆掩推覆体下部的含油气构造、圈定碳酸盐岩地区的低阻和中等电阻的沉积岩系构造。与其它电磁方法比较,有抗干扰能力强、信噪比高、受横向不均匀性的影响小等优点。本文简述了该方法的物理原理、野外测量技术、数据处理及其解释方法  相似文献   

与磁暴急始有关的瞬态地磁脉动          下载免费PDF全文

杨少峰  孙炜  徐宝连 《地球物理学报》1987,30(5):450-458

我们根据北京怀柔地磁脉动观测站在1982年6月至1983年5月的观测记录,分析了这时期发生的急始型磁暴中伴随SSC发生的瞬态地磁脉动。这种脉动的形态和地方时有关,白天有明显的衰减振荡,晚上则近似为非振荡的湾状扰动。我们分析了这种瞬态地磁脉动的振幅、持续时间、功率谱和急始形态的关系,并结合目前国外卫星的探测结果对这种脉动的形成和传播路径作了讨论。  相似文献   

黄河干流径流量暂态成分与时频分析及其预测   总被引：2，自引：1，他引：2       下载免费PDF全文

周后福  李春 《气象科学》2003,23(2):200-208

利用时间序列的研究方法对黄河干流径流量的暂态成分进行了分析，用小波方法研究了径流量的时频结构，结果表明：黄河上游水量与下游水量具有极好的一致性，径流量没有明显的下降趋势，径流量也没有突变现象，但基流径流量例外；径流量有准10a、3—4a左右的周期变化。用模拟性能极好的均值生成函数对径流量进行了预测。  相似文献   

Water and sediment movement around a coastal headland: Portland Bill,southern UK     

Bastos  A.  Collins  M.  Kenyon  N. 《Ocean Dynamics》2003,53(3):309-321

Numerical simulations of tidal flow and sand transport around a coastal headland (Portland Bill, southern UK) were undertaken to investigate patterns of sand transport during the development of tidally induced transient eddies. Results obtained from a 2-D finite-element hydrodynamic model (TELEMAC-2D) were combined with a sediment transport model (SEDTRANS), to simulate the sand transport processes around the headland. Simulation of the tidal flow around Portland Bill has shown the formation and evolution of tidally induced transient eddies, around the headland. During the evolution of these transient eddies, no current-induced bedload (transport) eddy is formed for either side of the headland. Net bedload sand transport direction, around a coastal headland, is the result of instantaneous gradients in bedload transport rates, during flood and ebb flows, rather than the average (residual) flow. Thus, the use of residual (water) circulation to describe patterns of sediment movement as bedload is not an appropriatedapproach. In the case study presented here, the distinct characteristics of the coastal and seabed morphology around the Isle of Portland (i.e. headland shape and the bathymetry) indicate that these parameters can be influencing tidal (flow) and sediment dispersion around the headland. Such an interpretation has broader implications and applications to headland-associated sandbanks elsewhere.Responsible Editor: Hans Burchard  相似文献   

On the three-dimensional oceanic density distribution in a millennium integration with an AO-GCM     

Jin-Song von Storch 《Ocean Dynamics》2003,53(1):11-20

 The three-dimensional time-mean density distribution in the ocean is determined not only by the time-mean fluxes of heat and freshwater at the sea surface, but also by time-mean vertical currents and time-mean density fluxes due to oceanic transients excited by fluctuating fluxes at the sea surface. The effects of these various processes on the global density fields are assessed using a balance equation of the variance of spatial density anomalies and a millennium integration with an atmosphere–ocean general circulation model. It is found that spatial density anomalies are generated by the time-mean heat fluxes at the sea surface and destroyed by the time-mean surface freshwater flux, by sinking of dense water and rising of less dense water, and finally by density fluxes associated with transients. The last two processes take place essentially in the oceanic interior. Since density fluxes of transient eddies act to reduce the existing density differences between the Atlantic/Southern Oceans and the other oceans, their presence could affect the global density balance, and from that the thermohaline circulation and the stability of this circulation. Received: 4 October 2001 / Accepted: 10 October 2002 Responsible Editor: Richard J. Greatbatch Acknowledgements I thank Ulrich Cubasch and his colleagues for providing me with the ECHAM3/LSG integration, Peter Müller and Richard Greatbatch for valuable suggestions.  相似文献   

Sensitivity analysis of a no-crossflow model for the transient flowmeter test     

Z. J. Kabala  H. K. El-Sayegh  H. P. Gavin 《Stochastic Environmental Research and Risk Assessment (SERRA)》2002,16(6):399-424

 Logarithmic sensitivities and plausible relative errors are studied in a simple no-crossflow model of a transient flowmeter test (TFMT). This model is identical to the model of a constant-rate pumping test conducted on a fully penetrating well with wellbore storage, surrounded by a thick skin zone, and situated in a homogeneous confined aquifer. The sensitivities of wellbore drawdown and wellface flowrate to aquifer and skin parameters are independent of the pumping rate. However, the plausible relative errors in the aquifer and skin parameters estimated from drawdown and wellface flowrate data can be proportionally decreased by increasing the pumping rate. The plausible relative errors vary by many orders of magnitude from the beginning of the TFMT. The practically important flowrate and drawdown measurements in this test, for which the plausible relative errors vary by less than one order of magnitude from the minimum plausible relative errors, can begin approximately when the dimensionless wellface flowrate exceeds q _D =q/Q≈0.4. During most of this stage of the test, the plausible relative errors in aquifer hydraulic conductivity (K _a ) are generally an order of magnitude smaller than those in aquifer specific storativity. The plausible relative errors in the skin hydraulic conductivity (K _s ) are generally larger than the plausible relative errors in the aquifer specific storativity when the thick skin is normal (K _s >K _a ) and smaller when the thick skin is damaged (K _s <K _a ). The specific storativity of the skin zone would be so biased that one should not even attempt to estimate it from the TFMT. We acknowledge Wiebe H. van der Molen for recommending the De Hoog algorithm and sharing his code. This research was partially supported by the US Geological Survey, USGS Agreement #1434-HQ-96-GR-02689 and North Carolina Water Resources Research Institute, WRRI Project #70165.  相似文献   

以反射系数为特征量的瞬变电磁电性界面的成像     

薛国强  宋建平  李貅 《CT理论与应用研究》2002,11(4):39-42

目的：为提高瞬变电磁探测精度，提出用反射系数作为特征量来对地下电性分界面成像，给出了方法的数学模型和实现步骤，并给出从实测数据中提取反射系数，对电性界面实现成像的思路，资料和方法：由野外实测资料出发，在频率域内用数字滤波技术计算波阻抗，再通过域的变换在时间域内建立含有反射系数的方程组。结果：最终后通过线性规划法求出反射系数，并以此值为参数来绘制成像断面。结论：数值模拟结果和实例的应用结果表明方法正确、有效。方法本身提高了瞬变电磁对电性层的分辨能力。  相似文献   

Modeling regional initiation of rainfall-induced shallow landslides in the eastern Umbria Region of central Italy   总被引：3，自引：6，他引：3  

Diana Salciarini  Jonathan W. Godt  William Z. Savage  Pietro Conversini  Rex L. Baum  John A. Michael 《Landslides》2006,3(3):181-194

We model the rainfall-induced initiation of shallow landslides over a broad region using a deterministic approach, the Transient Rainfall Infiltration and Grid-based Slope-stability (TRIGRS) model that couples an infinite-slope stability analysis with a one-dimensional analytical solution for transient pore pressure response to rainfall infiltration. This model permits the evaluation of regional shallow landslide susceptibility in a Geographic Information System framework, and we use it to analyze susceptibility to shallow landslides in an area in the eastern Umbria Region of central Italy. As shown on a landslide inventory map produced by the Italian National Research Council, the area has been affected in the past by shallow landslides, many of which have transformed into debris flows. Input data for the TRIGRS model include time-varying rainfall, topographic slope, colluvial thickness, initial water table depth, and material strength and hydraulic properties. Because of a paucity of input data, we focus on parametric analyses to calibrate and test the model and show the effect of variation in material properties and initial water table conditions on the distribution of simulated instability in the study area in response to realistic rainfall. Comparing the results with the shallow landslide inventory map, we find more than 80% agreement between predicted shallow landslide susceptibility and the inventory, despite the paucity of input data.  相似文献   

Hydrographic mesoscale structures and Poleward Current as a determinant of hake (Merluccius merluccius) recruitment in southern Bay of Biscay     

Sanchez  Francisco; Gil  Julio 《ICES Journal of Marine Science》2000,57(1):152-170

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