围压对冻结粉土动力特性的影响   总被引：1，自引：4，他引：1  

沈忠言  张家懿 《冰川冻土》1997,19(3):245-251

通过恒应速率控制下等应变幅三轴动强度，对不同围压下的冻结粉土的应力－应变关系，动强度、破坏时间和破坏振次以及退荷回弹动弹模的讨论，认为围压效应有增强效应（提高动强度）和减强效应（降低动强度）两部分合成。在低围压时，围压效应中增强效应占主导、动强度随围压增加而提高；围压达到一定值之后，减强效应起主导作用，动强度随围压增加而下降，导致这一特点的主要机理是，围压作用下冰点下降引起冻土的未冻水含量增大和基  相似文献   

冬季风爆发前西伯利亚高压的演变   总被引：2，自引：0，他引：2  

谢安  卢莹  陈受钧 《大气科学》1992,16(6):677-685

本文是一次个例的诊断分析,应用FGGE-Ⅲ_b资料分析了1979年11月12—17日的东亚寒潮过程,着重讨论冷空气爆发前,位于两伯利亚的冷堆的增强过程,运用准拉格朗日坐标系的热量方程和涡度方程诊断了500hPa冷中心的温度变化和地面冷高压上空涡度演变的物理过程,分析结果说明,冷堆的增强与高空槽后急流中心前方出口附近的侧向环流有密切关系,开始时500hPa冷中心就位于此侧向环流的上升支附近,绝热冷却是冷堆加强的主要因子,即动力因子是主要的,冷高压上空的涡度变化与相对的涡度平流关系密切,它也与高空急流的相对位置有关,在地面高压加强的后期,散度项和平流项对于温度变化的贡献相反,但它们的垂直分布都有利于下沉运动加剧.因此,在分析预报中要密切注意忽流的动态. 本文的分析结果将有助于进一步理解冷空气增强的物理机制,也为寒潮过程的分析预报提供一定的参考.  相似文献   

湖北省凤凰关地区前寒武纪大别杂岩内地壳冷却速率的估算     

王江海  吴金平 《地球科学》1991,(2)

本文提出了一个封闭体系的扩散数学模型,用来描述由于化学扩散而导致球状晶体发生的均匀化作用;结合扩散系数和一些岩石物化知识,就可能模拟待定岩石的温度—时间(T-t)史。作者根据斜长石的相图特征并应用该模型,提出了如何确定斜长石扩散初始条件的方法,描述了湖北省凤凰关地区混合岩浅色体中斜长石的均匀化作用;经计算表明:地壳冷却速率(s)为0.75℃/Ma;所提出的数学模型普遍适用于变质岩的冷却问题。  相似文献   

云南个旧锡铜多金属矿区新山和高峰山岩体中高温热演化史及其与成矿的关系     

李宝龙  季建清  龚俊峰  周晶  毛景文 《大地构造与成矿学》2016,(6):1154-1173

云南个旧是全球最大的锡铜多金属矿床,主要成矿作用是与燕山期花岗岩密切有关的岩浆–热液体系。本文依据锆石U-Pb测年和~(40)Ar/~(39)Ar年代学对矿区内新山和高峰山花岗岩体进行测试分析,数据揭示矿区内南部和北部的花岗岩体的高–中温阶段热演化史曲线具有相似的演化趋势,只是冷却时间存在3~6 Ma的间隔。南部新山岩体于89~85 Ma形成,此后岩体经历了快速冷却过程,冷却速率为58.70~62.08℃/Ma。之后进入中温400~250℃的缓慢冷却过程,冷却速率为17.39~19.32℃/Ma,并持续到68~69 Ma。北部岩体的热演化史曲线明显滞后于南部岩体,北部高峰山岩体于83~82 Ma形成,之后经历快速冷却过程,冷却速率为295.59℃/Ma和103.29℃/Ma,于80 Ma进入400~250℃,此后以冷却速率为7.14~5.69℃/Ma,进入极其缓慢冷却过程并持续至67 Ma。矿区内花岗岩体先遭受快速冷却后进入中温阶段的缓慢长时间冷却作用过程,为锡铜主期成矿作用提供了持续的热源和流体运移动力学过程,也与矿区南、北部的成矿作用差异相吻合。  相似文献   

福建紫金山矿田深部似斑状花岗闪长岩锆石SHRIMP U-Pb和单矿物~(40)Ar/~(39)Ar年龄及其地质意义     

黎敦朋  邱小平  张文慧  刘文元  于波 《大地构造与成矿学》2016,(4):798-812

通过对福建紫金山矿田深部与成矿作用有关的主期似斑状花岗闪长岩3组锆石SHRIMP U-Pb和2组角闪石、钾长石~(40)Ar/~(39)Ar测年,获得锆石~(206)Pb/~(238()U加权平均年龄为101.8±1.5 Ma(n=34,MSWD=1.0),代表紫金山矿田深部与成矿作用有关的主期似斑状花岗闪长岩的成岩年龄;同时获得角闪石~(40)Ar/~(39)Ar冷却年龄为100±11 Ma、102.2 Ma,钾长石的~(40)Ar/~(39)Ar冷却年龄为96.3±1.7 Ma、98.5 Ma。依据矿物封闭温度理论,估算紫金山矿田深部与成矿作用有关的主期似斑状花岗闪长岩由锆石结晶至角闪石40Ar/39Ar体系封闭、再到钾长石~(40)Ar/~(39)Ar体系封闭的岩石冷却速率分别是40.7~67.1℃/Ma、116.9~216.3℃/Ma,显示岩石的冷却速率较大;由古地温梯度推算主期似斑状花岗闪长岩结晶(101.8±1.5 Ma)至钾长石~(40)Ar/~(39)Ar体系封闭(96.3±1.7 Ma)期间岩体隆升剥露了约3 km,暗示地壳在这一时期发生了快速隆升剥蚀作用。紫金山矿田深部似斑状花岗闪长岩锆石206Pb/238U年龄佐证了紫金山矿田深部存在一个大岩基,并约束了紫金山矿田斑岩型矿床的成矿时代,单矿物的~(40)Ar/~(39)Ar年龄为矿区的隆升剥露研究提供新资料。  相似文献   

Numerical Simulations of Sea Surface Cooling by a Mixed Layer Model during the Passage of Typhoon Rex   总被引：3，自引：0，他引：3  

Wada  Akiyoshi 《Journal of Oceanography》2005,61(1):41-57

In order to investigate the formation mechanism of rapid decrease of maritime sea surface temperature (SST) observed by R/V Keifu Maru, the ocean response to Typhoon Rex is simulated using a mixed layer model. The rapid decrease of the maritime SST is successfully simulated with realistic atmospheric forcing and an entrainment scheme of which sources of turbulent kinetic energy (TKE) are production due to wind stress, generation during free convection, and production due to current shear. The rapid decrease at the observed station by R/V Keifu Maru is not produced by instant atmospheric forcing but is mainly produced by entrainment on the right side of the running typhoon as a part of cooling area during its passage, and remained during a few days. The sea surface cooling (SSC) is evident along the track and on the right side of the running typhoon, which is similar to the SSC of satellite observation by TRMM/TMI. The conspicuous SSC produced by both entrainment and upwelling is situated just under the track of typhoon when the typhoon moves slower. Intercomparison of entrainment schemes of the mixed layer model is implemented. Frictional velocity and buoyancy effects are effective for a gradual SSC covering the wide region. In contrast, the effect of current shear at the mixed layer base is related to the amount of SSC and the sharp horizontal gradient of SSC. The entrainment scheme including all three TKE sources has the best performance for SSC simulation.  相似文献   

Numerical study of the storm-induced circulation on the Scotian Shelf during Hurricane Juan using a nested-grid ocean model   总被引：2，自引：0，他引：2  

Jinyu Sheng  Xiaoming Zhai  Richard J. Greatbatch 《Progress in Oceanography》2006,70(2-4):233

A nested-grid ocean circulation modelling system is used to assess the upper ocean response of the Scotian Shelf and adjacent slope to Hurricane Juan in September 2003. The nested-grid system consists of a fine-grid inner model covering the Scotian Shelf/slope and a coarse-grid outer model covering the northwest Atlantic Ocean. The model-calculated upper ocean response to Hurricane Juan is characterized by large divergent surface currents forced by the local wind forcing under the storm, and intense near-inertial currents in the wake of the storm. The sea surface temperature (SST) cooling produced by the model is biased to the right of the storm track and agrees well with a satellite-derived analysis. Over the deep water, off the Scotian Shelf, some of the near-inertial energy input by the storm is advected eastward by the Gulf Stream away from the storm track. The hurricane also generates shelf waves that propagate equatorward with the coastline on their right. In comparison with the outer model results, the inner model captures more meso-scale structures, greater SST cooling and stronger near-inertial currents in the study region.  相似文献   

电厂温排水中余氯浓度预测   总被引：1，自引：0，他引：1       下载免费PDF全文

张?? 燕  孙英兰 《海洋科学》2007,31(2):5-8

利用有限元分步杂交方法,对胶州湾海域潮流场进行了数值模拟。考虑余氯在水体中的化学反应,利用前人大量实验成果选取余氯衰减系数,建立胶州湾余氯的二维输运-扩散模型,并将此模型应用于青岛市黄岛发电厂三期温排水工程,预测了温排水中余氯的浓度分布及影响范围,为电厂冷却水排放口邻近水域的生态环境保护提供依据。  相似文献   

电厂冷却系统对水环境生物影响的数值预测方法研究     

朱良生  温伟英 《热带海洋学报》1995,(2)

分析了冷却系统内热冲击、卷载冲击、化学冲击对生物的致死影响，以及小生物在海水中的运动机制，从而导出小生物迁移运动微分方程和生物损失率控制微分方程，给出了数值求解生物损失率数学模型的方法，并应用该模型预测了海南某电厂冷却系统冲击效应对海洋水环境生物的影响。  相似文献   

Rapidly varying accretion and AGN feedback     

Edward C. D. Pope 《Monthly notices of the Royal Astronomical Society》2007,381(2):741-746

Accretion rates on to active galactic nuclei (AGNs) are likely to be extremely variable on short time-scales; much shorter than the typical cooling time of X-ray emitting gas in elliptical galaxies and galaxy clusters. Using the Langevin approach it is shown that, for a simple feedback system, this can induce variability in the AGN power output that is of much larger amplitude, and persists for longer time-scales, than the initial fluctuations. An implication of this is that rich galaxy clusters are expected to show the largest and longest-lived fluctuations. Stochastic variations in the accretion rate also mean that the AGN injects energy across a wide range of time-scales. This allows the AGN to maintain a much closer balance with its surroundings than if it was periodically activated. The possible non-linear correlation between Bondi accretion rate and jet power, found by Allen et al., can be explained if the instantaneous accretion rate, scaled by jet power, varies log-normally. This explanation also implies that the duty cycle of AGN activity increases with the radiative losses of the surroundings, in qualitative agreement with Best et al.  相似文献