共查询到20条相似文献,搜索用时 15 毫秒
1.
岩石层底部切向应力场及地球大地水准面异常 总被引:1,自引:0,他引:1
傅容珊 《中国科学技术大学学报》1990,20(2):184-196
比较了两种不同方法,即Runcorn 方程和地幔对流模型,计算了作用于岩石层底部的切向应力场.讨论了在三种不同的边界模型下,核-幔边界对于地球大地水准面的贡献.结果表明:模型Ⅰ(自由核-幔边界;摩擦岩石层-地幔边界)和模型Ⅲ(刚性核-幔边界,摩擦岩石层-地幔边界)中,核幔边界对于地球大地水准面的贡献随球谐函数系数的增加而减少,在n≥2时可以忽略下边界的影响.而模型Ⅱ(摩擦核-幔边界,自由表面)中下边界影响不容忽视.证明使用Runcorn 方程计算岩石层底部的切向应力场是一个合理的近似. 相似文献
2.
为深入了解火灾过程的特点,采用大涡模拟方法对火羽流与自然对流引起的典型竖井中的流动进行了数值模拟研究。网格滤波截断的亚格子湍能远小于流场总能量,验证了大涡模拟方法的有效性。竖井内火羽流和自然对流的计算结果与文献给出的实验值总体上符合较好。在此基础上讨论了3种不同开口形式竖井内火灾及加热情况下的内部流场,发现两者在表观上具有一定相似性,但火灾状态下流场湍流更强,卷起的涡团更多,流场温度更高。此外,开口形式亦对竖井内流型产生很大影响。 相似文献
3.
Mantle plumes: Why the current skepticism? 总被引:1,自引:0,他引:1
Gillian R. Foulger 《科学通报(英文版)》2005,50(15):1555-1560
The present reappraisal of the mantle plume hypothesis is perhaps the most exciting current debate in Earth science. Nevertheless, the fundamental reasons for why it has arisen are often not well understood. They are that 1) many observations do not agree with the predictions of the original model, 2) it is possible that convection of the sort required to generate thermal plumes in the Earth's mantle does not occur, 3) so many variants of the original model have been invoked to accommodate conflicting data that the plume hypthesis is in practice no longer testable, and 4) alternative models are viable, though these have been largely neglected by researchers. Regardless of the final outcome, the present vigorous debate is to be welcomed since it is likely to stimulate new discoveries in a way that unquestioning acceptance of the conventional plume model will not. 相似文献
4.
通过对小型足球比赛的调查研究,分析了小型足球比赛的技、战术特点,认为与11人制足球比赛相比较,开展小型足球比赛和教学活动更有利于提高队员的技战术水平和培养其足球意识,是培养优秀足球运动员较好方式。 相似文献
5.
王爱林 《科技情报开发与经济》2006,16(17):285-286
简要介绍了灌区概况及工程现状,主要针对小型水利工程“以土为模,砼就地浇筑”的方法,从施工设计、工料投资、施工步骤、质量要求等方面进行了探讨,并提出了今后加强工程管理的几点设想。 相似文献
6.
HUANGJinshui ZHONGShijie 《科学通报(英文版)》2004,49(21):2311-2317
Scafloor topography and heat flux show clear dependence on the age of seafloor. A half-space cooling (HSC)model can reproduce seafloor topography and heat flux data for younger seafloor, but for older seafloor the observations show reduced variations with the age in comparison with the HSC model predictions. The deviation was attributed to the sub-lithospheric small-scale (SSC) convection first by Parsons and McKenzie (1978). While there is little doubt that the SSC can enhance heat flux at relatively old seafloor, questions were raised as to whether or not the SSC can actually lead to a reduced topography. In this study, the effects of SSC on scafloor topography and heat flux are investigated by formulating a 2-D thermal convection model that is parallel to plate motion. Instead of using closed boundary conditions,which will bring large pressure effects because of return flow,a flow through boundary condition is adopted. The results show that although the SSC enhances the surface heat flux, it has little effects on topography for the fluids with a more realistic rheology. The reason for this is that the SSC transports the heat from the bottom to the top and cools down the whole fluids, and with the existence of a stagnant lid, the whole effects on topography are negligible. 相似文献
7.
张海洋 《江苏技术师范学院学报》2005,11(5):50-53
中国封建小农经济的生成是社会发展中综合因素促成的结果.从被同人学者所忽略的人口密度与生产方式即经济形态的关系来论证,中国从战国以来就已经是一个人口密集的国家;正是这种人口密度大的状况,导致了中国封建社会没有走西欧封建社会那种领主制下的大庄园经济的道路,而是走了中国独特的地主制下的小农户经济的道路. 相似文献
8.
四川黑水-台湾花莲断面岩石圈与软流圈结构 总被引:14,自引:0,他引:14
运用现代构造解析理论和方法,对四川黑水-台湾花莲人工地震测深剖面与天然地震面波层析成像进行系统分析基础上,结合地质学、地球化学以及其它地球物理学标志等多学科综合研究显示,高速块体或幔块构造的几何结构样式是控制该区岩石圈构造格局和岩石圈表层构造变形最基本条件之一,首次建立起该断面岩石圈与软流圈结构模型,划分出岩石圈四种几何结构样式:克拉通陆根状结构,造山带楔状结构、碎块状结构和藕节状结构,以及岩石圈四类构造演化类型:克拉通型岩石圈、增厚型岩石圈、减薄型岩石圈和大洋型岩石圈.在系统论述断面及邻区岩石圈结构类型特征基础上,探讨了该断面软流圈结构特征、岩石圈与软流圈相互作用及其大陆动力学基本型式. 相似文献
9.
10.
通过对榆社县小型农田水利工程建设和管理情况的调查,分析了小型农田水利工程存在的问题,探讨了发展小型农田水利工程的对策。 相似文献
11.
方腔内混合对流换热的数值研究与模型实验 总被引:5,自引:0,他引:5
为研究方腔内混合对流向受迫对流过渡的临界参数,通过数值模拟和模型实验,得到了不同工况下的流场、温度场,并将数值结果与实验结果进行了对比,通过一系列的数值计算,取得了均匀通风方式时混合对流处于受迫对流占优状态、自然对流受到抑制时的特征参数,指出描述方腔内混合对流的特征参数Gr/Ren中的n不等于2,并发现当自然对流引起的旋涡消失时,自然对流对换热仍有一定的影响。 相似文献
12.
13.
14.
XU Liang XU Jisheng Koustov Alexandre Papitashvili Vladimir Rich Fedrich 《武汉大学学报:自然科学英文版》2007,12(2):279-283
Recently several studies indicated possible deterioration of accuracy in the SuperDARN convection measurements at large distances (〉2 500 km). In this study, the SuperDARN-derived convection was compared with ion drift measurements given by the DMSP satellites, focused on SuperDARN far-range measurements, to investigate the above-mentioned problem. Two different procedures of SuperDARN convection estimation were applied. An overall reasonable agreement between two observation systems were found though individual points in some passes show significant differences. Besides, a tendency is also clear that the SuperDARN-derived velocities were slightly smaller than those of DMSP ion drift measurements. Potential factors contributing to the velocity differences were explained. 相似文献
15.
微重力下对流换热的地面缩比-减压模拟技术 总被引:10,自引:0,他引:10
为了地面模拟空间飞行器在微重力条件下的对流换热 ,抑制自然对流 ,消除或减小重力的影响 ,研究了将缩小尺寸和减小压力相结合的缩比 -减压模拟技术 ,并通过数值计算对这一技术进行了验证。研究表明 ,缩比 -减压法可以克服缩比法和减压法在应用时的不足。不论缩小尺寸和减小压力的程度如何 ,只要缩减比相等 ,自然对流的抑制效果就相同。在工程应用中 ,对一定的原型工况 ,采用缩减比参数比采用 Gr/Re2 参数更直观 ,可以指导对地面模拟实验中合适的模型尺寸和工作压力的确定 相似文献
16.
文章通过σ坐标系的非静力学数值海洋模型,即卑尔根海洋模型(Bergen Ocean Model),对纳木措湖中入水河流的烟羽动力进行研究。同时,提供层化的纳木措湖中进行模拟实验的结果。 相似文献
17.
Opening and evolution of the South China Sea constrained by studies on volcanic rocks: Preliminary results and a research design 总被引:8,自引:0,他引:8
The South China Sea (SCS) is characterized by abundant seamounts, which provide important information about the evolution of the SCS and related deep processes. Cenozoic volcanism in the SCS and its surroundings comprises three stages relative to the spreading of the SCS:prespreading (>32 Ma), syn-spreading (32-16 Ma), and post-spreading (<16 Ma). The pre-spreading magmatism predominantly occurs on the northern margin of the SCS and in South China coastal areas and shows a bi-modal affinity. The syn-spreading magmatic activity was very limited on the periphery of the SCS, but may be concentrated in the SCS. However, seafloor samples of this stage are not available yet because of overlying thick sedimentary deposits. Post-spreading magmatism is widespread in the central and southwest sub-basins of the SCS, Hainan Island, Leizhou Peninsula, Thailand, and Vietnam. These are mainly alkali basalts with subordinate tholeiites, and display OIB-type geochemical characteristics. The Dupal isotope anomaly and presence of high-magnesian olivine phenocrysts suggests their possible derivation from the Hainan mantle plume. The temporal and spatial distribution of Cenozoic volcanism in the SCS and its surroundings may be accounted for either by plate stress re-organization before and after SCS spreading, or by ridge suction of plume flow during opening of the SCS. If the latter is the case, the volcanic rocks within the SCS basin may not be typical mid-ocean ridge basalts (MORB). It remains puz-zling, however, that the transition between the South China continental margin and the SCS basin does not have features typical of a volcanic rifted margin. Clearly, the relationship between mantle plume and SCS opening needs further evaluation. A better un-derstanding of the link between deep processes and opening of the SCS not only requires enhanced studies on igneous petrogene-sis, but also is heavily dependent on systematic sampling of seafloor rocks. 相似文献
18.
青藏高原东缘岩石圈及软流圈结构的研究是认识该区域地壳上地幔的构造形变及高原内部物质向东运移的重要手段。通过搜集四川区域数字地震台站和野外临时地震台站记录的观测资料,采用接收函数共转换点(CCP)偏移叠加成像方法对青藏高原东缘深部结构研究。研究结果揭示:青藏高原东缘的地壳厚度比四川盆地的地壳厚度大10~20km;在青藏高原东缘与四川盆地的过渡地带,莫霍面处存在大幅度的垂向错断和变形。从青藏高原东缘到四川盆地,岩石圈与软流圈分界面(LAB)显示出深度逐步增加、410km间断面深度则有变浅的趋势。在地壳的下界面和LAB界面间以及LAB界面与410km间断面间也存在多条不连续的分层。青藏高原东缘和四川盆地的LAB界面的下方都有明显的低速层分布,但它们之间存在差别,四川盆地的LAB界面的下方低速层分布较为完整,而青藏高原东缘LAB界面下方的低速层分布中可见离散的高速块体分布。青藏高原东缘与四川盆地深部结构的明显差异,体现了该地区的深部地球动力学背景的复杂性。 相似文献
19.
环形空间内导热、对流、辐射耦合问题的数值仿真 总被引:3,自引:0,他引:3
本文针对环形空间内自然对流的研究现状,采用扩大计算区域办法确定边界条件,对一端开口的环形空间进行了将导热、对流、辐射耦合在一起的数值模拟,并加入了氩气的物性,使得计算结果与快中子增殖反应堆的实际情况相一致。计算结果显示,流动呈现两细胞的半循环流动,该结论与前人的研究结果一致。此外,由于采用计算区域整体模拟的办法,同时得出了固体内的温度场。 相似文献
20.
采用焦耳加热法对不同尺寸的水平微细铜丝在水中加热,并将实验得到的努谢尔特数Nu与常规尺寸下经典准则关系式的计算值比较.实验结果表明,在相同壁面过热度下,实验Nu数要小于经典准则关系式的计算值,并且实验Nu数几乎保持不变.这说明微细铜丝与水的换热由对流为主转变为对流与导热共同作用为主或是纯导热,从而导致了实验值小于常规尺寸下的理论计算值. 相似文献