Comparison Between the Nutations of the Planet Mars and the Nutations of the Earth     

V. Dehant  T. Van Hoolst  P. Defraigne 《Surveys in Geophysics》2000,21(1):89-110

The nutations of the planets Mars andEarth are investigated and compared. Alarge number of interior structureparameters are involved in the nutationcomputations. The comparison between the observations and the computationsprovides several constraints on these parmeters andtherefore allows a better understanding of the physics of the interior of theplanet. For the Earth, the high precision of the observations of the nutationshas led to a very good determination of interior properties of the planet. ForMars, observations of nutations are not yet available, and we review how theamplitude of the Martian nutations depends on the hypotheses consideredfor its interior. Although Mars is very similar to the Earth, its interior is not well known;for example, we don't knowif its core is liquid or solid. Only if the core is liquid,the Free Core Nutation (FCN) normal mode exists and can alter the nutationswhich are close to the resonance. From the observed geoids, it is known thatboth planets are not in hydrostatic equilibrium. The departure is larger forMars than for the Earth, and consequently, the implication of considering a convective mantle instead of a mantle in hydrostatic equilibrium described byClairaut's equation for the initial equilibrium state of the planet is largeron the Martian nutations than on the Earth nutations. The consequences of theuncertainty in the core dimensions are also examined and shown to be of a veryhigh influence for Mars if the core is liquid, due to the potential changes inthe FCN resonance. The influence of the presence of an inner core, which isknown to exist for the Earth, could be more important for Mars than for theEarth if the inner core is large. Due to the presence of Tharsis on Mars, thetriaxiality of this planet has, additionally, larger effects than on Earth.  相似文献   

株洲与湘潭城市核心竞争力比较分析   总被引：4，自引：0，他引：4  

傅丽华 《热带地理》2004,24(2):173-176

通过对区域性中等城市株洲和湘潭的主要经济指标对比并进行优势分析,借助建立的数学模型对有关指标进行定量研究.结果表明,株洲的工业竞争力和湘潭的文化教育竞争力分别是两市的核心竞争力,并依此提出两市发挥城市的各自优势,注重城市的功能整合的建议,以更好地促进长株潭区域经济的可持续发展.  相似文献   

基于小波变换图像分割技术的电成像测井资料裂缝、孔洞面孔率提取方法          下载免费PDF全文

刘瑞林  谢芳  肖承文  张丽莉 《地球物理学报》2017,60(12):4945-4955

对于裂缝、溶蚀孔洞发育的碳酸盐岩缝洞储层,如何从测井资料中提取裂缝、溶蚀孔洞信息是评价储层有效性的关键问题.为了从电成像测井静态图像上准确地分割出清晰的裂缝、溶蚀孔洞子图像进而提取其参数信息,本文提出了一种基于小波变换模极大值图像分割技术的电成像测井资料缝洞面孔率提取方法.以钮扣电极电导率曲线为对象,先消除井壁凹凸不平导致的地层背景噪声的影响,利用小波变换模极大值图像分割方法得到包含裂缝和溶蚀孔洞目标的子图像,根据子图像提取裂缝-孔洞总面孔率、裂缝面孔率、孔洞面孔率等信息.本文利用塔里木盆地奥陶系碳酸盐岩地层的电成像测井数据提取了缝洞面孔率参数,还利用同井岩心CT扫描图像计算的平均缝洞面孔率、双侧向电阻率、常规测井资料三孔隙度模型计算的相对连通缝洞孔隙度进行了对比,并进行了试油验证.对比表明,电成像测井裂缝-孔洞总面孔率、裂缝面孔率、孔洞面孔率与岩心CT扫描图像平均缝洞面孔率、双侧向电阻率、相对连通缝洞孔隙度、试油结果均有较好的一致性.这一方面验证了采用本文方法提取的裂缝-孔洞总面孔率、裂缝面孔率、孔洞面孔率的合理性,另一方面表明所提取参数可用于指示缝洞型碳酸盐岩储层的渗透性和有效性.  相似文献   

云南鹤庆钻孔揭示的古生产力轨道尺度演化   总被引：1，自引：1，他引：0  

肖海丰  沈吉  肖霞云 《湖泊科学》2006,18(6):615-620

本文在分析鹤庆古湖泊不同演化阶段烧失量指标变化特点的基础上,采用频谱分析、滤波分析方法,探讨了该湖泊古生产力轨道尺度的演化特征．综合分析结果显示:在整个演化过程中,由于北半球夏季太阳辐射与南半球潜热输出相位关系的不同,导致斜率周期一直强于岁差周期;在987-1552 ka阶段,15 ka、10．7 ka和10 ka为较强周期,其中10 ka、10．7 ka周期是与100 ka周期强化有关的半岁差周期;在湖泊古生产力演化中存在与气候变化相一致的中更新世转型．  相似文献   

中印度洋洋盆GC11岩心富稀土深海沉积的元素地球化学特征   总被引：1，自引：1，他引：0  

张霄宇  黄牧  石学法  黄大松 《海洋学报》2019,41(12):51-61

对中印度洋洋盆的沉积GC11岩心开展了主量元素、微量元素和稀土元素分析研究，根据主微量元素相关性特征、稀土元素富集程度以及澳大利亚后太古代平均页岩归一化模式特征，初步探讨了GC11岩心的沉积地球化学特征，以及影响稀土元素富集的可能因素。研究表明，GC11岩心稀土元素总量在400.64×10?6～742.74×10?6，平均值为658.41×10?6，略低于邻近海域的GC02岩心，与沃顿海盆DSDP213岩心中含沸石型深海粘土层位中的稀土元素含量相当。δCe负异常明显，(La/Yb)_N为0.42，显示重稀土相对富集的特点。稀土元素与P₂O₅呈显著正相关性，CaO/P₂O₅的平均值为2.3，表明生物钙磷灰石可能是稀土元素的主要载体矿物，而铁锰水合物可能对富集稀土元素有一定的促进作用，但影响不大；GC11岩心中δCe负异常程度远低于GC02岩心，略低于DSDP213岩心，中稀土富集特征与GC02和DSDP213岩心基本一致。不同程度陆源物质的混入可能是导致以上不同岩心中稀土元素富集程度和分馏特征的主要原因。  相似文献   

空间科学虚拟观测台体系结构研究     

傅衍杰  邹自明  佟继周 《天文研究与技术》2011,(4)

科学观测数据的海量增长,使得旨在实现资源互操作的虚拟观测台(VO)应运而生,并迅速受到相关学科的支持和重视。国际虚拟天文台联盟(IVOA)、行星科学数据系统(PDS)和空间物理归档检索抽取标准(SPASE)等数据组织,正加快制定数据管理模型,推动VO的发展和跨学科应用。结合空间科学应用研究的特点,在借鉴国内外天文和空间科学VO研究成果的基础上,提出了一种针对空间科学数据的Hybrid型VO体系结构,并基于此体系结构发展了一个支持同步收割、格式化管道和事件关联发现的空间科学VO原型。实践和应用结果表明,基于这种体系结构建立的VO在解决全局资源的实时同步、异构应用的高度集成和面向科学问题的数据发现等问题上,有一定的普适性。  相似文献   

X-ray CT based numerical analysis of fracture flow for core samples under various confining pressures   总被引：1，自引：0，他引：1  

Noriaki Watanabe  Takuya Ishibashi  Yutaka Ohsaki  Yoshihiro Tsuchiya  Tetsuya Tamagawa  Nobuo Hirano  Hiroshi Okabe  Noriyoshi Tsuchiya 《Engineering Geology》2011,(4):338

The X-ray CT based numerical analysis of fracture flow for core samples, recently developed by the authors, was applied to two granite core samples having either a mated artificial or a mated natural fracture at confining pressures of 5 to 50 MPa. A third-generation medical X-ray CT scanner was used to image the samples within a core holder consisting of an aluminum liner and a carbon fiber overwrap. Fracture models (i.e., aperture distributions) were obtained by the CT images, the resolution of which was coarser than the apertures, and a single-phase flow simulation was performed using a local cubic law-based fracture flow model. Numerical results were evaluated by a fracture porosity measurement and a solution displacement experiment using NaCl and NaI aqueous solutions. These numerical results coincided only qualitatively with the experimental results, primarily due to image noise from the aluminum liner of the core holder. Nevertheless, the numerical results revealed flow paths within the fractures and their changes with confining pressure, whereas the experimental results did not provide such results. Different stress-dependencies in the flow paths were observed between the two samples despite the similar stress-dependency in fracture porosity and permeability. The changes in total area of the flow paths with confining pressure coincided qualitatively with changes in breakthrough points in the solution displacement experiment. Although the data is limited, the results of the present study suggest the importance of analyzing fluid flows within naturally fractured core samples under in situ conditions in order to better understand the fracture flow characteristics in a specific field. As demonstrated herein, X-ray CT-based numerical analysis is effective for addressing this concern. Using a multi-phase flow model, as well as a core holder constructed of an engineered plastic, should provide a useful, non-destructive, and non-contaminative X-ray CT-based fracture flow analysis for core samples under in situ conditions in future studies.  相似文献   

Scoping the effective marine environmental assessment of dredging and ocean disposal of coastal sediments in Korea   总被引：1，自引：0，他引：1  

Dae-In Lee  Ki-Hyuk Eom  Gui-Young Kim  Gun-Wook Baeck 《Marine Policy》2010

The application of scoping is reviewed to improve the efficiency and rationality of the marine environmental impact assessment system applied to the dredging of coastal sediments and the oceanic disposal of dredged material in Korea. Both the impact levels and those items requiring assessment vary in response to differing goals of the coastal activities involved and also to changes in the characteristics of different marine environments. As a consequence, different assessment fields need to be emphasized for evaluation of the impact that both dredging and dumping might have on the sites involved. The status of current assessment procedures is examined and its problems are diagnosed. Following a survey of interested parties and a review of case studies of the oceanic disposal of dredged sediment in other countries, checklists of core assessment items are proposed as part of a revamped review process, along with improvements to the assessment system.  相似文献   

Reconstructing large-scale remobilisation of deep-water deposits and its impact on sand-body architecture from cored wells: The Lower Cretaceous Britannia Sandstone Formation,UK North Sea     

J.T. Eggenhuisen  W.D. McCaffrey  P.D.W. Haughton  R.W.H. Butler  I. Moore  A. Jarvie  W.G. Hakes 《Marine and Petroleum Geology》2010

The Lower Cretaceous Britannia Sandstone Formation comprises deep-water sandstones deposited in the Witch Ground Graben, Outer Moray Firth, UK North Sea. The sandstones form a major gas condensate reservoir stratigraphically trapped against the Fladen Ground Spur. Although the first-order architecture is a simple northwards-thinning wedge, the lower part of the reservoir has a high degree of internal heterogeneity. The presence of thick debrites interleaved with or replacing sandstone units suggests that large-scale remobilisation has significantly impacted the sandstone distribution. This paper aims to reconstruct the style, geometry and history of the remobilisation over a 20 km², densely drilled area of the Britannia Field, focussing on the lower reservoir interval where remobilisation is thought to be prevalent. The study is based on documentation of approximately 2000 ft (610 m) of high quality core from 11 wells, together with wireline data from an additional 26 wells. Two main phases of remobilisation are recognised, each associated with excision surfaces removing up to 45 m of previously deposited stratigraphy. These surfaces are overlain by debrites that can be an order of magnitude thinner than the inferred excision depths, so that up to 40 m of differential topography was created as a consequence of the remobilisation. Subsequent sandstone intervals are shown to heal this differential topography, giving rise to a simple layer-like, large-scale architecture despite the complex internal remobilisation-induced heterogeneity. Remobilisation has thus affected the sand-body geometry both by removing previously deposited sand intervals and by controlling the thickness distribution of subsequent sandstones. Integration of the model with data from uncored wells shows that spatial variability may in some areas occur on distances smaller than current core-spacing (450 m), diminishing the geometric predictive value of the model in these areas. The fully mixed nature of the debrites is interpreted to indicate efficient transformation of the remobilised mass into a debris flow, controlling the highly evacuated morphology of the failure area. This link between morphology and process is used to characterise the Britannia remobilisation morphotype and place it into existing mass wasting classifications.  相似文献   

Fluid record of rock exhumation across the brittle–ductile transition during formation of a Metamorphic Core Complex (Naxos Island,Cyclades, Greece)     

L. SIEBENALLER  M. ‐C. BOIRON  O. VANDERHAEGHE  C. HIBSCH  M. W. JESSELL  A. ‐S. ANDRE‐MAYER  C. FRANCE‐LANORD  A. PHOTIADES 《Journal of Metamorphic Geology》2013,31(3):313-338

Fluid inclusions trapped in quartz veins hosted by a leucogneiss from the southern part of the Naxos Metamorphic Core Complex (Attic‐Cycladic‐Massif, Greece) were studied to determine the evolution of the fluid record of metamorphic rocks during their exhumation across the ductile/brittle transition. Three sets of quartz veins (V‐M2, V‐BD & V‐B) are distinguished. The V‐M2 and V‐BD are totally or, respectively, partially transposed into the foliation of the leucogneiss. They formed by hydrofracturing alternating with ductile deformation accommodated by crystal‐plastic deformation. The V‐B is discordant to the foliation and formed by fracturing during exhumation without subsequent ductile transposition. Fluids trapped during crystal–plastic deformation comprise two very distinct fluid types, namely a CO₂‐rich fluid and a high‐salinity brine, that are interpreted to represent immiscible fluids generated from metamorphic reactions and the crystallization of magmas respectively. They were initially trapped at ～625 °C and 400 MPa and then remobilized during subsequent ductile deformation resulting in various degrees of mixing of the two end‐members with later trapping conditions of ～350 °C and 140 MPa. In contrast, brittle microcracks contain aqueous fluids trapped at 250 °C and 80 MPa. All veins display a similar δ¹³C pointing to carbon that was trapped at depth and then preserved in the fluid inclusions throughout the exhumation history. In contrast, the δD signature is marked by a drastic difference between (i) V‐M2 and V‐BD veins that are dominated by carbonic, aqueous‐carbonic and high‐salinity fluids of metamorphic and magmatic origin characterized by δD between ?56‰ and ?66‰, and (ii) V‐B veins that are dominated by aqueous fluids of meteoric origin characterized by δD between ?40‰ and ?46‰. The retrograde P–T pathway implies that the brittle/ductile transition separates two structurally, chemically and thermally distinct fluid reservoirs, namely (i) the ductile crust into which fluids originating from crystallizing magmas and fluids in equilibrium with metamorphic rocks circulate through a geothermal gradient of 30 °C km^?1 at lithostatic pressure, and (ii) the brittle upper crust through which meteoric fluids percolate through a high geothermal gradient of 55 °C km^?1 at hydrostatic pressure.  相似文献