新疆塔里木河流域平原区土地利用覆盖变化及其对生态环境影响分析   总被引：1，自引：0，他引：1  

郭健 《地下水》2005,27(6):493-496

分析了塔里木河流域平原区近十余年土地利用覆盖变化和用水量的变化情况,对两者间的关系进行了研究,提出了为防止生态环境进一步恶化应采取的对策.  相似文献   

克拉玛依夏季日最高气温与08时 850hPa温度的关系   总被引：2，自引：0，他引：2  

冀新琪 《沙漠与绿洲气象(新疆气象)》2005,28(4):12-13

根据克拉玛依40年气温观测资料,分析克拉玛依夏季日最高气温与08时850hPa温度的关系,寻找预报夏季日最高气温关键因子.  相似文献   

Facies Clustering in Turbidite Successions: Case Study from Andaman Flysch Group, Andaman Islands, India     

Basab Mukhopadhyay  Partha Pratim Chakraborty  Soumen Paul 《Gondwana Research》2003,6(4):918-925

Bed thickness data of two turbidite sections viz., Corbyn's Cove section, South Andaman and Kalipur section, North Andaman those belong to Oligocene Andaman Flysch Group, a forearc submarine fan system, were assessed for facies clustering employing Hurst statistics. Both the sections show Hurst phenomenon and reveal clustering in terms of thick and thin beds. Forcing behind event (bed) depositions in either of the studied sections was assessed statistically and inferred to be non-random and with cyclicities of irregular physical length. The inferred paleogeography through Hurst criteria though worked well for distal fan setting i.e., basin floor sheet sandstones of Corbyn's Cove section, its unequivocal application in proximal fan deposits remains to be tested. The mismatch in paleogeographic interpretation between Hurst test result (lobe-interlobe) and field observation (channel-levee) for the inner fan deposit is explained through differential facies stacking between fans grow in sea-level lowstand and highstand. Lower bed amalgamation, poor sand to mud ratio and subordinately present thick event deposits may be the result of active growth of Andaman Flysch fan in sea level highstand and expressed in lower Hurst K value for inner fan channel-levee association (Kalipur section) compared to many of the channel-levee deposits of lowstand fan systems observed world over.  相似文献   

Compositional Geometry and Mass Conservation   总被引：1，自引：0，他引：1  

Robert F. Shurtz 《Mathematical Geology》2003,35(8):927-937

A geometrical structure is imposed on compositional data by physical and chemical laws, principally mass conservation. Therefore, statistical or mathematical investigation of possible relations between data values and such laws must be consistent with this structure. This demands that geometrical concepts, such as points that specify both mass and composition in linear space, and lines in projective space that specify composition only, be clearly defined and consistent with mass conservation. Mass thus becomes the norm in composition space in place of the Euclidean norm of ordinary space. Coordinate transformations inconsistent with this geometry are accordingly unnatural and misleading. They are also unnecessary because correlation arising from the constant mass presents no unusual difficulty in the analysis of the underlying quadratic form.  相似文献   

A statistical approach to evaluating distance metrics and analog assignments for pollen records     

Daniel G. Gavin  W. Wyatt Oswald  Eugene R. Wahl  John W. Williams 《Quaternary Research》2003,60(3):356-367

The modern analog technique typically uses a distance metric to determine the dissimilarity between fossil and modern biological assemblages. Despite this quantitative approach, interpretation of distance metrics is usually qualitative and rules for selection of analogs tend to be ad hoc. We present a statistical tool, the receiver operating characteristic (ROC) curve, which provides a framework for identifying analogs from distance metrics. If modern assemblages are placed into groups (e.g., biomes), this method can (1) evaluate the ability of different distance metrics to distinguish among groups, (2) objectively identify thresholds of the distance metric for determining analogs, and (3) compute a likelihood ratio and a Bayesian probability that a modern group is an analog for an unknown (fossil) assemblage. Applied to a set of 1689 modern pollen assemblages from eastern North America classified into eight biomes, ROC analysis confirmed that the squared-chord distance (SCD) outperforms most other distance metrics. The optimal threshold increased when more dissimilar biomes were compared. The probability of an analog vs no-analog result (a likelihood ratio) increased sharply when SCD decreased below the optimal threshold, indicating a nonlinear relationship between SCD and the probability of analog. Probabilities of analog computed for a postglacial pollen record at Tannersville Bog (Pennsylvania, USA) identified transitions between biomes and periods of no analog.  相似文献   

Theoretical Study on Stochastic Modeling of Combined Gravity-Magnetic-Electric-Seismic Inversion and Its Application     

YanHanjie YanHong LiYunping ZhangXiaofeng 《中国地质大学学报(英文版)》2003,14(3):227-233

As gravity field,magnetic field,electric field and seismic wave field are all physical fields,their object function,reverse function and compound function are certainly infinite contiuously differentiable func-tions which can be expanded into Taylor (Fourier) series within domain of definition and be further reduced in-to solving stochastic distribution function of series and statistic inference of optimal approximation,This is the basis of combined gravity-magnetic-electric-seismic inversion built on the basis of separation of field and source gravity-magnetic difference-value(D-value)trend surface,taking distribution-independent fault sys-tem as its unit,depths of seismic and electric interfaces of interests as its corresponding bivariate compound re-verse function of gravity-magnetic anomalies and using high order polynomial(high order trigonometric func-tion)approximating to its series distribution,The difference from current dominant inversion techniques is that,first,it does not respectively create gravity-seismic,magnetic-seismic deterministic inversion model from theoretical model,but combines gravity-magnetic-electric-seismic stochastic inversion model from stochastic model;second,after the concept of equivalent geological body being introduced,using feature of independent variable of gravity-magnetic field functions,taking density and susceptibility related to gravity-magnetic func-tion as default parameters of model,the deterministic model is established owing to better solution to the con-tradictioc of difficulty in identifying strata and less test analytical data for density and susceptibility in newly explored area;third,under assumption of independent parent distribution,a real modeling by strata,the prob-lem of difficult plane closure arising in profile modeling is avoided,This technology has richer and more detailed fault and strata information than sparse pattern seismic data in newly explored area,successfully inverses and plots structural map of Indosinian discontinuty in Hefei basin with combined gravity-magnetic-electric-seismic inversion,With development of high precision gravity-magnetic and overall geophysical technology,it is certain for introducing new methods of stochastic modeling and computational intelligence and promoting the develop-ment of combined gravity-magnetic-electric-seismic inversion to open a new substantial and promoting the develop-ment of combined gravity-magnetic-electric-seismic inversion to open a new substantial path.  相似文献   

The Origin and Significance of Antarctic Meteorites     

Ralph Harvey   《Chemie der Erde / Geochemistry》2003,63(2):93-147

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Turbulence Statistics Inside and Over Forest: Influence on Footprint Prediction   总被引：2，自引：0，他引：2  

Ü. Rannik  T. Markkanen  J. Raittila  P. Hari  T. Vesala 《Boundary-Layer Meteorology》2003,109(2):163-189

Observations of wind statistics within and above a Scots pine forest are comparedwith those predicted from an analytical second-order closure model. The roughnesssublayer (RSL) effects, and the influence of stability on similarity functions, arestudied using observations. The commonly accepted forms of similarity functionsdescribe the influence of diabatic effects above the RSL well. According to earlierstudies they are expected also to apply within the RSL. As an exception, the averagewind speed normalised with friction velocity was found to be invariant with stabilityclose to the canopy top under unstable conditions. Lagrangian stochastic trajectorysimulations were used to evaluate the influence of canopy turbulence profiles onfootprint prediction. The main uncertainty was found to arise from parameterisationof the random forcing term in the Lagrangian velocity equation. The influence ofdiabatic conditions was studied, and it was found that thermal stability affectssignificantly the footprint function above the forest canopy, but significantuncertainty exists because of uncertainties in the formulation of stability functions.  相似文献   

欠压实地层古地层压力恢复的统计模拟法及其在松辽盆地中的应用   总被引：1，自引：0，他引：1  

付广  庞雄奇  姜振学  张树林 《沉积学报》1996,(1)

恢复烃源岩古地层压力和对于研究其生留排烃过程具有重要意义。Ｎａｋａｙａｍａ［１］等在开展盆地模拟研究时应用Ｒｕｂｅｙ（１９５９）和Ｃｈａｐｍａｎ（１９７）等人提出的数学地质模型对欠压实地层的古地层压力进行恢复。本文通过对松辽盆地欠压实地层的研究发现欠压实因子随地层厚度、埋深、围岩渗透性等地质条件的不同而改变，在此基础上提出了欠压实地层压力恢复的统计模拟法，克服了目前Ｎａｋａｙａｍａ［１］等将地层埋藏过程中的欠压实因子视为常数的不足，从而使计算结果更接近实际。统计模拟法在松辽盆地的应用结果表明了这一方法在实用中的可行性和有效性。  相似文献   

Statistical analysis of the position of the monsoon trough     

G. Rajkumar  R. Narasimha 《Journal of Earth System Science》1996,105(3):343-355

Using surface charts at 0330GMT, the movement of the monsoon trough during the months June to September 1990 at two fixed longitudes, namely 79°E and 85°E, is studied. The probability distribution of trough position shows that the median, mean and mode occur at progressively more northern latitudes, especially at 85°E, with a pronounced mode that is close to the northern-most limit reached by the trough. A spectral analysis of the fluctuating latitudinal position of the trough is carried out using FFT and the Maximum Entropy Method (MEM). Both methods show significant peaks around 7.5 and 2.6 days, and a less significant one around 40–50 days. The two peaks at the shorter period are more prominent at the eastern longitude. MEM shows an additional peak around 15 days. A study of the weather systems that occurred during the season shows them to have a duration around 3 days and an interval between systems of around 9 days, suggesting a possible correlation with the dominant short periods observed in the spectrum of trough position.  相似文献