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1.
To study the effect of uncertain factors on the temperature field of frozen soil, we propose a method to calculate the spatial average
variance from just the point variance based on the local average theory of random fields. We model the heat transfer coefficient
and specific heat capacity as spatially random fields instead of traditional random variables. An analysis for calculating the random
temperature field of seasonal frozen soil is suggested by the Neumann stochastic finite element method, and here we provide the
computational formulae of mathematical expectation, variance and variable coefficient. As shown in the calculation flow chart, the
stochastic finite element calculation program for solving the random temperature field, as compiled by Matrix Laboratory
(MATLAB) software, can directly output the statistical results of the temperature field of frozen soil. An example is presented to
demonstrate the random effects from random field parameters, and the feasibility of the proposed approach is proven by comparing
these results with the results derived when the random parameters are only modeled as random variables. The results show that
the Neumann stochastic finite element method can efficiently solve the problem of random temperature fields of frozen soil based
on random field theory, and it can reduce the variability of calculation results when the random parameters are modeled as spatially
random fields. 相似文献
2.
A geologic anomaly is a geologic feature or structure that departs markedly from its surrounding environment with respect
to composition, texture, or genesis. The analysis of geologic anomalies related to mineralization is based upon specific geologic
factors and a combination of features, such as structural, temporal, and spatial, and draws upon special effects that are
due to ore-forming processes. An analysis of the geologic anomalies in the, middle-lower Yangtze area in southeastern China
has led to an interpretation of the relation between anomaly subtypes and the occurrence and spatial distribution of ore deposits.
Consequently, the following conclusions have been reached: the type of anomaly reflects the controlling factors that led to
the formation of iron, copper, and gold deposits in the area; sedimentary geologic anomalies are most closely associated with
stratiform deposits; structral complexity anomalies are most closely associated with Cu−Fe−Au deposits; magmatic anomalies
reflect geologic processes in which Fe and Cu elements were separated from magma and enriched into ores; and the geologic
combination entropy anomaly is proposed as a comprehensive variable that is related to favorable ore-forming environments
and that can serve as a quantitative index that can be used in mineral exploration. 相似文献
3.
自然地理要素空间插值的几个问题 总被引：77，自引：8，他引：69
资源管理、灾害管理、生态环境治理以及全球变化研究的需要强化了部分自然地理要素空间插值研究的重要性。这些要素空间插值的核心是建立充分逼近要素空间分布特征的函数方程。对于给定的区域与要素样本值 ,插值函数可以有多种模型形式。各类模型的精度受其理论基础、模型算法、时空尺度效应、样本数据属性等因素的综合影响。通过对国际主要插值研究成果进行分析 ,文章认为各类模型插值精度的差异缘于模型对插值要素空间变异性与空间相关性的反映 ,具体应用中 ,只有对已知样本数据进行变异性与相关性分析才能选出适当的插值方法。 相似文献
4.
In order to determine whether it is desirable to quantify mineral-deposit models further, a test of the ability of a probabilistic
neural network to classify deposits into types based on mineralogy was conducted. Presence or absence of ore and alteration
mineralogy in well-typed deposits were used to train the network. To reduce the number of minerals considered, the analyzed
data were restricted to minerals present in at least 20% of at least one deposit type. An advantage of this restriction is
that single or rare occurrences of minerals did not dominate the results. Probabilistic neural networks can provide mathematically
sound confidence measures based on Bayes theorem and are relatively insensitive to outliers. Founded on Parzen density estimation,
they require no assumptions about distributions of random variables used for classification, even handling multimodal distributions.
They train quickly and work as well as, or better than, multiple-layer feedforward networks. Tests were performed with a probabilistic
neural network employing a Gaussian kernel and separate sigma weights for each class and each variable. The training set was
reduced to the presence or absence of 58 reported minerals in eight deposit types. The training set included: 49 Cyprus massive
sulfide deposits; 200 kuroko massive sulfide deposits; 59 Comstock epithermal vein gold districts; 17 quartzalunite epithermal
gold deposits; 25 Creede epithermal gold deposits; 28 sedimentary-exhalative zinc-lead deposits; 28 Sado epithermal vein gold
deposits; and 100 porphyry copper deposits. The most common training problem was the error of classifying about 27% of Cyprus-type
deposits in the training set as kuroko. In independent tests with deposits not used in the training set, 88% of 224 kuroko
massive sulfide deposits were classed correctly, 92% of 25 porphyry copper deposits, 78% of 9 Comstock epithermal gold-silver
districts, and 83% of six quartzalunite epithermal gold deposits were classed correctly. Across all deposit types, 88% of
deposits in the validation dataset were correctly classed. Misclassifications were most common if a deposit was characterized
by only a few minerals, e.g., pyrite, chalcopyrite,and sphalerite. The success rate jumped to 98% correctly classed deposits
when just two rock types were added. Such a high success rate of the probabilistic neural network suggests that not only should
this preliminary test be expanded to include other deposit types, but that other deposit features should be added 相似文献
5.
Mineral resource evaluation requires defining grade domains of an ore deposit. Common practice in mineral resource estimation
consists of partitioning the ore body into several grade domains before the geostatistical modeling and estimation at unsampled
locations. Many ore deposits are made up of different mineralogical ensembles such as oxide and sulfide zone: being able to
model the spatial layout of the different grades is vital to good mine planning and management. This study addresses the application
of the plurigaussian simulation to Sivas (Turkey) gold deposits for constructing grade domain models that reproduce the contacts
between different grade domains in accordance with geologist’s interpretation. The method is based on the relationship between
indicator variables from grade distributions on the Gaussian random functions chosen to represent them. Geological knowledge
is incorporated into the model by the definition of the indicator variables, their truncation strategy, and the grade domain
proportions. The advantages of the plurigaussian simulation are exhibited through the case study. The results indicated that
the processes are seen to respect reproducing complex geometrical grades of an ore deposit by means of simulating several
grade domains with different spatial structure and taking into account their global proportions. The proposed proportion model
proves as simple to use in resource estimation, to account for spatial variations of the grade characteristics and their distribution
across the studied area, and for the uncertainty in the grade domain proportions. The simulated models can also be incorporated
into mine planning and scheduling. 相似文献
6.
Vein-hosted gold deposits are characterized by mineralization, which is spatially restricted to narrow vein structures. Drillholes intersecting a mineralized vein can lead to unreliable and biased assay values compared to selective mining unit scale block grades. In this work, a discrete fracture network is simulated and adapted to model gold mineralization within the veins. Veins are assumed planar and the required inputs are distributions of vein orientation, vein length, and vein intensity (i.e., density). These inputs are collected from drillhole data, geological mapping, and expert knowledge of the deposit. A spatial point process is then applied to model gold grade as discrete events or “nuggets,” which are spatially restricted to the simulated quartz veins for the case of incomplete mineralization of the veins; when the vein is completely mineralized, a vein thickness distribution is required. The methodology is applied to an epithermal gold deposit in northwestern British Columbia, Canada and shows improvement in restricting the influence of the high-grade gold samples without resorting to ad-hoc manipulation of input assays through capping or cutting. The final output of this methodology is a block model of gold grade, which better honors the spatial structure of the veins in the deposit and is suitable for use in mine planning or resource estimation. 相似文献
7.
公平导向的学校分配空间优化——以北京石景山区为例 总被引：6，自引：0，他引：6
空间优化正从地理学的一个研究方向成为学科分支,但公平导向的公共服务空间分配优化研究还较薄弱。学区配置是这方面的一个典型问题,受到社会的广泛关注。针对“多校划片”的随机入学方式,以各居住小区所获得的教育质量期望值的方差来定义入学指标空间分配的公平程度,构建了以该方差最小化为目标、包含最大上学距离约束的二次规划模型,探求各小区对所获得指标进行随机抽签的情景下,各校入学指标在各小区的公平最大化分配,并以北京市石景山区为案例进行了应用研究。结果表明,在维持学校布局和师资配置现状的前提下,与“就近入学”相比,公平最大化的“多校划片”能以有限的上学距离代价,显著降低教育分配的空间差异。在最大上学距离为5 km的约束下,各小区教育质量期望值的方差降幅高达99%,教育质量期望值有所提升的小区或学生比例高达约2/3;付出的上学距离代价较显著但可接受,平均上学距离增加到3.99倍,达到3.20 km,仍低于案例区实际平均上学距离。当模型的最大上学距离参数从5 km逐步增至8 km时,教育公平的改善呈指数增长,平均上学距离呈算数增长;当距离为7 km时,各小区教育质量期望值的方差趋近于0,可基本实现上学机会的空间均等化。本文进一步讨论了优化结果对入学政策的启示。 相似文献
8.
The Southern Uplands-Down-Longford Terrane in southeast Northern Ireland is prospective for Caledonian-age, turbidite-hosted orogenic gold mineralisation with important deposits at Clontibret in the Republic of Ireland and in Scotland. Geochemical and geophysical data from the DETI-funded Tellus project have been used, in conjunction with other spatial geoscience datasets, to map the distribution of prospectivity for this style of mineralisation over this terrane. A knowledge-based fuzzy logic modelling methodology using Arc Spatial Data modeller was utilised. The prospectivity analysis has identified several areas prospective for turbidite-hosted gold mineralisation, comparable to that at Clontibret and gold occurrences in the Southern Uplands of Scotland. A number of these either coincide with known bedrock gold occurrences or with areas considered prospective and targeted by previous exploration work, validating the predictive capability of the exploration model devised and its translation into a GIS-based prospectivity model. The results of the modelling suggest that as in other parts of the Southern Uplands the coincidence of regional strike-parallel structures and intersecting transverse faults are highly prospective, as these are likely to create zones of anomalous stress for fluid flow and deposit formation. Those areas in which there are no known gold occurrences are considered to be favourable targets for further exploration and should be followed up. 相似文献
9.
A Point-Based Intelligent Approach to Areal Interpolation 总被引：1，自引：0，他引：1
Areal interpolation is the data transfer from one zonal system to another. A survey of previous literature on this subject points out that the most effective methods for areal interpolation are the intelligent approaches, which often take two-dimensional (2-D) land use or one-dimensional (1-D) road network information as ancillary data to give insight on the underlying distribution of a variable. However, the 2-D or 1-D ancillary information is not always applicable for the variable of interest in a specific study area. This article introduces a point-based intelligent approach to the areal interpolation problem by using zero-dimensional (0-D) points as ancillary data that are locationally associated with the variable of interest. The connection between zonal variables and point locations can be modeled with a linear or a nonlinear exponential function, which incorporates the distribution of the variables in the transferring of the information from the source zone to the target zone. An experimental study interpolating the population data at a suburbanized area suggests that the proposed method is an attractive alternative to other areal interpolation solutions based on the evaluation of its resulting accuracy and efficiency. 相似文献
10.
Xuezhi Cang Wei Luo 《International journal of geographical information science》2018,32(10):2055-2075
The geographical detector model can be applied to either spatial or non-spatial data for discovering associations between a dependent variable and potential discrete controlling factors. It can also be applied to continuous factors after they are discretized. However, the power of determinant (PD), measuring data association based on the variance of the dependent variable within zones of a potential controlling factor, does not explicitly consider the spatial characteristics of the data and is also influenced by the number of levels into which each continuous factor is discretized. Here, we propose an improved spatial data association estimator (termed as SPatial Association DEtector, SPADE) to measure the spatial data association by the power of spatial and multilevel discretization determinant (PSMD), which explicitly considers the spatial variance by assigning the weight of the influence based on spatial distribution and also minimizes the influence of the number of levels on PD values by using the multilevel discretization and considering information loss due to discretization. We illustrate our new method by applying it to simulated data with known benchmark association and to dissection density data in the United States to assess its potential controlling factors. Our results show that PSMD is a better measure of association between spatially distributed data than the original PD. 相似文献
11.
中国北方荒漠区降水空间结构型及变异性研究 总被引：1，自引：0，他引：1
依据中国北方荒漠区35个站点1951—2005年降水资料,运用(旋转)经验正交函数分解(EOF/REOF)、主成分分析、分形理论及地统计学等方法探讨了北方荒漠区降水空间结构型及空间变异性。结果表明,降水空间分布以“相间复杂”型和“东西相反”型为主（对总体方差贡献分别为35.8%和20.4%）;降水趋势自西向东逐渐减弱,有西部增加、中部地区小幅增大而东部地区趋于干旱的可能。新疆地区对全区降水波动方差贡献率达70.4%。新疆地区及青海-河西-河套地区变异函数曲线符合球状模型,内蒙古高原中东部地区符合指数模型;随机因素引起的空间异质性占0.01%~1.62%。20世纪50年代和70年代青海-河西-河套地区变异性最强,新疆地区次之,内蒙古高原中东部地区最弱,90年代以后新疆地区最强,内蒙古高原中东部地区次之,青海-河西-河套地区最弱。新疆地区、青海-河西-河套地区及内蒙古高原中东部地区降水分别在南北方向、东西方向及东北-西南方向异质性最强。 相似文献
12.
Vesa Nykänen 《Natural Resources Research》2008,17(1):29-48
Among the more popular spatial modeling techniques, artificial neural networks (ANN) are tools that can deal with non-linear
relationships, can classify unknown data into categories by using known examples for training, and can deal with uncertainty;
characteristics that provide new possibilities for data exploration. Radial basis functional link nets (RBFLN), a form of
ANN, are applied to generate a series of prospectivity maps for orogenic gold deposits within the Paleoproterozoic Central
Lapland Greenstone Belt, Northern Fennoscandian Shield, Finland, which is considered highly prospective yet clearly under
explored. The supervised RBFLN performs better than previously applied statistical weights-of-evidence or conceptual fuzzy
logic methods, and equal to logistic regression method, when applied to the same geophysical and geochemical data layers that
are proxies for conceptual geological controls. By weighting the training feature vectors in terms of the size of the gold
deposits, the classification of the neural network results provides an improved prediction of the distribution of the more
important deposits/occurrences. Thus, ANN, more specifically RBFLN, potentially provide a better tool to other methodologies
in the development of prospectivity maps for mineral deposits, hence aiding conceptual exploration. 相似文献
13.
14.
G. Nishani Musafer M. Helen Thompson E. Kozan R. C. Wolff 《Natural Resources Research》2017,26(2):223-236
A real-world mining application of pair-copulas is presented to model the spatial distribution of metal grade in an ore body. Inaccurate estimation of metal grade in an ore reserve can lead to failure of a mining project. Conventional kriged models are the most commonly used models for estimating grade and other spatial variables. However, kriged models use the variogram or covariance function, which produces a single average value to represent the spatial dependence for a given distance. Kriged models also assume linear spatial dependence. In the application, spatial pair-copulas are used to appropriately model the non-linear spatial dependence present in the data. The spatial pair-copula model is adopted over other copula-based spatial models since it is better able to capture complex spatial dependence structures. The performance of the pair-copula model is shown to be favorable compared to a conventional lognormal kriged model. 相似文献
15.
Shihong Du Xiaonan Wang Chen-Chieh Feng Xiuyuan Zhang 《International journal of geographical information science》2017,31(3):542-568
The exponential growth of natural language text data in social media has contributed a rich data source for geographic information. However, incorporating such data source for GIS analysis faces tremendous challenges as existing GIS data tend to be geometry based while natural language text data tend to rely on natural language spatial relation (NLSR) terms. To alleviate this problem, one critical step is to translate geometric configurations into NLSR terms, but existing methods to date (e.g. mean value or decision tree algorithm) are insufficient to obtain a precise translation. This study addresses this issue by adopting the random forest (RF) algorithm to automatically learn a robust mapping model from a large number of samples and to evaluate the importance of each variable for each NLSR term. Because the semantic similarity of the collected terms reduces the classification accuracy, different grouping schemes of NLSR terms are used, with their influences on classification results being evaluated. The experiment results demonstrate that the learned model can accurately transform geometric configurations into NLSR terms, and that recognizing different groups of terms require different sets of variables. More importantly, the results of variable importance evaluation indicate that the importance of topology types determined by the 9-intersection model is weaker than metric variables in defining NLSR terms, which contrasts to the assertion of ‘topology matters, metric refines’ in existing studies. 相似文献
16.
This study proposes a modified Huff model that takes directly into account spatial competition between stores of the same brand, brand attraction based on actual brand performance and spatially variable substitution. The model uses only publicly available or easily acquirable data as input, whereas model output is extensively validated on various levels. These levels include comparison of modeled and real market shares on block, store and brand level for the Belgian food market. Results show that multi-objective optimization of model parameters yields comparable results on block level to other models in the literature but improved results on store and brand levels, thereby ensuring model robustness. This robustness also enables the application of the model for various business purposes as store location determination, leaflet distribution optimization, store and store concept benchmarking, without loss of spatial generality. 相似文献
17.
18.
杭州市人口密度空间分布及其演化的模型研究 总被引：56，自引：8，他引：56
基于四次人口普查数据 ,本文探讨了杭州城市人口密度的空间分布及其演化规律。首先提取了不同年份城市人口密度的空间分布数据 ;然后根据人口分布的曲线特征对各种可能出现的数学模型进行拟合、比较 ,发现杭州市的人口分布服从Clark模型的修正形式———加幂指数模型 ;借助模型参数进行城市增长及其空间动力学分析 ,发现反映信息熵的约束参数波动升高、渐次逼近于 1,从而揭示 :改革开放以来 ,随着城市演化过程中自组织能力的加强以及郊区化的发展 ,城市空间复杂性程度增高 ,城市内各功能单元的效用增强 ,城市的空间结构进一步趋向新的有序状态。本文借助前沿科学思想及郊区化理论 ,尝试提出一个分析城市人口时空变化规律的完整范例 ,对城市规划和管理工作也具借鉴意义 相似文献
19.
Gary L. Raines 《Natural Resources Research》2008,17(2):87-97
It has been proposed that the spatial distribution of mineral deposits is bifractal. An implication of this property is that
the number of deposits in a permissive area is a function of the shape of the area. This is because the fractal density functions
of deposits are dependent on the distance from known deposits. A long thin permissive area with most of the deposits in one
end, such as the Alaskan porphyry permissive area, has a major portion of the area far from known deposits and consequently
a low density of deposits associated with most of the permissive area. On the other hand, a more equi-dimensioned permissive
area, such as the Arizona porphyry permissive area, has a more uniform density of deposits. Another implication of the fractal
distribution is that the Poisson assumption typically used for estimating deposit numbers is invalid. Based on datasets of
mineral deposits classified by type as inputs, the distributions of many different deposit types are found to have characteristically
two fractal dimensions over separate non-overlapping spatial scales in the range of 5–1000 km. In particular, one typically
observes a local dimension at spatial scales less than 30–60 km, and a regional dimension at larger spatial scales. The deposit
type, geologic setting, and sample size influence the fractal dimensions. The consequence of the geologic setting can be diminished
by using deposits classified by type. The crossover point between the two fractal domains is proportional to the median size
of the deposit type. A plot of the crossover points for porphyry copper deposits from different geologic domains against median
deposit sizes defines linear relationships and identifies regions that are significantly underexplored. Plots of the fractal
dimension can also be used to define density functions from which the number of undiscovered deposits can be estimated. This
density function is only dependent on the distribution of deposits and is independent of the definition of the permissive
area. Density functions for porphyry copper deposits appear to be significantly different for regions in the Andes, Mexico,
United States, and western Canada. Consequently, depending on which regional density function is used, quite different estimates
of numbers of undiscovered deposits can be obtained. These fractal properties suggest that geologic studies based on mapping
at scales of 1:24,000 to 1:100,000 may not recognize processes that are important in the formation of mineral deposits at
scales larger than the crossover points at 30–60 km. 相似文献
20.
1990-2011 年山东省旅游节庆的时空变异特征及机理 总被引：4，自引：1，他引：3
以山东省为研究区域, 运用半变异函数、克里格空间插值等地统计学分析方法, 分析了1990、1999、2005、2011 年4 个时间点上旅游节庆活动的时空分布规律、结构特征及变异性, 并建立了拟合模型。结果表明:① 旅游节庆数量空间不均衡显著, 总体上呈现出“东高西低”的“三级阶梯状”分布格局;② 空间结构特征明显, 正负相关并存, 并随滞后距离的增加, 正相关性削弱, 负相关性增强;③ 与1990 年相比, 2011 年基台值增加了20.61 倍, 变程值由115.5 km增至335 km, 结构方差比则由69%下降至26%, 随机性因素的影响减弱, 而结构性因素的作用增强;④ 所有方向的分维数值呈下降趋势, 其空间差异性增大, 且全方向和东—西方向的差异性最大, 其余方向相对均衡, 其发展空间格局的板块状异向性分布特征明显;⑤ 经济发展水平、旅游供给能力、交通可达性是引起山东省旅游节庆差异演化规律的3个主要因素。 相似文献