Supervised neural network recognition of habitat zones of rice invertebrates     

WenJun Zhang 《Stochastic Environmental Research and Risk Assessment (SERRA)》2007,21(6):729-735

This study aimed to evaluate effectiveness and performance of several supervised neural network models and make pattern recognition on invertebrate habitat zones. Probabilistic, general regression, and linear neural networks, and discriminant analysis were used to recognize both known and unknown invertebrate habitat zones. The results showed that neural network models were better than traditional discriminant analysis in the recognition of known habitat zones. There was not distinctive variation in recognition from different neural network models. Sensitivity analysis indicated that the learning rate of the neural network would influence recognized results. An unknown invertebrate species from Lepidoptera was recognized to be soil-dweller (dryland) by both neural network models and discriminant analysis. In sensitivity analysis it was additionally recognized to be the type of plant canopy (terrestrial). Overall the species was estimated to be a soil-dweller (dryland) or live on plant canopy (terrestrial). It was concluded that neural network models can perform better than conventional statistic models in pattern recognition, but a comprehensive comparison among various models is necessary in order to achieve a high reliable recognition and prediction. Furthermore, sensitivity analysis can lead to an in-depth grasp on the mechanism in the recognition and is thus needed.  相似文献   

中国陆地生态系统脆弱带遥感模型   总被引：4，自引：0，他引：4  

布和敖斯尔  马建文  韩秀珍  马超飞 《遥感学报》2002,6(3):212-222

本研究通过对我国陆地生态系统8个典型样地的植被指数取样实验和图像计算结果发现，这8个样地植被指数随着水、热因子的季节变化，在时间和空间上具有一定的“绿波推移”和“景观更替”规律。在中国东部湿润的季风区（样地1－3），随着纬度的增高，其月平均植被指数与月平均气温有较大的相关。发现降水相对丰沛的地带，热量和光照条件的变化成为植被生长和变化的自然限制因子；而在中国北方森林－森林草原－典型昌原－荒漠草原－荒漠地带上，随着从东部（湿润地区）到西部（干旱地区）干湿条件的更替，月平均植被指数与降水多寡有较大的正相关关系。在8个样地上都呈现出共同的规律，即定向风的分布与植被指数的分布在时间和空间上具有逆相分布的“套合关系”。尤其在时间上有相逆套合关系，这正是中国北方沙尘暴和沙漠化加剧的自然原因。本研究定量地给出了我国陆地不同经纬度带生态系统脆弱季节和累积时间的分布。  相似文献   

远区重力数据对扰动位径向二阶梯度的影响     

赵东明  吴晓平 《测绘学院学报》2001,18(1):16-19

提出了利用地面重力异常数据计算地面扰动位径向二阶梯度时，远距离带区影响的误差公式，结果以级数形式给出，以其数学模型为基础，利用全球重力位模型GPM98，计算确定了不同平均异常网格大小情况下截断半径取一系列值时的远区影响，在将卫星重力梯度和航空重力梯度观测数据与地面重力数据进行联合处理时，文中提出了远区影响的数量关系，对于确定合理的截断半径大小具有一定的参考价值。  相似文献   

祁连山北坡中部气候特征及垂直气候带的划分   总被引：12，自引：2，他引：12  

张虎  温娅丽  马力  常宗强  王金叶 《山地学报》2001,19(6):497-502

通过对祁连山北坡中部气候特征，森林植被类型和土壤类型的定位预测研究，对祁连山北坡中部森林生态系统的主要气象要素垂直分布特征进行分析，应用气候指标和生物学原理，将祁连山林区按不同海拔高度划分为：1.山地荒漠草原气候带；2.山地草原气候带；3.山地森林草原气候带；4.亚高山灌丛草甸气候带；5.高山亚冰雪稀疏植被气候带；进而提出了合理开发祁连山山地气候资源，以促进当地经济发展。  相似文献   

赣东加里东变质混合岩带金地球化学特征和地球化学行为     

余达淦  梁荣斌 《华东地质学院学报》2001,24(2):91-97

赣东加里东变质混合岩带 ,是以混合岩体为主体 ,受韧性剪切带控制的多相、多型、递增变质带 ,是受区域深构造控制的热变质带。该带产有茅排式金矿。通过对该带金地球化学特征和地球化学行为研究 ,认为带中金丰度 0 .83× 10 - 9,呈峰式分布 ,为对数及双对数正态分布型式 ,Au与主元素成分无关 ,与微量元素组合是Au -Zn -Li-Pb -Cs ,在韧性剪切过程中Au具活化迁移富集特点  相似文献   

320矿区当冲组"硅化带"的特征及成因初探   总被引：1，自引：0，他引：1  

侯满平  高仕达 《华东地质学院学报》2001,24(4):277-281

分析研究了320矿区当冲组“硅化带”的形态、成分、结构、构造特征，应用构造地球化学原理，阐述了“硅化带”及其铀化矿的形成的过程。并表现出岩控、层控、构控、时控及“沉积－构造热液再造”等特点。当冲组富铀岩层不仅成为矿提供了物质基础，而且是矿床产生的直接围岩。  相似文献   

东营凹陷下第三系深部碎屑岩储层次生孔隙垂向分布及成因分析   总被引：26，自引：1，他引：26  

袁静  王乾泽 《矿物岩石》2001,21(1):43-47

东营凹陷下第三系埋深大于 30 0 0 m的深部碎屑岩储层普遍发育 2～ 4个次生孔隙带 ,Φ=10 %～ 30 % ,K=0 .1× 10 - 3μm2～ 30× 10 - 3μm2 ,为中孔低渗低孔低渗油气储层。综合有机质热演化过程、成岩作用和构造断裂等分析 ,认为东营凹陷埋深大于 30 0 0m碎屑岩地层中 ,第一、二个次生孔隙带埋深在 30 0 0 m～ 390 0 m之间 ,其形成主要与有机质成熟过程释放有机酸对长石等颗粒的溶解有密切关系 ,在深大断裂附近储层同时受到大气淡水的影响 ,而深陷带包裹于暗色泥岩中的浊积砂岩的次生孔隙发育情况还与泥质岩异常压力带有关 ;第三个次生孔隙带埋深一般为 390 0 m～ 430 0 m,主要成因于粘土矿物转化造成的还原环境 ,同时受到硫酸盐热化学氧化还原反应的影响。这三个次生孔隙发育带对储集油气有效。第四个孔隙发育带埋深在 470 0 m以下 ,主要是构造成因的微裂缝 ,较难成为有效的油气储层。  相似文献   

Geochemistry of groundwater in the alluvial plain of Tucumán province, Argentina   总被引：3，自引：0，他引：3  

Gabriela M. García  Margarita del V. Hidalgo  Miguel A. Blesa 《Hydrogeology Journal》2001,9(6):597-610

The Salí River hydrogeological basin is one of the most productive artesian basins in Argentina. It is located in the southeastern part of the province of Tucumán, northwestern Argentina, and its groundwater resources are developed for water supply and irrigation. The chemical composition of the water is strongly influenced by the interaction with the basinal sediments and by hydrologic characteristics such as the flow pattern and time of residence. Three hydrochemical zones are defined in the study area and the processes that control the chemical composition of the water are manifestly different in each zone. The dissolution of halite, sodium sulphate, and gypsum explains part of the contained Na⁺, K⁺, Cl^–, SO₄ ^2–, and Ca²⁺, but other processes, such as cation exchange, calcite precipitation, weathering of aluminosilicates, and gas exchange with the atmosphere, also contribute to the water composition. The assessment of contamination indicators, such as pH, dissolved organic matter, dissolved oxygen, phosphate, and nitrate, indicates that the groundwater is suitable for human consumption. However, biological contamination has been detected in samples from some wells, especially those near the Salí River. Electronic Publication  相似文献   

Three-dimensional structure of the crust and upper mantle beneath the south China area from long period surface waves     

《地震学报(英文版)》1993,6(3):619-629

In the present study the long period surface wave records of 238 wave-paths from 79 earthquakes within China and its adjacent regions received by 30 seismic network stations are measured by using the improved match-filtering frequency-time analysis technique and the grid dispersion inversion method to obtain the rayleigh pure-path dispersion values for 147 slant grids of 4° × 4° in this area, then a three-dimensional shear wave velocity model of the crust and upper mantle beneath south China area to a depth of 170 km is inversed. It is found that there are obvious differences among the main structural units, and there are also certain differences among the subordinate elements even in the individual unit. The crustal thickness of this area is ranging from 30 to 43 km, and is getting thicker gradually from the east to the west. The average shear velocity of crust is ranging form 3.48 to 3.68 km/s with the lowest in the northeast part and highest in the west part. No obvious crustal low velocity layer of large scale is detected. There exist upper mantle low velocity zones in the most of south China area with the starting depth ranging from 75 to 106 km. The lowest shear velocity within the low velocity zones is about 4.28–4.38 km/s. Despite of the existing of upper mantle low velocity zones beneath the most of south China area, the interfaces between the important layers are quite clear, the variation of the bedding surfaces is very gentle, and the lateral changes measured in a larger scale of the underground structure are rather small. It may indicate that the crustal and upper mantle structure of the main part of south China area belongs to the relatively stable structure of the continental blocks except for the fringe areas such as the fold-faulted region in the west part and the fault system along the southeastern coast which may belong to the tectonically active area. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 159–167, 1993. This subject is supported by the National Science Foundation of China.  相似文献   

Predicting DNAPL entrapment and recovery: the influence of hydraulic property correlation     

L. D.?LemkeEmail author  L. M.?Abriola 《Stochastic Environmental Research and Risk Assessment (SERRA)》2003,17(6):408-418

The influence of aquifer property correlation on multiphase fluid migration, entrapment and recovery was explored by incorporating correlated and uncorrelated porosity, permeability, and capillary pressure-saturation (P_c-Sat) parameter fields in a cross-sectional numerical multiphase flow model. Comparison of two-dimensional entrapped organic saturation distributions for a simulated tetrachloroethylene (PCE) spill in ensembles of aquifer realizations suggests that the degree of spatial correlation in P_c-Sat parameters exerts a controlling influence on dense nonaqueous phase liquid (DNAPL) spreading and redistribution in saturated aquifers. The predicted evolution of DNAPL source zones and resultant remediation efficiency under surfactant enhanced aquifer remediation (SEAR) also appear to be strongly influenced by the spatial correlation of aquifer parameters and multiphase flow constitutive relationships. Results for a limited number of realizations selected from each ensemble showed that removal of 60% to 99% of entrapped PCE could reduce dissolved contaminant concentration and mass flux by approximately two orders of magnitude under natural gradient conditions. Aqueous phase contaminant mass flux did not vary uniformly as a function of % DNAPL removed, however, and notable differences in behavior were observed for models incorporating correlated versus uncorrelated P_c-Sat and permeability fields. Although these results must be confirmed through analysis of additional realizations, it is likely that similar or larger differences between correlated and uncorrelated system behavior will be observed in aquifers with greater spatially variability than that of the nonuniform, homogeneous sand aquifer studied here. Funding for this research was provided by the United States Environmental Protection Agency, Great Lakes and Mid-Atlantic Center for Hazardous Substance Research under Grant No. R-825540, the Michigan Department of Environmental Quality under Contract No. Y80011, and the Strategic Environmental Research and Development Program under Project No. CU-1293. The content of this publication does not necessarily represent the views of these agencies and has not been subject to agency review.  相似文献