汛期旱涝趋势预测因子的选择和信息综合及应用          下载免费PDF全文

徐家良 《应用气象学报》2001,12(2):251-254

建立在统计模型基础上的旱涝趋势预测的稳定性和准确性, 依赖于预测因子的选择和综合。该文在选择前期预测因子时, 既考虑了因子的物理意义, 又从尺度对应原理出发, 对与预测对象相应时间尺度的因子作综合处理, 最大程度保留了可用预测信息。对长江三角洲汛期降水场进行试验比较, 证明该方法能显著提高预测技巧。  相似文献   

Breeding habitat selection by houbara bustard (Chlamydotis[undulata] macqueenii) in Mori, Xinjiang, China     

杨维康  乔建芳  姚军  高行宜  钟文勤 《中国科学D辑(英文版)》2002,45(Z1)

The breeding habitat selection by houbara bustards in Mori, Xinjiang, China duringthe breeding seasons from April to June 1998-2000 was studied. Most of habitats chosen forbreeding were short sub-shrubby and open areas close to high bushy patches. The nesting re-males clearly prefer Iow covered areas and avoid densely covered and high vegetation sites. Thenumber of herb species was significantly smaller at nest sites than at randomly selected sites.Only the distance to the closest fox den contributed the most to discrimination between successfuland predated nests. The average distance to the closest fox den was significantly longer at suc-cessful nests than at depredated nests. Vegetative density, plant species richness, topography anddistance to the closest fox den are possibly the most important factors that determined the nestsites selection of houbara bustard. The displaying males clearly prefer Iow covered areas andavoid densely covered and high vegetation sites. The vegetation density and number of plant spe-cies at display sites was significantly lower than that at randomly selected sites. The average dis-tance to the closest bushy patch was significantly shorter at display sites than at random sites.Plant species richness, vegetative density, vegetative cover and distance to the bushy patches arepossibly the most important factors for the display sites selection of houbara bustard.  相似文献   

沁水盆地煤层气高渗富集区遥感研究   总被引：1，自引：0，他引：1  

冯富成  毛耀保王永王新民  陈强华 《中国煤田地质》2002,14(2):24-25

本文针对我国煤层气地质选区中,如何引进新技术、采用综合勘探策略、提高勘探效益、降低勘探成本这一问题,以我国煤层气最具开发潜力的沁水盆地(面积5万km2)为例,阐述了应用遥感技术研究地质构造特征,寻找地下煤层裂隙发育区,探测煤层气高渗富集区的工作程序、方法和效果。选区结果目前已得到十多个煤层气试验井的证实。  相似文献   

高层建筑基础抗震选型评价指标与智能优选方法   总被引：5，自引：0，他引：5  

张世海  刘晓燕  欧进萍  王光远 《地震工程与工程振动》2002,22(4):28-35

文章规划了能全面表征高层建筑基础及其相关全系统、全性能、全寿命过程的各种影响因素、约束与要求等的基础抗震选型性能评价指标体系模型，为通过选型对基础的性能进行预测、评价、控制与优化等提供了依据。建立了带置信与变权因子的选型方法并给出了应用实例，该方法全面考虑了表征领域专家及决策者经验、知识、偏好及决策因素变化影响等方面的重要信息，使决策结果所包容的信息更丰富，完备和有效。给出了基于模糊评判、模糊辨识、模糊推理、BP神经网络、模糊神经网络技术的高层建筑基础智能优选算法和网络结构，为建立集成化、智能化、自动化的选型支持系统及提高基础选型质量与水平等奠定了基础。  相似文献   

岩体变形参数渐变取值模型及工程应用   总被引：5，自引：0，他引：5  

符文熹  尚岳全  孙红月  聂德新  刘高  张斌 《工程地质学报》2002,10(2):198-203

分析了当前岩体现场试验、变形参数取值和常规计算模式存在的问题。针对河谷、斜坡岩体从表部到深部 ,岩体风化、岩体波速和岩体地应力等彼此均呈现渐变性特征 ,提出了岩体变形参数渐变取值模型 ,并以黄河上游李家峡水电站初期蓄水监测资料 ,论证了岩体变形参数空间上连续性渐变取值的合理性和科学性 ,对今后其它岩体工程的力学参数取值和计算模型的概化提供了指导意义.  相似文献   

城市居民住宅区位选择的因子分析   总被引：48，自引：6，他引：48  

张文忠 《地理科学进展》2001,20(3):268-275

随着我国住房制度的改革 ,城市居民个人消费成为我国房地产市场的消费主体 ,居民对住宅区位选择行为由过去的被动接受转变为主动选择。本文主要研究在这种新的住房制度下 ,影响城市居民住宅区位选择的因子。作者认为 ,房价的高低、住宅区位的交通通达性、环境条件是决定城市居民住宅区位选择的客观条件 ,居民自身的社会、经济、文化等特征、以及对不同住宅区位和环境的偏好也左右着住宅区位选择过程和结果。  相似文献   

模糊数学与灰色系统理论在基地选择中的应用     

王京贵 《华东地质学院学报》1994,17(3):201-205

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WAVELENGTH SELECTION IN MULTICOMPONENT NEAR-INFRARED CALIBRATION     

PHILIP J.BROWN 《地理学报(英文版)》1992,(3)

Modern scanning(near-)infrared reflectance/absorption(NIR)spectroscopes measure the absorptions orreflectances at a sequence of around 1000 wavelengths.Training data may consist of 10-100 carefullydesigned sample mixtures for which the true composition of the mixture is either known by formulationor accurately determined by wet chemistry.In future one wishes to predict the true composition fromthe spectrum.In this paper we compare a simple wavelength selection approach with methods whichretain all the wavelengths.It offers a powerful yet simple technique for choosing those wavelengths thatare specific to each pure component as against the other components(including the medium)for thevarying compositions.In the presence of a defined range of ingredients it thus chooses wavelengths whichare highly selective for each particular component.It has the added advantage of selecting wavelengthswhich are little effected by interaction effects and consequent non-linearities.The calibration data used consist of 125 observations of three sugars,each varying at five levels in afull 5~3 design.The validation set consists of 21 further samples specially selected to have compositionsoutside the range of the training sample.The selection methods perform much better on this predictionset than methods which retain all the wavelengths,700 in this case.The leave-one-out cross-validationinternal to the calibration data would point to the opposite finding and suggests that such cross-validations may be overly flattering to techniques such as partial least squares and may encourageoverfitting.After selection,simple straightforward least squares methods may be used,eschewing theneed for‘shrinkage’methods such as partial least squares or ridge regression.  相似文献   

GENETIC ALGORITHMS AS A STRATEGY FOR FEATURE SELECTION     

R.LEARDI  R.BOGGIA  M.TERRILE 《地理学报(英文版)》1992,(5)

Genetic algorithms have been created as an optimization strategy to be used especially when complexresponse surfaces do not allow the use of better-known methods (simplex, experimental designtechniques, etc.). This paper shows that these algorithms, conveniently modified, can also be a valuabletool in solving the feature selection problem. The subsets of variables selected by genetic algorithms aregenerally more efficient than those obtained by classical methods of feature selection, since they canproduce a better result by using a lower number of features.  相似文献   

红山文化牛河梁遗址形成的环境背景与人地关系研究   总被引：8，自引：8，他引：8       下载免费PDF全文

莫多闻  杨晓燕  王辉  李水城  郭大顺  朱达 《第四纪研究》2002,22(2):174-181

本文对辽宁凌源市红山文化牛河梁遗址区的地形进行了考察,对建筑石料进行了鉴定,证明当时人类对地形和岩性的认识和利用已具有较高水平。对遗址文化层的动植物残体分析、孢粉分析及附近大凌河上游全新世沉积剖面的孢粉分析基础上,对牛河梁遗址形成的环境背景和红山文化晚期繁荣的原因及人地关系问题进行了分析探讨。  相似文献