简介:Thedrivingfactorsofrunoffchangescanbedividedintoprecipitationfactorandnon-precipitationfactor,andtheycanalsobedividedintonaturalfactorandhumanactivityfactor.Inthispaper,thewaysandmethodsofthesedrivingfactorsimpactingonrunoffchangesareanalyzedatfirst,andthenaccordingtotherelationshipbetweenprecipitationandrunoff,theanalyticalmethodaboutimpactsofprecipitationandnon-precipitationfactorsonbasin'snaturalrunoffisderived.Theamountandcontributionratesofthetwofactorsimpactingonnaturalrunoffbetweeneverytwoadjacentdecadesduring1956-1998arecalculatedintheYellowRiverBasin(YRB).Theresultsshowthattheamountandcontributionrateofthetwofactorsimpactingonnaturalrunoffaredifferentindifferentperiodsandregions.FortheYRB,thenon-precipitationimpactispreponderantfornaturalrunoffreductionafterthe1970s.Finally,bychoosingmainfactorsimpactingonthenaturalrunoff,oneerrorback-propagation(BP)artificialneuralnetwork(ANN)modelhasbeensetup,andtheimpactofhumanactivitiesonnaturalrunoffreductionintheYRBissimulated.Theresultshowsthatthehumanbackgroundof1956-1979.
简介:摘要:本文利用贡水1960—2018年径流资料,采用Mann-kendall检验和小波分析法对赣江源贡水径流演变规律进行分析。结果表明:年径流和枯水期径流呈增加趋势,丰水期径流呈减小趋势;年径流无明显的突变特征,从1970年中期以后径流呈增加变化;年径流存在28年的主周期,丰水期径流第一主周期为27年,枯水期存在7年的主周期。
简介:目的探讨血管性痴呆(VD)患者脑血流灌注显像特点.方法分别对12例血管性痴呆患者,13例血管性轻度认知功能障碍(VaMCI)患者和11名正常对照(NC)组进行单光子发射电子计算机断层扫描(SPECT)局部脑血流灌注显像,定量分析各脑区血流灌注情况.结果D组和VaMCI组与对照组相比;VD组与VaMCI组相比额叶、颞叶、顶叶,基底节局部脑血流灌注减少(P<0.05).尤以额叶、颞叶血流灌注减低最为显著(P<0.01),额叶、颞叶血流灌注减低与简易智能状态量表(MMSE)评分间呈正相关(r额=0.981,P<0.01,r颞=0.76,P<0.05),尤以额叶更显著.结论SPECT对VD患者有早期辅助诊断价值,即使对VaMCI患者SPECT也同样敏感.其对于VD的预测、早期治疗以及VCI与阿尔茨海默病的高危人群轻度认知障碍(MCI)的鉴别都有重要意义.