塔克拉玛干沙漠腹地太阳紫外辐射特征   总被引：1，自引：0，他引：1  

何清  金莉莉  李帅  艾力·买买提明  杨兴华  李振杰 《资源科学》2010,32(8):1462-1470

本文利用塔克拉玛干沙漠腹地(塔中站:83°40'E,39°01'N)2007年1月-12月紫外辐射和总辐射的观测资料,分析了塔克拉玛干沙漠腹地太阳紫外辐射的气候学特征。结果表明:①本地区太阳紫外辐射年总量为305.64MJ(/m2·a)。年平均日总量为0.84MJ/m2,大于黑河、太湖和青藏高原地区。紫外辐射年平均值在总辐射年平均值中所占比例为4.99%,小于太湖和北京,大于黑河地区和五道梁,月平均日总量7月最大;②其日变化,晴天呈现出标准的倒"U"型,即早晚小、中午大,正午达到一天中的最大值;③紫外辐射受云量、降水和沙尘的影响很大;④紫外辐射在总辐射中所占比例有明显的年、季节和日变化,其年变化分为三个明显不同的阶段,夏季大,冬季小。青藏高原地区春夏大,冬季小,北京地区和黑河地区相近,分别是冬季大,夏季小和冬季大,春夏小。  相似文献   

The mirror’s curse: Weight perceptions mediate the link between physical activity and life satisfaction among 727,865 teens in 44 countries     

Silvia Meyer  Rebekka Weidmann  Alexander Grob 《运动与健康科学(英文)》2021,10(1):48-54

Purpose:The present study aimed to examine the link between physical activity(PA)and life satisfaction in a large international study of adolescents.We also aimed to test whether overweight and underweight perceptions act as mediators and whether age and sex acted as moderators.Methods:For this purpose,we analyzed data from the Health Behavior in School-aged Children study,which comprises 727,865 observations from 44 nations at 4 measurement occasions.Results:Multilevel analyses revealed a positive link between PA and life satisfaction.In addition,underweight and overweight perceptions mediated the effect of PA on life satisfaction.We further found that age and sex acted as moderators.In older adolescents,stronger effects were found in the links between PA and life satisfaction,PA and overweight perception,and both weight perceptions and life satisfaction.In addition,in female adolescents,the link between overweight perception and life satisfaction was stronger.Conversely,the links between PA and both weight perceptions were stronger for boys.Conclusion:The results suggest that weight perception explains part of the relationship between PA and life satisfaction in adolescents and that these effects vary as a function of age and sex.  相似文献   

基于熵权-突变级数法的商业模式创新评价——以JF企业为例     

甄俊杰  孙慧 《科技管理研究》2021,41(1):48-53

根据JF企业2007-2018年数据,采用熵权-突变级数法评价其商业模式创新的变化情况.结果发现,评价结果与已有研究结论高度匹配,验证该评价思路的科学性和可行性;通过对评价结果的分析,可以将目标企业商业模式创新分为3个发展阶段与2个战略转型期,其中各个阶段又有其独特的商业模式;该公司商业模式创新呈现出"总体平稳、阶段波...  相似文献   

Joint upper & expected value normalization for evaluation of retrieval systems: A case study with Learning-to-Rank methods     

《Information processing & management》2023,60(4):103404

  相似文献   

高价值专利评估问题的对策研究     

刘勤 《科技管理研究》2022,(4)

我国经济已由高速增长阶段转向高质量发展阶段,高质量发展需要高价值专利保驾护航。高价值专利评估是推动高价值专利转化为现实生产力的重要环节。为有效评估高价值专利,首先对高价值专利的内涵进行了界定,其次在分析和评估现有专利价值评估方法基础上,以300件中国专利奖获奖专利为研究对象,从技术因素、法律因素、经济因素、市场因素等四个层面,挖掘高价值专利的典型性特征,构建专利价值评估指标体系和评估模型。通过验证发现,该模型准确性较高、可测性较好、实用性较强,能够为加快推进高价值专利评估工作,促进高价值培育和转移转化提供借鉴与参考。最后针对高价值专利评估问题,就健全评估体系、增强评估意识与能力、打造评估服务平台等提出了对策建议。  相似文献