Results 81 to 90 of about 25,407 (149)
Conservation Biology, Volume 40, Issue 4, August 2026.Abstract Ex situ plant collections may be increasingly needed to protect representative samples of threatened or rare species and provide plant material for conservation translocation. A primary problem in these ex situ collections is loss of intraspecific variation due to plant death. Different management actions would be required depending on whether
Rebecca Sucher +6 more
wiley +1 more source
四川大学学报. 自然科学版, 1996 对黑竹沟植物进行了初步考察表明：该区产维管束植物１１６科３５２属约１１００种．其中蕨类植物１６科２２属约６０种；裸子植物５科９属９种；被子植物９５科３２１属约１０００种．其区系成分主要以北温带分布和东亚分布为主 ...
何明友 +5 more
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Powerful representation of the poor? German welfare associations' narrative advocacy during COVID‐19
Policy Studies Journal, Volume 54, Issue 3, August 2026.Abstract The COVID‐19 pandemic sparked unprecedented experimentation in the German social assistance system, leading to changes previously considered impracticable by policymakers. This included a sanctions moratorium, easier access to benefits, and temporary cash transfers, all of which were advocated by welfare associations—key organized interests ...
Christopher Smith Ochoa
wiley +1 more source
Policy Studies Journal, Volume 54, Issue 3, August 2026.ABSTRACT Despite extensive research on policy diffusion, the ways in which policy attention influences this process remain underexplored. This study addressed this gap by distinguishing between three types of policy attention—political speeches, policy issuance and field visits—and investigating their differential impacts when delivered by central and ...
Xiangning Chen, Yahua Wang
wiley +1 more source
Imagined Integration: The Logics of Japanese Immigrant Integration Policy
Policy Studies Journal, Volume 54, Issue 3, August 2026.ABSTRACT As governments develop immigrant integration policies, they draw on and express conceptions about what successful integration looks like—what we call “imagined integration.” Yet this imagination likely displays variation that matters for implementation: integration policymaking is increasingly multilevel as it involves subnational layers of ...
Mariri Niino, William L. Allen
wiley +1 more source
Gaoya dianqi, 2015 为研究油纸套管的寿命分布以及发生层间击穿后的剩余寿命,结合绝缘材料寿命的威布尔分布理论,建立了套管绝缘层寿命模型。并利用蒙特卡罗方法仿真计算了某型号110 k V油纸套管的寿命分布以及发生层间击穿后的剩余寿命分布。研究表明,该型号油纸套管的寿命符合形状参数为19.68,尺度参数为22.05的威布尔分布。当发生一层和两层击穿之后,形状参数分别减小为5.47和0.22,这意味着发生层间击穿之后由于电场分布的改变使得套管的寿命会迅速减小,层间击穿对于套管内绝缘是一个自加速过程 ...
杨贤 +5 more
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Gaoya dianqi高频变压器的分布参数会影响其输出参数及性能，推导高频变压器副边分布电容以及漏感的解析表达式，发现绕组的绕制方式、分段分层结构、绝缘层厚度、绕组高度、绝缘介质等是影响其分布参数的主要因素。针对40 kV、20 kHz的高频变压器建立了电磁场有限元仿真模型，分别计算和分析了各因素对分布电容及漏感的影响规律。优化副边绕组分段分层结构，综合考虑漏感、分布电容及绕组损耗确定变压器绕组的绝缘厚度及高度，并据此设计加工了实验样机。测试结果表明分布电容和漏感的仿真计算结果与实测值的误差分别为9.5%和11.3 ...
江进波 +5 more
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北京山区天然次生林群落结构与种群分布格局研究——以雾灵山自然保护区为例
Shuitu Baochi Xuebao, 2007 在北京雾灵山自然保护区天然次生林内,设置了2个有代表性的固定标准地,应用相邻格子法获得野外调查资料,进行优势种群结构和空间分布格局的研究。结果表明:(1)以山杨为优势种群的群落I和以蒙椴为优势种群的群落II年龄结构呈塔型,群落高度结构呈"L"型,幼苗相当丰富,天然更新能力强。(2)山杨种群、白桦种群、黑桦种群均为衰退种群,蒙椴种群表现为增长型种群。(3)在分布格局上,不同群落优势种群均呈集群分布,白桦伴生种群呈随机分布,黑桦种群在不同群落中分布格局差异较大。不同群落在整体上呈集群分布,但不同发育阶段 ...
岳永杰 +4 more
doaj +2 more sources
Guangtongxin yanjiu, 2003 对多段保偏光纤 （PMF）组成的光纤链路的偏振模色散 （PMD）统计特性进行了数值仿真 ,分析比较了光纤段的长度、段数和级联角度不同的条件下 ,链路的群时延差 （DGD）分布特性 .仿真结果表明 ,在相同的条件下 ,级联的 PMF段数越多 ,仿真得到的 DGD分布就越趋向麦克斯维分布 ;随机变化的物理量越多 ,使 ...
沈晓强, 邵钟浩, 于娟
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Dianci bileiqi, 2014 雷电流幅值是研究区域雷电分布极其重要的一个参数,对云南省气象部门2011-2013年ADTD雷电监测网所收集的雷电数据进行数理统计分析,并按照IEEE工作组和DL/T推荐的特征函数进行拟合,结果表明:云南正负闪雷电流幅值频率分布和累计概率分布均存在显著差异,采用IEEE工作组推荐的公式对云南雷电流累计概率分布进行拟合效果最佳,在此基础上验证了云南雷电流幅值频率分布符合正态分布同时得出了云南地区雷电流幅值累计概率密度分布公式。为进一步研究云南雷电资源特征和防灾减灾工作提供了不可或缺的技术资料。
姜勇, 李鹏
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