基于逆周期的主权信用评级指标体系研究

现行国际主权信用评级呈现出明显的顺周期特征而广受诟病。在对评级指标体系优化的基础上，采用90个主权国家2005~2012年经济数据进行面板随机效应和门限效应回归，对主权信用评级决定模型进行估计，运用欧债危机发生前后的数据进行模拟评级，结果表明：优化后的指标体系显示出较好的逆周期特征。     

气吸式大豆精密排种器排种性能试验研究

在精密播种机中,精密排种器是其工作的核心部件,工作性能直接制约了播种机播种性能的优劣。为了探究影响气吸式排种器工作性能的主次因素,以大豆气吸式排种器为研究对象进行了台架性能试验测试。试验确定排种盘转速为影响排种器排种性能的主次因素,气室负压为次要因素;排种盘转速为20 r/min,气室负压为5 k Pa时该大豆气吸式排种器排种性能最优,合格指数高达91.13%。该研究结果对排种器结构改进以及性能优化提供了参考依据。     

Application of body size spectra to nematode trait-index analyses

Current trait-based indices of soil fauna for assessing soil quality rely on extensive knowledge of life history traits for hyper-diverse groups. We look at the effects of clear-cut forest harvesting and subsequent wood ash application on the free-living nematode community using trait-based indices and body size spectra. We test the hypothesis that body size is a unifying trait and that the body size spectra can be used to demonstrate changes in soil quality while overcoming taxonomic impediments. Undisturbed boreal forest floor soils were compared with clear-cut sites amended with zero, one-half calcium equivalent wood ash, equivalent calcium reintroduction, and twice calcium reintroduction. Total abundance, trait-based metrics for the Maturity Index, and two metrics of body size spectra were calculated. Nematode abundance was not a good indicator of soil disturbance, while traditional trait-based approaches (the summed Maturity Index) demonstrated predicted changes in community structure. Analysis of two types of body size spectra elucidated how the community had changed under disturbance, and revealed that smaller bodied organisms were lost under ash amended treatments compared to both clear-cut and undisturbed forest. Using the body size spectra for nematodes is a simple addition to current trait-based approaches that can supplement soil assessments for disturbance and quality without requiring taxonomic expertise.     

Precipitation or water capacity indices? An analysis of the benefits of alternative underlyings for index insurance

Eastern Germany is often hit by drought causing income risk for crop farmers. Index-based risk management instruments could help crop farmers to reduce their farm income risk. Such instruments have some important advantages over damage-based insurance, like e.g. less moral hazard and adverse selection. At the same time they typically have a high level of basis risk. Up to now, mainly precipitation-based weather derivatives have been discussed as an appropriate risk management instrument for farmers in Germany. As a potentially more effective alternative, we propose water capacity-based index insurance. In order to show the benefits of a precipitation-based and water capacity-based index insurance, several contract designs are compared. Using a whole farm risk program planning approach, we show that for an average agricultural producer in Eastern Germany water capacity-based index insurance offers greater benefits than precipitation-based index insurance.     

模极大值法在食醋近红外光谱定量分析中的应用

以镇江香醋中还原糖定量分析为例，研究小波分析中模极大值法在建立预测模型方面的应用，对基于模极大值处理光谱信息前后的预测模型进行比较发现，该方法可以有效地消除光谱的平移误差，且具备一定的分峰效果和提取光谱信息的功能，因此预测模型的预测精度和稳定性都有较大的提高，在光谱定量分析中有广泛的应用前景。     

车载式土壤光-电特性参数采集系统研究

土壤电导率是衡量土壤传导电流能力的一种固然属性,除了能够反映土壤质地外,还能够反映土壤的含水率、含盐量、有机物含量等特性。利用土壤光谱数据可以分析出土壤含水率、养分等,且测量过程中无需采样、搅动土壤。通过土壤电导率数据和光谱数据的综合、校正,能够提高系统的精度。基于嵌入式技术开发了土壤电导率和光谱反射率综合检测系统。土壤电导率测量系统采用基于改进的电流-电压四端法原理,使用深松犁的尖端作为电极传感器,能够在测量的同时完成松土的作用。光谱测量系统使用微型光谱传感器采集光谱数据,并进行实时处理。在采集土壤电导率、光谱数据的同时,系统同步采集GPS信息,并和土壤电导率、光谱数据一起保存,供进一步绘制土壤特性分布图使用。系统能够实时综合处理多种数据,并进行显示、保存等操作,具有良好的应用 前景。     

柴油机台架试验中综合指标的建立与应用

介绍了正交试验中多指标分析法,建立了柴油机综合性能指标并阐述了其在试验分析中的应用。     

Nitrogen dynamics during ecosystem development in tropical forest restoration

We considered whether ecological restoration using high diversity of native tree species serves to restore nitrogen dynamics in the Brazilian Atlantic Forest. We measured δ¹⁵N and N content in green foliage and soil; vegetation N:P ratio; and soil N mineralization in a preserved natural forest and restored forests of ages 21 and 52 years. Green foliage δ¹⁵N values, N content, N:P ratio, inorganic N and net mineralization and nitrification rates were all higher, the older the forest. Our findings indicate that the recuperation of N cycling has not been achieved yet in the restored forests even after 52 years, but show that they are following a trajectory of development that is characterized by their N cycling intensity becoming similar to a natural mature forest of the same original forest formation. This study demonstrated that some young restored forests are more limited by N compared to mature natural forests. We document that the recuperation of N cycling in tropical forests can be achieved through ecological restoration actions.     

不同玉米杂交种抗旱性比较及抗旱性鉴定指标的研究

在人工设置的土壤干旱条件下，对4个推广玉米杂交种的抗旱性以及与抗旱性有关的生理生化指标和农艺性状进行了比较与评价。结果表明，在供试的4个杂交种中奥玉3101的抗旱性最强。游离脯氨酸的累积含量、根冠比、叶片相对含水量可以作为鉴定玉米抗旱性的指标。     

小麦叶片氮含量与冠层反射光谱指数的定量关系

本文以3种蛋白质类型的小麦品种在不同施氮水平下的3年田间试验为基础，研究了小麦叶片氮含量与冠层反射光谱的定量关系。结果显示，不同试验中拔节后叶片氮含量均随施氮水平呈上升趋势，同时冠层光谱反射率在不同施氮水平下存在明显差异。对于低、中、高籽粒蛋白质含量的品种，叶片氮含量与冠层反射光谱的归一化植被指数NDVI (1 220, 710)和红边位置均有密切的定量关系，决定系数在0.80左右。对于不同品质类型小麦品种，均可利用统一的回归方程描述其叶片氮含量随反射光谱参数的变化，对于低蛋白类型品种，采用单独的回归系数即可提高叶片氮含量估测的准确性。本研究确立的小麦叶片氮含量与冠层反射光谱的定量关系可用于不同的小麦品种、生育时期和施氮水平，为小麦氮素营养的监测诊断与精确施肥等提供理论依据和技术途径。