Performance of DSSAT-Nwheat across a wide range of current and future growing conditions

Crop models are widely used in agricultural impact studies. However, many studies have reported large uncertainties from single-model-based simulation analyses, suggesting the need for multi-model simulation capabilities. In this study, the APSIM-Nwheat model was integrated into the Decision Support System for Agro-technology (DSSAT), which already includes two wheat models, to create multi-model simulation capabilities for wheat cropping systems analysis. The new model in DSSAT (DSSAT-Nwheat) was evaluated using more than 1000 observations from field experiments of 65 treatments, which included a wide range of nitrogen fertilizer applications, water supply (irrigation and rainout shelter), planting dates, elevated atmospheric CO₂ concentrations, temperature variations, cultivars, and soil types in diverse climatic regions that represented the main wheat growing areas of the world.DSSAT-Nwheat reproduced the observed grain yields well with an overall root mean square deviation (RMSD) of 0.89 t/ha (13%). Nitrogen applications, water supply, and planting dates had large effects on observed biomass and grain yields, and the model reproduced these crop responses well. Crop total biomass and nitrogen uptake were reproduced well despite relatively poor simulations of observed leaf area measurements during the growing season. The low sensitivity of biomass simulations to poor simulations of leaf area index (LAI) were due to little changes in intercepted solar radiation at LAI >3 and water and nitrogen stress often limiting photosynthesis and growth rather than light interception at low LAI.The responses of DSSAT-Nwheat to temperature variations and elevated atmospheric CO₂ concentrations were close to observed responses. When compared with the two other DSSAT-wheat models (CERES and CROPSIM), these responses were similar, except for the responses to hot environments, due to different approaches in modeling heat stress effects.The comprehensive evaluation of the DSSAT-Nwheat model with field measurements, including a comparison with two other DSSAT-wheat models, created a multi-model simulation platform that allows the quantification of model uncertainties in wheat impact assessments.     

E－凸集的几个基本性质

利用比较与分析的方法，由E-凸集的定义出发，研究了E-凸集的若干基本性质．所得结果丰富并深化了凸分析的基本内容，拓宽了广义凸性在优化理论及其应用中的研究范围．     

A Method of Analyzing the Parameter Sensitivity of Large Rotor Systems and Its Application

Based upon the eigenvalue sensitivity theory of non-self-adjoit system and the component mode synthesis method,a new technique is developed to analyze the eigenvalue sensitivity to variation of parameters of large rotor-bearing system. As an application, the influence of the journal bearing parameters on the stability of a large domestic turbine-generator set is analyzed and discussed.     

烟草成分对其品质影响程度的粗糙集判别方法

运用粗糙集理论研究了烟草主要化学成分 (总糖、还原糖、总氮、烟碱、氧化钾和氯离子 )对烟草品质影响程度的判别方法。对比已有的研究结果 ,表明基于粗糙集理论的计算方法简单 ,结果明了 ,而且还能量化烟草成分对品质的影响程度。     

基于灰色关联分析的区域保险差异影响因素分析

研究了经济学中广泛应用的决策模糊理论中模糊集覆盖系数的性质，并据此提出了无须通过繁杂的统计实验就能够计算覆盖系数的实用方法，进而提出了模糊集交并运算算子. 用两个算例说明了该方法和算子与实际情形相符，具有可行性.     

伐区作业类型划分与集材作业系统相适应性的研究

本应用模糊聚类分析方法,选取作业区坡度、单位面积出材量、集材距离以及地表承载能力等作为因子,对吉林林区伐区作业类型进行了区划。又应用层次分析法,对与每类伐区相适应的集材作用系统进行系统分析。     

成套小样园作为典型众数抽样调查单元的方法

本文介绍了用成套小样园作为典型众数抽样调查单元的方法测定两个不同林分小班的蓄积，并与用点抽样和不同形状样地的系统抽样结果相比较，表明用成套小样园作为典型众数抽样调查单元的方法能满足９０％以上的精度，而且工效很高；作者也探讨了使用此法的条件．     

凸Vague集的定义及性质

针对关于Vague集的凸性研究较少的现状,首先基于Vague集的真隶属度函数和假隶属度函数定义了凸Vague集,然后对凸Vague集的一些性质进行了研究,得出了几个有用的结论.     

Effect of set-size and storage temperature on bolting,bulbing and seed yield in two onion cultivars

The effects of three set-sizes (12.5, 17.5 and 22.5 mm in diameter) and seven storage temperatures (0, 5, 10, 15, 20, 25 and 30 °C) on bolting, bulbing and seed yield in two onion (Allium cepa L.) cultivars ‘Hygro’ and ‘Delta’ were investigated. The incidence of bolting increased linearly with set-size and curvi-linearly with decreasing storage temperature. Time to inflorescence emergence and floret opening showed a curvi-linear response to storage temperature with the earliest inflorescence emergence and floret opening occurring at 5 °C and the latest at 30 °C for ‘Hygro’ and at 25 °C for ‘Delta’. Seed yield per umbel also showed a curvi-linear response to storage temperature with the lowest seed yield occurring at 30 °C for ‘Hygro’ and at 25 °C for ‘Delta’ and the highest seed yield at 5 °C. For a seed crop, storage of large sets (22.5 mm) of these cultivars at 5 °C for 120 days appeared to be optimum with 5–12% higher seed yield per umbel than that of 90 days storage. Bulb yield showed a curvi-linear response to storage temperature with the highest bulb yield occurring at 25 °C and the lowest at 5 °C.     

聚类分析在西瓜抗枯萎病品系筛选中的应用

对28个西瓜品种进行抗枯萎病筛选．苗期用特定浓度接种，每隔7d调查其感病情况及植株生长情况．株高、茎粗、叶片数等生长势指标与发病率均呈极显著负相关，相关系数分别为－0．5480、－0．6052、－0．8114．利用聚类分析方法统计，把28个西瓜品种按其抗性表现归类，从而得出抗病水平不同的各组西瓜品种，并筛选出一组抗性水平相当高的品种．为选育高抗西瓜品种以及研究各西瓜品种的抗病性关系提供了一种简捷的科学方法．