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.     

中亚天然气C线管道SPS仿真模拟

中亚天然气C线管道属于典型的输送压力高、流量大、管道跨度大、压气站数目多、输送工艺复杂的输气管道。为研究中亚天然气C线管道正常工况和事故工况下水热力参数的变化规律以及各种事故下管道的自救时间,采用SPS软件建立了中亚天然气C线管道仿真模型。模拟了正常工况下管道全线压力和温度参数,模拟结果与实际运行数据最大相对误差分别为1.90%和12.24%,验证了模型的可靠性;在此基础上分析了环境温度和管道粗糙度变化对全线输气效率的影响规律,确定了各种事故工况下管道最长的自救时间,可为中亚天然气长输管道运行管理提供参考。     

几种利用乳中尿素氮浓度估测尿氮排泄量模型的评价

本文利用34组国内外报道的荷斯坦牛乳中尿素氮浓度和尿氮排泄量的实测数据，对目前提出的部分利用MUN估测尿氮排泄量的模型进行了比较。结果表明，Zhai（2005）提出的模型[UN（g/d）：10．1×MUN（mg／dL）＋47.3]预测效果较好（P〉0．05）。划分MUN浓度范围分别建立模型可能会提高预测的准确度。此外，根据34组数据做简单回归：UN（g/d）=12．78×MUN（mg/d1）＋28．15（n=34，R2=0．59）。     

人居环境视角下居民垃圾分类意愿实证研究及政策建议——基于河南省郑州、洛阳、商丘和漯河四地市的调研

基于河南省人居环境现状,分别对郑州、洛阳、商丘和漯河四地市进行了实地调研,通过建立二元Logistic模型,分析了影响居民垃圾分类意愿高低的因素。结果表明:文化程度、经济发展、政策支持对提高居民垃圾分类意愿具有较强的正相关影响,而居民人居环境满意度对提高垃圾分类意愿具有负相关影响;女性相比男性的垃圾分类意愿更高,城市居民相比农村居民的垃圾分类意愿更高。基于此结论,从政府和社会两个方面分别提出了相关建议,以供参考。     

Effect of Partial Replacement of Steam Rolled Corn With Soybean Hulls or Prickly Pear Cactus in the Horse's Diet in the Presence of Live Saccharomyces cerevisiae on In Vitro Fecal Gas Production

The aim of the study was to evaluate the fecal fermentation of partial replacing steam rolled corn with soybean hulls (SH) or prickly pear cactus (PC) as energy source in horse diets, in the presence of Saccharomyces cerevisiae. Steam rolled corn was replaced with SH at 0% (control), 7.5% (SH75), and 15% (SH150) in the first trial, whereas it was replaced with PC at 0% (control; the same of the first trial), 7.5% (PC75), and 15% (PC150) in the second trial. Yeast of S. cerevisiae was added at 0, 2, and 4 mg/g dry matter (DM) of incubated substrates. Fecal inoculum was obtained from four adult English Thoroughbred horses fed on an amount of commercial concentrate and oat hay ad libitum. Interactions observed between PC rations and yeast doses for the asymptotic gas production (GP), the rate of GP and carbon dioxide (CO₂) production during some incubation hours. Moreover, with no effect due to SH rations (P > .05), increased (P < .05) rate of GP was observed with the ration PC75 compared with other rations. Besides, PC75 and PC150 rations with 0 mg yeast/g DM linearly decreased (P < .05) CO₂ production at some incubation hours. However, SH75 and SH150 ration had increased (P = .005) DM degradability (DMD). Yeast addition at 2 mg/g DM increased the asymptotic GP (P = .048) with the SH75 and PC150 rations. The level of 4 mg yeast/g DM increased the asymptotic GP (P = .048) from the SH150 ration. Yeast addition at 2 and 4 mg/g DM increased (P < .05) ​the asymptotic GP from PC75 and PC150 rations, respectively, with increasing DMD with the both doses. Yeast addition increased (P < .05) CO₂ production from SH75, SH150, PC75, and PC150 rations. It could be concluded that SH and PC can replace steam rolled corn at levels of 7.5% to 15% without negative effect of fermentation kinetics and with better fermentation performance in the presence of yeast at 2 mg/g DM of substrates.     

玉米不同自交系幼苗光合对 UV-B 辐射增强的响应

为了探讨玉米不同自交系对UV-B辐射增强的响应，在摸拟光照培养条件下，研究了增强UV-B辐射对玉米不同自交系气体交换参数的影响。结果表明，五叶期UV-B辐射处理6 d后，供试的48个自交系中近一半以上材料的幼苗叶片光合速率、气孔导度和蒸腾速率显著降低10％以上，其材料比例分别为64．6％，47．9％，54．2％；而有62.5％的材料胞间CO2浓度表现为显著增加；相关分析发现，气孔导度与蒸腾速率对UV-B辐射增强的响应值间存在极显著正相关关系；根据气体交换参数对UV-B辐射增强的响应程度将48个材料分成6类，其中对增强UV-B辐射反应比较敏感的材料和能够忍耐UV-B辐射增强的材料均占12．5％。说明玉米不同自交系幼苗叶片气体交换参数对UV-B辐射增强反应敏感程度具有显著的基因型差异，从中能够筛选出对UV-B辐射增强反应敏感和有忍耐能力的材料。     

APSIM模型对宁夏海原地区草田轮作系统的适应性

为验证APSIM模型对宁夏海原地区草田轮作系统的适用性,基于10年生苜蓿(Medicago sativa)与小麦(Triticum aestivum)、谷子(Oryza sativa)草田轮作试验数据和同期气象资料,运用APSIM模型对系统进行了模拟。通过试错法和文献记载完成了苜蓿、小麦和谷子几个品种的参数本地化。用统计和图形校验方法评价了APSIM模型模拟结果的可靠性和准确性。结果表明,谷子-小麦-小麦(MWW)、小麦-谷子-小麦(WMW)、谷子-谷子-小麦(MMW)、谷子-小麦-谷子(MWM)、小麦-谷子-谷子(WMM)、小麦-小麦-谷子(WWM)6种轮作方式下产量实测值和模拟值的决定系数R2值范围在0.83至0.98之间,D值范围在0.94至0.99之间,表现出了良好的相关性和一致性。土壤含水量实测值和模拟值的决定系数R2值范围在0.52至1之间,D值范围在0.92至0.97之间,相关性和一致性表现良好。表明APSIM模型对宁夏海原地区苜蓿与小麦、谷子轮作具有较好的模拟能力,可以用来模拟分析该地区草田轮作系统生产潜力和土壤水分动态,对该地区气候变化影响下草田轮作的优化管理具有一定指导意义。     

高产小麦品种模式化选育的初步研究

本文探讨了高产小麦品种理想模式的概念、特点和品种模式化选育的理论依据及优点。对37个亩产400公斤以上的高产品种的产量与其构成因素、形态性状、生理性状以及这些性状之间的关系进行了多元和简单相关分析。针对山东的生态条件和品种的现状，优化了亩产600-650公斤的品种模式。探讨了各类性状间的有机联系和协调发展产量潜     

PTGS/ RNAi的作用机制及其应用

论述了双链RNA对同源基因的表达进行特异性的封闭而引起的转录后的基因沉默（PTGS/ RNAi）现象, PTGS/ RNAi的作用机理，作用模型，参与这一过程的酶、基因、起始因子和作用因子，介绍了PTGS/ RNAi在基因组功能研究、基因的时空表达调控以及在作物改良等方面的应用。     

盘式制动器摩擦特性的指数函数模型

以JF－132型汽车制动器试验台为试验设备，采用试验优化与回归分析技术，研究盘式制动器的准静态摩擦特性，以制动压力与初速度为试验因素，以制动力矩为试验指标，建立了盘式制动器摩擦特性的指数函数模型，并进行了统计检验。