Impact of climate change on maize yield in China from 1979 to 2016

Climate change severely impacts agricultural production, which jeopardizes food security. China is the second largest maize producer in the world and also the largest consumer of maize. Analyzing the impact of climate change on maize yields can provide effective guidance to national and international economics and politics. Panel models are unable to determine the group-wise heteroscedasticity, cross-sectional correlation and autocorrelation of datasets, therefore we adopted the feasible generalized least square(FGLS) model to evaluate the impact of climate change on maize yields in China from 1979–2016 and got the following results:(1) During the 1979–2016 period, increases in temperature negatively impacted the maize yield of China. For every 1°C increase in temperature, the maize yield was reduced by 5.19 kg 667 m–2(1.7%). Precipitation increased only marginally during this time, and therefore its impact on the maize yield was negligible. For every 1 mm increase in precipitation, the maize yield increased by an insignificant amount of 0.043 kg 667 m–2(0.014%).(2) The impacts of climate change on maize yield differ spatially, with more significant impacts experienced in southern China. In this region, a 1°C increase in temperature resulted in a 7.49 kg 667 m–2 decrease in the maize yield, while the impact of temperature on the maize yield in northern China was insignificant. For every 1 mm increase in precipitation, the maize yield increased by 0.013 kg 667 m–2 in southern China and 0.066 kg 667 m–2 in northern China.(3) The resilience of the maize crop to climate change is strong. The marginal effect of temperature in both southern and northern China during the 1990–2016 period was smaller than that for the 1979–2016 period.     

“藏粮于地”战略下高标准农田建设模式研究*

高标准农田建设是我国“藏粮于地”战略的重要抓手,是确保粮食产能的重要支撑。在梳理大量参考文献、政策文件和标准规范的基础上,针对现阶段高标准农田建设存在管理体制不完善、空间潜力不足、投资标准偏低、建设质量不高等问题,总结归纳高标准农田建设模式总体构架,通过对我国高标准农田建设综合评价结果排名靠前和提升较快的省份开展高标准农田建设模式调查研究,围绕管理体制、规划布局、建设标准、资金保障以及实施管理方面,提出系统构建高标准农田建设模式的对策建议,为提高高标准农田建设质量作有益参考。     

基于Netty的农业物联网服务器系统设计

为了方便对温室环境的监控和控制,使用Netty网络框架设计了一个农业物联网服务器系统,能够简化物联网服务器端的开发,实现下位机与上位机的实时通信。本文阐述了该系统的工作原理和总体设计,以期为实现大棚农作物生长的智能化和信息化管理。     

都市餐饮企业的净菜需求影响因素分析——以北京市为例

净菜的广泛使用能提高餐饮企业的出餐率,减少其后厨面积、劳动用工和厨余垃圾。基于北京地区708份餐饮企业净菜需求的问卷调查样本,运用垄断竞争市场理论和二元选择模型分析了影响餐饮企业净菜使用行为的具体因素。研究发现,对净菜了解程度不够和净菜价格偏高是制约餐饮企业使用净菜的主要因素,具有不同个体特征和环境特征的餐饮企业选择净菜的倾向性不同。建议在餐饮业大力开展净菜宣传科普工作;大力扶持净菜加工企业和发展相关技术支撑体系以降低净菜价格。     

饲养系统和日粮对羔羊屠宰性能和肌肉矿物质含量的影响

文章旨在探讨不同饲养系统和日粮对羔羊生长、屠宰性能及肌肉矿物质含量的影响。试验将平均体重为（13.97±0.55）kg的120只羔羊随机分为3组，每组4个重复，每个重复10只。T1组在室内饲喂基础浓缩料，每天补充100 g稻草，T2组在室内饲喂基础浓缩料，每天补充100 g稻草和锌硒复合矿物质（0.2 mg/d硒，50 mg/d锌），T3组在室外放牧，除了采食苜蓿草外，每天额外补充100 g稻草和100 g燕麦。试验时间为9周。结果：T1和T2组羔羊的末重、日增重、半胴体重、下肢深度、下肢重量、眼肌面积、颈、胸肌、肾重量均显著高于T3组（P＜0.05），但骨盆骨重量显著低于T3组（P＜0.05）。各处理组羔羊的可食用部分和骨盆肌肉重量无显著差异（P＞0.05）。T2组63 d羔羊血液硒含量较T1和T3组分别显著提高了19.83%和25.0%（P＜0.05），血液锌含量较T1和T3组分别显著提高了31.71%和45.91%（P＜0.05）。T3组羔羊肌肉钙含量较T1和T2组分别显著提高了8.79%和5.37%（P＜0.05）。T2羔羊肌肉硒和锌含量较T1和T3组分别显著提高了41.18%、65.52%和38.19%、46.15%（P＜0.05），T2和T3组羔羊肌肉钾含量较T1组分别显著提高了3.27%和4.28%（P＜0.05）。结论：在本试验条件下，放牧羔羊胴体的脂肪含量低于室内饲养的羔羊，室外放牧可以提高肌肉钙和钾含量，但肌肉硒含量降低。 [关键词]饲养系统|羔羊|屠宰性能|矿物质     

数值模型结构不确定性对模拟结果的影响分析

以内蒙古鄂托克旗为例,基于GMS中的MODFLOW模块构建了地下水流数值模拟模型,分析了模型结构(含水层厚度、参数分区)与模型参数不确定性因素对模拟结果的影响.研究结果表明:含水层不确定情景(含水层下边界概化为隔水底板平均值870 m)与实际情况水头差值绝对值的累计和最大为701 m,对模拟结果起了主控作用;当含水层下边界概化为910,940 m时,累计和分别增加为1 013,1 593 m;与仅考虑单个不确定性因素相比,同时考虑模型参数与含水层不确定情景累计和最大为738 m,同时考虑参数分区与含水层不确定情景累计和最大为791 m.因此,在构建地下水流数值模拟模型时,应优先考虑含水层空间结构概化的合理程度,同时考虑多个不确定性因素对模拟结果的综合影响,使地下水数值模拟模型能更精确地反映真实的地下水流状况.     

我国社会救助管理服务体系建设研究

我国社会救助体系不断完善的过程中涉及主体更多元、方式更多样。当前社会救助面临相关部门和组织多、信息复杂、经办分散、分类精准施救难度大等问题。基于我国社会救助模式的合理价值选择，提出管理服务体系建设的重要意义。进而分析社会救助在管理服务上面临的挑战和难题，从组织协调管理、信息网络系统、基层经办机构、社会参与机制四个方面提出构建多层次管理服务体系的思路。力求提高管理服务的效率和效能，促进互助共济社会救助共同体的形成，提升公众满意度，夯实我国民生保障基础。     

王正非林火蔓延模型改进研究

王正非林火蔓延模型是目前国内比较先进的森林火灾蔓延模型,但是由于林火行为的复杂性,此模型在准确率和普适性方面仍存在许多不足。本文结合已有的成果进一步改进王正非模型,增加了可燃物湿度对林火蔓延速度的影响,改进了林火初始速度的计算方式。针对各种坡度对林火蔓延行为的影响给出了一个计算公式。与改进前相比,改进后的模型使其对林火蔓延情况的预估更为精准。     

Vitrification of mouse two-cell and blastocyst stage embryos in simplified closed system using either a hemi-straw or a hollow fiber device

Two-cell stage and blastocyst stage mouse embryos were equilibrated in a medium containing 7.5% ethylene glycol (EG) and 7.5% dimethyl sulfoxide (DMSO) for 8–15 min. Vitrification was performed in a medium containing 0.5 M sucrose and either 15% EG + 15% DMSO, 17.5% EG + 17.5% DMSO, or 20% EG + 20% DMSO for 30 s. They were then placed either on a hemi-straw (HS) or a hollow fiber vitrification (HFV) device and vitrified by cooled air inside a 0.5-ml straw. In two-cell embryos, a 100% survival rate was obtained from all groups except the 20% HS group (P > .05). All vitrified two-cell groups showed similar rates of blastocyst development to that of fresh control group (P > .05), except 17.5% and 20% HFV groups, which were significantly lower than the other groups (P < .05). In the blastocyst embryos, the HFV groups were divided into two subgroups (non-collapsed; HFV-NC and collapsed; HFV-C blastocyst). Re-expansion rate in 15% HFV-NC, 17.5% HFV-NC, and 15% HFV-C groups was reduced (P < .05), whereas the rest were similar to control. In conclusion, we established a simplified, reliable, and closed system for HFV vitrification applying hemi-straw, which does not require skilled practitioners.     

Engineered-airlift pumps for aquaculture applications using multiphase flow analysis

Currently, very few aquaculture operations are employing airlift pump technology for water recirculation, aeration, and waste removal. This is likely due to the poor design and lower efficiency of traditional airlift design, the limited amount of research effort that has been invested in improving performance capabilities of air lift pumps and the general lack of awareness of the industry about the inherent advantages of airlift systems. A new efficient airlift pump is hydrodynamically designed by incorporating the Volume of Fluid (VOF) multi-phase model along with the K-ε turbulence model utilizing Computational Fluid Dynamics (CFD) tools. The pump is designed to offer a substantial reduction in total energy usage as well as an improved quality of the culture products in order to make it attractive to aquaculture industry. In this study, both numerical and experimental investigations were carried out for airlift systems operating under two different submergence ratios of 50% and 90% in a lab setting using 2.54 cm diameter pumps. Also, the performance of a large-scale pumps of 10.16 cm diameters were also tested in an aquaculture raceway to determine its effect on the operation. The numerical results were found to be in agreement with the experiments within ±20% which is considered very reasonable for multiphase flow analysis. The present study was found to present a great tool for modelling the airlift pump performance, and potentially proposing new designs.