Crop Input Response Functions with Stochastic Plateaus

Agronomic research on crop response to nitrogen fertilizer suggests that a plateau function may be appropriate, but the plateau varies across fields and years. Available models that treat the plateau as a stochastic variable are not readily extendable to handle field or year random effects as seems to be appropriate based on the agronomic data. This article develops a method of estimating a response function with a stochastic plateau that can capture random effects. The method is then used to determine economically optimal levels of nitrogen fertilizer for wheat ( Triticum aestivum ).     

基于宜居性和承载力提升视角的高原过渡地带村庄布局优化——以青海省大通县为例

[目的]高原过渡地带农村地势复杂,资源环境承载力弱,生态保护与民生发展难以兼顾,制约着农村地区的发展空间。基于宜居性和承载力提升视角,科学合理优化村庄布局,对于生态脆弱地区高原宜居乡村的建设和可持续发展具有指导意义。[方法]文章构建乡村宜居性评价体系,运用K-均值聚类法对大通县村庄进行分类识别,运用状态空间法从生态系统、资源环境和基础设施3个维度测算村庄的综合承载力。[结果]（1）通过聚类重构形成由集聚提升村、示范引领村、潜力优化村、生态保护村和生态搬迁村组成的高原乡村体系;（2）大通县乡村宜居性整体适中,空间上呈现出由中部向西北部、关键节点中心向四周逐渐递减的趋势;（3）乡村承载力水平在空间上差异显著,中部、南部地区整体高于北部,其中集聚提升类村庄的综合承载力最高。[结论]通过定性分析乡村宜居性和定量测算承载力,为不同类型村庄的人口、用地、产业规模等提出空间布局优化策略;基于最短路径与最优中心,引导搬迁村人口优先向周边可载的集聚提升村迁移,同步推进村庄迁建与发展,有利于形成与资源环境承载力相匹配、生产生活生态相协调的乡村发展新格局,保障乡村振兴发展。     

A multi-level spatial urban pressure analysis of the Giza pyramid plateau in Egypt

Urban sprawl has deleterious effects on natural and man-made landscapes and, therefore, on the attractiveness of visitor and tourist areas. The spread of urban land use has prompted a significant loss of biodiversity and an increasing vulnerability of fragile natural and man-made systems. A prominent example of this threat for cultural heritage is the urban pressure on the Giza pyramid complex in Cairo, Egypt. This paper analyses urban growth trends within the Greater Cairo Metropolitan Area, especially the city enclave that is encroaching on the pyramid complex. A distinction is made between macro- and micro-level spatial analysis of urban growth, focusing on the micro-level dimension, with direct consequences for the conservation of cultural heritage and architectural monuments. Clearly, if no actions are taken, the unique architectural legacy of the pyramids of Khufu, Khafre and Menkaure might be lost. By combining spatial land-use information with location awareness of the pyramid complex, this paper aims to shed light on the relevance of spatial analysis and urban growth models as tools to analyse the endangerment of valuable cultural heritage. This paper also suggests new directions for architectural heritage management, within the framework of micro-spatial analysis of the historico-cultural legacy in urban regions.     

高原地区轻钢结构-泡沫混凝土自保温墙体设计与制备研究

本文针对高原地区工程建设特点,设计新的轻钢结构-泡沫混凝土自保温墙体结构体系,研究掺加玻化微珠提高泡沫混凝土体积稳定性工艺及性能,对新型自保温墙体性能进行试验研究和工程应用。     

Modeling skewness with the linear stochastic plateau model to determine optimal nitrogen rates

Accurate modeling of skewness is needed to increase the actuarial fairness of crop insurance. We test Day's conjecture that crop yield skewness becomes negative as nitrogen rates increase and determine how well a linear response stochastic plateau (LRSP) production function matches the pattern of observed skewness using four long‐term nitrogen experiments. Stillwater wheat is consistent with Day's conjecture, but the skewness for Lahoma and Altus wheat yields as well as Altus cotton yields are not. The LRSP assumes normal random effects and can explain only a small part of observed skewness, so a new LRSP with skew‐normal random effects is introduced, which comes closer to explaining the observed skewness and should increase the accuracy of nitrogen rate recommendations. Negative skewness reduced optimal nitrogen rates and positive skewness increased optimal nitrogen rates.     

云南高原特色农业生态文明建设探讨

本文从云南高原特色农业生态文明建设的重要性出发,分析了云南高原特色农业发展过程中生态文明建设的现状,结合建设过程中存在的问题,笔者提出了推进云南高原特色农业生态文明建设的对策建议。     

黄土高原地区粮食生产潜力与发展途径

农业是国民经济的基础 ,粮食是基础的基础。黄土高原地区是中华民族文化的发祥地 ,也是我国历史上早期农牧业生产区和政治中心 ,粮食是该区人民赖以生存的最基本产业。探索其发展规律 ,分析其障碍因素 ,寻求其发展潜力 ,采取“一靠政府 ,二靠科技 ,三靠投入 ,四靠保护 ,五靠工作”的战略措施 ,对同类地区的粮食发展具有重要意义。     

提高公路货物运输能力促进钢铁物流快速发展

钢铁业的发展带动了钢铁物流的快速增长。钢铁企业从一开始建立就拥有自己的公路货运企业,其发展物流机会更大。运输是物流的关键环节,但运输做得再好也不是物流,公路货运企业应在做好企业内部物流的基础上适时发展综合物流。     

青藏高原农牧区社会保障制度现状、问题与发展

建立健全农村社会保障体系是近年来农村工作的热点和难点问题,而青藏高原农牧区社会保障建设更为至关重要。现阶段青藏高原农牧区的社会保障有了一定发展,但是仍存在着一些问题。需要从不同的角度对这些问题进行探讨和分析。反思青藏高原农牧区社会保障内在因素与解决对策。本文旨在从青藏高原农牧区社会保障的现实状况和存在问题出发,探究影响其发展的制约因素,进而提出完善青藏高原农牧区社会保障的建议。     

高高原航线运行控制研究

全球的高高原机场里,中国高高原机场数量所占的比例最高,且是运行难度最大的区域。为了更好地对高高原机场的航线进行运行控制,实现航班运行风险在可接受的水平,达到航班运行安全高效的目的,对空客A319-115机型在高高原航线的运行控制,从人、机、环、管四个维度做了深入的研究分析。结果表明高高原机场的运行环境是复杂多变的,高高原航线运行风险大,需要对不同的风险进行精准的运行控制。