渐开线圆柱齿轮的形位误差探讨

从误差角度分析，综述ＧＢ１００９５－８８《渐开线圆柱齿轮精度》误差的表达方法。     

农户视角下的面源污染防治政策梳理及完善策略

在供给侧结构性改革背景下,政策是进行面源污染防治的有效工具。市场经济环境下,农户的行为逻辑受多元因素影响。政策作为影响第一产业发展的关键要素,对农户具有制约、引导、激励和调节作用。与此同时,农户也对政策的推行效果具有深刻的影响。本文在进行面源污染防治政策演进分析时,尝试从经济激励引导型、命令控制型以及协同辅助型等不同政策类型入手,重视经济激励和制度激励的作用,收紧面源污染防控的监管口径,建立差别化的污染治理衡量机制,并重视技术推广在污染防控中的作用。提高农户积极性,提升农户对政策的反馈效果,最终提高农户对面源污染防治政策的遵循水平,提升面源污染防治效果。     

Heterogeneous returns to chemical fertilizer at the intensive margins: Insights from Nepal

Increased fertilizer use is considered important for agricultural development in low-income countries. Promoting increased use of chemical fertilizer by lowering its price may be ineffective if demand is price inelastic. In theory, the price elasticity of demand depends on the returns to its use, but the evidence is scarce. Furthermore, while returns are often estimated for small changes in chemical fertilizer use, returns to larger changes in its use (intensive margins) are less understood. Through the inter-zonal comparisons in Nepal, we provide indicative evidence that greater returns to chemical fertilizer are associated with greater price elasticities of demand. Moreover, the evidence suggests that returns at the intensive margins, rather than returns to small changes, may largely account for inter-zonal differences in returns to chemical fertilizer within Nepal. The results suggest that better understanding the returns at the intensive margins is critical for effective agricultural inputs policies in developing countries.     

候变化对我国种植业化肥投入的影响

气候变化不但会对农业产出产生影响，而且还会对农业生产要素投入产生影响。利用我国26个省2001—2012年的面板数据，实证分析气温和降水量变化对我国种植业生产中化肥使用强度的影响，结果表明：从整体看，年平均气温上升有助于降低化肥的使用强度，而年降水量的增加则会提升化肥的使用强度；对于热带亚热带季风气候区，降水量增加、气温上升均会导致化肥使用强度增加；对于温带季风气候区，气温上升会导致化肥使用强度下降，但是降水量增加对化肥使用强度的影响不显著。气候变化对不同气候区农业生产的化肥投入具有不同的影响，因此有关化肥控制的政策有必要考虑气候因素的影响，政策目标的设定也应体现区域差异。     

Reduction in nitrogen fertilizer use results in increased rice yields and improved environmental protection

Overuse of nitrogen fertilizer represents a considerable environmental problem globally, but especially in China. Recently, a recent approach on an experimental scale based on the diffusion of the so-called Three-Control Technology (TCT) successfully alleviated the overuse of nitrogen fertilizer in southern China villages in the Guangdong Province, serving as a reference point for other rice-producing countries tackling similar challenges. Here, we assessed the correlation between rice yields and reduction in the use of nitrogen fertilizer following the introduction of TCT. Our study was based on the collection of primary data from 248 households randomly selected from four rice-growing areas of Guangdong Province, China. Our results show that TCT significantly improved the efficiency in the use of nitrogen. Crucially, participating farmers, including both full adopters and partial adopters, were found to fundamentally change their application practices of nitrogen fertilizer, resulting in major improvements in the local soil and water systems.     

我国化肥价格波动与农民收入关系的实证分析

本文利用1978～2008年的时间序列数据,运用脉冲响应函数和方差分解技术考察化肥价格波动与农民收入之间的关系,发现化肥价格的波动与农民收入变化之间存在着双向的因果关系,即化肥价格的上涨导致农民增收缓慢,而化肥价格上涨的根本原因在于＂需求拉动＂和＂成本推动＂。今后必须从需求和供给两方面采取对策：一方面通过建立化肥直接补贴制度和化肥储备制度,从需求上控制化肥价格上涨;另一方面通过采用新型化肥生产技术和给予化肥生产企业生产用能以优惠政策,从供给上控制化肥价格上涨。     

我国农用化肥施用的影响因素——基于省际面板数据的实证分析

我国农用化肥施用量不断提高带来的环境污染问题日益严重。研究化肥施用的影响因素及其影响程度,为防止化肥滥施、保护生态环境提供依据意义重大。文章采用1999～2008年我国31个省(市、区)的面板数据,通过面板单位根检验、协整关系检验和多元回归方法分别对国内东、中、西三大区域化肥施用密度与其影响因素之间的关系进行了实证分析。研究结果表明,三大区域农民人均纯收入、人口规模对化肥施用密度具有显著的正向影响,三大区域化肥价格增长率、粮食种植面积比重、化肥产出效率对化肥施用密度具有显著的负向影响,三大区域种植产品生产价格、种植业劳动力数量、农产品国际贸易对化肥施用密度具有不同的影响效果或显著性。     

Uniform and Non-Uniform Second-Best Input Taxes

We investigate second-best, input-based taxes foragricultural nonpoint pollution control when marketprices are endogenous and production isheterogeneous. Theoretically, we derive the optimalforms of taxes which take account of heterogeneity(non-uniform taxes) and a tax which does not (auniform tax). Empirically, we use a multi-factor,market-equilibrium simulation model to determineoptimal tax rates and associated equity effects,particularly differences in landowner gains/lossesacross a heterogeneous region. When market prices areendogenous, second-best tax policies result inpecuniary externalities that affect existingenvironmental externalities. In particular, thepecuniary externalities amplify the effect of producerheterogeneity on determination of sub-regionaldifferences in tax rates and returns to land,particularly for the uniform policy. With endogenousprices, the uniform tax rate is considerably higherthan any of the non-uniform rates and, ironically, thenon-uniform taxes result in less dispersion oflandowner gains across sub-regions than the uniformtax.     

我国各区域农业生产资源配置效率分析

本文运用数据包络分析法测算了我国各区域农业经济的投入产出效率,指出目前我国各省市农业经济资源配置效率差异较大,其中人均化肥施用量对全国大多数省市农业劳动生产率都是最重要的,这种生产方式属于典型的“化肥农业”,并由此引发了一系列问题。文章认为,制度创新可以再造农业经济主体之间的相互关系,减少信息成本和不确定性,降低交易成本,提高生产要素配置效率,从而促进农业经济快速增长;在制度创新先行的前提下,实现农业经济组织创新与制度创新、知识创新的互动,是转变“化肥农业”生产方式,走可持续的新型农业发展道路的关键所在。