我国肉牛规模化养殖变动趋势及影响因素研究——基基于面板分位数回归的实证分析

目的 探究我国肉牛规模化养殖变动趋势及影响因素,为推动肉牛规模化养殖、提高牛肉生产能力以确保基本供给提供政策依据。方法 文章基于2007—2020年我国16个肉牛主产省面板数据,首先分析肉牛规模化养殖变动趋势及省际差异,然后采用面板分位数回归模型实证检验肉牛规模化养殖影响因素。结果 （1）我国肉牛规模化养殖水平东北地区相对较高,西南地区最低。（2）省域内饲草料生产能力、固定资产能力、机械化水平、城镇化率和工资性收入水平越高、牛肉消费潜力、政策扶持力度和环境规制强度越大,肉牛养殖规模化水平越高。（3）提高牧草生产能力对促进广西、贵州、云南和四川等西南地区的肉牛规模化养殖更为明显,提高饲料生产能力和牛肉市场消费潜力对促进辽宁、吉林和黑龙江等北方地区的肉牛规模化养殖更为明显。（4）小、中规模肉牛养殖受资源禀赋影响更大,中、大规模肉牛养殖受固定资产投入水平和政策扶持影响更大。结论 发展肉牛规模化养殖需充分考虑区域和规模的差异性,从稳固饲草基础保障、完善肉牛扶持政策和环境规制政策、加强人才队伍建设、提高养殖技术水平、优化养殖规模布局等方面着手,推动肉牛规模化养殖快速发展。     

基于RBF神经网络的高光谱遥感影像降维及分类

高光谱遥感影像数据量大,针对该特点,为尽可能保留数据中有价值的信息,首先采用线性判别分析(Linear Discriminant Analysis,LDA)方法对高光谱遥感影像数据进行降维,接着应用径向基函数(Radial Basis Function,RBF)神经网络方法对其进行分类处理。实验结果表明,分类精度可达到70%以上,具有良好的分类效果,证明了该方法的可行性。     

Multiple Inference and Market Integration: An Application to Swedish Fish Markets

This paper, in contrast to earlier studies, tests market integration using a methodology that accounts for the multiplicity problem inherent in testing several time series. This method minimises the risk of finding spurious evidence of market integration. We examine market integration among 12 fish species in Sweden by applying cointegration tests, which identify market integration for two separate clusters of species. Furthermore, we find that the Law of One Price holds for 6 of the 12 species considered.     

中国广义国家公园体系称谓问题初探

与其他国家的国家公园相比,中国广义国家公园体系在部门管理体制下逐步演变为9种类型,存在多园并存的现象,对我国9种类型的国家公园现状进行了分析和总结,通过各类型的国家公园在CNKI和互联网搜素引擎中的出现频次对专业学者和普通大众对其关注程度进行分析,指出了多园并存的合理性和局限性,并针对这种现状提出了改进建议。     

中国经济增长要素的实证分析

消费、投资、进出口被喻为拉动中国国民经济增长的三大要素。本文通过建立多元线性回归模型和创新模型,利用1990年到2010年的国民生产总值（GDP）、最终消费支出（FC）、资本形成总额（I）、货物进口总额（IM）、货物出口总额（EX）净出口（t）的数据,分析各个要素对中国GDP增长的贡献率的大小随着时间的变化规律,进而发现中国经济的主要影响因素,最终来确定不同时期GDP增长的主要贡献要素。     

Tractors on eBay: Differences between Internet and In-Person Auctions

We provide a systematic examination of the differences between Internet and in-person auction prices for used tractors. A hedonic model estimated with transactions pooled between eBay and in-person auctions reveals statistically distinct price surfaces for the two auction venues and predicts significantly lower prices for comparable equipment sold on eBay, though this difference is attenuated for tractors fully covered by eBay's buyer protection program and is fully absent for the most frequently traded tractor. An endogenous venue selection model reveals that larger, more valuable tractors from states with more valuable stocks of machinery are more likely to be offered on eBay.     

胆固醇认知对城镇居民鸡蛋食用量的影响

目的 鸡蛋胆固醇与身体健康问题是人们关注的焦点,直接关系到人们的鸡蛋食用量。方法 文章基于消费者视角,根据实地调研数据,采用分位数回归方法实证分析了胆固醇认知对城镇居民鸡蛋食用量的影响。结果 （1）城镇居民基本上实现了每人每日食用一枚鸡蛋,与鸡蛋实际食用量相比,调研到的样本目前还未达到认为合理的食用量。超过2/3的样本认为食用鸡蛋会导致胆固醇摄入量增加,从而会影响人体健康。（2）经模型验证,胆固醇认知对城镇居民鸡蛋食用量具有显著的负向影响,说明城镇居民为了身体健康以及减少胆固醇摄入量,会有意减少鸡蛋食用量,而且城镇居民鸡蛋胆固醇的负面认知更容易促使其鸡蛋食用量控制在自认为合理的范围以内。结论 基于此,该文结合胆固醇认知等对城镇居民鸡蛋食用量具有显著影响的变量,提出了引导消费者科学购买及食用鸡蛋的对策建议。     

政府补贴是否提升了粮食流通效率？——基于企业层面微观数据的验证

在粮食行业供给侧结构性改革过程中,政府补贴作为支持和引导粮食行业转型发展的直接手段,对于粮食企业转变发展方式、提高经营效率具有重要作用。文章利用我国粮食企业上市公司数据,考察了政府补贴对粮食企业流通效率的影响。实证研究发现：政府补贴有助于提升粮食企业流通效率;异质性检验表明,政府补贴对粮食企业流通效率的促进效应在非国有粮食企业以及粮食主产区和主销区表现更为明显,同时新一轮粮食流通改革强化了政府补贴的激励效应。面板门限回归结果显示,在市场化发展处于高水平、一般水平和低水平阶段时,政府补贴对粮食企业流通效率均会产生正向影响,但影响程度存在差异,处于高水平阶段时最大,处于一般水平阶段时次之,处于低水平阶段时最小。因此,现实中应该重视政府补贴的有效激励效用,以最大化政府补贴对于粮食企业流通效率的贡献;应充分考虑不同地区的市场化发展水平,以及针对企业性质和地区异质性,实施差异化的补贴方式,以最大化政府补贴的政策效果。     

基于科学发展观的河北林业科技创新系统研究

基于科学发展观、利用创新理论,结合河北省科技现状,提出以林业科技创新型企业为核心的多元主体合作的林业科技创新模式,强调多元主体的平等地位及制度供给创新;指出政府应建立产学研、官企学合作机制,通过多元主体合作联盟,建立完善科技创新型企业,培养科技型企业家,促进林业人力资源开发,进行适宜的技术战略,完善科技型企业发展的宏观政策环境,形成网络价值能力,以期构建和完善河北省林业科技创新体系,探索建立河北省林业科技创新系统的理论与模式,实现科技兴林的战略。     

Biophysical and socioeconomic determinants of tea expansion: Apportioning their relative importance for sustainable land use policy

Tea expansion, a typical process of regional land use and cover change (LUCC), has raised great concerns on regional sustainability. In this regard, exploring the determinants of tea expansion should provide critical implications for land use policy. It has been widely recognized that LUCC interacts nonlinearly with a set of determinants and their feedbacks should be rather complex. Policy makers are now facing the challenge to identify, apportion, and compare the determinants of regional tea expansion for designing more targeted political intervenes. Our paper utilizes a robust tool, the random forest (RF) regression in particular, to explore the determinants of tea expansion across two periods (1985–2007 and 2007–2016) in Anji County, a typical region of tea production in subtropical China. More specifically, tea is extracted from Landsat imageries and total tea cultivated area acts as the dependent variable. Exploratory variables include 38 potential determinants and these determinants are divided into two categories (biophysical and socioeconomic) at two levels (pixel and village). We obtain some similar findings, though the relative importance of determinants varies with the two periods. In general, biophysical determinants (e.g., topography, soil type, land use in the neighborhood) present greater relative importance than the socioeconomic determinants in both periods. In period 1985–2007, biophysical determinants at pixel level are more essential in governing tea expansion. In period 2007–2016, the relative importance of pixel level biophysical determinants is comparable with that of the village level determinants. Comparisons of the two periods indicate that relative importance of soil type and socioeconomic proximity becomes greater in period 2007–2016, while that of the total employees and non-agricultural population proportion becomes lower. Partial dependency plots are further drawn to visualize the marginal effect of each determinant. We finally propose three options for land use policy towards sustainability. Our study demonstrates that the RF regression is efficient for policy makers to understand the determinants of tea expansion with a nonlinear and complex nature.