食品中重金属铅、镉的电化学检测方法的研究进展

本文将通过结合现阶段有关食品中重金属铅、镉的电化学检测方面的研究著述,从简单论述检测食品中重金属铅、镉的重要性和相关限量标准出发,对食品中重金属铅、镉的电化学检测方法进行简要分析研究。     

长江中下游城市群农业面源污染氮排放评价及调控

基于清单分析法和排污系数法,对长江中下游城市群农业面源污染氮排放现状进行了评价,并运用灵敏度分析和情景分析方法,模拟和比较了不同调控方案对区域未来氮排放变化的影响。研究结果表明,2011年长江中下游城市群4种污染源向水环境排放的氮总量共计128.27万t,其中,农业种植和畜禽养殖的排放比例分别为58.92%和33.53%,是该区农业面源污染的主要氮污染源。如果不加大对面源污染的治理力度,2011~2020年和2020~2030年长江中下游城市群农业面源污染氮排放量将分别增加16.29%和18.78%;如果采取相关减排措施,2020年和2030年4个城市群的农业面源污染氮排放量将分别比2011年削减15%和25%,并有利于实现区域农村经济增长与环境健康发展的双重目标。建议今后全区农业面源污染氮排放调控的重点在于逐步削减肥料投入、合理优化用肥结构、控制畜禽养殖规模扩张以及促进专业化养殖畜禽废物循环利用等,主要控制地区包括武汉城市圈内的潜江市、孝感市、黄冈市和鄂州市,长株潭城市群内的长沙市和湘潭市,鄱阳湖生态经济区内的南昌市和鹰潭市,以及皖江城市带内的六安市和合肥市。     

Digital financial inclusion and investment diversification: Evidence from China

We examine the impact of digital financial inclusion on the diversification of individual stock investments in China using nationwide data from the Chinese Stock Market Individual Investor Survey and the Peking University Digital Financial Inclusion Index of China. We show that digital financial inclusion significantly increases the diversification of individual stock investments, primarily by reducing investors' perceived transaction costs and mitigating investors' limited attention. It also plays a more significant role among investors with lower conventional financial development, lower financial literacy, below 45 years old, shorter investment experience and females. We recommend the continued promotion of digital financial inclusion to optimise asset allocation in Chinese households.     

专利联盟成员技术竞合对成员创新绩效的影响

专利联盟存在竞合现象，联盟成员技术竞合究竟是阻碍创新还是激励创新？着眼于专利联盟成员竞合网络，将技术合作划分为探索式合作和利用式合作，将技术竞争划分为学习型竞争和诉讼型竞争，以2006—2019年MPEGLA公司12个专利联盟的76个成员为研究样本，运用负二项回归实证检验专利联盟成员技术竞合对联盟成员创新绩效的影响。研究发现：探索式合作、利用式合作和学习型竞争有利于成员创新绩效提升，而诉讼型竞争不利于成员创新绩效提升；学习型竞争和诉讼型竞争对双元合作的创新激励效应均具有显著负向调节作用。     

劳动力禀赋、耕地破碎化与农户生态耕种决策行为

目的 为清晰识别影响农户生态耕种决策行为的影响因素，为我国农业可持续发展，加快耕地数量、质量和生态“三位一体”保护目标的实现提供参考。方法 文章利用江西省11市47县（区）共1 488份农户的调研数据，从农户劳动力禀赋结构转变和小农生产造成耕地破碎的两大社会现象切入，采用双栏模型将农户生态耕种决策行为分为采纳意愿和采纳程度两个阶段进行实证分析研究。结果 （1）以中位数为划分依据，有生态耕种采纳意愿的农户数占样本总数的67.20%，有采纳意愿的农户对10项具体生态耕种行为的平均采纳数为5.323项；（2）家庭总人口对农户生态耕种采纳意愿与采纳程度均呈负相关、劳动力人数均呈正相关，兼业程度对农户生态耕种采纳程度呈正相关，耕地破碎化对农户生态耕种采纳意愿呈负相关；（3）农户生态耕种决策行为还受到受教育程度、农业收入占比、是否加入合作社、是否享受农业补贴等因素影响。结论 政府及相关管理部门一方面应注重农户临时务工平台搭建，拓展相关信息视野以提升生态耕种采纳度；另一方面应规范和推动土地流转与土地整治，促进土地规模化经营，降低破碎度。     

Use of high-frequency data to evaluate the performance of dynamic hedging strategies

The hedging performance results of generalized autoregressive conditional heteroskedasticity models are mixed; we address this herein by adopting an asymptotic setting to determine the relative performance of competing hedge ratios. The proxy variable is constructed through precise realized measures rather than through noisy squared returns because the substitution of the latent true hedged portfolio variance with a noisy proxy renders the loss function incapable of ranking forecasts consistently. The merits of allowing some features in modeling the spot–futures distribution are assessed. Empirical comparisons suggest that hedgers may favor the wrong model when the quality of the proxy variable deteriorates.     

新财税政策下的职工基本养老保险最优缴费率测算研究

企业职工基本养老保险缴费率作为养老保险制度的关键性要素,受到专家学者的普遍关注,企业缴费率高、缴费压力大已成为制约企业发展的重要因素。本文综合运用灰色关联、因子分析与回归、动态调整和模拟预测的方法,构建企业基本养老保险缴费率适度水平的因子测算模型,以上海市2008—2019年的数据作为样本进行测算与预测。结果显示:缴费率的适度水平处于19%～23%;增加国有资产划转10%补充社保基金以及中央调剂金制度等参数后,模拟预测2018—2025年的缴费率适度水平在14.8%～18.6%之间,说明企业职工基本养老保险的缴费率有进一步下降的空间。     

Effects of shared characteristics between eco-labels: A case for organic and local food

Food labels are created to reduce information asymmetry and help consumers make better food choices. However, the labels may have unanticipated effects, especially when they share common characteristics that may introduce confusion in making food choices. This study investigates how perceived relationships between different food labels may affect the price premiums of organic and local attributes for milk and fresh strawberries. Results show that the impacts of perception vary by product and label, and different food labels could positively affect price premiums on organic and local products. Results provide policy implications for better labeling and educational programs to reduce inadvertent confusion and improve consumer decision-making.     

Growth and optimal policies in an R&D-growth model with imperfect international capital mobility

In this paper, we examine the effects of international capital mobility on innovation, growth, and optimal growth policies in a small open economy with R&D-driven growth. Households can borrow funds from an imperfect international capital market to finance their investment in R&D firms. We show that the economy can reach a higher growth rate if international capital is more mobile. This result is consistent with recent empirical findings. Moreover, we show that the common growth-enhancing policies, such as patent protection and the R&D subsidies, have an additional negative welfare effect when households can access the international capital market. Accordingly, the optimal patent protection and R&D subsidy should be smaller when the degree of international capital mobility is higher.     

我国东中西部地区创新效率差异研究 ——基于电子及通信设备制造业产业聚集视角

利用2009-2019年我国电子及通信设备制造业省级面板数据，将产业创新过程划分为知识生产与成果转化两个阶段，利用区位熵指数对产业集聚度进行测量，通过Malmquist指数计算区域创新效率，构建两阶段知识生产模型，研究产业集聚对区域创新效率的影响。研究发现，产业集聚与区域创新效率并未呈现传统的东高西低分布特征，并且知识生产阶段的区域创新效率高于成果转化阶段。同时，面板随机前沿回归结果显示，产业集聚阻碍区域创新效率提升，不利于区域创新，而来自政府资金、政策等方面的支持会在知识生产阶段促进区域创新效率提升，在成果转化阶段阻碍区域创新效率提升。最后，根据研究结论，从政府与企业两个方面给出提高区域创新效率的相关建议。