基于DEA的传统农耕地区农业生产效率测度*——以皖北为例

［目的］农业生产效率是衡量农业生产的重要标准,其生产效率测度结果对研究区域农业经济发展具有重要意义。［方法］文章以皖北农耕地区为研究对象,通过采集2017年统计年鉴的相关数据,构建农业生产绩效评价指标体系,并引入虚拟决策单元,运用数据包络分析（DEA）方法,从自评和他评的角度对2017年皖北各县级单元的农业经济生产效率进行测度,并基于结果的迥异进行效率、冗余及空间分异的分析。［结果］皖北地区农业生产整体效率较低,呈现出粗放式的农业生产模式; 各种投入要素配置不尽合理,皆存在不同程度上的冗余,整体上看塑料薄膜冗余最高、化肥施用的冗余最低; 空间分异显著,南北表现为由北向南逐渐降低的“S”型趋势、东西呈现出两端高中间低的扁平状“v”型空间分异特征。［结论］粗放式的农业生产导致了皖北农业生产效率整体较低,应完善生产要素配置,大力推进农业现代化建设,促进皖北地区农业整体性协调发展,提升地区农业生产效率。     

北京地区1km2网格植物气候生产力的估算

该研究利用北京地区1km^2。网格的气候资料,应用桑斯维特纪念模型估算了北京地区植物气候生产力,并利用地理信息系统软件将网格植物气候生产力进行了可视化处理。此估算结果全面系统地表现了北京地区植物气候生产力的空间分布状况：平原区及山前暖区的植物气候生产力普遍大于山区,最大值出现在水热条件较好的平谷区,最小值出现在水热条件较差的西部山区。此估算结果为各级政府管理部门进行产业结构调整和生态环境保护提供了重要的科学依据。     

华北地区某污水处理厂升级改造工程实例

华北地区某城市污水处理厂升级改造工程处理规模为50万t/d,原设计为A/O脱氮工艺,执行《城镇污水处理厂污染物排放标准》(GB 18918-2002)二级排放标准。由于近年来进水水质严重恶化以及对污水排放标准的提高,需对原污水处理系统进行改造,通过技术方案对比,在原生物处理段增加厌氧池,使之变为A2/O脱氮除磷,新增深度处理工艺为反硝化生物滤池-加砂沉淀池-滤布滤池-紫外消毒,使出水水质达到一级A排放标准。     

Impact of modern communication infrastructure on productivity,production structure and factor demands of US industries: Impact revisited

This study investigates the contribution of modern communication infrastructure characterized by high speed broadband access network on the productivity growth, production structure and factor demands for US industries and for the aggregate economy. To evaluate such contribution, we modify the traditional cost function by incorporating communication infrastructure as input in production process in conjunction with other public infrastructures. The network externality and spillover effect of broadband access technology are captured by introducing broadband penetration rate as a shift factor in industry level production function. Empirical results show that the increased use of modern communications infrastructure increases the productivity of all industries with wide variations across industries. Estimated impacts on input demands show that increase in use of communications infrastructure service saves labor and materials and increase the demand for private capital. Finally, aggregate social rate of return on such investment has been estimated for policy implications.     

基于情感分析混合模型的用户评论主题分析 ——以vivo手机为例

为了帮助商家了解用户需求和产品问题,进一步提升产品和服务质量,对vivo手机评论数据进行基于关键词的词云图分析、社会语义网络分析、舆情时间序列可视化分析,挖掘用户关注焦点与手机特征的内在联系和用户情感倾向趋势;然后对评论数据进行基于LDA的主题特征分析,继而提出一种基于Word2vec和SVM、LDA的混合算法模型,挖掘用户正向和负向情感评论的潜在主题,得到不同情感倾向下用户对vivo手机不同方面的反映情况。分析结果表明,基于混合算法的挖掘结果比基于关键词的可视化分析、基于LDA的主题分析更清晰,更具准确性,为商家提供的建议更有意义。     

Mutual monitoring and corporate governance

Mutual monitoring in a well-structured authority system can mitigate the agency problem. I empirically examine whether the number two executive in a firm, if given authority, incentive, and channels for communication and influence, is able to monitor and constrain the potentially self-interested CEO. I find strong evidence that: (1) measures of the presence and extent of mutual monitoring from the No. 2 executive are positively related to future firm value (Tobin’s Q); (2) the beneficial effect is more pronounced for firms with stronger incentives for the No. 2 to monitor and with higher information asymmetry between the boards and the CEOs; and (3) mutual monitoring is a substitute for other governance mechanisms. The results suggest that mutual monitoring provides important checks and balances on CEO power.     

B2C模式下转换成本对网上顾客忠诚影响实证研究

基于转换成本的视角,本文构建了一个影响网上顾客忠诚的概念模型。实证研究表明,网络程序转换成本、网络财务转换成本与网络关系转换成本这三种网络转换成本均正向影响网上顾客的行为忠诚度,只有网络财务转换成本和网络关系转换成本正向影响网上顾客的态度忠诚度。三种类型转换成本的构成因子对顾客的态度忠诚和行为忠诚的影响机理是不同的:利益损失成本、个人关系损失成本和品牌关系损失成本起着正向影响顾客态度忠诚的作用;评估成本、学习成本、利益损失成本和品牌关系损失成本起着正向影响顾客行为忠诚的作用。     

Bailout uncertainty in a microfounded general equilibrium model of the financial system

This paper develops a micro-founded general equilibrium model of the financial system composed of ultimate borrowers, ultimate lenders and financial intermediaries. The model is used to investigate the impact of uncertainty about the likelihood of governmental bailouts on leverage, interest rates, the volume of defaults and the real economy. The distinction between risk and uncertainty is implemented by applying the multiple priors framework to beliefs about the probability of bailout.Results of the analysis include: (i) An unanticipated increase in bailout uncertainty raises interest rates, the volume of defaults in both the real and financial sectors and may lead to a total drying up of credit markets. (ii) Lower exante bailout uncertainty is conducive to higher leverage, which in turn raises moral hazard and makes the economy more vulnerable to expost increases in bailout uncertainty. (iii) Bailout uncertainty affects the likelihood of bubbles, the amplitude of booms and busts as well as the banking and the credit spreads. (iv) Higher bailout uncertainty is associated with higher returns’ variability in diversified portfolios and higher systemic risks, (v) Pre-crisis expansionary monetary policy reinforces those effects by inducing higher aggregate leverage levels. (vi) The larger the change in bailout uncertainty and the change in aversion to this uncertainty, the stronger the pre-crisis buildup and the deeper the ensuing crisis.A central policy implication of the analysis is that the vaguest is bailout policy prior to a crisis, the lower is the magnitude of investments destroyed or missed due to errors in evaluating bailout and other intervention policies. On the other hand, the clearer is bailout policy upon the eruption of a crisis, the smaller the contraction of credit and the destruction of investment activity.     

Experience,Learning, and Returns to Scale

The experience curve is a tool for forecasting future decreases in average cost as a function of cumulative output/volume. The extent of an experience effect has profound implications for both pricing strategy and the focus on market share as a managerial objective. At the same time, the underlying sources of the experience effect are not well understood. This article demonstrates that, as commonly measured, experience effects are aggregated with the effects of increasing returns to scale. This implies that standard experience curve estimates are misspecified because they suffer from an omitted variable bias. Strategic implications of the experience‐scale link are discussed.     

SVHC第23批新增4项物质测试方法研究

本文建立了同时测定欧盟高关注物质(SVHC)第23批新增的4种物质[1-乙烯基咪唑、-甲基咪唑、4-羟基苯甲酸丁酯、双(乙酰丙酮酸)二丁基锡的气相色谱质谱联用仪(GC-MS)]的检测方法。将样品用二氯甲烷超声后,采用选择离子监控模式(SIM)进行分析样品中的待测物。实验结果表明,4种物质在50 mg/L范围内线性关系良好,线性相关系数为0.995以上;样品加标回收率为94%110%,相对标准偏差(RSD)小于7%;方法检出限分别为2 mg/kg、10mg/kg、0.8 mg/kg、0.6 mg/kg,解决了欧盟新增加的4种SVHC测试问题。