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。     

油气管道环焊缝新型修复技术研究

为了寻求适应高钢级油气管道环焊缝缺陷的新型修复方法,克服传统修复技术的局限性,提出了电弧增材制造技术用于油气管道环焊缝修复的可行性。首先,对激光熔覆、冷喷涂、电弧增材制造3种新型修复技术进行对比分析后,采用电弧增材制造技术进行实验研究;其次,在X80管道环焊缝处沿轴线截取22 mm厚的试样,并在环焊缝处设计坡口角度为60°,坡口深度为11 mm的缺陷,采用电弧增材制造冷金属过渡工艺、ER50-6焊丝进行修复实验;最后,对修复试样进行力学实验测试,并对实验数据和断口形貌进行分析。实验结果表明,电弧增材制造修复后试件抗拉强度最高达639 MPa,强度与管体基材匹配。研究结果表明,电弧增材制造技术用于X80油气管道环焊缝缺陷的修复是可行的,具有沉积效率高、成本低、力学性能能满足修复要求的特点,对于高钢油气管道环焊缝缺陷修复的可行性和经济性具有重要的现实意义。     

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。     

西气东输工程用大口径X70级螺旋埋弧焊钢管的力学性能研究

以大量生产检验数据,对西气东输管线的力学性能进行了综合研究,并对其受包申格效应的影响情况进行了分析.     

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.     

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.     

Measuring the liquidity part of volume

Based on the concept that the presence of liquidity frictions can increase the daily traded volume, we develop an extended version of the mixture of distribution hypothesis model (MDH) along the lines of Tauchen and Pitts (1983) to measure the liquidity portion of volume. Our approach relies on a structural definition of liquidity frictions arising from the theoretical framework of Grossman and Miller (1988), which explains how liquidity shocks affect the way in which information is incorporated into daily trading characteristics. In addition, we propose an econometric setup exploiting the volatility–volume relationship to filter the liquidity portion of volume and infer the presence of liquidity frictions using daily data. Finally, based on FTSE 100 stocks, we show that the extended MDH model proposed here outperforms that of Andersen (1996) and that the liquidity frictions are priced in the cross-section of stock returns.