云南省耕地生产效率的时空差异及影响因素

以第二次全国土地调查完成以来的2009~2013年为研究时段,在测算云南省16个州(市)的耕地生产效率基础上,综合运用ESDA技术、基尼系数等方法系统分析云南省耕地生产效率的时空差异,并构建计量经济模型研究影响不同区域耕地生产效率变化的主要因素。结果表明:(1)2009~2013年,云南省耕地生产效率呈总体上升趋势,但增幅逐年降低;效率低值地区增长明显,高值地区则并不显著;(2)云南省耕地生产效率区域差异呈缩小态势,并表现出由西南向东北递减的空间分布特征;(3)滇中、滇西南等粮食主产区受≤6°耕地面积比重、旱涝保收面积的影响较大,而滇东地区则更易受到6°坡耕地面积和人均GDP的影响,滇西北地区受≤6°耕地面积比重和人均GDP的影响显著。     

市场机制引入对城镇新增建设用地配置效率的影响

市场机制引入是否可以提高城镇新增建设用地配置效率优化城镇新增建设用地配置体系是学界和政界关注的热点问题。本文以实施"地票"交易政策,尝试引入市场机制配置城镇新增建设用地的重庆市为典型区域,结合理论分析与实证检验,通过构建以Logit模型为基础的"地票"指标流转模型,利用重庆市2008—2012年38个区县的"地票"交易数据,定量分析"地票"指标市场化流转行为及其关键影响因素,从而探究市场机制引入对城镇新增建设用地配置效率的影响。研究结果表明,重庆市各区县城镇建设用地边际产出与区域"地票"指标的流入行为存在正向的作用关系,而与"地票"指标的流出行为存在负向的作用关系。在市场机制的作用下,市场上的"地票"指标主要由城镇建设用地边际产出较低的区域提供,而"地票"指标最终流入了城镇建设用地边际产出相对较高的区域,从而拉平了区域之间城镇建设用地边际产出,一定程度上提高了城镇新增建设用地配置效率。为此,认为伴随着"地票"交易政策的实施,重庆市逐步形成了一种计划配置为主、市场配置为辅的混合型城镇新增建设用地配置体系,这种配置体系极大地增加了指标供给的弹性并优化了指标的配置效率。因此,我国应积极尝试在现有城镇新增建设用地配置体系中引入市场机制,引导地方政府从"增量"、"计划"的用地理念逐步向"存量"和"市场"的用地理念过渡,最终形成以区域资源禀赋和实际需求为导向的城镇新增建设用地配置体系。     

Elasticity Ratio of Resource Consumption and the Resource Consumption

Today the resources are becoming scarcer, which should not be regarded as unexhausted any more. Correspondingly, the production would be constrained by the scarcity of resources clearly. Then the economic researchers would pay much more attention to reducing the consumption of natural resources in the future. Therefore this paper brings foreword the conception of elasticity ratio of resource consumption based on the concept of elasticity and analyzes the relationship between the parameters. For the certain relationships between the elasticity ratio of resource consumption and resource consumption, this paper will try to reveal, to keep economy growing while resource consumption reducing, what conditions should be met as to the relationships among resource productivity, its growth rate, energy saving efficiency, economic growth rate and elasticity ratio of resource consumption. This paper proves the relationship between the China＇s energy consumption and economy growth using statistic data from 1978 to 2003.     

颗粒层非稳态过滤捕集效率的研究

为计算颗粒层非稳态过滤效率,通过改进经典过滤理论模型,考虑颗粒在过滤介质中的沉积,理论推导得出非稳态过滤效率的计算公式,而经典颗粒层过滤效率计算公式仅为此计算公式的特例。因为理论计算公式是隐函数,不便于工程实际应用,所以,在常温条件下,对非稳态过滤时的过滤时间、过滤风速、过滤层厚度、粉尘浓度和颗粒层滤料均粒径等五个因素进行了正交实验研究。采用多元回归的方法得出各影响因素与过滤效率呈显性关系的效率关联计算公式,其计算结果与实验测试结果基本吻合。     

水资源短缺条件下绿洲的建设和发展——以卡拉—铁干里克垦区为例

在水资源短缺条件下,垦区农业发展采取了多种经营,发展以棉花、水果和养鹿为主的高效特色农业,同时加强工程建设,进行水资源开源节流,强化管理和对绿洲的保护,这些已成为维持绿洲稳定和促进绿洲农业经济发展的关键措施。     

二次旋流强化型气旋浮技术的分离特性

现有气旋浮装置在运行过程中普遍存在旋流强度衰减程度过大等问题,限制了其分离性能的提升,基于此,分析了二次旋流强化作用对气旋浮罐内旋流强度和分离性能的影响特性;借助CFD数值模拟方法和响应曲面法等手段对基于二次旋流强化气旋浮罐主要结构的参数进行了优化,对比分析了常规气旋浮罐和二次旋流强化气旋浮罐的内部流场和油水分离特性。结果表明,采用二次旋流强化结构可以有效提高旋流强度,加速“油滴-微气泡黏附体”向旋流中心汇聚,优化后的气旋浮罐油水分离效率提高至94.5%,较常规单级气旋浮罐提高了10%;二次旋流强化结构是提升气旋浮分离过程中旋流强度和提高气旋浮装置分离性能的有效途径。以上结果可进一步推动气旋浮装置性能的优化和结构创新,可丰富完善该技术设计的理论体系。     

印刷过程VOCs废气收集方式选择与优化

为提高印刷过程中VOCs废气的收集效率和合理控制废气净化系统规模,对废气收集方式进行了选择与优化,采用现场测试和数值模拟相结合的方法,对平版印刷过程中VOCs扩散模式进行分析,采用数值模拟方法对常用的外部接收罩、半密闭罩和密闭罩等3种收集方式的效果进行了估算并与实验数据进行了比较。结果表明：由数值模拟得到的VOCs浓度分布趋势与现场测试结果基本一致;密闭罩和半密闭罩达到90%以上收集效率时的最小控制风量分别为160 m³·h⁻¹和320 m³·h⁻¹;外部接收罩在最大设计风量(1 280 m³·h⁻¹)下,收集效率仅为80%;考虑到印刷过程操作条件的限制,在外部接收罩的基础上,增设垂直挡板和三角形格栅,对其进行结构优化,当控制风量为640 m³·h⁻¹时,外部接收罩收集效率由优化前的70%提高到91%。     

PRICING IRRIGATION WATER IN DEVELOPING COUNTRIES1

ABSTRACT Alternative combinations of water pricing and regulations are possible in allocating irrigation water. The best combination will depend on the value of water, ability to control deliveries, desire to subsidize agriculture, ownership traditions, crops grown, return flows, drainage problems, staff training, ability to collect fees, the number of farmers involved, etc. Marginal cost pricing is just one possible alternative and it is more a way of thinking about prices rather than a set system. The possibilities for achieving an equitable and efficient distribution of water are improved if some form of marginal cost pricing is included in the system of water charges.     

VALUATION OF IMPROVED IRRIGATION EFFICIENCY FROM AN EXHAUSTIBLE GROUNDWATER SOURCE1

This paper presents estimates made via a recursive linear programming model of the net benefits of improving irrigation application efficiency from an exhaustible groundwater source. Net benefits were derived for different application efficiency levels under furrow, sprinkler, and LEPA irrigation systems. In addition, net benefit estimates were obtained for the transition across irrigation systems. Solutions from the model indicate that low crop prices have a differential impact on net benefits across irrigation application efficiencies and irrigation systems. Also, the more limited groundwater situations consistently reduce the economic incentive to adopt improved irrigation application techniques across all irrigation systems.     

ECONOMIC EVALUATION OF ON-FARM WATER MANAGEMENT PROJECTS1

ABSTRACT: During the last three decades, developing countries have invested enormous amounts of resources (running into billions of dollars) in the development of large surface irrigation systems. Investment funds were largely spent on the development of the main systems such as dams, canals and distributaries. Very little attention and resources have been spent on the development of below-the-outlet subsystems, in spite of very low levels of water use efficiency due to lack of proper land leveling, high water losses in field channels, and skewed distribution of available water among farmers served by individual water courses. This state of affairs has resulted in a lack of confidence on the part of most farmers in the reliability of surface irrigation systems to deliver water on time and in adequate quantities which, in turn, has resulted in farmers using below optimum levels of all other complementary inputs except labor. Realizing the importance of improving water use efficiency, both the domestic governments and donor agencies are increasingly paying serious attention to these problems. On-Farm Water Management (OFWM) as a strategy to improve water use efficiency and consequently agricultural production in many developing countries has been currently receiving very wide and vigorous consideration among economists, water management experts, policymakers, and donor agencies. A judicious use of the newly allocated funds of OFWM projects obviously needs proper evaluation procedures so that money could be allocated for the most deserving purposes and projects. In particular, recently, private profitability calculations due to public investments in OFWM activities have received attention from economists and decision makers in developing countries’governments and in donor agencies are very much interested in knowing the impacts of their investments in OFWM activities on farmers’income and welfare. However, the evaluation procedures commonly used in empirical studies, using a production function approach, seem to be at variance and sometimes inconsistent with proper comparative-static procedures. Thus, the primary objective of this paper is to develop consistent procedures for evaluating the impacts created by OFWM investments on farmers’income and resource use. In this context, the paper examines the critical relationship between the market price of the agricultural output and production function parameters which are affected by the OFWM investments.