政府在耕地减少中的责任和在耕地保护中的作为

集成曲线估计模型和灰色数列模型,研究耕地总量在1983-2006年间的变化过程以及在2010～2020年间的变化态势,分析政府行为在耕地总量减少中的责任和在保护耕地中的作为.研究结果:2020年耕地总量可能低于新的耕地红线,政府对耕地减少负有不可推卸的责任.     

Impact of copula choice on the modeling of crop yield basis risk

A number of problems in agricultural economics involve modeling joint distributions for which the assumption of multivariate normality may not be warranted. Yet, very little work has been conducted evaluating competing methods for modeling joint dependence. We develop a simulation framework to evaluate the bias and efficiency impacts of copula choice in the context of evaluating county‐to‐farm basis risk. The results suggest significant differences in performance across various copulas and approaches. The findings have important implications for risk analysis, insurance, and policy modeling problems in agriculture regarding the selection of method to model dependence among random variables.     

Shifting cultivation and forest pressure in Cameroon

Shifting cultivation is often blamed as a principal cause of deforestation in tropical Africa. It is claimed that the practice is unsustainable because shortened fallow lengths result in soils too degraded to support forest vegetation. The decline in fallow lengths is often attributed to increases in population density and greater market participation. The conventional wisdom makes several claims that are as yet unsubstantiated. This article investigates whether there is evidence to support two of these claims in southern Cameroon. First, using both cross‐sectional and panel data, I find that there is indeed a robust negative association between fallow lengths and population density in the study area and weaker evidence for a negative relationship between fallow lengths and market participation. Second, a stochastic frontier production function approach is used to investigate the marginal contribution of fallow to output. Results indicate that fallow lengths are not low enough to be affecting yields and therefore do not appear to be resulting in declines in soil fertility. Thus overall, while some of the assumptions of the conventional wisdom appear to be true, there is little evidence to support its dramatic conclusion that shifting cultivators are causing deforestation in the forested region of Cameroon.     

"省地宜居型"住宅--城市人居环境建设的优选模式

通过对上海近期建设的分布于不同区位的不同模式住宅区的调查,分析了近年上海住宅区建设的趋势和存在的问题,并结合国外住宅发展经验,以"省地宜居型"住宅为目标,提出了具体建议.     

Public spending,public governance and economic growth at the Vietnamese provincial level: A disaggregate analysis

This study examines the role of economic governance in the relationship between public spending, private investment, and economic growth in Vietnam at the provincial level. The study data consist of sixty-two Vietnamese provinces for the period 2006–2015. Some notable results are attained by applying a sequential (two-stage) estimation. First, the marginal benefits to economic growth of increased Vietnamese provincial government expenditures may be constrained because of the inefficiency of expenditures on education, business services, and public administration. Second, public spending and private investment are found to be substitutes at the provincial level. Third, based on the Provincial Competitiveness Index (PCI) ranking, used as a proxy for provincial public governance in Vietnam, the significance of public governance can be observed. The study concludes that good governance, characterized by different attributes, such as lower informal charges, greater transparency, and unbiased policy, plays a critical role in improving the impact of government expenditure on economic growth in Vietnamese provinces, particularly through its interactions with private sector investment.     

经济密度、人口规模与环境污染——基于城市面板数据的实证分析

选取2005-2016年285个地级及以上城市数据,利用静态和动态短面板模型分析经济密度和人口规模对环境污染的影响,分析表明:经济密度与环境污染之间存在“倒U型”关系,人口规模扩大会抑制污染物排放;不同等级城市经济密度、不同规模城市人口对环境污染的影响方向一致,但影响程度有所差异;前期污染排放对当期具有正向影响,环境污染物排放存在路径依赖;经济发展水平、工业产值占比和对外开放也是影响污染物排放的重要因素,但各指标对三类污染物排放的影响方向和影响程度存在差异。据此认为,在综合考虑城市具体空间区位条件下,人口适度集聚,提高城市经济密度,优化产业结构以及加强环境监管是环境治理的重要方向。     

The Benefit Function Approach to Modeling Price-Dependent Demand Systems: An Application of Duality Theory

In this article, we advocate more extensive use of the benefit function in specifying price-dependent or inverse demand models. We demonstrate how duality theory may be used to establish the interrelationships between the Marshallian (or Hicksian) inverse demands and Luenberger's adjusted price functions, allowing estimable inverse demands to be derived directly from a benefit function. We estimate two systems of inverse demands for Japanese quarterly fish consumption. Results indicate that the procedures and methods employed here appear promising, and may prove beneficial for quantity and welfare analysis when modeling systems of inverse demand functions.     

基于耕地保护的中国城镇化发展战略研究

研究目的：研究中国城市位序 — 规模规律的演化和城市建成区人口密度同城市规模关系的变化,预测未来城镇化发展占用耕地情况,提出基于耕地保护的中国城镇化发展对策建议。研究方法：文献资料法、回归分析法和函数模型预测法。研究结果：中国城市建成区人口密度随城市人口规模的增加而增加,但正在快速下降,中国城镇化同耕地保护之间的矛盾日益突出。研究结论：为更加有效地保护耕地,中国应加快制定以发展大城市为主导,各级城市城镇全面发展的城镇化战略,推行高人口密度的城镇化发展政策措施,走紧凑型城镇化道路。     

基于Supermap和Google earth的城中村改造面积估算——以广州市海珠区为例

城中村多存在于经济发达的城市,广州是珠三角地区的发达城市之一,在广州市区内,共存在138个城中村。城中村的存在为广州市内广大的外来工作人员提供了价格低廉的住房。可是,近10年来,城中村的问题日益凸显,促使广州市政府对城中村进行大规模的整治和改造。对广州城中村的面积进行估算,能够得到广州城中村的面积、区位等数据。本文对广州城中村的面积估算方法进行探讨,并使用Supermap Deskpro软件和Google earth软件对广州市海珠区的城中村面积进行估算,从而了解广州城中村的规模、分布区位及其分布特征,为城中村的改造和整治提供基础数据。     

大频偏卫星扩频信号的基带处理算法的FPGA实现

多普勒频偏一直是卫星通信中不可忽视的消极因素。针对多路混叠的卫星扩频信号下变频以后所产生的大多普勒频偏,在匹配滤波结构中采取改进的部分相关算法,在基于并行导频的信道估计中根据信道状况改变估计长度,实现了大频偏下卫星扩频信号的基带处理。