基于内生经济增长理论的城市化进程中资源环境"尾效"分析

在经济和城市快速发展过程中,资源环境对经济增长和城市化进程的约束越来越凸显.本文正是基于这种背景,研究了有限资源环境对城市化进程的阻碍大小,即城市化进程中资源环境"尾效".首先通过内生增长理论构建资源环境对经济增长的"尾效"模型,再利用经济增长与城市化水平之间的半对数关系推导出城市化进程中资源环境"尾效"模型,然后以江西省为例对其城市化进程中的资源环境"尾效"进行实证分析.计量发现土地、能源、水资源和环境污染对江西省城市化进程的"尾效"大小分别为0.017 678 315,0.114 909 279,0.005 050 95和0.0214 665 3.可见,能源对城市化进程的阻尼作用是最为显著的,其次分别是环境污染、土地和水资源.显然,只有大力提高能源等资源的利用率,将生产方式转移到依靠技术进步上来,并且着力提高人们的节约和保护资源环境意识,江西省城市化才能走上可持续发展的道路.     

中国交通基础设施与经济增长的关系实证

交通基础设施通过乘数效应、旅行效应和外部效应促进经济增长,经济增长是交通基础设施需求增加和规划建设的重要前提.使用中国1952 -2006年相关统计数据,以GDP衡量经济增长,以公路铁路运营里程和货运量衡量交通基础设施,基于协整理论和Granger因果检验方法,分析得出交通基础设施与经济增长间存在长期均衡关系,前者是后者的Granger原因,反之不成立;引入Cobb - Douglas生产函数建立回归模型,采用主成分回归法修正最小二乘回归模型易受多重共线性影响的缺点,发现交通基础设施对经济增长具有显著的促进作用,且公路交通基础设施对经济增长的贡献率显著大于铁路交通基础设施;以1978年为时间断点,运用虚拟变量法,检验样本期内交通基础设施对经济增长影响是否发生结构性变化,发现1978年前后交通基础设施对经济增长的促进作用统计上相同.     

人力资本积累与地区经济增长的联动关系分析

人力资本积累与地区经济增长差距的关系问题,是国内外理论界关注的焦点之一.为什么中国的地区经济增长在经济转型期20世纪80年代呈现收敛而90年代后发散?人力资本究竟是怎样作用于经济增长的?已有的经验研究没有考虑人力资本积累自身的收敛性,因而没有考虑到人力资本积累与地区经济增长的联立互动关系.本文采用三阶段最小二乘法(3SLS)估计了中国地区经济增长与人力资本增长的联立模型,结果表明,人力资本积累存在自身收敛性,人力资本增长率与地区经济增长率存在同向变化特征;同时,人力资本水平对地区经济增长存在直接发散和间接收敛双重效应,欠发达地区较高的人力资本增长率是导致20世纪80年代地区经济增长收敛的一个重要因素.因此,加大欠发达地区的人力资本投入,促进人力资本积累,对于缩小地区间经济增长差异具有十分重要的意义.     

Detecting Density Dependence in Recovering Seal Populations

Time series of abundance estimates are commonly used for analyses of population trends and possible shifts in growth rate. We investigate if trends in age composition can be used as an alternative to abundance estimates for detection of decelerated population growth. Both methods were tested under two forms of density dependence and different levels of environmental variation in simulated time series of growth in Baltic gray seals. Under logistic growth, decelerating growth could be statistically confirmed after 16 years based on population counts and 14 years based on age composition. When density dependence sets in first at larger population sizes, the age composition method performed dramatically better than population counts, and a decline could be detected after 4 years (versus 10 years). Consequently, age composition analysis provides a complementary method to detect density dependence, particularly in populations where density dependence sets in late.     

中国区域TFP增长的R&D贡献测度与评价

论文基于中国各省级区域1997-2008年的数据,研究了R&D投入及其溢出对TFP增长的贡献.与现有文献不同的是,我们将R&D投入分解成不同类型:来自政府的投入和来自企业的投入,将区域技术成交额作为区域间R&D溢出的测度.同时,通过Malmquist指数把TFP增长区分出来自于技术效率和来自技术进步率两个因素.结果发现,12年来我国各地区TFP平均增长0.2%.其中,技术进步的贡献为0.9%,而技术效率不仅没有带来TFP增长,反而造成了0.7%的TFP损失.不同类型的R&D活动对TFP影响的程度和方向不同:企业R&D投入对TFP作用的效果最大,且对于东部地区TFP的作用大于中、西部;R&D溢出(技术交易)带来的TFP效应居其次,且对西部地区TFP的作用大于中部,对中部地区的作用大于东部;而政府R&D投入的TFP弹性在三个地区均为负值.这些差异给区域科技政策的制定提供了参考依据.     

丝孢酵母TX1降酚动力学研究及过程优化

针对自行分离筛选出的高效降酚丝孢酵母菌株TX1,通过不同初始浓度苯酚分批培养系列实验结果和分析,建立其降酚动力学模型,并在此基础上进行过程优化.结果表明,体系的生长动力学可以用Haldane方程描述,其参数分别为μmax=0.667 h-1,KS=51.14 mg/L,Ki=271.7 mg/L.参数说明TX1能较快地...     

絮凝剂产生菌B-7的培养条件优化及生长动力学研究

从成都市土壤中筛选分离了1株具有稳定高效的微生物絮凝剂产生菌B-7。考察了碳源、氮源、温度、培养时间、pH等多种因素对絮凝剂（MBF-7）絮凝效果的影响。实验结果表明,该菌株产絮凝剂的最佳培养条件为：碳源为淀粉,氮源为硫酸铵,培养时间为72 h,初始pH为7.0,温度为30℃,对0.4%高岭土悬浊液的絮凝率达到91.3...     

中国环境污染的库兹涅茨曲线检验——基于1997～2006年的面板数据的实证分析

选取我国1997～2006年间省际大气污染、污水和固体废弃物（“三废”）等环境质量指标的面板数据,对中国经济发展与环境污染关系进行了库兹涅茨曲线检验。实证分析表明,在时间区间内经济增长对环境质量有缓慢的改善作用,其他因素对“三废”指标的作用并不确定。发展指标与环境指标更多地呈现N或倒N型曲线关系,环境库兹涅茨曲线在中国省级层面面板数据层面并不成立。     

Dynamic emergy evaluation of a fish farm rearing process

The environmental sustainability of a fish farm rearing process was examined by means of emergy analysis. Many emergy analyses integrate data for a whole year smoothing short term variations and sometimes losing meaningful information (aliasing). For this reason we developed a model for an instantaneous emergy evaluation in an aquacultural system so that transformities, efficiency and effort spent at each moment during the fish rearing activity could be calculated. By means of the model and dynamic emergy calculations it is possible to recognize step by step the importance of the various emergy contributions and verify where and when to modify the system to move toward optimum production of a sustainable product. By the application of the model we confirmed that the emergy trends in a fish farm installation follow wide oscillations during a year due to variations in both internal and external emergy contributions. Among the fluxes considered, those due to the introduction of fingerlings represented the highest contributions to the total emergy budget. Thus, to improve the sustainability of the analyzed system the amount, frequency and timing of these fluxes must be carefully considered. For this purpose, a comparison between two different fry introduction schedules was performed to evaluate differences in the efficiency of the rearing process.     

Phytoremediation trials on metal- and arsenic-contaminated pyrite wastes (Torviscosa, Italy)

At a site in Udine, Italy, a 0.7 m layer of As, Co, Cu, Pb and Zn contaminated wastes derived from mineral roasting for sulphur extraction had been covered with an unpolluted 0.15 m layer of gravelly soil. This study investigates whether woody biomass phytoremediation is a realistic management option. Comparing ploughing and subsoiling (0.35 m depth), the growth of Populus and Salix and trace element uptake were investigated in both pot and field trials. Species differences were marginal and species selection was not critical. Impaired above-ground productivity and low translocation of trace elements showed that bioavailable contaminant stripping was not feasible. The most significant finding was of coarse and fine roots proliferation in surface layers that provided a significant sink for trace elements. We conclude that phytostabilisation and effective immobilisation of metals and As could be achieved at the site by soil amelioration combined with woody species establishment. Confidence to achieve a long-term and sustainable remediation requires a more complete quantification of root dynamics and a better understanding of rhizosphere processes.