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1.
文章通过泰尔指数发现从1990年到2005年,河南省区域经济的差距处于一个快速扩大的阶段。通过定量分析发现,河南省区域经济发展水平和发展速度与农业生产具有一定的负相关性,通过定性和定量分析发现,农业产业化对区域差距缩小具有一定的作用,但不起主要作用,一是由于目前河南省农业产业化水平相对还是比较低,农业收入还仅仅停留于农产品的买卖价格,工资性收入所占比重过低,二是农业产业化龙头企业带动能力还是比较弱,带动面小,限制了农区经济的发展水平和速度,最后提出了几点建议。 相似文献
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Exchanges of total N and C between a river and its floodplain forest have been enhanced by sedimentation processes during flood pulses at a 5‐ha bottomland hardwood forest located at the Olentangy River Wetland Research Park in central Ohio. In the spring of 2000, the forest was hydrologically restored by notching an artificial levee that had separated the Olentangy River and its floodplain forest for 100 years. One‐hundred flat sediment traps (30 cm × 30 cm) were used to collect sediment samples during spring/summer flooding events from 2003 to 2005. Results showed that sediment deposition is determined by the landscape variability during flooding events, Net sediment deposit in the wettest area averaged 134 ± 12 g‐dry wt m?2 in 2003, 127 ± 17 g‐dry wt m?2 in 2004 and 149 ± 23 g‐dry wt m?2 in 2005. Total N and C sedimentation ranged from 0.49 to 0.92 g‐N m?2 and 5.2 to 19.9 g‐C m?2. Fe dominates the sediment chemistry and results show the elemental abundance in the order of Al > Fe > Ca > K > Mg > S > P > Na > Mn > Zn > B > Cu > Mo. A hydrologic pulsing index (HPI) could be used as an indicator for mass changes of energies with hydrologic pulsing events. Restoration of seasonally flooded bottomland forests could stimulate potentially large nutrient and Fe releases, which would eventually lead to an enhanced forest productivity and biodiversity. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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本文研究了经济分析基本方法之一最优等效替代法的实质,系统地导出了被评价方案的绝对经济指标与相对经济指标的关系,并结合典型案例分析指出了该方法的应用条件,对正确进行建设项目的经济评价具有现实意义。 相似文献
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Cristina Vespro 《European Financial Management》2006,12(1):103-127
This paper provides further evidence of price and volume effects associated with index compositional changes by analysing the inclusions (exclusions) from the French CAC40 and SBF120 indices, as well as the FTSE100. I find evidence supporting the price pressure hypothesis associated with index fund rebalancing, but weak or no evidence for the imperfect substitution, liquidity and information hypotheses. The results improve on recent evidence from the S&P500 index. The evidence for the FTSE100 additions shows, in particular, that markets learn about an imminent inclusion and incorporate this information into prices, even before the announcement date. 相似文献
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Impacts of Declining U.S. Retail Beef Demand on Farm-Level Beef Prices and Production 总被引:1,自引:0,他引:1
A systems model was estimated to determine the effects of declining U.S. retail beef demand on farm-level beef prices and production. Retail beef demand declined by nearly 66% from 1976 to 1999. Results indicate autonomous shifts in retail demand significantly impacted farm-level demands and production. Based on equilibrium multipliers, the 1976–99 reduction in beef demand decreased real slaughter cattle prices and production by 32.1% and 11.2%, respectively. Real feeder cattle prices and production decreased by 8.0% and 22.6%, respectively. Combining the decreases in farm prices and production, slaughter and feeder cattle producers experienced a real revenue reduction of $13.3 billion (61%) due to the long-term decline in demand. 相似文献
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水利工程老化、失修是当前工程不能发挥正常效益的主要原因,建立工程老化指标评价体系是解决该问题的基础工作之一。老化是工程建成后在自然因素和人为活动长期连续的作用下,工程效益衰减、构件功能降低及材料性能逐渐变坏的自然现象。河道堤防以土石为主要材料,应以工程的功能为主建立老化指标体系。依据对工程效益和安全的影响程度,水利工程的综合老化度可分为四级。工程损坏后,在防洪工程运用年度内未能修复称为水利工程失修。解决老化问题主要依靠折旧或大修费,而解决失修问题主要依靠运行管理和维修养护费。 相似文献
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Mohammad Najand 《The Financial Review》2002,37(1):93-104
The study examines the relative ability of various models to forecast daily stock index futures volatility. The forecasting models that are employed range from naïve models to the relatively complex ARCH-class models. It is found that among linear models of stock index futures volatility, the autoregressive model ranks first using the RMSE and MAPE criteria. We also examine three nonlinear models. These models are GARCH-M, EGARCH, and ESTAR. We find that nonlinear GARCH models dominate linear models utilizing the RMSE and the MAPE error statistics and EGARCH appears to be the best model for forecasting stock index futures price volatility. 相似文献