关键驱动力作用下的新疆生态系统服务时空格局分析

[目的]恶劣的生态环境和有限的资源驱动着新疆特殊生态系统服务的形成,人类又通过对生态系统服务的消费来满足和提高自身福祉,需要研究其时空变化并辨识主要驱动因素,支持区域可持续发展。[方法]文章构建了融合不同土地利用类型生态系统服务的价值量排序及服务功能强度矩阵的生态系统服务评估体系,并耦合3种关键驱动因子以评估各个因子的驱动强度,实现对生态系统服务热点与冷点变化的驱动及迁移分析。[结果]2000—2010年全疆生态系统服务总体增加,这一时期生态系统服务的热点区大部分转变为2010—2015年的冷点区,且15年来生态系统服务总体呈现小幅下降趋势。3个时期北疆和南疆人为干扰强度均呈增加趋势,由其驱动的生态系统服务则相应减小;南疆地区植被覆盖范围极其有限,故对生态系统服务驱动强度低;降水在北疆和南疆都能够产生高生态系统服务,但降水量的不稳定性能够使生态系统服务产生较大波动。相比于南疆地区,北疆生态系统在外界干扰下能够体现出更强的抗性和整体性,从而实现相对高效的生态系统服务输出。[结论]对关键驱动因子作用下的生态系统服务进行时空变化分析,有助于理解当地生态系统产生变化的原因,从而为当地生态环境保护提供参考。     

刚度不均匀分布的连体结构的抗震性能分析

通过连接体将两个或两个以上的独立塔楼连接在一起,形成连体结构。在地震作用下,塔楼的变形和内力变化复杂,且两塔楼之间的耦联效果显著。本文采用弹塑性时程分析法,研究其在罕遇地震作用下的动力响应,并且通过对不同对称性、平面内不同刚度分布、不同跨度的结构进行弹塑性时程分析,分析结构的对称性、跨度的参数对结构动力响应的影响。     

Changing land use intensity in Europe – Recent processes in selected case studies

In recent decades the intensification of agricultural production in many European countries has been one of the key components of land-use change. The impact of agricultural intensification varies according to national and local contexts and a greater understanding of the drivers of intensification will help to mitigate against its negative impacts and harness potential benefits. This paper analyses changes in land use intensity in six case studies in Europe. A total of 437 landowners were interviewed and their responses were analysed in relation to changes in land use intensity and agricultural production between 2001 and 2011. In the case studies in Western and Eastern Europe we observed stabilisation during the last decade, and no clear tendency of increase or decrease of land use intensity. The use of fertilizers and pesticides seems to have decreased in our cases in Western Europe, which is contrary to trends in Eastern Europe. Agricultural production remained stable in almost all cases, except for an increase in Austria and Romania which may indicate that the farming efficiency has increased. A statistical analysis showed a division between study areas in Romania and Austria (increasing land use intensity) versus those in the Netherlands, Denmark and Greece (decreasing). In the Mediterranean cases we observe a process where agriculture is becoming increasingly marginalised, at the same time as changes in function with regard to urbanisation and recreational land uses have taken place. Logistic regression highlighted the importance of farm size and farmer type in understanding changes in land use intensity. The dominant pattern of stabilisation which has occurred over the past 10 years may also partly be a result of effective EU and national environmental and agricultural policies, which are increasingly concerned with improving environmental conditions in rural areas.     

农村土地流转中土地租金差异化动因及影响研究

随着城镇化的发展,大量农民进城务工,农村土地流转是必然趋势。经过调查研究发现,在土地流转中,不同主体对土地租金的期望不同,进城务工农民对土地租金的期望不高,而留守劳动力对土地的租金要求较高,且期望的租金还要包括劳动力机会成本。留守劳动力对土地租金的博弈直接导致了土地规模化经营中土地租金的高涨,使土地规模经营收益出现倒挂,但政府的补贴又维持了这种不健康的租赁关系。农地租金的非理性增长影响了自耕农的壮大和发展,使农地规模化经营偏向公司化,农业公司对利润的博弈导致了套取政策补贴、农地非粮化等问题,土地规模化经营前景堪忧。建议构建进城农民土地退出机制、扶持培养自耕农、建立多种途径的农业经营合作模式、提高农民社保水平等措施,促进农地经营良性发展。     

ARBITRAGE‐FREE BILATERAL COUNTERPARTY RISK VALUATION UNDER COLLATERALIZATION AND APPLICATION TO CREDIT DEFAULT SWAPS

We develop an arbitrage‐free valuation framework for bilateral counterparty risk, where collateral is included with possible rehypothecation. We show that the adjustment is given by the sum of two option payoff terms, where each term depends on the netted exposure, i.e., the difference between the on‐default exposure and the predefault collateral account. We then specialize our analysis to credit default swaps (CDS) as underlying portfolios, and construct a numerical scheme to evaluate the adjustment under a doubly stochastic default framework. In particular, we show that for CDS contracts a perfect collateralization cannot be achieved, even under continuous collateralization, if the reference entity’s and counterparty’s default times are dependent. The impact of rehypothecation, collateral margining frequency, and default correlation‐induced contagion is illustrated with numerical examples.     

候变化对我国种植业化肥投入的影响

气候变化不但会对农业产出产生影响，而且还会对农业生产要素投入产生影响。利用我国26个省2001—2012年的面板数据，实证分析气温和降水量变化对我国种植业生产中化肥使用强度的影响，结果表明：从整体看，年平均气温上升有助于降低化肥的使用强度，而年降水量的增加则会提升化肥的使用强度；对于热带亚热带季风气候区，降水量增加、气温上升均会导致化肥使用强度增加；对于温带季风气候区，气温上升会导致化肥使用强度下降，但是降水量增加对化肥使用强度的影响不显著。气候变化对不同气候区农业生产的化肥投入具有不同的影响，因此有关化肥控制的政策有必要考虑气候因素的影响，政策目标的设定也应体现区域差异。     

The role of inventories and capacity utilization as shock absorbers

We examine the role of inventories and capacity utilization (of both capital and labor) for the propagation of business cycle fluctuations. We document a new set of facts regarding the U.S. cyclical regularities of inventories and capacity utilization. First, we find that capital utilization and the flows of services from both capital and labor are procyclical, and comove with the holdings of inventories. Second, we find that labor utilization is procyclical as well, but is weakly negatively correlated with inventories. We build a model that accounts for these facts, and also accounts for the stylized inventory facts, i.e., inventory holdings are procyclical, while the inventory-to-sales ratio is countercyclical. The analysis is centered on the effects of two possible shocks: preference (demand) shocks and technology shocks. Our model shows that inventories and the rate of capital utilization are mostly complements, while inventories and the rate of labor utilization are mostly substitutes. It further shows that temporary demand shocks emphasize the role of inventories as being a “shock absorber,” whereas high-persistence demand shocks, as well as technology shocks of any persistence, emphasize the role of inventories as being a complement to consumption.     

Revisiting carbon disclosure and performance: Legitimacy and management views

With corporate disclosure of carbon emissions rapidly increasing, the long-standing question remains whether carbon disclosure has any influence on the improvement of carbon performance. Previous studies of environmental disclosure and performance have predominantly focused on whether disclosure is a substitute for poor performance. Little attention has been devoted to the more important question about how changes in disclosure may lead to subsequent changes in performance over time. Following the rationales taken by the legitimacy and management perspectives, we revisit the relationship between carbon disclosure and performance, with a focus on changes that disclosure may (or may not) create. Using a change analysis of Global 500 companies and their carbon emission and disclosure data released between 2008 and 2012, this study finds that the change in carbon disclosure levels is positively associated with a subsequent change in carbon performance (examined through direct and indirect carbon emission intensities). Thus, regardless of whether disclosure has been used as a legitimising tool for prior poor performance, this study confirms that carbon disclosure motivates companies and creates an ‘outside-in’ driven effect for subsequent change and improvement in carbon performance. However, the association between changes in carbon disclosure and performance is relatively weaker in high energy-intensive firms.     

最优能源强度与我国经济增长

本文通过一个内生增长模型对能源消费与经济增长的关系进行了分析,证实存在使经济增长率最大化的最优能源强度,并且最优能源强度与能源价格反方向变动.在此基础上,估计了近年来我国的最优能源强度,并测算了实际能源强度与最优值的差距.结果表明,近年来我国实际能源强度高于最优值达3万吨标准煤/亿元以上,且有不断上升的趋势.最后提出了在保持最优能源强度的前提下降低能源消耗的政策建议.