轮轨关系中的等效锥度对车辆动力学性能的影响

轮轨关系涉及到轨道车辆运行的稳定性和安全性,轮轨匹配问题越显的重要。作为轮轨匹配的最重要参数之一等效锥度,与车辆的动态横移量和滚动圆半径差存在着一定的关系,影响着车辆动力学性能。     

确定性等值法在经理股票期权定价中的应用研究

布莱克-斯科尔斯模型建国际上通用的期权定价模型，但这一模型应用于经理股票期权价值的确定却遭到越来越多的批判。针对经理股票期权的特征，文章拟采用“确定性等值法”束科学、合理地解决经理股票期权价值的确定问题。这将有利于股权激励机制的优化，从而达到最优激励效果。     

PBSZT大功率压电陶瓷介温特性的研究

为制备高性能、低损耗、高居里温度适于大功率应用的PZT基压电陶瓷,对Pb0.9Ba0.05Sr0.05(Sr1/3 Nb1/3)0.06(Zn1/3Nb2/3)0.06Ti0.44Zr0.44O3 0.5%Mn(NO3)2(质量分数)体系材料进行Sb2O3掺杂改性.结果表明,随着掺杂量增加,居里温度和介电常数均降低.而再添加ω(CeO2)=0.7%,掺杂后能得到较高的介电常数(εr=1783),更低的介电损耗(tanδ=0.41%)和较优的压电性能(d33=294),能满足大功率应用的要求.     

No Arbitrage Condition for Positive Diffusion Price Processes

Using the Ray-Knight theorem we give conditions for anonnegative diffusion without drift to reach zero or not. These results also givenecessary and sufficient conditions for such a diffusion process to be a martingale (and notjust a local martinagle). We apply these results in order to give necessary and sufficientconditions for nonnegative diffusion to have equivalent local martingale measures.     

分级填筑过程中软土路基稳定性失效的演化机制

为有效解决分级填筑过程中软土路基的沉降和侧向位移问题,确保路基质量和安全稳定,本文结合河北省沿海高速公路软土路基分级填筑工程实例,采用有限元技术通过对分级填筑荷载下的软土路基变形特征展开数值模拟计算,从土体相对抗剪强度、位移增量以及塑性区开展等三个方面研究了软土路基稳定性发生失效的演化机制,研究内容对路基稳定性分析、信息化施工等方面具有一定的理论指导意义和工程借鉴作用。     

Allocation of Time and Household-level Consumption Equivalent Welfare: A Case of South Korea

Using “2014 Time Usage and Quality of Life” of 17th KLIPS (Korean Labour and Income Panel Study), the first and most detailed time use survey of its kind in South Korea, we first document the patterns of time use in market work, nonmarket work (household work), child care, and a variety of definitions in leisure. We find that, while men work longer hours, men’s additional market work is well compensated by more leisure and less hours in nonmarket work and child care. We also find within-household unequal distribution of time use in nonmarket work, child care, and leisure in favour of men. Consistent with the cases of the US and other advanced economies, high-income earners tend to enjoy less hours of leisure while they spend more money on leisure activities. Secondly, we calculate the household-level consumption equivalent measure that considers consumption, leisure, life expectancy, and uncertainty. We find that taking into account non-separable preference over leisure and consumption and the quality of leisure is important and household-level welfare measures based solely on income or consumption are both incomplete and misleading.     

重力坝坝踵等效应力法

针对重力坝坝踵应力集中问题,在研究分析现有方法的基础上,提出重力坝坝踵等效应力法。这种方法思路是:承认离开坝踵一定区域外部分由有限元计算所得的结果,在坝踵部位用等效应力替代原有计算值。则此方法可以大大降低应力集中的影响且计算简便,同时具有一定精度,所以该方法有一定实用价值。     

基于改进价值当量因子的北京市生态-经济协调度实证分析

从城市生态经济系统协调的视角,构建生态系统服务价值和生态经济协调度指数测算模型框架。以北京市16个辖区为基本研究单元,基于修正后的当量因子法,利用北京市2009—2018年土地利用相关数据,对北京市辖区10年间的生态系统服务价值进行了动态估算,并分析了10年间生态-经济协调度的变动规律。研究结果表明:近10年人类活动或自然环境变化对未利用土地的影响最大,其次是建设用地、园地、耕地、水域及水利设施用地、草地、林地;生态系统服务总价值均呈现总体增长趋势,密云区、怀柔区、延庆区占比前三;大部分地区生态经济协调度总体上升为较高协调,局部生态经济协调度没有改善,整体生态经济协调度较好。并根据北京市的生态服务价值与土地利用动态变化特点,综合考虑生态-经济协调度发展等级分类等情况,提出北京市生态-经济协调发展及土地利用优化的对策和措施。     

Global warming: Efficient policies in the case of multiple pollutants

This article investigates efficient policies against global warming in the case of multiple greenhouse gases. In a dynamic optimization model conditions for an efficient combination of abatement activities are derived. It is shown how this solution can be decentralised by a system of emission charges. Since the determination of the charge rates should be based on a long time horizon, the impact of sequential planning methods is explored. The parameters of the model are specified with respect to the main greenhouse gases (carbon dioxide, methane, nitrous oxide, chlorofluorocarbons) and a scenario for an efficient charge system is calculated. For the main emission sources the tax base and the likely range of tax rates is derived. The results illustrate that efficient policy measures against global warming will not only affect the use of fossil fuels but will also impose a considerable burden on modern agriculture specialising in livestock and in intensive farming techniques.