Asymptotic comparison at optimal levels of reduced‐bias extreme value index estimators

In this article we are interested in the asymptotic comparison, at optimal levels, of a set of semi‐parametric reduced‐bias extreme value (EV) index estimators, valid for a wide class of heavy‐tailed models, underlying the available data. Again, as in the classical case, there is not any estimator that can always dominate the alternatives, but interesting clear‐cut patterns are found. Consequently, and in practice, a suitable choice of a set of EV index estimators will jointly enable us to better estimate the EV index γ, the primary parameter of extreme events.     

Tail risk in emerging markets of Southeastern Europe

This article examines the left-tail behaviour of returns on stocks in Southeastern Europe (SEE). We apply conditional extreme value theory (EVT) approach on daily returns of six stock market indices from SEE between 2004 and 2013. Predictive performance of value-at-risk (VaR) and expected shortfall (ES) based on EVT is compared against several alternatives, such as historical simulation and analytical approach based on GARCH with a single conditional distribution. Model backtesting with daily returns shows that EVT-based models provide more reliable VaR and ES forecasts than the alternative models in all six markets. Unlike the alternatives, the EVT-based models cannot be rejected as VaR confidence level is increased. This emphasizes the importance of extreme events in SEE markets and indicates that the ability of a model to capture volatility clustering accurately is not sufficient for a correct assessment of risk in these markets.     

出砂强敏感稠油油藏低效水驱转热采政策界限研究——以林东馆三段稠油油藏为例

林樊家油田林东馆三段地质条件复杂,地层敏感性强,供液差,产能低,油稠,出砂严重,多年来采用了各种工艺措施,均未取得好的水驱开采效果。文章运用数值模拟手段,分析了低水驱的主要原因和论证了低效水驱转蒸汽热采可行性。在此基础上,研究了该块低效水驱转蒸汽热采的开发经济技术政策界限。开发实践表明,低效水驱稠油油藏通过转热采可大幅提高采收率,同时研究成果对同类油藏的开发具有重要指导意义。     

改良剂修复重金属污染土壤及环境风险评价

采用改良剂修复技术治理重金属污染土壤是一种有效的技术,土壤改良后的风险评估是一项重要内容。综述了改良剂修复重金属污染土壤后的环境风险评估方法和分析方法,并对今后的研究进行了展望。     

Growth Optimal Investment Strategy: The Impact of Reallocation Frequency and Heavy Tails

The strategy to maximize the long‐term growth rate of final wealth (maximum expected log strategy, maximum geometric mean strategy, Kelly criterion) is based on probability theoretic underpinnings and has asymptotic optimality properties. This article reviews the allocation of wealth in a two‐asset economy with one risky asset and a risk‐free asset. It is also shown that the optimal fraction to be invested in the risky asset (i) depends on the length of the basic return period and (ii) is lower for heavy‐tailed log returns than for light‐tailed log returns.     

环境信息披露与企业环境绩效改善的管理者效应——基于中国重污染企业2011—2015年的数据分析

基于中国97家重污染上市企业2011—2015年间的短面板数据，对高管特征、环境信息披露和企业环境绩效之间的关系进行实证研究，结果显示高管性别、年龄、学历和任期与企业环境绩效均存在显著的正相关关系，企业环境绩效改善过程中存在管理者效应，且环境信息披露的调节效应显著；但高管特征的不同方面对国有企业和非国有企业的环境绩效影响存在差异，高管性别是影响企业环境绩效的重要方面。最后给出了促进中国重污染企业环境绩效改善的意见和建议。     

19世纪末-20世纪初俄国财政对重工业的支持

19世纪末20世纪初正是沙皇俄国逐步走上资本主义工业化发展道路的一段历史时期。在这一时期里,国家的发展重点毫无疑问是工业,尤其是重工业,于是国家财政也将重工业作为自己的扶持对象予以大力支持。     

重型门式脚手架在现浇箱梁施工中的应用

结合浙江省杭州市留石快速路二期工程古墩路跨线桥连续现浇预应力箱梁施工实例并根据以往的施工经验，介绍在支架方案的选择上结合实际地形情况采用多种支架组合，说明了影响现浇箱梁支架施工进度、成本的几个重要因素，指出现浇箱梁支架施工采用重型门式脚手架相比其他支架施工的优点，为项目的施工进度、成本控制提供借鉴。     

黄石市基本农田水稻中重金属污染评价分析

对黄石市基本农田稻米中重金属含量进行了分析测定并进行相应的分析评价,以明确该地区稻米中的重金属污染情况。结果表明：基本农田稻米整体上已经受到了Pb污染,大冶市和阳新县的稻米均为重度Pb污染（污染指数分别为5.469和3.689）,未受到其他重金属污染（其他重金属的污染指数均小于1）;分析不同样点的污染情况,62%的样点为重污染水平,18%的样点为中污染水平,16%的样点为轻污染水平,其他为清洁水平;分析污染原因可能主要由废水浇灌以及大气重金属尘沉降等引起。     

粮食重金属污染对粮食安全、人体健康的影响

介绍了重金属污染的起源、历史、后果和现状。首先叙述了北半球亚欧和北美地区重金属污染研究形势,接着论述了中国粮食重金属污染的严重程度。Cd、Hg、Pb、As、Cu和Zn对人体健康的影响作了概述,最后,对今后中国粮食安全研究提出了建议。