电分析化学法在重金属离子检测中的应用

简述了离子选择电极法、极谱分析法、溶出伏安法及电位溶出法用于环境样品检测的特点,着重介绍了国内外电分析化学技术在重金属离子检测中的应用,对电分析化学法在重金属形态分析中的应用进行了评述。分析表明,今后研究的重点应放在优化各种仪器的联用技术,制备新型电极材料,研发高灵敏度、高选择性、响应快、寿命长、微型化、可动态在线检测的新型电化学分析仪器。     

Agricultural Financial Risks Resulting from Extreme Events

Decision‐makers in the agricultural sector operate in a volatile and risky environment. The statistical assessment of agricultural commodity prices is necessary to deduce the stylised facts of agricultural markets and guide the action of market participants. This article examines the kurtosis values of 60 agricultural commodities and presents evidence that the distributions of their returns are fat‐tailed. We use power‐law distributions to model the tail returns and the possible time‐varying extreme event risks in commodity markets. Our results suggest that the usefulness of the value at risk and expected shortfall as risk management tools is questionable.     

业绩期望落差、股权集中度和企业环保投入

基于企业行为理论，以 2011~2015 年重污染上市公司为研究样本，本文理论分析并实证检验了业绩期望落差与企业环保投入的关系，并进一步考察了股权集中度的调节作用。研究结果表明：（1）当企业实际绩效低于渴望水平时，业绩期望落差与环保投入呈 U 型关系，即业绩期望落差存在一个阈值，低于该阈值时，业绩期望落差与环保投入负相关，高于该阈值时，业绩期望落差与环保投入正相关；（2）与股权集中度低的企业相比，股权集中度高的业绩期望落差与环保投入之间的 U 型关系将减弱。     

重载铁路双向土工格栅加固路堤边坡施工技术研究

本文以山西中南部铁路通道DK597+600-汤台K12+100段双向土工格栅加固路堤边坡施工为例,具体介绍了路堤边坡土工格栅防护加固机理、施工工艺和质量控制等措施。     

常规稠油油藏三次采油技术优选方法研究

随着世界经济的发展,全球的能源消耗将会呈现一直持续增长的趋势,而石油作为核心的能源,是工业经济的命脉。面对这个现状提高原油采收率就变得十分重要,而三次采油技术无疑就是能够提高采收率的主要方法。以下对三次采油技术优选方法、钻修等方面进行了具体的分析和研究。     

On and off China's turnpike

A reorientation towards emphasis on consumption has become a major issue in China, raising the question of the relationship between economic growth and the composition of output. The issue is addressed here, using insights from economic growth theories. These theories indicate that concentration on capital goods production generates the most rapid overall growth. With short‐term deviations and without explicit reference to any theory, Chinese practice in the past seems to have conformed. A shift to emphasizing output of consumption goods while resulting in an overall growth slowdown, will improve consumer welfare, suggesting the benefits of shifting to this criterion of economic success.     

液压无杆采油泵技术在油田的应用

随着油田开发的进一步深入,稠油开采难度逐渐加大,严重制约了油田的正常开发,因此急需探讨新的开采技术来解决稠油开采难题。本文阐述了液压双作用无杆采油泵技术在辽河油田的应用现状以及效果,从而为稠油开发提供了新的技术支撑。     

Calculation of ruin probabilities for a dense class of heavy tailed distributions

In this paper, we propose a class of infinite-dimensional phase-type distributions with finitely many parameters as models for heavy tailed distributions. The class of finite-dimensional phase-type distributions is dense in the class of distributions on the positive reals and may hence approximate any such distribution. We prove that formulas from renewal theory, and with a particular attention to ruin probabilities, which are true for common phase-type distributions also hold true for the infinite-dimensional case. We provide algorithms for calculating functionals of interest such as the renewal density and the ruin probability. It might be of interest to approximate a given heavy tailed distribution of some other type by a distribution from the class of infinite-dimensional phase-type distributions and to this end we provide a calibration procedure which works for the approximation of distributions with a slowly varying tail. An example from risk theory, comparing ruin probabilities for a classical risk process with Pareto distributed claim sizes, is presented and exact known ruin probabilities for the Pareto case are compared to the ones obtained by approximating by an infinite-dimensional hyper-exponential distribution.     

畜禽粪便中残留四环素类抗生素和重金属的污染特征及其控制

兽用抗生素和微量重金属作为饲料添加剂广泛用于畜禽养殖业，但超量使用是导致畜禽粪便中高浓度抗生素和重金属残留的根本原因。随着我国畜禽养殖业的规模化发展，畜禽粪便中残留的四环素类抗生素和重金属（铜、锌、砷）及其复合污染对生态环境和人类健康构成了巨大的潜在威胁。针对这种状况，总结了我国四环素类抗生素（包括四环素、土霉素和金霉素）和微量重金属元素（铜、锌、砷）在畜禽粪便中的残留量及其区域分布特征，并概述了这两类物质在畜禽粪便生物处理过程（堆肥和厌氧消化）中的转化、降解及其影响。畜禽粪便中残留的抗生素和重金属可导致环境中出现耐药菌与抗性基因，是环境与健康领域的又一重大挑战，其影响不容忽视。