ASD-ICP-AES联用快速测定土壤中部分重金属

采用样品全自动消解系统(Automated Sample Digestion)对土壤样品进行前处理,采用ICP-AES对土样中的重金属元素一次性测定.通过优化实验,获得土壤中各种重金属的最佳消解条件.结果表明,经优化的消解程序A1能够快速、稳定消解土壤样品,并获得理想测试结果.经检验,ASD-ICP-AES联用的土样测...     

基于瓦斯涌出量预测的近距离煤层群开采顺序优化选择

随着中厚煤层资源的枯竭,近距离薄煤层群开采成为我国资源的重要补充。煤层群开采时合理的采掘部署是防止工作面瓦斯集中涌出的关键,本文通过分析近距离煤层群开采时各回采顺序下工作面瓦斯涌出量,建立了以工作面瓦斯涌出量预测为基础的近距离煤层群开采优化模型,利用计算机编程实现了模型的可视化操作。该模型通过对比分析全部种回采顺序方案,选择整个回采期间瓦斯涌出量最均衡的方案为最优方案。对翔升煤矿进行了实例分析,结果显示合理的回采方案可以使工作面最大瓦斯涌出量大大减小,使整个回采期间工作面瓦斯涌出量趋于均衡。为煤层群开采优化技术中的瓦斯环节提供了理论依据。     

Resource abundance and financial development: Evidence from China

In this paper, we extend the debate on the resource curse by focusing on a new mechanism. Theoretically, resource abundance may have a negative influence on financial development by impacting trade openness, the demand for financial reforms, social capital accumulation and productive investments. Using provincial panel data of China, the empirical analysis confirms such a negative link between mineral resource abundance and financial development. The resource-rich regions tend to have a slower pace of financial development than resource-poor ones. Since the positive relationship between financial development and long-run growth is also confirmed by the analysis, our findings suggest that financial development constitutes an important mechanism through which resource abundance can impact economic performance.     

Aggregates in England—Economic contribution and environmental cost of indigenous supply

Aggregates represent one of the largest material flows in the UK economy; however, the importance of these minerals in underpinning economic activity is frequently not recognised. Features such as the spatial imbalance between resources and demand centres, exacerbated by changes in demographics and public perception, are placing increased pressure on the planning system to maintain supply. This paper sets out the direct and indirect economic contributions made by the indigenous aggregates industry to the English economy through Gross Value Added and employment sustained. It describes the key role of aggregates in construction activities, assesses the links between infrastructure development and economic growth. In 2005, aggregates extraction directly contributed £810 million of Gross Value Added to the English economy. Primary aggregates are, however, extracted at a cost to the environment and this cost, based on amenity value reduction, is estimated by updating previously published contingent valuation data. Estimates for the costs associated with carbon dioxide emissions are derived from values published by the European Union and, separately, by the UK Government. These two elements combined result in an environmental cost of indigenous extraction of £445 million in 2005. Additionally, an examination of the potential for a significant increase in the level of aggregate imports into England is made and the consequences assessed. This includes an evaluation of shipping costs and port capacity, and concludes that there are significant barriers to any substantial increase in the level of aggregate imports into England. As a consequence, indigenous supply is likely to predominate into the foreseeable future.     

The impact of commodity price risk management on the profits of a company

It is well recognized that for the producing companies hedging the commodity price using financial products like forwards or futures has become an important part of the company's production process. But apart from the direct impacts of hedging on the production and hedging costs the use of financial products affects the financing of the company: hedging the volatile commodity prices leads to a reduction of the risk premium the company has to pay for its debt capital, since hedging contributes to more confidence of the investors in the redemption of the debt. In this paper we therefore analyze this dependency of hedging and financing and derive optimal hedging extents for companies in different market situations based on a long-term model. By hedging the commodity price, companies can realize a surplus in profits. Thereby, the optimal hedging extent for a monopolist is often up to 100%, whereas for companies in a polypolistic market the optimum is always less than 100%. These results are illustrated by examples for a producing company.     

Laminar jet modelling for hazardous area classification

A previous article dealt with turbulent jet flow modelling with the aim at developing a method for estimating the size of explosive clouds following a high Reynolds number release, within hazardous area classification scheme. The results have demonstrated that the standard EN 60079-10 (2009) largely overestimates the real size of clouds resulting from a piping or a vessel leak. On the other hand, laminar jets are possible also at moderately high Reynolds numbers; furthermore, a reduced momentum, typical of laminar jets, is often assumed in QRA studies, as a conservative assumption, due to the expected lower air entrainment and to the corresponding larger size of the flammable cloud volume. These considerations have suggested the suitability to extend the previous analysis also to laminar regime, taking into account the effect of density and viscosity differences between air and flammable gas.     

Comparison of calculated data for the flammability and the oxidation potential according to ISO 10156 with experimentally determined values

The classification of flammable gas mixtures is based on either testing or calculation methods proposed by the revised international standard ISO 10156. This standard is used for classification of physical hazards in Chapters 2.2 and 2.4 of the UN Globally Harmonized System of Classification and Labelling of Chemicals (GHS) and in the UN Recommendations on Transport of Dangerous Goods (TDG). The test methods of flammability and oxidizing potential in this standard were developed by BAM. Earlier versions of this standard are not based on triangular diagrams and on the reference combustible substance “ethane”. The old material characteristics, especially in case of oxidizing potential, are based mostly on practical experience without any quantifiable test results. First time it is possible to compare experimental results from the CHEMSAFE database with the newly developed calculation method. In this paper the basic principles of the calculation methods are presented and the methods are validated by examples. A comparison of experimental flammability data with classification results gained by the calculation methods of ISO 10156 is demonstrated.     

基于PCT方法的京津冀冬季PM2.5重污染天气型分析

T模态斜交主成分分析法（PCT）分析的天气过程时间尺度越长,该算法的优势越明显,天气分型结果也更完整,可信度越高.利用京津冀地区2014年冬季-2019年冬季（每年12月-翌年2月）的环境监测资料,以区域平均PM_2.5日均值大于150 μg·m^-3为标准,筛选出72个京津冀地区PM_2.5重污染日,采用ERA5提供的0.25°×0.25°气象再分析资料,应用PCT算法将72个PM_2.5重污染日海平面气压场客观地分为高压前部型、锋前低压型、高压后部型、均压场型和弱低压型5种类型,分别占总PM_2.5重污染天数的34.72%、20.83%、16.67%、16.67%和11.11%.另外,对2017年2月12-16日京津冀地区PM_2.5重污染过程的分析表明,重污染天气过程中随着逐日天气型的演变,污染物浓度特征、近地面风场和大气污染物污染传输路径均发生相应变化.     

考虑颜色特征最优组合的CART决策树火灾图像识别方法*

针对火灾图像识别过程中颜色特征数量多、特征间相关性复杂、难以在多维特征融合过程中有效融合图像颜色特征等问题,提出1种考虑颜色特征最优组合的CART决策树火灾图像识别方法。首先,在Lab、RGB、HSV 3种色彩模式下基于图像颜色特征提取火灾图像特征序列;其次,分别在3种色彩模式下基于精细决策树与特征随机排列组合方法提取颜色特征中最优组合特征;最后,将提取的火灾图像最优组合特征序列作为CART决策树输入进行模型训练,并通过测试样本以及其他机器学习方法进行模型泛化能力的分析。研究结果表明:本文方法寻找出识别火灾图像的最优颜色特征组合为“Kb1+Var1+Kg+Kb2+Var2+Kh+Ks+Kv”;CART决策树方法对于火灾图像识别的测试准确度可达84.5%,其分类效果明显优于其他决策树类与集成树类方法;9折为最佳交叉验证折数,其测试准确度可达86.47%,与5折交叉验证相比明显提升14.77%。研究结果可为火灾图像识别提供方法基础。     

事故经济损失分类及评估方法研究综述*

为系统了解事故的经济损失分类、评估方法以及发展方向,通过文献综述的方法,回顾事故经济损失的研究起源,总结主要的分类方法,归纳评估方法的主要特点,分析评估难点并展望未来可能的研究方向。研究结果表明:事故经济损失统计项目难以全部列出,须在其构成价值与评估所需努力之间相权衡;在事后全面准确评估经济损失仍是未来的研究重点,其有益于统计标准的制修订,而事前评估则是1个新兴的方向;很难选择合适的直间比来评估间接经济损失,未来需开发1种简单灵活的评估方法。研究结果可为未来事故经济损失分类和评估的研究应用提供理论和数据支撑。