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111.
利用气质联用仪对水蒸馏法提取鲜桑(Morusalba)叶与干桑叶的精油挥发性组分进行分析,二者均含有醇类化合物、酸类化合物、烃类化合物、酮类化合物和酯类化合物。鲜桑叶精油挥发性组分中第一主成分为植醇,干桑叶精油挥发性组分中第一主成分为棕榈酸。鲜桑叶精油中含有丁基化羟基甲苯和质量分数较高的植醇,具有开发为化妆品的潜在价值。  相似文献   
112.
This article brings new insights on the role played by (implied) volatility on the WTI crude oil price. An increase in the volatility subsequent to an increase in the oil price (i.e. inverse leverage effect) remains the dominant effect as it might reflect the fear of oil consumers to face rising oil prices. However, this effect is amplified by an increase in the oil price subsequent to an increase in the volatility (i.e. inverse feedback effect) with a two-day delayed effect. This lead-lag relation between the oil price and its volatility is central to any type of trading strategy based on futures and options on the OVX implied volatility index. It is of interest to traders, risk- and fund-managers.  相似文献   
113.
介绍了项目质量成本的概念及内涵,分析了质量和成本之间的辩证关系,总结了消减质量成本的7项措施,并提出了质量改进成本投入与收益平衡分析的建议。实践证明,通过增加预防与改进成本,可提高项目施工质量,有效降低鉴定成本和非一致性成本,最终降低项目总的质量成本,大幅度提高项目经济效益。  相似文献   
114.
We examine the quantile serial dependence in crude oil prices based on the Linton and Whang’s quantile-based portmanteau test which we improved by means of quantile wild bootstrapping (QWB). Through Monte Carlo simulation, we find that the quantile wild bootstrap-based portmanteau test performs better than the bound testing procedure suggested by Linton and Whang. We apply the improved test to examine the efficiency of two crude oil markets – WTI and Brent. We also examine if the dependence is stable via rolling sample tests. Our results show that both WTI and Brent are serially dependent in all, except the median quantiles. These findings suggest that it may be misleading to examine the efficiency of crude oil markets in terms of mean (or median) returns only. These crude oil markets are relatively more serially dependent in non-median ranges.  相似文献   
115.
将抽油机井井口控制掺水量的闸门或档板改装设计成可调油嘴,使单井掺水量的控制更加方便灵活,减少岗位工人的劳动强度,同时对合理控制单井回油温度,提高和稳定掺水系统压力很有效。  相似文献   
116.
117.
Is Indonesia using the most effective possible strategies to derive revenue from its mineral resources? Auctions and work program bidding are the main ways of allocating mineral leases. In addition to the company taxes applied to all companies, governments can raise revenue from minerals owned by the state through auctions, royalties and rent taxes paid by private firms, and through dividends from state-owned firms. Indonesia uses work program bidding to allocate leases, and its production-sharing contracts are roughly equivalent to a rent tax at a high rate. This paper considers these options for raising revenues from mineral resources. It argues that efficiency and government revenue would both be increased if Indonesia relaxed direct controls on the operations of mining companies, and allocated leases by means of auctions, combined with a much lower rate of rent tax or, better still, a royalty.  相似文献   
118.
本文分析了南苏丹独立后中石油与苏丹油气合作面临的机遇、挑战及现状,针对合作中存在的问题提出中石油应通过结构性安排规避政治风险、提高项目管理能力、培养国际化人才、实施本土化策略等对策。  相似文献   
119.
Based on the approach developed by Elliott et al. (2005), we found that the loss function of a sample of oil price forecasters is asymmetric in the forecast error. Our findings indicate that the loss oil price forecasters incurred when their forecasts exceeded the price of oil tended to be larger than the loss they incurred when their forecast fell short of the price of oil. Accounting for the asymmetry of the loss function does not necessarily make forecasts look rational.  相似文献   
120.
论述了以"五精四细"为模式的精细化管理在渤海石油装备华油钢管公司内的构建和实施。详细阐述了"五精四细"的基本内涵,即五精之精化、五精之精髓、五精之精品、五精之精通、五精之精密、四细之细分、四细之细密、四细之细化、四细之细则。通过实施精细化管理,企业管理水平得到全方位提升  相似文献   
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