高效液相色谱法同时测定食用油中7种抗氧化剂的方法研究

本研究利用高效液相色谱同时测定食用油中没食子酸丙酯(PG)、没食子酸月桂酯(DG)、没食子酸辛酯(OG)、叔丁基对苯二酚(TBHQ)、叔丁基对羟基茴香醚(BHA)、2,6-二叔丁基对甲基苯酚(BHT)、2,6-二叔丁基-4-羟甲基苯酚(Ionox-100)7种抗氧化剂的测定方法,样品中的抗氧化剂经正己烷溶解、乙腈萃取后,经C18柱分离,乙腈-1.5%乙酸溶液体系为流动相进行梯度洗脱,紫外检测器检测,外标法定量。选择线性范围在1~100mg/L,结果表明7种抗氧化剂呈良好的线性关系,相关系数r大于0.999,方法的测定低限为0.8~2.0mg/kg,回收率在89.3%~110.1%,变异系数在1.5%~4.9%。该方法准确、快速、重现性好,可用于大批量食用油检测中7种抗氧化剂的定量分析。     

Covariance breakdowns and connectedness of crude oil futures markets with non-synchronous data

ABSTRACT

This article identifies the breakdowns in the covariance of three benchmark crude oil futures markets (WTI, Brent and Dubai) and investigates the changes of market connectedness across the breakdown periods. As the crude oil futures are traded in different regions, this article eliminates the non-synchronous trading data by employing the Vector Moving Average structure and the Bayesian data augmentation approach, which keeps the integrity of original data without changing its properties. The results show that there are significant breaks in the covariance structure of crude oil futures markets. The breakdown periods are consistent with the periods when the market volatilities are at high level and the returns are volatile. The changes of market connectedness are independent of the covariance states, which supports the globalization hypothesis for the crude oil market. The results also suggest that there is more information flow out of the WTI than to the WTI during the sample period, particularly during the breakdown periods in 2008–2009.     

Forecasting value‐at‐risk in oil prices in the presence of volatility shifts

Recent evidence suggests shifts (structural breaks) in the volatility of returns causes non‐normality by significantly increasing kurtosis. In this paper, we endogenously detect significant shifts in the volatility of oil prices and incorporate this information to estimate Value‐at‐Risk (VaR) to accurately forecast large declines in oil prices. Our out‐of‐sample performance results indicate that the model, which incorporates both time varying volatility (without making any distributional assumptions) and shifts in volatility, produces more accurate VaR forecasts than several benchmark methods. We make a timely contribution as the recent more frequent occurrences of unexpected large oil price declines has gained significant attention because of its substantial impact on the financial markets and the global economy.     

Revisiting global economic activity and crude oil prices: A wavelet analysis

Based on the wavelet analysis approach, this paper firstly examines the dynamic relationship between global economic activity (proxied by the Kilian economic index) and crude oil prices in both time- and frequency-domains. Our empirical results demonstrate significant correlation between crude oil prices and global economic activity at high frequencies (in the short run) during the entire sample period; however, the co-movement between the two at low frequencies (in the long run) is weaker and exists only during certain proportions of the sample period. We also document evidence that global economic activity and oil price are positively correlated, with dynamic lead-lag relationships across time. Our findings are robust to alternative choices of oil price indexes and controlling for other confounding factors such as geopolitical risk, armed conflicts, economic policy uncertainty and equity market uncertainty. The current study provides valuable implications for oil market investors based on the information of global economic situation and its dynamic relationships with oil prices.     

Oil price and automobile stock return co-movement: A wavelet coherence analysis

This paper explores possible co-movement between oil price and automobile stock return in a joint time-frequency domain. Daily price series from August 01, 1996 to June 20, 2017 is used in this analysis. The results indicate that the co-movement between oil price and automobile stock return is strong during November, 2000–December, 2002 and March, 2006–December, 2009. The co-movement is found to be more pronounced in the long-term and stock return is sensitive to the higher oil price emanating from the demand shock. This contravenes the conventional wisdom that crude oil is always counter-cyclical to the automobile stocks. For investor, this weakens the probable gain from including oil asset in a portfolio of automobile stocks as crude oil does not offer cushion against bearish automobile stock markets during the crisis period.     

电改环境下油气管道企业用电成本管控研究

电力体制改革为油气管道企业用电成本管控提供了政策支持。在梳理电力改革政策的基础上,简要介绍了适用于油气管道企业的新电力政策,详细分析了我国油气管道企业存在的基本电费偏高、力调电费偏高、用电类型不合理、用电管理有待完善等用电现状及其根本原因。在上述分析的基础上,提出了选取合适的用电类别、选择合理的电费计费方式降低基本电费、提高功率因数降低力调电费、积极利用直购电政策、健全用电成本管控激励和考核机制等对策建议,以期为油气管道企业用电成本管控提供参考借鉴。     

油气企业供应商管理存在的问题与建议——以CS公司为例

伴随着供应链管理的应用与发展,越来越多的企业认识到必须充分利用内外资源保持自身的竞争实力。作为重要的外部资源,供应商管理关系到企业成本与收益的平衡,而要做好供应端的成本管理首先要做好供应商的选择和优化。针对CS公司的供应商管理现状及存在的问题,探索适应企业的可操作性强的对策,以期为我国大型油气企业的供应商管理实践提供一定的参考。     

Impact of state-dependent oil price on US stock returns using local projections

In this paper, we investigate the impact of oil prices on both aggregate and industry US real stock returns over the period 1973–2017. The empirical analysis contributes to the related literature introducing a state-dependent oil price (high and low) and the local projections approach. Our main finding is that, depending on the nature of the shock and industry, the negative effects of oil price shocks become exacerbated -and the positive effects get moderated- if oil prices are already high.     

The non-linear impact of oil price on the oil demand

ABSTRACT

A panel smooth transition regression model was adopted to analyse the non-linear impact of oil prices on oil demand. Data for 42 countries was obtained from the International Energy Agency for the time period spanning from January 1990 to June 2017. The results indicate that a threshold value does exist. Furthermore, when the oil price was lower than this threshold value, a positive relationship between oil price and oil demand was observed. When the price of oil was higher than the threshold value, however, a negative relationship between price and demand was found.     

石油海运领域运筹优化方法应用研究综述

为研究运筹方法在石油海运领域的应用及前景,检索1980年至今的国内外相关文献,系统归纳提出石油海上运输优化问题的场景分类:海上运输优化、在港作业调度优化以及油船驳运,分析并对比了各研究的模型差异及算法优劣,最后提出了全局优化调度、根据实际添加特殊约束和设置变量、利用规划约束及人工智能等方式弥补线性规划求解的不足等研究建议。