基于变压器油中溶解气体的故障在线监测

随着电网建设的推进,各级调度中心要求更多的信息,以便及时掌握电网及变电站的运行情况,提高变电站的可控性。电力变压器作为电力系统中最重要的电气设备之一,维护其正常运行是整个系统可靠供电的基本保证。文中主要分析了变压器油中气体在线监测的优点。

Principal Component Analysis （PCA） on Multivariate Data of Lard Analysis in Cooking Oil

Discrimination of fatty acids （FAs） of lard in used cooking oil is important in halal determination. The aim of this study was to find the information related to the changes FAs of lard when frying in cooking oil. Quantitative analysis of FAs composition extracted from a series of experiments which involving frying cooking oil spiked with lard at three different parameters; concentration of spiked lard, heating temperatures and period of frying. The samples were analyzed using Gas Chromatography （GC） and Principal Components Analysis （PCA） technique. Multivariate data from chromatograms of FAs were standardized and computed using Unscrambler X10 into covariance matrix and eigenvectors correspond to Principal Components （PCs）. Results have shown that the first and second PCs contribute to the FAs mapping which can be visualized by scores and loading plots to discriminate FAs of lard in used cooking oil

Biodiesel Production by Enzymatic Catalysis Process Using Two Analytical Ways： Gas Chromatography and Total Glycerol Determination

Currently, biodiesel is presented as one of the best alternatives for gradually replacing the use of fossil fuels, but it has some factors that make it economically impractical if it does not have a government support. For this reason, research efforts focused on this area have been responsible for optimizing the process of biodiesel production by different catalytic routes to achieve greater efficiency at a lower cost. In this case, the biggest problem has been the high cost generated by an investigation, which in many occasions is the main factor to decide if an investigation could be carried out. Trying to reduce these costs, in the current study, we are using a technique of glycerol quantification by volumetric methods and comparing obtained results with the chromatographic method, which is conventionally used and comparatively much more expensive. Biodiesel employee was obtained by an enzymatic catalysis process varying one of three process variables：oil：alcohol molar ratio, temperature and proportion of catalyst. The numerical differences obtained between the two quantification methods generated relative errors lower than 10%, resulting in some occasions lower than 1%. By gas chromatography analysis the best yield was obtained at the same conditions of the volumetric method, a temperature of 45 ℃, an oil：alcohol ratio 1：4 and 8 wt.% of catalyst, but a yield of 95.5% and 97.1%, respectively. Due to the high precision of gas chromatography, this method is used to carry out a surface response analysis obtaining as ideal operating conditions a temperature of 43.5 ℃, 8.9 wt.%. of catalyst and an oil：alcohol ratio 1：4.

Extensive application of rate transient method in performance analysis for low permeability gas reservoirs

Rate transient method is a recently-developed performance analysis tool specially designed for low-permeability or tight gas reservoirs. This method, theoretically based on pressure transient analysis, integrates material balance principle and the concept of material balance pseudo-time proposed by Blansingame. With daily production data of gas well, it could be used to calculate OGIP, current formation pressure, permeability, skin factor, to identify complex geologic boundaries, to determine whether drainage boundary has been reached, to calculate drainage area and drainage radius for single well and to predict performance. It has been extensively employed in more than ten low-permeability gas fields. It proves that most problems in performance analysis for low permeability gas reservoirs could be solved by this method. Field practices show great economical benefits could be achieved by employing this method in gas field development.

Gas chromatography-mass spectrometry analysis of essential oils from five parts of Chaihu(Radix Bupleuri Chinensis)

OBJECTIVE: To analyze the essential oils from flowers, leaves, stems, roots, and fruits of Chaihu(Radix Bupleuri Chinensis).METHODS: We extracted essential oils from different parts of Chaihu(Radix Bupleuri Chinensis) using a steam distillation method. The essential oils were analyzed by gas chromatography-mass spectrometry(GC-MS). Data were collected in full scan mode(m/z 60-600). Volatile components were identified based on their retention indices and by comparing their mass spectra with those in the National Institute of Standards and Technology 2005 database assisted by tandem mass spectrometry information. The relative content of each constituent wasdetermined by area normalization.RESULTS: We identified 111 components, of which12 were common to all 5 parts, 30 were found only in roots, 14 were found only in flowers, 6 were found only in leaves, 4 were found only in stems,and 17 were found only in fruits.CONCLUSION: Our results show that the stems,flowers, leaves, and fruits of Chaihu(Radix Bupleuri Chinensis)contain a high concentration of essential oils, and that the exact composition of the essential oils differs among the plant parts. To develop new medicines and make full use of the Chaihu(Radix Bupleuri Chinensis)resource, it is important to characterize the essential oils from different parts of the plant. In future research, it will be important to determine the pharmacological effects of the various components and the essential oil mixtures.