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CO2 miscible displacement is an efficient method for enhanced shale-oil recovery. Understanding the movability of shale oil in different states of occurrence is important for CO2 miscible displacem...

The adsorbed and dissolved oil in the shale reservoirs can be produced during CO2 injection. However, the effects of different factors on the adsorption and dissolution behaviors of CO2 and oil mixtures in the shale were unclear, such as the oil composition, shale properties and temperature. In this study, a series of adsorption and dissolution tests of CO2 and different n-alkane mixtures in organic-rich shales were performed under different condition. The effects of the alkane type, shale properties and temperature on the adsorption and dissolution amount of mixtures and the replace ability of CO2 to n-alkane were discussed, respectively. The results indicate that the dissolution amount was decreased with the chain length of alkane and increased with TOC and temperature. The adsorption amount of the mixtures in shale was low and only account for 3–16% of total adsorption and dissolution amount, which mainly depended on the specific surface area of the shale samples. Additionally, the replace ability of CO2 to dissolved n-alkane was decreased with the chain length of alkane and temperature. However, there are no obvious rules between the replace ability with TOC of shale. This study can provide useful information for EOR of shale oil reservoirs by CO2 injection and the geological storage of CO2 in shale oil reservoir.

Rheological behaviors of microbial polysaccharides with different substituents in aqueous solutions have been systematically investigated. Both the saccharide side chains and acetyl substituents improve the gelation of welan gum (WG), diutan gum (DG) and gellan gum (GG) in pure water at 25 °C. For the polysaccharides with saccharide side chains (WG and DG), the relationship between the apparent viscosity and concentration conforms to the linear equation, while that of the polysaccharide with acetyl (GG) is exponential. More importantly, the roles of substituents on the stability of the molecular conformation of polysaccharides are significantly depended on the surrounding environment. Disaccharide side chains promote the stability of helical conformation and gel aggregates of GG at high temperature (85 °C) or in the presence of inorganic salts with the ionic strength of 2.0 mol L−1. The stability of gel structure containing acetyl (GG) shows higher temperature/salt sensitivity. Additionally, deacylated gellan gum (GG(d)) solutions transform into hydrogels in the presence of dodecyltrimethylammonium bromide (DTAB). This study will help to obtain a better understanding on the rheological properties of polysaccharides with respect to the conformation and applications.

AC/DC power electronic transformer is the core of the energy conversion device as a micro grid having a multi-port, high-capacity, high efficiency functions. Bipolar failure is one of the typical failures, causing the system does not work. This article aims to analyze the post bipolar DC microgrid faults in the AC/DC power electronic transformer is proposed to suppress over-voltage topology, analyzes the effects of lightning on the drive characteristics of a fault, and consider the safety of the system in order to run, reliability and economy, designed arrester parameters for the arrester between the valve outlet and the neutral point commutation. The energy simulation calculation of the arrester was carried out, and the effectiveness of the selection and configuration method of the arrester was verified by building a simulation platform that does not affect the normal operation. Suppressing the sub-module voltage can provide a reference for the selection of main equipment and insulation coordination.

The anti-vignetting glass (AVG) is the key material for super-second and third-generation low-light image intensifiers. With the development of low-light night vision technology, the requirements of high precision and low damage are put forward to AVG. However, traditional measurement methods, such as vernier calipers, micrometers, dial indicators, etc., are all contact measurement, which will inevitably cause damage to AVG during the measurement process. They cannot meet the technical requirements for low damage. Non-contact measurement technology is a non-destructive testing method that realizes the geometric measurement of AVG by writing measurement programs and setting measurement parameters. However, due to the special structure of AVG, the non-contact measurement technology has measurement errors and cannot meet the high-precision measurement requirements. In this paper systematically analyzes the causes of errors in non-contact measurement technology by studying the characteristics of the light source, the difference in light intensity, and the way of grabbing contour edges. Through the error correction technology, the error of the non-contact measurement technology is eliminated, the AVG high-precision and low-damage non-destructive testing is realized.

Through the influence of the temperature, concentration, acid type and acid dissolution time of the acid solution on the acid etching speed of the multi-fiber and the surface quality after acid etching, the acid dissolution mechanism of the acid solution flexible optical fiber image bundle is discussed. The weight loss method was used to test the acid dissolution rate of different acid-soluble glasses, combined with the breakage of the multi-fiber after acid dissolution, to study the effect of acid-soluble glass on the image quality of the flexible optical fiber image bundle. The experimental results show that using a suitable acid solution, a suitable acid solution concentration, a suitable temperature and a reasonable acid dissolution time has obvious effects on reducing the broken wire rate of the flexible optical fiber image bundle and improving the image transmission quality.

Flexible DC transmission lines have been used in some parts of the northern China electric power system. Due to unstable centralized penetration of renewable generators, pumped storage power stations have also been established to enhance the flexibility of the power system. This paper proposes a dispatch method for AC/DC hybrid power systems with flexible DC transmission lines and pumped storage power stations. In the proposed dispatch model, the objective contains transmission cost, generation cost, and penalty cost. Constraints of flexible DC transmission lines, pumped storage power stations, as well as regular generator and system-wide dispatch constraints are considered. Case studies demonstrate that the proposed model can handle unstable power outputs of renewable generators by pumped storage power stations, eliminate renewable generator variations, and regularize the transmission power to load center.

CO2 cyclic injection is a promising method for enhanced shale oil recovery. However, the enhanced shale oil recovery mechanism is unclear, especially the adsorption and dissolution of CO2 and oil in kerogen. Therefore, it is of great importance to study the adsorption and dissolution mechanisms of CO2 and oil mixtures in shale. In this study, a new experimental apparatus was designed to test the change in the mole fractions of CO2 and oil before and after adsorption and dissolution at equilibrium conditions. For simplicity, n-dodecane (n-C12) was used as the oil. The adsorption and dissolution amounts of CO2 and n-C12 were obtained using a mathematical method. Moreover, the adsorption and dissolution characteristics of the CO2 and n-C12 mixtures in shale and the effect of pressure on the adsorption and dissolution amounts were studied. Finally, the swelling factor of the shale, which was caused by the dissolution of the mixtures, was calculated from the experimental results. The results show that dissolve...

According to the characteristics of duplicate web pages in the meta search engine, a duplicate web pages detection algorithm is proposed based on a web page URL, title and abstract, and according to their different characteristics, different similarity computing method is proposed, firstly, the page URL is standardization processed in the algorithm, and then for the title detection, the algorithm improves the title string fuzzy matching algorithm and calculate the similarity based on the word frequency of each items in the query, for the abstract judgment, similarity computing is in accordance with the sentences of the abstract, for each sentence the algorithm gives three weights, and calculates the weights of similarity on base of each summary statement, the effect of the algorithm is obvious, it has been verified by experiment that the algorithm is superior to the traditional algorithm in the precision and recall rate.