Lithium ⁃ion batteries (LIBs) have been widely utilized in portable electronic devices due to their high energy density, long cycle life, and convenience of use. The graphite of commercial LIBs cannot meet the new commercial demand due to the low theoretical specific capacity and poor safety. Cobalt sulfide has attracted wide attentions as anode materials due to its high specific capacity and good thermal stability. This review summarized the defects of cobalt sulfide compounds (CoS, CoS2, Co3S4, Co1-xS, Co9S8) and the research progress in their modification for LIBs electrode materials. And the perspective of cobalt sulfide electrode materials was also discussed.
2⁃tert⁃butyl⁃p⁃cresol (2⁃TBC) was synthesized by alkylation of p⁃cresol with tert⁃butanol under microwave irradiation using HY with different n(Si)/n(Al) as catalyst. The effects of microwave irradiation time and power, reaction temperature, molar ratio of raw materials and kinds of solvents on the reaction were investigated using xylene as solvent. The results show that the conversion of p⁃cresol is increased about three times when HY zeolite with 5.4 n(Si)/n(Al) as catalyst, the molar ratio of raw material is n(tert⁃butanol)/n(p⁃cresol)=1.3, the microwave radiation power is 700 W, the microwave radiation heating time is only 1/8 of the oil bath heating time, the highest conversion of p⁃cresol was 72.91%; the yield of target product 2⁃TBC was 68.08%, and the selectivity was 93.32%; by⁃products are etherification product p⁃toluene tert⁃butyl ether (TBPE) and dialkylation product 2,6⁃di⁃tert⁃butyl p⁃cresol (2,6⁃DTBC)
Helium is one of the rare strategic materials indispensable to the development of national defense and high⁃tech industries. Helium resources in China are quite poor, and helium is basically imported from the United States. Although helium content in natural gas is relatively low and difficult to extract, natural gas is still the only source of industrial production of helium. Therefore, it is great significance to study and establish a suitable technology for the determination of helium content in natural gas in oilfield, and to provide a scientific basis for the extraction of helium from natural gas. Gas chromatographic method is used to survey and quantitative analysize the helium content in natural gas from Songliao basin. The helium content in natural gas from Songliao basin is relatively low, but the content is relatively stable
he biomass conversion to small molecule by gasification through pyrolysis is an important driving force to realize the replacement of fossil energy with bioenergy. Gasification through microwave⁃assisted pyrolysis is a common route for conversion of biomass to desired bioenergy and bioproducts. The review describes the technology of microwave enhanced pyrolysis and microwave⁃assisted catalytic gasification. In addition, this review discusses both the challenges and opportunities of biomass pyrolysis using microwave heating and the milestones that are necessary to be obtained in the future
ChCl/C6H8O7 deep eutectic solvent(DES) was synthesized by choline (ChCl) as hydrogen bond acceptor and citric acid (C6H8O7) as hydrogen bond donor. Meanwhile, twenty percent of water was added into ChCl/C6H8O7 to reduce the viscosity. The structure was characterized and analysed by FI⁃IR and 1H⁃NMR. The denitrification of basic nitrogen in simulated oil was studied by using ChCl/C6H8O7 DES as extractant. The results show that the removal rate of quinoline in the simulated oil can attach to 95.64%, when the mass ratio of solvent to oil is 1∶5, the extraction time is 35 min, and the extraction temperature is 20 ℃. At the same time, taking toluene and cyclohexene as examples, the effects of aromatic hydrocarbons and olefins on the denitrification of DES are investigated. The mechanism of denitrification of DES is determined by infrared spectroscopy
Solar⁃powered water evaporation as a solar⁃powered photothermal conversion application has attracted people's attention due to its high solar energy conversion efficiency and the industrial potential of clean water production. In recent years, solar⁃powered evaporation systems, which position energy conversion between solar energy and thermal energy at the air/liquid interface, have been proposed as an alternative to conventional volumetric heating evaporation because they can reduce heat loss and increase energy conversion efficiency. In this review, we discussed how to implement high⁃performance evaporation system design strategies, including porous nanostructures, interfacial evaporation structures, and wicking structures, as well as three systems that described solar⁃driven water evaporation, namely volume systems, interface systems, and Isolation system. This paper described the possibility of applying this solar⁃driven interface evaporation process to desalination and wastewater treatment, and discussed some of the problems and challenges.
Liquid hot water was applied to pretreat sunflower stalk to increase its accessibility for enzyme hydrolysis. Pretreatment temperatures, reaction times and pressurized gases were investigated. The results show that the yield of enzyme hydrolysis sugar sun flower stalk is increased after pretreatment. The highest total reducing sugar yield of 83.0% is obtained for the sample pretreated at 200 ℃ and 20 min. Compared with N2, CO2 pressurized high temperature liquid water treatment at low temperature and short time has catalytic effect. Finally, XRD and SEM analysis are used to investigate the microstructure of the sunflower stalk before and after the pretreatment.
Water shutoff is the main measure to control water and stabilize oil in Tahe clastic reservoir. However, due to the influence of deep burial, high temperature and high salinity, it is difficult to improve water shutoff efficiency in horizontal wells. In view of this, based on the principle of interpenetrating network polymerization, a composite gel with organic crosslinking agent and silicate as the main body was synthesized. The results show that with the addition of a heat stabilizer, the gelling time of the plugging agent is controllable from 4 hours to 50 hours.The plugging agent does not dehydrate in 30 days at 130 ℃. The water phase plugging rate is over 90%, and it has excellent oil⁃water phase selectivity and formation permeability selectivity. It is necessary to use high⁃efficiency oil wash agent as pre⁃liquid and cross⁃linked polymer as sealing agent to control pressure and inject at low speed during construction. Good application results have been achieved in the field
Microbial paraffin removal and prevention has the advantages of low cost, safe operation and no damage to the formation. The effects of complex environment on microbial degradation were introduced, the effects of microbial degradation enzymes were analyzed,the effects of organic solvents and biological surfactants produced by microorganisms on the degradation of waxy crude oil were elaborated. Based on this, it is pointed out that the microbial technology should strengthen the research on the production mechanism of microbial degradation enzyme, organic solvent and surfactant, so that the microbial degradation of waxy crude oil has a broader application prospect
The conditions of high temperature, high pressure and high sulfur content in deep well oil and gas exploitation put forward higher requirements for the sealing ability and service life of the downhole packer. K344 steel belt packer can improve the pressure bearing capacity of the expansion rubber cylinder and the stress condition in the process of pressure bearing and service life through the laminated steel belt between the inner and outer rubber cylinders, which is suitable for the requirements of deep well oil and gas exploitation. In this paper, the finite element software was used to simulate the setting process, the contact stress distribution law of the key components (inner rubber cylinder, outer rubber cylinder and laminated steel strip) and the mechanism of laminated steel strip to prevent the rubber cylinder from "shoulder protruding" were obtained. The optimal distance between the laminated steel strips at both ends and the optimal radius of the hoop fillet were selected through simulation analysis. It provided a reference for the optimization design of steel belt packer in practical production and application.
Taking LNG tank containers as research objects, the strength reserve and displacement field of the tank were given by establishing its finite element model under stacking test conditions. The stacking buckling of the tank frame structure under multiple real loads was analyzed and calculated by using the Block Lanczos method, and the buckling modes of the frame and the corresponding critical loads were given. The strength distribution, the weakness, stability modes and macro stability reserves of the tank structure were clarified. It was concluded that the weak parts of the tank under stacking test conditions were upper frame short section and connection between frame and tank. The upper frame short section was the preferred location for stiffness reinforcement. In addition,the analysis shows that the stability of the tank frame is high and strength is the primary consideration in the design of this type of tank frame. This paper provided a reference for the design and check of the strength and stability of similar structures.
In order to obtain the dynamic change law of reliability of redundant repairable system under the influence of common cause failure, a new algorithm combining improved GO method with dynamic bayesian network was proposed. Firstly, the GO diagram model was established according to the schematic diagram and flow chart of the system. Then, the GO model was converted into a DBN by using the conversion mapping rules of each operator and signal flow to the DBN. Finally, the model was solved by using DBN mature software and algorithms. After verification and comparison, it can be seen that this method is not only able to obtain the dynamic curve of system reliability and availability changing with time, but also to treat the influence of maintenance factors and common cause failures on the analysis results. In additional, that this method with the powerful ability of reverse reasoning, is able to obtain the weak links quickly and provide reference the fault diagnosis for the system
This paper focused on the consensus problem of linear multi⁃agent systems via a pinning controller with protocol failure. A network model of connection failure was established,the dwell time of the model was constant.A Lyapunov function approach based on such two states was developed to analyse its consensus. Concise conditions with smaller computation complexity were proposed and depended on such dwell times. Then, two sufficient conditions for the existence of a pinning consensus controller with failures were established. Finally, a practical example was used to demonstrate the effectiveness of the proposed methods.
Dissolved Gas Analysis (DGA) is one of the important methods for determining transformer internal faults.Aiming at the shortcomings of the traditional shallow⁃based machine learning method in transformer fault diagnosis in feature extraction and generalization ability, a transformer fault diagnosis method based on Convolutional Neural Network (CNN) was proposed. The convolution layer in the network was used for feature conversion of dissolved gas in oil, and fault sensitive features were extracted by combining with the ability of pooling layer to strengthen important features. The effects of the number of convolution kernels, the size of convolution kernels, pooling layer and network depth on the diagnostic performance of the model were studied experimentally. The models of Convolutional Neural Network, Support Vector Machine (SVM) and Back Propagation Neural Network (BPNN) were compared and analyzed by confounding matrix, ROC curve and PR curve. The experimental results show that the Convolutional Neural Network model has better diagnostic performance.
Taking X company as the research object, this paper constructed the evaluation index system of revenue information quality which was more fitted with the actual situation of X company. It evaluated the revenue information quality of X company from 2014 to 2017 by using entropy weight⁃TOPSIS method. It proved that the evaluation results accorded with the actual operation of X company, which provided development direction for the company's value promotion and sustainable development. Taking 2017 as an example, this paper made a comprehensive evaluation of the industry revenue quality, which provided a method reference for the comprehensive evaluation of enterprise income quality.
This article selected the empirical data from China's GEM listed companies from 2012 to 2017, based on the theory of financing constraints, and used regression analysis to explore the impact of corporate technology investment from the perspective of debt levels. The research results show that the input of technological innovation shows an inverted "U" trend with the increase of the asset⁃liability ratio. When the inflection point of the curve is reached, the incentive effect of the debt level on the input of technological innovation reaches a maximum.
