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This paper analyses the unusual mal-operation of the differential protection for transformer current differential protection during the external fault. The mal-operation reason is researched in detail, based on the mathematical analysis, the simulation, and the field recorded fault data analysis. It is disclosed that the CT saturation leads to the maloperation. Based on this, this paper analyses the improvement for the CT saturation identification method, and discusses the CT selection principles. This paper is aimed at attracting the attention on the problem of the CT saturation and proposing the reference of the analysis method the countermeasure for this problem.

Although the carbon fiber reinforced composite material has high specific strength and stiffness, design-versatility, anti-corrosion and other excellent features, but the impact resistance of composite structures is poor. Therefore, the composite laminates low-speed damage analysis has important significance. Based on a three-dimensional analysis theory of cumulative damage, using the commercial finite element analysis software ABAQUS to establish laminates subjected to low velocity impact finite element model. according to the numerical results and the consistency of the test results, shows that the used model of the article is reasonable and accurate, and the numerical simulation method is verified to be feasible. Finally, through the numerical simulation of process of laminated plates low speed impact damage, the damage characteristics and damage mechanism of the laminates at different times are analyzed, and the forming reasons and expanding rules of the main damage forms of fiber damage and matrix damage are revealed.

The re-injection of associated sour gas, with high H2S and CO2 content, into the reservoir is proposed to be an effective development method due to its low investment cost and high oil recovery. The aim of this work is to present the phase behavior and miscible mechanism of crude oil displaced by associated sour gas. Based on the equation of state and the phase equilibrium theory, the phase behavior of crude oil mixed with various gases (associated sour gas, H2S, CO2 and CH4) have been analyzed. Then, the miscibility of associated sour gas was determined by calculating its Minimum Miscible Pressure (MMP) and the effect of sour component fraction on miscibility was evaluated. Moreover, a series of numerical simulations modeling 1D slim-tube were conducted using a compositional simulator to study the miscible mechanism in the displacement of crude oil with associated sour gas. The results show that the injection of H2S can reduce the bubble point pressure of crude oil and therefore is beneficial to prevent the crude oil degassing; nevertheless, the injection of CO2 has little effect on it. The miscible ability of associated sour gas decreases as its sour component fraction decreases. It is observed that the crude oil displaced by associated sour gas and sweet gas both show a combined condensing/vaporizing mechanism, with miscible zone in the middle of transition zone. However, the vaporizing-gas drive mechanism is slightly stronger than the condensing-gas drive mechanism during the displacement by associated sour gas while is significantly stronger during the displacement by sweet gas.

Accurate calculation of heat efficiency in the process of superheated steam injection is important for the efficient development of heavy oil reservoirs. In this paper, an integrated analytical model for wellbore heat efficiency, reservoir heat efficiency and total heat efficiency was proposed based on energy conservation principle. Comparisons have been made between the new model results, measured data and Computer Modelling Group (CMG) results for a specific heavy oil reservoir developed by superheated steam injection, and similarity is observed, which verifies the correctness of the new model. After the new model is validated, the effect of injection rate and reservoir thickness on wellbore heat efficiency and reservoir heat efficiency are analyzed. The results show that the wellbore heat efficiency increases with injection time. The larger the injection rate is, the higher the wellbore heat efficiency. However, the reservoir heat efficiency decreases with injection time and the injection rate has little impact on it. The reservoir thickness has no effect on wellbore heat efficiency, but the reservoir heat efficiency and total heat efficiency increase with the reservoir thickness rising.

Sijiazhuang coal mine is taken as an example in this paper. Both the theoretic model and the numerical simulation are carried out to analyze the stress distribution regularity on the surrounding rock of stope face under different overlying strata combinations by using discrete element method. Under different combinations of the overlying strata, the results indicate that the regularity of stress distribution around stope face is roughly the same, i.e. the stress concentration of different degree appears in both ends, and the region of pressure relief exist above the stope face. Furthermore, destruction degree of the roof in stope face is different under various overlying strata combinations. On the eve of the first weighting, the different combinations present different phenomenon of concentration, especially the soft-hard-soft combination and hard-soft-hard combination.

In this research, the effects of three different pretreatment methods, physical pulverizing, steam blasting and hydrogen peroxide oxidizing, on ethanol preparation from corn straw were compared. The results showed that the content of reducing sugar in corn straw briquette with grinding and steam blasting pretreatment were 2 and 1.5 times higher than that without pretreatment. In the final product, the concentration of ethanol and rate of alcohol increased about 3.8 and 2 times, respectively. Besides, the reducing sugar content, ethanol content and alcohol yield in corn stalks soaked in hydrogen peroxide were 7 times higher than the untreated. The cellulose can be effectively isolated after being soaked in hydrogen peroxide with a concentration of 2.5% for 72 hours, as well as better degradation of lignin and hemicellulose. The amount of ethanol and the yield of alcohol were 1.9 and 3.3 times higher than physical pulverization and steam blasting. In brief, it is declared that hydrogen peroxide pretreatment can easily destroy the lignocellulosic cellulose of maize straw and improve the conversion rate of cellulose, which might be beneficial for the production of fuel ethanol.

The current situation of industrial structure and economic growth in China is analyzed first, and then collects, sorts, classifies and summarizes relevant studies on the correlations among economic growth, industrial structure, and carbon emissions, and reviews and summarizes the research methods.

Ventilation system’s effectiveness can be affected by walking-induced disturbances. A series of experiments were performed in a chamber in this study (6.0 m × 5.9 m × 2.5 m) to measure the walking-induced temperature/flow/pollution field fluctuation characteristics. A method for quantifying the robustness of a ventilation system in the control of walking-induced fluctuations was used in this study. The experimental results showed that the cumulative particle exposure levels under walking modes W1, W2 and W3 were 2.04 ± 0.27, 1.72 ± 0.26 and 0.87 ± 0.12 times the exposure levels without human walking. The four ventilation systems all performed well in indoor temperature disturbance control; however, different walking modes and ventilation systems would result in different walking-induced disturbances of the flow and pollutant fields. For the flow field, the highest range scale robustness value was achieved by the side supply and side return (SS) system. For the pollutant field, the range scale robustness value of the SS system was still the highest, 18.7% larger than the lowest value. With the increase in temperature from 18 °C to 28 °C , the range and time scale robustness of the different ventilation systems decreased by 7.7–18.4% and 1.3–15.7%, respectively.

Precise forecasts of the propagation patterns of social commerce information play a crucial part in precision marketing. Traditional forecast relies on machine learning diffusion models, in which the forecast accuracy is dependent on the quality of the designed features. Researchers using these models are required to have experience in this regard, but due to the complexity and variations of real-world social commerce information propagation, design of features for the prediction model turns out difficult and is likely to cause local or universal errors in the model. To address these problems, this study proposed an information propagation prediction model based on Transformer. First, the fully-connected neural network was employed to code the user nodes to low-dimension vectors; then, Transformer was employed to perform information of the user-node vectors; last, the output of the Transformer was uploaded to the output layer to forecast the next user node in information propagation. The model was tested on data sets obtained from Sina Weibo, and the test result shows that the proposed model outperformed baseline models in terms of the indicators of Acc@k and MRR.

Wearing facial masks has been indicated as an effective way to reduce the risk of COVID-19 transmission among people. To get a deeper understanding of the habit of using face masks in normal life during COVID-19 outbreak and seek ways to solve the problems of mask using, we conducted a large-scale survey in China through online questionnaires. Totally 1004 respondents, including community outreach workers, non-healthcare professionals, retired people, and students participated in this study. Detailed information regarding the types of masks that people usually use, the habit of changing masks, the methods of mask cleaning, and the attitude toward reusing masks and their potential impact on the environment were collected and analyzed. Results show that more than 98% of people in China used masks during the pandemic, and the types of masks using and frequency of masks changing/reuse varied between different people. Moreover, most of the respondents had a healthy mask-changing habit for preventing the spread of COVID-19 and worried about the safety of mask reusing. The study would help enhance public awareness and develop policies for a better habit in face of the pandemic.

In recent years, as the pace of people’s life is speeding up, more young people working far from their parents, the elderly have to live alone. With the increase of age, they tend to forget things which may create safety accidents. Therefore, a smart home system for the elderly will have good application prospects. In this paper, a smart system based on ZigBee wireless network is proposed. This system uses wireless network for transmitting information between sensor nodes and uses embedded technology to analyse the data. Once an emergency occurs, the system will send an alarm to notify the elderly. At the same time, the young people can know the situation of the house through mobile phone

First, a simulation model of the SOFC-MGT top-level combined cycle was established through Matlab/Simulink, and then the effect of different methane flow rates on the performance of the stack and the SOFC-MGT system was analyzed. The research results show that with the increase of methane flow, the power of the stack and SOFC-MGT system gradually increases, but the efficiency of the SOFC-MGT system gradually decreases with the increase of methane flow.

A MoSi2-CrSi2-SiC-Si coating was prepared on the surface of carbon/carbon (C/C) composites by a two-step pack cementation method. The microstructure and oxidation behaviour of the coating were studied. These results illustrated that the coating could effectively protect C/C composites from oxidation from oxidation in air above 1600 K, due to the protection of the compound glass. The weight loss of the coated C/C specimens was only 0.4% after oxidation at 1873 K for more than 150 h. The coating lacked effective oxidation resistance for C/C composites from 800 to 1600 K, as no obvious glass layer covered the coating surface and the cracks cannot be sealed because of the high viscosity of the compound glass.