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The development of Smart Grid and power electronic technologies has driven a lot of new development in power system, especially the development of power electronic transformer (PET). Comparing to the traditional electrical transformer, PET is a new kind of power transmission device, which combines the high-frequency transformer with the power electronic technologies. This paper takes improved power electronic transformer as the main analysis object, and proposes two new kinds of topologies for the transformer. The first kind is AC-AC push-pull power electronic transformer, and the second is AC-DC-AC push-pull power electronic transformer. These two are much simpler than the common transformer. They all need fewer components, but could get the equivalent power factor as the normal transformer. On the basis of theoretical analysis, the simulation is conducted by Matlab/Simulink, and results validate the effectiveness of schemes. [ABSTRACT FROM AUTHOR]

Solving big data must deal with three crucial problems; big data storage, big data analysis and big data management. Firstly, the definitions of big data and Hadoop ecosystem are summarized respectively. Secondly, how to face big data is discussed from the two aspects of commercial products and Hadoop ecosystem. The paper focuses on reviewing the big data solution based on Hadoop ecosystem; (1) HDFS, HBase and OpenTSDB are used to deal with storage problems; (2) Hadoop MapReduce (Hive) and HadoopDB do analytical problems; and (3) Sqoop and Ganglia solve management problems. For each partner, its architecture, principles and features are analyzed. And for some defects or problems existing in some key partners, we propose some solutions, ideas and viewpoints based on our research progress. It is predicted that Hadoop ecosystem is the preferable solution for the small and medium-sized enterprises. [ABSTRACT FROM AUTHOR]

Based on the observation data of 115 weather stations of mango planting areas in South China (Guangdong, Guangxi and Fujian) from 1961 to 2016, combined with mango cold and freezing injury index, the weighted comprehensive evaluation method was used to determine the cold and freezing injury hazard index of each meteorological station in the planting area, and then established a multiple linear regression model between the cold and freezing injury hazard index and geographical factors. Finally, the regionalization of cold and freezing injury to mango in South China was made based on GIS technology. The results showed that there was a close relationship between the risk of cold and freezing injury and geographical factors in South China mango planting areas, and an overall trend was that the risk of mango cold and freezing injury gradually increased from coast to inland. In addition, with the increase of latitude and altitude, the risk of cold and freezing injury gradually increased from south to north. The slight risk areas were mainly distributed in the southern coastal areas and the low altitude areas of some inland cities of South China mango planting areas, accounting for 56.85% of the planting area, which was suitable for large-scale mango planting. The moderate risk areas were mainly distributed in the inland low and middle altitude areas of the mango planting area in South China, and the high latitude coastal areas in the north, accounting for 37.03% of the planting area. Furthermore, the severe and over severe hazard areas were mainly distributed in the inland high altitude areas of mango planting areas in South China, accounting for 6.12% of the planting area. Through the verification of historical disaster and annual production information of each county, the zoning result was consistent well with the actual situation. The results of this study could provide reference for the optimal layout and disaster prevention and mitigation of mango in South China mango planting area. [ABSTRACT FROM AUTHOR]

Aiming at the problem of the computation of ventilation heat resistance in a roadway during mine fire, to the ventilation roadways with airflow temperature and density variation, a normative computing formula was deduced. It was pointed out that according to generalized ventilation principle, the ventilation resistance during mine fire includes frictional resistance and local resistance, as well as an additional resistance caused by the external ventilation source, namely fire smoke. In the new formula, the computation of ventilation resistance is expressed from two media, namely fluid and roadway, and the conception of roadway geometry air resistance were introduced. Geometry air resistance is the resistance characteristic of roadway itself, and it has nothing to do with fluid. Geometry air resistance includes frictional resistance and local resistance too. Conceptually, the new formula has a clear discrimination to the essence of heat resistance, so the mistakes easily appear during computation and analysis will be avoided. The conclusion that the ventilation resistance of high temperature smoke flow is in direct proportion to fire temperature was drawn. To verify the heat flow resistance effect, an experimental pipeline facility was designed to determine the variation of heat resistance with temperature. The experimental results are identical to the conclusion drawn from theoretical derivation. The additional resistance of exogenous smoke flow was extracted successfully by using the experimental facility. Experimental results show that exogenous resistance is the physical image of combustion process. A practical method for computing the heat resistance with the participation of exogenous gas is provided. [ABSTRACT FROM AUTHOR]

Based on the pyrolysis experiment comparison of coking-coal tailings and raw coking coal, the effect of final temperature, heating rate and high content of mineral in tailings on the pyrolysis of coking-coal tailings was studied, and the kinetic model of coking-coal tailings was established. The results show that the final temperature has great influence on the pyrolysis of coking-coal tailings, with the increase of final temperature,the decomposition of tailings and the precipitation of volatile become easy. After 850 °C,the effect of final temperature begins to weaken due to the higher content of mineral in tailings. Mineral in tailings has suppression effect on the total process of pyrolysis of tailings, and delay the pyrolysis of tailings to a high temperature. The process of tailings can be described as three second-order reactions and the active energy of tailings pyrolysis is 54. 7-131. 1 kJ/mol. [ABSTRACT FROM AUTHOR]