A cryogenic permanent magnet undulator (CPMU) prototype cooled by sub-cooled liquid nitrogen was developed in Shanghai Synchrotron Radiation Facility (SSRF) in 2016. The CPMU prototype mainly consist of NdFeB based hybrid magnet arrays with a period of 20 mm and a magnetic length of 1.6 m, a pair of girders to support the magnetic arrays, parallel SLN2 cooling loops attached to the girders, thermal spacers connecting the girders and the copper LN2 tubes, electric heaters to heat the girders and regulate the magnet working temperature at around 120 K, and stems made of stainless steel to support the girders. During the first magnetic field measurement, the RMS phase error of the CPMU prototype changed from 3.2 degree at room temperature to 4.5 degree at 135 K. By shimming the magnetic field, its RMS phase error is reduced to 3.5 at low temperature finally. This paper presents detailed analyses of temperature distribution and thermal deformation along the CPMU girder during cool down process. By comparison with test results, the deterioration of the RMS phase error is well explained. The analyses can provide guidance for magnetic field shimming and avoid or reduce the deterioration of the RMS phase error at low temperature.

In order to strengthen the management of circuit breakers and sense its operation status at any time, condition-based maintenance has been carried out in power grids. Depending on the advanced condition monitoring and diagnosis technology, the abnormality of equipment can be judged and the failure of equipment can be predicted effectively. This paper discusses the state parameters need to be monitored for deep state sensing of high voltage circuit breakers. Monitoring parameters mainly include the current of opening/closing coils and energy storage motor coil, primary current and displacement of operating mechanism, respectively. And then, aiming at the complex installation environment of switch cabinet, a small integrated depth sensing node architecture is designed.

The important component of transmission and transformation equipment in the power grid is whether the power grid can maintain a safe operation state depends on the safety and reliability of the transmission and transformation equipment itself. The application of Internet of things technology plays an important role in the management of transmission and transformation equipment. Therefore, in order to improve the high efficiency of transmission and transformation equipment, it is necessary to introduce and apply Internet of things technology. In order to improve the high efficiency of transmission and transformation equipment, it is necessary to introduce and apply Internet of things technology in power transmission and transformation equipment In the management of power transmission and transformation equipment, the application of Internet of things technology can promote the effective improvement of the accuracy of the monitoring results of equipment operation status to a certain extent, thus improving the operation quality of the whole power grid and promoting the construction of intelligent management system of power grid units. This paper first briefly expounds the technical meaning of Internet of things, and then analyzes the main application scenarios of layered network routing protocol in the management of transmission and transformation equipment, which provides an effective theoretical reference for the safe operation and high-quality operation of power grid.

To understand the latest research progress, research trends and future research hotspots of oil-water separation and oil absorption materials for oil spill and oily wastewater at home and abroad, through the web of science core collection database, Based on the literature analysis tools of web of Science (WOS) database, vosviewer visual analysis software and origin, the published literatures on oil-water separation materials and oil absorption materials were quantitatively analyzed in terms of the number of papers published at different times, the top 10 countries (regions), research institutions, research directions, journal sources, etc. The results show that: with the growth of time, the number of papers published gradually increases; China, the United States and India rank the top three, among which China accounts for 40% of the total, indicating that China is in the leading position in this field; among them, Chinese institutions are in the absolute leading position; chemistry, materials and engineering are the most concerned research directions.

In order to clarify the response of soil enzyme activities of cultivated salinealkali soil to sand cover in the Loess Plateau-Mu Us Sandy ecotone. In this study, the soil enzyme activities of the saline-alkali soils before and after sand-covering (CK) and after sand-covering for three consecutive years were taken as the research objects. The results showed that the activities of four soil enzymes (urease, catalase, protease, and alkaline phosphatase) all increased to varying degrees after covering with sand. Among them, the effect of covering with sand on soil urease and alkaline phosphatase was significant. In general, the activities of the four soil enzymes are negatively correlated with soil physical properties (except porosity) and positively correlated with soil chemical properties. This study provides data support for revealing the long-term effects of sand-covering on soil enzyme activities of cultivated saline-alkali soils, and provides a reasonable idea and theoretical reference for the feasibility of using sand-covered soil organic restructuring technology in saline-alkali soil management.

The effect of initial temperature and initial pressure on lower explosion limit (LEL) of RP-3 aviation kerosene vapor was investigated experimentally. The experiments were conducted in an explosion limit equipment at initial temperature of 40-160 °C and initial pressure 100-160 kPa. In the temperature-pressure range studied, the LEL decreases with the increase of the initial temperature, while increases as the initial pressure increases. A correlation formula established in the present study can predict the experimental data well. A comparison of the temperature dependence and pressure dependence indicates that the LEL of RP-3 aviation kerosene vapor is mainly affected by the initial temperature. This guides people to pay more attention to the aspect of the heat transfer in the fuel tank of aircrafts avoiding the explosion risk caused by high temperature.