Electric Power Filling Comound
Optical fiber sensors expose ultra-fine particles in the atmosphere
Detection of ultrafine particles in the atmosphere for the first time has a low-cost portable weapon. Recently, the research group led by Prof. Xiao Yunfeng and Academician Gong Qihuang of the School of Physics of Peking University successfully prepared an all-optical sensor based on a nanofiber array. The resolution of the single particle size of the new sensor reached 10 nm for the first time.
Sensitive detection of particulate matter is of great significance in environmental monitoring, national security, and biochemical research. Optical-based sensing technology has the advantages of non-physical contact, ease of operation, and high sensitivity. Therefore, traditional fiber-optic sensors have been used in high-sensitivity detection.
Xiao Yunfeng explained to the reporter of Science and Technology Daily: “International academic research shows that when the diameter of the optical fiber is reduced to the optical wavelength level, a significant evanescent field is generated outside the optical fiber (scale is on the order of hundreds of nanometers), which is weak to the surrounding environment. The change is extremely sensitive, so the scattering effect of particles in the evanescent field can be used to achieve sensing and size distribution measurements of ultrafine particles."
According to Xiao Yunfeng, in the new study, they first accurately calculated the relationship between the scattering efficiency and the size of the scatterer and the diameter of the fiber, predicted the optimal geometry and detection limit of the nanofiber sensor, and subsequently performed a highly sensitive nanofiber array. The design and preparation, and through the optimization of the fiber mode, enabled the sensing and measurement of a single standard polystyrene nanoparticle with a particle size resolution of 10 nanometers. electric power filling comound
The research team used this sensor to continuously monitor Beijing's winter atmospheric fine particles in 2015 and 2016, and directly obtained the particle size distribution information and real-time evolution map of the hundred nanometer-scale fine particles, and calculated the fine particles based on the data. The mass concentration data is in good agreement with the official data trend, showing that this result has a high application value.
Academician Gong Qihuang said: "Compared with other sensors, nanofiber sensor is not only accurate, but also has low cost, simple operation and portability. It can quickly and accurately detect ultrafine particles in the atmosphere. The mechanism of haze formation provides a new tool."
This achievement was published in the important optical journal "Light: Science and Application". The research was supported by the National Natural Science Foundation of China and the Ministry of Science and Technology.
About power system
Power system mainly includes power generation equipment and power supply equipment. The power generation equipment is mainly power station boilers, steam turbines, gas turbines, water turbines, generators, transformers, etc. The power supply equipment is mainly transmission lines, transformers, and contacts of various voltage levels. electric power filling comound
There are many power devices in the power system. According to their different roles in operation, they are usually divided into electrical primary devices and electrical secondary devices.
Power system that directly participates in the production, transformation, transmission, distribution, and consumption of electrical energy is called an electrical primary equipment. It mainly includes:
Equipment for electrical energy production and transformation, such as generators, motors, transformers, etc.;
Switching devices that switch on and off the circuit, such as circuit breakers, disconnectors, contactors, fuses, etc.
Current-carrying conductors and gas-insulated equipment. Such as busbars, power cables, insulators, wall bushings, etc.
Devices that limit overcurrent or overvoltage, such as current limiting reactors, surge arresters, etc.
Transformer equipment: reduce the high voltage and current in the primary circuit for measuring instruments and relay protection devices, such as voltage transformers and current transformers
Secondary power equipment
In order to protect and ensure the normal operation of electrical primary equipment, equipment that measures, monitors, controls, and regulates its operating status is called an electrical secondary equipment. There are various metering meters, various relay protection and automatic devices, and DC power supply equipment.
Power system overhaul
The secondary equipment of electric power constitutes a system, not only the equipment itself, such as AC, DC, and control loops. As there is no monitoring means for some circuits, real-time technical analysis and judgment cannot be made on the equipment status. Therefore, in the strict sense of the status quo of the application of electrical secondary equipment, most protections do not have the conditions for conditional maintenance.
Most of the planned maintenance systems used in power systems in power systems are seriously flawed, such as frequent temporary maintenance, inadequate maintenance, or over-maintenance, blind maintenance, etc., which makes the countries around the world spend huge sums on equipment maintenance each year. How to reasonably arrange maintenance of power equipment, save maintenance costs, reduce maintenance costs, and ensure high reliability of the system is an important issue for system operators. With the application of sensing technology, microelectronics, computer software and hardware and digital signal processing technology, artificial neural network, expert system, fuzzy set theory and other integrated intelligent systems in condition monitoring and fault diagnosis, based on equipment condition monitoring and advanced diagnostic technology The state maintenance research has been developed and has become an important research area in the power system. electric power filling comound