Research On Safety Evaluation Of High Frequency Electromagnetic Exposure In Subway Cab

At present,the total length of the national subway line is 4991.7 kilometers,and the total passenger traffic reaches 18.4 billion passengers in China.It is estimated that by 2020,the subway will achieve mileage of 7,000 kilometers.The subway has thus become an important driving force for urban infrastructure construction in China.In order to meet the development trend of subway intelligentization,more and more electronic equipments will be put into the construction and operation of subways,leading to an increasingly complicated electromagnetic environment.Based on epidemiological and experimental measurements,many research teams had shown that electromagnetic exposure in rail transit vehicles has health impact on the human body,but studies on high-frequency electromagnetic exposure of subways,especially subway drivers occupation exposure is still a blank domain.By assessing the safety of occupational electromagnetic exposure of subway drivers,this dissertation can further clarify the radiation impact of subway high-frequency electromagnetic environment on driver's human tissue,provide reference for subway driver's electromagnetic exposure safety protection,and make subway driver have a better understanding of highfrequency electromagnetic environment,and eliminate of subway drivers' fear of high-frequency electromagnetic radiation and anxiety about occupational diseases.At first this dissertation analyzes the development trend of international rail transit and reflects the necessity of safety assessment of high frequency electromagnetic exposure in the subway train cab.Based on rail transit electromagnetic compatibility and electromagnetic exposure research and development status,the research background and significance of this dissertation is proposed.Second,the bio-electromagnetic effect in high-frequency electromagnetic field,and the driver human body model that based on the ratio of standard human body model are illustrated.The finite element calculation method of high-frequency electromagnetic exposure safety evaluation,the mathematical method and design idea of modeling and simulation using high-frequency electromagnetic simulation software is introduced.The reliability of the high frequency electromagnetic structure simulation software HFSS for solving the high frequency electromagnetic exposure problems of the human body is verified.Thirdly,it is clarified that the high-frequency electromagnetic exposure source of subway driver cab is mainly composed of special wireless communication system antenna,train automatic control system antenna and passenger information system antenna.Based on the operating frequency,structural characteristics,physical dimensions,installation position structure and radiation performance index of different system antennas,the equivalent high-frequency radiation exposure sources corresponding to the three system antennas are designed.The distribution of radiation far-fields is simulated simultaneously.Then,this dissertation builds a complete high-frequency electromagnetic environment model of the subway cab based on the actual size of the subway cab and the human body model.The average specific absorption rate of the driver's human body model under the action of three different high-frequency electromagnetic radiation sources is further simulated,and the specific distribution of the electromagnetic radiation dose absorbed by different tissues in the driver's human body model is quantitatively analyzed.Compare the simulation results with the basic limits of occupational electromagnetic exposure restrict values established by the International Commission on Non-Ionizing Radiation Protection(ICNIRP),it demonstrates the subway driver is safe in this high-frequency electromagnetic environment,and the high-frequency electromagnetic radiation in the subway driver's cab will not cause health hazards to the subway driver.Compare the subway field electromagnetic environment measurement data with its simulated results,it verifies the reliability of assessing high frequency electromagnetic exposure method,and compare with the international electromagnetic exposure reference limit to evaluate the safety of subway electromagnetic environment.The main innovation of this dissertation is based on the theory of bioelectromagnetism,use the electromagnetic dosimetry method to model the high-frequency electromagnetic environment of the subway driver's cab under the action of electromagnetic radiation sources of different frequency bands,simulate the average specific absorption rate,the induced electric field strength and the induced magnetic field strength,the electromagnetic radiation dose distribution absorbed in the brain,skull,scalp and trunk in the sitting and standing human models is analyzed.Compare simulated results with the basic limits of occupational electromagnetic exposure values,the safety of occupational electromagnetic exposure in this high-frequency electromagnetic environment is ascertained which fills the gap in the field of occupational electromagnetic exposure safety assessment in the subway driver's cab.Through the measurement of the subway driver's cab and the next-door compartment,the influence of different high frequency electromagnetic exposure sources on the high frequency electromagnetic environment of subway driver's cab can be analyzed.Combine measurement data with the modeling and simulation of the subway high-frequency electromagnetic environment measurement area,the high-frequency electromagnetic environment of the subway cab is further clarified,which demonstrate the safety of the high frequency electromagnetic environment in the subway driver's cab.