The 16N monitoring system operates in a mixed neutron-gamma radiation field and is subject to high background radiation, thus triggering instability in the 16N monitoring system measurement data. Due to its property of actual physical process simulation, the Monte Carlo method was adopted to establish the model of the 16N monitoring system and design a structure-functionally integrated shield to realize neutron-gamma mixed radiation shielding. First, the optimal shielding layer with a thickness of 4 cm was determined in this working environment, which had a significant shielding effect on the background radiation and improved the measurement of the characteristic energy spectrum and the shielding effect on neutrons was better than gamma shielding with the increase in the shield thickness. Then, functional fillers such as B, Gd, W, and Pb were added to the matrix to compare the shielding rates of three matrix materials of polyethylene, epoxy resin, and 6061 aluminum alloy at 1 MeV neutron and gamma energy. The shielding performance of epoxy resin as the matrix material was better than that of the aluminum alloy and polyethylene, and the shielding rate of boron-containing epoxy resin was 44.8%. The γ-ray mass attenuation coefficients of lead and tungsten in the three matrix materials were simulated to determine the best material for the gamma shielding performance. Finally, the optimal materials for neutron shielding and gamma shielding were combined, and the shielding performance of single-layer shielding and double-layer shielding in mixed radiation field was compared. The optimal shielding material-boron-containing epoxy resin was determined as the shielding layer of the 16N monitoring system to realize the integration of structure and function, which provides a theoretical basis for the selection of shielding materials in a special working environment.
Studies investigating the diversity and structure of soil microbial systems in response to ionizing radiation are scarce. In particular, effects of long-term low-dose radiation is rarely studied because of its unique conditions. In this study, an area in Chengdu, China, which has been irradiated by the radionuclide thorium-232 for more than 10 years was investigated. Four groups of samples with absorbed dose rates ranging from 192.906 ± 5.05 to 910.964 ± 41.09 nGy/h were collected to analyze the compositional and functional changes of the soil microbial systems in the region. The diversity and structure of the soil microbial systems were determined using high-throughput sequencing. Our results showed that long-term low-dose ionizing radiation had no significant effect on soil bacterial diversity, but had a great impact on fungal diversity. Long-term ionizing radiation strongly affected soil microbial community structure. Long-term low-dose ionizing radiation was shown to have a promoting effect on iron-oxidizing bacteria and ectomycorrhizal fungi and have an inhibiting effect on predatory or parasitic fungi, further affecting the soil C/N ratio. This study is of great reference significance for future research on the impact of long-term low-dose ionizing radiation on soil ecosystems.
One of the core objectives of the Washington Agreement, the most influential international agreement on the mutual recognition of degrees in engineering education, is to ensure the continuous improvement of professional teaching. Education for sustainable development is a vital direction of teaching reform and development of higher engineering education. Taking a Raman spectroscopy course as an example, this paper discusses VR-based course design and the strengths and limitations of a VR-based course. The idea of computational thinking and immersive learning is realized by introducing VR technology. Based on the research status in the field of Raman spectroscopy, the contents of 10 Raman spectroscopy courses are redesigned. Through a questionnaire survey, peer review, and interview, the rationality of the course design is evaluated, and based on this, a feedback mechanism is established to ensure the continuous improvement of the course. Eventually, the advantages and disadvantages of the new curriculum are evaluated, and the development direction and limitations of the corresponding teaching model are put forward. According to the research, although 85% of the students said that it is difficult to accept the VR-based course at short notice, 90% and more of the students recognize this new teaching model. They believe that the VR-based course changes their traditional learning habits and helps cultivate self-learning ability. The research results can be utilized as a crucial reference for engineering education reform and provide a reliable model for the sustainable development of education.
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