Natural Hazards - Natural hazards, such as high winds, heavy rains and ice melting, can easily trigger the rockfall which usually leads to great personal injuries and property loss; therefore, the... 相似文献
The lack of sufficient direct observation data of typhoon fine structure is the main bottleneck that restricts the further development of typhoon discipline and forecasting. This paper briefly introduced the basic information of the National Key R&D Program of China, entitled “Experiment on Coordinated Observation of Offshore Typhoon in China”, which started in early 2019. Firstly, the importance and necessity of the program around the national needs on typhoon-related disaster reduction and prevention were explained. Then, the coordinated observation difficulties and frontiers in the current typhoon discipline situation from the development and improvement of the physical mechanism and key forecasting technologies were shown. The overview of the direct observation instrument and platform, the field campaign and the parameterization techniques related to physical process in typhoon numerical modeling was provided. Finally, the key scientific and technical issues and main research contents of the program were given. 相似文献
The long-lived debate on the principle of effective stress is rooted in the obscure physical significance of stresses. For the sakes of clarifying stress concepts and establishing a reasonable principle of effective stress, unsaturated soil is divided into six phases and the bearing structure of it, named generalized soil structure, is defined based on considering soil as a special structure. Then the essence of effective stress equation, named stress relation equation, is derived according to analysis of interphase interactions and independent-phase equilibrium. The stress relation equation indicates the corresponding relation between two series of stress variables used in mixed and multiphase continuum models, respectively. Furthermore, a reasonable concept of suction stress is redefined to describe interparticle connection properties. Then, a generalized stress framework is constructed by associating stress relation equation with suction stress. After demonstrating the concept of neutral stress, a generalized principle of effective stress is established and the total soil skeleton stress is searched out, which is the predominant stress controlling the strength and deformation of soil. Finally, the collapse phenomenon is analyzed and the time- and spatial-dependent stress frameworks are developed.
In this study, a systematic survey of cultural airborne fungi was carried out in the occurrence environments of wall paintings that are preserved in the Tiantishan Grottoes and the Western Xia Museum, China. A bio-aerosol sampler was used for sampling in four seasons in 2016. Culture-dependent and -independent methods were taken to acquire airborne fungal concentration and purified strains; by the extraction of genomic DNA, amplification of fungal ITS rRNA gene region, sequencing, and phylogenetic analysis, thereafter the fungal community composition and distribution characteristics of different study sites were clarified. We disclosure the main environmental factors which may be responsible for dynamic changes of airborne fungi at the sampling sites. The concentration of cultural airborne fungi was in a range from 13 to 1,576 CFU/m3, no significant difference between the two sites at the Tiantishan Grottoes, with obvious characteristics of seasonal variation, in winter and spring were higher than in summer and autumn. Also, there was a significant difference in fungal concentration between the inside and outside of the Western Xia Museum, the outside of the museum was far more than the inside of the museum in the four seasons, particularly in the winter. Eight fungal genera were detected, including Cladosporium, Penicillium, Alternaria, and Filobasidium as the dominant groups. The airborne fungal community structures of the Tiantishan Grottoes show a distinct characteristic of seasonal variation and spatial distribution. Relative humidity, temperature and seasonal rainfall influence airborne fungal distribution. Some of the isolated strains have the potential to cause biodeterioration of ancient wall paintings. This study provides supporting information for the pre-warning conservation of cultural relics that are preserved at local sites and inside museums. 相似文献