Search

The green, clean and efficient utilization of coal is an important way for the sustainable development of coal industry. Shaanxi province is rich in coal resources, which are mainly distributed in the five coal fields in the north of Shaanxi province, and the oil-rich coal resources rank first in China. In this paper, the distribution characteristics of oil-rich coal in Shaanxi Province and the geological factors affecting the tar yield of coal are discussed by collecting the previous geological exploration data and the coal core of a coal mine in Yushen mining area of northern Shaanxi Province. The results show that the Jurassic coal field in northern Shaanxi is the best oil-rich coal in Shaanxi Province, and the tar yield is distributed in the range of 7.6%-15.3%. Material composition, oil generation potential, thermal evolution degree and coal-forming environment control the size and distribution of tar yield in coal. The desmocollinite content, volatile matter content, H element content and H/C atomic ratio were positively correlated with the tar yield of coal, and the correlation coefficient was high. There is a high correlation between the hydrocarbon index and tar yield in rock pyrolysis parameters, which can be used as an index to quickly identify tar yield in coal. The tar yield of coal increases first and then decreases with the increase of thermal evolution degree, and reaches the maximum value when Ro is about 0.9%. The higher the coal tar yield value is in the peat swamp facies with micro-flow, strong reduction and shallow overlying water-micro-flow in sedimentary environment. The research results provide reference for geological prediction of oil-rich coal.

At present, the technology of embedded channels in shield tunnel segments has been applied in subway tunnels, achieving significant economic benefits. However, it has not yet been implemented in high-speed railway shield tunnels, mainly because of the strict requirements of the overhead contact system, where the embedded channel is intended solely for the contact network. The low utilization of full-ring embedded channels leads to considerable waste. This study focuses on the precise positioning and installation of embedded channels in high-speed railway shield tunnels, aiming to optimize the use of embedded channels, improve on-site construction, and enhance subsequent operation and maintenance. The research is of considerable importance. Based on the Zhanjiang Bay Submarine Tunnel Project of the Guangzhou - Zhanjiang High-speed Railway, a comprehensive technical analysis was conducted. Simplifications and standardization of the contact network anchor segment joints and suspension types were carried out. The appropriate embedded channel lengths and segment combinations were determined according to the different needs of the contact network. Assembly points and corresponding channel segment blocks that met the requirements were proposed, along with recommended assembly points. Through on-site assembly tests and expert reviews, the general suspension of individual embedded channel segments for the contact network, as well as the precise positioning and assembly of locally embedded channel segments in multiple rings for center anchoring and anchoring, and suspension anchor, were successfully validated. The feasibility of precise positioning and assembly of locally embedded channels in large-diameter shield tunnels for high-speed railways was verified. This approach was applied in the 7.55 km shield section of the entire tunnel. According to the assembly results, different types of embedded channel segments were assembled to the specified design positions, achieving a 100% assembly pass rate, and fulfilling the requirements of the contact network and relevant specifications. [ABSTRACT FROM AUTHOR]

This study investigates pore distribution and permeability behavior of tar-rich coal following high-temperature pyrolysis at 500°C using X-ray computed tomography (CT) scanning. Coal samples post-pyrolysis were CT scanned, generating 1755 cross-sectional slices for three-dimensional reconstruction. An axial algorithm extracted pore distribution features, and geometric parameters were computed. An Equivalent Pore Network Model analyzed permeability characteristics. The results show that Post-pyrolysis pore distribution in tar-rich coal exhibited nonuniformity with a significant range in pore size distribution. Pores displayed concentrated spatial patterns. Total porosity was 14.24%, with 12.34% being connected. Most pores in Representative Elementary Volume (REV) regions fell within 10-50 μιτι in width and 20-60 pm in length, constituting over 40% of the total. Pore surface area peaked between 200-100 pm2, also comprising over 40% of the total. The Pore Network Model showed distinct characteristics in two REV regions: REV-1 demonstrated an early stage of development with poor connectivity, while REV-2 displayed a well-developed network with a bimodal coordination number histogram. The study highlights nonuniform post-pyrolysis pore distribution and significant pore size variations in tar-rich coal. This study is crucial for understanding permeability behavior in tar-rich coal after high-temperature pyrolysis. [ABSTRACT FROM AUTHOR]

Background: Data on viral kinetics and variants affecting the duration of viral shedding were limited. Our objective was to determine viral shedding in distinct severe acute respiratory syndrome coronavirus 2 variants, including Omicron BA.4/5 and BF.7, and to identify the relevant influencing factors., Methods: We carried out a longitudinal cohort study at Beijing Xiaotangshan Fangcang shelter hospital from May to June 2022 (Omicron BA.4/5) and from November to December 2022 (Omicron BF.7). Nucleocapsid protein (N) and open reading frame (ORF) genes were considered as the target genes of the reverse transcription PCR. The daily results of cycle threshold (CT), including lowest ORF1ab-CT values for days 1-3 post-hospitalisation and lowest N-CT values for days 1-3 post-hospitalisation (CT3minN) and demographic and clinical characteristics were collected., Results: 1433 patients with coronavirus disease 2019 (COVID-19) were recruited from the Fangcang shelter hospital, in which 278 patients were diagnosed with Omicron BA.4/5 and 1155 patients with Omicron BF.7. Patients with BF.7 infection showed a longer duration of viral shedding. The duration of viral shedding was associated with the variants age, alcohol use, the severity of COVID-19 and CT3minN. Moreover, the nomogram had excellent accuracy in predicting viral shedding., Conclusions: Our results indicated that patients with Omicron BF.7 had a longer period of contagiousness than those with BA.4/5. The duration of viral shedding was affected by a variety of factors and the nomogram may become an applicable clinical instrument to predict viral shedding. Furthermore, we developed a new COVID-19 viral shedding predicting model that can accurately predict the duration of viral shedding for COVID-19, and created a user-friendly website to apply this prediction model (https://puh3.shinyapps.io/CVSP_Model/)., Competing Interests: Conflict of interest: The authors declare that they have no conflict of interest., (Copyright ©The authors 2024.)