This paper studies and introduces the successful case of gob-side entry retaining technology and the typical mining pressure law in Luan mining area, which is the main mining coal seam in Qinshui coalfield. Qinshui coalfield has an estimated coal reserve of 300 billion tons, accounting for 9.58% of the total national coal reserve in China, especially anthracite, chemical coal, and coking coal. The methods of field investigation, theoretical analysis, physical experiment, and industrial test are adopted. Through the field investigation, theoretical analysis, physical experiments, and industrial test, the following conclusions have been drawn in this study: (1) A thorough engineering geological investigation was conducted on the entry retaining along the gob side on noncoal pillar mining working face, which covers multiple periods of mining process including the roadway excavation period, primary mining period, primary mining stability period, and secondary mining influence period. A series of analysis and tests were conducted such as core sampling, rock mechanics property testing, borehole detection, and flexible formwork support evaluation, which laid a foundation for identifying the mining pressure law of gob-side entry retaining by using noncoal pillar mining. (2) The mining pressure law was studied through the collection of the field measurements taken from the entry retaining along the gob side on noncoal pillar mining working face. The keys to achieve the roadway surrounding rock stability through noncoal pillar mining are obtained. According to the study, the stability control of retained roadway surrounding rock mainly depends on the stability of top coal, coal side, and shoulder angle coal. (3) In this study, a roadway reinforcement scheme is proposed to improve the surrounding rock control technology for gob-side entry retaining by noncoal pillar mining, whose effectiveness has been verified by a series of industrial test. Therefore, the wide adoption of the noncoal pillar mining method in Number #3 coal mine can significantly relieve the predicament of coal pressing under a large number of buildings in Luan mining area, which provides insightful guidance to the coal-free pillar mining in the whole Luan mining area.
Heavy impurity doping leads to bandgap narrowing (BGN) and this causes perturbations to the value of the band offsets at the hetero-interface. As a result, the form and height of energy barriers in abrupt HBT is disturbed, which changes the value of the current flowing through its interfaces. The analysis is based on the thermionic field-diffusion model which combines the drift-diffusion transport in the bulk of the transistor with the thermionic emission and tunneling at the base-emitter interface. The calculations reveal a more important role to the transport of carriers played by the modification of the built-in potential than that of the range of barrier energies available for tunneling because the impact of the built-in potential on the current is exponential. Therefore, it is important for a better description of the currents to use an accurate dopant-dependent BGN distribution model between bands.
Greenway is a kind of corridors in the city that takes natural elements as the main constituent foundation and connects open spaces with functions such as leisure and recreation. The assessment of the built greenway is a review of the past construction experiences, and it is also a supplement and improvement to the future greenway planning concept system, which has important academic and application value. This study will explore how greenway design factors influenced the local cyclists’ perception of the landscape using on-site questionnaire and photo rating method. The results indicated that greenways with continuous cycling paths, high security awareness, open landscapes, and rich human activities evoke positive perceptions. Among the visual elements, natural elements such as plants and sky are more favorable than artificial elements. The research results show that the formation of greenway cyclists’ landscape imagery is affected by visual perception elements, which suggests that special consideration should be given to the laws of cyclists’ mental perception when designing greenways.
Programmed cell death 1 (PD-1) has recently been reported to have a genetic association in several autoimmune diseases. The object of this study was to investigate the association of PD-1 polymorphisms with aplastic anemia (AA) in the Chinese Han population. In a case-control association study, three single-nucleotide polymorphisms (SNP), PD-1.3 G/A, PD-1.5 C/T, and PD-1.9 T/C, were genotyped in 166 AA patients and 264 healthy controls using polymerase chain reaction-restriction fragment length polymorphism assay. All genotype distributions in the patients and the controls were in Hardy-Weinberg equilibrium. The associations of genotypes and alleles with AA were analyzed. No differences in genotype and allele frequencies were elucidated for SNPs in intron 4 and exon 5. In conclusion, we show no association of selected SNPs in PDCD1 gene with AA in the Chinese Han population.
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