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Ancherythroculter kurematsui ( A. kurematsui ) is a unique small-size freshwater fish in southwest China. In this study, the complete mitochondrial genome of A. kurematsui was determined (GenBank accession number is KU234534). The mitochondrial genome sequence of A. kurematsui was a circular molecule with 16,621 bp in length, and contained 37 typical animal mitochondrial genes including 2 ribosomal RNA genes, 13 protein-coding genes, 22 transfer RNA genes and a control region (D-loop). Four nucleotide compositions and their relative proportions of the entire mitogenome was 27.69% C, 16.16% G, 31.21% A and 24.93% T, with an A + T and G + C contents being 56.14% and 43.86%, respectively.

The peach fruit moth, Carposina sasakii belongs to Carposinidae in Lepidoptera. In this paper, we described the complete mitogenome of C. sasakii. It is 15,611 bp in length, including 13 PCGs, 2 rRNAs, 22 tRNAs and a major noncoding A + T-rich region, which revealed the typical gene content found in other metazoan mitogenomes. The overall base composition is 42.0% A, 39.5% T, 7.75% G and 10.75% C. The A + T-rich region is located between rrnS and trnM. There is a motif ATAGA in downstream of rrnS followed by a 19 bp Poly-T stretch. The Poly-A is not found in upstream of trnM, and the position of Poly-A is replaced by a stem-loop structure. There are eight mononucleotide repeat sequences (Tn/An) with the length of 7 bp-19bp, three dinucleotide repeat sequences (TA)n/(AT)n, and a longer repeat sequence (AATATATA)5 in A + T-rich region. The mononucleotide repeat sequences occur repeatedly in A + T-rich reigion of C. sasakii, which is special in insects sequenced of Lepidoptera.

Injection of high-temperature water or steam into low-permeability coalbed for efficient and rapid extraction of coalbed methane has been studied by our university for many years and will soon be implemented in the field. With comprehensive consideration of coupling of heat transfer, water seepage, desorption of coalbed methane, and coal-rock mass deformation, the paper establishes a more comprehensive mathematical model of the coupling effect of deformation-seepage-heat transfer on coalbed methane transport. Compared with the previous studies, this theoretical model considers the change of adsorbed and free coalbed methane at high temperature and the coalbed methane transport caused by a high-temperature gradient. Using the Tunlan Coal Mine of Shanxi Coking Coal Group to conduct the numerical simulations on the coalbed methane extraction project using heat injection technology, results show that (1) high-temperature water flowed towards the extraction hole along fractured fissures, with seepage towards the coal mass on both sides of the fissure at the same time, gradually heating the coalbed and forming an arcuate distribution of temperature from high to low for an area from the fractured fissure to the coalbed upper and lower boundaries. On the thirtieth day of heat injection, the temperature of the coalbed in the heat injection area ranged from 140°C to 260°C. (2) Under high temperatures, desorption of the coalbed gas was quick, and the adsorption gas content formed an oval funnel from the heat injection hole towards the extraction hole, centered by the fractured fissure, and migrating towards the coalbed upper and lower boundaries. Along with heat injection and extraction, the absorbed gas content rapidly decreased, and on the thirtieth day of injection, the absorbed gas content of the entire heat injection area decreased to 1.5 m3/t, only 7% of the original. (3) During heat injection, the coalbed gas pore pressure rapidly increased and reached 5.5 MPa on the tenth day, about 4.5 times the original, and the pore pressure steadied at 3.5 MPa on the thirtieth day of extraction. Such a high gas pressure gradient promoted the rapid flow and drainage of the gas.

The aims of this paper are to comprehensively explore both the dynamic mechanical properties and crack evolution characteristics of coal and rock during impact failure. First, experimental specimens are prepared from coal seam, direct roof rock strata and direct floor rock strata in the same area to highlight the correlations between test pieces. Second, a dynamic strain gauge and high-speed (HS) camera are adopted to reflect the stress wave signal and crack evolution. Then, based on digital image correlation (DIC) technology and the mass screening method, the evolution laws of surface cracks during crushing and the distribution characteristics of sample fragments after crushing are studied from the perspective of fractal, and finally compared with those of the simulation analysis. The results are as follows. (1) The coal and rock samples from the same area have both consistency and differences. The dynamic mechanical properties of coal and rock are affected by the impact velocity and the physical properties of the specimen. Higher impact speeds and densities lead to the more obvious brittleness of the specimen when destroyed. Conversely, the sample shows more plasticity and ductile yield. (2) The self-similarity is significantly manifested in the evolution of surface cracks during impact and the distribution characteristics of fragments after impact. The box dimension and quality screening dimension are applicable to quantitatively characterize the evolution process and results of coal and rock fractures. (3) The simulation results based on the Holmquist–Johnson–Cook (HJC) and Riedel–Hiermaier–Thoma (RHT) constitutive models agree well with the experimental results, and the RHT constitutive model is more consistent. This study may contribute to a more comprehensive understanding of the dynamic characteristics and crack evolution laws of coal and rock under impact loading and provide references for further research and discussion.

Abundant engineering practice shows that coal and rock dynamic disasters often occur in fault zones; hence, the detection of faults in coal mines is important. As an essential branch of seismic tomographic application, research shows that ultrasonic P-wave velocity can detect mine faults and provide technical support for dynamic disaster prewarning systems. Traditional P-wave testing mostly takes rock or raw coal as the research object, which has some shortcomings in controllability, homogeneity and comparability. This paper compares the difference in ultrasonic P-wave propagation velocity in jointless and jointed briquettes through laboratory research, focuses on the effect of macro-joints on P-wave velocity and makes a preliminary theoretical analysis. The results show that: (i) the three-dimensional P-wave velocity throughout a jointless briquette specimen is similar, which reflects the high homogeneity of this medium and avoids the influence of the random distribution of primary bedding, joints and structural planes; (ii) the P-wave velocity in jointless and jointed briquettes is positively correlated with density and forming pressure, and is negatively correlated with the angle between the ultrasonic wave and the joint surface in a sample and (iii) when the P-wave encounters the macroscopic joint surface, it may reflect and refract, changing the propagation direction and inducing wave mode conversion. This study provides the necessary technical support and a theoretical guide to optimise acoustic property analysis of coal and rock as well as a field application for seismic tomography technology.

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Engineering research on geothermal development, underground gasification of coal, and heat-injection-enhanced coal bed gas extraction is gaining more and more attention from the international community, and therefore the study of permeability of coal rock bodies under the effect of temperature has become almost a hot spot in the research of rock mechanics and seepage mechanics. However, the relationship between temperature and permeability that has been seen in the literature is different, and the mechanism explanation varies greatly. In this paper, the following conclusions were obtained from an experimental study of the fine-scale structural evolution of coking coal and fine sandstone specimens, using an experimental research method of simultaneous image observation of the pore structure evolution of coal rock samples by online heating. (1) With the increase of temperature, the inner areas of coal and rock mass with both solid particles and pure pores are affected by temperature. The microscopic experiment shows that the gray level of the image changes greatly, that is, the changes in pores are also large. These pores are the roar pores in the coal and rock mass. (2) With the increase in temperature, the solid skeleton of the coal specimen will produce expansion deformation. On the one hand, this expansion deformation will increase the pores between some skeletons and increase the overall porosity of the specimen. On the other hand, it will also reduce the pore area and reduce the overall porosity of the specimen due to the intrusion of the solid skeleton into the adjacent pores. These two phenomena occur at the same time with the increase in temperature. The dominant mode is determined by the type of coal. The physical structure and temperature of the section are affected jointly. (3) When the temperature increases, the porosity of coking coal samples increases first and then decreases, and 180°C is the turning point. The fine sandstone sample shows the law of decreasing first and then increasing, and 210°C is the turning point. (4) When the temperature increases, the smaller the porosity of coal and rock samples, the specimen shows the intrusion of the solid skeleton into adjacent pores, that is, the porosity decreases. After the turning temperature, the porosity increases with the increase of temperature.