Heat transfer and temperature evolution in underground mininginduced overburden fracture and ground fissures: Optimal time window of UAV infrared monitoring

Heat transfer and temperature evolution in overburden fracture and ground fissures are one of the essential topics for the identification of ground fissures via unmanned aerial vehicle(UAV) infrared imager. In this study, discrete element software UDEC was employed to investigate the overburden fracture field under different mining conditions. Multiphysics software COMSOL were employed to investigate heat transfer and temperature evolution of overburden fracture and ground fissures under the influence of mining condition, fissure depth, fissure width, and month alternation. The UAV infrared field measurements also provided a calibration for numerical simulation. The results showed that for ground fissures connected to underground goaf(Fissure Ⅰ), the temperature difference increased with larger mining height and shallow buried depth. In addition, Fissure Ⅰ located in the boundary of the goaf have a greater temperature difference and is easier to be identified than fissures located above the mining goaf. For ground fissures having no connection to underground goaf(Fissure Ⅱ), the heat transfer is affected by the internal resistance of the overlying strata fracture when the depth of Fissure Ⅱ is greater than10 m, the temperature of Fissure Ⅱ gradually equals to the ground temperature as the fissures’ depth increases, and the fissures are difficult to be identified. The identification effect is most obvious for fissures larger than 16 cm under the same depth. In spring and summer, UAV infrared identification of mining fissures should be carried out during nighttime. This study provides the basis for the optimal time and season for the UAV infrared identification of different types of mining ground fissures.

Abundance and characteristics of microplastics in shellfi sh from Jiaozhou Bay,China

As an emerging pollutant,the presence of microplastics in marine organisms has been concerned increasingly.Shellfi sh,which are both economically and ecologically important,are of particular concern.In this study,we investigated the microplastic pollution in wild and farmed oysters(Crassostrea gigas)and clams(Ruditapes philippinarum)in the Jiaozhou Bay,China,for the fi rst time.We found the microplastic pollution in shellfi sh in Jiaozhou Bay was at a moderate level.The abundance of microplastics in shellfi sh ranged from 0.16 to 12.09 items/g(wet weight,ww)or 1 to 9 items/ind.The average abundance of the ingested microplastics was 1.21 items/g(or 2.17 items/ind.)in all shellfi sh,1.51 items/g(or 2.00 items/ind.)in clams and 0.92 items/g(or 2.34 items/ind.)in oysters.The abundance of microplastics in clams was signifi cantly higher than that in oysters.Most microplastics(92.97%)were fi bers,followed by fragments.The predominant color of the microplastics was black(42.97%),followed by blue,transparent,and red.Cellophane and polyethylene terephthalate(PET)dominated the microplastic composition.According to shellfi sh consumption,it can be inferred that the average microplastic consumption through Chinese diet is 1.27×10^(3)items per capita per year.

Layered MoS2@graphene functionalized with nitrogen-doped graphene quantum dots as an enhanced electrochemical hydrogen evolution catalyst

A novel three-dimensional (3D) layered MoS2@graphene functionalized with nitrogen-doped graphene quantum dots (MoS2@N-GQDs-GR) composites as an enhanced electrochemical hydrogen evolution catalyst. The few layered MoS2 nanoflowers supported on N-GQDs-GR surface were elaborately fabricated by one-pot hydrothermal method, which MoS2 and N-GQDs-GR exist in a bonding manner of Mo-N. In addition, due to the layered MoS2 sheet edge exposes more hydrogen evolution active sites and N-GQDs-GR have high conductivity, the composites exhibit prominent electrocatalytic activity with a low overpotential 99 mV, a small Tafel slope 49.3 mV/dec. Therefore, that the current work will develop HER catalysts may replace Pt.

Nuclear EPL-HAM complex is essential for the development of chloroplasts

Chloroplasts most likely originated from the endosymbiosis of cyanobacterial ancestors,entering the eukaryotic lineage about 1.0-1.5 billion years ago(Parfrey et al.,2011;Archibald,2015).Consequently,their biogenesis depends on genetic information from both the nuclear and chloroplast genomes.Photosynthetic housekeeping genes of core components in photosystemsⅠandⅡ(PSI and PSII)are encoded by the plastid genome。

Effects of various donor:acceptor blend ratios on photophysical properties in non-fullerene organic bulk heterojunctions

The composition ratio of donor and acceptor materials in organic bulk heterojunction (BHJ) is one of the key parameters to govern the performance in organic solar cells (OSCs). Therefore, high-performance non-fullerene organic bulk heterojunction consisting of poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b' ]dithiophene))-co-(1,3-di(5-thiophene-2-yl)–5,7-bis(2-ethylhexyl) benzo[1,2-c:4,5-c']dithiophene-4,8-dione)] (PBDB-T) and 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))–5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2' ,3'-d' ]-s-indaceno[1,2-b:5,6-b' ]-dithio-phene (ITIC) are used to investigate the correlation among various donor: acceptor (D:A) ratios, photophysical properties and photovoltaic performance. Interestingly, the function of short-circuit current (Jsc) and D:A ratios demonstrates an axisymmetric trend. When the blending ratio of D:A deviates from the optimal ratio, the symmetrically decreased Jsc is derived from a reduction in the D:A interface or amorphous region. Research on the steady-state photoluminescence (PL), the time-resolved fluorescence spectroscopy measurements, atomic force microscopic (AFM) and grazing-incidence small angle X-rays scattering (GIWAXS) indicates no significant variation in energy loss in the process of changing D:A ratios in BHJs. With high donor or acceptor content, the domain size improves significantly, but the distance of π-π stacking corresponding to molecular packing has not changed significantly, and the bi-continuous percolation pathways were not obviously influenced.