Energy mechanism of bolt supporting effect to fissured rock under static and dynamic loads in deep coal mines

The stability control of fissured rock is difficult,especially under static and dynamic loads in deep coal mines.In this paper,the dynamic mechanical properties,strain rate evolution and energy dissipation of fissured and anchored rocks were respectively obtained by SHPB tests.It was found that bolt can provide supporting efficiency-improving effect for fissured rock against dynamic disturbance,and this effect increased quadratically with decrease in anchoring angles.Then,the energy dissipation mechanism of anchored rock was obtained by slipping model.Furthermore,bolt energy-absorbing mechanism by instantaneous tensile-shear deformation was expressed based on material mechanics,which was the larger the anchoring angle,the smaller the energy absorption,and the less the contribution to supporting efficiency improvement.On this basis,the functional relationship between energy dissipation of anchored rock and energy absorption of bolt was established.Taking the coal-gangue separation system of Longgu coal mine as an example,the optimal anchoring angle can be determined as 57.5°–67.5°.Field monitoring showed fissured rock with the optimal anchoring angle,can not only effectively control the deformation,but also fully exert the energy-absorbing and efficiency-improving effect of bolt itself.This study provides guidance to the stability control and supporting design for deep engineering under the same or similar conditions.

Characteristics of the Fish Assemblage in the Intertidal Salt Marsh and Mudflat of the Yangtze Estuary

During July 2015 to June 2016, two permanent sampling sites were established in Scirpus mariqueter salt marsh and its adjacent mudflat on the intertidal zone of Chongming-Dongtan in the Yangtze Estuary. Based on monthly trap net surveys of fishes, the characteristics of the fish assemblages in the different subhabitats, including the salt marsh and mudflat, and the monthly variations were analyzed. A total of 19 species of fishes were found belong to 12 Families. The characteristics including the dominant fish species were different in these two subhabitats. 18 species of fish were recorded in the mudflat, of which the dominant species were the Coilia ectenes, Pelteobagrus nitidus and Lateolabrax maculatus. Ten species of fish were recorded in the salt marsh of which the dominant species were the Coilia ectenes, Saurogobio dumerili, Liza haematocheila, Lateolabrax maculatus and Acanthogobius ommaturus. Pelteobagrus nitidus prefers to use the mudflat, while Lateolabrax maculatus and Liza haematocheila prefer to use the salt marsh. There was a significant difference in the monthly variation of fish abundance between the fish abundance of salt marsh and mudflat, while there was no significant difference in fish biomass. The Simpson index of the fish of the mudflat was significantly higher than that of the salt marsh, while the Margalef index and the Pielou index were lower than the salt marsh. The community can be divided into two groups: winter-spring (A) and summer-autumn (B). The abundance of fish in the mudflat and the salt marsh show a very significant correlation with the water temperature (r = 0.773, 0.830, respectively) and a significant correlation with the water salinity(r = 0.654, 0.648, respectively). The abundance of fish in mudflat and salt marsh are both significantly correlated with water temperature and salinity. The abundance of fish of the mudflat (r = 0.470, P > 0.05) is more related to the highest submerged depth than of the salt marsh (r = 0.087, P > 0.05).

Rheological mechanical properties and its constitutive relation of soft rock considering influence of clay mineral composition and content

Rheological mechanical properties of the soft rock are afected signifcantly by its main physical characteristics-clay mineral.In this study,taking the mudstone on the roof and foor in four typical mining regions as the research object,frstly,the clay mineral characteristic was analyzed by the X-ray difraction test.Subsequently,rheological mechanical properties of mudstone samples under diferent confning pressures are studied through triaxial compression and creep tests.The results show that the clay mineral content of mudstone in diferent regions is diferent,which leads to signifcant diferences in its rheological properties,and these diferences have a good correlation with the content of montmorillonite and illite-montmorillonite mixed layer.Taking the montmorillonite content as an example,compared with the sample with 3.56%under the lower stress level,the initial creep deformation of the sample with 11.19%increased by 3.25 times,the viscosity coefcient and longterm strength decreased by 80.59%and 53.94%,respectively.Furthermore,based on the test results,the damage variation is constructed considering the montmorillonite content and stress level,and the M–S creep damage constitutive model of soft rock is established.Finally,the test results can be ftted with determination coefcients ranging from 0.9020 to 0.9741,which proves that the constitutive relation can refect the infuence of the clay mineral content in the samples preferably.This study has an important reference for revealing the long-term stability control mechanism of soft rock roadway rich in clay minerals.

Thermocline Model for Estimating Argo Sea Surface Temperature Thermocline Model for Estimating Argo Sea Surface Temperature

Argo has become an important constituent of the global ocean observation system.However,due to the lack of sea surface measurements from most Argo profiles,the application of Argo data is still limited.In this study,a thermocline model was constructed based on three key thermocline parameters,i.e,thermocline upper depth,the thermocline bottom depth,and thermocline temperature gradient.Following the model,we estimated the sea surface temperature of Argo profiles by providing the relationship between sea surface and subsurface temperature.We tested the effectiveness of our proposed model using statistical analysis and by comparing the sea surface temperature with the results obtained from traditional methods and in situ observations in the Pacific Ocean.The root mean square errors of results obtained from thermocline model were found to be significantly reduced compared to the extrapolation results and satellite retrieved temperature results.The correlation coefficient between the estimation result and in situ observation was 0.967.Argo surface temperature,estimated by the thermocline model,has been theoretically proved to be reliable.Thus,our model generates theoretically feasible data present the mesoscale phenomenon in more detail.Overall,this study compensates for the lack surface observation of Argo,and provides a new tool to establish complete Argo data sets.

Regulating local chemical environment in O_(3)-type layered sodium oxides by dual-site Mg^(2+)/B^(3+)substitution achieves durable and high-rate cathode

The O_(3)-Na_(0.85)Ni_(0.2)Fe_(0.4)Mn_(0.4)O_(2)layered oxide cathode material possesses the advantages of high specific capacity,low cost,and simple synthesis.However,sluggish kinetics and complicated phase transition caused by the large size difference between Na+and tetrahedral gaps lead to poor rate and cycling performance.Therefore,a scalable and feasible strategy was proposed to modulate local chemical environment by introducing Mg^(2+)and B^(3+)into O_(3)-Na_(0.85)Ni_(0.2)Fe_(0.4)Mn0.4O_(2),which can distinctly improve kinetic transport rate as well as electrochemical performance.The capacity retention of O_(3)-(Na_(0.82)Mg_(0.04))(Ni_(0.2)Fe_(0.4)Mn_(0.4))B_(0.02)O_(2)(NFMB)increases from 43.3%and 12.4%to 89.5%and 89.0%at 1 C and 3 C after 200 cycles,respectively.Moreover,the electrode still delivers high rate capacity of 93.9 mAh/g when current density increases to 10 C.Mg^(2+)ions riveted on Na layer act as a“pillar”to stabilize crystal structure and inhibit structural change during the desodiumization process.B^(3+)ions entering tetrahedral interstice of the TM layer strengthen the TM-O bond,lower Na+diffusion energy barrier and inhibits the slip of TM layer.Furthermore,the assembled full batteries with the modified cathode material deliver a high energy density of 278.2Wh/kg with commercial hard carbon as anode.This work provides a strategy for the modification of high-performance SIB layered oxide materials to develop the next-generation cost-effective energy storage grid systems.

A three-dimensional biomimetic microfluidic chip to study the behavior of hepatic stellate cell under the tumor microenvironment

In this paper, we designed a three-dimensional cell co-cultured microfluidic chip, which generated interstitial flow and oxygen gradient to simulate the complex tumor microenvironment. It consisted of five parallel cell culture channels and one hypoxic channel. These channels were constructed for the culture of mouse liver tumor cells(Hepa1-6), mouse liver stellate cells(JS-1), the simulation of extracellular matrix, complex biochemical factors(hypoxia and interstitial flow), and the supply of cellular nutrients. The 3D-interstitial flow-hypoxia model was used to study the behavior of JS-1 cells under the effect of tumor microenvironment(TME). The results showed that by co-cultured with Hepa1-6 cells, hypoxia of Hepa1-6 cells, and adding TGF-β1 by interstitial flow, the migration of JS-1 cells could be promoted. Similarly,activated JS-1 cells could led to the epithelial-mesenchymal transformation in co-cultured Hepa1-6 cells,which secreted more TGF-β 1.

Development of nutritious rice with high zinc/selenium and low cadmium in grains through QTL pyramiding

Enriching zinc(Zn) and selenium(Se) levels,while reducing cadmium(Cd) concentration in rice grains is of great benefit for human diet and health.Large natural variations in grain Zn, Se, and Cd concentrations in different rice accessions enable Zn/Sebiofortification and Cd-minimization through molecular breeding. Here, we report the development of new elite varieties by pyramiding major quantitative trait loci(QTLs) that significantly contribute to high Zn/Se and low Cd accumulation in grains. A chromosome segment substitution line CSSLGCC7 with the PA64s-derived GCC7 allele in the 93-11 background, exhibited steadily higher Mn and lower Cd concentrations in grains than those of 93-11. This elite chromosome segment substitution line(CSSL) was used as the core breeding material to cross with CSSLs harboring other major QTLs for essential mineral elements, especially CSSLGZC6 for grain Zn concentration and CSSLGSC5 for grain Se concentration. The CSSLGCC7+GZC6 and CSSLGCC7+GSC5 exhibited lower Cd concentration with higher Zn and Se concentrations in grains, respectively. Our study thus provides elite materials for rice breeding targeting high Zn/Se and low Cd concentrations in grains.