A Fluorescent Sensor for Zinc Detection and Removal Based on Core-Shell Functionalized Fe 3

The magnetic Fe3O4@SiO2 nanoparticles (NPs) functionalized with 8-chloroacetylaminoquinoline as a fluorescent sensor for detection and removal of Zn2+ have been synthesized. The core-shell structures of the nanoparticles and chemical composition have been confirmed by TEM, XRD, FTIR, and XPS techniques. The addition of functionalized Fe3O4@SiO2 NPs into the acetonitrile solution of Zn2+ had an effect of visual color change as well as significant fluorescent enhancement. High-saturated magnetizations (24.7 emu/g) of functionalized Fe3O4@SiO2 NPs could help to separate the metal ions from the aqueous solution. The magnetic sensor exhibited high removal efficiency towards Zn2+ (92.37%). In this work, we provided an easy and efficient route to detect Zn2+ and simultaneously remove Zn2+

Study on Stress Relief of Hard Roof Based on Presplitting and Deep Hole Blasting

For the problem that the hard roof causes wider end-mining coal pillar, and the roadway is greatly affected by mining, this paper took Shanxi Luning Coal Mine as the engineering background; based on the stress distribution characteristics of the coal pillar, the calculation method of the limit end-mining coal pillar size was given; considering the formation conditions and transmission forms of the advanced abutment stress, a method combining presplitting and deep hole blasting was proposed to weaken the advanced abutment stress. The numerical simulation was used to analyze the stress distribution of coal pillars, which was verified by on-site industrial tests. The results showed that the presplitting can achieve the blocking of stress. The closer it is to the peak of the abutment stress, the better the blocking effect. Deep hole blasting can weaken the source of the advanced abutment stress and reduce the peak of abutment stress. With the combination of the two blasting methods, the end-mining coal pillar size of Luning Coal Mine can be reduced to 60 m. The method combining presplitting and deep hole blasting can effectively reduce the end-mining coal pillar size and reduce the impact of mining on the deformation of the dip roadway

Analysis of Failure Characteristics and Strength Criterion of Coal-Rock Combined Body with Different Height Ratios

In underground mining and roadway support engineering of coal mine, the coal and rock layers bear loads together; therefore, the deformation and mechanical characteristics of the coal-rock combined bodies are not the same as those of the pure coal or rock bodies. In this paper, conventional triaxial compression tests of coal-rock combined bodies with different height ratios were conducted. And the stress and deformation characteristics of coal-rock combined body were studied and the experimental results were analyzed with different strength criteria. The results show that the peak stress, elastic modulus, and strength reduction coefficient of coal-rock combined body are negatively correlated with the ratio of coal to coal-rock combination height and positively correlated with the confining pressure; the coal-rock combination shows obvious ductility under 10 MPa confining pressure. Under the conventional triaxial condition, the shear failure was the main cause of the lateral deformation of the coal body in the coal-rock combination, which was much larger than that of the rock body. The circle deformation value, volume strain value, and the deformation rate in the postpeak stage of coal-rock combination are much higher than those in the prepeak stage. Mohr–Coulomb and general Hoek–Brown strength criterion fit the experimental results well

Study on the Porosity of Saturated Fragmentized Coals during Creep Process and Constitutive Relation

Pore abundance and deformation characteristics of saturated fragmentized coals during creep process are of significant meaning to the study on ground sediment in the mined-out area. The law of porosity variation of saturated fragmentized coals during creep process and its creep constitutive model were studied by using the self-developed multiphase coupling creep test device. And, results have indicated that the porosity logarithm of fragmentized coal during creep process shows a linear negative correlation with the time ln(n−a) = −ct + lnb, and the porosity decrease is evidently divided into three phases. In addition, when the stress level is relatively low, the porosity decreases slowly; when the stress level rises up, the porosity decreases quickly; when the stress level remains stable finally, the porosity is smaller. Under the equal stress, as the grain size of fragmentized coals decreases, the porosity tends to decrease, and as the grain size of fragmentized coal tends to be stable, the porosity tends to increase; the creep constitutive equation of fragmentized coals with different grain sizes was established by using the Kelvin–Voigt model, and the correlation analysis shows that the Kelvin–Voigt creep model of fragmentized coals is reasonable

Particle Flow Code Simulation of the Characteristics of Crack Evolution in Rock-Like Materials with Bent Cracks

The distribution and propagation of rock cracks have a significant impact on geotechnical engineering. Taking rock-like materials with bent cracks as the research object, the particle flow code in two dimensions numerical simulation method was used to study the impact of the bend number on rock-like materials strength and crack evolution. According to the results, when the bend number was 1, 3, and 7, the strength of the specimens gradually increased; the elasticity modulus did not change significantly with the crack bend number. Uniaxial compression generated tensile cracks in all the specimens with bent cracks, but in terms of failure mode, the specimens with 0 bend tended to suffer penetrating failure along the fracture strike, while the specimens with 1, 3, and 7 bend tended to suffer penetrating failure along the diagonal direction. Both the fractal dimension and bend number were positively correlated with strain; with the gradual increase of the stress percentage, the damage variable of the specimens gradually increased at a growing rate. The research results provide a reference for predicting the stability of the underground engineering surrounding rocks containing bent cracks

Controlling the Deformation of a Small Coal Pillar Retaining Roadway by Non-Penetrating Directional Pre-Splitting Blasting with a Deep Hole: A Case Study in Wangzhuang Coal Mine

In longwall mining of coal mines, the large deformation of small pillar retaining roadways creates difficulties for the safe and efficient retreating of the mining panel. Based on the engineering background of a small coal pillar retaining roadway in Wangzhuang coal mine, pressure relief technology for non-penetrating directional pre-splitting blasting with a deep hole ahead was proposed. The influence of the non-penetrating fracture length on the pre-splitting effect was studied by numerical simulation. The results showed that the vertical stress in the coal pillar center, the small pillar retaining roadway deformation, and the energy accumulation on the pillar decreased with an increase in the non-penetrating fracture length. The vertical stress at the working face end increased with an increase in the non-penetrating fracture length. The field application and monitoring results indicated that non-penetrating directional pre-splitting blasting could effectively control the deformation of small pillar retaining roadways. The roof-to-floor and rib-to-rib maximum convergences of the 6208 tail entry were reduced by 53.66% and 52.62%, respectively, compared to the results with no blasting. The roadway section met the demands of mining panel high-efficiency retreating, thereby demonstrating the rationality of the technical and numerical simulation results. The research results shed light on the improvement of small coal pillar retaining roadway maintenance theory and technology

All-optical controllable electromagnetically induced transparency in coupled silica microbottle cavities

An all-optical control scheme of electromagnetically induced transparency (EIT) based on two coupled silica microbottle cavities coated with iron oxide nanoparticles is proposed and experimentally demonstrated. The specially designed and fabricated silica microbottle cavity with a short and spherical end, which is coated with iron oxide nanoparticles, possesses a quality (Q) factor of 1.39×108 and large all-optical tunability in a range of 282.32 GHz (2.25 nm) arising from the strong photothermal effect of the nanoparticles. Based on two coupled silica microbottle cavities, we achieve the EIT spectrum with a transparency window bandwidth of 2.3 MHz. The transparency window can be flexibly controlled by tuning the resonant frequency of the higher-Q microcavity. Besides, by tuning the resonant frequencies of the two microcavities separately, the whole EIT spectrum can be shifted with a range of 71.52 GHz, to the best of our knowledge, for the first time. Based on this scheme, we have realized all-optical and independent control of the transparency window and the whole EIT spectrum. We believe this work has great potential in applications such as light storage, optical sensing, and quantum optics