Search

In the process of coal seam mining, there are often hard thick key layers in the overlying strata. Due to the high strength and good integrity of the hard thick key layer, after the hard thick key layer is broken, the overlying strata will collapse and lose stability in a large area, which is very easy to induce dynamic disasters such as rock burst, mine earthquake, coal wall caving, and roof slab caving. Aiming at the hard and thick key layer overlying the working face, the dynamic response of the mine under the strong mine earthquake induced by the breaking of the main key layer of high-level magmatic rock is numerically simulated and analyzed by using FLAC2D numerical simulation software, and the variation laws of the stress field, displacement field, and velocity field of the coal seam roadway under different boundary conditions and different focal heights are studied. The research shows that the roof of solid coal roadway is prone to vibration in a small range, and the displacement increases and decreases with the disturbance. The displacement of the floor and two sides of the solid coal roadway and the top floor and two sides of the roadway along the goaf continues to increase in the initial stage of the disturbance, and the displacement will remain stable with the continuation of the disturbance. The displacement of both sides and roof and floor of gob roadway can reach stability in the later stage of disturbance, and with the increase of the number of adjacent goaf, the longer it takes for the displacement of surrounding rock to reach stability. When the focal height is lower than 90 m, the variation of surrounding rock response increases sharply with the decrease of focal height. When a strong earthquake occurs in the low rock stratum, the impact damage of roadway surrounding rock is almost inevitable. The influence degree of strong earthquake on the stability of roadway surrounding rock is arranged as follows: gob-side roadway (mined out on one side) > solid coal roadway (mined out on both sides) > solid coal roadway (mined out on one side). The evolution process also shows that the working face boundary conditions have an important influence on the energy propagation of mine earthquake. With the increase of the number of adjacent goafs, the faster the energy attenuation rate of mine earthquake propagation is. The research results have important reference significance for the safe mining of working face under similar geological conditions.

This paper introduces a scenario evolution model for maritime accidents, wherein Bayesian networks (BNs) were employed to predict the most probable causes of distinct types of maritime incidents. The BN nodes encompass factors such as accident type, life loss contingency, accident severity, quarter and time period of the accident, and type and gross tonnage of the involved ships. An analysis of 5660 global maritime accidents spanning the years 2005 to 2020 was conducted. Using Netica software, a tree augmented network (TAN) model was constructed, thus accounting for interdependencies among risk-influencing factors. To confirm these results, a validation process involving sensitivity analysis and historical accident records was performed. Following this, both forward causal inference and reverse diagnostic inference were carried out on each node variable to scrutinize the accident development trend and evolution process under preset conditions. The findings suggest that the model was competent in effectively predicting the likelihood of various accident scenarios under specific conditions, as well as extrapolating accident consequences. Forward causal reasoning unveiled that general cargo ships with a gross tonnage of 1–18,500 t were most prone to experiencing collision and stranding/grounding accidents in the first quarter. Reverse diagnostic reasoning indicated that, in the early morning hours, container ships, general cargo ships, and chemical ships with a tonnage of 1–18,500 t were less likely to involve life loss in the event of collision accidents.

In many mining areas, there is a lot of pressed coal under buildings, railways, and water bodies, and there are geological conditions of thick unconsolidated layers, so the surface subsidence has certain particularity. The key to solve the problem of pressed coal is the control technology of surface subsidence. The development of strip filling technology provides a kind of economical and effective surface subsidence control technology. With the passage of time, the natural weathering, flow, and fracture of some coal pillars may lead to the instability and failure of some coal pillars. Therefore, the selection of filling parameters plays an important role in the stability of coal pillars. In order to study the influence factors of surface movement and deformation, considering the influence factors of filling rate, key layer thickness, filling body strength, and unconsolidated layer thickness, FLAC 3D was used to simulate the surface movement deformation, and the orthogonal test method was used to analyze the simulation results, and the sensitivity of the main control factors affecting the surface deformation affected by strip filling mining was studied. The results show that the order of importance of the four factors on the four surface movement and deformation parameters is filling rate > key layer thickness > filling body strength > unconsolidated layer thickness. The influence of these four factors on the surface movement and deformation parameters is gradually decreasing, but the influence degree of different factors has drawn a certain gradient.

At the present time, it is of major significance to study the solid-liquid-gas three-phase coupling relationship of coal, water, and gas in deep-mining stopes in order to prevent and control coal and gas outbursts in high-gas mines. In this study, the influence rules of water on the mechanical characteristics of coal, as well as gas diffusion and migration processes, was examined by combining theoretical analysis and laboratory testing procedures. The results showed that with increases in water content, the mechanical characteristics of coal bodies presented change trends of first increasing and then decreasing. In this study, it was found that the water content levels which corresponded to the maximum shear strength of the coal in the No. 8 coal seam in the study area had ranged between 6.77% and 11.9%, and the water content level corresponding to the extreme point was 8.66%. It was observed that under different water content conditions, the gas desorption speeds of the coal bodies gradually decreased over time. The gas desorption speeds rapidly decreased during the initial desorption stage and then gradually decreased over time. Furthermore, under the different water content conditions, the amount of gas desorption in the coal bodies was observed to gradually increase over time, with the initial desorption amounts displaying rapid increases. Then, with the passage of time, the increase speeds of the gas desorption amount gradually decreased and finally tended to remain at a stable value. It was found that with the increases in water content, the desorption speeds, initial desorption speeds, and desorption amount of gas in the coal bodies continuously decreased. In other words, the water content levels in the coal bodies were negatively correlated with the gas desorption speeds and desorption amounts of the coal bodies. In addition, the gas desorption speeds, initial desorption speeds, and desorption amounts were observed to change more sharply with the increases in water content. The results of this research hold important guiding significance for the improvement of the understanding of the mechanical properties of high-gas coal seams and the implementation of effective gas control measures.

To examine the correlation between regional economic growth and inter-region transportation costs in China, this study establishes a regional economic growth model embedded with inter-region transportation costs based on the Cobb-Douglas production function. Based on a balanced growth empirical model, this study verifies the correlation by conducting a regression analysis of the panel data of 29 provinces, municipalities, and autonomous regions from 1985 to 2015. The empirical results show that: (1) The per capita GDP growth among the three regions (namely, the eastern, central, and western regions of China) meets a conditional convergence trend, and the decreasing of the inter-region transportation costs increases the convergence speed; (2) The per capita GDP growth is in line with the club convergence trend within each of the three regions; (3) The trend of the output elasticity of the inter-region transportation costs shows that the gradual decrease of inter-region transportation costs has a positive correlation with the narrowing of economic disparity after the year 2000, accelerating "common prosperity" across different regions in China. [ABSTRACT FROM AUTHOR]

A multistage carrier phase estimation (CPE) scheme for any m-ary quadrature amplitude modulation (QAM) formats is proposed and analyzed in coherent optical communication systems. The scheme is based on the crossed constellation transformation algorithm that is transparent to all modulation formats whose constellations are on the square grid. Simulation results show that the hardware complexity of the proposed CPE scheme can be significantly reduced by the group factors of 6.1/8.6, 4.7/6, and 2.6/3.3 (in the form of multipliers/adders) for 32-QAM, 64-QAM, and 128-QAM compared with the singlestage blind phase search algorithm. In 32-QAM, 64-QAM, and 128-QAM, coherent optical communication systems with 1-dB SNR penalty at bit error rate is 1 × 10-2, the comparable linewidth symbol duration can be reached with the values of 6 × 10-5, 4 × 10-5, and 8 × 10-6, respectively. [ABSTRACT FROM PUBLISHER]

Surface functionalization of nanomaterials with highly specific recognition elements, such as biomolecules and organic molecules, has made possible many novel nanosensors for bio/chemical analysis and target bioimaging. In this report, a fluorescent nanosensor which exhibits highly specific recognition capability towards Zn2+ over competing metal ions has been developed through covalently functionalizing carbon dots (C-dots) with the quinoline derivatives which show response to Zn2+. The nanosensor exhibits excellent water solubility, biocompatibility, and cell-membrane permeability, and demonstrates high selectivity towards Zn2+ with a detection limit as low as 6.4 nM. Additionally, the rapid response of the nanosensor towards Zn2+ can be achieved within 1 min. The large amount of recognition units on the outer surface of an individual nanoparticle enables the signal amplification, hence making the immediate and highly sensitive detection of Zn2+ possible. Therefore, a reliable and highly specific nanosensor has been demonstrated for both rapid quantitative detection of Zn2+ in aqueous solution and real-time imaging of intracellular Zn2+, suggesting its potential and significance in bioanalysis and biomedical detection in the future. [ABSTRACT FROM AUTHOR]

We propose an optical domain pilot-aided carrier phase recovery (PA-CPR) scheme used in a single-carrier Nyquist system. A comprehensive mathematical description of the proposed PA-CPR scheme is presented. Optimal parameters for the system are obtained through optimizations. Furthermore, we propose the two-stage PA-CPR algorithm combinations which use the maximum likelihood or constellation transformation phase estimation as the second stage just after the pilot phase compensation.We alsomake the evaluation and comparison of the linewidth tolerance performances among the proposed two-stage PA-CPR algorithm combinations and other typical CPR algorithms in a 28-Gbaud Nyquist polarization-division multi-plexed (PDM)-16QAM optical communication system. The calculation results show that the proposed two-stage PA-CPR algorithmcombinations, which have lower complexities, show better performances than others. [ABSTRACT FROM AUTHOR]

Advances in the controlled assembly of nanoscale building blocks have resulted in functional devices which can find applications in electronics, biomedical imaging, drug delivery etc. In this study, novel covalent nanohybrid materials based upo [Ru(bpy)3]2+-doped silica nanoparticles (SiNPs) and gold nanoparticles (AuNPs), which could be conditioned as OFF-ON probes for glutathione (GSH) detection, were designed and assembled in sequence, with the disulfide bonds as the bridging elements. The structural and optical properties of the nanohybrid architectures were characterized using transmission electron microscopy, UV-vis spectroscopy and fluorescence spectroscopy, respectively. Zeta potential measurements, x-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy were employed to monitor the reaction processes of the SiNPs-S-S-COOH and SiNPs-S-S-AuNPs synthesis. It was found that the covalent nanohybrid architectures were fluorescently dark (OFF state), indicating that SiNPs were effectively quenched by AuNPs. The fluorescence of the OFF-ON probe was resumed (ON state) when the bridge of the disulfide bond was cleaved by reducing reagents such as GSH. This work provides a new platform and strategy for GSH detection using covalent nanohybrid materials. [ABSTRACT FROM AUTHOR]

Limitations in bandwidth impact capabilities in mobile environments. Third-generation Freedom of Mobile Multimedia Access (FOMA) and Personal Handyphone System (PHS) were evaluated in a home-health setting in Japan with satisfactory results. [ABSTRACT FROM AUTHOR]