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Abstract Aiming at the reasonable width of the narrow coal pillar of a fully mechanized caving face and the safety support of roadway, taking the coal pillar in the section between 110503 and 110505 face of the Yushuling Coal mine as the research background, a model of the hard basic roof fracture structure of fully mechanized caving face is established through theoretical analysis, and the roadway with narrow coal pillar is analyzed mechanically. Combined with the geological conditions of the working face, it is concluded that the low‐stress area is less than 3.29 m. When the internal stress field of the low‐stress environment is considered in the roadway layout, the influence of mining and the essential roof hardness should be considered. The reasonable size of the narrow coal pillar is 3 ~ 6 m, thinking that the load borne by the coal pillar is less than the ultimate strength of the coal pillar. The limit equilibrium theory calculates that the reasonable width of a coal pillar is at least 4 m. The stress and displacement of coal pillars with different widths of 3, 4, 5 and 6 m are analyzed by numerical simulation, and the 4 m narrow coal pillars are simulated and verified. Field industrial tests show that coal pillar and roadway surrounding rock deformation are small under asymmetric surrounding rock control. The research results have been successfully applied to engineering practice and can provide a reference for the research method of narrow coal pillar width under a hard basic roof.

This article introduces a new risk metric of stock returns. It measures the fraction of the non-diversifiable risk relative to the individual risk of a typical stock in the stock market and is shown to be closely related to average correlation between individual stocks. Using the Korean stock market data, we show that the fractional non-diversifiable risk varies over time, and in particular, sharply rises during the financial crisis periods. We find that the relation between risk and return at the aggregate level is negative contemporaneously, but positive with a time lag. As a robustness check, we extend our analysis to the U.S. and the U.K. markets. Our results shed light on resolving the conflicting risk and return relations reported in the literature. [ABSTRACT FROM AUTHOR]

This paper presents an innovative trigeneration system designed to maximize energy utilization by simultaneously producing power, cooling, and freshwater. The system integrates multiple energy sources, including biomass, natural gas, and geothermal energy, and comprises a modified gas turbine cycle, a geothermal power plant, a triple-effect absorption refrigeration cycle, and a multi-effect desalination unit. Performance metrics are evaluated from both thermodynamic and economic perspectives across four case studies: Australia, the USA, China, and Russia. The economic feasibility analysis utilizes real-state economic data, incorporating natural gas prices, electricity prices for households, interest rates, and inflation rates specific to each country. The system achieved impressive outputs, with net power, cooling, and freshwater production rates of 6299 kW, 140.1 kW, and 13.41 kg/s, respectively. Exergy analysis revealed that the combustion chamber, heat exchanger, and multi-effect desalination units exhibit the highest irreversibility, with exergy destruction rates of 2961 kW, 1125 kW, and 995.3 kW, respectively. The fixed capital investment cost is estimated at $13.5 million, resulting in a payback period of 6.75 years and a net present value of $7.287 million. In Australia, the system demonstrated a particularly favorable economic performance, with a payback period of 3.98 years and a net present value of $36.19 million. Conversely, in China, the payback period exceeds the system's expected lifetime, highlighting the economic challenges in certain environments. These results underscore the system's potential for profitability and sustainability, particularly in regions with favorable economic conditions. • Integrating biomass, natural gas, and geothermal energies in a trigeneration system. • Using thermodynamic and economic modeling for performance evaluation. • The system produces 6299 kW power, 140.1 kW cooling, and 13.41 kg/s freshwater. • Exergy analysis showed an exergy efficiency of 43.32 % in the trigeneration mode. • Economic performance varies by country; best in the USA with a 3.41-year payback. [ABSTRACT FROM AUTHOR]