Preliminary Design and On-Site Testing Methodology of Roof-Cutting for Entry Retaining in Underground Coal Mine.

Entry retaining via roof cutting is a new longwall mining method that has emerged in recent years, and is characterized by high resource utilization and environmental friendliness. Due to the complexity of this method, a field study is commonly employed for process optimization. Roof blasting is a key operation for retaining the entry, and the current practice involves dynamically adjusting blasting parameters through on-site testing and postblasting monitoring. However, the existing literature lacks detailed descriptions of blasting operations, making it difficult for field engineers to replicate the results. In this study, based on a roof cutting project for entry retaining, a preliminary design of blasting parameters is made based on theories and on-site geological conditions. The on-site test methods and equipment for roof-cutting blasting are described in detail, and the fractural patterns under different blasting parameters are analyzed. After the retreat of the working face, the state of roof caving in the goaf is analyzed based on monitoring data, and the effectiveness of top cutting is evaluated through reverse analysis, leading to dynamic adjustments of the blasting parameters. This research provides a reproducible construction method for roof-cutting operations and establishes the relationship between blasting parameters and post-mining monitoring data. It contributes to the development of fundamental theories and systematic technical systems for entry retaining via roof cutting, offering high-quality case studies for similar geological engineering projects.

Process simulation and comprehensive evaluation of a system of coal power plant coupled with waste incineration.

The technology of coal power plant coupled with waste incineration is considered as a promising technology for fossil fuel conservation and waste disposal. In this paper, a system of coal power plant coupled with waste incineration is simulated by Aspen Plus software, and a conventional coal power plant is also simulated for comparison. Comprehensive evaluation including thermodynamic, economic and environmental impact performances are analysed and compared. Evaluation results indicate that the thermodynamic performance and environmental impact of the system of coal power plant coupled with waste incineration are worse, but the economic performance of the system is obviously better than the coal power plant. When the replacement ratio of waste is 20%, the energy and exergy efficiencies of the system are 38.54% and 37.27%, the internal rate of return and discounted payback period of the system are 21.83% and 9.14 years, and the environmental cost of the system is $3597.73 h-1. Therefore, the technology of coal power plant coupled with waste incineration has technical feasibility and economic advantages, and the environmental impacts need to be considered in the application of the technology.

Data Cleansing and Sub-Unit-Based Molecular Description Enable Accurate Prediction of The Energy Levels of Non-Fullerene Acceptors Used in Organic Solar Cells.

Non-fullerene acceptors (NFAs) have recently emerged as pivotal materials for enhancing the efficiency of organic solar cells (OSCs). To further advance OSC efficiency, precise control over the energy levels of NFAs is imperative, necessitating the development of a robust computational method for accurate energy level predictions. Unfortunately, conventional computational techniques often yield relatively large errors, typically ranging from 0.2 to 0.5 electronvolts (eV), when predicting energy levels. In this study, the authors present a novel method that not only expedites energy level predictions but also significantly improves accuracy , reducing the error margin to 0.06 eV. The method comprises two essential components. The first component involves data cleansing, which systematically eliminates problematic experimental data and thereby minimizes input data errors. The second component introduces a molecular description method based on the electronic properties of the sub-units comprising NFAs. The approach simplifies the intricacies of molecular computation and demonstrates markedly enhanced prediction performance compared to the conventional density functional theory (DFT) method. Our methodology will expedite research in the field of NFAs, serving as a catalyst for the development of similar computational approaches to address challenges in other areas of material science and molecular research.

Effects of alkali and alkaline earth metal species on the combustion characteristics and synergistic effects: Sewage sludge and its blend with coal.

A large amount of alkali and alkaline earth metal species (AAEMs) are contained in sewage sludge (SS) ash, which will affect the combustion characteristics and synergistic effects of the co-combustion of SS and coal. The main objective of this paper is to investigate the effects of K, Ca, Na and Mg on combustion characteristics and synergistic effects of the blend of SS and coal by TGA and single particle combustion methods. The ash-free sludge (AS), impregnated AS and the blends of AS and bituminous coal (BC) were prepared. A high speed camera was used to record the combustion process, which were processed to calculate the ignition delay time, burnout time and combustion temperature. The synergistic effect of co-combustion process was studied by comparing the experimental results with the theoretical calculation results. The synergistic effects main occur at 350-530 °C and the blends of AS and BC with 2 wt% Na has the strongest strength of synergistic effects. The K, Ca and Na are conducive to the shorter ignition delay time, burnout time, higher combustion temperature and stronger synergistic effects of the blends. However, Mg will increase the delay time and reduce the combustion temperature of char of the blends. There are optimal concentrations of AAEMs on the promotion of combustion and synergistic effects, and too high concentrations of AAEMs will have negative impacts. K and Na (alkali metals) have stronger promotion effects than Ca and Mg (alkaline earth metals) on combustion of volatiles and synergistic effects.