ABSTRACT
The construction and coal industries generate substantial industrial waste, including coal gangue and construction and demolition (C&D) waste, leading to environmental pollution and high disposal costs. Integrating recycled aggregates (RAs) and coal gangue powder (CGP) into concrete is an effective approach for waste management. However, CGP can affect the performance of traditional recycled concrete. This study primarily aims to optimize the utilization of RAs and CGP while maintaining concrete performance. They utilized orthogonal experimental designs and microscopic characterization techniques, including scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). Orthogonal experimental analysis indicated that with a water-cement ratio (WCR) of 0.5 and replacement rates of 10% for CGP and 60% for RA, compressive and splitting tensile strengths reached 73.6% and 77.4% of ordinary C30 concrete, respectively. This mix proportion minimizes strength decline in coal gangue powder-recycled aggregate concrete (CGP-RAC) while maximizing recycled material replacement. Microscopic analysis revealed that CGP increased the Ca/Si ratio in cement paste, impeding hydration reactions, resulting in a looser internal structure and reduced concrete strength. These findings are anticipated to provide fresh theoretical insights for solid waste recycling and utilization.
ABSTRACT
A compact millimeter-wave on-chip sensor for dielectric detection is presented using gallium arsenide technology based on spoof surface plasmon polaritons (SSPPs). The proposed structure is developed from traditional half-mode substrate integrated waveguide (HMSIW) and its dispersion characteristics is analyzed through electromagnetic simulations. Consequently, the operating frequency and bandwidth of the on-chip sensor can be easily adjusted, which provides more flexibility for the practical application of the sensor. The linear sensing for relative dielectric constant of the film materials is acquired, with thickness-insensitive property. Moreover, the low coupling to the nearby components can be achieved due to the strong field confinement characteristics of the SSPPs, which is of great significance in the application scenarios of on-chip integrated circuits for the suppression of electromagnetic interference.
ABSTRACT
The extraction of coal bed methane (CBM) by injecting CO2 into deeply buried unmined coal seams in competition with CH4 adsorption to provide a clean fuel is known as enhanced coal bed methane recovery (ECBM) and has proven to be an effective technological strategy to address global warming. The study of the interaction of coal with CO2 and CH4 under multi-physical field conditions is particularly necessary. In this work, a series of experiments were conducted on a home-made test system to investigate the competing sorption patterns of high and medium ash coal samples subjected to variables such as gas pressure, temperature, nodulation and lateral limit constraints. The results show that there is a sorption isotherm relationship between coal samples and exposure time. The adsorption capacity sorption of CH4/CO2 varied considerably for different ash coal samples. As the CO2 pressure increased from 2.3 to 5.5 MPa, the strain on the coal samples increased from 0.082 to 0.4%. The deformation in the vertical laminae direction is always greater than that in the parallel laminae direction. A correlation coefficient K exists between 1 and 2, and there is an internal expansion pattern in the adsorption deformation of coal. This paper can contribute to the improvement of ECBM efficiency.
ABSTRACT
On August 20, 2019, at 2 a.m., a disastrous debris flow occurred in Chediguan gully in Yinxing town, China. The debris flow destroyed the drainage groove and the bridge at the exit of the gully. In addition, the debris flow temporarily blocked the Minjiang River during the flood peak, flooding the Taipingyi hydropower station 200 m upstream and leaving two plant workers missing. To further understand the activity of the debris flow after the Wenchuan earthquake, the characteristics of this debris flow event were studied. Eleven years after the Wenchuan earthquake, a disastrous debris flow still occurred in the Chediguan catchment, causing more severe losses than those of earlier debris flows. In this paper, the formation mechanism and dynamic characteristics of this debris flow event are analysed based on a drone survey, high-definition remote sensing interpretations and other means. The catastrophic debris flow event indicates that debris flows in the Wenchuan earthquake area are still active. A large amount of dredging work in the main gully could effectively reduce the debris flow risk in the gully. In addition, it is also important to repair or rebuild damaged mitigation measures and to establish a real-time monitoring and early warning system for the high-risk gully.
