Variation Law of Infrared Radiation Temperature of Unloading Fracture of Composite Coal-Rock

For composite mining coal-rock dynamic disaster, combining the theory of thermodynamics, damage mechanics, and other disciplines, the thermodynamic coupling mathematical model of composite coal-rock under an unloading condition is deduced, and the simulation model of composite coal-rock is established for numerical simulation. And the variation law of thermal infrared radiation under triaxial loading and unloading of composite coal-rock is analyzed and verified by experiments. The results show the following findings: (1) The distribution of thermal infrared radiation temperature of composite coal-rock is different in different stages of stress. The overall temperature of the temperature field is lower than the initial temperature field in the three-dimensional stress loading stage and the stage of stress-keeping pressure, but the internal temperature of the coal body is the highest. In the first stage of “loading and unloading,” the temperature of a coal seam increases slightly, and the temperature of other parts of the rock layer increases except for the circular low-temperature zone. In the second stage of “loading and unloading,” an alternating zone of high and low temperatures appears in the rock mass, and the temperature field is enhanced, among which the temperature field reaches the strongest after unloading the confining pressure. After jumping over the maximum stress, the temperature field decreases as a whole at the instability and rupture stage. (2) The variation of surface average thermal infrared radiation temperature ( T ave ) of composite coal-rock can be divided into the initial fluctuation stage, the linear heating stage, the local decline stage, the temperature sudden increase stage, and the fracture decline stage. At three different unloading rates of 0.003 MPa/s, 0.03 MPa/s, and 0.05 MPa/s, the T ave of coal body, floor rock, and roof rock reach the maximum before composite coal-rock instability and fracture, and the temperature change of the coal body is the most obvious. (3) Under different confining pressure unloading rates, the T ave of roof rock, coal body, and floor rock shows a strong linear relationship with stress after linear fitting. And the correlation between simulation and experimental results after fitting is above 0.89. The larger the confining pressure unloading rate is, the shorter the peak time of T ave arrives, and the larger the peak value. The comparison between the experimental results and the simulation analysis shows that the two results are consistent, and the research results can provide a theoretical basis for the prevention and control of dynamic disasters in coal and rock mining.

Experimental Study on the Thermal Infrared Spectral Variation of Fractured Rock

Previous studies have shown that thermal infrared radiation (TIR) anomalies occur in the vicinity of fractures that form when a rock is loaded to failure. Different types of fracturing modes correspond to different TIR anomaly trends. However, the spectral features and the mechanisms responsible for the TIR changes in the fracturing stage remain poorly understood. In this paper, experiments involving observations of the thermal infrared spectrum (8.0–13.0 μm) of loaded sandstone during the fracturing stage were conducted under outdoor conditions. The experiment yielded the following results: (1) Different fracturing modes can lead to different trends in the spectral radiance variation; (2) when an extensional fissure appeared on the rock surface, the radiance increased with a local peak in the 8.0–9.7 μm range; 3) when local bulging formed at the surface, the radiance decreased, with a local valley in the 8.0–9.7 μm range. The radiance variation caused by morphologic changes is the combined result of changes in both the temperature and the emissivity. The characteristic waveband corresponding to the reststrahlen features (RF) of quartz was mainly related to the emissivity change. This study provides a preliminary experimental foundation for the detection of crustal surface fractures via satellite-based remote sensing technology.

Floral infrared emissivity estimates using simple tools

Background Floral temperature has important consequences for plant biology, and accurate temperature measurements are therefore important to plant research. Thermography, also referred to as thermal imaging, is beginning to be used more frequently to measure and visualize floral temperature. Accurate thermographic measurements require information about the object’s emissivity (its capacity to emit thermal radiation with temperature), to obtain accurate temperature readings. However, there are currently no published estimates of floral emissivity available. This is most likely to be due to flowers being unsuitable for the most common protocols for emissivity estimation. Instead, researchers have used emissivity estimates collected on vegetative plant tissue when conducting floral thermography, assuming these tissues to have the same emissivity. As floral tissue differs from vegetative tissue, it is unclear how appropriate and accurate these vegetative tissue emissivity estimates are when they are applied to floral tissue. Results We collect floral emissivity estimates using two protocols, using a thermocouple and a water bath, providing a guide for making estimates of floral emissivity that can be carried out without needing specialist equipment (apart from the thermal camera). Both protocols involve measuring the thermal infrared radiation from flowers of a known temperature, providing the required information for emissivity estimation. Floral temperature is known within these protocols using either a thermocouple, or by heating the flowers within a water bath. Emissivity estimates indicate floral emissivity is high, near 1, at least across petals. While the two protocols generally indicated the same trends, the water bath protocol gave more realistic and less variable estimates. While some variation with flower species and location on the flower is observed in emissivity estimates, these are generally small or can be explained as resulting from artefacts of these protocols, relating to thermocouple or water surface contact quality. Conclusions Floral emissivity appears to be high, and seems quite consistent across most flowers and between species, at least across petals. A value near 1, for example 0.98, is recommended for accurate thermographic measurements of floral temperature. This suggests that the similarly high values based on vegetation emissivity estimates used by previous researchers were appropriate.

Atmosphere response to pre-earthquake processes revealed by satellite and ground observations. Case study for few strong earthquakes in Xinjiang, China (2008-2014)

We are presenting the latest results of multi-sensor observations of short-term pre-earthquake phenomena preceding significant earthquakes. We study satellite thermal infrared radiation (OLR) anomalous signals in association with three major earthquakes, which occurred in Xinjiang province, China at different periods M7.3 of 02.12.2014; M6.2 of 08.12.2012; and M7.2 of 03.20.2008. We systematically apply multi-sensor satellite thermal data and ground temperature /humidity and estimates of the atmospheric chemical potential (ACP) parameter. Data analyses include NOAA NPOESS, the Chinese geostationary satellite FY-2D, and in-situ hourly NOAA data from the Hotan weather station. In all three cases, we detected atmospheric satellite OLR anomalies developed near the epicenter area and ACP increases (significant change for 2008 and 2014, weak for 2012) over the major Altyn Tagh fault lines within 10-20 days before the earthquake event. These findings demonstrate the occurrence and reoccurrence of transient variations of these parameters, implying their connection with the earthquake preparation process.

Thermal infrared characteristics of rock strata fracture in steeply inclined and extra thick coal seam

In view of the complexity of the rules of rock strata fracture in steeply inclined and extra thick coal seam, the mining method of horizontal section top coal caving was put forward. In this paper, the physical similarity simulation model is established to analyze the movement rules of rock strata. The relationship between the form of rock strata fracture and the thermal infrared radiation is analyzed according to studying the characteristics of the thermal infrared radiation temperature of the rock strata fracture. Meanwhile, the changes characteristics of abnormal area of thermal infrared radiation were mastered, and the precursors of thermal infrared radiation of rock strata fracture were predicted. The results showed that the rock strata fracture form of steeply inclined and extra thick coal seam is related to the mining depth.

Modelling summer water temperature on the Yenisei river

A summertime hydrothermal regime of the Yenisei River downstream of the Krasnoyarsk hydroelectric power plant is modeled based on a deterministic approach. To that end, the Fourier equation is used and the following physical processes contributing to the heat exchange between water and the surroundings are taken into consideration: absorption of direct and scattered solar radiation by water, absorption of downwelling thermal infrared radiation from the atmosphere by water surface, thermal infrared radiation back from the water surface, convection of heat and heat loss due to evaporation of water. A clear-skies river thermal regime under no wind is studied in a 124-km stream reach below the power plant and the obtained results are compared against temperatures recorded at gauging stations.