Development of a portable coal rock charge monitoring instrument and its application for rockburst control

Effective monitoring techniques and equipment are essential for the prevention and control of coal and rockdynamic disasters such as rockburst. Based on the fact that there is charge generation during deformation andrupture of coal rock body and the charge signals contain a large amount of information about the mechanicalprocess of deformation and rupture of coal rock, the rockburst charge sensing monitoring technology has beenformed. In order to improve the charge sensing technology for monitoring and early warning of rockburst disasters, this paper develops a new generation of portable coal rock charge monitoring instrument on the basis ofthe original instrument and carries out laboratory and underground field application. The primary advancementinvolves enhancing the external structure of the sensor and increasing the charge sensing area, which can morecomprehensively capture the charge signals from the loaded rupture of the coal rock body. The overall structure ofthe data acquisition instrument has been improved, the monitoring channels have been increased, and thefunction of displaying the monitoring data curve has been added, so that the coal and rock body force status canbe grasped in time. The results of the experimental study show that the abnormal charge signals can be monitoredduring the rupture process of rock samples under loading, and the monitored charge signals are in good agreement with the sudden change of stress in the rock samples and the formation of crack extension. There is aprecursor charge signal before the stress mutation, and the larger the loading rate is, the earlier the precursorcharge signal appears. The charge monitoring instrument can monitor the charge signal of the coal seam roadwayunder strong mining pressure. In the zone of elevated overburden pressure, the amount of induced charge is large,and anomalously high value charge signals can be monitored when a coal shot occurs. The change trend of thecharge at different measuring points of strike and inclination has a good consistency with the distribution ofoverrunning support pressure and lateral support pressure, which can reflect the stress distribution and the degreeof stress concentration of the coal body through the size and location of the charge, foster early warning andanalysis of rockburst, and provide target guidance for the prevention and control of rockburst.

Analysis of the internal charging data in medium earth orbit with numerical simulation and ground experiment

The deep dielectric charging effect monitor(DDCEM)has been designed to study the internal charging effect by measuring the charging currents and potentials inside the spacecraft.It is equipped on three Chinese navigation satellites in a circular medium earth orbit(MEO)with 22000 km average height and 55°inclinations.Numerical simulation based on the Geant4-RIC method was used to evaluate the data of DDCEM.The data during May to November 2019 on one of the three satellites show that the charging currents of DDCEM were negatively enhanced when the satellite moved into the outer radiation belt.The currents reached the negative maximum during a significant electron enhancement in September 2019.Positive currents were also detected besides negative currents that were caused by the deposition of electrons in the sensor.The causation of positive currents in the space environment may be that the low-energy electrons cannot penetrate the satellite skin and make it charging to negative potential,the reference ground of DDCEM that is connected to the satellite skin drops below zero by the low-energy electrons so that the output currents turn to positive.Ground experiment was used to simulate the causation of positive currents and the result verified our theory.

Characterization of odorous charge and photochemical reactivity of VOC emissions from a full-scale food waste treatment plant in China

Food waste treatment plants （FWTPs） are usually associated with odorous nuisance and health risks, which are partially caused by volatile organic compound （VOC） emissions. This study investigated the VOC emissions from a selected full-scale FWTP in China. The feedstock used in this plant was mainly collected from local restaurants. For a year, the FWTP was closely monitored on specific days in each season. Four major indoor treatment units of the plant, including the storage room, sorting/crushing room, hydrothermal hydrolysis unit, and aerobic fermentation unit, were chosen as the monitoring locations. The highest mean concentration of total VOC emissions was observed in the aerobic fermentation unit at 21,748.2-31,283.3 μg/m^3, followed by the hydrothermal hydrolysis unit at 10,798.1-23,144.4 μg/m^3. The detected VOC families included biogenic compounds （oxygenated compounds, hydrocarbons, terpenes, and organosulfur compounds） and abiogenic compounds （aromatic hydrocarbons and halocarbons）. Oxygenated compounds, particularly alcohols, were the most abundant compounds in all samples. With the use of odor index analysis and principal components analysis, the hydrothermal hydrolysis and aerobic fermentation units were clearly distinguished from the pre-treatment units, as characterized by their higher contributions to odorous nuisance. Methanthiol was the dominant odorant in the hydrothermal hydrolysis unit, whereas aldehyde was the dominant odorant in the aerobic fermentation unit. Terpenes, specifically limonene, had the highest level of propylene equivalent concentration during the monitoring periods. This concentration can contribute to the increase in the atmospheric reactivity and ozone formation potential in the surrounding air.