The surrounding rock in tunnelling engineering and coal mining will sometimes be exposed to high temperature. Rock failure is the result of energy dissipation, and the study of the evolution and transformation behavio...The surrounding rock in tunnelling engineering and coal mining will sometimes be exposed to high temperature. Rock failure is the result of energy dissipation, and the study of the evolution and transformation behavior of energy is of great significance for the in-depth understanding of the deformation and failure of rock after high temperature. This study analyzed the intrinsic connection between mechanical properties and acoustic emission(AE) energy under temperature effect. Based on the energy dissipation and release theory, the distribution and transformation of energy was analyzed, and the energy selfincentive and self-inhibition(EII) model was further established. The main findings are that temperature effect affects the confidence interval trend and the value of AE energy rate, which is related to the change in mechanical properties. The ability of sandstone to store elastic strain energy after exposure to high temperature is independent of the mechanical properties. In this study, the ratio of dissipated energy to elastic energy is used to characterize the stable state of the sandstone system, which can be used as the energy indicator of rock failure precursor. During the absorption, storage, and release of energy before the peak stress, there exists self-incentive and self-inhibition of energy(control behavior).展开更多
In countries suffering from heavy ambient air pollution,ventilation is a problem,as ventilation intakes outdoor air pollutants,such as particulate matter with an aerodynamic diameter less than 2.5 μm(PM_(2.5)),while ...In countries suffering from heavy ambient air pollution,ventilation is a problem,as ventilation intakes outdoor air pollutants,such as particulate matter with an aerodynamic diameter less than 2.5 μm(PM_(2.5)),while removing indoor air pollutants.Thus,it is important to identify appropriate ventilation-purification strategies to build healthy indoor environments with low energy consumption.This study reports the comparison of two sets of strategies,i.e.,mechanical ventilation with filters and natural ventilation with indoor air cleaners,in respect to energy consumption and the PMzs and carbon dioxide(CO_(2))exposure of occupants in a typical apartment in Beijing,China.A dynamic mass balance model was employed to calculate the PM2.5 and CO_(2) exposure concentrations,while the energy consumption of heating and cooling was simulated with the Designer's Simulation Toolkit.It was found that natural ventilation with air cleaners provided lower PIVhs exposure compared with that of mechanical ventilation with filters;however,mechanical ventilation achieved a lower CO_(2) exposure concentration.The annual cooling,heating,and fan energy consumption of natural ventilation strategies are lower than those of mechanical ventilation strategies.With respect to natural ventilation,an infiltration rate of 0.3-0.4 h^(-1)was the preferred setting,which led to low PM23 and CO_(2) exposure with lower energy consumption.The basic requirements for controlling indoor PM2.5 could be met if the threshold is set at 25 pg/m3.The results provide guidelines on how to combine multiple ventilation purification strategies to improve indoor air quality with lower energy usage.展开更多
Managers and regulators are concerned about potential human health effects from exposure on lands contaminated by chemicals and radionuclides. Determining target cleanup levels is partly dependent upon future land use...Managers and regulators are concerned about potential human health effects from exposure on lands contaminated by chemicals and radionuclides. Determining target cleanup levels is partly dependent upon future land use, and potential exposure from human use. This paper provides data from surveys of activity patterns of people attending festivals in four states, located in the vicinity of Department of Energy facilities. There were significant differences in both participation rates, and activity rates as a function of both location and ethnicity that can be used by managers to track exposure, land use, and preferred activities on natural lands. In general, 1) a higher percent of Native Americans engaged in consumptive activities than others, 2) a higher percent of Caucasians engaged in some non-consumptive activities than Native Americans, 3) a higher percentage of Native Americans engaged in activities on sacred grounds, 4) activity rates were generally higher for Native Americans for consumptive activities and religious/cultural than for Caucasians, 5) fishing rates were higher than other consumptive activities, and camping/hiking were higher than other non-con- sumptive activities, and 6) hunting rates were higher in subjects from Idaho than elsewhere. Baseline human use is critical for monitoring potential exposure, and provides the basis for monitoring, risk assessment and future land use, and these data can be used by managers for assessment and management. Tracking changes over time will reflect changing recreational, subsistence, and cultural/religious trends that relate to land use, public perceptions, and exposure.展开更多
基金supported by the Joint Program between National Natural Science Foundation of China and Shandong Province (No. U1806209)Fundamental Research Funds for the Central Universities (Nos. TP-19-021A3 and FRF-IDRY-19-002)。
文摘The surrounding rock in tunnelling engineering and coal mining will sometimes be exposed to high temperature. Rock failure is the result of energy dissipation, and the study of the evolution and transformation behavior of energy is of great significance for the in-depth understanding of the deformation and failure of rock after high temperature. This study analyzed the intrinsic connection between mechanical properties and acoustic emission(AE) energy under temperature effect. Based on the energy dissipation and release theory, the distribution and transformation of energy was analyzed, and the energy selfincentive and self-inhibition(EII) model was further established. The main findings are that temperature effect affects the confidence interval trend and the value of AE energy rate, which is related to the change in mechanical properties. The ability of sandstone to store elastic strain energy after exposure to high temperature is independent of the mechanical properties. In this study, the ratio of dissipated energy to elastic energy is used to characterize the stable state of the sandstone system, which can be used as the energy indicator of rock failure precursor. During the absorption, storage, and release of energy before the peak stress, there exists self-incentive and self-inhibition of energy(control behavior).
基金supported by the China Postdoctoral Science Foundation(No.2019M650013)Fundamental Research Funds for the Central Universities(No.FRF-TP-18-083A1)National Natural Science Foundation of China(No.51908032).
文摘In countries suffering from heavy ambient air pollution,ventilation is a problem,as ventilation intakes outdoor air pollutants,such as particulate matter with an aerodynamic diameter less than 2.5 μm(PM_(2.5)),while removing indoor air pollutants.Thus,it is important to identify appropriate ventilation-purification strategies to build healthy indoor environments with low energy consumption.This study reports the comparison of two sets of strategies,i.e.,mechanical ventilation with filters and natural ventilation with indoor air cleaners,in respect to energy consumption and the PMzs and carbon dioxide(CO_(2))exposure of occupants in a typical apartment in Beijing,China.A dynamic mass balance model was employed to calculate the PM2.5 and CO_(2) exposure concentrations,while the energy consumption of heating and cooling was simulated with the Designer's Simulation Toolkit.It was found that natural ventilation with air cleaners provided lower PIVhs exposure compared with that of mechanical ventilation with filters;however,mechanical ventilation achieved a lower CO_(2) exposure concentration.The annual cooling,heating,and fan energy consumption of natural ventilation strategies are lower than those of mechanical ventilation strategies.With respect to natural ventilation,an infiltration rate of 0.3-0.4 h^(-1)was the preferred setting,which led to low PM23 and CO_(2) exposure with lower energy consumption.The basic requirements for controlling indoor PM2.5 could be met if the threshold is set at 25 pg/m3.The results provide guidelines on how to combine multiple ventilation purification strategies to improve indoor air quality with lower energy usage.
文摘Managers and regulators are concerned about potential human health effects from exposure on lands contaminated by chemicals and radionuclides. Determining target cleanup levels is partly dependent upon future land use, and potential exposure from human use. This paper provides data from surveys of activity patterns of people attending festivals in four states, located in the vicinity of Department of Energy facilities. There were significant differences in both participation rates, and activity rates as a function of both location and ethnicity that can be used by managers to track exposure, land use, and preferred activities on natural lands. In general, 1) a higher percent of Native Americans engaged in consumptive activities than others, 2) a higher percent of Caucasians engaged in some non-consumptive activities than Native Americans, 3) a higher percentage of Native Americans engaged in activities on sacred grounds, 4) activity rates were generally higher for Native Americans for consumptive activities and religious/cultural than for Caucasians, 5) fishing rates were higher than other consumptive activities, and camping/hiking were higher than other non-con- sumptive activities, and 6) hunting rates were higher in subjects from Idaho than elsewhere. Baseline human use is critical for monitoring potential exposure, and provides the basis for monitoring, risk assessment and future land use, and these data can be used by managers for assessment and management. Tracking changes over time will reflect changing recreational, subsistence, and cultural/religious trends that relate to land use, public perceptions, and exposure.
