To investigate the creep and instability properties of a cemented gangue backfill column under a highstress area,the uniaxial compression creep tests were conducted by single-step and multi-step loading of prismatic s...To investigate the creep and instability properties of a cemented gangue backfill column under a highstress area,the uniaxial compression creep tests were conducted by single-step and multi-step loading of prismatic samples made of cemented gangue backfill material(CGBM)under the high stressstrength ratio.The creep damage was monitored using an electrical resistivity device,ultrasonic testing device,and acoustic emission(AE)instrument.The results showed that the CGBM sample has a creep hardening property.The creep failure strength(CFS)is slightly larger than the uniaxial compressive strength(UCS),ranging in ratio from 108.9%to 116.5%.The instantaneous strain,creep strain,and creep rate increase with increasing stress-strength ratio in the single-step loading creep tests.The instantaneous strain and creep strain decrease first and then increase during the multi-step loading creep process.The axial creep strain of the CGBM column can be expressed by the viscoelastic-plastic creep model.Creep instability is caused by the accumulation of strain energy under multi-step loading and the continuous lateral expansion at the unconstrained middle position during the creep process.The creep stability of a CGBM column in a high-stress area can be monitored based on the variation of electrical resistivity,ultrasonic pulse velocity(UPV),and AE signals.展开更多
Soil biogenic NO emission is one of the most important sources of atmospheric nitrogen oxides(NOx) worldwide. However, the estimation of soil source, especially in arid areas presents large uncertainties because of th...Soil biogenic NO emission is one of the most important sources of atmospheric nitrogen oxides(NOx) worldwide. However, the estimation of soil source, especially in arid areas presents large uncertainties because of the substantial lack of measurements. In this study, we selected the Ruoqiang oases on the southeastern edge of the Taklimakan Desert, China as the study area and applied Ozone Monitoring Instrument(OMI) NO2 retrievals(DOMINO v2.0, 2005–2011) to investigate the spatial distribution and seasonal variations in tropospheric NO2 vertical column density(VCD). High NO2 VCDs were observed over the oases(farmlands and natural vegetation), with the highest value obtained during summer, and lowest during winter. Pulses were observed during spring. We conducted in-situ measurements in June 2011 in Milan oasis and employed ground-based multi-axis differential optical absorption spectroscopy(MAX-DOAS) instruments to validate satellite NO2 retrievals. The findings are as follows: 1) in the study area soil biogenic NO emission is the dominant source of tropospheric NO2; 2) oases(farmlands) are hotspots of tropospheric NO2, and a higher increase in tropospheric NO2 is found in oases from winter to summer; and 3) enhancement of soil biogenic NO emission due to soil managements is predictable. Given the rapid agricultural development in the southern Uygur Autonomous Region of Xinjiang, researches on soil biogenic NO emission and increase in tropospheric NOx should be given more importance.展开更多
It is known that the performances of multi-phase reactors depend on the operating parameters(the temperature and the pressure of the system),the phase properties,and the design parameters(the aspect ratio(AR),the bubb...It is known that the performances of multi-phase reactors depend on the operating parameters(the temperature and the pressure of the system),the phase properties,and the design parameters(the aspect ratio(AR),the bubble column diameter,and the gas sparger design).Hence,the precise design and the correct operation of multi-phase reactors depends on the understanding and prediction of the fluid dynamics parameters.This paper contributes to the existing discussion on the effect of operating and design parameter on multi-phase reactors and,in particular,it considers an industrial process(e.g.,the LOPROX(low pressure oxidation)case study,which is typical example of two-phase bubble columns).Based on a previously-validated set of correlations,the influence of operating and design parameter on system performances is studied and critically analyzed.First,we studied the effects of the design parameter on the liquid–gas interfacial area,by keeping constant the fluid physical–chemical properties as well as the operating conditions;subsequently,we discussed for a fixed system design,the influence of the liquid phase properties and the operating pressure.In conclusion,this paper is intended to provide guidelines for the design and scale-up of multi-phase reactors.展开更多
基金supported by the National Natural Science Foundation of China(No.51974192)Shanxi Province Postgraduate Education Innovation Project(No.2020SY567)+2 种基金the Applied Basic Research Project of Shanxi Province(No.201801D121092)Distinguished Youth Funds of National Natural Science Foundation of China(No.51925402)Shanxi Science and Technology Major Project(No.20201102004)。
文摘To investigate the creep and instability properties of a cemented gangue backfill column under a highstress area,the uniaxial compression creep tests were conducted by single-step and multi-step loading of prismatic samples made of cemented gangue backfill material(CGBM)under the high stressstrength ratio.The creep damage was monitored using an electrical resistivity device,ultrasonic testing device,and acoustic emission(AE)instrument.The results showed that the CGBM sample has a creep hardening property.The creep failure strength(CFS)is slightly larger than the uniaxial compressive strength(UCS),ranging in ratio from 108.9%to 116.5%.The instantaneous strain,creep strain,and creep rate increase with increasing stress-strength ratio in the single-step loading creep tests.The instantaneous strain and creep strain decrease first and then increase during the multi-step loading creep process.The axial creep strain of the CGBM column can be expressed by the viscoelastic-plastic creep model.Creep instability is caused by the accumulation of strain energy under multi-step loading and the continuous lateral expansion at the unconstrained middle position during the creep process.The creep stability of a CGBM column in a high-stress area can be monitored based on the variation of electrical resistivity,ultrasonic pulse velocity(UPV),and AE signals.
基金Under the auspices of German Research Foundation and Max Planck Society(No.MA 4798/1-1)National Natural Science Foundation of China(No.31070384)
文摘Soil biogenic NO emission is one of the most important sources of atmospheric nitrogen oxides(NOx) worldwide. However, the estimation of soil source, especially in arid areas presents large uncertainties because of the substantial lack of measurements. In this study, we selected the Ruoqiang oases on the southeastern edge of the Taklimakan Desert, China as the study area and applied Ozone Monitoring Instrument(OMI) NO2 retrievals(DOMINO v2.0, 2005–2011) to investigate the spatial distribution and seasonal variations in tropospheric NO2 vertical column density(VCD). High NO2 VCDs were observed over the oases(farmlands and natural vegetation), with the highest value obtained during summer, and lowest during winter. Pulses were observed during spring. We conducted in-situ measurements in June 2011 in Milan oasis and employed ground-based multi-axis differential optical absorption spectroscopy(MAX-DOAS) instruments to validate satellite NO2 retrievals. The findings are as follows: 1) in the study area soil biogenic NO emission is the dominant source of tropospheric NO2; 2) oases(farmlands) are hotspots of tropospheric NO2, and a higher increase in tropospheric NO2 is found in oases from winter to summer; and 3) enhancement of soil biogenic NO emission due to soil managements is predictable. Given the rapid agricultural development in the southern Uygur Autonomous Region of Xinjiang, researches on soil biogenic NO emission and increase in tropospheric NOx should be given more importance.
文摘It is known that the performances of multi-phase reactors depend on the operating parameters(the temperature and the pressure of the system),the phase properties,and the design parameters(the aspect ratio(AR),the bubble column diameter,and the gas sparger design).Hence,the precise design and the correct operation of multi-phase reactors depends on the understanding and prediction of the fluid dynamics parameters.This paper contributes to the existing discussion on the effect of operating and design parameter on multi-phase reactors and,in particular,it considers an industrial process(e.g.,the LOPROX(low pressure oxidation)case study,which is typical example of two-phase bubble columns).Based on a previously-validated set of correlations,the influence of operating and design parameter on system performances is studied and critically analyzed.First,we studied the effects of the design parameter on the liquid–gas interfacial area,by keeping constant the fluid physical–chemical properties as well as the operating conditions;subsequently,we discussed for a fixed system design,the influence of the liquid phase properties and the operating pressure.In conclusion,this paper is intended to provide guidelines for the design and scale-up of multi-phase reactors.
