Non-oxidative conversion of methane to olefins,aromatics and hydrogen(MTOAH) has been reported recently over metal single sites such as iron and platinum.The reaction was proposed to involve catalytic activation of me...Non-oxidative conversion of methane to olefins,aromatics and hydrogen(MTOAH) has been reported recently over metal single sites such as iron and platinum.The reaction was proposed to involve catalytic activation of methane followed by gas phase C-C coupling of methyl radicals.This study using H atom Rydberg Tagging time-of-flight technique provides direct experimental evidence for the formation of hydrogen radicals during MTOAH reaction over a catalytic quartz wall reactor containing embedded iron species(denoted as Fe-reactor).Fe-reactor gives 7.3% methane conversion at 1273 K with 41.2% selectivity toward C2(ethane,ethylene and acetylene) and 31.8% toward BTX(benzene,toluene and xylene),respectively.The enhancing effects of hydrogen radicals on overall MTOAH performance are validated by cofeeding hydrogen donor benzene,which provides an additional route of methane activation apart from catalytic activation.展开更多
In clinics, especially in the emergency department, carbon dioxide (CO2) is considered as the sixth vital sign in evaluating a patient's medical status. However, its wide applications in developing countries are d...In clinics, especially in the emergency department, carbon dioxide (CO2) is considered as the sixth vital sign in evaluating a patient's medical status. However, its wide applications in developing countries are dissatisfactory due to their high cost compared to their economic growth. In order to develop a practical system for concentration detection of human exhaled CO2 gas for our own, we studied the detection principle based upon the non-dispersive infrared (NDIR) measuring technique and related Lambert-Beer's equation carefully, gave out our functional circuit design of the system, and provided the corresponding graphical user interface (GUI) for CO2 detection. Finally, the experiment shows that it may be a practical system, and will give benefits for the development of our medical care in the future.展开更多
The methane concentration profile from -1.5m depth in soil to 32m height in air was measured in alpine steppe lo-cated in the permafrost area. Methane concentrations showed widely variations both in air and in soil du...The methane concentration profile from -1.5m depth in soil to 32m height in air was measured in alpine steppe lo-cated in the permafrost area. Methane concentrations showed widely variations both in air and in soil during the study period. The mean concentrations in atmosphere were all higher than those in soil, and the highest methane concentration was found in air at the height of 16m with the lowest concentration occur-ring at the depth of 1.5m in soil. The variations of atmospheric methane concentrations did not show any clear pattern both temporally and spatially, although they exhibited a more steady-stable state than those in soil. During the seasonal variations, the methane concentrations at different depths in soil were sig-nificantly correlated (R2>0.6) with each other comparing to the weak correlations (R2<0.2) between the atmospheric concentra-tions at different heights. Mean methane concentrations in soil significantly decreased with depth. This was the compositive influence of the decreasing production rates and the increasing methane oxidation rates, which was caused by the descent soil moisture with depth. Although the methane concentrations at all depths varied widely during the growing season, they showed very distinct temporal variations in the non-growing season. It was indicated from the literatures that methane oxidation rates were positively correlated with soil temperature. The higher methane concentrations in soil during the winter were deter-mined by the lower methane oxidation rates with decreasing soil temperatures, whereas methane production rates had no reaction to the lower temperature. Relations between methane contribution and other environmental factors were not discussed in this paper for lacking of data, which impulse us to carry out further and more detailed studies in this unique area.展开更多
这份报纸针对气体在小、中型的煤矿引起的灾难的实际条件。为煤矿监视系统的新煤气的集中根据煤气察觉到的察觉和单个薄片的控制被开发。因为它为易燃、爆炸的气体有好敏感特征，监视系统把锡氧化物用作 N 类型半导体气体传感器的主要材...这份报纸针对气体在小、中型的煤矿引起的灾难的实际条件。为煤矿监视系统的新煤气的集中根据煤气察觉到的察觉和单个薄片的控制被开发。因为它为易燃、爆炸的气体有好敏感特征，监视系统把锡氧化物用作 N 类型半导体气体传感器的主要材料(例如甲烷，碳一氧化物) 。QM-N5-semiconductor 煤气的传感器被采用在不同煤气的集中下面检测抵抗的产量价值。故意地，系统拿数字薄片抵抗作为处理硬件结构分析并且判定输入的电路的核心珍视的 AT89C51，然后为超出煤气的集中的限制完成控制和警报。监视系统的煤气的集中有许多优点包括在结构，快反应时间，稳定的表演和低费用简单。因此，监视煤气的集中并且在小、中型的煤矿提供早警告能广泛地被用来。展开更多
Low-concentration methane(LCM) has been one of the biggest difficulties in using coal mine methane.And previous studies found that premixed combustion in porous media is an effective method of low calorific gas utiliz...Low-concentration methane(LCM) has been one of the biggest difficulties in using coal mine methane.And previous studies found that premixed combustion in porous media is an effective method of low calorific gas utilization. This paper studied the combustion of LCM in a divergent porous medium burner(DPMB) by using computational fluid dynamics(CFD), and investigated the effect of gas initial temperature on combustion characteristic, the distribution of temperature and pollutant at different equivalence ratios in detail. Besides, the comparison of divergent and cylindrical burners was also performed in this paper. The results show that: the peak temperature in DPMB increases as the increasing of equivalence ratio, which is also suitable for the outlet NO discharge; the linear correlation is also discovered between peak temperature and equivalence ratios; NO emission at the initial temperature of 525 K is 5.64 times,larger than NO emission at the initial temperature of 300 K. Thus, it is preferable to balance the effect of thermal efficiency and environment simultaneously when determining the optimal initial temperature range. The working parameter limits of divergent burner are wider than that of cylindrical one which contributes to reducing the influence of LCM concentration and volume fluctuation on combustion.展开更多
基金supported by the Chinese Academy of Sciences (XDB10020202)the National Natural Science Foundation of China (Grant Nos. 21621063, 21425312, 21761132035)the National Key R&D Program of China (2017YFA0403402)。
文摘Non-oxidative conversion of methane to olefins,aromatics and hydrogen(MTOAH) has been reported recently over metal single sites such as iron and platinum.The reaction was proposed to involve catalytic activation of methane followed by gas phase C-C coupling of methyl radicals.This study using H atom Rydberg Tagging time-of-flight technique provides direct experimental evidence for the formation of hydrogen radicals during MTOAH reaction over a catalytic quartz wall reactor containing embedded iron species(denoted as Fe-reactor).Fe-reactor gives 7.3% methane conversion at 1273 K with 41.2% selectivity toward C2(ethane,ethylene and acetylene) and 31.8% toward BTX(benzene,toluene and xylene),respectively.The enhancing effects of hydrogen radicals on overall MTOAH performance are validated by cofeeding hydrogen donor benzene,which provides an additional route of methane activation apart from catalytic activation.
文摘In clinics, especially in the emergency department, carbon dioxide (CO2) is considered as the sixth vital sign in evaluating a patient's medical status. However, its wide applications in developing countries are dissatisfactory due to their high cost compared to their economic growth. In order to develop a practical system for concentration detection of human exhaled CO2 gas for our own, we studied the detection principle based upon the non-dispersive infrared (NDIR) measuring technique and related Lambert-Beer's equation carefully, gave out our functional circuit design of the system, and provided the corresponding graphical user interface (GUI) for CO2 detection. Finally, the experiment shows that it may be a practical system, and will give benefits for the development of our medical care in the future.
基金funded by The National Basic Research Program (Grant No. G1998040800)Pre-studies project of National Basic Research Program (Grant No. 2005CCA05500)
文摘The methane concentration profile from -1.5m depth in soil to 32m height in air was measured in alpine steppe lo-cated in the permafrost area. Methane concentrations showed widely variations both in air and in soil during the study period. The mean concentrations in atmosphere were all higher than those in soil, and the highest methane concentration was found in air at the height of 16m with the lowest concentration occur-ring at the depth of 1.5m in soil. The variations of atmospheric methane concentrations did not show any clear pattern both temporally and spatially, although they exhibited a more steady-stable state than those in soil. During the seasonal variations, the methane concentrations at different depths in soil were sig-nificantly correlated (R2>0.6) with each other comparing to the weak correlations (R2<0.2) between the atmospheric concentra-tions at different heights. Mean methane concentrations in soil significantly decreased with depth. This was the compositive influence of the decreasing production rates and the increasing methane oxidation rates, which was caused by the descent soil moisture with depth. Although the methane concentrations at all depths varied widely during the growing season, they showed very distinct temporal variations in the non-growing season. It was indicated from the literatures that methane oxidation rates were positively correlated with soil temperature. The higher methane concentrations in soil during the winter were deter-mined by the lower methane oxidation rates with decreasing soil temperatures, whereas methane production rates had no reaction to the lower temperature. Relations between methane contribution and other environmental factors were not discussed in this paper for lacking of data, which impulse us to carry out further and more detailed studies in this unique area.
基金supported by the program of Science and Technology Innovative Research Team in Higher Educational Institutions of Hunan Provincethe Hunan Province and Xiangtan City Natural Science Joint Foundation(No.09JJ8005)+1 种基金the Industrial Cultivation Program of Scientific and Technological Achievements in Higher Educational Institutions of Hunan Province(No.10CY008)the Technologies R & D of Hunan Province (No.2010CK3031)
文摘这份报纸针对气体在小、中型的煤矿引起的灾难的实际条件。为煤矿监视系统的新煤气的集中根据煤气察觉到的察觉和单个薄片的控制被开发。因为它为易燃、爆炸的气体有好敏感特征，监视系统把锡氧化物用作 N 类型半导体气体传感器的主要材料(例如甲烷，碳一氧化物) 。QM-N5-semiconductor 煤气的传感器被采用在不同煤气的集中下面检测抵抗的产量价值。故意地，系统拿数字薄片抵抗作为处理硬件结构分析并且判定输入的电路的核心珍视的 AT89C51，然后为超出煤气的集中的限制完成控制和警报。监视系统的煤气的集中有许多优点包括在结构，快反应时间，稳定的表演和低费用简单。因此，监视煤气的集中并且在小、中型的煤矿提供早警告能广泛地被用来。
基金the supports by the National Basic Research Program of China (No. 2011CB201205)the National Natural Science Foundation of China (No. 51204169)+1 种基金the Research Fund for the Doctoral Program of Higher Education of China (No. 20110095120017)the Fund of China Postdoctoral Science Foundation of China (No. 20110491482)
文摘Low-concentration methane(LCM) has been one of the biggest difficulties in using coal mine methane.And previous studies found that premixed combustion in porous media is an effective method of low calorific gas utilization. This paper studied the combustion of LCM in a divergent porous medium burner(DPMB) by using computational fluid dynamics(CFD), and investigated the effect of gas initial temperature on combustion characteristic, the distribution of temperature and pollutant at different equivalence ratios in detail. Besides, the comparison of divergent and cylindrical burners was also performed in this paper. The results show that: the peak temperature in DPMB increases as the increasing of equivalence ratio, which is also suitable for the outlet NO discharge; the linear correlation is also discovered between peak temperature and equivalence ratios; NO emission at the initial temperature of 525 K is 5.64 times,larger than NO emission at the initial temperature of 300 K. Thus, it is preferable to balance the effect of thermal efficiency and environment simultaneously when determining the optimal initial temperature range. The working parameter limits of divergent burner are wider than that of cylindrical one which contributes to reducing the influence of LCM concentration and volume fluctuation on combustion.
