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
We propose optical experiments to study the depth of field for a thermal light lensless ghost imaging system. It is proved that the diaphragm is an important factor to influence the depth of field, and the ghost image...We propose optical experiments to study the depth of field for a thermal light lensless ghost imaging system. It is proved that the diaphragm is an important factor to influence the depth of field, and the ghost images of two detected objects with longitudinal distance less than the depth of field can be achieved simultaneously. The longitudinal coherence scale of the thermal light lensless ghost imaging determines the depth of field. Theoretical analysis can well explain the experimental results.展开更多
Light(sub-GeV)dark matter has gained increasing interest in terms of direct detection.Accelerated dark matter is a promising candidate that can generate detectable nuclear recoil energy within the sub-GeV range.Becaus...Light(sub-GeV)dark matter has gained increasing interest in terms of direct detection.Accelerated dark matter is a promising candidate that can generate detectable nuclear recoil energy within the sub-GeV range.Because of the large kinetic energy,its interactions with the nucleus are predominantly governed by inelastic scattering,including quasi-elastic and deep inelastic scattering.In this work,we calculated the inelastic effects in dark matter-Earth scattering mediated by a vector particle.Our analysis revealed that the impact of inelastic scattering relies on the mediator mass and the kinetic energy spectrum of dark matter.The results exhibited considerable disparity:the upper bounds of the exclusion limit for the spin-independent cross-section between accelerated dark matter and nuclei via a heavy mediator differ by several tens of times when inelastic scattering is considered.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.
基金Supported by the Beijing Natural Science Foundation under Grant No 4133086the Fundamental Research Funds for th Central Universities under Grant No 2-9-2014-022
文摘We propose optical experiments to study the depth of field for a thermal light lensless ghost imaging system. It is proved that the diaphragm is an important factor to influence the depth of field, and the ghost images of two detected objects with longitudinal distance less than the depth of field can be achieved simultaneously. The longitudinal coherence scale of the thermal light lensless ghost imaging determines the depth of field. Theoretical analysis can well explain the experimental results.
基金supported by the National Natural Science Foundation of China(Grant Nos.12275134,12275232,and 12335005)。
文摘Light(sub-GeV)dark matter has gained increasing interest in terms of direct detection.Accelerated dark matter is a promising candidate that can generate detectable nuclear recoil energy within the sub-GeV range.Because of the large kinetic energy,its interactions with the nucleus are predominantly governed by inelastic scattering,including quasi-elastic and deep inelastic scattering.In this work,we calculated the inelastic effects in dark matter-Earth scattering mediated by a vector particle.Our analysis revealed that the impact of inelastic scattering relies on the mediator mass and the kinetic energy spectrum of dark matter.The results exhibited considerable disparity:the upper bounds of the exclusion limit for the spin-independent cross-section between accelerated dark matter and nuclei via a heavy mediator differ by several tens of times when inelastic scattering is considered.
