Building highly active and stable noble metal single atom(MSA)catalyst onto photocatalyst materials for nitrogen reduction reaction(NRR)and CO2 reduction reaction(CRR)is a key to future renewable energy conversion and...Building highly active and stable noble metal single atom(MSA)catalyst onto photocatalyst materials for nitrogen reduction reaction(NRR)and CO2 reduction reaction(CRR)is a key to future renewable energy conversion and storage technologies.Here we present a design strategy to optimize the stability and electronic property of noble metal single atoms(MSAs,M=Rh,Pd,Ag,Ir,Pt,Au)catalyst supported on g-C3N4 and 2H-MoS2 photocatalysts towards NRR and CRR.Our results indicate that the MSAs tend to be trapped at the anion-vacancy sites of photocatalyst rather than the pristine photocatalyst surface.This anion vacancy can promise the MSAs with an optimized electron-captured ability in the photoexcitation process,thus decreasing the energy barriers of NRR and CRR on MSAs.Especially,it is revealed that the N-vacancy-stabilized Ir SA on g-C3N4 and the S-vacancy-stabilized RhSA on 2H-MoS2 own the lowest energy barrier in NRR.However,for CRR,the HCOOH is the main product on MSAs supported by gC3N4 and 2H-MoS2.The N-vacancy-stabilized PdSA on g-C3N4 and the S-vacancy-stabilized AuSA on 2H-MoS2 show the lowest energy barrier for HCOOH production in CRR.This finding offers an approach to design specific active MSA centres on photocatalysts by the anion vacancy engineering.展开更多
In this study, a backpropagation neural network algorithm was developed in order to predict the liquefaction cyclic resistance ratio (CRR) of sand-silt mixtures. A database, consisting of sufficient published data of ...In this study, a backpropagation neural network algorithm was developed in order to predict the liquefaction cyclic resistance ratio (CRR) of sand-silt mixtures. A database, consisting of sufficient published data of laboratory cyclic triaxial, torsional shear and simple shear tests results, was collected and utilized in the ANN model. Several ANN models were developed with different sets of input parameters in order to determine the model with best performance and preciseness. It has been illustrated that the proposed ANN model can predict the measured CRR of the different data set which was not incorporated in the developing phase of the model with the good degree of accuracy. The subsequent sensitivity analysis was performed to compare the effect of each parameter in the model with the laboratory test results. At the end, the participation or relative importance of each parameter in the ANN model was obtained.展开更多
To elucidate the molecular mechanisms underlying cellular radioresistance, clinically relevant radioresistant cell lines were established via long-term exposure to X-rays with stepwise dose escalation. Established cel...To elucidate the molecular mechanisms underlying cellular radioresistance, clinically relevant radioresistant cell lines were established via long-term exposure to X-rays with stepwise dose escalation. Established cells continue to proliferate despite exposure to 2 Gy X-rays/day for more than 30 days, a standard protocol in cancer radiotherapy. DNA repair fidelity in radioresistant and the parental cells by evaluating the mutation frequency at the hypoxanthine phosphoribosyltransferase (HPRT) locus after exposure to X-rays was determined. Mutation spectrum at the HPRT locus was examined by multiplex polymerase chain reaction. Rejoining kinetics of X-ray-induced DNA double strand breaks (dsbs) was evaluated by the detection of phosphorylated histone H2AX (γH2AX) after X-irradiation. The fold increase in the HPRT mutation frequency due to acute radiation was similar between radioresistant and the parental cell lines. However, fractionated radiation (FR) consisting of 2 Gy X-rays/day increased the mutation frequency at the HPRT locus in parental but not in radioresistant cells. Analysis of the FR-induced mutations at the HPRT locus revealed a high frequency of deletion mutations (>70%) in parental but not in radioresistant cells. As assessed by γH2AX immunostaining, DNA dsbs induced by acute exposure to 10 Gy of X-rays were repaired to the control level within 7 days in radioresistant but not in the parental cells. Moreover, 2 Gy × 5 FR increased the number of γH2AX-positive cells in parental cultures but not in radioresistant cultures. DNA dsbs induced by 2 Gy/day FR are repaired with fidelity in radioresistant but not in parental cells.展开更多
Soil liquefaction, and the permanent deformations that frequently result from it, have caused significant damage in past earthquakes. The procedures used in contemporary geotechnical earthquake engineering practice ar...Soil liquefaction, and the permanent deformations that frequently result from it, have caused significant damage in past earthquakes. The procedures used in contemporary geotechnical earthquake engineering practice are generally based on simplified procedures for the evaluation of the liquefaction potential. The work describes a framework for performance-based earthquake engineering and its use in the development of a performance-based procedure for liquefaction hazard evaluation. The performance-based procedure will be used to show how consistent application of conventional procedures for evaluation of liquefaction potential can influence performance prediction. Implications for liquefaction-resistant design will also be discussed. The purpose is to summarize current procedures for practical prediction of liquefaction behavior, to describe recent advances in the understanding of liquefaction behavior, and to describe the incorporation of this improved understanding into new solutions for detailed modeling of soil liquefaction, Simplified procedures for evaluation of liquefaction hazards will be reviewed relatively briefly, with more details devoted to emerging knowledge about the mechanics of liquefiable soil behavior, and methods for incorporating those mechanics into improved models for performance prediction. In particular it focuses about the influence on the evaluation of Cyclic Resistance Ratio （CRR） by different in-situ tests （Cone Penetration Test （CPT）. Standard Penetration Test （SPT） and Seismic Dilatometer Marchetti Test （SDMT）） and by different shear waves velocity measurements （Down Hole D-H. Cross Hole C-H, Seismic Dilatometer Marchetti Test SDMT）.展开更多
目的针对国内处理原料气在气质较富时乙烷回收装置单一、产物回收率低的问题,在原有工艺冷干气回流流程(cold residue reflux process,CRR)的基础上提出两种高效乙烷回收流程,即带闪蒸的冷干气回流流程(cold residue reflux process wit...目的针对国内处理原料气在气质较富时乙烷回收装置单一、产物回收率低的问题,在原有工艺冷干气回流流程(cold residue reflux process,CRR)的基础上提出两种高效乙烷回收流程,即带闪蒸的冷干气回流流程(cold residue reflux process with flash evaporator,CRR-FE)和部分原料气过冷分离的冷干气回流流程(cold residue reflux process with feed subcooled,CRR-PS)。方法在保证乙烷回收率高于95%的条件下,利用HYSYS软件模拟改进工艺流程,设置了3组逐渐变富的气质对CRR及改进流程进行了综合能耗和火用分析对比。结果改进后的流程有很好的节能效果,其中CRR-PS流程节能效果明显,在GPM值为4.3时,CRR-PS流程综合能耗节约了9.4%。3种流程火用损最大为主体设备压缩机中的外输压缩机,其次是塔设备中脱甲烷塔和丙烷制冷,最后是换热器、空冷器及水冷器;改进后的流程性能很好,整体火用效率在80%以上,总火用效率排序为CRR-PS>CRR-FE>CRR;当GPM值为4.3时,CRR-PS火用损为28471 kW,相比于CRR降低了3.9%,表明CRR-PS火用损失较少,有很好的节能潜力。结论CRR-PS流程对富气适应性更强,节能效果更好。展开更多
The embankment of the Qinghai-Tibet Railway(QTR)has been experiencing severe problems due to permafrost degradation,especially in warm and ice-rich permafrost regions.Based on ground temperature and deformation data o...The embankment of the Qinghai-Tibet Railway(QTR)has been experiencing severe problems due to permafrost degradation,especially in warm and ice-rich permafrost regions.Based on ground temperature and deformation data of the embankment at location K1497+150 of the QTR in 2006-2018,the thermal regime and deformation process were analysed.The results showed that 1)the degradation rate of permafrost under the embankment was faster than that under the natural site without engineering construction,and 2)the deformation rate of the embankment had exceeded the safety range for the QTR embankment before adopting mitigative measures.In addition,this study evaluated the cooling effect on the underlying permafrost and working mechanism of two strengthening measures.Two measures,crushed rock revetment(CRR)and thermosyphons,were adopted to protect the underlying permafrost from continual degradation.The individual cooling effect of the CRR was not as good as that of the thermosyphons.However,the combination of the two could enhance the protective effects of each on the underlying permafrost,effectively cooling the permafrost and improving the stability of the embankment.展开更多
基金financially supported by the Tencent Foundation through the XPLORER PRIZE,Chinathe National Natural Science Foundation of China(51671003)+3 种基金the National Basic Research Program of China(2016YFB0100201)start-up support from Peking Universitythe Young Thousand Talented Programthe computation support from Jincai Zhao's group of Institute of Chemistry,Chinese Academy of Sciences。
文摘Building highly active and stable noble metal single atom(MSA)catalyst onto photocatalyst materials for nitrogen reduction reaction(NRR)and CO2 reduction reaction(CRR)is a key to future renewable energy conversion and storage technologies.Here we present a design strategy to optimize the stability and electronic property of noble metal single atoms(MSAs,M=Rh,Pd,Ag,Ir,Pt,Au)catalyst supported on g-C3N4 and 2H-MoS2 photocatalysts towards NRR and CRR.Our results indicate that the MSAs tend to be trapped at the anion-vacancy sites of photocatalyst rather than the pristine photocatalyst surface.This anion vacancy can promise the MSAs with an optimized electron-captured ability in the photoexcitation process,thus decreasing the energy barriers of NRR and CRR on MSAs.Especially,it is revealed that the N-vacancy-stabilized Ir SA on g-C3N4 and the S-vacancy-stabilized RhSA on 2H-MoS2 own the lowest energy barrier in NRR.However,for CRR,the HCOOH is the main product on MSAs supported by gC3N4 and 2H-MoS2.The N-vacancy-stabilized PdSA on g-C3N4 and the S-vacancy-stabilized AuSA on 2H-MoS2 show the lowest energy barrier for HCOOH production in CRR.This finding offers an approach to design specific active MSA centres on photocatalysts by the anion vacancy engineering.
文摘In this study, a backpropagation neural network algorithm was developed in order to predict the liquefaction cyclic resistance ratio (CRR) of sand-silt mixtures. A database, consisting of sufficient published data of laboratory cyclic triaxial, torsional shear and simple shear tests results, was collected and utilized in the ANN model. Several ANN models were developed with different sets of input parameters in order to determine the model with best performance and preciseness. It has been illustrated that the proposed ANN model can predict the measured CRR of the different data set which was not incorporated in the developing phase of the model with the good degree of accuracy. The subsequent sensitivity analysis was performed to compare the effect of each parameter in the model with the laboratory test results. At the end, the participation or relative importance of each parameter in the ANN model was obtained.
文摘To elucidate the molecular mechanisms underlying cellular radioresistance, clinically relevant radioresistant cell lines were established via long-term exposure to X-rays with stepwise dose escalation. Established cells continue to proliferate despite exposure to 2 Gy X-rays/day for more than 30 days, a standard protocol in cancer radiotherapy. DNA repair fidelity in radioresistant and the parental cells by evaluating the mutation frequency at the hypoxanthine phosphoribosyltransferase (HPRT) locus after exposure to X-rays was determined. Mutation spectrum at the HPRT locus was examined by multiplex polymerase chain reaction. Rejoining kinetics of X-ray-induced DNA double strand breaks (dsbs) was evaluated by the detection of phosphorylated histone H2AX (γH2AX) after X-irradiation. The fold increase in the HPRT mutation frequency due to acute radiation was similar between radioresistant and the parental cell lines. However, fractionated radiation (FR) consisting of 2 Gy X-rays/day increased the mutation frequency at the HPRT locus in parental but not in radioresistant cells. Analysis of the FR-induced mutations at the HPRT locus revealed a high frequency of deletion mutations (>70%) in parental but not in radioresistant cells. As assessed by γH2AX immunostaining, DNA dsbs induced by acute exposure to 10 Gy of X-rays were repaired to the control level within 7 days in radioresistant but not in the parental cells. Moreover, 2 Gy × 5 FR increased the number of γH2AX-positive cells in parental cultures but not in radioresistant cultures. DNA dsbs induced by 2 Gy/day FR are repaired with fidelity in radioresistant but not in parental cells.
文摘Soil liquefaction, and the permanent deformations that frequently result from it, have caused significant damage in past earthquakes. The procedures used in contemporary geotechnical earthquake engineering practice are generally based on simplified procedures for the evaluation of the liquefaction potential. The work describes a framework for performance-based earthquake engineering and its use in the development of a performance-based procedure for liquefaction hazard evaluation. The performance-based procedure will be used to show how consistent application of conventional procedures for evaluation of liquefaction potential can influence performance prediction. Implications for liquefaction-resistant design will also be discussed. The purpose is to summarize current procedures for practical prediction of liquefaction behavior, to describe recent advances in the understanding of liquefaction behavior, and to describe the incorporation of this improved understanding into new solutions for detailed modeling of soil liquefaction, Simplified procedures for evaluation of liquefaction hazards will be reviewed relatively briefly, with more details devoted to emerging knowledge about the mechanics of liquefiable soil behavior, and methods for incorporating those mechanics into improved models for performance prediction. In particular it focuses about the influence on the evaluation of Cyclic Resistance Ratio （CRR） by different in-situ tests （Cone Penetration Test （CPT）. Standard Penetration Test （SPT） and Seismic Dilatometer Marchetti Test （SDMT）） and by different shear waves velocity measurements （Down Hole D-H. Cross Hole C-H, Seismic Dilatometer Marchetti Test SDMT）.
文摘目的针对国内处理原料气在气质较富时乙烷回收装置单一、产物回收率低的问题,在原有工艺冷干气回流流程(cold residue reflux process,CRR)的基础上提出两种高效乙烷回收流程,即带闪蒸的冷干气回流流程(cold residue reflux process with flash evaporator,CRR-FE)和部分原料气过冷分离的冷干气回流流程(cold residue reflux process with feed subcooled,CRR-PS)。方法在保证乙烷回收率高于95%的条件下,利用HYSYS软件模拟改进工艺流程,设置了3组逐渐变富的气质对CRR及改进流程进行了综合能耗和火用分析对比。结果改进后的流程有很好的节能效果,其中CRR-PS流程节能效果明显,在GPM值为4.3时,CRR-PS流程综合能耗节约了9.4%。3种流程火用损最大为主体设备压缩机中的外输压缩机,其次是塔设备中脱甲烷塔和丙烷制冷,最后是换热器、空冷器及水冷器;改进后的流程性能很好,整体火用效率在80%以上,总火用效率排序为CRR-PS>CRR-FE>CRR;当GPM值为4.3时,CRR-PS火用损为28471 kW,相比于CRR降低了3.9%,表明CRR-PS火用损失较少,有很好的节能潜力。结论CRR-PS流程对富气适应性更强,节能效果更好。
基金supported by the Strategic Priority Research Program of the Chinese Academy of Science(XDA20020102)Science and Technology Project of State Grid Corporation of China(SGQHDKYOSBJS201600077)+1 种基金the Natural Science Foundation of China(41101065)the State Key Laboratory of Frozen Soils Engineering Foundation(SKLFSE-ZT-34).
文摘The embankment of the Qinghai-Tibet Railway(QTR)has been experiencing severe problems due to permafrost degradation,especially in warm and ice-rich permafrost regions.Based on ground temperature and deformation data of the embankment at location K1497+150 of the QTR in 2006-2018,the thermal regime and deformation process were analysed.The results showed that 1)the degradation rate of permafrost under the embankment was faster than that under the natural site without engineering construction,and 2)the deformation rate of the embankment had exceeded the safety range for the QTR embankment before adopting mitigative measures.In addition,this study evaluated the cooling effect on the underlying permafrost and working mechanism of two strengthening measures.Two measures,crushed rock revetment(CRR)and thermosyphons,were adopted to protect the underlying permafrost from continual degradation.The individual cooling effect of the CRR was not as good as that of the thermosyphons.However,the combination of the two could enhance the protective effects of each on the underlying permafrost,effectively cooling the permafrost and improving the stability of the embankment.
