Thermal expansion control is always an obstructive factor and challenging in high precision engineering field.Here,the negative thermal expansion of NbF_(3)and NbOF_(2)was predicted by first-principles calculation wit...Thermal expansion control is always an obstructive factor and challenging in high precision engineering field.Here,the negative thermal expansion of NbF_(3)and NbOF_(2)was predicted by first-principles calculation with density functional theory and the quasi-harmonic approximation(QHA).We studied the total charge density,thermal vibration,and lattice dynamic to investigate the thermal expansion mechanism.We found that the presence of O induced the relatively strong covalent bond in NbOF_(2),thus weakening the transverse vibration of F and O in NbOF_(2),compared with the case of NbF_(3).In this study,we proposed a way to tailor negative thermal expansion of metal fluorides by introducing the oxygen atoms.The present work not only predicts two NTE compounds,but also provides an insight on thermal expansion control by designing chemical bond type.展开更多
Rational design of metallic active sites and its microenvironment is critical for constructing superoxide dismutase(SOD)nanozymes.Here,we reported a novel SOD nanozyme design,with employing graphene oxide(GO)as the fr...Rational design of metallic active sites and its microenvironment is critical for constructing superoxide dismutase(SOD)nanozymes.Here,we reported a novel SOD nanozyme design,with employing graphene oxide(GO)as the framework,andδ-MnO_(2)as the active sites,to mimic the natural Mn-SOD.This MnO_(2)@GO nanozyme exhibited multiscale laminated structures with honeycomb-like morphology,providing highly specific surface area for·O_(2)−adsorption and confined spaces for subsequent catalytic reactions.Thus,the nanozyme achieved superlative SOD-like catalytic performance with inhibition rate of 95.5%,which is 222.6%and 1605.4%amplification over GO and MnO_(2)nanoparticles,respectively.Additionally,such unique hierarchical structural design endows MnO_(2)@GO with catalytic specificity,which was not present in the individual component(GO or MnO_(2)).This multiscale structural design provides new strategies for developing highly active and specific SOD nanozymes.展开更多
Tianwen-1(TW-1)is the first Chinese interplanetary mission to have accomplished orbiting,landing,and patrolling in a single exploration of Mars.After safe landing,it is essential to reconstruct the descent trajectory ...Tianwen-1(TW-1)is the first Chinese interplanetary mission to have accomplished orbiting,landing,and patrolling in a single exploration of Mars.After safe landing,it is essential to reconstruct the descent trajectory and determine the landing site of the lander.For this purpose,we processed descent images of the TW-1 optical obstacle-avoidance sensor(OOAS)and digital orthophoto map(DOM)of the landing area using our proposed hybrid-matching method,in which the landing process is divided into two parts.In the first,crater matching is used to obtain the geometric transformations between the OOAS images and DOM to calculate the position of the lander.In the second,feature matching is applied to compute the position of the lander.We calculated the landing site of TW-1 to be 109.9259◦E,25.0659◦N with a positional accuracy of 1.56 m and reconstructed the landing trajectory with a horizontal root mean squared error of 1.79 m.These results will facilitate the analyses of the obstacle-avoidance system and optimize the control strategy in the follow-up planetary-exploration missions.展开更多
基金This study was co-supported by National Natural Science Foundation of China （51501219）, National Key Development Program of China （2016YFB 1192704）, NSFC -Liaoning Province United Foundation （U 1608259） and National Key Technology Research and Development Program of the Ministry of Science and Technology of China （2015BAFOBBO 1-01）.
基金the National Natural Science Foundation of China(Grant Nos.11774078 and 21905252)China Postdoctoral Science Foundation(Grant No.2019M652558)Innovation Scientists and Technicians Troop Construction Projects of Henan Province,China(Grant No.10094100510025).
文摘Thermal expansion control is always an obstructive factor and challenging in high precision engineering field.Here,the negative thermal expansion of NbF_(3)and NbOF_(2)was predicted by first-principles calculation with density functional theory and the quasi-harmonic approximation(QHA).We studied the total charge density,thermal vibration,and lattice dynamic to investigate the thermal expansion mechanism.We found that the presence of O induced the relatively strong covalent bond in NbOF_(2),thus weakening the transverse vibration of F and O in NbOF_(2),compared with the case of NbF_(3).In this study,we proposed a way to tailor negative thermal expansion of metal fluorides by introducing the oxygen atoms.The present work not only predicts two NTE compounds,but also provides an insight on thermal expansion control by designing chemical bond type.
基金supported by the National Natural Science Foundation of China(Nos.52202344,T2225026,82172087,and 82071308)the National Key R&D Program of China(No.2022YFA1205801)Beijing Institute of Technology Research Fund Program for Young Scholars.
文摘Rational design of metallic active sites and its microenvironment is critical for constructing superoxide dismutase(SOD)nanozymes.Here,we reported a novel SOD nanozyme design,with employing graphene oxide(GO)as the framework,andδ-MnO_(2)as the active sites,to mimic the natural Mn-SOD.This MnO_(2)@GO nanozyme exhibited multiscale laminated structures with honeycomb-like morphology,providing highly specific surface area for·O_(2)−adsorption and confined spaces for subsequent catalytic reactions.Thus,the nanozyme achieved superlative SOD-like catalytic performance with inhibition rate of 95.5%,which is 222.6%and 1605.4%amplification over GO and MnO_(2)nanoparticles,respectively.Additionally,such unique hierarchical structural design endows MnO_(2)@GO with catalytic specificity,which was not present in the individual component(GO or MnO_(2)).This multiscale structural design provides new strategies for developing highly active and specific SOD nanozymes.
文摘Tianwen-1(TW-1)is the first Chinese interplanetary mission to have accomplished orbiting,landing,and patrolling in a single exploration of Mars.After safe landing,it is essential to reconstruct the descent trajectory and determine the landing site of the lander.For this purpose,we processed descent images of the TW-1 optical obstacle-avoidance sensor(OOAS)and digital orthophoto map(DOM)of the landing area using our proposed hybrid-matching method,in which the landing process is divided into two parts.In the first,crater matching is used to obtain the geometric transformations between the OOAS images and DOM to calculate the position of the lander.In the second,feature matching is applied to compute the position of the lander.We calculated the landing site of TW-1 to be 109.9259◦E,25.0659◦N with a positional accuracy of 1.56 m and reconstructed the landing trajectory with a horizontal root mean squared error of 1.79 m.These results will facilitate the analyses of the obstacle-avoidance system and optimize the control strategy in the follow-up planetary-exploration missions.
