The elastic scattering angular distributions of ^(13)C at 340 MeV and ^(14)C at 294 MeV and 342 MeV on a ^(208)Pb target,which correspond to approximately five times the Coulomb barriers,were measured at the Radioacti...The elastic scattering angular distributions of ^(13)C at 340 MeV and ^(14)C at 294 MeV and 342 MeV on a ^(208)Pb target,which correspond to approximately five times the Coulomb barriers,were measured at the Radioactive Ion Beam Line in Lanzhou.The data were analyzed within the optical model and continuum-discretized coupled-channels(CDCC)framework,and the results of both calculations could effectively account for the experimental data.The differential cross sections of elastic scattering revealed no particular suppression at the Coulomb nuclear interference peak angles,suggesting that the breakup coupling effects on the elastic scattering angular distributions were negligibly small in this incident energy region.The contributions from the couplings with inelastic states to the elastic cross sections were of minor importance within the angular range covered by these experiments.展开更多
Location-based social network （LBSN） is at the forefront of emerging trends in social network services （SNS） since the users in LBSN are allowed to ＂check-in＂ the places （locations） when they visit them. The a...Location-based social network （LBSN） is at the forefront of emerging trends in social network services （SNS） since the users in LBSN are allowed to ＂check-in＂ the places （locations） when they visit them. The accurate geographi- cal and temporal information of these check-in actions are provided by the end-user GPS-enabled mobile devices, and recorded by the LBSN system. In this paper, we analyze and mine a big LBSN data, Gowalla, collected by us. First, we investigate the relationship between the spatio-temporal co- occurrences and social ties, and the results show that the co- occurrences are strongly correlative with the social ties. Sec- ond, we present a study of predicting two users whether or not they will meet （co-occur） at a place in a given future time, by exploring their check-in habits. In particular, we first intro- duce two new concepts, bag-of-location and bag-of-time-lag, to characterize user＇s check-in habits. Based on such bag rep- resentations, we define a similarity metric called habits sim- ilarity to measure the similarity between two users＇ check-in habits. Then we propose a machine !earning formula for pre- dicting co-occurrence based on the social ties and habits sim- ilarities. Finally, we conduct extensive experiments on our dataset, and the results demonstrate the effectiveness of the proposed method.展开更多
A convenient and efficient protocol for the synthesis of unnatural N-glycosyl cz-amino acids was developed. Condensation of 1,3,4,6-tetra-O-actyl-/%D-glucosamine hydrochloride, alkenyl boronic acid, and glyoxylic acid...A convenient and efficient protocol for the synthesis of unnatural N-glycosyl cz-amino acids was developed. Condensation of 1,3,4,6-tetra-O-actyl-/%D-glucosamine hydrochloride, alkenyl boronic acid, and glyoxylic acid was achieved in CH2C12 to give the derivatives of 2-（N-glycosyl）aminobut-3-enoic acid which may find applications in glycobiology research and medicinal chemistry.展开更多
The fatigue cracking and fracture behavior of cold-drawn copper subjected to cyclic torsional loading were investigated in this study.It was found that with increasing stress amplitude,the fracture mode of cold-drawn ...The fatigue cracking and fracture behavior of cold-drawn copper subjected to cyclic torsional loading were investigated in this study.It was found that with increasing stress amplitude,the fracture mode of cold-drawn copper gradually changes from a shear fracture on transverse maximum shear stress plane to a mixed shear mode on both transverse and longitudinal shear planes and finally turns to the shear fracture on multiple longitudinal shear planes.Combining the cracking morphology and the relationship between torsional fatigue cracking and the grain boundaries,the fracture mechanism of cold-drawn copper under cyclic torsional loading was analyzed and proposed by considering the effects of the microstructure and axial stress caused by torsion.Because of the promotion of the grain boundary distribution on longitudinal crack propagation and the inhibition of axial stress on transverse crack grown,the tendency of crack propagation along the longitudinal direction increases with increasing stress levels.展开更多
基金Supported by the National Natural Science Foundation of China (12122511,12105330)the Youth Innovation Promotion Association CAS (2020411)+1 种基金funding from the State Key Laboratory of Nuclear Physics and Technology,Peking University (NPT2023KFY04)V.G.would like to thank CNPq (303769/2021-1).
文摘The elastic scattering angular distributions of ^(13)C at 340 MeV and ^(14)C at 294 MeV and 342 MeV on a ^(208)Pb target,which correspond to approximately five times the Coulomb barriers,were measured at the Radioactive Ion Beam Line in Lanzhou.The data were analyzed within the optical model and continuum-discretized coupled-channels(CDCC)framework,and the results of both calculations could effectively account for the experimental data.The differential cross sections of elastic scattering revealed no particular suppression at the Coulomb nuclear interference peak angles,suggesting that the breakup coupling effects on the elastic scattering angular distributions were negligibly small in this incident energy region.The contributions from the couplings with inelastic states to the elastic cross sections were of minor importance within the angular range covered by these experiments.
文摘Location-based social network （LBSN） is at the forefront of emerging trends in social network services （SNS） since the users in LBSN are allowed to ＂check-in＂ the places （locations） when they visit them. The accurate geographi- cal and temporal information of these check-in actions are provided by the end-user GPS-enabled mobile devices, and recorded by the LBSN system. In this paper, we analyze and mine a big LBSN data, Gowalla, collected by us. First, we investigate the relationship between the spatio-temporal co- occurrences and social ties, and the results show that the co- occurrences are strongly correlative with the social ties. Sec- ond, we present a study of predicting two users whether or not they will meet （co-occur） at a place in a given future time, by exploring their check-in habits. In particular, we first intro- duce two new concepts, bag-of-location and bag-of-time-lag, to characterize user＇s check-in habits. Based on such bag rep- resentations, we define a similarity metric called habits sim- ilarity to measure the similarity between two users＇ check-in habits. Then we propose a machine !earning formula for pre- dicting co-occurrence based on the social ties and habits sim- ilarities. Finally, we conduct extensive experiments on our dataset, and the results demonstrate the effectiveness of the proposed method.
基金the Natural Science Foundation of Jiangsu Province(No.BK20130404)the Scientific and Technological Research Project of Lianyungang(No.CG1303)the project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘A convenient and efficient protocol for the synthesis of unnatural N-glycosyl cz-amino acids was developed. Condensation of 1,3,4,6-tetra-O-actyl-/%D-glucosamine hydrochloride, alkenyl boronic acid, and glyoxylic acid was achieved in CH2C12 to give the derivatives of 2-（N-glycosyl）aminobut-3-enoic acid which may find applications in glycobiology research and medicinal chemistry.
基金supported by the National Natural Science Foundation of China (No.51771208)the Natural Science Foundation of Liaoning (No.2019-ZD-0059)
文摘The fatigue cracking and fracture behavior of cold-drawn copper subjected to cyclic torsional loading were investigated in this study.It was found that with increasing stress amplitude,the fracture mode of cold-drawn copper gradually changes from a shear fracture on transverse maximum shear stress plane to a mixed shear mode on both transverse and longitudinal shear planes and finally turns to the shear fracture on multiple longitudinal shear planes.Combining the cracking morphology and the relationship between torsional fatigue cracking and the grain boundaries,the fracture mechanism of cold-drawn copper under cyclic torsional loading was analyzed and proposed by considering the effects of the microstructure and axial stress caused by torsion.Because of the promotion of the grain boundary distribution on longitudinal crack propagation and the inhibition of axial stress on transverse crack grown,the tendency of crack propagation along the longitudinal direction increases with increasing stress levels.
