Atomically dispersed catalysts exhibit significant influence on facilitating the sluggish oxygen reduction reaction(ORR)kinetics with high atom economy,owing to remarkable attributes including nearly 100%atomic utiliz...Atomically dispersed catalysts exhibit significant influence on facilitating the sluggish oxygen reduction reaction(ORR)kinetics with high atom economy,owing to remarkable attributes including nearly 100%atomic utilization and exceptional catalytic functionality.Furthermore,accurately controlling atomic physical properties including spin,charge,orbital,and lattice degrees of atomically dispersed catalysts can realize the optimized chemical properties including maximum atom utilization efficiency,homogenous active centers,and satisfactory catalytic performance,but remains elusive.Here,through physical and chemical insight,we review and systematically summarize the strategies to optimize atomically dispersed ORR catalysts including adjusting the atomic coordination environment,adjacent electronic orbital and site density,and the choice of dual-atom sites.Then the emphasis is on the fundamental understanding of the correlation between the physical property and the catalytic behavior for atomically dispersed catalysts.Finally,an overview of the existing challenges and prospects to illustrate the current obstacles and potential opportunities for the advancement of atomically dispersed catalysts in the realm of electrocatalytic reactions is offered.展开更多
Intraoperative imaging is vital for accurate placement of instrumentation in spine surgery. However, the use of biplanar fluoroscopy and other intraoperative imaging modalities is associated with the risk of significa...Intraoperative imaging is vital for accurate placement of instrumentation in spine surgery. However, the use of biplanar fluoroscopy and other intraoperative imaging modalities is associated with the risk of significant radiation exposure in the patient, surgeon, and surgical staff. Radiation exposure in the form of ionizing radiation can lead to cellular damage via the induction of DNA lesions and the production of reactive oxygen species. These effects often result in cell death or genomic instability, leading to various radiation-associated pathologies including an increased risk of malignancy. In attempts to reduce radiation-associated health risks, radiation safety has become an important topic in the medical field. All practitioners, regardless of practice setting, can practice radiation safety techniques including shielding and distance to reduce radiation exposure. Additionally, optimization of fluoroscopic settings and techniques can be used as an effective method of radiation dose reduction. New imaging modalities and spinal navigation systems have also been developed in an effort to replace conventional fluoroscopy and reduce radiation doses. These modalities include Isocentric Three-Dimensional C-Arms, O-Arms, and intraoperative magnetic resonance imaging. While this influx of new technology has advanced radiation safety within the field of spine surgery, more work is still required to overcome specific limitations involving increased costs and inadequate training.展开更多
The realization way of snake rolling was introduced. Flow velocity, strain and stress distribution of 7075 aluminum alloy plate during snake rolling and symmetrical rolling were analyzed in Deform 3D. Effects of veloc...The realization way of snake rolling was introduced. Flow velocity, strain and stress distribution of 7075 aluminum alloy plate during snake rolling and symmetrical rolling were analyzed in Deform 3D. Effects of velocity ratio, offset distance between two rolls and pass reduction on the distribution of equivalent strain and shear strain were analyzed. The results show that flow velocity and equivalent strain on the lower layer of the plate are larger than those of the upper layer because of the larger velocity of the lower roll and the gap is increased with the increase of velocity ratio and pass reduction. The shear strain of roiling direction in the center point is almost zero during symmetrical rolling, while it is much larger during snake rolling because of the existence of rub zone. The shear strain is increased with the increase of velocity ratio, offset distance and pass reduction. This additional shear strain is beneficial to improve the in_homogeneous strain distribution.展开更多
Traffic intersections are incredibly dangerous for drivers and pedestrians. Statistics from both Canada and the U.S. show a high number of fatalities and serious injuries related to crashes at intersections. In Canada...Traffic intersections are incredibly dangerous for drivers and pedestrians. Statistics from both Canada and the U.S. show a high number of fatalities and serious injuries related to crashes at intersections. In Canada, during 2019, the National Collision Database shows that 28% of traffic fatalities and 42% of serious injuries occurred at intersections. Likewise, the U.S. National Highway Traffic Administration (NHTSA) found that about 40% of the estimated 5,811,000 accidents in the U.S. during the year studied were intersection-related crashes. In fact, a major survey by the car insurance industry found that nearly 85% of drivers could not identify the correct action to take when approaching a yellow traffic light at an intersection. One major reason for these accidents is the “yellow light dilemma,” the ambiguous situation where a driver should stop or proceed forward when unexpectedly faced with a yellow light. This situation is even further exacerbated by the tendency of aggressive drivers to inappropriately speed up on the yellow just to get through the traffic light. A survey of Canadian drivers conducted by the Traffic Injury Research Foundation found that 9% of drivers admitted to speeding up to get through a traffic light. Another reason for these accidents is the increased danger of making a left-hand turn on yellow. According to the National Highway Traffic Safety Association (NHTSA), left turns occur in approximately 22.2% of collisions—as opposed to just 1.2% for right turns. Moreover, a study by CNN found left turns are three times as likely to kill pedestrians than right turns. The reason left turns are so much more likely to cause an accident is because they take a driver against traffic and in the path of oncoming cars. Additionally, most of these left turns occur at the driver’s discretion—as opposed to the distressingly brief left-hand arrow at busy intersections. Drive Safe Now proposes a workable solution for reducing the number of accidents occurring during a yellow light at inters展开更多
Exploring the atomic interaction mechanisms of dense single-atom catalysts(SACs)is of great significance for their application in oxygen reduction reaction(ORR).However,the intrinsic mechanism of the site-distance eff...Exploring the atomic interaction mechanisms of dense single-atom catalysts(SACs)is of great significance for their application in oxygen reduction reaction(ORR).However,the intrinsic mechanism of the site-distance effect on the catalytic performance has been largely ignored.Here,we demonstrate the site-distance effect of Fe-Rh_(x)@NC catalysts in ORR theoretically and experimentally.Bader charge analysis reveals that the strong interaction between Fe and Rh atoms at a certain atomic distance(dFe-Rh)alters the catalytic electronic structure,facilitating the optimization of catalyst adsorption strength.Motivated by the theoretical calculations,we designed and synthesized the Fe-Rhx@NC catalysts through a spatial confinement strategy.The characterization results prove that the Fe-Rh_(2)@NC has the optimal d_(Fe-Rh),which improves its intrinsic ORR activity,providing a half wave potential of 0.91 V,higher than that of the commercial Pt/C(0.86 V).This study emphasizes the importance of determining the basic mechanism of the site-distance effect in dissimilar metal atoms catalysts,which is conducive to the design of efficient catalyst systems for practical applications.展开更多
Unique shortest vector problem(uSVP)plays an important role in lattice based cryptography.Many cryptographic schemes based their security on it.For the cofidence of those applications,it is essential to clarify the co...Unique shortest vector problem(uSVP)plays an important role in lattice based cryptography.Many cryptographic schemes based their security on it.For the cofidence of those applications,it is essential to clarify the complex-ity of uSVP with different parameters.However,proving the NP-hardness of usVP appears quite hard.To the state of the art,we are even not able to prove the NP-hardness of usVP with constant parameters.In this work,we gave a lower bound for the hardness of usVP with constant parameters,i.e.we proved that uSVP is at least as hard as gap shortest vector problem(GapSVP)with gap of O(√n/log(n)),which is in NP n coAM.Unlike previous works,our reduction works for paramters in a bigger range,especially when the constant hidden by the big-O in GapsVP is smallerthan1.展开更多
This paper is focused on the structural behavior of the single shear bolted connections with thin-walled ferritic stainless steel.The purpose of this study is to investigate the ultimate behaviors,such as ultimate str...This paper is focused on the structural behavior of the single shear bolted connections with thin-walled ferritic stainless steel.The purpose of this study is to investigate the ultimate behaviors,such as ultimate strength and fracture mode of the single shear bolted connections of thin-walled ferritic stainless steel(low cost steel) rather than austenitic stainless steel(high cost steel).Bolt arrangement and end distance parallel to the direction of applied load are considered as main variables of the test specimens for bolted connections.Specimens have a constant dimension of edge distance perpendicular to the loading direction,bolt diameter,pitch,and gauge.A monotonic tensile test for specimens has been carried out and some bolted connections with long end distance showed curling(out of plane deformation) occurrence which led to strength reduction.The ultimate behaviors such as fracture mode,ultimate strength are compared with those predicted by current design codes.Further,conditions of curling occurrence and the strength reduction due to curling are investigated and modified strength equations are suggested considering the curling effect.展开更多
基金supported by the National Natural Science Foundation of China(22234005,21974070)the Natural Science Foundation of Jiangsu Province(BK20222015)。
文摘Atomically dispersed catalysts exhibit significant influence on facilitating the sluggish oxygen reduction reaction(ORR)kinetics with high atom economy,owing to remarkable attributes including nearly 100%atomic utilization and exceptional catalytic functionality.Furthermore,accurately controlling atomic physical properties including spin,charge,orbital,and lattice degrees of atomically dispersed catalysts can realize the optimized chemical properties including maximum atom utilization efficiency,homogenous active centers,and satisfactory catalytic performance,but remains elusive.Here,through physical and chemical insight,we review and systematically summarize the strategies to optimize atomically dispersed ORR catalysts including adjusting the atomic coordination environment,adjacent electronic orbital and site density,and the choice of dual-atom sites.Then the emphasis is on the fundamental understanding of the correlation between the physical property and the catalytic behavior for atomically dispersed catalysts.Finally,an overview of the existing challenges and prospects to illustrate the current obstacles and potential opportunities for the advancement of atomically dispersed catalysts in the realm of electrocatalytic reactions is offered.
文摘Intraoperative imaging is vital for accurate placement of instrumentation in spine surgery. However, the use of biplanar fluoroscopy and other intraoperative imaging modalities is associated with the risk of significant radiation exposure in the patient, surgeon, and surgical staff. Radiation exposure in the form of ionizing radiation can lead to cellular damage via the induction of DNA lesions and the production of reactive oxygen species. These effects often result in cell death or genomic instability, leading to various radiation-associated pathologies including an increased risk of malignancy. In attempts to reduce radiation-associated health risks, radiation safety has become an important topic in the medical field. All practitioners, regardless of practice setting, can practice radiation safety techniques including shielding and distance to reduce radiation exposure. Additionally, optimization of fluoroscopic settings and techniques can be used as an effective method of radiation dose reduction. New imaging modalities and spinal navigation systems have also been developed in an effort to replace conventional fluoroscopy and reduce radiation doses. These modalities include Isocentric Three-Dimensional C-Arms, O-Arms, and intraoperative magnetic resonance imaging. While this influx of new technology has advanced radiation safety within the field of spine surgery, more work is still required to overcome specific limitations involving increased costs and inadequate training.
基金Projects(2012CB619505,2010CB731703)supported by the National Basic Research Program of ChinaProject(CX2013B065)supported by Hunan Provincial Innovation Foundation for Postgraduate,ChinaProject(117308)supported by Postdoctoral Science Foundation of Central South University,China
文摘The realization way of snake rolling was introduced. Flow velocity, strain and stress distribution of 7075 aluminum alloy plate during snake rolling and symmetrical rolling were analyzed in Deform 3D. Effects of velocity ratio, offset distance between two rolls and pass reduction on the distribution of equivalent strain and shear strain were analyzed. The results show that flow velocity and equivalent strain on the lower layer of the plate are larger than those of the upper layer because of the larger velocity of the lower roll and the gap is increased with the increase of velocity ratio and pass reduction. The shear strain of roiling direction in the center point is almost zero during symmetrical rolling, while it is much larger during snake rolling because of the existence of rub zone. The shear strain is increased with the increase of velocity ratio, offset distance and pass reduction. This additional shear strain is beneficial to improve the in_homogeneous strain distribution.
文摘Traffic intersections are incredibly dangerous for drivers and pedestrians. Statistics from both Canada and the U.S. show a high number of fatalities and serious injuries related to crashes at intersections. In Canada, during 2019, the National Collision Database shows that 28% of traffic fatalities and 42% of serious injuries occurred at intersections. Likewise, the U.S. National Highway Traffic Administration (NHTSA) found that about 40% of the estimated 5,811,000 accidents in the U.S. during the year studied were intersection-related crashes. In fact, a major survey by the car insurance industry found that nearly 85% of drivers could not identify the correct action to take when approaching a yellow traffic light at an intersection. One major reason for these accidents is the “yellow light dilemma,” the ambiguous situation where a driver should stop or proceed forward when unexpectedly faced with a yellow light. This situation is even further exacerbated by the tendency of aggressive drivers to inappropriately speed up on the yellow just to get through the traffic light. A survey of Canadian drivers conducted by the Traffic Injury Research Foundation found that 9% of drivers admitted to speeding up to get through a traffic light. Another reason for these accidents is the increased danger of making a left-hand turn on yellow. According to the National Highway Traffic Safety Association (NHTSA), left turns occur in approximately 22.2% of collisions—as opposed to just 1.2% for right turns. Moreover, a study by CNN found left turns are three times as likely to kill pedestrians than right turns. The reason left turns are so much more likely to cause an accident is because they take a driver against traffic and in the path of oncoming cars. Additionally, most of these left turns occur at the driver’s discretion—as opposed to the distressingly brief left-hand arrow at busy intersections. Drive Safe Now proposes a workable solution for reducing the number of accidents occurring during a yellow light at inters
基金supported by the National Key R&D Program of China(2021YFA1600800 and 2020YFA0710203)the National Natural Science Foundation of China(12025505,22002147,22179125 and 12205304)+3 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB0450200)the University of China Innovation Program of Anhui Province(GXXT-2020-053)the Youth Innovation Promotion Association CAS(2015366 and 2022458)the Fellowship of China Postdoctoral Science Foundation(2021TQ0319)。
文摘Exploring the atomic interaction mechanisms of dense single-atom catalysts(SACs)is of great significance for their application in oxygen reduction reaction(ORR).However,the intrinsic mechanism of the site-distance effect on the catalytic performance has been largely ignored.Here,we demonstrate the site-distance effect of Fe-Rh_(x)@NC catalysts in ORR theoretically and experimentally.Bader charge analysis reveals that the strong interaction between Fe and Rh atoms at a certain atomic distance(dFe-Rh)alters the catalytic electronic structure,facilitating the optimization of catalyst adsorption strength.Motivated by the theoretical calculations,we designed and synthesized the Fe-Rhx@NC catalysts through a spatial confinement strategy.The characterization results prove that the Fe-Rh_(2)@NC has the optimal d_(Fe-Rh),which improves its intrinsic ORR activity,providing a half wave potential of 0.91 V,higher than that of the commercial Pt/C(0.86 V).This study emphasizes the importance of determining the basic mechanism of the site-distance effect in dissimilar metal atoms catalysts,which is conducive to the design of efficient catalyst systems for practical applications.
基金This work is funded by National Natural Science Foundation of China(Grants No.62172405).
文摘Unique shortest vector problem(uSVP)plays an important role in lattice based cryptography.Many cryptographic schemes based their security on it.For the cofidence of those applications,it is essential to clarify the complex-ity of uSVP with different parameters.However,proving the NP-hardness of usVP appears quite hard.To the state of the art,we are even not able to prove the NP-hardness of usVP with constant parameters.In this work,we gave a lower bound for the hardness of usVP with constant parameters,i.e.we proved that uSVP is at least as hard as gap shortest vector problem(GapSVP)with gap of O(√n/log(n)),which is in NP n coAM.Unlike previous works,our reduction works for paramters in a bigger range,especially when the constant hidden by the big-O in GapsVP is smallerthan1.
基金Project supported by the Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education,Science and Technology(MEST)(No.2012-00-2110)the Sustainable Building Research Center of Hanyang University funded by the SRC/ERC Program of MEST(No.2012-0000-723)
文摘This paper is focused on the structural behavior of the single shear bolted connections with thin-walled ferritic stainless steel.The purpose of this study is to investigate the ultimate behaviors,such as ultimate strength and fracture mode of the single shear bolted connections of thin-walled ferritic stainless steel(low cost steel) rather than austenitic stainless steel(high cost steel).Bolt arrangement and end distance parallel to the direction of applied load are considered as main variables of the test specimens for bolted connections.Specimens have a constant dimension of edge distance perpendicular to the loading direction,bolt diameter,pitch,and gauge.A monotonic tensile test for specimens has been carried out and some bolted connections with long end distance showed curling(out of plane deformation) occurrence which led to strength reduction.The ultimate behaviors such as fracture mode,ultimate strength are compared with those predicted by current design codes.Further,conditions of curling occurrence and the strength reduction due to curling are investigated and modified strength equations are suggested considering the curling effect.
