In response to the scarcity of infrared aircraft samples and the tendency of traditional deep learning to overfit,a few-shot infrared aircraft classification method based on cross-correlation networks is proposed.This...In response to the scarcity of infrared aircraft samples and the tendency of traditional deep learning to overfit,a few-shot infrared aircraft classification method based on cross-correlation networks is proposed.This method combines two core modules:a simple parameter-free self-attention and cross-attention.By analyzing the self-correlation and cross-correlation between support images and query images,it achieves effective classification of infrared aircraft under few-shot conditions.The proposed cross-correlation network integrates these two modules and is trained in an end-to-end manner.The simple parameter-free self-attention is responsible for extracting the internal structure of the image while the cross-attention can calculate the cross-correlation between images further extracting and fusing the features between images.Compared with existing few-shot infrared target classification models,this model focuses on the geometric structure and thermal texture information of infrared images by modeling the semantic relevance between the features of the support set and query set,thus better attending to the target objects.Experimental results show that this method outperforms existing infrared aircraft classification methods in various classification tasks,with the highest classification accuracy improvement exceeding 3%.In addition,ablation experiments and comparative experiments also prove the effectiveness of the method.展开更多
The F+H_(2)reaction has long been a benchmark system in reaction dynamics.We report here a combined experimental and theoretical study on the F+H_(2)(v=1,j=1)reaction at a collision energy of 0.62 kcal/mol.The rotatio...The F+H_(2)reaction has long been a benchmark system in reaction dynamics.We report here a combined experimental and theoretical study on the F+H_(2)(v=1,j=1)reaction at a collision energy of 0.62 kcal/mol.The rotational state-resolved differential cross sections(DCSs)as well as the integral cross sections(ICSs)were obtained by the crossed beam experiment and the quantum dynamical calculation.It is found that the rotationally excited state F+H_(2)(v=1,j=1)reaction produces rotationally hotter but vibrationally colder products,compared with the rotational ground state reaction at the same total energy.The stereodynamics of the F+H_(2)(v=1,j=1)reaction is also analyzed theoretically,showing that minor differences exist for the reactants initially prepared in different spatial alignments.展开更多
A design strategy for a research platform of a telepresence telerobot system based on virtual reality technology is put forward. The design frame of the system is described, and its important core techniques are descr...A design strategy for a research platform of a telepresence telerobot system based on virtual reality technology is put forward. The design frame of the system is described, and its important core techniques are described. An octrees data structure is utilized to build kinematic and dynamic modeling of the virtual simulation environment, Delphi+OpenGL+3DS MAX are adopted to carry through the virtual modeling and visible simulation exploitation of the slave-robot and its environment. Photo-correction is adopted to correct positioning deviation of the virtual geometric model and modeling errors. The cost of software and hardware equipment for the research platform realized is low. The master/slave robot (manipulator) system and all software in the system were designed and manufactured by our research group. The performance of the system has reached the level required for research. An indispensable experiment base is provided for the research of a telepresence telerobot system based on virtual reality technology.展开更多
Using the data of beach face high oscillations and waves and flows of the surf zones influenced by the swells, the characteristics including beach face variation trends, trend shapes, oscillation periods, oscillation ...Using the data of beach face high oscillations and waves and flows of the surf zones influenced by the swells, the characteristics including beach face variation trends, trend shapes, oscillation periods, oscillation intensions of different profile shapes, and the characteristic relations between different stake points on the same profile were analyzed comparatively. The relations between the beach face with high oscillations erosion and sediment and the surf zone infragravity waves were also analyzed based on the cress spectrum analysis. The results showed that the swash diffluences caused by the beach cusp rhythm topography hasten the sediment transport from the beach ridge to beach paddy, and the beach face of the swash zones has the infragravity periodic oscillations, and the oscillation intensions descend from the bottom to the top of the beach face, and the infragravity waves of the surf zones have significant effect on the high-frequency variations of erosion and sediment of the beach face.展开更多
A crossed molecular beams, state-to-state scattering study was carried out on the F＋H2→HF＋H reaction at the collision energy of 5.02 kJ/mol, using the highly sensitive H atom Rydberg tagging time-of-flight method. ...A crossed molecular beams, state-to-state scattering study was carried out on the F＋H2→HF＋H reaction at the collision energy of 5.02 kJ/mol, using the highly sensitive H atom Rydberg tagging time-of-flight method. All the peaks in the TOF spectra can be clearly assigned to the ro-vibrational structures of the HF product. The forward scattering of the HF product at v′=3 has been observed. The small forward scattering of the HF product at v′=2 has also been detected. Detailed theoretical analysis is required in order to fully understand the dynamical origin of these forward scattering products at this high collision energy.展开更多
Delay analysis method is adopted to study the service capacity of a widened intersection. Traffic simulation software VISSIM is used for microscopic simulation of a widened intersection so as to obtain a delay curve. ...Delay analysis method is adopted to study the service capacity of a widened intersection. Traffic simulation software VISSIM is used for microscopic simulation of a widened intersection so as to obtain a delay curve. The delay-volume model of a widened intersection is established based on traffic simulation. The suggested value of basic service capacity of the widened left-turn lane is given along with how to determine correction factors and practical service capacity.展开更多
Cellular automata modeling techniques and the characteristics of mixed traffic flow were used to derive the 2-dimensional model presented here for simulation of pedestrian’s crossing dynamics. A conception of “stop...Cellular automata modeling techniques and the characteristics of mixed traffic flow were used to derive the 2-dimensional model presented here for simulation of pedestrian’s crossing dynamics. A conception of “stop point” is introduced to deal with traffic obstacles and resolve conflicts among pedestrians or between pedestrians and the other vehicles on the crosswalk. The model can be easily extended, is very efficient for simulation of pedestrian’s crossing dy- namics, can be integrated into traffic simulation software, and has been proved feasible by simulation experiments.展开更多
Based on the cascade two-photon laser dynamic equation derived with the technique of quantum Langevin operators with the considerations of coherently prepared three-level atoms and the classical field injected into th...Based on the cascade two-photon laser dynamic equation derived with the technique of quantum Langevin operators with the considerations of coherently prepared three-level atoms and the classical field injected into the cavity, we numerically study the effects of atomic coherence and classical field on the chaotic dynamics of a two-photon laser. Lyapunov exponent and bifurcation diagram calculations show that the Lorenz chaos and hyperchaos can be induced or inhibited by the atomic coherence and the classical field via crisis or Hopf bifurcations.展开更多
The cracking patterns of a thin sheet with a pre-existing crack subjected to dynamic loading are numerically simulated to investigate the mechanism of crack branching by using the FEM method.Six numerical models were ...The cracking patterns of a thin sheet with a pre-existing crack subjected to dynamic loading are numerically simulated to investigate the mechanism of crack branching by using the FEM method.Six numerical models were set up to study the effects of load,tensile strength and heterogeneity on crack branching.The crack propagation is affected by the applied loads,tensile strength and heterogeneity.Before crack branching,the crack propagates by some distance along the direction of the pre-existing crack.For the materials with low heterogeneity,the higher the applied stress level is and the lower the tensile strength of the material is,the shorter the propagation distance is.Moreover,the branching angle becomes larger and the number of branching cracks increases.In the case of the materials with high heterogeneity,a lot of disordered voids and microcracks randomly occur along the main crack,so the former law is not obvious.The numerical results not only are in good agreement with the experimental observations in laboratory,but also can be extended to heterogeneity media.The work can provide a good approach to model the cracking and fracturing of heterogeneous quasi-brittle materials,such as rock,under dynamic loading.展开更多
We present the fabrication and testing of a silicon carbide （SiC） balanced mass doublended tuning fork that survives harsh environments without compromising the device strain sensitivity and resolution bandwidth. Th...We present the fabrication and testing of a silicon carbide （SiC） balanced mass doublended tuning fork that survives harsh environments without compromising the device strain sensitivity and resolution bandwidth. The device features a material stack that survives corrosive environments and enables high-temperature operation. To perform hightemperature testing, a specialized setup was constructed that allows the tuning fork to be characterized using traditional silicon electronics. The tuning fork has been operated at 600°C in the presence of dry steam for short durations. This tuning fork has also been tested to 64 000 G using a hard-launch, soft-catch shock implemented with a light gas gun. However, the device still has a strain sensitivity of 66 Hz/μe and strain resolution of 0. 045 μe in a 10 kHz bandwidth. As such, this balanced-mass double-ended tuning fork can be used to create a variety of different sensors including strain gauges, accelerometers, gyroscopes, and pressure transducers. Given the adaptable fabrication process flow, this device could be useful to micro-electro-mechanical systems （MEMS） designers creating sensors for a variety of different applications.展开更多
Abstract The cross-coupling corrections for the LaCoste ＆ Romberg airborne gravimeter are computed as a linear combination of 5 so-called cross-coupling monitors. The weight factors （coefficients） determined from m...Abstract The cross-coupling corrections for the LaCoste ＆ Romberg airborne gravimeter are computed as a linear combination of 5 so-called cross-coupling monitors. The weight factors （coefficients） determined from marine gravity data by the factory are obviously not optimal for airborne application. These coefficients are recalibrated by minimizing the difference between airborne data and upward continued surface data （external calibration） and by minimizing the errors at line crossings （internal calibration） respectively. An integrating method to recalibrate the above-mentioned coefficients and the beam scale factor simultaneously is also presented. Experimental results show that the systemic errors in the airborne gravity anomalies can be greatly reduced by using any of the recalibrated coefficients. For example, the systemic error is reduced from 4.8 mGal to 1.8 mGal in Datong test.展开更多
Highway capacity is defined as maximum volume of traffic flow through the particular highway section under given traffic conditions, road conditions and so on. Highway construction and management is judged by capacity...Highway capacity is defined as maximum volume of traffic flow through the particular highway section under given traffic conditions, road conditions and so on. Highway construction and management is judged by capacity standard. The reasonable scale and time of highway construction, rational network structure and optimal management mode of highway network can be determined by analyzing the fitness between capacity and traffic volume. All over the world, highway capacity is studied to different extent in different country. Based on the gap acceptance theory, the mixed traffic flow composed of two representative vehicle types heavy and light vehicles is analyzed with probability theory. Capacity model of the minor mixed traffic flows crossing m major lanes, on which the traffic flows fix in with M3 distributed headway, on the unsignalized intersection is set up, and it is an extension of minor lane capacity theory for one vehicle-type and one major-lane traffic flow.展开更多
The prototypical reaction of F+HD→DF+H was investigated at collision energies from 3.03 meV to 17.97 meV using a crossed molecular beam apparatus with multichannel Rydberg tagging time-of-flight detection.Significant...The prototypical reaction of F+HD→DF+H was investigated at collision energies from 3.03 meV to 17.97 meV using a crossed molecular beam apparatus with multichannel Rydberg tagging time-of-flight detection.Significant contributions from both the BornOppenheimer(BO)forbidden reaction F^(*)(^(2)P_(1/2))+HD→DF+H and the BO-allowed reaction F(^(2)P_(3/2))+HD→DF+H were observed.In the backward scattering direction,the contribution from the BO-forbidden reaction F^(*)(^(2)P_(1/2))+HD was found to be considerably greater than the BO-allowed reaction F(^(2)P_(3/2))+HD,indicating the non-adiabatic effects play an important role in the dynamics of the title reaction at low collision energies.Collision-energy dependence of differential cross sections(DCSs)in the backward scattering direction was found to be monotonously decreased as the collision energy decreases,which does not support the existence of resonance states in this energy range.DCSs of both BO-allowed and BO-forbidden reactions were measured at seven collision energies from 3.03 meV to 17.97 meV.It is quite unexpected that the angular distribution gradually shifts from backward to sideway as the collision energy decreases from 17.97 meV to 3.03 meV,suggesting some unknown mechanisms may exist at low collision energies.展开更多
We provide a microscopic calculation of neutron-proton and proton-proton cross sections in symmetric nuclear matter at various densities, using the Brueckner Hartree-Fock approximation scheme with the Argonne Va4 pote...We provide a microscopic calculation of neutron-proton and proton-proton cross sections in symmetric nuclear matter at various densities, using the Brueckner Hartree-Fock approximation scheme with the Argonne Va4 potential including the contribution of microscopic three-body force. We investigate separately the effects of three-body force on the effective mass and on the scattering amplitude. In the present calculation, the rearrangement contribution of three-body force is considered, which will reduce the neutron and proton effective mass, and depress the amplitude of cross section. The effect of three body force is shown to be repulsive, especially in high densities and large momenta, which will suppress the cross section markedly.展开更多
To investigate the relationship of the variation of virulence and the external capsid proteins of the pandemic duck hepatitis A virus type 1(DHAV-1) isolates,the virulence,cross neutralization assays and the complete ...To investigate the relationship of the variation of virulence and the external capsid proteins of the pandemic duck hepatitis A virus type 1(DHAV-1) isolates,the virulence,cross neutralization assays and the complete sequence of the virion protein 1(VP1) gene of nine virulent DHAV-1 strains,which were isolated from infected ducklings with clinical symptoms in Shandong province of China in 2007-2008,were tested.The fifth generation duck embryo allantoic liquids of the 9 isolates were tested on 12-day-old duck embryos and on 7-day-old ducklings for the median embryonal lethal doses(ELD 50 s) and the median lethal doses(LD 50 s),respectively.The results showed that the ELD 50 s of embryonic duck eggs of the 9 DHAV-1 isolates were between 1.9 × 10 6 /mL to 1.44 × 10 7 /mL,while the LD 50 s were 2.39 × 10 5 /mL to 6.15 × 10 6 /mL.Cross-neutralization tests revealed that the 9 DHAV-1 isolates were completely neutralized by the standard serum and the hyperimmune sera against the 9 DHAV-1 isolates,respectively.Compared with other virulent,moderate virulent,attenuated vaccine and mild strains,the VP1 genes of the 9 strains shared 89.8%-99.7% similarity at the nucleotide level and 92.4%-99.6% at amino acid level with other DHAV-1 strains.There were three hypervariable regions at the C-terminus(aa 158-160,180-193 and 205-219) and other variable points in VP1 protein,but which didn't cause virulence of DHAV-1 change.展开更多
Crossed grating stuck to metal surface was used as a strain sensor in the present work, and stress as well as strain were then investigated by accurately determining the change in the position of diffraction spot befo...Crossed grating stuck to metal surface was used as a strain sensor in the present work, and stress as well as strain were then investigated by accurately determining the change in the position of diffraction spot before and after deformed. A hardware testing system for linear CCD array, data gathering and processing was therefore developed for this purpose. Experimental results showed that the system has a good accuracy and can be used to measure stress and strain of metal surface in a real-time and quantitative manner.展开更多
Electrocarboxylation ofbenzalacetone was studied in the presence of an atmospheric pressure of CO2 The only carboxylic product obtained was α-phenyl levulinic acid in a one-compartment electrochemical cell equipped w...Electrocarboxylation ofbenzalacetone was studied in the presence of an atmospheric pressure of CO2 The only carboxylic product obtained was α-phenyl levulinic acid in a one-compartment electrochemical cell equipped with a Mg sacrificial anode at the controlled potential conditions. Influences of the solvents, the electrolytes, the cathode materials, the electrolysis potentials, the concentrations of substrate and the temperatures were studied to improve the yield. The maximal yield is 69% in MeCN-0.1 mol/L TEABF4 on Stainless steel-Mg under a controlled potential of-1.6 V vs.Ag/AgI until 2 F/mol of charge had passed through the cell at 0 ℃.展开更多
基金Supported by the National Pre-research Program during the 14th Five-Year Plan(514010405)。
文摘In response to the scarcity of infrared aircraft samples and the tendency of traditional deep learning to overfit,a few-shot infrared aircraft classification method based on cross-correlation networks is proposed.This method combines two core modules:a simple parameter-free self-attention and cross-attention.By analyzing the self-correlation and cross-correlation between support images and query images,it achieves effective classification of infrared aircraft under few-shot conditions.The proposed cross-correlation network integrates these two modules and is trained in an end-to-end manner.The simple parameter-free self-attention is responsible for extracting the internal structure of the image while the cross-attention can calculate the cross-correlation between images further extracting and fusing the features between images.Compared with existing few-shot infrared target classification models,this model focuses on the geometric structure and thermal texture information of infrared images by modeling the semantic relevance between the features of the support set and query set,thus better attending to the target objects.Experimental results show that this method outperforms existing infrared aircraft classification methods in various classification tasks,with the highest classification accuracy improvement exceeding 3%.In addition,ablation experiments and comparative experiments also prove the effectiveness of the method.
基金the National Natural Science Foundation of China(Nos.22288201,22173040,22241301,22103032)the Chinese Academy of Sciences(No.GJJSTD20220001),the Innovation Program for Quantum Scienceand Technology(No.2021ZD0303300)+2 种基金the Guangdong Science and Technology Program(Nos.2019ZT08L455,2019JC01X091)the Shenzhen Science and Technology Innovation Committee(Nos.JCYJ20210324103810029,20220815145746004,and 2021344670)the Shenzhen Science and Technology Program(No.DSYS20200421111001787).
文摘The F+H_(2)reaction has long been a benchmark system in reaction dynamics.We report here a combined experimental and theoretical study on the F+H_(2)(v=1,j=1)reaction at a collision energy of 0.62 kcal/mol.The rotational state-resolved differential cross sections(DCSs)as well as the integral cross sections(ICSs)were obtained by the crossed beam experiment and the quantum dynamical calculation.It is found that the rotationally excited state F+H_(2)(v=1,j=1)reaction produces rotationally hotter but vibrationally colder products,compared with the rotational ground state reaction at the same total energy.The stereodynamics of the F+H_(2)(v=1,j=1)reaction is also analyzed theoretically,showing that minor differences exist for the reactants initially prepared in different spatial alignments.
文摘A design strategy for a research platform of a telepresence telerobot system based on virtual reality technology is put forward. The design frame of the system is described, and its important core techniques are described. An octrees data structure is utilized to build kinematic and dynamic modeling of the virtual simulation environment, Delphi+OpenGL+3DS MAX are adopted to carry through the virtual modeling and visible simulation exploitation of the slave-robot and its environment. Photo-correction is adopted to correct positioning deviation of the virtual geometric model and modeling errors. The cost of software and hardware equipment for the research platform realized is low. The master/slave robot (manipulator) system and all software in the system were designed and manufactured by our research group. The performance of the system has reached the level required for research. An indispensable experiment base is provided for the research of a telepresence telerobot system based on virtual reality technology.
文摘Using the data of beach face high oscillations and waves and flows of the surf zones influenced by the swells, the characteristics including beach face variation trends, trend shapes, oscillation periods, oscillation intensions of different profile shapes, and the characteristic relations between different stake points on the same profile were analyzed comparatively. The relations between the beach face with high oscillations erosion and sediment and the surf zone infragravity waves were also analyzed based on the cress spectrum analysis. The results showed that the swash diffluences caused by the beach cusp rhythm topography hasten the sediment transport from the beach ridge to beach paddy, and the beach face of the swash zones has the infragravity periodic oscillations, and the oscillation intensions descend from the bottom to the top of the beach face, and the infragravity waves of the surf zones have significant effect on the high-frequency variations of erosion and sediment of the beach face.
基金This work was supported by the Chinese Academy of Sciences, the Ministry of Science and Technology and the National Natural Science Foundation of China.ACKN0WLEDGMENT This work was supported by the Chinese Academy of Sciences, the Ministry of Science and Technology and the National Natural Science Foundation of China.
文摘A crossed molecular beams, state-to-state scattering study was carried out on the F＋H2→HF＋H reaction at the collision energy of 5.02 kJ/mol, using the highly sensitive H atom Rydberg tagging time-of-flight method. All the peaks in the TOF spectra can be clearly assigned to the ro-vibrational structures of the HF product. The forward scattering of the HF product at v′=3 has been observed. The small forward scattering of the HF product at v′=2 has also been detected. Detailed theoretical analysis is required in order to fully understand the dynamical origin of these forward scattering products at this high collision energy.
文摘Delay analysis method is adopted to study the service capacity of a widened intersection. Traffic simulation software VISSIM is used for microscopic simulation of a widened intersection so as to obtain a delay curve. The delay-volume model of a widened intersection is established based on traffic simulation. The suggested value of basic service capacity of the widened left-turn lane is given along with how to determine correction factors and practical service capacity.
文摘Cellular automata modeling techniques and the characteristics of mixed traffic flow were used to derive the 2-dimensional model presented here for simulation of pedestrian’s crossing dynamics. A conception of “stop point” is introduced to deal with traffic obstacles and resolve conflicts among pedestrians or between pedestrians and the other vehicles on the crosswalk. The model can be easily extended, is very efficient for simulation of pedestrian’s crossing dy- namics, can be integrated into traffic simulation software, and has been proved feasible by simulation experiments.
基金The project partially supported by the Natural Science Foundation of Jiangsu Province of China under Grant No. BK2005062
文摘Based on the cascade two-photon laser dynamic equation derived with the technique of quantum Langevin operators with the considerations of coherently prepared three-level atoms and the classical field injected into the cavity, we numerically study the effects of atomic coherence and classical field on the chaotic dynamics of a two-photon laser. Lyapunov exponent and bifurcation diagram calculations show that the Lorenz chaos and hyperchaos can be induced or inhibited by the atomic coherence and the classical field via crisis or Hopf bifurcations.
基金Project(50820125405)supported by the National Natural Science Foundation of ChinaProject(51121005)supported by the National Natural Science Foundation of China
文摘The cracking patterns of a thin sheet with a pre-existing crack subjected to dynamic loading are numerically simulated to investigate the mechanism of crack branching by using the FEM method.Six numerical models were set up to study the effects of load,tensile strength and heterogeneity on crack branching.The crack propagation is affected by the applied loads,tensile strength and heterogeneity.Before crack branching,the crack propagates by some distance along the direction of the pre-existing crack.For the materials with low heterogeneity,the higher the applied stress level is and the lower the tensile strength of the material is,the shorter the propagation distance is.Moreover,the branching angle becomes larger and the number of branching cracks increases.In the case of the materials with high heterogeneity,a lot of disordered voids and microcracks randomly occur along the main crack,so the former law is not obvious.The numerical results not only are in good agreement with the experimental observations in laboratory,but also can be extended to heterogeneity media.The work can provide a good approach to model the cracking and fracturing of heterogeneous quasi-brittle materials,such as rock,under dynamic loading.
文摘We present the fabrication and testing of a silicon carbide （SiC） balanced mass doublended tuning fork that survives harsh environments without compromising the device strain sensitivity and resolution bandwidth. The device features a material stack that survives corrosive environments and enables high-temperature operation. To perform hightemperature testing, a specialized setup was constructed that allows the tuning fork to be characterized using traditional silicon electronics. The tuning fork has been operated at 600°C in the presence of dry steam for short durations. This tuning fork has also been tested to 64 000 G using a hard-launch, soft-catch shock implemented with a light gas gun. However, the device still has a strain sensitivity of 66 Hz/μe and strain resolution of 0. 045 μe in a 10 kHz bandwidth. As such, this balanced-mass double-ended tuning fork can be used to create a variety of different sensors including strain gauges, accelerometers, gyroscopes, and pressure transducers. Given the adaptable fabrication process flow, this device could be useful to micro-electro-mechanical systems （MEMS） designers creating sensors for a variety of different applications.
文摘Abstract The cross-coupling corrections for the LaCoste ＆ Romberg airborne gravimeter are computed as a linear combination of 5 so-called cross-coupling monitors. The weight factors （coefficients） determined from marine gravity data by the factory are obviously not optimal for airborne application. These coefficients are recalibrated by minimizing the difference between airborne data and upward continued surface data （external calibration） and by minimizing the errors at line crossings （internal calibration） respectively. An integrating method to recalibrate the above-mentioned coefficients and the beam scale factor simultaneously is also presented. Experimental results show that the systemic errors in the airborne gravity anomalies can be greatly reduced by using any of the recalibrated coefficients. For example, the systemic error is reduced from 4.8 mGal to 1.8 mGal in Datong test.
基金Supported by the National Natural Science Foundation of China（50478071）
文摘Highway capacity is defined as maximum volume of traffic flow through the particular highway section under given traffic conditions, road conditions and so on. Highway construction and management is judged by capacity standard. The reasonable scale and time of highway construction, rational network structure and optimal management mode of highway network can be determined by analyzing the fitness between capacity and traffic volume. All over the world, highway capacity is studied to different extent in different country. Based on the gap acceptance theory, the mixed traffic flow composed of two representative vehicle types heavy and light vehicles is analyzed with probability theory. Capacity model of the minor mixed traffic flows crossing m major lanes, on which the traffic flows fix in with M3 distributed headway, on the unsignalized intersection is set up, and it is an extension of minor lane capacity theory for one vehicle-type and one major-lane traffic flow.
基金supported by the National Natural Science Foundation of China(No.21822305,No.21688102,No.22003067)the Chinese Academy of Sciences(No.XDB17000000)。
文摘The prototypical reaction of F+HD→DF+H was investigated at collision energies from 3.03 meV to 17.97 meV using a crossed molecular beam apparatus with multichannel Rydberg tagging time-of-flight detection.Significant contributions from both the BornOppenheimer(BO)forbidden reaction F^(*)(^(2)P_(1/2))+HD→DF+H and the BO-allowed reaction F(^(2)P_(3/2))+HD→DF+H were observed.In the backward scattering direction,the contribution from the BO-forbidden reaction F^(*)(^(2)P_(1/2))+HD was found to be considerably greater than the BO-allowed reaction F(^(2)P_(3/2))+HD,indicating the non-adiabatic effects play an important role in the dynamics of the title reaction at low collision energies.Collision-energy dependence of differential cross sections(DCSs)in the backward scattering direction was found to be monotonously decreased as the collision energy decreases,which does not support the existence of resonance states in this energy range.DCSs of both BO-allowed and BO-forbidden reactions were measured at seven collision energies from 3.03 meV to 17.97 meV.It is quite unexpected that the angular distribution gradually shifts from backward to sideway as the collision energy decreases from 17.97 meV to 3.03 meV,suggesting some unknown mechanisms may exist at low collision energies.
基金supported by the Asia-Link project(CN/ASIA-LINK/008(94791))of the European Commissionin part by National Natural Science Foundation of China under Grant Nos.10775061,10505016,10575119,and 10175074+1 种基金the Knowledge Innovative Project of CAS under Grant No.KJCX3-SYW-N2the Major Prophase Research Project of Fundamental Research of the Ministry of Science and Technology of China under Grant No.2007CB815004
文摘We provide a microscopic calculation of neutron-proton and proton-proton cross sections in symmetric nuclear matter at various densities, using the Brueckner Hartree-Fock approximation scheme with the Argonne Va4 potential including the contribution of microscopic three-body force. We investigate separately the effects of three-body force on the effective mass and on the scattering amplitude. In the present calculation, the rearrangement contribution of three-body force is considered, which will reduce the neutron and proton effective mass, and depress the amplitude of cross section. The effect of three body force is shown to be repulsive, especially in high densities and large momenta, which will suppress the cross section markedly.
基金the Chinese National Natural Sciences Foundation(30871878)Shandong Province Higher Educational Science and Technology Program(J08LF07)the Science and Technology Commission of Shandong Province(2010GNC10914),China
文摘To investigate the relationship of the variation of virulence and the external capsid proteins of the pandemic duck hepatitis A virus type 1(DHAV-1) isolates,the virulence,cross neutralization assays and the complete sequence of the virion protein 1(VP1) gene of nine virulent DHAV-1 strains,which were isolated from infected ducklings with clinical symptoms in Shandong province of China in 2007-2008,were tested.The fifth generation duck embryo allantoic liquids of the 9 isolates were tested on 12-day-old duck embryos and on 7-day-old ducklings for the median embryonal lethal doses(ELD 50 s) and the median lethal doses(LD 50 s),respectively.The results showed that the ELD 50 s of embryonic duck eggs of the 9 DHAV-1 isolates were between 1.9 × 10 6 /mL to 1.44 × 10 7 /mL,while the LD 50 s were 2.39 × 10 5 /mL to 6.15 × 10 6 /mL.Cross-neutralization tests revealed that the 9 DHAV-1 isolates were completely neutralized by the standard serum and the hyperimmune sera against the 9 DHAV-1 isolates,respectively.Compared with other virulent,moderate virulent,attenuated vaccine and mild strains,the VP1 genes of the 9 strains shared 89.8%-99.7% similarity at the nucleotide level and 92.4%-99.6% at amino acid level with other DHAV-1 strains.There were three hypervariable regions at the C-terminus(aa 158-160,180-193 and 205-219) and other variable points in VP1 protein,but which didn't cause virulence of DHAV-1 change.
文摘Crossed grating stuck to metal surface was used as a strain sensor in the present work, and stress as well as strain were then investigated by accurately determining the change in the position of diffraction spot before and after deformed. A hardware testing system for linear CCD array, data gathering and processing was therefore developed for this purpose. Experimental results showed that the system has a good accuracy and can be used to measure stress and strain of metal surface in a real-time and quantitative manner.
基金Acknowlegement： This work was supported by National Nature Science Foundation of China （No. 20573037）, the Natural Science Foundation of Shanghai （No. 05JC470） and Shanghai Leading Academic Discipline Project （No. B409）.
文摘Electrocarboxylation ofbenzalacetone was studied in the presence of an atmospheric pressure of CO2 The only carboxylic product obtained was α-phenyl levulinic acid in a one-compartment electrochemical cell equipped with a Mg sacrificial anode at the controlled potential conditions. Influences of the solvents, the electrolytes, the cathode materials, the electrolysis potentials, the concentrations of substrate and the temperatures were studied to improve the yield. The maximal yield is 69% in MeCN-0.1 mol/L TEABF4 on Stainless steel-Mg under a controlled potential of-1.6 V vs.Ag/AgI until 2 F/mol of charge had passed through the cell at 0 ℃.
