This paper presents a novel view of the impact of electron collision off-axis positions on the dynamic properties and relativistic nonlinear Thomson inverse scattering of excited electrons within tightly focused, circ...This paper presents a novel view of the impact of electron collision off-axis positions on the dynamic properties and relativistic nonlinear Thomson inverse scattering of excited electrons within tightly focused, circularly polarized laser pulses of varying intensities. We examine the effects of the transverse ponderomotive force, specifically how the deviation angle and speed of electron motion are affected by the initial off-axis position of the electron and the peak amplitude of the laser pulse. When the laser pulse intensity is low, an increase in the electron's initial off-axis distance results in reduced spatial radiation power, improved collimation, super-continuum phenomena generation, red-shifting of the spectrum's harmonic peak, and significant symmetry in the radiation radial direction. However, in contradiction to conventional understandings,when the laser pulse intensity is relatively high, the properties of the relativistic nonlinear Thomson inverse scattering of the electron deviate from the central axis, changing direction in opposition to the aforementioned effects. After reaching a peak, these properties then shift again, aligning with the previous direction. The complex interplay of these effects suggests a greater nuance and intricacy in the relationship between laser pulse intensity, electron position, and scattering properties than previously thought.展开更多
BACKGROUND The critical shoulder angle(CSA)is a radiographic measurement that provides an assessment of both glenoid inclination and acromial length.Higher values may correlate with the presence of rotator cuff tears....BACKGROUND The critical shoulder angle(CSA)is a radiographic measurement that provides an assessment of both glenoid inclination and acromial length.Higher values may correlate with the presence of rotator cuff tears.However,it is difficult to obtain a high-quality true anteroposterior(AP)radiograph of the shoulder,with any excess scapular version or flexion/extension resulting in deviation from the true CSA value.Three-dimensional(3D)bony reconstructions of computed tomography(CT)shoulder scans may be able to be rotated to obtain a similar view to that of true AP radiographs.AIM To compare CSA measurements performed on 3D bony CT reconstructions,with those on corresponding true AP radiographs.METHODS CT shoulder scans were matched with true AP radiographs that were classified as either Suter-Henninger type A or C quality.3D bony reconstructions were segmented from the CT scans,and rotated to replicate an ideal true AP view.Two observers performed CSA measurements using both CT and radiographic images.Measurements were repeated after a one week interval.Reliability was assessed using intraclass correlation coefficients(ICCs)and Bland-Altman plots[bias,limits of agreement(LOA)].RESULTS Twenty CT shoulder scans were matched.The mean CSA values were 32.55°(±4.26°)with radiographs and 29.82°(±3.49°)with the CT-based method[mean difference 2.73°(±2.86°);P<0.001;bias+2.73°;LOA-2.17°to+7.63°].There was a strong correlation between the two methods(r=0.748;P<0.001).Intra-observer reliability was similar,but the best intra-observer values were achieved by the most experienced observer using the CT-based method[ICC:0.983(0.958-0.993);bias+0.03°,LOA-1.28°to+1.34°].Inter-observer reliability was better with the CT-based method[ICC:0.897(0.758-0.958),bias+0.24°,LOA-2.93°to+3.41°].CONCLUSION The described CT-based method may be a suitable alternative for critical shoulder angle measurement,as it overcomes the difficulty in obtaining a true AP radiographic view.展开更多
A three-dimensional elasto-plastic finite element analysis of pre-twist process for a torsional axis made of 45GrNiMoVA steel, was carried out using a commercial finite element analysis code, MSC MARC 2001. The result...A three-dimensional elasto-plastic finite element analysis of pre-twist process for a torsional axis made of 45GrNiMoVA steel, was carried out using a commercial finite element analysis code, MSC MARC 2001. The results show that the critical pre-twist strain angle is 0.027 rad and the maximum elastic shear stress after pre-twist is 1694MPa for the torsional axis.展开更多
Analyzed the support instable mode of sliding,tripping,and so on,and believed the key point of the support stability control of fully mechanized coal caving face with steep coal seams was to maintain that the seam tru...Analyzed the support instable mode of sliding,tripping,and so on,and believed the key point of the support stability control of fully mechanized coal caving face with steep coal seams was to maintain that the seam true angle was less than the hydraulic support instability critical angle.Through the layout of oblique face,the improvement of support setting load,the control of mining height and nonskid platform,the group support system of end face,the advance optimization of conveyor and support,and the other control tech- nical measures,the true angle of the seam is reduced and the instable critical angle of the support is increased,the hydraulic support stability of fully mechanized coal caving face with steep coal seams is effectively controlled.展开更多
Two problems of a one-dimensional(1D)piezoelectric quasicrystal(QC)wedge are investigated,i.e.,the two sides of the wedge subject to uniform tractions and the wedge apex subject to the concentrated force.By virtue of ...Two problems of a one-dimensional(1D)piezoelectric quasicrystal(QC)wedge are investigated,i.e.,the two sides of the wedge subject to uniform tractions and the wedge apex subject to the concentrated force.By virtue of the Stroh formalism and Barnett-Lothe matrices,the analytical expressions of the displacements and stresses are derived,and the generalized solutions for the critical wedge angles are discussed.Numerical examples are given to present the mechanical behaviors of the wedge in each field.The results indicate that the effects of the uniform tractions and the concentrated force on the phonon field displacement are larger than those on the phason field.展开更多
To enhance the image motion compensation accuracy of off-axis three-mirror anastigmatic( TMA)three-line array aerospace mapping cameras,a new method of image motion velocity field modeling is proposed in this paper. F...To enhance the image motion compensation accuracy of off-axis three-mirror anastigmatic( TMA)three-line array aerospace mapping cameras,a new method of image motion velocity field modeling is proposed in this paper. Firstly,based on the imaging principle of mapping cameras,an analytical expression of image motion velocity of off-axis TMA three-line array aerospace mapping cameras is deduced from different coordinate systems we established and the attitude dynamics principle. Then,the case of a three-line array mapping camera is studied,in which the simulation of the focal plane image motion velocity fields of the forward-view camera,the nadir-view camera and the backward-view camera are carried out,and the optimization schemes for image motion velocity matching and drift angle matching are formulated according the simulation results. Finally,this method is verified with a dynamic imaging experimental system. The results are indicative of that when image motion compensation for nadir-view camera is conducted using the proposed image motion velocity field model,the line pair of target images at Nyquist frequency is clear and distinguishable. Under the constraint that modulation transfer function( MTF) reduces by 5%,when the horizontal frequencies of the forward-view camera and the backward-view camera are adjusted uniformly according to the proposed image motion velocity matching scheme,the time delay integration( TDI) stages reach 6 at most. When the TDI stages are more than 6,the three groups of camera will independently undergo horizontal frequency adjustment. However, when the proposed drift angle matching scheme is adopted for uniform drift angle adjustment,the number of TDI stages will not exceed 81. The experimental results have demonstrated the validity and accuracy of the proposed image motion velocity field model and matching optimization scheme,providing reliable basis for on-orbit image motion compensation of aerospace mapping cameras.展开更多
The purpose of this paper is to study the critical sand starting velocity and transformation law of flow pattern based on gas-water-sand three-phase flow in an inclined pipe.Firstly,the indoor simulation experiment sy...The purpose of this paper is to study the critical sand starting velocity and transformation law of flow pattern based on gas-water-sand three-phase flow in an inclined pipe.Firstly,the indoor simulation experiment system of gas-water-sand three-phase flow was used to test the conversion law of flow pattern based upon the different gas void fraction.Secondly,the influence of slug bubbles on sand migration was investigated according to distinctive hole deviation angles,gas void fraction and sand concentration.Finally,the critical sand starting velocity was tested based on dissimilar hole deviation angles,gas void fraction,sand concentration and sand particle size,and then the influence of the abovementioned key parameters on the sand starting velocity was debated based on the force analysis of the sand particles.The experimental results illustrated that when the gas void fraction was less than 5%,it was bubbly flow.When it increased from 5%to 30%,the bubbly flow and slug flow coexisted.When it was between 30%and 50%,the slug flow and agitated flow coexisted.When it reached 50%,it was agitated flow.Providing that the hole deviation angle was 90°,the phenomenon of overall migration and wavelike migration on the surface of sand bed was observed.On the contrary,the phenomenon of rolling and jumping migration was recognized.The critical sand starting velocity was positively correlated with the hole deviation angle and sand particle size,but negatively associated with the gas void fraction and sand concentration.This research can provide a certain reference for sand-starting production in the field of petroleum engineering.展开更多
On super-sonic or trans-sonic planar cascade wind tunnel of free jet intermittent type, wind blowing experiments were performed on the typical sections of stator and rotor blades in the last stage of ultra-ultra-criti...On super-sonic or trans-sonic planar cascade wind tunnel of free jet intermittent type, wind blowing experiments were performed on the typical sections of stator and rotor blades in the last stage of ultra-ultra-critical steam turbine with extra-long blade of 1200mm. The influences of attack angle and Mach number on the aerodynamic performances of these sections of the blade profiles were verified, and their operating ranges were also specified.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos.10947170/A05 and 11104291)the Natural Science Fund for Colleges and Universities in Jiangsu Province (Grant No.10KJB140006)+2 种基金the Natural Sciences Foundation of Shanghai (Grant No.11ZR1441300)the Natural Science Foundation of Nanjing University of Posts and Telecommunications (Grant No.NY221098)the Jiangsu Qing Lan Project for their sponsorship。
文摘This paper presents a novel view of the impact of electron collision off-axis positions on the dynamic properties and relativistic nonlinear Thomson inverse scattering of excited electrons within tightly focused, circularly polarized laser pulses of varying intensities. We examine the effects of the transverse ponderomotive force, specifically how the deviation angle and speed of electron motion are affected by the initial off-axis position of the electron and the peak amplitude of the laser pulse. When the laser pulse intensity is low, an increase in the electron's initial off-axis distance results in reduced spatial radiation power, improved collimation, super-continuum phenomena generation, red-shifting of the spectrum's harmonic peak, and significant symmetry in the radiation radial direction. However, in contradiction to conventional understandings,when the laser pulse intensity is relatively high, the properties of the relativistic nonlinear Thomson inverse scattering of the electron deviate from the central axis, changing direction in opposition to the aforementioned effects. After reaching a peak, these properties then shift again, aligning with the previous direction. The complex interplay of these effects suggests a greater nuance and intricacy in the relationship between laser pulse intensity, electron position, and scattering properties than previously thought.
文摘BACKGROUND The critical shoulder angle(CSA)is a radiographic measurement that provides an assessment of both glenoid inclination and acromial length.Higher values may correlate with the presence of rotator cuff tears.However,it is difficult to obtain a high-quality true anteroposterior(AP)radiograph of the shoulder,with any excess scapular version or flexion/extension resulting in deviation from the true CSA value.Three-dimensional(3D)bony reconstructions of computed tomography(CT)shoulder scans may be able to be rotated to obtain a similar view to that of true AP radiographs.AIM To compare CSA measurements performed on 3D bony CT reconstructions,with those on corresponding true AP radiographs.METHODS CT shoulder scans were matched with true AP radiographs that were classified as either Suter-Henninger type A or C quality.3D bony reconstructions were segmented from the CT scans,and rotated to replicate an ideal true AP view.Two observers performed CSA measurements using both CT and radiographic images.Measurements were repeated after a one week interval.Reliability was assessed using intraclass correlation coefficients(ICCs)and Bland-Altman plots[bias,limits of agreement(LOA)].RESULTS Twenty CT shoulder scans were matched.The mean CSA values were 32.55°(±4.26°)with radiographs and 29.82°(±3.49°)with the CT-based method[mean difference 2.73°(±2.86°);P<0.001;bias+2.73°;LOA-2.17°to+7.63°].There was a strong correlation between the two methods(r=0.748;P<0.001).Intra-observer reliability was similar,but the best intra-observer values were achieved by the most experienced observer using the CT-based method[ICC:0.983(0.958-0.993);bias+0.03°,LOA-1.28°to+1.34°].Inter-observer reliability was better with the CT-based method[ICC:0.897(0.758-0.958),bias+0.24°,LOA-2.93°to+3.41°].CONCLUSION The described CT-based method may be a suitable alternative for critical shoulder angle measurement,as it overcomes the difficulty in obtaining a true AP radiographic view.
文摘A three-dimensional elasto-plastic finite element analysis of pre-twist process for a torsional axis made of 45GrNiMoVA steel, was carried out using a commercial finite element analysis code, MSC MARC 2001. The results show that the critical pre-twist strain angle is 0.027 rad and the maximum elastic shear stress after pre-twist is 1694MPa for the torsional axis.
基金the National Natrual Science Foundation of China(50504014)
文摘Analyzed the support instable mode of sliding,tripping,and so on,and believed the key point of the support stability control of fully mechanized coal caving face with steep coal seams was to maintain that the seam true angle was less than the hydraulic support instability critical angle.Through the layout of oblique face,the improvement of support setting load,the control of mining height and nonskid platform,the group support system of end face,the advance optimization of conveyor and support,and the other control tech- nical measures,the true angle of the seam is reduced and the instable critical angle of the support is increased,the hydraulic support stability of fully mechanized coal caving face with steep coal seams is effectively controlled.
基金Project supported by the National Natural Science Foundation of China(Nos.11972365,12102458,11972354)the China Agricultural University Education Foundation(No.1101-2412001)。
文摘Two problems of a one-dimensional(1D)piezoelectric quasicrystal(QC)wedge are investigated,i.e.,the two sides of the wedge subject to uniform tractions and the wedge apex subject to the concentrated force.By virtue of the Stroh formalism and Barnett-Lothe matrices,the analytical expressions of the displacements and stresses are derived,and the generalized solutions for the critical wedge angles are discussed.Numerical examples are given to present the mechanical behaviors of the wedge in each field.The results indicate that the effects of the uniform tractions and the concentrated force on the phonon field displacement are larger than those on the phason field.
基金Sponsored by the National High Technology Research and Development Program of China(Grant No.863-2-5-1-13B)the Jilin Province Science and Technology Development Plan Item(Grant No.20130522107JH)
文摘To enhance the image motion compensation accuracy of off-axis three-mirror anastigmatic( TMA)three-line array aerospace mapping cameras,a new method of image motion velocity field modeling is proposed in this paper. Firstly,based on the imaging principle of mapping cameras,an analytical expression of image motion velocity of off-axis TMA three-line array aerospace mapping cameras is deduced from different coordinate systems we established and the attitude dynamics principle. Then,the case of a three-line array mapping camera is studied,in which the simulation of the focal plane image motion velocity fields of the forward-view camera,the nadir-view camera and the backward-view camera are carried out,and the optimization schemes for image motion velocity matching and drift angle matching are formulated according the simulation results. Finally,this method is verified with a dynamic imaging experimental system. The results are indicative of that when image motion compensation for nadir-view camera is conducted using the proposed image motion velocity field model,the line pair of target images at Nyquist frequency is clear and distinguishable. Under the constraint that modulation transfer function( MTF) reduces by 5%,when the horizontal frequencies of the forward-view camera and the backward-view camera are adjusted uniformly according to the proposed image motion velocity matching scheme,the time delay integration( TDI) stages reach 6 at most. When the TDI stages are more than 6,the three groups of camera will independently undergo horizontal frequency adjustment. However, when the proposed drift angle matching scheme is adopted for uniform drift angle adjustment,the number of TDI stages will not exceed 81. The experimental results have demonstrated the validity and accuracy of the proposed image motion velocity field model and matching optimization scheme,providing reliable basis for on-orbit image motion compensation of aerospace mapping cameras.
基金supporting by the Youth Program of National Natural Science Foundation of China(52104012)the China Postdoctoral Science Foundation(2021M693494)+2 种基金the Key Program of the National Natural Science Foundation of China(51734010)the Key Natural Science Projects of Scientific Research Plan in Colleges and Universities of Xinjiang Uygur Autonomous Region(XJEDU2021I028)the Strategic Cooperation Technology Projects of CNPC and CUPB(ZLZX2020-01-01)
文摘The purpose of this paper is to study the critical sand starting velocity and transformation law of flow pattern based on gas-water-sand three-phase flow in an inclined pipe.Firstly,the indoor simulation experiment system of gas-water-sand three-phase flow was used to test the conversion law of flow pattern based upon the different gas void fraction.Secondly,the influence of slug bubbles on sand migration was investigated according to distinctive hole deviation angles,gas void fraction and sand concentration.Finally,the critical sand starting velocity was tested based on dissimilar hole deviation angles,gas void fraction,sand concentration and sand particle size,and then the influence of the abovementioned key parameters on the sand starting velocity was debated based on the force analysis of the sand particles.The experimental results illustrated that when the gas void fraction was less than 5%,it was bubbly flow.When it increased from 5%to 30%,the bubbly flow and slug flow coexisted.When it was between 30%and 50%,the slug flow and agitated flow coexisted.When it reached 50%,it was agitated flow.Providing that the hole deviation angle was 90°,the phenomenon of overall migration and wavelike migration on the surface of sand bed was observed.On the contrary,the phenomenon of rolling and jumping migration was recognized.The critical sand starting velocity was positively correlated with the hole deviation angle and sand particle size,but negatively associated with the gas void fraction and sand concentration.This research can provide a certain reference for sand-starting production in the field of petroleum engineering.
文摘On super-sonic or trans-sonic planar cascade wind tunnel of free jet intermittent type, wind blowing experiments were performed on the typical sections of stator and rotor blades in the last stage of ultra-ultra-critical steam turbine with extra-long blade of 1200mm. The influences of attack angle and Mach number on the aerodynamic performances of these sections of the blade profiles were verified, and their operating ranges were also specified.