In this paper, the kinematically admissible velocity field with surface crack on forward extruding bar is put forward during the axisymmetric cup-bar combined extrusion process, in accordance with the results of model...In this paper, the kinematically admissible velocity field with surface crack on forward extruding bar is put forward during the axisymmetric cup-bar combined extrusion process, in accordance with the results of model experiments.On the basis of velocity field, the necessary condition for surface crack formation on the forward extruding bar is derived, with the help of upper bound theorem and the minimum energy principle. Meanwhile, the relationships between surface crack formation and combination of reduction in area for the part of forward and backward extursions relative residual thickness of billet (T/R0),frictional factor (m) or relative land length of ram and chamber are calculated during the extrusion process. Therefore, whether the surface crack on forward exturding bar occurs can be predicted before extruding the lower-plasticity metals for axisymmetric cup-bar combined extrusion process.The analytical results agree very well with experimental results of aluminium alloy LY12 (ASTM 2024) and LC4 (ASTM 7075).展开更多
This paper is devoted to path-dependent kinetics equations arising, in particular, from the analysis of the coupled backward-forward systems of equations of mean field games. We present local well-posedness, global ex...This paper is devoted to path-dependent kinetics equations arising, in particular, from the analysis of the coupled backward-forward systems of equations of mean field games. We present local well-posedness, global existence and some regularity results for these equations.展开更多
The clutter direction-Doppler curves are not aligned on the near range bins for forward looking airborne radar. As a result, the performance of clutter suppression by Space-Time Adaptive Processing (STAP) degrades gre...The clutter direction-Doppler curves are not aligned on the near range bins for forward looking airborne radar. As a result, the performance of clutter suppression by Space-Time Adaptive Processing (STAP) degrades greatly because of the clutter range dependence. To deal with this problem, a new compensated method is proposed in this paper. The method rebuilds the clutter covariance matrix based on spatial high resolution Minimum Variance Distortionless Response (MVDR) spectrum, and then finds a matrix to transform the covariance matrix of short-range gate to the referred far-range gate. The method can compensate the clutter range dependence well. The simulation results show validity of the method.展开更多
目的:探讨无痛分娩下活跃期支撑式前倾坐位联合侧卧位接产在初产妇分娩中的应用效果。方法:选取2022年10月-2023年9月在江门市妇幼保健院进行无痛阴道分娩的120例初产妇作为研究对象,以随机数字表法分为对照组、试验组,各60例。对照组...目的:探讨无痛分娩下活跃期支撑式前倾坐位联合侧卧位接产在初产妇分娩中的应用效果。方法:选取2022年10月-2023年9月在江门市妇幼保健院进行无痛阴道分娩的120例初产妇作为研究对象,以随机数字表法分为对照组、试验组,各60例。对照组第一产程给予传统卧位待产护理,第二产程采用截石卧位接生;试验组第一产程进入活跃期后,给予支撑式前倾坐位待产,第二产程采用侧卧位接生。比较两组的产钳助产情况、会阴撕裂情况、产程时间、产后2 h出血量、疼痛程度、胎心音频率异常率及新生儿Apgar评分。结果:试验组第一产程时间短于对照组,产钳助产率、会阴撕裂率、产后2 h出血量、疼痛评分均显著低于对照组,差异均有统计学意义(P<0.05);两组胎心音频率异常率、第二产程时间及新生儿出生后1、5、10 min Apgar评分比较,差异均无统计学意义(P>0.05)。结论:无痛分娩下活跃期支撑式前倾坐位联合侧卧位接产对初产妇阴道分娩具有一定的临床效果,可减少产钳助产情况,缩短第一产程时间,减少会阴撕裂,改善产后出血量,临床应用安全可靠。展开更多
文摘In this paper, the kinematically admissible velocity field with surface crack on forward extruding bar is put forward during the axisymmetric cup-bar combined extrusion process, in accordance with the results of model experiments.On the basis of velocity field, the necessary condition for surface crack formation on the forward extruding bar is derived, with the help of upper bound theorem and the minimum energy principle. Meanwhile, the relationships between surface crack formation and combination of reduction in area for the part of forward and backward extursions relative residual thickness of billet (T/R0),frictional factor (m) or relative land length of ram and chamber are calculated during the extrusion process. Therefore, whether the surface crack on forward exturding bar occurs can be predicted before extruding the lower-plasticity metals for axisymmetric cup-bar combined extrusion process.The analytical results agree very well with experimental results of aluminium alloy LY12 (ASTM 2024) and LC4 (ASTM 7075).
文摘This paper is devoted to path-dependent kinetics equations arising, in particular, from the analysis of the coupled backward-forward systems of equations of mean field games. We present local well-posedness, global existence and some regularity results for these equations.
基金Supported by Education Department of Hunan Province Project (09C201)Hunan Provincial Natural Science Foundation of China (10jj6091) Planned Science and Technology Project of Hunan Province (2010FJ6015)
文摘The clutter direction-Doppler curves are not aligned on the near range bins for forward looking airborne radar. As a result, the performance of clutter suppression by Space-Time Adaptive Processing (STAP) degrades greatly because of the clutter range dependence. To deal with this problem, a new compensated method is proposed in this paper. The method rebuilds the clutter covariance matrix based on spatial high resolution Minimum Variance Distortionless Response (MVDR) spectrum, and then finds a matrix to transform the covariance matrix of short-range gate to the referred far-range gate. The method can compensate the clutter range dependence well. The simulation results show validity of the method.
文摘目的:探讨无痛分娩下活跃期支撑式前倾坐位联合侧卧位接产在初产妇分娩中的应用效果。方法:选取2022年10月-2023年9月在江门市妇幼保健院进行无痛阴道分娩的120例初产妇作为研究对象,以随机数字表法分为对照组、试验组,各60例。对照组第一产程给予传统卧位待产护理,第二产程采用截石卧位接生;试验组第一产程进入活跃期后,给予支撑式前倾坐位待产,第二产程采用侧卧位接生。比较两组的产钳助产情况、会阴撕裂情况、产程时间、产后2 h出血量、疼痛程度、胎心音频率异常率及新生儿Apgar评分。结果:试验组第一产程时间短于对照组,产钳助产率、会阴撕裂率、产后2 h出血量、疼痛评分均显著低于对照组,差异均有统计学意义(P<0.05);两组胎心音频率异常率、第二产程时间及新生儿出生后1、5、10 min Apgar评分比较,差异均无统计学意义(P>0.05)。结论:无痛分娩下活跃期支撑式前倾坐位联合侧卧位接产对初产妇阴道分娩具有一定的临床效果,可减少产钳助产情况,缩短第一产程时间,减少会阴撕裂,改善产后出血量,临床应用安全可靠。
