The microscopic structure change rule in high speed steel (HSS) after an additional cryogenic treatment was studied in this paper. Highly dispersed nano-carbide (η-Fe2 C) separated from tempering martensite was found...The microscopic structure change rule in high speed steel (HSS) after an additional cryogenic treatment was studied in this paper. Highly dispersed nano-carbide (η-Fe2 C) separated from tempering martensite was found distributed on twin planes of marten-site and dislocation places. Retained austenite was found sheared into martensite and nano-carbide separated at the same time. In addition, the tempering martensite was fine-grained. The stated changes of HSS evidently improve the lifespan of HSS cutter and fully show the advantages of nano-structure. The cryogenic treatment of HSS also improves the roughness of HSS cutter (decrease Ra number by about 50%) and greatly increases the wear resistance of HSS cutter. Further experiments on the wear characteristic of HSS cutter supported the findings mentioned above. The stated HSS treatment technology would implement nano-structure of traditional tool steel through phase change. It could be a new method to improve the performance of HSS cutter.展开更多
In this paper, we introduce a method to define generalized characteristic matrices of a defective matrix by the common form of Jordan chains. The generalized characteristic matrices can be obtained by solving a system...In this paper, we introduce a method to define generalized characteristic matrices of a defective matrix by the common form of Jordan chains. The generalized characteristic matrices can be obtained by solving a system of linear equations and they can be used to compute Jordan basis.展开更多
This paper proposes a linear frequency modulation (LFM signal) and biphase coding (BC signal) mixed modulation signal called LFM-BC signal. LFM-BC signal has both LFM signal and BC signal two kinds of traditional sign...This paper proposes a linear frequency modulation (LFM signal) and biphase coding (BC signal) mixed modulation signal called LFM-BC signal. LFM-BC signal has both LFM signal and BC signal two kinds of traditional signal advantages but makes up for their shortcomings. In this paper, LFM-BC signal, LFM and BC signals are studied and compared from the time characteristic and frequency characteristic of the signal, fuzzy function, pulse compression and Doppler characteristics and low probability of interception (LPI) characteristics.展开更多
This paper deals with non-linear vibration of rectangular reticulated shallow shells by applying non-linear elastic theory of such structures established by the author .Us-ing the assumed (generalized)Fourier series s...This paper deals with non-linear vibration of rectangular reticulated shallow shells by applying non-linear elastic theory of such structures established by the author .Us-ing the assumed (generalized)Fourier series solutions for transverse deflection (latticejoint transverse displacement )and force function,weighted means of the trial functions lead to the relations among the coefficients related to the solutions and vibration equ-ation which determines the unknown time function,and then the amplitude -frequeney relations for free vibration and forced vibration due to harmonic force are derived withthe aid of the regular perturbation method and Galerkin procedure,respectively.Nu-merical examples are given as well.展开更多
An experimental study is made on the resistance characteristic ofthe dense extrusion flow with pulverized coal and nitrogen as medium in thispaper. Through the analysis of gas compressibility , solids continuity and l...An experimental study is made on the resistance characteristic ofthe dense extrusion flow with pulverized coal and nitrogen as medium in thispaper. Through the analysis of gas compressibility , solids continuity and lam-mar flow of both gas and solids, a展开更多
A numerical simulation approach was adopted to investigate the uplift bearing characteristics of helical an-chors in Nantong silty sand and to predict their uplift bear-ing capacity.Finite element model validation was...A numerical simulation approach was adopted to investigate the uplift bearing characteristics of helical an-chors in Nantong silty sand and to predict their uplift bear-ing capacity.Finite element model validation was per-formed,and the uplift bearing mechanism of helical anchors was analyzed.The current code’s uplift bearing capacity calculation formula was optimized,and the accuracy and re-liability of the modified formula were evaluated.The results indicate that the critical embedment depth ratio of the anchor plate in Nantong silty sand is 5,and the critical spacing ra-tio ranges from 3 to 4.The current code’s formula underes-timates the uplift bearing capacity of helical anchors under these conditions.To improve the prediction accuracy,the optimization coefficients M and L,which account for the embedment depth ratio of the anchor plate,are introduced,and fitting formulas for these coefficients are provided to im-prove the prediction of uplift bearing capacity in Nantong silty sand and to serve as a reference for similar engineering applications.展开更多
A multistep characteristic finite difference method is given on the basis ofthe linear and quadratic interpolations for solving two-dimensional nonlinear convection-diffusion problems. The convergence of approximate s...A multistep characteristic finite difference method is given on the basis ofthe linear and quadratic interpolations for solving two-dimensional nonlinear convection-diffusion problems. The convergence of approximate solutions is obtained in L2.展开更多
文摘The microscopic structure change rule in high speed steel (HSS) after an additional cryogenic treatment was studied in this paper. Highly dispersed nano-carbide (η-Fe2 C) separated from tempering martensite was found distributed on twin planes of marten-site and dislocation places. Retained austenite was found sheared into martensite and nano-carbide separated at the same time. In addition, the tempering martensite was fine-grained. The stated changes of HSS evidently improve the lifespan of HSS cutter and fully show the advantages of nano-structure. The cryogenic treatment of HSS also improves the roughness of HSS cutter (decrease Ra number by about 50%) and greatly increases the wear resistance of HSS cutter. Further experiments on the wear characteristic of HSS cutter supported the findings mentioned above. The stated HSS treatment technology would implement nano-structure of traditional tool steel through phase change. It could be a new method to improve the performance of HSS cutter.
基金Foundation item： Supported by the Science Foundation of Liuzhou Vocational Institute of Technology（2007C03）
文摘In this paper, we introduce a method to define generalized characteristic matrices of a defective matrix by the common form of Jordan chains. The generalized characteristic matrices can be obtained by solving a system of linear equations and they can be used to compute Jordan basis.
文摘This paper proposes a linear frequency modulation (LFM signal) and biphase coding (BC signal) mixed modulation signal called LFM-BC signal. LFM-BC signal has both LFM signal and BC signal two kinds of traditional signal advantages but makes up for their shortcomings. In this paper, LFM-BC signal, LFM and BC signals are studied and compared from the time characteristic and frequency characteristic of the signal, fuzzy function, pulse compression and Doppler characteristics and low probability of interception (LPI) characteristics.
文摘This paper deals with non-linear vibration of rectangular reticulated shallow shells by applying non-linear elastic theory of such structures established by the author .Us-ing the assumed (generalized)Fourier series solutions for transverse deflection (latticejoint transverse displacement )and force function,weighted means of the trial functions lead to the relations among the coefficients related to the solutions and vibration equ-ation which determines the unknown time function,and then the amplitude -frequeney relations for free vibration and forced vibration due to harmonic force are derived withthe aid of the regular perturbation method and Galerkin procedure,respectively.Nu-merical examples are given as well.
文摘An experimental study is made on the resistance characteristic ofthe dense extrusion flow with pulverized coal and nitrogen as medium in thispaper. Through the analysis of gas compressibility , solids continuity and lam-mar flow of both gas and solids, a
基金The National Natural Science Foundation of China (No. 52378329)。
文摘A numerical simulation approach was adopted to investigate the uplift bearing characteristics of helical an-chors in Nantong silty sand and to predict their uplift bear-ing capacity.Finite element model validation was per-formed,and the uplift bearing mechanism of helical anchors was analyzed.The current code’s uplift bearing capacity calculation formula was optimized,and the accuracy and re-liability of the modified formula were evaluated.The results indicate that the critical embedment depth ratio of the anchor plate in Nantong silty sand is 5,and the critical spacing ra-tio ranges from 3 to 4.The current code’s formula underes-timates the uplift bearing capacity of helical anchors under these conditions.To improve the prediction accuracy,the optimization coefficients M and L,which account for the embedment depth ratio of the anchor plate,are introduced,and fitting formulas for these coefficients are provided to im-prove the prediction of uplift bearing capacity in Nantong silty sand and to serve as a reference for similar engineering applications.
文摘A multistep characteristic finite difference method is given on the basis ofthe linear and quadratic interpolations for solving two-dimensional nonlinear convection-diffusion problems. The convergence of approximate solutions is obtained in L2.
