Five kinds of WSi_2/MoSi_2 composites were successfully prepared bymechanical alloying, IP and high temperature sintering techniques. And their hardness and fracturetoughness were measured by the Vickers indentation f...Five kinds of WSi_2/MoSi_2 composites were successfully prepared bymechanical alloying, IP and high temperature sintering techniques. And their hardness and fracturetoughness were measured by the Vickers indentation fracture mode through an Hv-10A type sclerometer.The microstructure and morphology were investigated by a JSM-56001V scanning electron microscope.Results show that the addition of 50% WSi_2 (in mole fraction) has remarkable hardening andtoughening effects on the MoSi_2 matrix, whose hardness value and fracture toughness value areincreased about 60% and 86%, respectively. For WSi_2/MoSi_2 composite, the hardening mechanisms arefine-grain and the second phase particles strengthening, and the toughening mechanisms includefine-grain, grain drawing, crack deflection, microbridge and bowing toughening.展开更多
Abstract On the basis of analyzing floor strata mechanical circumstance of the roadway, the mechanical model was established. The relative displacement of roadway floor, narrow pillar floor coal mass and floor strata ...Abstract On the basis of analyzing floor strata mechanical circumstance of the roadway, the mechanical model was established. The relative displacement of roadway floor, narrow pillar floor coal mass and floor strata was calculated, the results showed that the high abutment pressure on coal mass beside the roadway was the main reason to lead to relative displacement of floor strata. And the roadway floor heave come mainly from three aspects. Firstly, the roadway floor strata is easily fractured by the stretch stress. Secondly, because the high abutment pressure is greater than the uniaxial compressive strength of floor strata, when the roadway floor strata are fractured, the coal mass floor strata at the same depth will be fractured, and broken rock will fluid into the open roadway. Thirdly, comparing with the coal mass floor, the roadway floor is relative ascending.展开更多
Dynamic running law of the hydraulic driving system decides the hoisting cage velocity curve in a hoisting cycle and is decided by the characteristic of the hydraulic driving system and by the operating speed of hoist...Dynamic running law of the hydraulic driving system decides the hoisting cage velocity curve in a hoisting cycle and is decided by the characteristic of the hydraulic driving system and by the operating speed of hoist driver. The paper studies the dynamic running law of hydraulic driving system, analyses the influence of driver operating speed on the dynamic running characteristic, and points out the reasonable driver operating speed to control the dynamic stress in rope and to reduce the oscillation of rope system.展开更多
Abstract The robust stability for some types of time varying interval matrices and nonlinear time varying interval matrices is considered and some sufficient conditions for robust stability of such interval matrices a...Abstract The robust stability for some types of time varying interval matrices and nonlinear time varying interval matrices is considered and some sufficient conditions for robust stability of such interval matrices are given. The main results of this paper are only related to the vertices set of a interval matrices, and therefore, can be easily applied to test robust stability of interval matrices. Finally, some examples are given to illustrate the results.展开更多
Abstract. In this paper we contribute with one main result to the interesting probleminitiated by Hong(1998) on the behaviour of Groebner bases under composition of polyno-mials. Polynomial composition is the operatio...Abstract. In this paper we contribute with one main result to the interesting probleminitiated by Hong(1998) on the behaviour of Groebner bases under composition of polyno-mials. Polynomial composition is the operation of replacing the variables of a polynomialwith other polynomials. The main question of this paper is: Does there exist a decisionprocedure that will determine whether a given composition is comPatible with a given termordering? If so, find one. We will give a better answer.展开更多
文摘Five kinds of WSi_2/MoSi_2 composites were successfully prepared bymechanical alloying, IP and high temperature sintering techniques. And their hardness and fracturetoughness were measured by the Vickers indentation fracture mode through an Hv-10A type sclerometer.The microstructure and morphology were investigated by a JSM-56001V scanning electron microscope.Results show that the addition of 50% WSi_2 (in mole fraction) has remarkable hardening andtoughening effects on the MoSi_2 matrix, whose hardness value and fracture toughness value areincreased about 60% and 86%, respectively. For WSi_2/MoSi_2 composite, the hardening mechanisms arefine-grain and the second phase particles strengthening, and the toughening mechanisms includefine-grain, grain drawing, crack deflection, microbridge and bowing toughening.
文摘Abstract On the basis of analyzing floor strata mechanical circumstance of the roadway, the mechanical model was established. The relative displacement of roadway floor, narrow pillar floor coal mass and floor strata was calculated, the results showed that the high abutment pressure on coal mass beside the roadway was the main reason to lead to relative displacement of floor strata. And the roadway floor heave come mainly from three aspects. Firstly, the roadway floor strata is easily fractured by the stretch stress. Secondly, because the high abutment pressure is greater than the uniaxial compressive strength of floor strata, when the roadway floor strata are fractured, the coal mass floor strata at the same depth will be fractured, and broken rock will fluid into the open roadway. Thirdly, comparing with the coal mass floor, the roadway floor is relative ascending.
文摘Dynamic running law of the hydraulic driving system decides the hoisting cage velocity curve in a hoisting cycle and is decided by the characteristic of the hydraulic driving system and by the operating speed of hoist driver. The paper studies the dynamic running law of hydraulic driving system, analyses the influence of driver operating speed on the dynamic running characteristic, and points out the reasonable driver operating speed to control the dynamic stress in rope and to reduce the oscillation of rope system.
文摘Abstract The robust stability for some types of time varying interval matrices and nonlinear time varying interval matrices is considered and some sufficient conditions for robust stability of such interval matrices are given. The main results of this paper are only related to the vertices set of a interval matrices, and therefore, can be easily applied to test robust stability of interval matrices. Finally, some examples are given to illustrate the results.
基金the Foundation of Nature Science of Hunan Province(98JJY2052)
文摘Abstract. In this paper we contribute with one main result to the interesting probleminitiated by Hong(1998) on the behaviour of Groebner bases under composition of polyno-mials. Polynomial composition is the operation of replacing the variables of a polynomialwith other polynomials. The main question of this paper is: Does there exist a decisionprocedure that will determine whether a given composition is comPatible with a given termordering? If so, find one. We will give a better answer.
