Based on the parametric analysis of the expanding zone of the vacuum dust suction mouth,the flow in the vacuum dust suction mouth was simulated by computational fluid dynamics(CFD)software,Fluent.The effects of the ex...Based on the parametric analysis of the expanding zone of the vacuum dust suction mouth,the flow in the vacuum dust suction mouth was simulated by computational fluid dynamics(CFD)software,Fluent.The effects of the expanding zone parameters on flow simulation were analyzed.The results show that simulation effects depend on threshold values of the expanding zone parameters of the dust suction mouth,and the threshold values of the expanding zone can be obtained according to the different structures of the vacuum dust suction mouth and be selected as the geometric parameters in calculating,and also corners of the expanding zone make unobvious difference in calculation accuracy and in computational efficiency compared with no corner.The simulation results provide practical guidance to the flow simulation on the dust suction mouth.展开更多
Long-rod penetration in a wide range ol" velocity means that the initial impact velocity varies in a range from tens of meters per second to several kilometers per second.The long rods maintain rigid state when t...Long-rod penetration in a wide range ol" velocity means that the initial impact velocity varies in a range from tens of meters per second to several kilometers per second.The long rods maintain rigid state when the impact velocity is low,the nose of rod deforms and even is blunted when the velocity gets higher,and the nose erodes and fails to lead to the consumption of long projectile when the velocity is very high clue to instantaneous high pressure.That is,from low velocity to high velocity,the projectile undergoes rigid rods,deforming non-erosive rods,and erosive rods.Because of the complicated changes of the projectile,no well-established theoretical model and numerical simulation have been used to study the transition zone.Based on the analysis of penetration behavior in the transition zone,a phenomenological model to describe target resistance and a formula to calculate penetration depth in transition zone are proposed,and a method to obtain the boundary velocity of transition zone is determined.A combined theoretical analysis model for three response regions is built by analyzing the characteristics in these regions.The penetration depth predicted by this combined model is in good agreement with experimental result.展开更多
The intensity of heat output of coal, the rate of oxygen consumption and the influence function of coal size are tested by the big coal spontaneous combustion experiment unit. The independence of the coefficient of he...The intensity of heat output of coal, the rate of oxygen consumption and the influence function of coal size are tested by the big coal spontaneous combustion experiment unit. The independence of the coefficient of heat convection is studied. And based on the conservation principle of energy and the real conditions, such as coal temperature,air temperature, the geometry size of roadway, air flux, the oxygen concentration in the loose coal around the roadway, the threshold parameters resulting coal spontaneous combustion are put forward, and the index determining the danger zone liable to self ignite are evaluated. Finally, the method determining the danger zone liable to spontaneous ignition around coal roadway at fully mechanized long wall top coal caving face is put forward. Based on the determination method and real conditions in the roadway, the coal around roadway can be divided four zones.展开更多
To investigate the relation between material’s cyclic plastic behaviour and fatigue crack growth, a new model is proposed. The model incorporated the two intrinsic properties of material’s cyclic plastic and crack ...To investigate the relation between material’s cyclic plastic behaviour and fatigue crack growth, a new model is proposed. The model incorporated the two intrinsic properties of material’s cyclic plastic and crack tip’s deformation dislocation to interpret fatigue crack threshold. The relation between material’s cyclic hardening parameters (cyclic hardening amplitude and cyclic hardening rate) and fatigue threshold is studied. Fatigue threshold is determined based on the dislocation-free zone (DFZ) model, the theory of cohesive zone and the cyclic deformation behaviour. The results show that fatigue threshold increases with the decrease of the amplitude of cyclic hardening and is independent of cyclic hardening rate, but fatigue crack growth rate increases with the increase of cyclic hardening rate.展开更多
由于γ射线对SiO_(2)的电离作用,会引起MOS管阈值电压负漂移和二极管死区漏电变化,负漂移和漏电变化程度随MOS管栅氧厚度增加而加大。这样在设计高压直采ADC时,实现稳定基准和低漏电开关是个难点,通常的解决方法是优化电路参数裕量和版...由于γ射线对SiO_(2)的电离作用,会引起MOS管阈值电压负漂移和二极管死区漏电变化,负漂移和漏电变化程度随MOS管栅氧厚度增加而加大。这样在设计高压直采ADC时,实现稳定基准和低漏电开关是个难点,通常的解决方法是优化电路参数裕量和版图,但很少考虑MOS管的反型和二极管的死区漏电。重点研究了MOS器件阈值和二极管死区漏电流变化对器件参数影响的机理,并提出一种不同电源电压MOS管结合设计思路,同时考虑了减小二极管死区漏电的影响。最后,通过使用不同电源电压MOS管设计和二极管死区漏电流分析,高压ADC在50 k rad(Si)总剂量条件下仍能达到设计要求。展开更多
基金Project(2012zzts082)supported by the Fundamental Research Funds of Central South University,ChinaProject(02JJY2005)supported by the Natural Science Foundation of Hunan Province,ChinaProject(20130843023)supported by China Scholarship Council
文摘Based on the parametric analysis of the expanding zone of the vacuum dust suction mouth,the flow in the vacuum dust suction mouth was simulated by computational fluid dynamics(CFD)software,Fluent.The effects of the expanding zone parameters on flow simulation were analyzed.The results show that simulation effects depend on threshold values of the expanding zone parameters of the dust suction mouth,and the threshold values of the expanding zone can be obtained according to the different structures of the vacuum dust suction mouth and be selected as the geometric parameters in calculating,and also corners of the expanding zone make unobvious difference in calculation accuracy and in computational efficiency compared with no corner.The simulation results provide practical guidance to the flow simulation on the dust suction mouth.
基金supported by the National Natural Science Foundation of China(No.11302031,11371069,11372053)
文摘Long-rod penetration in a wide range ol" velocity means that the initial impact velocity varies in a range from tens of meters per second to several kilometers per second.The long rods maintain rigid state when the impact velocity is low,the nose of rod deforms and even is blunted when the velocity gets higher,and the nose erodes and fails to lead to the consumption of long projectile when the velocity is very high clue to instantaneous high pressure.That is,from low velocity to high velocity,the projectile undergoes rigid rods,deforming non-erosive rods,and erosive rods.Because of the complicated changes of the projectile,no well-established theoretical model and numerical simulation have been used to study the transition zone.Based on the analysis of penetration behavior in the transition zone,a phenomenological model to describe target resistance and a formula to calculate penetration depth in transition zone are proposed,and a method to obtain the boundary velocity of transition zone is determined.A combined theoretical analysis model for three response regions is built by analyzing the characteristics in these regions.The penetration depth predicted by this combined model is in good agreement with experimental result.
文摘The intensity of heat output of coal, the rate of oxygen consumption and the influence function of coal size are tested by the big coal spontaneous combustion experiment unit. The independence of the coefficient of heat convection is studied. And based on the conservation principle of energy and the real conditions, such as coal temperature,air temperature, the geometry size of roadway, air flux, the oxygen concentration in the loose coal around the roadway, the threshold parameters resulting coal spontaneous combustion are put forward, and the index determining the danger zone liable to self ignite are evaluated. Finally, the method determining the danger zone liable to spontaneous ignition around coal roadway at fully mechanized long wall top coal caving face is put forward. Based on the determination method and real conditions in the roadway, the coal around roadway can be divided four zones.
基金Sponsored by the Fundamental Research Foundation of Harbin Engineering University(Grant No.HEUFT07007)
文摘To investigate the relation between material’s cyclic plastic behaviour and fatigue crack growth, a new model is proposed. The model incorporated the two intrinsic properties of material’s cyclic plastic and crack tip’s deformation dislocation to interpret fatigue crack threshold. The relation between material’s cyclic hardening parameters (cyclic hardening amplitude and cyclic hardening rate) and fatigue threshold is studied. Fatigue threshold is determined based on the dislocation-free zone (DFZ) model, the theory of cohesive zone and the cyclic deformation behaviour. The results show that fatigue threshold increases with the decrease of the amplitude of cyclic hardening and is independent of cyclic hardening rate, but fatigue crack growth rate increases with the increase of cyclic hardening rate.
文摘由于γ射线对SiO_(2)的电离作用,会引起MOS管阈值电压负漂移和二极管死区漏电变化,负漂移和漏电变化程度随MOS管栅氧厚度增加而加大。这样在设计高压直采ADC时,实现稳定基准和低漏电开关是个难点,通常的解决方法是优化电路参数裕量和版图,但很少考虑MOS管的反型和二极管的死区漏电。重点研究了MOS器件阈值和二极管死区漏电流变化对器件参数影响的机理,并提出一种不同电源电压MOS管结合设计思路,同时考虑了减小二极管死区漏电的影响。最后,通过使用不同电源电压MOS管设计和二极管死区漏电流分析,高压ADC在50 k rad(Si)总剂量条件下仍能达到设计要求。
