Considering the effect of strain and chemical composition onprecipitation behavior, new models for the start and end time of Nb（C,N） precipitation in austenite under the conditions of different temperatures and stra...Considering the effect of strain and chemical composition onprecipitation behavior, new models for the start and end time of Nb（C,N） precipitation in austenite under the conditions of different temperatures and strains have been investigated for Nb microalloyed steel. The value of n in the precipitation kinetic equation has been determined by using the available experimental data in literature, which indicated that n is a constant and independent of temperature. The values of the start and end time of the predicted precipitation are compared with the experimental values. Calculated results are in good agreement with the experimental results. Also, the evolution of austenite grains before ferrite transformation is simulated by taking the effect of precipitation into consideration. The measured austenite grain size is in good agreement with predicted one prior to ferrite transformation.展开更多
By using the pulsed laser single event effect facility and electro-static discharge （ESD） test system, the characteristics of the ＂high current＂, relation with external stimulus and relevance to impacted modes of ...By using the pulsed laser single event effect facility and electro-static discharge （ESD） test system, the characteristics of the ＂high current＂, relation with external stimulus and relevance to impacted modes of single event latch-up （SEL） and transient-induced latch-up （TLU） are studied, respectively, for a 12-bit complementary metal--oxide semiconductor （CMOS） analog-to-digital converter. Furthermore, the sameness and difference in physical mechanism between ＂high current＂ induced by SEL and that by TLU are disclosed in this paper. The results show that the minority carrier diffusion in the PNPN structure of the CMOS device which initiates the active parasitic NPN and PNP transistors is the common reason for the ＂high current＂ induced by SEL and for that by TLU, However, for SEL, the minority carder diffusion is induced by the ionizing radiation, and an underdamped sinusoidal voltage on the supply node （the ground node） is the cause of the minority carrier diffusion for TLU.展开更多
By using isothermal double hit compression tests and applying the 2% offset method, a new model was developed to predict the microstructural evolution of Nb-bearing steels at temperatures above and below the start tem...By using isothermal double hit compression tests and applying the 2% offset method, a new model was developed to predict the microstructural evolution of Nb-bearing steels at temperatures above and below the start temperature of strain-induced precipitation （Tp）. The Tp was developed as a function of true strain, initial austenite grain size and the Nb content. The activation energy of static recrystallization （Qrex） was expressed as a function of the content of different alloy elements. It was found that Nb played the most important role in increasing the value of Qrex, The microstructural observations and measurements confirmed the validity of the model developed in the present investigation.展开更多
A static recrystallization behavior between the roiling passes of a martensitic heatresistant stainless steel 403Nb has been studied by OM, TEM and double-hit thermomechanical simulator to explore the effects of defor...A static recrystallization behavior between the roiling passes of a martensitic heatresistant stainless steel 403Nb has been studied by OM, TEM and double-hit thermomechanical simulator to explore the effects of deformation temperature, strain rate, strain and the prior austenite grain size. The results show that increases of deformation temperature and strain rate and strain can promote the static recrystallization of 403Nb steel. Static recrystallization also proceeds faster when the prior austenite grain size is smaller. Microstructural observation indicates that the volume fraction of static recrystallization increases with prolonged interval of the rolling passes. Straininduced precipitation can lead to an appearance of a platform in the kinetic curve of static recrystallization. Different from the conventional micro-alloying steel, the strain-induced precipitates in 403Nb steel during hot rolling are carbides containing Nb and Cr.展开更多
Most rainfall-induced landslide forecasting models focus on the relation between landslides and rainfall,which is one of the dynamic factors,and seldom consider the stacitc factors,such as geological and geograpical f...Most rainfall-induced landslide forecasting models focus on the relation between landslides and rainfall,which is one of the dynamic factors,and seldom consider the stacitc factors,such as geological and geograpical factors.Landslide susceptibility,however,is determinded by both static and dynamic factors.This article proposes a static and dynamic factors-coupled forecasting model(SDFCFM) of regional rainfall-induced landslides,which quantitatively considers both the static and dynamic factors that affect landslides.The generalized additive model(GAM) is applied to coupling both factors to get the landslide susceptibility.In the case study,SDFCFM is applied to forecast the landslide occurrences in Shenzhen during a rainfall process in 2008.Compared with the rainfall logistic regression model,the resulting landslide susceptibility map illustrates that SDFCFM can reduce the forecast redundancy and improve the hit ratio.It is both applicable and practical.The application of SDFCFM in landslide warning and prevention system will improve its efficiency and also cut down the cost of human and matreial resources.展开更多
基金National Natural Science Foundation of China (50474086 and 50334010)
文摘Considering the effect of strain and chemical composition onprecipitation behavior, new models for the start and end time of Nb（C,N） precipitation in austenite under the conditions of different temperatures and strains have been investigated for Nb microalloyed steel. The value of n in the precipitation kinetic equation has been determined by using the available experimental data in literature, which indicated that n is a constant and independent of temperature. The values of the start and end time of the predicted precipitation are compared with the experimental values. Calculated results are in good agreement with the experimental results. Also, the evolution of austenite grains before ferrite transformation is simulated by taking the effect of precipitation into consideration. The measured austenite grain size is in good agreement with predicted one prior to ferrite transformation.
基金Project supported by the National Natural Science Foundation of China(Grant No.41304148)
文摘By using the pulsed laser single event effect facility and electro-static discharge （ESD） test system, the characteristics of the ＂high current＂, relation with external stimulus and relevance to impacted modes of single event latch-up （SEL） and transient-induced latch-up （TLU） are studied, respectively, for a 12-bit complementary metal--oxide semiconductor （CMOS） analog-to-digital converter. Furthermore, the sameness and difference in physical mechanism between ＂high current＂ induced by SEL and that by TLU are disclosed in this paper. The results show that the minority carrier diffusion in the PNPN structure of the CMOS device which initiates the active parasitic NPN and PNP transistors is the common reason for the ＂high current＂ induced by SEL and for that by TLU, However, for SEL, the minority carder diffusion is induced by the ionizing radiation, and an underdamped sinusoidal voltage on the supply node （the ground node） is the cause of the minority carrier diffusion for TLU.
基金This work was supported by the National Natural Science Foundation of China （No. 50474086 and No. 50334010） the Program for New Century Excellent Talents in Universities （NCET-04-0278） of the Ministry of Education of China.
文摘By using isothermal double hit compression tests and applying the 2% offset method, a new model was developed to predict the microstructural evolution of Nb-bearing steels at temperatures above and below the start temperature of strain-induced precipitation （Tp）. The Tp was developed as a function of true strain, initial austenite grain size and the Nb content. The activation energy of static recrystallization （Qrex） was expressed as a function of the content of different alloy elements. It was found that Nb played the most important role in increasing the value of Qrex, The microstructural observations and measurements confirmed the validity of the model developed in the present investigation.
基金supported by the Fundamental Research Funds for the Central Universities (No.N100507003)the National Natural Science Foundation of China (No.50634030)
文摘A static recrystallization behavior between the roiling passes of a martensitic heatresistant stainless steel 403Nb has been studied by OM, TEM and double-hit thermomechanical simulator to explore the effects of deformation temperature, strain rate, strain and the prior austenite grain size. The results show that increases of deformation temperature and strain rate and strain can promote the static recrystallization of 403Nb steel. Static recrystallization also proceeds faster when the prior austenite grain size is smaller. Microstructural observation indicates that the volume fraction of static recrystallization increases with prolonged interval of the rolling passes. Straininduced precipitation can lead to an appearance of a platform in the kinetic curve of static recrystallization. Different from the conventional micro-alloying steel, the strain-induced precipitates in 403Nb steel during hot rolling are carbides containing Nb and Cr.
文摘利用线性弹簧斜向布置的几何非线性产生非线性恢复力,提出了引入非线性恢复力的水下涡激振动(VIV)发电系统.该系统通过单向轴承、齿轮齿条机构、增速箱和转子发电机,将钝体横向往复运动转变为发电机的单向旋转运动.建立了综合考虑流-固-电耦合的水下涡激振动发电系统动力学方程,利用非线性振动理论,获得了钝体非线性振动的静态平衡点分岔和不同稳态运动的区间,重点研究了PF-2SN和2PF-2SN两种静态分岔情况下钝体的非线性动力学行为,获得了不同流速下钝体振动的Poincaré映射、相图和幅频图,分析了钝体在单周期小幅运动、大幅混沌运动和准周期大幅运动等运动模式下的振动行为及运动规律,并计算了在钝体处于不同稳态运动时的发电机功率.结果表明:在PF-2SN分岔方式中,系统处于二稳态运动时的振动和发电具有明显优势,平均振幅比为2.18、发电功率最大值为24.45 W.而在2PF-2SN分岔方式中,系统处于三稳态运动时的振动和发电更具优势,平均振幅比为1.98、发电功率最大值为18.32 W.
文摘目的分析排球运动员优势腿和非优势腿单脚站立和单腿下落的生物力学特征,探究优势腿和非优势腿动静态平衡能力的差异性,为排球运动员姿势控制训练方案设计提供理论方向。方法选取20名排球运动员优势腿和非优势腿进行30 s睁眼、闭眼单脚站立和40 cm跳箱单腿下落稳定性测试,比较静态站立足底压力中心(center of pressure,COP)参数、触地瞬间关节角度和关节运动幅度、稳定性指数、载荷率、峰值地面反作用力和到达峰值地面反作用力时间的差异。结果(1)静态平衡能力:睁眼单脚站立非优势腿和优势腿COP指标无显著性差异(P>0.05);闭眼单脚站立时,优势腿COP前后方向最大偏移距离和COP前后方向的平均速度与非优势腿相比具有显著性差异(P<0.05)。(2)动态平衡能力:由非优势腿和优势腿单腿落地时GRF所计算的前后稳定性指数、左右稳定性指数、垂直稳定性指数和动态稳定时间具有显著性差异(P<0.05);落地缓冲过程中,非优势腿的膝关节、踝关节活动度与优势腿相比具有显著性差异(P<0.05);计算优势腿和非优势腿单腿落地时载荷率具有显著性差异(P<0.05),载荷率对称性指数显示存在偏侧性。结论排球运动员优势腿和非优势腿之间的平衡能力存在偏侧性。在静态平衡能力方面,睁眼状态下,双下肢的静态平衡能力相似,而闭眼状态下,优势腿在矢状面的静态平衡能力更好,非优势侧的视觉补偿较多。在动态平衡能力方面,非优势腿优于优势腿,双下肢之间存在偏侧性。在排球运动员体能训练计划中应重点关注并加强非优势腿的闭眼静态平衡能力和优势腿的动态姿势控制训练,从而降低落地损伤的风险和提升单腿支撑发力动作的运动表现。
基金Supported by the National High Technology Research and Development Program of China ("863" Program) (Grant No.2007AA12Z216,2007AA120502)National Natural Science Foundation of China (Grant No.40701134)
文摘Most rainfall-induced landslide forecasting models focus on the relation between landslides and rainfall,which is one of the dynamic factors,and seldom consider the stacitc factors,such as geological and geograpical factors.Landslide susceptibility,however,is determinded by both static and dynamic factors.This article proposes a static and dynamic factors-coupled forecasting model(SDFCFM) of regional rainfall-induced landslides,which quantitatively considers both the static and dynamic factors that affect landslides.The generalized additive model(GAM) is applied to coupling both factors to get the landslide susceptibility.In the case study,SDFCFM is applied to forecast the landslide occurrences in Shenzhen during a rainfall process in 2008.Compared with the rainfall logistic regression model,the resulting landslide susceptibility map illustrates that SDFCFM can reduce the forecast redundancy and improve the hit ratio.It is both applicable and practical.The application of SDFCFM in landslide warning and prevention system will improve its efficiency and also cut down the cost of human and matreial resources.
