To improve the competitive relationship between strength and toughness,the effect of low undercooling in austenite(γ)on the microstructure and mechanical properties of commercial vanadium-containing wheel steels was ...To improve the competitive relationship between strength and toughness,the effect of low undercooling in austenite(γ)on the microstructure and mechanical properties of commercial vanadium-containing wheel steels was studied using an optical microscope(OM),a scanning electron microscope(SEM),a transmission electron microscope(TEM),and mechanical property tests.The results show that when the wheel steel is slightly cooled to an appropriate temperature above A c3 point for a short time after it has been austenitized at an elevated temperature,the solid-solved vanadium is pre-precipitated in the form of V(C,N)second phase semicoherent with the matrix in the originalγgrain.This phase hardly participates in matrix strengthening.Due to the small mismatch between V(C,N)and ferrite(α),during the subsequent-cooling phase transformation stage,the pre-precipitated second phase becomes theαnucleation point,causing granular and ellipsoidal intragranular ferrite(IGF,with an average size of 4-6μm)to nucleate in the originalγ.The IGF production and strength loss increases with the increasing undercooling degree.Based on this,Masteel Co.,Ltd.has developed a new heat-treatment step-cooling process that can promote the formation of IGF,considerably improving the level and uniformity of fracture toughness on the premise that the strength and hardness of the wheel are almost unchanged.展开更多
随着云计算的发展与普及,云计算环境下的安全问题日益突出.云取证技术作为事后追责与惩治技术手段,对维护云计算环境安全具有重大意义.云取证技术研究发展尚处于早期,云取证面临电子证据不完整、取证开销较大、取证过程智能化不足等难题...随着云计算的发展与普及,云计算环境下的安全问题日益突出.云取证技术作为事后追责与惩治技术手段,对维护云计算环境安全具有重大意义.云取证技术研究发展尚处于早期,云取证面临电子证据不完整、取证开销较大、取证过程智能化不足等难题.为缓解这些问题,提出一种基于软件定义安全(software defined security,SDS)和云取证趋势分析的智能云取证方法.首先,提出一种基于软件定义安全的云取证架构,实现云网络与云计算平台协同实时取证.其次,提出基于隐Markov模型的云取证趋势分析算法,实现云取证架构中的智能取证策略决策和智能取证资源调度.实验结果表明:相较于单独的网络取证与云计算平台取证,该方法取证能力提高至91.6%,而取证开销则介于两者之间.该方法对云服务商提供云取证服务具有广泛的借鉴意义.展开更多
文摘To improve the competitive relationship between strength and toughness,the effect of low undercooling in austenite(γ)on the microstructure and mechanical properties of commercial vanadium-containing wheel steels was studied using an optical microscope(OM),a scanning electron microscope(SEM),a transmission electron microscope(TEM),and mechanical property tests.The results show that when the wheel steel is slightly cooled to an appropriate temperature above A c3 point for a short time after it has been austenitized at an elevated temperature,the solid-solved vanadium is pre-precipitated in the form of V(C,N)second phase semicoherent with the matrix in the originalγgrain.This phase hardly participates in matrix strengthening.Due to the small mismatch between V(C,N)and ferrite(α),during the subsequent-cooling phase transformation stage,the pre-precipitated second phase becomes theαnucleation point,causing granular and ellipsoidal intragranular ferrite(IGF,with an average size of 4-6μm)to nucleate in the originalγ.The IGF production and strength loss increases with the increasing undercooling degree.Based on this,Masteel Co.,Ltd.has developed a new heat-treatment step-cooling process that can promote the formation of IGF,considerably improving the level and uniformity of fracture toughness on the premise that the strength and hardness of the wheel are almost unchanged.
文摘随着云计算的发展与普及,云计算环境下的安全问题日益突出.云取证技术作为事后追责与惩治技术手段,对维护云计算环境安全具有重大意义.云取证技术研究发展尚处于早期,云取证面临电子证据不完整、取证开销较大、取证过程智能化不足等难题.为缓解这些问题,提出一种基于软件定义安全(software defined security,SDS)和云取证趋势分析的智能云取证方法.首先,提出一种基于软件定义安全的云取证架构,实现云网络与云计算平台协同实时取证.其次,提出基于隐Markov模型的云取证趋势分析算法,实现云取证架构中的智能取证策略决策和智能取证资源调度.实验结果表明:相较于单独的网络取证与云计算平台取证,该方法取证能力提高至91.6%,而取证开销则介于两者之间.该方法对云服务商提供云取证服务具有广泛的借鉴意义.
