迁移理论与三段式教学法在工业催化原理教学中的应用

将迁移理论与三段教学法相结合,深入探讨学习迁移理论所涉及的各种因素对工业催化原理课教学效果的影响,归纳总结迁移理论在三段式教学实践中的应用策略,为大学理论课教学提供参考依据.     

Studies on induction hardening of powder-metallurgy-processed Fe-Cr/Mo alloys

Induction hardening of dense Fe-Cr/Mo alloys processed via the powder-metallurgy route was studied. The Fe-3Cr-0.5Mo, Fe-1.5Cr-0.2Mo, and Fe-0.85Mo pre-alloyed powders were mixed with 0.4wt%, 0.6wt%, and 0.8wt% C and compacted at 500, 600, and 700 MPa, respectively. The compacts were sintered at 1473 K for 1 h and then cooled at 6 K/min. Ferrite with pearlite was mostly observed in the sintered alloys with 0.4wt% C, whereas a carbide network was also present in the alloys with 0.8wt% C. Graphite at prior particle boundaries led to deterioration of the mechanical properties of alloys with 0.8wt% C, whereas no significant induction hardening was achieved in alloys with 0.4wt% C. Among the investigated samples, alloys with 0.6wt% C exhibited the highest strength and ductility and were found to be suitable for induction hardening. The hardening was carried out at a frequency of 2.0 kHz for 2-3 s. A case depth of 2.5 mm was achieved while maintaining the bulk (interior) hardness of approximately HV 230. A martensitic structure was observed on the outer periphery of the samples. The hardness varied from HV 600 to HV 375 from the sample surface to the interior of the case hardened region. The best combination of properties and hardening depth was achieved in case of the Fe-1.5Cr-0.2Mo alloy with 0.6wt% C.     

预应力加载条件下零件干磨削表面强化层特征

采用预应力复合干磨削加工技术,对未调质45#钢试件在不同预应力加载条件下实施表面磨削淬硬,观测不同磨削深度和进给速度条件下的试件表层金相组织,测量并分析试件在不同预应力条件下磨削淬硬层厚度、金相组织的变化状况,并通过试件截面不同位置硬度测定显示淬硬层厚度及金相成分的变化,得到试件施加预应力对淬硬强化层厚度的影响规律.研究表明,预应力淬硬磨削能使工件表面产生强化层,且大的磨削深度和小的进给速度有利于试件表面发生相变强化以及表层塑性变形的增大.     

A survey of occlusion detection method for visual object

Occlusion problem is one of the challenging issues in vision field for a long time , and the occlu-sion phenomenon of visual object will be involved in many vision research fields .Once the occlusion occurs in a visual system , it will affect the effects of object recognition , tracking, observation and operation , so detecting occlusion autonomously should be one of the abilities for an intelligent vision system .The research on occlusion detection method for visual object has increasingly attracted atten-tions of scholars .First, the definition and classification of the occlusion problem are presented . Then, the characteristics and deficiencies of the occlusion detection methods based on the intensity image and the depth image are analyzed respectively , and the existing occlusion detection methods are compared.Finally, the problems of existing occlusion detection methods and possible research directions are pointed out .     

高校图书馆大规模馆藏精准迁移模式探讨--以华北电力大学图书馆为例

书库藏书迁移的运作主要在于精心准备和周密筹划。详细介绍了华北电力大学图书馆利用汇文文献信息服务系统的强大分析功能并结合Excel软件的使用技巧,实现大规模馆藏迁移精准排架工作的经验。     

数据中心启发式反向人工蜂群虚拟机整合节能策略

针对数据密集型作业的特点,提出一个基于CPU和图形处理器(GPU)两个影响因素构建计算节点的能耗评估模型.该模型基于原虚拟机选择节能算法(ABCS)在虚拟机选择节能策略中的能效优势,进一步利用启发式思想改进蜂群优化算法,寻求虚拟机整合的最优解.在CloudSim 3.0云计算模拟器中的实验结果表明,启发式反向蜂群算法能在保证服务质量的前提下,有效降低虚拟机迁移次数,进而降低数据中心的能耗(节能25%~30%).     

对象迁移自动机在TDT中的聚类研究

对象迁移自动机(OMA)是一种能够较好地解决话题识别与跟踪(TDT)中聚类问题的方法,但是,传统OMA模型由于聚类速度慢等缺点,难以满足TDT实时和增量聚类的要求.针对这一问题,本文一方面改进传统的OMA模型中自动机的动作设计,同时提出文档选择策略,加快了OMA的聚类速度.改进的方法在中等文档集上进行了实验,实验结果表明,该方法具有较好的聚类效果.     

污染物在二层非饱和土中运移过程综合分析

假设填埋场下部为具有压实黏土衬里（CCL）、下卧土层及含水层的三层结构体系,基于Richards方程,在稳态渗流下,得到了CCL与下卧土层体积含水率的解析解.依据污染物在多孔介质中运移机制,建立了污染物在包含两层非饱和土层的三层结构体系中运移的一维计算模型.在计算模型中分别考虑了CCL的非线性吸附特性、污染物运移过程中的生物降解特性、垃圾的生物降解特性等.采用所建立的数学模型,对某一假想填埋场进行了具体计算,通过变动参数计算与分析,探讨了各种因素对污染物运移的影响.计算结果表明,非饱和土层的吸附与生物降解可显著影响污染物运移,特别是CCL的吸附与生物降解特性影响更为显著,为污染物运移的控制因素.非饱和土的体积含水率较大时,含水率变化对污染物运移影响较小.     

面向可扩展集群环境的快速虚拟机迁移方法

在集群环境下,为了提高虚拟机Xen的迁移效率,提出了一种面向可扩展集群环境的快速可靠的虚拟机迁移方法.通过在分布式文件系统GlusterFS中增加Heartbeat监测模块,实时监测集群环境中物理机节点的加入与退出,动态创建或修改GlusterFS文件系统的配置文件.为了使GlusterFS文件系统能够自动管理节点,设...     

电迁移加速氯盐传输作用下混凝土中钢筋锈蚀

采用电迁移氯离子法加速了混凝土中钢筋的锈蚀过程.应用腐蚀电位、线性极化法、电化学阻抗谱法和循环极化法对比了C50与C80混凝土试件中钢筋的锈蚀行为.比较了混凝土保护层的开裂情况和钢筋的腐蚀形貌.分析结果表明:掺硅灰的C80试件具有优化的孔结构和较大的电阻率,显著延缓了氯离子到达钢筋表面的时间,因而表现出较好的耐蚀性;而...