内燃机车主整流柜均流随车检测初探

本文针对内燃机车硅整流装置的故障问题,介绍了新的随车检测方案,可实现对整流柜均流值的实时检测.在分析整流装置及整流元件电流的基础上,提出了均流系数检测的不同方法,论述了检测过程中的关键技术问题,设计了整套软硬件方案.     

Grain refinement of low carbon steel produced by CSP process

In comparison with conventional production for hot strips, compact strip production (CSP) brings about some new micro-structural phenomena. Investigations were carried out to clarify the grain refinement mechanism of low carbon steel strips produced by the EAF-CSP process. Samples, obtained from the same rolling stock during continuous rolling, were examined through SEM,TEM and XEDS. Thin slabs have a dominant columnar structure and the spacing of the secondary dendrite arms ranges from 90 to ～125 μm. The average grain sizes for the central area of the samples from the 1st to 6th pass are 41.6, 25.2, 21.4, 20.2, 13.1, 6.7 μm,respectively. Large number of nanometer oxide and sulfide have been found in the low carbon steel produced by the CSP process.The grain refinement mechanism can be summarized as follows: finer solidification structure of the thin slab; austenite recrystalliza-tion at higher temperature and stain accumulation at lower temperature caused by the great reduction of single rolling pass during continuous rolling; nano-scaled precipitates of sulfide and oxide which drag grain boundaries of austenite or ferrite to prevent the grain coarsening.     

Droplet Deformation and 2-D/3-D Marangoni Flow Phenomena in Droplets Levitated by Electric Fields

An integrated numerical model is presented for free surface phenomena and Marangoni fluid flows in electrically levitated droplets under both terrestrial and microgravity conditions. The model development is based on the boundary element solution of the Maxwell equations simplified for electrostatic levitation applications and the free surface deformation that is primarily caused from the surface Maxwell stresses resulting from the applied electric fields. The electric and free surface model is further integrated with a finite element model for the surface-tension-induced fluid flows in the levitated droplets. Both 2-D and 3-D fluid flow structures may be developed in the electrically levitated droplets depending on the applied laser heating sources. The integrated model is applied to study the electric field distribution, free surface deformation, and 2-D and 3-D internal fluid flow structures in normal and microgravity for single, symmetric two-beam, four-beam, and six-beam laser heating arrangements. Among these arrangements, the six-beam arrangement with equal heating intensity gives the smallest temperature difference and the smallest maximum velocity.     

入侵检测系统概述

该文首先介绍了入侵检测系统的发展过程,接着阐述了入侵检测系统的功能、模型、分类,并在入侵检测系统的结构和标准化上做了深入的探讨。然后详细研究了入侵检测系统的检测技术,最后指出了目前入侵检测系统中存在的问题,提出了入侵检测系统的发展前景。     

Stimulated Collision-induced Fluorescence in XeCl-laser-pumped Barium Vapour at High Buffer-gas Pressures

Abstract

New stimulated collision-induced fluorescence lines at 551·9, 606·3 and 611·1 nm were observed in XeCl-laser-pumped barium vapour at high buffer-gas pressures. They correspond to barium 6s6d ³D₂-6s6p ³P₁ and 5d6p ³P_{2, 1}-6s5d ³D_{3, 2} transitions, following a preceding spin-forbidden transition 6s7p ¹P₁-6s6d ³D₂. A similarity was found to exist between this 6s7p ¹P₁-6s6d ³D₂ transition and the well studied 6s6p ¹P₁-6s5d ³D₂ transition.     

1 000 MW高效宽负荷率的超超临界锅炉开发

根据反平衡法对电站锅炉各项效率损失进行分析，潜力较大的是排烟损失和未完全燃烧损失，主要影响因素有过量空气系数、排烟温度、燃烧效率；1 000 MW高效宽负荷率超超临界煤粉锅炉的开发采用低过量空气系数设计理念，在炉膛选型、受热面布置、燃烧系统设计、降低锅炉漏风等方面采取措施。与传统设计相比，50% THA负荷下锅炉效率提升了0.96%。     

Deformation and fracture mechanisms of in situ synthesized TiC reinforced TC4 matrix composites produced by selective laser melting

In this study, TiC/TC4 composites were fabricated using selective laser melting (SLM), and the deformation mechanism and fracture characteristics of the composites with nano-sized TiC particles formed in situ were studied. The experimental results showed that the rapid melting and solidification characteristics of SLM and the Marangoni effect of the liquid pool promoted a considerably homogeneous dispersion of the in situ-formed nanoscale-TiC reinforcement in the TiC/TC4 composites. In particular, an enhanced compressive strength of 1490.2 MPa and a considerable fracture elongation of 21.5% were simultaneously achieved for the TiC/TC4 composites, which could be attributed to the load transfer effect and the formation of denser and more uniformly distributed dimples. Combined with the finite element (FE) analysis, the uneven stress distribution in the shear band of the TiC/TC4 composites led to the fracture. Further, the fracture surface analysis showed that the in situ nanoscale TiC reinforcement promoted the fracture of microbubbles from the α/β interface with the concentrated distribution of the V element to the interface between TiC and the Ti matrix because of the load transfer, which promoted the uniform distribution of the V element in the dimple.     

网络安全技术及策略在校园网中的应用研究

计算机技术的快速发展,也导致网络安全形势日益严峻。网络安全技术对于人们日常生活、工作以及学习所产生的影响愈发深远。在校园网络系统中,部分非法入侵者会将目标设定到某一局域网当中,从而导致正常的教学秩序受到干扰,对此必须要采取一些行之有效的应对策略,来保障校园网的正常运行。     

Colorimetric artificial nose for identification of Chinese liquor with different geographic origins

Colorimetric artificial nose was used to characterize and identify Chinese liquors from six different geographic origins. Using chemical dyes as the sensing elements, the developed colorimetric artificial nose showed a unique pattern of color changes upon its exposure to Chinese liquors. Data analysis was performed by chemometric techniques: Hierarchical cluster analysis (HCA), principal component analysis (PCA) and linear discriminant analysis (LDA). Each category of Chinese liquor could cluster together in PCA score plot. No errors in classification by HCA were observed in 45 trials. LDA model showed a 100% of prediction ability for Chinese liquor. The results demonstrated that colorimetric artificial nose was able to classify Chinese liquors from different geographic origins.