Optical diffraction gratings embedded in BK-7 glass by low-density plasma formation using femtosecond laser

The optical embedded diffraction gratings with the internal refractive index modification in BK-7 glass plates were demonstrated using low-density plasma formation excited by a high-intensity femtosecond (130 fs) Ti: sapphire laser (λp=790 nm). The refractive index modifications with diameters ranging from 400 nm to 4 μm were photoinduced after plasma formation occurred upon irradiation with peak intensities of more than 1×1013 W/cm2. The graded refractive index profile was fabricated to be a symmetric around the center of the point at which low-density plasma occurred. The maximum refractive index change (Δn) was estimated to be 1.5×10-2. Several optical embedded gratings in BK-7 glass plate were demonstrated with refractive index modification induced by the scanning of low-density plasma formation.     

Analysis of sensitization phenomenon in friction stir welded 304 stainless steel

This study evaluates the degree of sensitization (DOS) of 304 stainless steel joined by friction stir welding (FSW). Single-loop electrochemical potentiokinetic reactivation tests were performed using a 0.5 mol/L H₂SO₄ + 0.01 mol/L KSCN solution. Sensitization was promoted by exposition of the stainless steel at temperatures between 400°C and 850°C. The microstructure was characterized using optical microscopy to identify the weld zone and the base metal. The samples treated at 550°C showed the most severe intergranular corrosion. The DOS was lower in the weld zone than in the base metal after heat treatments. This reduction in the DOS for the weld zone indicates that FSW is a beneficial process in joining stainless steel.     

Effects of Boron Addition on Grain Refinement in TiAl-based Alloys

Solid state phase transformation characteristics of the body centred β(Ti) into the hexagonal closed packed α(Ti) in Ti45Al8Nb-(0, 0.3, 0.5 and 0.8 at. pct) B alloys were investigated by heat treatment to clarify γ/α2 lamellar microstructure refinement induced by B addition. Experimental results confirmed two kinds of boron-reduced grain refinement mechanisms through refining either β phase then α phase (β-refinement) or α phase directly (α-refinement) to refine lamellar microstructure at room temperature; ...     

考虑弹塑性本构的三维模态变形体离散元方法断裂模拟

三维模态变形体离散元(3MDEM)是针对离散块体系统在小应变、有限位移、有限转动条件下,用变形模态模拟块体变形,经过严格推导建立的一种离散元方法.该文在3MDEM平台实现对结构从弹性、到塑性再到断裂破坏的连续非连续全过程模拟.鉴于传统的接触破坏准则在塑性计算中的缺陷,该文提出基于塑性应变的接触破坏判断准则,并采用双块体...     

单向偏心结构的简化增量动力分析方法

增量动力分析方法(IDA)可以较为全面的评估结构的抗震性能,但需对结构进行大量的非线性时程分析,计算量巨大.该文将单向偏心结构的等效二自由度模型(EDDOF)应用于增量动力时程分析,提出了单向偏心结构的简化增量动力分析方法.然后选取20条实际地震记录和一栋5层偏心结构,基于等效二自由度模型和原型模型分别进行了增量动力时...     

Influence of Voids on the Tensile Performance of Carbon/epoxy Fabric Laminates

This paper aims at investigating the effect of voids on the tensile properties of [(±45)4/(0,90)/(±45)2] S and [(±45)/0 4/(±45)(0,90)] S composites.Specimens with void contents in the range of 0.4% to 9.0% were fabricated from carbon/epoxy fabric.The void content was determined by ultrasonic attenuation and optical image analysis,and microscopic inspection was also used to analyze the shape and size of the voids.The influence of voids on the tensile strength and modulus of both stacking sequence is compared in terms of the size and the shape of the voids.The effect of voids on the initiation and propagation of tensile failure of both stacking sequence composite was investigated.     

Preparation and Properties of Smart Thermal Control and Radiation Protection Materials for Multi-functional Structure of Small Spacecraft

Considering the unique properties of small spacecraft,such as light weight,low power-consumption and high heat flux density,a new kind of lightweight boron carbide(B 4 C) radiation-protection coating material was proposed.New techniques for preparing LSMO thermal control coating and B 4 C radiation-protection coating were developed.The sample piece of multi-functional structure was manufactured by using the proposed materials,and a series of performance tests,such as thermal control and radiation-protection behaviors were evaluated.Test results show that:the emissivity of the multi-functional structure varies from 0.42 to 0.86 at 240 K to 353 K and the phase transition temperature is about 260 K.The electron radiation-protection ability of the multi-functional structure is 3.3 times better than that of Al material.The performance index of this multi-functional structure can meet the requirements for space application in on-board electronic equipment.     

碱性染料在贵金属催化光度法中的应用

近年来,传统光度分析中常用的碱性染料在贵金属的催化光度法中得到了普遍应用,该方法操作简便,试剂易得,对责金属测定灵敏度很高,是一种具有较大发展空间和应用前景的分析方法.通过介绍碱性染料催化光度法测定责金属的方法原理及操作方法,综述了目前已建立并用于测定贵金属的多种碱性染料催化体系及其应用现状,总结方法的优点及存在的不足...     

粗煤气铁矿颗粒床高温除尘联产直接还原铁工艺及估算

在煤灰熔点高于直接还原铁还原温度200℃的条件下,以直接还原竖炉作为移动颗粒床除尘器为核心技术的3段连续除尘,以铁矿煤球团为直接还原铁原料和移动颗粒床除尘颗粒,粗煤气显热可以直接用于生产直接还原铁。粗煤气显热约占煤炭气化热值的13%,估算联产直接还原铁显热利用效率可达70%以上,与现有的粗煤气废锅发电比,综合热效率提高约2倍,直接还原铁能耗303kg（C）/t.Fe,可以实现温室气体近零排放,减排CO₂约1.7t/t.Fe。可以在不减少粗煤气化学热能（H₂+CO）,联产直接还原铁的同时解决粗煤气的高温除尘与净化问题。     

美国低碳炼铁新技术进展及应用前景分析

美国开发的低碳炼铁新技术主要有氢气闪速熔炼法和熔融氧化物电解法.介绍了氢气闪速熔炼法和熔融氧化物电解法的研究进展,对其应用前景进行了分析.