Recent progress on laser-induced breakdown spectroscopy for the monitoring of coal quality and unburned carbon in fly ash

Our recent progress on developments of laser-induced breakdown spectroscopy (LIBS) based equipments for on-line monitoring of pulverized coal and unburned carbon (UC) level of fly ash are reviewed. A fully software-controlled LIBS equipment comprising a self-cleaning device for on-line coal quality monitoring in power plants is developed. The system features an automated sampling device, which is capable of elemental (C, Ca, Mg, Ti, Si, H, Al, Fe, S, and organic oxygen) and proximate analysis (Q _ad and A _ad) through optimal data processing methods. An automated prototype LIBS apparatus has been developed for possible application to power plants for on-line analysis of UC level in fly ash. New data processing methods are proposed to correct spectral interference and matrix effects, with the accuracy for UC level analysis estimated to be 0.26%.     

傅里叶望远镜部分周期信号解调及对成像的影响

为了解决傅里叶望远镜高功率短脉宽激光只能包含部分周期信号的难题,本文提出多脉冲拼接技术并对其基本原理和应用范围进行深入研究.首先介绍高功率短脉宽激光与声光移频器移频带宽之间的矛盾,进而引出利用傅里叶望远镜传统时间解调公式进行部分周期信号解调存在的困难.然后给出多脉冲拼接技术的基本理论,推导出理想情况下移频频率、脉冲重复率和脉宽满足的拼接条件.进而详细分析移频频率稳定性和脉冲重复率稳定性对多脉冲拼接成像结果的影响,并通过计算机仿真研究一般情况下脉宽变化对多脉冲拼接成像结果的影响.最后得出移频频率和脉冲重复率对成像无影响,激光脉宽变化小于25％仍可识别目标轮廓的结论.     

Single 3D laser projector with speckle suppression

In this letter, a new single three-dimensional （3D） laser projector is proposed. As liquid crystal （LC） can produce two image patterns with orthogonal polarization states at 120 Hz, only one projector is required in this approach for reconstruction of a 3D object. The light source is made up of RGB （red, green, and blue） lasers because laser has lots of advantages such as longer life, higher brightness, and larger color gamut. A novel diffusive media with good polarization-maintaining quality is used as rear projection screen for its high transmission efficiency （-90%） and low reflection efficiency. When laser incidents into the diffusive media, which contains lots of spherical particles with sizes between 2 and 15 μm, laser is scattered randomly and the laser speckle is reduced. A spatial phase mask is also inserted into the optical path to reduce speckle. With these techniques, the speckle contrast is reduced to 0.1 and the quality of image oatterns has been greatlv imoroved.     

Mg2+掺杂Li4Ti5O12陶瓷靶材的制备及其性能研究

本实验以Mg(OH)2作为镁源,将1wt;、2wt;、3wt;、4wt;、5wt;的Mg(OH)2粉末与纯Li4Ti5O12粉末球磨混合,使用粉末冶金的方法烧结制备出了Mg2+掺杂的Li4Ti5O12陶瓷靶材,分别研究了烧结温度为880 ℃、900 ℃、930 ℃、950 ℃、980 ℃时Mg2+掺杂Li4Ti5O12陶瓷靶材的收缩率、致密度和力学性能的变化情况;通过对Mg2+掺杂Li4Ti5O12陶瓷靶材进行XRD衍射分析和断面的SEM分析可以得出,Mg(OH)2的最佳掺杂量为4wt;,陶瓷靶材的最佳烧结温度为950 ℃.可以得到抗弯强度为83.189 MPa、相对密度为96.041;、维氏硬度为的364.26HV500、物相单一的Mg2+掺杂的Li4Ti5O12陶瓷靶材.     

无机填料在改性两亲性水凝胶防污材料中的应用研究

水凝胶防污材料因其环保特性成为当前海洋防污领域的研究热点,然而其黏附及力学性能的不足仍是限制其实际应用的技术关键。本研究在油性结构单元增加黏附的两亲性水凝胶的基础上,通过物理共混引入Al₂O₃、 TiO₂、蒙脱土和高岭土赋予两亲性水凝胶涂层更多的黏附机制并考察它们对水凝胶涂层其它性能的影响。研究发现,随着无机填料的引入和含量的增加,水凝胶涂层的黏附性能大幅增加,静态泡板和动态划水的不脱落时间分别提高6倍和2.5倍。其中,TiO₂和高岭土能使水凝胶涂层的应力明显增强。虽然,无机填料的加入使两亲性水凝胶涂层抑制牛血清蛋白及小新月菱形藻吸附的能力下降,但在实海挂板实验中依然表现出相当的防污能力,且具有一定的实际应用价值。本研究为探讨无机填料对水凝胶涂层性能的影响提供了一些参考,并对提高两亲性水凝胶涂层黏附及力学性能提供了一种策略。     

傅里叶望远镜外场实验与结果分析

为了分析外场环境因素对傅里叶望远镜成像质量的影响和验证成像过程不受下行链路大气扰动影响的特点,开展了傅里叶望远镜外场实验研究.外场实验在室内实验的发射光学系统的基础上增加了主镜、次镜和会聚透镜组对目标散射光进行3次会聚仿真实际系统的成像过程,同时将目标与主镜、主镜与次镜分别拉开100 m距离验证成像系统不受下行链路大气扰动影响的特点.实验利用胶片打印的2种不同的卫星图片作为目标,获得了Strehl值分别为0.44、0.39的无大气扰动的外场重构图像和Strehl值分别为0.43、0.38的含大气扰动的外场重构图像.通过比较外场重构图像与室内重构图像的Strehl值,得出发射光学系统中光束的振动对成像有较大影响.分析发现无大气扰动外场重构图像与含大气扰动外场重构图像的Strehl值相近,从而验证傅里叶望远镜成像过程不受下行链路大气扰动的影响.     

微凹坑织构表面对脂润滑关节轴承摩擦特性的影响

为研究脂润滑下表面织构对关节轴承摩擦特性的影响,设计和制造了4组表面高度算术平均值相同、表面微凹坑面积占有率分别为7%、10%、15%和21%的关节轴承内圈表面形貌.使用Talysurf CCI Lite非接触式三维轮廓仪对试件表面进行测量,采用ISO25178定义的表面参数对试件表面形貌进行表征.在改造的HDM-20端面摩擦磨损试验机上,采用2#锂基脂润滑在不同载荷、转速条件下进行了一系列摩擦磨损试验,研究了表面形貌参数与摩擦系数的关系.在本试验中,选取表面高度算术平均值Sa和表面峰态Sku等表面高度参数、表面峰区平均材料体积Vmp、表面中心区平均空体体积Vvc和表面谷区平均空体体积Vvv等表面功能参数以及平均谷体积Sdv等表面特征参数对关节轴承表面形貌进行表征.结果表明:各表面参数对摩擦系数的影响不同,将表面高度参数、功能参数和特征参数这几种表面形貌参数结合对关节轴承表面形貌进行表征,更有利于脂润滑下关节轴承表面形貌的摩擦学设计.     

Frequency stabilization of diode laser to 1.637 μm based on the methane absorption line

The frequency of an external-cavity diode laser has been stabilized to 1.637 μm by using the reference of absorption lines of methane. The method can be applied to wavelength division multiplexed optical communication, fiber-optic sensing systems, as well as the high-sensitivity detection of methane. The derivative-like error signal yielded by frequency modulation and phase sensitivity detection technology is inputted into the PI feedback loop circuit in order to stabilize the frequency to the line center. After stabilization, the frequency fluctuation of diode laser is held within 5.6 MHz, and the root of Allan variance of error signal reaches a minimum of 1.66×10-10 for an average time of 10 s.     

Theoretical analysis of cavity saturation spectroscopy of weak molecular absorbance

A theoretical analysis of sub-Doppler molecular saturation spectroscopy by use of a confocal Fabry Perot (CFP) cavity is presented. The effects of gas pressure, cavity length and mirror reflectivity on the saturation dip amplitude are analysed. Such a treatment can provide the optimum conditions and a guidance for the experiment of saturating the weak molecular absorption lines.     

细长旋成体亚声速超大攻角非定常流动特性研究

空空导弹作为现代空战的主要攻击手段,要求比目标飞机更高的机动性和敏捷性.新型空空导弹在面对新一代飞机时必须具备全方位攻击能力,尤其对来自后方目标的威胁,则需要更高转弯率和更大机动包络线的航向反转机动等先进高效机动方法.为了保证高效机动的顺利完成,要求导弹在超大攻角(α=0° ～180°)范围内具有飞行和机动控制能力.以...