矿化剂对铝酸钙粉的结构与光谱性能的影响

研究了矿化剂对制备铝酸钙粉的结构与性能的影响.研究中以铝矾土和石灰石为原料,加入一定量的矿化剂,混合均匀,经高温煅烧制得铝酸钙粉.借助于红外光谱、X射线粉末衍射、差热-热重分析等手段对不同原料的铝酸钙粉的结构、组成及性能进行了表征和研究,并对矿化剂在合成铝酸钙中的矿化机理进行探讨.研究表明:加入矿化剂后,可在更低温度条件下煅烧制备出铝酸钙粉,有利于节能减排.红外光谱分析、XRD分析、DTA-TG分析显示:未加矿化剂煅烧时,生成的产物主要是Ca3Al10O18,CaAl2Si2O8.加入矿化剂后煅烧生成的产物主要是易浸出Al2O3的CaAl3BO7和Ca3Al10O18,而不易浸出Al2O3的CaAl2Si2O8的含量大大降低.同时显示,加入矿化剂后,原料中的方解石(CaCO3)分解更容易;CaCO3与铝矾土反应更充分;更有利于促使铝矾土中的Al-Si键断裂,将铝矾土中的Al释放出来;并可降低铝酸钙的煅烧温度.研究还显示:加入矿化剂后,可以改变原产物的晶体结构与成分,有利于降低煅烧反应温度.     

Damage and fracture prediction of plastic-bonded explosive by digital image correlation processing

By digital correlation processing of Scanning electronic microscopy (SEM) images, the paper presents the deformation and damage analysis of an energetic material—the plastic-bonded explosive (PBX) on mesoscopic scale. The analysis is made by observing the deformation field resulted from the digital image correlation (DIC) processing of the images corresponding to the loading steps and comparing with the surface profiles of the composite material so as to visualize the matter damage near a preset crack. The results show that the local deformation disturbance can reveal the material damage even happened underneath the specimen surface. The strain distribution in the front of the preset crack, can be used to predict the propagating route of the microcrack initiated from the tip of the pre-crack, which is related to the splitting fracture of the granular-based composite under compressive loading.     

Measuring the performance of the coaxial HOM coupler on a 2-cell TESLA-shape copper cavity

Coaxial High Order Mode (HOM) couplers have been fabricated at Peking University and their RF performance has been measured on a test device consisting of a coaxial transmission line and a 2-cellTESLA-shape copper cavity. The test results on the 2-cell TESLA-shape copper cavity with HOM couplers indicate that the coupler can cut off the fundamental mode TM010 and absorb HOMs effectively after a careful adjustment. The optimal angle of the HOM coupler with the beam tube is found. The initial test results of HOM couplers are presented in this paper.     

偏瘫患者辅助下肢外骨骼设计与仿真分析

针对偏瘫患者外骨骼康复机器人降低外骨骼质量的要求,设计了一种辅助下肢外骨骼机器人,采用柔索驱动的膝关节,具有结构简单,质量轻的特点。同时利用ADAMS建立了外骨骼关节柔索驱动的动力学模型,绳索模块建立了柔索驱动模型,通过Ariel生物运动分析软件,采集髋、膝、踝关节运动数据,运用Spline函数进行了仿真分析。经过仿真分析柔索驱动在上台阶运动过程中的不同拉簧预紧力和拉簧刚度下传动特性和驱动力矩,为进一步研究设计下肢外骨骼提供依据。     

面阵探测下的污染云团红外光谱仿真

研究污染云团的红外光谱仿真,对于利用仿真光谱进行光谱识别的算法研究十分重要.在单元探测器探测方式下污染云团的红外光谱仿真研究取得了一定成果,并且已经被应用于识别算法的研究工作中.针对基于成像光谱仪的污染云团识别算法研究缺乏实测数据的问题,利用具有高仿真精度的基于物理模型的污染云团扩散模型及其仿真结果网格化的特点,研究相应的云团红外光谱仿真多层模型,提出了面阵探测方式下污染云团红外光谱的仿真方法,生成了同时具有光谱维和空间维信息的数据立方体,为该研究领域提供了新的研究方法.提出的面阵探测方式下的污染云团红外光谱仿真直观地反映了污染云团的扩散,提供了完备且符合实际情况的污染云团红外光谱立方体数据,对于提高和完善红外光谱识别算法具有重要意义.     

利用Ag@SiO_2纳米粒子等离子体共振增强发光二极管辐射功率的数值研究

金属纳米粒子利用其局域表面等离子体共振效应(LSPR),可以增强附近荧光分子的自发辐射速率,因而在光学传感、光电器件等领域中具有潜在的应用价值.金属纳米粒子的LSPR与其自身的材料、形状、尺寸以及周围环境介质密切相关,这影响着纳米粒子在具体器件中的应用.本文利用三维时域有限差分法,研究了相同体积的球形、椭球形、立方形与三棱柱形银纳米粒子对薄膜发光二极管辐射功率的影响;计算了不同形状银纳米粒子对偶极子光源辐射功率和薄膜器件光出射强度的增强,并结合LSPR效应讨论了辐射功率变化的物理机理.研究结果表明:银纳米粒子自身形状尖锐程度的增加有利于提高LSPR的共振强度;同时纳米粒子的形状影响了LSPR共振电场与薄膜器件中偶极子辐射电场之间的耦合作用,其中立方形纳米粒子因为能实现最强的耦合作用而对器件的辐射功率增强最大.在此基础上进一步讨论了不同薄膜材料对LSPR共振及光源辐射功率的影响,发现较高的材料折射率有利于增强金属纳米粒子的LSPR与器件的耦合作用,从而改善发光二极管性能.     

High-temperature impedance spectroscopy of BaFe0.5Nb0.5O3 ceramics doped with Bi0.5Na0.5TiO3

Bi_0.5Na_0.5TiO₃ (BNT)-doped BaFe_0.5Nb_0.5O₃ (BFN) ceramics were synthesized by a two-step solid-state reaction. Temperature dependence of dielectric properties measured at different frequencies was investigated over broad temperature and frequency ranges. Impedance spectroscopy and universal dielectric response were employed to study the relaxation behavior and conductivity mechanism of the ceramics in a frequency range from 40 Hz to 100 MHz and a temperature range from 300 K to 800 K. The complex plane impedance data revealed the bulk and grain boundary contributions toward conductivity processes in the form of semicircular arcs. The high-temperature conductivity of ceramics is attributable to thermally activated second ionized oxygen vacancy.     

制备工艺对Zn1-xMgxO薄膜结构及光学性能的影响

采用脉冲激光沉积（PLD）方法在单晶Si（100）衬底上沿c轴方向生长单晶Zn_1-xMg_xO薄膜,通过X射线衍射（XRD）、原子力显微镜（AFM）、扫描电镜（SEM）和荧光光谱（PL）研究了膜厚、Mg含量、退火温度及氧气氛等制备工艺对Zn_1-xMg_xO薄膜的结构、形貌和光学性质的影响.实验结果表明,Mg含量x≤0.15时, Zn_{关键词： 1-x}Mg_xO薄膜')" href="#">Zn_1-xMg_xO薄膜 制备工艺 结构 光学性质