PLZST反铁电陶瓷电场诱导相变与相稳定性的研究

在三方铁电(FE)-四方反铁(AFE)的准同型相界附近制备了一系列组份为(Pb_0.97La_0.02)(Zr_1-x-ySn_yTi_x)O₃(x=0.09或0.1;0.16≤y≤0.38)的反铁电陶瓷.研究了Sn含量y对电场诱导AFE→FE相变电场E_c、反铁电双电滞回线损耗ΔE、以及温度诱导FE→AFE相变温度T_FE，AFE→顺电(PE)相变温度T_c的影响.沿AFE-FE相界Ti含量一定的条件下，E_c随着Sn含量y的增加而增大，ΔE减小，T_FE与T_c均降低.场诱相变的回线参量E_c，ΔE与相变温度T_FE和T_c相关联.在直流偏压下用原位X-射线衍射表征了相变时晶格结构的变化，结果表明，当电场达到AFE→FE相变临界场时，伴随相变的发生，晶格结构由四方相转变为三方相，晶胞体积增大. 关键词：     

Self‐Assembled Single‐Crystal Polyaniline Microplates and Their Anisotropic Electrical Transport Property

Self‐assembly of two‐dimensional (2D) structures from functional molecules is of great scientific importance. Herein, using a typical linear conducting polymer, polyaniline as building blocks, 2D single crystalline microplates are successively produced. The structure of 2D microplates is clearly defined by selected area electron diffraction, X‐ray diffraction, and Raman spectroscopy. Owing to the anisotropic arrangement of linear conjugated PANI molecules, the microplate shows a typical anisotropic electrical transport property.

     

扩压器几何参数对离心风机噪声的影响

本文试验研究了扩压器几何参数对一高速离心风机的噪声的影响。扩压器的几何参数包括叶片数、叶轮与扩压器的径向间隙和倾斜前缘倾角以及它们的耦合作用对风机噪声的影响。试验结果表明:(1)风机A声级噪声随扩压器叶片数增加而下降,但气动性能也随之下降;(2)扩压器前缘半径从R_3/R_2=1.03增加到1.07,在设计点风机A声级噪声降了约3 dB(A),继续增大至1.09则基本不变;(3)适当倾斜扩压器前缘可有效降低风机噪声,在设计点30°倾角扩压器相应的风机A声级噪声下降了约3.6 dB(A);(4)倾斜扩压器前缘与增大径向间隙的降噪效果不能叠加。     

搅拌器内部流动的无网格法三维数值模拟

本文将移动粒子半隐式法(MPS)的基本算法由二维扩展至三维。将圆柱坐标系引入到初场粒子的布置中,避免了在笛卡儿坐标系下处理不规则形状(如斜边或曲边)问题时粒子初场布置困难和精确度较低的问题,改善了对计算边界条件表达的精确性。引入移动边界模型,对直叶片搅拌器的内部流动进行了三维数值模拟。还提出了一种新的初始粒子布置简易方法,明显简化粒子初始布置时的复杂程度,提高了对三维复杂几何形状问题的可操作性。     

分形花及其网络上的平均测地距离

借助圆周映射计算距离函数在自相似测度上的积分,本文利用自相似测度得到分形花上的平均测地距离,并将此结果应用于分形花网络.     

雷诺校正法在煤发热量测定中的应用

介绍雷诺校正法计算煤发热量的原理、算法及应用.方法应用于燃煤发热量计算,结果表明,用雷诺校正法处理煤发热量测定时,其结果优于瑞方公式法和奔特公式法,与国标法相比,分析误差在规定范围内.在文中列出了雷诺校正法处理煤发热量的实用Matlab源程序.     

Mg2+-ENRX体系的荧光特性及恩诺沙星含量的测定

基于镁(Ⅱ)对恩诺沙星的荧光强度有显著的增敏作用,建立了镁(Ⅱ)增敏,荧光光度法快速测定恩诺沙星的新方法.在pH5.5的酒石酸-酒石酸钠缓冲溶液中,恩诺沙星在1.00×10-8-1.00×10-6mol/L范围内符合比耳定律,方法检出限为7.5×10-10mol/L.已用于片剂中恩诺沙星的测定,样品平均回收率为93.91％,RSD=0.55％.实验表明,该方法简单、快速、灵敏、准确.     

仿长耳鸮翼型的参数化研究

以长耳鸮翼型为仿生原型,采用逆向工程方法提取鸮翼翼型下表面特征点并利用B样条曲线进行拟合建立鸮翼仿生重构模型。通过数值求解耦合Langtry-Menter SST模型的雷诺时均Navier-Stokes方程,研究了仿生翼型的前缘弧线曲率、前缘厚度、前端倾角、翼型中部下表面曲率以及尾部厚度等参数对翼型升阻比的影响,获得了一种能有效抑制大攻角下流动分离发生的仿生翼型。正交试验结果表明:翼型前缘厚度对仿生翼型的升阻比影响最大,随着翼型前缘厚度的减少,翼型升阻比增加;翼型下表面中部曲率和翼型尾部厚度均存在最优值使仿生翼型升阻比最大。     

Determination of the calcium species in coal chars by Ca K-edge XANES analysis

Ca-based additives have been widely used as a sulfur adsorbent during coal pyrolysis and gasification. The Ca speciation and evolution during the pyrolysis of coal with Ca additives have attracted great attention. In this paper, Ca species in the coal chars prepared from the pyrolysis of Ca(OH)2 or CaCO3-added coals are studied by using Ca K-edge X-ray absorption near-edge structural spectroscopy. The results demonstrate that Ca(OH)2 , CaSO4 , CaS and CaO coexist in the Ca(OH)2-added chars, while Ca(OH)2 and CaSO4 are the main species in the Ca(OH)2-added chars. Besides, a carboxyl-bound Ca is also formed during both the pyrolysis for the Ca(OH)2-added and the CaCO3-added coals. A detailed discussion about the Ca speciation is given.