太阳能溴化锂吸收式制冷循环的改进

由于单效溴化锂吸收制冷循环受太阳能热源温度较低的限制,需要采用适当的辅助手段.本文对增压辅助型太阳能溴冷机循环流程提出了在冷凝器前加装隔离阀的改进方案,该方案可降低发生压力,以充分利用低温热源,并可有效回收压缩功.通过计算分析了改进循环的热力系数COP与热源温度和循环溶液质量分数差的关系.给出了在不同的热源温度下对应的最佳发生压力的调整范围.     

整式概念学习中常见错误例析

<正>整式分为单项式与多项式,对单项式与多项式的有关概念,教材中都作了严格的界定.但由于学生对概念的内涵理解不透彻、不到位,导致做题时出错;抑或对概念的外延所包含的特殊对象了解不够,认识不足,导致做题时出错.以下笔者结合实例,作一分析!1 在区分单项式和多项式时出错单项式与多项式只有一字之差,但意义却完全不同.单项式是数与字母的乘积组成的代数式,它包括三种类型：单独的数字;单独的字母;数与字母的乘积.     

黄铁矿处理重金属废水的光谱表征

将反射光谱和吸收光谱用于黄铁矿处理酸性重金属废水的研究,探讨了黄铁矿的表面反应以及黄铁矿与重金属的相互作用。漫反射红外光谱分析证实,在处理废水过程中,黄铁矿中表面羟基与重金属离子发生反应;并通过考察黄铁矿中碳酸盐,合理解释了黄铁矿处理酸性重金属废水后的溶液自然均趋于中性(pH 7)的现象。可见区的反射光谱用于表征处理过程中的黄铁矿的颗粒及比表面变化,解释了黄铁矿在重复使用时其活性反而增强的原因。吸收光谱及XPS表征表明,黄铁矿处理含Cr(Ⅵ)废水,是一个由Cr(Ⅵ)到Cr3+再到Cr(OH)₃的吸附沉淀过程。     

脉冲激光在液体中激发的声波特性研究

理论上分析了脉冲激光在液体中产生的声波波阵面随光声源形状的变化,以及不同激发机制下光声脉冲波形的差别,并从实验中得出了脉冲CO2激光光声脉冲频谱特性.结果表明光声波波阵面为球面或柱面,热弹机制激发双极性的光声脉冲,汽化机制激发单极性的光声脉冲,CO2脉冲激光在水中激发的声波频谱峰值主要在100 kHz以下.通过选择光声源的形状和激发机制可以获得所需的光声信号.     

有机/无机复合功能材料倒脊型波导热光开关

利用溶胶-凝胶技术自主合成了一种具有优良光学特性和高热稳定性的有机/无机复合芯层材料.这种功能材料的分子中含有有机柔性侧链,可形成环氧交联.与无机SiO2-TiO2体系相比,具有较高的热光系数(量级为10-4/K),以及更好的成膜性和可加工性.通过与实验室自行配制的P(MMA-GMA)包层材料相匹配,设计制备了基于这种有机/无机复合功能材料的倒脊型波导马赫-曾德尔型热光开关.器件的波导与热电极性能良好.插入损耗为10dB,驱动功率15mW,开关时间小于1ms,消光比15dB.     

Transport properties and magnetoresistance in La0.8Te0.2MnO3/ZrO2 composites

The transport properties and magnetoresistance of electron-doped manganate / insulator composites (La_0.8Te_0.2MnO₃)_{1 - x}/(ZrO₂)_x (x=0, 0.3, and 0.5) are investigated. It is found that the metal-insulator transition temperature of this system shifts to a lower value as the ZrO₂ content increases. The introduction of ZrO₂ enhances both the domain scattering and electron relative scattering in the metal transport region. In the adiabatic small polaron hopping transport region, the thermal activation energy seems invariable regardless of the ZrO₂ content. The application of a magnetic field promotes the charge transportation capabilities of the composites, and the magnetoresistance is enhanced with an increase of the ZrO₂ content. This could be attributed to the more remarkable modification effect of magnetic field on ordering degree in the composites than in pure La_0.8Te_0.2MnO₃.     

基于刀口仪的空气成像演示实验

利用刀口仪和球面反射镜设计了空气成像演示仪.将热源置于球面反射镜和刀口仪点光源之间,改变空气的温度分布,使球面反射镜的反射光线发生偏折,在刀口后方即可以直观地观察到热空气流动的状态,即实现空气成像的演示实验.该演示实验装置简单,使用CCD采集图像,现象明显且易于观察,利于学生理解光学检测技术中刀口仪的原理.     

All polymer asymmetric Mach-Zehnder interferometer waveguide sensor by imprinting bonding and laser polishing

We present an all polymer asymmetric Mach–Zehnder interferometer(AMZI) waveguide sensor based on imprinting bonding and laser polishing method. The fabrication methods are compatible with high accuracy waveguide sensing structure. The rectangle waveguide structure of this sensor has three sensing surfaces contacting the test media, and its sensing accuracy can be increased 5 times compared with that of one surface sensing structure. An AMZI device structure is designed. The single mode condition, the length of the sensing arm, and the length deviation between the sensing arm and the reference arm are optimized. The length deviation is optimized to be 19.8 μm in a refractive index range between1.470 and 1.545. We fabricate the AMZI waveguide by lithography and wet etching method. The imprinting bonding and laser polishing method is proposed and investigated. The insertion loss is between-80.36 dB and-10.63 dB. The average and linear sensitivity are 768.1 d B/RIU and 548.95 dB/RIU, respectively. And the average and linear detection resolution of the sensor are 1.30×10~(-6) RIU(RIU: refractive index unit) and 1.82×10~(-5) RIU, respectively. This sensor has a fast and cost-effective fabrication process which can be used in the cases of requiring portability and disposability.     

声子晶体中的多重拓扑相

研究了圆环型波导依照蜂窝结构排列的声子晶体系统中的拓扑相变.利用晶格结构的点群对称性实现赝自旋,并在圆环中引入旋转气流来打破时间反演对称性.通过紧束缚近似模型计算的解析结果表明,没有引入气流时,调节几何参数,系统存在普通绝缘体和量子自旋霍尔效应绝缘体两个相;引入气流后,可以实现新的时间反演对称性破缺的量子自旋霍尔效应相,而增大气流强度,则可以实现量子反常霍尔效应相.这三个拓扑相可以通过自旋陈数来分类.通过有限元软件模拟了多个系统中边界态的传播,发现不同于量子自旋霍尔效应相,量子反常霍尔相系统的表面只支持一种自旋的边界态,并且它无需时间反演对称性保护.     

一类对偶平坦的球对称的芬斯勒度量

In this paper,we study spherically symmetric Finsler metrics.By analysing the solution of the spherically symmetric dually flat equation,we construct several new families of dually flat spherically symmetric Finsler metrics.