Depolarization and Electrical Response of Porous PZT 95/5 Ferroelectric Ceramics under Shock Wave Compression

The release of bound charges by shock wave loading of poled lead zirconate titanate （PZT 95/5） ferroelectric ceramics can result in a high-power electrical energy output. In this study, a theoretical formulation describing the depolarization and electrical response of porous PZT 95/5 ceramics in the normal mode to shock wave compression loading perpendicular to the polarization direction is developed. The depoling process in porous poled PZT 95/5 ceramics is analyzed by using a parallel circuit consisting of a current source, capacitance, conductance and a circuit load. This modeling takes the effects of porosity on wave velocity and remanent polarization and dielectric constant into account, and the effects of variations in dielectric constant and conductivity in the shocked region are assessed. The output current characteristics of porous PZT 95/5 ceramics under short-circuit and resistive load conditions are analyzed and compared with the experiment, with the results showing that theoretical predictions taking into consideration the porosity of ferroelectric ceramics are in close agreement with the experimentally measured electrical response of porous PZT 95/5 under shock wave compression loading.     

图说“雾霾”和PM_(2.5)

<正>"雾霾"、"灰霾"和"霾""雾(Fog)"是由近地面细小水滴或冰晶组成,影响能见度小于1km的气象现象。成雾时,相对湿度通常高于90%。当相对湿度在70～90%之间,能见度下降在1～5km之间时,则称为"轻雾(Mist)"。纯净水气较难凝结,大气中凝结核(CCN)的存在会促使云雾水滴的形成。     

含吩噻嗪锌、镉配合物的双光子激发荧光光谱

报道了两种新型配体(10-乙基-3-甲酰吩噻嗪缩肼基二硫代甲酸甲酯(HL¹)及10-乙基-3-甲酰吩噻嗪缩肼基二硫代甲酸苄酯(HL²))及其锌、镉配合物的双光子(激发)荧光性质. 入射激光强度与荧光强度关系的实验测定证明了发射光为双光子激发荧光. 比较了它们在800和400 nm激发波长下的双光子激发光谱和单光子激发光谱特性. 在800 nm的脉冲激光的激发下, 它们均显示出较强的峰值位于550 ~ 595 nm的双光子激发荧光. 用开孔Z-扫描装置测得它们在1064 nm处均具有较大的双光子吸收截面.     

高效率掺Tm~(3+)双包层光纤及光纤激光器的研制

掺Tm3+光纤激光器有着广泛的应用前景,而掺Tm3+光纤是其核心与关键.本文采用改进的化学汽相沉积(MCVD)工艺和气相液相复合掺杂技术,在MCVD机车上实现了掺Tm3+石英光纤预制棒的制备,并制备了掺Tm3+石英双包层光纤(芯包比为10/125).利用上述光纤搭建直腔型全光纤激光器,在波长为793nm的LD抽运下,获得激光光谱中心波长为2002 nm,最大的激光输出功率30.7 W,光纤斜率效率为59.32%.     

高频红外碳硫分析仪测定土壤、粘土中的硫

应用高频红外碳硫分析仪测定土壤、粘土中的硫含量,对助熔剂的选择、分析时间、吹氧流量及称样量等分析条件进行优化后对标准样品中的硫含量进行测定,测定结果均在标准值范围内。土壤样品测定结果的相对标准偏差为5.10%(n=8),粘土样品测定结果的相对标准偏差为5.51%(n=8)。该方法对实际样品的测定结果与硫酸钡重量法测定结果相吻合。     

蜘蛛丝Ⅲ:超级抗损伤网

介绍蜘蛛丝独特的线弹性-软化-强非线性硬化的应力应变曲线对建造超级抗损伤的和超级带缺陷工作能力的蜘蛛网的作用.这种独特力学性质使得蜘蛛网一旦局部靶载荷超载,承载网丝在经历软化大变形后急剧非线性硬化,独自承担过量载荷,直至断裂,而其余网丝的内力继续保持在安全范围内,实现损伤局部化与极小化.仅改变一下应力应变曲线的形状,就使网具有了超级抗损伤能力,体现了蜘蛛应用力学知识的神奇.     

固相萃取-HPLC法测定蜂蜜中残留的10种磺胺类药物

研究了用固相萃取-高效液相色谱法同时测定蜂蜜中10种磺胺类药物残留量的方法。样品经三氯甲烷溶液提取,过Oasis HLB C18固相萃取柱净化,用乙腈洗脱10种磺胺,反相高效液相色谱-紫外检测器测定。检测波长为270nm,柱温45℃．流动相：磷酸水溶液-乙腈梯度洗脱．该方法前处理简单,梯度洗脱分离效果和重现性好,在0．010～1．0mg／kg添加水平,10种组分的回收率在86．5％～100．8％之间,室内相对标准偏差在3．5％～8．1％之间,线性范围为0．010～10μg／mL,检出限为0．005mg／kg。该方法快速、灵敏、专属,可用于食品中磺胺类药物残留量的常规检测。     

The basis of organic spintronics： Fabrication of organic spin valvesl

Organic spintronics focuses on utilizing the spin degree of freedom in organic materials because of the long spin relaxation time. The vertical organic spin valve （OSV） is a typical sample structure used to study the spin transport phe- nomena. However, the fabrication of high quality OSVs is difficult, which results in controversial experiment results and hence hinders the development of organic spintronics. In this work, we describe our recent study on the fabrication of typical vertical organic spin valves, Lao.67Sro.33MnO3 （LSMO）/Alq3/Co. The LSMO bottom electrodes are annealed to obtain an atomically smooth surface and improved magnetic properties. The top Co electrodes are deposited by an indirect deposition method to reduce the interfusion between Co and Alq3. The controlled fabrication process provides much better performance and sample yield of OSVs.     

多场耦合下透平冷却高温影响特性

透平进口温度持续提高,使得实验测试条件难以实现全温全压的测量,往往采用降温降压工况。本文采用耦合数值方法,分别针对耦合气膜冷却平板及耦合叶栅模型,分析多场耦合下的高-低温传热特征,探索透平冷却温度水平影响特性及机理。研究表明,综合冷却效率分布受金属、流体物性及内外部冷却多方面综合影响;比较无量纲参数相同的高-低温工况,高温使得有TBC涂层时综合冷效偏高,无TBC涂层时综合冷效偏低;无量纲参数相同的高-低温工况,在平板上综合冷却效率分布规律基本一致,在叶栅表面压力面和前缘较为一致,其余部分相差较多;在一定的温度差距内,高-低温工况结果仍可保持一定的一致性。