LOW-FREQUENCY INTERNAL FRICTION STUDY FOR SrBi2Ta2O9 FERROELECTRIC CERAMICS

Low-frequency internal friction (IF) of SrBi₂Ta₂O₉(SBT) ceramics has been measured at temperatures ranging from 293 to 623 K. Two IF peaks, with their locations around 393 K (P1) and 569 K (P2) (f≈1.58 Hz), respectively, are observed. P1 is found to be associated with a relaxation process with activation energy of 0.97 eV and pre-exponential factor of 3.58×10^-14 s. Peak shape analyses reveal that P1 can be well described by a broadened Debye peak with the width parameter β from 2.70 to 2.92. The mechanism responsible for P1 is proposed to be relaxation of oxygen vacancies near domain walls(DWs). P2 is considered to arise from viscous motion of DWs since it shows characteristics of static hysteresis type. Comparisons for the IF behavior between SBT and Pb(Zr, Ti)O₃(PZT) suggest that in SBT oxygen vacancies are much less localized near DWs than that in PZT. This result provides a possible explanation for the weak DW pinning due to oxygen vacancies in SBT.     

利用智能手机定量测量楼梯、电梯高度与垂直速度

随着智能手机与内置传感器技术的不断进步,利用智能手机探索物理实验逐渐增多.文章基于智能手机内置气压传感器(pressure sensor)和phyphox应用软件,定量测量人行楼梯、电梯升降高度与垂直速度.实验结果证实了该方法的可行性,测量精度在可接受范围.研究项目既增强了物理实验趣味性,又激发了学生学习兴趣和探究欲望...     

Geometric quantities of lower doubly excited bound states of helium

Expectation values of single electron and interelectronic geometric quantities such as $\langle r\rangle$, $\langle r_{12}\rangle$, $\langle r_<\rangle$, $\langle r_>\rangle$, $\langle \cos\theta_{12}\rangle$ and $\langle \theta_{12}\rangle$ are calculated for doubly excited $2{\rm p}n{\rm p}\,{}^1P^{\,\rm e}\,(3\leq n\leq5),\, 2{\rm p}n{\rm p}\,{}^3\!P^{\,\rm e}\,(2\leq n\leq5)$ and $2{\rm p}n{\rm d}\,{}^{1,3}D^{\,\rm o}\,(3\leq n\leq5)$ states of helium using Hylleraas-$B$-spline basis set. The energy levels converge to at least 10 significant digits in our calculations. The extrapolated values of geometric quantities except for $\langle \theta_{12}\rangle$ reach 10 significant digits as well; $\langle \theta_{12}\rangle$ reaches at least 7 significant digits using a multipole expansion approach. Our results provide a precise reference for future research.     

Polarization Self-Modulation Phenomenon in a Free Oscillated Nd：YAG Laser

Polarization self-modulation effect in a free oscillated Nd：YAG laser is investigated after a quarter wave plate is introduced independently in the two positions of the cavity. As described in the previous experiments, the intensity components in the orthogonal directions are modulated with a period of the round-trip time or twice. Different pulse shapes reveal that the seed field from the spontaneous emission is not uniform and seems to be stochastic for each pulse.     

自由基浓度测定方法的再验证及其在煤化学中应用

对前人建立的标准曲线法测煤中自由基浓度进行优化,以DPPH标准样品和基准样品的二次积分面积比值为新参数,结果显示新参数标准曲线法的实测值与理论值相对误差都在5%以内;重复性、复现性实验的相对标准偏差都小于3%。将新参数标准曲线法用于分析不同煤化程度煤和新疆黑山煤(HS)沥青质的自由基浓度,发现随着煤化程度增加,其煤中自由基浓度逐渐增大,从低阶褐煤的8.531×10~(17)/g上升到高阶无烟煤3.37899×10~(19)/g;而在HS煤液化过程中,随着加氢液化温度的升高,其沥青质自由基浓度逐渐下降,从290℃的1.5793×10~(18)/g降到450℃的7.410×10~(17)/g,沥青质自由基浓度变化趋势与其产率变化趋势相一致。     

测定饲料中喹乙醇含量的反相高效液相色谱法

建立了高效液相色谱法测定饲料中喹乙醇含量的方法 ;饲料用甲醇 -水提取 ,在380nm波长下检测 ,色谱柱为NOVA_PakC18(3.9mm×150mm ,4μm) ,流动相为甲醇 -水 (体积比为10∶90) ,流速为1.0mL/min ,喹乙醇质量浓度在2.5～20.0mg/L范围内与峰面积呈良好线性关系 ,相对标准偏差为1.2 %～1.6 % ,回收率为97 %～101%。     

部分药、食两用花卉中微量元素含量分析

采用原子吸收分光光度法对部分药、食两用花卉中微量元素进行了分析,并与普通叶菜类进行了对比。     

3-杂环硫亚甲基头孢菌素衍生物的半合成及抗菌活性研究

通过取代噁二唑硫酮、噻二唑硫酮及三唑硫酮分别和头孢菌素母体7-ACA反应,制得14种7-氨基-3-杂环硫亚甲基头孢菌素新母体2a-2n,用1-芳基-5-甲基-1H-1,2,3-三唑-4-甲酰氯与头孢菌素新母体缩合,制得2种新的7β-(1-芳基-5-甲基-1H-1,2,3-三唑-4-甲酰胺基)-3-(2-取代1,3,4-bI二唑-5-硫亚甲基)头孢菌素4c,4d.新化合物结构经元素分析、IR、¹HNMR及FAB-MS确认.初步体外抗菌结果表明,新母体化合物2对革兰氏阳性菌有抑制活性且在相同浓度下比7-ACA强20倍,而头孢菌素4c,4d对革兰氏阳性和阴性菌都有显著抑制活性.     

用于红外光谱检索的IRS-1程序

由于光谱、波谱技术在化学中的广泛应用,至今已积累了数量十分庞大的标准谱图(仅红外光谱一项就巳超过十万张),利用电子计算机对这些谱图数据进行存贮、检索,已日益受到重视并成为计算机在化学中应用的一个重要方面。从1979年5月起,我们进行了有机化合物谱图信息的计算机存贮、检索以及电子计算机辅助结构解析的研究,编制了供红外光谱检索用的IRS-1程序,并于今年年初完成了该程序检索性能的考核。 IRS一1程序以文献报导的标准红外光谱谱图为数据源。谱图信息的抽提是按预先规定的闭值和规则,自6.6~16.0协m波长范围内以0.1卜m为间隔,采用二进制的形式进行光谱数据的编码。     

层层纳米自组装锆基色谱填料的表面性质研究

硅胶具备了许多色谱载体应具有的合适的表面物理化学参数.但硅基填料可使用的pH值范围较窄及其表面裸露的硅羟基对碱性物质和含N生物大分子的不可逆吸附等缺点限制了其在一些重要领域中的应用.氧化锆由于其优异的化学稳定性,特别是对碱性化合物和生物大分子的分离适应性而在色谱应用方面受到极大的关注[1,2],极有可能成为通用的色谱基质填料之一[3].本文旨在制备具有良好表面性质的锆基色谱填料,结合硅胶和氧化锆的优点,采用层层纳米自组装方法(LbL)[4]在微米硅胶球模板表面包覆多层纳米氧化锆颗粒,制备了新型氧化锆基质填料ZrO2/SiO2,…