用溶胶-凝胶法合成La1-xCaxMn1.03O3(x≥0.5)薄膜的电磁性质

本文报道了用La、Ca、Mn的环烷酸盐溶液,采用溶胶－凝胶（sol-gel)方法,在LaAlO3(100）衬底上制备La1-xCaxMn1.03O3薄膜,并研究了它们的电磁性质。Ca含量x在0.5-0.621范围,电阻率随温度的变化关系,是从类半导体行为向金属导电行为转变,在x≥0.5的4个样品中并没有发现电荷有序绝缘体（COI）和反铁磁绝体（AFI）现象。     

冷原子吸收光谱法测定水中总汞

在盐酸或硝酸介质中,利用澳酸盐-溴化物试剂快速破开芳基—Hg和烷基—Hg两种键,将有机汞转变成无机汞,达到由水样中定量回收汞的目的。对还原性物质较多的废水则采用高锰酸钾预先氧化的方法提高消解速率,与常规硫酸-高锰酸钾消解法的可比性良好,适用于天然和废水中总汞的测定。     

La0.822Sr0.178MnxO3薄膜的输运性质

本文报道了用La、Sr、Mn的环烷酸盐溶液,采用两次旋转覆盖的溶胶－凝胶方法,在LaA-lO3(100)基底上合成了La0.822Sr0.178MnxO3薄膜,Mn含量x在0．944－1．196范围内,电阻率随着温度的变化关系,是从绝缘体内金属导电行为转变;对x＝0．9样品则表现为绝缘体,对x＝0．944样品,当T／Tc时,ρ∝exp(E/kT),说明载流子的迁移是以热激活方式进行的,热激活能为21meV;当T＜Tc时,符合ρ＝ρ0＋AT^2．5,说明电子－声子和电子－磁极化子散射占主要,对x＝0．97、0．99、1．196样品,T／Tc时则更好地符合指数关系。     

3种头发消解方法的对比研究

采用3种不同的消解方法处理同一发样,利用火焰原子吸收光谱法测定发样中Fe、Zn、Ca的含量,通过实验得出,3种消解方法对测定结果影响不大。对3种头发消解预处理方法进行分析比较,结果发现非完全消解法是值得推广的样品消解方法。     

微波消解-氢化物发生原子吸收光谱法测定食物中的汞

本文采用微波消解,氢化物发生原了上光谱测定食物中的汞,研究了微波消解样品的最佳条件,并和国家标准消解方法进行了比较,结果令人满意。     

La_(0.822)Sr_(0.178)Mn_xO_3薄膜的输运性质

本文报道了用La、Sr、Mn的环烷酸盐溶液 ,采用两次旋转覆盖的溶胶 凝胶方法 ,在LaA lO3( 10 0 )基底上合成了La0 .82 2 Sr0 .178MnxO3薄膜 .Mn含量x在 0 .94 4～ 1.196范围内 ,电阻率随着温度的变化关系 ,是从绝缘体向金属导电行为转变 ;对x =0 .9样品则表现为绝缘体 .对x=0 .94 4样品 ,当T >Tc 时 ,ρ∝exp(E/kT) ,说明载流子的迁移是以热激活方式进行的 ,热激活能为 2 1meV ;当T 相似文献   

ICP-AES测定湖泊沉积物中微量元素的样品微波消解研究

为正确测定鄱阳湖沉积物中微量元素而研究样品消解方法,采用密闭式微波消解系统处理样品,以ICP-AES法测定多种微量元素.分别从不同的消解液、用酸量、消解工序以及样品消解量等方面进行研究和优化,最终确定了一个最适合消解鄱阳湖沉积物的前处理消解体系为:消解样用量为0.5 g,180℃电热板上预处理约15 min,消解体系选择酸比例为4:4:2的HNO3-HF-H2O2体系和HNO3-HF-HClO4体系均可,消解工序为5 atm/3 min-10 atm/2 min-15 atm/5 min-20 atm/10 min的逐步加热工序.这种消解方法简单快速、效率高、劳动强度低,为以后鄱阳湖沉积物的测定做了样品准备工作.     

微波消解-CTAB增敏-HG-ICP-AES法测定中药黄芪中的痕量铅

采用微波消解技术处理样品,建立了CTAB增敏-氢化物发生-电感耦合等离子体发射光谱法(HG-ICP-AES)测定中药黄芪中痕量铅的分析方法。讨论了微波消解试剂、微波消解参数对消解效果的影响,系统地研究了氢化物发生的最佳条件。采用HNO₃+H₂O₂+H₂O为微波消解最佳试剂,在选定的最佳氢化物发生条件下,铅的线性范围为0.23～800 μg·L-1, 相关系数为0.999 9,检出限为0.23 μg·L-1,相对标准偏差为1.02%, 样品加标回收率为98.8%～100.1%。结果表明,微波消解法处理中草药,具有快速、简便、节省试剂、消解完全等特点,测定结果的精密度和准确度令人满意。     

微波消解-ICP-AES测定香烟接装纸中的汞、砷、铅、铬、镉和硒

采用HNO3-HCl-HF-H2O2消解体系对香烟接装纸进行湿法消解和微波消解,去除有机成分,保留待测元素。结果表明:不同种类的接装纸中各元素含量也不尽相同,但是大量吸烟对身体的有害程度还是显而易见的。采用微波消解-电感耦合等离子体-原子发射光谱法测定香烟接装纸中的As、Cd、Cr、Hg、Pb、Se等的含量。重金属元素加标回收率为96.7%—104.8%,检出限在0.000075—0.1288μg/mL范围内。     

碘催化合成α,α'-双亚苄基环己酮

研究了碘催化苯甲醛与环己酮反应合成了α,α’-双亚苄环烷己酮.考察了反应物摩尔比、催化剂用量、反应时间对收率的影响.实验结果表明,以二氯甲烷为溶剂,在回流条件下,当苯甲醛的加入量为0.1mol,环己酮的加入量为0.1 mol,即醛酮物质的量比为1∶1,催化剂用量5.1g,反应120min时,α,α'-双亚苄基环烷酮收率可达到72.8％,且具有很高的纯度.     

扩散平面光波导的传递函数方法

引入一种计算光波导传播特性的新方法传递函数方法。给出了公式推导,计算了扩散各向同性及扩散各向异性平面光波导的传播特性,并与其它方法所得结果进行了比较。结果表明用传递函数方法处理折射率渐变分布的光波导问题,计算相对简单,可以得到精确的数值结果。     

变焦距镜头高斯光学设计的新方法

突破了对像面漂移量的有理函数计算传统，考虑到组元运动曲线的间断性，给出了变焦距镜头高斯光学全新的最优化设计方法，供助于切比雪夫多项式，做到了任意组元联合直线运行的光学补偿，以及实现了简便的和有效的任意组元任意变焦方式的机械补偿。     

Reconstruction of holograms generated by using a combination of an iterative method and an error diffusion method

Two-level quantized phase holograms produced by using a combination of an iterative method and an error diffusion method are presented. By using a previously proposed iterative method, images reconstructed from two-level quantized phase holograms are rapidly improved with small amounts of iterative operations but further improvement of the image quality is difficult even if the iterations are greatly increased. Therefore, in order to exceed the improvement limitation of the image quality, the combination of the iterative method and an error diffusion method was used for the hologram-making process. Experimental results using the combination method showed better images than those obtained by the iterative method alone, when referred to results from synthesized holograms.     

原子力显微镜测试光学超光滑表面微轮廓的研究

论述了使用原子力显微镜测量超光滑光学表面的优点及其在光学领域中的重要应用。列举了用这种方法测试得到的超光滑光学表面微轮廓图及纳米量级的微缺陷,以及这些表面镀膜前后表面形态结构和微粗糙度的变化。作为比较,列举了用干涉轮廓仪测得相同表面的微粗糙度参数等８。由于原子力显微镜有三维的高精度,而干涉方法只有一维的高精度,所以前者可以得出表面真实形貌和微轮廓。     

镨钕氧化物(或合金)中稀土杂质元素的测定

用岛津ICPS-7500发射光谱仪测定镨钕氧化物(或合金)中的La、Ce、Sm、Y.试样经盐酸低温分解,制备成含0.6mol/L盐酸的待测试液,La、Sm、Y用直接法测量,Ce用固定法测量.回收率为98.20%-102.32%.     

URA编码孔径的层析成像

URA编码孔径成像是X射线成像的一项新技术.它不但提高了信噪比,而且具有层析分辨能力.本文详细论述了URA编码孔径的层析成像原理,并提供了一种改善层析成像质量的叠代方法.并应用迭代方法成功地进行了计算机模拟实验.     

An application of a transcorrelated procedure to the calculation of the energy of the hydrogen molecule

The ground-state energy of the hydrogen molecule is calculated using both the standard variational method and a new transcorrelated method. The value obtained with the new method compares favourably with that obtained by the standard method. If the method used in this paper can be extended to more complicated systems, it is expected that it will enable more accurate energies to be calculated for these systems than is possible using the standard variational method.     

Evaluation of spectral pretreatments,spectral range,and regression methods for quantitative spectroscopic analysis of soil organic carbon composition

Although there is an increasing interest in using infrared spectroscopy for the simple, rapid, and inexpensive prediction of soil organic carbon content, few studies have used this technique to measure organic carbon chemistry. In this paper, based on both near-infrared and mid-infrared diffuse reflectance spectroscopy, we compared the use of instrumentation, spectral pretreatment, and regression method for the prediction of three parameters related to organic carbon content, one related to isotopic composition, and five related to organic carbon chemistry. A total of 140 soil samples collected from seven oriental oak forest sites across East China were used as the data set for the calibration-validation procedure. Calibrations using sample set partitioning based on joint x-y distances method significantly outperformed those using Kennard-Stone method. Compared to models using linear method (i.e., partial least squares), those using non-linear regression method (i.e., support vector machines) greatly improved the prediction precision of the alkyl-to-O-alkyl ratio and performed slightly better for the other organic carbon chemical compositions. Instrumentation had a large effect as mid-infrared models had higher average prediction accuracies than near-infrared models. We finally proposed a model using second derivative preprocessing, joint x-y distances based sample set partitioning, mid-infrared spectra, and support vector machines regression to quantify organic carbon chemistry in this study. The results are helpful for the further study of soil composition measurement.     

利用级数展开的Z扫描理论分析

利用级数展开的方法，对薄介质的Z扫描理论进行了分析，并对于通常所采用的级数展开和菲涅耳衍射分析方法进行了讨论，证明了在分析利用高斯光束对薄介质进行Z扫描测量时，即使对于大的非线性相移，高斯分解方法和菲涅耳衍射积分方法仍具有等效性，澄清了人们认识上的一些误解。同时分析了远场小孔的归一化透射率与积分限的关系，并对采用高斯分解方法时级数求和的振荡原因进行了分析和讨论，给出了消除振荡所需的最小求和数的判据。针对高斯分解方法和菲涅耳衍射积分方法的使用场合，也进行了讨论。根据所得结论，可以在具体的实验和理论分析中，正确地选择更高效的分析方法。     

Synthetic aperture imaging using sources with finite aperture: deconvolution of the spatial impulse response

A method for ultrasonic synthetic aperture imaging using finite-sized transducers is introduced that is based on a compact, linear, discrete model of the ultrasonic measurement system developed using matrix formalism. Using this model a time-domain algorithm for deconvolution of the transducer's spatial impulse responses (SIRs) is developed that is based on a minimum mean square error (MMSE) criterion. The algorithm takes the form of a spatiotemporal filter that compensates for the SIRs associated with a finite-sized transducer at every point of the processed image. A major advantage of the proposed method is that it can be used for any transducer, provided that its associated SIRs are known. This is in contrast to the synthetic aperture focusing technique (SAFT), which treats the transducer as a point source. The performance of the method is evaluated with simulations and experiments, performed in water using a linear phased array. The results obtained using the proposed method are compared to those obtained with a classical time-domain SAFT algorithm. For a finite aperture source, it is clearly shown that the resolution obtained using the proposed method is superior to that obtained using the SAFT algorithm.