Axi-symmetric wave propagation in a cylinder coated with a piezoelectric layer

This paper presents the wave propagation in a cylinder coated with a thin piezoelectric layer. The piezoelectric coupling effects are fully modeled in the mechanics model for this piezoelectric coupled cylindrical shell with bending resistance. The decoupled torsional wave velocity and the dispersion curves for the two- mode shell model are obtained theoretically. The cut-off frequency and phase velocities at limit wave number are also derived. The numerical simulations are conducted to present the results of wave propagation in this cylindrical shell and as well as to compare the results by the current bending theory and the membrane shell theory. From the comparisons, the results display obvious deference of wave propagations in terms of dispersion characteristics by different shell theories when thicker piezoelectric layer are used and when higher wave number is considered. The results of this paper can serve as a reference for future study on wave propagation in coupled structures as well as in the design of smart structures incorporating piezoelectric materials.     

一种提高生物体拉曼光谱痕量测量精度的方法

微量物质拉曼光谱测量精度的提高是拉曼分析技术的难点之一,特别是高荧光背景下生物体中微量物质的测量。根据拉曼谱峰突发、离散特点,分别给出荧光背景和噪声拟合函数,通过监测总体拟合偏差A类不确定度函数实现拉曼谱峰定位和干扰信号滤波;进一步根据谱峰位置划分光谱区间,在单调区间内弱化非谱峰信号,实现谱峰信号增强。与其他光谱处理方法比较,可以准确拆分重叠特征峰,不会降低特征峰高度,提供更加灵敏的半谱峰面积指标。实验表明,该方法在处理皮肤拉曼光谱时,可以准确得到螺旋构象的酰胺I带、神经酰胺和CO的归属拉曼谱峰;另外经过该方法处理后数据建立水溶性糖(水稻叶片)含量测量模型,其精度优于小波分解、多项式拟合和非线性最小二乘法。     

Photoionization of Ru(bpy)32+ ions in aqueous solutions containing sodium dodecyl sulfate. Influence of ion binding

Sodium dodecyl sulfate (SDS) augments the yield of biphotonic ionization of tris-2,2′-bipyridyl ruthenium(II) ions (3.75×10⁻⁵ mol dm⁻³) in aqueous solution at room temperature to different extents at two different concentration ranges: by a factor 4 at [SDS] just below the critical concentration for precipitation (4.5×10⁻⁴ mol dm⁻³) and by a factor 1.4 at [SDS] above the critical micellar concentration (8×10⁻³ mol dm⁻³). The augmentation of the photoionization yield is explained in terms of ion binding, i.e. electrostatic interaction between Ru(bpy)₃²⁺ ions and dodecyl sulfate ions which results in a partial charge neutralization with the consequence of a decrease in the ionization potential.     

An unusual electrochemically induced demetalation of iron-substituted Keggin-type undecatungstozincate ZnW11FeIII(H2O)O7−39

Firstly reported for Fe-containing transition metal substituted polyoxometalates was an unusual Fe-centered demetalation process induced by the reduction of ZnW₁₁Fe^III to ZnW₁₁Fe^II, which resulted in a new couple of Fe-relating redox waves at positive potentials.     

Study on Molybdenum(v)-Thiocyanate Complex in Solvent of Dimethyl Sulfoxide with Water in Different Proportional Volume by Spectrophotometry

The stability constant(β_i), molar absorbency (Δε_i), and percentage of composition([MoO(SCN)_i]^3-i%) (i=1,2,3) of molybdenum(V)-thiocynate complex were determined. All reagents employed are analytical grade.     

高效液相色谱法快速测定冰淇淋中的糖精钠

用高效液相色谱法快速测定了冰淇淋中的糖精钠。使用反相径向加压柱,紫外检测定量。样品用硫酸铜及氢氧化钠处理后,滤液不用萃取即可上机检测。方法的最低检测限为0．38mg／kg,变异系数为1．72％,回收率为96．25％。     

新型二维气相色谱系统的理论研究──双柱条件对保留时间及峰扩展的影响

从色谱动力学角度推导出微填充柱-毛细管柱二维气相色谱系统流出曲线一级矩及二级中心矩的表达式,并据此讨论了柱温、柱间分流比等条件对保留时间及峰扩展的影响规律。结果表明:柱间分流是主毛细管柱与预微填充柱之间联系的纽带,分流比是影响峰特征的重要因素。预柱条件的改变对二维气相色谱保留时间及峰扩展的影响较小。双柱条件对峰特征的影响表现出一些特殊的规律性。     

Free vibration of thermo-elastic microplate based on spatiotemporal fractional-order derivatives with nonlocal characteristic length and time

A fractional-order thermo-elastic model taking into account the small-scale effects of the thermo-elastic coupled behavior is developed to study the free vibration of a higher-order shear microplate. The nonlocal strain gradient theory is modified with the introduction of the fractional-order derivatives and the nonlocal characteristic length. The Fourier heat conduction is replaced by the non-Fourier heat conduction with the introduction of the fractional order and the memory characteristic tim...     

多值Φ-强伪压缩映象不动点和多值Φ-强增生映象方程解的Ishikawa迭代逼近

在一般的Banach空间中,研究了多值Φ-强伪压缩映象不动点和多值Φ-强增生映象方程解的Ishikawa迭代逼近问题.     

双钙钛矿卤化物Cs2AgFeX6（X = Cl，Br，I）电子结构和光学性质的第一性原理研究

近年来,银卤化物双钙钛矿作为铅基杂化卤化物钙钛矿的潜在环保替代品得到了广泛的研究。最近实验上合成的新型无铅双钙钛矿单晶材料Cs2AgFeCl6是一种立方结构半导体,吸收光谱可拓宽至800 nm。本论文采用密度泛函理论的第一性原理方法,对Cs2AgFeX6（X = Cl,Br,I）的电子结构和光学性质进行研究,讨论了二者之间的内在关联,并分析了X位元素的改变对材料性质的影响。电荷密度计算结果显示,由Cl到I,Fe-X键逐渐减弱,即原子对电荷的束缚能力减弱。另一方面,三种材料的带隙宽度是逐渐减小的,Cs2AgFeCl6和Cs2AgFeBr6带隙分别为1.40 eV和0.91 eV,而Cs2AgFeI6则呈现金属性质。Cs2AgFeX6双钙钛矿的光谱特征峰随 X 位原子序数的增加明显红移,且在可见至红外光波段均有明显的光吸收：Cs2AgFeCl6在534 nm处的吸收系数达到21.28×104 cm-1,Cs2AgFeBr6在712 nm处的吸收系数为20.54×104 cm-1,而Cs2AgFeI6在1200 nm后的红外波段有一极宽的吸收峰,吸收系数可以达到10×104 cm-1。本论文为Cs2AgFeX6（X = Cl,Br,I）在光电子器件领域的广泛应用提供了理论指导。