Dielectric,impedance and modulus spectroscopy of Ta-based layered perovskite

PbBi₂Ta₂O₉ ceramic samples were fabricated by high-temperature mixed oxide method. X-ray diffraction determines the structure as orthorhombic. The scanning electron microscopy confirms the formation of densely packed grains in the sample. The dielectric measurements, complex impedance and complex modulus study were carried out in a frequency range of 1?kHz–1?MHz and a temperature rangeof 25–500°C. The conduction mechanism of the material is discussed in details using variable range hoping, nearest neighbor hopping relaxation model and dc activation energy at two different temperature regimes. From the J-E characteristics studies, the occurrence of non-linear curves endorses the non-Ohmic nature of the material.     

传送带类问题归类分析

本文中的传送带类问题是指以皮带传送装置(传送带)为载体而构建的各类物理问题．传送带类问题丰富多彩，能够很好地再现物理知识和考查各种能力，因而值得我们分类探究．     

Modeling and testing of static pressure within an optical fiber cable spool using distributed fiber Bragg gratings

Based on the force analysis, we establish a theoretical model to study the static pressure distribution of the fiber cable spool for the fiber optic guided missile (FOG-M). Simulations indicate that for each fiber layer in the fiber cable spool, the applied static pressure on it asymptotically converges as the number of fiber layers increases. Using the distributed fiber Bragg grating (FBG) sensing technique, the static pressure of fiber cable layers in the spool on the cable winding device was measured. Experiments show that the Bragg wavelength of FBG in every layer varies very quickly at the beginning and then becomes gently as the subsequent fiber cable was twisted onto the spool layer by layer. Theoretical simulations agree qualitatively with experimental results. This technology provides us a real-time method to monitor the pressure within the fiber cable layer during the cable winding process.     

一种光纤光栅水听器灵敏度校准技术研究

为了校准光纤光栅水听器的灵敏度,开展了光纤光栅水听器灵敏度校准技术研究.本文首先介绍了光纤光栅水听器的工作原理;其次,采用可调谐激光器和带工作点控制的强度调制法,实现了光纤光栅水听器的信号解调和稳态测量;在此基础上,利用比较法建立了一种光纤光栅水听器校准系统,校准频率范围为20 Hz～10 kHz;最后,在该频率范围内对采用等效相移布喇格光栅研制的一只光纤光栅水听器的灵敏度进行了校准,对系统的测量不确定度进行了估算.结果表明,该系统可准确校准光纤光栅水听器的灵敏度,扩展不确定度为0.9 dB(k＝2).     

周期性加隔板有限长圆柱壳声散射

研究内部真空周期性加隔板圆柱壳在水中的声散射特性.壳体振动用薄壳理论的Donnell方程描述,隔板振动用相互独立的薄板纯弯曲振动和平面应力状态下的振动方程描述.考虑轴向、切向、径向三个方向的力和弯矩共同作用导出了散射声场的解析表达式.数值计算给出远场收发合置情况下的角度-频率谱图,并据此进行机理分析.通过与内部周期性加环肋圆柱壳声散射的角度-频率谱图比较发现,除周期加肋产生的Bragg散射波与弯曲Bloch-Floquet波外,加隔板的情况还存在明显的隔板共振亮线,并且发生隔板共振与壳体弹性波、Bragg散射波、弯曲Bloch-Floquet波耦合的现象.通过实验对理论进行了验证,在实验的频率范围内,Bragg散射亮线与理论符合得很好,部分Bloch-Floquet波散射亮线和隔板共振散射亮线也与理论符合.     

BSRF圆二色谱研究进展

圆二色（ＣＤ）谱是一种特殊的吸收谱，它对手性分子的构象十分敏感，因此它是最重要的光谱实验之一。北京同步辐射装置（ＢＳＲＦ）３Ｂ１Ｂ生物光谱实验站已经投入运行，它提供单色聚焦的同步辐射光，波长覆盖范围１７０ｎｍ～５００ｎｍ该站的主要设备是一台圆二色谱仪，用这台仪器成功地获取了活性生物样品～捕光色素（ＬｉｇｔＨａｒｖｅｓｔＣｈｌｏｒｏｐｈｙｌｌ）的ＣＤ谱，同时测得樟脑磺酸（ＣａｍｐｈｏｒＳｕｌｆｏｎｉ     

Experimental Study on Single Frequency Semiconductor Lasers with Fiber Bragg Reflector External Cavity

ＥｘｐｅｒｉｍｅｎｔａｌＳｔｕｄｙｏｎＳｉｎｇｌｅＦｒｅｑｕｅｎｃｙＳｅｍｉｃｏｎｄｕｃｔｏｒＬａｓｅｒｓｗｉｔｈＦｉｂｅｒＢｒａｇｇＲｅｆｌｅｃｔｏｒＥｘｔｅｒｎａｌＣａｖｉｔｙ￥ＡＮＨｏｎｇｌｉｎ；ＬＩＮＸｉａｎｇｚｈｉ；ＹＡＮＨｏｎｇ；ＣＵＩＸ...     

Mixed spin- and spin- Ising models with random nearest-neighbour interactions

Using the effective field theory with correlations, we study mixed spin?3/2 and spin?1/2 Ising models with random bonds and crystal-field interactions on the honeycomb lattice. The nearest-neighbour couplings J_ij are taken as random variables with distribution P(J_ij) = pδ(J_ij ? J)+(1 ? p)δ(J_ij ? αJ), where J > 0 and |α| ≤ 1. In a certain range of negative values of α, the phase diagrams exhibit re-entrant behaviour. In detail, we investigate separately two kinds of disorder: Bond dilution (α = 0) and random ±J interactions (α = ?1). In both cases, the influence of the an-isotropy on the phase diagrams shows some new outstanding features.     

硫酸铜诱导烟草多酚氧化酶抗变性的研究

为了进一步探讨外源铜与多酚氧化酶的相互作用 ,通过酶活性测定 ,荧光光谱和圆二色光谱 (CD)对外源Cu2 + 诱导烟草多酚氧化酶抗变性进行了研究 .荧光光谱结果表明 ,没有外源铜存在的情况下 ,盐酸胍诱导的烟草多酚氧化酶变性是一个二态过程 ,烟草多酚氧化酶在 6mol/L盐酸胍中变性 5min ,酶活性降至 18.6 % ,变性30min便彻底失活 ;10 .0mmol/L外源铜存在时 ,盐酸胍诱导的烟草多酚氧化酶变性是一个三态过程 ,上述相同盐酸胍浓度下变性相同时间 ,酶的剩余活性分别为 6 0 .6 %和 2 4 .9% .CD谱数据结果表明 ,6mol/L盐酸胍中变性 30min ,烟草PPO二级结构中α 螺旋、反平行 β 折叠、β 转角 /平行 β 折叠、芳香残基和二硫键、无规卷曲 /γ 转角的百分含量分别为 1.1、3.8、3.3、7.5和 84 .3;在 10 .0mmol/LCu2 + 存在时 ,上述相同变性条件下 ,各种二级结构百分含量分别为 34.2、13.7、2 1.0、9.5和 2 1.6 .适量外源铜可明显提高烟草多酚氧化酶结构的稳定性 .     

Switchable multi-wavelength erbium-doped fiber lasers by using cascaded fiber Bragg gratings written in high birefringence fiber

A novel and simple Erbium-doped fiber laser by using cascaded fiber Bragg gratings (FBGs) written in high-birefringence fibers for switchable multi-wavelength operation is proposed. Due to two-peak reflection with orthogonal polarizations of the FBG, the polarization hole-burning effect in the cavity is greatly enhanced. Experimental results show that the stable dual- and three-wavelength lasing operation with very narrow wavelength separation (0.39 nm) can be generated at room temperature. The configuration is simple and flexible. Only by adjusting polarization controllers (PCs), the laser can be switched among the stable single-, dual- and three-wavelength lasing operations.