Phase transitions and metastable states in TlGaSe2

The results of measurements of the dielectric constant of TlGaSe₂ in temperature range of successive phase transitions are presented. An anomaly in the temperature dependence of the real part of dielectric constant in TlGaSe₂ has been observed at about 242?K in addition to anomalies at 115, 108, and also near 65?K as reported in previous publications. The presence of temperature hysteresis effects in temperature interval between 115 and 242?K allowed making a conclusion about possible existence of an incommensurate phase in the mentioned temperature range. A model of succession of the structural phase transitions in TlGaSe₂ has been suggested.     

A theoretical and experimental study on all-normal-dispersion Yb-doped mode-locked fiber lasers

We report on a theoretical and experimental study of an all-normal-dispersion (ANDi) Yb-doped mode-locked fiber laser, in which nonlinear polarization rotation (NPR) is used to realize mode-locking without any dispersion compensation. Based on the coupled nonlinear Schrdinger (CNLS) equation, a model simulating the mode-locked process of an allnormal-dispersion ring fiber laser is developed, which shows that the achievement of stable mode-locking depends on the alignment of the polarization controller (PC) along the fast-polarization axis of the fiber, the birefringence intensity, and the net cavity dispersion. According to the theoretical analysis, stable mode-locked pulses with pulse duration 300 ps and average output power 33.9mW at repetition rate 36MHz are obtained.     

Paraxial designing of planar waveguide variable-index focusing elements: Part 1—lenses of circular symmetry

A paraxial ray equation is used to evaluate refractive index profiles for a family of radially symmetric planar waveguide lenses. Two cases are considered: the (theoretically) full-aperture solution, and the solution with smooth index variation (non-full-aperature case). In deriving the latter case a new method has been applied that consists of the proper choice of a continuous deflection function. Both types of index profiles are described by exceptionally simple formulas.     

Dielectric response of frustrated water down to a single‐molecule contribution

A theory of dielectric response of water under nanoscale confinement was long overdue. This work addresses the problem by establishing a relation between dielectric response and hydrogen‐bond frustration subsumed in a non‐Debye polarization term. The results hold down to the single‐molecule contribution and are validated vis‐à‐vis experimental measurements on a system where dielectric modulation entails removal of a single water molecule. The frustrated dielectric response down to molecular scales is assessed by contrasting two enantiomeric ligands in association with the same protein, with the complexes differing in the removal of a single interfacial water molecule.

     

Triboelectrification of granular insulating materials as affected by dielectric barrier discharge (DBD) treatment

The aim of this paper is to point out the influence of dielectric barrier discharge treatment on tribocharging of granular insulating materials. Particles of Polyvinyl Chloride (PVC) and Polypropylene (PP) were subjected to an AC dielectric barrier discharge (DBD) plasma treatment in ambient airprior to tribocharging in a vibratory device. The charge to mass ratio was measured for treated and untreated materials. Electrostatic separation of a mixture of granular materials (PVC and PP) to measure the effectiveness of DBD treatment was evaluated by processing treated and untreated PVC/PP granular mixtures in a free-fall electrostatic separator. The obtained results clearly indicate that DBD has the capability to influence surface charging proprieties of polymer granular materials. In case of short treatment time, typically less than 3 s, a marked increase in the charge to mass ratios was observed for both PVC (about 35%) and PP (roughly 45%). In the same way, the quantity of DBD-treated materials, recovered after electrostatic separation, was increased by about 104% and 30% for PVC and PP, respectively, as compared to untreated case. The DBD treatment time is a key factor to increase the tribo electric effect.     

透过式光纤陀螺偏振特性的分析

偏振波动是谐振式光纤陀螺(R-FOG)的主要噪声之一,它对信号检测精度具有重要影响。通过矩阵法得到了透过式R-FOG中由偏振波动引起的系统零漂与偏振噪声相关参数、环形谐振腔结构参数间的关系表达式。在一定的透过式R-FOG系统结构参数下,对上述解析表达式进行了数值拟合,通过估算可满足高精度透过式R-FOG系统对偏振相关参数的要求,为偏振波动噪声的理论分析和R-FOG系统的实际搭建提供了理论基础。     

多方向偏振片及1/4波片对全偏振检测的影响研究

理论上推导了光线通过任意方向偏振片和任意方向1/4波片的出射光强与全Stokes参量关系的表达式,利用自然背景下的人造目标为对象开展全偏振检测实验,并以目标与背景偏振度对比为主要指标,研究了多方向情况下上述两种偏振器件影响全偏振检测的因素。研究表明下述三种情况方程组秩小于4导致全偏振检测无效:固定1/4波片方向而改变偏振片方向;固定偏振片方向改变1/4波片方向,且四组角度中两器件平行及垂直的关系同时出现;偏振片与1/4波片有三组角度相同,第四组角度关系为平行或垂直。实验表明,固定偏振片方向改变1/4波片方向,探测结果与固定偏振片方向的取值有关;采用偏振片与1/4波片三组方向相同,第四组夹角45°的全偏振检测方式,偏振度对比较高。     

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通过测量大气压介质阻挡放电等离子体辐射信号,建立偶极子辐射模型,利用快速傅立叶变换,计算了大气压介质阻挡放电等离子体中离子速度分布。计算结果表明,速度分布偏离麦克斯韦分布,并且随着放电过程的进行,离子速度及相对离子数进行有规律的变化。     

Processing of Spectropolarization Video Images

This paper considers the possibilities and results of using spectropolarization video photography of scenes for discriminating artificial and natural objects. A number of new methods for processing spectropolarization video images are proposed.     

Static magneto-polarizability of cylindrical nanostructures

The static polarizability of cylindrical systems is shown to have a strong dependence on a uniform magnetic field applied parallel to the tube axis. This dependence is demonstrated by performing exact numerical diagonalizations of simple cylinders (rolled square lattices), armchair and zig-zag carbon nanotubes (rolled honeycomb lattices) for different electron-fillings. At low temperature, the polarizability as function of the magnetic field has a discontinuous character where plateau-like region are separated by sudden jumps or peaks. A one to one correspondence is pointed out between each discontinuity of the polarizability and the magnetic-field induced cross-over between the ground state and the first excited state. Our results suggest the possibility to use measurements of the static polarizability under magnetic field to get important informations about excited states of cylindrical systems such as carbon nanotubes. Received 29 March 2001 and Received in final form 8 August 2001