Photocatalytic degradation of an azo reactive dye,Reactive Yellow 84, in water using an industrial titanium dioxide coated media

The photocatalytic degradation of an azo reactive dye, Reactive Yellow 84 (RY84), in aqueous solutions using industrial titanium dioxide coated non-woven paper was studied. The experiments were carried out to investigate the factors that influence the dye photocatalytic degradation, such as adsorption, initial concentration of dye, temperature, and solution pH. The experimental results show that adsorption is an important parameter controlling the apparent kinetics constant of degradation. The photocatalytic degradation rate was favored by a high concentration of solution in respect to Langmuir–Hinshelwood model. The degradation was enhanced by the temperature and was favored in acidic pH range.     

Study of TL properties of LaAlO3:Ce,Dy crystals for UV dosimetry

Thermoluminescence properties of lanthanum aluminum oxide (LaAlO₃) crystals doped with optically active rare earth ions have been investigated for ultraviolet dosimetry purposes. Single crystals co-doped with 5.0 at.% of Ce³⁺ and 1.0 at.% of Dy³⁺ ions have two thermoluminescent (TL) peaks at 151 °C and 213 °C which can be sensitized after 1 h of UV exposure. The material shows very high TL output and linear response for UV spectral irradiance ranging from 0.04 to 1.20 mJ cm⁻², that corresponds to 10 times the TL response of the Al₂O₃:C oxides. From 0.62 to 148.0 mJ cm⁻² the dependence is linear with the logarithm of the spectral irradiance. The investigation demonstrates that LaAlO₃:Ce,Dy crystals are very attractive to be investigated as UV dosimeters.     

Interrelation of intrinsic and extrinsic defects – congruent, stoichiometric, and regularly ordered lithium niobate

A new approach to the intrinsic and extrinsic defect subsystems, considering them as one integrated functional system, is developed for complex oxides. The strong interrelation of these subsystems becomes especially apparent when concentrations of both defect classes are comparable. A new parameter, reflecting the total intrinsic defect concentration, is introduced to determine the degree of crystal imperfection. The necessity of at least two calibrated samples – congruent and regularly ordered crystals – is substantiated. The accuracy by which the parameter can be determined can serve as a criterion in comparison of different methods of crystal characterisation. A procedure for crystal calibration by several physical characteristics is illustrated. Such a heuristic generalisation of the concept of mutual correlation of the whole defect system and the material only became possible on the basis of experimental and theoretical study of large numbers of LiNbO₃ crystals. The spectra of EPR, NMR, ENDOR, and other properties of crystals with different compositions, diverse modifiers (K, Mg,...), and various probe impurities have been analysed. It is found that crystals with vanishingly small concentration of intrinsic defects offer extraordinary informative opportunities. Their micro- and macroscopic properties are discussed. The developed ideas have a general character; therefore they should also be valid for other non-stoichiometric complex oxides. Received: 3 December 1998 / Revised version: 15 February 1999 / Published online: 12 April 1999     

Proton-exchange influence on the polar phonons of LiTaO3 optical waveguides

Refractive index change and Raman scattering of Z-cut proton-exchanged LiTaO₃ optical waveguides with different composition have been studied. Probing of the waveguide depth was carried out by using micro-Raman spectroscopy in order to distinguish layers with different phase states. Varying the proton-exchange and post-exchange annealing regimes, two phases –α and β– in addition to the pure LiTaO₃, were clearly observed. The behaviour of the A ₁ vibrations of the TaO₆ groups was found to be very sensitive to the phase changes. Using data from waveguide Raman spectra, normal and oblique E(TO, LO) phonons were sorted and their properties were followed in the α and β phases. The OH-stretchings are considered to correspond to dipoles turned out of the oxygen planes. Received: 9 July 1999 / Accepted: 11 October 1999 / Published online: 24 March 2000     

具有双螺旋链结构的3-吡啶丙烯酸镝配合物的水热合成及晶体结构

采用水热法制备了一种新型稀土配位聚合物[Dy(3-PA)3(H2O)]n(3-PA=3-吡啶丙烯酸)(1),并通过X射线单晶衍射结构分析、元素分析、红外光谱、热重分析对配合物1进行了结构表征.结构分析表明,标题配合物属于三斜晶系,Pī空间群,晶胞参数为:a=0.617 16(5)nm,b=1.270 45(11)nm,c=1.564 03(13)nm,α=111.557 0(10)°,β=90.307 0(10)°,γ=95.342 0(10)°,V=1.134 54(16)nm3,Z=2.金属离子Dy(III)通过配体3-AP羧基的桥联作用,链接成为一维双螺旋链状配位聚合物.     

Offline and online weighted least squares estimation of nonstationary power ARCH processes

This paper proposes two estimation methods based on a weighted least squares criterion for non-(strictly) stationary power ARCH models. The weights are the squared volatilities evaluated at a known value in the parameter space. The first method is adapted for fixed sample size data while the second one allows for online data available in real time. It will be shown that these methods provide consistent and asymptotically Gaussian estimates having asymptotic variance equal to that of the quasi-maximum likelihood estimate (QMLE) regardless of the value of the weighting parameter. Finite-sample performances of the proposed WLS estimates are shown via a simulation study for various sub-classes of power ARCH models.     

Least squares estimators of the regression function with twice censored data

We propose least squares estimators of E(Y/X=x) for Y censored on the right by R and min(Y,R) left censored. We establish their convergence in the L₂-norm. This work extends a known result in the context of right censoring.     

Visible and infrared dispersion of the refractive indices in periodically poled and single domain Nd:Mg:LiNbO3 crystals

3 crystals are measured in the transparency region (with the accuracy ±0.0002) and for the upper phonon polariton branch (with the accuracy ±0.003–±0.05), from 0.44 μm up to 10.5 μm. The method of spontaneous parametric light scattering is used for measurement of the ordinary refractive index dispersion in the mid-infrared region and for determination of the domain grating period d=5.6±0.2 μm in the periodically-poled crystal. Received: 29 January 1997/Revised version: 10 July 1997     

Eu2+,Dy3+共掺杂硼铝锶长余辉玻璃陶瓷

首次介绍了一种新型长余辉材料:Eu^2 ,Dy^3 共掺杂硼铝锶长余辉玻璃陶瓷，该玻璃陶瓷用紫外灯、日光、荧光灯均可激发，发射黄绿色余辉，余辉的发射峰位于516nm，来自于Eu^2 的5d→^8S7/2跃迁。用12000 lx的荧光灯激发样品20分钟，停止激发后10秒时，该玻璃陶瓷的余辉亮度为3．53cd/m^2，色坐标为：x=0.2842,y=0.5772;停止激发后5小时55分钟，该玻璃陶瓷的余辉亮度为0．01cd/m^2；停止激发30小时后，余辉在黑暗中仍肉眼可见。文中对该玻璃陶瓷的相关性质进行了表征，并提出了可能的长余辉机理。