The effect of In doping on optical properties of Fe:LiNBO3 crystals

Fe:LiNbO₃ and In:Fe:LiNbO₃ crystals were grown by Czochralski method. The absorption spectra were measured to investigate their defect structure. The photo damage resistance and photorefractive properties were measured. The photo damage resistance of the In:Fe:LiNbO₃ crystal in which the In concentration is above the threshold value is one order of magnitude higher than that of the Fe:LiNbO₃ crystal. The mechanisms of the violet shift of the absorption edge and the enhancement of the photorefractive effect of In:Fe:LiNbO₃ crystals were investigated.     

In组分梯度渐变的n-i-p结构InGaN太阳能电池性能研究

为了优化InGaN太阳能电池结构并有效地指导实际电池的制备,研究了n-i-p(p层在下)In组分梯度渐变结构的InGaN太阳能电池的性能特征。通过APSYS软件模拟计算,对比采用p-i-n渐变结构(p层在上)和n-i-p渐变结构(p层在下)的InGaN太阳能电池的器件性能。结果表明,采用n-i-p渐变结构的InGaN电池,i-InGaN层在低In组分下没有明显的优势,而在高In组分下的器件性能较好。在In组分为0.62时,转换效率最高达到8.48%。分析表明,p层在下的n-i-p渐变结构使得InGaN电池的极化电场与耗尽区的内建电场方向一致,有利于载流子的输运。采用n-i-p渐变结构有利于制备高性能的InGaN太阳能电池。     

InxGa1-xN薄膜的弯曲因子及斯托克斯移动研究

采用常压金属有机化学汽相沉积(MOCVD)技术以Al2O3为衬底在GaN膜上生长了InxGa1-xN薄膜。以卢瑟福背散射／沟道技术、光透射谱、光致发光光谱对InxGa1-xN／GaN／AI2O3样品进行了测试。研究了InxGa1-xN薄膜的弯曲因子及斯托克斯移动。结果表明，采用光透射谱、光致发光光谱得到的InxGa1-xN薄膜的禁带宽度一致，InxGa1-xN薄膜并不存在斯托克斯移动。InxGa1-xN薄膜的In组分分别为0．04，0．06，0．24，0．26时，其弯曲因子分别为3．40,2．36，1．82，3．70。随In组分变化。InxGa1-xN薄膜的弯曲因子的变化并没有一定的规律，表明InxGa1-xN薄膜的禁带宽度随In组分的变化关系复杂。     

γ射线在LSO晶体中的能量沉积

采用蒙特卡罗程序MCNP计算了γ射线在LSO晶体中的能量沉积分布并与相应的实验结果进行了对比,验证了该方法的正确性。在此基础上计算了不同能量的γ射线在LSO晶体中的能量沉积分布,分析了γ射线与物质的不同作用对晶体中能量沉积分布的影响,总结出在晶体轴向和径向的能量沉积分布规律。轴向上,不同能量γ射线在LSO晶体中的能量沉积近似为指数分布,在表面能量沉积密度较小;在径向方向,γ射线在入射轴线上能量沉积密度很高,在距入射轴较近的区域,主要是次级电子产生沉积能量,随着距离的增大,γ射线能量沉积逐渐减小;在距入射轴较远的区域,能量沉积主要是散射γ射线产生。     

AgInSbTe薄膜的短波长记录性能分析

采用自制的装置研究了Ag5In5Sb47Te33薄膜的静态记录性能与记录激光的功率和脉冲宽度的关系，并对其记录畴形貌特点进行了直接观察。结果表明只有记录激光的功率和脉冲宽度在一定范围之内才能起到信息记录的作用，所得的记录畴形貌十分清晰，基本为非晶态Ag5In5Sb47Te33；小于该范围的激光能量不能使材料结构发生较大的变化，所得的记录畴形貌模糊，反射率对比度低于2％；大于该范围所得的记录畴由烧蚀区和其周围的非晶态Ag5In5Sb47Te33组成。另外，得到了记录激光功率为12mW、脉冲宽度为90ns的Ag5In5Sb47Te33薄膜的短波长最佳记录条件，其记录畴的反射率对比度为22％，直径为380nm-400nm。     

丁酰胆碱和硫代胆碱与CdTe量子点的络合特征以及光谱性质的理论研究

本文利用密度泛函理论,研究了丁酰胆碱和硫代胆碱在CdTe量子点上的络合特征.优化了稳定的络合构型,计算了吸附能、电荷密度、前沿分子轨道以及紫外可见吸收光谱.研究发现：丁酰胆碱在CdTe量子点上的吸附能较小、与量子点之间的电子相互作用较弱,属于物理吸附,紫外可见光吸收强度较弱.而硫代胆碱与量子点之间存在化学吸附,存在强的电子相互作用,紫外可见光吸收强度增强.我们的研究结果为实验中使用CdTe量子点检测丁酰胆碱酯酶提供了理论支持.     

Kinetic investigation on sono-degradation of Reactive Black 5 with core–shell nanocrystal

The experimental data of sonocatalytic degradation of Reactive Black 5 (RB5) as an azo dye by core–shell nanocrystals (CdS–TiO₂) were applied to the proper kinetic models. In this work, two kinetic models were proposed and fitted properly to the data. In the first one, the heterogeneous reaction was considered similar to the Langmuir–Hinshelwood (L–H) mechanism and the kinetic rate parameters were determined. In this model, short time of sonication with initial concentration changes has been applied and the contribution of the reaction intermediates has been neglected in degradation. Hence, this model may not be valid for longer reaction times where the reaction intermediates effects prevail. In the second one, two first-order reactions in series provided the most convincing rate form for the sonodegradation of dyes adsorbed on the synthesized nanocomposite. In these series reactions, the first step is the conversion of colored dye to colored intermediate, and the second step is the conversion to colorless product(s). The obtained results were in good agreement with the proposed kinetic models. The rate constants of degradation of catalyzed reaction were higher than that obtained without catalyst, solar and UV irradiation.     

Water softening by combination of ultrasound and ion exchange

Ion exchange resin used in this work was styrene-divinylbenzene co-polymer with sulfonic acid group as a strong acid cation resin. This resin is particularly well suited for the removal of water hardness. In water treatment, commonly used softening processes are chemical precipitation and ion exchange. In this study, a combination of ultrasound and ion exchange was applied for reducing the hardness of water. The rate of exchange or kinetics of ion exchange is governed by several parameters. Therefore, important variables such as intensity of ultrasound, amount of resin, concentration of ions and contact time were investigated. The experimental data related to the removal of magnesium and calcium ions were fitted properly with Langmuir model. The kinetic of removal for both ions was pseudo-first-order. In point of mechanism, the internal porous and film diffusion were both effective in the process. The capacity of sorption and the velocity of removal were higher in the presence of ultrasound than control method and this is related to the cavitation process.     

β-苄基苯乙酮吸收与发射光谱的密度泛函研究

β-苯基羰基化合物的光化学特征历来受到重视,是n,π*羰基三线态猝灭机理的典型代表。研究了气相和甲醇中β-苄基苯乙酮的基态结构和激发态结构,模拟了其吸收和发射光谱,并从分子轨道角度阐明了其发光机制。研究发现:(1)在甲醇中,β-苄基苯乙酮的基态结构与气相结构非常接近,只是在羰基官能团附近键长有差别;(2)在甲醇中,β-苄基苯乙酮的S1态无法维持平面构型,且αC—C键显著拉长;(3)在气相中,β-苄基苯乙酮的吸收光谱很弱,而在甲醇中很强;(4)气相中,β-苄基苯乙酮的荧光光谱的发光机制与甲醇中不同;(5)在气相中,β-苄基苯乙酮荧光光谱的最大发射峰蓝移到228.67nm处,发射强度(f=0.306 1)比吸收光谱大幅增加;(6)从分子轨道角度看,荧光光谱是吸收光谱的逆过程;(7)在气相中,β-苄基苯乙酮的磷光光谱在252.58和246.04nm处有两个较强的发射峰,而甲醇中只在258.88nm处有一个很强的发射峰。     

干涉成像光谱仪中宽谱段傅氏光学系统设计

设计了一种宽谱段前置光孔远心光学系统,其孔径光阑位于透镜组的焦面上,该设计集宽谱段自动复消色差、长工作距、前置光孔及远心等特点于一体. 讨论了这样一种特殊光组的设计. 选用国产牌号的光学玻璃配对,价格低廉且在校正色差后,自动校正宽谱段二级光谱,并实现了透镜组两侧同时具有长工作距. 设计结果表明,光学系统的残余二级光谱很容易控制在千分之一焦距以内,波面平行差小于0.000 22弧度.     

Fluorescence Titration of Some Purines Determination of Lowest Excited-State Ionization Constants

Abstract

Excited-state ionization equilibria of 6-methyl purine and xanthine were investigated in a wide range of pH.

6-Methyl purine is known to have two ionization equilibria in its ground-state. It was found that it had one more ionization equilibrium in strongly acidic region. In the excited state, four ionization equilibria were observed. The pK? values of three of them were determined by means of fluorescence titration.

In the case of xanthine, there exist three ground-state equilibria. In the excited-state, four equilibria were observed. The pK? values of two of them were determined by means of fluorescence titration.     

多重谱线拟合（MSF）扣除光谱干扰法在电感耦合等离子体发射光谱？…

在用用电感耦合等离子体发射光谱法测定钢铁中磷时,已有的研究报告中大多采用Ｐ１７８ｎｍ作分析谱线,但因其发射强度低而使测定精度和检出限不理想。本文在采用多重谱线拟合（ＭＳＦ）法扣除光谱干状的基础上,测定了存在严重光谱干扰的Ｐ２１４ｎｍ、Ｐ２１３ｎｍ谱线,同时测定了没有光谱干扰的Ｐ１７８ｎｍ,Ｐ１７７ｎｍ谱线,结果表明,Ｐ２１３ｎｍ谱线的测定精密度和检出限最好,比常用Ｐ１７８ｎｍ谱线的精密精密度高５倍     

Ultrasound diffusion for crack depth determination in concrete

The determination of the depth of surface-breaking cracks in concrete specimens using an ultrasound diffusion technique is discussed. Experiments were carried out on precracked concrete specimens of varying crack depths (0%-40% of the specimen thickness). Contact transducers were placed at the specimen surface with source and receiver separated by the crack. Tone-burst excitations over a frequency range of 400-600 kHz were used. At these frequencies, ultrasound is scattered considerably by the heterogeneities in the concrete. In the limit of many scattering events, the evolution of energy may be modeled as a diffusion process. The arrival of the peak diffuse energy at the receiver is delayed due to the presence of crack. This delay is the prime indicator used for determining crack depth. Numerical and analytical analyses were also used for comparison. These results are in basic agreement with the experiments. In addition, these analyses are used to study the limits of this technique. In particular, it is shown that this technique is applicable to cracks greater than the scattering mean-free path, which is estimated at about 1 cm for these specimens. Aspects of practical implementation are also discussed.     

基于光谱信息的空间目标模式识别算法研究

在观测空间目标时,往往会受到地基观测仪器等因素的制约,导致无法利用目标图像信息从外形上进行识别。根据不同空间目标表面组成材料不同,其产生的反射光谱会存在差异这一特性,可利用空间目标特有的光谱信息进行识别分类。基于此,从光谱学角度对空间目标识别算法进行研究,在K最近邻算法(KNN)的基础上,采用了一种自适应权重局部超平面方法(AWKH),算法主要在计算预测样本与超平面距离时加入对特征权重的考虑,构建了以样本特征组间差与组内差的比值作为特征权重值的超平面模型,从而提高了分类效果和分类效率。为验证算法的分类效果,本文进行了四组验证实验,第一组实验将美国地质勘探局数据库中提取出的九种常用材料光谱随机选出三种混合成多类进行识别;第二、三组实验将四种常用空间目标材料的光谱作为纯物质光谱,分别从可见光和近红外波段对其混合物质进行分类;第四组实验通过实测四个方形模型样本六个面的光谱对其进行识别分类。实验过程中将实验结果与目前常用的支持向量机(SVM)进行对比,对比结果表明改进后的AWKH算法在识别精度和样本适用范围上具有更高的优越性。     

Comparison of different electrode arrangements for gas decomposition efficiency using experimental method

The environmental pollution is a central issue in the present industrial societies. Within that the air pollution and the removal of hazardous components of flue and exhaust gases are very much important.In this paper the target is to decrease of the NO_x emission by means of a technology similar to that is used in the electrostatic precipitators. In most of the papers dealing with this technique cylindrical precipitator is used as a discharge chemical reactor, and fast rising electric discharges are applied for energizing the reactor. In the industry the over helming majority of the electrostatic precipitators are plate type one.In the cylindrical precipitator the discharge electrode is parallel with the gas flow, and the corona discharge filament is perpendicular to both of them. In the case of plate type industrial electrostatic precipitator the discharge electrodes are positioned vertically, and the flow of the flue gas is horizontal. Consequently, the discharge filaments are mainly perpendicular to both the flow and the discharge electrode.In cylindrical precipitator the decomposition of NO_x is done in one filament very soon, but there is no chance to modify the byproducts with a new pulse, because the energization is the same for the whole length of the discharge electrode.In the present paper a cylindrical precipitator, a plate type precipitator with horizontal electrode, and a plate type precipitator with vertical electrode were tested. The total length of the discharge electrodes of all of the precipitators was the same.The results of the NO_x decomposition were experimentally determined, and the differences between the precipitators were investigated. The cylindrical and the plate type precipitators with vertical electrodes had shown basically similar decomposition rate, while the plate type one with horizontal discharge electrode had proven inferior to the others.     

A kinematically complete measurement of K^+ \to \pi^+ \pi^0 \pi^0 decays

In a kinematically complete setting, the decays of stopped were measured. In the frame work of the Weinberg polynomial expansion, the coefficients up to quadratic terms were deduced. The results are in good agreement with previous measurements and consistent with CP conservation expectations. The empirical rule is violated. Received: 16 October 1999 / Published online: 27 January 2000     

Synthesis and optical properties of N-In codoped ZnO nanobelts

N-In codoped ZnO nanobelts were successfully synthesized via high-temperature chemical vapor deposition for the first time, using the mixture of In/ZnO as a precursor. The EDX spectrum showed that In was introduced into ZnO nanobelts. In order to better understand the optical properties of N-In codoped ZnO nanobelts, the Raman and low-temperature PL spectra of the undoped, In-doped and N-In codoped ZnO nanostructures were measured. By contrasting, N is incorporated into the nanobelts. The temperature dependent photoluminescence (PL) spectra were investigated. Their PL spectra in the temperature from 9 K to room temperature were dominated by an A^oX emission of excitons bound to 2No-In_Zn acceptor complexes. The dissociation energy of the acceptor complexes is estimated to be 89-112 meV.     

Effects of deuteration on the structure of NH_4H_2PO_4 crystals characterized by neutron diffraction

A series of deuterated ammonium dihydrogen phosphate(DADP) crystals were grown and their structures were investigated by using powder neutron diffraction method. In the entire composition range, the deuterated level in the crystals is lower compared with the aqueous growth solution. The deuterium segregation coefficient in the crystals decreases with increasing deuterium content of the solution. The deuterium content in the NH_4~+ group is higher than that in H_2PO_4~- group.In addition, the variations of lattice parameters are shown here.     

Double-layer indium doped zinc oxide for silicon thin-film solar cell prepared by ultrasonic spray pyrolysis

Indium doped zinc oxide(ZnO:In) thin films were prepared by ultrasonic spray pyrolysis on corning eagle 2000 glass substrate.1 and 2 at.% indium doped single-layer ZnO:In thin films with different amounts of acetic acid added in the initial solution were fabricated.The 1 at.% indium doped single-layers have triangle grains.The 2 at.% indium doped single-layer with 0.18 acetic acid adding has the resistivity of 6.82×10-3Ω·cm and particle grains.The doublelayers structure is designed to fabricate the ZnO:In thin film with low resistivity(2.58×10-3Ω·cm) and good surface morphology.It is found that the surface morphology of the double-layer ZnO:In film strongly depends on the substratelayer,and the second-layer plays a large part in the resistivity of the double-layer ZnO:In thin film.Both total and direct transmittances of the double-layer ZnO:In film are above 80% in the visible light region.Single junction a-Si:H solar cell based on the double-layer ZnO:In as front electrode is also investigated.     

被动调Q自拉曼Nd∶GdVO4激光器

对激光二极管(LD)抽运的自拉曼Nd∶GdVO4被动调Q激光器进行了详细的理论和实验研究。实验中采用Nd∶GdVO4晶体同时作为激光介质和拉曼晶体,分别用了两块不同初始透射率的Cr4 ∶YAG晶体,得到并比较了采用不同初始透射率的Cr4 ∶YAG晶体时被动调Q自拉曼激光器的性能。测量了平均输出功率、脉冲宽度和脉冲重复率随抽运功率的变化关系。当Cr4 ∶YAG的初始透射率为0.91,输入功率是5.7 W时,得到的拉曼光的最高功率为244.6 mW,相应的转换效率为4.3%。通过数值求解基频光和拉曼光空间分布的速率方程并应用到被动调Q自拉曼Nd∶GdVO4激光器。获得的理论结果与实验结果大致相符。