连续渐变周期的一维光子带隙结构全能反射器

采用转移矩阵法设计了一种具有连续渐变周期的一维光子带隙结构全能反射器,它在一般材料选取情况下(如TiO2/SiO2),在可见光区能达到几十甚至几百纳米量级的带隙宽度全向反射.研究表明,其带隙宽度随着周期数和渐变周期的大小改变而改变.当周期数不断增大时,带隙宽度不断增大;当渐变周期的大小在一定范围内不断增大时,带隙宽度同样不断增大.这主要是光波在各层之间的传播随着周期和渐变周期的大小不断增大而产生的相干散射和干涉效应不断增强所导致的.  

Large-scale purification of single-wall carbon nanotubes: process, product, and characterization

Received: 13 February 1998  

纳米固体材料的性能与界面微观结构

综述了纳米陶瓷ＴｉＯ２和纳米金属Ａｇ的力学性能，以及纳米离子导体ＣａＦ２和ＰｂＦ２等的离子导电性能，结合其界面微观结构特征，对上述纳米固体材料的优异性能进行了初步解释  

Quantum Secure Direct Communication Network with Two-Step Protocol

An efficient quantum secure direct communication network protocol with the two-step scheme is proposed by using the Einstein-Podolsky-Rosen （EPR） pair block as the quantum information carrier. The server, say Alice, prepares and measures the EPR pairs in the quantum communication and the users perform the four local unitary operations to encode their message. Anyone of the legitimate users can communicate another one on the network securely. Since almost all of the instances in this scheme are useful and each EPR pair can carry two bits of information, the efficiency for qubits and the source capacity both approach the maximal values.  

冲击波作用下多组分粉体的细化与均化研究

 研究了冲击波作用下Al-C、Al-Si和Si-C三种粉体的细化与均化情况。结果表明，冲击波对微米级粉体有明显的细化和均化作用，各组分的细化程度与其晶体结构和力学特性有关，其中，冲击波作用后的Si-C粉体粒度达到300 nm以下。  

QUANTUM FLUCTUATIONS IN MESOSCOPIC RESISTANCE-INDUCTANCE-CAPACITANCE ELECTRIC CIRCUITS AT FINITE TEMPERATURE

By using the charge and current in a quantization resistance-inductance-capacitance (RLC) electric circuit, we construct a pair of canonical variables. Using this pair of variables and the thermal field dynamics, we obtain the fluctuations of charge and current in the RLC electric circuit at finite temperatures. It is shown that the fluctuations increase with increasing temperature and decrease with prolonging of time.  

The fabrication and characterization of ZnO UV detector

ZnO films were deposited on GaAs substrates by radio frequency (rf) magnetron sputtering followed by an ambient-controlled heat treatment process for arsenic doping. In Hall measurements, the As-doped ZnO films showed the characteristics of p-type semiconductor. The ZnO thin film p–n homojuctions were then fabricated to investigate the electrical properties of the films. The p–n homojunctions exhibited the distinct rectifying current–voltage (I–V) characteristics. The turn-on voltage was measured to be 3.0 V under the forward bias. When ultraviolet (UV) light (λ = 325 nm) was irradiated on the p–n homojunction, photocurrent of 2 mA was detected. Based on these results, it is proposed that the p–n homojunction herein is a potential candidate for UV photodetector and optical devices.  

胶原调制磷酸钙矿化成核位点的红外光谱研究

对胶原、胶原 /CaCl2 、胶原 /羟基磷灰石等几种体系的红外光谱进行了比较研究。发现胶原矿化后 ,红外光谱中胶原的酰胺Ⅰ ,Ⅱ ,Ⅲ带的吸收强度显著降低 ,Ⅱ ,Ⅲ带接近消失 ,Ⅰ带发生红移现象。提出胶原中的羧基 (COOH )、羰基 (CO )为胶原矿化的两类成核位点 ,钙盐在成核位点上结晶。脱钙胶原(胶原 /羟基磷灰石经盐酸处理 )的红外光谱与纯胶原相似 ,酰胺Ⅰ ,Ⅱ ,Ⅲ带的吸收强度恢复正常 ,表明 :钙盐对胶原中酰胺基的影响是由于钙盐在该成核位点上结晶而导致的“包裹”作用。根据酰胺 3个吸收带的不同振动方式 ,用“包裹”作用解释了胶原 /钙盐复合物中 ,酰胺Ⅰ与Ⅱ ,Ⅲ带的降低程度不同的原因。分析了胶原 /磷酸钙生物矿化的作用机制。  

泡沫镍制备中化学镀镍研究

 探讨了泡沫镍制备过程中，聚氨酯泡沫模板上的低温化学镀镍工艺，考察了镀液温度、pH值、主盐与还原剂浓度对沉积速率的影响。得出了适宜的工艺条件：硫酸镍30 g/L、次亚磷酸钠30 g/L、柠檬酸钠10 g/L、氯化铵30 g/L,镀液pH=9.0～9.5、温度45 ℃。在该工艺条件下，化学镀过程稳定，沉积速率可达40 mg/(cm³×h)。化学镀镍后经电镀、热解和还原退火处理制得泡沫镍，其样品呈3维网络状结构，密度为0.74 g/cm³,孔隙率为91.7%。  

Effect of Bi-substitution on the dielectric properties of polycrystalline yttrium iron garnet

The effect of Bi-substitution on the dielectric properties of yttrium iron garnet (YIG) was studied in this paper. The Bi-substituted YIG (YIG:Bi) polycrystalline samples, having composition of Y_3−xBi_xFe₅O₁₂, were prepared by the solid-state reaction method. x varied from 0 to 1.2. The phase formation and microstructure were performed by X-ray diffraction and scanning electron microscopy, respectively. Ions valency was identified by X-ray photoelectron spectroscopy. The impedance analyzers are used to measure the frequency dependence and the temperature dependence of relative dielectric constant (_r) and loss tangent (tan δ). The experimental results show that the Bi-substitution lowers the phase formation and sintering temperature. Electronic carrier concentration drops dramatically due to limitation of ferric valency variation. Hence, _r and tan δ decrease with addition of Bi. Dispersion characteristic indicates non-Debye-type dispersion. A maximum of _r appears as the temperature rises.