CdS/ZnO核壳结构纳米微粒的合成及其发射光谱研究

采用单分子前驱体热分解的方法合成了单分散CdS纳米晶,以CdS纳米晶作为核,在CTAB辅助下,对其表面进行修饰,荧光光谱表明CdS/ZnO核壳结构被成功合成。考查了温度对包覆的影响,结果表明,随着温度的升高晶体结晶越好,包覆越来越完全,ZnO包覆在CdS纳米晶的表面而掩盖了CdS纳米晶的缺陷,使得缺陷发光减弱而带隙发光增强。     

一种基于组合赋权法的Web服务选择策略*

针对Web服务选择中服务请求偏好权重表达的模糊性及服务质量(QoS)属性值间存在的相互制约关系等问题,提出一种基于组合赋权法的Web服务选择策略。首先利用模糊层次分析法(FAHP)和主成分分析法(PCA)分别计算主观QoS权重和客观QoS权重;然后综合主、客观QoS权重利用组合赋权法(CWA)计算服务请求的综合QoS权重;最后提出一种综合评价函数,以保障所选择的服务在满足服务请求偏好的基础上,能更准确地反映候选Web服务总体QoS水平。实例分析表明该方法是有效的。     

First Principles Study on the Effects of Cu Doping on the Magnetic Moment and Electronic Properties of V-Doped ZnO

The CASTEP program was used to study the effects of Cu on the structure, magnetic moment and electronic properties of V-doped ZnO. The calculated enthalpies showed that the Cu atoms were inclined to stay near the V atoms. Cu neutralized the delocalized electrons in V-doped ZnO. Cu also suppressed the magnetic moments of Zn and O more than those of the V ions. The different amounts of suppression caused the moments to concentrate on the V atoms. The magnetic moments decreased in Cu and V co-doped ZnO. The suppressions of the magnetic moments and concentrations of the Cu atoms were verified with density of states calculations. The states showed that Cu increased the conduction in V-doped ZnO. The calculated spin isospheres showed that Cu improved the concentration of the magnetic moments on the V sites. The improved concentration enhanced the performance of diluted magnetic semiconductors based on V-doped ZnO. These results help in understanding the role of Cu in V-doped ZnO. They also provide a reference for preparing diluted magnetic semiconductors based on V-doped ZnO     

高光谱遥感考古探索研究

高光谱遥感与以往遥感技术相比,具有图谱合一的特征和从可见光到热红外的一系列波段,是一种综合性的遥感技术手段.文物遗存在地面的信息一般比较微弱,高光谱遥感具有识别微弱信息和定量探测的优势,但高光谱遥感目前在考古中却未得到有效的应用.本文以秦始皇陵区为研究区,较系统地阐述了高光谱遥感在考古中的创新应用研究,以及所取得的考古成果.表明高光谱遥感技术在考古中的应用有广阔的前景.     

Study on the effect of measuring methods on incident photon-to-electron conversion efficiency of dye-sensitized solar cells by home-made setup

An experimental setup is built for the measurement of monochromatic incident photon-to-electron conversion efficiency (IPCE) of solar cells. With this setup, three kinds of IPCE measuring methods as well as the convenient switching between them are achieved. The setup can also measure the response time and waveform of the short-circuit current of solar cell. Using this setup, IPCE results of dye-sensitized solar cells (DSCs) are determined and compared under different illumination conditions with each method. It is found that the IPCE values measured by AC method involving the lock-in technique are sincerely influenced by modulation frequency and bias illumination. Measurements of the response time and waveform of short-circuit current have revealed that this effect can be explained by the slow response of DSCs. To get accurate IPCE values by this method, the measurement should be carried out with a low modulation frequency and under bias illumination. The IPCE values measured by DC method under the bias light illumination will be disturbed since the short-circuit current increased with time continuously due to the temperature rise of DSC. Therefore, temperature control of DSC is considered necessary for IPCE measurement especially in DC method with bias light illumination. Additionally, high bias light intensity (>2?sun) is found to decrease the IPCE values due to the ion transport limitation of the electrolyte.     

基于注意力机制的规范化矩阵分解推荐算法

近年来,矩阵分解(MF)技术因其有效性和简便性在推荐系统中得到广泛应用.但是,数据稀疏和冷启动问题导致MF学习到的用户特征向量不能准确地代表用户的偏好以及反映用户间的相似关系,影响了模型的性能.为了解决该问题,规范化矩阵分解(RMF)技术引起了研究者的关注.挖掘用户间可靠的相似关系,是RMF需要解决的问题.此外,MF将目标用户特征向量和目标项目特征向量的内积作为目标用户对目标项目的评分,这种简单的线性关系忽略了用户对项目各个属性特征不同的关注度.如何分析用户对项目属性特征的关注度,获取用户更准确的偏好,仍然是一个挑战.针对上述问题,提出了基于注意力机制的规范化矩阵分解模型(ARMF).具体地,为了获取用户间可靠的相似关系解决数据稀疏和冷启动问题,该模型同时依据用户信任网络和评分记录构建用户-项目异构网络,并基于该异构网络挖掘用户间的相似关系;为了进一步提升模型性能,通过在MF中引入注意力机制,分析用户对项目各个属性特征不同的关注度来获取用户更准确的偏好.最后,在两个真实数据集上对比ARMF与现有工作,实验结果证明,ARMF有更好的准确性和健壮性.     

The water resistance of surface-modified APP with melamine-TDI in LLDPE

Ammonium polyphosphate (APP) which was surface-modified with melamine (MA) and 2,4-toluene diisocyanate(TDI) in turn was used as flame-retardant in linear low density polyethylene (LLDPE). Its water resistance in LLDPE was respectively evaluated with its water-solubility, the limited oxygen index(LOI) changes and P content changes of the LLDPE which being immersed in water 180 h at room temperature. Its compatibility with LLDPE was observed with scanning electron microscope (SEM). As a result, the water-solubility of the surface-modified APP reduced. When the LLDPE was treated with surface-modified APP, its LOI and P content changes were less than that treated with unmodified-APP after being immersed in water. The surface-modified APP was better compatible with LLDPE than unmodified APP.     

化学链制氧技术中铜-锆氧载体的动力学分析

化学链空气分离制氧是利用氧载体在脱氧反应器中脱氧-在吸氧反应器中吸氧、再生实现连续或间断制氧的新颖技术。本研究通过机械混合法制备铜-锆氧载体, 并对制备材料的物相组成、表面形貌及比表面积进行表征, 在STA409PC热重分析仪上采用程序升温法作相关机理探索, 分析气体流量、样品质量、升温速率、惰性载体添加比例对铜-锆氧载体脱氧和吸氧性能的影响。采用等转化率法求解活化能, 采用主曲线法确定动力学模型机理函数。 结果表明, 所制备的铜-锆氧载体物相稳定, 没有烧结现象的发生, 随ZrO₂添加比例的增大, 制备氧载体的比表面积逐渐增大; 当气体流量大于30 mL/min, 样品质量小于10 mg时, 氧载体的转化速率已不受样品传热和传质等内外扩散的影响; 随升温速率的增大及惰性载体添加比例的减小, 氧载体反应起始温度、最大反应速率出现温度及转化完全温度均向高温移动。等转化率法计算得到不同转化率下氧载体的活化能基本相同, 且不同惰性载体添加比例下活化能数值也相差不大; 氧载体脱氧和氧化反应都可用成核和核增长机理模型描述, 但模型中两种反应的级数不同, 前者为3, 后者为1.5。     

基于激光网格标记的计算机视觉测量技术研究

基于激光网格标记的视觉测量技术是一种高精度的三维坐标测量技术。该技术采用交叉投射激光网线的方式对待测物体进行标记,然后分别采集这两组交叉的标记图像并进行标记提取;提取出的两组标记线在经过去噪、细化、后处理以及匹配之后将被合成测量所要求的网格点图像,这些网格点就是测量所需要的特征点。采用这种交叉标记并合成网格点的方式,可以简化以后的网格点匹配算法。本文最后给出了比较详细的测试实例,证明了本技术的有效性。     

Peer To Peer计算技术的应用领域与典型问题讨论

With the rapid development of computer networks there are more and more resources involoved in it,such as CPU cycles,PC‘‘s disk space and network bandwidth.Many people believe that peer to peer computing can harness these disruptive powers.In this paper we describe the applied fields,research issues and typical problems in peer to peer computing.