Synthesis and luminescence properties of a novel phosphor Ca2–x/2Si1–xPxO4:Eu2+for near UV-excited white-light-emitting diodes

A novel green-emitting phosphor,Eu2+-doped Ca2-x/2 Si1-x Px O4(0.25≤x≤0.30),was prepared through a conventional solidstate reaction.X-ray diffraction(XRD),photoluminescence(PL) and decay studies were employed to characterize the sample,which was assigned to P63mc space group in the hexagonal system.The effect of P-doping on the α-Ca2 SiO4 was studied and P2 O5 broken down by the raw material of(NH4)2 HPO4 played an important role in stabilizing α-Ca2 SiO4 which can only be stable at high temperature.The XRD patterns of the Ca2-x/2 Si1-x Px O4 host were found pure and optimized when the mole fraction of P2 O5 was 14.5%.The diffuse reflectance spectra of the Ca1.855 Si0.71 P0.29 O4 and Ca1.845 Si0.71 P0.29 O4 :0.01Eu2+covered the spectral region of 230-400 nm,implying that the phosphor was suitable for UV or near-UV LED excitation.The phosphor could be effectively excited in the near UV region with the maximum at 372 nm.The emission spectrum of the Ca1.845 Si0.71 P0.29 O4 :0.01Eu2+phosphor showed an asymmetrical single intensive band centered at 513 nm,which corresponded to the 4f65d1→4f7transition of Eu2+.Eu2+ions might occupy two types of Ca2+sites in the Ca1.855 Si0.71 P0.29 O4 lattice and form two corresponding emission centers,which led to the asymmetrical emission of Eu2+in Ca1.855 Si0.71 P0.29 O4.The effects of Eu2+-doped concentration in Ca1.855-x Si0.71 P0.29 O4 :xEu2+on the PL were also discussed,the optimum doping concentration of Eu2+was 1 mol.% and the critical distance of the energy transfer was also calculated by the concentration-quenching method.The non-radiative energy transfer between Eu2+seemed to be caused by the multipole-multipole interaction.The fluorescence lifetime of Eu2+was found to be 0.55711 μs.The results suggested that these phosphors might be promising candidates used for near UV light excited white LEDs.     

Davidoff的倡导性城市规划理论

本文从分析20世纪60至70年代西方城市发展和社会政治状况入手,整理PaulDavidoff的倡导性城市规划理论产生的社会、经济背景与理论渊源,介绍其规划理论的主要内容,并对这一理论做简单的评价和分析.     

谈网版印刷在高等艺术院校教学中的架构

网版印刷一向被行业人士爱称为万能印刷,缘于它几乎无所不印的印刷方式,个性鲜明、系统完整的工艺流程,丰富多彩、经济实用的物料设备,在工业、电子、轻纺、制造、商业以及艺术创作等领域大行其道,创造了庞大的产业结构和辉煌的经济效益,倍受人们的喜爱。尽管在我国网印工艺可以追溯到     

一种新型宏模块和标准单元的混合模式布局算法

本文针对包含有宏模块和标准单元的超大规模集成电路布局问题, 提出了一个新的混合模式布局算法MMP.该算法综合应用了自底向上的结群策略,数学规划和Slicing划分等技术.MMP算法可以对宏模块和小单元同时求解,算法稳定性好,实用性强,不但求解质量高,而且运算速度快.我们对一组来自工业界的设计实例进行了测试,实验结果表明,MMP是非常实用而高效的.     

一种新的基于单元扩大的拥挤度驱动的布局算法

描述了一种新的基于单元扩大的拥挤度驱动的布局算法 .这个方法用概率估计模型和星型模型来评价线网的走线 .使用全局优化和划分交替的算法来进行总体布局 .提出了单元的虚拟面积的概念 ,单元的虚拟面积不仅体现了单元的面积 ,而且指出了对布线资源的需求 .单元的虚拟面积可以由单元的扩大策略来得到 .把单元的虚拟面积用到划分过程中 ,从而减小拥挤度 .并且使用了单元移动的策略来进一步减小走线的拥挤 .用来自美国公司的一些例子测试了这个算法 ,结果显示布局的结果在可布性方面有了很大的提高     

一种新的基于单元扩大的拥挤度驱动的布局算法

描述了一种新的基于单元扩大的拥挤度驱动的布局算法．这个方法用概率估计模型和星型模型来评价线网的走线．使用全局优化和划分交替的算法来进行总体布局．提出了单元的虚拟面积的概念,单元的虚拟面积不仅体现了单元的面积,而且指出了对布线资源的需求．单元的虚拟面积可以由单元的扩大策略来得到．把单元的虚拟面积用到划分过程中,从而减小拥挤度．并且使用了单元移动的策略来进一步减小走线的拥挤．用来自美国公司的一些例子测试了这个算法,结果显示布局的结果在可布性方面有了很大的提高．     

GYB 通信电缆过电压保安器研制与应用

一、前言为解决高压输电线路对城市电话系统的电磁危险影响问题,经与沈阳市三龙微电子设备厂协作,共同研制了 GYB 系列通信电缆过电压保安器(以下简称 GYB)。通过试验室中间试验和工程实用,证明 GYB 是解决市话电缆线路防强电影响较为经济实用的设备。GYB 的关键是以三极充气陶磁放电管来保护通信电缆和通信设备(即放电管接在电缆芯线上,公共端接于电缆金属外皮并可靠接地)。60年代,工业较发达国家通过大量试验、逐步在通信电缆上,使用放电管来防止过电压,由于充气陶磁放电管参数范围、质量不断提高,这种方法基本成熟。至今,英、法、联     

超高效液相色谱-四级杆-飞行时间串联质谱法检测中药及保健食品中21种非法添加的降脂类药物

目的建立超高效液相色谱-四级杆-飞行时间串联质谱仪(ultra performance liquid chromatography/quadrupole-time-of-flight mass spectrometry,UPLC/Q-TOF-MS)快速检测中药及保健食品中的21种降脂类药物。方法样品经甲醇超声提取后,采用Agilent Poroshell 120 SB-C_(18)色谱柱分离,以0.1%甲酸水溶液和乙腈作为流动相进行梯度洗脱,流速为0.4 mL/min;质谱采用Q-TOF-MS作检测器,采用电喷雾离子源(electronic spray ion,ESI)正负离子模式,以保留时间、精确分子量和二级碎片比对进行定性分析。结果 21种降脂类药物的检出限为0.05~25 ng。对96批市售中成药及保健食品进行定性检测,结果 1批片剂中检出洛伐他丁,其余均未检出。结论本方法灵敏、准确、高效,可适用常见降脂类药物的快速检测。     

Photoluminescence properties of Tb3+ and Ce3+ co-doped Sr2MgSi2O7 phosphors for solid-state lighting

Sr2Mg Si2O7:Tb3+,Ce3+ phosphors were synthesized by solid-state reaction and placed in a muffle furnace in a reducing atmosphere at 1300 oC for 3 h. Photoluminescence properties and energy transfer were investigated. The Ce3+/Tb3+ energy transfer was thoroughly investigated by their emission/excitation spectra and photoluminescence lifetime, there was shortened lifetime of Ce3+(from 51.31 to 50.06 ns) which could support evidence of energy transfer from Ce3+ to Tb3+ in the host. The varied emitted color of Sr1.97–yMg Si2O7:0.03Tb3+,y Ce3+ phosphors could be achieved by altering the concentration of Ce3+, the chromaticity coordinates(x, y) varied from(0.225, 0.376) to(0.172, 0.231). In Sr1.96 Mg Si2O7:0.03Tb3+,0.01 Ce3+ phosphors, the results indicated that Sr2 Mg Si2O7:Tb3+,Ce3+ might be useful as tunable phosphors for ultraviolet white-light-emitting diodes.     

基于RBV视角的烟台葡萄酒文化旅游产业竞争力研究

烟台作为中国最大的优质葡萄酒酿造产区,是葡萄酒文化旅游产业的发祥地之一,提升烟台葡萄酒文化旅游产业的竞争力,能够增强区域发展的新动能,推动烟台经济从高速发展向高质量发展转换。通过对烟台葡萄酒文化旅游产业竞争力现状进行研究,发现区域依赖性使其产业竞争力受制于资源状况,以基础资源论(RBV)视角对烟台葡萄酒文化旅游园区资源进行分类,整合葡萄酒文化旅游园区资源竞争力机制。结合资源现状给予提升烟台葡萄酒文化旅游产业竞争力的针对性建议,以吸引更多游客参与。