White up-conversion emission in Ho/Tm/Yb tri-doped glass ceramics embedding BaF2 nanocrystals

Ho³⁺/Tm³⁺/Yb³⁺ tri-doped glass ceramics with white light emitting have been developed and demonstrated. Pumped by 980 nm laser diode (LD), intensive red, green and blue up-conversions (UC) were obtained. The green emission is assigned to Ho³⁺ ion and the blue emission is assigned to Tm³⁺ ion, whereas the red emission is the combination contribution of the Ho³⁺ and Tm³⁺ ions. The RGB intensities could be adjusted by tuning the rare-earth ion concentration and pump power intensity. Thus, multicolor of the luminescence, including perfect white light with CIE-X=0.329 and CIE-Y=0.342 in the 1931 CIE chromaticity diagram can be obtained in 0.15 Ho³⁺/0.2Tm³⁺/3Yb³⁺ tri-doped glass ceramics embedding BaF₂ nanocrystals pumped by a single infrared laser diode source of 980 nm at 500 mW. The up-conversion luminescence mechanism of Yb³⁺ sensitize Ho³⁺ and Tm³⁺ ions and the energy transfer from Ho³⁺ to Tm³⁺ in oxy-fluoride silicate glass ceramics were analyzed.     

Ab initio studies on the electronic structure of CeSi5

We investigated the electronic properties of CeSi₅ by band structure calculation based on the density functional theory within LDA, LDA+U, and fully relativistic schemes. The calculated band structure scheme shows that the spin-orbit coupling splits the Ce 4f states into three manifolds. When the on-site Coulomb potential is added to the Ce-derived 4f orbitals, the degeneracy between the f orbitals would be lifted and they are split into lower Hubbard bands and upper Hubbard bands. It was found that quasiparticle mass enhancement inferred by comparing γ to the density of states (DOS) at the Fermi level indicates the effective mass of CeSi₅ is enhanced with the fully relativistic results.     

银杏叶中硒与多糖的季节分布

银杏叶中总硒和各种溶解形态硒含量随着季节而变化,实验研究了不同采摘期银杏叶中总硒及不同溶解态硒含量分布.7月、9月和霜降之后采摘的银杏叶总硒的含量分别为1.873,2.136,0.815 mg·kg-1,硒的形态以水溶态硒为主.银杏叶粗多糖含量分布依次为9月＞7月＞11月.7月份采集的银杏叶中得到粗多糖为棕褐色固体粉末...     

氮化镓基发光二极管结构中粗化 p型氮化镓层的新型生长方法

提出了一种新型p型氮化镓粗化外延生长方法,这种生长方法的本质特征是利用低温生长的p型氮化镓作为粗化层的"晶籽"层,然后在这一层的基础上高温快速生长p型氮化镓,使粗化程度得到放大. 经实际制作尺寸为12 mil×10 mil的蓝光发光二极管器件并进行验证测试,与未进行p型氮化镓粗化的结果相比,通过这种方法粗化的发光二极管光通量可提升45%;结果同时表明,该方法有效解决了低温生长p型氮化镓带来的漏电流大,及预通镁源带来的前置电压高的问题. 关键词： 粗化 氮化镓 p型氮化镓 发光二极管     

应用级联倍频方法提高倍频系统输出稳定性研究

提出应用级联倍频方法提高倍频系统输出稳定性,并就该方法的有效性进行了理论分析和模拟计算.分析和计算结果不但证明级联倍频方法能实现倍频系统稳定输出,而且还表明可以通过仔细调节第一块倍频晶体中波矢方向 k 与光轴间夹角、两块倍频晶体间的间隔,能调节改变实现倍频系统最稳输出时所需第二块晶体的理论计算长度,使之与第二块倍频晶体的实际加工长度一致,最终实现系统稳定倍频输出.级联倍频方法在实现高输出稳定性的同时能实现高的倍频转换效率,对应用于光参量啁啾脉冲放大系统的高稳定抽运源系统的设计建造具有重要参考意义. 关键词： 级联倍频 稳定倍频输出 光参量啁啾脉冲放大     

具有横向磁晶各向异性的钴纳米线的微波吸收性能

使用电化学脉冲沉积法制备了磁晶各向异性易磁化方向(c轴)垂直纳米线长轴方向的钴纳米线.受到磁晶各向异性、静磁相互作用等因素与形状各向异性相互竞争的结果,纳米线阵列的磁滞回线显示出较弱的磁各向异性.此外,在2—18 GHz频率范围内,纳米线/石蜡复合材料的介电色散谱的虚部在5 GHz处有一个主峰,在10 GHz附近有一个较弱的峰;德拜弛豫特性和材料的电导率对这两个峰的形成均有贡献.同时,其磁导率色散谱的虚部在频率为6.1 GHz处有一个主峰,在10 GHz以上有两个较微弱的峰. 前一个峰源于自 关键词： 钴纳米线 介电色散谱 磁导率色散谱 微波吸收剂     

Z箍缩驱动器与丝阵负载耦合特性研究

以丝阵内爆零维模型为基础,采用Pspice模拟行为建模方法,建立了丝阵内爆动态电感与Z箍缩驱动器耦合的全电路模型,实现驱动器放电过程与丝阵内爆过程的自洽求解,并研究了丝阵参数、电路参数对内爆过程的影响.结果表明:丝阵负载与驱动器存在强耦合关系,丝阵参数、电路参数对丝阵峰值箍缩电流、内爆时间、内爆动能影响很大;在驱动器参数不变,内爆时间不超过电路固有放电周期1/4的前提下,峰值箍缩电流、内爆时间、内爆动能随丝阵质量的增加而增大,内爆时间随丝阵初始半径的增加而增大;在丝阵参数不变时,随着驱动器等效电容的增大,内爆时间减小,丝阵内爆动能增大,但驱动器储能转化为内爆动能的效率却先增大后减小.对于特定的驱动器,优化的丝阵参数应使内爆过程充分利用驱动器固有放电周期的上升沿,使丝阵快速收缩的时间起点接近电路固有放电周期的四分之一,以获得最大的动能效率. 关键词： Z箍缩驱动器 零维内爆模型 模拟行为建模 耦合特性     

采用圆偏振啁啾飞秒激光脉冲操控CS2分子的相干拉曼散射过程

采用两束圆偏振啁啾飞秒激光脉冲,非共线相干激发三原子分子CS₂液体. 在相位匹配的方向上,探测到由CS₂频率为397 cm^-1的振动模式产生的强度对称分布的相干反斯托克斯拉曼散射(CARS)信号和相干斯托克斯拉曼散射(CSRS)信号. 当调整两束激发光的圆偏振状态时,CARS,CSRS信号的强度、偏振、波长均发生规律性的改变:CARS,CSRS信号的强度分布反映了CS₂ 在不同极化状态下的受激拉曼散射截面大小;信号光的 关键词： 啁啾脉冲 相干反斯托克斯拉曼散射(CARS) 相干斯托克斯拉曼散射(CSRS) 2')" href="#">CS₂     

交换弹簧磁性多层膜的磁矩取向及磁滞回线的解析研究

本文以界面交换耦合常数Jⁱ和软磁相厚度L^s为主要参变量,研究了易轴与膜面平行情况下的Nd₂Fe₁₄B/α-Fe磁性多层膜的磁矩随外场变化的取向及磁滞回线,并得到了成核场的解析公式.分析发现,Jⁱ对磁矩取向、钉扎场和矫顽力机理有着较大的影响.当L^s较小时,钉扎场等于成核场,随着Jⁱ的减小 关键词： 成核场 钉扎场 矫顽力 磁滞回线     

Thermal activation and reaction of allyl alcohol on Ni(100)

The thermal chemistry of allyl alcohol (CH₂CHCH₂OH) on a Ni(100) single-crystal surface was studied by the temperature programmed desorption (TPD) and the X-ray photoelectron spectroscopy (XPS). The allyl alcohol adsorbs molecularly on the metal surface at 100 K. Intact molecular desorption from the surface occurs at temperatures around 180 K, but some molecules exhibit chemical reactivity on the surface: activation of the OH, CC, and CO bonds produces η¹(O)-allyloxy CH₂CHCH₂O_(a), η²(C, C) allyl alcohol (C_(a)H₂C_(a)HCH₂OH), and η³(C, C, O)-alkoxide (C_(a)H₂C_(a)CH₂ O_(a)) intermediates. Further thermal activation of allyl alcohol on the surface yields propylene (CH₂CHCH₃), 1-propanol (CH₃CH₂CH₂OH), propanal (CH₃CH₂CHO), and combustion and dehydrogenation products (H₂O, H₂, and CO). Propylene desorbs from the surface at temperatures of around 270 K. Hydrogenation to the η³(C, C, O)-alkoxide intermediate leads to the production of propanal which desorbs from the surface around 320 K, while hydrogenation of the η²(C, C) allyl alcohol intermediate produces 1-propanol, which desorbs at around 310 K. The co-adsorption of hydrogen atoms on the surface enhances the formation of the saturated alcohol, while co-adsorption of oxygen enhances the formation of both the saturated alcohol and the saturated aldehydes.