Gd_3Ga_5O_(12)晶体中铬离子对钕离子的荧光敏化

报导钕和铬离子激活Gd_3Ga_5O_(12)晶体中荧光光谱和振荡性能的研究。证实由铬离子向钕离子能量转移过程具有高的效率。例如,Gd_3Ga_5O_(12)晶体中Cr~(3 )-Nd~(3 )相互影响的基本作用几率较Y_3Al_5O_(12)。晶体高11倍。所得结论是,铬离子对钕离子的荧光敏化效应对连续或脉冲工作的钕激光器的能量特性均可提高几倍。对自由振荡参数的研究表明,在Gd_3Ga_5O_(12):Cr,Nd晶体中,钕的振荡极限微分效率较同样条件下的YAG:Nd~(3 )晶体高2.6倍。     

飞机发动机叶尖间隙光纤测量系统

随着涡轮机技术的发展,对叶尖间隙精确测量的要求越来越迫切。目前开发的光纤激光尖间隙测量系统既能测量单个叶尖间隙,又能测量平均叶尖间隙,可用于螺旋桨、压力机和涡轮机的叶尖间隙测量。探头适合涡轮机的工作环境和现场安装要求。测量系统由光学分系统、电子学分系统以及计算机图像处理终端组成。台架试验和环境试验都表明,该系统能满足考虑涡轮机工作时的温度、压力、振动影响在内的叶尖间隙测量要求。     

油菜施硼后的叶肉细胞电镜观察

国内外研究表明硼素对植物生殖器官的形成和发育有着密切的关系。硼素丰富可促进作物成熟提高座花率,起到明显的增产效果。实践证明适量的施硼对油菜有良好的增产效果。若用量过低增产效益不明显,若用量过高,甚至可能引起微量元素中毒症。1982年以来,我们试图通过电镜观察不同施硼量对油菜叶肉细胞的变化影响,以探讨喷硼的适宜范围。     

五磷酸钕激光器评述

五磷酸钕是一种晶体材料,具有很高的钕的浓度(比掺钕(1％)YAG高30倍)和低的浓度猝灭。对制成1.05微米振荡的光泵浦小型低阀值激光器来说是一种良好的材料。本文评述了包括与激光特性有关的光谱特性的材料特性,总结了用这种材料的脉冲和连续激光作用的试验,包括最近完成的具有横截面12×12微米小型纤维激光器。     

油菜雌蕊的亚细胞钙离子分布

自六十年代发现钙调素(Calmodulin,CaM)之后,与此有关的Ca~(++)的研究受到很大的注意。近十年来的研究表明,Ca~(++)在植物体内并不是一个简单的大量元素,而是参与调节植物体内许多生理过程的代埘和发育的主要调节物。有报道认为花粉管的生长被Ca~(++)所促进,花粉管到达胚珠的向性生长可能是从柱头到胚珠钙含量徒度的反应。本实验用甘蓝油菜为材料,用焦锑酸钾沉淀技术,对花粉管生长途径的细胞进行钙离子定位,并结合细胞结构研究花粉管在雌蕊中的生长与Ca~(++)的关系。     

稀土钕离子对立方晶型FeS2结构及光性能的影响

采用真空、无氧退火方法对立方晶型FeS2进行了稀土钕掺杂实验.利用X射线衍射仪和紫外可见分光光度计对样品的结构及光吸收谱进行了研究.利用Rietveld方法对掺杂样品的结构进行了精修.结果显示:由于稀土钕离子的进入,使得立方晶型FeS2晶格结构发生畸变,从而导致样品光电性能改变.     

读友信箱

钕磁铁和输出变压器 Q 我是一名音响爱好者,但是我对技术不怎么 懂,经常看到有文章中说某某喇叭用了钕磁 铁,这钕磁铁到底是什么?它又有何优点呢?另外, 为什么电子管功放都有输出变压器,而晶体管功放 却没有？输出变压器和电源变压器有何区别? 山东省济宁车站东路 李仲煜 A 钕磁铁是现代扬产器产品中常用的高级磁铁, 它由钕、铁、硼三种元素所构成,是目前磁性最     

稀土钕离子对立方晶型FeS2结构及光性能的影响

采用真空、无氧退火方法对立方晶型FeS2进行了稀土钕掺杂实验．利用X射线衍射仪和紫外可见分光光度计对样品的结构及光吸收谱进行了研究．利用Rietveld方法对掺杂样品的结构进行了精修．结果显示：由于稀土钕离子的进入，使得立方晶型FeS2晶格结构发生畸变，从而导致样品光电性能改变     

四磷酸钕锂的红外光谱研究

本文报导了四磷酸钕锂(LNP)的红外光谱,对比五磷酸钕(NPP)和其它的稀土四偏磷酸盐的红外光谱,对LNP的结构特性作了探讨,解释了LNP中无羟基OH吸收和桥键P—O—P高频位移的现象,以及谱带裂分现象.     

一种新型微波叶尖间隙传感器

针对恶劣环境下航天发动机、涡轮机等旋转机械对叶尖间隙实时测量的需求,设计了一种用于涡轮发动机叶尖间隙测量的新型微波传感器。该传感器基于多嵌套式分裂环谐振器(NSRR)结构,将铂(Pt)金属浆料组成的闭环电路集成于高温共烧陶瓷(HTCC)中,以此来适应发动机及涡轮机内部的极端测试条件。经过仿真设计,可知传感器的工作频率为2.44 GHz,且在2.5～5 mm仿真间隙范围内最低灵敏度为8.33 dB/mm。通过传统的HTCC工艺及厚膜技术,对设计的传感器进行制备和测试,测试结果验证了仿真结果的正确性,表明该传感器能为所需应用环境提供准确可靠的数据。     

Length optimization of single-mode rare-earth doped waveguidesusing saturated absorption

Absorption saturation was demonstrated to provide a high, uniform population inversion over a length of waveguide longer than the material absorption length. The small signal gain was measured experimentally in single-mode waveguides, made by silver ion exchange, on a commercially available neodymium doped glass. The ratio of the excited states was calculated as a function of waveguide length and was shown to be a convenient criteria to determine the optimum device length     

腔内倍频Nd~(3 )∶GdVO_4/LBO深蓝456nm激光器的工作特性

在激光二极管(LD)抽运腔内倍频Nd3 ∶GdVO4/LBO深蓝456 nm激光器中,为对比激光晶体掺杂浓度对倍频输出功率的影响,利用同样尺寸为3 mm×3 mm×2 mm,稀土离子掺杂原子数分数分别为0.15和0.25的Nd3 ∶GdVO4晶体作为对比。实验中利用同样长为20 mm的线性直腔,在使用10 mm长、按基频光为914 nm方向切割的Ⅰ类相位匹配倍频晶体LBO,在抽运功率为2.85 W时,前者获得了输出功率为105 mW的深蓝456 nm激光,明显高于后者。通过对准三能级激光晶体的最佳长度分析表明,掺杂原子数分数为0.15的Nd3 ∶GdVO4晶体与0.25的相比,其实际长度更加接近于最佳长度。通过对倍频晶体LBO的最佳切割角和温度控制等分析表明,利用针对914 nm基频光切割的LBO晶体在912 nm激光器中,其切割角的差别可以通过温控的改变得到补偿。     

钕激光对家兔牙髓的影响

目的 :研究钕激光对家兔牙髓的影响。方法 :采用脉冲式钕玻璃激光器 ,将激光束聚焦到 1毫米的光斑 ,照射于实验动物 ( 8只家兔 )实验牙齿颊面的龈嵴上 ,评价家兔牙髓的反应按四个等级的方法来区分。结果 :激光照射家兔牙齿后立即作检查 ,仅在 2个标本上看到牙齿表面形成明显的洞 (标本 43和 3 8) ,从标本的组织学切片也证实 ,在牙本质上有明显的洞形 ,并有牙髓反应。结论 ;钕激光对家兔牙髓的影响与周围正常牙髓组织有明显区别 ,仅在暴露于激光束下邻近牙本质小管的牙髓处才有影响     

外源信号物质对肉苁蓉种子萌发体的影响研究

肉苁蓉（Cistanche deserticola Y.C.Ma）是沙生根寄生植物。采用激光扫描共聚焦显微镜（LSCM）,对种子经外源信号物质氟草敏（Norflurazon）、2,6-二甲氧基对苯醌（DMBQ）处理后萌发产生的类胚根状体、初生吸器的细胞形态;Ca2＋浓度、囊泡运输的变化情况进行了观察研究。结果表明,肉苁蓉种子萌发产生的类胚根状体顶部的细胞为多面体,细胞小,排列紧密,内含物较多,中部大多为长方形薄壁细胞,内含物少;经DMBQ处理后类胚根状体细胞的钙离子浓度升高,囊泡运输加强。研究结果为揭示外源信号物质对肉苁蓉寄生影响提供了理论依据。     

Spectral control of laser oscillators by secondary light sources

Frequency and polarization selection of neodymium glass laser oscillators was achieved by directing secondary radiation into the laser cavity. The rapid energy transfer between the neodymium ions allowed the laser emission to duplicate the spectral properties of this secondary radiation.     

Study of the activator impurity distribution in active elements of solid-state lasers by means of acousto-optical combination-scattering spectroscopy

The operating principles of a Raman acousto-optical spectrometer (a combination-scattering spectrometer) and an experimental setup incorporating this spectrometer are described. The combination-scattering spectra of the active element of a neodymium-doped yttrium aluminum laser are presented for various points located along the sample length. The interpretation of these spectra allows estimation of the distribution of the average concentration of activator ions (neodymium ions) and the nonuniformity of this concentration (the deviation from the average value) along the laser rod.     

掺钕双频微片激光器功率均衡实验研究

为了探究掺钕晶体对激光器功率均衡机制的影响 ,实验对不同参数的掺钕晶体双频微片激光器进行了功率均衡实 验研究。在实验中,通过改变抽运功率和调节热沉温度等手段,研究了双频微片激光器功率 在均衡状态时,热沉温度、 抽运功率和双频激光功率积等参数之间的关系。研究结果表明:对于功率均衡的掺钕双频微 片激光器,当抽运功率增加 时,热沉温度随之降低且与之呈负相关,需要降低热沉温度以实现双频激光的功率重新均衡 ;重新均衡后的双频激光波 长与频差不随抽运功率的变化而变化;功率均衡的双频激光功率积随抽运功率的增大而增大 ,且呈正相关。此结果说明 对于不同参数的掺钕晶体双频微片激光器,均可通过改变抽运功率和热沉温度可以实现功率 可调的功率均衡的双频激光 信号输出。这种输出功率可调谐的双频微片激光器在光生毫米波等领域有较大用途。     

The growth, structure, and magnetic properties of thin epitaxial films of GdMnO3 multiferroics

Thin epitaxial gadolinium manganite (GdMnO₃) films were manufactured on single-crystal substrates of neodymium gallate (001) (NdGaO₃) and strontium titanate (001) (SrTiO₃) by the high-frequency magnetron sputtering method. The RBS analysis demonstrated that the thickness of the obtained films was ??100 nm and the chemical composition corresponded to the stated stoichiometry. It was established by the X-ray diffraction analysis of the structure and phase composition of the obtained films that all films were single-phase but, depending on the temperature of the substrate during sputtering they have one or several types of orientations relative to the substrate. The X-ray diffraction analysis and high-resolution electron microscopy data on gadolinium manganite films on neodymium gallate substrates were verified. Features pointing to phase transitions in GdMnO₃ that were earlier discovered on bulk single-crystal samples were found in the temperature dependence of the magnetic susceptibility.     

Floating-point division and square root using a Taylor-series expansion algorithm

Hardware support for floating-point (FP) arithmetic is a mandatory feature of modern microprocessor design. Although division and square root are relatively infrequent operations in traditional general-purpose applications, they are indispensable and becoming increasingly important in many modern applications. Therefore, overall performance can be greatly affected by the algorithms and the implementations used for designing FP-Div and FP-Sqrt units. In this paper, a single-precision fused floating-point multiply/divide/square root unit based on Taylor-series expansion algorithm is proposed. We extended an existing multiply/divide fused unit to incorporate the square root function with little area and latency overhead since Taylor's theorem enables us to compute approximations for many well-known functions with very similar forms. The implementation results of the proposed fused unit based on standard cell methodology in IBM 90 nm technology exhibits that the incorporation of square root function to an existing multiply/divide unit requires only a modest 18% area increase and the same low latency for divide and square root operation can be achieved (12 cycles). The proposed arithmetic unit exhibits a reasonably good area-performance balance.     

Waveguide lasers operating at 1084 nm in neodymium-diffused lithiumniobate

The authors report the demonstration of waveguide lasers in lithium niobate into which the active element neodymium has been introduced by thermal diffusion. The waveguides were fabricated using conventional Ti indiffusion and optical feedback was provided by the polished endfaces alone. The absorbed power threshold of one waveguide laser was estimated at 13±3 mW for pumping at 814 nm, and its slope efficiency in terms of total lasing output as a function of absorbed pump power was estimated to be 55±8%. Laser output powers in excess of 100 mW were observed