BGO晶体的热释光效应及光损伤后晶体的恢复

本文介绍 BGO 晶体的热释光效应,BGO 大单晶光损伤后恢复的实验。BGO 晶体热释光曲线的次峰位温度约在200℃,光伤后的 BGO 大单晶一般通过200～250℃保温5～7h 的热处理就能使晶体完全恢复。     

锗酸铋晶体光电导性质的研究

生长了六种掺杂锗酸铋(简称 BGO)晶体(分别掺 Fe、Cr、Mn、W、Pb 和 Ce)。在合适的测试条件下,测量了它们的光吸收系数、光电导参数和暗电导率,并与未掺杂样品进行了比较。计算出了样品的特征参量μφτ,为上述材料光折变性质的研究提供了必不可少的数据。在此基础上,对 BG0∶Cr、BGO∶Fe 和BGO∶Mn 晶体的光折变机制进行了简略的讨论,认为 BGO∶Cr 中的光折变中心可能是:Cr~(3+)作为施主,Cr~(4+)作为电子陷阱;或 Cr~(4+)作为受主,Cr~(3+)为空穴陷阱。     

锥形六面体BGO大单晶的表面处理与均匀性

闪烁晶体锗酸铋(简称 BGO)的均匀性除依赖于晶体的质量、外形外,还强烈地依赖于晶体表面的性质。本文以(?)×24×(?)cm~3锥形六面体 BGO 大单晶为对象,研究晶体一对粗糙侧面的加工方法和热处理对晶体的光输出、均匀性和能量分辨率的影响,从而确定合适的表面粗糙度及其相应的表面处理工艺,实验结果表明,通过合宜工艺提高了锥形六面体晶体的光输出和均匀性,同时也改善了晶体的能量分辨率。     

光纤电压互感器中电光晶体对测量精度的影响

光纤电压互感器中电光晶体BGO(Bi4Ge3O12)的缺陷、杂质及内部残余应力引起自然双折射,降低仪器的电压测量精度.从理论上分析了晶体在不同方向承受应力时不同通光方向上的双折射;又从热光效应的原理出发,推导出调制度的变化与温度、电压之间的定量关系,得出调制深度对温度的变化率与调制度本身成正比、与外施电压成正比的结论.因此,为提高仪器的温度稳定性,保证必要的灵敏度,必须使施加到电光晶体上的电压合理.BGO晶体的吸收和色散较小,对光纤电压互感器测量精度的影响不大.     

BGO∶TR(TR=Nd,Er),Cr,Fe晶体的吸收光谱和发光光谱

在化学计量的Bi_2O_3(5N)和 GeO_2(6N)的配料里,加入0.01wt%Nd_2O_3,0.01wt%Er_2O_3,0.02wt%Cr_2O_3或0.02wt%Fe_2O_3,用 Bridgman 方法生长 Bi_4Ge_3O_(12)掺杂晶体。给出 eulytite 的结构投影和 BGO 晶体的点阵常数。掺杂稀土 BGO 晶体的室温吸收光谱由稀土离子所特有的几个吸收带所组成。采用3d~3电子的能量久期方程计算 O_h 场下掺 Cr~(3+)BGO 的库仑相互作用参数和内晶体场参数,其吸收光谱是由基态~4A_2到~2E,~4T_2和~4T_1跃迁的三个带组成。以300nm 激发观察到纯锗酸铋强的宽带发光,其峰值位置在498和550nm。这种发射被认为是 Bi~(3+)的~3P_1→~1S_0跃迁。由于存在大的 Stokes 迁移,Bi~(3+)系统猝灭心受到阻止。另外,由于~3P-~1S 能级差别大,使多声子过程中的非辐射衰减亦受到限制。通过接收498nm 发射波长,测量纯 BGO 室温激发光谱,其峰值位置在250、272和285nm,这和 M.J.Weber 测定的吸收收和反射光谱的结果基本一致。按不同波长范围分别采用光电倍增管和 PbS 接收,测量了 BGO 掺 Nd~(3+)的~4F_(3/2)→~4I_(11/2),~4I_(13/2)跃迁;掺 Er~(3+)的~4I_(13/2)→~4I_(15/2)跃迁的荧光光谱。强的荧光发射以及发射带宽界于 YAG和玻璃之间,表明掺杂稀土的 BGO 晶体是一类有希望的激光材料。     

调制晶体及其应用

分别研究分析几种调制晶体(电光晶体、磁光晶体、弹光晶体和声光晶体)的性质及其应用,推导出要比较全面的研究晶体的情况,就要将晶体看成同时承受一系列外界作用而同时在许多方面作出响应的一个整体,综合考虑各种效应及其之间的相互耦合相互联系。     

面向磁光应用的CeF3晶体生长与性能表征

随着高功率激光和光通信技术的迅速发展,如何消除光学系统内部产生的反射噪声是一个至关重要的问题。磁光隔离器是依据法拉第效应设计而成的磁有源器件,能够有效隔离大部分反射光以保证光学系统稳定工作,而法拉第磁光材料作为磁光隔离器的核心部件,其研究和应用推动了磁光隔离器的更新与发展。CeF₃晶体具有高透过率、宽透过区间和高Verdet常数等优点,近年来获得了广泛关注,但是其传统生长方法存在成本高、周期长等缺点。本研究通过坩埚下降生长技术,优化温场结构和生长工艺,采用多孔坩埚成功获得多根CeF₃晶体。与商用TGG(Tb₃Ga₅O₁₂)晶体相比, CeF₃晶体的透过率得到明显提高,最高达到92%,并且在近红外波段两者的Verdet常数相当。CeF₃晶体的比热较高,表明晶体拥有较强的抗热冲击能力和较高的抗激光损伤能力。本研究使用多孔坩埚技术生长CeF₃晶体,实现了规模化和低成本生产;生长的CeF₃晶体物理性...     

顶部籽晶法生长大尺寸、高品质钇铁石榴石晶体（英文）

钇铁石榴石(Y₃Fe₅O₁₂, YIG)晶体具有优异的磁学和磁光性质,在微波和磁光器件中有着广泛的应用。目前商用的磁光材料是采用液相外延技术在Gd₃Ga₅O₁₂(GGG)衬底上沉积的YIG单晶薄膜。本研究以无铅B₂O₃-BaF₂为复合助熔剂,采用顶部籽晶法技术(TSSG)生长YIG单晶材料, YIG晶体尺寸和重量分别可达43 mm×46 mm×11 mm和60 g。该晶体具有较窄的铁磁共振线宽(0.679 Oe)、高透明度(75%)和法拉第旋转角(200 (°)·cm^–1@1310 nm, 160 (°)·cm^–1@1550 nm)等优异的综合性能,是微波和磁光器件的良好候选材料。更为重要的是,这种生长技术非常适合大尺寸YIG单晶或稀土掺杂YIG单晶,结合定向籽晶生长和提升工艺,可以显著降低生产成本。     

磁光透明陶瓷的研究进展

磁光材料是指从紫外到红外波段具有磁光效应的光功能材料, 按照材料的类型可将其分为磁光玻璃、磁光晶体、磁光透明陶瓷等。其中, 磁光透明陶瓷是近年来出现的一种新型磁光介质材料, 具有高Verdet常数、大尺寸、高热导率、高激光损伤阈值等优点, 因而是用于高功率激光器中法拉第隔离器最理想的材料之一。目前已经报道的磁光透明陶瓷材料主要包括铽镓石榴石(Tb₃Ga₅O₁₂, TGG)陶瓷、铽铝石榴石(Tb₃Al₅O₁₂, TAG)陶瓷以及一些倍半氧化物陶瓷, 如氧化铽(Tb₂O₃)陶瓷、氧化钬(Ho₂O₃)陶瓷、氧化镝(Dy₂O₃)陶瓷等。本文首先介绍了几种常见的磁光效应, 详细阐述了法拉第效应和克尔效应的基本原理。着重对几种磁光透明陶瓷材料的研究进展、材料性能、应用前景进行了综述和介绍, 并对这几种磁光透明陶瓷的性能进行了比较和分析, 指出了它们存在的问题和今后的研究方向。     

光子在闪烁晶体中传输的蒙特卡罗模拟

为了找到构筑闪烁晶体探测器的优化方法，使用蒙特卡罗方法对闪烁晶体BGO（Bi4Ge3O12，锗酸铋）的光收集效率进行了模拟研究。模拟结果表明：入射面为粗糙面，其余为抛光面，同时外层包装上高反射率的材料，可得到最大的光输出（约59．1％的光子被收集）；耦合剂的折射率的得到高的光输出也起着非常重要的作用。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from     

CNAS Passes APLAC's PTP Review

正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively.     

新闻(英文)

正China and Greece Sign the Standardization Cooperation Agreement Witnessed by Chinese Premier Li Keqiang and Greek Prime Minister Antonis Samaras,AQSIQ Minister Zhi Shuping and ELOT Chairman and Executive Director Angelos Tolkas signed the SAC-ELOT Standardization Cooperation Agreement.The Agreement is one of the critical cooperation documents signed during Li Keqiang’s visit in Greece,encouraging China and Greece to