大尺寸 Ce:Lu1.6Y0.4SiO5闪烁晶体的生长和光谱特性

采用中频感应提拉法生长出尺寸为φ60mm×110mm的CeLu1.6Yo.4SiO5(LYSO)晶体,与LSO晶体相比,LYSO晶体的优势是提高了晶体质量、降低了熔点和原料成本等.在室温下测试了LYSO晶体的透过光谱、激发光谱和发射光谱,结果表明Y的加入使LSO晶体的吸收边向短波方向偏移.Ce3+的4f1→5d1跃迁吸收导致紫外区产生三个吸收带.发射光谱具有Ce3+典型的双峰特征,经Gaussian多峰值拟合,双峰395nm和418nm归属于Ce1发光中心,而435nm的发光峰与Ce2发光中心有关.     

掺铈硅酸镥(Lu2SiO5:Ce)晶体的生长与闪烁性能

用Czochralsky方法和铱坩埚感应加热技术生长出了尺寸为φ35mm×40mm的掺铈硅酸镥(LSO:Ce)闪烁晶体.透射光谱表明,由于铈离子的掺入,使晶体的吸收边由纯LSO晶体的195nm红移至380nm.LSO:Ce晶体的紫外激发波长按强度递减的顺序依次为380、333、319和216nm,其光发射为带状谱,波长覆盖范围从390nm至560nm.X射线激发的发射谱具有典型的双峰特征,峰值波长为393nm和.426nm.这些特征与Ce3+离子基态能级4f1因自旋-轨道耦合而产生的两个分裂能级和Ce+离子在LSO晶体中占据两个不同的结晶学格位有关.     

Ce∶YAG晶体色心和缺陷的伽马射线辐照研究

利用伽玛射线研究了Ce3+∶Y3Al5O12晶体的辐照色心缺陷,比较了采用提拉法和温梯法生长的Ce3+∶Y3Al5O12晶体中产生的不同色心缺陷,并利用吸收光谱、激发发射光谱和退火等方法分析了晶体中235nm和370nm色心吸收带的形成原因,指出晶体中的235nm吸收带由F+色心引起。进一步分析了YAG晶体的辐照,证实了370nm色心的来源,表明370nm吸收带与F-类色心相关。     

Ce:YAG晶体色心和缺陷的伽马射线辐照研究

利用伽玛射线研究了Ce3+:Y3Als O12晶体的辐照色心缺陷,比较了采用提拉法和温梯法生长的Ce3+;Y3Al5O12晶体中产生的不同色心缺陷,并利用吸收光谱、激发发射光谱和退火等方法分析了晶体中235nm和370nm色心吸收带的形成原因,指出晶体中的235nm吸收带由F+色心引起.进一步分析了YAG晶体的辐照,证实了370hm色心的来源,表明370nm吸收带与F-类色心相关.     

掺铈硅酸镥(Lu2SiO5:Ce)晶体的生长与闪烁性能

用Czochralsky方法和铱坩埚感应加热技术生长出了尺寸为φ35mm×40mm的掺铈硅酸镥(LSO:Ce)闪烁晶体.透射光谱表明,由于铈离子的掺入,使晶体的吸收边由纯LSO晶体的195nm红移至380nm.LSO:Ce晶体的紫外激发波长按强度递减的顺序依次为380、333、319和216nm,其光发射为带状谱,波长覆盖范围从390nm至560nm.X射线激发的发射谱具有典型的双峰特征,峰值波长为393nm和.426nm.这些特征与Ce³⁺离子基态能级⁴f₁因自旋-轨道耦合而产生的两个分裂能级和Ce⁺离子在LSO晶体中占据两个不同的结晶学格位有关.     

Cs2LiYCl6:Ce闪烁晶体的光学及闪烁性能

用坩埚下降法生长得到Cs₂LiY _0.95Cl₆: 5%Ce(CYLC)闪烁晶体, 通过X射线衍射分析证明Cs₂LiYCl₆:Ce的晶体结构属于钾冰晶石结构, 并与理论计算结果基本吻合。在吸收光谱中观测到源于Ce³⁺离子从4f向5d_1~5电子跃迁的吸收峰和自陷激子吸收峰。X射线和紫外激发和发射光谱测试表明, 位于300 nm的发光属于Cs₂LiYCl₆:Ce晶体的本征芯价发光, 321 nm的发光归因于自陷激子发光, 350~450 nm范围的发光属于Ce³⁺离子5d-4f 跃迁发光。在³⁷Cs源伽马射线激发下, CYLC晶体的能量分辨率达到8.1%, 衰减时间分别为58 ns和580 ns。综上所述可知, Cs₂LiYCl₆:Ce晶体将是一种在中子和伽马射线分辨领域具有广泛应用前景的闪烁晶体。     

分步滴定法制备YAG荧光粉

在室温下,采用分步滴定法得到高亮度LED所用的Y3-x-yGdxCeyAl5O12荧光粉,并以0.1mol/L的碳酸氢铵和氨水为沉淀剂,将其分步滴入金属盐离子混合液中,研究了s杂Gd离子对荧光粉发光性能的影响。结果表明,以Ce为激活中心,最佳掺量为0.06,加入助熔剂后,荧光粉的发光性能提高了50%左右;随着Gd3+取代量的增加,荧光粉样品发射光谱的峰值波长可红移5~10nm,同时,Gd3+对发光中心Ce3+的影响增强,当取代浓度x为0.1时发光最强。XRD测试结果表明Gd离子的s入对YAG相的形成并没有影响。     

三价铈离子掺杂氯化钾的光致发光性能

采用水热蒸发法制备了KCl∶Ce3+荧光粉。测量并分析了材料在室温下的真空紫外激发光谱及相应的发射光谱。结果表明激发谱显示6个峰,峰位分别为149、194、206、219、233和251nm。其中149nm的激发峰是基质吸收引起的;194、206、219、233和251nm是Ce3+离子的4f→5d跃迁引起的。发射峰显示双峰结构,峰位分别是311和326nm。此峰对应于Ce3+离子的5d→4f(2F5/2,2F7/2)跃迁。     

高质量自调Q激光晶体Cr4+,Nd3+:Gd3Ga5O12的生长

用固相合成、共沉淀等方法合成了Cr4+,Nd3+GGG晶体的单相多晶材料.讨论了共沉淀法和固相合成法合成GGG单相的技术参数.用合成的单相多晶原料生长了高质量的Cr4+,Nd3+GGG单晶.通过测晶体的光谱性质发现Cr4+,Nd3+GGG晶体在400nm和520nm附近存在Cr3+离子的强的吸收峰.在808nm附近存在Nd3+离子宽的吸收带,能与InGa二极管激光有效的耦合;在1100附近有Cr4+的较强的吸收带,可实现对Nd3+的自调Q输出.Cr4+,Nd3+GGG晶体的荧光光谱与NdGGG晶体的一样,发光中心也位于1062nm,但其强度约为NdGGG的1/5～1/6.Cr4+,Nd3+GGG晶体是一种非常有潜力的自调Q激光晶体,可以实现大功率激光器的小型化和全固化.     

新型黄绿色发光材料Sr2MgSi3O9:Ce3+,Tb3+的合成及光谱分析

采用凝胶-燃烧法在活性炭弱还原气氛下成功合成了新型荧光粉Sr2MgSi3O9 :Tb3+、Sr2MgSi3O9:Ce3+,Tb3+,用X射线粉末衍射仪(XRD)、扫描电镜(SEM)、荧光分光光度计等对合成产物进行了分析和表征.结果表明,所合成的发光材料与Sr2MgSi2O7具有相似的晶体结构,同属四方晶系.样品一次颗粒近似球形,粒径在100nm左右.Sr2MgSi3O9:Tb3+的激发光谱为一位于249nm的宽带,发射光谱主要由473、491、547、585nm等一系列发射峰组成,其中473nm(5D3→<7F3)为主发射峰,547nm(5D4→7F5)为次发射峰;样品Sr1.955MgSi3O9:Tb3+0.04,Ce3+0.005的激发光谱由峰值分别位于249和335nm的双激发带组成,其中后者为主激发带.在335nm激发下,其发射光谱由两部分组成,其中400nm附近的带状发射对应于Ce3+的发射,而491、547、588nm处的发射峰归属为Tb3+的5+D4→7FJ(J=6,5,4)跃迁发射,最强峰位于547nm,对应Tb3+的5D4→7F5跃迁.此外,探讨了Ce3+掺杂量对样品发光亮度的影响,发现Ce3+可以把能量传递给Tb3+,对Tb3+起到敏化作用.     

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.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...     

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.