无机闪烁晶体及其产业化开发

在高能粒子或射线（如X射线、γ射线等）的作用下能够发出脉冲光的物体,被称为闪烁体。它是光电功能材料,被广泛用于高能物理、核物理、空间物理、核医学、地质勘探、安全检查以及国防工业等领域。闪烁体分为无机闪烁体和有机闪烁体两大类。根据形态、成份以及结构特点,可进一步将前者分为无机闪烁晶体、闪烁玻璃、闪烁陶瓷和闪烁气体,而后者可分为有机闪烁晶体、液体闪烁体和塑料闪烁体。其中,数量最多、应用最广的当推无机闪烁晶体。本文将主要介绍无机闪烁晶体及其应用以及有关晶体的开发状况,同时对无机闪烁晶体的发展趋势也将做一简要评述。     

无机闪烁材料研究进展

闪烁材料的发展已有一百多年的历史,其中无机闪烁材料应用最广、数量最多。无机闪烁材料主要包括陶瓷闪烁材料、晶体闪烁材料和玻璃闪烁材料三大类型。闪烁材料的闪烁性能主要包括光输出、透明性、衰减速率、高能粒子阻止能力和抗辐照损伤能力等。无机闪烁材料在影像核医学诊断、高能离子探测、工业在线无损检测以及油井勘测等领域有着广泛的应用。介绍了无机闪烁材料的三大发展阶段与三大类型,对部分重要无机闪烁材料的闪烁性能做了对比,并概括了闪烁材料的应用,展望了其发展前景。     

双读出量能器用闪烁晶体研究进展

双读出量能器是一种全新设计的高能粒子探测装置, 它能同时测量到Cherenkov光和闪烁光, 因而能更全面地获得高能粒子的信息。目前, 双读出量能器主要有三种设计方式: (1)采用石英纤维产生Cherenkov光, 塑料闪烁纤维生成闪烁光; (2)分别以未掺杂的晶体纤维作为Cherenkov辐射体、Ce掺杂的同种晶体纤维作为闪烁体; (3)采用同种闪烁晶体有效分离Cherenkov光和闪烁光。第三种设计可以消除取样涨落、提高量能器的分辨率, 因而备受关注。本文基于第三种设计方式探讨了钨酸铅(PbWO₄)、锗酸铋(Bi₄Ge₃O₁₂)、硅酸铋(Bi₄Si₃O₁₂)和镥铝石榴石(Lu₃Al₅O₁₂)四种。闪烁晶体在双读出量能器方面的研究进展和可能的应用。Pr掺杂PWO晶体以及硅酸铋晶体都有可能用于双读出量能器, 而后者由于吸收边比锗酸铋更短, 更易于分离Cherenkov光和闪烁光, 在双读出量能器应用方面显示出明显的优势。稀土离子掺杂有望进一步提高硅酸铋晶体的性能, 开发出更适合双读出应用的闪烁材料。     

镥基闪烁晶体的研究进展

由于高能物理实验、核医学成像、安全检查和地质探矿等领域的迫切需要,具有高密度、快衰减、高光输出和低成本等优良特性的闪烁晶体成为关注的焦点,特别是Ce~(3+)激活的镥(Lu)基化合物,其开发、研究和应用方兴未艾。简要综述了硅酸镥、氧化镥和铝酸镥等闪烁晶体的生长技术、闪烁性能和应用,并展望了镥基闪烁晶体的发展趋势。     

无机闪烁体的研究进展

闪烁体能够快速地将光子如X射线、γ射线或高能粒子如α粒子、β粒子转换成紫外-可见脉冲荧光,因此在过去的几十年中备受学术界和产业界关注,目前已经在核医学成像、安全检查、工业探测、高能物理等领域广泛应用。由于稀土离子如Ce~(3+)、Pr~(3+)和Eu~(2+)等具有5d-4f快偶极允许跃迁,所形成激子衰减时间一般在几十至几百纳秒之间,具有快闪烁响应特性,通常作为发光中心掺杂入不发光的基质中形成闪烁晶体。主要介绍了近几十年来无机闪烁晶体主要包括卤化物、铝酸盐和硅酸盐三类在学术界和产业界中的研究进展。     

无机闪烁体的研究进展

闪烁体能够快速地将光子如X射线、γ射线或高能粒子如α粒子、β粒子转换成紫外-可见脉冲荧光,因此在过去的几十年中备受学术界和产业界关注,目前已经在核医学成像、安全检查、工业探测、高能物理等领域广泛应用。由于稀土离子如Ce~(3+)、Pr~(3+)和Eu~(2+)等具有5d-4f快偶极允许跃迁,所形成激子衰减时间一般在几十至几百纳秒之间,具有快闪烁响应特性,通常作为发光中心掺杂入不发光的基质中形成闪烁晶体。主要介绍了近几十年来无机闪烁晶体主要包括卤化物、铝酸盐和硅酸盐三类在学术界和产业界中的研究进展。     

热激活延迟荧光增强型钙钛矿闪烁体及其X射线探测器（英文）

金属卤化物钙钛矿材料具有极高的射线衰减系数和优良的光电性能,基于其制备的光电探测器和闪烁体已成功用于X射线和γ-射线探测.然而,充分吸收高能射线需要相对较厚的光吸收层,但所需的厚度对于溶液法制备的钙钛矿薄膜来说很难达到.在这项工作中,我们设计了一种复合型器件,其不需要厚的钙钛矿吸收层,而是利用高荧光效率的钙钛矿闪烁体和性能优良的钙钛矿薄膜光电探测器充分吸收和利用X射线,从而提高X射线探测性能.而考虑到钙钛矿闪烁体严重的自吸收,我们将CsPbBr₃与含Cu(Ⅰ)的热激活延迟荧光配合物(MAC^*)Cu(Cz)混合,有效地实现了下转换发光,最大限度地提高了辐射发光量子效率.与商业闪烁体相比,混合闪烁体还实现了更短的余辉.此外,我们系统地研究对比了CsPbIBr₂探测器以及复合型探测器的性能指标,发现复合型探测器对X射线的探测灵敏度有显著提高,并且能够实现在X射线下清晰的成像.这项工作为提高X射线探测性能提供了一种新的思路,在应用层面具有巨大的潜力.     

无机闪烁晶体及其应用

本世纪４０年代后期发现ＮａＩ：Ｔｌ晶体具有优良的闪烁特性后，ＮａＩ：Ｔｌ被广泛应用于Ｘ射线和γ射线的探测技术。随着核探测技术在医学、物理、化学、地质勘探等科学技术领域中的发展，一系列无机闪烁晶体，如ＢＧＯ、ＣＷＯ、ＣｓＩ：Ｔｌ、ＣｓＩ等相继问世，并在这些领域中得到了应用。近年来，为了提高核医疗设备如ＰＥＴ等的性能和建造大型高能物理实验装置，如ＳＳＣ和ＬＨＣ，对新型快速、高密度、耐辐照的无机闪烁晶体     

铪化合物在先进陶瓷中的应用

简要介绍了氧化铪、硼化铪、碳化铪和其他铪酸盐作为先进陶瓷应用的一些研究现状,并初步归纳了其主要的应用研究方向.文章强调指出,鉴于铪化合物具有很高的熔点,可用于各种超高温环境;同时铪的有效原子系数高,其化合物对高能射线的吸收能力强,是潜在的闪烁材料,这些优点使铪化合物具有重要的使用价值和广泛的应用前景.     

中子探测用含6Li玻璃闪烁材料最新进展

自上世纪50年代第一代玻璃闪烁材料开发以来, 玻璃闪烁材料在核物理、高能物理、工业探测(中子能谱测量、中子射线照相术及极端环境下α、β与γ射线的探测等)等领域发挥着越来越难以替代的作用. 中子探测用玻璃闪烁材料的研究集中于镧系离子(Ce³⁺、Tb³⁺、Pr³⁺等)掺杂含6Li、10B等中子吸收截面较大核素的硅酸盐、磷酸盐、铝酸盐上. 本文由中子探测用玻璃闪烁材料的性能特点、发展历程与发光机理出发, 重点关注了含⁶Li硅酸盐玻璃、磷酸盐玻璃、氟氧玻璃及其它玻璃闪烁材料的制备方法、光学性能、荧光衰减时间及中子探测效率等性能研究, 并对玻璃闪烁材料的发展趋势及未来应用方向作出了展望.     

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.……     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

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.……     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

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 ...