光阴极材料GaAs／AlGaAs的组分分析

为探索砷化我阴极的光电灵敏度的影响因素,利用Ｘ射线光电子能谱、二次离子擀谱和电化学方法测试和分析了国内和国外ＧａＡｓ光阴极材料ＧａＡｓ／ＡｌＧａＡｓ的Ｃ,Ｏ含量的空穴深度分布。实验发现,国内的材料在ＧａＡｓ／ＡｌＧａＡｓ 面及ＡｌＧａＡｓ层的Ｏ含量分别为７．６％和１０．６％,Ｃ深度分别为５．２×１０＾１８ａｔｏｍｓ／ｃｍ＾３和１．０×１０＾１９ａｔｏｍｓ／ｃｍ＾３,而国外的材料的Ｏ含量相应为１．０     

国产金属有机化合物TMGa,TMAl,TMIn和TMSb的MOVPE鉴定

利用我们研制的常压ＭＯＶＰＥ设备对国产ＴＭＧａ、ＴＭＡｌ、ＴＭＩｎ和ＴＭＳｂ进行了鉴定，为此分别生长了ＧａＡｓ、ＡｌＧａＡｓ、ＩｎＰ、ＧａＳｂ外延层和ＧａＡｓ／ＡｌＡｓ、ＧａＳｂ／ＩｎＧａＳｂ超晶格和ＧａＡｓ／ＡｌＧａＡｓ量子阱结构。表征材料纯度的７７Ｋ载流予迁移率分别达到ＧａＡｓ：μ＿ｎ＝５６６００ｃｍ￣２／Ｖ·ｓ，Ａｌ＿（０．２５）Ｇａ＿（０．７５）Ａｓ：μ＿ｎ＝５１６０ｃｍ￣２／Ｖ·ｓ，ＩｎＰ：μ＿ｎ＝６５３００ｃｍ￣２／Ｖ·ｓ，ＧａＳｂ：μ＿ｐ＝５０７６ｃｍ￣２／Ｖ·ｓ。由１０个周期的ＧａＡｓ／ＡｌＡｓ超晶格结构组成的可见光区布拉格反射器已观测到很好的反射光谱和双晶Ｘ射线回摆曲线上高达±２０级的卫星峰。ＧａＡｓ／Ａｌ＿（０．３５）Ｇａ＿（０．６５）Ａｓ量子阱最小阱宽为１０，在ｌｉＫ下由量子尺寸效应导致的光致发光峰能量移动为３９０ｍｅＶ，其线宽为１２ｍｅＶ。这些结果表明上述金属有机化合物已达到较高质量。     

n型GaSb,InGaAsSb的MBE生长和特性研究

本文报导了非故意掺杂ＩｎＧａＡｓＳｂ本底浓度的降低和掺Ｔｅｎ型ＧａＳｂ和ＩｎＧａＡｓＳｂ的ＭＢＥ生长与特性的研究结果。结果表明，通过生长工艺的优化，ＧａＳｂ和ＩｎＧａＡｓＳｂ的背景空穴浓度可分别降至１．１×１０~（１６）ｃｍ~（－３）和４×１０~（１６）ｃｍ~（－３），室温空穴迁移率分别为９４０ｃｍ２／ｖ．ｓ和２６０ｃｍ~２／ｖ．ｓ。用Ｔｅ作ｎ型掺杂剂，可获得载流子浓度在１０~（１６）～１０~（１８）ｃｍ~（－３）的优质ＧａＳｂ和ＩｎＧａＡｓＳｂ外延层，所研制的材料已成功地制备出Ｄ_λ~＊＝４×１０~（１０）ｃｍＨｚ~（１／２）／Ｗ的室温ＩｎＧａＡｓＳｂ红外探测器和室温脉冲ＡｌＧａＡｓＳｂ／ＩｎＧａＡｓＳｂ双异质结激光器。     

碳掺杂GaAs的MBE生长

本文在国内首次采用自行设计的碳纤维束源炉及固态源ＭＢＥ技术生长了优质碳掺杂ＧａＡｓ、ＡｌＧａＡｓ及δ碳掺杂ＧａＡｓ外延层。获得了空穴浓度从４×１０１４ｃｍ－３到２×１０１９ｃｍ－３的ＧａＡｓ材料。用霍尔效应测量仪、电化学ＣＶ剖面仪和Ｘ射线双晶衍射仪分析了外延层的质量。用Ｎｏｍａｒｓｋｉ干涉显微镜和原子力显微镜分析了ＧａＡｓ的生长过程。结果表明碳是ＧａＡｓＩＩＶ族化合物半导体的极好的ｐ型掺杂剂。     

δ－掺杂GaAs／AlxGa_（1－x）As二维电子气结构材料的GSMBE生长与特性

本文用ＧＳＭＢＥ技术生长纯度ＧａＡｓ和δ－掺杂ＧａＡｓ／Ａｌ_ｘＧａ_（１－ｘ）Ａｓ结构二维电子气材料并对其电学性能进行了研究。对于纯度ＧａＡｓ的ＧＳＭＢＥ生长和研究，在低掺Ｓｉ时，载流子浓度为２×１０~（１４）ｃｍ~（－３），７７Ｋ时的迁移率可达８４，０００ｃｍ~２／Ｖ．ｓ。对于用ＧＳＭＢＥ技术生长的δ－掺杂ＧａＡｓ／Ａｌ_ｘＧａ_（１－ｘ）Ａｓ二维电子气材料，在优化了材料结构和生长工艺后，得到了液氮温度和６Ｋ迁移率分别为１７３，５８３ｃｍ~２／Ｖ．５和７．６７×１０~５ｃｍ~２／Ｖ．ｓ的高质量ＧａＡｓ／Ａｌ_ｘＧａ_（１－ｘ）Ａｓ二维电子气材料。     

电子束蒸镀半导体光电器件的增透膜

用自动电子束蒸发设备，蒸镀用于光纤通信等中的ＧａＡｓ和ＩｎＰ系列双异质结红外发光二极管的增透膜。结果表明，对波长为０．８μｍ左右的ＧａＡｌＡｓ／ＧａＡｓ发光二极管，蒸镀四分之一波长厚的Ａｌ２Ｏ３介质膜后，其输出光功率在５０ｍＡ和１００ｍＡ电流注入，可增加２５－３５％，最大可增加－５０％。对１．３μｍ波长的ＩｎＰ系列红餐发光管，用ＺｒＯ２作介质增透膜效果更好。     

准连续在功率二维层叠量子阱激光器列阵

研究了大功率列阵器件的量子阱结构，材料生长，列阵结构，了技术与封装技术，研制了６条层叠ＧａＡｓ／ＡｌＣａＡｓ量子阱激光器列阵，其峰值功率为４０４Ｗ，电－光转换效率高达４３．３％。     

GaAs／GaAlAs低阈值垂直腔面发射激光器

通过对增益波导型ＧａＡｓ／ＧａＡｌＡｓ垂直腔面发射激光器的材料生长和工艺制作的研究，实现了在室温下的脉冲激射。其激射阈值电流低达１０ｍＡ，输出光功率不低于０．３ｍｗ，有的可达０．７ｍｗ以上，器件单横模、单纵模工作，线宽小于４人。     

用电诱导液相外延法制备铝组分稳定的高铝值镓铝砷外延层

本文对用于制造高效率半导体发光器件的材料──Ｇａ_（１－ｘ）Ａｌ_ｘＡｓ（ｘ＝０．７５）外延层沿生长方向上铝组分的分布进行了详细地讨论。采用电液相外延法能获得铝组分高度稳定的Ｇａ_（１－ｘ）Ａｌ_ｘＡｓ外延层，并用电流诱导效应作了初步理论解释。     

AlGaAsSb/InGaAsSb多量子阱结构的光致发光谱

用固态源ＭＢＥ技术生长了ＡｌＧａＡｓＳｂ／ＩｎＧａＡｓＳｂ多量子阱材料,研究了通过改变多量子阱ＡｌＧａＡｓＳｂ／ＩｎＧａＡｓＳｂ中的结构参数,如多量子阱中ＩｎＧａＡｓＳｂ的阱宽,ＡｌＧａＡｓＳｂ的垒宽及垒层中Ａｌ组分和阱层中的Ｉｎ组分,多量子阱中的阱数等,来提高ＡｌＧａＡｓＳｂ／ＩｎＧａＡｓＳｂ多量子阱的ＰＬ强度。     

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.……     

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.     

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.     

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 ...