太赫兹时域谱技术快速定性检测奶粉中的三聚氰胺

采用太赫兹时域谱(THz-TDS)技术测量了奶粉中三聚氰胺在0.2~1.8 THz频段的吸收谱和折射率谱,同时运用密度泛函理论(DFT)计算了三聚氰胺在太赫兹波段的振动频率,并据此对实验光谱吸收峰进行了指认,计算结果与实验光谱特征峰很好吻合.表明太赫兹时域谱技术对快速测定识别奶粉中三聚氰胺成分具有良好前景.     

等离子体中太赫兹波传输及成像探测特性研究

本文根据散射矩阵方法模拟等离子体并建立了非均匀等离子体理论模型,并在此基础上计算了0.1 THz^10 THz频段的全波段太赫兹波在其中的传输特性。根据介质阻挡放电原理在实验室环境下搭建等离子体射流产生装置并产生非均匀等离子体,进行了太赫兹时域光谱(THz-TDS)以及宽带太赫兹源在等离子体中的透射光谱测量以及太赫兹波对等离子体遮挡下目标物的反射成像的试验。理论和实验结果均表明,较高频太赫兹波在等离子体中有良好的穿透性,这为太赫兹波在黑障区的通信以及雷达探测应用打下研究基础。     

基于虚拟锁相放大器的接地网无损检测系统

在接地网无损探测的工程实际中,复杂强干扰会给数据采集带来困难。锁相放大技术能有效从强背景干扰下稳定地提取出微弱的可用信号,在分析变电站测量环境噪声成分的基础上,基于锁相放大器原理,运用虚拟仪器技术设计一种虚拟数字锁相放大器。该锁相放大器利用数据采集卡内部的可编程滤波器进行抗混叠处理,同时对两路传感器输出信号进行采集,利用虚拟信号发生器产生精确的两路0°和90°参考信号,再用数字低通滤波器得到信号的实部和虚部,最后利用成像算法得到接地网的结构图。通过实验室内测试,该锁相放大器具有较高的频率稳定性、幅值和相位测量精度及较强的抗干扰能力。将该锁相放大器用于接地网无损探测系统,在实际变电站得到工程应用。结果表明:该无损探测系统能够应对变电站复杂的电磁环境,可在现场正常工作,并准确探测到接地网结构。     

太赫兹技术在水泥基材料研究中的应用

本文介绍了太赫兹波的特性以及太赫兹技术的工作原理及其应用,重点介绍了太赫兹时域光谱技术和太赫兹成像技术在水泥水化过程、水泥基材料的微观结构检测和水泥基材料耐久性能三方面的研究进展.利用太赫兹光谱技术可跟踪硅酸三钙、硅酸二钙以及主要水化产物水化硅酸钙、氢氧化钙在水化过程中的变化情况;利用水分对太赫兹波强烈吸收的特性,能够...     

膜厚对导电氧化锌宽带抗反射涂层的太赫兹传输影响

利用直流磁控溅射方法,在石英基底上制备了可用于太赫兹电磁波频率范围内的宽带抗反射涂层的掺铝氧化锌导电薄膜。在太赫兹时域光谱频率0.1~1.0THz范围内研究不同厚度的氧化锌薄膜的介电响应,得到了与频率相关的电导率、吸收和薄膜折射率,着重研究了膜厚对太赫兹波传输特性的调制作用。实验结果很好地符合了经典的Drude模型,表明可以通过控制氧化锌薄膜的厚度来改变太赫兹波的传输特性,并且导电氧化锌薄膜能够作为太赫兹频段范围的宽带抗反射涂层应用于衬底和光学器件上。     

锁相放大器直流输出分析——输入占空比可调矩形波信号

锁相放大器在微弱信号检测中具有广泛的应用,为了更好地了解锁相放大器的工作特性,采用占空比可调的矩形波信号作为信号源输入,系统研究锁相放大器的直流输出与输入信号的相位及占空比的关系。实验结果表明:采用幅值相同、不同占空比的矩形波信号通过锁相放大器其直流输出值不同,输入不同占空比的矩形波的被测信号在锁相放大器直流输出与相位和占空比的关系图像为三角波形,当占空比为0.5时有最大输出值。     

磁控溅射超薄金属膜在太赫兹波段的光学特性

采用THz时域光谱测试技术，对Fe扣Co的超薄金属膜在0.2～2，5THz波段的吸收特性、透射特性以及折射率进行了研究。在室温并去除水份影响的氮气环境中，获得了不同种类扣不同厚度的薄金属膜在太赫兹波段的时域谱．利用Origin7．0扣Matlab7，0软件处理得到这些金属薄膜对太赫兹波的透射率，吸收系数扣折射率．对比发现金属超薄膜在太赫兹波段的光学特性随薄膜厚度以及太赫兹波频率的变化有很大的改变，也就是具有明显的尺寸效应．同时根据所得到的折射率开口吸收系数还可以理论上计算出不同种类与厚度的超薄金属膜在太赫兹波段的复介电函数．     

基于光导开关脉冲偏置电压的太赫兹时域光谱系统

利用光导开关产生脉冲偏置电压的方式改进了基于光电导天线的太赫兹时域光谱系统.在分析光电导天线产生THz波原理的基础上,重点研究了目前基于光电导天线的太赫兹时域光谱系统存在的问题,探讨了解决斩波器引起的机械噪声和光电导天线脉冲偏置电压之间矛盾的途径.最后,通过对光导开关的特性测试,提出了利用高压直流电源、光导开关和纳秒激...     

SiC和Si_3N_4粉体的太赫兹时域光谱研究

采用太赫兹时域光谱装置测试SiC和Si3N4粉体在0.4～2.4 THz的透射光谱,研究SiC和Si3N4粉体对太赫兹波的吸收性能与其电导率的关系,分析SiC和Si3N4粉体对太赫兹波的散射特性。结果表明,SiC是一种半导体材料,其内部含有较多可以自由移动的载流子,对太赫兹波的吸收较强;Si3N4是绝缘性很好的材料,对太赫兹波的吸收很小;SiC和Si3N4粉体对太赫兹波的散射作用属于瑞利散射,但是测试波长比粉体粒径大得多,散射效果不明显。     

十字架金属微结构的太赫兹波吸收器研究

设计了一种十字架金属微结构的太赫兹波吸收器,其结构是将金属十字架置于硅基体之上,基体的背面再覆盖一层金属,以此为单元结构经周期排列组成.针对该太赫兹波吸收器提出了一种等效电路分析模型,通过仿真和加工测试证实了该吸收器的中心吸收频率位于0.571THz,吸收率为99.6%,反射率为0.38%,透过率为0,吸收带宽为29GHz.等效电路模型计算结果与测试结果相吻合.结果表明,提出的等效电路模型分析方法是简单有效的,从而为今后太赫兹波器件的研究提供了一种很好的思路.     

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.……     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

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.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.