PAN碳纤维的介电 半导体行为及其表征

用2801西林电桥研究了0℃～160℃聚丙烯腈(PAN)碳纤维的介电损耗因数ε、介质损耗角正切tgδ的频率特性;用微电导测试仪研究了温度、电场对PAN碳纤维的电导率γ的影响。     

高压电桥的灵敏度及误差分析

本文详述了高压电桥灵敏度的基本问题及其测量误差,并结合现场广泛采用的QS1型电桥进行了剖析,提出了包含电桥灵敏度误差在内的tgδ及被试品电容测量误差估算公式。一、高压电桥灵敏度的表示方法高压电桥是一种比较量仪表。图1是原理接线图。高压电桥的灵敏度是指电桥在电压U_2(称参考电压)和U_1(为试验电压,可取U_1=U_2或U≠U_2)作用下,阻抗Z_3或Z_4有增量ΔZ     

测量介质损失角正切值易忽视的几个问题

文章对测量介质损失角正切值易忽视的几个问题进行了说明     

侧向辐射的平面小天线的数值分析

在短距离移动通信中，由于系统对天线的效率和增益要求不高，人们大量使用FR4（玻璃纤维双面铜板）构造的天线，但未见损耗的分析报道。分析了一种构造于廉价的玻璃纤维电路板上的侧向辐射的小型平面天线，首次给出了天线在不同的介质损耗正切（tgδ）下的天线阻抗带宽，天线辐射效率以及方向图和天线增益的数值分析结果。     

参杂尖晶石型镍基铁氧体的磁性能与介电性能

采用溶胶-凝胶法制备了立方晶系尖晶石型镍基铁氧体微粉Ni0.5M0.5Fe2O4（M=Zn、Mn、Cu）,采用X射线衍射仪、扫描电子显微镜、振动样品磁强计和矢量网络分析仪对粉末的结构、形貌、磁性以及电磁性能进行了表征,结果表明,三种粉末在室温下具有超顺磁性,其饱和磁化强度MS分别为76．0、59．4和54．4emu·g-1。在2—11GHz范围内,Ni0.5M0.5Fe2O4的电磁损耗角正切值tgδ随频率的增大而逐渐减小;Ni0.5M0.5Fe2O4和 Ni0.5M0.5Fe2O4的tgδ随频率的增大先增大后减小。     

高频标准介质样品及其应用

在电气和电子工程领域中,介质(绝缘)材料得到广泛的应用。介质材料在很大程度上决定着电子仪器、无线电通讯设备、电子计算机等的耐久性和可靠性。由于介质测量的普遍开展以及各种介质测量仪器的不断涌现,迫切要求国家统一介质电性能的测量量值,研制介电性能标准和检定介质测量仪器。本文介绍的高频标准介质样品(见本期封底广告)就是统一我国介质材料高频性能参数中,相对介电常数ε_γ和介质损耗角正切(tgδ)的标准量具。     

BaMnZnCoTi—W型铁氧体微波吸收特性的研究

对用Co2 + 、Ti4 + 置换Fe3 + 的BaMnZn -W型铁氧体的制备和微波吸收性能进行了分析研究 ,发现涂层厚为 1.0 6mm在 7.0～ 12 .0GHz频率范围内有 3个损耗吸收峰 ,峰值最高达 3 4dB以上 ;同时测量了复数磁导率 μ～( =μ′ -jμ″) ,复介电常数ε～( =ε′ -jε″) ,求出了磁损耗角正切tgδm 和介电损耗角正切tgδe,初步分析了 3个损耗吸收峰可能产生的机制。比较了在相同工艺条件下 ,随Co2 + 、Ti4 + 含量增加 ,铁氧体的吸收频率特性和涂层厚度的关系。     

LCR测量仪电容器损耗角正切测量不确定度的评定

电容器介质损耗是电容器的重要质量指标之一,是电容器介质损耗角正切的简称。LCR测量仪是测量电容值、电容损耗因数tanδ(或D值)等功能的测量仪器,本文采用电容器介质损耗的典型表示,对其进行测量不确定度的评定。一、校准条件1.校准依据JJF1095-2002《电容器介质损耗测量仪校准规范》。2.环境条件     

TPUE相态网络结构与力学性能间相关性的研究 Ⅱ.TPUE大形变弹性分子理论同实验的对比

本文以单向拉伸和动态力学分析法研究了两种类型(聚酯和聚醚型)热塑型聚氨酯弹性体的硬段含量和软段平均分子量对其弹性行为和损耗角正切(tgδ)的依赖性,得到了剪切模量(G_(sh))同硬段含量(W_h)和软段平均分子量倒数(1/_(ns))间及tgδ同硬段含量倒数(1/W_h)和C2/(C_1+C_3)间等的线性关系。以上述实验数据验证了前报所提出的热塑型聚氨酯弹性体大形变弹性分子理论,该理论同实验能较好地符合。结果表明该理论能在较大形变范围内定量地预测大形变弹性力学形为、损耗角正切同(1/W_h)问和G_(sh)同W_h和(1/_(lls))间等线性关系。从而成功地把聚氨酯弹性体的弹性行为同聚氨酯组成中的硬段含量(W_h)和软段平均分子量(1/)联系起来。     

基于变电站容性设备介损测量算法的研究

变电站电容型设备的绝缘故障不仅影响整个变电站的安全运行,同时还危及其它设备和人身的安全。测量其介质损耗角正切tan5并观察历次试验结果的变化,能够较好的判断介质绝缘状况的变化,及时发现其中的绝缘故障。本论文对实际应用中常用的几种介质损耗的测量方法进行了对比介绍,比较了它们的原理以及优缺点,并介绍了相应问题的改进算法。     

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 ...     

Effect of Oxide Assisted Metal Nanoparticles on Microstructure and Morphology of Gallium oxide Nanowires

Several researches have been reported about the characteristic of β-Ga2O3 nanowires which was synthesized on nickel oxide particle. But indeed, recent researches about synthesis of β-Ga2O3 nanowires on oxide-assisted transition metal are limited to nickel or cobalt oxide catalyst. In this work, Gallium oxide (β-Ga2O3 ) nanowires were synthesized by a simple thermal evaporation method from gallium powder in the range of 700 - 1000℃ using the iron, nickel, copper, cobalt and zinc oxide as a catalyst, respectively. The β-Ga2O3 nanowires with single crystalline without defects were successfully synthesized at the reaction temperature of 850, 900 and 950℃ in all the catalysts. But optimum experimental condition in synthesis of nanowires varied with the kind of catalyst. As increasing synthesis temperature,the morphology of gallium oxide nanowires changed from nanowires to nanorods, and its diameter increased. From these results, we could be proposed that the growth mechanism of β-Ga2O3 nanowires was changed with synthesis temperature of nanowires. Microstructure and morphology of Synthesized nanowire was characterized by HR-TEM, FE-SEM, EDX and XRD.     

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