Modeling of Thermal Processes in Thermal Resistors with a Positive Temperature Coefficient of Resistance

The space-time temperature distribution in materials with a positive temperature coefficient of resistance under the action of electric current on them has been analyzed by numerical methods. The nonstationary boundary-value heat-conduction problem with a nonlinearity of the third kind has been solved. The results obtained theoretically have been compared to experimental data. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 4, pp. 97–101, July–August, 2005.     

Low Temperature Electronic Transport in RuO2-Based Cermet Resistors

We have studied the temperature (T) dependence of resistance (R) of RuO₂-based thick films down to 1.2 K. Samples were prepared from inks containing conductive RuO₂ powders (<-10% wt.), high lead-silicate glass particles and Mn (≤1.4% wt.). We found that the resistance fits the exponential lawR=R ₀ exp (T ₀/T)^x with x=1/4 and the most resistive samples show a cross-over to the x=1/2 regime as the temperature decreases. Both the fitting parametersR ₀ andT ₀ scale down as the RuO₂ fraction increases and they are affected in a similar way by a change of the Mn content. The presence of the two regimes is similar to that observed inn-type GaAs [Phys. Rev. B39, 8059 (1989)] andn-type CdSe [Phys. Rev. Lett.64, 2687 (1990)] whilst it disagrees with the behaviour predicted for grain to grain hopping [Phys. Rev. B27, 2583 (1983)] and with that expected for resonant tunneling between metallic particles [J. Appl. Phys.48, 5152 (1977)]. We conclude that in our systems the driving charge transport mechanism is electron hopping within the glassy matrix. Since in our case the hopping length is of the same order of the localization length, the puzzling questions arising from our experiments are whether and how the variable range hopping model can be extended beyond its conventional limits.     

热电偶参考端温度的修正

本文主要介绍了热电偶参考端温度不为0℃时产生的影响及几种修正方法.     

环形标准电感器温度系数研究

本文分析了影响环形标准电感器温度系数的各种因素 ,推导出横截面为圆的环形电感器的温度系数计算公式 ,介绍了一种具有温度补偿结构的环形标准电感器。理论分析与实验结果证明这种电感器的温度系数仅为 3 0× 10 -6/℃。     

The Temperature Coefficient of Tungsten Filament Lamps

The results of an investigation of the effect of temperature drift of the lamp base on the brightness temperature produced by a tungsten filament lamp are presented. The dependence of the temperature coefficient of gas-filled and vacuum lamps on the brightness temperature is determined. The error in the calibration characteristic of the lamp, connected with the temperature instability of the lamp base with time, is estimated.     

关于负温度系数热敏电阻R—T特性的探讨

本文介绍了几种求解负温度系数热敏电阻R-T关系的方法,并对各种方法的应用范围、特点等进行了分析.     

SrO/CaO比对无碱铝硼硅酸盐玻璃热膨胀系数与低温特征粘度参考点的影响

恒定无碱铝硼硅酸盐玻璃中碱土金属氧化物的质量百分比不变,研究了SrO和CaO的相互替代对玻璃的热膨胀系数、应变点温度、玻璃转变温度、退火点温度、膨胀软化点温度等低温特征粘度参考点的影响。结果表明:玻璃的热膨胀系数随着n(SrO)/n(CaO)比值的增大而逐渐减小,低温特征粘度参考点在n(RO)/n(Al2O3)=0.96时达到极大值。     

Method of Determining the Coefficient of Visual Extinction of Materials with Variable Optical Density

The present article describes methods of determining the coefficient of visual extinction that are fundamental in the technology of digital processing of video information along with methods of determining the transmission spectrum in the visible region of optically semitransparent materials. The article is also concerned wtih the case of materials subjected to the action of high-energy optical radiation. The investigations demonstrated that the proposed designs would be useful in estimating the optical properties of materials in aids for the protection of eyes.     

Determining Reference Values and Degrees of Equivalence in Key Comparisons

Various approaches are considered to determining the reference value in key comparisons. The purposes of key comparisons are compared with those of other interlaboratory experiments. Models are proposed for the key comparison data in accordance with the purposes of the key comparisons and available a priori information on those data.     

Temperature at the Reference Points of Scale MTSh-90

It is shown that the lack of a clear definition of one of the main concepts underlying temperature scales – the reference-point temperature – is causing uncertainty in the realization of the temperatures corresponding to the reference points on scale MTSh-90. An analysis is made of the advantages and disadvantages of different approaches to determining the temperature at reference points. It is proposed that this temperature be the temperature at which a given substance of a specified degree of purity begins to crystallize. That temperature corresponds to thermodynamic equilibrium of the liquid phase having the specified initial concentration of impurities.     

炭黑填充聚偏氟乙烯复合材料的PTC效应

以聚偏氟乙烯（PVDF）为基体,经与炭黑等混合后挤出成型辐照。研究了两种不同类型导电炭黑（CB）对复合物导电性和正电阻温度系数（PTC）的影响,辐射剂量对PTC性能的影响,以及HDPE/PVDF配比对复合物PTC性能的影响。通过CB在HDPE/PVDF中配比不同时分布的扫描电镜（SEM）观测,随着PVDF含量的增加,C...     

不依赖于长度基准的光栅细分精度的评定方法

分析了光栅细分精度与利萨如图形的关系，给出了通过利萨如图形评定光栅细分精度的方法。该方法将对测量条件要求极高的细分误差评定工作转化为普通的电压测量和计算，使光栅细分精度的评定不再依赖于高精度的长度基准。该方法适用于各种误差模型的光栅信号，也适用于其它任何以相位差为９０度的两种信号进行细分计量仪器。     

Evaluation of the Long-Term Stability and Temperature Coefficient of Dew-Point Hygrometers

The continuous quest for improved specifications of optical dew-point hygrometers has raised customer expectations on the performance of these devices. In the absence of a long calibration history, users with a limited prior experience in the measurement of humidity, place reliance on manufacturer specifications to estimate long-term stability. While this might be reasonable in the case of measurement of electrical quantities, in humidity it can lead to optimistic estimations of uncertainty. This article reports a study of the long-term stability of some hygrometers and the analysis of their performance as monitored through regular calibration. The results of the investigations provide some typical, realistic uncertainties associated with the long-term stability of instruments used in calibration and testing laboratories. Together, these uncertainties can help in establishing initial contributions in uncertainty budgets, as well as in setting the minimum calibration requirements, based on the evaluation of dominant influence quantities.     

实验室标准传声器静压和温度修正系数的测量

为测量实验室标准传声器的静压和温度修正系数,在耦合腔互易法声压基准的基础上建立了静压调节系统和温度控制装置。对不同静压和温度条件下利用耦合腔互易法获得的传声器声压灵敏度进行线性拟合,得到不同频率条件下的静压修正系数和温度修正系数。实验结果表明低频段静压修正系数和温度修正系数基本保持不变,频率值在传声器膜片谐振频率值的1/2处,静压修正系数和温度修正系数分别存在最大值和最小值。     

Temperature Coefficient of Electrical Resistance of Simple Liquid Metals

The temperature coefficient of electrical resistance has for the first time been numerically determined for 15 simple liquid metals in view of the third-order term with respect to the pseudopotential of electron–ion interaction. The perturbation theory series for electrical resistance is constructed by the asymptotic expansion method. For all metals, the third-order term turns out to be positive and ranges from several percent to several tens of percent of the second-order term. Its inclusion improves considerably the agreement between the theoretical and experimental values of the temperature coefficient.     

宽温度、大功率微波铁氧体材料研究

宽温度稳定性、大功率一直是微波铁氧体材料研究的重点。本文利用氧化物工艺,通过Gd3+、Sn4+离子对YIG的取代,制成了饱和磁化强度为943Gs、在-40℃~100℃范围内具有良好的温度稳定性的大功率YGdCaSnIG微波石榴石铁氧体。     

具有负温度系数效应的导电硬质聚氨酯泡沫

采用高能球磨分散方法制备了稳定的聚合物多元醇/碳纳米管分散液,并通过原位聚合制备了导电聚氨酯（PU）/碳纳米管（CNTs）硬质泡沫复合材料。采用扫描电镜（SEM）表征了泡沫复合材料的结构,研究了CNTs含量对泡沫材料导电性的影响以及泡沫材料的负温度系数（NTC）效应,通过压缩测试考察了泡沫材料的力学性能。结果表明,CN...     

Negative Temperature Coefficient of Resistivity in Bulk Nanostructured Ag

1. IntroductionIn 1980s, Glener et al.11'2] studied the relationshipbetween resistivity and temperature for nanocrystalline metals (such as Cu, Pd and Fe) and the changerule of the temperature coefficient of resistivity (or)with the grain size. It was shown that the resistivityincreases linearly with temperatuxe (the Mathiessenrule). This is similar to what appears in the relativelypure ordered metals with coarse grains. The decreaseof a with the drop of the density was reported inthe nanost…     

低α精密电阻材料

本文介绍一种航天航空等高技术产品中精密电位器用的低电阻温度系数电阻合金，材料的电阻率和电阻温度系数是相互矛盾的物理量，要同时降低这两个参数是困难的，这正是本研究要解决的关键。本研究除根据有关资料设计了最佳合金成分外，着重研究了氧含量对合金电性能的影响，所研究的连续除气熔炼工艺使合金中氧含量降低到最低限度，从而使合金的电阻率保持在０．２６μΩ．ｍ时，电阻温度系数降低到１０×１０＾－６／℃以下。     

温度误差修正与微分膨胀系数

提出一种更切合实际的温度误差补偿和修正方法：采用微分膨胀系数代替平均膨胀系数。同时介绍了微分膨胀系数的测量方法及其测量不确定度。