低延性陶瓷材料高温KR-曲线行为

在高温下采用加载－卸载技术与柔度标定相结合的方法测量了SiC陶瓷材料的KR－曲线行为。结果表明：在高温下陶瓷材料KR随裂纹长度的增加而提高。随温度提高，陶瓷材料韧化指数m减小，裂纹阻力降低，其KR曲线越平坦。陶瓷材料在高温下增大的KR曲线行为，与裂纹的转向及裂纹尾区裂纹表面之间的相互作用密切相关，加载－卸载技术与柔度标定相结合的试验方法，对测量陶瓷材料高温KR－曲线是一种有效简便的方法。     

Temperature measurement in microfluidic systems using a temperature-dependent fluorescent dye

A technique is described for the measurement of fluid temperatures in microfluidic systems based on temperature-dependent fluorescence. The technique is easy to implement with a standard fluorescence microscope and CCD camera. In addition, the method can be used to measure fluid temperatures with micrometer spatial resolution and millisecond time resolution. The efficacy of the method is demonstrated by measuring temperature distributions resulting from Joule heating in a variety of microfluidic circuits that are electrokinetically pumped. With the equipment used for these measurements, fluid temperatures ranging from room temperature to 90 degrees C were measured with a precision ranging from 0.03 to 3.5 degrees C-dependent on the amount of signal averaging done. The spatial and temporal resolutions achieved were 1 microm and 33 ms, respectively.     

Measurement of low temperature heat capacity of metals under pressure

An alternating heat flow method is used to measure the heat capacity of metals at low temperatures under hydrostatic compression. The phase shift method is developed for taking account of the losses in the medium. The method was tested by measuring the heat capacity of Sn at pressures up to 10 k bar. The errors of measurements are ～3%.     

Measurement of surface temperature and emissivity by a multitemperature method for Fourier-transform infrared spectrometers

Surface temperatures are estimated with high precision based on a multitemperature method for Fourier-transform spectrometers. The method is based on Planck's radiation law and a nonlinear least-squares fitting algorithm applied to two or more spectra at different sample temperatures and a single measurement at a known sample temperature, for example, at ambient temperature. The temperature of the sample surface can be measured rather easily at ambient temperature. The spectrum at ambient temperature is used to eliminate background effects from spectra as measured at other surface temperatures. The temperatures of the sample are found in a single calculation from the measured spectra independently of the response function of the instrument and the emissivity of the sample. The spectral emissivity of a sample can be measured if the instrument is calibrated against a blackbody source. Temperatures of blackbody sources are estimated with an uncertainty of 0.2-2 K. The method is demonstrated for measuring the spectral emissivity of a brass specimen and an oxidized nickel specimen.     

Measurement of the RMS value of alternating current by the method of equal and constant temperatures

A method of quickly measuring the rms value of current with electrothermal transducers is examined. High speed is achieved due to the constancy of the temperatures of the transducers during the measurement. The designs of two transducers for measuring rms current are considered and their dynamics and low-frequency error are analyzed. Translated from Izmeritel’naya Tekhnika, No. 7, pp. 53–59, July, 1999     

Method to determine the thermal expansion of epoxies,inorganic cements and polyester resins at cryogenic temperatures

An apparatus for measuring the integral thermal expansions at cryogenic temperatures is described. The thermal expansions are given for a number of commercial epoxy resins, commercial polyester resins and inorganic cements. A method to reduce the thermal expansion of the resins by the use of quartz powder fillers is reported.     

Comparison of a Uniaxial Force Displacement Tester with a Ring Shear Tester for Assessing Powder Cake Strength

This article highlights the use of a novel easy to use uniaxial force displacement tester (FDT) for measuring powder cake strength. A comparative study was undertaken of the FDT with a standard ring shear tester (RST) for measuring the cake strength of a powder. The powder used in the study was maltodextrin DE 21 which is an amorphous powder which readily cakes at temperatures at or above its glass transition. The powder was first equilibrated at 50% relative humidity over a five month period and it was then exposed to temperatures at and above its glass transition. The powder cake strength was measured using both the FDT and RST and the measured results were compared. The results showed that the cake strengths measured by the FDT correlated well with those of the RST. This demonstrated that the FDT is a realistic, easy to use method for assessing the cake strength of a powder.     

A laboratory objective spectropyrometer

Conclusion The SPP-58 objective spectropyrometer can be used mainly in state inspection laboratories for measurement techniques for checking standard temperature lamps which are calibrated in brightness temperatures.By means of this spectropyrometer, temperature lamps which are calibrated in color temperatures can be checked by measuring monochromatic brightness temperatures corresponding to two different wavelengths.Moreover, this spectropyrometer can be successfully used for accurate measurement of brightness and color temperatures and also for measuring monochromatic brightness, illumination, luminous intensity, and other light quantities.     

Feasibility of measuring low temperatures using uranyl compounds

We consider the possibility of using uranyl compounds as sensors for measuring cryogenic temperatures by an optical method in which the temperature-dependent ratio of the intensities of two bands in the luminescence spectrum of the material of the sensor is measured.Translated from Izmeritel'naya Tekhnika, No. 6, pp. 32–35, June, 1994.     

Oxygen transmission rates of packages at ambient,chill and freezing temperatures measured by the AOIR method

The ambient oxygen ingress rate (AOIR) method is an alternative or supplementary method to Ox‐Tran for measuring the oxygen transmission rate (OTR) of packages. The method has high capacity, requires relatively inexpensive equipment and measures OTR at different temperatures and humidity conditions. The aim of this study was, on the one hand, to study the effect of temperature on the OTR for packages produced from different polymer materials and laminates, and on the other hand to evaluate the suitability of the AOIR method at freezing temperature conditions. The OTR for 10 packages with different polymer compositions was measured at 23°C, 6°C and ?25°C. The AOIR method was shown to be a reliable test method for measuring OTR of packages at all the applied test conditions, also at frozen storage temperature. The OTR for the packages decreased with lower temperatures, especially for the packages with the highest OTR values at 23°C. In order to avoid higher packaging expenses than necessary to obtain the required shelf‐life for different food products, the OTR for alternative packages should be measured at the temperature and humidity conditions of intended use. Copyright © 2004 John Wiley & Sons, Ltd.     

Radiance Temperatures and Normal Spectral Emittances (in the Wavelength Range of 1500 to 5000 nm) of Tin, Zinc, Aluminum, and Silver at Their Melting Points by a Pulse-Heating Technique

The radiance temperatures at four wavelengths (in the range of 1500 to 5000 nm) of tin, zinc, aluminum, and silver at their respective melting points were measured by a pulse-heating technique using a high-speed fiber-coupled four-wavelength infrared pyrometer. The method is based on rapid resistive self-heating of a sample from room temperature to its melting point in less than 1 s while measuring the radiance emitted by it in four wavelength bands as a function of time. A plateau in the recorded radiance-versus-time traces indicates melting of the sample. The melting-point radiance temperatures for a given sample are determined by averaging the measured temperatures along the plateau at each wavelength. The melting-point radiance temperatures for each metal are, in turn, determined by averaging results for several samples. The normal spectral emittances at the melting transition of each metal are derived from the measured radiances at each wavelength and the published values of the thermodynamic (true) melting temperatures.     

Universal method for determining electrolyte temperatures in capillary electrophoresis

Temperature increase in capillary electrophoresis (CE) due to Joule heating is an inherent limitation of this powerful separation technique. Active cooling systems can decrease the temperature of a large part of the capillary but they leave "hot spots" at the capillary ends which can completely ruin some CE analyses despite their short lengths. Here, we introduce a "universal method for determining electrolyte temperatures" (UMET) that can determine temperatures in both efficiently- and inefficiently-cooled parts of the capillary. UMET can be applied to all electrolytes, as it does not involve any probe; it requires only measuring current versus voltage for different voltages and processing the data using an iterative algorithm. To demonstrate the universality of UMET, we measured temperatures for electrolytes of different ionic strengths as well as for different capillary diameters. We further propose a "simplified universal method for predicting electrolyte temperatures" (SUMET) which only requires one measurement of current and voltage (that can be completed in 1 min) and uses two empirical equations to predict temperatures in the efficiently- and inefficiently-cooled parts of the capillary. The equations include several instrument-specific empirical parameters that are determined using a large set of current-voltage data obtained with UMET for a range of electrolytes and different capillaries. To demonstrate the utility of SUMET, we obtained the required data set for a Beckman MDQ CE instrument and produced all required empirical parameters that enable a user of this instrument to predict the temperature for every new experimental set in a matter of minutes. We confirmed the accuracy of SUMET by measuring the temperature-sensitive dissociation rate constant of a protein-DNA complex. We foresee that UMET will be used to produce instrument-specific empirical parameters for all CE instruments and then SUMET will be routinely used for temperature prediction in CE.     

Characterization of an optical-fiber reflectometer for in situ measurement applications

We present studies of apparatus based on optical-fiber probes for measuring the reflectivity of opaque materials. The probes are designed for in situ applications at high temperatures and in situations for which access is difficult. First, we present a method in which the hemispherical reflectivity and the angular distribution of the reflected flux are obtained from bidirectional measurements. Second, we describe a method to measure the reflectivity in only the normal direction; this method is available only for diffuse materials. Both methods of use of the device were validated through the use of commercial diffuse standards and specific materials with particular surface microstructures.     

Radiance temperatures (in the wavelength range 523–907 nm) of group IVB transition metals titanium,zirconium, and hafnium at their melting points by a pulse-heating technique

The melting-point radiance temperatures (at six wavelengths in the range 523–907 nm) of the Group IVB transition metals titanium, zirconium, and hafnium were measured by a pulse-heating technique. The method is based on rapid resistive self-heating of the specimen from room temperature to its melting point in less than 1 s and on simultaneously measuring the specimen radiance temperatures every 0.5 ms with a high-speed six-wavelength pyrometer. Melting was manifested by a plateau in the radiance temperature-versus-time function for each wavelength. The melting-point radiance temperatures for a given specimen were determined by averaging the measured temperatures along the plateau at each wavelength. The melting-point radiance temperatures for each metal were determined by averaging results for several specimens at each wavelength as follows: Based on estimates of the random and systematic errors arising from pyrometry and specimen conditions, the combined uncertainty (95% confidence level) in the reported values is about ±8K at each wavelength.     

New Method for Measuring the Rotation Inertia of a Single 4He Crystal

A new method for measuring the nonclassical rotation inertia of a helium single crystal is presented. This takes advantage of large crystals grown under conditions minimizing stresses and structural defects. High quality and large mass of crystals allow significantly increasing inertia signals and therefore sensitivity of measurements and accuracy of results. A method is tested at temperatures from 0.6 to 1.7 K in a frequency range of 100–1000 Hz. It is also used for studying internal friction in a helium single crystal.      

Simplified determination of long-term viscoelastic behavior of amorphous resin

The time-temperature superposition principle has been applied to predict accurately the long-term viscoelastic behavior of amorphous resin at a temperature below the glass transition temperature from measuring the short-term viscoelastic behavior at elevated temperatures. A simplified method for the determination of the long-term viscoelastic behavior of amorphous resin using dynamic mechanical analysis is proposed. The automatic horizontal and vertical shifting method is used to construct the smooth storage modulus master curve, and then the accurate time-temperature shift factors can be obtained. The validity of our simplified determination method is confirmed experimentally.     

Proposed method to test the relative seal strength of plastic bottles and its use in optimizing sealing parameters

A test method for measuring the strength of the seal on a flexible bottle is proposed. The method measures seal strength as the compression force applied to the side of the bottle required to make the seal fail. The technique has the advantage of using standard equipment and reproduced failure conditions as closely as possible. The method was used to compare the seal strengths of a foil laminate heat-seal on a retortable gamma bottle under various sealing conditions. The results for various sealing pressures, temperatures and times are reported and optimum conditions are identified.     

一个高温持久/蠕变测控温及试验管理系统

介绍了采用测控分开形式对近百台五六十年代制造的高温持久/蠕变试验机进行测控温系统改造的工作.改造后的控温系统创造了不同热电偶数量(测控温共偶,1～3支)都可实现对试样温度和梯度的稳定控制,系统具有较强抗外界干扰能力,而且控温过程中对电网无干扰.测量系统测量误差≤±0.1%FS.测控温系统采取单炉闭环控制、30台集中巡回...     

Precise Density Measurements for Electromagnetically Levitated Liquid Combined with Surface Oscillation Analysis

A new method is proposed for accurately measuring the densities of high-temperature liquids which involves analyzing the surface oscillations of levitated droplets. This method makes it easy to improve on the accuracy of density measurements obtained by using conventional electromagnetic levitation systems. In addition, the errors in density measurements made on the ground are further reduced by applying a static magnetic field to suppress surface oscillations in levitated liquid droplets. The magnetic field interacts with electrical currents in the levitated droplet, thereby generating a Lorentz force; this force suppresses flow within the liquid droplet. By combining both these methods, the scatter in density measurements for molten Si at temperatures in the range from 1,500 K to 1,900 K is reduced by an order of magnitude compared with previously reported data. Using this new method, the density of molten SiGe has been measured at temperatures from 1,350 K to 1,650 K.     

Ambient oxygen ingress rate method—an alternative method to Ox‐Tran for measuring oxygen transmission rate of whole packages

The ambient oxygen ingress rate method (AOIR) is an alternative method to Ox‐Tran for measuring the oxygen transmission rates (OTR) of whole packages. The objective of the present work was (a) to compare OTR values obtained by the two methods, and (b) to evaluate the use of the AOIR method for measuring OTR at realistic food storage temperatures and humidity levels. The AOIR method gave equal OTR values compared to the Ox‐Tran method for the five different types of whole packages used in the experiment, with OTR values in the range 0.06–1.48 ml O₂/day. The repeatability of the AOIR method measured on an HDPE bottle was ±2.6% of the measured value in this experiment. This is slightly higher than the general specifications of the Ox‐Tran method (1% of reading for packages). However, the AOIR method can be considered to be a reliable, precise and cheap alternative method to the Ox‐Tran method for measuring OTR of whole packages. The capacity of the method is also high. The AOIR method showed satisfactory results when comparing OTR for packages tested under realistic food storage conditions covering 23°C/50% relative humidity (RH) and at 4°C/60% RH on the outside, combined with water (100% RH) or dry air inside the packages. Copyright © 2000 John Wiley & Sons, Ltd.