Measurement of internal strains in concrete

Summary An electrical resistance strain gauge was embedded in the concrete during its casting to measure the internal strains due to uniaxial compressive loading. Details are given of the method of preparation of the strain gauge, embedding the strain gauge and comparisons have been made between the strains measured inside and on the surface of the specimen. It has been found that the internal strains were more than the surface strains.

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Résumé Afin de mesurer les déformations internes dues à un effort de compression uniaxiale, on a noyé dans le béton lors de son coulage une jague de déformation à résistance électrique. On donne des précisions sur la méthode de préparation de la jauge, sur sa mise en place et sur l’étude comparative qui a été faite entre les déformations mesurées à l’intérieur et à la surface de l’éprouvette. On a constaté que les déformations internes avaient des valeurs supérieures aux déformations superficielles.

     

Measurements of static strains on titanium under rapid heating

The behaviour of various strain gauges on unstressed titanium IMI 317 under various heating rates is investigated systematically. Testing methods, gauge preparation, evaluation of tests and results are presented.     

Radiation resistance of the internal memory of programmable logic devices

An investigation was made of the radiation resistance of the internal memory of programmable logic devices. It was established that the internal memory of CMOS devices shows enhanced sensitivity to ionizing radiation when their outputs are shorted together. Information stored in the internal memory of the devices is erased at an absorbed dose substantially below the level at which the device fails. It is suggested that this effect may be used as a method of erasing information. Pis’ma Zh. Tekh. Fiz. 24, 29–32 (November 26, 1998)     

Measurements of single electron transistor devices combined with aCCC: progress report

The BNM-LCIE is developing a current standard based on single electron transistor (SET) pumps. This paper gives an overview of the experimental set-up. It includes the circuit details, in particular the combination of miniature filters and homemade lines giving high attenuation in a wide frequency band, and a cryogenic current comparator (CCC) with winding ratio of 10000:1 for high accuracy amplification of the current. The results of the testing of the circuit and CCC are presented, together with the first measurements of the current through a SET carried out by means of a CCC. Coulomb blockade oscillations with an amplitude less than 200 fA have been observed with a signal to noise ratio approaching 100 and at bias voltages as small as a 100 nV     

Microwave-stimulated relaxation of internal strains in GaAs-based device heterostructures

We have studied the effect of microwave radiation (frequency, 2.45 GHz; specific power density, 1.5 W/cm²) on the relaxation of internal mechanical strains in the (i)n-n ⁺-GaAs structures, (ii) Au-Ti-n-n ⁺-GaAs diode structures with Schottky barriers, and (iii) GaAs-based Schottky-barrier field-effect transistors (SFETs). It is shown that exposure of the samples to the microwave radiation for a few seconds leads to relaxation of the internal mechanical strains and improves the quality of the semiconductor surface layer structure. This results in improved parameters of the GaAs-based device structures of both (diode and SFET) types, as manifested by increased Schottky barrier height, reduced ideality factor and back current in the diode structures, and increased gain slope and initial drain current in the SFETs.     

Application of frustrated total internal reflection devices to analytical laser spectroscopy

Novel implementations of single-fiber laser-induced breakdown spectroscopy and laser-induced fluorescence spectroscopy systems that gated light switches based on frustrated total internal reflection are described. The switching devices are largely wavelength independent, with full temporal and spatial separation of laser and fluorescence light. Wavelength-independent beam separation or beam combination schemes can be implemented for coaxial optical setups, e.g., in single-fiber or telescopic experimental arrangements. Selected practical examples of schemes for qualitative and quantitative analytical spectroscopy are discussed.     

Measurements of internal friction coefficient of SiC and Al2O3 powders

The frictional strength of the powder of two ballistic materials (SiC and Al₂O₃) under low confining pressures has been studied statically and dynamically. In the static tests, the influence of the ceramic fragment size upon the internal friction coefficient value was investigated. In the dynamic tests, the effect of the ceramic fragment size, the relative sliding velocity and the confinement load were studied. It was found in the experimental conditions, that the influence of the fragment size and of the relative sliding velocity upon the internal friction coefficient value of comminuted SiC and Al₂O₃ is important.     

Correction: Facile low-temperature synthesis of nickel oxide by an internal combustion reaction for applications in electrochromic devices

Journal of Materials Science -     

Low temperature synthesis of silver-palladium alloy powders internal electrodes for multilayer ceramic devices

Physical and electrical properties of three types of Ag-Pd pastes, which consist of different metal fine powders, i.e., a coprecipitated powder, an agglomerated alloy powder made by heat treatment and a pulverized alloy powder produced by improved pulverization method, have been studied. The paste prepared from pulverized alloy powder showed a higher film packing density (6.3 g/cm³) than those made of the other powders. The film consisting of pulverized alloy powder showed a lower expansion at around 500 °C, a lower shrinkage from 700 °C to 1100 °C and a lower electric resistivity. The results indicated that the paste which consists of an pulverized Ag-Pd alloy powder was superior in performance to the other two pastes for an internal electrode material of multilayer ceramic device.     

High-throughput fabrication of organic nanowire devices with preferential internal alignment and improved performance

We demonstrate that arrays of nanowires of conjugated polymers can be easily produced by a simple embossing protocol, compatible with very large scale integration technology. The embossing process is shown to have the supplementary virtue to increase the internal degree of order of the nanowires, significantly enhancing their performance. This is applied to the fabrication of nanowire-based devices consisting of a liquid crystalline light-emitting polymer, of a liquid crystalline semiconducting polymer, and of an amorphous conducting polymer, illustrating the versatility and wide applicability of the method.     

Measurements of complex refractive indices of metals at several wavelengths by frustrated total internal reflection due to surface plasmon resonance

By employing a modified Otto's configuration for measuring surface plasmon resonance that has been proposed by Bliokh and his coworkers [Appl. Phys. Lett.89, 021908 (2006)APPLAB0003-695110.1063/1.2220540] we have obtained complex refractive indices of metals at several wavelengths. We demonstrate that the configuration has high potential for obtaining dispersion relations of metal conductors in bulk samples as well as in thin films from the visible to the near-infrared wavelength region. Furthermore, we show that the configuration enables us to obtain the complex refractive indices of metals or a thickness or refractive index of a dielectric layer on the metal at different points simultaneously. We have constructed a measurement system and carried out basic experiments. The experimental results agreed well with numerically simulated values or published ones.     

Nonlinear surface impedance of YBCO thin films: Measurements, modeling, and effects in devices

High-T _c thin films continue to be of interest for passive device applications at microwave frequencies, but nonlinear effects may limit the performance. To understand these effects we have measured the nonlinear surface impedanceZ _s in a number of YBa₂Cu₃O_7–x thin films as a function of frequency from 1 to 18 GHz, rf surface magnetic fieldH _rf to 1500 Oe, and temperature from 4 K toT _c . The results at lowH _rf are shown to agree quantitatively with a modified coupled-grain model and at highH _rf with hysteresis-loss calculations using the Bean critical-state model applied to a thin strip. The loss mechanisms are extrinsic properties resulting from defects in the films. We also report preliminary measurements of the nonlinear impedance of Josephson junctions, and the results are related to the models of nonlinearZ _S . The implications of nonlinearZ _S for devices are discussed using the example of a five-pole bandpass filter.The authors thank Dr. Alfredo Anderson of Lincoln Laboratory for many YBCO films and technical discussions concerning film properties. We thank Dr. J. Halbritter for numerous discussions and ideas. We thank also Prof. S. Sridhar, B. Willemsen, N. Belk, and Dr. J. Herd for technical discussions. We are deeply indebted to R. P. Konieczka and D. J. Baker for resonator assembly and technical support. Drs. R. W. Ralston, T. C. L. G. Sollner, and P. Carr are thanked for technical guidance and support.     

Effects of internal strains on the elastic constants of HCP hydrogen and deuterium

Expressions for effects of internal strains on elastic properties of solids are derived for the case of an anharmonic crystal and applied to hydrogen and deuterium. The calculation is carried out within the framework of the self-consistent phonon approximation. Onlyc ₁₁,c ₁₂, andc ₆₆ = 1/2(c₁₁ – c₁₂) are affected, and the resulting corrections are 10% ofc ₁₁ and 30% ofc ₁₂ for the present case. When due allowance is made for these effects, a previous calculation which did not include them is in better overall agreement with experiment.     

New Measurements of Wetting by Helium Mixtures

We have measured the contact angle of the ³He–⁴He interface on a sapphire window in the temperature range from 50 to 845 mK. Contrary to what had been found by Ueno et al. in two successive experiments, we have found complete wetting by the ⁴He-rich phase. Our new results have two consequences: first, we suspect that there were some artefacts in the experiments by Ueno et al. Secondly, we now believe that the critical Casimir forces are dominated by the van der Waals force in this experimental situation.     

Classification of measuring devices by their accuracy

Conclusions It is proposed to divide the general criterion for the accuracy of measures and measuring instruments expressed by a conventional sign or number into two notations, those of accuracy categories and accuracy classes. Categories of accuracy should be assigned to such groups of measuring devices (sets of measures of various nominal values) for which it is impossible to establish a single-valued characteristic expressed in relative units or measurement units. Categories of accuracy represent a nominal characteristic and its content can only be determined by evaluating the relation between a scale of a certain grade of accuracy and the numerical parameters which determine the accuracy of measurement by means of a given device without introducing corrections. Classes of accuracy characterize devices for which a given error characterizes completely and in a single-valued manner their metrological properties.For a more complete metrological characterization of measures and measuring instruments, it is advisable to indicate on the measures or measuring instruments, or in their certificates, in addition to their nominal categories and classes also their ranges, scale factors, or scale values.It is possible to use a double classification system, i.e., to assign to a single measure or measuring instrument both its category and class of accuracy. It has already been pointed out that the category characterizes the degree to which a measure of measuring instrument approaches its maximum attainable accuracy with the existing technique for measuring the given physical value. The class of accuracy indicates the tolerated and actually attainable limiting measurement error.     

Viscosity Measurements of Ceramic Oxides by Aerodynamic Levitation

The aerodynamic levitation technique has been used to achieve contactless surface tension and viscosity measurements of oxide liquids at high temperature (T>2000 K). An analytical approach (hydrodynamic equations) and a new recent approach, the energetic approach, are presented. The energetic approach is interesting because it can be applied to all cases, including ceramic oxides, even for droplets far from spherical shape. A device (VITI: VIscosity Temperature Installation) has been developed to perform viscosity measurements on corium using the aerodynamic levitation method. Specific experimental setups for the preparation and for the heating of the sample have been developed. This device has been successfully tested up to 1950 K for viscosity measurements and up to 2900 K without sample. These steps are indispensable to accomplish the final goal of VITI device: the measurement of rheological properties on oxides corium in this field of temperature. Viscosity models at high temperature for molten oxides are presented and compared.