Absolute Power Measurements Research Articles

ChemInform Abstract: SIMULTANEOUS MEASUREMENT OF DENSITY, ELECTRICAL CONDUCTIVITY AND ABSOLUTE THERMOELECTRIC POWER OF LIQUID RUBIDIUM UP TO 1400°C AND 400 BAR

Chemischer InformationsdienstVolume 7, Issue 47 Physical Inorganic Chemistry ChemInform Abstract: SIMULTANEOUS MEASUREMENT OF DENSITY, ELECTRICAL CONDUCTIVITY AND ABSOLUTE THERMOELECTRIC POWER OF LIQUID RUBIDIUM UP TO 1400°C AND 400 BAR H. P. PFEIFER, H. P. PFEIFERSearch for more papers by this authorW. FREYLAND, W. FREYLANDSearch for more papers by this authorF. HENSEL, F. HENSELSearch for more papers by this author H. P. PFEIFER, H. P. PFEIFERSearch for more papers by this authorW. FREYLAND, W. FREYLANDSearch for more papers by this authorF. HENSEL, F. HENSELSearch for more papers by this author First published: November 23, 1976 https://doi.org/10.1002/chin.197647008AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URLThe site is currently under maintenance and this functionality is not available right now. Please try later. Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume7, Issue47November 23, 1976 RelatedInformation

Simultaneous Measurement of Density, Electrical Conductivity and Absolute Thermoelectric Power of Liquid Rubidium up to 1400°C and 400 bar

AbstractThe paper reports new experimental results of the temperature and pressure dependence of the electrical conductivity, absolute thermoelectric power, and density of liquid rubidium up to 1400°C and 400 bar. To enable a direct experimental correlation between the separate variation of temperature and density and the change of the electrical transport properties, the PVT data and the electrical quantities have been measured simultaneously. For this purpose a new experimental set‐up has been designed, the principle of which is described shortly.

Measurement of absolute power of a nuclear reactor

Measurement of absolute power of a nuclear reactor

A High Resolution Dynamic Technique of Thermoelectric Power Measurements

A new technique, principally applicable to metals and alloys, has been developed for high resolution absolute thermoelectric power (TEP) and differential thermoelectric power measurements. It utilizes two continuously monitoring dc nanovolt amplifiers, one for the sample couple thermoelectric voltage and the other for a thermocouple voltage proportional to temperature differences developed across the samples. The outputs of these amplifiers are attached to the channels of an X-Y recorder, thus yielding direct slope-proportional data. By using heat from a low-mass, electrostatically guarded heater to develop transient temperature gradients across samples, it is possible to dynamically determine the absolute TEP of a sample versus lead (Pb) or the differential TEP of two nearly similar samples, one of whose composition or history of treatment has been slightly altered. Reducing thermal time constants with an independent heat leak permits the completion of a TEP measurement in a few seconds, thus yielding high resolution determinations under adverse experimental conditions. The use of a special sample necking and ``heat sinking'' techniques, as well as a low melting point, low TEP, ternary eutectic indium alloy solder, make it possible to obtain results with a range of high resolutions. The experimental resolution attainable with these two dynamic techniques can be summarized as ±[10−3)(ΔT)−1(μV/K)+1.0%] for absolute TEP and ±[ΔT)−2+Sabsolute2]1/2 10−3(μV/K) for differential TEP, where ΔT is the range 0.01–1.0 K increment of differential temperature and Sabsolute is the approximate value of the thermopower of one of the samples. Data utilizing this newly developed technique are presented on Chromel-P, Wood's metal solder, and the ternary eutectic InSnCd solder alloy, as well as differential TEP measurements of two opposing Chromel-P samples over the temperature range of T = 1.5–300 K.

Antiferromagnetism and Electrical Transport Properties of Chromium-Aluminum Alloys

Electrical resistivity ρ of Cr–Al alloys containing 0.3-, 1.2-, 1.9-, 3.7-, and 6.2-at.% Al has been studied as a function temperature. The onset of antiferromagnetism causes small anomalies in the ρ vs T curves from which the Néel temperature TN can be determined. TN decreases rapidly with additions of small amounts of Al and then increases with larger Al concentrations. A minimum in the TN vs Al content curve occurs at about 1.2-at.% Al. This minimum results from the fact that below about 1.5-at.% Al level, the Cr–Al alloys possess an incommensurable antiferromagnetic structure. Above this concentration, the antiferromagnetic phase is of the commensurable type. The absolute thermoelectric power measurements on alloys containing 0.3 and 1.2-at.% Al support the determinations of TN from the electrical resistivity studies.

Absolute power measurements in small angle X-ray scattering with gas scattering calibration

The calibration of a high intensity X-ray beam from a rotating anode tube has been accomplished with the small angle scattering from three heavy gases used as primary standards because their scattering cross sections at zero angle could be calculated. The scattering of the three gases permitted calibration of the incident beam and geometry to ±2%. A scattering 10% in excess of that predicted from the thermodynamic relationships was observed for water, ethyl alcohol, xylene, and benzene. This excess was ascribed to double scattering. Possible application of these methods to determine the molecular weight of macromolecules was investigated. Scattering observed from solutions of metmyoglobin was within 3% of the predicted scattering. For ribonuclease a 35% excess over predicted scattering was observed and was ascribed to aggregation, of the molecules, shown by ultra centrifuge methods to occur in these solutions.

Radiation-pressure instrument for absolute measurements of power at 35 GHz

The paper is concerned with the measurement and application of radiation-pressure forces, operating at millimetre wavelengths on low-loss dielectric situated in the electromagnetic field, when there is a gradient of stored energy in the material. To strengthen the applied field, the dielectric is placed in a resonant cavity, and observations of the mechanical force show it to be substantially in accordance with theory. A novel experimental wattmeter operated by such a force is described, and a further development of it, which uses a twin system of cavities giving differential forces arising from forward- and backward-travelling waves in the main power-carrying guide, is shown to yield a practical instrument for absolute power measurements.

Current Distribution in Barretters and Its Application to Microwave Power Measurements

This paper describes a mathematical analysis for determining the microwave current distribution in a barretter in a rectangular waveguide. This distribution, when used with another analysis which calculates substitution error for any given current distribution, provides a missing step necessary for the calibration of microwave and millimeter-wave barretters for absolute power measurements.

C0 2 Lasers as a heat source for engineering applications

Work at Birmingham University is directed to developing integrated manufacturing systems for industrial use. System requirements are sought on the basis of quantitative process experiments. Absolute power measurement by a black-body sphere calorimeter is included. Fore-optics are necessary to optimise spot size and power intensity. The behaviour of irradiated engineering materials is examined. Achievement of maximum total power requires a sacrifice in peak power intensity available. Applications exist for conduction processes but cutting or welding relies on a non-conducting limiting mode of energy transfer when power exceeds a threshold value. At present, this mechanism cannot be achieved with metals. Available experimental data is scant but tables are given showing known cutting and welding data.

Wire calorimeter for absolute and accurate laser-power measurements

A calorimeter, acting in a self-balancing bridge circuit and designed for absolute measurements of radiation power from continuous-wave lasers, is described. The calorimeter contains a wire-cone absorber with an effective absorptivity of 99.5±0.2%. The arrangement, consisting of a d.c. bridge, a galvanometer amplifier and a transistor current regulator, is suitable for absolute-power measurements in the range 30μW to 30mW with an accuracy of within 1%.

The absolute thermoelectric powers of some liquid alloys

Abstract Measurements of the absolute thermoelectric powers of several liquid alloys as a function of temperature and composition are reported. The alloys Hg-In and Hg-Tl were studied. In both cases the absolute thermoelectric powers show a minimum when plotted against concentration at low concentrations. The system Hg-Na was measured over the range 0 at. % to 10 at. % Na. The absolute thermoelectric power shows a very sharp minimum at about 5.0 at. % Na. This minimum becomes sharper with increasing temperature. The effect is more marked in this case than in the previous two cases. Measurements of absolute thermoelectric power of the alloys of cadmium in mercury and gold in mercury show that it becomes less negative as the metals are added to mercury. This is the opposite effect to that found in the previous two alloys. Measurements made on the Cd-In system show no minimum. The results on these alloys are discussed with relation to Mott's theory for liquid mercury (Mott 1966).

A Bistatic Radar Method for the Determination of ε and µ for a Smooth Spherical Target

This paper presents an application of the concept of differential reftectivity relating to the determination of the permeability and permittivity of the material composing a smooth reftecting sphere. Expressions for these parameters are derived which depend on measurements of relative scattered power in a bistatic radar or optical experiment. Absolute power measurements are not necessary; only the ratio of the powers received by two quadratically opposed antennas is needed. This ratio must be determined for two different configurations of source, target, and observation point. The first‐order terms obtained by this method can be readily verified by geometrical optics.

Microwave Harmonic Generation by Ferrimagnetic Crystals

The experimental behavior of isotropic ferrimagnetic insulators in second harmonic generation at microwave frequencies has been investigated and compared with the behavior predicted by the equations of motion with Landau-Lifshitz and with Bloch-Bloem-bergen damping. In general, a close agreement between experiment and theory was found. The experiments were carried out with small samples of single-crystal manganese ferrite, YIG, and other ferrimagnetic materials. Since harmonic generation results from asymmetries in the precessional orbit, measurements were made with disk-shaped specimens in which the demagnetizing fields create the asymmetry. The technique employed a cavity simultaneously resonant to 8.5 and 17 kMc. Absolute values of field intensities and magnetizations were computed from absolute power measurements. A figure of merit F for a ferrimagnet is defined. In a practical 2ω generator the output power P2ω is expected to vary as the product F2Pi2, where Pi is the input ω power. In comparing materials at ferrimagnetic resonance (FMR), F should vary as χ0″. This was verified experimentally, even at high drive levels. At constant frequency and drive level F should be nearly independent of Hdc. Only slight deviations from this were found at low drive levels.

Absolute power measurement at microwave frequencies

Absolute power measurement at microwave frequencies

Absolute power measurement at microwave frequencies

The radiation pressure of electromagnetic waves on a reflecting surface may be used as the basis of a method of power measurement at microwave frequencies. The method is absolute, depending only on measurements of mass, length and time; no secondary electrical standards are involved in the experimental procedure. Moreover, no appreciable power is absorbed by the apparatus. This method has been compared with a balanced calorimeter wattmeter, and agreement to within 1?2 watts has been obtained in the range 10?50 watts. The major difficulty encountered in obtaining greater accuracy with the radiation-pressure apparatus described is the disturbing effect of convection currents of air, caused by the heating of the reflector by the small fraction of the incident microwave power which is not reflected.