An apparatus is described in which a pure dynamic shear strain is produced in a small sample of liquid or other material, and the resulting shear stress is measured in the frequency range between 20 and 1000 cps. The shear stress is decomposed into its real and imaginary parts, which yield the shear rigidity and the shear viscosity. Design and working equations are derived. Two liquids are investigated and the data shown. The effect of impurity molecules is discussed, and a possible application to lubrication theory is suggested.
The Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument is a 10-channel earth limb-viewing sensor that measures atmospheric emissions in the spectral range of 1.27 µm to 16.9 µm. SABER is part of NASA's Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) mission, which was successfully launched in December 2001. Uncommon among limb-viewing sensors, SABER employs an on-axis telescope design with reimaging optics to allow for an intermediate field stop and a Lyot stop. Additional stray light protection is achieved by an innovative inner Lyot stop, which is placed conjugate to the secondary obscuration and support structure. Presented in this paper is the off-axis response of SABER as measured in the Terrestrial Black Hole off-axis scatter facility at the Space Dynamics Laboratory. The measurement was made at visible wavelengths; thus, the response is only representative of SABER's short wavelength channels. The measurement validated the stray light design and complemented the APART software model, which predicts that mirror scatter is the dominant stray light mechanism at short wavelengths. In addition, estimates of the mirror bi-directional reflectance distribution function (BRDF) were made. The off-axis response measurement indicates that SABER is an exceptional stray light suppression telescope.
Both cooperative behavior, involving breakup and re-formation of molecular aggregates, and environmental dissimilarities, attributed to incompleteness of short-range order, have been proposed earlier by two of the authors as possible mechanisms giving rise to the distribution of shear-relaxation times exhibited by most liquids. Experimental evidence is presented here giving qualitative indication that environmentaldissimilarity effects indeed can be operative in a liquid together with cooperative phenomena. Shearrelaxation characteristics are studied at a number of temperatures for a host liquid, hexachlorobiphenyl, having methanol and toluene in various concentrations as separate impurity liquids. Small amounts of the additive liquids are found to lessen the decay rate of cooperative behavior with increasing temperature, a result attributed to both degraded cooperative behavior and an environmental-dissimilarity mechanism. Although cooperative behavior predominates throughout the temperature and concentration range investigated, in the low-temperature region the impurity additive primarily decomposes aggregates of cooperative molecules, whereas at higher temperatures the impurity markedly enhances environmental dissimilarities and the distribution function widens with increasing (small) concentration. Toluene impurity additive displays greater degradation effect on cooperative behavior as well as greater enhancement of environmental dissimilarities than does methanol. Critical solution temperatures are noted as a matter of interest, and a method is presented for determining analytically the distribution of relaxation times associated with our experimentally determined components of shear modulus.
The sinusoidal pressure generator (SPG) produces pressure changes suitable for fundamental studies of liquids and also for calibration of pressure gauges. The present model yields pressure up to ten atmospheres at any frequency from zero to well over 10 000 cps. The pressures are proportional to the excitation voltage within ±5% from zero to 10 000 cps. The SPG consists of a piezoelectric driver (24 disks of a BaTiO3 ceramic), a fluid cavity and provisions for mounting test devices. All components are contained in a heavy-walled brass cylinder 4.0 in. in diameter and 3.2 in. high. The peak displacement obtainable without undue heating of the BaTiO3 is approximately 10−5 cm. The fluid cavity is approximately 1.25 in. in diameter and 0.040 in. deep and is sealed by a thin Mylar membrane. The monitor crystal is a BaTiO3 cylinder, 116 in. o.d. and 116 in. high (output sensitivity approximately 40 mv per atmosphere). The cavity forms one end of an interchangeable plug which accommodates pressure gauges having diameters up to about one inch. This plug can also be provided with a thick diaphragm, directly behind the fluid cavity, for deflection measurements by means of a very sensitive capacitance-type device, the Resonant Bridge Carrier System. Typical calibrations of commercial pressure gauges will be shown.
Measured current waveforms in an RLC circuit are used as a basis for obtaining information on the behavior of wire material at various stages of the explosion. In the premelt region, there is, as expected, complete agreement between measured current and current calculated on the assumption that temperature and resistivity are linear with energy input. After absorption of an energy which under static condition leads to solid-liquid transition, the fit is unsatisfactory but can be improved by treating the wire as a superheated solid for a period of about 20 nsec. During the vaporization stage, resistance and energy are derived from the measured current. If all the energy input is assigned as latent heat of vaporization, the calculated current deviates drastically from the measured current, indicating that for all capacitor voltages used in this study, the process is far from static condition. Furthermore, the higher the energy input rate, the greater the containment forces and the more energy is required to expand a given portion of the wire. A sharp boundary is assumed to separate the unvaporized conducting core from the nonconducting sheath of vapor. The inward displacement of the boundary is determined from calculated data for resistance and energy.
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