Diam Sphere Research Articles

Standard‐target calibration of a parametric sonar over the difference‐frequency band, 1–6 kilohertz.

The Kongsberg TOPAS PS18 parametric sub‐bottom profiling sonar operates over the frequency band 15–21 kHz, with nonlinearly generated difference‐frequency radiation in the band 0.5–6 kHz. The TOPAS transducer mounted on R/V G. O. Sars is flush with the hull in the near‐horizontal plane. The sonar has been calibrated by the standard‐target method using a 280‐mm diam sphere of aluminum alloy 6082 T6 [K. G. Foote et al., J. Acoust. Soc. Am., 121, 1482–1490 (2007)]. The target was suspended beneath the vessel at each of three ranges, successively 100, 200, and 300 m. Because of conditions in Soerfolla fjord on Dec. 10, 2008, the target sphere was moving slowly relative to the vessel. Its instantaneous position was determined by geometrical considerations through synchronous observation with the Simrad EK60/38‐kHz scientific echo sounder, with split‐beam transducer mounted approximate to the TOPAS transducer. Data were collected for a number of parameter settings for each of three signal types: continuous wave...

Effect of Energy Pulse on 3-D Edney IV Interaction

This study investigates the effect of energy deposition on pressure and thermal loads generated by an Edney IV interaction. This complex supersonic jet impingement problem is formed by the intersection of an oblique shock generated by a 15-deg wedge with a Mach 3.45 bow shock in front of a 0.0254-m diam sphere. The full three-dimensional Reynolds-averaged Navier-Stokes equations are solved with the k-w turbulence model. Mesh-resolved simulations show that surface pressure without energy addition is in good agreement with experiments. The peak value is 1.8 times that observed without the impinging shock. Results from a grid resolution study confirm that the surface pressure is less sensitive than the heat flux. For flow control, a spherical energy pulse with a volume of 3 mm 3 and energy of 283 mJ is deposited upstream of the primary triple point. The unsteady interaction of the energy spot and its induced blast wave with the oblique shock, the distorted bow shock, and the impinging supersonic jet is elucidated in the context of the lensing phenomenon. The simulations indicate significant impact of the energy deposition on the surface pressure and heat flux. The instantaneous surface pressure and heat flux rise when the blast wave and high-energy spot hit the surface and fall when the expansion waves reach the surface. However, the overall integrated stress and thermal loads are reduced, mainly due to the effect of the expansion waves.

Response measures used in free-field localization

Two response measures, verbal spherical angles, and manual pointing, were compared in a free-field localization task. Verbal spherical angles refers to speaking the stimulus’ azimuth and elevation angles with respect to the center of one’s head. Manual pointing refers to pointing the stylus tip of an electromagnetic position digitizer onto a 12-in.-diam sphere and recording the azimuth and elevation of the tip with respect to the center of the sphere. Continuous visual and aural stimuli were presented from 272 directions around each of the five subjects, whose head motions were unrestrained. The accuracy and reaction times of the subjects were measured and compared. Pointing was more accurate than the verbal response, 10 and 22 deg, respectively. Pointing was about three times faster than the verbal response. The manual pointing technique is being used in other experiments to compare free-field and headphone localization performance.

An electrostatic levitator for high-temperature containerless materials processing in 1-g

This article discusses recent developments in high-temperature electrostatic levitation technology for containerless processing of metals and alloys. Presented is the first demonstration of an electrostatic levitation technology which can levitate metals and alloys (2–4 mm diam spheres) in vacuum and of superheating-undercooling-recalescence cycles which can be repeated while maintaining good positioning stability. The electrostatic levitator (ESL) has several important advantages over the electromagnetic levitator. Most important is the wide range of sample temperature which can be achieved without affecting levitation. This article also describes the general architecture of the levitator, electrode design, position control hardware and software, sample heating, charging, and preparation methods, and operational procedures. Particular emphasis is given to sample charging by photoelectric and thermionic emission. While this ESL is more oriented toward ground-based operation, an extension to microgravity applications is also addressed briefly. The system performance was demonstrated by showing multiple superheating-undercooling-recalescence cycles in a zirconium sample (Tm=2128 K). This levitator, when fully matured, will be a valuable tool both in Earth-based and space-based laboratories for the study of thermophysical properties of undercooled liquids, nucleation kinetics, the creation of metastable phases, and access to a wide range of materials with novel properties.

A WARMING MATTRESS FOR PREMATURE INFANTS

We measured temperatures and metabolic rate of healthy infants (gestational age 28-33 wks and postnatal age 2-26 days) in contact with a heated water mattress. Infants were randomized with/without the mattress ≥8 hrs in a single wall forced convection incubator, unrestrained, diapered and supine. Tmattress (35.2±.1°C) was regulated by continuous circulation of H2O through a thermostatically controlled bath. Mid-inc air temp (Ta) was within the thermoneutral range. No humidity was added to inc. Heating effects measured q half hrly: skin temp at 6 sites → mean skin temp (Ts), esophageal temp (Te), heart rate (HR), resp rate (RR) and O2 consumption (VO2) at the end of each period. N=10 patients. Results(mean±SD): No mattress vs mattress p value by paired t-test: Ta (°C) 32.4±1.3 vs 31.6±0.9 p<0.05; Ts (°C) 35.3±0.3 vs 36.3±0.3 p<0.01; Te (°C) 36.5±0.3 vs 37.2±0.4 p<0.01; HR (beats/min) 155±8 vs 161±10 p<0.01; RR (breaths/min) 41±6 vs 48±8 p<0.01; VO2 (ml/kg/min) STPD 5.33±1.4 vs 4.94±1.55 NS. Results indicate that heat storage occurred due to alteration of balance between body heat production and losses. To determine the rate of dry (sensible) heat exchange we used a metabolic simulator, an electrically-heated 10 cm diam sphere. At a representative incubator Ta of 31.5°C and simulator Ts of 35°C, the dry heat loss was reduced from 60 W/m2 to 35 W/m2 on the heated pad. This was brought about by a combination of heat conduction to the simulator and decreased radiation losses from the simulator to the surrounding mattress.

Further Tests on Ocean Wave Forces on Sphere

Wave force coefficients have been obtained for a 28.8-in diam sphere. The work was done at a test site in 37 ft of water offshore from Honolulu. The peak flow velocities encountered during the tests were usually in the 2-fps to 3-fps range. The highest measured flow speed was 4.6 fps. Thus, the maximum-particle-velocity Reynolds numbers involved are in the range of 5 x 10\u5 to 11 x 10\u5. These values, coupled with high turbulence levels in the flow because of the cycling of the sphere.s wake, assure that the data obtained are for transcritical situations. Tight statistical distributions of drag and inertia coefficients were found. However, it was felt most useful to consider a maximum total force coefficient, and this had the variation shown later in this note.

Autoregulation of cerebral blood flow during early experimental renal hypertension in the conscious dog.

Using the radioactive microsphere technique, cerebral blood flow (CBF) was measured in six conscious dogs before intervention and again on the 3rd-5th days after inducing hypertension by the one-kidney Goldblatt (1-KGH) procedure. Sham-operated controls were also studied. The normal temporal variability of CBF, as well as the precision of the microsphere technique in measuring CBF were also determined in other normal dogs. A left atrial catheter was used for the microsphere injections (15 micrometer diam spheres) and an aortic catheter was used for cardiac output and blood pressure measurements. On the 3rd-5th days after 1-KGH, mean aortic pressure increased from a control value of 94 +/- 7 mmHg to 135 +/- 20 mmHg (P less than 0.005). CBF did not change significantly from the control flow of 57.1 +/- 7.9 ml/100 g per min. Calculated cerebral vascular resistance increased by 47 percent (P less than 0.025) above the control value. Hence, the early phase of experimental renal hypertension is associated with adequate autoregulation of cerebral blood flow.

Use of a hot wire anemometer as a particle velocity detector in standing sound waves

It has been determined experimentally that the hot wire anemometer can, with restrictions, be used as a linear-amplitude response particle velocity detector in a longitudinal mode standing sound wave. In the case of a straight filament proper orientation of both the hot wire and the velocity field are important. Maximum sensitivity is obtained for a horizontal hot wire in a vertically oriented particle velocity field, but the output of a hot wire inclined 45°/135° to vertical in a horizontal standing wave tube is phase sensitive to the sense of the particle velocity vector. High-pass filtering is required to remove low frequency nonlinear components of the repetitive driveup–free-decay amplitude modulation. Traverses of the particle velocity field near a 0.9525 cm diam sphere in a 5.08 cm i.d. cylindrical cavity are presented for both straight and curved hot wires.

Localized Measurements of Wake Density Fluctuations Using Pulsed Laser Holographic Interferometry

A new technique of measuring localized wake turbulent fluctuations using pulsed laser holographic interferometry in a ballistic range has produced new data in a region normally inaccessible to support-free magnetically suspended wind-tunnel model testing (restricted to X/D ^ 10) or ballistic range anemometer measurements (restricted to X/D ^ 400). Extensive data were obtained with in. diam spheres and preliminary data with 12.5° half-angle, f in. base diam cones fired at about 6000 fps at 1 atm in TRW Ballistic Range A. Sphere wake fringe data were reduced to obtain power spectral density, autocorrelation, cross correlation, cross spectra, and integral scale of the turbulent fluctuations in density. The present integral-scale data for sphere wakes appear to be somewhat above the LeesHromas-Webb theory for 25 ^ X/D ^ 400 but within the projected range of wake anemometer data.

Modulation of a Fluorescent Light Beam by an Optically Pumped Vapor Undergoing a Double-Quantum Resonance

The high-frequency modulation of a light beam scattered by optically-pumped ${\mathrm{Rb}}^{85}$ vapor undergoing a double-quantum resonance in the ground state has been studied both experimentally and theoretically. The vapor cell used in the experiment was an evacuated 3-in.-diam sphere with paraffin-coated walls. It was subjected simultaneously to a ${\ensuremath{\sigma}}^{+}$-polarized ${D}_{1}$ pumping beam and a $\ensuremath{\pi}$-polarized unfiltered monitoring beam at right angles to the pumping beam. The scattered light was detected in a third orthogonal direction after passage through a $\ensuremath{\sigma}$ polarizer and a ${D}_{2}$ filter. A superheterodyne amplifier was used to select the component of the scattered light modulated at twice the frequency of the pulsed rf driving field. A theoretical analysis has been developed which predicts the existence of two pairs of nonvanishing off-diagonal elements of the excited-state density matrix oscillating at twice the applied frequency under these conditions, and also predicts a corresponding modulation of the scattered light. Despite the feebleness of the observed signal caused by heavy damping in the excited state of ${\mathrm{Rb}}^{85}$, such a modulation has been observed, and its resonant behavior has been found to agree with theory.

High-Homogeneity Tape-Wound Superconducting Coil

A 100 kG superconducting magnet with field uniformity better than 1 part in 104 over a 1 cm diam sphere has been constructed from composite Nb3Sn superconducting tape. Data showing the performance of the coil are presented. The field profiles depend both on the magnitude of the field and on the field history; field uniformity is considerably reduced at low fields after an excursion to higher fields, because of trapped flux. Neither the field nor the field profile at a given current agrees with the values calculated for a copper coil of identical geometry. The discrepancy results from the anisotropic diamagnetic properties of the superconducting tape winding, and is semiquantitatively understood from an analysis based on the critical-state model. The construction of the coil is described, particularly the electrical connections between modules and the methods used to obtain field uniformity.

Acoustic Scattering of FM Pulses from Aluminum Spheres in Water

Experimental measurements of acoustic backscattering of FM pulses from a family of precision-solid and hollow-aluminum spheres of 7 in. o.d. are presented and compared with computed echo pulse forms. The present paper is an extension of work reported by Diercks, Goldsberry, and Hickling for 5-in.-diam spheres [J. Acoust. Soc. Am. 40, 1258 (A) (1966)]. The spheres studied had i.d./o.d. ratios of 0.95, 0.8, and 0.0, with either air or water inside the hollow spheres. The incident FM pulses had a nondimensionalized center frequency of ka = 20 (approximately 54 kHz) with nondimensionalized frequency ranges of 15–25 and 10–30 during the pulse. Incident pulse lengths were selected in the nondimensionalized form Δτ = 0.5, 1.0, or 5.0, where Δτ relates the range extent of the pulse to the radius of the sphere according to 2Δτ = c2Δt/a, where 2Δt is the pulse length in seconds, c is the velocity of sound in water, and a is the radius of the sphere. Detailed comparison of experimental and theoretical results shows generally good agreement in frequency structure and amplitude for FM pulses having a range extent equal to or shorter than the sphere diameter. Comparisons for longer pulses are also shown. [This work was done under contract with the U. S. Office of Naval Research, Code 463, and the U. S. Naval Ordnance Test Station, Pasadena, California.]

Determining the material properties of a remote target by analyzing deceleration-time impact data.

A method for predicting the strength and density of a material from the deceleration-time history a(t) of an instrumented impact probe is of particular interest for determining properties of the surface of the moon or a planet. A mathematical model is established for analyzing the motion of a nondeforming probe impacting a target material. The mass, geometry, and velocity of the probe, the strength and density of the target, and the variation of the resisting forces caused by increasing contact area as the probe penetrates the surface are taken into account. Numerical examples depict the effects of these variables on a(t). Supporting experimental data from other investigators for 3-in.-diam spheres penetrating balsa wood, sand, and soil, and by the present authors for 6-mm-diam spheres and 0.30-caliber armorpiercing (AP) projectiles penetrating several classes of polymeric materials, are presented.

Radar absorption effect in hypersonic ballistic ranges

USAL and Blore1 have recently proposed an explanation for the anomalously large decrease in radar cross section that occurs when -g-in. diam spheres are observed by 4- or 8-mm wavelength radars at velocities near 13,000 fps and pressures of 10 mm Hg. This decrease is anomalous in that the plasma sheath around the sphere is far too thin to cause enough real power absorption in the lossy plasma layer. The new explanation hinges on the diffractive effect of sharp angular gradients in the plasma sheath surrounding the sphere. Some comparisons between this new theory and experiment are presented here for two different bodies and range conditions using General Motors Defense Research Laboratories (GM DRL) data.2 It can be shown, 1 using the techniques of physical optics, that the radar cross section of a metal sphere covered by a thin plasma layer is (7

The Measurement of Eta and Other Nuclear Properties of U233and U235in Critical Aqueous Solutions

The thermal value of eta for U//sup 233/ and U//sup 235/ is determined in experiments on unreflected homogeneous aqueous solutions of the two isotopes. These experiments also yield a value for the neutron age and the limiting concentrations of the fissile isotope in the aqueous solutions for infinlte volumes. Auxiliary experiments, establishing limits of error, testing certain aspects of the theoretical model employed, and experimentally determining the parameters in the critical equation, are also performed. Experiments performed with 27-in.- and 48-in.-diam spheres, and 5-ft- and 9-ft-diam cylinders yield consistent values of eta. Measurements of the nonleakage probability in cylindrical geometry give values consistent with those predicted by a two-group model in which the theoretical value of the age is used. Within the experimental error no differences are found in the ages of fission neutrons for U/sup 233/ and U/sup 235/. The average thermal values of eta determined are 2.292 plus or minus 0.015 for U/sup 233/ and 2.076 plus or minus 0.015 for U//sup 235/. The 2200 meters/sec values are the same since the g-factors for eta are unity. The value of the neutron age to the indium resonance energy for U//sup 235/fission neutrons in water is found to bemore » 25.6 plus or minus 1.3 cm/sup 2/. The minimum U/sup 233/ and U/sup 235/ critical densities for these nitrate solutions are found to be 11.25 plus or minus 0.10 and 12.30 plus or minus 0.10 gm/liter for U/sup 233/ and U/sup 235/, respectively. (auth)« less

Composite Spherical Sonar Transducers

This paper describes the construction of and behavior of a large spherical transducer formed as a mosaic of ceramic elements with no inactive material Formulas are shown that describe the several elements which form the building block of the assembly. The developed techniques indicate spheres up to 30 in. in diameter can be easily constructed and a modification of the basic element will permit much larger spheres to be built. Complete evaluation of a 10-in.-diam sphere is shown with efficiencies approaching 100%. Correlation between its evaluation and the theoretical report of S. Hanish at NRL is shown. Behavior in water indicates a good acoustic loading and wide-band operation.

Electron Microscope Observation of Precipitates on Grown-In Dislocations in MgO

The defect structure of undeformed, single-crystal, Norton MgO has been examined by transmission in the electron microscope. It is observed that precipitate particles in the form of 0.2-\ensuremath{\mu} diam spheres and short rods are present in large numbers on as-grown dislocations. By using special etching and optical techniques which are described, the concentration of the precipitate spheres is shown to average ${10}^{9}$ "balls"/cc (but range from ${10}^{7}$ to ${10}^{10}$ "balls"/cc) for a large number of samples examined. Qualitative evidence is presented which indicates that these precipitates are the origin of Tyndall scattering frequently observed in MgO.

Fundamental Studies of Actual-Size-Scintlgram

An actual-size scintigram of a thyroid gland was obtained using five different iodine-131 source shapes. The cps of every point are expressed as a percentage of the maximum counts of the source. By adjusting the background cut- off circuit to the optimum cps (%) of each source, the actual-size scintigram is obtained. Optimum cps (%) are as follows 37.5 mm diam sphere 30%; 37.5 mm diam by 1 mm thick disk 60%: 37.5 mm diam by 11 mm thick disk 60%; 40 mm by 20 mm by 10 mm cuboid 60%; and human thyroid 40%.. Drawing iso-cps (%) lines of each source, it is found that the line shapes are similar to the outline of the source; their distribution and shape are independent of source intcnsity. In the clinic, iso-cps (%) lines are convenient for establishing the distribution of iodine-131, and particularly for locating a thyroid tumor. (N.W.R.)

Transit-Time Accelerometer

An omnidirectional transit-time accelerometer, developed for measuring the drag acceleration of spheres dropped from rockets, is described. The ambient density and temperature of air may be calculated from the drag acceleration. In the device, a bobbin is periodically caged and released within a cavity. The time for the bobbin to traverse the distance to the cavity, which distance is the same in any direction, is telemetered and measured. The accelerometer range is about 5×10−3 to 5 g. Systematic errors and standard deviations over the range are about 1%. The accelerometer was used successfully in a rocket flight in which the drag acceleration of a 7-in. diam sphere was measured.