Techniques for Determining Acoustics of Amphitheaters by Scale Model Studies with High Frequency Sounds

1950 ◽  
Vol 22 (5) ◽  
pp. 679-679
Author(s):  
H. C. Hardy ◽  
F. G. Tyzzer
Keyword(s):  
High Frequency ◽  
Scale Model ◽  
Model Studies

Shallow subsurface mapping by electromagnetic sounding in the 300 kHz to 30 MHz range: Model studies and prototype system assessment

Geophysics ◽  
1994 ◽  
Vol 59 (8) ◽  
pp. 1201-1210 ◽  
Author(s):  
Duff C. Stewart ◽  
Walter L. Anderson ◽  
Thomas P. Grover ◽  
Victor F. Labson
Keyword(s):  
Dielectric Permittivity ◽  
High Frequency ◽  
Low Frequency ◽  
Computer Programs ◽  
Thin Layers ◽  
Depth Range ◽  
Frequency Range ◽  
Model Studies ◽  
New Instrument ◽  
Displacement Currents

A new instrument designed for frequency‐domain sounding in the depth range 0–10 m uses short coil spacings of 5 m or less and a frequency range of 300 kHz to 30 MHz. In this frequency range, both conduction currents (controlled by electrical conductivity) and displacement currents (controlled by dielectric permittivity) are important. Several surface electromagnetic survey systems commonly used (generally with frequencies less than 60 kHz) are unsuitable for detailed investigation of the upper 5 m of the earth or, as with ground‐penetrating radar, are most effective in relatively resistive environments. Most computer programs written for interpretation of data acquired with the low‐frequency systems neglect displacement currents, and are thus unsuited for accurate high‐frequency modeling and interpretation. New forward and inverse computer programs are described that include displacement currents in layered‐earth models. The computer programs and this new instrument are used to evaluate the effectiveness of shallow high‐frequency soundings based on measurement of the tilt angle and the ellipticity of magnetic fields. Forward model studies indicate that the influence of dielectric permittivity provides the ability to resolve thin layers, especially if the instrument frequency range can be extended to 50 MHz. Field tests of the instrument and the inversion program demonstrate the potential for detailed shallow mapping wherein both the resistivity and the dielectric permittivity of layers are determined. Although data collection and inversion are much slower than for low‐frequency methods, additional information is obtained inasmuch as there usually is a permittivity contrast as well as a resistivity contrast at boundaries between different materials. Determination of dielectric permittivity is particularly important for hazardous waste site characterization because the presence of some contaminants may have little effect on observed resistivity but a large effect on observed permittivity.

Conceptual Design of the Flow Noise Simulator

2003 ◽  
Author(s):  
Ryuichi Sato ◽  
Takayuki Mori ◽  
Ryo Yakushiji ◽  
Kenji Naganuma ◽  
Masaharu Nishimura ◽  
...  
Keyword(s):  
Conceptual Design ◽  
Large Scale ◽  
Scale Model ◽  
Variable Pressure ◽  
Cavitation Noise ◽  
Flow Noise ◽  
Model Studies ◽  
Surface Ship ◽  
Noise Measurements ◽  
Under Construction

The Flow Noise Simulator (FNS) of the 1st Research Center of TRDI/JDA (Japan Defense Agency) is a large, variable pressure, recirculating water tunnel with very low background noise level. The tunnel is 20m high and 49m long, containing 2000m3 of water. The test section has a square cross section of 2m × 2m with 10m in length. It will accept large size surface ship models of 6m, submarine models of 4m in length and full scale ship appendix models. The FNS is currently under construction and will be accomplished in 2005. It will be used for a wide variety of hydrodynamic and hydroacoustic testing of surface ships and submarines, such as propeller cavitation noise measurements and propeller-hull interaction observation, with sufficiently large scale models. Conceptual design of the FNS was started in 1996 and evaluated by following scale model studies. This paper discusses some technical issues of the FNS.

A method for obtaining depth estimates from the geometry of Slingram profiles

Geophysics ◽  
1991 ◽  
Vol 56 (10) ◽  
pp. 1543-1552 ◽  
Author(s):  
K. Duckworth ◽  
H. T. Calvert ◽  
J. Juigalli
Keyword(s):  
Linear Relationship ◽  
Free Space ◽  
Phase Inversion ◽  
Spatial Separation ◽  
Depth Estimation ◽  
Scale Model ◽  
Model Studies ◽  
Scale Modelling ◽  
Host Rocks ◽  
Method Show

An approximate method for deriving conductor depth estimates from the geometry of horizontal coplanar coil Slingram type electromagnetic profiles is based on a transformation of the recorded profile to a form which is free of the influence of coil separation. Depth estimates are derived from an empirically determined linear relationship between the spatial separation of maxima on the transformed profile and the depth of the conductor. Field examples and electromagnetic scale modelling indicate that the method works well on both thin and thick conductors with dips ranging from 90 to 60 degrees. Field examples and model results also show that the method works well when a conductive overburden is present, even if the overburden causes phase inversion. Examples of the application of the method show that while knowledge of the conductance of a target will aid in depth estimation, good depth estimates can be made even if the conductance of the target cannot be determined. Comparative scale model studies of conductors located first in free‐space and then in a conductive host suggest that the method will also give good results for targets located in conductive host rocks.

scholarly journals LARGE SCALE MODEL TESTS OF PLACED STONE BREAKWATERS

1976 ◽  
Vol 1 (15) ◽  
pp. 147 ◽  
Author(s):  
Charles K. Sollitt ◽  
Donald H. Debok
Keyword(s):  
Large Scale ◽  
Scale Model ◽  
Small Scale ◽  
Stable Model ◽  
Model Studies ◽  
Drag Forces ◽  
Port Facilities ◽  
Large Scale Model ◽  
Wave Heights ◽  
Water Depths

Large scale model studies reveal that Reynolds scaling can affect the apparent stability and wave modifying properties of layered breakwater structures. Results of a study for a breakwater configuration designed to protect offshore power and port facilities in water depths to 60 feet are presented and discussed. The armor layer of this structure is formed from quarried rock of irregular rectangular parallelepiped shape, individually placed perpendicular to 1:2 seaward slope and crest. The resulting armor layer is relatively smooth, densely packed and very stable. Model studies of similar configurations were studied at 1:10, 1:20 and 1:100 scale ratios. Stability, runup, rundown and reflection were measured for a variety of water depths, wave heights and periods. Analysis of the large scale test results establish that the placed stone armor is approximately as stable as dolos armor units. Runup, rundown and reflection respond similar to rough, impermeable slopes. Comparison of large and small scale results demonstrate that relative increases in drag forces at lower Reynolds numbers decrease stability and runup in small scale models.

scholarly journals Cloud condensation nuclei production associated with atmospheric nucleation: a synthesis based on existing literature and new results

2012 ◽  
Vol 12 (24) ◽  
pp. 12037-12059 ◽  
Author(s):  
V.-M. Kerminen ◽  
M. Paramonov ◽  
T. Anttila ◽  
I. Riipinen ◽  
C. Fountoukis ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Large Scale ◽  
Cloud Condensation Nuclei ◽  
Large Fraction ◽  
Scientific Information ◽  
Scale Model ◽  
Condensation Nuclei ◽  
Uncertainty Range ◽  
Model Studies ◽  
Atmospheric Nucleation

Abstract. This paper synthesizes the available scientific information connecting atmospheric nucleation with subsequent cloud condensation nuclei (CCN) formation. We review both observations and model studies related to this topic, and discuss the potential climatic implications. We conclude that CCN production associated with atmospheric nucleation is both frequent and widespread phenomenon in many types of continental boundary layers, and probably also over a large fraction of the free troposphere. The contribution of nucleation to the global CCN budget spans a relatively large uncertainty range, which, together with our poor understanding of aerosol-cloud interactions, results in major uncertainties in the radiative forcing by atmospheric aerosols. In order to better quantify the role of atmospheric nucleation in CCN formation and Earth System behavior, more information is needed on (i) the factors controlling atmospheric CCN production and (ii) the properties of both primary and secondary CCN and their interconnections. In future investigations, more emphasis should be put on combining field measurements with regional and large-scale model studies.

Inductive interaction between closely spaced steeply dipping tabular conductors located in a resistive host

Geophysics ◽  
2001 ◽  
Vol 66 (4) ◽  
pp. 1052-1058 ◽  
Author(s):  
K. Duckworth ◽  
B. Clement
Keyword(s):  
Scale Model ◽  
Strong Increase ◽  
Initial Increase ◽  
Moving Source ◽  
Model Studies ◽  
Coil System ◽  
True Target ◽  
Physical Scale ◽  
Inductive Interaction ◽  
The Individual

Physical scale‐model studies of the responses provided by horizontal coplanar and vertical coincident coil moving‐source electromagnetic systems when operated over closely spaced, steeply dipping, tabular conductors located in a resistive host are presented. For separations of the conductors that permit separate anomalies to be identified, the detected effect of inductive interaction between the conductors depends on the configuration of the exploration device. As conductors are moved closer together, the horizontal coplanar coil system produces responses for each conductor that become progressively weaker than the individual responses when each conductor is isolated. By comparison, vertical coincident coils detect an initial increase of the anomalies from the individual conductors as the conductor separation is reduced until just before the separate anomalies merge. As the anomalies merge, the vertical coincident coil responses decline in magnitude. After the anomalies merge and present the appearance of the response of a single conductor, both coil systems record an expected strong increase of response which exceeds the response when the conductors are in contact. These mutual inductive interactions cause significant variations in the depth estimates provided by horizontal coplanar coils. Depth estimates provided by vertical coincident coils are always smaller than the true target depths. The vertical coincident coil configuration displays an ability to identify separate conductors at significantly smaller conductor separations than can the horizontal coplanar coils.

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