A Reverberation‐Time Scale for High Speed Level Recorders

1939 ◽  
Vol 10 (4) ◽  
pp. 300-301 ◽  
Author(s):  
Keron C. Morrical
Keyword(s):  
Time Scale ◽  
High Speed ◽  
Reverberation Time ◽  
Speed Level

Motion of Descending Solid Particles and Local Flow Around the Particles in Downward Turbulent Water Duct Flow (Keynote)

2011 ◽  
Author(s):  
Yoshimichi Hagiwara ◽  
Hideto Fujii ◽  
Katsutoshi Sakurai ◽  
Takashi Kuroda ◽  
Atsuhide Kitagawa
Keyword(s):  
Reynolds Number ◽  
Time Scale ◽  
High Speed ◽  
Fluid Velocity ◽  
Stokes Number ◽  
Solid Particles ◽  
Duct Flow ◽  
Local Flow ◽  
Particle Reynolds Number ◽  
Turbulent Water

The Stokes number, the ratio of the particle time scale to flow time scale, is a promising quantity for estimating changes in statistics of turbulence due to particles. First, we explored the Stokes numbers in some recent studies. Secondly, we discussed the results of our direct numerical simulation for turbulent flow with a high-density particle in a vertical duct. In the discussion, we defined the particle Reynolds number from the mean fluid velocity in the near-particle region at any time. We evaluated a new local Stokes number for the particle. It is found that the Stokes number is effective for the prediction of the distance between the particle center and one wall. Finally, we carried out experiments for turbulent water flow with aluminum balls of 1 mm in diameter in a vertical channel. The motions of aluminum balls and tracer particles in the flow were captured with a high-speed video camera. We found that the experimental results for the time changes in the wall-normal distance of the ball and the particle Reynolds number for the ball are similar to the predicted results.

scholarly journals Interplanetary Response to Solar Long Time-Scale Phenomena

1980 ◽  
Vol 91 ◽  
pp. 105-125
Author(s):  
C. D'Uston ◽  
J. M. Bosqued
Keyword(s):  
Solar Wind ◽  
Time Scale ◽  
High Speed ◽  
Coronal Holes ◽  
Observational Evidence ◽  
Solar Wind Flow ◽  
Speed Solar Wind ◽  
Long Time ◽  
Outer Corona ◽  
High Speed Solar Wind

In this paper, we briefly review the experimental knowledge gained in the recent years on the interplanetary response to solar long-time scale phenomena such as the coronal magnetic structure and its evolution. Observational evidence that solar wind flow in the outer corona comes from the unipolar diverging magnetic regions of the photosphere is discussed along with relations to coronal holes. High-speed solar wind streams observed within the boundary of interplanetary magnetic sectors are associated with these structures. Their boundaries appear as very narrow velocity shears.

PORTABLE SPECKLE INTERFEROMETRY CAMERA SYSTEM

2013 ◽  
Vol 02 (02) ◽  
pp. 1340008 ◽  
Author(s):  
R. M. GENET
Keyword(s):  
Time Scale ◽  
High Speed ◽  
Low Cost ◽  
Coherence Time ◽  
Speckle Interferometry ◽  
Ccd Cameras ◽  
Camera System ◽  
Double Stars ◽  
Wide Range

Speckle interferometry of close double stars avoids seeing limitations through a series of diffraction-limited high speed observations made faster than the atmospheric coherence time scale. Electron multiplying CCD cameras have low read noise at high read speeds, making them ideal for speckle interferometry. A portable speckle camera system was developed based on relatively low cost, off-the-shelf components. The camera's modular components can be exchanged to adapt the system to a wide range of telescopes.

Probability of Ship High-Runs from Phase-Space Data

2019 ◽  
Author(s):  
Ioannis Kontolefas ◽  
Kostas J. Spyrou
Keyword(s):  
Phase Space ◽  
Coherent Structures ◽  
High Speed ◽  
Statistical Information ◽  
Motion Patterns ◽  
Following Seas ◽  
Probability Calculation ◽  
Speed Level ◽  
Surf Riding ◽  
Space Data

A clustering scheme has been applied for capturing qualitatively different surge motion patterns in the phase space. The scheme enables the identification of “high-run” incidents as soon as such motions are triggered and while their phenomenology has not yet been well developed. A “high run” is a surf-riding–like behavior, appearing in irregular following seas. The concept of finite-time coherent sets is exploited for deriving estimates of the probability of high-runs. The method is verified by identifying independently the corresponding hyperbolic Lagrangian coherent structures; then, consistency is sought between the two approaches. An important feature of the method is that it does not rely on the use of some empirical criterion for the high-run threshold, such as one based on the exceedance of an arbitrary high-speed level. Despite its computational burden, the proposed scheme offers “objective” statistical information on a ship’s high-run tendency that can be used for benchmarking simpler (approximative) probability calculation schemes.

Probability of Ship High-Runs from Phase-Space Data

2019 ◽  
Author(s):  
Ioannis Kontolefas ◽  
Kostas J. Spyrou
Keyword(s):  
Phase Space ◽  
Coherent Structures ◽  
High Speed ◽  
Statistical Information ◽  
Motion Patterns ◽  
Following Seas ◽  
Probability Calculation ◽  
Speed Level ◽  
Surf Riding ◽  
Space Data

A clustering scheme has been applied for capturing qualitatively different surge motion patterns in the phase space. The scheme enables the identification of “high-run” incidents as soon as such motions are triggered and while their phenomenology has not yet been well developed. A “high run” is a surf-riding–like behavior, appearing in irregular following seas. The concept of finite-time coherent sets is exploited for deriving estimates of the probability of high-runs. The method is verified by identifying independently the corresponding hyperbolic Lagrangian coherent structures; then, consistency is sought between the two approaches. An important feature of the method is that it does not rely on the use of some empirical criterion for the high-run threshold, such as one based on the exceedance of an arbitrary high-speed level. Despite its computational burden, the proposed scheme offers “objective” statistical information on a ship’s high-run tendency that can be used for benchmarking simpler (approximative) probability calculation schemes.

Stress-Strain Testing of Rubber at High Rates of Elongation

1963 ◽  
Vol 36 (1) ◽  
pp. 28-49
Author(s):  
Mark L. Dannis
Keyword(s):  
Tensile Strength ◽  
Time Scale ◽  
High Speed ◽  
Dynamic Properties ◽  
Stress Strain ◽  
High Frequencies ◽  
Apparent Modulus ◽  
Strain Testing ◽  
Considerable Body ◽  
Very High

Abstract It is well known that the properties of rubbery materials depend upon the speed or rate at which they are tested or used. A considerable body of work has shown that the dynamic properties of rubber change with the time scale of the test and, in particular, at very short times or at very fast rates, the properties approach those of plastics, i.e., high modulus and low elongation. These dynamic properties are measured by oscillation methods, usually at small strains. In contrast to this class of information, where the material is rarely strained to failure, one can also strain rubbers unidirectionally to failure at strain rates that correspond to the high frequencies of dynamic measurements. In linear extension experiments, as the rate of stretching increases tensile strength rises, elongation drops, apparent modulus increases, and relaxation losses may go up or down depending upon the particular rubber and the time scale of the phenomenon that is being investigated. Extrapolating the change in tensile strength with rate of testing suggests that tensile strength as we know it should change drastically when measured at very high rates of speed. That is, since the viscoelastic properties of rubber are time dependent, and also dependent upon the speed at which they are tested, the tensile properties of rubbers measured at room conditions with the ordinary Scott or Instron machines probably do not have the same values as at the speeds and frequencies that might be encountered in such situations as tire wear. Hence, we should like to measure the properties of rubbers at very high rates of speed, presumably comparable to those encountered in tire tread wear, in order to find out how much properties do change as the speed of test is increased. In order to measure stress-strain properties at rates of elongation comparable to those we believe exist in tire tread usage, we had to develop a small high speed tensile machine. The purpose of this paper is to describe that machine and some results obtained with it.

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