Results 211 to 220 of about 1,123,293 (252)

Modified String Flowmeter for Measuring Breath Velocity

Review of Scientific Instruments, 1949
An instrument is described which measures instantaneous breath velocities without incurring high flow resistances. It records reciprocating flows, such as those of the full breath cycle, within the limits of normal breath velocities with high frequency resolution and yields accurate and reproducible measurements when suitably calibrated.
H, SPECHT, H F, BRUBACH
openaire   +2 more sources

Analysis of critical whirling velocity of drill string

Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2021
During the drilling process, the whirling motion often occurs, which will cause the drill string to vibrate violently, accelerate the fatigue damage of the drill string, and eventually cause the bo...
Jialin Tian, Changyue Fan, Lai Wei, Yanzhi Wang   +3 more
openaire   +1 more source

Extending the velocity-dependent one-scale string evolution model [PDF]

Physical Review D, 2002
We provide a general overview of the velocity-dependent one-scale model for cosmic string evolution and discuss two further extensions to it. We introduce and justify a new ansatz for the momentum parameter $k$, and also incorporate the effect of radiation backreaction.
Carlos J.A.P. Martins, E P S Shellard
exaly   +3 more sources

Carrier drift velocity in semiconducting strings

Physica E: Low-dimensional Systems and Nanostructures, 2003
Abstract The carrier drift velocity in a 1D semiconducting sample attached to electrodes is derived from the Luttinger model, where the electric field generated by image charges within the electrodes is explicitly taken into account. If the length of the electrode is small enough compared to the sample length, the drift velocity vd can be estimated ...
S Kuwata, Y Koyama, K Fukeda
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Dynamics Stability of a Translating String With a Sinusoidally Varying Velocity

Volume 8: Dynamic Systems and Control, Parts A and B, 2010
A new parametric instability phenomenon characterized by infinitely compressed, shock-like waves with a bounded displacement and an unbounded vibratory energy is discovered in a translating string with a constant length and tension and a sinusoidally varying velocity. A novel method based on the wave solutions and the fixed point theory is developed to
W. D. Zhu, X. K. Song, N. A. Zheng
openaire   +1 more source

Plunger Lift Versus Velocity Strings

Journal of Energy Resources Technology, 1999
Plunger lift and velocity strings are two common methods of attacking liquid loading problems in gas wells. This paper shows how to compare the calculated performance of both methods at downhole producing conditions on one plot.
openaire   +1 more source

Coiled Tubing Velocity Strings - Expanding the Cases

SPE/ICoTA Coiled Tubing Roundtable, 1998
Abstract Coiled tubing is a preferred remedial method of extending the flowing life for gas wells. but selection of a size that will accomplish the task of removing bottomhole liquids is not simple. The difficult, in predicting results that guide coiled tubing selectivity is partly caused by the changing gas to ...
Alec Martinez, John Martinez
openaire   +1 more source

Method for determining drill string velocity

The Journal of the Acoustical Society of America, 1989
The invention is a method of determining the acoustic velocity of a drill string (28) in a borehole (10). An acoustic signal is generated at a first location(34) along the drill string, and detected at a second location (7). The detected signal is autocorrelated and the time of occurrence of multipath reflections on the autocorrelation record is ...
openaire   +1 more source

Completion Leak Repair with Corrosion Resistant CT Velocity String

SPE/ICoTA Well Intervention Conference and Exhibition, 2023
Abstract An operator company in Bolivia needed a solution to a corrosion and pressure integrity problem caused by the presence of CO2 gas in the production fluids, resulting in deep tubing corrosion over certain sections of completion components with measured penetrations up to 96% of tubing's wall thickness.
Erick Aguirre, Martin Nebiolo
openaire   +1 more source

Modeling Coiled-Tubing Velocity Strings for Gas Wells

SPE Production & Facilities, 1998
Summary Because of its ability to prolong well life, its relatively low expense, and the relative ease with which it is installed, coiled tubing has become a preferred remedial method of tubular completion for gas wells. Of course, the difficulty in procuring wireline-test data is a drawback to verifying the accuracy of the assumptions ...
John Martinez, Alec Martinez
openaire   +1 more source