scholarly journals The formation of a double layer leading to the critical velocity phenomenon

1987 ◽  
Vol 5 (2) ◽  
pp. 197-210 ◽  
Author(s):  
A. C. Williams
Keyword(s):  
Kinetic Energy ◽  
Critical Velocity ◽  
Double Layer ◽  
Efficient Mechanism ◽  
Neutral Gas

The formation of a double layer is proposed as the mechanism which produces the critical velocity phenomenon. We examine this hypothesis, qualitatively, and find that the double layer can be a very efficient mechanism for transferring the kinetic energy of the neutral gas into the kinetic energy of electrons which, in turn, will ionize the neutral gas if the critical velocity has been reached or exceeded.

scholarly journals Discovery of the Carina Flare with NANTEN; Evidence for a Supershell That Triggered the Formation of Stars and Massive Molecular Clouds

1999 ◽  
Vol 51 (6) ◽  
pp. 751-764 ◽  
Author(s):  
Yasuo Fukui ◽  
Toshikazu Onishi ◽  
Rihei Abe ◽  
Akiko Kawamura ◽  
Kengo Tachihara ◽  
...  
Keyword(s):  
Kinetic Energy ◽  
Molecular Clouds ◽  
Galactic Plane ◽  
Far Infrared ◽  
Infrared Emission ◽  
High Mass ◽  
Stellar Winds ◽  
Neutral Gas ◽  
Supernova Explosions ◽  
Current Kinetic

Abstract We present extensive observations of the Carina arm region in the 2.6 mm CO (J = 1−0) emission with the NANTEN telescope in Chile. The observations have revealed 120 molecular clouds which are distributed in an area of 283° < l < 293° and 2° .5 < b < 10°. Because of its vertical elongation to the galactic plane, the clouds are named the Carina flare. H I and far-infrared emission show a cavity-like distribution corresponding to the molecular clouds, and soft X-ray emission appears to fill this cavity. It is shown that the Carina flare represents a supershell at a distance of a few kpc that has been produced by about 20 supernova explosions, or equivalent stellar winds of OB stars, over the last ∼ 2×107 yr. The supershell consisting of molecular and atomic neutral gas involves a total mass and kinetic energy of ≳ 3×105M⊙ and ≳ 3×1050 erg, respectively, and the originally injected energy required is about 100-times this current kinetic energy in the shell. It is unique among supershells known previously because of the following aspects: i) it exhibits evidence for the triggered formation of intermediate-to-high-mass stars and massive molecular clouds of 102 − 104M⊙, and ii) the massive molecular clouds formed are located unusually far above the galactic plane at z ∼ 100–500 pc.

The interaction of a moving neutral gas with a stationary magnetized plasma

1981 ◽  
Vol 25 (3) ◽  
pp. 491-497 ◽  
Author(s):  
J. F. McKenzie ◽  
R. K. Varma
Keyword(s):  
Inverse Problem ◽  
Critical Velocity ◽  
Terminal Velocity ◽  
Magnetized Plasma ◽  
Neutral Gas ◽  
Stationary Plasma

In this paper it is shown that a stationary plasma can be accelerated by a moving neutral gas only if the velocity of the neutral gas exceeds Alfvén's critical velocity. An expression for the terminal velocity of the interaction is given which shows that, in the limit of high incoming neutral gas speeds, the composite plasma is accelerated up to one quarter of the gas speed. We also discuss terminal velocities associated with the inverse problem, namely the deceleration of a magnetized plasma as a result of its motion through, and interaction with, a stationary neutral gas.

The negative electromagnetic attractive forces arising from kinetic energy of conduction electrons in double-layer metallic nanowire arrays

2012 ◽  
Vol 152 (13) ◽  
pp. 1186-1190
Author(s):  
Renlong Zhou ◽  
Xiaoshuang Chen ◽  
Bingju Zhou ◽  
Xiaojuan Liu ◽  
Hui Deng ◽  
...  
Keyword(s):  
Kinetic Energy ◽  
Double Layer ◽  
Nanowire Arrays ◽  
Conduction Electrons

Modification of W and Re Powders by Plasma Technique

2010 ◽  
Vol 165 ◽  
pp. 130-135 ◽  
Author(s):  
Tomasz Majewski
Keyword(s):  
Kinetic Energy ◽  
Internal Stresses ◽  
High Current ◽  
Plasma Technique ◽  
Neutral Gas ◽  
Plasma Spheroidization ◽  
Electric Contacts ◽  
Measurement Results ◽  
Powder Particles ◽  
Shape And Size

Selected measurement results of plasma spheroidization of tungsten and rhenium powders are presented in the paper. The powders can be applied for production of sinters intended for armor-piercing penetrating cores (kinetic energy penetrators) or high-current electric contacts. Spheroidization of these powders was carried out on the stand for plasma spraying in a chamber filled with neutral gas. Changes of shape and size of powder particles after spheroidization are demonstrated. Measurement results of internal stresses in powder particles are presented.

scholarly journals Sheaths and Double Layers with Instabilities

2021 ◽  
Vol 2 (1) ◽  
pp. 70-92
Author(s):  
Reiner L Stenzel ◽  
Johannes Grünwald ◽  
Codrina Ionita ◽  
Roman Schrittwieser ◽  
Manuel Urrutia
Keyword(s):  
Double Layer ◽  
Secondary Electron Emission ◽  
Low Frequency ◽  
Negative Electrode ◽  
Density Perturbation ◽  
Magnetized Plasma ◽  
Double Layers ◽  
Electrode Current ◽  
Neutral Gas ◽  
The Impact

The properties of sheaths and associated potential structures and instabilities cover a broad field which even a review cannot cover everything. Thus, the focus will be on about a dozen examples, describe their observations and focus on the basic physical explanations for the effects, while further details are found in the references. Due to familiarity the review focuses mainly on the authors work but compared and referenced related work. The topics start with a high frequency oscillations near the electron plasma frequency. Low frequency instabilities also occur at the ion plasma frequency.The injection of ions into an electron-rich sheath widens the sheath and forms a double layer. Likewise, the injection of electrons into an ion rich sheath widens and establishes a double layer which occurs in free plasma injection into vacuum. The sheath widens and forms a double layer by ionization in an electron rich sheath. When particle fluxes in "fireballs" gets out of balance the double layer performs relaxation instabilities which has been studied extensively. Fireballs inside spherical electrodes create a new instability due to the transit time of trapped electrons. On cylindrical and spherical electrodes the electron rich sheath rotates in magnetized plasmas. Electrons rotate due to $\mathbf E \times \mathbf B_0$ which excites electron drift waves with azimuthal eigenmodes. Conversely a permanent magnetic dipole has been used as a negative electrode. The impact of energetic ions produces secondary electron emission, forming a ring of plasma around the magnetic equator. Such "magnetrons" are subject to various instabilities. Finally, the current to a positively biased electrode in a uniformly magnetized plasma is unstable to relaxation oscillations, which shows an example of global effects. The sheath at the electrode raises the potential in the flux tube of the electrode thereby creating a radial sheath which moves unmagnetized ions radially. The ion motion creates a density perturbation which affects the electrode current. If the electrode draws large currents the current disruptions create large inductive voltages on the electrode, which again produce double layers. This phenomenon has been seen in reconnection currents. Many examples of sheath properties will be explained. Although the focus is on the physics some examples of applications will be suggested such as neutral gas heating and accelerating, sputtering of plasma magnetrons and rf oscillators.

Failure Behavior of Double-Layer-Domes Subjected to Impact

2020 ◽  
pp. 2150015
Author(s):  
E. Nazari ◽  
B. Shekastehband
Keyword(s):  
Kinetic Energy ◽  
Failure Mechanism ◽  
Double Layer ◽  
Shear Failure ◽  
Progressive Failure ◽  
Time History ◽  
Failure Behavior ◽  
Finite Element Software ◽  
Local Shear ◽  
The Impact

The dynamic failure behavior of double-layer-domes subjected to impact is studied numerically through the nonlinear finite element software LS-DYNA. The parameters considered in this work include the mass, velocity, and size of impactor, impact direction, roof weigh, geometric imperfection, rise-to-span ratio, and depth of dome. The dynamic time-history response and energy conversion of the structure are utilized to distinguish between the failure mechanism types. For the cases studied, it is found that failure of the structures falls into one of the three categories: (1) local shear failure, (2) partial progressive failure, and (3) full progressive failure. Non-failure case dominates the dome response when the kinetic energy of the impactor is small enough, and the structure can convert most of the kinetic energy into the strain energy, thereby absorbing the impact. Local shear failure occurs in a double-layer-dome when an impactor with very high kinetic energy strikes the dome. For an impactor striking with a mass of 5 to 300[Formula: see text]ton and a velocity of 50 to 120[Formula: see text]m/s, the double-layer-dome studied will suffer from partial progressive failure. Varying mass and velocity of the impactor in the range of 1 to 300[Formula: see text]ton and 200 to 400[Formula: see text]m/s, respectively, results in a tendency of the dome to exhibit local shear failure. Although impact direction does not cause a change in the failure mechanism type, there is a reduction in the severity of failure of the system as the impact angle increases. Roof weight has no dominant effect on the failure mechanism of the double-layer-dome. A small initial member imperfection with amplitude 0.001[Formula: see text] does not change the progressive failure type. A large member imperfection of 0.01[Formula: see text] triggers member buckling and leads to local shear failure of the dome. Except for some loading cases, the change in the rise to span ratio and depth of the dome does not seriously affect the failure mode.

Dependence of the joint configuration on the dynamic immobility fulcrum

2019 ◽  
pp. 108-114
Author(s):  
A. D. Kozlov ◽  
Yu. P. Potekhina
Keyword(s):  
Kinetic Energy ◽  
Convex Surface ◽  
The Other ◽  
Concave Surface ◽  
Joint Configuration ◽  
Articular Surfaces

Although joints with synovial cavities and articular surfaces are very variable, they all have one common peculiarity. In most cases, one of the articular surfaces is concave, whereas the other one is convex. During the formation of a joint, the epiphysis, which has less kinetic energy during the movements in the joint, forms a convex surface, whereas large kinetic energy forms the epiphysis with a concave surface. Basing on this concept, the analysis of the structure of the joints, allows to determine forces involved into their formation, and to identify the general patterns of the formation of the skeleton.

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