Linear Stability of a Plasma Diode

1969 ◽  
Vol 24 (8) ◽  
pp. 1235-1243 ◽  
Author(s):  
M Dobrowolny ◽  
F Engelmann ◽  
A Sestero
Keyword(s):  
Boundary Conditions ◽  
Linear Stability ◽  
Plane Waves ◽  
The Other ◽  
Other Hand ◽  
Free Particles ◽  
Plasma Diode ◽  
The Stability

AbstractThe stability of a plasma diode with respect to longitudinal oscillations is investigated. If there are free particles emitted by the electrodes, the perturbations do not have the same dynamics as they would in an infinite plasma, contrary to the case where only particles trapped in the diode are present. This can be interpreted as due to a coupling of plane waves of different wave lengths, introduced by the boundary conditions at the electrodes. The occurrence of resonant-particle effects, on the other hand, is subjected to precisely the same conditions as in an infinite plasma.

On Wake-Induced Flutter of a Circular Conductor in the Wake of Another

1980 ◽  
Vol 102 (2) ◽  
pp. 125-137 ◽  
Author(s):  
Y. T. Tsui ◽  
C. C. Tsui
Keyword(s):  
Transmission Line ◽  
Coupling Coefficient ◽  
Frequency Ratio ◽  
Horizontal Axis ◽  
The Other ◽  
Two Dimensional ◽  
Coupling Ratio ◽  
Aeroelastic Stability ◽  
Other Hand ◽  
The Stability

This paper, which is an extension of [1], treats two-dimensional aeroelastic stability of two coupled conductors. It is found that the wake-induced flutter is symmetric with respect to the horizontal axis of the wake for all cases provided that the sign of the static coupling coefficient, ε = kxy/kxx, is changed. It appears that the spacer coupling ratio, K/kxx = Ω/ωx, is the most important factor in determining stability. For practical purposes, the system is almost always stable for K/kxx = Ω/ωx = 0.8, because the frequency ratio, κ = ωy/ωx, deviates less than ten percent from unity for a typical transmission line. On the other hand, within our range of interest, damping has little or no effect on the stability of coupled conductors. When the windward conductor is fixed, i.e., K = 0, then damping does influence the stability of the leeward conductor.

Isoprene and Rubber. XVIII. Viscosity Studies on Balata

1930 ◽  
Vol 3 (3) ◽  
pp. 516-518 ◽  
Author(s):  
H. Staudinger ◽  
E. O. Leupold
Keyword(s):  
Colloidal Particles ◽  
Colloidal Particle ◽  
Colloidal Solution ◽  
Elementary Particles ◽  
The Other ◽  
Colloidal Solutions ◽  
Specific Viscosity ◽  
Micellar Structure ◽  
Other Hand ◽  
The Stability

Abstract Varied views prevail as to the structure of the colloidal particles present in a rubber solution. According to Harries, Pummerer, and many others, these colloidal particles are formed through the association or aggregation of smaller molecules. According to Meyer and Mark they have a micellar structure, the micelles forming through the apposition of main valence chains. On the other hand, it was assumed by one of the present authors that the elementary particles in a colloidal solution of rubber are identical with the rubber molecules, these large, especially labile molecules being called macromolecules. Thus the existence of much larger molecules than any hitherto known was postulated. This view was confirmed by the conversion of rubber to hydro-rubber capable of forming colloidal solutions, and also by the pyrogenic decomposition of rubber. In order to decide definitely between the two conceptions, the stability of the colloidal particle in a rubber solution was studied by means of viscosity measurements at various temperatures as was done in the case of the polystyrols. If these colloidal particles form aggregates or if they have a micellar structure, they should decrease in size with increase in temperature, and this change should be evidenced by a diminution of the specific viscosity of the colloidal solution. On the other hand, if such a solution is composed of molecules, the specific viscosity at various temperatures is the same, provided that the molecules are not decomposed at higher temperatures. This line of research led to an explanation of the constitution of the colloidal particles in a polystyrol solution and was now applied to balata, since the latter is especially easily purified.

scholarly journals STUDIES ON OXIDATION AND REDUCTION BY PNEUMOCOCCUS

1924 ◽  
Vol 39 (5) ◽  
pp. 745-755 ◽  
Author(s):  
Oswald T. Avery ◽  
James M. Neill
Keyword(s):  
Hydrogen Peroxide ◽  
Molecular Oxygen ◽  
Hemolytic Activity ◽  
Active Agent ◽  
Organic Peroxide ◽  
Cell Extract ◽  
The Other ◽  
Cell Extracts ◽  
Other Hand ◽  
The Stability

In the present work on oxidation and reduction by sterile extracts of pneumococcus, the preparations employed contain among other constituents, a hemolytic substance the properties of which have been described by Cole (1, 2) in his studies on pneumococcus hemotoxin. Pneumococcus extracts prepared by the methods described are actively hemolytic, 0.005 cc. of extract causing complete lysis of 2.5 cc. of a 1 per cent suspension of red cells from rabbit blood. This hemolytic property of pneumococcus extracts is destroyed by 10 minutes exposure to 55°C. When pneumotoxin-containing extracts are protected from the action of molecular oxygen, their hemolytic activity remains unimpaired for considerable periods of time. In the presence of air, on the other hand, the stability of the hemolytic substance depends upon whether the particular type of extract contains a "complete" or "incomplete" oxidation-reduction system. Sterile broth extracts of unwashed pneumococci are reactive with molecular oxygen, and as a result of this union peroxide is formed whenever these extracts are exposed to air. The hemolytic activity of "complete" extracts of this type is rapidly decreased and finally destroyed in the presence of molecular oxygen. On the other hand, the "incomplete" type of extract prepared by saline extraction of washed pneumococci may be exposed to air with little or no loss of hemolytic power. This "incomplete" washed cell extract, unless reactivated, does not undergo autoxidation in the presence of air; under these circumstances peroxide is not formed and the hemolytic activity of this type of extract is not impaired by exposure to air. The stability of the hemolytic agent in the "incomplete" type of extract is evidence that this substance is itself not reactive with or affected by molecular oxygen, even in the presence of the cell enzymes. The destruction of the same hemolytic substance in extracts capable of undergoing autoxidation may be ascribed to the action of some peroxide formed by the union of molecular oxygen with easily oxidized or autoxidizable substances of the extract. It is now known that a peroxide, having the reactions of hydrogen peroxide, accumulates in sterile pneumococcus extracts during oxidation. It has been shown in the present study that the addition of preformed hydrogen peroxide destroys the hemolytic activity of pneumococcus extracts, although higher concentrations were required than were detected in oxidized extracts themselves. These facts and the known action of superoxides in analogous types of reaction make it seem not unlikely that the active agent in the destruction of pneumotoxin in oxidized cell extracts may be a peroxide; either hydrogen peroxide or some higher organic peroxide formed during autoxidation of the extract.

PARADOXICAL KINEMATIC ACAUSALITY IN WEINBERG’S EQUATIONS FOR MASSLESS PARTICLES OF ARBITRARY SPIN

1992 ◽  
Vol 07 (22) ◽  
pp. 1967-1974 ◽  
Author(s):  
D.V. AHLUWALIA ◽  
D.J. ERNST
Keyword(s):  
Wave Equations ◽  
Classical Group ◽  
Arbitrary Spin ◽  
The Other ◽  
Finite Mass ◽  
Massless Particles ◽  
Paradoxical Situation ◽  
Other Hand ◽  
Free Particles

Weinberg’s equations for massless free particles of arbitrary spin are found to have acausal solutions. On the other hand, the m→0 limit of Joos-Weinberg’s finite-mass wave equations satisfied by (j, 0)⊕(0, j) j) covariant spinors are free from all kinematic acausality. This paradoxical situation is resolved and corrected by carefully studying the transition from the classical group theoretical arguments to quantum mechanically interpreted equations.

LINEAR STABILITY ANALYSIS GENERALIZED TO A THERMALLY-DRIVEN FLOW

1999 ◽  
Vol 09 (02) ◽  
pp. 415-425
Author(s):  
JEAN-MICHEL CORNET ◽  
CLAUDE-HENRI LAMARQUE
Keyword(s):  
Stability Analysis ◽  
Numerical Methods ◽  
Linear Stability ◽  
Linear Stability Analysis ◽  
The Other ◽  
Basic Solution ◽  
Driven Cavity ◽  
Convective Flows ◽  
Other Hand ◽  
Thermally Driven

We intend to establish a methodology suited to the search of the first bifurcations of convective flows using a linear stability analysis so that it permits us to define a relationship between amplitude and frequency of the perturbation. We use a particular combination of various numerical methods to compute on one hand the basic solution. On the other hand the perturbation is applied to the search for the bifurcations in a thermally-driven cavity.

scholarly journals Stability and Volumetric Properties of Colored Asphalt Mixtures Containing Iron Oxide

2021 ◽  
Vol 24 (2) ◽  
pp. 130-136
Author(s):  
Samer Ali Naji ◽  
Alaa H. Abed
Keyword(s):  
Iron Oxide ◽  
The Other ◽  
Volumetric Properties ◽  
Oxide Content ◽  
Test Results ◽  
Other Hand ◽  
Marshall Test ◽  
The Stability ◽  
Limestone Dust ◽  
Marshall Stability

The objective of this paper is find the effect of using iron oxide as a filler on the Marshall stability, flow and the volumetric properties of HMA and compared the results with conventional HMA using limestone dust. Three blends were used: coarse, mid and fine with neat bitumen (AC 40-50). One aggregate type (crushed) with two types of fillers: limestone and iron oxide III (α- ) with three different filler content 6%, 8% and 10%. The Marshall mix design was conducted on the three blends and the optimum binder content is computed for each blend. The Marshall stability test results and the volumetric properties analysis showed that increasing the iron oxide content from 6% to 10%  increases the stability about 28%, 17% , 16% for the coarse , mid and fine mixtures respectively. This increment in stability of mixtures using iron oxide related to the increment in specific gravity of the mix (Gmb) by (1.3% to 1.5% about 30 to 50 kg/m3). On the other hand, the flow of mixtures is decreased about (5%) for mixes using iron oxide than the ones that used limestone as filler. The fine blend with 10% iron oxide exhibit the highest stability of 13.3 kN. While the coarse blend stability was 10 kN for the same filler type and content. Generally, the Marshall Test results of HMA using iron oxide as filler showed better resistance to plastic deformation, also produce denser HMA with higher stiffness. On the other hand, the volumetric properties analysis showed lesser values as compared with conventional mixture where the void in mineral aggregates and void filled with asphalt has decreased but within the acceptable limits.

scholarly journals Triangular fully packed loop configurations of excess 2

2015 ◽  
Vol DMTCS Proceedings, 27th... (Proceedings) ◽  
Author(s):  
Sabine Beil
Keyword(s):  
Boundary Conditions ◽  
Young Diagram ◽  
Rotational Invariance ◽  
The Other ◽  
Necessary Condition ◽  
Grand Nombre ◽  
Other Hand ◽  
International Audience ◽  
Linear Expression ◽  
Link Pattern

International audience Triangular fully packed loop configurations (TFPLs) came up in the study of fully packed loop configurations on a square (FPLs) corresponding to link patterns with a large number of nested arches. To a TFPL is assigned a triple $(u,v;w)$ of $01$-words encoding its boundary conditions. A necessary condition for the boundary $(u,v;w)$ of a TFPL is $\lvert \lambda(u) \rvert +\lvert \lambda(v) \rvert \leq \lvert \lambda(w) \rvert$, where $\lambda(u)$ denotes the Young diagram associated with the $01$-word $u$. Wieland gyration, on the other hand, was invented to show the rotational invariance of the numbers $A_\pi$ of FPLs corresponding to a given link pattern $\pi$. Later, Wieland drift was defined as the natural adaption of Wieland gyration to TFPLs. The main contribution of this article is a linear expression for the number of TFPLs with boundary $(u,v;w)$ where $\lvert \lambda (w) \rvert - \lvert\lambda (u) \rvert - \lvert \lambda (v)\rvert \leq 2$ in terms of numbers of stable TFPLs that is TFPLs invariant under Wieland drift. These stable TFPLs have boundary $(u^{+},v^{+};w)$ for words $u^{+}$ and $v^{+}$ such that $\lambda (u) \subseteq \lambda (u^{+})$ and $\lambda (v) \subseteq \lambda (v^{+})$. Les configurations de boucles compactes triangulaires (”triangular fully packed loop configurations”, ou TFPLs) sont apparues dans l’étude des configurations de boucles compactes dans un carré (FPLs) correspondant à des motifs de liaison avec un grand nombre d’arcs imbriqués. À chaque TPFL on associe un triplet $(u,v;w)$ de mots sur {0,1}, qui encode ses conditions aux bords. Une condition nécessaire pour le bord $(u,v;w)$ d’un TFPL est $\lvert \lambda(u) \rvert +\lvert \lambda(v) \rvert \leq \lvert \lambda(w) \rvert$, où $\lambda(u)$ désigne le diagramme de Young associé au mot $u$. D’un autre côté, la giration de Wieland a été inventée pour montrer l’invariance par rotation des nombres $A_\pi$ de FPLs correspondant à un motif de liaison donné $\pi$. Plus tard, la déviation de Wieland a été définie pour adapter de manière naturelle la giration de Wieland aux TFPLs. La contribution principale de cet article est une expression linéaire pour le nombre de TFPLs de bord $(u,v;w)$, où $\lvert \lambda (w) \rvert - \lvert\lambda (u) \rvert - \lvert \lambda (v)\rvert \leq 2$, en fonction des nombres de TFPLs stables, <i>i.e</i>., les TFPLs invariants par déviation de Wieland. Ces TFPLs stables ont pour bord $(u^{+},v^{+};w)$, avec $u^{+}$ et $v^{+}$ des mots tels que $\lambda (u) \subseteq \lambda (u^{+})$ et $\lambda (v) \subseteq \lambda (v^{+})$.

scholarly journals Beggars, scammers, discriminated against by the whole of Europe: Romania’s Roma in Finnish tabloids, 2008-2011

2012 ◽  
Vol 4 (2) ◽  
pp. 87-109 ◽  
Author(s):  
Kari Alenius
Keyword(s):  
The Other ◽  
Significant Part ◽  
Radical Right ◽  
Recent Case ◽  
Short Term ◽  
Host Countries ◽  
Other Hand ◽  
The Stability ◽  
Critical Perspectives

The unrestricted movement of EU citizens from one country to another has been one of the fundamental principles of the Union. On the other hand, this issue has also attracted criticism, particularly from the radical right and so-called populist parties, or the supporters of these movements. Part of the population of Europe regards immigration and the unrestricted movement of people as a threat to the stability and prosperity of their own society. Through these critical perspectives, permanent immigration is viewed as a larger problem, as its effects on the host countries are more permanent than in the case of temporary residence. Through the same perspectives, the short-term but uncontrolled stay of foreigners is often linked to crime. This study concentrates on what kind of image a significant part of the Finnish media has given of a recent case of the foreigners that have attracted large attention in the country.

The Stability of Plane Poiseuille Flow in a Finite-Length Channel

2021 ◽  
Author(s):  
Lei Xu ◽  
Zvi Rusak
Keyword(s):  
Kinetic Energy ◽  
Boundary Conditions ◽  
Linear Stability ◽  
Finite Length ◽  
Poiseuille Flow ◽  
Weak Form ◽  
Plane Poiseuille Flow ◽  
Various Boundary Conditions ◽  
New Perspective ◽  
The Stability

Abstract The linear stability of plane Poiseuille flow through a finite-length channel is studied. A weakly-divergence-free basis finite element method with SUPG stabilization is used to formulate the weak form of the problem. The linear stability characteristics are studied under three possible inlet-outlet boundary conditions and the corresponding perturbation kinetic energy transfer mechanisms are investigated. Active transfer of perturbation kinetic energy at the channel inlet and outlet, energy production due to convection and dissipation at the flow bulk provide a new perspective in understanding the distinct stability characteristics of plane Poiseuille flow under various boundary conditions.

scholarly journals Theoretical Nonradial Pulsation of β Cephei Models

1980 ◽  
Vol 5 ◽  
pp. 461-462
Author(s):  
Hideyuki Sato
Keyword(s):  
Massive Stars ◽  
The Other ◽  
Excitation Mechanism ◽  
Ionization Zone ◽  
B Stars ◽  
Other Hand ◽  
The Stability ◽  
Nonradial Pulsation ◽  
Radial Pulsations

The excitation mechanism for the pulsations of β Cephei stars and variable B stars is not yet understood. Recently, Stellingwerf (1978) found that an opacity bump located near the He+ ionization zone has a significant effect on the stability of radial pulsations in massive stars. However, the opacity bump, according to current opacities, is probably not enough to excite radial pulsations. On the other hand, some observational facts suggest that nonradial pulsations may participate in the variations of β Cephei stars and variable B stars. Therefore, it is interesting and important to examine the effect of the opacity bump on nonradial pulsations in massive stars.

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