A comparative study of the instabilities of two classes of nonlinear waves in cold plasmas

1986 ◽  
Vol 35 (3) ◽  
pp. 529-539 ◽  
Author(s):  
F. J. Romeiras ◽  
G. Rowlands
Keyword(s):  
Nonlinear Waves ◽  
Transverse Electric ◽  
Longitudinal Direction ◽  
Dispersion Relations ◽  
Cold Electron ◽  
Circularly Polarized ◽  
Electron Plasmas ◽  
Cold Plasmas ◽  
Set Up ◽  
The Stability

Results are presented of the stability analysis against small parallel perturbations of two classes of nonlinear waves in cold unmagnetized electron plasmas emphasizing similarities and differences. The first class is a stationary longitudinal wave set up by two counter-streaming cold electron beams; the second class is a mixed transverse-longitudinal standing wave in a relativistic plasma with a circularly polarized transverse electric field whose amplitude is periodically modulated in the longitudinal direction. The perturbation dispersion relations are discussed for all perturbation wavenumbers and all nonlinear wave amplitudes. Particular attention is given to the appearance of gaps in those dispersion relations.

Stability of strong electromagnetic waves in overdense plasmas

1982 ◽  
Vol 27 (2) ◽  
pp. 239-259 ◽  
Author(s):  
F. J. Romeiras
Keyword(s):  
Nonlinear Waves ◽  
Electromagnetic Waves ◽  
Longitudinal Direction ◽  
Electron Plasma ◽  
Cold Electron ◽  
Small Perturbations ◽  
Circularly Polarized ◽  
Instability Growth ◽  
Linear Differential ◽  
The Stability

We consider the stability against small perturbations of a class of exact wave solutions of the equations that describe an unmagnetized relativistic cold electron plasma. The main feature of these nonlinear waves is a transverse circularly polarized electric field with periodic amplitude modulation in the longitudinal direction. Floquet's theory of linear differential equations with periodic coefficients is used to solve the perturbation equations and obtain the instability growth rates.

Stability of strong electromagnetic waves in overdense plasmas against long-wavelength perturbations

1985 ◽  
Vol 33 (2) ◽  
pp. 285-301 ◽  
Author(s):  
F. J. Romeiras ◽  
G. Rowlands
Keyword(s):  
Dispersion Relation ◽  
Nonlinear Waves ◽  
Electromagnetic Waves ◽  
Modulation Depth ◽  
Longitudinal Direction ◽  
Transverse Component ◽  
Ion Density ◽  
Long Wavelength ◽  
The Stability ◽  
Two Parameters

We consider the stability against long-wavelength small parallel perturbations of a class of exact standing wave solutions of the equations that describe an unmagnetized relativistic overdense cold electron plasma. The main feature of these nonlinear waves is a circularly polarized transverse component of the electric field periodically modulated in the longitudinal direction. Using an analytical method developed by Rowlands we obtain a dispersion relation valid for long-wavelength perturbations. This dispersion relation is a biquadratic equation in the phase velocity of the perturbations whose coefficients are very complicated functions of the two parameters used to define the nonlinear waves: the normalized ion density and a quantity related to the modulation depth. This dispersion relation is discussed for the whole range of the two parameters revealing, in particular, the existence of a region in parameter space where the nonlinear waves are stable.

scholarly journals Galloping Stability and Wind Tunnel Test of Iced Quad Bundled Conductors considering Wake Effect

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Xiaohui Liu ◽  
Ming Zou ◽  
Chuan Wu ◽  
Mengqi Cai ◽  
Guangyun Min ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Transmission Lines ◽  
Degrees Of Freedom ◽  
Wind Tunnel Test ◽  
Aerodynamic Coefficients ◽  
Wake Effect ◽  
Aerodynamic Coefficient ◽  
Set Up ◽  
The Stability ◽  
Three Degrees Of Freedom

A new quad bundle conductor galloping model considering wake effect is proposed to solve the problem of different aerodynamic coefficients of each subconductor of iced quad bundle conductor. Based on the quasistatic theory, a new 3-DOF (three degrees of freedom) galloping model of iced quad bundle conductors is established, which can accurately reflect the energy transfer and galloping of quad bundle conductor in three directions. After a series of formula derivations, the conductor stability judgment formula is obtained. In the wind tunnel test, according to the actual engineering situation, different variables are set up to accurately simulate the galloping of iced quad bundle conductor under the wind, and the aerodynamic coefficient is obtained. Finally, according to the stability judgment formula of this paper, calculate the critical wind speed of conductor galloping through programming. The dates of wind tunnel test and calculation in this paper can be used in the antigalloping design of transmission lines.

Dissipative instability of the MHD tangential discontinuity in magnetized plasmas with anisotropic viscosity and thermal conductivity

1996 ◽  
Vol 56 (2) ◽  
pp. 285-306 ◽  
Author(s):  
M. S. Ruderman ◽  
E. Verwichte ◽  
R. Erdélyi ◽  
M. Goossens
Keyword(s):  
Thermal Conductivity ◽  
Dispersion Equation ◽  
Viscosity Coefficient ◽  
Tangential Discontinuity ◽  
Stability Criteria ◽  
Threshold Velocity ◽  
Cold Plasmas ◽  
The Difference ◽  
The Stability ◽  
Anisotropic Viscosity

The stability of the MHD tangential discontinuity is studied in compressible plasmas in the presence of anisotropic viscosity and thermal conductivity. The general dispersion equation is derived, and solutions to this dispersion equation and stability criteria are obtained for the limiting cases of incompressible and cold plasmas. In these two limiting cases the effect of thermal conductivity vanishes, and the solutions are only influenced by viscosity. The stability criteria for viscous plasmas are compared with those for ideal plasmas, where stability is determined by the Kelvin—Helmholtz velocity VKH as a threshold for the difference in the equilibrium velocities. Viscosity turns out to have a destabilizing influence when the viscosity coefficient takes different values at the two sides of the discontinuity. Viscosity lowers the threshold velocity V below the ideal Kelvin—Helmholtz velocity VKH, so that there is a range of velocities between V and VKH where the overstability is of a dissipative nature.

The Mitigation of the French Nuclear Option: New Industrial Realism and Technical Democracy

2002 ◽  
Vol 13 (2) ◽  
pp. 263-279 ◽  
Author(s):  
Dominique Finon
Keyword(s):  
Waste Management ◽  
Electricity Markets ◽  
Social Preferences ◽  
Public Inquiry ◽  
The Future ◽  
Parliamentary Committee ◽  
Set Up ◽  
The Stability ◽  
The Cost ◽  
Phase Out

Nuclear phase-out policies and the European obligation to liberalise electricity markets could put the French nuclear option dramatically at risk by influencing social preferences or by constraining power producers' investment choices in the future. So far, the particular institutional set-up which has allowed the efficient build-up and operation of several series of standardised reactors preserves the stability of the main elements of the option. However, important adaptations to the evolving industrial and political environment occur and contribute to changing the option. Some institutional changes (such as local public inquiry, creation of a Parliamentary committee, independence of safety authorities) and divergence between industrial interests already allow debates on internal options such as reprocessing, type of waste management deposits, ordering of an advanced PWR. These changes improve the cost transparency, even if internalisation of nuclear externalities (cost of insurance, provisions for waste management) is still incomplete. However, when effective, this internalisation would not affect definitively the competitive position of the nuclear production because of the parallel internalisation of CO2 externalities from fossil fuel power generation in the official rationale. Consequently the real issue for the future of the nuclear option in France remains the preservation of social acceptability in the perception of nuclear risks.

scholarly journals A Study of the Stability of a Plate-Like Load Towed beneath a Helicopter

1971 ◽  
Vol 13 (5) ◽  
pp. 330-343 ◽  
Author(s):  
D. F. Sheldon
Keyword(s):  
Equations Of Motion ◽  
Physical Parameters ◽  
Recent Experience ◽  
Wind Tunnel Testing ◽  
Stability Derivatives ◽  
Direct Indication ◽  
Metric Dimensions ◽  
Set Up ◽  
The Stability ◽  
Derivative Information

Recent experience has shown that a plate-like load suspended beneath a helicopter moving in horizontal forward flight has unstable characteristics at both low and high forward speeds. These findings have prompted a theoretical analysis to determine the longitudinal and lateral dynamic stability of a suspended pallet. Only the longitudinal stability is considered here. Although it is strictly a non-linear problem, the usual assumptions have been made to obtain linearized equations of motion. The aerodynamic derivative data required for these equations have been obtained, where possible, for the appropriate ranges of Reynolds and Strouhal number by means of static and dynamic wind tunnel testing. The resulting stability equations (with full aerodynamic derivative information) have been set up and solved, on a digital computer, to give direct indication of a stable or unstable system for a combination of physical parameters. These results have indicated a longitudinal unstable mode for all practical forward speeds. Simultaneously the important stability derivatives were found for this instability and modifications were made subsequently in the suspension system to eliminate the instabilities in the longitudinal sense. Throughout this paper, all metric dimensions are given approximately.

Nonlinear TE surface waves in a ferrite slab bounded by Kerr-type metamaterials

2017 ◽  
Vol 26 (03) ◽  
pp. 1750028 ◽  
Author(s):  
Burhan Zamir ◽  
Rashid Ali
Keyword(s):  
Boundary Conditions ◽  
Surface Waves ◽  
Transverse Electric ◽  
Dispersion Relations ◽  
Double Negative ◽  
Propagation Characteristics ◽  
Special Cases ◽  
Tangential Field ◽  
Effective Wave ◽  
Ferrite Slab

In this paper, nonlinear transverse electric surface waves in a structure consisting of a ferrite slab sandwiched between a Kerr-type double-negative metamaterial (DNG-MTM) have been investigated. In addition to a DNG-MTM, two special cases with nonlinear single-negative metamaterials (SNG-MTMs) have also been discussed. The dispersion relations are obtained by applying the boundary conditions to the tangential field components of each layer. The propagation characteristics are plotted numerically for the effective wave index versus propagation frequency.

scholarly journals Enhancement the stability of power system using optimal location of FACTS devices

2020 ◽  
Vol 18 (2) ◽  
pp. 648
Author(s):  
Ali Najim Abdullah ◽  
Ahmed Majeed Ghadhban ◽  
Hayder Salim Hameed ◽  
Husham Idan Hussein
Keyword(s):  
Power Network ◽  
Performance Factors ◽  
Facts Devices ◽  
Clearing Time ◽  
Thyristor Controlled Series Capacitor ◽  
Overall Performance ◽  
Set Up ◽  
The Stability ◽  
And Control ◽  
Better Than

<p><span>This paper proposes a steady-state of the Static Var Compensator (SVC) &amp; Thyristor Controlled Series Capacitor (TCSC) set up for enhancing the damping overall performance and growing the integral clearing time (CCT) of a power network. The indispensable clearing time is carried out through increasing the time fault interval until the gadget loses stability. Increasing the CCT can be contribute to reliability of the safety gadget, decrease the protection machine ranking and cost. In order to attain most enhancement of machine stability via optimizing location, sizing and control modes of SVC and TCSC. Models and methodology for putting and designing shunt FACT’s units SVC (injected reactive strength Q) and series FACT’s devices TCSC (chose capacitive region) are examined in a 6-bus system. Performance factors are described to show validation of SVC and TCSC on extraordinary conditions. It is proven that the SVC is better than TCSC. </span></p>

scholarly journals THE QUESTION OF BOOM LIFTING EQUIPMENT OPERATION STABILITY ON A WHEELED CHASSIS

2021 ◽  
pp. 100-108
Author(s):  
В.И. Токарев ◽  
Н.В. Бабоченко
Keyword(s):  
Longitudinal Direction ◽  
Equipment Operation ◽  
Mathematical Expressions ◽  
Maximum Stability ◽  
Operation Stability ◽  
Quality Of Movement ◽  
The Stability ◽  
The Masses ◽  
Constituent Elements ◽  
Lifting Equipment

В статье представлены на рассмотрение характеристики стабильности работы стреловых грузоподъемных средств на колесном шасси в форме математических выражений. Математические выражения представлены в виде не громоздких зависимостей от конкретно заданных параметров. Качество движения зависит от возрастания линейных размеров, масс, моментов инерции, а также скоростей и других механических параметров грузоподъемных средств. Достижение стабильности работы выносных стреловых грузоподъемных средств достигается путем распределения нагрузки между утлегарью (выносной стрелой грузоподъемного средства) и опорными колесами колесного шасси. Считаем, что при существовании ряда концепцией со своими теориями. возможно определение стабильности работы стрелового грузоподъемного средства на колесном шасси. Нами установлено, что возможно обеспечить стабильность работы путем выбора целесообразных значений механических составляющих всех звеньев рабочего механизма для спланировано составленных рабочих ситуаций. В зависимости от возможного размещения грузоподъемного устройства показатели стабильности работы меняются и это подтверждают составленные нами математические выражения, которые приводятся в статье. Установлено, что путем варьирования различными вариантами положений и массой составляющих элементов конструкции грузоподъемного средства, а также графически определяя возможные варианты перемещения груза в зависимости от заданной длины утлегарьи, имеет место выражение, позволяющее определить ряд значений масс, безопасно поднимаемых грузоподъемным средством. Нами получены значения необходимых для графических построений грузовых характеристик грузоподъемного средства, выражающие зависимость между массой груза и вылетом утлегарьи с весом ее элементов. Реакции в шарнирах утлегарьи и усилия в ее составляющих звеньях возможно установить из данных грузовой характеристики. Стремление обеспечить максимальную стабильность работы грузоподъемного средства накладывает ограничения на контроль за несколькими подвижными операциями одновременно, что неблагоприятно сказывается на эффективности рабочего процесса. Установили, что обеспечение стабильности работы в поперечной и продольной плоскостях грузоподъемного средства является необходимым компонентом безопасной эксплуатации. По зависимостям для определения показателя грузового равновесия возможно определение предварительного места установки выносных опор грузоподъемного средства. Как подтверждают полученные результаты, стабильность работы грузоподъемного средства в продольном направлении определяется аналогично стабильности работы в поперечном направлении и для номинальной массы груза при наибольшем вылете утлегарьи и выставленных выносных опорах. В итоге отметим, что показателем грузового равновесия служит отношение удерживающего момента относительно ребра опрокидывания, создаваемого весом грузоподъемного средства на колесном шасси с учетом уменьшающих его дополнительных внешних нагрузок и влияния уклона площадки к опрокидывающему моменту, создаваемому рабочим грузом. The article presents for consideration the characteristics of the stability of the boom lifting equipment on a wheeled chassis in the form of mathematical expressions. Mathematical expressions are presented in the form of not cumbersome dependencies on specified parameters. The quality of movement depends on the increase in linear dimensions, masses, moments of inertia, as well as speeds, and other mechanical parameters of the lifting equipment. Achievement of the stability of the outboard boom lifting device is achieved by distributing the load between the jib boom (outboard boom of the lifting device) and the support wheels of the wheeled chassis. We believe that with the existence of a number of concepts with their theories, it is possible to determine the stability of the boom lifting device on a wheeled chassis. It has been found that it is possible to ensure the stability of work by choosing the appropriate values of the mechanical components of all links of the working mechanism for planned working situations. Depending on the possible placement of the lifting device, the stability indicators are changed, and this is confirmed by the mathematical expressions we compiled, which are given in the article. It has been established that by varying the positions and the mass of the constituent elements of the structure of the lifting device, as well as graphically defining the possible options of the load moving, depending on the given length of the jib boom, an expression takes place that makes it possible to determine a number of values of the masses safely lifted by the lifting device. There have been obtained the values of the cargo characteristics of the lifting device necessary for graphic constructions, expressing the relationship between the weight of the cargo and the overhanging of the jib boom with the weight of its elements. The reactions in the joints of the jig boom and the forces in its constituent links can be established from the data of the load characteristics. The desire to ensure maximum stability in the operation of the lifting device imposes restrictions on the control of several mobile operations at the same time, which adversely affects the efficiency of the work process. It has been established that ensuring the stability of operation in the transverse and longitudinal planes of the lifting device is a necessary component of safe operation. According to the dependencies for determining the indicator of cargo balance, it is possible to determine the preliminary installation site of the outriggers of the lifting device. As the results obtained confirm, the stability of the operation of the lifting device in the longitudinal direction is determined similarly to the stability of the operation in the transverse direction and for the nominal weight of the load with the greatest overhanging of the jib boom and the set outriggers. As a result, we note that the ratio of the holding moment relative to the overturning rib created by the weight of the lifting device on the wheeled chassis, taking into account the additional external loads that reduce it and the influence of the platform slope to the overturning moment created by the working load, serves as an indicator of the cargo balance.

New fixed point of on-orbit calibration scale based on the In-Bi eutectic alloy for application in novel high-stable space-borne standard sources

2021 ◽  
pp. 32-37
Author(s):  
Andrei A. Burdakin ◽  
Valerii R. Gavrilov ◽  
Ekaterina A. Us ◽  
Vitalii S. Bormashov
Keyword(s):  
Phase Transition ◽  
Fixed Point ◽  
Fixed Points ◽  
Eutectic Alloy ◽  
Earth Observation ◽  
Melt Temperature ◽  
Phase Transition Temperatures ◽  
Set Up ◽  
The Stability ◽  
Observation Space

The problem of ensuring stability of Earth observation space-borne instruments undertaking long-term temperature measurements within thermal IR spectral range is described. For in-flight reliable control of the space-borne IR instruments characteristics the stability of onboard reference sources should be improved. The function of these high-stable sources will be executed by novel onboard blackbodies, incorporating the melt↔freeze phase transition phenomenon, currently being developed. As a part of these works the task of realizing an on-orbit calibration scale within the dynamic temperature range of Earth observation systems 210−350 K based on fixed-point phase transition temperatures of a number of potentially suitable substances is advanced. The corresponding series of the onboard reference blackbodies will be set up on the basis of the on-orbit calibration scale fixed points. It is shown that the achievement of the target lies in carrying out a number of in-flight experiments with the selected fixed points and the prospective onboard fixed-point blackbodies prototypes. The new In-Bi eutectic alloy melt temperature fixed point (~345 K) is proposed as the significant fixed points of the future on-orbit calibration scale. The results of the new fixed point preliminary laboratory studies have been analyzed. The results allowed to start preparation of the in-flight experiments investigating the In-Bi alloy for the purpose of its application in the novel onboard reference sources.

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