scholarly journals Study of the weak to heavy-current transition in high-frequency discharge in nitrogen

2006 ◽  
Vol 19 (2) ◽  
pp. 209-217
Author(s):  
Iliycho Iliev ◽  
Snezhana Gocheva-Ilieva
Keyword(s):  
Experimental Data ◽  
Radio Frequency ◽  
Electric Power ◽  
Cross Section ◽  
High Frequency ◽  
Physical Processes ◽  
Current Discharge ◽  
One Dimensional ◽  
Current Transition ◽  
Plasma Technologies

Variety of electron, ion and plasma technologies as well as gas discharge devices operate in fixed form of the discharge. The transition from weak to heavy current in radio-frequency low-current discharge leads to instabilities in physical processes and it is very critical for the normal functionality of the technology or device. In this paper by means of Townsend criterion the influence of the incoming electric power and voltage on this transition in a cross-section of the discharge is numerically simulated. The calculations show a possible change of applied designed power up to 32% without weak to heavy-current transition. It is also obtained that the rise in 40% of the pressure can change the critical breakdown power only up to 12%. These results are in agreement with the simple analytical one-dimensional models and experimental data.

Effects on electrostatic fields excited by radio-frequency waves in a bounded plasma due to the ponderomotive force

1992 ◽  
Vol 47 (2) ◽  
pp. 271-279
Author(s):  
C. R. Gutiérrez-Tapia
Keyword(s):  
Radio Frequency ◽  
Driving Forces ◽  
Ponderomotive Force ◽  
Plasma Layer ◽  
Physical Processes ◽  
One Dimensional ◽  
Electrostatic Fields ◽  
Bounded Plasma ◽  
Linearly Polarized ◽  
Radio Frequency Waves

A one-dimensional model explaining the mechanism of excitation of electrostatic fields by linearly polarized radio-frequency waves in a plasma layer is presented. It is shown that the ponderomotive and driving forces influence this process strongly; however, these forces act at different times when a wave front passes through the plasma. We consider a semi-infinite plasma, and a plasma layer with and without current. It is observed that near to the plasma boundaries, where the electric field is large, there arise amplitude field oscillations, which are slowly exponentially damped in space. It is shown that the physical processes arising near the boundary x = L are similar to those at the boundary x = 0. It is seen that the current in the plasma block excitation at the boundary x = L.

Groundbreaking Contributions to Downburst Monitoring, Modeling, and Detection

2020 ◽  
Author(s):  
Massimiliano Burlando ◽  
Djordje Romanic
Keyword(s):  
Experimental Data ◽  
High Frequency ◽  
Research Field ◽  
Frequency Of Occurrence ◽  
Physical Processes ◽  
Quantitative Measurements ◽  
Physical Experiments ◽  
Structures And Properties ◽  
Modeling Techniques ◽  
Observing Systems

Severe winds produced by thunderstorm outflows cause damage to structures and properties worldwide. Due to their high frequency of occurrence, these winds can be considered one of the most high-risk phenomena in the plethora of the dangerous manifestations of the weather in the troposphere. Through the analysis of experimental data that initiated with visual observations and followed with quantitative measurements, the downburst phenomenon was first discovered and measured in the second half of the last century. Since then, the physical processes responsible for downburst formation have been identified thanks to the advances in observing systems, numerical modeling techniques, as well as smaller scale physical experiments carried out under well-controlled and confined conditions. The purpose of this chapter is to summarize what has been learned about kinematics, dynamics, and thermodynamics of downbursts and unveil the physics behind this phenomenon, running through the most relevant discoveries over the last half century in this research field.

scholarly journals Simulation of Electromagnetic-Acoustic Heating of the Oil Layer in Laboratory Conditions

2021 ◽  
Vol 16 (1) ◽  
pp. 109-116
Author(s):  
Gulnara R. Izmailova
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Mathematical Model ◽  
High Frequency ◽  
Additional Term ◽  
Oil Reservoir ◽  
Combined Effects ◽  
Physical Processes ◽  
The Mathematical Model ◽  
Account Heat

This paper describes an experiment to study the combined effects of high-frequency electromagnetic and acoustic fields on a model of an oil reservoir. A mathematical model is described that describes the physical processes that occur in the reservoir. The heat equation takes into account heat transfer with the environment by introducing an additional term. The largest discrepancy between theoretical and experimental data does not exceed 28%. Qualitative coincidence of theoretical and experimental curves indicates the adequacy of the mathematical model.

Analysis of Flow in a Two-Dimensional Collapsible Channel Using Universal “Tube” Law

1994 ◽  
Vol 116 (4) ◽  
pp. 469-476 ◽  
Author(s):  
Y. Matsuzaki ◽  
T. Ikeda ◽  
T. Kitagawa ◽  
S. Sakata
Keyword(s):  
Experimental Data ◽  
Pressure Drop ◽  
High Frequency ◽  
Small Amplitude ◽  
Simplified Model ◽  
High Frequency Oscillation ◽  
Two Dimensional ◽  
Frequency Oscillation ◽  
One Dimensional ◽  
Wide Range

This paper presents an extension of the previous analyses on the collapsible tubeflow problem using a simplified model based on a two-dimensional channel conveying a one-dimensional flow. The main objective of the paper is to exploit the static and dynamic behavior of the model, by comparing with available experimental data and examining the accuracy of calculated results obtained for different numerical resolutions. The main revision from the previous analyses is the incorporation of a universal “tube” law that is valid for a wide range of positive and negative transmural pressure. Most of the numerical results agree qualitatively with the experimental observations. Self-excited high-frequency oscillation with very small amplitude of the membrane wall is, however, predicted to occur in a flow range where the slope of the pressure drop curve is positive. It is seen that the high-frequency oscillation is associated with the motion of the separation point of the flow.

Control-Oriented High-Frequency Turbomachinery Modeling: Single-Stage Compression System One-Dimensional Model

1995 ◽  
Vol 117 (1) ◽  
pp. 47-61 ◽  
Author(s):  
O. O. Badmus ◽  
S. Chowdhury ◽  
K. M. Eveker ◽  
C. N. Nett
Keyword(s):  
Experimental Data ◽  
High Frequency ◽  
Closed Loop ◽  
Rotating Stall ◽  
Single Stage ◽  
Model Parameters ◽  
Compression System ◽  
One Dimensional ◽  
First Order ◽  
Direct Model

In this paper, a one-dimensional unsteady compressible viscous flow model of a generic compression system previously developed by the authors is applied to a multistage axial compressor experimental rig configured for single-stage operation. The required model parameters and maps are identified from experimental data. The resulting model is an explicit system of nine first-order ODEs. The model inputs are compressor speed, nozzle area, compressor discharge bleed area, plenum bleed area, inlet total pressure and entropy, and nozzle and bleed exit static pressures. The model and experimental data are compared with respect to both open-loop uncontrolled and closed-loop controlled behaviors. These comparisons focus on (i) forced transients and (ii) global nonlinear dynamics and bifurcations. In all cases the agreement between the model and experimental data is excellent. Of particular interest is the ability of the model, which does not include any hysteretic maps, to predict experimentally observed hysteresis with respect to the onset and cessation of surge. This predictive capability of the model manifests itself as the coexistence of a stable equilibrium (rotating stall) and a stable periodic solution (surge) in the model at a single fixed set of system input values. Also of interest is the fact that the controllers used for closed-loop comparisons were designed directly from the model with no a posteriori tuning of controller parameters. Thus, the excellent closed-loop comparisons between the model and experimental data provide strong evidence in support of the validity of the model for use in direct model based controller design. The excellent agreement between the model and experimental data summarized above is attributed in large part to the use of effective lengths within the model, as functions of axial Mach number and nondimensional compressor rotational speed, as prescribed by the modeling technique. The use of these effective lengths proved to be far superior to the use of physical lengths. The use of these effective lengths also provided substantial improvement over the use of physical lengths coupled with fixed first-order empirical lags, as proposed by other authors for the modeling of observed compressor dynamic lag. The overall success of this model is believed to represent a positive first step toward a complete experimental validation of the approach to control-oriented high-frequency turbomachinery modeling being developed by the authors.

High-frequency, "quantum" and electromechanical effects in quasi-one-dimensional charge density wave conductors

2013 ◽  
Vol 183 (1) ◽  
pp. 33-54 ◽  
Author(s):  
Vadim Ya. Pokrovskii ◽  
Sergey G. Zybtsev ◽  
Maksim V. Nikitin ◽  
Irina G. Gorlova ◽  
Venera F. Nasretdinova ◽  
...  
Keyword(s):  
Charge Density ◽  
High Frequency ◽  
Charge Density Wave ◽  
Density Wave ◽  
One Dimensional ◽  
Electromechanical Effects

Fusion and Breakup Reactions of 17S + 208Pb and 15C + 232ThHalo Nuclei Systems

2015 ◽  
Vol 11 (2) ◽  
pp. 2972-2978
Author(s):  
Fouad A. Majeed ◽  
Yousif A. Abdul-Hussien
Keyword(s):  
Experimental Data ◽  
Cross Section ◽  
Fusion Reaction ◽  
Fusion Cross Section ◽  
Reaction Cross ◽  
Recent Experimental Data ◽  
Barrier Distribution ◽  
Coupled Channel ◽  
Total Fusion ◽  
Full Quantum

In this study the calculations of the total fusion reaction cross section have been performed for fusion reaction systems 17F + 208Pb and 15C + 232Th which involving halo nuclei by using a semiclassical approach.The semiclassical treatment is comprising the WKB approximation to describe the relative motion between target and projectile nuclei, and Continuum Discretized Coupled Channel (CDCC) method to describe the intrinsic motion for both target and projectile nuclei. For the same of comparsion a full quantum mechanical clacualtions have been preforemd using the (CCFULL) code. Our theorticalrestuls are compared with the full quantum mechaincialcalcuations and with the recent experimental data for the total fusion reaction  checking the stability of the distancesThe coupled channel calculations of the total fusion cross section σfus, and the fusion barrier distribution Dfus. The comparsion with experiment proves that the semiclassiacl approach adopted in the present work reproduce the experimental data better that the full quantal mechanical calcautions. 

SETTING A DIAGRAM APPROACH TO CALCULATING VIBRATED, CENTRIFUGED AND VIBROCENTRIFUGED REINFORCED CONCRETE COLUMNS WITH A VARIATROPIC STRUCTURE

2020 ◽  
pp. 22-34
Author(s):  
Л. Р. Маилян ◽  
С. А. Стельмах ◽  
Е. М. Щербань ◽  
М. П. Нажуев
Keyword(s):  
Experimental Data ◽  
Reinforced Concrete ◽  
Bearing Capacity ◽  
Cross Section ◽  
Concrete Columns ◽  
Reinforced Concrete Columns ◽  
The Cross ◽  
Concrete Elements ◽  
Diagram Approach

Состояние проблемы. Железобетонные элементы изготавливаются, как правило, по трем основным технологиям - вибрированием, центрифугированием и виброцентрифугированием. Однако все основные расчетные зависимости для определения их несущей способности выведены, исходя из основного постулата - постоянства и равенства характеристик бетона по сечению, что реализуется лишь в вибрированных колоннах. Результаты. В рамках диаграммного подхода предложены итерационный, приближенный и упрощенный способы расчета несущей способности железобетонных вибрированных, центрифугированных и виброцентрифугированных колонн. Выводы. Расчет по диаграммному подходу показал существенно более подходящую сходимость с опытными данными, чем расчет по методике норм, а также дал лучшие результаты при использовании дифференциальных характеристик бетона, чем при использовании интегральных и, тем более, нормативных характеристик бетона. Statement of the problem. Reinforced concrete elements are typically manufactured according to three basic technologies - vibration, centrifugation and vibrocentrifugation. However, all the basic calculated dependencies for determining their bearing capacity were derived using the main postulate, i.e., the constancy and equality of the characteristics of concrete over the cross section, which is implemented only in vibrated columns. Results. Within the framework of the diagrammatic approach, iterative, approximate and simplified methods of calculating the bearing capacity of reinforced concrete vibrated, centrifuged and vibrocentrifuged columns are proposed. Conclusions. The calculation according to the diagrammatic approach showed a significantly better convergence with the experimental data than that using the method of norms, and also performs better when using differential characteristics of concrete than when employing integral and particularly standard characteristics of concrete.

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