Development of Turbulence by the Interaction of Gas Flow with Plasmas

1973 ◽  
Vol 28 (8) ◽  
pp. 1281-1289 ◽  
Author(s):  
Lutz Niemeyer ◽  
Klaus Ragaller
Keyword(s):  
Gas Flow ◽  
Light Emission ◽  
Supersonic Nozzle ◽  
Physical Nature ◽  
Point Of View ◽  
Theoretical Point ◽  
High Current ◽  
Axial Pressure ◽  
Plasma Properties ◽  
Axial Pressure Gradient

A high current electric arc in the axis of a supersonic nozzle flow is studied experimentally and theoretically in order to clarify the physical nature of light emission fluctuations which are observed inside the nozzle. The gas flow is produced by discharging a high pressure reservoir of 20 at N2 through a nozzle of 12 mm throat diameter. The arc is fed with a rectangular current pulse of 1.9 kA amplitude and 5 ms duration. The light emission fluctuations of the arc are observed by photographic and photoelectric methods. The results of the observations are compared to theoretical estimates and lead to the conclusion that the fluctuations are caused by hydrodynamic turbulence. This turbulence is shown to be generated by the combined occurrence of a strong axial pressure gradient and a strong radial density gradient in the boundary layer between the arc and the surrounding cold gas flow. The influence of specific plasma properties on the character of the turbulence is briefly discussed from a theoretical point of view.

scholarly journals Area-Weighting of Sunspot Group Positions and Proper Motion Artifacts

1993 ◽  
Vol 141 ◽  
pp. 123-126
Author(s):  
K. Petrovay
Keyword(s):  
Proper Motion ◽  
Sunspot Group ◽  
Physical Nature ◽  
Decay Rates ◽  
Motion Artifacts ◽  
Point Of View ◽  
Theoretical Point ◽  
Analysis Process ◽  
The Mean ◽  
Sunspot Groups

AbstractTwo simple examples are presented to show that concepts about the physical nature of sunspot groups may significantly influence the statistical data analysis process. In particular, the second example shows that the well-known difference in the decay rates of preceding (p-) and following (f-) polarity parts of sunspot groups may lead to a fake proper motion effect when area-weighted group positions are used. This effect may be responsible for some recent contradictory findings concerning the motions of sunspot groups. It is therefore argued that while area-weighting is adequate when calculating the mean positions of p- and f-parts of a sunspot group separately, defining the position of the group as a whole by the unweighted average of the mean positions of the p- and f-parts is more satisfactory from the theoretical point of view (whenever it is possible to distinguish between spots of different polarities). Similarly, it is best not to “correct” sunspot proper motions for internal differential rotation within groups.

scholarly journals General considerations on the theory of the separation of H 1 and H 2 by electrolysis of water

1934 ◽  
Vol 144 (852) ◽  
pp. 452-466 ◽  
Keyword(s):  
A Priori ◽  
Point Of View ◽  
Theoretical Point ◽  
High Current ◽  
Hydrogen Electrode ◽  
Effective Separation ◽  
A Value ◽  
Rates Of Evolution ◽  
Wide Range ◽  
Current Densities

1. The Facts .―In a solution of NaOH (or KOH) with nickel (perhaps with other) electrodes and at high current densities of the order of 1 ampere per cm. 2 of electrode the observed rates of evolution E 1 and E 2 of H 1 and H 2 at the cathode obey an equation of the type E 1 /E 2 = q D 1 /D 2 , (1) where D 1 and D 2 are the relative concentraction of the H 1 and H 2 atoms in the water as a whole. The coefficient q has been shown to be independent of D 1 /D 2 over a very wide range of relative concentrations. Under the conditions most favourable to separation, which appear to be those just specified, q can have a value as great as 6, or perhaps 7. With other metals than nickel for the electrodes and with lower current densities the factor q may fall to a value well below 2 or even to a value so nearly unity that no effective separation occurs. The dependence of q (if any) on the temperature of the solution is not known. 1.1. The Arguments .―The facts have already been commented on by Polanyi from the theoretical point of view. He has been led to conclude from them that the separation is to be attributed to a difference of " over potential" for the deposition of H 1 and H 2 ions on the cathode, and consequently that Gurney's theory of the over-potential of the hydrogen-electrode at low current densities (as measured, for example, by Bowden) must be discarded. These conclusions if correct and unavoidable are of the greatest importance. It is most general way possible, in order to see that no types of mechanism have been overlooked which could lead to the observed results. When this is done it is found that the mechanism discussed by Polanyi which refers the separation to differences of over-potential is not the only mechanism which must be held possible a priori . The observed separation could perfectly well occur by a mechanism consistent with Gurney's theory. It does not yet appear to be possible to decide confidently between the two possibilities on experimental grounds.

Timber Auctions in the Context of the Modern Auction Theory

2007 ◽  
pp. 86-94
Author(s):  
A. Manakov
Keyword(s):  
Theoretical Analysis ◽  
Auction Theory ◽  
Point Of View ◽  
Theoretical Point ◽  
English Auction ◽  
Analysis And Evaluation

The article provides theoretical analysis and evaluation of the timber auctions reforms in Russia. The author shows that the mechanism of the "combined auctions", which functioned until recently, is more appropriate from the theoretical point of view (and from the point of view of the Russian practice) as compared to the officially approved format of the English auction.

A novel cryptosystem based on abstract automata and Latin cubes

2015 ◽  
Vol 52 (2) ◽  
pp. 221-232
Author(s):  
Pál Dömösi ◽  
Géza Horváth
Keyword(s):  
Block Cipher ◽  
Finite Automata ◽  
Theoretical Background ◽  
Point Of View ◽  
Theoretical Point ◽  
Transition Matrices ◽  
Encryption And Decryption ◽  
Secret Keys ◽  
Automata Network ◽  
Fully Functioning

In this paper we introduce a novel block cipher based on the composition of abstract finite automata and Latin cubes. For information encryption and decryption the apparatus uses the same secret keys, which consist of key-automata based on composition of abstract finite automata such that the transition matrices of the component automata form Latin cubes. The aim of the paper is to show the essence of our algorithms not only for specialists working in compositions of abstract automata but also for all researchers interested in cryptosystems. Therefore, automata theoretical background of our results is not emphasized. The introduced cryptosystem is important also from a theoretical point of view, because it is the first fully functioning block cipher based on automata network.

Graffiti als Version und Subversion–Praxen kultureller Re-Regulierung und die Möglichkeit von Gratiforschung

2010 ◽  
Vol 55 (2) ◽  
pp. 11-25 ◽  
Author(s):  
Bernd Dollinger
Keyword(s):  
Social Life ◽  
Point Of View ◽  
Theoretical Point ◽  
Research Practice ◽  
Wird Eine ◽  
Multiple Perspectives

Der Beitrag geht von Versuchen aus, integrative Perspektiven einer überaus heterogenen Graffitiforschung zu bestimmen. In Auseinandersetzung insbesondere mit Bruno Latours Ansatz des »Iconoclash« wird eine kulturtheoretische Referenz bestimmt, die Graffiti als Version identifiziert, d. h. als semiotisch orientierte Veränderung räumlich situierter Ordnungs- und Regulierungspraxen. Ihnen kann, wenn auch nicht zwingend, eine subversive Qualität zukommen. Durch die Ausrichtung am Konzept einer Version wird beansprucht, Forderungen einer normativ weitgehend abstinenten, nicht-essentialistischen und für komplexe Fragen der Identitäts- und Raumpolitik offenen Forschungspraxis einzulösen.<br><br>The contribution attempts to integrate multiple perspectives of current largely heterogeneous graffiti scholarship. Referring to Bruno Latour’s concept »iconoclash«, we discuss graffiti from a cultural-theoretical point of view as a »version«. It appears as a semiotically oriented modification of spatially situated practices that regulate social life. Often, but not necessarily, these practices involve subversive qualities. The concept of »version« facilitates a non-normative and non-essentialist strategy of research. This enables an explorative research practice in which the complex matters of identity and space politics that are associated with graffiti can be addressed.

scholarly journals How Digital Inclusion Increase Opportunities for Young People: Case of NEETs from Bulgaria, Romania and Turkey

2021 ◽  
Vol 13 (14) ◽  
pp. 7894
Author(s):  
Gabriela Neagu ◽  
Muhammet Berigel ◽  
Vladislava Lendzhova
Keyword(s):  
Data Analysis ◽  
Rural Areas ◽  
Secondary Data ◽  
Point Of View ◽  
Multidimensional Analysis ◽  
Theoretical Point ◽  
Digital Inclusion ◽  
Virtual Mobility ◽  
Alternative Research ◽  
High Share

This paper examines the perspectives of rural NEETs in the information society. Our analysis focuses on the situation of three European countries—Bulgaria, Romania, and Turkey—characterized by a high share of rural areas and a population of NEETs. From a methodological point of view, we use alternative research methods (secondary data analysis) with statistical methods (simple linear regression). From a theoretical point of view, we will opt for a multidimensional analysis perspective: the theory of digital divide, digital inclusion, virtual mobility, etc. Through data analysis, we expect to obtain a more complete and detailed picture of the ICT situation in rural areas (level of digital skills, level of digital inclusion) to demonstrate the importance of ICT in optimizing virtual mobility for the living conditions of the population, especially the NEET population.

scholarly journals Verbena officinalis Verbenaceae (Lamiales): a new plant model system for phyllotaxis research

2021 ◽  
Author(s):  
Beata Zagórska-Marek ◽  
Magdalena Turzańska ◽  
Klaudia Chmiel
Keyword(s):  
Vascular System ◽  
Cumulative Effect ◽  
Point Of View ◽  
Theoretical Point ◽  
Inflorescence Axis ◽  
Organ Identity ◽  
Lateral Organ ◽  
Complex Relationships ◽  
Secondary Transitions

AbstractPhyllotactic diversity and developmental transitions between phyllotactic patterns are not fully understood. The plants studied so far, such as Magnolia, Torreya or Abies, are not suitable for experimental work, and the most popular model plant, Arabidopsis thaliana, does not show sufficient phyllotactic variability. It has been found that in common verbena (Verbena officinalis L.), a perennial, cosmopolitan plant, phyllotaxis differs not only between growth phases in primary transitions but also along the indeterminate inflorescence axis in a series of multiple secondary transitions. The latter are no longer associated with the change in lateral organ identity, and the sequence of phyllotactic patterns is puzzling from a theoretical point of view. Data from the experiments in silico, confronted with empirical observations, suggest that secondary transitions might be triggered by the cumulative effect of fluctuations in the continuously decreasing bract primordia size. The most important finding is that the changes in the primary vascular system, associated with phyllotactic transitions, precede those taking place at the apical meristem. This raises the question of the role of the vascular system in determining primordia initiation sites, and possibly challenges the autonomy of the apex. The results of this study highlight the complex relationships between various systems that have to coordinate their growth and differentiation in the developing plant shoot. Common verbena emerges from this research as a plant that may become a new model suitable for further studies on the causes of phyllotactic transitions.

scholarly journals Modeling and theoretical description of magnetic hybrid materials—bridging from meso- to macro-scales

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Andreas M. Menzel ◽  
Hartmut Löwen
Keyword(s):  
Colloidal Particles ◽  
Colloidal Particle ◽  
Theoretical Description ◽  
Point Of View ◽  
Material Behavior ◽  
Theoretical Point ◽  
Mechanical Stiffness ◽  
Theoretical Approaches ◽  
Theoretical Predictions ◽  
Particle Level

Abstract Magnetic gels and elastomers consist of magnetic or magnetizable colloidal particles embedded in an elastic polymeric matrix. Outstanding properties of these materials comprise reversible changes in their mechanical stiffness or magnetostrictive distortions under the influence of external magnetic fields. To understand such types of overall material behavior from a theoretical point of view, it is essential to characterize the substances starting from the discrete colloidal particle level. It turns out that the macroscopic material response depends sensitively on the mesoscopic particle arrangement. We have utilized and developed several theoretical approaches to this end, allowing us both to reproduce experimental observations and to make theoretical predictions. Our hope is that both these paths help to further stimulate the interest in these fascinating materials.

Long-pulse plasma source for SMOLA helical mirror

2021 ◽  
Vol 87 (2) ◽  
Author(s):  
Ivan A. Ivanov ◽  
V. O. Ustyuzhanin ◽  
A. V. Sudnikov ◽  
A. Inzhevatkina
Keyword(s):  
Magnetic Field ◽  
Gas Flow ◽  
Supply Voltage ◽  
Hydrogen Plasma ◽  
Plasma Source ◽  
Lanthanum Hexaboride ◽  
Plasma Stream ◽  
Plasma Parameters ◽  
Plasma Properties ◽  
Plasma Gun

A plasma gun for forming a plasma stream in the open magnetic mirror trap with additional helicoidal field SMOLA is described. The plasma gun is an axisymmetric system with a planar circular hot cathode based on lanthanum hexaboride and a hollow copper anode. The two planar coils are located around the plasma source and create a magnetic field of up to 200 mT. The magnetic field forms the magnetron configuration of the discharge and provides a radial electric insulation. The source typically operates with a discharge current of up to 350 A in hydrogen. Plasma parameters in the SMOLA device are Ti ~ 5 eV, Te ~ 5–40 eV and ni ~ (0.1–1)  × 1019 m−3. Helium plasma can also be created. The plasma properties depend on the whole group of initial technical parameters: the cathode temperature, the feeding gas flow, the anode-cathode supply voltage and the magnitude of the cathode magnetic insulation.

The expectation marker of course in a cross-linguistic perspective

2004 ◽  
Vol 4 (1) ◽  
pp. 13-43 ◽  
Author(s):  
Anne-Marie Simon-Vandenbergen ◽  
Karin Aijmer
Keyword(s):  
English Learners ◽  
Native Speakers ◽  
Point Of View ◽  
Theoretical Point ◽  
Pragmatic Markers ◽  
Semantic Fields ◽  
Explanatory Account ◽  
Semantics And Pragmatics ◽  
Multilingual Corpus ◽  
Core Meaning

The study of of course presented in this article has an applied, a descriptive and a theoretical aim. Since of course proves to be very frequent in English, learners will need to know what meanings the item has and in what pragmatic contexts it is used. It has indeed been shown that some learners tend to use of course in contexts where it is felt by native speakers to be inappropriate. In order to explain such inappropriate uses we need detailed descriptions of the semantics and pragmatics of of course. From a theoretical point of view such multifunctional items raise the question of whether semantic polysemy or pragmatic polysemy is the best explanatory account. It is argued in this paper that empirical cross-linguistic work can contribute to providing answers to all three research questions. First, the study of correspondences and differences between languages with regard to the meanings and uses of pragmatic markers is a necessary step in the explanation of learner problems. Second, the bidirectional approach to equivalents, which involves going back and forth from sources to translations, enables us to show to what extent the equivalents have partially overlapping pragmatic functions. An in-depth comparison of the semantic fields in which the translation equivalents operate is the ultimate goal. Third, the translation method helps to see to what extent a core meaning account is justified. In this paper three languages are brought into the picture, viz. English, Swedish and Dutch. The cross-linguistic data have been gathered from three translation corpora, i.e. the English-Swedish Parallel Corpus, the Oslo Multilingual Corpus and the Namur Triptic Corpus.

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