Janez Krek

Characterizing the dominant ions in low-temperature argon plasmas in the range of 1–800 Torr

The dominant ions in low-temperature rare gas plasmas can be either molecular ions or atomic ions depending on the discharge regime. In this paper, the dominant ions in low-temperature argon plasmas are characterized in a wide range of gas pressure (1–800 Torr). The channels for creation of molecular ions include atom assisted association, dissociative recombination, dissociation by atom impact (DAI), and dissociation by electron impact (DEI). The latter two were previously less often considered. It is found that the DEI reaction has a significant impact on the ion fractions, while the effect of the DAI reaction is much less important in the whole investigated gas pressure regime. As the gas pressure increases from 1 to 800 Torr, the atomic ion fraction drops rapidly in conjunction with an increase of the molecular ion fraction. This phenomenon confirms that in low-temperature argon plasmas the dominant ion will be the atomic ion in the low pressure regime but the molecular ion in the high pressure regime...

Why there is no education ethics without principles

Abstract Moral education and ethical reflection are always dependent on the content of the internalized norms, principles and values of the individual. As we demonstrate, this also means that there is no instance of feeling, emotion, spontaneity, or care that can be independent of norms, rules, and values outside human discourse. In light of this, Noddings’ theory of the ethic of care is a contentious theory of child education, as it is linked with the presupposition that we can turn a blind eye to the symbolic field, to the network of rules/principles and their values, when we educate. Education that is derived only from caring, without being derived from reflection on education’s specific values, can lead to education that supports, for instance, racist ideology and racist education. This is not, of course, something that the ethic of care would advocate; however, as an educational theory, it is flawed in that, due to the rejection of reflection through principles in general, it fails to provide the educator with a conceptual apparatus through which he/she could analyze and reflect upon—could understand—what he/she is doing with regard to the norms of his/her culture. Society and educators cannot tacitly allow or be benevolent toward such fundamental mistakes in moral education.

Development of an automatic marketplace using virtual collaboration

Original scientific paper New product development is vital for the development of business enterprises and the society where the enterprise operates. The paper presents a case example of an automated marketplace development, which took place in the P-ino d.o.o. company. Developing such a complex product required the participation of experts from different areas, and it included also students, who definitely contributed to greater creativity and openness of the development team. More than 85 % of all the communication within the development team took place in virtual form. Testing of the finished prototype was also more or less virtual. Virtual communication in the development of such a complex product as an automated marketplace proved to be a very suitable method of interpersonal communication within the development team in all development phases of the product. It was particularly efficient because the members of the development team had different skills and were coming from different institutions and companies.

Theory and simulations of a thermionic emissions in a plain diode

The problem of biased diodes with thermionic emission has been first presented by Langmuir1 with a theoretical solution predicting the dependence on diode current on bias voltage in plane and cylindrical geometries. It has been shown that increase of density of emitting particles naturally leads to potential barrier with a non-monotonic potential profile. For many years, the value of potential minimum and its position have been considered as free parameters of this problem. Analytic, i.e. explicit, expressions for these parameters have been found only many years later2. However, the question of a stability of such a structure, with the potential bias as external control parameter, has not been fully investigated. In this paper we deal with this problem using grid-less tree-code method, in similar manner as was already done by Christlieb3 and Krek4 for the case of short-cut diode. The last investigations where focused into confirming high reliability of tree-code method, i.e. the same as in direct summation method, while in the present investigation, we apply our method to particular cases of engineering importance. Namely, we use same cases as exploited in Refs. [1, 2], which, in addition, implies cases with an arbitrary finite diode bias voltages ranging from zero (short-cut) to values much higher that the emitted particles thermal energy.

Kinetic theory and simulations of moderately strong stationary double layers with warm ions

Summary form only given. In this paper we present results obtained via kinetic theory and simulation on double layer structures (DLs) joining separating two non-isothermal plasmas with different ion and electron temperatures and densities such that DLs potential barrier strengths range from rather low to “infinite” (in comparison to particle thermal energies) in either of plasmas. This strongly non-linear problem, which consists of solving the so-called force balance equation subject to four boundary conditions (quasineutralities and generalized Bohm criteria), has been already solved self-consistently in fluid approach resulting in a modified form of Langmuir criterion, which however, suffers of a singularity for moderately strong double layers. In addition, boundary conditions have been imposed as free parameters of the problem instead of being calculated self-consistently, as done, e.g., in Ref. 3, for particular ionization rate distributions (proportional to electron density). For possible taking the same approach as in Ref. 3, i.e., to obtain a controllable DL with inhomogeneous ionization distributions, as an integral part of the discharge, and finding the double layer conditions (instead of imposing them in advance), here we obtain enough “experimental” observations and compile data from kinetic simulations, performed with our branch of a 1D PIC PTSG code. Thus the only free parameters that remain in maintaining a DL with desired strenght, are only those which all are contained within the ion-source term distribution, i.e., the external discharge parameters to be controlled by an experimentalist.

Investigations of a virtual cathode under complex conditions using grid-free treecode method

Summary form only given. A treecode numerical method was first introduced by Barnes and Hut in astrophysics [1] for simulation of many-body particle systems interacting in a gravitational field. Main advantage of this newly developing method is that it is grid-free, i.e. there is no need to define a grid in advance. This means that during a simulation of the motion of particles in external field, particles are grouped in clusters based on some well advanced criteria, e.g., the particle local number density. First attempt to develop a treecode method for a bounded plasma has been done by Christlieb, Krasny and Verboncoeur [2] with the application to the particle dynamics in a diode with a single mono-energetic particles. In a previous work of Krek et al. [3] the treecode method code was upgraded for more than a one kind of mono-energetic species and effects of imbalance of particle densities to the diode behavior was investigated. In the present work we proceed with investigations of plasma diode under more complex conditions (both volume particle generation and surface particle injection with finite arbitrary temperatures of Maxwellian distributed particles). Here we present the effects of these new parameters to the diode behavior using treecode method with these new incorporated features in comparison with the results obtained using Particle-In-Cell (PIC method [4]) and discuss both physical results and computational advantages and disadvantages of treecode method.