Effect of a weak ion collisionality on the dynamics of kinetic electrostatic shocks

In strictly collisionless electrostatic shocks, the ion distribution function can develop discontinuities along phase-space separatrices, due to partial reflection of the ion population. In this paper, we depart from the strictly collisionless regime and present a semi-analytical model for weakly collisional kinetic shocks. The model is used to study the effect of small but finite collisionalities on electrostatic shocks, and they are found to smooth out these discontinuities into growing boundary layers. More importantly, ions diffuse into and accumulate in the previously empty regions of phase space, and, by upsetting the charge balance, lead to growing downstream oscillations of the electrostatic potential. We find that the collisional age of the shock is the more relevant measure of the collisional effects than the collisionality, where the former can become significant during the lifetime of the shock, even for weak collisionalities.Comment: Published in J. Plasma Phy

Őshonos tyúkfajták tartásának lehetőségei és korlátai a Közép-magyarországi Régióban

A BCE, Kertészettudományi Kar, Kísérleti Üzem és Tangazdaságában, az Ökológiai és Fenntartható Gazdálkodási Rendszerek Tanszékének 17 hektáros minősített öko-területén több éves vizsgálat folyt, amelyben őshonos baromfi fajták vándor-ólas tartásának lehetőségét vizsgáltuk. Célunk olyan, az ökológiai tartás feltételeit is kielégítő tartási rendszer értékelése volt, amely kisgazdasági körülmények között is alkalmas akár termék előállításra, akár önellátásra

Business process development with the application of simulation technique

The object of our work to increase production efficiency with the use of cost-efficient development tools at a Hungarian small enterprise. We apply data gathering techniques besides process modelling and diagnostic methods to reduce the total process time of the assembly process so as to induce cost reduction in the production. In this respect we investigate and rank root causes of wastes by cost-effective process development tools, like timebased FMEA (failure mode and effects analysis) as well as the 5 whys method. With the use of Monte-Carlo simulation companies can evaluate the change in the process, therefore, they can decide whether they want to carry out corrective measures or not. The accomplished changes can generate increasing competitive edge in the long run

Characteristics of microinstabilities in electron cyclotron and ohmic heated discharges

Characteristics of microinstabilities in electron cyclotron (EC) and ohmic heated (OH) discharges in the T10 tokamak have been analyzed by linear electrostatic gyrokinetic simulations with gyro [J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)] aiming to find insights into the effect of auxiliary heating on the transport. Trapped electron modes are found to be unstable in both OH and the EC heated scenarios. In the OH case the main drive is from the density gradient and in the EC case from the electron temperature gradient. The growth rates and particle fluxes exhibit qualitatively different scaling with the electron-to-ion temperature ratios in the two cases. This is mainly due to the fact that the dominant drives and the collisionalities are different. The inward flow velocity of impurities and the impurity diffusion coefficient decreases when applying EC heating, which leads to lower impurity peaking, consistently with experimental observations

Analysis of activity times in the process of a wooden box manufacturing

The main target of companies is to earn money and achieve profit. In order to fulfil these needs, companies have to reduce their costs. Cost reduction is often associated with bad quality products, but it could be done in a different way. Sometimes it is enough to examine only their own processes and then benefit from the process optimization, process improvement or process scheduling. In this article a case study is presented, in which the differences in a production scheduling are evaluated with the application of Monte-Carlo simulation and descriptive statistics. At the end of the paper the most efficient material sequence is selected at the manufacturing company by using weighted sum mode

Fast collisional electron heating and relaxation in thin foils driven by a circularly polarized ultraintense short-pulse laser

The creation of well-thermalized, hot and dense plasmas is attractive for warm dense matter studies. We investigate collisionally induced energy absorption of an ultraintense and ultrashort laser pulse in a solid copper target using particle-in-cell simulations. We find that, upon irradiation by a $2\times10^{20}{\rm\,W\,cm^{-2}}$ intensity, $60{\rm\,fs}$ duration, circularly polarized laser pulse, the electrons in the collisional simulation rapidly reach a well-thermalized distribution with ${\sim}3.5{\rm\,keV}$ temperature, while in the collisionless simulation the absorption is several orders of magnitude weaker. Circular polarization inhibits the generation of suprathermal electrons, while ensuring efficient bulk heating through inverse bremsstrahlung, a mechanism usually overlooked at relativistic laser intensity. An additional simulation, taking account of both collisional and field ionization, yields similar results: the bulk electrons are heated to ${\sim}2.5{\rm\,keV}$, but with a somewhat lower degree of thermalization than in the pre-set, fixed-ionization case. The collisional absorption mechanism is found to be robust against variations in the laser parameters. At fixed laser pulse energy, increasing the pulse duration rather than the intensity leads to a higher electron temperature.Comment: Published in Journal of Plasma Physic

Collisional effects on the electrostatic shock dynamics in thin-foil targets driven by an ultraintense short pulse laser

We numerically investigate the impact of Coulomb collisions on the ion dynamics in high-$Z$, solid density caesium hydride and copper targets, irradiated by high-intensity ($I\approx2{-}5\times10^{20}{\rm\,Wcm^{-2}}$), ultrashort (${\sim}10{\rm\,fs}$), circularly polarized laser pulses, using particle-in-cell simulations. Collisions significantly enhance electron heating, thereby strongly increasing the speed of a shock wave launched in the laser-plasma interaction. In the caesium hydride target, collisions between the two ion species heat the protons to ${\sim}100{-}1000{\rm\,eV}$ temperatures. However, in contrast to previous work (A.E. Turrell etal., 2015 Nat. Commun. 6, 8905), this process happens in the upstream only, due to nearly total proton reflection. This difference is ascribed to distinct models used to treat collisions in dense/cold plasmas. In the case of a copper target, ion reflection can start as a self-amplifying process, bootstrapping itself. Afterwards, collisions between the reflected and upstream ions heat these two populations significantly. When increasing the pulse duration to $60{\rm\,fs}$, the shock front more clearly decouples from the laser piston, and so can be studied without direct interference from the laser. The shock wave formed at early times exhibits properties typical of both hydrodynamic and electrostatic shocks, including ion reflection. At late times, the shock is seen to evolve into a hydrodynamic blast wave

Egy gyanús eltűnés poligráfos vizsgálatának módszertana és tanulságai

The authors provide an overview of how the social network of disappeared victims can be identified.A szerzők áttekintést nyújtanak arról, hogyan lehet azonosítani az eltűnt áldozatok közösségi hálóját