Methoden der kontrolle der mehlqualität für brotproduktion

Brot ist eines der wichtigsten Lebensmittel, das die Menschen jeden Tag verbrauchen. Dieses Lebensmittelprodukt wird durch das Backen des Teigs erhalten, der mindestens aus Mehl und Wasser besteht. Meistens wird noch Salz hinzugefügt sowie auch Backpulver benutzt, solches wie Hefe. Für Brotproduktion benutzt man Weizenmehl und Roggenmehl, seltener Maismehl, Gerstenmehl und anderes

Electron Modulation Instability in the Strong Turbulent Regime for Electron Beam Propagation in Background Plasma

We study collective processes for an electron beam propagating through a background plasma using simulations and analytical theory. A new regime where the instability of a Langmuir wave packet can grow locally much faster than ion frequency ({\omega}_pi) is clearly identified. The key feature of this new regime is an Electron Modulational Instability that rapidly creates a local Langmuir wave packet, which in its turn produces local charge separation and strong ion density perturbations because of the action of the ponderomotive force, such that the beam-plasma wave interaction stops being resonant. Three evolution stages of the process and observed periodic burst features are discussed. Different physical regimes in the plasma and beam parameter space are clearly demonstrated for the first time.Comment: 19 pages, 3 figure

Physical Regimes of Electrostatic Wave-Wave nonlinear interactions generated by an Electron Beam Propagation in Background Plasma

Electron-beam plasma interaction has long been a topic of great interest. The validities of Quasi-Linear (QL) theory and Weak Turbulence (WT) theory are limited by the requirement of sufficiently dense mode spectrum and small wave amplitude. In this paper, by performing a large number of high resolution two-dimensional (2D) particle-in-cell (PIC) simulations and using analytical theories, we extensively studied the collective processes of a mono-energetic electron beam emitted from a thermionic cathode propagating through a cold plasma. We show that initial two-stream instability between the beam and background cold electrons is saturated by wave trapping rather than QL theory. Further evolution occurs due to strong wave-wave nonlinear processes. We show that the beam-plasma interaction can be classified into four different physical regimes in the parameter space for the plasma and beam parameters. The differences between the different regimes are analyzed in detail. For the first time, we identified a new regime in strong Langmuir turbulence featured by what we call Electron Modulational Instability (EMI) that creates a local Langmuir wave packet faster than ion frequency ({\omega}_pi) and ions initially do not respond to EMI in the initial growing stage. On a longer timescale, the action of the ponderomotive force produces very strong ion density perturbations so that the beam-plasma wave interaction stops being resonant. Consequently, in this EMI regime beam-plasma interaction is a periodic burst (intermittent) process. The beams are strongly scattered, and the Langmuir wave spectrum is significantly broadened, which gives rise to the strong heating of bulk electrons. Some interesting phenomena in the strong turbulent regime are also discussedComment: 65 pages, 19 figure

Ключові аспекти двостороннього співробітництва України і Китайської Народної Республіки на сучасному етапі (Key aspects of the bilateral cooperation between Ukraine and the people’s Republic of China at the present stage)

У статті досліджено ключові аспекти двостороннього співробітництва України та Китайської Народної Республіки. Визначено стан відносин, виокремлено пріоритетні сфери співпраці та перспективи подальшого партнерства. Проаналізовано проблеми та виклики у відносинах на сучасному етапі. (The article highlights the key aspects of bilateral cooperation between Ukraine and the People’s Republic of China. The state of relations is defined, priority areas of cooperation and prospects of further partnership are highlighted. The problems and challenges in the relations at the present stage are analyzed.

Direct Implicit and Explicit Energy-Conserving Particle-in-Cell Methods for Modeling of Capacitively-Coupled Plasma Devices

Achieving entire large scale kinetic modelling is a crucial task for the development and optimization of modern plasma devices. With the trend of decreasing pressure in applications such as plasma etching, kinetic simulations are necessary to self-consistently capture the particle dynamics. The standard, explicit, electrostatic, momentum-conserving Particle-In-Cell method suffers from tight stability constraints to resolve the electron plasma length (i.e. Debye length) and time scales (i.e. plasma period). This results in very high computational cost, making this technique generally prohibitive for the large volume entire device modeling (EDM). We explore the Direct Implicit algorithm and the explicit Energy Conserving algorithm as alternatives to the standard approach, which can reduce computational cost with minimal (or controllable) impact on results. These algorithms are implemented into the well-tested EDIPIC-2D and LTP-PIC codes, and their performance is evaluated by testing on a 2D capacitively coupled plasma discharge scenario. The investigation revels that both approaches enable the utilization of cell sizes larger than the Debye length, resulting in reduced runtime, while incurring only a minor compromise in accuracy. The methods also allow for time steps larger than the electron plasma period, however this can lead to numerical heating or cooling. The study further demonstrates that by appropriately adjusting the ratio of cell size to time step, it is possible to mitigate this effect to acceptable level

Numerical thermalization in 2D PIC simulations: Practical estimates for low temperature plasma simulations

The process of numerical thermalization in particle-in-cell (PIC) simulations has been studied extensively. It is analogous to Coulomb collisions in real plasmas, causing particle velocity distributions (VDFs) to evolve towards a Maxwellian as macroparticles experience polarization drag and resonantly interact with the fluctuation spectrum. This paper presents a practical tutorial on the effects of numerical thermalization in 2D PIC applications. Scenarios of interest include simulations which must be run for many thousands of plasma periods and contain a population of cold electrons that leave the simulation space very slowly. This is particularly relevant to many low temperature plasma discharges and materials processing applications. We present numerical drag and diffusion coefficients and their associated timescales for a variety of grid resolutions, discussing the circumstances under which the electron VDF is modified by numerical thermalization. Though the effects described here have been known for many decades, direct comparison of analytically derived, velocity-dependent numerical relaxation timescales to those of other relevant processes has not often been applied in practice due to complications that arise in calculating thermalization rates in 1D simulations. Using these comparisons, we estimate the impact of numerical thermalization in several example low temperature plasma applications including capacitively coupled plasma (CCP) discharges, inductively coupled plasma (ICP) discharges, beam plasmas, and hollow cathode discharges. Finally, we discuss possible strategies for mitigating numerical relaxation effects in 2D PIC simulations