Simulation of the spatio-temporal evolution of the electron energy distribution function in a pulsed hollow-cathode discharge

This article presents the 2D simulation results of a nanosecond pulsed hollow cathode discharge obtained through a combination of fluid and kinetic models.The spatio-temporal evolution of the electron energy distribution function(EEDF)of the plasma column and electrical characteristics of the nanosecond pulsed hollow cathode discharge at a gas pressure of 5 Torr are studied.The results show that the discharge development starts with the formation of an ionization front at the anode surface.The ionization front splits into two parts in the cathode cavity while propagating along its lateral surfaces.The ionization front formation leads to an increase in the fast isotropic EEDF component at its front,as well as in the anisotropic EEDF component.The accelerated electrons enter the cathode cavity,which significantly contributes to the formation of the highenergy EEDF component and EEDF anisotropy.

Current self-limitation in a transverse nanosecond discharge with a slotted cathode

A high-voltage transverse pulsed nanosecond discharge with a slotted hollow cathode was found to be a source of high-energy （few kV） ribbon electron beams. Conditions for the formation and extinction of electron beams were experimentally studied in discharges in helium at pressures of 1-100 Torr. It was found that interaction of fast electrons with a non-uniform electric field near the slotted cathode led to limitation of the magnitude of the discharge current. A physical model was developed to describe the discharge current self-limitation that was in satisfactory agreement with the experimental results. Some technical solutions that are expected to increase the upper current limits in transverse nanosecond discharge are discussed.

The dynamics of a nanosecond gas discharge development with an extended slot cathode in argon

The article presents the results of an experimental study and numerical modelling for the formation and development dynamics of a high-voltage transverse nanosecond discharge generated by a slot cathode in an argon medium at a pressure range of 1–10 Torr. Numerical modelling was carried out under similar experimental conditions for the processes of formation and propagation of ionisation waves, electron density distribution, excited atom and average electron energy in the discharge gap, including the cavity inside the cathode. At a pressure of p=1 Torr, a classical version of a high-voltage discharge is demonstrated to take place with no penetration of the plasma into the cathode cavity and no observed hollow cathode effect. An increase in gas pressure to 5 Torr leads to a penetration of plasma into the cathode cavity with the formation of a cathodic potential drop(CPD) region. Electrons emitted from the side surfaces of the cavity pass through the CPD region without collisions, oscillate inside the cathode cavity;the hollow cathode effect is fully manifested. At р=10 Torr, the modelling results qualitatively coincide with the results at р=5 Torr;in this case, however, hardly any accelerated electrons are observed in the gap between the electrodes, due to their energetic relaxation both inside the cathode cavity and when exiting from it. In both cases, the plasma structure formed at the exit of the cathode cavity involves a concentration of charged particles an order of magnitude higher than that in the rest of the gap, leading to a self-limiting discharge current effect. The results of the numerical modelling are in good agreement with experimental data.

Stability of High-Order Linear ItôEquations with Delays

A novel general stability analysis scheme based on a non-Lyapunov framework is explored. Several easy-to-check sufficient conditions for exponential p-stability are formulated in terms of M-matrices. Stability analysis of applied second-order It? equations with delay is provided as well. The linearization technique, in combination with the tests obtained in this paper, can be used for local stability analysis of a wide class of nonlinear stochastic differential equations.

Frumkin-melik-gaykazan model in the potentiodynamic and galvanodynamic regimes of functioning

The main purpose of this article is to study the behavior of a metallic electrode in the electrolyte which contains a surface-active substance with the property of adsorbtion-desorbtion, in the galvanodynamic and potentiodynamic rejimes. The study of the electrochemical behavior of a metallic electrode is carried out by operational impedance method, based on the Ohms low on the interaction between the Laplace-transformed expression of current, voltage and complex resistance (impedance). It is obtained the analytical expression of interface voltage-time dependence in a solution which contains a surface-active indifferent substance with the property of adsorbtion-desorbtion;also it is obtained the analytical expression of current density-time dependence which is passing through electrochemical cell in potentiodynamic regime of functioning of the Frumkin- Melik-Gaykazan model. It is established that the relation between the interface metallic electrode-indifferent electrolyte with property of adsorbtion-desorbtion voltage in the galvanodynamic rejime has the character of second order parabola;the relation between current density which is passing through a cell and time in potentiodynamic rejime of functioning in the Frumkin-Melik-Gaykazan model has exponential character.

Behaviour of the electrochemical intrgrator on the basis of solid electrolyte in galvanoharmonic charging mode

Behaviour of the Electrochemical integrator on the basis of Solid Electrolyte is studied in the galvanoharmonic charging mode. The possibility of application of simpler and more graphic calculation technigue and separation of impedance of electrochemical systems into active and reactive components is shown. The plotting of the dependences of the active and reactive impedance components on ac freguency was used to find the values of parameters of the studied equivalent electric cuircuits.

Dissolved oxygen in aeration-driven piezo-catalytic for antibiotics pollutants removal in water

The misuse of antibiotics and oxygen-lacking in aquaculture causes serious water environmental problems.Herein,a piezoelectic odd-layered MoS_(2)is prepared and applied to piezo-catalytic remove tinidazole(TNZ)and other antibiotic pollutants with aeration as a piezo-driving force.About 89.6%of TNZ can be degraded by MoS_(2)under aeration in the presence of dissolved oxygen with a reaction rate constant of0.15 min^(-1),which is 2.4 times higher than that under N2atmosphere and quiescence conditions.Quenching experiments and electron paramagnetic resonance(EPR)tests identify that singlet oxygen(^(1)O_(2))and superoxide radical(O_(2)^(·-))are dominant reactive oxygen species in MoS_(2)/aeration system.These results demonstrate that MoS2can trigger a piezoelectric effect and produce charge carriers to generate reactive oxygen species with dissolved oxygen(DO)for contaminant degradation with the turbulence and water bubbles rupture driven by aeration.

Enhanced persulfate activation process by magnetically separable catalysts for water purification:A review

In recent years,persulfate(PS)-based advanced oxidation processes(AOPs)have become a hot research topic for degrading environmental pollutants due to their excellent oxidation capacity,selectivity,and stability.PS-AOPs can generate sulfate radicals(SO^(·-)_(4))with strong oxidation ability,but single PS produces limited or no radicals.Therefore,activation of PS by energy input or catalyst dosing is used to improve its oxidation performance.However,the addition of disposable catalyst not only causes a waste of resources,but also may lead to secondary pollution.Therefore,magnetically separable catalysts for activating PS have received widespread attention due to their reusability.Although there are few literature reviews on the activation of PS by carbon-or iron-based magnetic materials,the mechanism analysis of the activation of PS by magnetic materials to degrade pollut-ants is not deep enough,and the discussion of material types is not comprehensive and detailed.Moreover,the discussion of magnetic materials in terms of recycling properties is lacking.Therefore,this review firstly sum-marizes and analyzes the mechanism of magnetically separable catalysts activating PS to degrade pollutants.Then,the research progress of zero-valent iron(ZVI,Fe^(0))-based,iron oxide-based,bimetallic oxide-based,and other magnetically separable catalyst is introduced,and the tailoring engineering approaches and reusability of magnetically separable catalysts are discussed.Finally,some possible material optimization suggestions are proposed in this paper.In conclusion,this review is expected to provide useful insights for improving the per-formance and reusability of magnetically separable materials activated PS in the future.

Supercritical CO_2: Properties and Technological Applications-A Review

The main goal of the present paper is to assess the available information so as to obtain a general procedure for dealing with the critical enhancement of the thermodynamic and transport properties of supercritical CO_2 and CO_2 containing binary mixtures for practical and scientific applications. The present review provides comprehensive analysis of the thermodynamic and transport properties of supercritical carbon dioxide and CO_2 containing binary mixtures(experiment and theory) and their various technological and scientific applications in different natural and industrial processes. The available information for the thermodynamic and transport properties(experiment and theory) enhancement(anomaly) of supercritical carbon dioxide and SC CO_2 + solute mixtures is comprehensively reviewed. The effect of long-range order parameter fluctuations on the thermodynamic and transport properties of supercritical fluids(SC CO_2) will be discussed. Simplified scaling type equation based on mode-coupling theory of critical dynamics with two critical amplitudes and one cutoff wave number as fluid-specific parameters was used to accurately predict of the transport properties of supercritical carbon dioxide. The recommended values of the specific parameters(asymptotic critical amplitudes) of the carbon dioxide for practical(prediction of the thermodynamic and transport properties of the supercritical CO_2 for technological applications) and scientific use were provided. The role of the critical line shapes of the carbon dioxide containing binary mixture(SC CO_2+solvent) in determination of the critical behavior of the mixture near the critical point of pure supercritical solvent(CO_2) is discussed. Krichevskii parameter concept for a description of thermodynamic behavior of dilute near-critical SC CO_2+solute mixtures is also discussed. The structural and thermodynamic properties of the carbon dioxide containing binary mixtures near the critical point of pure solvent(CO_2) are discussed.

Influence of a laser profile in impedance mismatch techniques applied to carbon EOS measurement

We present a recent numerical analysis of impedance mismatch technique applied to carbon equation of state measurements.We consider high-power laser pulses with a Gaussian temporal profile of different durations.We show that for the laser intensity(≈1014W/cm2)and the target design considered in this paper we need to have laser pulses with rise-time less than 150 ps.

Shock dynamics and shock collision in foam layered targets

We present an experimental study of the dynamics of shocks generated by the interaction of a double-spot laser in different kinds of targets:simple aluminum foils and foam-aluminum layered targets.The experiment was performed using the Prague PALS iodine laser working at 0.44μm wavelength and irradiance of a few 10^(15)W/cm^(2).Shock breakouts for pure Al and for foam-Al targets have been recorded using time-resolved self-emission diagnostics.Experimental results have been compared with numerical simulations.The shocks originating from two spots move forward and expand radially in the targets,finally colliding in the intermediate region and producing a very strong increase in pressure.This is particularly clear for the case of foam layered targets,where we also observed a delay of shock breakout and a spatial redistribution of the pressure.The influence of the foam layer doped with high-Z(Au)nanoparticles on the shock dynamics was also studied.

Hard life in cold waters:Size distribution and gonads show that Greenland halibut temporarily inhabit the Siberian Arctic

The range of the Greenland halibut Reinhardtius hippoglossoides(Walbaum,1792)includes vast areas in the northern parts of the Atlantic and Pacific oceans,as well as the seas of the Arctic Ocean.Despite its commercial importance and decades of study,many aspects of its life cycle and reproduction remain poorly understood.Here,we evaluate the size distribution of Greenland halibut in the catches of research surveys in the Barents,Kara,and Laptev seas and conduct micro-and macroscopic studies of their gonads in the Laptev Sea.The size of Greenland halibut individuals increases from west to east,which is associated with the settling of pelagic juveniles and the subsequent residency of growing individuals near their settling sites.To the greatest extent,this size imbalance is manifested in the areas most remote from spawning grounds,i.e.the Kara and Laptev seas.The process of maturation in large individuals of Greenland halibut in the Arctic seas is characterized by a state of inhibitionwaiting in the early stages of gametogenesis(previtellogenesis).The data obtained indicate that Greenland halibut in the North Atlantic and the Siberian Arctic have a continuous range.The continental slope of the Barents Sea is a spawning and maturing ground,while the northern parts of the Barents and Kara seas,as well as the continental slope of the Laptev Sea,are feeding grounds for juveniles.The results of this study might serve as a necessary basis for monitoring condition of halibut stocks as well as for reallocation of the total allowable catch between countries that exploited them in the Norwegian and Barents seas.