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High-voltage and discharge plasma technology is playing an increasingly important role in the construction of national economy and social development, and has attracted extensive attention from both academia and industry. As a novel molecular activation method, discharge plasma can enable thermodynamically difficult reactions to occur under relatively mild conditions, and its effectiveness has successfully been demonstrated in gas cleaning and material surface treatment. In recent years, discharge plasma is continuously showing its outstanding performance in energy, medicine, food, agriculture, aerospace industry, etc. However, new challenges have been brought for the theoretical research and technological development of discharge plasma due to the continuous expansion of its application fields. The in-depth research is necessary to unravel basic characteristics, develop diagnostic technologies, and design efficient sources for discharge plasma, and to promote its applications in practice. In the last two years, significant advances of fundamental and applied achievements have been made in the above areas including theory, modeling and numerical simulations, experimental and diagnostic techniques, plasma sources and applications. In this context, the 2020 National Conference on High Voltage and Discharge Plasmas (HVDP 2020) was held in Harbin, China, on October 23-25, 2020, hosted by the Committee of Plasmas and Applications, China Electrotechnical Society, the Division of Plasma Physics in Chinese Physics Society, and the Committee of Plasma Science and Technology, Chinese Society of Theoretical and Applied Mechanics. This event attracted more than 580 participates from 103 universities, research institutes and enterprises all over China. The program included 4 plenary talks, 38 invited talks, 218 oral presentations and 116 poster presentations, which focused discussions on 11 topics including high voltage, pulsed power technology, basic process of plasma, simulation, diagnosis, materials processing and modifications, biomedicine, energy and chemical engineering, aerospace, environment and fusion, as well as two symposiums on linear plasma devices, disinfection, sterilization and protection against COVID-19. This well-established event provides a platform for the attendees to discuss, exchange and present their innovative ideals and latest achievements on discharge plasma and applications. It also benefits from helping young scientists to learn more about discharge plasmas and their potential practical applications, and facilitating interactions and collaborations between academic researchers and potential application users.

A paper by El Saghir and Shannon (2012 Plasma Sources Sci. Technol. 21 025003) raises the question about the validity of the widely-used Druyvesteyn formula for obtaining the electron energy distribution function by cylindrical probes. They conclude that there are deviations between the Druyvesteyn formula for cylindrical and for spherical probes. In this comment this conclusion is questioned and the correct expressions are derived. It is shown that no such difference exists when all three velocity components are correctly accounted for. Furthermore, the disturbance to the plasma introduced by the probe is estimated.

In this reply we respond to the comment made by E A Bogdanov, M V Krasilnikov and A A Kudryavtsev on our review 'Non-thermal plasma instabilities induced by deformation of the electron energy distribution function'.

This comment points out that the conditions of the local approximation applicability have to be considered more clearly. Moreover, the discussion of influence of ambipolar field has to be presented.

We analyse biased ensembles of trajectories for the random-field Ising model on a fully-connected lattice, which is described exactly by mean-field theory. By coupling the activity of the system to a dynamical biasing field, we find a range of dynamical phase transitions, including spontaneous symmetry breaking into ordered states. For weak bias, the phase behaviour is controlled by extrema of the free energy, which may be local minima or saddle points. For large bias, the system tends to states of extremal activity, which may differ strongly from free energy minima. We discuss connections of these results to random first-order transition theory of glasses, which motivates an extension of the analysis to random-field Ising models where the dynamical activity is not symmetric under magnetisation reversal., 26 pages, 10 figures

Run-and-tumble (RnT) motion is an example of active motility where particles move at constant speed and change direction at random times. In this work we study RnT motion with diffusion in a harmonic potential in one dimension via a path integral approach. We derive a Doi-Peliti field theory and use it to calculate the entropy production and other observables in closed form. All our results are exact.

We acknowledge the support of the UK EPSRC, Grant Number EP/N028694/1, and the EC's Laserlab-Europe H2020 EC-GA Nos. 654148 and 871124. A theoretical model is developed to describe the formation of microstructures due to plasma streaming instabilities in radially convergent geometries. Microstructures in the form of radial spokes are found experimentally in laser wakefield accelerators. The eigenvalues of a set of coupled linear ordinary differential equations are obtained and the complex wavenumbers calculated to give the local growth rates. The predictions are confirmed using particle-in-cell (PIC) simulations carried out for two counter-propagating converging/diverging plasma annuli. The simulations consistently demonstrate unstable growth for interactions between two counterpropagating annuli with different number densities. The growth rates obtained from the PIC simulations agree well with the growth rates from the semi-analytical model. The theory presented in this paper can provide powerful insight into converging plasma beams found in space and laboratory scale plasma. Publisher PDF

Funder: Royal Society under the Newton International Fellowship, The implementation of static artificial magnetic fields in ultracold atomic systems has become a powerful tool, e.g. for simulating quantum-Hall physics with charge-neutral atoms. Taking an interacting bosonic flux ladder as a minimal model, we investigate protocols for adiabatic state preparation via magnetic flux ramps. Considering the fact that it is actually the artificial vector potential (in the form of Peierls phases) that can be experimentally engineered in optical lattices, rather than the magnetic field, we find that the time required for adiabatic state preparation dramatically depends on which pattern of Peierls phases is used. This can be understood intuitively by noting that different patterns of time-dependent Peierls phases that all give rise to the same magnetic field ramp, generally lead to different artificial electric fields during the ramp. As an intriguing result, we find that an optimal choice allows for preparing the ground state almost instantaneously in the non-interacting system, which can be related to the concept of counterdiabatic driving. Remarkably, we find extremely short preparation times also in the strongly-interacting regime. Our findings open new possibilities for robust state preparation in atomic quantum simulators.

Funder: ATTRACT Investigator Grant, Luxembourg National Research Fund Oppenheimer Research Fellowship, University of Cambridge, Funder: Junior Research Fellowship, St Catharine's College, Funder: Aker Scholarship, We investigate the steady-state entropy production rate (EPR) in the hydrodynamic Vicsek model (HVM) and diffusive flocking model (DFM). Both models display a transition from an isotropic gas to a polar liquid (flocking) phase, in addition to travelling polar clusters and microphase-separation in the miscibility gap. The phase diagram of the DFM, which may be considered an extension of the HVM, contains additional structure at low densities where we find a novel crystal phase in which a stationary hexagonal lattice of high-density ridges surround low density valleys. From an assessment of the scaling of the EPR at low noise, we uncover that the dynamics in this limit may be organised into three main classes based on the dominant contribution. Truly nonequilibrium dynamics is characterised by a divergent EPR in this limit, and sustains global time-reversal symmetry (TRS) violating currents at zero noise. On the other hand, marginally nonequilibrium and effectively equilibrium dynamics have a finite EPR in this limit, and TRS is broken only at the level of fluctuations. For the latter of these two cases, detailed balance is restored in the small noise limit and we recover effective Boltzmann statistics to lowest nontrivial order. We further demonstrate that the scaling of the EPR may change depending on the dynamical variables that are tracked when it is computed, and the protocol chosen for time-reversal. Results acquired from numerical simulations of the dynamics confirm both the asymptotic scaling relations we derive and our quantitative predictions.

We use first-principles density functional theory to conduct an extensive structure search using the AIRSS package for elemental sulfur in the range 50–550 GPa. We then obtain the low-temperature phase diagram of sulfur in the same pressure range, including vibrational effects through the harmonic approximation. We do not find any structures lower in energy than those already reported in experiment, although the phase diagram below 100 GPa is found to be crowded with structures separated by only a few meV. We report the transition sequence I 4 1 / acd → P 1 ¯ → ICM → C 2 / m → R 3 ¯ m → I m 3 ¯ m and obtain accurate pressures for each transition, although we find the second-order C 2 / m → R 3 ¯ m transition particularly difficult to define. Contrary to previous first-principles works (Pavel et al; Rudin and Liu 1999 Phys. Rev. Lett. 83 3049–52), we do not reproduce a trigonal → simple cubic transition at either the static lattice or harmonic level. We also undertake a detailed analysis of the incommensurately modulated (ICM) phase of sulfur phase using a commensurate approximant found in the structure search. We find that the modulation amplitude is zero above 96 GPa; some 40 GPa below the experimentally reported transition to the unmodulated phase. We find that the body-centred atoms in the relaxed ICM approximant are, in addition to the dominant transverse modulation (which is a frozen-in optical phonon mode), slightly displaced longitudinally in the b-direction. We subsequently discover that this (small) longitudinal modulation is coupled to the transverse mode, and hence report previously unnoticed weak-mode coupling between transverse and longitudinal optical phonons in the ICM phase.

We investigate the effect of controlling large-scale, logarithmic-layer turbulent structures, which have a characteristic size and aspect ratio that scale with the distance from the wall. The aim is to quantify the effect of suppressing these structures while leaving the near-wall turbulent dynamics unaltered. By affecting only the logarithmic-layer structures, it might be possible to isolate their contribution to the drag from that of the other scales in the flow. We conduct direct numerical simulations of turbulent channel flows at friction Reynolds number ReT ?s 500-1000 and artificially remove certain streamwise and spanwise wavelengths of the wall-normal velocity across a range of heights. The wavelengths chosen depend on the target height (and size) of the structures that we wish to target. When these wavelengths are removed, we observe a positive, outward shift of the mean velocity profile above the target height, due to a local reduction in Reynolds shear stress, and a subsequent increase in viscous stress. Our preliminary results suggest that this shift in the mean velocity profile scales in outer units.

The paper analyses the details of the application of the hybrid model for calculation of the formation of high-pressure gas discharge in conditions where the transition of electrons into runaway mode is possible. In hybrid model, PIC MC method is used only for calculation of runaway electrons, and the standard hydrodynamic approach is used for calculation of plasma electrons. Using such model can significantly reduce computing resources. The results of calculation of kinetics of electrons emitted from a micro-spike on the cathode during the formation of the cathode layer of nanosecond and sub-nanosecond high-pressure gas discharge are presented. The conditions of transition of electrons into runaway mode at this stage and their influence on the further formation of the gas discharge are analyzed. © 2018 Institute of Physics Publishing. All rights reserved. The work was supported by RFBR, Grant 16-08-00894.

In this work, non-thermal plasma has been applied to treat polyacrylamide (PAM) wastewater. We have investigated the influence of the rule of PAM wastewater initial pH, solution concentration and discharge time, discharge voltage on chemical oxygen demand (COD) degradation rate. At the same time, the effect of pH and discharge time on the viscosity removal rate of PAM solution was also studied. Then, the effect of pH on the viscosity removal rate of 1.0 g l−1 PAM solution was studied separately. Through orthogonal test, the factors affecting the COD degradation rate of PAM wastewater were determined as follows: discharge time > discharge voltage > solution concentration > wastewater initial pH. The COD highest removal rate of PAM wastewater reached 85.74%, when the optimal conditions are as follows: discharge voltage 40 kV, discharge time 5 h, solution concentration 1.0 g l−1, pH 1.5. This research provides some basic data and new theoretical basis for PAM wastewater purification.

Excess sludge is an unavoidable by-product in wastewater treatment. The conventional methods(landfill, incineration etc.) may cause secondary pollution. In this study, both reduction and heavy metals removal of excess sludge by radio frequency discharge plasma(RFDP) were investigated. The experimental results showed that RFDP was an effective removal method on total chemical oxygen demand (TCOD) and mixed liquid suspended solids(MLSS). Discharge process could also damage the cell structure of sludge, so that organic matter and heavy metals within the cell structure could enter the liquid phase. At the same time, combined with spectral diagnosis, the radical reactions was discussed.

The focusing NLS equation is the simplest universal model describing the modulation instability (MI) of quasi monochromatic waves in weakly nonlinear media, considered the main physical mechanism for the appearance of rogue (anomalous) waves (RWs) in Nature. In this paper we study, using the finite gap method, the NLS Cauchy problem for periodic initial perturbations of the unstable background solution of NLS exciting just one of the unstable modes. We distinguish two cases. In the case in which only the corresponding unstable gap is theoretically open, the solution describes an exact deterministic alternate recurrence of linear and nonlinear stages of MI, and the nonlinear RW stages are described by the 1-breather Akhmediev solution, whose parameters, different at each RW appearance, are always given in terms of the initial data through elementary functions. If the number of unstable modes is >1, this uniform in t dynamics is sensibly affected by perturbations due to numerics and/or real experiments, provoking O(1) corrections to the result. In the second case in which more than one unstable gap is open, a detailed investigation of all these gaps is necessary to get a uniform in $t$ dynamics, and this study is postponed to a subsequent paper. It is however possible to obtain the elementary description of the first nonlinear stage of MI, given again by the Akhmediev 1-breather solution, and how perturbations due to numerics and/or real experiments can affect this result.

In this paper, the theory of collisional and turbulent transport of impurities in tokamak plasmas is reviewed. The results are presented with the aim of providing at the same time a historical reconstruction of the scientific progress and a complete description of the present theoretical knowledge, with a hopefully sufficiently complete reference to the works which have been published in the field in the last decades. After a general introduction on the physics challenges offered by the problem of impurity transport and their relevance for practical nuclear fusion energy, the theory of collisional transport is presented. Here a specific section is also dedicated to the transport parallel to the magnetic field lines. A complete review of the transport mechanisms produced by turbulence follows. The corresponding comparisons between theoretical predictions and experimental observations are also presented, highlighting the influence that the validation activities had in motivating further theoretical investigations. The paper is completed by a section on the direct interactions between collisional and turbulent transport and by a final specific review dedicated to the progress in the theory–based modelling activities. In the writing of this review paper, the main goal has been to combine readability with completeness and scientific rigour, providing a comprehensive list of references for deeper documentation on specific aspects.

International audience; The theoretical account of electron transport in crystalline solids is often taught to graduate students through a semiclassical equation which is a classical kinetic equation amended with elements of quantum physics in a non-systematic way. This blending of classical and quantal elements accounts for many experimental features of electron transport, save for a few ones observed over short distances. For students acquainted with solid-state quantum mechanics, it is preferable to derive the semiclassical equation from quantum dynamics so as to pinpoint the shortcomings and approximations underlying the semiclassical picture of transport. This paper explores the pathway leading from quantum dynamics to semiclassical kinetics within a simplified model not exceeding the proficiencies of a graduate student in physics or electronic engineering. In this model an electron moves in a crystal under the joint influences of the periodic crystal potential, an external electrostatic field and a set of lattice imperfections haphazardly distributed in the crystal volume. The first influence is treated exactly by means of standard energy-band theory and the other two are handled perturbatively. Following a procedure already tested in free-space issues, we replace Schrödinger’s wave function in position space with a Wigner function defined in the phase (position-pseudomomentum) space of semiclassical kinetics. The dynamical equation on the Wigner function is worked out and approximated so as to retrieve the semiclassical equation. The errors incurred in making use of the latter are assessed quantitatively. It is explained how a time-irreversible evolution equation ---governing a phase-space occupancy--- arises from a reversible Schrödinger dynamics ---governing a complex-valued probability amplitude. Besides clarifying the foundation of the semiclassical picture of electron transport and providing an explicit quantum-coherence correction to that picture, this paper may help students in general physics to better grasp, in a concrete issue, the interplay between classical and quantum concepts.; La théorie du transport électronique dans un solide cristallin est souvent présentée aux doctorants au moyen d'une équation semi-classique, qui est une équation cinétique classique amendée par des éléments de physique quantique d'une manière non systématique. Cette alliance d'éléments classiques et quantiques rend compte de nombreux aspects du transport électronique, sauf quelques uns observés sur de courtes distances. Pour qui est familier de la mécanique quantique du solide, il est préférable de dériver l'équation semi-classique de la dynamique quantique pour identifier les défauts et les approximations qui sous-tendent l'image semi-classique du transport. Cet article explore le chemin qui mène de la dynamique quantique à la cinétique semi-classique dans le cadre d'un modèle simplifié à la portée d'un doctorant de physique ou d'ingéniérie électronique. Dans ce modèle, un électron se déplace dans le cristal sous les influences du potentiel périodique cristallin, d'un champ électrostatique extérieur et d'un ensemble d'imperfetions de réseau réparties au hasard dans le volume du cristal. La première influence est traitée exactement au moyen de la théorie standard des bandes d'énergie et les deux autres sont abordées comme des perturbations. En suivant un procédé déjà éprouvé dans le vide, on remplace la fonction d'onde de Schrödinger définie dans l'espace des positions par une fonction de Wigner définie dans l'espace des phases (positions et pseudo-impulsions) de la cinétique semi-classique. L'équation dynamique régissant la fonction de Wigner est transformée et approximée de façon à retrouver l'équation semiclassique du transport. Les erreurs commises dans cette dernière sont évaluées de manière quantitative. On explique comment une équation d'évolution irréversible-portant sur l'occupation en phase-découle de la dynamique réversible de Schrödinger-portant sur une amplitude de probabilité complexe. Outre qu'il clarifie le fondement de l'image semi-classique du transport électronique et qu'il fournit une correction explicite de cohérence quantique, l'article peut être utile en physique générale en montrant, sur un problème concret, les relations mutuelles entre les concepts classiques et quantiques.

Because the larger metallic surrounds are heated by the eddy current, which is generated by the AC current flowing through the AC busbar in the International Thermonuclear Experimental Reactor (ITER) poloidal field (PF) converter system, shielding of the AC busbar is required to decrease the temperature rise of the surrounds to satisfy the design requirement. Three special types of AC busbar with natural cooling, air cooling and water cooling busbar structure have been proposed and investigated in this paper. For each cooling scheme, a 3D finite model based on the proposed structure has been developed to perform the electromagnetic and thermal analysis to predict their operation behavior. Comparing the analysis results of the three different cooling patterns, water cooling has more advantages than the other patterns and it is selected to be the thermal dissipation pattern for the AC busbar of ITER PF converter unit. The approach to qualify the suitable cooling scheme in this paper can be provided as a reference on the thermal dissipation design of AC busbar in the converter system.

International audience; During the working of electrical fuses, inside the fuse element the silver ribbon first begins to melt, to vaporize and then a fuse arc appears between the two separated parts of the element. Second, the electrodes are struck and the burn-back phenomenon takes place. Usually, the silver ribbon is enclosed inside a cavity filled with silica sand. During the vaporization of the fuse element, one can consider that the volume is fixed so that the pressure increase appears to reach pressures higher than atmospheric pressure. Thus, in this paper two pressures, 1 atm and 10 atm, are considered. The electrical field inside the plasma can reach high values since the distance between the cathode surface and the anode surface varies with time. That is to say from zero cm to one cm order. So we consider various electrical fields: 102 V/m, 103 V/m, 5×103 V/m, 104 V/m at atmospheric pressure and 105 V/m at a pressure of 10 atm. This study is made in heavy species temperature range from 2,400 K to 10,000 K. To study the plasma created inside the electric fuse, we first need to determine some characteristics in order to justify some hypotheses. That is to say: are the classical approximations of the thermal plasmas physics justified? In other words: plasma frequency, the ideality of the plasma, the Debye-HÜckel approximation and the drift velocity versus thermal velocity. These characteristics and assumptions are discussed and commented on in this paper. Then, an evaluation of non-thermal equilibrium versus considered electrical fields is given. Finally, considering the high mobility of electrons, we evaluate the electrical conductivities.

This paper presents a spatial domain quantum watermarking scheme. For a quantum watermarking scheme, a feasible quantum circuit is a key to achieve it. This paper gives a feasible quantum circuit for the presented scheme. In order to give the quantum circuit, a new quantum multi-control rotation gate, which can be achieved with quantum basic gates, is designed. With this quantum circuit, our scheme can arbitrarily control the embedding position of watermark images on carrier images with the aid of auxiliary qubits. Besides reversely acting the given quantum circuit, the paper gives another watermark extracting algorithm based on quantum measurements. Moreover, this paper also gives a new quantum image scrambling method and its quantum circuit. Differ from other quantum watermarking schemes, all given quantum circuits can be implemented with basic quantum gates. Moreover, the scheme is a spatial domain watermarking scheme, and is not based on any transform algorithm on quantum images. Meanwhile, it can make sure the watermark be secure even though the watermark has been found. With the given quantum circuit, this paper implements simulation experiments for the presented scheme. The experimental result shows that the scheme does well in the visual quality and the embedding capacity.

This paper is devoted to the derivation of macroscopic fluid dynamics from the Boltzmann mesoscopic dynamics of a binary mixture of hard-sphere gas particles. Specifically the hydrodynamics limit is performed by employing different time and space scalings. The paper shows that, depending on the magnitude of the parameters which define the scaling, the macroscopic quantities (number density, mean velocity and local temperature) are solutions of the acoustic equation, the linear incompressible Euler equation and the incompressible Navier–Stokes equation. The derivation is formally tackled by the recent moment method proposed by [C. Bardos, et al., J. Stat. Phys. 63 (1991) 323] and the results generalize the analysis performed in [C. Bianca, et al., Commun. Nonlinear Sci. Numer. Simulat. 29 (2015) 240].

In this paper, to simulate the arc motion in an air circuit breaker (ACB), a three-dimensional magneto-hydrodynamic (MHD) model is developed, considering the influence of thermal radiation, the change of physical parameters of arc plasma and the nonlinear characteristic of ferromagnetic material. The distributions of pressure, temperature, gas flow and current density of arc plasma in the arc region are calculated. The simulation results show some phenomena which discourage arc interruption, such as back commutation and arc burning at the back of the splitter plate. To verify the simulation model, the arc motion is studied experimentally. The influences of the material and position of the innermost barrier plate are analyzed mainly. It proved that the model developed in this paper can efficiently simulate the arc motion. The results indicate that the insulation barrier plate close to the top of the splitter plate is conducive to the arc splitting, which leads to the significant increase of the arc voltage, so it is better for arc interruption. The research can provide methods and references to the optimization of ACB design.

In the frame of the European objectives in terms of CO2 emissions, the aeronautics is looking for a technological rupture to achieve them, in particular, the aircraft design domain pursuits this through the research of innovative architectures. One of these innovative configurations currently being explored includes the hybrid electric energy source (thermal/electric) for Distributed Electric Propulsion (DEP) architecture. This Paper details a code developed to size a general aviation aircraft at concept level, by only defining its top level requirements and the main architecture parameters. The code can manage both conventional and hybrid power source as well as concentred or distributed propulsion architectures in order to allow the user to evaluate and compare the feasibility and benefits respectively of these innovative architectures. This code is a branch of the code “FAST-CS25” (Future Aircraft Sizing Tool for conventional CS-25 type) held by ONERA/ISAE-SUPAERO. The presented work aims at the expansion of the FAST code to CS-23 conventional type, hybrid electric energy source, and distributed propulsion system configurations. Through this paper, the models and the main sizing loops for the concept design are described, but putting special emphasis on the distributed propulsion aerodynamics and wing mass estimation. These detailed models where validated with the NASA X-57 DEP aircraft satisfactory. The whole concept design loop of a hybrid energy aircraft was validated with the eGenius hybrid energy aircraft.

This paper presents the study on the Jeffery Hamel nanofluid flow and heat transfer through non-parallel channel taking into account radiation effect. The fluid with porous medium flowing through the non-parallel channel is formulated utilizing momentum and energy equations. Since the model obtained are nonlinear, higher order systems of equations, the Akbari Ganji novel approximate method is adopted in this paper. As reported in the graphical representation of the result, it is depicted that the porous medium limits flow due to increased dynamic viscosity leading to pressure drop while the radiation parameter enhances heat loss through the non-parallel plates. This evidently leads to energy loss. The Akbari–Ganji method is used in this study to investigate the parametric behavior of rheological parameters on the flow and heat transfer owing to its high accuracy. Results obtained in this study compared against analytical and numerical solution obtained in literature shows satisfactory conclusion. Therefore, results from this paper may be useful in advancing studies of nanofluid with porous medium.

The Zakharov-Kuznetsov equation plays a key role in the plasma physics, and its solution has always been a hot topic, however its variational principle has not been studied. So this paper develops a variational formulation for the (3+1)-dimensional extended quantum Zakharov-Kuznetsov equation by the semi-inverse method, which shows an energy conservation law for the dust-ion-acoustic solitary waves in a magnetized two-ion-temperature dusty plasma. The whole derivation process is presented in detail. The obtained results in this paper are expected to shed a bright light on the study of theoretical basis for the magnetized plasma. FullText for HTML: https://doi.org/10.1209/0295-5075/132/44002

In the paper [Angelini M C, Parisi G, and Ricci-Tersenghi F, Ensemble renormalization group for disordered systems, Phys. Rev. B 87 134201 (2013)] we introduced a real-space renormalization group called Ensemble Renormalization Group (ERG) and we applied it to the Edwards-Anderson model, obtaining estimates for the critical exponents in good agreement with those from Monte Carlo simulations. Recently the paper [Castellana M, Real-space renormalization-group methods for hierarchical spin glasses, J. Phys. A: Math. Theor. 52 445002 (2019)] re-examined the ERG method from a different perspective, concluding that the previous results were wrong, and claiming that the ERG method predicts trivially wrong critical exponents. In this comment we explain why the conclusions reached by Castellana are wrong, as they are based on a misinterpretation of finite-size effects. We conclude that the ERG method remains a good RG method to obtain critical exponents in strongly disordered models (if properly used)., Comment on arXiv:1910.04521

Edge codes such as SOLPS-ITER find distributions of impurity ions, e.g. of C, N and Ne, in the divertor and SOL which are quite non-uniform spatially, both poloidally and radially. Poloidally, impurity ion density distributions often have strong peaks near the targets as well as a peak on/near the separatrix in the main SOL near the outside midplane. A high density of low-Z impurities near the targets is quite desirable since cold, dense divertor plasma conditions there result in very efficient radiative dissipation of power. By contrast, impurity concentration near the outside midplane separatrix is often quite undesirable since the impurity density there is essentially the boundary value for impurity levels in the confined plasma. In order to better understand the poloidal distribution of impurities in the edge plasma, a simple analytic 1D impurity fluid model, 1DImpFM, has been developed for the transport along open field lines of impurity ions in a specified fuel-plasma background. Often, the strongest parallel forces acting on impurity ions in the edge plasma are (i) FiG, the (fuel) ion temperature parallel-gradient force ('thermal force'), and (ii) FF, the friction force between fuel and impurity ions ('friction force'). Recently, Senichenkov et al [1] reported the extremely useful and informative result that the impurity ion parallel velocity calculated by the SOLPS-ITER code can be remarkably well reproduced by assuming the simple force balance FF + FiG = 0. In the present paper the basis for, and a number of basic predictions of, the 1DImpFM are reported including an assessment of the circumstances under which FF + FiG = 0 can be expected to be a good approximation. The 1DImpFM is used to elucidate the competing roles of thermal and friction forces, as they control three key features of edge impurity behavior: (a) leakage of impurity ions from the divertor, (b) the peaking of impurity density near the targets, and (c) impurity ion accumulation near the midplane separatrix; the model provides simple analytic expressions for estimating the divertor leakage rate [ions/m2/s] and impurity density peaking/accumulation [ions/m3]. A subsequent paper will report comparisons of results from the 1DImpFM and from SOLPS-ITER modeling of some ITER cases with neon impurities.

Microwave-induced active coke discharge has been used in many researches in environment and energy due to its kinetics and thermal effect. However, the mechanisms of discharge for submillimeter particles are still not clear. The paper presents that the particle shape and gap distance between particles are the possible mechanisms of the microwave discharge. This paper also gives the scope of application of several mechanisms for different particulate materials. Submillimeter particles with about 40-110° tip angle and micron gap distance have the best effect on microwave electric field enhancement. The gap effect is only applicable to material with large refractive index, in detail, n > 3 or k > 2 for 300 μm particle. When gap distance is too narrow, the electron loss is large enough, leading to the failure of discharge.

This paper introduces an n-order network model with Y circuits to investigate the electrical properties, and it is an entirely new question that has seldom been addressed in the academic world. We carry out the research by means of building an equivalent model. Firstly, we use Kirchhoff's law to build a second-order nonlinear recurrence equation model. Secondly, by using variable substitution we transform the nonlinear equation into a linear difference equation. Thirdly, we name the process recurrence transformation of n-order network, called N-RT for short. Based on the linear difference equation, an analytical solution is offered to the problem of the equivalent resistance of the n-order network with Y circuits. This research is going to find specific application in many cases. What's important, this paper further investigates the equivalent complex impedance of LC network and the electrical properties of complex impedance, and illustrates the oscillation and resonance characteristics of LC network with 3D graphs.

The results of the experimental dimensionless scan in this paper confirm that there is an increase in density peaking towards lower collisionality and that this can be partly linked to a shift in the turbulence regime from ITG towards TEM. However at the lowest collisionality, the changes in turbulence and transport are much more pronounced than expected from direct collisionality effect on the turbulence. In this paper, the collisionality, ν ∗ is varied by a factor 5, while keeping ρ ∗, q, β, M, fixed. Additionally, a 3 Hz gas puff modulation is applied to modulate the electron density profile and extract the perturbed transport coefficients using two diagnostics. The transport analysis shows that the increase in density peaking at low ν ∗ is linked to an increase in the inward particle pinch and not an increase in core fueling. These observations are not only in agreement with prior modeling scans of how turbulence changes as a function of collisionality and its impact upon the particle fluxes, but also with the multi-machine database (Fable E. et al 2010 Plasma Phys. Control. Fusion 52 015007) (Angioni C. et al 2003 Phys. Rev. Lett. 90 205003). The changes in turbulence across the collisionality scan were captured at large scale by the BES and at smaller scale by the DBS. A comparison with gradient-driven GENE simulations showed similar trends at both scales. Moreover, the changes observed in overall transport are in agreement with gradient-driven TGLF particle flux simulations. This indicates that TGLF/GENE when given the gradients as input, are able to reproduce the experimentally observed turbulence changes.

In this paper, a second order model for Korteweg-type fluids is derived within the GENERIC formalism, whose standard application to Korteweg-type fluids is studied in detail in Part I of this series of papers. The higher-order model contains the second-order gradient of the density in the constitutive relation concerning internal energy, and the resulting Korteweg stress covers the original model proposed by Korteweg. This is in contrast to the model derived by Dunn and Serrin, which lacks the term of the second-order gradient of density. The higher-order model is thermodynamically consistent and includes interstitial working, as in Dunn and Serrin's model. The GENERIC formalism provides a fairly simple derivation of higher-order models for Korteweg-type fluids. Another possible formulation based on the concept of microforces introduced by Gurtin is also presented and discussed in relation to the GENERIC formalism.

This paper aims at the better understanding of the correlations between rotor loads and the wake meandering inside a wind farm. The flow rotor dynamics are simulated by means of Large Eddy Simulations coupled to Actuator Disk models. The wake meandering is captured through a centerline tracking, itself based on the available power in the flow. Two turbulence intensities are investigated, TIs = 6% and 10%. Results show that the yawing moment is very well correlated to the wake movement, even for wind turbines located deeper into the the wind farm. Correlations can also be found between the wake oscillation and the root bending moments. Wake signatures can also be identified from the amplitude of the high-frequency oscillations of the root bending moments; however, the correlation is sometimes less visible, and deviations can be correlated to wind events or wake decay.

Strong field ionisation is known as optical tunnelling of an electron through the barrier created by the laser field and core potential. Time-dependent analytical R-matrix takes advantage of the semiclassical nature of electron dynamics in strong laser fields and naturally incorporates complex-valued trajectories in time propagation. The language of trajectories enables straightforward 'kinematic' interpretation of several new phenomena such as 'inversion' of the conventional propensity rules in photo-ionisation (Barth and Smirnova 2011 Phys. Rev. A 84 063415) and generation of spin-polarised electrons (Barth and Smirnova 2013 Phys. Rev. A 88 013401) during ionisation in strong laser fields. Both phenomena are due to the kinematics of the electron motion under the barrier and were predicted for short-range potentials, i.e. neglecting the electron–core interaction. However, the electron–core interaction can and does affect the kinematics of tunnelling defining the ionisation propensity rules (companion paper I) and spin-polarisation. The latter is the focus of this paper. We consider orbitals with arbitrary angular momentum and extend our results to positively charged ions.

Versão dos autores para esta publicação., In this paper we derive a BGK relaxation model for a mixture of polyatomic gases with a continuous structure of internal energies. The emphasis of the paper is on the case of a quaternary mixture undergoing a reversible chemically reaction of bimolecular type. For such a mixture we prove an H-theorem and characterize the equilibrium solutions with related mass action law of chemical kinetics. Further, a Chapman-Enskog asymptotic analysis is performed in view of computing the first-order non-equilibrium corrections to the distribution functions and investigating the transport properties of the reactive mixture. The chemical reaction rate is explicitly derived at the first-order and the balance equations for the constituent number densities are derived at the Euler level., The paper is partially supported by the Italian National Group GNFM of INdAM and by the Portuguese Funds FCT Project UID/MAT/00013/2013. One of the Authors (AJS) thanks the Italian institution for the financial support given in her visiting professor program in Italy., info:eu-repo/semantics/publishedVersion

In this paper we study the transition to synchrony in an one-dimensional array of oscillators with non-local coupling. For its description in the continuum limit of a large number of phase oscillators, we use a corresponding Ott–Antonsen equation, which is an integro-differential equation for the evolution of the macroscopic profiles of the local mean field. Recently, it was reported that in the spatially extended case at the synchronisation threshold there appear partially coherent plane waves with different wave numbers, which are organised in the well-known Eckhaus scenario. In this paper, we show that for Kuramoto–Sakaguchi phase oscillators the phase lag parameter in the interaction function can induce a Benjamin–Feir-type instability of the partially coherent plane waves. The emerging collective macroscopic chaos appears as an intermediate stage between complete incoherence and stable partially coherent plane waves. We give an analytic treatment of the Benjamin–Feir instability and its onset in a codimension-two bifurcation in the Ott–Antonsen equation as well as a numerical study of the transition from phase turbulence to amplitude turbulence inside the Benjamin–Feir unstable region.

Background-oriented Schlieren (BOS) technique is a recently invented non-intrusive flow diagnostic method which has yet to be fully explored in its capabilities. In this paper, BOS technique has been applied for investigating the general flow field characteristics inside a generic scramjet inlet-isolator with Mach 5 flow. The difficulty in finding the delicate balance between measurement sensitivity and measurement area image focusing has been demonstrated. The differences between direct cross-correlation (DCC) and Fast Fourier Transform (FFT) raw data processing algorithm have also been demonstrated. As an exploratory study of BOS capability, this paper found that BOS is simple yet robust enough to be used to visualize complex flow in a scramjet inlet in hypersonic flow. However, in this case its quantitative data can be strongly affected by 3-dimensionality thus obscuring the density value with significant errors.

The objective of active power control in wind farms is to provide ancillary grid services. Improving this is vital for a smooth wind energy penetration in the energy market. One of these services is to track a power reference signal with a wind farm by dynamically de- and uprating the turbines. In this paper we present a computationally efficient model predictive controller (MPC) for computing optimal control signals for each time step. It is applied in the PArallelized Large-eddy simulation Model (PALM), which is considered as the real wind farm in this paper. By taking measurements from the PALM, we show that the closed-loop controller can provide power reference tracking while minimizing variations in the axial forces by solving a constrained optimization problem at each time step. A six turbine simulation case study is presented in which the controller operates with optimised turbine yaw settings. We show that with these optimized yaw settings, it is possible to track a power signal that temporarily exceeds the power harvested when operating under averaged greedy control turbine settings. Additionally, variations in the turbine's force signals are studied under different controller settings.

Liquid hydrogen has excellent physical properties, high latent heat and low viscosity of liquid, as a coolant for superconductors like MgB2. The knowledge of Departure from Nucleate Boiling (DNB) heat flux of liquid hydrogen is necessary for designing and cooling analysis of high critical temperature superconducting devices. In this paper, DNB heat fluxes of liquid hydrogen were measured under saturated and subcooled conditions at absolute pressures of 400, 700 and 1100 kPa for various flow velocities. Two wire test heaters made by Pt-Co alloy with the length of 200 mm and the diameter of 0.7 mm were used. And these round heaters were set in central axis of a flow channel made of Fiber Reinforced Plastic (FRP) with inner diameters of 8 mm and 12 mm. These test bodies were vertically mounted and liquid hydrogen flowed upward through the channel. From these experimental values, the correlations of DNB heat flux under saturated and subcooled conditions are presented in this paper., Advances in Cryogenic Engineering: Proceedings of the Cryogenic Engineering Conference (CEC) 2017 (previous edition: CEC-2015) 9–13 July 2017, Madison, Wisconsin, USA.

Future devices like JT-60SA, ITER and DEMO require quantitative predictions of pedestal density and temperature levels, as well as inter-ELM and ELM divertor heat fluxes, in order to improve global confinement capabilities while preventing divertor erosion/melting in the planning of future experiments. Such predictions can be obtained from dedicated pedestal models like EPED, and from non-linear MHD codes like JOREK, for which systematic validation against current experiments is necessary. In this paper, we show progress in the quantitative validation of the JOREK code using JET simulations. Results analyse the impact of diamagnetic terms on the dynamics and size of the ELMs, and evidence is provided that the onset of type-I ELMs is not governed by linear MHD stability alone, but that a nonlinear threshold could be responsible for large MHD events at the plasma edge. This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014–2018 under grant agreement No 633053, and from the RCUK Energy Programme (grant number EP/I501045). To obtain further information on the data and models underlying this paper please contact PublicationsManagerccfe.ac.uk. This work used the HELIOS supercomputer (IFERC-CSC), Japan, under the Broader Approach collaboration, implemented by Fusion for Energy and JAEA. The views and opinions expressed herein do not necessarily reflect those of the European Commission or the ITER Organization. The HEC ARCHER computer (UK), as part of the Plasma HEC Consortium EPSRC grant EP/L000237/1, and the MARCONI computer at CINECA in Italy, were also used.

In this paper, an efficient boundary condition is applied to solve the photoionization rate, and a two-dimensional numerical simulation is carried out for the development and propagation of an air streamer at low temperature and sub-atmospheric pressure. The results show that the new boundary condition improves the calculation accuracy, but the influence of photoionization on the streamer discharge process is not obvious. The discharge current in the development of streamer discharge is defined, and the corresponding expression of the positive and negative streamer discharge current is given. The influence of the electric field exceeding the threshold value on the discharge process is preliminarily introduced. In the process of discharge, only the propagation velocity of the streamer is obviously higher than that of normal temperature and pressure, and the trend of the other parameters is basically the same as that described in the previous paper. The above results give us a deeper understanding of the discharge characteristics under low temperature and sub-atmospheric pressure, which has certain significance for the development of aviation and high voltage engineering.

In order to carry out the wind tunnel test of the parachutes in 2.4m×2.4m transonic wind tunnel of CARDC which is located at Mianyang, a supporting mechanism for the attack angle from 0 to 25 degrees at Mach 0.4 and 0.8 is designed and optimized in the present paper. Three section shapes (circle, ellipse, and airfoil) are utilized to analyze the aerodynamic characteristics and mechanical performances of the designed supporting mechanism. The aerodynamic and mechanical simulated results of the three different section shapes are compared and discussed. The optimized design is verified by wind tunnel experiments. The results show that the section shape of circle has the largest modal frequency of first order (53.497Hz), the smallest Mises stress (34.1MPa) and displacement (0.4735mm). It is the best section shape of the three for the supporting mechanism. The investigation in the present paper has a good significant meaning to the testing technologies of the wind tunnel experiments for parachutes.

Quantum Fisher information matrix (QFIM) is a core concept in theoretical quantum metrology due to the significant importance of quantum Cram\'{e}r-Rao bound in quantum parameter estimation. However, studies in recent years have revealed wide connections between QFIM and other aspects of quantum mechanics, including quantum thermodynamics, quantum phase transition, entanglement witness, quantum speed limit and non-Markovianity. These connections indicate that QFIM is more than a concept in quantum metrology, but rather a fundamental quantity in quantum mechanics. In this paper, we summarize the properties and existing calculation techniques of QFIM for various cases, and review the development of QFIM in some aspects of quantum mechanics apart from quantum metrology. On the other hand, as the main application of QFIM, the second part of this paper reviews the quantum multiparameter Cram\'{e}r-Rao bound, its attainability condition and the associated optimal measurements. Moreover, recent developments in a few typical scenarios of quantum multiparameter estimation and the quantum advantages are also thoroughly discussed in this part., Comment: ~70 pages, close to published version, open access

Nowadays, Electrostatic precipitator (ESP) is an important large-scale equipment for reducing dust elimination and reducing pollution in industrial production. As the second working step of ESP, dust charging is very important, and its charge directly affects the subsequent work of the electrostatic precipitator and the dust removal efficiency. In this paper, the charging mechanism of dust particles in the discharge area of ESP is studied. The charge and its influencing factors of dust particles with different particle sizes under different mechanisms are analyzed. The research results have certain effect on how to increase the charge of dust particles. The research in this paper is of great significance to improve the dust removal efficiency of ESP.

Under investigation in this paper is a (3+1)-dimensional generalized wave equation, which is the second equation in the Kadomtsev–Petviashvili hierarchy. Linear partial differential conditions presented in this paper are different from the previous study. Pfaffian and extended Pfaffian solutions with a real function (y) have been obtained based on these linear partial differential conditions, where y is the scaled space coordinate, and compared with the solutions obtained in the previous articles, the advantage of our ones is that (y) could represent an inhomogeneous medium to influence or control the shape of waves. Specific solutions, namely the first- and second-order exact solutions from the Pfaffian and extended Pfaffian solutions are discussed. Discussions indicate that the first- and second-order exact solutions are of the same shape as the corresponding one- and two-soliton solutions on the x−t or z−t plane but of the different shape on the y−t plane.

In this paper we discuss the magnetic Purcell effect of a magnetic dipole near a semi-infinite antiferromagnet. Contrary to the electric Purcell effect, the magnetic one is not so well studied in the literature. We derive the dispersion relation of the surface wave existing at an antiferromagnetic-dielectric interface from the calculation of the reflection coefficient of the structure. After characterizing the surface wave we quantize the electromagnetic vector potential of the surface wave. This allows us to discuss the magnetic Purcell effect via the Fermi golden rule. Copyright (C) EPLA, 2019, BAF and NMRP acknowledge discussions on the topic of this paper with Bruno Amorim and Gil Farias, and the Center of Physics of the University of Minho and the University of Porto for funding in the framework of the Strategic Financing UID/FIS/04650/2013. NMRP acknowledges support from the European Commission through the project "Graphene-Driven Revolutions in ICT and Beyond" (Ref. No. 785219), COMPETE2020, PORTUGAL2020, FEDER and the Portuguese Foundation for Science and Technology (FCT) through project POCI-01-0145-FEDER-028114.

This paper presents a theoretical study of the electrical properties of two different samples of nanofluids (MgO and Si–TiO2 nanoparticles in ethylene glycol EG as the base fluid) using an artificial neural network (ANN) model. Experimental data were extracted from previous experimental studies and used as inputs. A learning ANN method was applied based on the back propagation technique. The optimal network structure, which produces the most acceptable performance, was attained. Electrical conductivity and permittivity in terms of nanoparticle concentration, temperature and frequency were simulated and predicted using the ANN model. A new nonlinear equation describing the behavior of electrical properties of nanofluids was obtained. The simulation results of the ANN model are highly accurate in comparison with experimental data. Predictions of values that are not involved in the experimental data range were carried out and provide excellent results. The mean squared error and regression coefficient were also determined. Their values support the success of the ANN model. The main purpose of the paper is to show the ability and power of an ANN model in estimating and predicting electrical properties of nanofluids. According to this research, the ANN model can be utilized as an efficient tool to predict the electrical properties of nanofluids. It can also achieve great links between practical and theoretical branches.

In the paper by Bazeia D. et al., EPL, 119 (2017) 61002, the authors demonstrate the equivalence between the second-order differential equation of motion and a family of first-order differential equations of Bogomolnyi type for the cases of single real and complex scalar field theories with non-canonical dynamics. The goal of this paper is to demonstrate that this equivalence is also valid for a more general classes of real scalar field models. We start the paper by demonstrating the equivalence in a single real scalar model. The first goal is to generalize the equivalence presented in papers by Bazeia et al. to a single real scalar field model without a specific form for its Lagrangian. The second goal is to use the setup presented in the first demonstration to show that this equivalence can be achieved also in a real multi-component scalar field model again without a specific form for its Lagrangian. The main goal of this paper is to show that this equivalence can be achieved in real scalar field scenarios that can be standard, or non-standard, with single, or multi-component, scalar fields., Comment: 4 pages; version published in EPL