Sabine Ogier‐Collin, Philipp Ulbl, Wladimir Zholobenko
et al.
ABSTRACT Accurate modeling of turbulent transport in magnetic confinement fusion devices requires extending first‐principles gyrokinetic simulations from the core to the edge and scrape‐off layer (SOL), where additional physics—particularly plasma–neutrals interactions—must be included. Neutrals in these regions reshape radial profiles, influencing gradient‐driven instabilities, and modifying transport across the separatrix and in the SOL. We present a tightly coupled scheme between a continuum gyrokinetic plasma model and a simplified fluid model for neutrals. Specifically, we extend the full‐, electromagnetic, collisional code GENE‐X with a neutrals density evolution equation, where charge exchange is treated as a diffusive process. This hybrid approach represents a first step toward a consistent fluid treatment of neutrals within gyrokinetic plasma simulations. We focus here on the derivation and implementation of Krook‐type source terms for ionization, recombination, and associated radiative losses. These operators are constructed to ensure strict conservation of mass, total momentum, and total energy, including kinetic, binding, and radiative components. The coupling is verified in terms of its numerical convergence and in three‐species relaxation tests (with electrons, deuterium ions, and neutral deuterium), with a particular focus on its impact on plasma moments, as well as, the distribution functions. Results indicate that even with a simplified neutrals model, the coupling introduces kinetic modifications to the plasma, whose influence on macroscopic quantities will need to be assessed in forthcoming turbulence simulations.
Field-aligned current (FAC) is of importance in energy transfer from space to the Earth. The Region 1 current, which flows in the polar region, is the most significant one, but the generation region and mechanism are long-lasting questions. By using the global magnetohydrodynamics (MHD) simulation, we traced packets of the Alfvén waves traveling parallel to the magnetic field in the rest frame of moving plasma. The low-latitude magnetospheric boundary layer is found to be the major generation region, where the plasma pulls newly reconnected magnetic field lines. The generation region is far from the original magnetic field lines extending from the Region 1 FAC in the ionosphere because of low Alfvén velocity in the outer magnetosphere and beyond. The Region 1 FACs are surrounded by the integral curves of the Poynting vector (called S-curve). The S-curve shows a helix with its center moving toward the Earth. The Region 1 FACs, circular motion of plasma (probably related to the magnetospheric convection), and transfer of magnetic energy to the Earth are closely related with each other. The new method can be widely applied to search for the generation region of FACs and useful for better understanding of the dynamics of the magnetosphere.
Ismail Benchebiba, Mohamed Mostefaoui, Ahmed Nour El Islam Ayad
et al.
A one-dimensional fluid model is developed to analyze the effects of temperature and pressure on the characteristics of radiofrequency dielectric barrier discharge plasma. The model is run for an argon-helium mixture, in order to plot the maximum peak values of electron temperature, electric field strength and various species densities including electrons, atoms, ions and excited species as a function of plasma temperature in the range 300-550K, and as a function of plasma pressure in the range 0.2-1atm. The results show that an increase in the plasma temperature leads to an increase in electron temperature and electron density, and a decrease in electric field strength and non-electron species densities. In addition, an increase the plasma pressure leads to a decrease in electron temperature, an increase in electric field strength, and an increase in all species densities.
Lane formation dynamics of driven three-dimensional pair-ion plasmas (PIP) is investigated. Extensive Langevin dynamics simulation is performed to study the influence of an external electric field on the behaviour of the PIP system. In our model, one half of the particles are pushed into the field direction by an external force $\boldsymbol {F}_{A}$ while the other half are pulled into the opposite direction by an external force $\boldsymbol {F}_{B}$. We show that if $\boldsymbol {F}_{A}$ and $\boldsymbol {F}_{B}$ are parallel, the system undergoes a non-equilibrium phase transition from a disordered state to a lane formation state parallel to the field direction with increasing field strength. The lanes are formed by the same kind of particles moving collectively with the field. The lane order parameter has been implemented to detect phase transition. Further, we show the lane formation in the presence of a time-varying external electric field. In particular, the effect of parallel forces are investigated. Unlike the previously reported two-dimensional case (Sarma, et al., Phys. Plasmas, vol. 27, 2020, p. 012106; Baruah, et al., J. Plasma Phys., vol. 87, issue 2, 2021, p. 905870202), for the time-varying electric field case, spontaneous formation and the breaking of lanes are not observed for all values of applied frequencies; however, the orderness varies and spontaneous formation and breaking of lanes is observed for values close to a critical frequency $\omega _c$. Further, some aspects of the lane formation dynamics of a PIP system are also studied in the presence of an external magnetic field, which reveals that the presence of an external magnetic field accelerates the lane formation process and introduces a drift of the lanes in a direction perpendicular to both electric and magnetic fields.
Hydrodynamic instabilities widely exist in the fields of weapon physics, aerospace, and inertial confinement fusion (ICF). The understanding of the mechanism of hydrodynamic instabilities is of great importance for engineering applications. In ICF, the target pellet is driven by high energy laser, resulting in high density and high temperature plasma impacting the interface, causing Richtmyer-Meshkov instability (RMI). Previous studies have shown that the magnetic field perpendicular to the incident shock front can inhibit the development of plasma RMI, but the research on the influence of magnetic field on RMI coupling with secondary shock is less. In this paper, the discrete Boltzmann method based on mesoscopic non-equilibrium statistical physics is used to study the RMI and magnetic field control method under secondary shock, including the hydrodynamic non-equilibrium (HNE) effects, thermodynamic non-equilibrium (TNE) effects, and critical magnetic field for controlling. The results show that the non-organized momentum flux is most pronounced near the shock wave, but weaker in the rest of the flow field. The non-organized energy flux is most pronounced near the disturbance interface, but weaker in the rest of the flow field. The magnetic field perpendicular to the incident shock front always inhibits the development of the interface, and the applied magnetic field helps to relax the shock wave strength requirements for secondary shock.
We present a study of the linear properties of the ion-temperature gradient (ITG) modes with collisions modelled for the first time by the linearized gyrokinetic (GK) Coulomb collision operator (Frei et al., J. Plasma Phys., vol. 87, issue 5, 2021, 905870501) in the local limit. The study is based on a Hermite–Laguerre polynomial expansion of the perturbed ion distribution function applied to the linearized GK Boltzmann equation, yielding a hierarchy of coupled equations for the expansion coefficients, referred to as gyromoments. We explore the collisionless and high-collisional limits of the gyromoment hierarchy analytically. Parameter scans revealing the dependence of the ITG growth rate on the collisionality modelled using the GK Coulomb operator are reported, showing strong damping at small scales as the collisionality increases and, therefore, the need for a steeper gradient for the ITG onset at high collisionality to overcome the finite Larmor radius (FLR) collisional stabilization. The predictions on the ITG growth rate by the GK Coulomb operator are compared with other collision operator models, such as the Sugama, the Dougherty, as well as the momentum-conserving pitch-angle scattering and the Hirshman–Sigmar–Clarke collision operators derived for the first time in terms of gyromoments. The importance of FLR terms in the collision operators is pointed out by the appearance of a short wavelength ITG branch when collisional FLR terms are neglected, this branch being completely suppressed by FLR collisional effects. Energy diffusion is shown to be important at high collisionality and at small scale lengths. Among the GK collision operators considered in this work, the GK Sugama collision operator yields, in general, the smallest deviation compared with the GK Coulomb collision operator, while the largest deviations are found with the GK Dougherty operator. Convergence studies of the gyromoment method are reported and show that the drifts associated with the gradient and curvature of the magnetic field increase the required number of gyromoments at low collisionality. Nevertheless, the low number of gyromoments necessary for convergence at high collisionality constitutes an attractive numerical and analytical feature of the gyromoment approach to study the plasma dynamics in the boundary of fusion devices.
GaAs-based nanowires are among the most promising candidates for realizing a monolithical integration of III-V optoelectronics on the Si platform. To realize their full potential for applications as light absorbers and emitters, it is crucial to understand their interaction with light governing the absorption and extraction efficiency, as well as the carrier recombination dynamics determining the radiative efficiency. Here, we study the spontaneous emission of zincblende GaAs/(Al,Ga)As core/shell nanowire arrays by $\mu$-photoluminescence spectroscopy. These ordered arrays are synthesized on patterned Si(111) substrates using molecular beam epitaxy, and exhibit an exceptionally low degree of polytypism for interwire separations exceeding a critical value. We record emission spectra over more than five orders of excitation density for both steady-state and pulsed excitation to identify the nature of the recombination channels. An abrupt Mott transition from excitonic to electron-hole-plasma recombination is observed, and the corresponding Mott density is derived. Combining these experiments with simulations and additional direct measurements of the external quantum efficiency using a perfect diffuse reflector as reference, we are able to extract the internal quantum efficiency as a function of carrier density and temperature as well as the extraction efficiency of the nanowire array. The results vividly document the high potential of GaAs/(Al,Ga)As core/shell nanowires for efficient light emitters integrated on the Si platform. Furthermore, the methodology established in this work can be applied to nanowires of any other materials system of interest for optoelectronic applications.
AdvancedCeramics are gaining a foothold in the lightweight aerospace, electronics, and structural engineering component markets. These ceramics could be extensively used in modern industry, such as ballistic body armour, ceramic carbon fibre composite automoti ve brakes, diesel particulate filters, prosthetic limbs, piezoelectric sensors, and computer memory products, due to their higher compressive strength, resistance to abrasion, lower thermal expansion coefficient, higher density, and chemical stability. Ceramics are notori ously difficult to handle due to the increased hardness and brittleness. Low electric-conductive ceramics, on the other hand, can be machined using the EDM technique, in which plasma energy is used to accurately remove the material by continuous sparking between the surface and the electrode submerged in dielectric. It is observed that EDM can be applied to the material having electrical resistivity below 100 ?.cm. Most recently it has been observed that EDM could be applied to insulating ceramics too. An attempt has been made in this paper to critically review the machining of ceramics by the EDM process.
Ammonia is a critically important industrial chemical and is largely responsible for sustaining the growing global population. To provide ammonia to underdeveloped regions and/or regions far from industrial production hubs, modular systems are targeted that often involve unconventional production methodologies. These novel approaches for ammonia production can tap renewable resources at smaller scales located at the point of use while decreasing the CO2 footprint. Plasma-assisted catalysis and electrochemical ammonia synthesis have promise owing to their atmospheric pressure and low-temperature operation conditions and the ability to construct units at scales desired for modularization. Fundamental and applied studies are underway to assess these processes, although many unknowns remain. In this review, we discuss recent developments and opportunities for unconventional ammonia synthesis with a focus on plasma-stimulated systems. Expected final online publication date for the Annual Review of Chemical and Biomolecular Engineering, Volume 11 is June 8, 2020. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
This article is an extended research on the linear elasticity of glucose with the author’s defined GH-modulus or M2 cited in Reference 7 (Part 1 or his paper no. 346). The main purpose of this study is twofold. First, it is to study the biomedical meaning of the GH modulus which depends on a patient’s severity of type 2 diabetes (T2D) over a period of time. Second, it is to discover when its linear elastic features would appear, under what kind of conditions, and which easier path for patients to utilize this for their daily glucose control. Here is the simple linear formula previously defined in References 2, 3, and 4 for predicting the postprandial plasma glucose (PPG): Predicted PPG= (FPG* 0.97) + (carbs/sugar intake grams * M2) - (post-meal waking K-steps * 5) In Reference 7 (paper No. 346), the author connected the biomedical glucose prediction equation with a basic concept of stress and strain in engineering, along with the Young’s modulus of engineering strength of materials. Using his collected 11,580 data of glucose, food, and exercise, he has demonstrated that a “pseudo-linear” relationship existing between the carbs/sugar intake amount which is similar to the “stress” part on the engineering system; and the incremental PPG amount which is similar to the “strain” part of the engineering system. A newly defined coefficient of “GH-modulus” (the M2 multiplier for carbs/sugar intake amount) is remarkably similar to the role of Young’s modules on relating stress and strain on the subject of engineering strength of materials. During his “better controlled” period of diabetes from 7/1/2015 to 10/13/2020, his average PPG is 116 mg/dL which is below 120 mg/dL and located within the normal range from diabetes concerns. Only within this “better-controlled” glucose range, the relationship between carbs/sugar intake and incremental PPG would then be “linear” or “pseudo-linear”. Otherwise, for severe T2D patients who has elevated PPG level above 180 mg/dL (hyperglycemia) most of the time and then suddenly decreased to below 70 mg/dL (hypoglycemia or insulin shock), the relationship between food and PPG would then follow a nonlinear plastic pattern where the defined linear relationship would not be applicable. By 2019, approximately 6% of worldwide population (or 463 million people) have diabetes. Although he believes that his linear elastic glucose behavior of GH modulus is only applicable for patient’s glucose levels below 180 mg/ dL and above 70 mg/dL, but it is already a wide enough range for lots of diabetes patients to use. In regard to nonlinear plastic zone, more hyperglycemic cases and associated data are required to collect and then conduct a further complex analysis. At least, this linear elastic glucose behavior is the first stage of getting sufficient information to move further into a more complicated nonlinear plastic glucose zone. Based on two diabetes patients’ data, for either fixed M2 or variable M2 values, a linear relationship between carbs/ sugar intake amount and incremental PPG amount have been observed. This defined GH-modulus (i.e. M2 value) is easier to be applied over a reasonable long period, for example, either 3 months or 4 months in order to match with the lab-tested HbA1C value. Since blood and liver cells are organic material, the GH-modulus changes according to the severity of a patient’s diabetes conditions. However, the author would like to recommend using a fixed GH-modules or M2 value within a period of 3 to 4 months due to the simplicity of calculation and practical usage. The author has spent four decades as a practical engineer, but he does understand the importance of basic concepts, sophisticated theories, and practical equations which serve as the necessary background of all kinds of applications. Therefore, he focused his time and energy to investigate glucose related subjects using a variety of methods he learned in the past, including this particularly interesting stress-strain approach. In addition, he understood the importance and urgency in helping diabetes patients to control their glucoses. That is why, over the past few years, he has continuously simplified his findings regarding diabetes and derived more useful formulas or practical tools in meeting the general public’s interest on controlling chronic diseases and their complications to reduce pain and death probability.
In this paper, the characteristics of laser-induced plasmas are studied by investigation of the spectral line features in laser-induced breakdown spectroscopy (LIBS) experiments. The plasma is produced by focusing of a Nd:YAG laser on standard Al-alloy samples at 30 mJ energy. Here, with the assumption of having a homogenous plasma and by using a semiemperical technical method, the plasma temperature is calculated by the proposal of a new two-lines method. Moreover, by utilizing some theoretical equations, the plasma parameters and the self-absorption magnitude are evaluated according to the radiative transfer equations in local thermodynamic equilibrium (LTE) conditions. The main advantages of this method are that without discrimination between thin plasmas and thick ones, and as well as without straight quantification of the degree of self-absorption, the plasma temperature can be calculated. The results showed that determination of the intensities of the spectral lines, transition parameters, and Stark broadening parameter is adequate for plasma characterization in a typical LIBS experiment.
Visco-resistive magnetohydrodynamic (MHD) computations with the NIMROD code (Sovinec C R et al 2004 J. Comput. Phys. 195 355) are applied to a model tokamak configuration that is subjected to induced vertical displacement. The modeling includes anisotropic thermal conduction within an evolving magnetic topology, and parameters separate the Alfvénic, resistive-wall, and plasma-resistive timescales. Contact with the wall leads to increasingly pervasive kink and tearing dynamics. The computed 3D evolution reproduces distinct thermal-quench and current-quench timescales, a positive bump in plasma current, and net horizontal forcing on the resistive wall. The MHD dynamo effect electric field, E f = − V ˜ × B ˜ , is analyzed for understanding the nonlinear effects of the fluctuations on the spreading of parallel current density and the resulting bump in plasma current. Forces on the resistive wall are consistent with Pustovitov’s analysis (Pustovitov V D 2015 Nucl. Fusion 55 113032); the plasma remains in approximate force-balance with the wall, so net force is accurately computed from integrating stress over the wall’s outer surface. Improvements to the modeling that are needed for predictive simulation of asymmetric vertical displacement events are discussed.
From the data bank of livestock census in India, the total sheep in the country is 65 million numbers in 2012, declined by about 9.09% over census 2007. The total sheep contributes around 12.7% of the total livestock population. Karnataka (South Indian province) contributes second highest in sheep population first is Andra Pradesh. Growth and development are continuous and dynamic processes require integration of numerous physiological functions, they influenced by nutrition, efficiency of metabolism, respiration, hormonal regulation, immune responses, physiological status, and maintenance of homeostasis. The physiological and endocrinological events involved in the onset of puberty and estrus cycle are of primary importance. Appropriate thyroid glands function and activity of thyroid hormones (TH) are considered crucial to sustain the productive performance in domestic animals (growth, milk, hair fiber production) and circulating TH can be considered as indicators of the metabolic and nutritional status of the animals. A total of 24 female Bannur sheep (age from 3.5 month to 11 month) were used in this study. Blood samples were collected from the jugular vein of 24 clinically healthy animals in four groups along with body weight also recorded (GI (>3-5 m), GII (>5-7m), GIII (>7-9m) and GIV (>9-11)). Triidothyroxine and Thyroxine estimation was done using immunoassay test kit method. In the present study, the mean serum Triidothyronine (ng/mL) levels ranged from 1.17 ± 0.01 to 1.80 ± 0.01 ng/mL. Positive correlation was observed between the levels of thyroid hormones (T3) and the age of animal and body weight gain in Bannur ewes. The mean serum thyroxin (μg/dl) levels ranged from 3.98 ± 0.18 to 7.61 ± 0.05 μg/dl. T4 concentrations elevated at premature phase, where during fattening period growing lambs needed to increase the basal metabolic rate, protein synthesis in their muscles and more of energy to achievements these biological functions, therefore plasma T4 and glucose concentrations increased in the two last months of fattening period. The age of sheep influenced statically significantly all the investigated parameters. Blood thyroid hormones levels are considered to be good indicators of the nutritional status of an animal. K e y w o r d s Serum thyroxin, Plasma, Lambs, Hormones and immunoassay Accepted: 26 July 2018 Available Online: 10 August 2018 Article Info International Journal of Current Microbiology and Applied Sciences ISSN: 2319-7706 Volume 7 Number 08 (2018) Journal homepage: http://www.ijcmas.com Int.J.Curr.Microbiol.App.Sci (2018) 7(8): 4628-4635