Top PDF Radiative processes in an intense magnetic field

Radiative processes in an intense magnetic field

Radiative processes in an intense magnetic field

-iv- 3 Cyclotron emission and absorption in a magnetic field of 108 gauss is studied as a possible mechanism for the observed degree of circular polarization in the optical emission from[r]

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INDUCED MAGNETIC FIELD EFFECTS ON FREE CONVECTIVE FLOW OF RADIATIVE, DISSIPATIVE FLUID PAST A POROUS PLATE WITH TEMPERATURE GRADIENT HEAT SOURCE

INDUCED MAGNETIC FIELD EFFECTS ON FREE CONVECTIVE FLOW OF RADIATIVE, DISSIPATIVE FLUID PAST A POROUS PLATE WITH TEMPERATURE GRADIENT HEAT SOURCE

This paper focuses on the effects of radiation and viscous dissipation heat on a magneto-hydrodynamic, steady mixed convective heat and mass transfer flow over an infinite vertical porous plate with constant suction taking into account the induced magnetic field, in the presence of temperature gradient heat source. The fluid considered is an optically thin gray gas. The present study may have useful applications to several transport processes as well as magnetic materials processing. The analytical results for some particular cases are found in good agreement with Raptis and Perdikis (2003) and Ahamad .S (2010).
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Perturbative analysis of two-temperature radiative shocks with multiple cooling processes

Perturbative analysis of two-temperature radiative shocks with multiple cooling processes

Physical factors other than the cooling processes and geometry also affect the stability properties of a radiative shock. The effects of mass loss from the sides of the post-shock accretion column were examined by Dgani & Soker (1994) by including a sink term in the mass continuity equation. They found that the transverse leakage has a stabilizing effect in the presence of several single power- law radiative cooling processes, and this stabilization was less effective when the cooling had a lower temperature index. ToÂth & Draine (1993) investigated radiative shocks that were subject to thermal instability but were supported by a transverse magnetic field. This magnetic pressure support is decisive in determining the stability properties, rather than the characteristics of the radiative cooling alone.
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The Processes of DNA Replication and the Shortening of the Telomere are Influenced by the Action of the Magnetic Field

The Processes of DNA Replication and the Shortening of the Telomere are Influenced by the Action of the Magnetic Field

While the mapping of the DNA process has opened up a great diversity of opinion, researchers world-wide intended to continue on a wider scale concerning its properties and functions and therefore an intense exploration of the biological and electrical properties and functions of DNA is taking place. The electrical potential of DNA and its nano- scale have given researchers a great hope to investigate and exploit the properties of DNA in an attempt to build nano- electric technology; A-T and C-G base pairs combination aim to replace the semiconductor devices.
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ENTROPY GENERATION OF UNSTEADY RADIATIVE CASSON FLUID FLOW THROUGH POROUS MEDIUM OVER A PERMEABLE STRETCHING SURFACE WITH INCLINED MAGNETIC FIELD

ENTROPY GENERATION OF UNSTEADY RADIATIVE CASSON FLUID FLOW THROUGH POROUS MEDIUM OVER A PERMEABLE STRETCHING SURFACE WITH INCLINED MAGNETIC FIELD

The study of heat transfer and entropy generation over stretching sheet for under different physical conditions has attracted the attention of researcher’s due to their various applications in engineering/industrial disciplines. These applications include extrusion processes, wire and fiber coating, polymer processing, food-stuff processing, and design of heat exchangers and chemical processing equipment, in glass fiber, metal extrusion, materials handling conveyors, production of plastic and rubber, cooling, temperature exchangers, and turbo machinery. Due to the presence of temperature gradient every thermal process has some kind of irreversibility and entropy generation is the measure of irreversibility of the system. It causes efficiency loss and reduction of quality. Chauhan et al. (2011a, 2011b, 2011c) investigated second law analyzed during compressible fluid flow in a partially filled channel, stretching sheet and annular pipe with a porous medium and MHD effect. Jain et al. (2017a) examined entropy Generation for MHD Radiation effect on viscous fluid in a partially filled channel. Entropy generation minimization has been investigated by several researchers several researchers (Bejan (1996), Jangili et al. (2016), Qing et al. (2016) and Bhatti et al. (2016)) for both Newtonian and non-Newtonian fluid over different geometries
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Magnetic field swimmer positioning

Magnetic field swimmer positioning

metre swimming pool by the smartphone used in our experiment, placed flat on the water surface and towed from one end to the other at constant speed. Figure 1(b) shows the same pool 6 months later, in a different lane in the pool, at a faster speed. The magnetic signature does not change over time or lane change, except for a constant offset due to the lane change. Fig. 1(c) and 1(d),1(e) show magnetic signatures of two other pools. The pool in Fig. 1(d) & (e) is interesting, as it shows a different signature when swum in opposite directions. All other pools tested showed the same profile in both directions. We believe this to be due to the movable depth floor of this pool, which uses two lines of scissor jacks beneath the floor. Perturbation of the magnetic field measurement for the vertical line of jacks changes depending on the magnetometer’s orientation relative to it, which differs when swimming one direction or the other, unlike orientation relative to bottom of a standard pool.
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Hubbard ladders in a magnetic field

Hubbard ladders in a magnetic field

We acknowledge interesting discussions with A. Ho- necker and K. Le Hur. This work has been partially sup- ported by the EC TMR Programme Integrability, non perturbative effects and symmetry in quantum field the- ory (A.D.M. and P.S.). The research of D.C.C. is par- tially supported by CONICET and Fundaci´ on Antorchas, Argentina (grant No. A-13622/1-106). A.D.M. was also supported in part by the DFG under the Gerhard-Hess program and P.S. by NSERC of Canada.

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The Magnetic Field in the Stability  of the Stars

The Magnetic Field in the Stability of the Stars

In order to make an adequate theoretical analysis of the problem, it will be assumed that they are gaseous ob- jects where the self-generated magnetic field has lost much of its original intensity but, that in the position of maximum compression keeps enough of it, so as to reduce the oscillation preventing the final collapse. Next, and with the help of radiation pressure and that of hot gases, that diminished magnetic field bounces, starting the subsequent expansion. If it is admitted that the Cepheids are in a stage of their evolution such that the fluid that forms them is no longer totally supported by the superstructure formed by the magnetic lines of force, it can be stated that the important dynamic agents acting on them are the huge gravitational force as well as the combined pressures of radiation and hot gases. Subject to these dynamic conditions, the Cepheids variables oscillate around some equilibrium position losing and recovering brightness alternately, as they expand and contract themselves with a noticeable regularity and with a perfectly determined period.
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ELECTRIC AND MAGNETIC FIELD MANAGEMENT

ELECTRIC AND MAGNETIC FIELD MANAGEMENT

Natural earth processes and thus climate and human environment are influenced by the Sun–Earth-Moon system which encompasses the atmosphere, hydrosphere and the lithosphere [1]. An accelerated charged particle produces electromagnetic field. In other words, artificial electrical facilities produce power frequency electromagnetic fields. The present article presents that those power frequency fields may disturb working of sensitive electronic equipment, human’s biological system. Here it is discussed that the non-ionizing Extremely Low frequency Electromagnetic Fields (ELF EMF) produced due to electrical utilities affects the environment. The influence of ELF EMF around power frequency sources has been evaluated in history & at present, as well and it is found that they have significant effect on technical and health aspects. However, professional organizations like Electrical Power Research Institute of India (EPRI) are also carrying out the field management research. Several research programmes have been initiated on long run to identify exact association of power frequency fields with electrical and electronic instruments and human civilization. The objective of present article is to examine and identify methods to reduce the contact level to electromagnetic fields around the electrical utilities, electronic devices and environment. In the present study, an attempt has been made to analyse the different Maxwell’s equations and their applications, effects as well as EMF MGT in different electrical, electronic and biogenic systems. Present article deals almost all the possible issues in concern to power frequency ELF EMF management.
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Electrodynamics in a Strong Magnetic Field

Electrodynamics in a Strong Magnetic Field

mass-shell, it gives the index of refraction of the strong-field region, which is then evaluated numerically and plotted. This makes it possible for photon-splittin[r]

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Magnetic field dependence of the maximum magnetic entropy change

Magnetic field dependence of the maximum magnetic entropy change

When dealing with the matter it is essential to distinguish between the two paradigmatic cases in room-temperature refrigeration, namely, between refrigerants experiencing a first-order phase transition and those which undergo a phase transition of second order. In the former case the growth of (− S) max takes place in weak to moderate magnetic fields

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Magnetohydrodynamics modeling of coronal magnetic field and solar eruptions based on the photospheric magnetic field

Magnetohydrodynamics modeling of coronal magnetic field and solar eruptions based on the photospheric magnetic field

the MHD relaxation method constructed in the modern MHD scheme (Feng et al. 2010), successfully captured the sigmoid structure of the magnetic field observed before the flare and demonstrated that the eruption was driven by the torus instability (Fig. 8a). An important advan- tage of this study seems to be that the same algorithm was used in both the NLFFF and MHD simulations. Kliem et al. (2013) also studied this eruption by setting the NLFFF as the initial condition of their MHD sim- ulation (Fig. 8b). The NLFFF was reconstructed using the magnetic field observed on 8 April 2010, using the flux rope insertion and the magnetofrictional method. The NLFFF of this active region was thoroughly stud- ied by Su et al. (2011). Kliem et al. (2013) found a critical value of the axial flux in the flux rope deter- mined the stability. They reported that the criteria for the onset of a flare is that the axial flux be in the range of 5 × 10 20 to 6 × 10 20 Mx; in this case, the decay index is in the range of 1.3 to 1.8. For this eruption, the simulation results were in good agreement with some of the observations, such as those during the initial ris- ing phase leading to the eruption. Amari et al. (2014) also successfully demonstrated a flux tube eruption in their MHD simulations, as shown in Fig. 8c. The flux tube was reconstructed by using the Grad-Rubin type method (Amari and Aly 2010) combined with the pho- tospheric magnetic field observed by the Hinode solar optical telescope (SOT; Tsuneta et al. (2008)) 6 h before the X3.4-class flare in AR10930 at 02:40 UT on 13 Decem- ber 2006. The authors found that 6 h before the flare, the NLFFF was destabilized with flux cancellation, the gas motion in characteristic of a sunspot moat flow or photospheric turbulent diffusion, and this resulted in the eruption. On the other hand, 2 days before the flare, the NLFFF predicted no eruption for the same situation. The authors pointed out the importance of the formation of a significantly large flux tube and the moving out from equilibrium.
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Iron Electrodeposition in a Magnetic Field

Iron Electrodeposition in a Magnetic Field

constant value around - 0.98 V, as soon as the measurement was started. But the potential value clearly depended on the magnetic field. It shifted toward more anodic direction with increasing in the B intensity. For example, it changed from - 0.985 V vs. Ag/AgCl at 0 T to -0.975 V at 5 T. The potential difference is probably caused by the ohmic resistance rather than the kinetic factor. The rest potential relating to the equilibrium state of the iron electrodeposition/dissolution reaction has been reported to be unchanged in a high magnetic field [30]. Probably the magnetic field energy is not as large as that of the electric field. Therefore the electrochemical reaction controlled by the charge transfer is hardly influenced by the magnetic field. On the other hand, MHD convection generated in a magnetic field can remove the hydrogen gas bubble sticking the electrode surface [19] and reduce the void fraction of the electrolyte between the working and reference one [19, 31]. The present result demonstrates that the MHD convection can actively pump the solution as well as the natural convection induced by the uprising gas bubbles.
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Radiative Processes in Astrophysical Gases: From the Intergalactic and Interstellar Medium to Exoplanetary Atmospheres

Radiative Processes in Astrophysical Gases: From the Intergalactic and Interstellar Medium to Exoplanetary Atmospheres

As a first step in our clump-finding procedure, we find the total angular momentum of gas particles within 10 (physical) kpc from the center of mass of the galaxy and determine the Euler angles of the face-on projection in the simulation’s coordinate system. Next, we form a two-dimensional 10 kpc × 10 kpc grid in the face-on projection, with cell size of 50 pc. We project the location of every particle within 10 kpc radius from the center of the galaxy on to the grid and for the sake of computational convenience deposit the entire particle into the corresponding cell (i.e. ignoring the particle’s SPH kernel). We construct the gas surface density map by dividing the entire gas mass contained in a cell with its surface area. Using all cells with non-zero surface density, we find the mean value of gas surface density and the standard deviation. We use these two values in our definition of clumps– clumps correspond to regions which are at least one standard deviation above the mean surface density. The threshold values are chosen in this way because they provide the best match to what we visually identify as clumps in the gas surface density maps. Appendix 3.B contains more details on how changing the threshold value may affect our results. Finally, we smooth the gas surface density field using a Gaussian filter with the standard deviation of 50 pc (full width at half-maximum of ∼ 120 pc) and the radius of the Gaussian kernel of 450 pc. The ∼ 100 pc scale roughly coincides with the lower end of the reported size distribution of observed giant clumps at high redshift. This smoothing scale should be large enough to mitigate the effect of ignoring the SPH kernel in creating gas surface density maps. To find clumps in the gas surface density map, we make use of a Python package astrodendro5 to compute dendrograms – trees of hierarchical structure in our simulated data. To find clumps, we need to specify three parameters: (1) the minimum value of gas surface density which is used as a threshold to define clumps, which we set to be equal to one standard deviation above the mean surface density of all non-empty (unsmoothed) cells in that snapshot; (2) the minimum difference in the surface density between a large structure and any substructure within it, which we set to 10% of the mean surface density (this parameter is not very important in our particular study, since we primarily care about large clumps, and not so much
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Effects of interactions on the relaxation processes in magnetic nanostructures

Effects of interactions on the relaxation processes in magnetic nanostructures

increasing exchange strength. 'Contributions to the experimental damping constant due to inhomogeneous line broadening cannot be ruled out, however, these are expected to be consistent between samples; the major eect of reducing the thickness of the grain boundaries is the variation in the exchange coupling as shown in the hysteresis behavior. We have constructed a realistic model of granular media using the Landau-Lifshitz-Bloch model. By simulating the optical FMR technique to probe relaxation processes we have determined how the damping is aected by the key parameters governing the interactions (exchange and saturation magnetisation). The model calculations show a decrease of eective damping with increasing exchange, consistent with the experimental data for small exchange. It is argued that the increase in damping for the largest exchange eld, arising in a lm without exchange coupling, is due to the onset of a dierent reversal mechanisms involving domain nucleation and propagation. For practical perpendicular recording media, which are more exchanged decoupled, the decrease in damping with exchange strength predicted by the model calculations is the most likely scenario. Further investigations of the phenomenon using spin wave theory provide further insight and ascribe the reduction in damping due to increasing intergranular exchange as arising from a reduction in the degeneracy of nite k-vectors with the frequency of the k=0 (ferromagnetic resonance) mode. These calculations show a direct correlation between the degeneracy and the damping shown by the numerical model with a similar trend for xed exchange stiness and varying M s . Our numerical
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Tripolar electric field Structure in guide field magnetic reconnection

Tripolar electric field Structure in guide field magnetic reconnection

Our finding may have applications in space observations. For instance, it may be used to infer the strength of a guide field, which is usually difficult to pinpoint solely from mag- netic field measurements. The strength of a guide field is im- portant because it determines the degree of electron magne- tization as well as the electron energization efficiency in the vicinity of the diffusion region (Pritchett, 2006; Scudder and Daughton, 2008). With the measurement of this new convec- tive electric field, we may be able to deduce the guide field strength based on the linear relation derived in this study. Hence this could be a supplemental way to infer the guide field strength.
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Diffusion processes modeling in magnetic resonance imaging

Diffusion processes modeling in magnetic resonance imaging

The ADC is a relative value and depends on the equip- ment characteristics, scan parameters, and image quality [1, 2]. Therefore, ADC values between different regions of interest should be compared only within a single study [3, 4]. Currently, there is no unitary standard for DWI despite a large number of publications and the widespread utilization. Incorrect field uniformity correc- tion may result in incomplete fat suppression, signal summation, and the appearance of artifacts. Also, in some, tissue’s perfusion effects are present. They are as- sociated with the blood flow in the capillary bed and can be conditionally considered as accelerated diffusion of water molecules. The isotropic diffusion restriction asso- ciated with the multicomponent environment (macro- molecules, cellular structure) is poorly studied and difficult to simulate, although it occupies a significant place in clinical practice. Some publications introduce mathematical models describing the relationship be- tween ADC, signal-to-noise ratio, and other technical characteristics [2].
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Magnetodisc modelling in Jupiter's magnetosphere using Juno magnetic field data and the paraboloid magnetic field model

Magnetodisc modelling in Jupiter's magnetosphere using Juno magnetic field data and the paraboloid magnetic field model

In this paper we consider magnetic field measurements made by the Juno spacecraft in Jupiter’s magnetosphere, paying particular attention to the middle magnetosphere measure- ments where Jupiter’s magnetodisc field plays a major role. The structure and properties of the Jovian magnetodisc have been described in many papers, starting from the first space- craft flybys of Jupiter, discussed for example by Barbosa et al. (1979) and references therein. In particular, the em- pirical magnetodisc model presented by Connerney et al. (1981), derived from Voyager-1 and -2 and Pioneer-10 ob- servations, has been employed as a basis in numerous sub- sequent studies, including predictions for the Juno mission by Cowley et al. (2008, 2017). Detailed physical models have also been constructed by Caudal (1986), who derived
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Effects of interactions on the relaxation processes in magnetic nanostructures

Effects of interactions on the relaxation processes in magnetic nanostructures

exchange strength. Contributions to the experimental damping constant due to inhomogeneous line broadening cannot be ruled out, however, these are expected to be consistent between samples; the major effect of reducing the thickness of the grain boundaries is the variation in the exchange coupling as shown in the hysteresis behavior. We have constructed a realistic model of granular media using the Landau-Lifshitz-Bloch model. By simulating the optical FMR technique to probe relaxation processes we have determined how the damping is affected by the key parameters governing the interactions (exchange and saturation magnetization). The model calculations show a decrease of effective damping with increasing exchange, consistent with the experimental data for small exchange. It is argued that the increase in damping for the largest exchange field, arising in a film without exchange coupling, is due to the onset of a different reversal mechanisms involving domain nucleation and propagation. For practical perpendicular recording media, which are more exchange decoupled, the decrease in damping with exchange strength predicted by the model calculations is the most likely scenario. Further investigations of the phenomenon using spin- wave theory provide further insight and ascribe the reduction in damping due to increasing intergranular exchange as arising from a reduction in the degeneracy of finite k vectors with the frequency of the k = 0 (ferromagnetic resonance) mode. These calculations show a direct correlation between the degeneracy and the damping shown by the numerical model with a similar trend for fixed exchange stiffness and varying M s . Our
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A flexible, on-line magnetic spectrometer for ultra-intense laser produced fast electron measurement

A flexible, on-line magnetic spectrometer for ultra-intense laser produced fast electron measurement

We have developed an on-line magnetic spectrometer to measure energy dis- tributions of fast electrons generated from ultra-intense laser-solid interactions. The spectrometer consists of a sheet of plastic scintillator, a bundle of non- scintillating plastic fibers, and an sCMOS camera recording system. The design advantages include on-line capturing ability, versatility of detection arrangemen- t, and resistance to harsh in-chamber environment. The validity of the instru- ment was tested experimentally. This spectrometer can be applied to the char- acterization of fast electron source for understanding fundamental laser-plasma interaction physics and to the optimization of high-repetition-rate laser-driven applications.
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