Reconfigurable Surface Micropatterns Based on the Magnetic Field-Induced Shape Memory Effect in Magnetoactive Elastomers

A surface relief grating with a period of 30 µm is embossed onto the surface of magnetoactive elastomer (MAE) samples in the presence of a moderate magnetic field of about 180 mT. The grating, which is represented as a set of parallel stripes with two different amplitude reflectivity coefficients, is detected via diffraction of a laser beam in the reflection configuration. Due to the magnetic-field-induced plasticity effect, the grating persists on the MAE surface for at least 90 h if the magnetic field remains present. When the magnetic field is removed, the diffraction efficiency vanishes in a few minutes. The described effect is much more pronounced in MAE samples with larger content of iron filler (80 wt%) than in the samples with lower content of iron filler (70 wt%). A simple theoretical model is proposed to describe the observed dependence of the diffraction efficiency on the applied magnetic field. Possible applications of MAEs as magnetically reconfigurable diffractive optical elements are discussed. It is proposed that the described experimental method can be used as a convenient tool for investigations of the dynamics of magnetically induced plasticity of MAEs on the micrometer scale.

On the opportunity of Laser Plasma simulation of Plasma Jets formation in moderate magnetic fields ∼ kGs

Today a number of various experiments with Laser-Produced Plasmas (LPP), done at very-high Magnetic Fields (up to B0 > MG) are using to model the physics of Astrophysical and Space Jets, a various processes of their formation and possible long-range propagation at various angles S to magnetic fields. We discuss the opportunity and present the first results of new-type experiments on simulation of Jets with LPP at KI-1 facility of ILP, at moderate magnetic field ∼ kGs, oriented quasi-transverse (S ≍ 600) of LPP-blob expansion (with velocity V 0) relative to B 0. They were done on the base of all our preliminary studies, both at large-scale, high-vacuum chamber (0120 cm of KI-1) and others devices with LPP (oriented earlier at V0 transverse to B0, with $ = 900).

Electrically driven cylindrical free shear flows under an axial uniform magnetic field

We consider a mathematical model of two-dimensional electrically driven laminar axisymmetric circular free shear flows in a cylindrical vessel under the action of an applied axial uniform magnetic field. The mathematical approach is based on the studies by J.C.R. Hunt and W.E. Williams (J. Fluid. Mech., 31, 705, 1968). We solve a system of stationary partial differential equations with two unknown functions of velocity and induced magnetic field. The flows are generated as a result of the interaction of the electric current injected into the liquid and the applied field using one or two pairs of concentric annular electrodes located apart on the end walls. Two lateral free shear layers and two Hartmann layers on the end walls and a quasi-potential flow core between them emerge when the Hartmann number Ha >> 1. As a result, almost all injected current passes through these layers. Depending on the direction of the current injection, coinciding or two counter flows between the end walls are realized. The Hartmann number varies in a range from 2 to 300. When a moderate magnetic field (Ha = 50) is reached, the flow rate and the induced magnetic field flux cease to depend on the magnitude of the applied field but depend on the injected electric current value. Increasing magnetic field leads only to inner restructuring of the flows. Redistributions of velocities and induced magnetic fields, electric current density versus Hartmann number are analyzed. Figs 18, Refs 21.

Reversibility of the Magnetocaloric Effect in the Bean-Rodbell Model

The applicability of magnetocaloric materials is limited by irreversibility. In this work, we evaluate the reversible magnetocaloric response associated with magnetoelastic transitions in the framework of the Bean-Rodbell model. This model allows the description of both second- and first-order magnetoelastic transitions by the modification of the η parameter (η<1 for second-order and η>1 for first-order ones). The response is quantified via the Temperature-averaged Entropy Change (TEC), which has been shown to be an easy and effective figure of merit for magnetocaloric materials. A strong magnetic field dependence of TEC is found for first-order transitions, having a significant increase when the magnetic field is large enough to overcome the thermal hysteresis of the material observed at zero field. This field value, as well as the magnetic field evolution of the transition temperature, strongly depend on the atomic magnetic moment of the material. For a moderate magnetic field change of 2 T, first-order transitions with η≈1.3−1.8 have better TEC than those corresponding to stronger first-order transitions and even second-order ones.

INTERPRETASI POLA PENYEBARAN BATUAN DAN DAERAH TERAKUMULASI AIR TANAH MENGGUNAKAN METODE MAGNETIK DESA OEMATNUNU KABUPATEN KUPANG

Abstrak Telah dilakukan penelitian interpretasi pola penyebaran batuan dan daerah terakumulasi air tanah menggunakan metode magnetik di Desa Oematnunu Kabupaten Kupang. Tujuan penelitian ini untuk mengetahui pola sebaran batuan dan daerah terakumulasinya air tanah serta membuat pemetaannya. Akuisisi data dilakukan dengan Proton Precession Magnetometer (PPM) tipe GSM–19T dan data yang diperoleh berupa nilai medan magnet total serta variasi harian yang diolah serta diinterpretasikan secara kualitatif dan kuantitatif. Interpretasi kualitatif menunjukkan nilai anomali medan magnet total berkisar -250 nT sampai 450 nT dan terbagi atas anomali medan magnet rendah pada kisaran -250 nT sampai -10 nT, anomali medan magnet sedang dengan kisaran nilai -10 nT sampai 110 nT serta anomali medan magnet tinggi di kisaran 110 nT sampai 450 nT. Untuk interpretasi kuantitatif menunjukkan struktur batuan yang diduga berupa batu pasir (aquifer) berada di bagian utara hingga barat laut dengan kedalaman sekitar 0 m - 100 m. Kata kunci: Metode magnetic; suspeptibilitas; akuifer; Oematnunu Abstract Interpretation of rock distribution patterns and areas groundwater accumulation using magnetic methods in Oematnunu Village Kupang District. The purpose of this research was to determine the pattern distribution of rocks and areas of groundwater accumulation and to make the mapping. The acquisition data was carried out by using the GSM-19T Proton Precession Magnetometer (PPM) and the data obtained in the form of total magnetic field values and daily variations were processed and interpreted qualitatively and quantitatively. The qualitative interpretation shows the total magnetic field anomaly values ranging from -250 nT to 450 nT and is divided into low magnetic field anomalies in the range -250 nT to -10 nT, moderate magnetic field anomalies with values ranging from -10 nT to 110 nT, and high magnetic field anomalies. in the range 110 nT to 450 nT. For quantitative interpretation, it shows the rock structure which is thought to be sandstone (aquifer) in the north to the northwest with a depth of about 0 m - 100 m.Keywords: Magnetic method; suspension; aquifer; Oematnunu

Influence of induced magnetic field and slip conditions on convective Prandtl fluid flow over a stretching surface with homogeneous and heterogeneous reactions

PurposeThe aim of the present paper is to investigate the homogeneous and heterogeneous reactions on Prandtl fluid flow at a stretching sheet with an induced magnetic field and slip boundary conditions.Design/methodology/approachThe governing equations include the continuity, induced magnetic field, momentum, energy and homogeneous–heterogeneous equations. Initially, with suitable similarity variables, the governing partial differential equations and converted into a system of ordinary differential equations. Then, the nonlinear ordinary differential equations are solved by a shooting technique with the help of the BVC5C Matlab package.FindingsThe results of the present investigation are presented through graphs for different values of the various parameters. The authors observed that the large values of the stretching ratio and the induced magnetic parameters are moderate magnetic field, velocity and temperature primarily. Also, the authors found the more velocity and temperatures by boosting the slip parameters.Originality/valueIn addition, the values of the skin friction and the rate of heat transfer for various values of physical parameters are tabulated and deliberated in detail.

The 2019 super-Eddington outburst of RX J0209.6−7427: detection of pulsations and constraints on the magnetic field strength

ABSTRACT In 2019 November, MAXI detected an X-ray outburst from the known Be X-ray binary system RX J0209.6−7427 located in the outer wing of the Small Magellanic Cloud. We followed the outburst of the system with NICER, which led to the discovery of X-ray pulsations with a period of 9.3 s. We analysed simultaneous X-ray data obtained with NuSTAR and NICER, allowing us to characterize the spectrum and provide an accurate estimate of its bolometric luminosity. During the outburst, the maximum broad-band X-ray luminosity of the system reached (1–2) × 1039 erg s−1, thus exceeding by about one order of magnitude the Eddington limit for a typical 1.4 M⊙ mass neutron star (NS). Monitoring observations with Fermi/GBM and NICER allowed us to study the spin evolution of the NS and compare it with standard accretion torque models. We found that the NS magnetic field should be of the order of 3 × 1012 G. We conclude that RX J0209.6−7427 exhibited one of the brightest outbursts observed from a Be X-ray binary pulsar in the Magellanic Clouds, reaching similar luminosity level to the 2016 outburst of SMC X-3. Despite the super-Eddington luminosity of RX J0209.6−7427, the NS appears to have only a moderate magnetic field strength.

Momentum-space and real-space Berry curvatures in Mn$_{3}$Sn

Mn_{3}3X (X= Sn, Ge) are noncollinear antiferromagnets hosting a large anomalous Hall effect (AHE). Weyl nodes in the electronic dispersions are believed to cause this AHE, but their locus in the momentum space is yet to be pinned down. We present a detailed study of the Hall conductivity tensor and magnetization in Mn_{3}3Sn crystals and find that in the presence of a moderate magnetic field, spin texture sets the orientation of the kk-space Berry curvature with no detectable in-plane anisotropy due to the Z_6Z6 symmetry of the underlying lattice. We quantify the energy cost of domain nucleation and show that the multidomain regime is restricted to a narrow field window. Comparing the field dependence of AHE and magnetization, we find that there is a distinct component in the AHE which does not scale with magnetization when the domain walls are erected. This so-called ‘topological’ Hall effect provides indirect evidence for a non-coplanar spin components and real-space Berry curvature in domain walls.