Magnetic Form Research Articles

Magnetic Curvature and Existence of a Closed Magnetic Geodesic on Low Energy Levels

Abstract To a Riemannian manifold $(M,g)$ endowed with a magnetic form $\sigma $ and its Lorentz operator $\Omega $ we associate an operator $M^{\Omega }$, called the magnetic curvature operator. Such an operator encloses the classical Riemannian curvature of the metric $g$ together with terms of perturbation due to the magnetic interaction of $\sigma $. From $M^{\Omega }$ we derive the magnetic sectional curvature $\textrm{Sec}^{\Omega }$ and the magnetic Ricci curvature $\textrm{Ric}^{\Omega }$ that generalize in arbitrary dimension the already known notion of magnetic curvature previously considered by several authors on surfaces. On closed manifolds, under the assumption of $\textrm{Ric}^{\Omega }$ being positive on an energy level below the Mañé critical value, with a Bonnet–Myers argument, we establish the existence of a contractible periodic orbit. In particular, when $\sigma $ is nowhere vanishing, this implies the existence of a contractible periodic orbit on every energy level close to zero. Finally, on closed oriented even dimensional manifolds, we discuss about the topological restrictions that appear when one requires $\textrm{Sec}^{\Omega }$ to be positive.

Magnetically‐Programmed Instability‐Driven Pattern Transformations in Soft Materials

AbstractA class of transformable materials is introduced with magnetic defect‐defined switchable configurations. The soft material can be magnetically‐programmed to transform into various encoded patterns utilizing the rich interplay of magnetic interactions and instability phenomenon. The strategy allows us to break the limit of admissible configurations of the instability‐induced patterns that dictate the post‐transformation behavior. The phenomenon is experimentally realized in a material system consisting of periodically distributed magnetic inclusions in a soft matrix. The programmable magnetic interactions between the inclusions act as smart defects redirecting the material transformations to targeted geometric configurations. Moreover, the role of magnetic spacing and field strength is systematically investigated to map the transition between mechanically‐dominant and magnetics‐dominant instability patterns. Lastly, the idea of reconfigurable material design is showcased by embedding binary information in magnetic form, which can be read out through the unique repositioning of inclusions via the applied mechanical deformation.

Supercondutividade magnética

This paper serves as a primer on superconductivity, inviting students for further investigation. Although the theory of superconductivity is a many-body quantum theory, here we take a more didactic route based on thermodynamics and symmetry. We briefly survey the more than a century-old field and provide a one-sentence definition of a superconductor. Surprisingly, many textbooks lack such a definition, usually introducing superconductors through their properties rather than by definition. We explain the concept of an order parameter, symmetry, and symmetry breaking. Based on this, we clarify the difference between conventional and unconventional superconductors, which is frequently a confusing topic for newcomers. We provide the reader with a taste of a current research topic in the field of unconventional superconductivity and magnetism. For this, we explain the concept of time-reversal symmetry breaking in condensed matter physics, which is usually associated with a form of magnetism. Here, we show that time-reversal symmetry might be broken in superconductors, leading to magnetic properties due to superconductivity itself. For this purpose, we utilize the method of the Ginzburg-Landau theory for phase transitions. We discuss the field of chiral superconductivity and guide the interested reader to further study.

The symplectic cohomology of magnetic cotangent bundles

We construct a family version of symplectic Floer cohomology for magnetic cotangent bundles, without any restrictions on the magnetic form, using the dissipative method for compactness introduced by Groman (2023). As an application, we deduce that if N is a closed orientable manifold and is a magnetic form that is not weakly exact, then the \pi_1 1-sensitive Hofer–Zehnder capacity of any compact set in the magnetic cotangent bundle determined by \sigma is finite.

Green, Eco-Friendly, Highly Biocompatible and Bioactive Nanocomposite-Based Biopolymers Loaded with ZnO@Fe3O4 Nanoparticles.

Biocompatibility is a major concern for promising multifunctional bioactive materials. Unfortunately, bioactive materials lack biocompatibility in some respects, so active ingredient formulations are urgently needed. Bimetallic nanoparticles have demonstrated drawbacks in stabilized biocompatible formulations. This study examined the preparation of biomaterial-based multifunctional biopolymers via an eco-friendly formulation method using ultrasound. Bimetallic zinc oxide/iron oxide (magnetic form) nanoparticles (ZnO@Fe3O4NPs) were formulated using casein and starch as capping agents and stabilizers. The formulated nanocomposite was characterized using ultraviolet-visible spectroscopy (UV-vis), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermal gravimetric analysis (TGA), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HR-TEM). Herein, the formulated nanocomposite was shown to have a thermally stable nanostructure, and the bimetallic ZnO@Fe3O4 NPs were measured as 85 nm length and 13 nm width. Additionally, the biocompatibility test showed its excellent cytocompatibility with Wi 38 and Vero normal cell lines, with IC50 550 and 650 mg/mL, respectively. Moreover, the antimicrobial activity was noted against six pathogens that are represent to the most common pathogenic microbes, with the time required for killing of bacteria and unicellular fungi being 19 h and 61 h for filamentous fungi with remarket an excellent antioxidant activity.

Analytical Model for Electromagnetic Performance Prediction of IPM Motors Considering Different Rotor Topologies

Aiming at the problem of long computation time of finite element analysis (FEA) and poor calculation universality of existing analytical models, this paper proposes a general hybrid analytical model to predict the no-load and load performance of interior permanent magnet motors with any slot-pole combination, where the form of magnet can be V-shape, U-shape or flat-shape. The magnets are equivalent correspondingly according to the rotor structure in the modeling process and the motor can be divided into eight types of subdomains, the no-load and load magnetic field of the motors can be obtained by solving the equations established by boundary conditions, where the nonlinear of core is calculated by local MEC. The proposed model can be used to calculate the air-gap magnetic field, no-load back electromotive force, cogging torque and electromagnetic torque of IPM motors with different rotor topologies. The effectiveness of the proposed model is verified by both FEA and experiments. Compared with FEA, this model can consume less time with the acceptable accuracy, which brings convenience to the design and optimization of related types of motors.

Analytic characterization of sub-Alfvénic turbulence energetics

Magnetohydrodynamic (MHD) turbulence is a cross-field process relevant to many systems. A prerequisite for understanding these systems is to constrain the role of MHD turbulence, and in particular, the energy exchange between kinetic and magnetic forms. The energetics of strongly magnetized and compressible turbulence has so far resisted attempts to understand them. Numerical simulations reveal that kinetic energy can be orders of magnitude higher than fluctuating magnetic energy. We solved this lack-of-balance puzzle by calculating the energetics of compressible and sub-Alfvénic turbulence based on the dynamics of coherent cylindrical fluid parcels. Using the MHD Lagrangian, we proved analytically that the bulk of the magnetic energy transferred to kinetic energy is the energy that is stored in the coupling between the ordered and fluctuating magnetic field. The analytical relations are in strikingly good agreement with numerical data, up to second-order terms.

Neurostimulation for dry eye disease.

To review the neuroanatomy and physiology of the basal and reflex tearing and present the available and developing therapies using the concept of neurostimulation in dry eye disease (DED). The most prevalent current DED treatments seek to supplement low tear volume and tear components or reduce inflammation. Neurostimulation is a unique approach gaining momentum in recent years, geared toward increasing the production of all basal tear components by stimulating the nerves responsible for producing the various tear components. The neuroanatomy of the lacrimal unit provides several possible access points to stimulate tear production through two arms of the sensory trigeminal nerves. Modes of stimulation include chemical or energy in electrical or magnetic form. Research thus far has shown that neurostimulation can achieve lacrimal, goblet cell, and meibomian gland stimulation. Subjectively it improves symptoms of DED. Clinically, neurostimulation has improved the signs and symptoms of DED by increasing basal tear production and tear volume. Neurostimulation using electrical, mechanical, or chemical means is a novel concept to increase tear production and was demonstrated to be an effective, safe, and well-tolerated method for managing DED.

Micro Forming and its Applications: An Overview

A Micro forming was primarily developed in order to view the usage and significance of micro metal forming technology. It is implemented for the manufacturing and production of micro metallic devices like micro pump, micro gears (Polyoxymethylene polymer), Biodegradable implants (Polylactic acid) etc. The die assembly is provided with a DLC (Diamond like coating) coating during work study to resolved small size dimensional accuracy issue and enhanced tribological properties. Various High Energy Metal Forming processes (HERF) is discussed like ultrasonic vibration, explosive forming, magnetic forming, electro hydraulic forming, ultrasonic vibration and heating process for enhancement in formability and accuracy to the product of micro scale dimension. The detailed review of Micro forming and its applications in various fields that utilized the various high energy processes is discussed in this paper. Keywords: Biodegradable, Tribological Properties, HERF (High Energy Rate forming), Formability.

Effect of magneto-active filling on the effectiveness of methane fermentation of dairy wastewaters

ABSTRACT The goal of this study was to determine the effectiveness of methane fermentation in dairy wastewaters in terms of the volume and qualitative composition of biogas produced in an anaerobic reactor with magneto-active filling (MAF) mounted in the zone of hydrolysis and acidogenesis. Experiments were conducted on the fractional-technical scale in a vertical fermentation reactor with a labyrinth flow. Synthetic dairy wastewaters prepared based on milk powder were used as a substrate. The analyzed filling was made of plastic covered with iron and copper powders and was additionally equipped with fluid magnetizers (FM) in the form of neodymium magnets. The study demonstrated that MAF incorporation into the technological system significantly improved the effectiveness of biogas production, increased methane concentration and lowered the content of hydrogen sulfide in gaseous metabolites of fermentative bacteria. A significant increase was also observed in the effectiveness of COD removal from dairy wastewaters. The reported experiments proved a correlation between the effectiveness of methane fermentation and the number of MAF elements introduced into the anaerobic reactor.

Integrated study on obtaining oxide pellets from brown iron ore

Introduction. Currently, the main raw materials for the production of cast iron and steel at metallurgical plants are iron concentrates obtained from magnetite (ferrous) quartzites, titanium-magnetite, and skarn ores. The existing technologies for processing these types of ores, which mainly include separation processes based on magnetic properties, size, separating of equally falling grains, and surface wettability allow us to produce both ordinary iron concentrates and high quality ones. The use of such schemes in the processing of brown iron ore does not allow obtaining high rates of mineral concentration. One of the methods for processing this type of ore is a roasting-magnetic scheme, which allows converting weakly magnetic (non-magnetic) forms of iron into strongly magnetic ones. Research objective is to develop the mode of magnetizing roasting of brown iron ore, technology of concentrating of the burn-out product in order to obtain iron concentrate and oxide pellets. Methods of research. The duration of heat treatment of the charge consisting of iron ore from the Abail deposit and coal from the Ekibastuz deposit and the required mass fraction of solid carbon contained in the coal are determined. Technological studies of the roasted product were carried out in order to obtain a concentrate with a mass fraction of iron at least 67%. According to the developed technology, a batch of iron concentrate was developed in order to obtain and study raw and oxide pellets. Results. The modes of magnetizing roasting of brown iron ore from the Abail deposit and cooling of the roasted material have been developed. A scheme for mineral processing of the roasted material has been developed in order to obtain a concentrate with at least 67% of iron mass fraction. The process of obtaining strong raw and roasted pellets from iron concentrate is studied. Conclusions. The developed mode of magnetizing roasting of the charge consisting of coal and ore from the Abail deposit makes it possible to obtain a roasted product with a degree of magnetization of 93%. The using of desliming of the roasted product makes it possible to remove magnetic floccules from the processing that reduce the concentrate quality, and to obtain a concentrate with a mass fraction of iron of at least 67% in the last stage of magnetic separation. From the iron concentrate, it is possible to obtain oxidized pellets with a strength of at least 200 kg/pellet at temperature of pellets firing of 1325 °C.

СИНТЕЗ ДОПЛЕРОГРАМ КВАЗІВЕРТИКАЛЬНОГО ЗОНДУВАННЯ ІОНОСФЕРИ ДОПЛЕРІВСЬКИМ ВЧ РАДАРОМ ІЗ РОЗНЕСЕНИМ ПРИЙМАННЯМ

Purpose: The ionospheric channel is widely used for the communication, radio navigation, radar, direction finding, radio astronomy, and remote radio probing systems. The radio channel parameters are characterized by nonstationarity due to the dynamic processes in the ionosphere, and therefore their study is one of the topical problems of space radio physics and earth-space radio physics of geospace. This work aims at presenting the results of synthesis of temporal variations in the Doppler spectra obtained by the Doppler probing of the ionosphere at vertical and quasi-vertical incidence. Design/methotology/approach: One of the most effective methods of ionosphere research is the Doppler sounding technique. It has a high time resolution (about 10 s), a Doppler shift resolution (0.01–0.1 Hz), and the accuracy of Doppler shift measurements (~0.01 Hz) that permits monitoring the variations in the ionospheric electron density (10–4–10–3) or the study of the ionospheric plasma motion with the speed of 0.1-1 m/s and greater. The solution of the inverse radio physical problem, consisting in determination of the ionosphere parameters, often means solving the direct radio physical problem. In the Doppler sounding technique, it belongs with the construction of variations in Doppler spectra and comparing them with the Doppler spectra measurements. Findings: For the radio wave ordinary component, three echoes being produced by three rays are observed. Influence of the geomagnetic fi eld and large horizontal gradients in the electron density of δ≥10 % give rise to complex ray structures with caustic surfaces. The ionospheric disturbances traveling along the magnetic meridian form the skip zones. The longitudinal and transverse displacement of the ray reflection point attains a few tens of kilometers along the vil. Haidary to vil. Hrakove quasi-vertical radiowave propagation path, for which the great circle range is 50 km. For the vertical incidence, the signal azimuth at the receiver coincides with the traveling ionospheric disturbance azimuth. The synthesis of temporal variations in the HF Doppler spectra has been made and compared with the temporal variations in the Doppler spectra recorded with the V. N. Karazin Kharkiv National University radar. The estimate of δ=15 % obtained confirms the existence of large horizontal gradients in electron density. Conclusions: Temporal variations in Doppler spectra and in azimuth have been calculated for the vertical and quasi-vertical incidence with allowance for large horizontal gradients of the electron density caused by traveling ionospheric disturbances. Key words: ionosphere, Doppler sounding at oblique incidence, synthesis of temporal variations in HF Doppler spectra, traveling ionospheric disturbances, electron density

Radial spatiotemporal evolution of rf magnetic field and plasma current in a very-high-frequency plasma source over a wide range of plasma density and pressure.

We present detailed spatiotemporal measurements of rf magnetic fields and plasma conduction current as well as the corresponding plasma density profiles when very-high-frequency 100-MHz waves are introduced to a parallel plate plasma. The magnetic probe, optical emission, and plasma absorption probe measurements support a model in which the interaction of high-frequency waves with the moving plasma sheath at specific phases of the very high frequencies (VHF) period leads to local reversals in the vertical rf electric field which can lead to conduction current reversals and circulations. The presence of current reversals and circulation correlate with measured plasma uniformity. In particular, measured electric field and current reversals coincide with the strongly center-peaked plasma density profiles frequently observed in VHF plasma. The magnitude of the center peak increases with the number and magnitude of the current reversal cells. The scale length of the current reversal cells is on the order of what is expected for plasma surface waves. Measurements indicate that plasma conductivity is the common scaling factor for both plasma uniformity and the circulation. The propagation of high-frequency waves and the generation of rf current reversal in one phase of the rf cycle rather than another results in the appearance of harmonics in Fourier decomposed magnetic probe wave forms. These harmonics turn out not to be actual waves or evidence of standing waves at these frequencies but rather consequences of packets of wave propagation that occur periodically.

Lower hybrid current drive in a tokamak for correlated passes through resonance

Standard quasilinear descriptions are based on the constant magnetic field form of the quasilinear operator so improperly treat the trapped electron modifications associated with tokamak geometry. Moreover, successive poloidal transits of the Landau resonance during lower hybrid current drive in a tokamak are well correlated, and these geometrical details must be properly retained to account for the presence of trapped electrons that do not contribute to the driven current. The recently derived quasilinear operator in tokamak geometry accounts for these features and finds that the quasilinear diffusivity is proportional to a delta function with a transit or bounce averaged argument (rather than a local Landau resonance condition). The new quasilinear operator is combined with the Cordey (Nucl. Fusion, vol. 16, 1976, pp. 499–507) eigenfunctions to properly derive a rather simple and compact analytic expression for the trapped electron modifications to the driven lower hybrid current and the efficiency of the current drive.

Size and Phase Purity–Dependent Microstructural and Magnetic Properties of Spinel Ferrite Nanoparticles

The urea-assisted combustion pathway was selected to synthesize different spinel ferrite nanoparticles (SFNPs). Synthesized spinel ferrite nanoparticles MFe2O4 (M = Zn, Ni, Cu and Co) were investigated using various techniques likely to be used by XRD, SEM, TEM and VSM to study their structural, morphological and magnetic behaviours. The crystalline sizes of the spinel ferrite nanoparticles were calculated from the major XRD peak (311) which confirms that the prepared spinel powders are in nanoscale (21–55 nm) range. Secondary peaks free XRD spectrum of Cu, and Ni ferrite nanoparticles exhibit pure single-phase cubic spinel structures. Few secondary impurities are observed in Zn and Co ferrite nanoparticles due to the presence of α-Fe2O3. Spherical-shaped nanoparticles have been examined by TEM. Room temperature magnetic measurements of different spinel ferrite nanoparticles suggest that the prepared spinel ferrites exhibit different forms of magnetism that are strongly affected by phase purity and particle size.

Laboratory disruption of scaled astrophysical outflows by a misaligned magnetic field

The shaping of astrophysical outflows into bright, dense, and collimated jets due to magnetic pressure is here investigated using laboratory experiments. Here we look at the impact on jet collimation of a misalignment between the outflow, as it stems from the source, and the magnetic field. For small misalignments, a magnetic nozzle forms and redirects the outflow in a collimated jet. For growing misalignments, this nozzle becomes increasingly asymmetric, disrupting jet formation. Our results thus suggest outflow/magnetic field misalignment to be a plausible key process regulating jet collimation in a variety of objects from our Sun’s outflows to extragalatic jets. Furthermore, they provide a possible interpretation for the observed structuring of astrophysical jets. Jet modulation could be interpreted as the signature of changes over time in the outflow/ambient field angle, and the change in the direction of the jet could be the signature of changes in the direction of the ambient field.

Grid Integration of a Residential PV-based Hybrid Renewable Energy System Using High-Frequency Multi-winding Transformer

In this paper, a topology of a residential hybrid renewable energy system based on a high-frequency multi-winding transformer is introduced and analyzed. The system includes a PV and a wind-turbine as renewable energy sources, a battery as energy storage and their energies are integrated through a high-frequency transformer. In fact, the transformer integrates the energies in a magnetic form and also isolates the system inputs and outputs. The integrated output from renewables and battery is a DC high-voltage and is transferred to a grid-connected inverter to supply the residential loads and also injected to the grid on request. A phase shift control technique is used to control the power flow between the sources, storage and loads. Detail of the control system is presented and also validated through experimental tests.

Macroscopic manifestation of domain-wall magnetism and magnetoelectric effect in a N\xe9el-type skyrmion host

We report a magnetic state in GaV4Se8 which emerges exclusively in samples with mesoscale polar domains and not in polar mono-domain crystals. It is manifested by a sharp anomaly in the magnetic susceptibility and the magnetic torque, distinct from other anomalies observed also in polar mono-domain samples upon transitions between the cycloidal, the Néel-type skyrmion lattice and the ferromagnetic states. We ascribe this additional transition to the transformation of distinct magnetic textures, confined to polar domain walls (DW), to the ferromagnetic (FM) state. The emergence of these DW-confined magnetic states is likely driven by the mismatch of different spin spirals, hosted by the adjacent domains. A clear anomaly in the magneto-current indicates that the DW-confined magnetic states also have strong contributions to the magnetoelectric response. We expect polar DWs to commonly host such confined magnetic edge states and, thus, offer a fertile ground to explore novel forms of magnetism.

Probing of mechanical behaviour, quantum mechanism of spin exchange and magnetism of SnV2O4 and SnCr2O4 spinel oxides by DFT

ABSTRACT The spinel oxides SnV2O4 and SnCr2O4 are analysed to reveal the mechanical, electronic and magnetic properties using Wien2k software. The negative formation energy and positive elastic constants shows the studied materials are thermodynamically and mechanically favorable. In ferromagnetic (FM) state more energy release than antiferromagnetic (AFM) state. The above room temperature magnetism is elaborated by spin polarisation, exchange mechanism, direct Δx(d) and indirect Δx(pd) exchange energy and crystal field energy Δx(CF). The shifting of magnetic moment form V/Cr sites to Sn/V sites illustrate the ferromagnetism is caused by pd hybridisation that affects the net orientation of electrons spin and hence, it increases the importance of the materials for spin-dependent electronic applications.

Exploring Relationship of Family Variables on Intrapersonal Intelligence of Young Adolescent Girls

There is a wide gap between the popularity of intrapersonal intelligence as a concept and its application in society. People often misinterpret intrapersonal intelligence for a form of magnetism or gregariousness. They don't perceive it as something that can be improved and they identify it as, “either one has it or one doesn't”. By understanding what intrapersonal intelligence really is and how we can administer it in our lives, we can commence to leverage all if that intelligence, education and experience stored over a period of time. Similar idea was proposed by Howard Gardner in the theory of multiple intelligences, where human intelligence differentiates into specific 'modalities', rather than seeing intelligence as dominated by a single general ability. Ecological Systems Theory bestowed by Bronfenbrenner (1979) discribes that there are five systems arranged from the closest to the individual to the farthest and these systems directly or indirectly affects the human development. The present study was designed to study the level of intrapersonal intelligence and impact of various human ecological factors affecting it. To achieve this aim, standardized Multiple Intelligence Assessment Tool developed by Kaur (2006) was administered on a study sample consisting of 200 students from higher secondary schools of both areas of Mahendergarh (Haryana), i.e., rural and urban. Results revealed that parental occupation, caste and discipline by the parents were found to be significantly associated with intrapersonal intelligence of the respondents. Yet other human ecological factors such as frequency of visit to relatives/ friends by respondents, exposure to mass media, type of people living in nearby area and availability of newspaper at home had no effect on intrapersonal intelligence of the young adolescents.