Action Of Field Research Articles

Nickel ferrite decorated noble metal containing nitrogen-doped carbon nanotubes as potential magnetic separable catalyst for dinitrotoluene hydrogenation

The 2,4-toluenediamine (TDA) is one of the most important chemicals in the polyurethane industry, produced by the catalytic hydrogenation of 2,4-dinitrotoluene (DNT). The development of novel catalysts that can be easily recovered from the reaction mixture is of paramount importance. In our work, a NiFe2O4/N-BCNT supported magnetic catalyst was prepared by a modified coprecipitation method. The catalyst support alone also showed activity in the synthesis of TDA. Platinum nanoparticles were deposited on the catalyst support surface by a fast, relatively simple, and efficient sonochemical method, resulting in a readily applicable catalytically active system. The prepared catalyst exhibited high activity in hydrogenation tests, which was proved by the exceptionally high DNT conversion (100% for 120 min at 333 K) and TDA yield (99%). Furthermore, the magnetic catalyst can be easily recovered from the reaction medium by the action of an external magnetic field, which can greatly reduce catalyst loss during separation.

Black hole outflows initiated by a large-scale magnetic field

Context. Accreting black hole sources show variable outflows at different mass scales. For instance, in the case of galactic nuclei, our own Galactic center Sgr A* exhibits flares and outbursts in the X-ray and infrared bands. Recent studies suggest that the inner magnetospheres of these sources have a pronounced effect on these emissions. Aims. Accreting plasma carries the frozen-in magnetic flux along with it down to the black hole horizon. During the infall, the magnetic field intensifies, and this can lead to a magnetically arrested state. We investigate the competing effects of inflows at the black hole horizon and the outflows that develop in the accreting plasma through the action of the magnetic field in the inner magnetosphere, and we determine the implications of these effects. Methods. We started with a spherically symmetric Bondi-type inflow and introduced a magnetic field. In order to understand the influence of the initial configuration, we started the computations with an aligned magnetic field with respect to the rotation axis of the black hole. Then we proceeded to the case of magnetic fields that are inclined to the rotation axis of the black hole. We employed the 2D and 3D versions of the code HARM for the aligned field models and used the 3D version for the inclined field. We compared the results of computations with each other. Results. We observe that the magnetic lines of force start to accrete with the plasma while an equatorial intermittent outflow develops. This outflow continues to push some material away from the black hole in the equatorial plane, while some other material is ejected in the vertical direction from the plane. In consequence, the accretion rate fluctuates as well. The direction of the black hole spin prevails at later stages. It determines the flow geometry near the event horizon. On larger scales, however, the flow geometry remains influenced by the initial inclination of the field.

The effect of hydrostatic pressure, temperature and impurity factor on linear and nonlinear optical properties of InxGa1-xAs tuned quantum dot with modified Gaussian potential under the action of a vertical magnetic field

This study presents a detailed theoretical analysis of the effects of hydrostatic pressure, temperature, impurity factors, and external electric fields on the optical properties of InxGa1-xAs tuned quantum dot. A uniform magnetic field, directed perpendicular to the quantum dot plane, is applied. The system is excited using a monochromatic electromagnetic field, considering electron intersubband transitions. Energy levels and wave functions are determined using the parabolic band approximation and effective mass approximation. The linear and nonlinear optical absorption coefficients and refractive index changes are computed using the compact-density matrix approach and the iterative method. Numerical results indicate that the peaks of the linear and nonlinear optical absorption coefficients and refractive index changes shift towards lower energies (red shift) and higher energies (blue shift) under varying hydrostatic pressure, temperature, and impurity factor strength. Additionally, the peak values of the absorption coefficients and refractive index changes increase or decrease based on these parameter variations. These results have significant implications for the design and optimization of quantum dot-based optoelectronic devices.

Математическое моделирование мягкого экзоскелета из магнитно-реологических модулей с интеллектуальным управлением

The article considers a fundamentally new generation of soft exoskeletons based on magnetic rheological modules. A model of an exoskeleton link with adjustable rigidity is proposed, for which a system of differential equations of motion is compiled. A model of an exoskeleton for human lower extremities, composed of modules with magnetic rheological fluid, has been developed. The problems of kinematics and dynamics that arise when controlling the movement of an exoskeleton are presented. A block diagram of an algorithm for controlling the movement of an exoskeleton has been developed, solving control problems taking into account neural network methods. A qualitative study by analytical methods of the proposed mathematical model of an exoskeleton with links with adjustable stiffness is carried out. The use of regulation of the rigidity of the links of the exoskeleton modules in the necessary way will make it possible to create devices that are comfortable for the user, both from the physiological and psychological points of view. Soft exoskeletons will be in demand in many industries and medicine. The use of electromagnetic actuators, which, as a rule, have smaller dimensions and energy consumption, an almost instantaneous response speed in comparison with pneumatic drives, hydraulic drives and electric drives, is promising and technically, energetically, environmentally, economically more acceptable. Under the action of electric or magnetic fields, the stiffness of electroelastic and magneto-rheological materials can change by more than an order of magnitude. This makes it possible to create exoskeleton links with adjustable stiffness. Regulation of the rigidity of the elements of the exoskeleton modules in real time is a complex control task. Therefore, exoskeleton motion control requires the development of adaptive type algorithms based on a neuro-fuzzy approach, using information received from feedback. Neural network algorithms for self-learning in the process of functioning are a logically expedient part of a soft bionic exoskeleton. Also, as a necessary component of the exoskeleton, along with the actuator part, a sensor system is needed with sensitive sensors for the user’s neuromuscular impulses and various sensors for position, speed, acceleration, force, moment of force of the exoskeleton. A comprehensive study of scientific and technical problems of the functioning of the model of the magnetic-rheological medium, exoskeleton modules and their compilation into a single multi-link structure, its movement using the technology of modern mathematical modeling was carried out. The construction of neuro-fuzzy control systems for soft exoskeletons is described as part of the development of new mathematical methods for modeling complex technical objects using modern mechatronics and cyborgics.

Spin torque-driven electron paramagnetic resonance of a single spin in a pentacene molecule.

Control over quantum systems is typically achieved by time-dependent electric or magnetic fields. Alternatively, electronic spins can be controlled by spin-polarized currents. Here, we demonstrate coherent driving of a single spin by a radiofrequency spin-polarized current injected from the tip of a scanning tunneling microscope into an organic molecule. With the excitation of electron paramagnetic resonance, we established dynamic control of single spins by spin torque using a local electric current. In addition, our work highlights the dissipative action of the spin-transfer torque, in contrast to the nondissipative action of the magnetic field, which allows for the manipulation of individual spins based on controlled decoherence.

Electromigration effect of nano-Fe3O4 in concrete under chloride erosion environment

In order to improve the effectiveness of electro-migration repair technology, researchers have introduced new materials to address the adverse effects of electrochemical repair on concrete, such as interface softening in reinforced concrete. In this study, a dispersed solution of nano-Fe3O4 was selected as the anode electrolyte. Concrete specimens were subjected to electric treatment for repair, and the entry of nano particles into the concrete under the action of an external electric field was investigated. The microstructure and mechanical properties of the repaired concrete material were analyzed using techniques such as potentiodynamic polarization curve, chemical titration, scanning electron microscopy, energy spectrum analysis, mercury intrusion porosimetry, and pull-out test. The results showed that after 15 days of electrochemical nano-repair, the passivation film on the steel reinforcement was repaired, resulting in a 57 % reduction in corrosion rate and prevention of further chloride ingress, thus improving the corrosion resistance of the reinforcement. Furthermore, the electrochemical nano-repair did not affect the outward migration of chloride ions from the concrete, with a chloride removal efficiency as high as 72.6 %. When the treatment duration was 15 days and the current density was 3 A/m2, the bond strength exhibited the greatest improvement, with an increase of 99.15 %. Compared to electrochemical chloride removal, the electrochemical nano-repair reduced the porosity in the middle and inner layers by 17.8 % and 14.8 %, respectively. Microstructural analysis revealed that the electromigrated nano-Fe3O4 particles were uniformly dispersed within the concrete, replacing harmful byproducts and filling the pores.

Simulation and experimental study on precise aeration and electric field for synergistic demulsification of emulsified oil

Numerical simulations of the deformation, aggregation, and migration processes of emulsified oil droplets under the influence of a multiphase field were conducted using COMSOL software. Combined with laboratory experiments, an existing process was improved and optimized by introducing the concept of "precise aeration." The results indicate that aeration can enhance the efficiency of electrochemical demulsification, with the gas field accelerating the deformation, aggregation, and migration processes of the oil droplets. Leveraging the numerical simulation results, laboratory experiments were conducted to optimize the aeration intensity and duration, which were reduced to 1.5 L/min and 60 min. At this point, the oil content and chemical oxygen demand (COD) of the emulsified oil wastewater were only 4.98 mg/L and 101 mg/L, respectively. The demulsification mechanism was analyzed, revealing that under the combined action of the electric field and gas field, oil droplets underwent a polarization reaction and were aggregated into larger droplets. Aeration expedited the weakening of the mechanical strength at the oil-water interface of the droplets, which significantly improved the demulsification, coalescence, and flotation removal of the emulsified oil droplets. This study holds significant importance for the process improvement and mechanistic analysis of electrochemical demulsification for oil removal.

High-voltage AlGaN/GaN heterojunction lateral photoconductive semiconductor switch based on semi-insulating 4H-SiC substrate

A novel high-power AlGaN/GaN heterojunction lateral photoconductive semiconductor switch (PCSS) based on the SiC substrate is proposed, which achieves high dark-state resistance characteristics by groove etching. Under the action of biased electric field and incident laser, a high concentration of two-dimensional electron gas is formed at the heterojunction interface. The photo-generated free carriers transport along the heterojunction interface, which improves the utilization efficiency of photo-generated carriers. Moreover, the simulation of the current density distribution of the PCSS provides theoretical support for this phenomenon. Compared with the conventional GaN PCSS, the power capacity and conduction characteristics are further improved. The test results show that the output current of the device increases significantly after the introduction of the AlGaN/GaN heterojunction. At the biased voltage of ∼34 kV, the maximum output current of the AlGaN/GaN PCSS reaches 205 A.

Quantum anomalous Hall effect and half-metal state of valley in VGe2N4 monolayer

Understanding the physical properties of valley and achieving its half metal state is the key to applying the valley degree of freedom. In this study, by first-principles calculations, the VGe2N4 monolayer is demonstrated as a ferrovalley semiconductor with a valley polarization of 48 meV. Furthermore, two means of compressive strain and regulating the electron correlation effect are explored to achieve the half-metal state of valley in the present VGe2N4 monolayer. Interestingly, topological phase transitions from ferrovalley, half-valley metal to quantum anomalous Hall effect state appear with the increase of strain in the VGe2N4 monolayer. More interestingly, half-metal state of valley induced by electronic correlation or strain can occur in VGe2N4 monolayer, which means 100% spin-polarized valley carriers will be excited. In this case, with the action of an in-plane electric field, the VGe2N4 monolayer will present an anomalous valley Hall effect. Based on these results, the related valleytronics devices are designed. Our work emphasizes the entire process from ferrovalley to topological phase transition, and a method for achieving the half-metal state of valley is proposed. Our finding is of great significance for the development of valleytronics.

Desorption of Positive and Negative Ions from Areoles of Opuntia microdasys Cactus at Atmospheric Pressure: Cactus-MS.

The areoles and spines of cacti can be used to desorb ions of ionic liquids (ILs) by the mere action of an electric field into the atmospheric pressure (AP) interface of a mass spectrometer. The small cactus species Opuntia microdasys bears numerous very fine hairs on its areoles and tiny sharp spines that appeared suited to serve as needle electrodes sharp enough for field desorption of ions to occur. In fact, positive and negative ions of four ILs could be desorbed by a process analogous to AP field desorption (APFD). In contrast to APFD where activated field emitters are employed, the ILs were deposited onto one or two adjacent areoles by applying 1-3 µL of a dilute solution in methanol. After evaporation of the solvent, the cactus was positioned next to the spray shield electrode of a trapped ion mobility-quadrupole-time-of-flight instrument. Desorption of IL cations and IL anions, respectively, did occur as soon as the electrode was set to potentials in the order of ±4.5 kV, while the cactus at ground potential was manually positioned in front of the entrance electrode to bring the areole covered with a film of the sample into the right position. Neither did mixing of ILs occur between neighboring areoles nor did the cactus suffer any damage upon its use as a botanical field emitter.

Experimental Study on the Combined Effect of Electromagnetic and Electrochemical Processes on Descaling and Anticorrosion

In this study, a circulating water experimental system was constructed to investigate the scale inhibition, scale removal, corrosion inhibition, and disinfection effects of industrial circulating water under the combined action of electromagnetic and electrochemical fields. The influence of these effects on water quality parameters and their scale inhibition and corrosion inhibition effects on hanging plate experiments were examined. Qualitative and quantitative analyses of scale samples were conducted using XRD (X-ray diffraction) and SEM (scanning electron microscopy), along with the evaluation of changes in water quality parameters (such as conductivity, hardness, Chemical Oxygen Demand (COD), turbidity, iron ions, and chloride ions) before and after the experiments. The results showed that after 360 h of circulation experiment, at a water temperature of 30 °C, electromagnetic field frequency of 1 kHz, electrochemical scale removal device voltage of 24 V, current of 10 A, and water flow rate of 0.6 m/s, the transformation of calcite to aragonite in CaCO3 scale samples occurred, with a 76.6% increase in aragonite content. Moreover, the conductivity decreased by 11.6%, hardness decreased by 42.0%, COD decreased by 59.7%, turbidity decreased by 48.1%, and chloride and iron ion concentrations decreased by 36.6% and 63.1%, respectively. The scale inhibition efficiency reached 53.8%, surpassing the effects of electromagnetic and electrochemical actions individually. These findings demonstrate that the combined action of electromagnetic and electrochemical fields can effectively enhance scale inhibition, scale removal, corrosion inhibition, and disinfection and algae removal effects.

Exploring the stabilization mechanism of NH3/CH4 non-premixed flames under gradient magnetic fields

This study explores the stabilization of non-premixed NH3/CH4 flames using gradient magnetic fields, overcoming challenges like low flame speed and instability inherent in ammonia—a carbon-free fuel and efficient hydrogen carrier. The action of the magnetic field modified the flame flow field, resulting in the suppression of emissions. By applying magnetic fields, the blending ratio of ammonia in the diffusion flame was elevated, resulting in an increase of 69% in the limit concentration to a near-pure level of 0.914. Measurements with Particle Image Velocimetry and schlieren system, alongside computational fluid dynamics, reveal how gradient magnetic fields mitigate flame detachment, lift-off, and blowout by altering flame root stabilization mechanisms. Specifically, gradient magnetic fields reduce localized flow velocity at the flame root and improve mass transfer. This indicates that gradient magnetic fields can significantly enhance the stability of NH3/CH4 flames, suggesting a promising route toward cleaner energy production and environmental sustainability.

A nonconservative kinetic model under the action of an external force field for modeling the medical treatment of autoimmune response

In this paper, we develop a nonconservative kinetic framework to be applied to the study of immune system dysregulation. From the modeling viewpoint, the model regards a system composed of stochastically interacting agents, under the action of an eternal force field. According to the application perspectives of this paper, the external force field has a specific analytical shape. In this case, some analytical results are proved, i.e. existence, uniqueness, positivity, and boundedness of solution of the related Cauchy problem, at least locally in time. Then, the model is refined to be implemented for the study of treatment strategies in case of autoimmune response. Specifically, we distinguish the autonomous case from the nonautonomous one, representing the absence or delivery of drugs, respectively. The former allows us to gain some stability results. Whereas, the latter is qualitatively studied. Numerical simulations are provided for both schemes.

Gradient failure mechanism and control technology of deep roadways under the action of deviatoric stress field

Deformation control of deep roadways is a major challenge for mine safety production. Taking a deep roadway with a burial depth of 965 m in a mine in North China as the engineering background, on-site investigation found that significant creep deformation occurred in the surrounding rock of the roadway. The original supporting U-shaped steel support failed due to insufficient supporting strength. The rock mass near the roadway experienced a transition from triaxial stress conditions to biaxial and even uniaxial stress states as a result of excavation and unloading, leading to a gradient stress distribution in the surrounding rock. From the perspective of the roadway's deviatoric stress field distribution, we investigated the gradient failure mechanism of the roadway and validated it through theoretical analysis and numerical simulations. The study found that the ratio of horizontal principal stress and vertical principal stress determines the distribution shape of the surrounding rock deviatoric stress field. The gradient distribution of the stress field in the roadway will cause time-related deformation of the roadway, which will lead to large deformation and failure of the roadway. Based on this, the control mechanism of roadway gradient failure was studied, and then a combined support technology of CFST supports with high bearing capacity was proposed.

Formation of Wave Fields in a Metal Melt under the Influence of Magnetic-Pulse Loading and Discharge Current Pulses

Based on mathematical modeling, a study of the wave fields in molten aluminum formed by the action of a pulse, electric discharge and combined sources was carried out. A comparative analysis of their influence on the wave fields in the melt was performed. An increase in the intensity of the wave fields under the influence of a combined method of loading the melt was registerd. The occurrence of cavitation in the melt under the influence of the considered sources of pressure pulses has been determined. The energy features of the action of pressure fields on the melt are noted. The influence of the mass of the melt on the pressure fields arising in it is shown.

Parameters of dust particle chains levitated vertically in a gas discharge plasma

The structural parameters of the dust particle chains suspended vertically in the electric field of a gas discharge are studied here. The investigations are performed by a numerical multi-block model based on a mean field approximation. The model describes the movement of ions and dust particles under the action of an external electric field, the electric field (Coulomb) of each charged dust particle, and the field of bulk plasma charge (ions and electrons) that screens the charges of dust particles. The gravity and the ion drag forces acting on the dust particles are also taken into account. Self-consistent chain parameters are calculated and compared for different number (1, 3, 5, and 7) and two different diameters (3.4 and 8.94 mcm) of dust particles in the chains. It is shown that an “ion wake” is formed behind the dust structures, and it grows with the number of dust particles and their size. With an increase in the number of dust particles in the chain, the charge of the first (top) dust particle increases. In the case of small dust particles, with an addition of new particles into the chain, the centers of the chains almost remain at the position of a single particle in the vertical direction. The chains of big dust particles move as a whole down in the direction of gravity with an increase in the number of particles.

Numerical Coupling Simulation of the Vertical Blowing Suspension Position of Tea Leaves Based on Computational Fluid Dynamics and the Discrete Element Method

To provide reference for the design of the air-suction tea sorting device, the coupled numerical simulation model was established by the coupling method of computational fluid dynamics (CFD) and discrete element method (DEM) with tea of different quality as test objects, and the model was verified experimentally. Regarding tea particles of different quality, when the test tea particle mass was 0.215, the test value was located in the simulation value with a minimum error of 9 mm, which an error rate of 3.33%, and maximum error of 19 mm, with an error rate of 7.03%. When the test tea particle mass was 0.145, the minimum error of the test value was 5 mm and the error rate was 1.54%, and the maximum error was 9 mm and the error rate was 3.33%. The verification results established the accuracy of the model. During the suspension test and simulation, tea particles were affected by the air flow field of the observation tube, and tea particles fluctuated. During suspension, tea particles were attached to the inner wall of the observation tube under the action of the air flow field. An in-depth study showed that the relationship between the different distances from the initial position of the particles during suspension and the simulation time was a peak function. The extreme function is used to fit the actual trajectory, and the fitting degree is good. The fitting degree of the particle closest to the initial position was 0.9455, and the fitting degree of the particle farthest from the initial position was 0.9981.

P‐76: The Influence of Bending FFC Transmission Line on High‐Speed Signal Channels

Generally, display devices interconnect FFC transmission lines with circuits to form a transmission line network system to achieve data communication between Tcon and Driver. Due to the limitations of the external shape and internal space structure of the display device, the FFC transmission cable presents a curved shape from 0 to 180 degrees during the wiring process. Under the action of spatial electromagnetic fields, the display device will involve the field‐circuit hybrid problem of electromagnetic coupling of the FFC transmission line's bent line and circuit conduction interference, which will cause severe electromagnetic interference(EMI), resulting in deterioration of the high‐speed channel signal at the receiving end and even inability to correctly restore and decode the signal, thus causing signal distortion, which in turn leads to display image distortion or pixel loss.

SUB-NANOSECOND SWITCHING OF HIGH-VOLTAGE TRIGATRONS

The paper studies the mode of sub-nanosecond switching operation of trigatrons with an operating voltage of up to 1 MV. It is shown that the mode of such activation takes place because of the creation of primary volume streamer in the trigatron discharge gap under the action of a strong non-uniform electric field. The streamer occupies the entire gap and has a weak glow brightness. An estimated analytical calculation of the trigatron switching process in 0.3 ns is given. The process of sub-nanosecond breakdown of a trigatron with an operating voltage of up to 1 MV is presented. During the process the impact ionization after the incoming of a control pulse with a front of no more than 4 ns and an amplitude of 70 kV in the trigatron occurs along the entire length of the discharge gap of down to 12 mm: between the control electrode and opposing main one as well as between the control electrode and the main one covering it. The experimental data on the increase in the brightness of the discharge glow in the trigatron already after the end of the switching process are given. References 12, figures 6.

A numerical code for the analysis of magnetic white-dwarf spectra that includes field effects on the chemical equilibrium

We present a new magnetic-atmosphere model code for obtaining synthetic spectral fluxes of hydrogen-rich magnetic white dwarfs. To date, observed spectra have been analyzed with models that neglect the magnetic field's effects on the atomic populations. In this work, we incorporate state-of-art theory in the evaluation of numerical densities of atoms, free electrons, and ions in local thermodynamical equilibrium under the action of a magnetic field. The energy distribution of atoms is rigorously evaluated for arbitrary field strength. This energy pattern includes going from tightly bound states to metastable or truly bound, highly excited states embedded in the continuum, that is, over the first Landau level. Finite nuclear mass effects and the coupling between the internal atomic structure and the motion of the atom across the magnetic field are also considered. Synthetic fluxes are generated with integrations of numerical solutions of polarized radiative transfer over the visible stellar disk using a spherical $t$-design method. The atmosphere code is tested with observations from the Sloan Digital Sky Survey for a group of known magnetic white dwarfs. Physical stellar parameters are obtained from least-squares fits to the observed energy distribution and compared with results of previous works. We show that the use of zerofield ionization equilibrium in spectral analyses can lead to underestimated effective temperatures for highly magnetic white dwarfs.