Effects Of Magnetic Flux Density Research Articles

Bioethanol production in bioreactor assisted by magnetic field: Correlation between S. cerevisiae H+ effluxes and fermentative efficiency

This study simultaneously evaluated fermentation kinetics and H+ fluxes during fermentation by Saccharomyces cerevisiae in order to elucidate the biochemical mechanisms behind bioethanol production induced by ELF magnetic fields. Fermentation kinetics were monitored by glucose uptake, ethanol production, secondary products (glycerol), pH, biomass, and biochemical characterization of ATPase activity through proton efflux density measurements.A face-centered central composite design 22 was performed, considering independent variables such as recycling arrangements (bioreactor with a spiral-shaped tube, whole bioreactor, and bioreactor with a U-shaped tube) and magnetic flux density (5, 10, and 15 mT), while alcoholic fermentation efficiency and H+ efflux density of the P-ATPase were the response variables.ELF magnetic fields induced substrate consumption and bioethanol formation in all experimental configurations when compared to fermentations without the field. However, the whole bioreactor exposed to 10 mT was the most attractive condition, resulting in an average increase of approximately 40 % and 18 % in the overall volumetric productivity of glucose consumption and ethanol production, respectively, compared to the control experiment. The effect of magnetic flux density on fermentative efficiency and H+ efflux density was statistically significant (p < 0.1). A direct correlation between H+ efflux and yeast performance during fermentation under magnetic fields was found through the application of a method for simultaneous optimization of the experimental results. The data are discussed in relation to the biological mechanism of action involved and the potential applications of this technology at an industrial scale are envisioned.

Effect of Magnetic Flux Density on Control Range of Output Power of a Commercial-Scale, Nonequilibrium MHD Generator

Effect of Magnetic Flux Density on Control Range of Output Power of a Commercial-Scale, Nonequilibrium MHD Generator

Modeling study of EMBr effects on molten steel flow, heat transfer and solidification in a continuous casting mold

During continuous casting process, the internal molten steel flow pattern of the mold is one of the important factors affecting the quality of slab products. The application of electromagnetic braking (EMBr) technology in the slab caster provides an effective solution to improve the molten steel flow pattern in the mold. In the current research, one of the commonly used EMBr technology is studied, namely the Ruler-EMBr technology. In detail, the effect of magnetic flux density on the behavior of the molten steel jet flow, heat transfer, and solidification in a 1450 mm × 230 mm slab mold is numerically simulated through a Reynolds-averaged Navier-Stokes (RANS) turbulence model together with an enthalpy-porosity approach. The simulation results indicate that the electromagnetic force generated by the Ruler-EMBr can significantly suppress the diffusion of the impinging jet to the narrow face of the mold with the increase of magnetic flux density. By that, the impact of the upward backflow on the meniscus region in the mold is suppressed. Correspondingly, the uniformity of the temperature distribution in the mold is effectively improved. The parametric studies suggest that the optimized magnetic flux density is 0.3 T to ensure the improvement of steel quality with a casting speed of 1.6 m/min. By applying the magnetic flux density of 0.3 T, the Ruler-EMBr has a better capability to reduce the maximum amplitude of the surface velocity by 24.5% and increase the average surface temperature of the molten steel by 0.25% when compared to the case of No-EMBr. With this electromagnetic parameter, the Ruler-EMBr technology can well prevent the mold flux entrapment and promote solidified shell uniform growth along the casting direction.

Effects of magnetic flux density on germination and seedling growth in Oryza sativa var. Glutinosa

Effects of magnetic flux density on germination and seedling growth in Oryza sativa var. Glutinosa

Experimental analysis and numerical simulation of flow behavior of fresh steel fibre reinforced concrete in magnetic field

• A numerical method was developed to investigate flow behavior of steel fibre concrete. • Magnetic flux density, initial position of steel fibre and resistance of mortar affect orientation. • Fluidity along magnetic field direction decreases with increase of magnetic flux density. Fluidity is an important index to describe the performance of fresh concrete, which has a great influence on the transportation and casting process of concrete. By applying a magnetic field to steel fibre reinforced concrete, in which steel fibre can be oriented to improve flow performance and strength. In this paper, the mechanical model of steel fibre in magnetic field was established in EDEM, and the simulations of magnetic field orientation as well as slump of steel fibre concrete were carried out and compared with the experiment. The errors between numerical and experimental results are less than 5%, which confirms the validity of the model. The effects of magnetic flux density and duration on the orientation of steel fibre and the effect of orientation on flow of mortar were analyzed. It was found that the larger the magnetic flux density, the better orientation of steel fibre. And regardless of the magnitude of magnetic flux density, most steel fibres can be oriented in a relatively short time. Due to the effect of gravity, orientation of mortar in the bottom is more difficult than that in the upper. The magnetic flux density, the initial position of the steel fibre and the resistance to the steel fibre affect the final orientation. When the magnetic field direction is horizontal, the fluidity of mortar along the magnetic field direction decreases with the increase of magnetic flux density, while the fluidity along the vertical magnetic field direction increases. The vertical magnetic field has no obvious effect on the fluidity.

Femtosecond laser drilling in superalloy with water-based magnetic assistance

Experiment of femtosecond laser drilling in superalloy with water-based magnetic assistance was carried out. The effects of different environments (in air, magnetic assistance, water assistance and water-based magnetic assistance) on the hole morphology, hole diameter, taper angle and sidewall roughness after femtosecond laser drilling were compared and analyzed. The effects of magnetic flux density on the hole diameter, taper angle and sidewall quality with water-based magnetic assistance were discussed. The mechanism of femtosecond laser drilling in superalloy with water-based magnetic assistance was revealed. The results show that transverse magnetic assistance and water assistance could both improve the hole quality and drilling efficiency, and the effect of water assistance was greater than that of magnetic assistance. The drilling efficiency was the highest with water-based magnetic assistance, which was mainly manifested in the increase of the hole diameter, and the increase of the hole cross-section size; on the other hand, the hole quality was the best, which were mainly manifested in the increase of the perpendicularity of the hole cross-section, the decrease of the taper angle, the reduction of irregular micro scale defects such as grooves on the hole sidewall, and the decrease of the roughness of the hole sidewall. Compared with that in air, the hole taper angle was reduced by 24.63 %, and the hole sidewall roughness was reduced by 38.38 % with the water-based magnetic assistance. With the water-based magnetic assistance, the higher the magnetic flux density, the higher the hole quality. This research provided theoretical basis and technical support for femtosecond laser drilling.

Refinement of Eutectic Carbides in M2 High Speed Steel by Adjusting Magnetic Flux Density During Magnetic Controlled ESR Process

The current study examines the effect of magnetic flux density (MFD) on the morphology of the metal pool and the refinement of eutectic carbides in magnetic controlled electroslag remelting (MC-ESR, M2 high speed steel). When a transverse static magnetic field (TSMF) with a larger MFD was used, it was easier to obtain a shallower metal pool and finer eutectic carbides. These phenomena are explained by the smashing effect of the droplet neck (stronger at higher MFD values) induced by electromagnetic vibration, resulting in smaller/more dispersed droplets and thus a more uniform temperature distribution in the metal pool. Additionally, as MFD increased, the local solidification time (LST) decreased (0 to 140 mT) and the number of inclusions serving as heterogeneous nuclei for eutectic carbide formation increased (0 to 65 mT), resulting in a gradual size reduction of eutectic carbides. However, the refinement of eutectic carbides in MC-ESR must consider the above two factors comprehensively, and the MFD of applied TSMF need not be excessively large.

Effect of magnetic flux density of bar magnet on removal rate of magnetic material in powder

In this study, in order to improve the iron removal rate of iron remover, the effects of magnetic flux density, number of magnetic poles and powder fluidity on the removal rate of filed SUS304 particles mixed with high-purity spherical silica powders of different particle sizes were investigated. The iron removal tests were performed using an iron removal testing device equipped with a single bar magnet. The silica powders mixed with filed SUS304 particles were sifted, and the weight of the filed SUS304 particles captured by the bar magnet was measured. Three types of bar magnets were prepared in order to investigate the effect of the maximum magnetic flux density and the number of magnetic poles. As a result, the number of magnetic poles was more effective in improving iron removal performance than the maximum magnetic flux density. In addition, the iron removal rate decreased with decreasing the nominal particle size of the silica powder. As a result of the constant load direct shear test, the shear cohesion of silica powders increased with decreasing the average particle size [Formula: see text]. Therefore, it was found that the iron removal performance deteriorates when the powder cohesion increases.

Magnetic field dependent viscoelasticity of a highly stable magnetorheological fluid under oscillatory shear

In our previous works, a new kind of magnetorheological fluid (MRF) consisting of high viscosity linear polysiloxane (HVLP) as carrier and carbonyl iron particles (CIPs) as magnetoactive dispersions, i.e., HVLP MRF, was proposed. HVLP MRF is a promising candidate in the field of heavy equipment for its long-term suspension stability. In this study, we further investigate the viscoelastic properties of HVLP MRF under oscillatory shear in order to evaluate its work performance. HVLP MRFs with different CIP concentrations (0, 20, 40, 60, and 70 wt. %) were synthesized. SEM microstructure, visible MR effect, and magnetic properties were performed. The effects of magnetic flux density, CIP concentration, shear strain, and shear angular frequency on the viscoelastic moduli were examined by using a Physica MCR-301 rheometer. The results show that the viscoelastic moduli are magnetic field dependent. The storage modulus increases with increasing the magnetic flux density, while the loss modulus presents a tendency of rising up at the beginning and declining in late. A critical particle concentration threshold (∼70 wt. %) was found to maximize the magneto-storage modulus increment. Both the upper limit of linear viscoelastic region and the flow point increase as the magnetic flux density increases. It reveals that the field dependent viscoelasticity of HVLP MRF is the result of competition between the structure-enhancement of magneto-induced particle chains and structural deformation under oscillatory shear. Additionally, in the linear viscoelastic region, HVLP MRF shows little dependence on shear angular frequency, implying an excellent working stability in a complex environment.

Unveiling the induced lipid production in Chlorella vulgaris under pulsed magnetic field treatment

The pulsed magnetic field (PMF) was adopted for the enhancement of lipid in Chlorella vulgaris. The average biomass and lipid content in outdoor conditions were found to be 0.315 g.L−1 and 20–25% respectively. The effect of magnetic flux density in the range of 600–900 mG on biomass production and lipid content was studied. A magnetic flux density of 700 mG at 1Hz for 4 h per day was found to be optimum, which yielded a maximum dry cell weight of 0.61 g.L−1, two-fold than the normal condition, with a lipid content of 55.2%. FTIR analysis evidenced that the PMF treatment increased the active oxygen, which could be attributed to the enhancement of growth and lipid of C. vulgaris.

Development of a design and characterization framework for fabrication of functionally graded materials using magnetic field-assisted digital light processing stereolithography

• A design, manufacturing, and characterization framework is established to fabricate functionally graded materials. • The correlation between the local magnetic particle contents and Young. • The correlation between the magnetic flux density and resulting particle contents is established to facilitate the design and manufacturing of FGMs. Functionally graded materials (FGMs) offer several advantages over traditional materials. Fabrication of FGMs via additive manufacturing (AM) processes would allow creating a part with a complex geometry while controlling the graded structure and has gained significant interest in the recent years. Magnetic field-assisted digital light processing (DLP) stereolithography is a promising technique to fabricate FGMs. However, it is still challenging to be able to fabricate FGMs with precisely controlled structures and properties. In this study, a design, manufacturing, and characterization framework is developed for using DLP to fabricate FGMs. In this work, a customized DLP printer with assisitve magnetic field is developed and used to fabricate polymeric composites with embedded magnetic particles. By varying the magnetic field, different gradients of particle concentration can be achieved. The particle distribution within the sample is characterized by nano-computed tomography and the greyscale analysis using optical microscopy. Nanoindentation is performed to measure the local material properties in the graded area. Standard tensile tests are also conducted on samples with preset particle contents, and the results are cross compared with nanoindentation results. A finite element model is developed to analyze the effect of magnetic flux density on the resulting particle content. Correlations between the magnetic flux density and particle content, and between the particle content and the local material behavior are shown, which form the foundation of the proposed framework. This framework provides a guided method for designers and manufacturers to create FGMs with more predictable results.

Study on association solubilization and inhibition of scale in recirculating cooling water system under S-HGMF

Abstract The present study conducted an investigation on the effect of a superconducting high gradient magnetic field (S-HGMF) on the association solubilization of recirculating cooling water and the crystal form change of scale. The effects of magnetic flux density, flow rate and cycle-index on the solubility of scale-forming ions were investigated, and the effects of viscosity and surface tension on the molecular internal energy and order degree of the circulating water were analyzed. The scale was ground and mixed with water and placed in an S-HGMF system to study the effect of S-HGMF on the crystal form change of CaCO3. The experimental results showed us that S-HGMF could increase the solubility of scale-forming ions. It could enhance the interaction between water molecules by increasing viscosity and reducing surface tension, so as to improve the stability of water quality, reduce ion precipitation, and achieve the effect of scale inhibition. At the same time, it could also change the crystal structure of CaCO3, promote the transformation of calcite to aragonite, and realize the purpose of scale inhibition. In a word, S-HGMF treatment can effectively solve the scaling problem of a recirculating cooling water system, which provides a reference for scale inhibition of recirculating cooling water.

Load-Carrying Capacity Prediction of Magnetic Fluid Hydrodynamic Bearing Under External Magnetic Field

To decrease the negative influence of the poor working environment on lubricating performance, a new hydrodynamic bearing with magnetic fluid is developed, whose lubricating performance can be significantly improved by external magnetic field. The mathematical model of magnetic intensity generating by a solenoid, which is designed as external magnetic field, is deduced according to Biot-Savart Law and validated by measurement experiment. The direct relationship of load-carrying capacity of bearing and magnetic intensity of external magnetic field is built, through analyzing the effect of magnetic flux density on magnetic fluid viscosity. The results showed that solenoid is reasonable to apply as external magnetic field, and its theory works. Magnetic intensity of external magnetic field can enhance and monitor the bearing load-carrying capacity until magnetic fluid reaches magnetic saturation.

The Effect of Axial Magnetic Field on The Breakdown Voltage of Air at Low Pressure

To add more details about the effect of the axial magnetic field on the plasma profile, the breakdown voltage of air was investigated at low pressure (9-15 Pa) in the presence of axial magnetic field (0.01-0.04T). The air was ignited by a DC voltage between two plain electrodes of aluminum separated by a distance (8.5cm). The measurements showed that the discharge voltage decreases to a minimum value, then returns to increase over the minimum with increasing the magnetic field strength, at all pressures in the range. It was also observed that a maximum decrease in the discharge voltage is obtained near the minimum of Paschen curve from the right side. The decrease in the discharge voltage was caused mainly by the effect of magnetic flux density on the diffusion of charged particles to the walls, especially on that of free electrons which were borne during the breakdown process.

Modeling of surface roughness in a novel magnetorheological gear profile finishing process

Fine finishing of spur gears reduces the vibrations and noise and upsurges the service life of two mating gears. A new magnetorheological gear profile finishing (MRGPF) process is utilized for the fine finishing of spur gear teeth profile surfaces. In the present study, the development of a theoretical mathematical model for the prediction of change in surface roughness during the MRGPF process is done. The present MRGPF is a controllable process with the magnitude of the magnetic field, therefore, the effect of magnetic flux density (MFD) on the gear tooth profile has been analyzed using an analytical approach. Theoretically calculated MFD is validated experimentally and with the finite element analysis. To understand the finishing process mechanism, the different forces acting on the gear surface has been investigated. For the validation of the present roughness model, three sets of finishing cycle experimentations have been performed on the spur gear profile by the MRGPF process. The surface roughness of the spur gear tooth surface after experimentation was measured using Mitutoyo SJ-400 surftest and is equated with the values of theoretically calculated surface roughness. The results show the close agreement which ranges from −7.69% to 2.85% for the same number of finishing cycles. To study the surface characteristics of the finished spur gear tooth profile surface, scanning electron microscopy is used. The present developed theoretical model for surface roughness during the MRGPF process predicts the finishing performance with cycle time, improvement in the surface quality, and functional application of the gears.

The study on the mechanical properties of magnetorheological elastomers under triaxial compression

In order to design magnetorheological elastomers (MREs) based craftsmanship for metal forming, a comprehensive study on the mechanical properties of MREs under triaxial compression is required. An experimental setup integrating free compression and triaxial compression is designed to characterize isotropic MREs specimens under compression mode. The results showed that the MREs specimen in mold had successively experienced free compression stage, transition stage and triaxial compression stage during the experiment. The stress-strain curves of the MREs specimen changed when the concentration of magnetic particles increased from 0 to 44.7%, and the strain required to reach the transition stage was reduced. The effect of magnetic flux density on the stress-strain curves of the MREs specimen depended on the concentration of magnetic particles. The measured data obtained at different strain rates revealed maximum changes of 15.7% and 0.096% in volume compression modulus and Poisson ratio, respectively, which occurred under the magnetic flux density of 200 mT and CIP concentrations of [Formula: see text]. In this study, through a set of experiments, the stress-strain curves of the MREs specimen under different concentrations was elucidated, and their effects on the volume compression modulus and Poisson ratio were discussed.

Measurement and evaluation of magnetic field assistance on fatigue life and surface characterization of Inconel 718 alloy processed by dry electrical discharge turning

In the present study, a new hybrid machining method namely magnetic field assisted dry electrical discharge turning (EDT) was developed to understand effect of magnetic flux density on surface integrity and low cycle fatigue life of cylindrical In718. A specific tool made of copper was designed and fabricated to shape fatigue sample in round bars. It is found from the results that application of magnetic field reduces the tensile residual stress at the work surface and subsurface layers as well it improves surface quality. Also, it reduces porosity of machined surface which yields further hard surface. It is evident from the X-ray diffraction (XRD) test that distance between crystalline plane reduces as the magnetic field applied to the process. The abovementioned reasons caused low cycle fatigue (LCF) life of the sample processed by novel process increase up to 73% times compared to these machined by EDT without magnetic field.

A novel method improving the temperature uniformity of hot-plate under induction heating

In the paper, a novel method to improve the uniformity of the temperature distribution on the surface of the hot-plate is presented. Firstly, the effect of magnetic flux density under coupling of the electromagnetic and heat transfer on target surface temperature is studied numerically by using the commercial simulation software COMSOL Multiphysics. To evaluate the uniformity of the temperature distribution on the target surface, the temperature nonuniformity index on the target surface was firstly employed in terms of a specific designed electric coil. Secondly, the principal components analysis combined with the orthogonal test method is employed to analyze the shape parameters and obtain optimized temperature distribution at the target surface of the hot-plate. The simulated results show that the uniformity of temperature can be greatly improved by appropriately adjusting distribution of magnetic flux and the uniform temperature distribution can be achieved on a heating surface of 130 mm in length, 130 mm in width, and 30 mm in height. Finally, the optimizations of target surface temperature on hot-plate with different target temperatures were studied as well.

Electrical discharge turning by assistance of external magnetic field, part I: Study of MRR and dimensional accuracy

Hybrid machining process is increasing its importance toward processing of advanced materials with complex geometries. Electrical discharge machining is a type of non-conventional machining process that is extensively used for creating micro and macro features in hard material. The process has capability to be used for flat samples and round bars that former application is more common. In the present study an experimental work has been made to produce sharp edge grooves in round bard made of AISI D2 by electrical discharge turning process. To do so, an external magnetic flux density has been applied around machining gap to enhance the performance measures. Series of experiments have been carried out in order to find effect of magnetic flux density (0, 0.2 and 0.4T), discharge current (5, 10, 15A), pulse on time (600, 800 and 1000μs), and work rotational speed (50, 150 and 250RPM) on material removal rate (MRR) and overcut (OC). Finally optimization has been carried out in different machining modes to find how the optimum value of magnetic field is varied in roughing and finishing. Results indicated that irrespective to the machining regime, application of high intensity magnetic field (i.e. 0.4T) is dominant in increasing the machining rate as well as enhancing the dimensional accuracy. Therefore, the method can be useful for performing the electrical discharge turning process.

The effect of constant magnetic field on convective heat transfer of Fe3O4/water magnetic nanofluid in horizontal circular tubes

In this paper, the heat transfer and flow characteristics of Fe3O4/water magnetic nanofluids were experimentally studied under the effect of a magnetic field. The experimental results were combined with a magnetic flux density distribution. The effects of magnetic flux density, magnetic field gradient, and different magnetic field orientations on the local Nusselt number and flow pressure drop were analyzed. The results show that, increasing the magnetic flux density and magnetic field gradient can achieve a significant improvement in the convective heat transfer. At the Re of 1080 and the magnetic field of 415 gauss, the local Nusselt number for 0.5 vol% Fe3O4/water magnetic nanofluids increased by 4.36%, whereas the corresponding value for the magnetic field of 700 gauss increased by 7.19%. Additionally, the local Nusselt number increased by 32.0% under a magnetic field gradient of 28.6 gauss/mm. The occurrence of chain-like structure is the main reason for the increased convective heat transfer. In addition, the flow disturbance caused by the magnetic field increases the pressure drop. However, the effect is weaker than the enhancement of heat transfer.