Effect Of Magnetic Field Strength Research Articles

Nanoscopic spin-wave channeling along programmable magnetic domain walls in a CoFeB/BaTiO3 multiferroic heterostructure

We report a micromagnetic study on spin-wave propagation along magnetic domain walls in a ferromagnetic/ferroelectric bilayer. In our system, strain coupling between the two ferroic materials and inverse magnetostriction produce a fully correlated domain pattern wherein straight and narrow ferroelectric domain walls pin the magnetic domain walls. Consequently, an external magnetic field does tailor the spin structure of the magnetic domain walls instead of moving them. We use experimental parameters from a previously studied CoFeB/BaTiO3 material system to investigate the potential of artificial multiferroics for programmable nanoscopic spin-wave channeling. We show that spin waves are transported along the pinned magnetic domain walls at zero magnetic field and low frequency due to a local demagnetizing field. Further, switching of the domain wall spin structure from a head-to-tail to a head-to-head configuration abruptly changes the propagating spin-wave mode. We study the effect of magnetic field strength on the localized modes and discuss reversible control of spin-wave channeling via electric-field-driven magnetic domain wall motion. Nanoscopic guiding of propagating spin waves by an electric field, in combination with positional robustness to and mode programming by an external magnetic field, offers prospects for low-power and reconfigurable domain-wall-based magnonic devices.

Effects of magnetic field, fluid properties, and geometric parameters on double-diffusive convection of liquid metals

<sec>Thermal convection in conducting fluids under the influence of a magnetic field is a hot research topic. In this study, a high-precision and high-resolution numerical method is used to directly simulate the double-diffusive convection of liquid metal in a two-dimensional cavity. The study covers the effects of magnetic field strength (<i>Ha</i>), Prandtl number (<i>Pr</i>), Lewis number (<i>Le</i>), and aspect ratio on the dynamics of flow and heat/mass transfer under both horizontal magnetic field and vertical magnetic field. The study considers magnetic field intensities ranging from 0 to 100, Prandtl numbers from 0.01 to 1, Lewis numbers varying from 1 to 100, and aspect ratios spanning from 1 to 12. Within these specified parameter ranges, the outcomes under conditions of no magnetic field (<i>Ha</i> = 0), weak magnetic field (<i>Ha</i> = 10), and strong magnetic field (<i>Ha</i> = 50) are compared with each other.</sec><sec>The results show that the magnetic field primarily suppresses flow, heat transfer, and mass transfer. Under the same strength of the magnetic field, the horizontal magnetic field has a greater suppressing effect than the vertical magnetic field. However, the cases of weak magnetic field and strong magnetic field, their effects on heat and mass transfer are similar. Regardless of the orientation and strength of the magnetic field, the heat transfer efficiency and mass transfer efficiency always increase with Prandtl number increasing. The application of a magnetic field can reduce the increase in heat and mass transfer, and when the magnetic field strength reaches a certain level, the Lorentz force predominates, making the influence of the Prandtl number on heat and mass transfer very small. In the presence of a magnetic field, a bifurcation phenomenon is observed around <i>Pr</i> = 0.9.</sec><sec>Additionally, as the Lewis number increases, the flow transforms from steady flow to periodic flow, and the influence on mass transfer efficiency becomes more significant. For example, under a horizontal magnetic field, the mass transfer efficiency at the maximum Lewis number is about six times that at the minimum Lewis number. Similarly, under a weak vertical magnetic field, the mass transfer efficiency is about nine times higher. The influence of Lewis number on heat transfer efficiency is relatively minor.</sec><sec>Within the range of considered aspect ratios, the heat transfer efficiency and mass transfer efficiency exhibit oscillatory behavior under no magnetic field and weak magnetic field as the aspect ratio increases. However, the heat transfer efficiency and mass transfer efficiency under a strong magnetic field are less affected by the aspect ratio. For flows with the same number of vortices, lower aspect ratio can lead to stronger heat and mass transfer.</sec>

Magnetic feature and regression analysis of Reiner-Philippoff boundary layer flow

The design and optimization of magnetic fluid-based processes, such as magnetohydrodynamic power generation and magnetic drug targeting, have become significant in recent times. To understand the magnetic and radiation features, as well as the sensitivity of engineering physical quantities to each dimensionless parameter in fluid flow, the Reiner-Philippoff (RP) fluid is best suited in this instance, as it exhibits shear-thickening, shear-thinning, and Newtonian behavior. The non-similar transformation is used to transform the partial differential equations that describe the flow into two-variable differential equations. The transformed dynamical equations are solved numerically using a spectral-based numerical technique; namely, the bivariate simple iteration method (BSIM). The effects of magnetic field strength and radiation parameter on the stretching and shrinking sheets are examined. The investigation reveals that both the magnetic field strength and radiation parameter have a significant impact on the flow behavior and rate of heat transfer. For the radiation parameter R∈[0,0.5], the skin friction coefficient and Nusselt number increase by 22.6% and 5.98%, respectively. Additionally, an 100% increment in Prandtl parameter reduces the Nusselt number by 287.36%. Regression analysis is performed to identify the most significant parameter affecting the engineering quantities. The results show that the Bingham constant, γ, is the only parameter that is not significant on the skin friction coefficient, while all the parameters have significant impact on the Nusselt number. The findings in this study have important implications in the biomedical industry, the design of machines, and the fourth industrial revolution.

Effect of magnetic field strength on the performance characterization of a low-power wall-less Hall thruster

The wall-less Hall thruster is expected to overcome the issue of wall erosion in miniaturized Hall thrusters. A unique structure of negative gradient magnetic field is used to constrain the plasma behavior. In this paper, permanent magnet rings with different thicknesses were used to adjust the magnetic field strength, and its effect on discharge characteristics and thrust performance was experimentally investigated. The experiment results show that increasing the magnetic field strength can reduce the current oscillation and increase the maximum operating voltage. Within a limited range, increasing the magnetic field strength can significantly improve thrust performance. However, excessive magnetic field strength leads to a decrease in anode efficiency. The optimal magnetic field strength appears at 121 mT, with a thrust of 5.5 mN, a specific impulse of 935 s, a thrust power ratio of 51 mN/kW, and an anode efficiency of 23.1 %. Based on the analysis of different efficiency parameters and plume images, under excessively high magnetic field strength, the shortening of the ionization region may lead to intensified leakage of neutral atoms, which may be the primary reason for the reduction in propellant utilization and anode efficiency.

On the impacting dynamics of ferrofluid droplets on porous substrates in the presence of magnetic field

This article presents experimental and theoretical studies of the impacting behavior of ferrofluid droplets on porous substrates under the influence of magnetic fields. The effects of magnetic field strength and porous substrates on the falling, impacting, and spreading of the droplets are investigated. Theoretical models are successfully derived to predict the droplet impacting velocity in the presence of the magnetic field and the maximum spreading factor of the droplets on the porous substrates without considering magnetic field effects, respectively. Moreover, a universal scaling law is constructed for the maximum spreading factor of the ferrofluid droplets on both of the porous and smooth substrates in the presence of the magnetic field. The findings of this study can provide a foundation for understanding the impacting dynamics of ferrofluid droplets on the substrates and optimizing their applications in various fields, such as three-dimensional printing and microfluidic technology.

Application of Water-Based Ferrofluid for Water Electrolysis

A combination of renewable energies and water electrolysis has been attracting much attention as an environmentally-friendly method to produce hydrogen, which has been expected as promising future energy storage and carrier media. And micro-gravity induces the adsorption of gas-bubbles on the surface of electrodes and this leads the declination of water electrolysis. In the present study, a new method which has the potential to dramatically enhance the water electrolysis efficiency was proposed by utilizing the magnetic buoyancy. Using water-based ferrofluids as an electrolyte and directly electrolyzing them in the presence of inhomogeneous magnetic fields enhance the desorption of gas-bubbles adsorbed on electrodes.When non-magnetic bodies are placed in the ferrofluid and are exposed to an inhomogeneous magnetic field, the magnetic buoyancy force acts on the non-magnetic bodies. Because the gradient of the magnetic field gives the magnetic buoyancy force, the non-magnetic body moves as the non-magnetic body is ejected from the magnetic field. When the water-based ferrofluid is used as an electrolyte and magnets are placed nearby electrodes, the magnetic buoyancy force acts on the bubbles (H2 and O2) generated from the surface of the electrodes, resulting in the water electrolysis enhancement.However, the effect of the magnetic fields on the water electrolysis using the ferrofluid is not well understood. In the present study, to understand the effect of the magnetic field on the water electrolysis, the chronoamperometry measurements in the presence of the magnetic field was carried out. The results showed that the water electrolysis is found to be enhanced by increasing the magnetic field intensity due to the magnetic buoyancy force. The present study showed that our proposed method has a great potential to enhance the water electrolysis substantially.In addition, we investigated the effect of magnetic field strength on the water electrolysis process by a dynamic impedance method. The Nyquist plot was obtained by the dynamic impedance method. The tested electrolyte was a water-based ferrofluid adding Na2SO4 with 0.1 mol/L. When the magnetic field intensity increases, Z Re decreases, which represents that the resistance in the water electrolysis becomes smaller. The equivalent circuit fits the experimental data well, resulting in that it is possible to divide the whole resistance into the charge-transfer and solution resistances. The charge-transfer resistance dramatically decreases with the magnetic field strength, while the solution resistance doesn't change. This phenomenon explains that the magnetic buoyancy sufficiently enhances the bubble desorption, resulting in the water electrolysis enhancement.

Effects of magnetic nozzle strength and orientation on radio-frequency plasma expansion

To improve the efficiency of radio-frequency magnetic nozzle plasma thrusters, it is important to better understand the coupling between plasma expansion and a convergent–divergent magnetic field. This study explores the effects of magnetic field strength and orientation on plasma expansion in a magnetic nozzle. Two-dimensional measurements of the plasma characteristics obtained both in the source and in the expansion region are presented to investigate the influence of magnetic field strength on the formation of high-density conics in a symmetric magnetic nozzle. The measurements are repeated in a deflected magnetic nozzle using a novel magnetic steering system. Measurements of the ion saturation current and floating potential profiles are used respectively to qualitatively assess the plasma density distribution and the presence of high-energy electrons for the magnetic field configurations analysed. In the symmetric magnetic nozzle configuration, it is observed that the ion saturation current peaks on axis in the plasma source, but downstream of the nozzle throat, a double-peaked hollow profile is observed for all cases studied. The location of the high-density conics structure matches the most radial field lines that intersect the antenna and can freely expand downstream outside the source. Negative values of the floating potential are measured in the same peripheral regions, which could be a sign of the presence of high-energy electrons. When the magnetic field is deflected, the ion saturation current profile shows only a single peak centred around the bent field line that reconnects to the antenna. Again, a region of negative floating potential is measured at the location of the maximum ion current. Thus, it is shown how, independent of magnetic field strength and orientation, the magnetic field lines interacting with the antenna dictate the local plasma profiles downstream from the magnetic nozzle.

Thermal Analysis of Magneto-Natural Convection Flows within a Partially Thermally Active Rectangular Enclosure

In this study, we numerically investigate heat transfer enhancement in a partially thermally active rectangular enclosure. The enclosure is filled with a ternary hybrid nanofluid (water, Carbon Nanotube, Al2O3, and Graphene). It is subjected to a magnetic field and uniform internal heat generation. The study also investigates the effect of magnetic field strength and direction on the natural convection flow, which arises from density fluctuations caused by partial heating of the left vertical wall. To solve the dimensionless governing equations, the finite element approach is employed. The parameters studied in detail include Rayleigh number (Ra), Hartmann number (Ha), nanoparticle volume fraction (ϕ), and heat generation coefficient (λ). The findings are presented graphically for the range of the parameters as follows: 103≤Ra ≤106, 0≤Ha≤20, 0.01≤ϕ≤0.05, and 0≤λ≤15. It is noted that these parameters have an impact on heat transfer enhancement, flow patterns, and temperature fields. The results show that the average Nusselt number (Nu¯) increases with an increasing value of ϕ. Moreover, it has been noted that Nu¯ decreases as the value of Ha increases, and the impact becomes more obvious at higher Ra values. Finally, the influence of the heat generation coefficient on the heat transfer rate inside an enclosure is examined.

Simulation Analysis of the Motion of Superparamagnetic Particles in Liquid-Phase Fluid under a Magnetic Field

Based on the magnetic response of magnetic particles, the targeting of particles to a target area under the modulation of an external magnetic field has been used in many applications. An accurate kinematic model is helpful to achieve accurate targeting of magnetic particles and to investigate the factors influencing the motion of the particles. In the present paper, a segmental magnetization model was proposed based on the real magnetization process of superparamagnetic particles to calculate the magnetic force, and this was compared with a traditional magnetization model. The effects of magnetic field strength and particle diameter on the trajectory of magnetic particles in fluids under a magnetic field were further analyzed using a finite element analysis software. The simulation results show that changing the particle size only affected the velocity of the particles and did not affect the trajectory. When magnetic field strength changed, magnetic particles showed different trajectories. Notably, when the magnetic field force in the Y direction was too large, meaning the gravity could be neglected, the trajectory of the particles no longer changed when the magnetic field strength was varied.

Magnetic-assisted strategy for performance enhancement of flow-by capacitive deionization

Capacitive deionization is an environment friendly electro-sorption desalination technology that has broad application prospects in high-efficiency seawater desalination and brackish water purification. However, the insufficient ion separation performance and desalination capacity restrict the large-scale application of capacitive deionization with flow-by structure. Since the separation of cations and anions is intensified via the synergetic manipulation of the electric field force and Lorentz force, a magnetic-assisted strategy was proposed to enhance the performance of capacitive deionization. The effects of magnetic field strength and layout on the desalination performance of capacitive deionization were experimentally investigated. The results confirmed the feasibility of performance enhancement via the effect of the magnetic field. The performance of capacitive deionization under a vertical magnet layout was increased by 25.2 % at a magnetic field strength of 0.33 T, compared to that without a magnetic field. However, the deionization performance decreased when the magnetic field strength was further increased to 0.45 T, which indicates the existence of a critical magnetic field strength. Benefitting from the superposition of magnetic fields, the horizontal layout of magnets can provide a stronger average magnetic field than the vertical layout. This study provides insights into a new design of flow-by capacitive deionization.

A CASE (Computer-Assisted Structure Elucidation) for Bench-Top NMR Systems in the Undergraduate Laboratory for De Novo Structure Determination: How Well Can We Do?

The recent popularity of benchtop (BT) NMR systems has prompted its applications in undergraduate laboratories around the world. Owing to their low maintenance cost, due to the lack of a superconducting magnetic core, and simple operation, these BT NMR systems can fulfill many of the learning objectives outlined in the undergraduate organic chemistry curricula. With a variety of BT NMR systems currently available (e.g., 43, 60, 80, and 100 MHz), it can be overwhelming for instructors to determine which system is appropriate for their needs. When used as a structure elucidation tool, the focus is often placed solely on solving chemical structures, prompting the eventual question of the magnetic field strength requirements for de novo structure elucidation. To answer this question, two artificial intelligence (AI) software packages, namely Structural Elucidator (v.2020.1.2) from ACD/Laboratories and Mnova Structure Elucidation (v 14.2.3) from Mestrelab Research, were used. These software provide an unbiased, yet separate, metric to gauge the effect of magnetic field strength on the accuracy of the determined structures. For comparison purposes, results from these two BT magnetic field strengths will be compared to those obtained from a high field NMR (500 MHz) spectrometer, providing a complete overview of the advances, as well as limitations in current BT systems for undergraduate education. In addition, the spectral data presented in this work can be used as a practical example in class to illustrate the effect of spectral resolution on the accuracy of determined structures, which is fundamental to understanding structure elucidation within organic chemistry.

Effects of magnetic field strength on the microwave discharge cusped field thruster

The microwave discharge cusped field thruster is a novel electric propulsion concept developed for the space-borne Gravitational Wave detection mission. It is an effective combination of the cusped magnetic field and the ECR microwave plasma source, which provide the thruster strong confinement for the plasma and the ability to operate on low mass flow rate conditions. To meet the requirements on the high accuracy, low noise thrust over a wide range, a series of studies are carried out on the microwave discharge cusped field thruster. Since the magnetic field strength is one of the critical factors with a significant impact on the thruster, a plume plasma diagnosis is performed to analyze the discharge performance and plasma characteristics with different magnetic field strength conditions. A Faraday probe, a retarding potential analyzer, and an emissive probe are employed to characterize the plume. The results show that the variation of the magnetic field strength performs strong effects on the plume structure, the ion acceleration, and the electron conduction process. As the magnetic field strength weakens, the single-peaked plume profile transforms to a hollow cone structure, which is attributed to the conversion of acceleration mechanism. The thruster prototype performs a continuous thrust of 2–26.9 μN and a highest specific impulse of 248s with superior reproducibility in a low mass flow rate of 0.1sccm.

Analysis of Stable Chelate-free Gadolinium Loaded Titanium Dioxide Nanoparticles for MRI-Guided Radionuclide Stimulated Cancer Treatment.

Recent studies demonstrate that titanium dioxide nanoparticles (TiO2 NPs) are an effective source of reactive oxygen species (ROS) for photodynamic therapy and radionuclide stimulated dynamic therapy (RaST). Unfortunately tracking the in vivo distribution of TiO2 NPs noninvasively remains elusive. Given the use of gadolinium (Gd) chelates as effective contrast agents for magnetic resonance imaging (MRI), this study aims to (1) develop hybrid TiO2-Gd NPs that exhibit high relaxivity for tracking the NPs without loss of ROS generating capacity; and (2) establish a simple colorimetric assay for quantifying Gd loading and stability. A chelate-free, heat-induced method was used to load Gd onto TiO2 NPs, which was coated with transferrin (Tf). A sensitive colorimetric assay and inductively coupled plasma mass spectrometry (ICP-MS) were used to determine Gd loading and stability of the TiO2-Gd-Tf NPs. Measurement of the relaxivity was performed on a 1.4 T relaxometer and a 4.7 T small animal magnetic resonance scanner to estimate the effects of magnetic field strength. ROS was quantified by activated dichlorodihydrofluorescein diacetate fluorescence. Cell uptake of the NPs and RaST were monitored by fluorescence microscopy. Both 3 T and 4.7 T scanners were used to image the in vivo distribution of intravenously injected NPs in tumor-bearing mice. A simple colorimetric assay accurately determined both the loading and stability of the NPs compared with the expensive and complex ICP-MS method. Coating of the TiO2-Gd NPs with Tf stabilized the nanoconstruct and minimized aggregation. The TiO2-Gd-Tf maintained ROS-generating capability without inducing cell death at a wide range of concentrations but induced significant cell death under RaST conditions in the presence of F-18 radiolabeled 2-fluorodeoxyglucose. The longitudinal (r1 = 10.43 mM-1s-1) and transverse (r2 = 13.43 mM-1s-1) relaxivity of TiO2-Gd-Tf NPs were about twice and thrice, respectively, those of clinically used Gd contrast agent (Gd-DTPA; r1 = 3.77 mM-1s-1 and r2 = 5.51 mM-1s-1) at 1.4 T. While the r1 (8.13 mM-1s-1) reduced to about twice that of Gd-DTPA (4.89 mM-1s-1) at 4.7 T, the corresponding r2 (87.15 mM-1s-1) increased by a factor 22.6 compared to Gd-DTPA (r2 = 3.85). MRI of tumor-bearing mice injected with TiO2-Gd-Tf NPs tracked the NPs distribution and accumulation in tumors. This work demonstrates that Arsenazo III colorimetric assay can substitute ICP-MS for determining the loading and stability of Gd-doped TiO2 NPs. The new nanoconstruct enabled RaST effect in cells, exhibited high relaxivity, and enhanced MRI contrast in tumors in vivo, paving the way for in vivo MRI-guided RaST.

The dielectric breakdown strength of transformer oil based magnetic fluids: effect of magnetic field strength and exposure time

The dielectric breakdown strength of transformer oil based magnetic fluids: effect of magnetic field strength and exposure time

Effects of racetrack magnetic field strength on structure and properties of amorphous carbon coatings deposited by HiPIMS using deep oscillation pulses

In this study, non‑hydrogenated diamond like carbon (DLC) coatings were deposited by sputtering a graphite target in argon (Ar) by high power impulse magnetron sputtering (HiPIMS) using deep oscillation pulses. The effects of the magnetic field strength (B) tangential to surface of the target racetrack on the deposition parameters were studied. The structure, adhesion, and mechanical properties of DLC coatings deposited at different B were investigated by scanning electron microscopy (SEM), Raman spectroscopy, atomic force microscopy (AFM), scratch test, and nanoindentation. The tribological properties of the DLC coatings were evaluated using ball on disk wear test under dry and lubricated test conditions. It was found that the peak target current and substrate current density increased as B increased due to the enhanced electron confinement which results in an increased ionization efficiency. The enhanced ion bombardment was beneficial for improving the structure and properties of DLC coatings. As B increased, the DLC coatings exhibited more compact structure, smaller carbon mounds, and higher sp3 bond fractions. The improvement of the microstructure of the DLC coatings contributed to improved hardness and wear resistance of the coatings in both dry and lubricated test conditions. However, the deposition rate decreased at higher B owing to the high probability of back-attraction of carbon ions. The results suggested that controlling B in the range of 600 G to 700 G is important for achieving fully dense structure, high sp3 bond fractions, and high hardness for the DLC coatings deposited using HiPIMS. A further increase in B to 850 G showed no significant changes in the magnetic field induced effects on the structure and properties of the coatings.

Maximum Spreading of Impacting Ferrofluid Droplets under the Effect of Nonuniform Magnetic Field.

This article investigates the maximum spreading of ferrofluid droplets impacting on a hydrophobic surface under nonuniform magnetic fields. A generalized model for scaling the maximum spreading is developed. It is observed that, if the magnetic field strength is zero, a ferrofluid droplet not only demonstrates similar spreading dynamics as the water droplet but also obeys the same scaling law for the maximum spreading factor. Therefore, this article emphasizes the effects of magnetic field strength. In this regard, a dimensionless parameter (Nm) is introduced as the ratio between inertial force and Kelvin force, with an assumption that the kinetic energy mainly transforms to thermal energy. This parameter allows us to rescale all experimental data on a single curve with the Padé approximant, which is applicable to a wide range of impact velocities and magnetic field strengths.

Magnetophoretic Control of Diamagnetic Particles Inside an Evaporating Droplet.

The present study reports the magnetophoresis of diamagnetic particles in an evaporating ferrofluid droplet. Both solid and ring magnet arrangements are used to investigate the effect of magnetic field distribution. The distance of the magnet from the droplet is varied to study the effect of magnetic field strength. The magnetic field distribution is computed using COMSOL multiphysics software. Magnetometer measurements have been carried out to validate the simulation results. The motion of particles and the drying pattern of evaporating ferrofluid droplets are visualized using the confocal microscopy technique. Both bright-field and fluorescence imagings have been carried out to observe the differential deposition of the fluorescent particle (microparticle) and magnetic nanoparticles in the absence and presence of a magnetic field. The velocity of diamagnetic particles as a function of magnetic field distribution and strength has been studied using the micro-PIV technique. In the absence of the magnetic field, a ring-shaped deposition pattern is observed. The mixture of microparticles (diamagnetic) and nanoparticles (magnetic) is deposited between the outer and inner edges of the ring. The diamagnetic particles occupy the inner and outer edges of the ring. Magnetic particles travel toward the higher magnetic field zone and diamagnetic particles move toward the smaller magnetic field zone when a magnetic field is applied by a solid magnet placed over the droplet. This can be attributed to the negative magnetic force originating from the difference between the susceptibility of magnetic and nonmagnetic particles. The negative magnetic force on the microparticle increases as the magnetic field intensity increases, causing the microparticle to convect faster toward the contact line. The deposition behavior can be reversed or suppressed using a ring magnet in place of a solid magnet. In this case, the negative magnetic force is stronger at the contact line region of the droplet and decreases as it approaches the center region of the droplet. The deposition behavior of diamagnetic particle depends on the balance between the Marangoni force and the magnetophoretic force. Overall, the present study demonstrates the capability of the controlled deposition of diamagnetic polystyrene particles by suitable arrangement of the solid and ring magnet.

The effect of magnetic field strength on the positron range and projected annihilation artifact in integrated PET/MR systems: A GATE Monte Carlo study.

With improvements in positron emission tomography/magnetic resonance imaging (PET/MRI) over the last decade, there is a need to investigate the projected annihilation (shine-through) artifact and resolution impact for different PET radiopharmaceuticals, magnetic field (MF) strengths, and tissues. The GATE Monte Carlo (MC) simulation was used to simulate the annihilation distribution of positrons in different tissues and MFs. The positron distribution was studied in magnetic field (MF) intensities up to 15 T for 11 C, 13 N, 15 O, 18 F, 68 Ga, and 82 Rb. Moreover, the image quality in terms of the occurrence of projected annihilation artifacts was investigated using the 4D anthropomorphic digital extended cardiac-torso (XCAT) phantom. Positron ranges were restricted across the directions perpendicular to the MF, but no change along the direction of the MF was detected. The projected annihilation artifacts were observed with the presence of MF in the sagittal and coronal view of PET images prepared from the XCAT phantom. The intensity of artifact was constant in MFs higher than 3 T. The significant effect of the MF on resolution improvement was observed in soft tissue for 68 Ga in 7 T and 82 Rb in 3 and 7 T, while higher MFs have no impact on resolution. The improvement of resolution in the lung tissue was observed for the medium- and high-energy radionuclides in 7 T MF. The MF can create the projected annihilation artifact in the boundary of air cavities and other tissues for medium- and high-energy radionuclides especially for 68 Ga in clinical studies. In addition, the strength of the MFs more than 3 T was ineffective on the intensity of the projected annihilation artifact. In a clinical PET/MR scanner, MF has remarkable spatial resolution improvement in lung tissue, especially for medium- and high-energy radionuclides, and negligible effect in bone and soft tissue for most radionuclides.

Boundary Layer Flow and Heat Transfer Analysis by Using the Correlation Coefficient and Regression Model Over a Stretching Bullet-Shaped Object

The boundary layer theory is important when fluid flows over a solid surface that is moving or stationary. In presence of the boundary layer, the effective shape of the body may change leading to changes in pressure distribution, as a result, the overall lift and drag forces change. Therefore, the Boundary layer theory helps in designing aerofoil’s, to compute the lift and drag forces for the aerospace and automobile designers, to control the heat transfer rate from the device, etc. So, the present problem will help design the various types of bullet-shaped objects in the field of automobile engineering. Therefore, the current problem has focused on the two-dimensional axisymmetric BL flow over a stretching bullet-shaped object for the effect of magnetic field strength (M), linear stretching parameter (M), and surface thickness parameter (s). Therefore, the main goal of this work is to determine the relation by applying the correlation coefficient among the physical parameters and velocity field, temperature field, shear stress (τw), Nusselt number (Nux). Hence, the novelty of the current paper is to develop the relationship among the dependent and independent parameters by the correlation coefficient and also developed the numerical method to solve these highly nonlinear equations. The numerical results are discussed for the three different values of the stretching ratio parameter and two values of the surface thickness parameter. The velocity and temperature distribution equations are compressed into a system of ODEs with similarity transformations. These ODEs are then solved using a spectral quasi-linearization method (SQLM) by applying Taylor series expansions that can be used to linearize the non-linear terms in the equations. These resulting linearized systems of equations are determined by the spectral collocation method. The convergence of the numerical solutions was performed by using the residual error of the PDEs. The error analysis is established for the validity of the present model. This error norm is applied to establish the validity and convergence of the numerical solution. The outcome of the mentioned dimensionless parameters over the fluid velocity field, temperature field, skin friction coefficient (Cf), and Nusselt number (Nux) are displayed graphically. It is observed that the parameters M and M are positively correlated with fluid velocity distribution within the BL but the surface thickness parameter(s) are negatively correlated. The rate of temperature increases for the parameter M and Pr but decreases for M and s. Therefore, the boundary layer thickness reduces for increasing the values of M and M but increases for increasing the values of s. The velocity of the fluid is about 80% higher in the case of a thinner surface (s = 0.2) than the thicker surface (s = 2.0) and the heat transfer rate is also igher in the case of a thinner surface comparatively thicker surface. The innovation of this present problem lies in the unification of more physical parameters into the governing equations and an attempt to give a thorough analysis of how the flow properties are affected by these parameters.

Variable Gap Sealing Technology of a Hydraulic Cylinder Based on Magnetic Shape Memory Alloy

The synergistic control of resistance reduction and sealing poses challenges to enhancing the rapid dynamic response ability of servo hydraulic cylinders; the key to solving this problem is effectively controlling the sealing gap value. In this study, a micro-variation between the hydraulic cylinder and the piston based on the disadvantage of conventional seals, constant gap seals, and lip gap seals was constructed; MSMA assist support blocks were designed on the piston to form a gap seal strip; then, the sealing gap value could be changed by controlling the magnetic field intensity. Simultaneously, the effects of magnetic field strength, parts-manufacturing precision, temperature, and hysteresis on the micro-variation in the MSMA were analyzed, and effective solutions were proposed. Finally, experiments on the magnetic field, temperature, and hysteresis were conducted by the measurement system. The results showed that the variable value of the sealing gap with the MSMA is feasible under ideal conditions, and can effectively change the amount of MSMA expansion by controlling the magnetic field strength, temperature, preload, etc., and then change the amount of the sealing gap of the hydraulic cylinder. This is the key to achieving friction and sealing control, which plays a crucial and active role in improving the efficiency of hydraulic systems. However, the impact of hysteresis effects cannot be ignored, which will be the main problem to be solved in the future.