The main goal of this paper is to investigate natural convective heat transfer and flow characteristics of non-Newtonian nanofluid streaming between two infinite vertical flat plates in the presence of magnetic field ...The main goal of this paper is to investigate natural convective heat transfer and flow characteristics of non-Newtonian nanofluid streaming between two infinite vertical flat plates in the presence of magnetic field and thermal radiation.Initially,a similarity transformation is used to convert momentum and energy conservation equations in partial differential forms into non-linear ordinary differential equations (ODE) applying meaningful boundary conditions.In order to obtain the non-linear ODEs analytically,Galerkin method (GM) is employed.Subsequently,the ODEs are also solved by a reliable numerical solution.In order to test the accuracy,precision and reliability of the analytical method,results of the analytical analysis are compared with the numerical results.With respect to the comparisons,fairly good compatibilities with insignificant errors are observed.Eventually,the impacts of effective parameters including magnetic and radiation parameters and nanofluid volume fraction on the velocity,skin friction coefficient and Nusselt number distributions are comprehensively described.Based on the results,it is revealed that with increasing the role of magnetic force,velocity profile,skin friction coefficient and thermal performance descend.Radiation parameter has insignificant influence on velocity profile while it obviously has augmentative and decreasing effects on skin friction and Nusselt number,respectively.展开更多
As an integrated control unit that directly transfo rm s digital electric signals into analogy hydraulic signals, High-speed response solenoid valve (HSV) plays an important role in determining an electro-hydrauli c a...As an integrated control unit that directly transfo rm s digital electric signals into analogy hydraulic signals, High-speed response solenoid valve (HSV) plays an important role in determining an electro-hydrauli c automatic system’s overall performance. In the process of designing an HSV, o ne should well understand that various soft magnetic material properties and geo metries greatly affect HSV’s magnetic field design that accordingly has a direc t influence on HSV’s electric performance. As an approach of improving HSV perf ormance, this paper presents an optimal design method on HSV’s magnetic field b y making a full consideration of the effects of various soft magnetic material a nd geometries. The proposed optimal design method, based on HSV’s three-dimens ion solid modeling with the PRO/E software, simplifying from the previous three -dimension solid model to the axially symmetric plane model of the magnetic fie ld and the consequent the magnetic finite element method simulating within ANSYS analysis environment for obtaining accurate results on the distribution of HSV ’s magnetic field and flux-line as well as the magnetic force, can achieve lar ger magnetic force and lower power of an HSV by adjusting the structure paramete rs of the solenoid valve and selecting various soft magnetic materials which are of different B-H (flux density vs. field intensity) curves. Considering the no nlinearity and saturation of various soft magnetic materials, this paper process es the nonlinearity simulated calculation and experiment measure of three soft m agnetic materials and different structure parameters. The comparison of the simu lating and experimenting results proves that the simulating calculation and the proposed optimal design method are effective in HSV’s designing and its perform ance prediction. The researching results show that, for HSV’s designing, the pr oposed optimal design method can well simulate HSV’s the magnetic field, enhanc e the reliability and accuracy, reduce the cost, shorten the cycle, and henc e has practical value for engineering purpose.展开更多
This investigation numerically examined the combined impacts of different turbulator shapes,Al_(2)O_(3)/water nanofluid,and inclined magnetic field on the thermal behavior of micro-scale inclined forward-facing step(M...This investigation numerically examined the combined impacts of different turbulator shapes,Al_(2)O_(3)/water nanofluid,and inclined magnetic field on the thermal behavior of micro-scale inclined forward-facing step(MSIFFS).The length and height for all turbulators were considered 0.0979 and 0.5 mm,respectively,and the Reynolds number varied from 5000 to 10000.In order to compare the skin friction coefficient(SFC) and the heat transfer rate(HTR)simultaneously,the thermal performance factor parameter(TPF) was selected.The results show that all considered cases equipped with turbulators were thermodynamically more advantageous over the simple MSIFFS.Besides,using Al_(2)O_(3)/water nanofluid with different nanoparticles volume fractions(NVF) in the presence of inclined magnetic field(IMF)increased HTR.With an increment of NVF from 1% to 4% and magnetic field density(MFD) from 0.002 to 0.008 T,HTR and subsequently TPF improved.The best result was observed for MSIFFS equipped with a trapezoidal-shaped turbulator with 4% Al_(2)O_(3) in the presence of IMF(B=0.008 T).The TPF increased with the augmentation of Re,and the maximum value of it was 5.2366 for MSIFFS equipped with a trapezoidal-shaped turbulator with 4% Al_(2)O_(3),B=0.008 T,and Re=10000.展开更多
In this study,the stagnation point transport of second grade fluid with linear stretching under the effects of variable thermal conductivity is considered.Induced magnetic field impact is also incorporated.The nonline...In this study,the stagnation point transport of second grade fluid with linear stretching under the effects of variable thermal conductivity is considered.Induced magnetic field impact is also incorporated.The nonlinear set of particle differential equations is converted into set of ordinary differential equations through appropriate transformation.The resulting equations are then resolved by optimal homotopy analysis method.The effect of pertinent parameters of interest on skin friction coefficient,temperature,induced magnetic field,velocity and local Nusselt number is inspected by generating appropriate plots.For numerical results,the built-in bvp4 c technique in computational software MATLAB is used for the convergence and residual errors of obtained series solution.It is perceived that the induced magnetic field is intensified by increasing β.It can also be observed that skin friction coefficient enhances with increasing value of magnetic parameter depending on the stretching ratio a/c.For the validness of the obtained results,a comparison has been made and an excellent agreement of current study with existing literature is found.展开更多
Numerical study was performed for a better understanding on thermomagnetic convection under magnetic quadrupole field utilizing the lattice Boltzmann method. Present problem was examined under non-gravitational and gr...Numerical study was performed for a better understanding on thermomagnetic convection under magnetic quadrupole field utilizing the lattice Boltzmann method. Present problem was examined under non-gravitational and gravitational conditions for a wide range of magnetic force number from 0 to 1000. Vertical walls of the square cavity were heated differentially while the horizontal walls were assumed to be adiabatic. Distributions of the flow and temperature field were clearly illustrated. Under non-gravitational condition, the flow presents a two-cellular structure with horizontal symmetry, and the average Nusselt number increases with the augment of magnetic force number. Under gravitational condition, two-cellular structure only occurs when the magnetic field is relatively strong, and the average Nusselt number decreases at first and then rises with the enhancing magnetic field. Results show that the magnetic field intensity and the Rayleigh number both have significant influence on convective heat transfer, and the gravity plays a positive role in heat transfer under weak magnetic field while a negative one for magnetic force numbers larger than 1×10~5.展开更多
The powerful alternate magnetic field treatment is an effective not-heat treatment, which improves the coriaceous performance of the material. In order to reveal the effect rule of the powerful alternate magnetic fiel...The powerful alternate magnetic field treatment is an effective not-heat treatment, which improves the coriaceous performance of the material. In order to reveal the effect rule of the powerful alternate magnetic field on the structure capability after thermal plastic forming, the experimental methods were adopted to compare the microcosmic structure of the LY12 aluminium alloy test pieces before and after the powerful alternate magnetic field treatment. The mechanism of the structure refining was analyzed theoretically. According to the effect rule of the alternate magnetic field on critical grain growth work and the magnetic vibration-constriction mechanism, the structure dynamics factors were analyzed. The results show that, after a certain powerful alternate magnetic field treatment, the mechanical capability of the LY12 aluminium alloy after thermal plastic forming can be reinforced, the structure intertwist deriving from the thermal plastic forming becomes even and the branch crystal is also smashed, consequently refines the structure. The powerful alternate magnetic field treatment can be regarded as an effective method to improve metal structure performance after heat plastic forming.展开更多
In the case of three-layered(air-seawater-seabed)model,the analytical expressions of the static electric and static magnetic field produced by the static electric dipole located in seawater were derived by using the m...In the case of three-layered(air-seawater-seabed)model,the analytical expressions of the static electric and static magnetic field produced by the static electric dipole located in seawater were derived by using the mirror image theory.Combined with the distribution of the underwater electric potential measured in laboratory,an electric dipole model for physical scale of ship was established and the distribution characteristics of an actual ship' s corrosion related magnetic field were obtained.Based on established models,theoretical analysis and calculation were made to catch out the distribution characteristics of static magnetic field related with corrosion and anticorrosion,which can not be measured directly in seawater.The results show that the static magnetic field related with corrosion and anticorrosion is a kind of noteworthy obstacle signal for degaussed ships.展开更多
The influence of a magnetic field on the stability of a shaped charge jet is experimentally investigated at standoffs of 490,650 and 800 mm.The experimental results without and with the magnetic field are compared in ...The influence of a magnetic field on the stability of a shaped charge jet is experimentally investigated at standoffs of 490,650 and 800 mm.The experimental results without and with the magnetic field are compared in terms of the shaped charge jet form,stability and penetration ability.A theoretical model based on one-dimension fluid dynamics is then developed to assess the depth of penetration of the shaped charge at those three standoffs and magnetic conditions.The results show that the penetration capability can be enhanced in more than 70%by the magnetic field.The theoretical calculations are compared with the experimental results with reasonably good correlation.In addition,the parameters introduced in the theory are discussed together with the experiments at three standoffs studied.展开更多
Fe3O4 magnetic nanoparticles with diameters varying from 10 to 426 nm were synthesized and characterized.Heating effects of Fe3O4 magnetic nanoparticles under radiofrequency capacitive field(RCF) with frequency of 27....Fe3O4 magnetic nanoparticles with diameters varying from 10 to 426 nm were synthesized and characterized.Heating effects of Fe3O4 magnetic nanoparticles under radiofrequency capacitive field(RCF) with frequency of 27.12 MHz and power of 60-150 W were investigated.When the power of RCF is lower than 90 W,temperatures of Fe3O4 magnetic nanoparticles(75-150 mg/mL) can be raised and maximal temperatures are all lower than 50 ℃.When the power of RCF is 90-150 W,temperatures of Fe3O4 magnetic nanoparticles can be quickly raised and are all obviously higher than those of normal saline and distilled water under the same conditions.Temperature of Fe3O4 magnetic nanoparticles can even reach 70.2 ℃ under 150 W RCF.Heating effects of Fe3O4 magnetic nanoparticles are related to RCF power,particle size and particle concentration.展开更多
It is established that the large-scale and global magnetic fields in the Sun's atmosphere do not change smoothly, and long-lasting periods of gradual variations are superseded by fast structural changes of the glo...It is established that the large-scale and global magnetic fields in the Sun's atmosphere do not change smoothly, and long-lasting periods of gradual variations are superseded by fast structural changes of the global magnetic field. Periods of fast global changes on the Sun are accompanied by anomalous manifestations in the interplanetary space and in the geomagnetic field. There is a regular recurrence of these periods in each cycle of solar activity, and the periods are characterized by enhanced flaring activity that reflects fast changes in magnetic structures. Is demonstrated, that the fast changes have essential influencing on a condition of space weather, as most strong geophysical disturbances are connected to sporadic phenomena on the Sun. An explanation has been offered for the origin of anomalous geomagnetic disturbances that are unidentifiable in traditionally used solar activity indices. Is shown, main physical mechanism that leads to fast variations of the magnetic fields in the Sun's atmosphere is the reconnection process.展开更多
A sputtering-type microwave multipolar ECR plasma processing for preparing thin films, is built with Nd-Fe-B magnets and 2.45 GHz, TE<sub>10</sub> mode microwave. The plasma distributions in the axial dire...A sputtering-type microwave multipolar ECR plasma processing for preparing thin films, is built with Nd-Fe-B magnets and 2.45 GHz, TE<sub>10</sub> mode microwave. The plasma distributions in the axial direction, which is important for preparing thin films, are found to be very sensitive to the magnetic potential fields in plasma chamber. The plasma parameters are also influenced by the background gas pressure.展开更多
In recent years,magnetic fields have been widely applied in catalysis to increase the performance of electrocatalysis,photocatalysis,and thermocatalysis through an important noncontact way.This work demonstrated that ...In recent years,magnetic fields have been widely applied in catalysis to increase the performance of electrocatalysis,photocatalysis,and thermocatalysis through an important noncontact way.This work demonstrated that doping CsPbCl_(3) halide perovskite nanocrystals with nickel ions(Ni^(2+))and applying an external magnetic field can significantly enhance the performance of the photocatalytic carbon dioxide reduction reaction(CO_(2)RR).Compared with its counterpart,Ni-doped CsPbCl_(3) exhibits a sixfold increase in CO_(2)RR efficiency under a 500 mT magnetic field.Insights into the mechanism of this enhancement effect were obtained through photogenerated current density measurements and X-ray magnetic circular dichroism.The results illustrate that the significant enhancement in catalytic performance by the magnetic field is attributed to the synergistic effects of magnetic element doping and the external magnetic field,leading to reduced electron‒hole recombination and extended carrier lifetimes.This study provides an effective strategy for enhancing the efficiency of the photocatalytic CO_(2)RR by manipulating spin-polarized electrons in photocatalytic semiconductors via a noncontact external magnetic field.展开更多
The effects of magnetic field intensity, roasting temperature and roasting time on digestion rate and settling performance of bauxite with different iron contents were investigated systematically. The results indicate...The effects of magnetic field intensity, roasting temperature and roasting time on digestion rate and settling performance of bauxite with different iron contents were investigated systematically. The results indicate that such magnetic treatment can profoundly change the microstructure and digestion performance of bauxite. For the two samples carrying different iron contents, phase transformation of the aluminum oxide phase proceeds faster in the high iron bauxite than the low one. The optimal pretreatment conditions of low iron bauxite are roasting temperature 550 ℃ and magnetic field intensity 6 T, while for high iron bauxite are 500 ℃ and 9 T. The digestion rate of alumina can reach 95% and 92% at digestion temperature of 190 ℃ and 250 ℃. The settling performances of roasted ore by intense magnetic field after digestion are enhanced through pretreatment.展开更多
The interference of carrier magnetic field to geomagnetic field has been a difficult problem for a long time,which influences on the deviation of navigation compass and the error of geomagnetic measurement. To increas...The interference of carrier magnetic field to geomagnetic field has been a difficult problem for a long time,which influences on the deviation of navigation compass and the error of geomagnetic measurement. To increase the geomagnetic measuring accuracy required for the geomagnetic matching localization,the strategy to eliminate the effect of connatural and induced magnetic fields of carrier on the geomagnetic measuring accuracy is investigated. The magnetic-dipole's magnetic field distributing theory is used to deduce the magnetic composition in the position of the sensor installed on the carrier. A geomagnetic measurement model is established by using the measuring data with the ideal sensor. Considering the magnetic disturbance of carrier and the error of sensor,a geomagnetic measuring compensation model is built. This model can be used to compensate the errors of carrier magnetic field and magnetic sensor in any case and its parameters have clear or specific physical meaning. The experimented results show that the model has higher geomagnetic measuring accuracy than that of others.展开更多
To degrade the organic compounds in the electroplating wastewater,magnetic field was tentatively introduced into electrocatalytic oxidation on Ti-PbO2 anode.The magnetic field assisted electrocatalytic oxidation can p...To degrade the organic compounds in the electroplating wastewater,magnetic field was tentatively introduced into electrocatalytic oxidation on Ti-PbO2 anode.The magnetic field assisted electrocatalytic oxidation can promote anion movement and the generation of active species,resulting more organic compounds to be oxidized and degraded.Oxidation parameters such as treatment time,current density and initial pH of the wastewater were systematically discussed and optimized.The mineralization of organic compounds is improved by over 15% under a magnetic density of 22 mT while the current density is 50 A/m2,pH is 1.8 and the reaction time is 1.5 h.The results indicate that the magnetic field assisted electrocatalytic oxidation has considerable potential in electroplating wastewater treatment.展开更多
In this work,the chromium aluminum nitride(CrAlN)coatings were prepared on TC11 titanium alloy by composite magnetic field cathodic arc ion plating with controllable pulse electromagnetic combined with permanent magne...In this work,the chromium aluminum nitride(CrAlN)coatings were prepared on TC11 titanium alloy by composite magnetic field cathodic arc ion plating with controllable pulse electromagnetic combined with permanent magnet.The effects of electromagnetic frequency on the morphology,microstructure,nano-hardness and elastic modulus of the coatings were investigated by scanning electron microscope(SEM),X-ray diffraction(XRD)and nano-indenter.This paper has mainly studied the influence of CrAlN coatings which are prepared at various electromagnetic frequencies on the wear and erosion resistance through a series of wear and solid particle erosion experiments.It was found that the deposition rate of CrAlN coatings increases with the increase of electromagnetic frequency.And CrAlN coatings all preferentially grew along the(111)crystal plane.At 16.7 Hz,with the increase of pulsed electromagnetic frequency,the hardness is the highest(23.6 GPa)and the adhesion is the highest(41.5 N).In addition,the coating deposition exhibited the best wear and solid erosion resistance at 16.7 Hz and 33.3 Hz,the friction coefficient is about 0.35,and the erosion rate is about 0.2μm/g at 30°and less than 1μm/g at 90°,respectively.These results indicate that the CrAlN coating formed at an appropriate pulsed electromagnetic frequency can achieve excellent mechanical properties,wear and solid erosion resistance.展开更多
Polyaniline(PAn)doped with multiple sulfonic acid system of dodecylbenzenesulfonic acid(DBSA)and sulfosalicylic acid(SSA)was synthesized by emulsion polymerization using ammonium persulfate(APS)as an oxidizing agent i...Polyaniline(PAn)doped with multiple sulfonic acid system of dodecylbenzenesulfonic acid(DBSA)and sulfosalicylic acid(SSA)was synthesized by emulsion polymerization using ammonium persulfate(APS)as an oxidizing agent in the presence and the absence of a constant magnetic field(MF)of 0.8 T.The structure and properties of the PAn were characterized by X-ray diffractometer(XRD),thermogravimetric apparatus(TGA),FT-IR spectroscope(FT-IR)and four probe digital multimeter.The results indicate that,when the molar ratio of DBSA to SSA is 1/3,that of dopant to An is 3/2,that of APS to An is 4/5 in the synthesizing media,and the doping time is 3 h,the conductivity of the PAn synthesized in the presence of the MF of 0.8 T reaches 5.88 S/cm,which is higher than that of the PAn synthesized in the absence of the MF.The thermal stability,the crystallinity and the doping degree of the PAn synthesized in the presence of the MF are also improved.MF not only enhances the conductivity,but also reduces the doping time,the dosage of the dopant and the oxidizing agent when the conductivity reaches the maximum.展开更多
The effect of a high magnetic field up to 30T on phase transformation temperature and microstructure of Fe-based alloys has been reviewed. A high magnetic field accelerates ferrite transformation, changes the morpho...The effect of a high magnetic field up to 30T on phase transformation temperature and microstructure of Fe-based alloys has been reviewed. A high magnetic field accelerates ferrite transformation, changes the morphology of the transformed microstructures and increases the A3 and A1 temperature. In a magnetic field of 30T, the A1 temperature increases by about 37.1℃ for Fe-0.8C, the A3 temperature for pure Fe increases by about 33.1℃. The measured transformation temperature data are not consistent with calculation results using Weiss molecular field theory. Ferrite grains are elongated and aligned along the direction of magnetic field in Fe-0.4C and Fe-0.6C alloys by ferrite transformation, but elongated and aligned structure was not found in pure Fe, Fe-0.05C alloy and Fe-1.5Mn-0.11C-0.1V alloy.展开更多
文摘The main goal of this paper is to investigate natural convective heat transfer and flow characteristics of non-Newtonian nanofluid streaming between two infinite vertical flat plates in the presence of magnetic field and thermal radiation.Initially,a similarity transformation is used to convert momentum and energy conservation equations in partial differential forms into non-linear ordinary differential equations (ODE) applying meaningful boundary conditions.In order to obtain the non-linear ODEs analytically,Galerkin method (GM) is employed.Subsequently,the ODEs are also solved by a reliable numerical solution.In order to test the accuracy,precision and reliability of the analytical method,results of the analytical analysis are compared with the numerical results.With respect to the comparisons,fairly good compatibilities with insignificant errors are observed.Eventually,the impacts of effective parameters including magnetic and radiation parameters and nanofluid volume fraction on the velocity,skin friction coefficient and Nusselt number distributions are comprehensively described.Based on the results,it is revealed that with increasing the role of magnetic force,velocity profile,skin friction coefficient and thermal performance descend.Radiation parameter has insignificant influence on velocity profile while it obviously has augmentative and decreasing effects on skin friction and Nusselt number,respectively.
文摘As an integrated control unit that directly transfo rm s digital electric signals into analogy hydraulic signals, High-speed response solenoid valve (HSV) plays an important role in determining an electro-hydrauli c automatic system’s overall performance. In the process of designing an HSV, o ne should well understand that various soft magnetic material properties and geo metries greatly affect HSV’s magnetic field design that accordingly has a direc t influence on HSV’s electric performance. As an approach of improving HSV perf ormance, this paper presents an optimal design method on HSV’s magnetic field b y making a full consideration of the effects of various soft magnetic material a nd geometries. The proposed optimal design method, based on HSV’s three-dimens ion solid modeling with the PRO/E software, simplifying from the previous three -dimension solid model to the axially symmetric plane model of the magnetic fie ld and the consequent the magnetic finite element method simulating within ANSYS analysis environment for obtaining accurate results on the distribution of HSV ’s magnetic field and flux-line as well as the magnetic force, can achieve lar ger magnetic force and lower power of an HSV by adjusting the structure paramete rs of the solenoid valve and selecting various soft magnetic materials which are of different B-H (flux density vs. field intensity) curves. Considering the no nlinearity and saturation of various soft magnetic materials, this paper process es the nonlinearity simulated calculation and experiment measure of three soft m agnetic materials and different structure parameters. The comparison of the simu lating and experimenting results proves that the simulating calculation and the proposed optimal design method are effective in HSV’s designing and its perform ance prediction. The researching results show that, for HSV’s designing, the pr oposed optimal design method can well simulate HSV’s the magnetic field, enhanc e the reliability and accuracy, reduce the cost, shorten the cycle, and henc e has practical value for engineering purpose.
文摘This investigation numerically examined the combined impacts of different turbulator shapes,Al_(2)O_(3)/water nanofluid,and inclined magnetic field on the thermal behavior of micro-scale inclined forward-facing step(MSIFFS).The length and height for all turbulators were considered 0.0979 and 0.5 mm,respectively,and the Reynolds number varied from 5000 to 10000.In order to compare the skin friction coefficient(SFC) and the heat transfer rate(HTR)simultaneously,the thermal performance factor parameter(TPF) was selected.The results show that all considered cases equipped with turbulators were thermodynamically more advantageous over the simple MSIFFS.Besides,using Al_(2)O_(3)/water nanofluid with different nanoparticles volume fractions(NVF) in the presence of inclined magnetic field(IMF)increased HTR.With an increment of NVF from 1% to 4% and magnetic field density(MFD) from 0.002 to 0.008 T,HTR and subsequently TPF improved.The best result was observed for MSIFFS equipped with a trapezoidal-shaped turbulator with 4% Al_(2)O_(3) in the presence of IMF(B=0.008 T).The TPF increased with the augmentation of Re,and the maximum value of it was 5.2366 for MSIFFS equipped with a trapezoidal-shaped turbulator with 4% Al_(2)O_(3),B=0.008 T,and Re=10000.
文摘In this study,the stagnation point transport of second grade fluid with linear stretching under the effects of variable thermal conductivity is considered.Induced magnetic field impact is also incorporated.The nonlinear set of particle differential equations is converted into set of ordinary differential equations through appropriate transformation.The resulting equations are then resolved by optimal homotopy analysis method.The effect of pertinent parameters of interest on skin friction coefficient,temperature,induced magnetic field,velocity and local Nusselt number is inspected by generating appropriate plots.For numerical results,the built-in bvp4 c technique in computational software MATLAB is used for the convergence and residual errors of obtained series solution.It is perceived that the induced magnetic field is intensified by increasing β.It can also be observed that skin friction coefficient enhances with increasing value of magnetic parameter depending on the stretching ratio a/c.For the validness of the obtained results,a comparison has been made and an excellent agreement of current study with existing literature is found.
基金Project(11572056)supported by the National Natural Science Foundation of ChinaProject(15A006)supported by the Scientific Research Fund of Hunan Provincial Education Department,China
文摘Numerical study was performed for a better understanding on thermomagnetic convection under magnetic quadrupole field utilizing the lattice Boltzmann method. Present problem was examined under non-gravitational and gravitational conditions for a wide range of magnetic force number from 0 to 1000. Vertical walls of the square cavity were heated differentially while the horizontal walls were assumed to be adiabatic. Distributions of the flow and temperature field were clearly illustrated. Under non-gravitational condition, the flow presents a two-cellular structure with horizontal symmetry, and the average Nusselt number increases with the augment of magnetic force number. Under gravitational condition, two-cellular structure only occurs when the magnetic field is relatively strong, and the average Nusselt number decreases at first and then rises with the enhancing magnetic field. Results show that the magnetic field intensity and the Rayleigh number both have significant influence on convective heat transfer, and the gravity plays a positive role in heat transfer under weak magnetic field while a negative one for magnetic force numbers larger than 1×10~5.
基金Project(50675190) supported by the National Natural Science Foundation of China
文摘The powerful alternate magnetic field treatment is an effective not-heat treatment, which improves the coriaceous performance of the material. In order to reveal the effect rule of the powerful alternate magnetic field on the structure capability after thermal plastic forming, the experimental methods were adopted to compare the microcosmic structure of the LY12 aluminium alloy test pieces before and after the powerful alternate magnetic field treatment. The mechanism of the structure refining was analyzed theoretically. According to the effect rule of the alternate magnetic field on critical grain growth work and the magnetic vibration-constriction mechanism, the structure dynamics factors were analyzed. The results show that, after a certain powerful alternate magnetic field treatment, the mechanical capability of the LY12 aluminium alloy after thermal plastic forming can be reinforced, the structure intertwist deriving from the thermal plastic forming becomes even and the branch crystal is also smashed, consequently refines the structure. The powerful alternate magnetic field treatment can be regarded as an effective method to improve metal structure performance after heat plastic forming.
基金Sponsored by National Defense Pre-research Foundation(51444070105JB11)
文摘In the case of three-layered(air-seawater-seabed)model,the analytical expressions of the static electric and static magnetic field produced by the static electric dipole located in seawater were derived by using the mirror image theory.Combined with the distribution of the underwater electric potential measured in laboratory,an electric dipole model for physical scale of ship was established and the distribution characteristics of an actual ship' s corrosion related magnetic field were obtained.Based on established models,theoretical analysis and calculation were made to catch out the distribution characteristics of static magnetic field related with corrosion and anticorrosion,which can not be measured directly in seawater.The results show that the static magnetic field related with corrosion and anticorrosion is a kind of noteworthy obstacle signal for degaussed ships.
基金National Natural Science Foundation of China(Grant No.11972196)Youth fund of Jiangsu Natural Science Foundation(Grant Nos.BK20190433)National Natural Science Funds for Distinguished Young Scholar of China(Grant No.11702144)to provide fund for conducting experiments.
文摘The influence of a magnetic field on the stability of a shaped charge jet is experimentally investigated at standoffs of 490,650 and 800 mm.The experimental results without and with the magnetic field are compared in terms of the shaped charge jet form,stability and penetration ability.A theoretical model based on one-dimension fluid dynamics is then developed to assess the depth of penetration of the shaped charge at those three standoffs and magnetic conditions.The results show that the penetration capability can be enhanced in more than 70%by the magnetic field.The theoretical calculations are compared with the experimental results with reasonably good correlation.In addition,the parameters introduced in the theory are discussed together with the experiments at three standoffs studied.
基金Projects(30571779,10775085) supported by the National Natural Science Foundation of ChinaProject(Z07000200540704) supported by Beijing Municipal Science and Technology Commission,China
文摘Fe3O4 magnetic nanoparticles with diameters varying from 10 to 426 nm were synthesized and characterized.Heating effects of Fe3O4 magnetic nanoparticles under radiofrequency capacitive field(RCF) with frequency of 27.12 MHz and power of 60-150 W were investigated.When the power of RCF is lower than 90 W,temperatures of Fe3O4 magnetic nanoparticles(75-150 mg/mL) can be raised and maximal temperatures are all lower than 50 ℃.When the power of RCF is 90-150 W,temperatures of Fe3O4 magnetic nanoparticles can be quickly raised and are all obviously higher than those of normal saline and distilled water under the same conditions.Temperature of Fe3O4 magnetic nanoparticles can even reach 70.2 ℃ under 150 W RCF.Heating effects of Fe3O4 magnetic nanoparticles are related to RCF power,particle size and particle concentration.
基金Supported by the China-Russia Joint Research Center on Space Weather,Chinese Academy of Sciences
文摘It is established that the large-scale and global magnetic fields in the Sun's atmosphere do not change smoothly, and long-lasting periods of gradual variations are superseded by fast structural changes of the global magnetic field. Periods of fast global changes on the Sun are accompanied by anomalous manifestations in the interplanetary space and in the geomagnetic field. There is a regular recurrence of these periods in each cycle of solar activity, and the periods are characterized by enhanced flaring activity that reflects fast changes in magnetic structures. Is demonstrated, that the fast changes have essential influencing on a condition of space weather, as most strong geophysical disturbances are connected to sporadic phenomena on the Sun. An explanation has been offered for the origin of anomalous geomagnetic disturbances that are unidentifiable in traditionally used solar activity indices. Is shown, main physical mechanism that leads to fast variations of the magnetic fields in the Sun's atmosphere is the reconnection process.
文摘A sputtering-type microwave multipolar ECR plasma processing for preparing thin films, is built with Nd-Fe-B magnets and 2.45 GHz, TE<sub>10</sub> mode microwave. The plasma distributions in the axial direction, which is important for preparing thin films, are found to be very sensitive to the magnetic potential fields in plasma chamber. The plasma parameters are also influenced by the background gas pressure.
基金supported by the National Key R&D Program of China(2021YFA1501003)the Joint Funds of the National Natural Science Foundation of China(U23A2081)+5 种基金the National Natural Science Foundation of China(92261105,22221003)the Anhui Provincial Key Research and Development Project(2023z04020010,2022a05020053)the Anhui Provincial Natural Science Foundation(2108085UD06,2208085UD04)the USTC Research Funds of the Double First Class Initiative(YD2060002029,YD2060006005)the Fundamental Research Funds for the Central Universities(WK2060000004,WK2060000021,WK2060000025,WK9990000155)the Joint Funds from Hefei National Synchrotron Radiation Laboratory(KY2060000180,KY2060000195).
文摘In recent years,magnetic fields have been widely applied in catalysis to increase the performance of electrocatalysis,photocatalysis,and thermocatalysis through an important noncontact way.This work demonstrated that doping CsPbCl_(3) halide perovskite nanocrystals with nickel ions(Ni^(2+))and applying an external magnetic field can significantly enhance the performance of the photocatalytic carbon dioxide reduction reaction(CO_(2)RR).Compared with its counterpart,Ni-doped CsPbCl_(3) exhibits a sixfold increase in CO_(2)RR efficiency under a 500 mT magnetic field.Insights into the mechanism of this enhancement effect were obtained through photogenerated current density measurements and X-ray magnetic circular dichroism.The results illustrate that the significant enhancement in catalytic performance by the magnetic field is attributed to the synergistic effects of magnetic element doping and the external magnetic field,leading to reduced electron‒hole recombination and extended carrier lifetimes.This study provides an effective strategy for enhancing the efficiency of the photocatalytic CO_(2)RR by manipulating spin-polarized electrons in photocatalytic semiconductors via a noncontact external magnetic field.
基金Projects(U1202274,51004033,51204040,50974035)supported by the National Natural Science Foundation of ChinaProjects(2010AA03A405,2012AA062303)supported by the National High Technology Research and Development Program(863 Prograam)of ChinaProject(N100302005)supported by the Fundamental Research Funds for the Central Universities,China
文摘The effects of magnetic field intensity, roasting temperature and roasting time on digestion rate and settling performance of bauxite with different iron contents were investigated systematically. The results indicate that such magnetic treatment can profoundly change the microstructure and digestion performance of bauxite. For the two samples carrying different iron contents, phase transformation of the aluminum oxide phase proceeds faster in the high iron bauxite than the low one. The optimal pretreatment conditions of low iron bauxite are roasting temperature 550 ℃ and magnetic field intensity 6 T, while for high iron bauxite are 500 ℃ and 9 T. The digestion rate of alumina can reach 95% and 92% at digestion temperature of 190 ℃ and 250 ℃. The settling performances of roasted ore by intense magnetic field after digestion are enhanced through pretreatment.
基金Sponsored by National Defence the 11th Five-Year Pre-research Project (51309060301)
文摘The interference of carrier magnetic field to geomagnetic field has been a difficult problem for a long time,which influences on the deviation of navigation compass and the error of geomagnetic measurement. To increase the geomagnetic measuring accuracy required for the geomagnetic matching localization,the strategy to eliminate the effect of connatural and induced magnetic fields of carrier on the geomagnetic measuring accuracy is investigated. The magnetic-dipole's magnetic field distributing theory is used to deduce the magnetic composition in the position of the sensor installed on the carrier. A geomagnetic measurement model is established by using the measuring data with the ideal sensor. Considering the magnetic disturbance of carrier and the error of sensor,a geomagnetic measuring compensation model is built. This model can be used to compensate the errors of carrier magnetic field and magnetic sensor in any case and its parameters have clear or specific physical meaning. The experimented results show that the model has higher geomagnetic measuring accuracy than that of others.
基金Project(2008ZX07101-006-09) supported by the Major Science and Technology Program for Water Pollution Control and Treatment of China
文摘To degrade the organic compounds in the electroplating wastewater,magnetic field was tentatively introduced into electrocatalytic oxidation on Ti-PbO2 anode.The magnetic field assisted electrocatalytic oxidation can promote anion movement and the generation of active species,resulting more organic compounds to be oxidized and degraded.Oxidation parameters such as treatment time,current density and initial pH of the wastewater were systematically discussed and optimized.The mineralization of organic compounds is improved by over 15% under a magnetic density of 22 mT while the current density is 50 A/m2,pH is 1.8 and the reaction time is 1.5 h.The results indicate that the magnetic field assisted electrocatalytic oxidation has considerable potential in electroplating wastewater treatment.
基金Projects(2017GDAS CX-0202,2017GDAS CX-0111,2018 GDAS CX-0402) supported by Guangdong Academy of Science’ Special Project of Science and Technology Development,ChinaProject(2014B070705007) supported by Guangdong Science and Technology Plan Project,China+1 种基金Project(2016A030312015) supported by Scientific Research Fund of Guangdong Province,ChinaProject(2017A070701027) supported by Guangdong Science and Technology Program,China。
文摘In this work,the chromium aluminum nitride(CrAlN)coatings were prepared on TC11 titanium alloy by composite magnetic field cathodic arc ion plating with controllable pulse electromagnetic combined with permanent magnet.The effects of electromagnetic frequency on the morphology,microstructure,nano-hardness and elastic modulus of the coatings were investigated by scanning electron microscope(SEM),X-ray diffraction(XRD)and nano-indenter.This paper has mainly studied the influence of CrAlN coatings which are prepared at various electromagnetic frequencies on the wear and erosion resistance through a series of wear and solid particle erosion experiments.It was found that the deposition rate of CrAlN coatings increases with the increase of electromagnetic frequency.And CrAlN coatings all preferentially grew along the(111)crystal plane.At 16.7 Hz,with the increase of pulsed electromagnetic frequency,the hardness is the highest(23.6 GPa)and the adhesion is the highest(41.5 N).In addition,the coating deposition exhibited the best wear and solid erosion resistance at 16.7 Hz and 33.3 Hz,the friction coefficient is about 0.35,and the erosion rate is about 0.2μm/g at 30°and less than 1μm/g at 90°,respectively.These results indicate that the CrAlN coating formed at an appropriate pulsed electromagnetic frequency can achieve excellent mechanical properties,wear and solid erosion resistance.
基金Project(20176066)supported by the National Natural Science Foundation of China
文摘Polyaniline(PAn)doped with multiple sulfonic acid system of dodecylbenzenesulfonic acid(DBSA)and sulfosalicylic acid(SSA)was synthesized by emulsion polymerization using ammonium persulfate(APS)as an oxidizing agent in the presence and the absence of a constant magnetic field(MF)of 0.8 T.The structure and properties of the PAn were characterized by X-ray diffractometer(XRD),thermogravimetric apparatus(TGA),FT-IR spectroscope(FT-IR)and four probe digital multimeter.The results indicate that,when the molar ratio of DBSA to SSA is 1/3,that of dopant to An is 3/2,that of APS to An is 4/5 in the synthesizing media,and the doping time is 3 h,the conductivity of the PAn synthesized in the presence of the MF of 0.8 T reaches 5.88 S/cm,which is higher than that of the PAn synthesized in the absence of the MF.The thermal stability,the crystallinity and the doping degree of the PAn synthesized in the presence of the MF are also improved.MF not only enhances the conductivity,but also reduces the doping time,the dosage of the dopant and the oxidizing agent when the conductivity reaches the maximum.
文摘The effect of a high magnetic field up to 30T on phase transformation temperature and microstructure of Fe-based alloys has been reviewed. A high magnetic field accelerates ferrite transformation, changes the morphology of the transformed microstructures and increases the A3 and A1 temperature. In a magnetic field of 30T, the A1 temperature increases by about 37.1℃ for Fe-0.8C, the A3 temperature for pure Fe increases by about 33.1℃. The measured transformation temperature data are not consistent with calculation results using Weiss molecular field theory. Ferrite grains are elongated and aligned along the direction of magnetic field in Fe-0.4C and Fe-0.6C alloys by ferrite transformation, but elongated and aligned structure was not found in pure Fe, Fe-0.05C alloy and Fe-1.5Mn-0.11C-0.1V alloy.
