Numerical analysis of external magnetic field for mitigating backward flow momentum in weld pool

The external magnetic field is applied to mitigating backward flow jet of molten metal in weld pool so that humping bead may be suppressed during high speed gas metal arc welding（GMAW）. Therefore, the external magnetic field distribution in workpiece is critical to understand the interaction mechanisms of the external magnetic field with molten metal flow. In this study, the steady state external magnetic field induced by excitation device is numerically analyzed by using the the finite element software ANSYS and the three dimensional static magnetic scalar method. The distribution of external transverse magnetic field By in workpiece and arc area is calculated, and the influence of excitation current and air-gap distance on the distribution of transverse magnetic field By has been discussed. The magnetic field distribution in workpiece is measured by using a Tesla-Meter and compared with the simulated result. It is found that both are in good agreement.

The Analysis and Calculation for the Toroidal Magnetic Field of HT-7U

The HT-7U super-conducting tokamak is a full super-conducting magnetically confined fusion device, It mainly consists of super-conducting toroidal field (TF) coils and super conducting poloidal field (PF) coils. This paper describes the distribution of magnetic field, ripple and electromagnetic loads of TF system, some results are necessary to analyze and calculate the stresses and deformation on TF system by a finite element method. Meanwhile, in this paper, the main scope of the calculation is carried out for the case of constant magnetic field on conductor of the TF coil winding in order to provide electromagnet parameters for the quench analysis of Cable-in-Conduit Conductor (CICC) of TF system in HT-7U.

Statistical analysis of geomagnetic field variations during the partial solar eclipse on 2011 January 4 in Turkey

Some geophysical parameters, such as those related to gravitation and the geomagnetic field, could change during solar eclipses. In order to observe geomagnetic fluctuations, geomagnetic measurements were carded out in a limited time frame during the partial solar eclipse that occurred on 2011 January 4 and was observed in Canakkale and Ankara, Turkey. Additionally, records of the geomagnetic field spanning 24 hours, obtained from another observatory （in Iznik, Turkey）, were also analyzed to check for any peculiar variations. In the data processing stage, a polynomial fit, following the application of a running average routine, was applied to the geomagnetic field data sets. Geomagnetic field data sets indicated there was a characteristic decrease at the beginning of the solar eclipse and this decrease can be well-correlated with previous geomagnetic field measurements that were taken during the total solar eclipse that was observed in Turkey on 2006 March 29. The behavior of the geomagnetic field is also consistent with previous observations in the literature. As a result of these analyses, it can be suggested that eclipses can cause a shielding effect on the geomagnetic field of the Earth.

Nonlinear vibration analysis of an embedded branched nanofluid-conveying carbon nanotube:Influence of downstream angle,temperature change and two dimensional external magnetic field

In this study,non-linear thermal-mechanical stability and vibration analyses of different end-shaped single-walled carbon nanotube conveying viscous nano-magnetic fluid embedded in non-linear visco-elastic foundation under the influence of magnetic fields are presented.The development of the equation of motion was based on Euler-Bernoulli theory,Hamilton principle and nonlocal elasticity theory.The results of the analytical solutions using Galerkin decomposition differential transform method(GDDTM)were validated with existing experimental results.From the parametric studies,it was shown that decreasing the temperature difference as well as increasing the downstream angle decreased the system's stability for pre-bifurcation analysis but increased stability of the system for post bifurcation analysis.Also,the results obtained from the dynamic behaviour of the system indicated that the magnetic effect had an attenuating impact of about 45%on the system's response at any mode and for any boundary condition considered.It is hoped that this work will enhance the design and optimization of nano-devices with I,V,Y,L,K and T-shaped junctions under the influence of thermal-magneto-mechanical flow induced vibration.

AN ANALYSIS OF AXISYMMETRIC MAGNETIC FIELD OF LINEAR OSCILLATION MOTOR

In this paper, using axial field finite analysis method, the field of a movable core type linear oscillation motor is analyzed. The program of axial field finite analysis is worked out. Using this program, we analyze various fields, including the field excited by permanent magnet materials, the field by two coils respectively, and the fields with the core moving to various positions.

PERTURBATION ANALYSIS FOR MAGNETO-PLASTIC INSTABILITY OF FERROMAGNETIC BEAM-PLATES WITH GEOMETRIC IMPERFECTION

The magneto-plastic instability of a ferromagnetic beam-type plate with simple supports and small initial imperfection is analytically investigated in this paper for that the plastic deformation of the plate with a linear-strain hardening relation is considered when the plate is located in a strong uniformly distributed magnetic ?eld. After the distribution of magnetic ?elds related to the de?ected con?guration of plate is imaginably divided into two parts, i.e., one is related to the ?at plate and the other dependent on the perturbation of magnetic ?elds for which the plate con?guration changes from the ?at into the deformed state, the perturbation technique is employed to analyze the distribution of the perturbation magnetic ?elds in and out-of the magnetic medium of the ferromagnetic structure in a transverse magnetic ?eld, which leads to some analytical formulae/solutions for the magnetic ?elds and the resulting magnetic force exerted on the plate. Based on them, the magneto-plastic buckling and snapping of the plate in a transverse magnetic ?eld is discussed, and the critical magnetic ?eld is analytically formulated in terms of the parameters of geometry and material of the plate employed by solving the governing equation of the magneto-plastic plate in the applied magnetic ?eld. Further, the sensitivity of the initial imperfection on the magneto-plastic instability, expressed by an ampli?cation function, is obtained by solving the dynamic equation of de?ection of the plate after the inertial force in the transverse direction is taken into account. The results obtained show that the critical magnetic ?eld is sensitive to the plastic characteristic, e.g., hardening coe?cient, and the instability mode and de?ection of the plate are dependent on the geometrical imperfection as well.

Analysis of the Harmonic Response of a Modulation Permanent Magnetic Transmission Equipment Based on ANSYS

This paper analyzes the structure and transmission principles of a modulation permanent magnet gear transmission. Its 3D data model is built based on the known optimized parameters from research team. Its structure of the harmonic response is analyzed and discussed under the software ANSYS. The displacement response and the initial 6 order response frequency and phase angle are obtained. The change rule of these responses is known under the forced vibration.

FE Stress Analysis of the Toroidal Field Magnets of HT-7U

In this paper, the mechanical strength of the toroidal field (TF) magnets of HT-7U with the electromagnetic force in different magnetic fields is emphatically analyzed by means of finite element method. The model and feasible method of computation are put forward. Some important conclusions are made available for reference in the design and construction of TF for HT-7U.

TiO_2-water nanofluid in a porous channel under the effects of an inclined magnetic field and variable thermal conductivity

The TiO2-water based nanofluid flow in a channel bounded by two porous plates under an oblique magnetic field and variable thermal conductivity is formulated as a boundary-value problem(BVP). The BVP is analytically solved with the homotopy analysis method(HAM). The result shows that the concentration of the nanoparticles is independent of the volume fraction of TiO2nanoparticles, the magnetic field intensity, and the angle. It is inversely proportional to the mass diffusivity. The fluid speed decreases whereas the temperature increases when the volume fraction of the TiO2nanoparticles increases. This confirms the fact that the occurrence of the TiO2nanoparticles results in the increase in the thermal transfer rate. The fluid speed decreases and the temperature increases for both the pure water and the nanofluid when the magnetic field intensity and angle increase. The maximum velocity does not exist at the middle of the symmetric channel, which is in contrast to the plane-Poiseuille flow, but it deviates a little bit towards the lower plate, which absorbs the fluid with a very low suction velocity. If this suction velocity is increased, the temperature in the vicinity of the lower plate will be increased.An explicit expression for the friction factor-Reynolds number is then developed. It is shown that the Hartmann number of the nanofluid is smaller than that of pure water,while the Nusselt number of the nanofluid is larger than that of pure water. However,both the parameters increase if the magnetic field intensity increases.

Lossless Compression Method for the Magnetic and Helioseismic Imager(MHI)Payload

The Solar Polar-orbit Observatory(SPO),proposed by Chinese scientists,is designed to observe the solar polar regions in an unprecedented way with a spacecraft traveling in a large solar inclination angle and a small ellipticity.However,one of the most significant challenges lies in ultra-long-distance data transmission,particularly for the Magnetic and Helioseismic Imager(MHI),which is the most important payload and generates the largest volume of data in SPO.In this paper,we propose a tailored lossless data compression method based on the measurement mode and characteristics of MHI data.The background out of the solar disk is removed to decrease the pixel number of an image under compression.Multiple predictive coding methods are combined to eliminate the redundancy utilizing the correlation(space,spectrum,and polarization)in data set,improving the compression ratio.Experimental results demonstrate that our method achieves an average compression ratio of 3.67.The compression time is also less than the general observation period.The method exhibits strong feasibility and can be easily adapted to MHI.

Optimal design of modular dual-field modulated permanent magnet linear motors with thrust characteristics

To reduce thrust ripple and cost and improve the average thrust of permanent magnet linear motors,a modular dual-field modulation permanent magnet linear motor was studied,and the parameters were optimized.First,sensitive parameters were selected using the Taguchi method,and then the optimal variables were sampled using the optimal Latin hypercube experimental design method and an ensemble of surrogates model of optimization objectives,and its accuracy was verified.Next,a multi-objective particle swarm optimization algorithm was used to optimize the purpose of“maximum average thrust and minimum thrust ripple”,and the Pareto front of average thrust and thrust ripple was obtained.Finite element analysis showed that the optimized modular dual flux-modulation permanent magnet linear motor(MDFMPMLM)had a 29.5%reduction in thrust ripple and a 5%increase in average thrust compared to the original motor.This study provided an effective method for improving the performance of permanent magnet linear motors.

An Integrated Study of ULF Magnetic Field Variations in Association with the 2008 Sichuan Earthquake, on the Basis of Statistical and Critical Analyses

The ultra-low frequency (ULF) magnetic field data at a station very close to the 2008 Sichuan earthquake (EQ) (on 12 May, 2008;M = 8.0) are extensively studied on the basis of combined statistical and natural time analyses. Two effects in ULF are treated: one is the well-known ULF radiation from the lithosphere, and the other is the non-conventional depression of ULF horizontal magnetic field. The simple statistical analysis has yielded: 1) no clear evidence of the presence of precursory ULF radiation, and 2) a significant effect of depression of ULF horizontal field a few days before the EQ (as a signature of ionospheric perturbations). The recently introduced natural time analysis has also been performed in order to study the critical features of the lithosphere and essentially new information has been brought about. The parameter “polarization”, as the ratio of vertical to horizontal components, showed critical features in the time period of 17 - 27 April, about one month to two weeks before the EQ as a signature of lithospheric radiation. Then, the natural time analysis has reconfirmed the presence of ionospheric perturbations a few days before the EQ, together with an additional time window found on 19 - 23 April, about one month before the EQ, exhibiting critical features in the ULF depression.

Analysis of the Comprehensive Physical Field for a New Flywheel Energy Storage Motor/Generator on Ships

A novel flywheel energy storage （FES） motor/generator （M/G） was proposed for marine systems. The purpose was to improve the power quality of a marine power system （MPS） and strengthen the energy recycle. Two structures including the magnetic or non-magnetic inner-rotor were contrasted in the magnetostatic field by using finite element analysis （FEA）. By optimally designing the size parameters, the average speed of FEA results of was 17 200 r/m, and the current was controlled between 62 and 68 A in the transient field. The electrical machine electromagnetism design was further optimized by the FEA in the temperature field, to find the local overheating point under the normal operation condition and provide guidance for the cooling system. Finally, it can be concluded from the comprehensive physical field analysis that the novel redundant structure M/G can improve the efficiency of the M/G and maintain the stability of the MPS.

Identification and classification of transient pulses observed in magnetometer array data by time-domain principal component analysis filtering

A method for identification of pulsations in time series of magnetic field data which are simultaneously present in multiple channels of data at one or more sensor locations is described. Candidate pulsations of interest are first identified in geomagnetic time series by inspection. Time series of these ＂training events＂ are represented in matrix form and transpose-multiplied to generate time- domain covariance matrices. The ranked eigenvectors of this matrix are stored as a feature of the pulsation. In the second stage of the algorithm, a sliding window （approxi- mately the width of the training event） is moved across the vector-valued time-series comprising the channels on which the training event was observed. At each window position, the data covariance matrix and associated eigen- vectors are calculated. We compare the orientation of the dominant eigenvectors of the training data to those from the windowed data and flag windows where the dominant eigenvectors directions are similar. This was successful in automatically identifying pulses which share polarization and appear to be from the same source process. We apply the method to a case study of continuously sampled （50 Hz） data from six observatories, each equipped with three- component induction coil magnetometers. We examine a 90-day interval of data associated with a cluster of four observatories located within 50 km of Napa, California, together with two remote reference stations-one 100 km to the north of the cluster and the other 350 km south. When the training data contains signals present in the remote reference observatories, we are reliably able to identify and extract global geomagnetic signals such as solar-generated noise. When training data contains pulsations only observed in the cluster of local observatories, we identify several types of non-plane wave signals having similar polarization.

Novel magnetic field computation model in pattern classification

Field computation, an emerging computation technique, has inspired passion of intelligence science research. A novel field computation model based on the magnetic field theory is constructed. The proposed magnetic field computation （MFC） model consists of a field simulator, a non-derivative optimization algo- rithm and an auxiliary data processing unit. The mathematical model is deduced and proved that the MFC model is equivalent to a quadratic discriminant function. Furthermore, the finite element prototype is derived, and the simulator is developed, combining with particle swarm optimizer for the field configuration. Two benchmark classification experiments are studied in the numerical experiment, and one notable advantage is demonstrated that less training samples are required and a better generalization can be achieved.

Predicting the evolution of photospheric magnetic field in solar active regions using deep learning

The continuous observation of the magnetic field by the Solar Dynamics Observatory(SDO)/Helioseismic and Magnetic Imager(HMI)produces numerous image sequences in time and space.These sequences provide data support for predicting the evolution of photosphericmagnetic field.Based on the spatiotemporal long short-term memory(LSTM)network,we use the preprocessed data of photospheric magnetic field in active regions to build a prediction model for magnetic field evolution.Because of the elaborate learning and memory mechanism,the trained model can characterize the inherent relationships contained in spatiotemporal features.The testing results of the prediction model indicate that(1)the prediction pattern learned by the model can be applied to predict the evolution of new magnetic field in the next 6 hours that have not been trained,and predicted results are roughly consistent with real observed magnetic field evolution in terms of large-scale structure and movement speed;(2)the performance of the model is related to the prediction time;the shorter the prediction time,the higher the accuracy of the predicted results;(3)the performance of themodel is stable not only for active regions in the north and south but also for data in positive and negative regions.Detailed experimental results and discussions on magnetic flux emergence and magnetic neutral lines finally show that the proposed model could effectively predict the large-scale and short-term evolution of the photospheric magnetic field in active regions.Moreover,our study may provide a reference for the spatiotemporal prediction of other solar activities.

Design and Magnetic Field Uniformity of Giant Magnetostrictive Ultrasonic Transducer for Progressive Sheet Forming

Design of a giant magnetostrictive ultrasonic transducer for progressive sheet forming was presented.A dynamic analysis of the theoretically designed ultrasonic vibration system was carried out using the finite element method(FEM).In addition,simulations were performed to verify the theoretical design.Then,a magnetically conductive material was added between the giant magnetostrictive rod and the permanent magnet.Besides,magnetic field simulations of the transducer were performed.The influence of the material thickness of the magnetically conductive material on uniformity of the induced magnetic field was studied.Furthermore,the impedance analysis and amplitude measurement were performed to compare the performance of transducers with and without the magnetically conductive material.The experimental results show that the magnetic field uniformity is the highest when the magnetically conductive material has a thickness of about 1.6 mm.The output amplitude of the giant magnetostrictive transducer is improved by adding the magnetically conductive material.Moreover,the mechanical quality factor and impedance are reduced,while the transducer operates more stably.

MagneFi: Multiuser, Multi-Building and Multi-Floor Geomagnetic Field Dataset for Indoor Positioning

Indoor positioning and localization have emerged as a potential research area during the last few years owing to the wide proliferation of smartphones and the inception of location-attached services for the consumer industry.Due to the importance of precise location information,several positioning technologies are adopted such as Wi-Fi,ultrawideband,infrared,radio frequency identification,Bluetooth beacons,pedestrian dead reckoning,and magnetic field,etc.Although Wi-Fi and magnetic field-based positioning are more attractive concerning the deployment of Wi-Fi access points and ubiquity of magnetic field data,the latter is preferred as it does not require any additional infrastructure as other approaches do.Despite the advantages of magnetic field positioning,comparing the performance of positioning and localization algorithms is very difficult due to the lack of good public datasets that cover various aspects of the magnetic field data.Available datasets do not provide the data to analyze the impact of device heterogeneity,user heights,and time-specific magnetic field mutation.Moreover,multi-floor and multibuilding data are available for the evaluation of state-of-the-art approaches.To overcome the above-mentioned issues,this study presents multi-user,multidevice,multi-building magnetic field data which is collected over a longer period.The dataset contains the data from five different smartphones including Samsung Galaxy S8,S9,A8,LG G6,and LG G7 for three geographically separated buildings.Three users including one female and two males collected the data for various path geometry and data collection scenarios.Moreover,the data contains the magnetic field samples collected on stairs to test multifloor localization.Besides the magnetic field data,the data from inertial measurement unit sensors like the accelerometer,motion sensors,and barometer is provided as well.

Computation of the Magnetic Field and Ripple for the Toroidal Coils in HL-2M Tokamak

The magnetic induction and its ripple due to reconstructive toroidal coils are calculated. The field ripple is so small that the influence of ripple can be omitted for the plasma discharge.

Application of empirical mode decomposition in early diagnosis of magnetic memory signal

In order to eliminate noise interference of metal magnetic memory signal in early diagnosis of stress concentration zones and metal defects, the empirical mode decomposition method combined with the magnetic field gradient characteristic was proposed. A compressive force periodically acting upon a casing pipe led to appreciable deformation, and magnetic signals were measured by a magnetic indicator TSC-1M-4. The raw magnetic memory signal was first decomposed into different intrinsic mode functions and a residue, and the magnetic field gradient distribution of the subsequent reconstructed signal was obtained. The experimental results show that the gradient around 350 mm represents the maximum value ignoring the marginal effect, and there is a good correlation between the real maximum field gradient and the stress concentration zone. The wavelet transform associated with envelop analysis also exhibits this gradient characteristic, indicating that the proposed method is effective for early identifying critical zones.