Total Field Distribution Research Articles

Machine learning based prediction of mechanical properties of WC-Co cemented carbides from magnetic data only

Based on experimental data and extensive experience, magnetic coercivity and saturation moment are traditionally used to estimate the microstructure and quality of cemented carbides, especially in the manufacturing industry. This work demonstrates that predictions of the structural and mechanical properties of manufactured WC-Co elements can be derived in principle from magnetic data alone using an artificial neural network (ANN). A collection of WC-Co pellet samples with a wide variety of powder compositions and processing parameters was produced to cover a wide range of characteristic features for ANN training. The total field distribution, extracted from first-order-reversal-curves, serves as input data for the ANN. Microstructural parameters such as mean grain size and mechanical properties such as hardness and fracture toughness can be derived from the purely magnetic measurements with high accuracy, while the transverse rupture strength shows large errors and cannot be predicted.

Experimental study on flow field characteristics of TBCC multibypass combustor

The turbine-based combined cycle (TBCC) engine, as a hypersonic air-breathing propulsion system, involves the transition between multiple bypasses during flight. During the transition process, the flow field of the combustor is affected. In this paper, the flow field of a TBCC multibypass combustor with typical structures is investigated experimentally. The effect of the combined structure on the mixing performance, total pressure loss and flow field distribution downstream of the TBCC multibypass combustor is investigated by changing the inlet aerodynamic parameters and structural parameters of the combustor. The results show that the diffusion ratio increased from 1.0 to 1.4, the thermal mixing efficiency decreased by 24.7%, and the total pressure recovery coefficient increased by 1.86%. Meanwhile, the recirculation zone is wider, and the velocity distribution behind the stabilizer is more uniform. The thermal mixing efficiency increases by 55.8% with the increase in the down inclination (35°∼45°) of the lobe mixer. The mixing characteristic of the triple-bypass combustor is greater than that of the double-bypass combustor. There is an obvious “phase difference” of the vortex shedding in the double-bypass combustor at different spanwise sections, while it does not exist in the triple-bypass combustor. The turbulence disturbance degree in the recirculation zone behind the stabilizer in the triple-bypass combustor is slightly higher than that in the double-bypass combustor, but the velocity distribution is more uniform. The increase in inlet Mach number increases the flow losses and decreases the mixing performance. However, the thermal mixing efficiency is positively impacted with respect to the inlet temperature. In addition, the turbulent kinetic energy of the shear layer behind the stabilizer is large, while it is relatively small in the recirculation zone. There is not only spanwise vortices but also radial vortices behind the stabilizer.

Finite element analysis of total electric field distribution on the roof of flat-roofed buildings near HVDC lines

Finite element analysis of total electric field distribution on the roof of flat-roofed buildings near HVDC lines

Global field performance of monopile-supported offshore wind turbines with sinusoidal layouts using innovative combined grating conditions

For the global performance of monopile wind farms, the desired wave field distribution using traditional layout methods is hard to obtain. In this study, the investigation aims to efficiently explore the potential wave response reduction of the multiple layer design of wind farm layouts using novel grating conditions. It is very important and necessary to optimize the layouts of monopile-supported OWTs (offshore wind turbines) by analyzing the wave field performance, especially considering scour protection and avoiding the proximity of the wave frequency to natural frequency of OWTs. This paper presents a layout and a design method of monopile-supported OWTs using combined grating theorems, which can take space modulation into account to deal with various issues in existing layouts. The results show that the present method can modulate the wave field responses more evenly than the conventional cases. More specifically, total wave field distribution sensitivities were discussed under different wavelengths, amplitudes, layouts, pile-radius, and the angles of incident waves. It can be illustrated that the monopile-supported OTWs with sinusoidal configurations can have more modulation effects on wave fields in an appropriate wavelength band. As indicated, this method not only provides wave space modulation control but also sheds light on the wave field reduction mechanisms.

Measurement of low Reynolds number flow emanating from a Turing pattern microchannel array using a modified Bernoulli equation technique

An experimental investigation of the air flow emanating from a Turing pattern microchannel array into an open atmosphere at very low Reynolds (Re) numbers is presented. As designed, the microchannel structure has channel sizes ranging between 0.6 mm and 1.5 mm with a depth of 0.6 mm. The development of a modified Bernoulli equation analysis method to determine fluid flow speed is introduced. Specifically, a low cost, large (11.11 mm inner diameter) flexible tube probe was employed to measure the fluid total pressure field distribution at a fixed distance from the outlets of the microchannel array. Using subsequent numerical modeling of the outlet-to-tube fluid flow interactions, a flow speed dependent correction factor for the determined dynamic pressure field is proposed. The experimentally measured fluid flow distribution is consistent with the expected flow field pattern obtained by additional computational modeling of flow through and exiting the entire Turing pattern microchannel manifold structure. The pressure measurement and post-processing technique for determining flow velocity may be adapted to a wide range of low-speed (e.g., Re≤100) fluid flow measurement scenarios.

Line source diffraction by double strips with different fractional boundary conditions

In this study, the cylindrical wave diffraction by double strips with different lengths and boundary conditions are investigated. The scattered fields are found by the Numerical-Analytical Approach. The double-strip structure satisfies integral boundary conditions which are the generalization of Dirichlet and Neumann boundary conditions. The electric field, current distribution, and Total Radar Cross Sections are investigated. The results are compared with other methods and previous findings such as the Method of Moments and Physical Optics. The theoretical and numerical analyses indicate that the fractional order, the position of the line source have tremendous effects on the total-field distributions.

Measurement of Far Field Magnetic Moment Vector of a Moving Ferromagnetic Object

In magnetic anomaly detection, it is a prerequisite to master the far-field magnetic moment vector information of the target. It is important to measure the magnetic moment of the target in target location, recognition and degaussing. In the paper, we proposed a method of measuring the magnetic moment vector of the target based on the total geomagnetic field. In this method, a sensor array with the scalar magnetometers was constructed and the quantitative factors of the magnetometer were analyzed. In order to eliminate the time-varying and uneven spatial distribution of geomagnetic total field, a double gradient algorithm was applied to magnetic moment measurement in this method. And a criterion function of determining the magnitude and direction of the target magnetic moment was defined. The proposed method was validated by the theoretical calculation and real experimental data. The results showed that the measured magnetic field data were qualitatively in good agreement with the theoretical curve. For the magnitude of magnetic moment, the average relative deviation was 5.1%. And the average relative deviation of inclination and declination of the moment were 3.2% and 2.5%, respectively. In addition, we attempted to separate the induced magnetic moment and the intrinsic magnetic moment of the target. The proposed method can be used as a reference for the target magnetic location and demagnetization.

Tolerance and asymptotic modelling of dynamic thermoelasticity problems for thin micro-periodic cylindrical shells

The problem of linear dynamic thermoelasticity in Kirchhoff–Love-type circular cylindrical shells having properties periodically varying in circumferential direction (uniperiodic shells) is considered. In order to describe thermoelastic behaviour of such shells, two mathematical averaged models are proposed—the non-asymptotic tolerance and the consistent asymptotic models. Considerations are based on the known Kirchhoff–Love theory of elasticity combined with Duhamel-Neumann thermoelastic constitutive relations and on Fourier’s theory of heat conduction. The non-asymptotic tolerance model equations depending on a cell size are derived applying the tolerance averaging technique and a certain extension of the known stationary action principle. The consistent asymptotic model equations being independent on a microstructure size are obtained by means of the consistent asymptotic approach. Governing equations of both the models have constant coefficients, contrary to starting shell equations with periodic, non-continuous and oscillating coefficients. As examples, two special length-scale problems will be analysed in the framework of the proposed models. The first of them deals with investigation of the effect of a cell size on the shape of initial distributions of temperature micro-fluctuations. The second one deals with study of the effect of a microstructure size on the distribution of total temperature field approximated by sum of an averaged temperature and temperature fluctuations.

The classical boundary problem of the transition of a spherical type-I superconductor to the normal state with increasing of the applied uniform magnetic field

A complicated boundary value problem of the transition of a macroscopic massive spherical type-I superconductor to the intermediate and normal state with increasing of the applied uniform magnetic field has been solved. Taking into account a penetration effect and exact boundary conditions the boundary problem has been solved completely and rigorously within the framework of the classical (non-quantum) electrodynamics of continuous mediums and the modified (simplified) nonlocal Pippard electrodynamics of spatially homogenous type-I superconductors. The principal object of this work is a self-consistent and exact setting of the boundary value problem and also its mathematically rigorous solution taking into account surface effects and nonlocality of Pippard type-I superconductors. The solution novelty is a description of the surface effects within the framework the modified (simplified) nonlocal Pippard electrodynamics. It is shown that disregarding for the surface effects in a theory of low-temperature superconductors can lead not only to computational mistakes, but also to incorrect qualitative conclusions. The conclusions about nature of a macroscopic spherical type-I superconductor to the intermediate and normal state have been drawn on the ground of a rigorous solution of the boundary problem and determination of the total magnetic field distribution in the whole space (inside and outside the superconducting sphere). These conclusions are in agreement with those, which have been drawn earlier by other authors on the ground of different approximate models and methods. Since the scientific results have been obtained by the authors on the basis of rigorous and self-consistent solution of the exactly set boundary problem, the work is undoubtedly of theoretical and methodical interest.

Experimental Study on the Aperture of Geomagnetic Location Arrays

A method of locating a magnetic target based on geomagnetic total field is proposed. In the method, a conjugate gradient algorithm is introduced to eliminate the time-varying and uneven spatial distribution of geomagnetic total field. Then a structure of the measuring array of geomagnetic total field is designed. In the measuring array, the array aperture is a primary factor for the conjugate gradient algorithm. To determine an optimal aperture, we analyze the relationship between the array aperture and the localization accuracy. According to the localization theory based on geomagnetic total field, we simulate the process of determining an optimum array aperture. Based on the simulation, we propose the basis and principle of determining the optimum array aperture. To prove it, we use optically pumped magnetometers with different array apertures to carry out the experiments of locating a car in a suburb. Through the experiment, we get the experimental relationship between apertures and location accuracy. And the relationship agrees with the theory. The result shows that the method is feasible to determine the optimum aperture.

Magnetic field asymmetry at external phases of shielded single-pole three-phase flat high-current busduct

The article shows the total magnetic field distribution in two outer conductors of the flat, three-phase single-pole shielded, high-current busduct is asymmetric. The phase currents in the shielded conductors decide about the magnetic field of such a high-current busduct. The components of this field reflect the magnetic field of the reverse reaction fields of the eddy currents induced in the conductors of the adjacent phases as the results of the proximity effect and the skin effect. The field distribution is shown in the outer area of the outer phases as the function of the parameters reflecting the current frequency, the conductivity, and the transverse dimensions of the tubular conductors.

On the Use of Focused Incident Near-Field Beams in Microwave Imaging

We consider the use of focused incident near-field (NF) beams to interrogate the object of interest (OI) in NF microwave imaging (MWI). To this end, we first discuss how focused NF beams can be advantageously utilized to suppress scattering effects from the neighbouring objects whose unknown dielectric properties are not of interest (i.e., undesired scatterers). We then discuss how this approach can also be helpful in reducing the required measured data points to perform imaging. Driven by the relation between the electromagnetic inverse source and inverse scattering problems, our approach emphasizes the importance of tailoring the induced contrast sources in the imaging domain through the utilized incident NF beams. To demonstrate this idea, we consider two recently-proposed NF beams, and simulate them for imaging applications. The first one is a subwavelength focused NF beam generated by a passive NF plate, and the other is a Bessel beam generated by a leaky radial waveguide. Simple imaging examples are considered to explore the potential advantages of this approach, in particular, toward mainly seeing the object of interest, and not the unknown undesired scatterers. The scope of this paper is limited to homogeneous dielectric objects for which the induced total field distributions in the interrogated objects are similar to the incident field distributions (e.g., those that satisfy the Born approximation). Simple inversion results for focused and non-focused beams are presented accompanied by discussions comparing the achieved reconstructed values.

Simulation on motion characteristics of space charge in single oil-paper insulation

PurposeThe purpose of this paper is numerical calculation of total electric field in oil-paper insulation. Now, there is no effective method to consider the influence of space charges when calculating the total electric field distribution in the main insulation system of the valve-side winding of an ultra-high-voltage direct current converter transformer.Design/methodology/approachTo calculate the total electric field in an oil-paper insulation system, a new simulation method in single-layer oil-paper insulation based on the transient upstream finite element method (TUFEM) is proposed, in which the time variable is considered. The TUFEM is used to calculate the total electric field in an oil-paper insulation system by considering the move law of space charges. The simulation method is verified by comparing the simulation results to the test data. The move law of space charges and distribution characteristics of the electric field under difference voltage values in single-layer oil-paper insulation were presented.FindingsThe results show that the TUFEM has an excellent accuracy compared with the test data. When carrier mobility is a constant, the time to reach the steady state is inversely correlated with the initial electric field intensity, and the distortion rate of the internal total electric field is positively correlated with the initial electric field intensity.Originality/valueThis paper provides an exploratory research on the simulation of space charge transport phenomenon in oil-paper and has guiding significance to the design of oil-paper insulation.

Magnetic field and sheet-current density of a thin type-II superconducting annulus

We investigate theoretically the sheet-current density and total magnetic field (MF) distribution due to a thin, type-II superconducting annulus sample. We have supposed a washer (with the inner and outer radii a and b) carrying sub-critical currents subject to an applied magnetic field. The sample is an ideal washer with no bulk pinning, under two different situations: (a) when flux is focused into the central hole and net current flowing around the washer is zero but the external field Ha=Ba/μ is on, and (b) in the presence of a potential barrier of geometrical origin. Our calculations show that the net MF is maximum in the near-edge region and in the between is weaker than other areas. Moreover, the effect of geometrical barrier on spatial distribution of the field for several superconducting washers of different radii has been analyzed. At the end, we have shown the behavior of field distribution as external field, Ha , is oriented at any arbitrary angle α.

The influence of the discharge current axial component on the magnetic field distribution in the cathode region of magnetron sputtering system

The paper includes the description of the mathematical model, which simulates magnetic field distribution in the cathode area of the sputtering system discharge considering the current created by electrons moving along the surface of cathode-target. Presented results of the numerical modeling were received using the developed model. It is also shown that the current component, directed along the cathode surface significantly impacts total magnetic field distribution in the magnetron discharge.

Turbulence dependence on winds and stability in a weak‐wind canopy sublayer over complex terrain

AbstractThe daytime and nighttime turbulence profiles within a weak‐wind forest canopy were investigated by using data collected within a temperate mixed conifer canopy in northern Idaho, USA. Turbulence measurements made at three heights on a single tower within a Douglas fir canopy were compared. Data were split between the daytime and nighttime to determine the relationships among the local temperature gradient, wind direction, wind speed, and turbulence levels. The total flow field distributions and vertical statistical profiles were determined for the overnight and daytime periods to observe how the overall flow changed with time of day. During the day, the wind probability distribution function was consistent between heights but depended on the canopy depth overnight. The skewness changed with the dominant wind direction. The kurtosis increased with depth into the canopy and from during the day to overnight. The range of wind speeds observed was higher under unstable conditions than stable conditions. Daytime turbulence had no dependence on wind direction. Overnight, the relationship between turbulence and wind speed changed with wind direction and canopy depth. The highest turbulence values were associated with downslope winds near the canopy top, but the wind direction for the highest turbulence was variable within the trunk space.

Spatial coupled-mode theory for surface plasmon polariton excitation at metallic gratings

We develop a framework of the spatial coupled-mode theory for surface plasmon polariton (SPP) excitation at metallic gratings. The spatial mode coupling process is investigated in order to understand the spatial field distribution during the SPP excitation. We show that the spatial mode coupling coefficients are constrained by the energy conservation, the time-reversal symmetry, and the geometry mirror symmetry. As the result, a semi-analytical form is obtained to fast compute the total field distribution for an arbitrary incident light. This study paves the way for optimizing the incident light modulation to dynamically control the localized intensity distribution of the SPP excitation, which is practically significant in surface-enhanced applications, such as plasmonic tweezers, optical sensors, and spectroscopy.

Report on the magnetic survey in Slovakia for the 2014.5 epoch

Abstract The models of the distribution of the elements of the geomagnetic field must be updated regularly. For this purpose geomagnetic measurements have to be carried out repeatedly at geomagnetic observatories as well as at temporary observation points. In this paper the results of the geomagnetic survey that was carried out in Slovakia in the year 2014 are presented. The measurements were performed at 12 observation points and they were reduced to the 2014.5 epoch. The secular variation between 2007.5 and 2014.5 was also calculated. The obtained values of the geomagnetic elements were used for calculating a 1st-degree polynomial model for the distribution of magnetic declination, inclination and total field. The comparison with the IGRF model showed that the polynomial model provided more accurate results for magnetic inclination and total field. For magnetic declination, on the contrary, the IGRF model produced slightly better results than the polynomial model.

Novel 1 × N ultrasonic power splitters based on self-imaging effect of phononic crystal waveguide arrays

We present an appropriate design and simulated results of novel 1 × N (N represents an integer larger than 1) ultrasonic power splitters based on self-imaging effect with symmetric interference of phononic crystal waveguide arrays. Such sonic devices with two and three output channels are discussed in detail as examples. The finite element method is used to calculate the distribution of total displacement field and evaluate the efficiency of these structures. Results show that these devices exhibit new and interesting characteristics, such as compact size, wide bandwidth, and high-transmission. The approach provides a novel method and compact model for exporting freely ultrasonic waves to N channels and can present practical applications in future acoustic wave circuits.

Zonal disintegration mechanism of isotropic rock masses around a deep spherical tunnel

In order to investigate zonal disintegration mechanism of isotropic rock masses around a deep spherical tunnel, a new mechanical model subjected to dynamic unloading under hydrostatic pressure condition is proposed. The total elastic stress-field distributions is determined using the elastodynamic equation. The effects of unloading rate and dynamic mechanical parameters of isotropic deep rock masses on the zonal disintegration phenomenon of the surrounding rock masses around a deep spherical tunnel as well as the total elastic stress field distributions are considered. The number and size of fractured and non-fractured zones are determined by using the Hoek-Brown criterion. Numerical computation is carried out. It is found from numerical results that the number of fractured zones increases with increasing the disturbance coefficient, in-situ stress, unloading time and unloading rate, and it decreases with increasing parameter geological strength index, the strength parameter and the uniaxial compressive strength of intact rock.