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1
Swidinsky, Andrei, e Chester J. Weiss. "On coincident loop transient electromagnetic induction logging". GEOPHYSICS 82, n. 4 (1 luglio 2017): E211—E220. http://dx.doi.org/10.1190/geo2017-0134.1.
Testo completoAbstract (sommario):
Coincident loop transient induction wireline logging is examined as the borehole analog of the well-known land and airborne time-domain electromagnetic (EM) method. The concept of whole-space late-time apparent resistivity is modified from the half-space version commonly used in land and airborne geophysics and applied to the coincident loop voltages produced from various formation, borehole, and invasion models. Given typical tool diameters, off-time measurements with such an instrument must be made on the order of nanoseconds to microseconds — much more rapidly than for surface methods. Departure curves of the apparent resistivity for thin beds, calculated using an algorithm developed to model the transient response of a loop in a multilayered earth, indicate that the depth of investigation scales with the bed thickness. Modeled resistivity logs are comparable in accuracy and resolution with standard frequency-domain focused induction logs. However, if measurement times are longer than a few microseconds, the thicknesses of conductors can be overestimated, whereas resistors are underestimated. Thin-bed resolution characteristics are explained by visualizing snapshots of the EM fields in the formation, where a conductor traps the electric field while two current maxima are produced in the shoulder beds surrounding a resistor. Radial profiling is studied using a concentric cylinder earth model. Results found that true formation resistivity can be determined in the presence of either oil- or water-based mud, although in the latter case, measurements must be taken several orders of magnitude later in time. The ability to determine true formation resistivity is governed by the degree that the EM field heals after being distorted by borehole fluid and invasion, a process visualized and particularly evident in the case of conductive water-based mud.
2
Klose, Tim, Julien Guillemoteau, François-Xavier Simon e Jens Tronicke. "Toward subsurface magnetic permeability imaging with electromagnetic induction sensors: Sensitivity computation and reconstruction of measured data". GEOPHYSICS 83, n. 5 (1 settembre 2018): E335—E345. http://dx.doi.org/10.1190/geo2017-0827.1.
Testo completoAbstract (sommario):
In near-surface geophysics, small portable loop-loop electromagnetic induction (EMI) sensors using harmonic sources with a constant and rather small frequency are increasingly used to investigate the electrical properties of the subsurface. For such sensors, the influence of electrical conductivity and magnetic permeability on the EMI response is well-understood. Typically, data analysis focuses on reconstructing an electrical conductivity model by inverting the out-of-phase response. However, in a variety of near-surface applications, magnetic permeability (or susceptibility) models derived from the in-phase (IP) response may provide important additional information. In view of developing a fast 3D inversion procedure of the IP response for a dense grid of measurement points, we first analyze the 3D sensitivity functions associated with a homogeneous permeable half-space. Then, we compare synthetic data computed using a linear forward-modeling method based on these sensitivity functions with synthetic data computed using full nonlinear forward-modeling methods. The results indicate the correctness and applicability of our linear forward-modeling approach. Furthermore, we determine the advantages of converting IP data into apparent permeability, which, for example, allows us to extend the applicability of the linear forward-modeling method to high-magnetic environments. Finally, we compute synthetic data with the linear theory for a model consisting of a controlled magnetic target and compare the results with field data collected with a four-configuration loop-loop EMI sensor. With this field-scale experiment, we determine that our linear forward-modeling approach can reproduce measured data with sufficiently small error, and, thus, it represents the basis for developing efficient inversion approaches.
3
Guillemoteau, Julien, Niels Bøie Christensen, Bo Holm Jacobsen e Jens Tronicke. "Fast 3D multichannel deconvolution of electromagnetic induction loop-loop apparent conductivity data sets acquired at low induction numbers". GEOPHYSICS 82, n. 6 (1 novembre 2017): E357—E369. http://dx.doi.org/10.1190/geo2016-0518.1.
Testo completoAbstract (sommario):
Electromagnetic induction (EMI) sensors using sufficiently low-frequency harmonic sources and sufficiently small loop separations operate in the low-induction-number (LIN) domain for a relatively wide range of background conductivity. These systems are used in diverse near-surface investigations including applications from soil sciences, hydrology, and archaeology. The special case of portable multiconfiguration EMI sensors operating at frequencies [Formula: see text] offers the possibility of using a fast linear deconvolution method to interpret multichannel data sets in three dimensions. Here, we have developed a fast 3D inversion/deconvolution method regularized with 3D smoothness constraints and formulated in the hybrid spectral-spatial domain. Compared with other linear approaches, the spectral-spatial domain formulation significantly reduces the computational cost of the processing and opens the door for real-time 3D interpretation of large data sets consisting of more than 100,000 data points. First, we test our proposed algorithm on synthetic data sets computed with the full Maxwell theory. Then, we apply our method to a real four-configuration EMI data set acquired to map the thickness of peat layers embedded in a sandy environment. For the synthetic and the field example, we compared our result with the result obtained using a standard point-by-point 1D nonlinear inversion approach. This comparison demonstrates that the proposed methodology provides superior lateral resolution compared with the 1D nonlinear inversion, at the same time significantly reducing the computational cost of the processing.
4
Guillemoteau, Julien, Pascal Sailhac, Charles Boulanger e Jérémie Trules. "Inversion of ground constant offset loop-loop electromagnetic data for a large range of induction numbers". GEOPHYSICS 80, n. 1 (1 gennaio 2015): E11—E21. http://dx.doi.org/10.1190/geo2014-0005.1.
Testo completoAbstract (sommario):
Ground loop-loop electromagnetic surveys are often conducted to fulfill the low-induction-number condition. To image the distribution of electric conductivity inside the ground, it is then necessary to collect a multioffset data set. We considered that less time-consuming constant offset measurements can also reach this objective. This can be achieved by performing multifrequency soundings, which are commonly performed for the airborne electromagnetic method. Ground multifrequency soundings have to be interpreted carefully because they contain high-induction-number data. These data are interpreted in two steps. First, the in-phase and out-of-phase data are converted into robust apparent conductivities valid for all the induction numbers. Second, the apparent conductivity data are inverted in 1D and 2D to obtain the true distribution of the ground conductivity. For the inversion, we used a general half-space Jacobian for the apparent conductivity valid for all the induction numbers. This method was applied and validated on synthetic data computed with the full Maxwell theory. The method was then applied on field data acquired in the test site of Provins, in the Parisian basin, France. The result revealed good agreement with borehole and geologic information, demonstrating the applicability of our method.
5
Guillemoteau, Julien, François-Xavier Simon, Guillaume Hulin, Bertrand Dousteyssier, Marion Dacko e Jens Tronicke. "3-D imaging of subsurface magnetic permeability/susceptibility with portable frequency domain electromagnetic sensors for near surface exploration". Geophysical Journal International 219, n. 3 (26 agosto 2019): 1773–85. http://dx.doi.org/10.1093/gji/ggz382.
Testo completoAbstract (sommario):
SUMMARY The in-phase response collected by portable loop–loop electromagnetic induction (EMI) sensors operating at low and moderate induction numbers (≤1) is typically used for sensing the magnetic permeability (or susceptibility) of the subsurface. This is due to the fact that the in-phase response contains a small induction fraction and a preponderant induced magnetization fraction. The magnetization fraction follows the magneto-static equations similarly to the magnetic method but with an active magnetic source. The use of an active source offers the possibility to collect data with several loop–loop configurations, which illuminate the subsurface with different sensitivity patterns. Such multiconfiguration soundings thereby allows the imaging of subsurface magnetic permeability/susceptibility variations through an inversion procedure. This method is not affected by the remnant magnetization and theoretically overcomes the classical depth ambiguity generally encountered with passive geomagnetic data. To invert multiconfiguration in-phase data sets, we propose a novel methodology based on a full-grid 3-D multichannel deconvolution (MCD) procedure. This method allows us to invert large data sets (e.g. consisting of more than a hundred thousand of data points) for a dense voxel-based 3-D model of magnetic susceptibility subject to smoothness constraints. In this study, we first present and discuss synthetic examples of our imaging procedure, which aim at simulating realistic conditions. Finally, we demonstrate the applicability of our method to field data collected across an archaeological site in Auvergne (France) to image the foundations of a Gallo-Roman villa built with basalt rock material. Our synthetic and field data examples demonstrate the potential of the proposed inversion procedure offering new and complementary ways to interpret data sets collected with modern EMI instruments.
6
Kozhevnikov, N. O., e E. Yu Antonov. "Aftereffects in the Transient Electromagnetic Method: Magnetic Viscosity". Russian Geology and Geophysics 63, n. 3 (1 marzo 2022): 312–20. http://dx.doi.org/10.2113/rgg20204306.
Testo completoAbstract (sommario):
Abstract One of the aftereffects inherent in geological materials is magnetic viscosity. This phenomenon consists in the time lag of changes in magnetic characteristics in relation to changes in the external magnetic field. In rocks, magnetic viscosity is mainly associated with magnetization of superparamagnetic particles. In the transient electromagnetic method, magnetic viscosity is manifested as a slowly decreasing voltage induced in a receiving loop, or, in some cases, as a nonmonotone transient voltage response. Eddy currents and viscous magnetization establish and decay independently; therefore, the induction transient response measured with a fixed-geometry TEM array gives no way of finding the vertical distribution of magnetic viscosity. In order to find it, geometric soundings are needed. At later times, the voltage induced in the receiving loop due to the magnetization decay is vastly larger than that induced by the eddy currents. Because of this, magnetic viscosity contribution to the total transient response limits the sounding depth of the transient electromagnetic method.
7
Sasaki, Yutaka, Jung-Ho Kim e Seong-Jun Cho. "Multidimensional inversion of loop-loop frequency-domain EM data for resistivity and magnetic susceptibility". GEOPHYSICS 75, n. 6 (novembre 2010): F213—F223. http://dx.doi.org/10.1190/1.3503652.
Testo completoAbstract (sommario):
Electromagnetic (EM) induction measurements are affected by resistivity and magnetic susceptibility. Thus, inverting EM data for resistivity alone can give misleading models if susceptible effects are strong. An inversion algorithm is presented to simultaneously recover multidimensional distributions of resistivity and susceptibility from various types of loop-loop frequency-domain EM data. The algorithm adopts a staggered-grid finite-difference method for the 3D forward solutions and computes the sensitivities with respect to resistivity and susceptibility from the forward solutions using the reciprocity principle. The algorithm is tested on synthetic data sets from ground-based small-loop, airborne, and Slingram EM surveys. It is shown that the simultaneous inversion of the small-loop EM data collected at a singleheight is unstable and likely to produce unreliable susceptibility models because the effect of susceptibility is nearly independent of the frequency. However, if the data are obtained for multiple heights or different loop configurations, simultaneous inversion can produce more reliable susceptibility and resistivity models even if the data are contaminated by offset errors. It is also shown that although the simultaneous inversion of airborne EM data is relatively stable, adding data obtained at different heights helps to increase the reliability of the resistivity and susceptibility models. Among the loop-loop EM methods discussed here, the Slingram method is relatively insensitive to susceptibility anomalies and thus cannot be used to recover the susceptibility distribution via inversion even if the data are obtained using different loop configurations.
8
Guillemoteau, Julien, e Jens Tronicke. "Evaluation of a rapid hybrid spectral-spatial domain 3D forward-modeling approach for loop-loop electromagnetic induction quadrature data acquired in low-induction-number environments". GEOPHYSICS 81, n. 6 (novembre 2016): E447—E458. http://dx.doi.org/10.1190/geo2015-0584.1.
Testo completoAbstract (sommario):
When exploring subsurface environments using electromagnetic (EM) induction (EMI) tools, approximate forward-modeling methods based on a homogeneous half-space kernel have been extensively evaluated in the past. For large-scale exploration methods, such as magnetotellurics, marine EM, airborne EM, transient EM, and large offset loop-loop harmonic EM, such forward-modeling approaches are limited because the kernel depends strongly on the subsurface distribution of electrical conductivity. However, the response of small portable EMI loop-loop sensors applied in a low-induction number (LIN) context are known to be more linearly related to the true distribution of electrical conductivity. Thus, data collected using such sensors are more adapted to an approximate forward-modeling with a conductivity-independent kernel. We have evaluated the bias of such an approximate modeling for the case of portable multiconfiguration system measurements in 1D, 2D, and 3D contexts. Our result shows that the approximate approach tends to underestimate the conductivity of more conductive targets but is able to reproduce the right structural information. Compared with previous algorithms presented in the literature, we solved the approximate forward-modeling problem in the hybrid spectral-spatial domain to speed up the computation. Considering the level of accuracy in structural modeling as well as the computational efficiency of our hybrid spectral-spatial approach, we conclude that this method is especially suitable for near-surface, large-scale mapping applications in LIN environments as typically encountered in soil sciences and archaeological studies. For such applications, our approach can be implemented in rapid multichannel deconvolution procedures.
9
Kamm, Jochen, Michael Becken e Laust B. Pedersen. "Inversion of slingram electromagnetic induction data using a Born approximation". GEOPHYSICS 78, n. 4 (1 luglio 2013): E201—E212. http://dx.doi.org/10.1190/geo2012-0484.1.
Testo completoAbstract (sommario):
We present an efficient approximate inversion scheme for near-surface loop-loop EM induction data (slingram) that can be applied to obtain 2D or 3D models on a normal desktop computer. Our approach is derived from a volume integral equation formulation with an arbitrarily conductive homogeneous half-space as a background model. The measurements are not required to fulfill the low induction number condition (low frequency and conductivity). The high efficiency of the method is achieved by invoking the Born approximation around a half-space background. The Born approximation renders the forward operator linear. The choice of a homogeneous half-space yields closed form expressions for the required electromagnetic normal fields. It also yields a translationally invariant forward operator, i.e., a highly redundant Jacobian. In connection with the application of a matrix-free conjugate gradient method, this allows for very low memory requirements during the inversion, even in three dimensions. As a consequence of the Born approximation, strong conductive deviations from the background model are underestimated. Highly resistive anomalies are in principle overestimated, but at the same time difficult to resolve with induction methods. In the case of extreme contrasts, our forward model may fail in simultaneously explaining all the data collected. We applied the method to EM34 data from a profile that has been extensively studied with other electromagnetic methods and compare the results. Then, we invert three conductivity maps from the same area in a 3D inversion.
10
Thiesson, Julien, Alain Tabbagh, Michel Dabas e Antoine Chevalier. "Characterization of buried cables and pipes using electromagnetic induction loop-loop frequency-domain devices". GEOPHYSICS 83, n. 1 (1 gennaio 2018): E1—E10. http://dx.doi.org/10.1190/geo2016-0476.1.
Testo completoAbstract (sommario):
The detection and characterization of buried cables and metal pipes has become a key component of field surveys carried out prior to excavation work on construction sites. The very high conductivity and magnetic permeability contrast between any buried cables/pipes compared with the soil makes electromagnetic induction (EMI) instruments very useful for their detection. We have developed a seminumerical method that can be used to model the responses of this type of target. A straight horizontal conductor is equivalent to a series of magnetic dipoles, the magnitude of which can be determined in the spectral domain and then converted back into the spatial domain through the use of an inverse fast Fourier transform. Simulations and case studies allow to establish rules of thumb for the estimation of (1) the nature of the metal: the in-phase response of magnetic cables is of the opposite sign from the conducting ones, (2) the sensitivity to the target characteristic: the influence of the cable/pipe diameter is greater than that of the metal properties, and (3) the depth of the cables. The simulations also underline the role of the coil configuration: Vertical coplanar and perpendicular responses allow a more precise location of the cable/pipe, whereas the horizontal coplanar response is less dependent on the orientation. As ground truth, a known electric cable buried at a depth of 0.5 and 0.002 m in diameter is determined at 0.56 m. The first field test is related to the detection of a buried military cable from World War I, between 2.5 and 3 m below the original ground level. The second field test is related to the detection of a water pipe 0.35 m deep. The modeling technique can be applied to all EMI prospecting methods, and thus it opens the way to the correction of the disturbances generated by cables and pipes.
11
Yin, Changchun, e Ruo Wang. "Power line ground resistance detection using helicopter electromagnetic systems". GEOPHYSICS 80, n. 2 (1 marzo 2015): E125—E133. http://dx.doi.org/10.1190/geo2014-0421.1.
Testo completoAbstract (sommario):
Power line grounding can be a serious concern for the power supply industry. Only a small amount of ground resistance is acceptable because a good electric contact of power line towers with the earth reduces the possibility of the natural hazard associated with lightning. We investigated the possibility of using helicopter-borne electromagnetic (HEM) apparatus to detect the ground resistances of power line towers. Two induction systems were considered: a transmitter-earth-receiver system and a power line loop-earth-receiver system. The transmitter-earth-receiver system built the background signal in the HEM receiver, whereas the power line loop-earth-receiver system produced the signal used for resolving the power line ground resistances. By ignoring the mutual coupling between the two systems, we calculated the induced electromotive forces in the power line loop above which the HEM bird was flown and its two immediate neighbor loops. We replaced other loops along the power line with the Norton-Thevinin equivalence and solved the current flow in the power line loop by the mesh current method. Using the current in the power line loop as induction source, we calculated the electromagnetic responses in the HEM receiver from the power line loop-earth-receiver system. For identification of the poorly grounded towers, we introduced ratios of in-phase and quadrature to signal amplitude and the HEM phase. We evaluated numerical experiments showing that these parameters can well identify power line towers with high ground resistances, and they were insensitive to the flight altitude and direction. Moreover, we also took the catenaries of the power line into consideration so that the elevation differences between towers resulting from rugged mountains could be easily incorporated into the interpretation. We considered vertical coaxial (VCA) and horizontal coplanar (HCP) coil configurations. It was found that the signal for HCP coil has multiple peaks, whereas the VCA coil signal has only a single peak, so we recommend the VCA coil array for power line ground resistance detection. The inversion of synthetic data showed that the power line ground resistances can be resolved from the HEM survey.
12
Spies, Brian R. "Local noise prediction filtering for central induction transient electromagnetic sounding". GEOPHYSICS 53, n. 8 (agosto 1988): 1068–79. http://dx.doi.org/10.1190/1.1442543.
Testo completoAbstract (sommario):
Local noise prediction filtering (LNPF) is a method of noise reduction designed for use with the in‐loop transient electromagnetic (TEM) method of exploration. LNPF is based on simultaneous measurements of three orthogonal magnetic‐field components and the calculation of a time‐domain filter which predicts the vertical component from the two horizontal components. For in‐loop, or central induction, sounding over a horizontally layered earth, the TEM signal is contained wholly within the vertical component. Thus the predicted time series obtained with LNPF is the predicted electromagnetic noise which can be subtracted from the measured vertical component in subsequent processing. For low‐frequency noise, the method results in improvements in the signal‐to‐noise ratio of about a factor of five using a three‐point prediction filter. Longer filters give superior performance but are computationally intensive. The depth of exploration should increase by 40 percent, due to the five‐fold increase in signal‐to‐noise ratio, a figure which could be obtained otherwise only by increasing the transmitter power or the acquisition time by a factor of 25. In areas with lateral variations in conductivity the TEM response has both horizontal and vertical components. Applying LNPF in nonlayered areas will bias the vertical‐component TEM signal by a proportion of any horizontal TEM signal present. This bias error will generally be less than 5 to 10 percent, and usually will be insignificant in geologic environments where EM soundings are carried out. A new parameter, termed TEM tipper by analogy with magnetotellurics, is defined as the ratio of horizontal‐to‐vertical TEM response and is used to estimate the maximum LNPF bias error. The TEM tipper is useful for interpretation of TEM in‐loop data in areas of complex geology.
13
Vinothraj, C., N. Praveen Kumar e T. B. Isha. "Bearing Fault Analysis in Induction Motor Drives Using Finite Element Method". International Journal of Engineering & Technology 7, n. 3.6 (4 luglio 2018): 30. http://dx.doi.org/10.14419/ijet.v7i3.6.14928.
Testo completoAbstract (sommario):
Diagnosis of faults in induction motor is an indispensable process in industries to improve the reliability of the machine and reduce the financial loss. Among the various faults occurring in induction motors (IM), bearing fault is the predominant one which covers nearly 60% of faults. In this paper, a study of the electromagnetic field of an induction motor with bearing fault fed from both the mains and a three phase voltage source PWM inverter in open loop is carried out using Finite element method (FEM). Electromagnetic field parameters like flux lines distribution, flux density distribution and radial air gapflux density are analyzed. The presence of bearing fault can be detected from the spatial FFT spectrum of radial air gap flux density. From the FFT spectrum, it is seen that the amplitude of fundamental component of radial air gap flux density decreases and those around 100 mm distance increases with the severity of fault.
14
Smith, Richard S., e G. F. West. "Electromagnetic induction in an inhomogeneous conductive thin sheet". GEOPHYSICS 52, n. 12 (dicembre 1987): 1677–88. http://dx.doi.org/10.1190/1.1442284.
Testo completoAbstract (sommario):
Distinguishing between the electromagnetic (EM) response of a subsurface conductor and the EM response of an overburden whose conductivity and/or thickness varies laterally requires a capability to calculate the EM response of both types of conductor. While methods for calculating the response of some simple subsurface conductors such as dipping rectangular sheets are already available, methods for computing the response of an irregular overburden are not common. Using Price’s analysis, we have formulated two numerical techniques for calculating the response of a laterally varying overburden which is thin and flat, and which lies on a perfectly resistive subspace. The first technique is a frequency‐domain method in which a large matrix equation is solved to find the horizontal‐wavenumber components of the secondary vertical magnetic field. The method is best suited to calculating the response of the overburden when the EM source and receiver are located above the sheet, such as in airborne EM systems. Helicopter EM profiles calculated using this technique have been checked against a simple scale model. The second method calculates the time‐domain step response of the overburden by time‐stepping the vertical component of the magnetic field. The method is suitable for calculating the response of the overburden when the EM source is a large transmitter loop close to the overburden. Using the time‐domain method to investigate the response of simple conductance structures illustrates that the zero crossing of the vertical magnetic field moves more slowly across conductive regions than across resistive regions. This is because the rate of decay of the vertical field in a region varies in proportion to the resistance of the region. A response profile from a UTEM survey shows a response that could be interpreted as due to a dipping subsurface conductor. This response has been modeled using the time‐domain method, and a geologically acceptable pattern of lateral variations in the overburden conductance yields a response close to the measured EM response. Thus, a subsurface conductor need not lie below the profile line to explain the response.
15
Haas, Christian, Sebastian Gerland, Hajo Eicken e Heinz Miller. "Comparison of sea‐ice thickness measurements under summer and winter conditions in the Arctic using a small electromagnetic induction device". GEOPHYSICS 62, n. 3 (maggio 1997): 749–57. http://dx.doi.org/10.1190/1.1444184.
Testo completoAbstract (sommario):
Drillhole‐determined sea‐ice thickness was compared with values derived remotely using a portable small‐offset loop‐loop steady state electromagnetic (EM) induction device during expeditions to Fram Strait and the Siberian Arctic, under typical winter and summer conditions. Simple empirical transformation equations are derived to convert measured apparent conductivity into ice thickness. Despite the extreme seasonal differences in sea‐ice properties as revealed by ice core analysis, the transformation equations vary little for winter and summer. Thus, the EM induction technique operated on the ice surface in the horizontal dipole mode yields accurate results within 5 to 10% of the drillhole determined thickness over level ice in both seasons. The robustness of the induction method with respect to seasonal extremes is attributed to the low salinity of brine or meltwater filling the extensive pore space in summer. Thus, the average bulk ice conductivity for summer multiyear sea ice derived according to Archie's law amounts to 23 mS/m compared to 3 mS/m for winter conditions. These mean conductivities cause only minor differences in the EM response, as is shown by means of 1-D modeling. However, under summer conditions the range of ice conductivities is wider. Along with the widespread occurrence of surface melt ponds and freshwater lenses underneath the ice, this causes greater scatter in the apparent conductivity/ice thickness relation. This can result in higher deviations between EM‐derived and drillhole determined thicknesses in summer than in winter.
16
Bryakin, Ivan V., e Igor V. Bochkarev. "Hybrid Induction Sensing Method for Detection of Underground Cable Lines and Pipelines". Electrotechnical Systems and Complexes, n. 2(43) (28 giugno 2019): 70–78. http://dx.doi.org/10.18503/2311-8318-2019-2(43)-70-78.
Testo completoAbstract (sommario):
The analysis of the principles of searchers construction was carried out. It was found that induction route methods based on measurements of secondary electromagnetic fields, which are created by currents induced in a cable by independent radiating systems using third-party power sources, have received the greatest use. For the implementation of these methods, radiating systems of various types are used, such as frame or vibrator antennas. When building locators, the mutual distribution of the receiving and transmitting coils is of particular importance. The research group considered options for the mutual arrangement of the coils. It was found that when building a track finding equipment, two basic methods of control are widely used: the response method of the electromagnetic field parameters to the internal or surface impedance of the medium when the electromagnetic field propagates in or above the ground, respectively, and the input impedance response method of the receiving frame on the electromagnetic properties of the medium being probed. Based on the features of these two methods, a new hybrid method of induction sounding was proposed, which actually combines these two methods. When implementing this hybrid method, an induction probe (IP), which is an induction transducer of a magnetic field into an electrical signal, contains a receiving ferrite antenna (FA) and a loop antenna (LA), and LA combines the functions of transmitting and receiving antennas. A design variant of an IP with coplanar placement of FA relative to LA, which provides full geometric compensation of the primary field, is proposed. When IP operates, information is recorded on one information channel from LA (the current value of the amplitude of the exciting current) and on two information channels from the FA (current values of the amplitudes of the voltages of the active and reactive components of the output signal of the FA, respectively). The implementation of such information redundancy significantly increases the information content, efficiency and reliability of the proposed hybrid method.
17
Moghadas, Davood, Frédéric André, Harry Vereecken e Sébastien Lambot. "Efficient loop antenna modeling for zero-offset, off-ground electromagnetic induction in multilayered media". GEOPHYSICS 75, n. 4 (luglio 2010): WA125—WA134. http://dx.doi.org/10.1190/1.3467936.
Testo completoAbstract (sommario):
Retrieval of the subsurface electrical properties from electromagnetic induction (EMI) data using inverse modeling relies in particular on the accuracy of the considered EMI model. We have developed a new EMI approach whereby a zero-offset, off-ground loop antenna is efficiently modeled using frequency-dependent, complex linear transfer functions and the air subsurface is described by a Green’s function for wave propagation in 3D multilayered media. To ensure proper calibration of the system, vector network analyzer (VNA) technology is used as the transmitter and receiver. An optimal integration path is proposed for fast evaluation of the spatial Green’s function from its spectral counterpart. We validated the antenna model in laboratory conditions with measurements performed with a loop antenna in free space and at different heights above a perfect electrical conductor. Provided that the loop antenna is high enough above the reflector (off-ground condition), the measured and modeled Green’s functions agreed remarkably well. In addition, inversion of the EMI data resulted in accurate estimates of the antenna heights. Yet, as expected, signal-to-noise-ratio issues occurred for the higher antenna heights and frequencies away from the loop resonant frequency. The method appears to be promising for accurate and robust soil characterization, but needs high VNA dynamic range and antenna gain.
18
Martinelli, Patricia, e María Celeste Duplaá. "Laterally filtered 1D inversions of small-loop, frequency-domain EMI data from a chemical waste site". GEOPHYSICS 73, n. 4 (luglio 2008): F143—F149. http://dx.doi.org/10.1190/1.2917197.
Testo completoAbstract (sommario):
We made a study in the backyard of an agrochemical plant using a small-loop, frequency-domain electromagnetic induction (EMI) system. Such systems are very sensitive to conductive structures buried at shallow depths. Frequently, they are only used to locate and delimit these structures by direct observation of data. However, much more information can be obtained by applying numerical modeling techniques to the data. First we mapped an anomalous zone that indicates the possible presence of buried waste or some other underground contamination by visualizing data. Then we applied a 1D inversion method to the data from this zone. By joining 1D inversion results, this method builds 2D images of the subsoil structure below survey lines. Because the code applies smoothness constraints to the 1D inversions, the subsoil properties in these 2D images change gradually with depth. The code does not impose any correlation between the data or 1D models corresponding to neighboring points, so sharp lateral changes can appear. Several of them do not represent real features of the subsoil. We designed and applied two spatial filters to smooth the spurious lateral variations in our models. One correlates the data acquired at adjacent points prior to inversions. The other applies an analogous correlation to the inverse models obtained from the original data. Both filters greatly improve the quality of the 2D images. Compiling these results, we obtained a 3D model of the subsoil that characterizes the anomalous structure. Excavations made later at the site confirmed the results.
19
Zhang, Shuang Yu, Zhi Nan Wang, Xue Di Hao e Miao Wu. "Flow Rate Measurement Method and Apparatus of Thick Pastes". Advanced Materials Research 605-607 (dicembre 2012): 945–50. http://dx.doi.org/10.4028/www.scientific.net/amr.605-607.945.
Testo completoAbstract (sommario):
Research on the rheological characteristics and delivery resistance needs precise flow rate in pipes of thick pastes which is the basis of delivery capacity calculation and equipment selection for a pipeline system. However, the existing apparatuses are not suitable for flow rate measurement of the thick pastes, so it is necessary to design a kind of apparatus applicable to the above requirements. This paper by using an electromagnetic induction coil as a sensor, designs a kind of flow rate measurement apparatus of thick pastes. It describes the measurement method and its principle, and analyzes the error of this apparatus. A loop-pipe transportation test of coal slime was conducted, and it shows the relative test experimental error of this apparatus is less than 1%.
20
Zhang, Hai Jiao, Hui Juan Liu, Rui Fang Li e Shuang Xia Niu. "Simulation Study of High-Frequency Circulating Bearing Currents of 300kW Induction Motor". Applied Mechanics and Materials 448-453 (ottobre 2013): 2109–13. http://dx.doi.org/10.4028/www.scientific.net/amm.448-453.2109.
Testo completoAbstract (sommario):
Bearing electrical erosion caused by circulating bearing current exists in the high-power induction motor, which affects the safety of drive system. This paper presents a theoretical analysis of the generation of circulating bearing current based on electromagnetic field theory. 2D finite element analysis is adopted to calculate the parasitic capacitance and loop current method based electrical network theory is used to analysis the distribution of the common mode current. A new and reasonable circulating current equivalent circuit is built up. A 300kW induction motor fed by PWM inverter is simulated with MATLAB /SIMULINK software and the circulating bearing current of the motor is calculated.
21
Milykh, V. I., e M. G. Tymin. "A comparative analysis of the parameters of a rotating magnetic field inductor when using concentric and loop windings". Electrical Engineering & Electromechanics, n. 4 (29 luglio 2021): 12–18. http://dx.doi.org/10.20998/2074-272x.2021.4.02.
Testo completoAbstract (sommario):
Introduction. Three-phase inductors of a rotating magnetic field are used in grinders, separators and stirrers for the technological processing of bulk and liquid substances. This occurs in a cylindrical working chamber under the influence of ferromagnetic elements in the form of pieces of iron wire, which move together with the field. Problem. By analogy with three-phase induction motors, for the stator of inductors a concentric winding is adopted, which is a diametric single-layer winding. When moving from such motors to an inductor, its operating conditions have changed due to the significantly increased non-magnetic space inside the inductor compared to the motor clearances. The difference in the frontal parts of the phase windings has become essential for the electromagnetic parameters and the structure of the magnetic field in the inductor working chamber. Therefore, a loop shortened stator winding, which is symmetrical, can be considered as an alternative to a concentric diametric winding. Goal. The aim of the work is to compare the dimensional and electromagnetic parameters of a rotating magnetic field inductor in two versions of its three-phase winding: concentric single-layer diametrical and loop shortened two-layer. Methodology. Comparison of the windings is carried out through a detailed analysis of the geometrical parameters of their frontal parts, as well as through numerical-field calculations of the electromagnetic parameters of the inductor as a whole and the distribution of the magnetic field in its working chamber. Results. A significant difference in the geometrical parameters of the frontal parts of the two windings under inductor conditions was revealed. The loop version of the winding makes it possible to reduce the length of the winding conductor, its active resistance, as well as the reactance of its frontal dissipation. At the same time the asymmetry of the phase windings is excluded and an increase in the homogeneity of the magnetic field in the inductor working chamber is provided. Originality. The scientific novelty of the work lies in the development of a method of comparative analysis of the windings under the conditions of the rotating magnetic field inductor and in revealing the advantages of a loop shortened winding compared to the used concentric diametric winding. Practical value. The loop shortened stator winding recommended for the inductor will eliminate the asymmetry of its electromagnetic system. Thereby, the quality of its work in the technological processing of different substances is significantly increased due to ensuring the homogeneity of the magnetic field in the working chamber. At the same time, the copper conductor of the winding is still saved, and the efficiency of the inductor is also increased by reducing the power of electrical losses.
22
Krotkov, Evgenij A., Nadezhda V. Bezmenova e Aleksandr A. Shchobak. "Accounting for wire saggingоn span of 220 kV OHL whendetermining current, induced in ground wire by phase current magnetic fields". Vestnik of Samara State Technical University. Technical Sciences Series 30, n. 1 (16 giugno 2022): 106–17. http://dx.doi.org/10.14498/tech.2022.1.7.
Testo completoAbstract (sommario):
Overhead ground-wire cable (GW) is more prone to ice formation compared to 220 kV overhead lines. Ice-melting methods for GW using special power source have certain engineering constraints and required is connection of overhead line. Preventive heating of GW to above-zero temperature is an equivalent method to ice-melting. Preventive heating shall be provided by induction from electromagnetic field (EMF) of 220 kV overhead lines while in service. Induction methods of 220 kV OHL GW heating have been summarized and briefly described. Mathematical models of GW inductive heating do not consider the influence of wire and GW saggingon EMF parameters and equivalent circuit ground wire-earth. Therefore, sufficient mathematical model is required to use induction method of GW heating at 220 kV OHL segment. We propose induction heating for GW of double-circuit 220 kV OHL inclosed circuit ground wire-additional conductor top reventice formation. Mathematical model have been developed to calculate current, induced in circuit ground wire-additional conductor by magnetic fields of 220 kV OHL current while in service. Influence of wire and GW saggingon EMF parameters and equivalent circuit ground wire-additional conductor has been estimated. Due to mathematical model we could estimate induced current to prevent ice formation on GW of double-circuit 220 kV OHL while in service. Closed circuit ground wire-additional conductor is recommended for practical use, with capacitor loop included into circuit, its capacitance to be determined based on voltage resonance conditions.
23
Dobrucky, Branislav, Slavomir Kascak e Michal Prazenica. "Speed/Position Sensorless Control of Two-Phase Induction Motor Drive System Using Virtual Injection Method". Solid State Phenomena 198 (marzo 2013): 577–82. http://dx.doi.org/10.4028/www.scientific.net/ssp.198.577.
Testo completoAbstract (sommario):
The paper deals with speed/position servosystem with 2-phase electrical induction motor for robotic applications. The new developed method has been used for speed/position control. The precision of position determination is less than 2.5 o el. in steady-state operation in spite of virtual sensorless method. It needs for real time control - high computing power for control algorithms and very small time sampling interval. Maximum of motor electromagnetic torque is providing by field oriented control (FOC).
24
Kotenev, Viktor I., e Alexander D. Stulov. "Method for calculating the resistance of an asynchronous squirrel cage motor according to passport data and estimation of its error". Vestnik of Samara State Technical University. Technical Sciences Series 29, n. 3 (13 ottobre 2021): 98–110. http://dx.doi.org/10.14498/tech.2021.3.6.
Testo completoAbstract (sommario):
A simpler method is proposed for determining the resistances of an induction motor (total inductive resistance, active resistance of the stator and reduced active resistance of the rotor) according to reference data. Three algebraic equations are obtained from the equations of reactive power dissipation and electromagnetic power in the nominal mode and the equation of electromagnetic power in the critical mode: the first is relative to three resistances, the second is the equation of the dependence of the active resistance of the stator relative to the total inductive resistance, and the third is the active resistance of the rotor relative to the total inductive resistance. An iterative method is proposed for solving this system of equations, which gives a small error already at the second step of the calculations.
When assessing the error of the method, the specified values of the electromagnetic power and the multiplicity of the maximum torque were used, which are expressed relative to the reference resistances of the control motors. An estimate is given of the total error from the imperfection of the method and the discrepancy between the reference values of the multiplicity of the maximum torque and power on the motor shaft with their refined values calculated from the resistances from the reference book.
Based on the calculated resistances in the nominal mode, the dependences of the active and inductive resistances of the motor are constructed using an accurate and approximate method.
25
Leppin, Michael. "Electromagnetic modeling of 3-D sources over 2-D inhomogeneities in the time domain". GEOPHYSICS 57, n. 8 (agosto 1992): 994–1003. http://dx.doi.org/10.1190/1.1443325.
Testo completoAbstract (sommario):
A numerical method is presented by which the transient electromagnetic response of a two‐dimensional (2-D) conductor, embedded in a conductive host rock and excited by a rectangular current loop, can be modeled. This 2.5-D modeling problem has been formulated in the time domain in terms of a vector diffusion equation for the scattered magnetic induction, which is Fourier transformed into the spatial wavenumber domain in the strike direction of the conductor. To confine the region of solution of the diffusion equation to the conductive earth, boundary values for the components of the magnetic induction on the ground surface have been calculated by means of an integral transform of the vertical component of the magnetic induction at the air‐earth interface. The system of parabolic differential equations for the three magnetic components has been integrated for 9 to 15 discrete spatial wavenumbers ranging from [Formula: see text] to [Formula: see text] using an implicit homogeneous finite‐difference scheme. The discretization of the differential equations on a grid representing a cross‐section of the conductive earth results in a large, sparse system of linear equations, which is solved by the successive overrelaxation method. The three‐dimensional (3-D) response has been computed by an inverse Fourier transformation of the cubic spline interpolated scattered magnetic induction in the wavenumber domain using a digital filtering technique. To test the algorithm, responses have been computed for a two‐layered half‐space and a vertical prism embedded in a conductive host rock. These examples were then compared with results obtained analytically or numerically using frequency‐domain finite‐element and time‐domain integral equation methods. The new numerical procedure gives satisfactory results for a wide range of 2-D conductivity distributions with conductivity ratios exceeding 1:100, provided the grid is sufficiently refined at the corners of the conductivity anomalies.
26
Wang, B., C. Kang e S. Chen. "Experimental study on magnetic flaw detection of micro-defects in ERW tubes". Journal of Physics: Conference Series 2198, n. 1 (1 maggio 2022): 012033. http://dx.doi.org/10.1088/1742-6596/2198/1/012033.
Testo completoAbstract (sommario):
Abstract Chassis lightweight is one of the implementation of vehicle lightweight, the use of Electric Resistance Welding(ERW)welded pipe by bending and internal high pressure molding from the parts are an important part of the chassis components. Due to the limitation of welded pipe size, thin wall, high temperature and continuous production, the conventional nondestructive testing method is difficult to meet the continuous dynamic testing requirements of ERW welded pipe. In view of the small defect of ERW welded pipe, a method for detection of welded pipe defects based on the principle of electromagnetic induction is presented. Firstly, the fuzzy evaluation model of weld quality was established based on the fuzzy mathematics principle. Secondly, the welding mechanism of ERW was analyzed, and the microstructure of the weld was observed by metallographic microscope, and the microstructure of the weld was obtained. Finally, eddy current method, the low-frequency electromagnetic scanning method and magnetic induction method were used to detect ERW welded pipes. The data analysis shows that the magnetic induction method can realize dynamic detection and accurate localization of welded pipe defects, and the comprehensive detection effect is the best.
27
Wang, Lulu. "Three-Dimensional Holographic Electromagnetic Imaging for Accessing Brain Stroke". Sensors 18, n. 11 (9 novembre 2018): 3852. http://dx.doi.org/10.3390/s18113852.
Testo completoAbstract (sommario):
The authors recently developed a two-dimensional (2D) holographic electromagnetic induction imaging (HEI) for biomedical imaging applications. However, this method was unable to detect small inclusions accurately. For example, only one of two inclusions can be detected in the reconstructed image if the two inclusions were located at the same XY plane but in different Z-directions. This paper provides a theoretical framework of three-dimensional (3D) HEI to accurately and effectively detect inclusions embedded in a biological object. A numerical system, including a realistic head phantom, a 16-element excitation sensor array, a 16-element receiving sensor array, and image processing model has been developed to evaluate the effectiveness of the proposed method for detecting small stroke. The achieved 3D HEI images have been compared with 2D HEI images. Simulation results show that the 3D HEI method can accurately and effectively identify small inclusions even when two inclusions are located at the same XY plane but in different Z-directions. This preliminary study shows that the proposed method has the potential to develop a useful imaging tool for the diagnosis of neurological diseases and injuries in the future.
28
Shirai, Haruhiko, Hiromichi Mitamura, Nobuaki Arai e Kazuyuki Moriya. "Study of Energy Harvesting from Low-Frequency Vibration with Ferromagnetic Powder and Non-magnetic Fluid". Plasmonics 15, n. 2 (23 novembre 2019): 559–71. http://dx.doi.org/10.1007/s11468-019-01067-9.
Testo completoAbstract (sommario):
AbstractThe movement of the creature and the almost wave in the ocean is a low vibration of random energy with a frequency range of 0.1–10 Hz. Because of its low frequency, the opinion has been that electrical energy generation from this low-frequency wave motion through the electromagnetic induction method is difficult. In this study, an electrical generator was created by the electromagnetic induction method by putting a small mass of ferromagnetic powder in nonmagnetic fluid. A broadband vibration energy harvesting model was created in which vibrations are broadened through a multi-degree of freedom oscillation system using ferromagnetic powder. To generate electricity from low-frequency vibrations (1 Hz or less), a non-resonant type model was created by adding fluid to the ferromagnetic powder model and the simulation results confirmed using computational fluid dynamics by creating a working energy harvesting device.
29
Yin, C., e H. ‐M Maurer. "Electromagnetic induction in a layered earth with arbitrary anisotropy". GEOPHYSICS 66, n. 5 (settembre 2001): 1405–16. http://dx.doi.org/10.1190/1.1487086.
Testo completoAbstract (sommario):
The traditional model for interpreting geoelectromagnetic data is a layered isotropic earth, but in regions with distinct dipping stratification, this model is inadequate. In this case, it is useful to extend the model to a layered earth with general anisotropy, assigning each layer a symmetrical [Formula: see text] resistivity tensor. The electromagnetic (EM) field is presented by two scalar potentials which describe the poloidal and toroidal part of the magnetic field. After stripping off the horizontal coordinates by a 2‐D Fourier transform, we obtain two coupled ordinary differential equations in the vertical coordinate. To stabilize the numerical calculation, the wavenumber domain is divided into two parts. For small wavenumbers, the EM field is calculated through continuation from layer to layer, where the tranverse isotropy requires an extra treatment because the two potentials are in this case uncoupled and the requirement for the field continuation is not satisfied. To calculate the EM field for greater wavenumbers, a Green’s function is applied. The apparent resistivities in the controlled source audio‐magnetotellurics (CSAMT) method and the EM field in the earth are calculated for this model. From both EM fields and the apparent resistivities, one can clearly recognize the effect of the electrical anisotropy of the earth on the CSAMT measurements.
30
Li, Haixia, Jican Lin e Ziguang Lu. "Three Vectors Model Predictive Torque Control Without Weighting Factor Based on Electromagnetic Torque Feedback Compensation". Energies 12, n. 7 (11 aprile 2019): 1393. http://dx.doi.org/10.3390/en12071393.
Testo completoAbstract (sommario):
Finite control set-model predictive torque control (FCS-MPTC) depends on the system parameters and the weight coefficients setting. At the same time, since the actual load disturbance is unavoidable, the model parameters are not matched, and there is a torque tracking error. In traditional FCS-MPTC, the outer loop—that is, the speed loop—adopts a classic Proportional Integral (PI) controller, abbreviated as PI-MPTC. The pole placement of the PI controller is usually designed by a plunge-and-test, and it is difficult to achieve optimal dynamic performance and optimal suppression of concentrated disturbances at the same time. Aiming at squirrel cage induction motors, this paper first proposes an outer-loop F-ETFC-MPTC control strategy based on a feed-forward factor for electromagnetic torque feedback compensation (F-ETFC). The electromagnetic torque was imported to the input of the current regulator, which is used as the control input signal of feedback compensation of the speed loop; therefore, the capacity of an anti-load-torque-disturbance of the speed loop was improved. The given speed is quantified by a feed-forward factor into the input of the current regulator, which is used as the feed-forward adjustment control input of the speed controller to improve the dynamic response of the speed loop. The range of the feed-forward factor and feed-back compensation coefficient can be obtained according to the structural analysis of the system, which simplifies the process of parameter design adjustment. At the same time, the multi-objective optimization based on the sorting method replaces the single cost function in traditional control, so that the selection of the voltage vector works without the weight coefficient and can solve complicated calculation problems in traditional control. Finally, according to the relationship between the voltage vector and the switch state, the virtual six groups of three vector voltages can be adjusted in both the direction and amplitude, thereby effectively improving the control performance and reducing the flow rate and torque ripple. The experiment is based on the dSPACE platform, and experimental results verify the feasibility of the proposed F-ETFC-MPTC. Compared with traditional PI-MPTC, the feed-forward factor can effectively improve the stability time of the system by more than 10 percent, electromagnetic torque feedback compensation can improve the anti-load torque disturbance ability of the system by more than 60 percent, and the three-vector voltage method can effectively reduce the disturbance.
31
Mansoor, Muhammad, e Muhammad Shahid. "On the Designing, Efficiency, and Stirring Force of an Induction Coil for the Processing of Prototype Al Based Nanocomposites". Journal of Metallurgy 2014 (31 dicembre 2014): 1–6. http://dx.doi.org/10.1155/2014/637031.
Testo completoAbstract (sommario):
Induction melting could be a potential fabrication method for aluminum matrix nanocomposites, owing to its characteristics stirring action and rapid heating. In the present work, an induction coil for small scale composite fabrication was designed through geometric, thermal, and electromagnetic analyses. Subsequently, the designed coil was simulated for its thermal efficiency and stirring force using finite element method magnetics software. The designed coil yielded more than 60% of the total energy supplied into thermal efficiency with a stirring force <3 mN, which could be significant for efficient melting and stirring to fabricate the aluminum matrix nanocomposites.
32
Moghadas, Davood, e Jasper A. Vrugt. "The Influence of Geostatistical Prior Modeling on the Solution of DCT-Based Bayesian Inversion: A Case Study from Chicken Creek Catchment". Remote Sensing 11, n. 13 (29 giugno 2019): 1549. http://dx.doi.org/10.3390/rs11131549.
Testo completoAbstract (sommario):
Low frequency loop-loop electromagnetic induction (EMI) is a widely-used geophysical measurement method to rapidly measure in situ the apparent electrical conductivity (ECa) of variably-saturated soils. Here, we couple Bayesian inversion of a quasi-two-dimensional electromagnetic (EM) model with image compression via the discrete cosine transform (DCT) for subsurface electrical conductivity (EC) imaging. The subsurface EC distributions are obtained from multi-configuration EMI data measured with a CMD-Explorer sensor along two transects in the Chicken Creek catchment (Brandenburg, Germany). Dipole-dipole electrical resistivity tomography (ERT) data are used to benchmark the inferred EC fields of both transects. We are especially concerned with the impact of the DCT truncation method on the accuracy and reliability of the inversely-estimated EC images. We contrast the results of two different truncation approaches for model parametrization. The first scenario considers an arbitrary selection of the dominant DCT coefficients and their prior distributions (a commonly-used approach), while the second methodology benefits from geostatistical simulation of the EMI data pseudosection. This study demonstrates that DCT truncation based on geostatistical simulations facilitates a robust selection of the dominant DCT coefficients and their prior ranges, resulting in more accurate subsurface EC imaging from multi-configuration EMI data. Results based on geostatistical prior modeling present an excellent agreement between the EMI- and ERT-derived EC fields of the Chicken Creek catchment.
33
Emil Hasan, Amilia, Haryani Hassan e Ismadi Bugis. "Variable Speed Vector Control for Induction Motor of Electric Vehicle". Applied Mechanics and Materials 699 (novembre 2014): 759–64. http://dx.doi.org/10.4028/www.scientific.net/amm.699.759.
Testo completoAbstract (sommario):
This paper presents the speed performance of an induction motor by using a vector control. The control scheme used is an indirect vector control for define speed command. The main focus of this research is to observe on the dynamic speed performance of the induction motor when the command speed is given to the motor. In this study, the system of indirect vector control will be built by using Matlab Simulink. In fact, the expression of exciting flux linkage and electromagnetic torque are used to create a simple embedded system which to find out the effects of flux weakening in motor while, the gain of the speed controller is 100. The result shows that the vector control method will cause immediate the motor speed response with a small electromagnetic torque ripple. Furthermore, the output mechanical torque starts to decrease when the motor speed above the base speed to maintain a constant output power operation. This paper contributes a new algorithm to analysis the system when the speed motor is higher than a base speed.
34
Masuda, Hiroshi, Yoshifumi Okamoto e Shinji Wakao. "Multistage topology optimization of induction heating apparatus in time domain electromagnetic field with magnetic nonlinearity". COMPEL - The international journal for computation and mathematics in electrical and electronic engineering 38, n. 3 (7 maggio 2019): 1009–22. http://dx.doi.org/10.1108/compel-10-2018-0386.
Testo completoAbstract (sommario):
Purpose The purpose of this paper is to solve efficiently the topology optimization (TO) in time domain problem with magnetic nonlinearity requiring a large-scale finite element mesh. As an actual application model, the proposed method is applied to induction heating apparatus. Design/methodology/approach To achieve TO with efficient computation time, a multistage topology is proposed. This method can derive the optimum structure by repeatedly reducing the design domain and regenerating the finite element mesh. Findings It was clarified that the structure derived from proposed method can be similar to the structure derived from the conventional method, and that the computation time can be made more efficient by parameter tuning of the frequency and volume constraint value. In addition, as a time domain induction heating apparatus problem of an actual application model, an optimum topology considering magnetic nonlinearity was derived from the proposed method. Originality/value Whereas the entire design domain must be filled with small triangles in the conventional TO method, the proposed method requires finer mesh division of only the stepwise-reduced design domain. Therefore, the mesh scale is reduced, and there is a possibility that the computation time for TO can be shortened.
35
Nakamura, Takuto ,,, Takuya Hirata, Eko Setiawan e Ichijo Hodaka. "A Practical Method for Estimating Mutual Inductance in Wireless Power Transmission System". International Journal of Circuits, Systems and Signal Processing 16 (1 giugno 2022): 1027–34. http://dx.doi.org/10.46300/9106.2022.16.125.
Testo completoAbstract (sommario):
This paper proposes a practical method for estimating mutual inductance in wireless power transmission system based on the principle of electromagnetic induction. Conventional estimation methods utilize a voltage, current, and phase of current in transmitter side, while our method requires only an amplitude of the voltage and current in transmitter side. Our method is designed so that the mutual inductance can be estimated under challenging situation which there is a measurement noise. Numerical simulations show that if the system has a small mutual inductance, a relative error and standard derivation of estimated mutual inductance tend to become larger. However, it will be shown that these factors can be improved to make a voltage of voltage source in the system high.
36
Lima, Cláudio de Andrade, James Cale e Kamran Eftekhari Shahroudi. "Rotor Position Synchronization in Central-Converter Multi-Motor Electric Actuation Systems". Energies 14, n. 22 (9 novembre 2021): 7485. http://dx.doi.org/10.3390/en14227485.
Testo completoAbstract (sommario):
The aerospace industry is increasingly transitioning from hydraulic and pneumatic drives to power-electronic based drive systems for reduced weight and maintenance. Electromechanical thrust reverse actuation systems (EM-TRAS) are currently being considered as a replacement for mechanical based TRAS for future aircraft. An EM-TRAS consists of one or more power-electronic drives, electrical motors, and gear-trains that extend/retract mechanical members to produce a drag force that decelerates the aircraft upon landing. The use of a single (“central”) power electronic converter to simultaneously control a set of parallel induction machines is a potentially inexpensive and robust method for implementing EM-TRAS. However, because the electrical motors may experience different shaft torques—arising from differences in wind forces and a flexible nacelle—a method to implement rotor position synchronization in central-converter multi-motor (CCMM) architectures is needed. This paper introduces a novel method for achieving position synchronization within CCMM architecture by using closed-loop feedback of variable stator resistances in parallel induction machines. The feasibility of the method is demonstrated in several case studies using electromagnetic transient simulation on a set of parallel induction machines experiencing different load torque conditions, with the central converter implementing both voltage-based and current-based primary control strategies. The key result of the paper is that the CCMM architecture with proposed feedback control strategy is shown in these case studies to dynamically drive the position synchronization error to zero. The initial findings indicate that the CCMM architecture with induction motors may be a viable option for implementing EM-TRAS in future aircraft.
37
Wang, Zhi, e Sinan Fang. "Three-Dimensional Inversion of Borehole-Surface Resistivity Method Based on the Unstructured Finite Element". International Journal of Antennas and Propagation 2021 (24 settembre 2021): 1–13. http://dx.doi.org/10.1155/2021/5154985.
Testo completoAbstract (sommario):
The electromagnetic wave signal from the electromagnetic field source generates induction signals after reaching the target geological body through the underground medium. The time and spatial distribution rules of the artificial or the natural electromagnetic fields are obtained for the exploration of mineral resources of the subsurface and determining the geological structure of the subsurface to solve the geological problems. The goal of electromagnetic data processing is to suppress the noise and improve the signal-to-noise ratio and the inversion of resistivity data. Inversion has always been the focus of research in the field of electromagnetic methods. In this paper, the three-dimensional borehole-surface resistivity method is explored based on the principle of geometric sounding, and the three-dimensional inversion algorithm of the borehole-surface resistivity method in arbitrary surface topography is proposed. The forward simulation and calculation start from the partial differential equation and the boundary conditions of the total potential of the three-dimensional point current source field are satisfied. Then the unstructured tetrahedral grids are used to discretely subdivide the calculation area that can well fit the complex structure of subsurface and undulating surface topography. The accuracy of the numerical solution is low due to the rapid attenuation of the electric field at the point current source and the nearby positions and sharply varying potential gradients. Therefore, the mesh density is defined at the local area, that is, the vicinity of the source electrode and the measuring electrode. The mesh refinement can effectively reduce the influence of the source point and its vicinity and improve the accuracy of the numerical solution. The stiffness matrix is stored with Compressed Row Storage (CSR) format, and the final large linear equations are solved using the Super Symmetric Over Relaxation Preconditioned Conjugate Gradient (SSOR-PCG) method. The quasi-Newton method with limited memory (L_BFGS) is used to optimize the objective function in the inversion calculation, and a double-loop recursive method is used to solve the normal equation obtained at each iteration in order to avoid computing and storing the sensitivity matrix explicitly and reduce the amount of calculation. The comprehensive application of the above methods makes the 3D inversion algorithm efficient, accurate, and stable. The three-dimensional inversion test is performed on the synthetic data of multiple theoretical geoelectric models with topography (a single anomaly model under valley and a single anomaly model under mountain) to verify the effectiveness of the proposed algorithm.
38
Nian, Shih-Chih, Che-Wei Lien e Ming-Shyan Huang. "Experimental rapid surface heating by induction for injection molding of large LCD TV frames". Journal of Polymer Engineering 34, n. 2 (1 aprile 2014): 173–84. http://dx.doi.org/10.1515/polyeng-2013-0243.
Testo completoAbstract (sommario):
Abstract The use of electromagnetic induction heating on achieving high mold temperature has been proven to effectively improve the appearance quality of injection molded parts. However, until now, the method has only successfully been used on heating small mold surfaces. This study aims to apply the method on a large injection mold that is used for producing 42-inch LCD TV frames. With the goals of achieving heating efficiency and uniformity, the main focus in this research is designing the induction coil. Initially, three types of induction coils – a single-layered coil with currents that flow in one direction, a single-layered coil with currents that flow in opposite directions, and a two-layered coil – were compared to confirm their heating rates; the best one was then chosen. Additionally, evaluation of various induction coils was preceded with commercial simulation software that supports electromagnetic and thermal analyses. An experiment involving heating a simple workpiece with a heated area similar to that of the male mold plate of the LCD TV frames was conducted to confirm its heating rate and uniformity. Real injection molding LCD TV frames assisted with induction heating was then carried out. Experimental results depicted that: (1) a single-layered coil with currents that flow in one direction performed best; (2) that it heated the simple workpiece at a high heating rate of 5.5°C/s with reasonable temperature uniformity (standard deviation: 5.1°C); and (3) induction heating of a 42-inch LCD TV frame mold surface in practical injection molding provided a high heating rate of 4.5°C/s with favorable temperature uniformity (standard deviation: 4.0°C).
39
Bensdorp, Silvian, Steen A. Petersen, Peter M. van den Berg e Jacob T. Fokkema. "An approximate 3D computational method for real-time computation of induction logging responses". GEOPHYSICS 79, n. 3 (1 maggio 2014): E137—E148. http://dx.doi.org/10.1190/geo2013-0233.1.
Testo completoAbstract (sommario):
Over many years, induction logging systems have been used to create well formation logs. The major drawback for the utilization of these tools is the long simulation time for a single forward computation. We proposed an efficient computational method based on a contrast-type of integral-equation formulation, in which we applied an approximation for the 3D electromagnetic field. We assumed that the dominant contribution in the integral equation is obtained by the contribution around the singularity of Green’s kernel. It is expected that the approximation yields reliable results when the (homogeneous) background conductivity around the logging tool is close to the actual conductivity at the location of the tool. We have developed a data-driven method to determine this background conductivity from the dominant part of the measured coaxial magnetic fields, which are mainly influenced by the conductivity at the tool sensors. For a synthetic model, the results were compared to the ones of a rigorous solution of the integral equation and show a good simulation response to small-scale variations in the medium. Further, the method was used to simulate the response of a realistic reservoir model. Such a model is created by a geological modeling program. We concluded that our approximate method was able to improve the approximation results in highly heterogeneous structures compared to the Born approximation and provide an effective medium-gradient around the tool. Our method, based on the wavefield approximation, also estimates the error, and hence yields a warning when the method becomes unreliable.
40
Huang, Min, Gang Wang, Hui Hui Luo e Yuan Sheng Liang. "A Novel Protection of Transmission Lines for Two ±500kV HVDC Systems Erected on the same Tower". Advanced Materials Research 383-390 (novembre 2011): 3669–74. http://dx.doi.org/10.4028/www.scientific.net/amr.383-390.3669.
Testo completoAbstract (sommario):
Up to now, there is no precedent of applying two bipole lines (TBL) on the same tower technology of long-distance HVDC transmission project in the world. Owing to mutual influence between the two HVDC circuits on the same tower, the traditional protection of transmission line is faced with technical difficulties on fault pole identification, especially high grounded fault loop impedance. A new protection scheme of transmission lines for the double ±500kV HVDC circuits on the same tower is proposed. Based on electromagnetic decoupling method for TBL on same tower is proposed by analyzed the characteristic of coupling mutual induction, a four module components is proposed to decouple the network equation and analyze the fault modal network. On this basis, a novel method of fault pole identification based on the polarity comparison of line-mode back traveling wave is proposed. It has been made that validates the advantage of this novel protection strategy to identify the fault pole by simulation of PSCAD/EMTDC on the model of the TBL ±500kV HVDC system on the same tower in Xiluodu-Guangdong China.
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Deleersnyder, Wouter, Benjamin Maveau, Thomas Hermans e David Dudal. "Inversion of electromagnetic induction data using a novel wavelet-based and scale-dependent regularization term". Geophysical Journal International 226, n. 3 (6 maggio 2021): 1715–29. http://dx.doi.org/10.1093/gji/ggab182.
Testo completoAbstract (sommario):
SUMMARY The inversion of electromagnetic induction data to a conductivity profile is an ill-posed problem. Regularization improves the stability of the inversion and a smoothing constraint is typically used. However, the conductivity profiles are not always expected to be smooth. Here, we develop a new inversion scheme in which we transform the model to the wavelet space and impose a sparsity constraint. This sparsity constrained inversion scheme will minimize an objective function with a least-squares data misfit and a sparsity measure of the model in the wavelet domain. A model transform to the wavelet domain allows to investigate the temporal resolution (periodicities at different frequencies) and spatial resolution (location of the peaks) characteristics of the model, and penalizing small-scale coefficients effectively reduces the complexity of the model. The novel scale-dependent regularization term can be used to favour either blocky or smooth structures, as well as high-amplitude models in globally smooth structures in the inversion. Depending on the expected conductivity profile, a suitable wavelet basis function can be chosen. The scheme supports multiple types of regularization with the same algorithm and is thus flexible. Finally, we apply this new scheme on a frequency domain electromagnetic sounding data set, but the scheme could equally apply to any other 1-D geophysical method.
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Walker, P. W., e G. F. West. "A robust integral equation solution for electromagnetic scattering by a thin plate in conductive media". GEOPHYSICS 56, n. 8 (agosto 1991): 1140–52. http://dx.doi.org/10.1190/1.1443133.
Testo completoAbstract (sommario):
An integral equation solution for electromagnetic (EM) scattering by a thin plate robustly models scattering in either perfectly resistive, very resistive, or conducting host media. Because the solution is not restricted to modeling certain ranges of host conductivity, it can be used to model scattering over the large ranges in conductivity encountered in geophysics. The solution is developed around a pair of coupled integral equations for the scattering distributions on the plate. In one equation, the scattering distribution is the scalar potential set up by the scattered charge distribution. In the other, it is the component of the scattered magnetic field perpendicular to the plate. The equations are solved numerically using the Galerkin method with simple polynomial basis functions. To find the fields scattered by the conductor, the scattered current density is first calculated from the scalar potential and the magnetic field. The scattered fields can then be found by integrating over the scattered current density. To test the solution, we model horizontal loop EM responses with our solution and compare the results with those from two established integral equation solutions. One of these solutions models pure induction and is used to test our solution when the host is perfectly resistive. Agreement with this solution is very good. Comparisons with the other solution, an electric field integral equation, tests our solution when the host medium is conductive. Agreement with the latter solution is good where induction is not too strong: i.e., where the electric‐field solution is known to work well. Our solution therefore can accurately model EM scattering by a plate in a host medium with any conductivity.
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Uto, Shotaro, Takenobu Toyota, Haruhito Shimoda, Kazutaka Tateyama e Kunio Shirasawa. "Ship-borne electromagnetic induction Sounding of Sea-ice thickness in the Southern Sea of Okhotsk". Annals of Glaciology 44 (2006): 253–60. http://dx.doi.org/10.3189/172756406781811510.
Testo completoAbstract (sommario):
AbstractRecent observations have revealed that dynamical thickening is dominant in the growth process of Sea ice in the Southern Sea of Okhotsk. That indicates the importance of understanding the nature of thick deformed ice in this area. The objective of the present paper is to establish a Ship-based method for observing the thickness of deformed ice with reasonable accuracy. Since February 2003, one of the authors has engaged in the core Sampling using a Small basket from the icebreaker Soya. Based on these results, we developed a new model which expressed the internal Structure of pack ice in the Southern Sea of Okhotsk, as a one-dimensional multilayered Structure. Since 2004, the electromagnetic (EM) inductive Sounding of Sea-ice thickness has been conducted on board Soya. By combining the model and theoretical calculations, a new algorithm was developed for transforming the output of the EM inductive instrument to ice + Snow thickness (total thickness). Comparison with total thickness by drillhole observations Showed fair agreement. The probability density functions of total thickness in 2004 and 2005 Showed Some difference, which reflected the difference of fractions of thick deformed ice.
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Huo, Y., e B. Q. Li. "Boundary/Finite Element Modeling of Three-Dimensional Electromagnetic Heating During Microwave Food Processing". Journal of Heat Transfer 127, n. 10 (16 maggio 2005): 1159–66. http://dx.doi.org/10.1115/1.2035112.
Testo completoAbstract (sommario):
A three-dimensional 3D finite element-boundary integral formulation is presented for the analysis of the electric and magnetic field distribution, power absorption, and temperature distribution in electrically conductive and dielectric materials. The hybrid finite/boundary method represents an optimal approach for modeling of large-scale electromagnetic-thermal materials processing systems in which the volume ratio of the sample over the entire computational domain is small. To further improve the efficiency, the present formulation also incorporates various efficient solvers designed specifically for the solution of large sparse systems of linear algebraic equations. The resulting algorithm with a compressed storage scheme is considered effective and efficient to meet the demand of 3D large scale electromagnetic/thermal simulations required for processing industries. Examples of 3D electromagnetic and thermal analysis are presented for induction and microwave heating systems. Numerical performance of the computer code is assessed for these systems. Computed results are presented for the electric field distribution, power absorption, and temperature distribution in a food load thermally treated in an industrial pilot scale microwave oven designed for food sterilization. Computed temperature distribution in a food package compares well with experimental measurements taken using an infrared image camera.
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Hu, Yao, Hong Lu Hu e Ding Jin Huang. "The Design and Simulation of the Array Induction Logging Tools’ Signal Conditioning Circuit". Applied Mechanics and Materials 241-244 (dicembre 2012): 1010–13. http://dx.doi.org/10.4028/www.scientific.net/amm.241-244.1010.
Testo completoAbstract (sommario):
Array induction logging tools (AILT) detects the stratum conductivity based on the principle of electromagnetic induction, as a result, the signal of the amplitude using the AILT is in microvolt level. The small-signal is always drowned by noise at high-temperature and high-pressure condition. In order to collect the weak signal accurately, we propose a design method of signal modulator circuits based on the principle of differential amplifier and active band-pass filter with second band limitless gain and multi-path negative feedback. First, make the induction signal obtained from the coil two stages amplification. Then Execute two-order band-pass filter to the enlarged signal. At last, process the filtered signal by the backward circuits. Simulating the circuits by Pspice16.3, The result of simulation indicated that the gain relative error of preamplifier is less than 1% and the center frequency relative error of band filter is less than 4%. These data suggest that the relative error of the design circuits is less than routine instrument by 5%. So the Simulation verifies the feasibility of the signal modulator circuit.
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Warren, R. K., e L. J. Srnka. "Exploration in the basalt‐covered areas of the Columbia River Basin, Washington, using electromagnetic array profiling (EMAP)". GEOPHYSICS 57, n. 8 (agosto 1992): 986–93. http://dx.doi.org/10.1190/1.1443324.
Testo completoAbstract (sommario):
The electromagnetic array profiling (EMAP) exploration method was tested at three basalt‐covered locations on the Columbia Plateau in central Washington state. Three 16 km survey lines were located to intersect test wells drilled by Shell. The data were EMAP filtered, and inverted using a nonlinear 1-D Riccati approach developed for conventional magnetotelluric (MT) processing. Large and small features on the resulting resistivity cross‐sections produced by EMAP filtering near the drill hole closely approximated the electric induction logs. Sedimentary units within the survey area appear to be thin, with some thickening indicated toward the center of the basin. Structuring within the sediments is mild within the limits of the survey, although there is appreciable structure within the Miocene flood basalts on one test line.
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Yang, Jiameng, Wenfang Zhang, Liang Zou, Yali Wang, Youliang Sun e Yingchun Feng. "Research on Distribution and Shielding of Spatial Magnetic Field of a DC Air Core Smoothing Reactor". Energies 12, n. 5 (11 marzo 2019): 937. http://dx.doi.org/10.3390/en12050937.
Testo completoAbstract (sommario):
With the rapid development of ultra-high-voltage direct current (UHVDC) transmission, air core smoothing reactors have become the main source of electromagnetic contamination in converter substations. The actual magnetic field distribution was obtained by measuring the magnetic induction intensity of the polar busbar smoothing reactor under full load operation condition of the Jiaodong ±660 kV converter substation. A method combined with the measured data to eliminate the influence of the geomagnetic field is proposed. The magnetic field distribution model of the smoothing reactor is established and the rationality and validity of the model for magnetic field distribution is verified. Some magnetic shielding measures are proposed and their effectiveness is verified by simulation and small-scale experiments.
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Kolaj, Michal, e Richard Smith. "Mapping lateral changes in conductance of a thin sheet using time-domain inductive electromagnetic data". GEOPHYSICS 79, n. 1 (1 gennaio 2014): E1—E10. http://dx.doi.org/10.1190/geo2013-0219.1.
Testo completoAbstract (sommario):
With the inductive electromagnetic geophysical method, the laterally varying conductance of thin sheet models can be estimated either through a direct transform of the measured data or through inversion. The direct transform (called the simplified solution) does not require grid or line data and is simple enough to be performed in the field because the conductance at a location is calculated directly from the ratio of two measured magnetic fields (the vertical spatial and temporal derivative of the vertical magnetic field) at that location. However, the simplified solution assumes that the secondary horizontal magnetic fields are zero and/or that the sheet has a uniform conductance. Our nonapproximate solution (called the full inversion) does not make these assumptions, but requires gridded data, measurements of the secondary horizontal magnetic fields, and more complicated inversion algorithms. Through forward modeling, we found that the full inversion provides better results than the simplified solution when the spatial gradient of the resistance is strong and/or when the horizontal magnetic fields are large. Because the simplified solution may be preferable due to its simplicity, we introduce two unreliability parameters, which assess the unreliability of the conductance calculated using the simplified solution. A comparison of the simplified solution and full inversion in a fixed in-loop survey collected overtop a dry tailings pond in Sudbury, Ontario, Canada, revealed that there were small differences around large conductance contrasts, which coincided with elevated unreliability parameters. The simplified solution is recommended if fast in-field interpretations are required, or additionally, as a first-pass survey that can be performed with sparse station spacing to identify areas of interest. Denser grid data can then be collected, for the more reliable full inversion, over areas of interest and/or zones where the simplified solution is expected to be unreliable as predicted by the unreliability parameters.
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Schulze, Martin, e Egbert Baake. "Tailored heating of forging billets using induction and conduction heating approaches". COMPEL - The international journal for computation and mathematics in electrical and electronic engineering 39, n. 1 (16 dicembre 2019): 100–107. http://dx.doi.org/10.1108/compel-05-2019-0217.
Testo completoAbstract (sommario):
Purpose This paper aims to deal with different induction and conduction heating approaches to realize a tailored heating of round billets for hot forming processes. In particular, this work examines the limits in which tailor-made temperature profiles can be achieved in the billet. In this way, a flow stress distribution based on the temperature field in the material can be set in a targeted manner, which is decisive for forming processes. Design/methodology/approach For the heating of round billets by induction, the rotationally symmetric arrangement is used and a parameterized 2D finite element method model is created. The harmonic electromagnetic solution is coupled with the transient thermal solution. For heating by means of conduction, the same procedure is used only with the use of a 3D model. Findings First results have shown that both methods can achieve very good results for billets with small diameters (d < 30 mm). For larger diameters, an adapted control of the heating process is necessary to ensure through heating of the material. Further investigations are carried out. Practical implications Using tailored heating for forging billets, several forming steps can be achieved in one step. Among other things, higher energy efficiency and throughput rates can be achieved. Originality/value The peculiarity of the tailored heating approach is that, in contrast to inhomogeneous heating, where only partial areas are heated, the entire component is heated to the target.
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Zhang, Ziyi, Mohammed Roula e Richard Dinsdale. "Magnetic Induction Spectroscopy for Biomass Measurement: A Feasibility Study". Sensors 19, n. 12 (20 giugno 2019): 2765. http://dx.doi.org/10.3390/s19122765.
Testo completoAbstract (sommario):
Background: Biomass measurement and monitoring is a challenge in a number of biotechnology processes where fast, inexpensive, and non-contact measurement techniques would be of great benefit. Magnetic induction spectroscopy (MIS) is a novel non-destructive and contactless impedance measurement technique with many potential industrial and biomedical applications. The aim of this paper is to use computer modeling and experimental measurements to prove the suitability of the MIS system developed at the University of South Wales for controlled biomass measurements. Methods: The paper reports experimental measurements conducted on saline solutions and yeast suspensions at different concentrations to test the detection performance of the MIS system. The commercial electromagnetic simulation software CST was used to simulate the measurement outcomes with saline solutions and compare them with those of the actual measurements. We adopted two different ways for yeast suspension preparation to assess the system’s sensitivity and accuracy. Results: For saline solutions, the simulation results agree well with the measurement results, and the MIS system was able to distinguish saline solutions at different concentrations even in the small range of 0–1.6 g/L. For yeast suspensions, regardless of the preparation method, the MIS system can reliably distinguish yeast suspensions with lower concentrations 0–20 g/L. The conductivity spectrum of yeast suspensions present excellent separability between different concentrations and dielectric dispersion property at concentrations higher than 100 g/L. Conclusions: The South Wales MIS system can achieve controlled yeast measurements with high sensitivity and stability, and it shows promising potential applications, with further development, for cell biology research where contactless monitoring of cellular density is of relevance.