The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
T. Matsumura - One of the best experts on this subject based on the ideXlab platform.
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hysteretic dependence of Magnetic Flux Density on primary ac current in flat type inductive fault current limiter with ybco thin film discs
Journal of Physics: Conference Series, 2014Co-Authors: Masayuki Harada, Yasunobu Yokomizu, T. MatsumuraAbstract:This paper focuses on a flat-type inductive superconducting FCL (FIS-FCL) consisting of a pancake coil and a YBCO thin layer disc. AC current injection experiments and Magnetic field analysis were carried out for two kinds of FIS-FCL, single-disc model and double-discs model. In the former, the pancake coil was putted on the YBCO disc. In the latter, the pancake coil was sandwiched with two YBCO discs. The double-discs model cancels out the Magnetic Flux Density more effectively than the single-disc model. In the double-discs model, the superconducting state period is longer than in the single-disc model. Thus, it may be concluded that the double-discs model is considered to be suitable for FIS-FCL.
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periodic behavior of Magnetic Flux Density in flat type inductive fault current limiter with ybco thin film discs during ac over current carrying period
International Conference on Electric Power Equipment – Switching Technology, 2013Co-Authors: Masayuki Harada, Yasunobu Yokomizu, Kohei Okuda, T. MatsumuraAbstract:We focus on a flat-type inductive fault current limiter (FCL), which consists of a pancake coil and superconducting thin film discs. This paper describes an experimental and computational approach for the FCL where the primary coil is sandwiched in between two YBCO thin film discs which have different critical current each other. In this experiment, the periodic behaviors of Magnetic Flux Density arising in the FCL were measured by pick-up coil while AC over-current injected to the primary coil of the FCL. It was found out that the Magnetic Flux Density changes hysteretic way for injected current and the YBCO film turns into Flux-flow resistive state from superconducting state at the different time. Similar result has been confirmed by the calculation using a finite element method.
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observation of transient behavior of Magnetic Flux in inductive type fault current limiter with ybco thin film disc
Physics Procedia, 2012Co-Authors: Kosuke Higuchi, Yin Guan, Yasunobu Yokomizu, T. MatsumuraAbstract:Abstract Recently, the installation of fault current limiters (FCLs) in power systems is expected for controlling large short circuit currents. In this study, we focus on inductive-type FCLs having a YBCO superconducting thin film disc that is fabricated by metal-organic deposition. AC currents were injected into the FCL so that the periodic transient behavior of the apparent Magnetic Flux Density around the FCL could be measured by using a pick-up coil. The Magnetic Flux Density exhibited hysteresis when AC current was injected into the FCL. The transition between the conducting states in the YBCO layer was explained by the hysteresis relationship between the Magnetic Flux Density and current.
Edson Costa Santos - One of the best experts on this subject based on the ideXlab platform.
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effect of crack opening on distribution of Magnetic Flux Density around fatigue cracks
Advanced Materials Research, 2013Co-Authors: Hirotaka Tanabe, Tohru Takamatsu, Katsuyuki Kida, Yui Izumi, Jun Shimada, Edson Costa SantosAbstract:In order to identify the mechanisms of changes in the Magnetic Flux Density distribution around fatigue cracks that occur during crack propagation, JIS SCM440 specimens were fatigue tested, and the relation between crack morphology and Magnetic Flux Density distribution was investigated. Two features were observed: a high intensity area around the crack tip, and a low intensity area around the crack root. The low intensity area grew larger for wide open cracks and disappeared when the crack was closed by external force. It was hence found that the Magnetic Flux Density distribution is strongly affected by the crack opening.
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observation of Magnetic Flux Density around fatigue crack tips in bearing steel using an shpm with a three dimensional small gap probe
International Journal of Fatigue, 2012Co-Authors: Katsuyuki Kida, Edson Costa Santos, Takashi Honda, Hitonobu Koike, Justyna RozwadowskaAbstract:Abstract Fatigue failure of steel occurs when cracks form in a component and continue to grow to a size large enough to cause failure. In order to understand the strength of a steel component it is important to locate these cracks. We developed a scanning Hall probe microscope (SHPM) equipped with a GaAs film sensor and observed fatigue cracks at room temperature in air while they were growing. In this paper we report two important findings regarding the Magnetic field properties: a decrease in the Magnetic Flux Density at the early fatigue stage and the polarization of the Magnetic field ahead of the fatigue cracks occurring during crack growth.
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the influence of stress ratio on changes in Magnetic Flux Density around fatigue crack tips of carbon tool steel
Applied Mechanics and Materials, 2011Co-Authors: Takashi Honda, Katsuyuki Kida, Edson Costa Santos, Hitonobu Koike, Justyna Rozwadowska, Megumi Uryu, K Houri, Hirotaka TanabeAbstract:Fatigue failure of steel occurs when cracks form in a component and continue to grow to a size large enough to cause fracture. In order to understand the strength of a steel component, it is important to locate these cracks. We developed a scanning Hall probe microscope (SHPM), equipped with GaAs film sensors to observe fatigue cracks at room temperature in air while they were growing. In our previous works [1,2], the correlation between crack growth and Magnetic field in high carbon tool steels (JIS SKS93 and JIS SUJ2) were determined. We also reported the sensitivity of the SHPM equipped with a three-dimensional line-probe that was developed to decrease the sensor gaps. By using the line-probe sensor we succeeded to measure the Magnetic Flux Density distributions in very close proximity to the specimen’s surface. However, in order to further understand the relation between Magnetic Flux Density and crack growth, other materials, microstructures and fatigue test conditions should be evaluated. In the present work, we focus on the effect of stress ratios on the changes of the Magnetic Flux Density in annealed carbon tool steel.
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observation of Magnetic Flux Density distribution around fatigue crack and application to non destructive evaluation of stress intensity factor
Procedia Engineering, 2011Co-Authors: Hirotaka Tanabe, Tohru Takamatsu, N Itoh, Katsuyuki Kida, Edson Costa SantosAbstract:In order to develop a new technique to evaluate fatigue damage non-destructively based on Magnetic information, changes in the Magnetic Flux Density around fatigue cracks during their propagation process were observed. The correlation between the change behavior of the distribution of the Magnetic Flux Density and the stress intensity factor was examined. Four-point bending fatigue tests were carried out under six different conditions on JIS SCM440 steel specimens with an artificial slit. Magnetic Flux Density distributions near the fatigue crack tips were observed using a newly developed apparatus consisting of an MI sensor (Magneto-Impedance sensor) and an x-y stage. It was found that the distribution of Magnetic Flux Density moved with crack propagation. A strong correlation between the movements of the Magnetic Flux Density distribution and stress intensity factor was recognized, regardless of the loading conditions, maximum load or stress ratio. The results suggest that non-destructive evaluation of the stress intensity factor of fatigue cracks would be possible using this relationship. © 2011 Published by Elsevier Ltd. Selection and peer-review under responsibility of ICM11
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observation of Magnetic Flux Density distribution around fatigue crack and application to non destructive evaluation of stress intensity factor
Procedia Engineering, 2011Co-Authors: Hirotaka Tanabe, Tohru Takamatsu, N Itoh, Katsuyuki Kida, Edson Costa SantosAbstract:In order to develop a new technique to evaluate fatigue damage non-destructively based on Magnetic information, changes in the Magnetic Flux Density around fatigue cracks during their propagation process were observed. The correlation between the change behavior of the distribution of the Magnetic Flux Density and the stress intensity factor was examined. Four-point bending fatigue tests were carried out under six different conditions on JIS SCM440 steel specimens with an artificial slit. Magnetic Flux Density distributions near the fatigue crack tips were observed using a newly developed apparatus consisting of an MI sensor (Magneto-Impedance sensor) and an x-y stage. It was found that the distribution of Magnetic Flux Density moved with crack propagation. A strong correlation between the movements of the Magnetic Flux Density distribution and stress intensity factor was recognized, regardless of the loading conditions, maximum load or stress ratio. The results suggest that non-destructive evaluation of the stress intensity factor of fatigue cracks would be possible using this relationship. © 2011 Published by Elsevier Ltd. Selection and peer-review under responsibility of ICM11
Robert D. Lorenz - One of the best experts on this subject based on the ideXlab platform.
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achieving low Magnetic Flux Density and low electric field intensity for a loosely coupled inductive wireless power transfer system
IEEE Transactions on Industry Applications, 2018Co-Authors: Guangqi Zhu, Robert D. LorenzAbstract:In most loosely coupled inductive wireless power transfer systems, the air-gap Magnetic Flux Density between coils is still far above the safety limit, which is a potential threat to human beings and animals. In addition, less attention is paid to the air-gap electric field intensity, which increases significantly as the operating frequency and the number of turns increase. In this paper, a multi-kW loosely coupled inductive wireless power transfer system general design methodology that can inherently achieve low air-gap center plane Magnetic Flux Density and electric field intensity is proposed. The coil-to-coil efficiency, Magnetic and electric field distributions of different winding configurations are compared. The effects of coil radius, number of turns, interturn distance, transfer distance, and operating frequency on transfer efficiency, and Magnetic and electric field distributions are investigated. The proposed methodology is evaluated with a 3 kW, 30 cm distance wireless power transfer design example by finite element analysis (FEA) and experiment tests.
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Achieving low Magnetic Flux Density and low electric field intensity for an inductive wireless power transfer system
2017 IEEE Energy Conversion Congress and Exposition (ECCE), 2017Co-Authors: Guangqi Zhu, Robert D. LorenzAbstract:In most loosely coupled inductive wireless power transfer systems, the air-gap Magnetic Flux Density between coils is still far above safety limit, which is a potential threat to human beings and animals. In addition, less attention is paid to the air-gap electric field intensity, which increases significantly as the operating frequency increases. In this paper, a multi-kW inductive wireless power transfer system general design methodology that can inherently achieve low air-gap center plane Magnetic Flux Density and electric field intensity is proposed. The effects of coil radius, number of turns, inter-turn distance and operating frequency are investigated. Proposed methodology is evaluated with a 3 kW, 30 cm distance wireless power transfer design example by FEA and experiment tests. Power scaling law within air-gap center plane Magnetic field and electric field safety limits is developed.
Ohin Kwon - One of the best experts on this subject based on the ideXlab platform.
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noise analysis in fast Magnetic resonance electrical impedance tomography mreit based on spoiled multi gradient echo spmge pulse sequence
Physics in Medicine and Biology, 2014Co-Authors: Woo Chul Jeong, Ohin Kwon, Ji Eun Kim, Saurav Z K Sajib, Hyung Joong Kim, Eung Je WooAbstract:Magnetic resonance electrical impedance tomography (MREIT) is a promising non-invasive method to visualize a static cross-sectional conductivity and/or current Density image by injecting low frequency currents. MREIT measures one component of the Magnetic Flux Density caused by the injected current using a Magnetic resonance (MR) scanner. For practical in vivo implementations of MREIT, especially for soft biological tissues where the MR signal rapidly decays, it is crucial to develop a technique for optimizing the Magnetic Flux Density signal by the injected current while maintaining spatial-resolution and contrast. We design an MREIT pulse sequence by applying a spoiled multi-gradient-echo pulse sequence (SPMGE) to the injected current nonlinear encoding (ICNE), which fully injects the current at the end of the read-out gradient. The applied ICNE-SPMGE pulse sequence maximizes the duration of injected current almost up to a repetition time by measuring multiple Magnetic Flux Density data. We analyze the noise level of measured Magnetic Flux Density with respect to the pulse width of injection current and relaxation time. In due consideration of the ICNE-SPMGE pulse sequence, using a reference information of values in a local region of interest by a short pre-scan data, we predict the noise level of Magnetic Flux Density to be measured for arbitrary repetition time TR. Results from phantom experiment demonstrate that the proposed method can predict the noise level of Magnetic Flux Density for an appropriate TR = 40 ms using a reference scan for TR = 75 ms. The predicted noise level was compared with the noise level of directly measured Magnetic Flux Density data.
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optimization of multiply acquired Magnetic Flux Density b z using icne multiecho train in mreit
Physics in Medicine and Biology, 2010Co-Authors: Hyun Soo Nam, Ohin KwonAbstract:The aim of Magnetic resonance electrical impedance tomography (MREIT) is to visualize the electrical properties, conductivity or current Density of an object by injection of current. Recently, the prolonged data acquisition time when using the injected current nonlinear encoding (ICNE) method has been advantageous for measurement of Magnetic Flux Density data, Bz, for MREIT in the signal-to-noise ratio (SNR). However, the ICNE method results in undesirable side artifacts, such as blurring, chemical shift and phase artifacts, due to the long data acquisition under an inhomogeneous static field. In this paper, we apply the ICNE method to a gradient and spin echo (GRASE) multi-echo train pulse sequence in order to provide the multiple k-space lines during a single RF pulse period. We analyze the SNR of the measured multiple B(z) data using the proposed ICNE-Multiecho MR pulse sequence. By determining a weighting factor for B(z) data in each of the echoes, an optimized inversion formula for the Magnetic Flux Density data is proposed for the ICNE-Multiecho MR sequence. Using the ICNE-Multiecho method, the quality of the measured Magnetic Flux Density is considerably increased by the injection of a long current through the echo train length and by optimization of the voxel-by-voxel noise level of the B(z) value. Agarose-gel phantom experiments have demonstrated fewer artifacts and a better SNR using the ICNE-Multiecho method. Experimenting with the brain of an anesthetized dog, we collected valuable echoes by taking into account the noise level of each of the echoes and determined B(z) data by determining optimized weighting factors for the multiply acquired Magnetic Flux Density data.
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noise analysis and mr pulse sequence optimization in mreit using an injected current nonlinear encoding icne method
Physiological Measurement, 2007Co-Authors: Ohin Kwon, Chunjae ParkAbstract:Magnetic resonance current Density imaging (MRCDI) and Magnetic resonance electrical impedance tomography (MREIT) visualize an internal distribution of current Density and/or conductivity by injecting current into an electrically conductive object such as the human body using an MRI scanner. MREIT measures the induced Magnetic Flux Density which appears in the phase part of the acquired MR image data. Recently, the injected current nonlinear encoding (ICNE) method in MREIT extended the duration of the current injection until the end of a reading gradient to maximize the signal intensity of the Magnetic Flux Density. In this paper, we investigate the signal-to-noise ratio (SNR) of the Magnetic Flux Density measured by the ICNE method in the presence of a zero-mean Gaussian random noise in measured k-space MR data. Based on the analysis of the noise standard deviation of the Magnetic Flux Density, we determine an optimal combination between the current injection pulse width Tc and data acquisition time Ts which minimize the noise level of the measured Magnetic Flux Density for a given echo time TE. On one hand, theoretically, the proposed ICNE MR pulse sequence using the optimal data acquisition time Ts* reduces the noise level of the measured Magnetic Flux Density by about 42.3% compared with the optimal data acquisition time of the conventional MREIT pulse sequence. On the other hand, practically, the prolonged Ts* may result in undesirable artifacts including blurring, chemical shift and phase error along the phase encoding direction. We observe that the noise level is a function of the data acquisition time Ts and the rate of change in the noise level is slow near Ts = Ts*. Numerical phantom experiments show that a compromised Ts between the ordinary data acquisition time and the optimal Ts* reduces a relatively large amount of undesirable artifacts and almost maintains the optimized noise level of the measured Magnetic Flux Density.
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analysis of recoverable current from one component of Magnetic Flux Density in mreit and mrcdi
Physics in Medicine and Biology, 2007Co-Authors: Chunjae Park, Byung Il Lee, Ohin KwonAbstract:Magnetic resonance current Density imaging (MRCDI) provides a current Density image by measuring the induced Magnetic Flux Density within the subject with a Magnetic resonance imaging (MRI) scanner. Magnetic resonance electrical impedance tomography (MREIT) has been focused on extracting some useful information of the current Density and conductivity distribution in the subject ? using measured Bz, one component of the Magnetic Flux Density B. In this paper, we analyze the map from current Density vector field J to one component of Magnetic Flux Density Bz without any assumption on the conductivity. The map provides an orthogonal decomposition J = JP + JN of the current J where JN belongs to the null space of the map . We explicitly describe the projected current Density JP from measured Bz. Based on the decomposition, we prove that Bz data due to one injection current guarantee a unique determination of the isotropic conductivity under assumptions that the current is two-dimensional and the conductivity value on the surface is known. For a two-dimensional dominating current case, the projected current Density JP provides a good approximation of the true current J without accumulating noise effects. Numerical simulations show that JP from measured Bz is quite similar to the target J. Biological tissue phantom experiments compare JP with the reconstructed J via the reconstructed isotropic conductivity using the harmonic Bz algorithm.
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measurement of induced Magnetic Flux Density using injection current nonlinear encoding icne in mreit
Physiological Measurement, 2007Co-Authors: Chunjae Park, Ohin Kwon, Byung Il Lee, Eung Je WooAbstract:Magnetic resonance electrical impedance tomography (MREIT) measures induced Magnetic Flux densities subject to externally injected currents in order to visualize conductivity distributions inside an electrically conducting object. Injection currents induce Magnetic Flux densities that appear in phase parts of acquired MR image data. In the conventional current injection method, we inject currents during the time segment between the end of the first RF pulse and the beginning of the reading gradient in order to ensure the gradient linearity. Noting that longer current injections can accumulate more phase changes, we propose a new pulse sequence called injection current nonlinear encoding (ICNE) where the duration of the injection current pulse is extended until the end of the reading gradient. Since the current injection during the reading gradient disturbs the gradient linearity, we first analyze the MR signal produced by the ICNE pulse sequence and suggest a novel algorithm to extract the induced Magnetic Flux Density from the acquired MR signal. Numerical simulations and phantom experiments show that the new method is clearly advantageous in terms of the reduced noise level in measured Magnetic Flux Density data. The amount of noise reduction depends on the choice of the data acquisition time and it was about 24% when we used a prolonged data acquisition time of 10.8 ms. The ICNE method will enhance the clinical applicability of the MREIT technique when it is combined with an appropriate phase artefact minimization method.
Tetsuya Osaka - One of the best experts on this subject based on the ideXlab platform.
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preparation of high Magnetic Flux Density conifeb film by electroless deposition for application to Magnetic recording devices
Electrochimica Acta, 2007Co-Authors: Masahiro Yoshino, Yuta Kikuchi, Atsushi Sugiyama, Tetsuya OsakaAbstract:Abstract A CoNiFeB soft Magnetic thin film with high saturation Magnetic Flux Density ( B s ) for use as a Magnetic recording head core material or as a soft Magnetic underlayer of a double perpendicular Magnetic recording medium was prepared by electroless deposition. When the CoNiFeB alloy thin film was deposited on a evaporated Cu (100 nm thick)/glass substrate, the saturated Magnetic Flux Density was found to increase up to 2.0 T by increasing the concentration of FeSO 4 . The coercivity ( H c ) was found to decrease to 6 Oe while the saturated Magnetic Flux Density was maintained higher than 1.8 T by optimizing the concentrations of tartaric acid and citric acid in the electroless plating solution. An X-ray diffraction (XRD) study showed that the intensity of the assigned peak in the bcc (1 1 0) of CoNiFeB film decreased as the concentration of tartaric acid was decreased. Moreover, the coercivity of the CoNiFeB film formed on a NiFe substrate exhibits lower coercivity than that formed on a Cu substrate.
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electrochemical preparation of soft Magnetic conifes film with high saturation Magnetic Flux Density and high resistivity
Journal of The Electrochemical Society, 1997Co-Authors: Madoka Takai, Katsuyoshi Hayashi, M Aoyagi, Tetsuya OsakaAbstract:A soft Magnetic CoNiFeS film as a write head core material for the next generation was prepared by electrodeposition. In this system, thiourea was used as an additive in the CoNiFe ternary alloy plating bath. The most suitable Magnetic properties were obtained at the film composition of (Co 73 Ni 12 Fe 15 ) 99.1 S 0.9 [atomic percent (a/o)] with a high saturation Magnetic Flux Density (B s ) of 1.7 T, a high resistivity (p) of 51 μΩ cm, and a low saturation magnetostriction (λ s ) of 4.4 x 10 -6 . The film consisted of fine minute crystal grains 5 to 10 nm in diameter. The S content of ca. 0.9 a/o is believed to be responsible for the formation of small crystal grains with low coercivity and high resistivity.
