• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.7
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• pp.129-136
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• 2019

In this study, the magnetic flux leakage technique was applied to diagnose steel plate damage, imaging technique was applied through those signals. Steel plate specimens with different thicknesses were prepared for the imaging the magnetic flux leakage signal, and 6 different depths of damage were artificially processed at the same locations on each specimen. The sensor head consist hall sensor and magnetization yoke was fabricated to magnetize the steel plate specimen and measure the magnetic flux leakage signal. In order to remove the noise and increase the resolution of the image in the signal collected from the hall sensor, various of signal processing was performed. P-P value was analyzed for each channel to analyze the magnetic flux leakage signals measured from each damaged part. Based on the above processed signals and analysis, it was converted into heatmap image. Through this, it was possible to identify the damage on the steel plate at glance by imaging magnetic flux leakage signal.

• 제어로봇시스템학회:학술대회논문집
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• 1989.10a
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• pp.1053-1058
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• 1989

This paper presents the preliminary studies on measurements of dynamic torque in the rotating shaft by utilizing the magnetic lattice. The intensity of torque can be detected as the phase differences between two magnetic sinusoidal signals recorded on magnetic tapes wound on the shaft. This research describes, from the data concerning with phase differences including noise, a method of signal processing to estimate the true value of the torque.

• Journal of Magnetics
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• v.13 no.2
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• pp.70-75
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• 2008

In this study, a MOKE (Magneto-optical Kerr effect) measurement method for magnetic nanostructures is proposed. Theoretically, the MOKE signal enhancement can be predicted and confirmed when an anti-reflection coated substrate is used. Since MOKE is a ratio of reflectivity and the difference between the reflectivities for two magnetic states, when the reflectivity of the substrate part is reduced by employing an anti-reflection coated substrate, MOKE signal enhancement can be achieved. The enhancement is confirmed by simple numerical MOKE calculations. When the reflectivity of an anti-reflection coated substrate is 0.7%, the calculated MOKE signal is about 79% of its bulk values for the 100-nm wide Fe nanowire with a 1500-nm radius laser beam. It was found that, for various numerical calculations, a larger MOKE signal is obtained relative to a smaller substrate reflectivity.

• Investigative Magnetic Resonance Imaging
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• v.19 no.3
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• pp.200-204
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• 2015

Image findings of hepatic lymphoma have been reported as variable, ranging from single or multiple small nodules to diffuse infiltrative patterns. On MRI, most hepatic lymphomas show T1 low signal intensity, T2 high signal intensity. Dynamic imaging reveals a hypointense appearance in the arterial phase, followed by delayed enhancement in the portal venous and transitional phase. In the hepatobiliary phase using a hepatocyte-specific contrast agent (which have recently aided in increasing the access to the focal liver lesions), hepatic lymphoma is known to exhibit low signal intensity. We report a case of hepatic lymphoma, which shows iso-signal intensity on hepatobiliary phase, using gadoxetic acid (Gd-EOB-DTPA).

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.05a
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• pp.402-403
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• 2014

Micro-magnetic detection system is used to detect small particles in an automatic transmission valve body, which signal noise and time-delay may occurs in process of signal transmitting and filtering. In this paper, we present the design and implement of a micro-magnetic detection system based on wireless sensor networks. Micro-magnetic detection system consists of five modules which are magnetic sensor detector, signal processing unit, wireless sensor networks, system control unit and system monitoring unit. The experimental results show that signal noise and time-delay decreased.

• Journal of Magnetics
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• v.21 no.3
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• pp.330-339
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• 2016

A magnetic field sensing system with a single primary sensor and multiple reference sensors deployed locally and orthogonally, was proposed for downlink signal reception and interference cancelling for Through-the-Earth Communication (TEC). This paper mathematically analyzes a design optimization process for a search coil magnetometer (SCM), and applies that process to minimize the bandwidth of the primary SCM for TEC signal reception and the volume of reference SCMs for multiple distributions. The primary SCM achieves a 3-dB bandwidth of 7 Hz, a sensitivity threshold of 120 fT/${\surd}$Hz, and a volume of $2.32{\times}10^{-4}m^3$. The entire sensing system volume is as small as $10^{-2}m^3$. Experiments with interference from industrial frequency harmonics demonstrated an average of 36 dB and 18 dB improvements in signal-to-interference ratio and signal-to-interference plus noise ratio, respectively, using multichannel recursive-least-squares algorithm. Thus, the proposed sensing system can reduce the interference effectively and allows reliable downlink signal reception.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.6
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• pp.1146-1151
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• 2011

There are two methods for train control in information transmission by using track circuit system and installing wayside transmitter. Information signal is transmitted to the on-board antenna by using rails. Continuous information about train intervals, speed and route is received by on-board antenna in AF track circuit system. The information signal is included with carrier wave and received by magnetic coupling in the on-board antenna. Therefore, it is important to define standard current level in the AF track circuit system. When current flowed to rails is low, magnetic sensors are not operated by decreasing magnetic field intensity. Hence, SNR is decreased because electric field intensity is decreased. When the SNR is decreased, there is the serious influence of noise upon demodulation. So, the frequency of information signal is not extracted in frequency response. Thus, it is possible to happen to train accident and delay as the information signal is not analyzed in the on-board antenna. In this paper, standard energy density is calculated by using Parseval's theory in UM71c track circuit. Hence, detection time of information signal is presented.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.2
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• pp.32-40
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• 1994

In this study by using EMAT(electro magnetic acoustic transducer)the artificial slit is installed on 12B-SUS pipe test piece. By making 4 cycle SH-burst (EMA) incidence to 45 .deg. angle, the signal data of pulse, received from EMAT are translated into digital-signal-processing- method SSP(Split Spectrum Processing) and Deconvolution method. The main conclusions obtained are as follows; (1) the signal data received from EMAT are translated with digital signal proc- essing of SSP-method and Deconvolution-method and this method shows exellent results more than Ultrasonic testing method does; (2) noise can well be removed by SSP with signal data, and resolution and S/N ratio are advanced; (3) when used with Ultrasonic wave general stainless steel has proporties of multiscattering and reflection phenomena, but resolution is progressed by using Deconvolution method;and (4) as addition-averaging-processing mumber is increasing, the resolution and S/N ratio are improved and the satisfactory signal is obtained.

• Journal of Preventive Medicine and Public Health
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• v.31 no.4 s.63
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• pp.644-665
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• 1998

This study was conducted to evaluate the health hazards and to develop early diagnostic methods of the manganism in experienced welders and to know the meaning of signal intensities on the brain Magnetic Resonance images. It was carried out from December 1996 to february 1997 with 277 male welders, the duration of welding was at least 5 years or more. The study was consisted of a questionnaire, physical examination and measurements of blood & urine manganese concentrations. Brain Magnetic Resonance imaging was done on 19 study subjects by random sampling. As the duration of welding increases, the positive rates of clinical symptoms, neurological examinations and blood manganese concentrations were also increased. However, physical examinations and urine manganese concentrations were not statistically significant with the duration of welding. Authors couldn't observe any Parkinsonism-like diseases. There were statistically significant correlations between duration of welding and blood manganese concentration(r=0.16, p<0.01). There were not statistically significant correlations between duration of welding and urine manganese concentrations (r=0.06). There were statistically significant correlations between blood & urine manganese concentration(r=0.34, p<0.01). By viewing brain Magnetic Resonance images, 13 welders(68.4 %) among 19 welders were found to have signal intensities. The positive rates of clinical symptoms, physical examinations, neurological examinations and blood & urine manganese concentrations were not statistically different between those with signal intensities and those without signal intensities. We would like to suggest that some non-specific clinical symptoms and neurological signs are correlated with the duration of welding but any Parkinsonism-like diseases had not been observed with these welders. Next we suggest that the high signal intensities on TlWI of brain Magnetic Resonance images are not the sign of manganese intoxication but the sign of manganese deposition.

• Investigative Magnetic Resonance Imaging
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• v.25 no.2
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• pp.101-108
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• 2021

Purpose: To identify characteristic magnetic resonance imaging (MRI) features to differentiate between Krabbe disease and metachromatic leukodystrophy (MLD) in young children. Materials and Methods: We collected all confirmed cases of Krabbe disease and MLD between October 2004 and September 2020 at Seoul National University Children's Hospital. Patients with initial MRI available were included. Their initial MRIs were retrospectively reviewed for the following: 1) presence of white matter signal abnormality involving the periventricular and deep white matter, subcortical white matter, internal capsule, brainstem, and cerebellum; 2) presence of volume decrease and signal alteration in the corpus callosum and thalamus; 3) presence of the tigroid sign; 4) presence of optic nerve hypertrophy; and 5) presence of enhancement or diffusion restriction. Results: Eleven children with Krabbe disease and 12 children with MLD were included in this study. There was no significant difference in age or symptoms at onset. Periventricular and deep white matter signal alterations sparing the subcortical white matter were present in almost all patients of the two groups. More patients with Krabbe disease had T2 hyperintensities in the internal capsule and brainstem than patients with MLDs. In contrast, more patients with MLD had T2 hyperintensities in the splenium and genu of the corpus callosum. No patient with Krabbe disease showed T2 hyperintensity in the corpus callosal genu. A decrease in volume in the corpus callosum and thalamus was more frequently observed in patients with Krabbe disease than in those with MLD. Other MRI findings including the tigroid sign and optic nerve hypertrophy were not significantly different between the two groups. Conclusion: Signal abnormalities in the internal capsule and brainstem, decreased thalamic volume, decreased splenial volume accompanied by signal changes, and absence of signal changes in the callosal genu portion were MRI findings suggestive of Krabbe disease rather than MLD based on initial MRI. Other MRI findings such as the tigroid sign could not help differentiate between these two diseases.