• Journal of the Korean Magnetics Society
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• v.6 no.4
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• pp.264-271
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• 1996

A magnetically shielded room has been constructed for biomagnetic applications. The room has internal dimensions of $2\;m(length){\times}2\;m(width){\times}2.5\;m(height)$ and it consists of high permeability Mumetal and high conductivity alummum, utilizing ferromagnetic shielding and eddy current shielding. The de shielding factor around the center of the room is above 60 dB, and the ac shielding factors at 1 and 10 Hz are larger than 60 and 80 dB, respectively. The internal magnetic field noise at 1 Hz is $500\;fT/{\sqrt}Hz$ and at 10 Hz is $100\;fT/{\sqrt}Hz$, and the field gradient noise at 1 Hz is below $7\;fT/cm{\sqrt}Hz$. Successful measurements of cardiomagnetic fields usmg SQUID magnetometer and neuromagnetic fields using SQUID gradiometer have been done.

• Journal of the Korean Magnetics Society
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• v.23 no.3
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• pp.83-88
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• 2013

The soft magnetic Fe-Si-Cr flakes with the thickness of about 1 ${\mu}m$ were annealed at 500 and $700^{\circ}C$ for 1 h, and the composite sheets for electromagnetic wave noise absorber available for quasi-microwave band were fabricated by using these annealed flakes and polymer. Further the power loss characteristics of the composite sheets was investigated to clarify the annealing effect on electromagnetic wave absorption properties. The power loss decreased in the frequency range of several GHz when the annealed flakes were used as compared to the sheet using the as-milled FeSiCr alloy flakes. Moreover the sheets using annealed flakes exhibited lower value of real and imaginary part of complex permeability. These inferior electromagnetic wave absorption properties of the composite sheets using annealed alloy flakes were considered to be obtained by the enhanced eddy current effect upon annealing-induced recovery of microstructure and resulted low complex permeability.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.1
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• pp.9-15
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• 2008

A new ECT probe to separate the ECT signal distortion due to PVC (permeability variation clusters) and ordinary defects created in SG tubes has been developed. The hystersis loops of PVC which are extracted from retired SG (steam generator) tubes of Kori-1 NNP were measured. The tensile tests were performed to identify the mechanism of PVC creation. The conditions detecting the PVC created in 56 tubes were investigated using computer simulation, and the signal processing circuits were inserted in the probe for the digital signal transmission. The new Probe can measure and separate the PVC signal which is created in the SG tubes, and also measures the defects in Ni-sleeving part of SG tubes. furthermore the new ECT probe can measure the defects as fast as bobbin probe, and enhance the testing speed as well as reliability of the defect detection of SG tubes.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.3
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• pp.325-330
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• 2016

Sea level is upward trend since the end of 19th century, it is accelerating after 20th century. Because sea level height has regional differences, we concerned sea level change in Korean Peninsula. We used Topex/Poseidon, Jason-1 and Jason-2 satellite altimetry data which has $1/4^{\circ}$ resolution. From 1993 to 2013, for 21 years, monthly mean sea level anomaly was negative between January and April, positive between March and October. Bohai Bay in China, affected the continental climate, showed big sea level changes. Mean sea level data showed remarkably affecting the continental climate in Bohai Bay in China, the Kuroshio Current and eddy affects the sea level change.

• Journal of Mechanical Science and Technology
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• v.15 no.3
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• pp.291-299
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• 2001

Recently, severe wear on the shutdown rod cladding of Ulchin Nuclear Power Plant #1, #2 were observed by the Eddy Current Test(E.C.T.). In particular, the wear at the sixth card location was up to 75%. The test results indicated that the Flow Induced Vibration(F.I.V.) might be the cause of the fretting wear resulting from the contact between Rod Cluster Control Assemblies(RCCAs) and their spacing cards(guide plates) arranged in the guide tube. From reviewing RCCAs fretting wear repots and analyzing the general characteristics of F.I.V. mechanism in the reactor, geometric layout and flow conditions around the control rod, it is concluded that the turbulence excitation is the most probable vibration mechanism of RCCA. To identify the governing mechanism of RCCA vibration, an experiment was performed for a representative rod position in which the most serious fretting wear experienced among the six rod positions. The experimental rig was designed and set up to satisfy the governing nondimensional numbers which are Reynolds number and mass damping parameter. The vibration amplitude measurement by the non-contact laser displacement sensor showed good agreements in the frequency and the maximum wearing(vibration) location with Ulchin E.C.T. results and Framatome report, respectively. The sudden increase in the vibration amplitude was sensed around the 6th guide plate with mass flow rate variation. Comparing the similitude rod behaviour with the idealized response of a cylinder in flow induced vibration, it was found that he dominant mechanism of vibration was transferred from turbulence excitation to periodic shedding at the mass flow ate 90ι/min. Also the critical velocity of the vibration in RCCAs was determined and the vibration can be prevented by reducing the bypass flow rate below the critical velocity.

• Ocean and Polar Research
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• v.31 no.1
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• pp.11-29
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• 2009

Variability of sea surface temperature (SST) in the Japan/East Sea (JES) was studied using complex empirical orthogonal function (CEOF) analysis. Two daily data sets were analyzed: (1) New Generation 0.05o-gridded SST from Tohoku University, Japan (July 2002-July 2006), and (2) 0.25o-gridded SST from the Japan Meteorological Agency (October 1993-November 2006). Linkages with wind stress curl were revealed using 6-h 1o-gridded surface zonal and meridional winds from ancillary data of the Sea- WiFS Project, a special National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) product (1998-2005). SST anomalies (SSTA) were obtained by removing the seasonal signal, estimated as the leading mode of the CEOF decomposition of the original SST. Leading CEOF modes of residual SSTA obtained from both data sets were consistent with each other and were characterized by annual, semiannual, and quasi-biennial time scales estimated with 95% statistical significance. The Semiannual Mode lagged 2 months behind the increased occurrence of the anticyclonic (AC) wind stress curl over the JES. Links to dynamic processes were investigated by numerical simulations using an oceanic model. The suggested dynamic forcings of SSTA are the inflow of subtropical water into the JES through the Korea Strait, divergence in the surface layer induced by Ekman suction, meridional shifts of the Subarctic Front in the western JES, AC eddy formation, and wind-driven strengthening/weakening of large-scale currents. Events of west-east SSTA movement were identified in July-September. The SSTA moved from the northeastern JES towards the continental coast along the path of the westward branch of the Tsushima Current at a speed consistent with the advective scale.

• Resources Recycling
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• v.21 no.3
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• pp.48-55
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• 2012

Recently, the recycling with environmentally friendly method has been an issue for various fields. An effective removal method of coating layers from coated copper wires is one critical factor for recycling copper wire. We have adopted a high frequency heating routine for removing the coating layers on the coated copper wires, and attempted to find optimum conditions. The experimental results show that the copper wires should be maintained at or above $950^{\circ}C$ for rapid removal of the polyester. The simulation and experimental results are discussed with respect to the microstrucrual evolution during heating of the copper wires.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.55 no.2
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• pp.68-71
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• 2006

Active thermography has been used for several years in the field of remote non-destructive testing. It provides thermal images for remote detection and imaging of damages. Also, it is based on propagation and reflection of thermal waves which are launched from the surface into the inspected component by absorption of modulated radiation. For energy deposition, it use external heat sources (e.g., halogen lamp or convective heating) or internal heat generation (e.g., microwaves, eddy current, or elastic wave). Among the external heat sources, the ultrasound is generally used for energy deposition because of defect selective heating up. The heat source generating a thermal wave is provided by the defect itself due to the attenuation of amplitude modulated ultrasound. A defect causes locally enhanced losses and consequently selective heating up. Therefore amplitude modulation of the injected ultrasonic wave turns a defect into a thermal wave transmitter whose signal is detected at the surface by thermal infrared camera. This way ultrasound thermography(UT) allows for selective defect detection which enhances the probability of defect detection in the presence of complicated intact structures. In this paper the applicability of UT for fast defect detection is described. Examples are presented showing the detection of defects in PCB material. Measurements are performed on various kinds of typical defects in PCB materials (both Cu metal and non-metal epoxy). The obtained thermal image reveals area of defect in row of thick epoxy material and PCB.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.24 no.4
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• pp.150-157
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• 1988

The oceanographic condition around the set net fishing ground in Yeosu Bay was investigated by the oceanographic observation in June, July and August, 1988. Also the catch of the set net was analized by daly catch data of the three set net fishing ground from April to September, 1988. The results obtained are as follows: 1) The coastal surface water is high temperature and low salinity through the influence of land, and the off shore water and bottom water are low temperature and high salinity. 2) The eddy current and the sharp thermocline in June appeared in August at the set net fishing ground, and a good catch appeared in June and August. 3) The surface temperature and salinity at the set net fishing ground are 11$^{\circ}C$ to 27$^{\circ}C$ and 31.60$\textperthousand$ to 34.80$\textperthousand$. The surface temperature and salinity of a maximum good catch are 21$^{\circ}C$ and 33.80$\textperthousand$ to 33.99$\textperthousand$ respectively. 4) The dominant species of fish were spanish mackerel, scad, anchovy, sardine, common mackerel, hairtail, crab, yellow tail, in order of catch.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.1
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• pp.13-19
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• 2010

In this paper, we study a new estimation system for the prediction of steam generator tube defects. In the previous research works, defect size estimators were independently designed for each defect types in order to estimate the defect size. As a result, the structure of estimation system is rather complex and the estimation performance gets worse if the classification performance is degraded for some reason. This paper studies a new estimation system that does not require the classification of defect types. Although the previous works are expected to achieve much better estimation performance than the proposed system since it uses the estimator specialized in each defect, the performance difference is not so large. Therefore, it is expected that the proposed estimator can be effectively used for the case where the defect type classification is imperfect.