• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.28 no.3
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• pp.252-261
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• 1992

The accuracy of the position fixing with telemetry techniques depends in general on the accuracy of the location of the receiving point(hydrophone). To increase the accuracy of the coordinates of four hydrophones suspended down at both sides of the vessel anchored, each hydrophone motion is compensated using a depth pinger mounted on the seabed of 30m depth. The pinger location is calculated with a hyperbolic method. Using this technique so called hydrophone coordinates calibration, the movement of the Remotely Operated Vehicle(ROV), which has the same type of pinger mentioned above could be tracked down more accurately. Under the maximum variation ranges of a hydrophone of 5.2m in athwartships, 3.2m in alongship, and about 0.2m/s of the moving velocity in both directions, the ROV track with calibration is more close to the reality than that without calibration Tow depth pingers of same frequency can be distinguished by the use of three factors; The pulse period, the phase and the pulse period variation allowed in acquisition of the pinger as far as its pulse period is varied in smooth.

• Journal of Astronomy and Space Sciences
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• v.36 no.1
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• pp.11-20
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• 2019

Being a torque free motion of the rotating Earth, Chandler wobble is the major component in the Earth's polar motion with amplitude about 0.05-0.2 arcsec and period about 430-435 days. Free core nutation, also called nearly diurnal free wobble, exists due to the elliptical core-mantle boundary in the Earth and takes almost the whole part of un-modelled variation of the Earth's pole in the celestial sphere beside precession and nutation. We hereby present a brief summary of their theories and report their recent features acquired from updated datasets (EOP C04 and ECMWF) by using Fourier transform, modelling, and wavelet analysis. Our new findings include (1) period-instability of free core nutation between 420 and 450 days as well as its large amplitude-variation, (2) re-determined Chandler period and its quality factor, (3) fast decrease in Chandler amplitude after 2010.

• Journal of Astronomy and Space Sciences
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• v.4 no.2
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• pp.69-80
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• 1987

A photometric solutions of T LMi were derived with the Wilson and Devinney model using the BV photoelectric light curves of Okazaki(1977) and orbital period changes are discussed from the all of the collected times a available in the literature. We obtained a variation with a period of $62.^y01$ and an amplitude of $0.^d0425$ form the (O-C) diagram. According to the physical properties of T LMi on the basis of derived photometric solution, it have a doubt the credibility of the existence of "R CMa type".ype".uot;.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.27 no.6
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• pp.733-753
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• 1994

Monthly mean sea levels from 103 tidal stations in Korea, Japan, and Russia are analyzed to study long-period sea level variations. Barometric adjustment are done for all the sea level data, using monthly air pressures at sea levels from meteorological stations near tidal stations. Seasonal variation is dominant in most of study area. It is the largest in the coasts along the Tsushima Current, and the smallest in the Russian coasts. The cross-correlations of seasonal variations are very high between the coasts along the Tsushima Current. In these marginal seas, seasonal variations seem to be related with the Tsushima Current. The phase of seasonal variations is generally getting late from south to north, and also from west to east. On the other hand, longer-period variations(longer than seasonal variation) have the largest amplitudes and the earliest phases in the coasts along the Pacific Ocean, which shows that they propagate from the Pacific Ocean. Shorter-period variations (shorter than seasonal variation) have generally lower cross correlations. Their values do not show any dictinct difference between areas, and show a common tendency that they are inversely proportional to distance. It implies that the shorter period waves are generated all over the study areas, and propagate in all the directions with faster dissipations. The trends of sea levels in the study area are generally negative in the coasts along the Pacific Ocean and positive in the other areas during the period of 1965 to 1985. By the trends, the mean volume transport between Cheju and Sasebo can be reduced by about 1 Sv during the period. The seasonal variation of volume transport obtained by sea level difference is about 2 Sv in the Korea Strait. The values are comparable to previous reports.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.37 no.1
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• pp.65-72
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• 2004

Fish catch by a set net in Hamdeuk fishing ground off Jeju Island were studied to determine seasonal variation of species composition and catch from 1998 to 2000. A total 72,022.9 kg was caught during the survey period, including Scomber japonicus and Trachurus japonicus of $76.4\%$ in the total. The other dominant species were Siganus fuscescens, Loligo chinesis, Seriola dumerili, Sepioteuthis lessoniana, Sardinops melanostictus, and Seriola lalandi accounting to $20.0\%$ of the total. The fishing period conducted by a set net in Hamdeuk fishing ground were from May to November. The catch by a set net were higher in summer than in spring and autumn and closely related with the seasonal variation of sea water temperature. The catch was higher in 1998 than In 1999 and 2000, which was related to the sea water temperature in fishing ground.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.17 no.5
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• pp.391-397
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• 1984

The seasonal and portional variation in the composition of uronic acid of alginic acid from Eckionia cava was investigated. The sample was collected from the coast of Ieechun Illkwangmyun, Yangsangun, Kyungnam, Korea, in the period of January to December in 1982. In seasonal variation of the content of alginic acid, the range of variation was larger in the frond than in the stipe, It was the highest content in between February to April, and the lowest in between August to October, and the content was more in the stipe than in the frond. The uronic acid ratio(M/G ratio) was varied seasonaly in a relationship with the variation of the alginic acid content. The maximum M/G ratio appeared in the period of December to March and minimum May to August, and the average values of the M/G ratios in the periods were 3.08, 2.64 in the frond and 2.91, 1.39 in the stipe, respectively. Additively a year mean values were 3.22 in the frond and 2.18 in the stipe.

• Korean Journal of Remote Sensing
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• v.16 no.2
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• pp.117-133
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• 2000

We studied the sea level variations at Kerguelen island in the South Indian Ocean with ARGOS data and meteorological data during about 1 year(May 1993~April 1994) through using filter, spectral analysis, coherency and phase, and found characteristics for the two oceanic signal levels(detided oceanic signal level, h$_{detided}$ and seasonal oceanic level, h$_{corr.ib}$). The forms of atmospheric pressure variations are good agreed to between ARGOS data and meteorological data in the observed periods. This Kerguelen area shows the inflow of an air temperature(gain of a radiant heat) into the sea water and the stagnation of high atmospheric pressure bands in summer, and the outflow of a sea water temperature(loss of sensible and latent heat) toward the atmosphere and the stagnation of low atmospheric pressure bands in winter. The seasonal difference of sea level between summer and winter is about 1.6cm. Both the detided oceanic signal level(h$_{detided}$) variation and the inverted barometer level(h$_{ib}$) variation have a strong correlation for T>1day period bands. The characteristics of h$_{detided}$ variation are not decided by the influence of any meteorological distributions (atmospheric pressure), but the influence of other factors(bottom water temperature) for T>2days periods bands. h$_{corr.ib}$ plays a very important role of sea level variation in the observed periods (especially T>about 180days period bands).

• Journal of Conservation Science
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• v.29 no.3
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• pp.223-229
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• 2013

It is not known in details for the A.D. period as the archaeomagnetic dating method to be fully facilitated in Korea but it has prepared for the revised shape of standard curve to trace the geomagnetic field variation, and there were cases to increase the survey on relics on the B.C. period to find out for the detailed archaeomagnetic field variation on the Bronze Age to the Early Iron Age. Furthermore, the survey cases on the relics on the Neolithic Age began to emerge a little by little archaeomagnetic field variation of the Neolithic Age through 34 pieces of the archaeomagnetic measurement data as making active advancement around mid-western region. Data is insufficient yet that it is difficult to find out the detailed trend of modification but it is estimated for approximate appearance. The archaeomagnetic field variation of the Neolithic Age made changes without breaking away from the scope of changes in the A.D. period as in the same way with the Bronze Age, and comparing to the variation of archaeomagnetic field for the Bronze Age, the magnetic inclination shifted within the scope of having almost no difference, but the declination is shown to skewed toward the east in its overall appearance. In addition, the comparison was made with the data of the Jomon Age in Japan and the archaeomagnetic measurement data of Korea has a little bit more depth for while the declination is skewed toward the east for 10 degree or more compared to those of Japan. However, in the part where the data is concentrated most intensely, the data for both countries has significant part to overlap to each other that the archaeomagnetic field variation of the Neolithic Age of Korea showed overall similar variation with certain partial changes when compared to those of Japan.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.947-950
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• 2008

This paper reports of traceable and repeatable time resolved colorimetric measurements of the luminance- and colour variation occurring during the frame refresh period of FPD's. During one frame period a number of measurements are performed, and for the dynamic artifacts a simulated smooth pursuit eye tracking algorithm is included.

• Journal of Astronomy and Space Sciences
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• v.27 no.4
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• pp.319-327
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• 2010

We examine the ionospheric F2-layer electron density variation by solar activity in middle latitude by using foF2 observed at the Kokubunji ionosonde station in Japan for the period from 1997 to 2008. The semi-annual variation of foF2 shows obviously in high solar activity (2000-2002) than low solar activity (2006-2008). It seems that variation of geomagnetic activity by solar activity influences on the semi-annual variation of the ionospheric F2-layer electron density. According to the Lomb-Scargle periodogram analysis of foF2 and Ap index, interplanetary magnetic field (IMF) Bs (IMF Bz <0) component, solar wind speed, solar wind number density and flow pressure which influence the geomagnetic activity, we examine how the geomagnetic activity affects the ionospheric F2-layer electron density variation. We find that the semi-annual variation of daily foF2, Ap index and IMF Bs appear clearly during the high solar activity. It suggests that the semi-annual variation of geomagnetic activity, caused by Russell-McPherron effect, contributes greatly to the ionospheric F2-layer semi-annual electron density variation, except dynamical effects in the thermosphere.