• Journal of Ocean Engineering and Technology
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• v.30 no.5
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• pp.389-399
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• 2016

This paper presents the explorations of hydrothermal vents located in the Marina Arc and Back Arc Basin using the deep-sea ROV Hemire. These explorations were conducted by KRISO and KIOST to demonstrate the capability of Hemire in various applications for deep-sea scientific research. The missions included the following: (1) to search the reported vents, (2) conduct visual inspections, (3) deploy/recover a sediment trap and bait traps, (4) sample sediment/water/rock, (5) measure the magnetic field at the vent site, and (6) acquire a detailed map using multi-beam sonar near the bottom. We installed three HD cameras for precise visual inspection, a high-temperature thermometer, a three-component magnetometer, and a multi-beam sonar to acquire details of the bottom contour or identify vents in the survey area. The explorations were performed in an expedition from March 23 to April 5, 2016, and the missions were successfully completed. This paper discusses the operational process, navigation, and control of Hemire, as well as the exploration results.

• Korean Journal of Remote Sensing
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• v.19 no.2
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• pp.117-133
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• 2003

A field survey and Landsat ETM+ image acquisition carried out simultaneously. Using these data, we attempted to establish relationships between tidal flat environmental factors and reflectance observed by ETM+, and to set up a new critical grain size useful for optical remote sensing. Although the grain size of 4 $\Phi$ has been conventionally used as a critical size by sedimentologists, the correlation with optical reflectance was very low. Instead, the grain size of 2 $\Phi$ showed a relatively high correlation coefficient, 0.699, with ETM+ band 4, except near tidal channels in upper tidal flat. We concluded that the grain size of 2 $\Phi$ would be better to use for a critical grain size in Gomso Bay. The grain size also correlated well with moisture content having a correlation coefficient of -0.811 when the 2 $\Phi$ criterion was used. The results of factor analysis showed moisture content was more important parameter than topographic relief, and they were different from German tidal flats in which topographic relief was the prior factor This can be explained by finer grain composition of the Gomso bay tidal flat. In short, moisture content and topography as well as grain size should be considered in tidal flat remote sensing.

• Korean Journal of Remote Sensing
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• v.16 no.3
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• pp.211-220
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• 2000

Even though recurring eddies at the terminal end of the East Korean Warm Current have been identified in the thermal infrared imagery from the NOAA/AVHRR sensor and ocean color data from Orbview-2/SeaWiFS sensor, it is difficult to make observation in the field regarding recurring eddies located around the Wonsan coastal area in North Korea. But we could get in situ data related to an eddy from an ARGOS satellite tracking drifter trapped in the eddy on January 4th, 1999. An ARGOS drifter, a NOAA satellite tracked buoy was trapped by the eddy during January 4th.March 18, 1999. The ARGOS drifter rotated 10 times per 72 days on the edge of the eddy located at $39^{\circ}N$, $129^{\circ}E$. The diameter of the eddy was about 100 km. The horizontal rotation velocity of the recurring cold-core anti-cyclonic eddy was 1.53 km/h(42 cm/sec). The sea surface temperatures of the eddy varied from $14.7^{\circ}C$ on January 5, 1999 to $9.6^{\circ}C$ on March 18,1999. To study the mechanism of the recurring eddy. we tried to find out the relationship between the vector of the drifter moving in the eddy and the wind vector in Sokcho and Ulleung Island located near the eddy in southern Korea, and the difference in sea level between Ulleung Island and Mukho. We hope the results of this study would be useful for calibration and validation data of simulation and numerical modeling studies of the recurring eddy.

• Korean Journal of Remote Sensing
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• v.24 no.4
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• pp.309-324
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• 2008

In this study the retrieval algorithms have been developed to retrieve total precipitable water (TPW) from Terra/Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) infrared measurements using a physical iterative retrieval method and a split-window technique over East Asia. Retrieved results from these algorithms were validated against Defense Meteorological Satellite Program (DMSP) Special Sensor Microwave/Imager (SSM/I) over ocean and radiosonde observation over land and were analyzed for investigating the key factors affecting the accuracy of results and physical processes of retrieval methods. Atmospheric profiles from Regional Data Assimilation and Prediction System (RDAPS), which produces analysis and prediction field of atmospheric variables over East Asia, were used as first-guess profiles for the physical retrieval algorithm. We used RTTOV-7 radiative transfer model to calculate the upwelling radiance at the top of the atmosphere. For the split-window technique, regression coefficients were obtained by relating the calculated brightness temperature to the paired radiosonde-estimated TPW. Physically retrieved TPWs were validated against SSM/I and radiosonde observations for 14 cases in August and December 2004 and results showed that the physical method improves the accuracy of TPW with smaller bias in comparison to TPWs of RDAPS data, MODIS products, and TPWs from split-window technique. Although physical iterative retrieval can reduce the bias of first-guess profiles and bring in more accurate TPWs, the retrieved results show the dependency upon initial guess fields. It is thought that the dependency is due to the fact that the water vapor absorption channels used in this study may not reflect moisture features in particular near surface.

• Korean Journal of Comparative Education
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• v.24 no.3
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• pp.227-244
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• 2014

This study is to explore and compare the main research area of national and international universities, figure out the differences of the research trends depending on national and international universities, and suggest which area Korea universities could focus on and head to. The study is conducted on the fields of 'Communication and Media' in humanities and 'Electrical Engineering' in engineering for the cases of 10 national and international universities. The data is based on the 3 years journals published between 2009 and 2011 by 10 universities, and analyzed using network analysis. The data is processed with three steps and visualized using Ucinet, Gephi, Netdraw program. These result show, in case of 'Communication and Media', the focus of the universities in Korea mainly on the classical research fields with only a few new research area comparing with international universities. In case of 'Electrical Engineering', national and international universities covers various areas, from classic ones to emerging ones. But the specific research areas are different. These results suggest the research areas which ares the universities in Korea will pursue in near future.

• Journal of The Geomorphological Association of Korea
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• v.19 no.3
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• pp.51-69
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• 2012

Physical strength of the rock is the most important factor of resistance to erosion and has been measured through various way. Bedrock microforms, like potholes and grooves, are the forms sculpted by the erosional processes of flow and the location and morphology are strongly affected by the differential erosion. It also assumed that the physical strength of the rock controls the erosion rate and mode of erosion. The schmidt hammer has been used to measure the rock strength in the field for the geomorphological research. To find the relationship between the rock strength and microforms, Schmidt hammer's R(rebound) were measured in the Baeksuktan, middle reach of Gilancheon, Cheongsong, Gyungsangbuk do. The overall values of rebound of the local sandstone showed over 65 in most cases, so it can be regarded as 'very strong'. It is found that the rebound values of the rock surface decreased towards current water level. It also, however, found that there was no systematic differences in rebound values among the topographically high and lows in the bedrock surface. There was no statistically significant difference in rebound values of the area with well developed microforms and others. The values of R from the exposed faces and inside of the microforms are similar. In the case of conglomerate, the part with the gravel showed higher values that the parts with sands. The rebound values are decreased near of(<1cm) the geological discontinuities(including joint and faults), so this line of weakness could be the point of initiation of active erosion to form microforms. However there is large variations in rebound values within this part. It also should be mentioned that topological relation between the strike of the geologic discontinuities and flow direction looks control the mode of erosional processes.

• Journal of the Korean earth science society
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• v.40 no.5
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• pp.502-517
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• 2019

Global warming and rapid climate change have long affected the characteristics of typhoons in the Northwest Pacific, which has induced increasing devastating disasters along the coastal regions of the Korean peninsula. Synthetic Aperature Radar (SAR), as one of the microwave sensors, makes it possible to produce high-resolution sea surface wind field around the typhoon under cloudy atmospheric conditions, which has been impossible to obtain the winds from satellite optical and infrared sensors. The Geophysical Model Functions (GMFs) for sea surface wind retrieval from SAR data requires the input of wind direction, which should be based on the accurate estimation of the center of the typhoon. This study estimated the typhoon centers using Sentinel-1A images to improve the problem of typhoon center detection method and to reflect it in retrieving the sea surface wind. The results were validated by comparing with the typhoon best track data provided by the Korea Meteorological Administration (KMA) and Japan Meteorological Agency (JMA), and also by using infrared images of Himawari-8 satellite. The initial center position of the typhoon was determined by using VH polarization, thereby reducing the possibility of error. The detected center showed a difference of 23.76 km on average with the best track data of the four typhoons provided by the KMA and JMA. Compared to the typhoon center estimated by Himawari-8 satellite, the results showed an average spatial variation of 11.80 km except one typhoon located near land with a large difference of 58.73 km. This result suggests that high-resolution SAR images can be used to estimate the center and retrieve sea surface wind around typhoons.

• Journal of the Korean Solar Energy Society
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• v.31 no.2
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• pp.82-88
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• 2011

The artificial increase in the solar intensity incident on solar cells using lenses or mirrors can allow solar cells to generate equivalent power with a lower cost. There are two types of concentration optics for solar energy conversion. One is to use mirrors, and the other is to use Fresnel lenses. The gains that can be achieved with a Fresnel lens or a parabolic mirror are compared. The result showed the gains are comparable and the two configurations were developed competitively. In application areas of Fresnel lenses as solar concentrators, several variations of design were devised and tested. Some PV systems still use commercially available flat Fresnel lenses as concentrators. A convex linear Fresnel lens to improve the concentration ratio and the efficiency is devised and flat linear Fresnel lens in thermal energy collection is utilized. In this study, we designed and optimized flat Fresnel lens and the 'light pipe' to develop 500X concentrated solar PV system. In the process, we compare the transmission efficiencies according to groove types. We performed rigorous ray tracing simulation of the flat Fresnel lenses. The computer aided simulation showed the 'grooves in case' has the better efficiency than that of 'grooves out case'. Based on the ray-trace results we designed and manufactured sample Fresnel lenses. The optical performance were measured and compared with ray-trace results. Finally, the optical efficiency was measured to be above 75%. All the design and manufacturing were performed based on that InGaP/InGaAs/Ge triple junction solar cell is used to convert the photon energy to electrical power. Field test will be made and analyzed in the near future.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.14 no.5
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• pp.375-384
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• 2021

The development of the European Railway Traffic Management System (ERTMS) began in 1989 as part of the European Union policy to establish a unified and interoperable railway route in Europe. It is a trend that ERTMS/ETCS(European Train Control System) is becoming an international standard in the railway signaling system. As the solution to this situation, the domestic railway signaling field is also at a time when it is more necessary to develop the technology of the train control system considering interoperability. The European Railway Agency (ERA) has proposed B3R2 (Baseline 3 Release 2) for new ETCS-equipped trains after 2020.12.31. In Korea, Baseline 2.2.0 to 2.3.0d on Gyeongbu Line, Honam Line, Jeolla Line, and Gyeongchun Line was installed and now is under operating. As the Baseline upgrade continues, technical considerations and economic considerations are an occurring trend. In this paper, we analyzed the main functions and compatibility of the currently distributed European standard ERTMS/ETCS Baseline 3 and presented a plan to apply the domestic KTCS(Korean Train Control System) Baseline in the near future.

• Korean Journal of Remote Sensing
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• v.37 no.5_2
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• pp.1307-1315
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• 2021

The Changjiang Diluted Water (CDW) spreads over the East China Sea every summer and significantly affects the sea surface salinity changes in the seas around Jeju Island and the southern coast of Korea peninsula. Sometimes its effect extends to the eastern coast of Korea peninsula through the Korea Strait. Specifically, the CDW has a significant impact on marine physics and ecology and causes damage to fisheries and aquaculture. However, due to the limited field surveys, continuous observation of the CDW in the East China Sea is practically difficult. Many studies have been conducted using satellite measurements to monitor CDW distribution in near-real time. In this study, an algorithm for estimating Sea Surface Salinity (SSS) in the East China Sea was developed using the Geostationary Ocean Color Imager (GOCI). The Multilayer Perceptron Neural Network (MPNN) method was employed for developing an algorithm, and Soil Moisture Active Passive (SMAP) SSS data was selected for the output. In the previous study, an algorithm for estimating SSS using GOCI was trained by 2016 observation data. By comparison, the train data period was extended from 2015 to 2020 to improve the algorithm performance. The validation results with the National Institute of Fisheries Science (NIFS) serial oceanographic observation data from 2011 to 2019 show 0.61 of coefficient of determination (R²) and 1.08 psu of Root Mean Square Errors (RMSE). This study was carried out to develop an algorithm for monitoring the surface salinity of the East China Sea using GOCI and is expected to contribute to the development of the algorithm for estimating SSS by using GOCI-II.