• Atmosphere
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• v.31 no.4
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• pp.405-420
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• 2021

Forest fire happens every year at Yeongdong, Gangwon-do, due to the strong local wind during the spring time and it causes a huge damage. This wind is named "Yangganjipung" or "Yanggangjipung" that blows along Yeongdong. However, the occurrence conditions of the wind have been still unclear. To identify the occurrence mechanism of local strong wind through three-dimensional observation data, Gangwon Regional Meteorological Administration performed Joint Gangwon-Yeongdong 3D Observation Project in 2020. The special observation was carried out for 6 times from March to April. The observation data was analyzed by focusing on the structure of synoptic pressure distribution and inversion layer. The result showed that the strength of wind is different depending on the latitude of low pressure, intensity of inversion layer, and changes on height in the south-high and north-low pressure distribution. As the interval of the upper and lower parts of the inversion layer was narrow, the strength of the wind became stronger, which is one of the observational characteristics of the springtime wind pattern at Yeongdong, Gangwon-do. In future, the clear mechanism of the local wind in the Yeongdong during the spring time is expected to be verified based on the accumulative observation data and close analysis.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.34 no.6
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• pp.303-314
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• 2022

The persistence analysis of marine physical environment factors is a basic analysis that must precede the use of sea areas as an analysis required in the coastal engineering such as downtime and design. In this study, the persistence analysis was implemented for wind speed and significant wave height data from four observation points of Deokjeokdo, Oeyeondo, Geomundo, and Geojedo among the marine meteorological observation buoys of the Korea Meteorological Administration. The persistence time means the consecutive time of observation data beyond specific level. The threshold wind speed and significant wave height were set in the range of 1~15 m/s and the range of 0.25~3.0 m, respectively. Then, the persistence time was extracted. As a result of the analysis, the persistence time of wind speed and significant wave height decreased rapidly as the reference value increased. The median persistence times under the maximum reference thresholds were assessed as a maximum of 5 hours for wind speed and a maximum of 8 hours for significant wave height. When the reference wind speed and significant wave height were 15 m/s and 3 m, respectively, the persistence time that could occur with a 1% probability were 52 and 56 hours. This study can be expanded to all coastal areas in Korea, and it is expected that various engineering applications by performing a persistence analysis of the metocean data.

• Journal of Ocean Engineering and Technology
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• v.16 no.2
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• pp.21-26
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• 2002

In this study, the characteristics of long period waves are analyzed by field observation at Sokcho harbor on the eastern coast of Korea. firstly. the pressure data obtained from field observation are transformed into water surface elevations and the wave by wave analysis is applied to the observed wave data. also, we select long period waves by setting up the range 30-200sec, and suggest the relationship between ordinary waves and long period waves using the concept of the significant wave height. and, we examine the effects oft he long period waves on the rate of the harbor operation. The observation results demonstrate that the long period waves with heights of 1.2-14.6cm and periods of 35.8-162sec exist at Sokcho harbor. also, we found the rates of harbor operation based on long period waves are 61.8%-99.5% lower than the usual rates of 93.8%-100%.

• Atmosphere
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• v.32 no.3
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• pp.191-206
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• 2022

Assimilation trials were performed using the Korea Institute of Atmospheric Prediction Systems (KIAPS) Korea Integrated Model (KIM) semi-operational forecast system to assess the impact of ground-based Global Navigation Satellite System (GNSS) Zenith Total Delay (ZTD) on forecast. To use the optimal observation in data assimilation of KIM forecast system, in this study, the ZTD observation were pre-processed. It involves the bias correction using long term background of KIM, the quality control based on background and the thinning of ZTD data. Also, to give the effect of observation directly to data assimilation, the observation operator which include non-linear model, tangent linear model, adjoint model, and jacobian code was developed and verified. As a result, impact of ZTD observation in both analysis and forecast was neutral or slightly positive on most meteorological variables, but positive on geopotential height. In addition, ZTD observations contributed to the improvement on precipitation of KIM forecast, specially over 5 mm/day precipitation intensity.

• Transactions of Materials Processing
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• v.19 no.8
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• pp.480-485
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• 2010

In this work, the closing behavior of cylindrical-shaped voids was experimentally investigated according to various parameters such as reduction ratio in height, initial void size and billet rotation during hot open die forging process. The reduction ratio in height, number of path, and billet rotation were chosen as key process parameters which influence the void closing behavior including the change of void shape and size. On the other hand, values of die overlapping and die width ratio were set to be constant. Void closing behavior was estimated by microscopic observation. Based on the observations, it was confirmed that application of billet rotation is more efficient to eliminate the void with less reduction ratio in height. The experimental results obtained from this study could be helpful to establish the optimum path schedule of open die forging process.

• Proceedings of the KSRS Conference
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• 2008.10a
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• pp.394-397
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• 2008

This research aimed at developing a technique for estimating the tree height using BRF (Bi-directional Reflectance Factor) through the clarification of the relation between shape of the tree crown and the tree height and the relations between the shape of the tree crown and BRF. This paper, reports the results of analyses of data acquired by field measurements done to clarify relation between crown shape and tree height.

• Atmosphere
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• v.28 no.4
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• pp.369-382
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• 2018

Planetary boundary layer height (PBLH), produced by the Local Data Assimilation and Prediction System (LDAPS), was verified using RawinSonde (RS) data obtained from observation at Daegwallyeong (DGW) and Sokcho (SCW) during the International Collaborative Experiments for Pyeongchang 2018 Olympic and Paralympic winter games (ICE-POP 2018). The PBLH was calculated using RS data by applying the bulk Richardson number and the parcel method. This calculated PBLH was then compared to the values produced by LDAPS. The PBLH simulations for DGW and SCW were generally underestimation. However, the PBLH was an overestimation from surface to 200 m and 450 m at DGW and SCW, respectively; this result of model's failure to correctly simulate the Surface Boundary Layer (SBL) and the Mixing Layer (ML) as the PBLH. When the accuracy of the PBLH simulation is low, large errors are seen in the mid- and low-level humidity. The highest frequencies of Planetary boundary layer (PBL) types, calculated by the LDAPS at DGW and SCW, were presented as types Ι and II, respectively. Analysis of meteorological factors according to the PBL types indicate that the PBLH of the existing stratocumulus were overestimated when the mid- and low-level humidity errors were large. If the instabilities of the surface and vertical mixing into clouds are considered important factors affecting the estimation of PBLH into model, then mid- and low-level humidity should also be considered important factors influencing PBLH simulation performance.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.14 no.1
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• pp.34-40
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• 2002

In order to estimate the height of long period wave from character of deep water wave, field observation is carried out three wave gauge are arranged by a straight line from the seashore to offshore direction and the result is analyzed. In addition, the existing theory of the mechanism for long period wave producer is verified by field observation, and the relation between deep water wave and long period wave of shallow area is examined. Observed long period wave is coincided with the existing theory for the most part. In order to add the change of time and space of long period wave, the height of long period wave is calculated by the composition of long period wave in each position. As a result, the relation of long period wave and deep water wave is presented more clear. Estimate formula is drew through them.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.36 no.1
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• pp.1-8
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• 2018

To compensate for the shortcomings of spirit leveling, research on the determination of GNSS (Global Navigation Satellite System)-derived orthometric height has been actively carried out. However, most analyses were primarily performed inland. In this study, the influences of the arrangement of control points, observation duration, and geoid model on the accuracy of the GNSS-derived orthometric height have been analyzed to suggest the proper method to apply the determination of GNSS-derived orthometric height to the leveling loop disconnected area. As a result, it was found that two known points located near the unknown points need to be fixed in the leveling loop disconnected area. Further, 3 cm level of accuracy can be achieved if the GNSS survey is performed over two days, for four hours per day. In terms of the geoid model, the latest national geoid model should be applied rather than the EGM08 (Earth Gravitational Model 2008) to minimize regional bias and increase accuracy. Future research is necessary to apply the determination of the GNSS-derived orthometric height technique as a method to connect with the islands because the vertical reference system used inland and that used for the islands in Korea are still different.

• Proceedings of the KSRS Conference
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• 2008.10a
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• pp.344-347
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• 2008

Ocean surface waves may be modified by ocean current and their observation may be severely distorted if the observer is on a moving platform with changing speed. Tidal current near a sill varies inversely with the water depth, and results spatially inhomogeneous modulation on the surface waves near the sill. For waves propagating upstream, they will encounter stronger current before reaching the sill, and therefore, they will shorten their wavelength with frequency unchanged, increase its amplitude, and it may break if the wave height is larger than 1/7 of the wavelength. These small scale (${\sim}$ 1 km changes is not suitable for satellite radar observation. Spatial distribution of wave-height spectra S(x, y) can not be acquired from wave gauges that are designed for collecting 2-D wave spectra at fixed locations, nor from satellite radar image which is more suitable for observing long swells. Optical images collected from cameras on-board a ship, over high-ground, or onboard an unmanned auto-piloting vehicle (UAV) may have pixel size that is small enough to resolve decimeter-scale short gravity waves. If diffuse sky light is the only source of lighting and it is uniform in camera-viewing directions, then the image intensity is proportional to the surface reflectance R(x, y) of diffuse light, and R is directly related to the surface slope. The slope spectrum and wave-height spectra S(x, y) may then be derived from R(x, y). The results are compared with the in situ measurement of wave spectra over Keelung Sill from a research vessel. The application of this method is for analysis and interpretation of satellite images on studies of current and wave interaction that often require fine scale information of wave-height spectra S(x, y) that changes dynamically with time and space.