• Journal of Ocean Engineering and Technology
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• v.32 no.4
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• pp.228-236
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• 2018

The performance of a porous swash bulkhead for the reduction of the resonant liquid motion in a swaying rectangular tank was investigated based on the assumption of linear potential theory. The Galerkin method (Porter and Evans, 1995) was used to solve the potential flow model by adding a viscous frictional damping term to the free-surface condition. By comparing the experimental results and the analytical solutions, we verified that the frictional damping coefficient was 0.4. Darcy's law was used to consider the energy dissipation at a porous bulkhead. The tool that was developed with a built-in frictional damping coefficient of 0.4 was confirmed by small-scale experiments. Using this tool, the free-surface elevation, hydrodynamic force (added mass, damping coefficient) on a wall, and the horizontal load on a bulkhead were assessed for various combinations of porosity and submergence depth. It was found that the vertical porous bulkhead can suppress sloshing motions significantly when properly designed and by selecting the appropriate porosity(${\approx}0.1$) and submergence depth.

• International Journal of Contents
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• v.8 no.1
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• pp.55-60
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• 2012

Most Korean and overseas major portal sites include map servers to provide map services, and offer open APIs to allow their users to make use of maps or spatial information directly. At the early design stage, geographic spatial data do not tend to require high accuracy, and thus there would be no problem using data which have been obtained and then utilized through map servers provided by portal sites. This study has chosen the shortest route between starting point and destination, using GIS techniques. Moreover, for the chosen route, it also has calculated the elevation for the cross-section, using Google map and GPS measurements. This study aims to create APIs, which can extract vertical profile of routes from the Google Map server, by using JAVA, and to compare centerline profile results obtained by GPS(Global Positioning System) to explore their utilize abilities. The result demonstrated a height error of 0.5 to 1 m, compared to the GPS results, but they were mutually satisfactory. In short, the data extracted in this study are useful for centerline profile drawings in selecting routes, such as streets, Olle roads, and bike lanes.

• Journal of the Korean Institute of Educational Facilities
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• v.10 no.3
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• pp.5-13
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• 2003

This paper is a series of study for the development of rural elementary school facilities model applying to the regional characteristics. Therefore, main theme of this paper is to pile up and analysis of elementary school facilities data in Po Cheon through a series of actual survey and interview with teachers. The results are summarized as follows ; First of all, in case of Po Cheon, it needs to study for urban model type as well as rural elementary school facilities model type. Second, extension type of buildings has separated as three types-zigzag extension type, vertical & horizontal extension type, separate building type. But another characteristics, such as type of site plan, type of corridor and module of classroom unit, outdoor space and elevation design, are monotonous. Third. the results of this analysis show that it is desirable to locate houses for teachers within boundaries. Finally, the future paper needs to be studying more various module of classroom unit, extension type, space program, type of floor plan and site plan.

• Atmosphere
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• v.25 no.4
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• pp.591-600
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• 2015

We have analyzed wind and eddy covariance data collected within roughness sublayer over sloping terrain. The study site is located on non-flat terrain with slopes in both south-north and east-west directions. The surface elevation change is smaller than the height of roughness element such as building and tree. This study examines the directional wind shear for data collected at three levels in the lowest 10 m in the roughness sublayer. The wind direction shear is caused by drag of roughness element and terrain-induced motions at this site. Small directional shear occurs when wind speed at 10 m is strong and wind direction at 10 m is southerly which is the same direction as upslope flow near surface at this site during daytime. Correlation between vertical shear of lateral momentum and lateral momentum flux is smaller over steeply sloped surface compared to mildly sloped surface and lateral momentum flux is not down-gradient over steeply sloped surface. Quadrant analysis shows that the relative contribution of four quadrants to momentum flux depends on both surface slope and wind direction shear.

• Ocean and Polar Research
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• v.30 no.1
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• pp.33-46
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• 2008

In order to investigate seasonal variations of the physical environments in the region of Jinhae Bay-Nakdongpo, we carried out hydrographic surveys from November 2000 to November 2001. Horizontal and vertical distribution of salinity and temperature shows large seasonal variations. Water column is well mixed in winter and stratified in summer. Low-salinity water is distributed in the form of patches because of the drainage control at the Nakdong River. Seasonal variations in the sea near Gadeok-Sudo are affected by topography, river discharge and tidal current. Currents have been measured using a bottom mounted ADCP and DCM12 between November 2000 and August 2001 in the Gadeok-Sudo. The current in the Gadeok-Sudo shows a distinct two-layer structure with reversed current. Low-pass filtered time series of wind, sea elevation and current are coherent for the period of 1-2 days and are attributed to Ekman-like dynamics. Spatial and temporal circulation pattern shows a slight different. The subtidal current in Jinhae Bay goes northward, however is reversed in the Gadeok-Sudo mouth.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.933-938
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• 2014

The combined method utilizing airborne LiDAR and GIS data is suggested to extract 3-dimensional hybrid city model including roads and buildings. Combining the two types of data is more efficient to estimate the elevations of various types of roads and buildings than using either LiDAR or GIS data only. This method is particularly useful to model the overlapped roads around the so called spaghetti junction. The preliminary model is constructed from the LiDAR data, which can give wrong information around the overlapped parts. And then, the erratic vertex points are detected by imposing maximum vertical grade allowable on the elevated roads. For the purpose of efficiency, the erratic vertex points are corrected through linear interpolation method. To avoid the erratic treatment of the LiDAR data on the facades of buildings 2 meter inner-buffer zone is proposed to efficiently estimate the height of a building. It is validated by the mean value (=5.1%) of differences between estimated elevations on 2 m inner buffer zone and randomly observed building elevations.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2012.07a
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• pp.174-175
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• 2012

본 논문에서는 가정용 TV 환경에서 실감효과를 향상시키기 위한 정면 수직음상정위에 기반한 오디오 시스템을 제안하고 이를 구현한다. 제안된 시스템은 가정용 대형 TV 환경에서 TV 하단에 배치된 오디오 시스템으로 인해 음상이 TV 의 하단에 맺히게 되어 재생되는 영상과 위치적인 불일치 문제를 해결하기 위하여, 오디오 신호에 정면 수직음상정위 기법을 적용하여 고도감이 향상된 신호를 생성해 준다. 본 논문에서의 정면 수직음상정위 기법은 청취자의 신체적 특성을 반영하기 위한 머리전달함수 모델, 고도에 따라 달라지는 주파수 특성을 반영하기 위한 spectral notch 및 특정 주파수 대역 boosting 으로 구성된다. 제안된 오디오 시스템의 정면 수직음상정위 기법의 성능을 평가하기 위하여 원음과 이 원음에 정면 수직음상정위 기법을 적용하여 생성한 음원을 TV 오디오 시스템으로 재생한 후의 청취 선호도 조사를 수행하였으며, 그 결과 정면 수직음상정위 기법을 포함하는 제안된 오디오 시스템을 통해 청취한 음원에 대한 선호도가 높았다.

• Korean Journal of Remote Sensing
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• v.34 no.1
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• pp.17-24
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• 2018

Grounding line of a glacier or ice shelf where ice bottom meets the ocean is sensitive to changes in the polar environment. Recent rapid changes of grounding lines have been observed especially in southwestern Antarctica due to global warming. In this study, ERS-1/2 and Sentinel-1A Synthetic Aperture Radar (SAR) image were interferometrically acquired in 1996 and 2015, respectively, to monitor the movement of the grounding line in the western part of Ronne Ice Shelf near the Antarctic peninsula. Double-Differential Interferometric SAR (DDInSAR) technique was applied to remove gravitational flow signal to detect grounding line from the interferometric phase due to the vertical displacement of the tide. The result showed that ERS-1/2 grounding lines are almost consistent with those from Rignot et al. (2011) which used the similar dataset, confirming the credibility of the data processing. The comparison of ERS-1/2 and Sentinle-1A DDInSAR images showed a grounding line retreat of $1.0{\pm}0.1km$ from 1996 to 2015. It is also proved that the grounding lines based on the 2004 MODIS Mosaic of Antarctica (MOA) images and digital elevation model searching for ice plain near coastal area (Scambos et al., 2017), is not accurate enough especially where there is a ice plain with no tidal motion.

• Structural Engineering and Mechanics
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• v.59 no.3
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• pp.539-558
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• 2016

Minarets are almost the inevitable part of Mosques in Islam and according to some, from a philosophical point of view, today they symbolize the spiritual elevation of man towards God. Due to slenderness, minarets are susceptible to earthquakes and wind loads. They are mostly built in a masonry style by using cut limestone blocks or occasionally by using bricks. In this study, one minaret (M1 Minaret) of one of the charmest mosques of Turkey, Sultan Ahmed Mosque, popularly known as Blue Mosque, built between 1609 and 1616 on the order of Sultan Ahmed by the architect Mehmet Agha is investigated under some registered earthquake loads. According to historical records, a great earthquake hit Istanbul and/or its close proximity approximately every 250 years. Ottomans tackled with the problem of building earthquake resistant, slender minarets by starting to use forged iron connectors with lead as a filler to fix them to the upper and lower and to adjacent stones instead of using traditional mortar only. Thus, the discrete stones are able to transfer tensile forces in some sense. This study investigates the contribution of lead to the energy absorption capacity of the minaret under extensive earthquakes occurred in the region. By using the software ANSYS/LS-DYNA in modelling and investigating the minaret nonlinearly, it is found out that under very big recorded earthquakes, the connectors of vertical cast iron-lead mechanism play very important role and help to keep the structure safe.

• Ocean and Polar Research
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• v.27 no.4
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• pp.497-507
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• 2005

This paper presents a method for obtaining mosaic aerial photographs that are useful for a long-term shoreline change study in the Nakdong estuary. Although this method involves digital photogrammetry software of the shelf its usage can be simplified to accomodate the shoreline change study. Ground control points, which are common in aerial photographs, were measured from digital maps. Block triangulation was highly affected by land-based GCPs. Extension of tie points near the shoreline to vertical control points gave more reliable results for the block triangulation. A constant Digital Elevation Model (DEM), close to mean sea level, was employed to produce ortho-rectified photographs, from which mosaic photographs were made. Accuracy of photographs were found to be acceptable for the analysis of long-term shoreline change, and the promising construction of a shoreline change database in the Nakdong estuary.