• The KIPS Transactions:PartD
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• v.18D no.3
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• pp.157-168
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• 2011

Recently flash memory has been being utilized as a main storage device in mobile devices, and flashSSDs are getting popularity as a major storage device in laptop and desktop computers, and even in enterprise-level server machines. Unlike HDDs, on flash memory, the overwrite operation is not able to be performed unless it is preceded by the erase operation to the same block. To address this, FTL(Flash memory Translation Layer) is employed on flash memory. Even though the modified data block is overwritten to the same logical address, FTL writes the updated data block to the different physical address from the previous one, mapping the logical address to the new physical address. This enables flash memory to avoid the high block-erase cost. A flashSSD has an array of NAND flash memory packages so it can access one or more flash memory packages in parallel at once. To take advantage of the internal parallelism of flashSSDs, it is beneficial for DBMSs to request I/O operations on sequential logical addresses. However, the B-tree structure, which is a representative index scheme of current relational DBMSs, produces excessive I/O operations in random order when its node structures are updated. Therefore, the original b-tree is not favorable to SSD. In this paper, we propose AS(Always Sequential) B-tree that writes the updated node contiguously to the previously written node in the logical address for every update operation. In the experiments, AS B-tree enhanced 21% of B-tree's insertion performance.

• The KIPS Transactions:PartB
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• v.18B no.3
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• pp.117-130
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• 2011

The purpose of this study is to produce a better way to detect crossroad accidents, which involves an efficient method to produce background images in consideration of object movement and preserve/demonstrate the candidate accident region. One of the prior studies proposed an employment of traffic signal interval within crossroad to detect accidents on crossroad, but it may cause a failure to detect unwanted accidents if any object is covered on an accident site. This study adopted inverse perspective mapping to control the scale of object, and proposed different ways such as producing robust background images enough to resist surrounding noise, generating candidate accident regions through information on object movement, and by using edge information to preserve and delete the candidate accident region. In order to measure the performance of proposed algorithm, a variety of traffic images were saved and used for experiment (e.g. recorded images on rush hours via DVR installed on crossroad, different accident images recorded in day and night rainy days, and recorded images including surrounding noise of lighting and shades). As a result, it was found that there were all 20 experiment cases of accident detected and actual effective rate of accident detection amounted to 76.9% on average. In addition, the image processing rate ranged from 10~14 frame/sec depending on the area of detection region. Thus, it is concluded that there will be no problem in real-time image processing.

• Journal of the Korea Institute of Building Construction
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• v.20 no.6
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• pp.505-514
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• 2020

This research introduces the method of developing Korea BIM standard (KBIMS) architectural and structural element library and the methodology of converting KBIMS IFC property names with special characters. Diverse BIM tools are utilizing in project, however BIM library researches lack diversity on BIM tool selection. This research described the method to generate twelve categories and seven hundred and ninety-three elements library containing geometrical and numerical data in CATIA V6. KBIMS has its special property data naming systems which was the challenge inputting to ENOVIA IFC database. Three mapping methods for special naming characters had been developed and the ASCII code method was applied. In addition, the convertor prototype had been developed for searching and replacing the ASCII codes into the original KBIMS IFC property names. The methodology was verified by exporting 2,443 entities without data loss in the sample model conversion test. This research would provide a wider choice of BIM tool selection for applying KBIMS. Furthermore, the research would help on the reduction of data interoperability issues in projects. The developed library would be open to the public, however the continuous update and maintenance would be necessary.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.38 no.6
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• pp.663-670
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• 2020

In the present study, we assessed the accuracy of aerial triangulation using a UAV (Unmanned Aerial Vehicle) capable of network RTK (Real-Time Kinematic) survey in a disaster situation that may occur in a semi-urban area mixed with buildings. For a reliable survey of check points, they were installed on the roofs of buildings, and static GNSS (Global Navigation Satellite System) survey was conducted for more than four hours. For objective accuracy assessment, coded aerial targets were installed on the check points to be automatically recognized by software. At the instance of image acquisition, the 3D coordinates of the UAV camera were measured using VRS (Virtual Reference Station) method, as a kind of network RTK survey, and the 3-axial angles were achieved using IMU (Inertial Measurement Unit) and gimbal rotation measurement. As a result of estimation and update of the interior and exterior orientation parameters using Agisoft Metashape, the 3D RMSE (Root Mean Square Error) of aerial triangulation ranged from 0.153 m to 0.102 m according to the combination of the image overlap and the angle of the image acquisition. To get higher aerial triangulation accuracy, it was proved to be effective to incorporate oblique images, though it is common to increase the overlap of vertical images. Therefore, to conduct a UAV mapping in an urgent disaster site, it is necessary to acquire oblique images together rather than improving image overlap.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.39 no.6
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• pp.469-476
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• 2021

The framework plan for the development of an integrated underground space map was established of preventing ground subsidence. The mapping process is expected to be completed to the level of nationwide municipal government standards by end of this year. To facilitate the utilization of the integrated underground space map, paper-based drawings for specialized organizations in underground safety impact assessment have been provided since September 2018, and services for local government officials have been provided in the underground information utilization system since May 2019. However, the map is utilized based on the information at the time of the initial development of the map, without any updates, thereby resulting in a lack of accuracy and latest information. This has led to a decrease in the utilization and reliability of the information. Therefore, in this study, for the underground structures(subway, underground shopping mall, underground passage, underground roadway, underground parking lot, utility tunnel), which are the key components of the integrated underground space map, a standard format for the submission of completed drawings is designed in accordance with Article 42 (2) of the Special Act on Underground Safety Management, which aims at laying the foundation for establishing the updated system of the integrated underground space map. In addition, through the verification of the automatically updated underground structure data based on the standard format, the reliability of the data can be assured. This format is expected to contribute to the improved utilization of the integrated underground space map in the future.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.24 no.3
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• pp.483-494
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• 2019

From the cosmopolitan superiority of the as the first world map completed in 1402 with surprisingly detailed images and contents on the Africa Continent it is reasonable to think that the Koreans in early fifteen century were already with highly up-to-date perspectives on the universe and world history and cultures. However, some 490 year later the first phytohydrographic plankton investigation in the neritic seas of Korea was performed by a Japanese company with sampling points covering from Tokyo Bay through Jeju neritic waters to Shanghai estuary, which was in turn preceded by the first oceanographic investigation other than the simple mapping Koreans seas by using two French sailboats. The first phytohydrographic plankton investigation in Korean seas were behind the world first oceanic plankton exploration, the German Plankton Expedition, by 25 years. Starting from the oceanographic investigation including phytohydrographic samplings in the whole Yellow Sea in 1915 the full-scale phytohydrographic plankton studies were tried in Korean seas which is well represented by the 1921 oceanographic investigation on the whole East Sea with 80 sampling stations. In 1932 two separate oceanographic investigations followed, one in the East Sea where 78 stations from Busan to southern Sakhalin Island were simultaneously visited by 50 research vessels for the physical, chemical, and biological oceanographic studies, and the other one in southern coast and western East Sea of Korea where ocean current observation as well as plankton sampling were made in 120 stations to understand the relationship between the ocean current and plankton distribution in the region. In 1933-1934 more intensified investigations on phytohydrography were carried out particularly in the East Sea as an integral part of the basic marine ecosystem studies for the Myeong-Tae (Alaska Pollock) resources estimation. Scientists' attitude for the marine investigation and research activities seemed to be almost unchanging even to the year 1943, which could be reflected by the fact that publication of the results from the investigations performed in 1945 were finally done in 1967 at Tokyo. Some 70 years later from the mid-twenty century we might be standing on the turning-point of "need to be prepared" for the new era of changing paradigm by reviewing, archiving, and analyzing the prior information big data from the previous ocean observation and biohydrographic investigations. At the same time each professional societies for the above mentioned sciences might trigger a continuous project to reorganize and update the records on related bibliography and its history every 30 years.