• Journal of KIISE:Databases
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• v.31 no.1
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• pp.30-38
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• 2004

In many scientific and commercial applications such as Earth Observation System (EOSDIS) and mobile Phone services tracking a large number of clients, it is a daunting task to archive and index ever increasing volume of complex data that are continuously added to databases. To efficiently manage multidimensional data in scientific and data warehousing environments, R-tree based index structures have been widely used. In this paper, we propose a scalable technique called seeded clustering that allows us to maintain R-tree indexes by bulk insertion while keeping pace with high data arrival rates. Our approach uses a seed tree, which is copied from the top k levels of a target R-tree, to classify input data objects into clusters. We then build an R-tree for each of the clusters and insert the input R-trees into the target R-tree in bulk one at a time. We present detailed algorithms for the seeded clustering and bulk insertion as well as the results from our extensive experimental study. The experimental results show that the bulk insertion by seeded clustering outperforms the previously known methods in terms of insertion cost and the quality of target R-trees measured by their query performance.

• 한국지구물리탐사학회:학술대회논문집
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• 2005.05a
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• pp.9-14
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• 2005

For the understanding the locus of the Quinling-Dabie-Sulu continental collision's boundary and the underground structure of the sedimentray basin in the Yellow Sea, three dimensional density modelling is carrid out by using gravity dataset (Free Air Anomaly), which is measured by Tamhae 2, KIGAM in a period 2000 - 2002. The measured gravity anomaly in the investigations area is mainly responsed by depth distribution of the sedimentary basin. After comparing the sea-measured gravity data to CHAMP-GRACE satellite gravity data, I suggested that the high density model bodies extend mainly from the southern part of China to the middle-western part of the Korean Peninsula., which might be emplaced along the continental collision's boundary. The total volume of very low density bodies modified by modelling might be about $20000\;km^3$.

• Geophysics and Geophysical Exploration
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• v.9 no.1
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• pp.44-49
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• 2006

In this study, the resolution capabilities of electrical resistivity tomography (ERT) in the monitoring of $CO_2$ injection are investigated. The pole-pole and bipole-bipole electrode configuration types are used between two uncased boreholes straddling the $CO_2$ plume. Forward responses for an initial pre-injection model and three models for subsequent stages of $CO_2$ injection are calculated for the two different electrode configuration types, noise is added and the theoretical data are inverted with both L1- and L2-norm optimisation. The results show that $CO_2$ volumes over a certain threshold can be detected with confidence. The L1-norm proved superior to the L2-norm in most instances. Normalisation of the inverted models with the pre-injection inverse model gives good images of the regions of changing resistivity, and an integrated measure of the total change in resistivity proves to be a valid measure of the total injected volume.

• Progress in Superconductivity and Cryogenics
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• v.22 no.2
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• pp.7-11
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• 2020

When rivers and lakes are contaminated with numerous contaminants, usually the contaminants are finally deposited on the sediments of the waterbody. Many clean up technologies have been developed for the contaminated sediments. Among several technologies dredging is one of the best methods because dredging removes all the contaminated sediments from the water and the contaminated sediments can be completely treated with physical and chemical methods. However the most worried phenomenon is suspension of fine particles during the dredging process. The suspended particle can release contaminants into water and resulted in spread of the contaminants and the increase of risk due to the resuspension of the precipitated contaminants such as heavy metals and toxic organic compounds. Therefore the success of the dredging process depends on the prevention of resuspension of fine particles. Advanced dredging processes employ pumping the sediment with water onto a ship and release the turbid water pumped with sediment into waterbody after collection of sediment solids. Before release of the turbid water into lake or river, just a few minutes allowed to precipitate the suspended particle due to the limited area on a dredging ship. However the fine particle cannot be removed by the gravitational settling over a few minutes. Environmental technology such as coagulation and precipitation could be applied for the settling of fine particles. However, the process needs coagulants and big settling tanks. For the quick settling of the fine particles suspended during dredging process magnetic separation has been tested in current study. Magnetic force increased the settling velocity and the increased settling process can reduce the volume of settling tank usually located in a ship for dredging. The magnetic assisted settling also decreased the heavy metal release through the turbid water by precipitating highly contaminated particles with magnetic force.

• Journal of the Korean Geotechnical Society
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• v.19 no.6
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• pp.161-168
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• 2003

Most natural deposits of sandy soil possess some degree of cementation resulting from the deposition and precipitation of cementing agents. The presence of cementation can have a significant influence on the stiffness and volume change behavior, and the strength of soils. An important feature of deposits of cemented sandy soils is their ability to remain stable in surprisingly high and almost vertical man-made cuts as well as natural slopes. Numerous field observations and studies of failures in slopes of cemented soils have reported that application of conventional analysis techniques of slope stability is inadequate. That is not only due to the fact that the failure surface of the slope is not circular, but also the fact that the average shear stress along the failure surface is much smaller than the shear strength measured in laboratory shear experiments. This observation alerts us to the fact that a mechanism different from conventional Mohr-Coulomb shear failure takes place, which may be related to fracture processes, which in turn are governed by fracture mechanics concepts and theory. In this study, steep slopes in cemented sand were assessed using fracture mechanics concepts. The results showed that FEM coupled with fracture mechanics concepts provides an excellent alternative in the design and safety assessment of earth structures in cemented soils.

• Atmosphere
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• v.25 no.3
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• pp.473-482
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• 2015

In this study, street canyons with a higher downwind building (so called, step-up street canyons) are considered for understanding characteristics of flow and reactive pollutants' dispersion as a basic step to understand the characteristics in wider urban areas. This study used a CFD_NIMR_SNU coupled to a chemistry module just including simple $NO_X-O_3$ photochemical reactions. First, flow characteristics are analyzed in step-up street canyons with four aspect ratios (0.33, 0.47, 0.6, 0.73) defined as ratios of upwind building heights to downwind building height. The CFD_NIMR_SNU reproduced very well the main features (that is, vortices in the street canyons) which appeared in the wind-tunnel experiment. Wind speed within the street canyons became weak as the aspect ratio increased, because volume of flow incoming over the upwind building decreased. For each step-up street canyon, chemistry transport model was integrated up to 3600 s with the time step of 0.5 s. The distribution patterns of $NO_X$ and $O_3$ were largely dependent on the mean flow patterns, however, $NO_X$ and $O_3$ concentrations were partly affected by photochemical reactions. $O_3$ concentration near the upwind lower region of the street canyons was much lower than background concentration, because there was much reduction in $O_3$ concentration due to NO titration there. Total amount of $NO_X$ in the street canyons increased with the aspect ratio, resulting from the decrease of mean wind intensity.

• 한국지구물리탐사학회:학술대회논문집
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• 2003.11a
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• pp.142-149
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• 2003

Blind hydraulic backfilling is a commonly used technique for subsidence control of the strata over unapproachable waterlogged underground excavations. In this investigation model studies on all the three variants of this technique, namely, hydro-pneumatic or air-assisted gravity backfilling, pumped-slurry backfilling and simple gravity backfilling, have been carried out in fully transparent models of the underground excavations. On examination of the filling process, it was revealed that in all the three cases, the basic process of filling occurs by sand transport along one or more meandering channels. The relative influence of sand, water and air flow rates on the area of filling from a single inlet point and the hydraulic pressure loss per unit length were studied in details. In hydro-pneumatic backfilling process, the air bubbles while moving upward through the meandering channels provide an additional buoyant force over and above the available hydraulic head. In this way the area of filling from a single borehole may be quite large even at small flow rates of water. During actual field implementation the injected air, if not released completely from the rise side holes, may cause troubles by way of creating potholes on the surface. The pumped-slurry technique has shown its capability of filling a relatively larger area at faster rate, especially when high-volume, low-pressure method was selected. But simple gravity filling was also found to be equally effective method as slurry pumping, especially when flow rates were high. In the second and third method discussed above, examination of variations of injection pressure was also done and its relation with physical phenomenon was also attempted. Some empirical relationships were also developed using multivariate regression with a view to help the practicing engineers.

• Korean Journal of Construction Engineering and Management
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• v.17 no.1
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• pp.101-109
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• 2016

During road construction, minimizing haul and return distances as well as keeping a balance between cut and fill quantities are two of the key tasks for earthmoving operation planning. The result of the earthwork planning has a significant impact on the construction cost and duration. Although there have been research efforts regarding optimized earthwork planning using linear programming, the current practice of selecting earthwork planning methods typically depends on a field manager's intuitive and/or experimental knowledge. Furthermore, there is no system considering earthwork influential field factors including the transportation distance, the earthwork quantity, and the recycling ratio of earth volume. Therefore, this research focuses on the development of such a model for planning the optimized earthwork to increase the efficiency of a road construction. The proposed model is developed based upon the transportation problem method which is a part of Linear Programming. The application result of optimization model on a case study shows that the duration and cost for earthwork ha sbeen reduced approximately 19% and 11% respectively

• Journal of the Korean Association of Geographic Information Studies
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• v.10 no.4
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• pp.142-152
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• 2007

Geotechnical information database, foundation of underground geographic information system in 2nd NGIS plan, had been developing by Ministry of Construction and Transportation since 2000. This database contains not only soil condition, such as depth, type and color of layer, and ground water level, but also engineering properties used for foundation design and construction, for instance, standard penetration test, compression test. But, it is difficult to apply this database for analyzing and designing geotechnical works, because report document is only offered. In this paper, we have developed web-based geospatial information system for the effective uses. First, underground cross-section model is generated by location, layer, and engineering properties of geotechnical information database at the realtime process. Second, earth volume, bearing capacity, and settlement is calculated and potentials of soft ground, liquefaction are evaluated through pre-defined empirical formula. This process is operated by web-based client. We wish to strengthen the application capacity through this system in construction planning and design works.

• Journal of Korean Society for Atmospheric Environment
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• v.19 no.E4
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• pp.177-186
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• 2003

The total of 1,454 aerosol samples were collected by high volume tape sampler at the Gosan Site in Jeju Island from 1992 to 1999, and the major water-soluble ionic components were chemically analyzed. The mean concentrations of nss-S $O_4$$^{2-}$, N $H_4$$^{＋}$, and N $O_3$$^{[-10]}$ showed high values, which were 6.73, 1.45, and 1.45 ${\mu}{\textrm}{m}$/㎥, respectively, while $Ca^{2+}$ and $K^{+}$ concentrations were low with the values of 0.49 and 0.42 $\mu\textrm{g}$/㎥. The concentrations of most components increased in spring but decreased in summer, especially with the remarkable increase of $Ca^{2+}$ and N $O_3$$^{[-10]}$ concentrations in spring. The seasonal comparison of nss-S $O_4$$^{2-}$ concentrations showed higher values with the order of spring > fall 〉 winter〉 summer, but spring 〉 winter〉 fall 〉 summer for N $O_3$$^{[-10]}$ Meanwhile, the concentration levels of N $a^{+}$ and C $l^{[-10]}$ increased more in winter season. According to the investigation of wind direction effect, the concentrations of most aerosol ionic components showed higher values consistently at the westerly and northerly wind conditions. Based on the factor analysis, the atmospheric aerosols in the Gosan Site are considered to be largely affected by marine sources, followed by anthropogenic and soil sources.urces..