• Journal of the Economic Geographical Society of Korea
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• v.14 no.2
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• pp.116-128
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• 2011

Some subway passengers may want to have their fresh vegetables purchased through internet at a service facility within the subway station of the Metropolitan Seoul subway system on the way to home, which raises further questions about which stations are chosen to locate service facilities and how many passengers can use the facilities. This problem is well known as the pickup problem, and it can be solved on a traffic network with traffic flows which should be identified from origin stations to destination stations. Since flows of the subway passengers can be found from the smart card transaction database of the Metropolitan Seoul smart card system, the pickup problem in the Metropolitan Seoul subway system is to select subway stations for the service facilities such that captured passenger flows are maximized. In this paper, we have formulated a model of the pickup problem on the Metropolitan Seoul subway system with subway passenger flows, and have proposed a fast heuristic algorithm to select pickup stations which can capture the most passenger flows in each step from an origin-destination matrix which represents the passenger flows. We have applied the heuristic algorithm to select the pickup stations from a large volume of traffic network, the Metropolitan Seoul subway system, with about 400 subway stations and five millions passenger transactions daily. We have obtained not only the experimental results in fast response time, but also displayed the top 10 pickup stations in a subway guide map. In addition, we have shown that the resulting solution is nearly optimal by a few more supplementary experiments.

• The Journal of the Korea Contents Association
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• v.20 no.10
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• pp.190-198
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• 2020

The development in smartphone technology has brought convenience to the life of the mankind, but an excessive use of smartphones sometimes causes various accidents. This research tried to propose an application service 'Smombie Safe Go' UI(User Interface) that allows the prevention of such accident while using smartphones when walking. For this, after research and user observations, produced walker journey maps and derived necessary main functions needed for safety, and the result showed that transparent interface, obstacle location alert, warning of dangers functions were necessary. To make the contents of the service more detailed, hazardous situations faced during smartphone use when walking were classified into 3 situations : 1. Obstacle appearing in front, 2. traffic lights on crosswalks 3. No traffic lights on crosswalks. Scenarios by hazardous situation were written, and the flow and UI of the app service that warns its users in each situation of hazards were designed. it is predicted that 'Smombie Safe Go' may be possible to be utilized as an app service that provides a safe walking experience for not only regular pedestrians but also the blind population.

• Journal of the Korean Geotechnical Society
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• v.15 no.5
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• pp.217-228
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• 1999

The three methods of analysis (i) REV(representative elemental volume), (ii) non-REV and (iii) joint network analysis are introduced in this paper to analyze the groundwater flow in jointed rock mass and the inflow into underground excavations. The results from those methods are compared one another to reveal their characteristics by varying the number of joints and the diameter of the opening. The pre-processor, the so-called sequential analysis, is introduced to predict the equivalent hydraulic conductivity of a jointed rock mass having a number of intersecting joints. Using the finite element mesh, joint map and sequential analysis, the equivalent hydraulic conductivities are calculated for all 445 elements. The hydraulic inhomogeneity and the determination of the representative properties of jointed rock masses are discussed. In the REV analysis where the entire rock mass is homogenized through the representative properties, the inflow is increased regularly and consistently by increasing the joint density, the opening size and the conductivity contrast value. Though the non-REV analysis showed irregular variation of the inflow due to the local inhomogeneity allowed to individual elements, the inflow approached the REV results as the characteristic length increases. The joint network analysis showed the most sensitive reaction to the joint density, the opening size and the presence of the network crossing the opening. The reliability of the network analysis depends on the geometric data of individual joints. In view of the limited field data on joint geometry and possible uncertainty the REV and non-REV methods are considered more practical and rational than the joint network analysis.

• Journal of Korean Society for Geospatial Information Science
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• v.15 no.2 s.40
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• pp.59-66
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• 2007

The digital working environment and its related technology have been rapidly expanding. In the surveying field, we have changed from using optical film cameras and plotters to digital cameras, multi sensors like GPS/INS etc,. The old analog work flow is replaced by a new digital work flow. Accurate data of the land is used in various fields, efficient utilization and management of land, urban planning, disaster and environment management. It is important because it is an essential infrastructure. For this study, LiDAR surveying was used to get points clouds in the study area. It has a high vegetation penetrating advantage and we used a digital process from planning to the final products. Contour lines were made from LiDAR data and compared with national digital base maps (scale 1/1,000 and 1/5,000). As a result, the accuracy and the economical efficiency were evaluated. The accuracy of LiDAR contour data was average $0.089m{\pm}0.062\;m$ and showed high ground detail in complex areas. Compared with 1/1,000 scale contour line production when surveying an area over $100\;km^2$, approximately 48% of the cost was reduced. Therefore we prepose LiDAR surveying as an alternative to modify and update national base maps.

• Journal of Korea Water Resources Association
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• v.41 no.9
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• pp.895-905
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• 2008

To analyze hydrologic processes in a watershed requires both various geographical data and hydrological time series data. Recently, not only geographical data such as DEM(Digital Elevation Model) and hydrologic thematic map but also hydrological time series from numerical weather prediction and rainfall radar have been provided as grid data, and there are studies on hydrologic analysis using these grid data. In this study, GRM(Grid based Rainfall-runoff Model) which is physically-based distributed rainfall-runoff model has been developed to simulate short term rainfall-runoff process effectively using these grid data. Kinematic wave equation is used to simulate overland flow and channel flow, and Green-Ampt model is used to simulate infiltration process. Governing equation is discretized by finite volume method. TDMA(TriDiagonal Matrix Algorithm) is applied to solve systems of linear equations, and Newton-Raphson iteration method is applied to solve non-linear term. Developed model was applied to simplified hypothetical watersheds to examine model reasonability with the results from $Vflo^{TM}$. It was applied to Wicheon watershed for verification, and the applicability to real site was examined, and simulation results showed good agreement with measured hydrographs.

• Ecology and Resilient Infrastructure
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• v.2 no.1
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• pp.64-79
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• 2015

We investigated the tidal current, hydrographic data, and benthic environment of major sea cucumber (Holothuroidea, de Blainville, 1834) habitats in Baengnyeongdo, Jindo and Uljin to understand the optimal environmental or ecological habitat for sea cucumbers. The three study areas were characterized by a cold-water mass of temperatures ranging $12{\sim}18^{\circ}C$, with an active circulation between the surface and deep waters. According to an analysis of the tidal current map, a strong flow velocity of $100{\sim}120cm\;s^{-1}$ appeared in Baengnyeongdo and Jindo. The three sea cucumber habitats showed the common characters of a bottom sediment composed of sand-silt, a diverse seaweed colony and benthic organisms, and boulders and rocks which provide a hideout for the organisms. We aimed to draw the optimal habitat condition for sea cucumbers in Korea, and the result showed that the low water temperature, rapid water flow, active vertical mixing between surface and deep waters, bottom composed by sand-silt, large rocks, and diverse seaweed colony and benthic organism were important factors. The optimal habitat for Juvenile sea cucumbers was the intertidal areas characterized by a muddy bottom, reef, and seaweed. The optimal habitat for adult sea cucumbers was characterized by a place where sand and mud are mixed, and the body size of the sea cucumber was proportional to water depth, and the relatively large boulders and rocks compared to the intertidal area.

• Korean Journal of Agricultural and Forest Meteorology
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• v.9 no.4
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• pp.234-246
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• 2007

The role of macropore in the hydrological processes is important at the hillslope scale. Developments and distribution of macropores have not been investigated in conjunction with the characteristics of the hillslope such as topography, soil property, and soil moisture. In this study, macropore properties, such as macropore flow and saturation hydraulic conductivity were measured at a hillslope located in Gwangneung Research Forest, Pochun-gun, Gyeonggi-do, South Korea. An intensive field survey provided a refined Digital Elevation Model (DEM) for surface and subsurface topography. Spatial distributions of upslope area and topographic index were obtained through the digital terrain analysis. The total number of monitoring points was 22, and the selected points were distributed along the transect of the digital contour map. Vertical fluxes through macropores were measured using a tension infiltrometer at the depth of 0.1 m from the surface. Spatial and temporal distributions of soil moisture were obtained using an on-line measurement system, TRASE, installed in the study area. Soil moisture for the aforementioned points was measured at 0.1 and 0.3m depths below the surface. The results from tension infiltrometer experiments present that the macropore flows ranged between 21 and 94%, and the measured macroporosities varied from 1.4 to 47%. Macropore flows and macroporosities tended to increase as the measurement location moved to downslope. The ability for water conduction through macropores becomes increasingly developed as the location approaches the outlet of the hillslope.

• Journal of Environmental Science International
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• v.15 no.8
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• pp.775-784
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• 2006

In this study, CN value was estimated by using detailed soil map and land cover characteristic against upper basin of Kumho watermark located on the upper basin of Kumho river and the hydrologic morphological characteristic factors were extracted from the basin by using the DEM document. Also the runoff analysis was conducted by the WMS model in order to study how the assumed CN value affects the runoff characteristic. First of all, as a result of studying the soil type in this study area, mostly D type soil was Identified by the application of the 1987 classification criteria. However, by that in 1995, B type soil and C type soil were distributed more widely in that area. When CN value was classified by the 1995 classification criteria, it was estimated lower than in 1987, as a result of comparing the estimated CNs by those standars. Also it was assumed that CN value was underestimated when the plan for Geum-ho river maintenance was drawn up. As a result of the analysis of runoff characteristic, the pattern of generation of the classification criteria of soil groups appeared to be similar, but in the case of the application of the classification criteria in 1995, the peak rate of runoff was found to be smaller on the whole than in the case of the application of the classification criteria in 1987. Also when the statistical data such as the prediction errors, the mean squared errors, the coefficient of determination and other data emerging from the analysis, was looked over in total, it seemed appropriate to apply the 1995 classification criteria when hydrological soil classification group was applied. As the result of this study, however, the difference of the result of the statistical dat was somewhat small. In future study, it is necessary to follow up evidence about soil application On many more watersheds and in heavy rain.

• Current Research on Agriculture and Life Sciences
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• v.16
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• pp.37-44
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• 1998

The estimation of PMP (Probable Maximum Precipitation) and the analysis of characteristics of PMF (Probable Maximum Flood) according to the types of time distribution of rainfall and variations of base flow for the determination of design flood of major hydraulic structures in the watershed area of Wi stream were analysed. The PMP was estimated by the hydro-meteorological method suggested by the guideline of the World Meteorological Organization(WMO). The Blocking method was cited to transpose from PMP to PMS (Probable Maximum Storm) with time distribution. The unit hydrograph, applied for the estimation of PMF was derived by Clark's method. The summaryzed results : (1) The 72 hrs duration PMP in the area is 477.3mm which is 80mm less than the PMP map in Korea and 134 mm lager than the maximum precipitation of 342.9mm in Taegu, near the Wi stream watershed. (2) According to the types of time distribution and variations of base flow, the ranges of PMF for advanced type, central type and delayed type are 3,145.3~3,348.3cms, 3,774.6~3,977.7cms and 3,814.6~4,017.3cms, respectively. Those mean that peak discharge of advanced type is 600cms less than the central type and delayed type. (3) Delayed type among three types by Blocking method has been estimated the largest PMF of 4,017.3cms, and the advanced type has been estimated the smallest PMF of 3,145.3cms. The mean value of the peak PMF of 3,653.6cms may probably be resonable PMF in the Wi stream watershed. The mean PMF could probably be 1.7 times lager than the result of Gajiyama's equation. It is equivalent to the flood of return period 1,000 to 10,000 yrs.

• Ecology and Resilient Infrastructure
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• v.10 no.2
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• pp.40-49
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• 2023

To reduce the damage of extreme flooding caused by climate change and to create flood mitigation sections in a nature-friendly riparian area, it is necessary to restore the floodplain area by referring to the past floodplain section of the current inland waterfront area before the levee was built. This study proposed a method of selecting a location for floodplain restoration using old maps of the Geum River study section and analyzed the effect of flood level reduction through unsteady flow numerical simulations using the floodplain as a flood mitigation space. As a result of analyzing changes in the river areas using old maps, the river section was estimated to gradually reduce by 27.8% (1,059,380 m²) in 2020 compared to 1919, and it was found to have an effective storage capacity of 2,200,868 m³ when restored to offline storage. The flood level and discharge control effects analyzed based on HEC-RAS unsteady flow simulation were 16 cm and 219.01 m³/s, respectively, in the downstream cross-section. In the numerical simulation in this paper, the flood mitigation space was applied as an offline reservoir. The effect of reducing the flood level may differ if levee retreat/relocation is applied.