• Journal of the Korea Academia-Industrial cooperation Society
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• 제15권6호
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• pp.3950-3960
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• 2014

In this study, the drag forces on a submerged square cylinder were analyzed using a three dimensional hydrodynamic model. The numerical results were compared with the experimental results to check the reliability of the numerical simulations, and the characteristics of the drag forces with the relative depths were analyzed by analyzing the pressure acting on the cylinder surface, which are normally difficult to measure experimentally. The numerical results showed that the drag forces acting on a submerged square cylinder originate mainly from the pressure forces, and component of the shear forces decreased with increasing relative depth. The pressure coefficient distributions showed that in the case of a low relative depth, a relatively high pressure was formed in the front of a cylinder, and a relatively low pressure was formed in the rear, which gives a high drag coefficient. In a high relative depth, the pressure in the front decreased and pressure in the rear increased, which is a similar phenomenon to that normally observed in two dimensional square cylinder flow. The effect of the static pressure was analyzed and the surface elevation difference between the front and rear zone of a cylinder has a limited effect on the drag forces. Finally, the numerical results showed that the drag forces acting on a submerged square are dominated by the dynamic pressure formed by three dimensional flow and the distribution of local surface elevation.

• Proceedings of the KSRS Conference
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• 대한원격탐사학회 1999년도 Proceedings of International Symposium on Remote Sensing
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• pp.343-348
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• 1999

Delineation of watersheds is one of the most basic steps for water resource management and National Park management. The purpose of this study is to investigate how to utilize Thematic Mappers scenes to compare watersheds created by running a model with those produced by digitizing topographic maps of Keum River basin. A methodology is designed and tested using Geographic Information Systems (GIS) and remote sensing to map areas with various thematic maps. A CAD data on watersheds from the Decision Support system for Water Quality is converted into GIS format. The digital elevation model with 100-meter resolution is used to create watershed by cumulative watershed method. TM scenes are also classified by new procedures including stacking method, NDVI, NDWI, and unsupervised classification methods. To evaluate the relative correctness Kyerongsan National Park was studied intensively whose area was divided into 6 watersheds in both cases. The boundaries of watershed from the model are less correct than those of the topographic maps. This result shows that automated watershed creating system needs higher-resolution digital elevation model than 100-meters.

• Journal of The Korean Society of Agricultural Engineers
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• 제57권6호
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• pp.1-7
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• 2015

Most of chloride diffusion models based on finite difference method (FDM) could not express the diffusion in horizontal direction at each elevation. To overcome these weakness, two dimensional chloride ion penetration model based on finite element method (FEM) to be able to combine various multi-physics simultaneously was suggested by introducing moving mesh technique. To avoid the generation of mesh being able to be distorted depending on the relative movement of water level to static concrete, a rectangular type of mesh was intentionally adopted and the total number of meshes was empirically selected. The simulated results showed that the contents of surface chloride decreased following to the increase of elevation in the top part of low sea level, whereas there were no changes in the bottom part of low level. In the DuraCrete model, the diffusion coefficient of splashed zone is generally smaller than submerged zone, whereas the trend of Life365 model is reverse. Therefore, it could be understood that the developed model using moving mesh technique effectively reflects $DuraCrete^{TM}$ model rather than $Life365^{TM}$ model. In the future, the model will be easily expanded to be combined with various multi-physics models considering water evaporation, heat of hydration, irradiation effect of sun and so on because it is based on FEM.

• Journal of the Korean Solar Energy Society
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• 제23권3호
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• pp.23-28
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• 2003

The purpose of this study is to procure basic data to be used for solar power plant and concentrating collector designs. Site elevation is one of the major factors which influences the incoming insolation to the earth surface. Because the nonpermanent gases such as ozone, water vapor are unmixed components of the atmosphere and their concentrations are the function of height, the site elevation effects the relative proportion of the atmospheric constituents. We have measured solar radiation on Jiri Mt. (1,400m) and in Gurye area(115m) at the near same latitude. These values were then compared to obtain their characteristics and to investigate the potential for the solar utilization for both high and low elevated areas. From the experimental results, we concluded that 1) Daily mean horizontal global radiation and normal beam radiation on Mt. Jiri are 9.5%, and 35.3% higher than Gurye area respectively for a clear day. 2) A significant difference in atmospheric clearness index is observed between Mt. Jiri and Gurye areas.

• Journal of The Geomorphological Association of Korea
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• 제28권1호
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• pp.1-12
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• 2021

This study tried to reveal relative surface denudation resistance and ranking by geologic types in the Southern Korean Peninsula using an 1:250,000 digital geologic map and ASTER GDEM. Among rock types such as igneous, sedimentary and metamorphic rocks, metamorphic rock showed the greatest resistance to surface denudation. The most resistant rock to surface denudation by geologic periods (e.g., the Precambrian, Paleozoic, Mesozoic and Cenozoic) was found from the Precambrian. Among the major tectonic settings in the Southern Korean Peninsula such as the Gyeonggi massif, Okcheon belt, Yeongnam massif, Gyeongsang basin and Pohang basin, the Okcheon belt indicated the greatest resistance. The most and least resistant rocks from the representative nine rocks in the Southern Korean Peninsula were Paleozoic limestone, and Cretaceous sedimentary rock and Cenozoic sedimentary rock, respectively. This study suggests that Paleozoic limestone, Cretaceous volcanic rock, Paleozoic sedimentary rock and Precambrian gneiss can be regarded as hard rocks with high elevation, steep slope and complicated relief, while soft rocks with low elevation, gentle slope and simple relief are Jurassic granite, Cretaceous sedimentary rock and Cenozoic sedimentary rock.

• Journal of Ecology and Environment
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• 제44권3호
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• pp.162-177
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• 2020

Background: Ecologists have achieved much progress in the study of mechanisms that maintain species coexistence and diversity. In this paper, we reviewed a wide range of past research related to these topics, focusing on five theoretical bodies: (1) coexistence by niche differentiation, (2) coexistence without niche differentiation, (3) coexistence along environmental stress gradients, (4) coexistence under non-equilibrium versus equilibrium conditions, and (5) modern perspectives. Results: From the review, we identified that there are few models that can be generally and confidently applicable to different ecological systems. This problem arises mainly because most theories have not been substantiated by enough empirical research based on field data to test various coexistence hypotheses at different spatial scales. We also found that little is still known about the mechanisms of species coexistence under harsh environmental conditions. This is because most previous models treat disturbance as a key factor shaping community structure, but they do not explicitly deal with stressful systems with non-lethal conditions. We evaluated the mainstream ideas of niche differentiation and stochasticity for the coexistence of plant species across salt marsh creeks in southwestern Denmark. The results showed that diversity indices, such as Shannon-Wiener diversity, richness, and evenness, decreased with increasing surface elevation and increased with increasing niche overlap and niche breadth. The two niche parameters linearly decreased with increasing elevation. These findings imply a substantial influence of an equalizing mechanism that reduces differences in relative fitness among species in the highly stressful environments of the marsh. We propose that species evenness increases under very harsh conditions if the associated stress is not lethal. Finally, we present a conceptual model of patterns related to the level of environmental stress and niche characteristics along a microhabitat gradient (i.e., surface elevation). Conclusions: The ecology of stressful systems with non-lethal conditions will be increasingly important as ongoing global-scale climate change extends the period of chronic stresses that are not necessarily fatal to inhabiting plants. We recommend that more ecologists continue this line of research.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• 제32권1호
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• pp.19-27
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• 2014

Kompsat-3 is an optical high-resolution earth observation satellite launched in May 2012. In addition to its 0.7m spatial resolution, Kompsat-3 is capable of in-track stereo acquisition enabling quality Digital Elevation Model(DEM) generation. Typical DEM generation procedure requires accurate control points well-distributed over the entire image region. But we often face difficult situations especially when the area of interests is oversea or inaccessible area. One solution to this is to use existing geospatial data even though they only cover a part of the image. This paper aimed to assess accuracy of DEM from Kompsat-3 with different scenarios including no control point, Rational Polynomial Coefficients(RPC) relative adjustment, and RPC adjustment with control points. Experiments were carried out for Kompsat-3 stereo data in USA. We used Digital Orthophoto Quadrangle(DOQ) and Shuttle Radar Topography Mission(SRTM) as control points sources. The generated DEMs are compared to a LiDAR DEM for accuracy assessment. The test results showed that the relative RPC adjustment significantly improved DEM accuracy without any control point. And comparable DEM could be derived from single control point from DOQ and SRTM, showing 7 meters of mean elevation error.

• Journal of Periodontal and Implant Science
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• 제36권2호
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• pp.345-359
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• 2006

Loss of maxillary molar teeth leads to rapid loss of crestal bone and inferior expansion of the maxillary sinus floor (secondary pneumatization). Rehabilitation of the site with osseointegrated dental implants often represents a clinical challenge because of the insufficient bone volume resulted from this phenomenon. Boyne & James proposed the classic procedure for maxillary sinus floor elevation entails preparation of a trap door including the Schneiderian membrane in the lateral sinus wall. Summers proposed another non-invasive method using a set of osteotome and the osteotome sinus floor elevation (OSFE) was proposed for implant sites with at least 5-6mm of bone between the alveolar crest and the maxillary sinus floor. The change of grafted material in maxillary sinus is important for implant survival and the evaluation of graft height after maxillary sinus floor elevation is composed of histologic evaluation and radiomorphometric evaluation. The aim of the present study was radiographically evaluate the graft height change after maxillary sinus floor elevation and the influence of the graft material type in height change and the bone remodeling of grafts in sinus. A total of 59 patients (28 in lateral approach and 31 in crestal approach) who underwent maxillary sinus floor elevation composed of lateral approach and crestal approach were radiographically followed for up to about 48 months. Change in sinusgraft height were calculated with respect to implant length (IL) and grafted sinus height(BL). It was evaluated the change of the graft height according to time, the influence of the approach technique (staged approach and simultaneous approach) in lateral approach to change of the graft height, and the influence of the type of graft materials to change of the graft height. Patients were divided into three class based on the height of the grafted sinus floor relative to the implant apex and evaluated the proportion change of that class (Class I, in which the grafted sinus floor was above the implant apex; Class II, in which the implant apex was level with the grafted sinus floor; and Class III, in which the grafted sinus floor was below the implant apex). And it was evaluated th bone remodeling in sinus during 12 months using SGRl(by $Br\ddot{a}gger$ et al). The result was like that; Sinus graft height decreased significantly in both lateral approach and crestal approach in first 12 months (p$MBCP^{TM}$ had minimum height loss. Class III and Class II was increased by time in both lateral and crestal approach and Class I was decreased by time. SGRI was increased statistically significantly from baseline to 3 months and 3 months(p<0.05) to 12 months(p$ICB^{(R)}$ single use, more reduction of sinusgraft height was appeared. Therefore we speculated that the mixture of graft materials is preferable as a reduction of graft materials. Increasing of the SGRI as time goes by explains the stability of implant, but additional histologic or computed tomographic study will be needed for accurate conclusion. From the radiographic evaluation, we come to know that placement of dental implant with sinus floor elevation is an effective procedure in atrophic maxillary reconstruction.

• Journal of Korea Water Resources Association
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• 제41권4호
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• pp.365-377
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• 2008

In this study, PROMETHEE(Preference Ranking Organization METHod for Enrichment Evaluations) which is one of the multi criteria decision making methods is applied to estimate the relative inundation risk of the urban subcatchment. For this purpose, several factors which have an effect on the inundation risk are selected and used to perform PROMETHEE. Those are elevation average, slope average, density of conduit, population and sediment yields per unit area of each subcatchment. Based on them, PROMETHEE is performed and the relative inundation risk for each subcatchment is estimated. For the validation of the suggested method, the results from the suggested method are compared with the historical inundation records occured on 1998 and the relative inundation risk estimated by the method considering sediment yields per unit area only. From the comparison, it is found that the suggested method may generate better results to estimate the relative inundation risk of each subcatchment than the method considering sediment yields per unit area only. Also, it can be applied to establish a rehabilitation order of subcatchments for mitigating the inundation risk.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• 제8권1호
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• pp.36-49
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• 1998

The purpose of this study is to investigate the relationship between the work postures and upper extremity cumulative trauma disorders(CTDs) in female medical insurance bill reviewers(n=448). This study included diagnosis for CTDs, anthropometry and job analysis (workstations and posture). The characteristics of subject were 33.6 years of average age and 8.7 years of average work duration. The results were as fallows. Ergonomic conditions of workstation were unsuitable compared with anthropometry result. The height of work surface(79.5 cm) and chair(43.0 cm)were high. work space was small, and legs space under the table was limited. Work postures were awkward compared with recommended neutral postures. Neck flexion($21.0-36.0^{\circ}$), elbow elevation, shoulder abduction ($46.0-47.0^{\circ}$). wrist radial and ulnar deviation, forearm supination and pronation, and wrist repeated motion(12.7-21.5 freq./min) were analyzed as hazardous risk factors by job analysis. The prevalence of CTDs was 32.8 % by medical diagnosis. The prevalence rate of CTDs in hazardous work posture group was significantly greater than safe work posture group both neck-shoulder (relative prevalence = 5.2, p<0.001) and wrist-hand (relative prevalence = 2.5, p<0.05).