• Journal of Korea Water Resources Association
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• v.45 no.7
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• pp.643-656
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• 2012

There has been an increase for the landslide areas and restoration expenses due, in large part, to the increased locally heavy rains caused by recent climate change as well as the reckless development. This study carried out a slope stability analysis by the application of distributed wetness index, using the GIS-based infinite slope stability model, which took the root cohesion effect into consideration, for part of Mt. Umyeon in Seoul, where landslide occurred in July 2011, in order to compensate the defects of existing analysis method, and subsequently compared its result with the case on the exploitation of lumped wetness index. In addition, this study estimated the distributed wetness index by methodology, applying three methods of specific catchment area calculation: single flow direction (SFD), multiple flow direction (MFD), and infinity flow direction (IFD), for catchment area, one of the variables of distributed wetness indices, and finally implemented a series of comparative analysis for slope stability by methodology. The simulation results showed that most unstable areas within the study site were dominantly located in cutting-area surroundings along with the residential area and the mountaintop and unstable areas of IFD and lumped wetness index method were similar while SFD and MFD provided smaller unstable areas than the two former methods.

• Korean Journal of Agricultural and Forest Meteorology
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• v.18 no.4
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• pp.378-388
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• 2016

International societies are currently working together to achieve the Climate-Smart Agriculture (CSA) initiative which aims the triple wins: (1) sustainably increasing agricultural productivity and incomes; (2) adapting and building resilience to climate change; and (3) mitigating greenhouse gases emissions. In terms of its scope and context, CSA follows the '3Nong (三農)' vision cast about 200 years ago by Dasan Jeong Yak-Yong who emphasized the triad of governance, management and monitoring towards comfortable, profitable and noble agriculture. Yet, the CSA provides the practical aims that facilitate the development of holistic indicators for quantitative evaluation and monitoring, on which decision-making support system is based. In this study, we introduce an agent-based model, i.e. Mathematical Programming Multi-Agent Systems (MP-MAS), as a tool for supporting the decision-making toward CSA. We have established the initial version of MP-MAS adapted for domestic use and present the preliminary results from an application to the rice farming case in Haenam, Korea. MP-MAS can support both farmers and policy-makers to consider diverse management options from multiple perspectives. When the modules for system resilience and carbon footprint are added, MP-MAS will serve as a robust tool that fulfills not only CSA but also Dasan's '3Nong' vision of sustainable agricultural-societal systems.

• Journal of Elementary Mathematics Education in Korea
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• v.23 no.1
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• pp.19-41
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• 2019

In this study, we present an analysis framework based on the 2015 revised curriculum to analyze how mathematical contents and achievement standards for domains of numbers and computations have changed in the curriculum of elementary mathematics in Korea. Based on this, we classified the achievement standards by type and investigated their characteristics. The achievement standards for numbers and computations can be divided into the successive, the extinctive, and the additive achievement standards depending on their characteristics. The successive achievement standards are the ones that have consistently existed without being removed from the 1-st curriculum to the latest revision in 2015. The extinctive achievement standards are the ones that have been removed at some point during the revisions of nine times and do not remain in the current revision in 2015. The characteristics of the extinctive achievement standards were analyzed to be different before and after the 4-th curriculum. The additive achievement standards refer to the ones that have been newly added to the curriculum or that have been removed at a certain moment but added back in later and thus exist in the current revision in 2015. The characteristics of each type according to the changes of the achievement standards can be thought to be the results that the revision for the mathematics curriculum in Korea has been faithfully conducted. Based on the results of this study, we suggest some implications for organizing the achievement standards in the future curricular development.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.7 no.1
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• pp.75-90
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• 1995

A mathematical model for the dynamic analysis of a riser system with the inclusion of internal flow and nonlinear effects due to large structural displacements is developed to investigate the effect of internal flow on marine riser dynamics. The riser system accounts fir the nonlinear boundary conditions and includes a steady flow inside the pipe which is modeled as an extensible or inextensible. tubular beam subject to nonlinear three dimensional hydrodynamic loads such as current or wave excitation. Galerkin's finite element approximation and time incremental operator are implemented to derive the matrix equation of equilibrium for the finite element system and the extensibility or inextensibility condition is used to reduce degree of freedom of the system and the required computational time in the case of a nonlinear model. The algorithm is implemented to develop computer programs used in several numerical applications. The investigations of the effect of infernal flow on riser vibration due to current or wave loading are performed according to the change of various parameters such as top tension, internal flow velocity, current velocity, wave period, and so on. It is found that the effect of internal flow can be controlled by the increase of top tension. However, careful consideration has to be given in the design point particularly for the long riser under the harmonic loading such as waves. And it is also found that the consideration of nonlinear effects due to large structural displacements increases the effect of internal flow on riser dynamics.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.5
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• pp.305-315
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• 2016

Due to the change from small volume production to small quantity batch production systems, individual companies have been attempting to produce a wide range of operating strategies, maximize their productivity, and minimize their WIP level by operating with the proper cycle time to defend their market share. In particular, using a complex workflow and process sequence in the manufacturing line has some drawbacks when it comes to designing the production strategy by applying analytical models, such as mathematical models and queueing theory. For this purpose, this paper uses three heuristic algorithms to solve the job release problem at the bottleneck workstation, product mix problem in multi-purpose machine(s), and batch size and sequence in batch machine(s). To verify the effectiveness of the proposed methods, a simulation analysis was performed. The experimental results demonstrated that the combined application of the proposed methods showed positive effects on the reduction of the cycle time and WIP level, and improvement of the throughput.

• Journal of Soil and Groundwater Environment
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• v.11 no.3
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• pp.52-58
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• 2006

Kim and Lee (2005) suggested Minimum Entropy Deconvolution (MED) to estimate the temporal sequence of the relative recharge. However this study by Kim and Lee (2005) was just related to the verification of the conceptual approach with MED. In this study, we try to characterize the applicability of MED in the case of spatially heterogeneous recharge (distance from recharge area). Simulated results were recorded with some specific sampling points. Estimated results from this study show higher than 0.8 in cross-correlation with the original recharge sequence. In addition, the physical and mathematical meanings of the applied filter length was also investigated. It was revealed that the length of filter is highly related to the spatial distance between recharge area and the monitoring site, and the apparent shape of hydraulic head change.

• Journal of Wetlands Research
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• v.20 no.1
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• pp.1-13
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• 2018

Glaux maritima var. obtusifolia is distributed in very limited areas in South Korea and thus designated and protected as an endangered species. This study aimed to identify the diversity of vegetation in the Dangsa coast wetlands, the southern limit of G. maritima var. obtusifolia and to assess determinants of the vegetation and the importance of habitats. The phytosociological method of the $Z{\ddot{u}}rich-Montpellier$ School was used for vegetation classification and mathematical and statistical analyses were also conducted to analyze environmental factors and their relationship with the vegetation. The results of this study showed that there were 4 vegetation units in the Dangsa coast wetlands: Glaux maritima var. obtusifolia-Triglochin maritimum community (included three subcommunities), Puccinellia nipponica s.l. community, Beckmannia syzigachne-Isachne globosa community and Typha laxmannii-Phragmites communis community. It was also found that major determinants of the vegetation include moisture environment, soil depth, water level disturbance, vegetation height, community structure, etc. Glaux maritima was identified to grow most dominantly in the typicum subassociation of Glaux. maritima var. obtusifolia-Triglochin maritimum community, and the species compositions and dominant situations were observed to be similar to those in the southern limit in Japan, adjacent to South Korea. The assessment results indicated that the Dangsa coastal wetlands have a significant meaning from phytogeographical and syngeographical aspects, and contribute as a shelter for diverse species. It is required to establish conservation strategies to accurately determine the value of the wetlands of the Dangsa coast from various perspectives, and to protect and manage them.

• Journal of Korean Ophthalmic Optics Society
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• v.14 no.3
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• pp.17-27
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• 2009

Purpose: This review article was written to determine the effects of parameters characterizing a hard contact lens (RGP included), such as BCs, diameters, edge angles, on the time interval for tight fitted lens to return to the equilibrium when it was decentered from blinking. Methods: A mathematical formulation was established to relate or calculate the restoring forces and thickness of lacrimal layer beneath the cornea with the various lens parameters when the tight fitted lens was decentered from blinking. Based on this formulation the differential equations and their numerical solution program were set up to describe the time dependence of the lens on the position and to estimate the time for the lens's return to the equilibrium after blink. Results: It is found that the time interval for the tight fitted lens to return to the equilibrium decreases as either the BC decreases or the diameter increases because both the reduction in BC and increase in diameter result in the increase in the lacrimal layer thickness between the lens and cornea increase which yielded the lowering of the viscous friction in the lens motion. As the edge angle of tight fitted lens increases the time for recentering decreases due to the increase in restoring force without change in lacrimal thickness beneath the lens. In the case of flat fitted hard lens (RGP included), the lacrimal layer thickness under the lens increases as either BC or diameter increases which results in reduction in viscous friction so that the time for the lens's return to the equilibrium were to decrease. The edge angle of flat fitted lens does not affect the lens motion. Conclusions: The effect of BCs on the lens motion (time to approach the equilibrium) was concluded to be significant with both tight and flat fitted lens where its results are contrary with each other. The edge angle of lens only affects the motion in tight fitted lenses.

• Journal of the Korean Society of Radiology
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• v.7 no.4
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• pp.259-264
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• 2013

Total body irradiation in the treatment of childhood leukemia, which is one of the pre-treatment with stem cell transplantation is being used, the current organization using compensators are treated. However, under the terms of the compensator organization long-term impact on the human body, it is difficult to assess directly. In this study, we use the mathematical simulation of radiation exposures body energy and the distance to the crew and the patient (source surface distance, SSD), and patients with tissue compensators change of the distance along the body of the organ doses were evaluated. As a result, the surface dose of energy 4 MV, SSD 280 cm, tissue compensators and the patient when the distance 30 cm 5.84 G / min showed the highest levels. In addition, patients with tissue compensators and the distance apart when 30 cm TBI represents the ideal dose distribution was found.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.135-142
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• 2017

This study employs an analytical mathematical model to estimate the optimal debt ratio of Korean agricultural corporations, more sensitive to the government debt ratio policy compared to other industries, and the estimation of the optimal debt ratio based on objective data. The analytical model utilizes the equation for ROE, with the debt ratio as an independent variable, and related parameters include ROS, TAT, and NFCL. Regarding the NFCL, the optimal debt ratio standard is defined as the debt ratio that maximizes the ROE by analytical procedures such as adding an equation concerning the debt ratio and a linearity relationship to the analytical model, and from these equations, a quadratic equation with the debt ratio as an independent variable describes the ROE. This methodemploys fourteen years of corporate data. Results show that 138% of debt ratio is the optimal debt ratio to increase the ROE of the corporations, which implies that the existing debt ratio of Korean agricultural corporations is higher than optimal. Consequently, it is required for authorities to change future debt ratio policies in view that the purpose of debt ratio management is to maintain safety and increase profitability.Management should emphasize characteristics of the specific industry rather than standardized judgements based on numerical indexes.