• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.1
• /
• pp.679-687
• /
• 2017

This study examines financial factors affecting cash holdings of firms in the domestic capital markets. Specifically, this study focuses on regional firms with headquarters in Chungcheong province, the Republic of Korea, which features little previous research concentrating on the firms in the particular region. Three primary hypotheses were empirically tested utilizing robust econometric models, including static panel data, Tobit regression, and logistic models.Results reveal only five explanatory variables, including DSO, LIQUID, LEVERAGE, PMARGIN, and SIZE, showed statistically significant effects on the level of cash holdings among the nine variables studied. In addition two IDVs, LEVERAGE and FOS, showed significant differentiated effects between firms with headquarters in North and South Chungcheong regions. With continued debate among interested parties on the optimal level of cash reserves, the study provides a new vision for the optimal cash reserves for firms with headquarters in Chungcheong Province, where unprecedented socio-economic factors are driven.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2023.05a
• /
• pp.404-404
• /
• 2023

최근 국지성 집중호우 등 기상이변의 영향으로 침수피해의 위험성은 점차 증가하는 추세이고, 도시화로 인한 불투수면적의 증가, 녹지공간의 감소, 도시의 난개발 등 물순환 체계의 왜곡에 따른 침수로 인한 피해가 다수 발생하고 있다. 침수 발생 시 막대한 인적 및 물적 피해가 발생할 수 있기에 재난초기에 재난관리자원의 신속한 확보와 동원은 피해확산 방지에 매우 중요하고, 자원의 부족이나 동원의 지연으로 초기 대응이 늦어질 경우 피해가 확대될 수 있기에 침수발생 특성에 따른 필요 자원의 비축 및 동원이 필요하다. 하지만, 재난관리자원은 종류가 다양하고 요구되는 비축량이 많기에 모든 재난관리자원을 보유하고, 활용하기에는 어려움이 따른다. 따라서 침수피해재난을 중심으로 최적 자원 비축을 통한 효율적인 재난관리자원 운영 및 관리체계의 마련이 필요하다. 본 연구에서는 과거 20년(2001년~2020년) 동안 발생한 침수피해 관련 재난(호우, 태풍, 풍랑)사례를 통해 재난발생 시 동원된 자원현황을 분석하였다. 재해연보, 관련 백서 및 보고서, 침수흔적도 등의 수집 및 분석을 통해 지자체 침수피해 현황을 분류하고, 침수재난과 관련된 자원의 비축 및 운용 사례 분석을 통해 장비 28종, 자재 6종을 확인하였다. 본 연구는 침수재난 발생 시 지자체별 침수피해 규모와 필요한 재난관리자원을 도출한 점에서 그 의미가 있으며, 향후 재난관리자원의 효율적인 비축 및 관리계획 수립에 기초자료로 활용할 수 있을 것으로 기대된다.

• Journal of Korea Spatial Information System Society
• /
• v.9 no.3
• /
• pp.25-33
• /
• 2007

The local governments of major cities in Korea are giving focus on public transportation to reduce congestion and improve accessibility in city areas. In this regards, the proper measurement of accessibility is now a key policy requirement for reorganizing the public transport network. Public transport routing problems, however, are considered to be highly complicated since a multi-mode travel generates different combinations of accessibility. While most of the previous research efforts on measuring transport accessibility are found at zone-levels, an alternative approach at a finer scale such as bus links and stops is presented in this study. We proposes a method to compute the optimal route choice of origin-destination pairs and measure the accessibility of the chosen modes combination based on topological configuration. The genetic algorithm is used for the computation of the journey paths, whereas the space syntax theory is used for the accessibility. This study used node-link data in GIS instead of axial lines which are manually drawn in space syntax. The resulting accessibilities of bus stops are calibrated by O-D survey data and the proposed process is tested on a CBD of Seoul.

• Journal of the Korean Geographical Society
• /
• v.41 no.3 s.114
• /
• pp.319-330
• /
• 2006

The objective of this research is to achieve an objectivity of site decision after extracting site decision factors on a large-scale discount store(LSDS) and utilize any hidden information using the association rules mining through huge database. To catch this objective, we collect a census, economic, and environmental dataset related with locating of LSDS. And then, we construct a spatial data on the research area. These data is used for the extraction of a spatial association rules. To verify whether the extracted rules are suitability or not, we use the sales of some LSDS. As the result of test, the more sales, the more factors of the extracted rules relate with the sales it coincides. Consequently, the spatial association rules mining is efficient method which support the ideal site decision of LSDS.

• Korean Journal of Remote Sensing
• /
• v.36 no.2_1
• /
• pp.179-197
• /
• 2020

Topographic normalization reduces the terrain effects on reflectance by adjusting the brightness values of the image pixels to be equal if the pixels cover the same land-cover. Topographic effects are induced by the imaging conditions and tend to be large in high mountainousregions. Therefore, image analysis on mountainous terrain such as estimation of wildfire damage assessment requires appropriate topographic normalization techniques to yield accurate image processing results. However, most of the previous studies focused on the evaluation of topographic normalization on satellite images with moderate-low spatial resolution. Thus, the alleviation of topographic effects on multi-temporal high-resolution images was not dealt enough. In this study, the evaluation of terrain normalization was performed for each band to select the optimal technical combinations for rapid and accurate wildfire damage assessment using PlanetScope images. PlanetScope has considerable potential in the disaster management field as it satisfies the rapid image acquisition by providing the 3 m resolution daily image with global coverage. For comparison of topographic normalization techniques, seven widely used methods were employed on both pre-fire and post-fire images. The analysis on bi-temporal images suggests the optimal combination of techniques which can be applied on images with different land-cover composition. Then, the vegetation index was calculated from the images after the topographic normalization with the proposed method. The wildfire damage detection results were obtained by thresholding the index and showed improvementsin detection accuracy for both object-based and pixel-based image analysis. In addition, the burn severity map was constructed to verify the effects oftopographic correction on a continuous distribution of brightness values.

• Journal of the Korea Society of Computer and Information
• /
• v.25 no.10
• /
• pp.59-67
• /
• 2020

With the development of wearable devices, individuals' health status can be checked in real time and risks can be predicted. For example, an application has been developed to detect an emergency situation of a patient with heart disease and contact a guardian through analysis of health data such as heart rate and electrocardiogram. However, health data is seriously damaging when it is leaked as it relates to life. Therefore, a method to protect personal information is essential in collecting health data, and this study proposes a method of collecting data while protecting the personal information of the data owner through a LDP(Local Differential Privacy). The previous study introduced a technique of transmitting feature point data rather than all data to a data collector as an algorithm for searching for fixed k feature points. Next, this study will explain how to improve the performance by up to 75% using an algorithm that finds the optimal number of feature points k.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.22 no.1
• /
• pp.29-36
• /
• 2004

This study describes the development of coordinate transformation tool for transforming the digital map using newly derived transformation parameters which are determined from the data referred to the local geodetic datum and the geocentric datum (ITRF2000) and the distortion modelling derived from collocation method. We prepared 190 common points and used 107 points to calculate 7 transformation parameters. In order to evaluate an accuracy of coordinate transformation, 83 common points were tested. In this study, we used Molodensky-Badekas model to derive the 7 transformation Parameters. An accuracy of 0.22m was obtained applying 7 Parameters transformation and the distortion modelling together. It shows that the accuracy of coordinate transformation is improved 72% against the result of 7 parameters transformation only. We developed the transformation tool, GDKtrans, which can be transformed the digital map of scales 1/50,000, 1/25,000 and 1/5,000. We also analyzed the digital map of l/5,000 at six urban areas by GPS observations. The result shows less RMSE of about 1.9 m and large disagreement at position and features. Consequently, we suggests that l/5,000 digital map is necessary of whole revision.

• KIPS Transactions on Software and Data Engineering
• /
• v.3 no.9
• /
• pp.369-374
• /
• 2014

Path generation methods are required for safe and efficient driving in unmanned autonomous vehicles. There are two kinds of paths: global and local. A global path consists of all the way points including the source and the destination. A local path is the trajectory that a vehicle needs to follow from a way point to the next in the global path. In this paper, we propose a novel method for local path generation through machine learning, with an effective curve function used for initializing the trajectory. First, reinforcement learning is applied to a set of candidate paths to produce the best trajectory with maximal reward. Then the optimal steering angle with respect to the trajectory is determined by training an artificial neural network. Our method outperformed existing approaches and successfully found quality paths in various experimental settings, including the cases with obstacles.

• Journal of Korean Society of Transportation
• /
• v.10 no.1
• /
• pp.55-62
• /
• 1992

교통수요는 교통정책 및 교통시설 계획의 수립 및 평가에 중요한 영향을 미치게 되므로 교통수요의 예측은 교통연구에서 중요한 부문을 차지하고 있다. 도로밑에 설치된 전자차량감지기(Electronic Vehicle Detector)로부터 자동 수집된 링크 교통량 자료(Traffic Counts)를 주요 입력자료로 이용하여 계획지역의 기종점 통행표(Origin Destination Trip Matrix)를 작성할 수 있는 기법 들이 최근 수년동안 많이 발달하게 되었다. 이러한 새로운 기법들은 가구조사(Home Inteview), 노변면접조사(Road-Side Interview)등을 토하여 조사된 자료를 기초로하는 전통적은 4단계 교통수요추정방법(Conventional 4-Stage Estimation Method)-통행발생(Generation), 통행분포(Distribution), 수단선택(Modal Split), 교통배분(Assignment)-과 비교하여 첫째로 정확도가 높은 링크 교통량 자료를 별도의 조사를 거치지 않고서도 수집이 가능하기 때문에 조사비용이 거의 들지 않아도 되어 경제적이고, 둘째로 전통적인 수요예측방법들에서 요구되어지는 복잡한 모형수립 및 계수조정(Parameter Calibration)이 필요하지 않아 간편하고 셋째로 오래전에 작성된 기종점 통행표를 단순히 링크 교통량 자료만을 이용하여 쉽게 보완할 수 있어 지속적인 자료의 축적(Data Age-ing)이 가능하며 더 나아 가서 소위 연속적인 교통 계획 및 교통시설관리(Continuous Transport Planning and Management)를 가능케 하는 등의 여러 장점 때문에 많은 주목을 받아 오고 최근 몇 년이 꾸준히 실무에 유용하게 적용이 되고 있는 실정이다. 본 연구는 링크 교통량자료를 이용하여 기종점 통행표를 작성하기 위하여 개발된 기존의 여러 기법들 가운데 특히 용량제약조건(Capacity-Restrained Condition)하에서 기존의 방법들을 상호 검토한 후 Wardrop의 교통망 평형원칙(Wardrop's First Network Equilibrium Principle)을 만족하는 새로운 추정기법을 제의하고 이의 시험결과를 논의하는 것을 주요내용으로 한다. 링크 교통량 자료를 이용하여 기종점 통행표를 작성하는 기법들의 근본 목표는 조사된 링크 교통량(Ob-served Traffic Counts)에 가장 근접한 교통망 통행 배정 링크 교통량(Assigned Link Volumes)을 재현(Re-producing)할 수 있는 기종점 통행표들 중에서 최적의 기종점 통행표를 발견하는 것이다. 따라서 교통망에서 통행자의 여행 경로 배정을 가장 잘 반영할 수 있는 현실적인(Realistic) 교통망 통행 배정 모형(Net-work Traffic Assignment Model)의 선택은 중요한 요소가 되며 특히 교통망에 교통체증(Traffic Conges-tion)이 심할 경우 교통망 통행자 평형조건(Network Traffic Equilibrium Condition)을 고려하기 위한 특별한 처리가 요구되어진다. 본 연구는 Whllumsen(Hall, Van Vliet and Willumsen, 1980)에 의하여 개발된 ME2(Maximum Entropy Matrix Estimation)기법에서 반복식 추정방법(Sequential Estimation Method)을 사용할 경우 Wardrop의 평형조건을 만족하는 기종점 통행표를 구할 수 없다는 단점을 극복하기 위한 방안으로서 엔트로피 극대화문제와 교통망 평형 조건(Entropy Maximisation and Network Equilibrium Condition)의 두 문제를 동시에 해결할 수 있는 새로운 수식모형과 이를 풀기 위한 알고리즘(Simultaneous Solution Algorithm)을 제의하였다. 제의된 수식모형과 알고리즘을 예제 교통망(Example Network)을 이용한 시험하고 그 결과를 ME2 의 반복식 추정 방법으로부터 구한 기종점 통행표와 비교 검토하였다.

• Journal of Bio-Environment Control
• /
• v.32 no.4
• /
• pp.278-284
• /
• 2023

Recently, a closed-type plant factory has been receiving attention as a advanced agricultural method. It has diverse advantages such as climate-independence, high productivity and stable year-round production. However, high energy cost caused by environmental control system is considered as a challenges of a closed-type plant factory. In order to reduce the energy cost, investigation about energy load which is directly connected to energy consumption needs to be conducted. In this study, energy load changes of a plant factory have been analytically analyzed according to the environmental changes. The target plant factory was a lettuce growing container farm. Firstly, the impact of photoperiod, set temperature and relative humidity change were examined. Under the climate condition of Daejeon in South Korea, increase of photoperiod and set temperature rose a yearly energy demand of a container farm. However, increase of set relative humidity decreased a yearly energy demand. Secondly, the climate environment effect was compared by investigating the energy demand under 9 different climate conditions. As a result, the difference between maximum and minimum value of the yearly energy demand showed 21.7%. Lastly, sensitivity analysis of each parameter (photoperiod, set temperature and relative humidity) has been suggested under 3 different climate conditions. The ratio of heating and cooling demand was varied depending on the climate, so the effect of each parameter became different.