• Korean Journal of Agricultural and Forest Meteorology
• /
• v.16 no.2
• /
• pp.93-102
• /
• 2014

This quantitative research aims to examine the connectivity of forest networks in seven metropolitan cities of South Korea using a graph-theoretical approach. We first estimated an overall network connectivity at multi-scales (i.e., dispersal distances), ranging from 100 m to 20 km, and quantified the contribution of small forest patches (less than 10 ha) to the overall network connectivity by comparing networks according to the presence and absence of small ones. As a result, the cities were divided into two groups depending on the network connectivity; one group of cities with high connectivity such as Daegu, Daejeon, and Ulsan and the other group of cities with low connectivity including Gwangju, Busan, Seoul, and Incheon. The result showed that small forest patches, especially in the cities with low connectivity, played a key role as stepping stones that connect large forested patches, thereby contributing to maintaining connectivity. This study also suggests that large and well-connected forest areas may be the key factor to preserve the connectivity in the cities with high connectivity, while the cites with low connectivity are in need of some complementary strategies. Through the study, we suggest that the creation of new forest patches in the areas where a gap in connectivity presents is needed in order to improve connectivity; and that the conservation of the existing small forest patches is essential in order to maintain the current connectivity level.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.39 no.6
• /
• pp.526-534
• /
• 2011

The MFS (Mlti-Functional Structure) concept, which integrates the electronics, thermal control and structure into a single packaging system, has been developed and applied to reduce the volume and weight of the satellite. Therefore, this MFS can eliminate the bulky chassis/frames, cables and connectors of the electronic equipment. The main point of this traditional MFS is the replacement of the electrical chassis/frames with MCMs (Multi-Chip Modules) that require much costs and efforts for developing. This paper shows the new MFS concept that effectively saves the volume and weight. The structure including the thermal control and radiation shielding elements will be designed and manufactured as the rectangular grid-stiffened structure. The rectangular grid-stiffened structure is the modification of the iso-grid structure, and provides the enough spaces for putting the general PCBs without the chassis/frames.

• Tunnel and Underground Space
• /
• v.11 no.3
• /
• pp.279-288
• /
• 2001

Jointed rock mass can be analyzed by either continuum model or discontinuum model. Finite element method or finite difference method is mainly used for continuum modelling. Although discontinuum model is very attractive in analyzing the behavior of each block in jointed blocky rock masses, it has shortcomings such that it is difficult to investigate each joint exactly with the present technology and the amount of calculation in computer becomes trio excessive. Moreover, in case of the jointed blocky rock mass which has more than 2 dominant joint sets, it is impossible to model the behavior of each block. Therefore, a model such as ubiquitous joint model theory which assumes the rock mass as a continuum, is required. In the case of tunnels, unlike slopes, it is not easy to obtain safety factor by utilizing analysis method based on limit equilibrium method because it is difficult to assume the shape of failure surface in advance. For this reason, numerical analyses for tunnels have been limited to analyzing stability rather than in calculating the safety factor. In this study, the behavior of a tunnel excavated in jointed rock mass is analyzed numerically by using ubiquitous joint model which can incorporate 2 joint sets and a method to calculate safety factor of the tunnel numerically is presented. To this end, stress reduction technique is adopted.

• Tunnel and Underground Space
• /
• v.9 no.1
• /
• pp.48-55
• /
• 1999

One of the major roles of concrete lining is the supplementary support of ground load. Therefore, if there are cracks or deformation found in the lining, the causes should be carefully examined. Tunnel Soundness Evaluation System (DW-TSES) was developed to meet such requirements. Main facility of the system was intended to find the probable causes on the basis of the apparent changes in lining and the environmental conditions. It also includes facilities for evaluating the soundness of a tunnel and indicating the method for repair or reinforcement. The characteristic feature of damages is used for reasoning in case of deterioration and leakage, and artificial neural network is used in external pressure. This process depends on the results of the case analyses and FDM, which have a collection of the typical features of different types of damages as well as the unusual changes caused by the external pressure. The comparison of the outputs of this system with those of expert's diagnoses draws the following conclusions. 1) Artificial neural network was a suitable tool to find to causes of damages by external pressure. 2) The environmental conditions improved the accuracy in reasoning. 3) The result of finding causes and evaluating soundness was helpful to suggest effective methods concerning tunnel maintenance.

• Tunnel and Underground Space
• /
• v.28 no.1
• /
• pp.111-124
• /
• 2018

The purpose of this study is to analyze ventilation design factor for network-type double-deck road tunnel that have been developed actively around the world. A numerical analysis was carried out through computational fluid dynamics (CFD) to derive shock loss coefficient that occurs due to the change in cross sectional area at both merging section and diverging section. The model used for the numerical analysis is real-scale model and the reliability of the result is secured by comparing with the coefficient of the previous studies. As a result of this study, shock loss coefficient was calculated depending on the change in cross-sectional area ratio and was higher than the result of previous studies in case of both merging section and diverging section. It is considered that the characteristics of the geometrical structure of network-type double-deck road tunnel have a great impact on shock loss coefficient. Therefore, the result of this study is expected to be helpful for more accurate ventilation design of network-type double-deck road tunnel.

• Korean Journal of Remote Sensing
• /
• v.31 no.5
• /
• pp.395-408
• /
• 2015

High-resolution satellite image mosaics are becoming increasingly important in the field of remote sensing image analysis as an essential image processing to create a large image constructed from several smaller images. In this paper, we present an automatic seamline extraction technique and the procedure to generate a mosaic image by this technique. For more effective seamline extraction in the overlap region of adjacent images, an NDVI-based seamline extraction technique is developed, which takes advantage of the computational time and memory. The Normalized Difference Vegetation Index(NDVI) is an index of plant "greeness" or photosynthetic activity that is employed to extract the initial seamline. The NDVI can divide into manmade region and natural region. The cost image is obtained by the canny edge detector and the buffering technique is used to extract the ranging cost image. The seamline is extracted by applying the Dijkstra algorithm to a cost image generated through the labeling process of the extracted edge information. Histogram matching is also conducted to alleviate radiometric distortion between adjacent images acquired at different time. In the experimental results using the KOMPSAT-2/3 satellite imagery, it is confirmed that the proposed method greatly reduces the visual discontinuity caused by geometric difference of adjacent images and the computation time.

• Korean Journal of Remote Sensing
• /
• v.34 no.2_2
• /
• pp.313-326
• /
• 2018

This paper introduces core techniques on ship detection and tracking based on a compact HF radar platform which is necessary to establish a wide-area surveillance network. Currently, most HF radar sites are primarily optimized for observing sea surface radial velocities and bearings. Therefore, many ship detection systems are vulnerable to error sources such as environmental noise and clutter when they are applied to these practical surface current observation purpose systems. In addition, due to Korea's geographical features, only compact HF radars which generates non-uniform antenna response and has no information on target information are applicable. The ship detection and tracking techniques discussed in this paper considers these practical conditions and were evaluated by real data collected from the Yellow Sea, Korea. The proposed method is composed of two parts. In the first part, ship detection, a constant false alarm rate based detector was applied and was enhanced by a PCA subspace decomposition method which reduces noise. To merge multiple detections originated from a single target due to the Doppler effect during long CPIs, a clustering method was applied. Finally, data association framework eliminates false detections by considering ship maneuvering over time. According to evaluation results, it is claimed that the proposed method produces satisfactory results within certain ranges.

• Journal of Korean Society of Transportation
• /
• v.36 no.2
• /
• pp.112-128
• /
• 2018

We are implementing pedestrian priority zone policy to certain districts to reduce greenhouse gas and to develop eco-friendly city which has more focus on pedestrians' walking environment. This policy has contributed to citizens' satisfaction level with improved public transportation service as well as more spacious streets for walk. Despite highly positive influence of pedestrian priority zone policy to the walking environment, we need to anticipate the impact of this to traffic environment as it may have bad effect to the overall traffic flow around the zone where the policy is implemented. This research has analyzed the change of characteristics of traffic accidents around the eco-traffic area of Hang-Gung dong, Suwon city, to understand impact of the pedestrian priority zone policy to the traffic surroundings, with pre-post analysis methodology. As a result, number of accidents related to pedestrians showed decrease as pedestrian priority zone is designed operated with focus to pedestrians. But accidents related illegal U-turn and violation of the traffic signal showed (significant) increase as there was a restriction of turns and decrease of overall traffic speed. To prevent the accidents above, we need to notice drivers to pay special attention before the pedestrian priority zone event, and information from this research should be given to the drivers through safety signs and mobile application at the place near to the event.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2007.05a
• /
• pp.622-627
• /
• 2007

최근 하천의 모습은 이수 및 치수를 위해 설치된 수공구조물과 각종 오염원으로 인한 수질악화, 산업화 및 도시화에 따른 물순환시스템의 변화로 하천의 물순환 시스템이 바뀌게 되고 하천을 찾는 시민들의 환경의식 미성숙으로 인한 직간접적인 하천오염 활동이 이루어지고 있다. 하천에 대한 이러한 변화는 수질, 수량 및 하천의 구조적 측면에서 하천 생태계에 많은 영향을 끼치고 있다. 따라서 하천의 정상적인 기능을 회복시켜 하천 생태계 보전과 환경적으로 안정된 하천 조성이 이루어지도록 하기 위해서는 하천을 보다 자연스럽고 지속적으로 관리하기 위한 효율적인 환경유량의 관리가 필요하다. 하천의 전체적인 생태시스템을 고려한 환경유량의 관리를 위해서는 기존 환경유량의 개념, 산정방법 등 현황을 분석하고 하천 생태계에 영향을 미치는 인자들에 대한 관리방안을 마련하는 것이 중요하다. 본 연구의 목표는 하천생태계에 대한 영향인자의 장단점을 분석하고 이들이 어느 정도의 영향을 미치고 있는지를 정량적으로 파악함으로써 사회적으로 요구되는 환경유량을 산정할 때 어류 및 식생 등 하천의 생태계와 하천의 수량 및 수질, 하천의 수리구조물 등 하천의 구조적인 변화를 고려할 수 있는 방안을 마련하는 것이다. 이를 위하여 우선적으로 국외 선진국에서 활용되고 있는 다학제간 전문가 그룹(Multi-disciplinary Expert Team, MET)을 통해 하천 생태시스템을 분석하고 환경유량 산정 모형을 활용하여 저수지 댐과 연계 운영함으로써 어류 및 식생 등 생태서식처와 사회환경 개선에 필요한 유량을 유지할 수 있는 방안을 적용하고자 한다. 본 연구에서는 대상유역인 금강유역에 대해 환경유량을 산정하기 위한 개념모형을 구축하였다. 개념모형은 대청댐 건설 이전, 대청댐 건설이후${\sim}$용담댐 건설 이전, 대청댐과 용담댐 건설 이후 등 3개의 시나리오를 통해 하도 및 수변공간과 유량변화에 따른 유황분석 등을 통해 손실된 생태시스템을 정량화하여 궁극적으로는 복원을 위한 대응방안을 마련하도록 할 수 있도록 구축되었다. 또한 댐으로 인한 하류지역의 영향범위 및 하천생태계에 미친 영향을 감소하기 위하여 적절한 환경유량을 산정하기 위한 것이다. 구축된 개념모형을 바탕으로, 금강유역에 대한 기초적인 수문, 하천특성, 현장조사 등을 실시하였다. 향후에는 본 연구결과를 기초로 하여 환경유량을 산정하기 위한 모형을 개발하고 산정된 환경유량을 확보 및 관리하기 위한 방안과 친환경적인 댐 운영방안을 마련하게 될 것이다.

• Journal of the Korean association of regional geographers
• /
• v.3 no.2
• /
• pp.1-17
• /
• 1997

Geographic Information Systems(GIS) are very useful for spatial analysis and policy in local government administration. Recognizing the value of GIS, Chungnam province authorities put a spur on the introduction and development of it. But they have some difficulty in this process because of technical restraint, expertise shortage and budget limit. This study has surveyed current achievement and conditions for GIS development and presented general framework and subordinate tasks to build up GIS. First of all, there are a few prior conditions to guarantee the success of GIS: First, we should set up reasonable long-term plan and follow systematic procedures according to the plan. Second, it is essential to clarify what initiatively manage to whole business and so we should make up GIS-Board as an institutional center for this job. Third, we must research how to take advantage of already existing NGIS(National Geographic Information System), so that we may eliminate redundancy of investment. We can save a lot of finance and human resources through it. Fourth, we must focus on the importance of accurate mapping by utilizing new technology like GPS(Global Positioning System). Fifth, we should arrange efficient training program to constantly produce excellent human resources for GIS.