• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
• /
• v.4 no.2
• /
• pp.4-10
• /
• 1993

In mobile radio communication, propagation paths are time or spacial varying because of the motion of mobile unit. The propagation path loss not only involves frequency and distance but also the antenna height at both the base station and the mobile unit, terrain configuration, and the man made en- vironment. Thhese additional factors make the prediction of propagation path loss of mobile radio signals more difficult. In this paper, it is measured field strenght of mobile radio signals in Daejeon and Seoul area, also calculated local median, 500m sample mean, and stadard deviation. As the result of analysis, it can be seen that propagation path loss of measured data is similiar to predicted field strength, especially local median is dependent upon base antenna height, terrain configuration and the man-made environment. The standard deviation has been noted to lie between 2 and 10 dBuV.

• Journal of the Korean Geographical Society
• /
• v.42 no.4
• /
• pp.469-487
• /
• 2007

Grain-Size Trend Analysis is the methodology to identify net sediment transport pathways, based on the assumption that the movement of sediment from the source to deposit leaves the identifiable spatial pattern of mean, sorting, and skewness of grain size. It can easily be implemented with low cost, so it has great potentials to contribute to geomorphological research, whereas it can also be used inadequately without recognition of its limitations. This research aims to compare three established methods of grain-size trend analysis to search for the adequate way of application, and also suggest the research tasks needed in improving this methodology 1D pathway method can corporate the field experience into analyzing the pathway, provide the useful information of depositional environments through X-distribution, and identify the long-term trend effectively. However, it has disadvantage of the dependence on subjective interpretation, and a relatively coarse temporal scale. Gao-Collins's 2D transport vector method has the objective procedure, has the capability to visualize the transport pattern in 2D format, and to identify the pattern at a finer temporal scale, whereas characteristic distance and semiquantitative filtering are controversial. Le Roux's alternative 2D transport vector method has two improvement of Gao-Collins's in that it expands the empirical rules, considers the gradient of each parameters as well as the order, and has the ability to identify the pattern at a finer temporal scale, while the basic concepts are arbitrary and complicated. The application of grain sire trend analysis requires the selection of adequate method and the design of proper sampling scheme, based on the field knowledge of researcher, the temporal scale of sediment transport pattern targeted, and information needed. Besides, the relationship between the depth of sample and representative temporal scale should be systematically investigated in improving this methodology.

• Journal of Environmental Impact Assessment
• /
• v.30 no.1
• /
• pp.13-23
• /
• 2021

In this study, we performed a Random Walker analysis to predict the Major Movement Paths of otters. The scope of the research was a simulation analysis with a radius of 7.5 km set as the final range centered on the Ansim-wetland in Daegu City, and a field survey was used to verify the model. The number of virtual otters was set to 1,000, the number of moving steps was set to 1,000 steps per grid, and simulations were performed on a total of 841 grids. As a result of the analysis, an average of 147.6 objects arrived at the boundary point under the condition of an interval of 50 m. As a result of the simulation verification, 8 points (13.1%) were found in the area where the movement probability was very high, and 9 points (14.8%) were found in the area where the movement probability was high. On the other hand, in areas with low movement paths probabilities, there were 8 points (13.1%) in low areas and 4 points (6.6%) in very low areas. Simulation verification results In areas with high otter values, the actual otter format probability was particularly high. In addition, as a result of investigating the correlation with the otter appearance point according to the unit area of the evaluation star of the movement probability, it seems that 6.8 traces were found per unit area in the area where the movement probability is the highest. In areas where the probability of movement is low, analysis was performed at 0.1 points. On the side where otters use the major movement paths of the river area, the normal level was exceeded, and as a result, in the area, 23 (63.9%), many form traces were found, along the major movement paths of the simulation. It turned out that the actual otter inhabits. The EN-Simulator analysis can predict how spatial properties affect the likelihood of major movement paths selection, and the analytical values are used to utilize additional habitats within the major movement paths. It is judged that it can be used as basic data such as to grasp the danger area of road kill in advance and prevent it.

• Journal of KIISE:Information Networking
• /
• v.33 no.6
• /
• pp.461-472
• /
• 2006

In this paper, we propose a novel on-demand multicasting algorithm, 'Durable Distance Vector Multicasting(DDVM),' for Mobile Ad hoc Network(MANET). DDVM has a more efficient routing-control complexity than Link State Routing(LSR) and with the smaller complexity, DDVM provides a high delivery ratio for MANET with high mobility by adapting to dynamic topological changes. This is achieved by adding 'combined path durability' statistic into the routing-control information of Distance Vector Routing(DVR). The routing-path duration statistic is computed in a fully distributed manlier at each node in the network based on only local information from neighbour nodes. We show by simulation studies the effectiveness of DDVM compared with On-demand Multicast Routing Protocol(ODMRP).

• Journal of the Institute of Electronics Engineers of Korea CI
• /
• v.45 no.6
• /
• pp.33-44
• /
• 2008

Multipath routing protocols with load balance, fault tolerance, aggregated bandwidth in Ad-hoc Networks provide improved throughput and reliable route as compared with singlepath routing protocols. However, multipath routing protocols have not been explored thoroughly in the domain of overhead in Ad-hoc Networks. In this paper, we analyze and compare on-demand singlepath and multipath routing with IEEE 802.11 DCF in terms of Routing overhead and MAC overhead. The results reveals that in comparison with singlepath routing protocol, multipath routing mechanism creates more overheads but provides better performance in congestion and capacity provided that the route length is within a certain upper bound which is derivable. The analytical results are further confirmed by simulation.

• The Journal of the Acoustical Society of Korea
• /
• v.14 no.3
• /
• pp.105-113
• /
• 1995

For the case of using analog FM system and CDMA system together in the mobile communications, we experimentally calculate the appropriate frequency offset to improve the frequency efficiency by analizing the interference between both systems. As the results of the analysis, we obtained that frequency offset is 840KHz(Path Loss : 80dB) and 720KHz(Path Loss : 120dB) for the Path Loss when a output of CDMA Base Station is 0.91 W ERP. Therefore, to minimize the frequency offset, a output of Base Station will be controlled corresponding to Cover Area.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2022.11a
• /
• pp.156-158
• /
• 2022

차량이 사용자에게 다양한 서비스를 제공하기 위해서 차량의 위치 정보를 요구하는 환경에서 차량의 위치를 예측해 미리 알 수 있다면 높은 품질의 서비스를 만드는 것에 도움이 된다. 차량은 도시 환경에서 비교적 느린 속도를 갖는다는 특징이 있고 차량의 위치를 표시하는 방법도 여러 가지다. 본 논문은 Long Short-Term Memory(LSTM)을 사용해 차량의 이동 경로를 예측하는 과정에서 이동 속도와 위치 표현 방법이 미치는 영향을 분석하였다. 실험 결과 차량의 속도가 증가할수록, 차량의 이동 표현 방법이 세밀할수록 차량 이동 경로 예측이 어렵다는 것을 확인하였다.

• Proceedings of the Korean Association of Geographic Inforamtion Studies Conference
• /
• 2004.03a
• /
• pp.45-49
• /
• 2004

최적경로문제는 한 지점에서 다른 지점으로 이동할 때, 최소한의 비용으로 이동할 수 있는 경로를 찾는 문제를 의미하며, 최근 인터넷을 이용한 경로 안내 시스템에 적용되어 왔다. 이때, 보통 시간비용을 최소로 하는 경로를 제공하는 것이 일반적이다. 그러나 현실적으로 우리는 타인에게 어떠한 경로를 설명하거나 알려 줄 때, 인지도나 접근성이 높은 경로를 포함하는 경우가 많다. 이에 본 연구에서는 교통경로를 산출할 때 접근성이 높은 경로를 포함하여 경로를 구성하는 방안을 제시하였다 이를 구현하기 위해 건축, 도시공간에서 접근성 분석에 사용되고 있는 Space Syntax라는 방법론을 적용하였다. GIS 데이터 구조를 이용하기 위해 알고리즘을 일부 수정하였으며, 일반적으로 최단거리 산출에 많이 사용되고 있는 Dijkstra 알고리즘과 결합하여 구축하였다. 이렇게 구축된 알고리즘을 소규모의 교통 네트웍상에 적용하여 테스트하였다.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.35 no.1
• /
• pp.67-76
• /
• 2011

An exact curved path has to be fixed and velocity profile for travelling on the curved path is required by a moving stage. In this study, we decide the curved path on the basis of the information on three point locations. The path of the moving stage is traced by simulating the designed curve path and the velocity profile, and the results are compared with the given three points to determine how closely the moving stage follows the given path. Further, we propose a method to calibrate a curved path and velocity profile. The proposed moving paths were evaluated by performing experiments. Finally, the designed curved path and the actual path were compared.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.25 no.1
• /
• pp.1-8
• /
• 2007

People tend to spend more time in indoor spaces than before such as shopping malls and subway stations. As buildings become larger and more complex, people feel difficulty in finding their ways to destinations. Consequently, a means to provide better paths can aid people in reducing time for finding ways. Routing information in large indoor spaces is especially required in emergency cases as fire, power failure and terror. This study suggests to compute optimal paths using $A^*$ algorithm based on raster GIS data structure. The suggested method can be used either in daily lives for path provision or in emergency cases for evacuation, and is illustrated on a campus building.