• 한국게임학회 논문지
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• 제13권2호
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• pp.49-58
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• 2013

본 연구에서는 게임의 실외 지형을 구성하는 많은 수의 다양한 나무를 효율적이고 자연스럽게 표현하기 위한 나무 성장 모델을 설계한다. 제안하는 나무 성장 모델은 (1) 다양한 종류의 나무를 보다 직관적이면서 자연스럽고 효율적으로 모델링하기 위한 성장 볼륨 및 약수 함수의 합성 곱 기반의 나무 모델링 방법, (2) 복잡한 구조의 다수 나무들의 실시간 처리를 위하여 인스턴싱 기반의 가지의 세분화 단계를 통한 렌더링 방법, 그리고 (3) 이를 조합하여 게임 배경을 효율적으로 구축하는 방법으로 구성된 나무 성장 모델이다. 제안한 나무 성장 모델을 통하여 자연스럽고 다양한 나무의 성장과 이를 통한 자연스러운 게임 배경의 구축 가능성 및 실시간 처리의 효율성을 실험을 통해 확인한다.

• 한국산림과학회지
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• 제95권3호
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• pp.240-249
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• 2006

최근, 소나무재선충(Bursaphelenchus xylophilus)에 의한 소나무림의 피해에 대한 사회적 심각성이 크게 대두되고 있다. 소나무 재선충에 의한 산림피해는 피해지 내에서는 매개충인 솔수염하늘소의 자연적인 영역확장에 의해 확산되는 반면, 전국적으로는 감염목의 인위적 반출 및 이동에 의해 확산이 진행되고 있다. 본 연구에서는 부산 대변항의 재선충 피해지내에서 항공사진 및 현지조사에 의해 피해목의 공간적인 위치를 파악하였고, 공간통계학적인 방법을 통하여 피해목의 공간분포유형, 피해발생과 지형인자간의 관계를 분석하였다. 또한, 지형공간자료를 통계학적 Tree 모형에 적용한 CART(Classification and Regression Trees)모형을 이용하여 재선충 피해의 자연적인 확산 예측 지도를 작성하였다. 본 연구를 통해 공간통계학적인 분석과 CART모형이 소나무재선충 피해의 공간분포 및 자연적 확산유형을 파악하는데 유용한 도구로 활용될 수 있음을 확인할 수 있었다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권4호
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• pp.1975-1988
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• 2019

Short-term traffic flow prediction plays an important role in intelligent transportation systems (ITS) in areas such as transportation management, traffic control and guidance. For short-term traffic flow regression predictions, the main challenge stems from the non-stationary property of traffic flow data. In this paper, we design an ensemble cascading prediction framework based on extremely randomized trees (extra-trees) using a boosting technique called EET to predict the short-term traffic flow under non-stationary environments. Extra-trees is a tree-based ensemble method. It essentially consists of strongly randomizing both the attribute and cut-point choices while splitting a tree node. This mechanism reduces the variance of the model and is, therefore, more suitable for traffic flow regression prediction in non-stationary environments. Moreover, the extra-trees algorithm uses boosting ensemble technique averaging to improve the predictive accuracy and control overfitting. To the best of our knowledge, this is the first time that extra-trees have been used as fundamental building blocks in boosting committee machines. The proposed approach involves predicting 5 min in advance using real-time traffic flow data in the context of inherently considering temporal and spatial correlations. Experiments demonstrate that the proposed method achieves higher accuracy and lower variance and computational complexity when compared to the existing methods.

• 한국환경과학회지
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• 제19권9호
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• pp.1129-1136
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• 2010

This study investigated the status of planting status of school's flower of 11 elementary schools located in Chung-ju and its results were as follows. Totally 3,502 trees were planted in the 11 schools and the number of species of the trees was 103. For tall tree Thuja orientalis was planted most frequently and for shrub Buxus microphylla was done in the largest number of the schools. In addition, the number of trees planted in a school was averagely two times more in the model schools than in the other ones, and the average number of species of trees was also over three times more in the model schools. When the number of species of trees was examined according to their types, decidous broad leaved tree was found most frequently overall and the model schools had more various species of decidous tree compared to the other ones. Investigation on designation of school's flower and tree with the 11 elementary school, revealed similar results with those of previous studies performed with the schools in other areas and the tendency meant that the designation was uniform to some degree. Moreover, as only a few school's flower and tree were planted or no one was done in some schools, the species of school's flower and tree needed to be determined by considering characteristics and school percepts of a school as well as local features and circumstances of a region. In addition, more efforts should be made to infuse love for school and to improve quality of education by increasing the planting rate of school's flower and tree and by focusing them.

• 한국환경복원기술학회지
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• 제25권2호
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• pp.39-53
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• 2022

The purpose of this study is to find out the applicability of LANDIS-II model to Korea. The case study was carried out in Daecheong Dam basin. In order to operate the model, a total of 63,107 cells of 100x100m unit were constructed, each cell consists of ecoregion map, initial communities map, plant physiological data, and climate change prediction data using SSP2-4.5 scenario. Forest distributions of year 2050 and 2100 were predicted by distribution intensity and interference among trees based on field surveys of 147 points in 2020. As a result, trees of decreased distribution area in the future are in the order of Quercus mongolica, Pinus rigida, Pinus densiflora and Robinia pseudoacacia, which characterized vulnerable to the effects of climate change or artificially planted trees. While warm climate trees of Quercus variabilis, Quercus serrata, Quercus acutissima and Quercus aliana are predicted to increase their distribution area in the order. These results analyzed using the LANDIS-II model are consistent with the studies on potential natural vegetation and succession tendency in Korea. In conclusion, the applicability of LANDIS-II model in Korea is highly effective and it is also expected to serve as a scientific basis for determining forest policies on afforestation and restoration.

• Journal of the Korean Statistical Society
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• 제25권1호
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• pp.1-24
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• 1996

In selecting a final tree, Breiman, Friedman, Olshen, and Stone(1984) compare the prediction risks of a pair of tree, where one contains the other, using the standard error of the prediction risk of the larger one. This paper proposes an approach to selection of a final tree by using the standard error of the difference of the prediction risks between a pair of trees rather than the standard error of the larger one. This approach is compared with CART's for simulated data from a simple regression model. Asymptotic results of the approaches are also derived and compared to each other. Both the asymptotic and the simulation results indicate that final trees by CART tend to be smaller than desired.

• 전자공학회논문지A
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• 제32A권12호
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• pp.209-219
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• 1995

As a new algorithm for RC tree delay estimation, we propose a $\tau$-model of the driver and a moment propagation method. The $\tau$-model represents the driver as a Thevenin equivalent circuit which has a one-time-constant voltage source and a linear resistor. The new driver model estimates the input voltage waveform applied to the RC more accurately than the k-factor model or the 2-piece waveform model. Compared with Elmore method, which is a lst-order approximation, the moment propagation method, which uses $\pi$-model loads to calculate the moments of the voltage waveform on each node of RC trees, gives more accurate results by performing higher-order approximations with the same simple tree walking algorithm. In addition, for the instability problem which is common to all the approximation methods using the moment matching technique, we propose a heuristic method which guarantees a stable and accureate 2nd order approximation. The proposed driver model and the moment propagation method give an accureacy close to SPICE results and more than 1000 times speedup over circuit level simulations for RC trees and FPGA interconnects in which the interconnect delay is dominant.

• 대한공간정보학회지
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• 제18권4호
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• pp.11-20
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• 2010

도시화에 따른 이산화탄소의 발생이 증대되고 있는 실정에서 이를 해결할 수 있는 대안으로 도시의 녹지화가 추진되고 있다. 도시지역에서 수목은 이산화탄소를 저감시킬 뿐만 아니라 심미적인 효과가 있다. 본 연구에서는 이러한 수목의 공간정보를 효율적으로 추출하기 위하여 라이다 자료를 이용하는 방법론을 제안하였다. 제안한 방법론에서는 수목추출에 따른 작업의 효율성을 향상시키기 위하여 점, 면, 영상기반의 복합적 자료처리를 수행하였다. 기존의 정규화된 수치표면모델은 건물과 수목정보를 모두 포함하고 있어 수목 추출 시 자료처리의 복잡성이 높은 문제점을 안고 있다. 따라서 이러한 문제점을 개선하기 위하여 본 연구에서는 건물추정영역을 제거한 수치표면모델을 이용하였다. 제안한 방법론의 적용성을 평가하기 위하여 도시지역 내의 건물과 수목이 공존하는 3개의 지역을 선정하였으며 수목추출의 정확도는 디지털 카메라에 의해 촬영된 디지털 영상과 비교하였다.

• Nuclear Engineering and Technology
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• 제40권5호
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• pp.365-374
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• 2008

Dependability-critical systems, such as digital instrumentation and control systems in nuclear power plants, necessitate engineering techniques and tools to provide assurances of their safety and reliability. Determining system reliability at the architectural design phase is important since it may guide design decisions and provide crucial information for trade-off analysis and estimating system cost. Despite this, reliability and system engineering remain separate disciplines and engineering processes by which the dependability analysis results may not represent the designed system. In this article we provide an overview and application of our approach to build architecture-based, dynamic system models for dependability-critical systems and then automatically generate dynamic fault trees (DFT) for comprehensive, tool-supported reliability analysis. Specifically, we use the Architectural Analysis and Design Language (AADL) to model the structural, behavioral and failure aspects of the system in a composite architecture model. From the AADL model, we seek to derive the DFT(s) and use Galileo's automated reliability analyses to estimate system reliability. This approach alleviates the dependability engineering - systems engineering knowledge expertise gap, integrates the dependability and system engineering design and development processes and enables a more formal, automated and consistent DFT construction. We illustrate this work using an example based on a dynamic digital feed-water control system for a nuclear reactor.

• 한국콘텐츠학회논문지
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• 제11권10호
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• pp.49-58
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• 2011

결함 트리 분석(Fault Tree Analysis)은 결함 트리를 구축하여 시스템의 안전성 분석을 수행한다. 그러나 결함 트리를 구성하는 작업은 대상 시스템의 도메인에 대한 지식과 경험을 필요로 하며 많은 시간과 노력을 소요한다. 이 논문에서는 시스템 설계 산출물인 상태 전이 모델을 기반으로 결함 트리를 체계적으로 구성하는 방법을 제안한다. 이를 위해 시스템 상태 전이 모델의 안정성 확보에 필요한 조건들을 식별하고 결함 트리를 구성할 수 있는 템플리트를 개발한다. 이 논문에서는 제안된 방법을 철도 건널목 제어 시스템에 적용한 결과도 기술한다.