• 한국대기환경학회지
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• 제18권2호
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• pp.67-83
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• 2002

The coupled model (SMART) of dynamic meteorology model and particle dispersion model was developed. The numerical experiment on the relationship between change of land use and diffusion behavior in complex terrain was carried out using this model. It tried to investigate the change of particle diffusion behavior and local weather under the condition in which land-land breeze and sea breeze and mountain breeze intermingled. The numerical experiment results are as follows; 1) The more complicated local circulation field of the interaction of sea breeze, mountain breeze and Land -land breeze is formed. Then, the region circulation in which the urbanization is specific by location of the region is strengthened and is weakened. 2) Though in the region with dominant sea breeze, Land-land breeze does not appear directly, the progress of the sea wind to the inland is affected. 3) In the prediction of the air diffusion, emission high quality and accurate information of the emission site are important. That is to say, the dispersion predicting result which emission high quality and small error of the site perfectly vary for Land - land breeze in the effect may be brought about.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2004년도 제28회 KOSCO SYMPOSIUM 논문집
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• pp.102-111
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• 2004

Partial quenching structure of turbulent diffusion flames in a turbulent mixing layer is investigated by the method of flame hole dynamics to develope a prediction model for the turbulent lift off. The present study is specifically aimed to remedy the problem of the stiff transition of the conditioned partial burning probability across the crossover condition by adopting level-set method which describes propagating or retreating flame front with specified propagation speed. In light of the level-set simulations with two model problems for the propagation speed, the stabilizing conditions for a turbulent lifted flame are suggested. The flame hole dynamics combined with level-set method yields a temporally evolving turbulent extinction process and its partial quenching characteristics is compared with the results of the previous model employing the flame-hole random walk mapping. The probability to encounter reacting' state, conditioned with scalar dissipation rate, demonstrated that the conditional probability has a rather gradual transition across the crossover scalar dissipation rate in contrast to the stiff transition of resulted from the flame-hole random walk mapping and could be attributed to the finite response of the flame edge propagation.

• 한국통신학회논문지
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• 제34권3B호
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• pp.213-224
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• 2009

Most of existing routing methods in wireless sensor networks to counter the local eavesdropping-based packet-tracing deal with a single asset and suffer from the packet-delivery latency as they prefer to take a separate path of many hops for each packet being sent. Recently, the author proposed a routing method, GSLP-w(GPSR-based Source-Location Privacy with crew size w), that enhances location privacy of the packet-originating node(i.e., active source) in the presence of multiple assets, yet taking a path of not too long. In this paper, we present a refined routing(i.e., next-hop selection) procedure of it and empirically study privacy strength and delivery latency with varying the crew size w(i.e., the number of packets being sent per path). It turns out that GSLP-w offers the best privacy strength when the number of packets being sent per path is randomly chosen from the range [$1,h_{s-b}/4$] and that further improvements on the privacy are achieved by increasing the random walk length TTLrw or the probability prw that goes into random walk(where, $h_{s-b}$ is the number of hops of the shortest path between packet-originating node s and sink b).

• International Journal of Advanced Culture Technology
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• 제2권1호
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• pp.1-13
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• 2014

In next-generation wireless networks, provisioning of IP-based network architecture and seamless transmission services are very important issues for mobile nodes. For this reason, a mobility management mechanism to support global roaming is highly regarded. These technologies bring a broader life by using a global roaming account through the connection of multiple devices or technology to mobile users; they also provide real-time multimedia services. This paper presents a comprehensive performance analysis of fast handover for hierarchical mobile IPv6 (F-HMIPv6), hierarchical mobile IPv6 (HMIPv6), Proxy Mobile IPv6 (PMIPv6), and fast Proxy Mobile IPv6 (FPMIPv6) using the fluid-flow model and random-walk model. As a result, the location update cost of the PMIPv6 and FPMIPv6 is better than that of HMIPv6 and F-HMIPv6. These results suggest that the network-based mobility management technology is superior to the hierarchical mobility management technology in the mobility environment.

• 한국지하수토양환경학회지:지하수토양환경
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• 제20권3호
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• pp.51-64
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• 2015

In the present study, we develop two history matching techniques based on Markov chain Monte Carlo method where radial basis function and Gaussian distribution generated by unconditional geostatistical simulation are employed as the random walk transition kernels. The Bayesian inverse methods for aquifer characterization as the developed models can be effectively applied to the condition even when the targeted information such as hydraulic conductivity is absent and there are transient hydraulic head records due to imposed stress at observation wells. The model which uses unconditional simulation as random walk transition kernel has advantage in that spatial statistics can be directly associated with the predictions. The model using radial basis function network shares the same advantages as the model with unconditional simulation, yet the radial basis function network based the model does not require external geostatistical techniques. Also, by employing radial basis function as transition kernel, multi-scale nested structures can be rigorously addressed. In the validations of the developed models, the overall predictabilities of both models are sound by showing high correlation coefficient between the reference and the predicted. In terms of the model performance, the model with radial basis function network has higher error reduction rate and computational efficiency than with unconditional geostatistical simulation.

• 한국해양환경ㆍ에너지학회지
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• 제12권3호
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• pp.124-132
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• 2009

하수의 해양방류시스템의 형식과 방류위치 결정을 위해 해수유동모의, 근해역 희석률 모의 그리고 원해역 확산모의가 수행되었다. 방류 후보지점 주변의 조위와 조류는 관측조위 및 조류를 잘 재현하는 2차원 유한요소모형에 의해 수행되었으며, 계산된 조위 및 조류 모의결과에 기초하여 방류 후보지점이 결정되었다. 방류시스템으로는 단일확산관과 다공확산관이 고려되었다. 단일확산관과 다공확산관을 통한 하수 방류의 근역 확산이 CORMIX모형에 의해 검토되었으며, 원역 확산이 2차원 Random-walk 확산모형에 의해 실시되었다. 모의결과로부터 수심, 조류, 방류위치, 방류속도, 확산관 길이 등이 확산범위와 희석률에 미치는 영향이 다각도로 검토되었다.

• 한국통신학회논문지
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• 제36권12C호
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• pp.738-743
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• 2011

고해상도 3차원 깊이 영상은 고품질의 3차원 방송을 위해 필요한 중요한 정보이다. 깊이 카메라는 정확한 깊이 정보를 실시간으로 얻을 수 있지만, 카메라 물리적 한계로 인해 저해상도의 깊이 영상만 이용한다. 본 논문에서는 저해상도의 깊이 영상과 색상 영상을 이용하여 색상 영상을 보간 하는 방법을 제안한다. 제안하는 방법은 랜덤워크 확률 모델을 이용하여 각 화소들이 초기 깊이값과 같을 확률값을 정의하여 가장 높은 확률을 가지는 초기 깊이값을 나머지 화소들에 복사한다. 제안한 방법은 인접한 화소들만을 이용하는 것이 아니라 경로를 따라 비용을 계산함으로써, 여러 화소에 걸친 색상의 변화율이 고려되어 물체의 경계 주변에서 색상 영역과 깊이 영상간의 경계가 일치하는 향상된 깊이 영상을 얻을 수 있다.

• 한국광학회지
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• 제14권2호
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• pp.155-160
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• 2003

일반 통신용 단일모드 광섬유를 회전 감지용 광섬유로 사용하는 비편광 광섬유 자이로스코프를 제작하고 특성을 측정하였다. 이 자이로스코프의 잡음특성을 계산하여 예측하고, 신호대 잡음비가 최대가 되는 적정 변조진폭 둥의 최적 동작조건을 추출하였다. 자이로의 불규칙잡음계수를 여러 위상차 변조진폭에 대하여 측정한 결과, 위상차 변조진폭이 2.4 rad인 경우에 0.7$\times$$10^{-3}$ deg/√hr의 작은 불규칙잡음계수를 얻을 수 있었으며, 변조진폭에 따른 잡음특성의 경향이 계산에 의한 예측치와 거의 일치하였다.

• 한국해양환경ㆍ에너지학회지
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• 제7권2호
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• pp.82-88
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• 2004

투과성 항만구조물 주변에서 해수유동을 평가하기 위하여, 흐름 저항을 고려한 수치모형을 사용하였다 조석 조류수치모형에서 임의 물체에 대한 흐름 저항을 고려하기 위하여 수심적분된 전통적인 동수력학 방정식에 항력항을 첨가하였다. 그리고 해수교환율을 평가하기 위하여 임의행보(random walk) 수치모형을 사용하였다. 본 모형은 부산항의 잔교식 항만구조물의 설계에 이용되었으며, 이 때 투과성 구조물은 불투과성 구조물의 경우보다 유속이 증가하고 해수교환율이 향상되는 결과를 보였다. 본 모형은 앞으로 투과성 구조물의 설계에 있어서 유용하게 사용될 수 있을 것으로 기대된다.

• Journal of Mechanical Science and Technology
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• 제19권12호
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• pp.2312-2320
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• 2005

The aerodynamic effects of leading-edge accretion can raise important safety concerns since the formulation of ice causes severe degradation in aerodynamic performance as compared with the clean airfoil. The objective of this study is to develop a numerical simulation strategy for predicting the particle trajectory around an MS-0317 airfoil in the test section of the NASA Glenn Icing Research Tunnel and to investigate the impingement characteristics of droplets on the airfoil surface. In particular, predictions of the mean velocity and turbulence diffusion using turbulent flow solver and Continuous Random Walk method were desired throughout this flow domain in order to investigate droplet dispersion. The collection efficiency distributions over the airfoil surface in simulations with different numbers of droplets, various integration time-steps and particle sizes were compared with experimental data. The large droplet impingement data indicated the trends in impingement characteristics with respect to particle size ; the maximum collection efficiency located at the upper surface near the leading edge, and the maximum value and total collection efficiency were increased as the particle size was increased. The extent of the area impinged on by particles also increased with the increment of the particle size, which is similar as compared with experimental data.