• Asian Journal of Innovation and Policy
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• 제4권2호
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• pp.242-262
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• 2015

The relationship between geographical proximity and academics' formal and informal knowledge-transfer activities in the network is analyzed with a mixed research method. With social network analysis as a basis, we have explored the networks between academics and firms in the 16 regions of South Korea. The result shows Seoul and Gyunggi are identified as central nodes, meaning that the academics in other regions tend to collaborate with firms in these regions. An econometric analysis is performed to confirm the localization of knowledge-transfer activities. The intensity of formal channels measured by the number of academic papers is negatively, but significantly associated with the geographical proximity. However, we have not found any significant relationship between the formality of the channels and geographical proximity. Possibly, the regional innovation systems in South Korea are neither big enough nor strong enough to show a localization effect.

• Asia pacific journal of information systems
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• 제26권3호
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• pp.427-448
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• 2016

The stochastic phenomena of traffic network condition, such as traffic speed and density, are affected not only by exogenous traffic control but also by endogenous changes in service time during congestion. In this paper, we propose a mixed M/G/1 queuing model by introducing a condition-varying parameter of traffic congestion to reflect structural changes in the traffic network. We also develop congestion indices to evaluate network efficiency in terms of traffic flow and economic cost in traffic operating system using structure-changing queuing model, and perform scenario analysis according to various traffic network improvement policies. Empirical analysis using Korean highway traffic operating system shows that our suggested model better captures structural changes in the traffic queue. The scenario analysis also shows that occasional reversible lane operation during peak times can be more efficient and feasible than regular lane extension in Korea.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2005년도 Proceedings of ISRS 2005
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• pp.34-37
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• 2005

An efficient and robust neural network-based scheme is introduced in this paper to perform automatic cloud detection. Unlike many existing cloud detection schemes which use thresholding and statistical methods, we used the artificial neural network methods, the multi-layer perceptrons (MLP) with back-propagation algorithm and radial basis function (RBF) networks for cloud detection from Geostationary satellite images. We have used a simple scene (a mixed scene containing only cloud and clear sky). The main results show that the neural networks are able to handle complex atmospheric and meteorological phenomena. The experimental results show that two methods performed well, obtaining a classification accuracy reaching over 90 percent. Moreover, the RBF model is the most effective method for the cloud classification.

• 한국경영과학회지
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• 제36권2호
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• pp.1-14
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• 2011

In this paper, we deal with an access network design problem of fiber-to-the-home passive optical network (FTTH-PON). The FTTH-PON network design problem seeks to minimize the total cost of optical splitters and cables that provide optical connectivity between central office and subscribers. We develop a flow-based mixed integer programming (MIP) model with nonlinear link cost. By developing valid inequalities and preprocessing rules, we enhance the strength of the proposed MIP model in generating tight lower bounds for the problem. We develop an effective Tabu Search (TS) heuristic algorithm that provides good quality feasible solutions to the problem. Computational results demonstrate that the valid inequalities and preprocessing rules are effective for improving the LP-relaxation lower bound and TS algorithm finds good quality solutions within reasonable time bounds.

• 디지털산업정보학회논문지
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• 제8권2호
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• pp.81-94
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• 2012

This paper suggests PARED algorithm, a modified RED algorithm, that actively reacts to dynamic changes in network to apply packet drop probability flexibly. The main idea of PARED algorithm is that it compares the target queue length to the average queue length which is the criterion of changes in packet drop probability and feeds the gap into packet drop probability. That is, when the difference between the average queue length and the target queue length is great, it reflects as much as the difference in packet drop probability, and reflects little when the difference is little. By doing so, packet drop probability could be actively controled and effectively dealt with in the network traffic situation. To evaluate the performance of the suggested algorithm, we conducted simulations by changing network traffic into a dynamic stat. At the experiments, the suggested algorithm was compared to the existing RED one and then to ARED one that provided the basic idea for this algorithm. The results proved that the suggested PARED algorithm is superior to the existing algorithms.

• 한국경영과학회지
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• 제30권1호
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• pp.1-15
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• 2005

In this paper, we deal with a mesh network design problem arising from the deployment of WDM for the optical internet. The mesh network consists of mesh topology for satisfying traffic demand while minimizing the cost of WDM, OXC, and fiber cables. The problem seeks to find an optimal routing of traffic demands in the network such that the total cost is minimized. We formulate the problem as a mixed-integer programming model and devise a tabu search heuristic procedure. Also we develop an optical internet design system that implements the proposed tabu search heuristic procedure. We demonstrate the computational efficacy of the proposed algorithm, compared with CPLEX 8.0.

• 정보처리학회논문지B
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• 제14B권3호
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• pp.215-222
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• 2007

최근 정보기술의 발달과 함께 문자 인식의 중요성이 높아지고 있다. 특히, 유비쿼터스 시대가 도래하면서 개인휴대용 정보 단말기, 태블릿 PC 등 유비쿼터스 컴퓨팅 장비가 급속도로 대중화 되고 있다. 이에 사람마다 다양한 필체로 인한 문제가 발생하고 있으며, 인식률을 높일 수 있는 문자 인식에 대한 연구가 필요한 실정이다. 본 연구에서는 다중 해상도 병합을 이용한 수정된 적응 공명 이론 신경망을 제안한다. 이는 자율 학습 신경망과 다중 해상도의 관점에서 접근하여 문자 인식 문제에 적용시켜 본 것이다. 노이즈와 문자 특성 정보를 구별하고 인식률을 높이기 위해 고해상도와 저해상도 정보를 같이 이용하는 다중 해상도 병합 방법을 제안한다. 또한, 다중 해상도 병합 방법의 효과를 극대화할 수 있는 적응 공명 이론 신경망의 유사도 측정 방법을 제안하여 기존의 방법보다 우수한 실험 결과를 제시하였다.

• 콘크리트학회논문집
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• 제14권4호
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• pp.457-466
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• 2002

현대사회에서 건설전반에 보편화되어 있는 레미콘은 다양한 사용재료의 물리 화학적 성분이 생산지 및 조성광물에 따라 다르므로 구해지는 결과 값 또한 무수한 변수가 있기 마련이다. 또한 콘크리트의 배합설계는 배합요소의 다변화로 인해 정확한 검정은 그리 간단하지가 않다. 신경망의 학습에 소요되는 시간은 컴퓨터의 성능 및 학습횟수(epoch)에 따라 다르고, 학습시 학습횟수를 최고 백만번까지 반복하도록 하였으며 학습 종료조건으로 최소자승법에 의해 목표 오차량이 0.10~0.001 사이가 될 때까지로 하였다. 신경망의 적용에는 현재 경북지방에 위치한 레미콘 회사중 A, B사에서 사용하는 콘크리트 시방배합표를 가지고 신경망 이론에 따라 학습시킨 후에 물시멘트비, 잔골재율, 단위수량, 단위시멘트량, 강모래의 단위량(S1), 부순모래의 단위량(S2), 단위굵은골재량 혼화제량을 추정하였고, 다음으로 압축강도 및 슬럼프 값을 각각 추정하였다. 배합요소 추정의 검정에 사용된 규격으로는 호칭강도 180~300kgf/${cm}^2$, 목표슬럼프값 8cm, 15cm를 사용하였고, 압축강도 및 슬럼프 값 추정에 사용된 규격으로는 회사별 최근 생산량이 가장 많은 호칭강도 210~240kgf/${cm}^2$, 목표 슬럼프 값 12, 15cm를 각각 사용하였다. 본 논문에서는 컴퓨터에 의한 학습 및 시뮬레이션을 통해 콘크리트의 배합요소, 압축강도 및 슬럼프 값을 추정하여 직접 실험 값과 비교함으로써 실험을 통하지 않고도 콘크리트의 배합요소 및 강도를 추정하는데 목적이 있다. 결과적으로 압축강도 및 슬럼프의 추정은 회사에 관계없이 오차량에 만족하여 수렴하는 것으로 나타나 인공신경망이론이 압축강도 및 슬럼프를 예측하는데 효율적인 것으로 판명되었다.

• 한국정보처리학회논문지
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• 제3권1호
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• pp.55-62
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• 1996

MRNS(Mixed Radix Number System) 네트워크는 슈퍼컴퓨터나 MIMD의 모 델로 널리 쓰이고 있으며 많은 연구가 진행되고 있는 하이퍼큐브의 일반적인 대수학적 모델이다. 본 논문에서는 MRNS 네트워크상에서 메세지의 전송 알고리즘을 연구 하였다. 우리가 이 네트워크상에서 임의의 발신 노드부터 수신노드까지 n개의 패킷들을 동시에 보내려고할 때 이들 패킷들의 빠르고, 안전하게 수신 노도까지 도달하기 위해서는 1번 째의 경로가 다른 모든 경로들로부터 node-disjoint 되어야 한다. 이를 위해 우리는 특수한 메트릭스인 HCLS(Hamiltonian Circuit Latin Squre)[1〕를 응용하여 선형 병렬 전송알고리즘을 개발하였다.

• 산업공학
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• 제18권3호
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• pp.277-287
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• 2005

In this paper, we deal with a new techno-economic modeling and analysis for optical access networks. In deploying the fiber-to-the-home (FTTH) architecture, network planner needs to consider the following techno-economic issues: when do we need to upgrade existing local access network to FTTH network? how much do we invest to maximize profit? In order to answer these techno-economic questions, we need to consider the impact of emerging technologies and business environment. Toward this end, we develop a new techno-economic modeling to deal with the inherent complexity of technology evolution and cost economics. In particular, the new modeling approach provides us with an techno-economic analysis of technology alternatives such as ethernet passive optical network (E-PON) and wavelength division multiplex passive optical network (WDM-PON). In this analysis, we focus on the impact of critical factors such as the cost characteristic of proposed architecture and digital subscriber line (DSL) subscriber's churn-in to FTTH service and churn-out. We develop mixed integer-programming models for finding the evolution path of local access networks to broadband network architectures.