• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.8A
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• pp.743-751
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• 2010

OFDMA femtocell becomes an effective solution to support indoor high data rate services instead of the macrocell systems. Although the advantage of the femtocell, the co-channel interference between the femocell and the macrocell is the most significant problem that reduces the system performance. Macrocell users who have no permission to access the femtocell suffer from interference of the downlink transmission of femtocell. Therefore, the femtocell should use transmission power as small as possible to reduce interference to macrocell users. In this paper, we define the margin adaptive power allocation problem for the femtocell and propose a heuristic power allocation algorithm to solve the problem. Simulation results show the performance of the proposed algorithm.

• Journal of the Korean Society for Railway
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• v.12 no.6
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• pp.1018-1023
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• 2009

This paper describes a reduction in the peaks of traction energy for metro railways in timetabling. We develope a mixed integer programming (MIP) model, which minimizes the number of trains running simultaneously. We suggest two approaches. In the first approach, we use the commercial MIP solver, CPLEX. In the second approach, we propose a heuristic algorithm. We apply both methods to the current daily timetable of the Korea Metropolitan Subway. We determine an optimal solution, which results in an improvement of approximately 25% over the current timetable.

• 한국IT서비스학회:학술대회논문집
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• 2003.05a
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• pp.550-559
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• 2003

mobile IP는 단순히 이동성을 지원하는 것만을 목표로 제안되었기 때문에, 새로운 네트워크로의 연결만을 보장할 뿐, 핸드오프 후의 QoS는 보장하지 못한다. mobile IT에서 QoS는 이동 환경에서 멀티미디어 서비스나 실시간 서비스 제공 시 매우 중요시 되는 문제로, 핸드오프에 의한 지연과 밀접히 연관되어있다. 이에 따라 이동 환경에서 QoS를 보장하기 위해, 핸드오프 지연 문제는 주요 이슈로서 활발히 연구되고 있다. 본 논문에서는 이러한 문제를 해결하기 위해, 선행 연구로 액티브 네트워크에서의 정보기반 라우팅에 키워드 관리 방법을 추가한 SNMP 정보 기반 라우팅을 제시하고, 이를 이용하여 핸드오프 지연을 최소화하는 QoS 향상 기법을 제시한다. 또한 라우팅 컨버전스 시간을 설정하여 기존 핸드오프 방법과 함께 제시한 기법에서 필요한 요소를 모델링한 후 NS-2를 사용하여 시뮬레이션 하였다. 시뮬레이션 결과는 제시한 기법이 핸드오프 지연을 최소화함으로써, 결과적으로 QoS가 향상되었음을 입증한다.

• Journal of the Korean Institute of Intelligent Systems
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• v.16 no.5
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• pp.562-567
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• 2006

Model Predictive Control(MPC) system uses the current input which minimizes the difference between the desired output and the estimated output in the receding horizon scheme. In many cases (for example, system with constraints or nonlinear system), however, it is not easy to find the optimal solution to the above problem. In this paper, we show that real number coding genetic algorithm can be used to solve the optimal problem for MPC effectively. Also, we show by simulation that the real coding algorithm is mote natural and advantageous than the digital coding one.

• Journal of Creative Information Culture
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• v.7 no.2
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• pp.69-77
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• 2021

In the past, computer programming was a course taken by students of computing domain majors. With the advent of the fourth industrial revolution, students in all major fields are taking it as the general required course. However, students have difficulties in learning new subject such as unfamiliar computational problem solving approach and general purposed programming language, which can lead to negative phenomena such as learning effectiveness, confidence, and decreased interest. In this paper, the causes of difficulties experienced by non-majors students while learning programming language are analyzed and identified through qualitative and quantitative research on questionnaires, journals, and achievements. Thus, we suggest that designing an educational plan that minimizes difficulties.

• Journal of the Korea Convergence Society
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• v.8 no.10
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• pp.19-28
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• 2017

Recently the cargo transportation is increasing according to lager containerships in the container terminal. Thus, the various ways(such as efficient vehicle scheduling and minimizing delay time) are applied to increase productivity to handle the increasing cargo transportation in the container terminal. In this paper, the optimized model(Solvers) is applied to improve the existing heuristic method as a way of increasing productivity. The experimental design is that the result of two objective functions(minimizing travel and delay time of the empty vehicle) is compared to the result of the existing heuristic method by six sample problems. As a result of the two objective function experiments, the optimized model draws 5.3% more improved performance than the heuristic method in four of six problem samples.

• Journal of the Korean Institute of Intelligent Systems
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• v.17 no.4
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• pp.460-465
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• 2007

In this paper, we propose a novel pattern classification method based on statistical properties of the given data and fuzzy-rough set to minimize the coupling problem of the rules. In the proposed method, statistical properties is used by a selection criteria for deciding a partition number of antecedent fuzzy sets, and for minimizing an coupling problem of the generated rules. Moreover, rough set is used as a tool to remove unnecessary attributes between generated rules from the numerical data. In order to verify the validity of the proposed method, we compared the classification results (i.e, classification precision) of the proposed with the conventional pattern classification methods on the Fisher's IRIS data. From experiment results, we can conclude that the proposed method shows relatively better performance than those of the classification methods based on the conventional approaches.

• Journal of the Korean Institute of Intelligent Systems
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• v.14 no.2
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• pp.130-135
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• 2004

This paper presents a new design methods of the short-term load forecasting system (STLFS) using the data mining. The structure of the proposed STLFS is divided into two parts: the Takagi-Sugeno (T-S) fuzzy model-based classifier and predictor The proposed classifier is composed of the Gaussian fuzzy sets in the premise part and the linearized Bayesian classifier in the consequent part. The related parameters of the classifier are easily obtained from the statistic information of the training set. The proposed predictor takes form of the convex combination of the linear time series predictors for each inputs. The problem of estimating the consequent parameters is formulated by the convex optimization problem, which is to minimize the norm distance between the real load and the output of the linear time series estimator. The problem of estimating the premise parameters is to find the parameter value minimizing the error between the real load and the overall output. Finally, to show the feasibility of the proposed method, this paper provides the short-term load forecasting example.

• The Transactions of the Korea Information Processing Society
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• v.5 no.5
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• pp.1151-1161
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• 1998

In this paper, we are considering a heterogeneous processor system in which each processor may have different performance and reliability characteristics. In other to fully utilize this diversity of processing power it is advantageous to assign the program modules of a distributed program to the processors in such a way that the execution time of the entire program is minimized. This assignment of tasks to processors to maximize performance is commonly called load balancing, since the overloaded processors can perform their own processing with the performance degradation. For the task assignment problem, we propose a new objective function which formulates this imbalancing cost. Thus the task assignment problem is to be carried out so that each module is assigned to a processor whose capabilities are most appropriate for the module, and the total cost is minimized that sum of inter-processor communication cost and execution cost and imbalance cost of the assignment. To find optimal assignment is known to be NP-hard, and thus we proposed an efficient heuristic algorithm with time complexity $O(n^2m)$ in case of m task modules and n processors.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.564-564
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• 2012

유역내에서 발생한 고탁수는 저수지로 유입됨으로써 용수 공급에 지장을 초래하고, 수환경 악화 및 하류지역의 정수비용 부담을 가중시키는 등 사회, 경제적으로 여러 가지 문제를 일으키고 있다. 우리나라 대부분의 다목적댐은 홍수기에 탁수로 인하여 다양한 문제를 겪고 있다. 탁수문제는 수중생태계를 파괴하고, 상수원을 오염시키며, 물이 가지는 관광자원으로서의 가치를 심각하게 훼손시키는 등 심각한 문제를 야기 시키고 있다. 특히, 최근에는 잦은 이상 집중강우 현상 때문에 탁수의 장기화 문제가 대두되면서 중요한 사회문제로 떠오르고 있다. 수자원의 효율적 이용을 극대화하기 위한 댐의 연결사업은 탁수의 인위적인 외곡이 발생하기 때문에 적절한 조절을 통해 그 영향을 최소화할 필요가 있다. 댐에서 물의 밀도는 온도, 염도 및 탁도 등의 변화로 인하여 일정하지 않고 시간과 공간에 따라 변화하며, 일반적으로 혼합되지 않고 밀도와 두께가 다른 층에 분리되어 존재한다. 여름철 집중 강우 시 유입되는 고탁수층은 저수지의 밀도성층으로 인하여 표수층 하부에 위치하며, 이를 적기에 배제하지 않을 경우에는 수평방향의 확산현상과 연직방향의 전도현상으로 인해 저수지 전역에 분포하게 되어, 탁수현상의 장기화를 유발한다. 본 연구에서는 EFDC의 댐의 수리 및 수질예측모형을 이용해 여름철 집중강우시 유입되는 고탁수의 도달시간과 탁수량 등을 예측 평가하였다. 댐의 취수탑이 설치되는 위치는 댐의 상류측으로 일반적인 댐 주변의 온도 및 탁수거동과는 다르기 때문에 이 부분을 반영하여 평가하여야 한다. 본 연구에서는 EFDC의 댐 수리 및 수질예측모형을 이용하여 여름철 댐으로 유입되는 탁수거동을 평가하고, 댐 연결터널로 유입되는 취수탑 앞의 탁수농도를 예측하여 적절한 선택취수를 통해 댐 연결로 인한 고탁수의 댐간 이동을 최소화하기 위한 취수설비 운영방안을 제시하였다. 총 6개의 홍수사상('99년 홍수, '02년 루사, '03년 매미, '06년 에위니아, '09년 홍수 등)을 선정하여, 홍수사상에 대한 시단위의 유입량자료를 이용하여 양 댐간 연결로 인한 탁수거동을 분석하였다.