• 한국통신학회논문지
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• 제13권2호
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• pp.138-148
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• 1988

본 논문에서는 호스트 프로세서가 지니고 이는 억세스 제어 프로그램을 대신 수행하여 호스트 프로세서의 효율을 향상시키고 또한 네트워크의 확장을 용이하게 하고 그 설치비용을 절감시키는 목적으로의 FEP시스템을 설계하는데 중점을 둔다. FEP시스템 설계는 앞으로 정보화 사회에서 구축될 종합 정보 통시낭 규격에 근거하여 채널의 기본전송속도를 64Kbps로 한 하드웨어와 전송소프트웨어를 제시하고, 이 시스템을 통해서 이루어지는 파일 서비스의 내용을 FTAM서비스에 근거하여 소개한다.

• 한국생산제조학회지
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• 제24권2호
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• pp.186-191
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• 2015

Presently, rapidly changing and unstable global economic environments demand engineers. Products should be designed to increase profits by lowering costs and provide distinguished performance compared with competitors. This study aims to optimize the design of the power-transmission drive shaft. The mass is reduced as an objective function, and the stress is constrained under a constant value. To reduce the number of experiments, CCD (central composite design) and D-Optimal are used for the experimental design. RSM (response surface methodology) is employed to construct a regression model for the objective functions and constraint function. In this problem, there is only one objective function for the mass. The other objective function gives 1; thus, NSGA-II is used.

• 대한산업공학회지
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• 제23권1호
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• pp.115-127
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• 1997

A GDHS(Geothermal District Heating System) is a heating system supplying a group of districts with heat extracted from geothermal sources. The advantages of GDHS include saving fuel consumption as well as reducing air pollution. This paper presents a case study for the economic feasibility model and analysis of a GDHS with which central/individual heating systems are replaced. Configuring to a simplified GDHS which consisits of subsurface systems, surface systems, and transmission/distribution systems, we find out the properties of the system and the model parameters affecting the initial investment/operating costs in order to develop a classical economic feasibility model given geothermal temperature. Based on our model parameter space, we analyzed the geothermal development project of the Jejoo Island probabilistically given prior information such as the expected geothermal power, the demand size and the length of transmission/distribution pipes.

• Clinical and Experimental Pediatrics
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• 제64권7호
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• pp.322-327
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• 2021

School closures during the coronavirus disease 2019 (COVID-19) pandemic have been outlined in studies from different disciplines, including economics, sociology, mathematical modeling, epidemiology, and public health. In this review, we discuss the implications of school closures in the context of the current COVID-19 pandemic. Modeling studies of the effects of school closures, largely derived from the pandemic influenza model, on severe acute respiratory syndrome coronavirus 2 produced conflicting results. Earlier studies assessed the risk of school reopening by modeling transmission across schools and communities; however, it remains unclear whether the risk is due to increased transmission in adults or children. The empirical findings of the impact of school closures on COVID-19 outbreaks suggest no clear effect, likely because of heterogeneity in community infection pressure, differences in school closure strategies, or the use of multiple interventions. The benefits of school closings are unclear and not readily quantifiable; however, they must be weighed against the potential high social costs, which can also negatively affect the health of this generation.

• ETRI Journal
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• 제15권3_4호
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• pp.47-59
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• 1994

A capacity expansion planning problem with buy-or-lease decisions is considered. Demands for capacity are deterministic and are given period-dependently at each period. Capacity additions occur by buying or leasing a capacity, and leased capacity at any period is reconverted to original source after a fixed length of periods, say, lease period. All cost functions (buying, leasing and idle costs) are assumed to be concave. And shortages of capacity and disposals are not considered. The properties of an optimal solution are characterized. This is then used in a tree search algorithm for the optimal solution and other two algorithms for a near-optimal solution are added. And these algorithms are illustrated with numerical examples.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2002년도 봄 학술발표논문집 Vol.29 No.1 (A)
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• pp.10-12
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• 2002

사용자의 요구와 인터넷 어플리케이션의 발달로 규모가 큰 미디어 오브젝트의 수가 급증하고 있다. 따라서 네트워크 전송비용은 반드시 고려해야 하는 중요한 요소이다. 본 논문에서는 기존 프락시 캐시 교체 정책들을 분석하고, 이를 개선한 G-N 및 L-N 정책을 제안한다. 이것은 프락시 캐시 소프트웨어인 'Squid'에서 채택하고있는 GDSF와 LFU-DA 정책에 네트워크 전송 비용을 추가하여 확장한 알고리즘이다. 시뮬레이션을 통하여 기존의 알고리즘과 비교해 본 결과, 평균 응답 시간을 10%이상 감소시킬 수 있었으며, 추가로 드는 비용(Processing Overhead)은 3게 증가하지 아니 하였음을 확인하였다.

• 대한전기학회논문지
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• 제41권1호
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• pp.1-8
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• 1992

Hopfield neural network has been applied to the problem of economic load dispatch(ELD) of electric power. The optimum values of neuron potentials are represented in terms of large numbers. The differential synchronous transition mode is used in this simulation. Through case studies, we have shown the possibility of the application of neural network to ELD. In case of including the transmission losses, the proposed method has an advantage that the problem can be solved simply with one neural network, without calculating incremental fuel costs and incremental losses required by traditional method.

• International Journal of Railway
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• 제2권4호
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• pp.139-146
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• 2009

Vehicle braking in non-electrified rail systems wastes energy. Advanced flywheel technology presents a way to capture and reuse this braking energy to improve vehicle efficiency and so reduce the operating costs and environmental impact of diesel trains. This paper highlights the suitability of flywheels for rail vehicle applications, and proposes a novel mechanical transmission system to apply regenerative braking using a flywheel energy storage device. A computational model is used to illustrate the operation and potential benefits of the energy storage system.

• Journal of Electrical Engineering and Technology
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• 제3권1호
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• pp.52-59
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• 2008

This paper describes the secant method for solving the economic dispatch (ED) problem with generator constraints and transmission losses. The ED problem is an important optimization problem in the economic operation of a power system. The proposed algorithm involves selection of minimum and maximum incremental costs (lambda values) and then the evaluation of optimal lambda at required power demand is done by secant method. The proposed algorithm has been tested on a power system having 6, 15, and 40 generating units. Studies have been made on the proposed method to solve the ED problem by taking 120 and 200 units with generator constraints. Simulation results of the proposed approach were compared in terms of solution quality, convergence characteristics, and computation efficiency with conventional methods such as lambda iterative method, heuristic methods such as genetic algorithm, and meta-heuristic methods like particle swarm optimization. It is observed from different case studies that the proposed method provides qualitative solutions with less computational time compared to various methods available in the literature.

• 한국인터넷방송통신학회논문지
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• 제13권6호
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• pp.269-274
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• 2013

본 논문에서는 기존의 피킹 (Picking) 시스템이 가지는 인건비 문제와 유지보수 비용이 많이 드는 단점을 해결하기 위해 지그비 무선 통신을 이용한 피킹 시스템 설계 및 구현방법을 제안한다. 지그비 (Zigbee)를 이용한 신뢰성 있는 데이터 전송을 하기 위해 멀티 라우터 기반 스타-트리 토폴로지를 기본 라우팅 토폴로지로 설정하고 이를 위한 ID 설정 방법과 데이터 송수신 방법에 대해 정의하였다. 실험을 통해 멀티 라우터 기반 피킹 시스템의 데이터 전송 성공률이 최대 20% 더 높다는 것을 확인하였다.