• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.97.1-97.1
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• 2011

Dimethyl ether (DME) is an attractive fuel as a hydrogen carrier for mobile PEMFC applications. However, its reforming technologies are rarely studied especially by using autothermal reforming (ATR) method. This work explored the impact of operating conditions to the performance of DME ATR. Temperature, Steam to carbon ratio(SCR), Oxygen to carbon ratio(OCR) and Gas hourly space velocity(GHSV) were considered as the operating conditions. As results, conversion efficiency was increased as the temperature increased, but saturated around $700^{\circ}C$. There was no significant effect of SCR on conversion efficiency, but high SCR led reactions in endothermic manner. High OCR substantially suppressed conversion efficiency, but it helped to sustain the temperature by stimulating exothermic reactions. Conversion efficiency was decreased as GHSV increased. The optimized operating conditions was suggested: $700^{\circ}C$, SCR of 1.5, OCR of 0.45 and GHSV below 15000/h and conversion efficiency was ~85% at the conditions.

• Journal of Korea Water Resources Association
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• v.46 no.4
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• pp.373-387
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• 2013

For the efficient operation and management of the water resources system, coordinated operation of weirs and reservoirs is required. A simulation based, and an optimization based approaches are available to deal with the operation and management problems. The simulation based approach does not guarantee an optimal solution, and the optimization based approach is not so flexible to consider, complex, nonlinear problems we will face when trying to allocate water to different uses, various demand sectors in a basin. Hence, it is important to develop a model that would compensate for the weak points in both models. We will compare and contrast intrinsic and extrinsic properties of two modeling approaches, addressing issues related to setting system operation and control rules that would lead us to more efficient use of water in the basin. As a result, we propose to use CoWMOM(Coordinated weirs and multi-reservoir operating model), a "simulation based" optimization model for a simple simulation of the past periods, and for the real-time simulation process considering uncertain inflow.

• International Journal of Naval Architecture and Ocean Engineering
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• v.7 no.2
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• pp.270-287
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• 2015

According to the increase of the operating cost and material cost of a ship due to the change of international oil price, a demand for the lightening of the ship weight is being made from various parties such as shipping companies, ship owners, and shipyards. To satisfy such demand, many studies for a light ship are being made. As one of them, an optimal design method of an existing hull structure, that is, a method for lightening the ship weight based on the optimization technique was proposed in this study. For this, we selected a hatch cover of a bulk carrier as an optimization target and formulated an optimization problem in order to determine optimal principal dimensions of the hatch cover for lightening the bulk carrier. Some dimensions representing the shape of the hatch cover were selected as design variables and some design considerations related to the maximum stress, maximum deflection, and geometry of the hatch cover were selected as constraints. In addition, the minimization of the weight of the hatch cover was selected as an objective function. To solve this optimization problem, we developed an optimization program based on the Sequential Quadratic Programming (SQP) using C++ programming language. To evaluate the applicability of the developed program, it was applied to a problem for finding optimal principal dimensions of the hatch cover of a deadweight 180,000 ton bulk carrier. The result shows that the developed program can decrease the hatch cover's weight by about 8.5%. Thus, this study will be able to contribute to make energy saving and environment-friendly ship in shipyard.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.8
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• pp.737-743
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• 2009

Design optimization process and results of Loop Heat Pipe(LHP) using Tabu Search have been presented in this study. An objective of optimization is to reduce a mass of the LHP with satisfying operating temperature of a Lithium Ion battery onboard an aircraft. The battery is assumed to be used as power supply of air borne high energy laser system because of its high specific energy. The analytical models are based on a steady state mathematical model and the design optimization is performed using a Meta Model and Tabu Search. As an optimization results, the Tabu search algorithm guarantees global optimum with small computation time. Due to searching by random numbers, initial value is dominant factor to search global optimum. The optimization process could reduce the mass of the LHP which express the same performance as an published LHP.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.11
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• pp.1215-1220
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• 2014

Breaking time is an important performance indicator of a circuit breaker. Thus, the operating mechanism of the circuit breaker should be optimized for reducing the breaking time. The operating mechanism in a gas circuit breaker is made up of several latches. Specifically, the geometry and relative positions of latches influence the dynamic behaviors of the operating mechanism. In this study, a three-stage latch operating mechanism is analyzed on the basis of the verified multibody dynamics model constructed using the MSC.ADAMS program. The relative positions and lengths of latches are selected as design variables. The dominant design variables are selected by a design study. Optimization is performed using a genetic algorithm (GA). The study results demonstrate that the performance of the circuit breaker improves by about 22.5.

• Journal of Korean Society of Transportation
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• v.27 no.2
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• pp.199-206
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• 2009

In relation with economical efficiency analysis on investment evaluation of transportation system, among vehicle operating cost saving benefit that is applied to general preliminary assessment guidelines and investment evaluation guidelines, oil expense calculated data which concentrated and analyze on the relationship between oil consumption amount on running state and running speed. For uninterrupted flow which does not have stopped delay due to traffic signal, consideration for reduction benefit is possible due to the changes of running speed and travel time however, for interrupted flow which the stopping occurs due to signal control on actual signal intersection has no consideration for stopping delay time reduction and stopping rate improvement thus reflection of reality on improved effect analysis is difficult. Therefore, this research makes a framework to analyze benefits that reflects the features of signalized intersections by benefits associated with decrease of stopping delay time with existing research and developing vehicle operating cost calculation model formula. Vehicle operating cost has been redefined considering the stopping delay time by applying the oil consumption amount at idling and the economical benefit between conventional model and newly developed model when applied for the optimization of traffic signal system on the two roads in Seosan city has been analyzed comparative. While the importance of traffic system maintenance is being emphasized due to the increase of congested areas on roads, it is expected to assist in more realistic economical analysis which reflect the delay improvement through the presentation of an economic analysis model that considers the features of signalized intersections in signal optimization system improvements and effect analysis of congestion improvement projects`.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.6
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• pp.749-762
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• 2019

In recent years, in urban areas, underground of roads are being promoted in order to resolve traffic congestion and to secure green spaces, and due to the low ratio of large vehicles, they are planned or constructed as road tunnels for small cars only. In addition, the tunnels being built in the city is a tendency to be enlarged to play the role of main roads. Accordingly, the capacity of the ventilation system is increasing and various ventilation methods are required, and the importance of maintenance after the completion of the tunnel such as the operating cost of the ventilation system is emphasized. Therefore, the need for optimization of the operation stage for reducing the power consumption of the ventilation system and the study of the ventilation system operation control logic is increasing. In this study, the study on the necessity of the optimization of operation stage and control logic of the ventilation system was carried out to realize the energy-saving operation for the small car only passing through tunnels which is applied of ① jet fan and combination ventilation system (② jet fan + air purifying equipment, ③ jet fan + vertical shaft, ④ jet fan + supply air semi-transverse). As a result of this study, there can be various operating combinations in the case of the combined ventilation system, and even though the amount of ventilation air is the same, the operating power varies greatly according to the operating combinations. It was found that operating the axial fan first rather than the jet fan first operation method has an effect on power saving.

• Journal of the military operations research society of Korea
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• v.7 no.1
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• pp.118-138
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• 1981

In many response surface optimization problems for industrial processes, there are more than two responses of interest, and we want to find the optimal levels of the factors that influence the responses. This paper is to propose how to set up the desirability functions to find the optimum for a given set of data, and to propose how to analyse the data and the desirability functions to determine an optimal operating condition for the factors. To implement the proposed method in practice, a FORTRAN computer program was written and explained. Finally, an industrial example is illustrated to explain the proposed technique and the source list of the computer program is attached for the users.

• Proceedings of the Korean Society for Quality Management Conference
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• 1998.11a
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• pp.556-567
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• 1998

Robust design in industry is an approach to reducing performance variation of quality characteristic value in products and processes. Taguchi has used the signal-to-noise ratio(SN) to achieve the appropriate set of operating conditions where variability around target is low in the Taguchi parameter design. Taguchi has dealt with having constraints on both the mean and variability of a characteristic (the dual response problem) by combining information on both mean and variability into an SN. Many Statisticians criticize the Taguchi techniques of analysis, particularly those based on the SN. In this paper we propose a substantially simpler optimization procedure for robust design to solve the dual response problems without resorting to SN. Two examples illustrate this procedure. in the two different experimental design(product array, combined array) approaches.

• Proceedings of the KIEE Conference
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• 2008.04c
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• pp.122-124
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• 2008

Interior permanent magnet synchronous motor(IPMSM) has become a popular choice in electric vehicle applications, due to their excellent power to weight ratio. In order to maximize the efficiency in such applications, this paper proposes the Adaptive-FNIS(Fuzzy Neural Network Inference System). The controllable electrical loss which consists of the copper loss and the iron loss can be minimized by the optimal d-axis current $i_d$. This paper considers the parameter variation about the motor operation. The operating characteristics controlled by efficiency optimization control are examined in detail.