• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.1107-1114
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• 2003

In this thesis, the dynamic characteristic analysis of carriage structure supported by air bearings were peformed. Toward this end, the characteristics of air bearing were numerically analyzed to estimate the stiffness of the air bearing and the clearance between air bearing and guide surface. The modal analysis of the carriage structure was peformed by using finite element method, and the experimental modal analysis was also performed to validate the finite element model, where rigid body modes were compared to validate the stiffness of the air bearings. From the results, the air spring stiffness can be estimated within the range of acceptable accuracy under any pressure and clearance condition.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.3140-3141
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• 2008

The output power efficiency of the fuel cell system depends on the demanded current, stack temperature, air excess ratio, hydrogen excess ratio and inlet air humidity. Thus, it is necessary to determine the optimal operation condition for maximum power efficiency. In this paper, we developed a dynamic model of fuel cell system which contains mass flow model, diffusivity gas layer model, membrane hydration and electrochemistry model. In order to determine the maximum output power and minimum use of hydrogen in a certain power condition, response surface methodology (RSM) optimization based on the proposed PEMFC stack model is presented. The results provide an effective method to optimize the operation condition under varied situations.

• 연구논문집
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• s.23
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• pp.5-13
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• 1993

The present work deals with the theoretical prediction of static & dynamic characteristic of annular type externally pressurized thrust air bearings with metal-sintered porous media. For the evaluation of surface loading effect by machining, it is assumed that the flow at the porous surface is dominant and which is equivalent to the flow through orifice. Finite different method with over-relaxation method is used to solve the numerical problems. The influences of radius ratio, supply pressure and squeeze number on performances are investigated, as the results. The results of this study can be used to predict the optimal running condition and stable realm of porous bearings.

• Journal of Information Technology Applications and Management
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• v.24 no.3
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• pp.93-105
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• 2017

Demands of cosmetics are affected not only by the well-known elements such as brand, price, and customer's consumption capacity, but also by some latent factors, for example, weather and air environment. Due to complexity and dynamic changes of the above factors, their influences can hardly be estimated in an accurate way by the traditional approaches such as survey and questionnaires. Through modeling and statistical analysis of big data, this article studied the impacts of weather condition and air quality on customer flow and sales of the cosmetics distributors in China, and found several hidden influencing factors. It provided a big-data based method for the analysis of unconventional factors on cosmetics marketing in the changing weather condition and air environment.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.3
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• pp.408-415
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• 1998

This study presents experimental results on the shut-down and start-up characteristics of a residential split-system air-conditioner with capillary tube, using R410A as a R22 alternative refrigerant. During shut-down, the transient characteristics are evaluated by measuring the high side and low side pressures and temperatures of the system. The dynamic behavior of the system after start-up is also investigated at the high temperature cooling test condition. All experiments are performed in psychrometric calorimeter. The cooling capacity, power consumption, dehumidification capacity and cycle characteristics after start-up are analyzed.

• Journal of Electrical Engineering and Technology
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• v.6 no.5
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• pp.613-617
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• 2011

In the present paper, a new type of electrical actuator, an electromagnetic force driving actuator (EMFA), applicable to air circuit breaker is developed and analyzed. Transient analysis is performed to obtain the dynamic characteristics of EMFA. The distribution of static magnetic flux is obtained using the finite element method. The coupled problems of electrics and mechanics governing equations are solved using the time-difference method. According to the interception rate of each contactor, investigation of the contactor spring load condition is conducted and applied to the threelink system. Comparisons of the dynamic characteristics of the three-link simulation and experimental data are performed.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.12
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• pp.1070-1077
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• 2003

This study was undertaken to judge the quality of air-tightened exhibition cases and to predict the dynamic variation of the relative humidity in the showcase. We performed a lot of experiments for the a few conditions and we numerically calculated the air change rate and the relative humidity in the showcase with the Artsorb under the same conditions. In all cases we confirmed that the numerical results about the relative humidity in the showcase had a good agreement with the experimental ones. Through the experiments of humidity control, we found out that the adsorption efficiency is varied with the location and the amount of the Artsorb. And the numerical results showed that the adsorption material is always needed to keep on the appropriate humidity condition in the showcase even though any kind of the showcases are used.

• Wind and Structures
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• v.20 no.2
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• pp.143-168
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• 2015

A numerical model for analyzing air-train-track interaction is proposed to investigate the dynamic behavior of a high-speed train running on a track in crosswinds. The model is composed of a train-track interaction model and a train-air interaction model. The train-track interaction model is built on the basis of the vehicle-track coupled dynamics theory. The train-air interaction model is developed based on the train aerodynamics, in which the Arbitrary Lagrangian-Eulerian (ALE) method is employed to deal with the dynamic boundary between the train and the air. Based on the air-train-track model, characteristics of flow structure around a high-speed train are described and the dynamic behavior of the high-speed train running on track in crosswinds is investigated. Results show that the dynamic indices of the head car are larger than those of other cars in crosswinds. From the viewpoint of dynamic safety evaluation, the running safety of the train in crosswinds is basically controlled by the head car. Compared with the generally used assessment indices of running safety such as the derailment coefficient and the wheel-load reduction ratio, the overturning coefficient will overestimate the running safety of a train on a track under crosswind condition. It is suggested to use the wheel-load reduction ratio and the lateral wheel-rail force as the dominant safety assessment indices when high-speed trains run in crosswinds.

• 한국연소학회:학술대회논문집
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• 2015.12a
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• pp.169-172
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• 2015

This paper presents a numerical investigation on kerosene-air mixture detonation and behaviors of thermal elasto-plstic thin metal tube under detonation loading based on multi-material analysis. The detonation loading is modeled by the kerosene-air mixture detonation which is compared with CJ condition and experimental cell size. And the thermal softening effect on elasto-plstic model of metal tube is indicated by different dynamic response of detonation loaded tube in various temperature and tube thickness.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.6 s.261
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• pp.531-538
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• 2007

In this study, an air conditioning system using carbon dioxide as a refrigerant was developed for automotive cabin cooling. Experiments have been carried out to examine the steady state and dynamic characteristics of this system. The system consists of a compressor, a gas cooler, an evaporator, an expansion device, an internal heat exchanger and an accumulator. The compressor is a variable displacement type, driven by the electric motor, and the gas cooler and the evaporator are aluminum extruded heat exchangers of micro channel type. The $CO_2-refrigerant$ charge, the compressor speed, the air inlet temperature of the gas cooler, the air inlet temperature and the air flow rate of the evaporator and the cooling load are varied and the performance of the system is experimentally investigated. As the compressor speed increased, cooling capacity increased, but the coefficient of performance was deteriorated. As the cabin air temperature or the air flow rate to the cabin was set high, both the cooling capacity and the COP increased. In the cool down experiment with 1.0 or 2.0 kW of heat load, the dynamic characteristics of the air-conditioning system were investigated. For a given capacity of compressor, cool down speed was monitored, and the temperature change was acceptable fur low heat load condition.