• Proceedings of the Korean Institute of Industrial Safety Conference
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• 2002.05a
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• pp.95-100
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• 2002

본 연구에서는 교각구조물의 안전도 평가를 위하여 먼저 대상구조물을 선정하고, 현장조사에 의해 구조물의 제원 및 손상도를 조사하였으며, 구조해석 결과에 의해 휨에 대한 안전성 검토 및 전단에 대한 안전도 검토를 강도설계법에 의해 수행하였다. 본 연구에서 수행된 풍하중을 고려한 교각구조물의 구조안전도 평가 사례는 차후의 교각구조물 안전성 검토에 대한 기초자료로 사용될 수 있을 것으로 사료된다.(중략)

• Journal of the Korea Concrete Institute
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• v.19 no.3
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• pp.377-383
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• 2007

In recent years the field application of high performance concrete has been increased to improve the quality and reliability of concrete structures. The mix design of the high performance concrete includes the 2 set-off mixture theory of mortar and coarse aggregate and that of paste and aggregate. The 2 set-off mixture theory of mortar and coarse aggregate has a problem of having to determine its value through repeated experiments in applying the rheological characteristics of mortar. The 2 set-off mixture theory of paste and aggregate has never been applied to high performance concrete since it doesn't take into account the relationship between optimum fine aggregate ratio and unit volume of powder nor does it consider the critical aggregate volume ratio. As the mixture theory of these high performance concretes, unlike that of general concrete, focuses on flowability and charge-ability, it does not consider intensity features in mix design also, the unit quantity of the materials used is determined by trial and error method in the same way as general concrete. This study is designed to reduce the frequency of trial and error by accurately calculating the optimum fine aggregate ratio, which makes it possible to minimize the aperture of aggregate in use by introducing the maximum density theory to the mix design of high performance concrete. Also, it is intended to propose a simple and reasonable mix design for high performance concrete meeting the requirements for both intensity and flowability. The mix design proposed in this study may reduce trial and error and conveniently produce high performance concrete which has self-chargeability by using more than the minimum unit volume of powder and optimum fine aggregate with minimum porosity.

• Journal of the Korean Society for Railway
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• v.16 no.6
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• pp.454-459
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• 2013

Pressure waves are generated and propagate in a tunnel when train enters tunnel high speed. A compression wave due to the entry of train head propagates along the tunnel and is reflected at tunnel exit as an expansion wave. An expansion wave due to the entry of the train tail propagates along the tunnel and is reflected at tunnel exit as a compression wave. These pressure waves are repeatedly propagated and reflected at the tunnel entrance and exit. Severe pressure changes causes ear-discomfort for passengers in the cabin and micro pressure waves around the tunnel exit. It is necessary to analyze the transient pressure phenomena in tunnels qualitatively and quantitatively, because pressure change rate is considered as one of the major design parameters for optimal tunnel cross sectional area and repeated fatigue force on car body. In this study, we developed a characteristics method based on a fixed mesh system and boundary conditions for crossing trains and analyzed this system using an X-t diagram. The results of the simulation show that offsetting of pressure waves occurs for special entry conditions of a crossing train.

• Journal of the Korean Institute of Intelligent Systems
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• v.22 no.1
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• pp.94-99
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• 2012

This paper discusses a decentralized sampled-data control problem for large-scale nonlinear systems. The system is represented in Takagi-Sugeno's form. Next, we design a decentralized analog controller based on the overlapping decomposition technique. The final step is to apply the intelligent digital redesign scheme for converting the analog controller into the sampled-data one. Design condition is represented in terms of linear matrix inequalities. A simulation result is provided for the effectiveness of the proposed design method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.9
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• pp.903-912
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• 2009

This study is focused on simulation-based dimensional tolerance optimization process (DTOP) to minimize vehicle pulls by reduction of dimensional variation in front suspension system. In previous studies, the effect of tires and wheel alignment sensitivity have mainly been investigated to eliminate vehicle pulls in nominal design condition without allocating optimal tolerance level for selected components, among various factors regarding vehicle pulls such as vehicle design parameters, vehicle weight balance, tires, and environmental factors. Unfortunately, there are wide variations in the real vehicle, and these have impacted actual vehicle pulls, especially wheel alignment effects from suspension geometry variation has not been considered in the previous studies. In the tolerance design of suspension, tolerance variables with the uncertainty such as parts dimensional variation, assembly process, datum position and direction, and assembly tool tolerance has a great influence on the variation of the suspension dimensional performances. This study introduces total vehicle pull prediction model in considering major key factors for vehicle pull sensitivity. The Monte Carlo-based tolerance analysis model using Taguchi robust method is developed to optimize dimensional tolerance parameters, satisfying on the target variation level.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1585_1586
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• 2009

본 논문에서는 다구찌 기법을 사용하여 최적설계 한 중심 주파수가 920MHz인 휴대용 RFID 리더안테나를 제안한다. 제안한 안테나는 모서리가 절단되고 정사각형 마이크로스트립 패치에 네 변으로부터 슬롯을 갖는 구조이다. 이러한 슬롯구조는 마이크로스트립 패치안테나를 소형화 시킬 수 있으며, 슬롯이 없는 구조에 비해서 약 18%의 안테나 크기 감소가 가능함을 실험을 통해 확인 하였다. 슬롯의 구조를 갖게 되는 소형의 안테나는 복잡한 설계변수에 따라 변화하므로 최적의 안테나 설계를 위해서는 해석 및 시험단계에 수많은 반복이 요구된다. 본 연구에서는 해석 및 실험 횟수를 최소화할 수 있는 실험계획법인 다구찌법의 직교배열 표를 도입하여 설계할 때의 주요 요소들의 민감도 해석을 수행하고 그 영향성을 분석하여 해석결과를 바탕으로 설계반복을 최소화 하면서 최적의 구조를 갖는 안테나를 설계 하였으며 유전율이 4.4이고, 두께가 3.2mm 인 Epoxy 1.6T의 기판상에 제작한 안테나 특성에 대한 실험 결과를 제시하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.3
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• pp.554-562
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• 2004

It was recommended for all ship engaged in international voyages to carry the Satellite Emergency position Indicating Radio Beacon according to Global Maritime Distress ＆ Safety System but also it is tending to be diffused to require the satellite EPIRB installed in small vessel such as a fishery boat by domestic regulations of each countries. Otherwise the domestic regulation can't evaluate exactly the compatibility with the satellite system and the performance of the equipment itself required by international regulation. And even if it is required the performing of the performance inspection in accordance with international regulation, it is difficult to grasp the characteristics of equipment by a generalized measuring equipment. Hence this study performed the measurement for the matters related with an wave forms, modulation characteristics, frequency and the power, etc through the design and implementation of the test bench capable of ensuring most of test items regulated by international regulation. Through this study, it has been paved the way being capable of preparation of the standard regarding to transmission repetition period, phase variation and frequency stability related with the system compatibility and in conclusion, it is enable to improve the performance of a main distress communication equipment directly connected with the life of a survivor.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.11 no.6
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• pp.90-95
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• 1997

In designing a resonant circuit of the inverter which puts induction heating with high frequency to the load, an inductance L of the circuit, the coupling coefficient of a transformer transfering the output power to load, and the coupling coefficient of load circuit heating with coil affect to the output power of a resonant circuit, the circuit Q and the frequency. Those characteristics of the circuit are analyzed through Thevenan's equivalent circuit of the coupling coefficient type which is derived from the T-type equivalent circuit of a transformer. On this equivalent circuit, the impedance of a transformer referred to its primary side is not only proportional the square of turn ratio, nZ, but also the square of coupling coefficient, K2 This paper proposed a more accurate fundamental method to design a resonant circuit of the inverter by using the Thevenan's equivalent circuit.

• Journal of Welding and Joining
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• v.16 no.5
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• pp.134-141
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• 1998

In this study, a fillet size for bending fatigue strength of one side fillet welded T-joint, used in box type girder and other welding structure, was investigated by bending fatigue test with or without edge preparation and burn through, with variation of joint shape. As a result, the following conclusions were obtained. (1) In one side fillet welded T-joint, the larger the leg length, the greater the bending fatigue strength. The increase in bending fatigue strength. (2) One side filet welded T-joint with edge preparation showed higher bending fatigue strength than that with twofold-large leg length and without edge preparation. (3) In one side fillet welded T-joint without edge preparation, both manual welding and automatic welding were carried out with same condition. In this case, automatic welding shoed deeper penetration and more increased horizontal leg length than manual welding, so that automatic welding offers grater bending fatigue strength. (4) For one side fillet welded T-joint without edge preparation, the ratio(h/t) of the leg length (h) and the main plate thickness (t) in which toe crack can occur was 1.2 over. (5) In one side fillet welded T-joint with edge preparation, the burn through led to reduced bending fatigue strength. However, this bending fatigue strength was higher than that of one side fillet welded T-joint without edge preparation and with a larger leg length.

• Journal of the Korean Institute of Intelligent Systems
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• v.15 no.3
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• pp.324-329
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• 2005

In this paper, a robust $H\infty$ stabilization problem to a uncertain discrete-time nonlinear systems with time-delay via fuzzy static output feedback is investigated. The Takagj-Sugeno (T-S) fuzzy model is employed to represent an uncertain nonlinear system with time-delayed state. Then, the parallel distributed compensation technique is used for designing of the robust fuzzy controller. Using a single Lyapunov function, the globally asymptotic stability and disturbance attenuation of the closed-loop fuzzy control system are discussed. Sufficient conditions for the existence of robust $H\infty$ controllers are given in terms of linear matrix inequalities via similarity transform and congruence transform technique. We have shown the effectiveness and feasibility of the proposed method through the simulation.