• 한국정보통신학회논문지
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• 제5권7호
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• pp.1346-1353
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• 2001

본 논문에서는 2차원 분모분리형 디지털 필터의 선계에 대한 알고리즘을 제안한다. 제안된 알고리즘은 진폭 특성과 위상특성으로 주어진 2차원 디지털 필터의 주파수 영역 설계명세조건을 특이치 분해를 이용하여 1차원 디지털 필터의 설계명세조건으로 분해한다. 따라서, 2차원 디지털 필터 설계문제는 1차원 디지털 필터의 설계 문제로 귀착되며 이는 계산적으로 유효하며 수치적으로 안정한 설계법으로 고려되며 설계 예로부터 유효성을 확인한다.

• Structural Engineering and Mechanics
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• 제62권2호
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• pp.125-138
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• 2017

Reliability-based design optimization (RBDO) is a powerful tool for design optimization when considering probabilistic characteristics of design variables. However, it is often computationally intensive because of the coupling of reliability analysis and cost minimization. In this study, the concept of reliability mapping function is defined based on the relationship between the reliability index obtained by using the mean value first order reliability method and the failure probability obtained by using an improved response surface method. Double-loop involved in the classical RBDO can be converted into single-loop by using the reliability mapping function. Since the computational effort of the mean value first order reliability method is minimal, RBDO by using reliability mapping functions should be highly efficient. Engineering examples are given to demonstrate the efficiency and accuracy of the proposed method. Numerical results indicated that the proposed method has the similar accuracy as Monte Carlo simulation, and it can obviously reduce the computational effort.

• 한국산업융합학회 논문집
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• 제26권5호
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• pp.885-894
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• 2023

Setting RAM target value for a defense system plays a crucial role in the development and design phases and the production phase as well. It is apparent that the achieved RAM target value can help maximizing the combat capability of a defense system and improving its performance throughout the system's life cycle from acquisition phase to disposal. Usually a defense system operates according to its OMS/MP (Operational Mode Summary / Mission Profile) and it consists of several subsystems which are supposed to be operated at each utilization rate under its operating conditions and the mission profiles assigned. In this study, a method of setting RAM target value is proposed for a defense system that are composed of several independent subsystems considering their utilization rates and the mission profiles assigned. And the case study of applying the proposed method of setting RAM target value to system A is dealt with.

• 한국안전학회지
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• 제2권1호
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• pp.59-71
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• 1987

A study has been made of the damping force phenomena of the shockabsorber for automobile. The main results obtained are as follows; 1) We can neglect friction loss between cylinder and piston, as it is very small compared to other damping force. 2) Damping force due to coil spring and disc valve shows comparatively stable at various piston speed and oil temperature. 3) Theoretical and experimental values are well agreed on relatively low piston speed. 4) Theoretical value on piston speed of 600mm/sec, 900mm/sec at oil temperature $20^{\circ}C$, $40^{\circ}C$, $60^{\circ}C$ and $80^{\circ}C$ is about 82% of experimental value. 5) Theretical value at oil temperature $-20^{\circ}C$, $0^{\circ}C$ is about 67% of experimental value.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.322-325
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• 2000

In the previous report1), the grinding characteristics of quartz were investigated. In this paper, the grinding mechanisms of brittle materials including ceramics and quartz are modeled and a new parameter SDR(Surface roughness Direction Ratio) is proposed to characterize the grinding mechanisms of such materials. A set of experiments were performed to verify the effectiveness of the suggested parameter. The experimental results indicate that the plastic deformation is the dominant material removal mode at the grinding conditions which show the higher value of SDR. In the case of quartz, the material was removed by brittle fracture in a lower value of SDR and by plastic deformation in a higher value of it. SDR is not affected by wheel mesh size when brittle fracture occured. But in the plastic deformation case, SDR value increases with wheel mesh size.

• Journal of Electrical Engineering and Technology
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• 제11권2호
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• pp.383-392
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• 2016

This paper proposes the design considerations of resonant network and transformer magnetics for 500 kHz high switching frequency LLC resonant converter. The high power density can be effectively achieved by adopting high switching frequency which allows small size passive components in the converter. The design methodology of magnetizing inductance is derived for zero voltage switching (ZVS) condition, and the design methodology of the transformer and output capacitance is derived to achieve high power density at high operating frequency. Moreover, the structure of transformer is analyzed to obtain the proper inductance value for high switching operation. To verify the proposed design methodology, simulation and experimental results will be presented including temperature of passive and active components, and power conversion efficiency to evaluate dominant power loss. In addition, the validity of magnetics design will be evaluated with operating waveforms of the prototype converter.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 B
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• pp.654-656
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• 2002

The pole shape. turn-on angle. and turn-off angle are important design factors that largely influence Switched Reluctance Motor' s performance when designing a switched reluctance motor. These design factors must be considered simultaneously because an independent factor restricts the improvement of the switched reluctance motor' s performance. After performing the analysis using nonlinear same characteristic finite element method that contains a operating circuit, the influence upon the torque characteristics was analyzed by the pole shape and the angles. This paper presents the most suitable design value according to input conditions and various speeds. Especially.the most suitable angles were derived from the voltage equation. and an effective design range is showed from the angles.

• 한국정보통신학회논문지
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• 제6권4호
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• pp.589-594
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• 2002

Hairpin 형태의 필터는 크기를 작게 설계할 수 있지만 설계방법이 복잡하다는 단절이 있다. 본 논문에서는 기존의 전송선로 이론과 J 인버터 회로를 이용하여 Hairpin Line 필터 설계에 새롭게 적용하였으며, 설계하는데 필요한 J 와 b 파라미터를 정확히 구하는 방법을 제시하고 있다. 인접하는 소자간의 상호 결합이 없는 부분을 고려하였으며, 각 단에서의 결합성분에 대한 전기적인 결합선로 길이를 J 와 b 파라미터로부터 구할 수 있다. 제시하고 있는 설계방법으로 Serenade 8.0을 이용하여 중심 주파수 2.6GHz에서 동작하는 소형의 Hairpin Line 대역 통과 필터를 설계하고 컴퓨터 시뮬레이션을 통하여 특성을 확인하였다.

• Structural Engineering and Mechanics
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• 제32권1호
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• pp.147-165
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• 2009

This study proposes a certain measure or investment strategy for decision making associated with seismic retrofitting. This strategy reduces the risk of a large-scale malfunction such as water supply loss under seismic risks. The authors developed a stochastic value index that will be used in the overall evaluation of social benefit, income gain, life cycle costs and failure compensation associated with existing lifeline systems damaged by an earthquake during the remaining service period. Optimal seismic disaster prevention investment of deteriorated lifeline systems is discussed. Finally, the present study provides a performance-based design method for seismic retrofitting strategies of existing lifelines which are carried out using the target probabilities of value loss and structural failure.

• 동력기계공학회지
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• 제13권4호
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• pp.68-73
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• 2009

The mathematical model has a different response character with the real system because this mathematical model has the modeling errors and the imprecise value of system's parameters. Therefore to find the value of system parameters as possible as near by real value in the model is necessary to design the controlled system. This study concern about the identification method to estimate the parameter for the magnetic bearing system with RCGA(Real Coded Genetic Algorithm). Firstly, we will get the mathematical model from the current amplifier circuit and the magnetic bearing system. Secondly we will get the step response data in this circuit and system. Finally, we will estimate the unknown parameter's value from the data.