• 한국소음진동공학회논문집
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• 제25권11호
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• pp.731-738
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• 2015

This study proposed the method of the multi-crack detection using the sensitivity coefficient matrix which is calculated from the change of eigenvalues and eigenvectors before and after the crack. Each crack is modeled by a rotational springs. The method is applied to the cantilever beam with miulti-crack. The eigenvalues and eigenvectors are determined for different crack locations and depths. The prediction of multi-crack detection are in good agreement with the results of structural reanalysis.

• Journal of Mechanical Science and Technology
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• 제15권9호
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• pp.1292-1301
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• 2001

The mean-line method using empirical models is the most practical method of predicting off-design performance. To gain insight into the empirical models, the influence of empirical models on the performance prediction results is investigated. We found that, in the two-zone model, the secondary flow mass fraction has a considerable effect at high mass flow-rates on the performance prediction curves. In the TEIS model, the first element changes the slope of the performance curves as well as the stable operating range. The second element makes the performance curves move up and down as it increases or decreases. It is also discovered that the slip factor affects pressure ratio, but it has little effect on efficiency. Finally, this study reveals that the skin friction coefficient has significant effect on both the pressure ratio curve and the efficiency curve. These results show the limitations of the present empirical models, and more resonable empirical models are reeded.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.179-184
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• 2005

Shear strength parameters obtained from filed survey are important factors in the analysis of slope stability. In this study, sensitivity analysis was performed to evaluate the effect of input parameters on the analysis of slope stability. The input parameters selected for sensitivity analysis were slope angle, cohesion, and friction angle. Monte-Carlo Simulation method was used for calculating input parameters and the factor of safety was computed by means of limit equilibrium method. A rock slope, which has failed in the field, was used for the sensitivity analysis in the analysis of slope stability. The result of analysis shows that the factor of safety of the rock slope was a little low. From partial correlation coefficient(PPC) of input parameters determined from the sensitivity analysis, slope stability was dependant on cohesion and slope angle. The effect of friction angle was lower than that of cohesion and slope angle on slope stability.

• 제어로봇시스템학회논문지
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• 제10권3호
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• pp.205-215
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• 2004

The characteristic ratio assignment (CRA) method〔1〕 is new polynomial approach which allows to directly address the transient responses such as overshoot and speed of response time in time domain specifications. The method is based on the relationships between time response and characteristic ratios($\alpha_i$ ) and generalized time constant (T), which are defined in terms of coefficients of characteristic polynomial. However, even though the CRA can apply to developing a linear controller that meets good transient responses, there are still some fundamental questions to be explored. For the purpose of this, we have analyzed several sensitivities of a linear system with respect to the changes of coefficients itself and $\alpha_i$ of denominator polynomial. They are (i) the unnormalized root sensitivity : to determine how the poles change as $\alpha_i$ changes, and (ii) the function sensitivity to determine the sensitivity of step response to the change of o, and to analyze the sensitivity of frequency response as o, changes. As an other important result, it is shown that, under any fixed T and coefficient of the lowest order of s in denominator, the step response is dominantly affected merely by $\alpha_1, alpha_2 and alpha_3$ regardless of the order of denominator higher than 4. This means that the rest of the$\alpha_i$ s have little effect on the step response. These results provide some useful insight and background theory when we select $\alpha_i$ and T to compose a reference model, and in particular when we design a low order controllers such as PID controller.

• 한국소음진동공학회논문집
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• 제16권5호
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• pp.470-478
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• 2006

An efficient method for change of eigenvectors and eigenvalues due to the modifying proportional damping structure using sensitivity coefficients is presented. Sensitivity coefficients are determined by iteration with eigenvalue and eigenvectors before modification of system. The proposed method is applied to examples of 3 degrees of freedom system and plate by modifying mass and stiffness. The predicted change of eigenvectors and eigenvalues are in a good agreement with these from the structural re-analysis after modification of mass and stiffness.

• 한국통신학회논문지
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• 제38C권7호
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• pp.643-649
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• 2013

본 논문에서는 무선통신기기에서 필수적으로 사용되는 안테나의 근접 전자기장 변화에 의한 반사계수의 변화를 토대로 하여 사람의 심박신호를 검출한다. 반사되는 신호를 검출하기 위하여 20 dB의 directional coupler를 사용하여 송신신호에 영향을 주지 않고 안테나의 반사계수를 검출하는 회로를 사용하였다. 사람의 심박에 의한 다이폴 안테나의 반사계수는 약 0.07 dB 가량 변하게 되어 검출하기 어려우므로, 민감도를 향상시키는 방법을 적용하여 심박신호를 깨끗하게 잡아내었다. Discrete한 소자의 사용으로 오차가 발생하는 것을 감안하여 안테나의 위치를 움직여 최적 지점에서 더 좋은 심박신호의 결과를 나타내는 것을 확인하였고, 일반적인 통신신호에서도 가능한지 확인하기 위하여 4 MHz 대역의 FM신호를 사용하여 잘 동작하는 것을 검증하였다.

• 지질공학
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• 제4권3호
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• pp.311-319
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• 1994

본 논문은 누수를 포함하는 프락탈 대수층의 수리상수의 최적값을 구하기 위한 민감성 분석에 대한 것이다. 민감성 분석은 최소자승법을 이용한다. 민감성 분석에 의하여 수리상수(일반화 투수량계수와 일반화 저유계수)는 여러가지 흐름의 차원과 여러 값의 누수계수에 대해서 쉽게 결정될 수 있다. 아울러, 민감성, 분석은 다수의 양수정의 다단계 양수에도 적용되었다. 민감성 분석을 이용한 프락탈 대수층의 수리상수 산출을 위하여 컴퓨터 프로그램이 개발되었다.

• Smart Structures and Systems
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• 제25권2호
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• pp.169-181
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• 2020

Sensor placement is a crucial aspect of bridge health monitoring (BHM) dedicated to accurately estimate and locate structural damages. In addressing this goal, a sensor placement framework based on the deflection influence line (DIL) analysis is here proposed, for the optimal design of damage detection-oriented BHM system. In order to improve damage detection accuracy, we explore the change of global stiffness matrix, damage coefficient matrix and DIL vector caused by structural damage, and thus develop a novel sensor placement framework based on the Fisher information matrix. Our approach seeks to determine the contribution of each sensing node to damage detection, and adopts a distance correction coefficient to eliminate the information redundancy among sensors. The proposed damage detection-oriented optimal sensor placement (OSP) method is verified by two examples: (1) a numerically simulated three-span continuous beam, and (2) the Pinghu bridge which has existing real damage conditions. These two examples verify the performance of the distance corrected damage sensitivity of influence line (DSIL) method in significantly higher contribution to damage detection and lower information redundancy, and demonstrate the proposed OSP framework can be potentially employed in BHM practices.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.760-763
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• 2003

This study proposed the analysis of damage defection due to the change of the stiffness of structure by using the original and modified dynamic characteristics. The method is applied to examples of a cantilever and 3 degree of freedom by modifying the stiffness. The predicted damage detections are in good agreement with these from the structural reanalysis using the modified stiffness.

• 대한기계학회논문집
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• 제15권6호
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• pp.2109-2124
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• 1991

본 연구에서는 축류 터빈의 최적 설계 계산에서 사용 용도에 따라 달리 적용 될 수 있는 특정 제한조건, 즉 유량 계수, 압력비, 출력 그리고 하중 계수를 각각 고 려하였을 경우에 최대 효율을 가지기 위한 최적 조건을 계산하고자 한다. 또한 단일 설계 변수의 민감도(sensitivity) 뿐만 아니라, 단일 민감도에서 성능에 큰 영향을 주 는 설계 변수들에 대하여 복수 민감도를 나타내어 설계 변수 및 설계 제한 조건이 축 류 터빈의 성능에 미치는 영향을 조사하고자 한다.