• Structural Engineering and Mechanics
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• 제27권3호
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• pp.263-276
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• 2007

This paper presents a fuzzy finite element model for the analysis of structures in the presence of multiple uncertainties. A new methodology to evaluate the cumulative effect of multiple uncertainties on structural response is developed in the present work. This is done by modifying Muhanna's approach for handling single uncertainty. Uncertainty in load and material properties is defined by triangular membership functions with equal spread about the crisp value. Structural response is obtained in terms of fuzzy interval displacements and rotations. The results are further post-processed to obtain interval values of bending moment, shear force and axial forces. Membership functions are constructed to depict the uncertainty in structural response. Sensitivity analysis is performed to evaluate the relative sensitivity of displacements and forces to uncertainty in structural parameters. The present work demonstrates the effectiveness of fuzzy finite element model in establishing sharp bounds to the uncertain structural response in the presence of multiple uncertainties.

• Journal of Plant Biology
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• 제18권2호
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• pp.45-52
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• 1975

Effects of air pollutants on vegetation were reviewed and discussed with special reference to sulfur dioxide. Main contents were on the sources, meteorological factors, injury symptoms, relative sensitivity, growth/yield, indicator/diagnosis, combined effects, injury mechanism and effects on plant metabolism, injury diminishing measures, and future research needs.

• 환경영향평가
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• 제15권6호
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• pp.385-394
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• 2006

Land resources should be managed not only for human utilizations but also for environmental preservation. Based on that, environmental capacity should be estimated in both environmental and developmental ways. This study was performed for developing an estimation model for relative environmental capacity, considering both Development Tolerance Index(DTI), which shows environmental and ecological conservation value and is based on national environmental assessment indicators of the Korea Ministry of Environment, and Development Attractiveness Index(DAI), which shows topographical characteristics and geographical accessibility. The relative environmental capacity in this study can be helpful to coping with the conflict in planning and managing the use of land resources. The relative environmental capacity in this study, however, did not include either environmental or ecological sensitivity of land resources. This limitation should be solved through further research.

• 센서학회지
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• 제5권3호
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• pp.33-40
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• 1996

$(Ba_{0.5}\;Ca_{0.5})TiO_{3}$ 감습소자를 고상반응법으로 제조하고, 그 전기적 특성을 조사하였다. 상대습도에 대한 임피던스 변화가 선형적인 우수한 감도를 나타냈으며, 충 방전 전류 특성으로부터 흡습시 주요 캐리어는 이온성 캐리어임을 나타내며, 고온 및 고습영역으로 갈수록 전기전도도가 증가함을 알 수 있다. 고습영역으로 갈수록 유전율이 증가하며, 활성화에너지는 상대습도가 증가할수록 감소함을 알 수 있다.

• Nuclear Engineering and Technology
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• 제36권5호
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• pp.430-449
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• 2004

A quantitative model for a control system that integrates human operators, systems, and their interactions is developed based on discrete functions. After identifying the major entities and the key factors that are important to each entity in the control system, a quantitative analysis to estimate the recovery failure probability from an abnormal state is performed. A numerical analysis based on assumed values of related variables shows that this model produces reasonable results. The concept of 'relative sensitivity' is introduced to identify the major factors affecting the reliability of the control system. The analysis shows that the hardware factor and the design factor of the instrumentation system have the highest relative sensitivities in this model. T도 probability of human operators performing incorrect actions, along with factors related to human operators, are also found to have high relative sensitivities. This model is applied to an analysis of the TMI-2 nuclear power plant accident and systematically explains how the accident took place.

• 열처리공학회지
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• 제26권5호
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• pp.233-240
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• 2013

Rapid and homogeneous heating in heat treatment has been a challenging engineering issue throughout a heating temperature over $1,000^{\circ}C$. Induction heating has been widely used in field of heat treatment compared with conventional heating system. Advantages in homogeneous heating, simple fabrication, and repeatable use can be efficiently made with the induction heater. In this paper, numerical analysis of an induction coil system for heat flux gauge heating is performed. The effect of configuration on the heating performance was considered in various cases of the coil radius, distance between the winding, relative height difference between the heat flux gauge and the coil, and the applied current frequency. Temperature distribution within the heat flux gauge at frequency-steady state was calculated with a finite element method. Sensitivity analysis was also performed and the relative importance of 2 key parameters; coil radius, distance between the winding, were taken as main contributors for induction heating.

• 한국진공학회지
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• 제10권2호
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• pp.225-233
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• 2001

Oxygen flooding을 이용한 Secondary ion Mass Spectrometry(SIMS) 분석에 있어서 표면에 산화막이 있을 때 발생하는 SIMS depth profile의 왜곡현상에 대한 원인을 분석하고 이를 보정하였다. 이러한 왜곡현상은 표면 산화막에서와 Si 매질에서의 sputter rate이 다른 데서 발생하는 깊이 보정 오류와 상대감도인자(relative sensitivity factor, RSF)가 다른 데서 발생하는 농도보정 오류로부터 발생됨이 밝혀졌다. 깊이보정 오류를 바로잡기 위하여 $N^a+$ 이온을 산화막과 Si 매질의 계면에 대한 marker로 사용하였으며 산화막 두께는 SEM 및 XPS로 측정하였다. 산화막과 Si 매질에서의 sputter rate 및 RSF의 차이는 주로 oxygen flooding이 유발한 산화막 형성시의 부피팽창에 의한 것으로 해석되었으며 이를 보정한 depth profile은 oxygen flooding없이 분석한 경우와 거의 동일한 결과를 보여주었다.

• Structural Engineering and Mechanics
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• 제18권6호
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• pp.709-729
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• 2004

This paper presents numerical and experimental investigations on damage detection of mono-coupled multistory buildings using natural frequency as only diagnostic parameter. Frequency equation of a mono-coupled multistory building is first derived using the transfer matrix method. Closed-form sensitivity equation is established to relate the relative change in the stiffness of each story to the relative changes in the natural frequencies of the building. Damage detection is then performed using the sensitivity equation with its special features and minimizing the norm of an objective function with an inequality constraint. Numerical and experimental investigations are finally conducted on a mono-coupled 3-story building model as an application of the proposed algorithm, in which the influence of modeling error on the degree of accuracy of damage detection is discussed. A mono-coupled 10-story building is further used to examine the capability of the proposed algorithm against measurement noise and incomplete measured natural frequencies. The results obtained demonstrate that changes in story stiffness can be satisfactorily detected, located, and quantified if all sensitive natural frequencies to damaged stories are available. The proposed damage detection algorithm is not sensitive to measurement noise and modeling error.

• 재무관리연구
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• 제23권2호
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• pp.85-107
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• 2006

이 논문에서는 새로운 뉴스에 대해 선물시장이 현물시장보다 더 민감하게 반응하는지와 더 큰 가격변동폭을 보이는지를 검증한다. 뉴스에 대한 민감도는, 선물가격의 일간변동을 이론가격 변동에 관해 회귀시킨 식의 회귀계수에 의해 측정한다. 그리고 가격변동폭은 선물가격과 이론가격의 평균범위차이($\overline{RD}$), 평균고가차이($\overline{HD}$) 및 평균저가차이($\overline{LD}$)라는 세 가지 척도를 사용하여 측정한다. 이 논문에서 사용한 자료는 코스피200 지수선물시장의 개설 초기인 1996년 7월부터 최근의 2005년 12월말까지 최근월물과 차근원물의 선물가격과 이론가격이다. 민감도의 차이를 나타내는 $\hat{\beta}$는 1과 크게 유의한 차이를 보이지 않으므로 뉴스에 대한 두 시장의 민감도는 대체로 큰 차이가 있는 것으로 보이지 않는다. 그러나 최근기간(2002년 11월${\sim}$2005년 12월)에는 최근월물 및 차근월물 모두 1보다 큰 값을 보이고 있어 선물시장이 더 민감하게 반응하고 있다. 또 최근기간에 최근월물의 가격이 좋은 뉴스에 대해 현물시장보다 더 민감하게 반응하였다. 전체기간 및 하위기간의 ($\overline{RD}$)는 대체로 0과 유의한 차이를 갖지 않는다. 그러나 최근월물의 평균고가차이($\overline{HD}$)는 전체기간과 하위기간 모두에서 뚜렷하게 유의한 양의 값을 보이고 있다. 이것은 최근월물 선물가격의 좋은 뉴스에 대한 가격변동폭이 현물가격보다 더 크다는 것을 의미한다.

• Smart Structures and Systems
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• 제4권5호
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• pp.629-640
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• 2008

A new algorithm is proposed to determine optimal accelerometer locations (OAL) when a structure is identified by frequency domain system identification (SI) method. As a result, a guideline is presented for selecting OAL which can reflect modal response of a structure properly. The guideline is to provide a minimum number of necessary accelerometers with the variation in the number of measurable target modes. To determine OAL for SI applications effectively, the modal sensitivity effective independence distribution vector (MS-EIDV) is developed with the likelihood function of measurements. By maximizing the likelihood of the occurrence of the measurements relative to the predictions, Fisher Information Matrix (FIM) is derived as a function of mode shape sensitivity. This paper also proposes a statistical approach in determining the structural parameters with a presumed parameter error which reflects the epistemic paradox between the determination of OAL and the application of a SI scheme. Numerical simulations have been carried out to examine the proposed OAL algorithm. A two-span multi-girder bridge and a two-span truss bridge were used for the simulation studies. To overcome a rank deficiency frequently occurred in inverting a FIM, the singular value decomposition scheme has been applied.