• 한국신뢰성학회지:신뢰성응용연구
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• 제3권2호
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• pp.127-136
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• 2003

This paper investigates the effect of individual observations in regression models with MA(1) errors through the 'hat matrix' It shows that the first observation has the largest hat matrix diagonal component for $\theta$＜0 in the regression model with an intercept. This provides additional evidence for retaining the first observation in performing estimation in this setting. When the regression model goes to the origin and the independent variable has a deterministic trend, the last observation has the greatest leverage for │$\theta$│＜1 and may have potentially large impact on parameter estimation.

• 전자공학회논문지
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• 제53권3호
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• pp.99-106
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• 2016

본 논문에서는 잡음이 내포된 관측행렬에서 손실 데이터를 보정하는 방법과 그 잠재적 잡음에 대한 불확실성 분석에 대해서 다룰 것이다. 관측행렬에 잡음과 손실 데이터가 없을 경우는 SVD 행렬인수분해 방법에 의해 정확한 복원 결과를 얻을 수 있다. 그렇지만 일반적으로 관측행렬의 일부 요소는 손실되거나 잡음 영향을 받게 된다. 이러한 경우는 3차원 복원 오차를 유발시킬 뿐만 아니라 그 해결책 또한 찾기가 쉽지 않은 문제가 있다. 따라서 3차원 복원 오차를 최소화하기 위해서는 무엇보다도 잡음 환경에서 손실 데이터를 신뢰성 있게 보정하고, 그 보정된 결과를 정량적으로 평가를 해줄 필요가 있다. 본 논문은 2차원 투영 객체와 3차원 복원 형상 사이의 기하학적 특성을 이용해 손실 데이터를 보정 하는 방법을 소개하고, 그 보정 성능을 정량적으로 평가할 수 있는 SVD rank이론을 이용한 관측행렬의 잡음 레벨 추정 방법에 대해서 제안할 것이다.

• 대한기계학회논문집A
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• 제29권6호
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• pp.795-803
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• 2005

This paper studies the observability of calibration system with a measurement operator. The calibration system needs a simple digital indicator to measure the mobile table movements with respect to the MC coordinate. However, it yields the concern about the poor parameter observability due to measuring only a part of the movements. We uses the QR-decomposition to find the optimal calibration configurations maximizing the linear independence of rows of an observation matrix. The number of identifiable parameter is examined by the rank of the observation matrix, which represents the parameter observability. The method is applied to a 6-axis MC with parallel tilting table and the calibration results are presented. These results verify that all necessary kinematic parameters are observable and the calibration system has robustness to the noise using optimal calibration configurations.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1512-1517
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• 2003

This paper presents the calibration for the parallel typed tilting table. The calibration system needs only simple sensing device which is a digital indicator to measure the orientation of a table. The calibration algorithm is developed by a measurement operator. It eliminates the concern about the poor parameter observability due to a large number of parameters of parallel-mechanism. This paper uses the QR-decomposition to find the optimal calibration configurations maximizing the linear independence of rows of a observation matrix. The number of identifiable parameters is examined by the rank of the observation matrix, which represents the parameter observability. The method is applied to a Parallel-typed Tilting Table and all the necessary kinematic parameters are identifiable.

• 대한기계학회논문집A
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• 제27권4호
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• pp.647-655
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• 2003

This paper studies the observability of calibration system with a constraint movement by a constraint operator. The calibration system with the constraint movement need only simple sensing device to check whether the constraint movements are completed within an established range. However, it yields the concern about the poor parameter observability due to the constraint movements. This paper uses the QR-decomposition to find the optimal calibration configurations maximizing the linear independence of rows of a observation matrix. The number of identifiable parameters are examined by the rank of the observation matrix, which represents the parameter observability. The method is applied to a parallel typed machining center and the calibration results are presented. These results verify that the calibration system with low-cost indicators and simple planar table is accurate as well as reliable.

• 한국공작기계학회논문집
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• 제10권6호
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• pp.42-47
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• 2001

In this study, fatigue limit of ductile cast iron is evaluated based on phenomena of the microscopic observation, such as matrix structure, spheroidal ratio, size of graphite and distribution. Three different ferrite-pearlite matrix structure, GCD 45-), GCD 50, GCD 60 series, all of which contain more than 70% spheroidal ratio of graphite, were used to obtain the correlation between maximum size of graphite and fatigue strength. It was concluded as fellows. (1) In Ductile cast iron of ferrite-pearlite matrix, the fatigue limit of GCD 60 series with 73% pearlite structure was the highest. (2) From observation of the starting point of crack of all specimens, it is noted that the crack initiates, in graphite, goes through ferrite and propagates into pearlite. (3) A good quality of Ductile cast iron used in this experiment can be checked from uniformly distributed graphite. The negligible interaction effect between graphites was verified by microscopic observation and fracture mechanics investigation in surface and interior of the specimen.

• Earthquakes and Structures
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• 제22권4호
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• pp.387-399
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• 2022

To study the seismic damage of masonry structures and understand the characteristics of the multi-intensity region, according to the Dujiang weir urbanization of China Wenchuan earthquake, the deterioration of 3991 masonry structures was summarized and statistically analysed. First, the seismic damage of multistory masonry structures in this area was investigated. The primary seismic damage of components was as follows: Damage of walls, openings, joints of longitudinal and transverse walls, windows (lower) walls, and tie columns. Many masonry structures with seismic designs were basically intact. Second, according to the main factors of construction, seismic intensity code levels survey, and influence on the seismic capacity, a vulnerability matrix calculation model was proposed to establish a vulnerability prediction matrix, and a comparative analysis was made based on the empirical seismic damage investigation matrix. The vulnerability prediction matrix was established using the proposed vulnerability matrix calculation model. The fitting relationship between the vulnerability prediction matrix and the actual seismic damage investigation matrix was compared and analysed. The relationship curves of the mean damage index for macrointensity and ground motion parameters were drawn through calculation and analysis, respectively. The numerical analysis was performed based on actual ground motion observation records, and fitting models of PGA, PGV, and MSDI were proposed.

• Journal of Electrical Engineering and Technology
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• 제12권3호
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• pp.996-1006
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• 2017

Phasor Measurement Unit (PMU) placement is a crucial problem for State Estimation (SE) of the power system, which can ensure that the power network is fully observed. Further, the observation reliability problem of the system has been concerned in the operation conditions. In this paper, based on modified weighted adjacent matrix ($A_w$), an optimal placement method is proposed to solve simultaneously two problems involving the optimal PMU placement problem and the observation reliability enhancement problem of the system. The purpose of the proposed method is to achieve both the minimum total cost and the maximum observation reliability, with a focus on increasing the security of observability, strengthening the observation reliability of buses as well as enhancing the effectiveness of redundancy. Simulations on IEEE 14, 24, 30 and 57 bus test systems are presented to justify the methodology. The results of this study show that the proposed method is not only ensuring the power network having the observability effectively but also enhancing significantly the observation reliability. Therefore, it can be a useful tool for SE of the power system.

• 한국정보통신학회논문지
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• 제20권3호
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• pp.527-535
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• 2016

3차원 형상과 모션을 추정하기 위한 통계학적 최적화 알고리즘들이 다양하게 개발되고 있다. 그렇지만 통계적 접근은 카메라의 기하학적 위치나 관측시야각 등의 설정에 따른 SfM(Shape form Motion)의 민감한 영향을 분석하는데는 한계가 있다. 본 논문은 SfM의 모호성을 예측하기 위해 카메라 촬영 구성 요소를 이용하여 관측행렬의 불확실성을 정량적으로 추정할 수 있는 방법을 제안한다. 제안한 방법은 SfM 알고리즘의 최종적인 복원 성능을 예측하는데도 매우 효과적인 방법이다. 또한 합리적인 복원 결과를 기대할 수 있도록 카메라 촬영 구성을 설정하기 위한 직접적인 가이드라인을 제공할 수 있다는 점에서 중요하다. 실험결과는 이러한 카메라 촬영 구성을 이용하여 관측행렬의 불확실성에 대한 정량적 추정을 실험적으로 검증하고 본 알고리즘의 효율성을 확인한다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 추계학술발표대회 논문집
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• pp.54-54
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• 2003

We have developed a Cu-based bulk amorphous composite reinforced with a micron-sized crystalline phase, the (Cu60Zr30Ti10)95Ta5 amorphous matrix composite. The composite demonstrates the ultimate strength of 2332 MPa with a dramatically enhanced fracture strain of 15.3 %. Macroscopic observation of the fractured (Cu60Zr30Ti10)95Ta5 amorphous matrix composite showed the development of multiple shear bands along with numerous branching and deflection of shear bands. Microscopic observation on the amorphous matrix of the composite showed that cracks propagate through the residual amorphous matrix located between nanocrystallites, which had formed during deformation. Simulations based on finite element method were conducted to understand the formation mechanisms of multiple shear bands, the initiation site of shear bands, and interaction of shear bands with crystalline particles. Other microscopic fracture mechanism responsible for the enhanced plasticity was discussed.