• 한국전산유체공학회지
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• 제8권4호
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• pp.41-49
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• 2003

This study presents a numerical model to analyze dynamic thermal behavior of a hot chuck designed for flip-chip bonders. The hot chuck of concern is a heater which has been specifically developed for accomplishing high-speed and ultra-precision soldering. The characteristic features are radiative heat source and the heating tool made of a material of high thermal diffusivity. A physical modeling has been conducted for the network of heat transport. A simplified finite volume model is deviced to simulate time-dependent thermal behavior of the heating tool on which soldering is achieved. The reliability of the proposed numerical model is verified experimentally. A series of numerical tests illustrate the usefulness of the numerical model in design analysis.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 하계종합학술대회 논문집
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• pp.349-352
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• 1999

In this paper, we present simplified fault set which is made by analyzing fault relation to design specification in CMOS operational amplifier. The hard fault is easily modeled because an effect of hard fault is out of all design specification. However, the soft fault is not easily modeled because an effect of soft fault on design specification is varied according to position and depth of fault. We simulated hard and soft fault by HSPICE, varying threshold voltage and W/L ratio from 90% increase to 90% decrease. The decrease of test time and the production of high reliability mixed-mode IC are possible by the proposed fault set.

• 해양환경안전학회지
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• 제21권3호
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• pp.297-302
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• 2015

To prevent cargo accidents by repeated loads, a continuous monitoring for securing rope or additional safety measures are needed, but most of prevention measures have been conducted only by operator's own experience not a quantitative assessment. Hence, the Load-Displacement curve and approximation formula of securing rope were drawn in this research for a quantitative assessment and simplified measurement on a tension of securing rope using a tensiometer. Moreover, a com parison was conducted between m easuring tension and calculated tension on securing rope with portable tensiometer, 'Load-Displacement' approximation formula. The calculated tension of securing rope is obtained 153.3kfg using the formula and that result has not much difference with initial tension 150.0kgf. Lastly, an analysis of the characteristics of various ropes was suggested to enhance the reliability about quantitative assessment of securing rope's tension through further research.

• KIEE International Transactions on Electrophysics and Applications
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• 제4C권3호
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• pp.81-89
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• 2004

Frequency Domain Spectroscopy (FDS) measurements were performed on pressboard samples containing different moisture contents and on insulation system of power transformers. The results were used for evaluating sensitivity of the so-called X - Y model, which is applied for estimating moisture content in transformer insulation using the results of FDS measurements. Based on the observations of this analysis a simplified model, called X model, was introduced in which the presence of spacers in transformer insulation has been neglected. Finally, reliability of the X model was assessed by comparing estimates of moisture contents based on FDS measurements on field installed power transformers with moisture contents obtained from chemical analyses of their oil samples.

• KIEE International Transactions on Power Engineering
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• 제5A권1호
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• pp.56-61
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• 2005

This paper presents an evaluation of the interruption costs for commercial customers in Korea using customer survey methodology. When various research results are examined, the evaluation of direct interruption costs becomes much more simplified. Especially, in the case of commercial customers, it is known that the evaluation of direct interruption costs is more useful. Accordingly, this paper selected the customer survey method to evaluate the interruption costs for commercial customers in Korea considering interruption and customer characteristics.

• 한국융합학회논문지
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• 제3권2호
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• pp.7-12
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• 2012

최근 안드로이드 기반 상용 스마트워크 단말이 개발/보급되면서 다양한 형태의 앱이 개발되어 사용 중에 있으나 앱을 통해 사용자도 모르게 다양한 형태의 공격이 급증하고 있어 이에 대한 능동적 대응 방안이 제시되어야 한다. 본 연구에서는 안드로이드 기반 상용 스마트워크 단말의 사용자 환경을 중심으로 공격 등이 발생하였을 경우 이를 탐지하고 능동적으로 대응할 수 있는 기술에 대해 연구하였다. 본 연구에서 제시한 보안 취약성 분석 및 대응기법인 경우 기존 방식보다 간편하고 최소화된 메모리 구조를 이용하여 단말내 이상현상을 모니터링 할 수 있으면서도 효율적으로 스마트워크 단말의 공격에 대한 능동적 대응 기능을 제공한다.

• 한국산학기술학회논문지
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• 제17권9호
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• pp.724-731
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• 2016

지진으로 인한 구조물의 피해가 지속적으로 증가하면서, 구조물의 취약성을 평가하는 일은 지진 대비에 필수적으로 여겨지고 있다. 지진 취약도 곡선은 지진에 대한 구조물의 안전도에 대한 확률 지표로써 널리 이용되고 있으며, 많은 연구자들에 의해 보다 정확하고 효율적인 취약도 곡선 도출을 위한 노력이 계속되고 있다. 하지만 기존의 대부분의 연구에서는 취약도 곡선 도출시 수치해석 시간 절약을 위해 단순화된 2차원 해석모델을 사용해 왔는데, 많은 경우에 있어 2차원 모델은 정확한 구조물의 내진 거동 및 지진 취약성을 평가하기에 적당하지 않을 수 있다. 이에 본 연구에서는 3차원 해석 모델을 사용하여 더욱 정확하면서도 여전히 효과적으로 지진 취약도 곡선을 도출할 수 있는 방법을 제시한다. 이 방법은 신뢰성 해석 소프트웨어인 FERUM과 구조해석 소프트웨어인 ZEUS-NL을 서로 연동시켜 상호 자동적인 데이터 교환이 가능하게 하고, 샘플링 기법이 아닌 FORM 해석 기법을 통해 구조물의 파괴확률을 구한다. 이는 3차원 모델을 사용의 경우에도 효율적으로 구조 신뢰성 해석이 가능하게 해준다. 이를 이용해 RC 프레임 구조물의 3차원 해석 모델을 사용하여 지진 취약성 평가를 수행하였다.

• 대한조선학회지
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• 제24권2호
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• pp.29-35
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• 1987

As offshore activities move into deeper ocean, conventional fixed-base platforms drastically increase in size and cost, One of alternatives available is a guyed tower, in which environmental loads are supported by guylines instead of structural members. The guying system of the guyed tower is designed on one hand to be stiff enough to limit the structural displacement in normal operations, but on the other hand to be soft enough to permit large slow sways during the presence of design-level storms. This compliancy provides an efficient means of withstanding harsh environment so that the disproportionate increase in size of deep water platforms can be kept to a rational limit. Novel configurations contain always some degrees of potential risks mainly due to the lack of experience. The most critical hazard inherent to a guyed tower may be the pullout of anchor piles. Once it happens, the guyline fails to function and it may eventually lead to the total collapse of the system. It is the aim of this paper to discuss and quantify the anchor-pullout risk of a guyed tower. A stochastic analysis is made for evaluating the first-upcrossing probability of the tension acting on anchor piles over the uplift capacity. Nonlinearities involved in the mooring stiffness and hydrodynamics are taken into account by using time-domain analysis. A simplified two dimensional dynamic model is developed to exemplify the underlying concept. Real hurricane data in the Gulf of Mexico spanning over 70 years are incorporated in a numerical example of which result clearly indicates highly potential risk of anchor pullout.

• 한국지능시스템학회논문지
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• 제18권4호
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• pp.445-450
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• 2008

퍼지시스템의 신뢰도를 분석하기 위해서 기존의 연구에서는 퍼지시스템의 구성요소의 신뢰도를 0과 1사이의 실수, 퍼지숫자, 신용구간, 모호집합, 구간값 퍼지집합 등으로 표현하였다. 본 논문에서 우리는 전체집합 [0, 1]에서 정의되는 구간값 모호집합을 기반으로 퍼지시스템의 신뢰도를 표현하고 분석하는 방법을 제안한다. 구간값 모호집합에서는 기존 모호집합[12, 14]의 상한과 하한을 각각 구간으로 표현한다. 그러므로 퍼지시스템의 신뢰도를 더 유연한 방법으로 표현하고 분석하는 것을 가능하게 한다. 제안한 방법은 Kumar[14]가 언급한 복잡한 퍼지 사다리꼴숫자 연간보다는 퍼지 삼각숫자의 간단한 산술연산을 사용하기 때문에 제안된 방법의 실행속도는 기존의 방법보다 실행이 더 빠르다.

• Earthquakes and Structures
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• 제15권5호
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• pp.487-498
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• 2018

Buckling-restrained braces are passive control devices with high level of energy dissipation ability. However, they suffer from low post-yield stiffness which makes them vulnerable to severe ground motions, especially near-field earthquakes. Among the several methods proposed to improve resistance of BRB frames, mega-brace configuration can be a solution to increase frame lateral strength and stiffness and improve distribution of forces to prevent large displacement in braces. Due to the limited number of research regarding the performance of such systems, the current paper aims to assess seismic performance of BRB frames with mega-bracing arrangement under near-field earthquakes via a detailed probabilistic framework. For this purpose, a group of multi-story mega-BRB frames were modelled by OpenSEES software platform. In the first part of the paper, simplified procedures including nonlinear pushover and Incremental Dynamic Analysis were conducted for performance evaluation. Two groups of near-fault seismic ground motions (Non-pulse and Pulse-like records) were considered for analyses to take into account the effects of record-to-record uncertainties, as well as forward directivity on the results. In the second part, seismic reliability analyses are conducted in the context of performance based earthquake engineering. Two widely-known EDP-based and IM-based probabilistic frameworks are employed to estimate collapse potential of the structures. Results show that all the structures can successfully tolerate near-field earthquakes with a high level of confidence level. Therefore, mega-bracing configuration can be an effective alternative to conventional BRB bracing to withstand near-field earthquakes.