• 전기학회논문지P
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• 제64권1호
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• pp.23-28
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• 2015

Measuring the distances between signals in the signal space is usually determined by obtaining the ideal metric which is not easy to obtain. In this research we have investigated the scheme that measures the distances between the signals constructed with the measured voltage signals connected to electric apparatus using Kalman filter and exponential mapping. The metric is defined on the feature signals obtained via the estimation process of a Kalman filter and the mapping process using the exponential transformation. Diagnosis is on the voltage fluctuations is applied to determining whether the system is in the stable state or not due to the unexpected accidents, such as power overcharge, discharge, outages flow may be the cause of the accident. The decision making scheme evaluated with respect to the effectiveness and the degree of complication with different variances. Two methods, the Hard Limit Threshold Scheme(HLTS) and the Interval Energy Scheme(IES) are proposed and compared. In experiments the IES shows better tolerance to impulse noise than the HLTS.

• Steel and Composite Structures
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• 제28권2호
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• pp.195-207
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• 2018

First-order reliability method (FORM) is enhanced based on the search direction using relaxed conjugate reliability (RCR) approach for the embedded nanocomposite beam under buckling failure mode. The RCR method is formulated using discrete conjugate map with a limited scalar factor. A dynamical relaxed factor is proposed to control instability of proposed RCR, which is adjusted using sufficient descent condition. The characteristic of equivalent materials for nanocomposite beam are obtained by micro-electro-mechanical model. The probabilistic model of nanocomposite beam is simulated using the sinusoidal shear deformation theory (SSDT). The beam is subjected to external applied voltage in thickness direction and the surrounding elastic medium is modeled by Pasternak foundation. The governing equations are derived in terms of energy method and Hamilton's principal. Using exact solution, the implicit buckling limit state function of nanocomposite beam is proposed, which is involved various random variables including thickness of beam, length of beam, spring constant of foundation, shear constant of foundation, applied voltage, and volume fraction of ZnO nanoparticles in polymer. The robustness, accuracy and efficiency of proposed RCR method are evaluated for this engineering structural reliability problem. The results demonstrate that proposed RCR method is more accurate and robust than the excising reliability methods-based FORM. The volume fraction of ZnO nanoparticles and the applied voltage are the sensitive variables on the reliable levels of the nanocomposite beams.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.365-370
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• 2004

Generally, component and FR-4 board are connected by solder joint. Because material properties of components and FR-4 board are different, component and FR-4 board show different coefficients of thermal expansion (CTE) and thus strains in component and board are different when they are heated. That is, the differences in CTE of component and FR-4 board cause the dissimilarity in shear strain and solder joint' failure. The first order Taylor series expansion of the limit state function incorporating with Tresca failure criterion is used in order to estimate the failure probability of solder joints under heated condition. Using shear stresses and shear strains appeared on the solder joint, we estimate the failure probability of solder joints with the Tresca failure criterion. The effects of random variables such as CTE, distance of the solder joint from the neutral point(DNP), temperature variation and height of solder on the failure probability of the solder joint are systematically studied by using the failure probability model with first order reliability method(FORM).

• 한국지진공학회논문집
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• 제26권6호
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• pp.255-265
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• 2022

In order to determine fragility curves, the limit state of piers for each damage level is suggested in this paper based on the previous test results in Korea, including our test results. In previous studies, the quantitative measures for damage levels of piers have been represented by curvature ductility, lateral drift ratio, or displacement ductility. These measures are transformed to lateral drift ratios of piers for consistency, and the transformed values are compared and verified with our push-over test results for flexural RC piers with a circular cross-section. The test specimens are categorized concerning the number of lap-splices in the plastic hinge region and whether seismic design codes are satisfied or not. Based on the collected test results in Korea, including ours, the lateral drift ratio for each pier damage level is suggested.

• Nuclear Engineering and Technology
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• 제55권9호
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• pp.3213-3228
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• 2023

As an important part of the digital reactor, the pin-by-pin wise fine coupling calculation is a research hotspot in the field of nuclear engineering in recent years. It provides more precise and realistic simulation results for reactor design, operation and safety evaluation. CORCA-K a nodal code is redeveloped as a robust pin-by-pin wise neutronics and thermal-hydraulic coupled calculation code for pressurized water reactor (PWR) core. The nodal green's function method (NGFM) is used to solve the three-dimensional space-time neutron dynamics equation, and the single-phase single channel model and one-dimensional heat conduction model are used to solve the fluid field and fuel temperature field. The mesh scale of reactor core simulation is raised from the nodal-wise to the pin-wise. It is verified by two benchmarks: NEACRP 3D PWR and PWR MOX/UO₂. The results show that: 1) the pin-by-pin wise coupling calculation system has good accuracy and can accurately simulate the key parameters in steady-state and transient coupling conditions, which is in good agreement with the reference results; 2) Compared with the nodal-wise coupling calculation, the pin-by-pin wise coupling calculation improves the fuel peak temperature, the range of power distribution is expanded, and the lower limit is reduced more.

• Geomechanics and Engineering
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• 제29권5호
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• pp.487-496
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• 2022

Most of the pile's vertical static load tests in construction sites are the proof load tests, which is difficult to accurately estimate the ultimate bearing capacity and analyze the reliability of piles. Therefore, a reliability analysis method based on the proof load-settlement (Q-s) data is proposed in this study. In this proposed method, a simple ultimate limit state function based on the hyperbolic model is established, where the random variables of reliability analysis include the model factor of the ultimate bearing capacity and the fitting parameters of the hyperbolic model. The model factor M = R_uR / R_uP is calculated based on the available destructive Q-s data, where the real value of the ultimate bearing capacity (R_uR) is obtained by the complete destructive Q-s data; the predicted value of the ultimate bearing capacity (R_uP) is obtained by the proof Q-s data, a part of the available destructive Q-s data, that before the predetermined load determined by the pile test report. The results demonstrate that the proposed method can easy and effectively perform the reliability analysis based on the proof Q-s data.

• 한방재활의학과학회지
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• 제24권1호
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• pp.111-118
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• 2014

The objective of this study is to report the effectiveness of Korean medical rehabilitation for total knee replacement. Three female patients who had total knee replacement were treated by Korean medical rehabilitation with protocol. We evaluated the consequences by checking numeric rating scale (NRS), Lysholm knee score, physical examination of knee joint and walking state. After Korean medical rehabilitation, we find out that the pain and function were improved. NRS, Lysholm knee score, physical examination of knee joint, walking state of patients were also improved. Korean medical rehabilitation can be effectively used for total knee replacement patients. There is a limit that this study hasn't sufficient number of cases. Further studies are needed to set up a Korean medical rehabilitation protocol.

• 한국산학기술학회논문지
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• 제3권4호
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• pp.325-332
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• 2002

본 논문은 최적리콜보험계약의 설계와 관련된 논문의 survey이다. 리콜보험 뿐만이 아니라 최적보험계약을 만들기 위해서는 보험계약의 조건들이 내생적이라는 가정하에서 연구모형을 구축하고 분석의 과정에서는 보험구매를 위한 의사결정 원칙으로 기대효용이론, 비기대효용이론, 및 상태귀속적인 (state-dependent) 효용함수를 사용하였다. 어떠한 이론을 사용하더라도 최적보험의 조건들은 존재한다. 다만 계약조건에 관련되어서는 보험의 비용, 자기부담금, 보상한도액 등이 차이가 날 수 있다. 보험의 비용은 지급보험금과 선형, 오목형, 볼록형의 관계가 성립할 수 있으나 잠식비용과 고정비용의 존재를 인정하여야 한다. 이를 바탕으로 최적보험을 위한 비용 설계가 이루어져야 한다. 또한 전부보험이냐 일부보험이냐를 결정하는 자기부담금의 존재는 일률자기부담금형태와 점감식자기부담금형태가 가능하다. 자기부담금 수준의 결정과 관련하여 담보되는 모든 위험에 동일한 수준을 적용시킬 것인가 혹은 차별화시킬 것인가는 보험의 종류에 따라 달라질 수밖에 없다. 보상한도와 관련되어서는 특히 리콜보험에 있어서는 기업의 파산위험성이 상당히 존재하고 있으므로 계약당사자의 파산선고를 포함한 이익이 충분히 고려되어야 한다. 또한 제약조건으로는 불완전시장에 대한 이해를 필요로 하며 담보할 수 없는 배경위험의 존재에 대한 배려가 있어야 한다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.121-124
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• 2008

FRP를 적용하는 대표적인 보강공법으로는 외부부착공법으로서, FRP Plate 또는 fiber sheet를 사용하여 노후화된 보강면에 FRP 보강재를 부착하는 형식이다. 하지만, 이러한 외부부착공법은 FRP보강재의 인장특성을 충분히 발휘하지 못하는 단점이 있다. 따라서 외부부착공법의 단점을 보완하기 위해 표면매립공법, 즉, Near Surface Mounted(이하 NSM)공법이 제안되었다. 이는 FRP 보강재를 매립함으로써 부재와 보강재의 부착 성능을 증가시킴에 따라 효율적인 응력전달 및 조기 debonding을 사전에 방지할 수 있으며, 이로 인해 FRP 보강재의 인장특성이 효율적으로 발휘될 수 있다. 효율적인 NSM 보강을 위해서는, 구조물에 가해지는 하중, 구성재료, 구조물의 기하학적 형상 등이 갖는 불확실 특성을 반영하여, 보강 후 구조물의 신뢰도를 기준으로 한 보강성능 평가가 필요하다. 본 연구에서는 노후화된 철도교 실교량 모델을 선정하여 외부하중, 재료 및 기하학적 형상의 불확실성을 Monte Carlo Simulation확률기법을 적용하여 그 분포특성을 분석한 후, NSM 보강에 대한한계상태 함수를 통해 목표신뢰도에 부합할 수 있는 휨보강비를 도출하고자 하였다. 해석결과 LS-25하중을 상회하는 내하력 증진효과를 확률분포로써 확인할 수 있었다. 따라서 확률신뢰성기법을 적용한 보강설계의 유효성을 확인할 수 있었으며, 추후 다양한 보강공법으로의 적용이 가능할 것으로 판단된다.

• 콘크리트학회논문집
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• 제23권6호
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• pp.731-740
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• 2011

KCI 2007, ACI 318-08에 제시된 모멘트재분배 방법은 등분포 중력하중을 받는 연속 휨재에 대하여 검증된 방법이다. 횡하중에 의한 모멘트재분배 및 비탄성 거동은 중력하중과 전혀 다른 메커니즘을 발생된다. 이 연구에서는 기초역학에 근거하여 중력하중과 횡하중을 받는 철근콘크리트 모멘트골조의 보에 발생되는 모멘트재분배와 소성변형의 관계를 정량화하고, 이로부터 보의 소성변형능력에 근거한 모멘트재분배 설계법을 제안하였다. 제안된 모멘트재분배비는 KCI 2007, ACI 318-08 등 기존 설계기준과 마찬가지로 극한한계상태의 단면해석으로 결정되는 철근의 인장변형률로 정의된다. 또한 모멘트재분배비는 경간, 철근비, 단면강성, 변형경화 거동에 의하여 영향을 받는다. 제안된 방법을 사용하여 탄성해석으로 구한 설계모멘트를 재분배시키는 설계 가이드라인 및 예제를 제시하였다.