• The Journal of Advanced Prosthodontics
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• 제12권3호
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• pp.173-180
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• 2020

PURPOSE. This study compared digital (reference point matching) and replica methods for measuring marginal and internal fit of full coverage restorations. MATERIALS AND METHODS. A maxillary left first molar typodent was fixed on to an aluminum base and prepared to receive all-ceramic full coverage restoration. The model was scanned with an intraoral scanner (CEREC Omnicam, Sirona, York, PA, USA). Twelve crowns were fabricated from lithium disilicate blocks (IPS emax CAD, Ivoclar Vivadent) and then crystalized. Marginal and internal fit of each restoration was measured by two examiners using replica and a new digital three-dimensional technique. Reliability between the two methods and two examiners was assessed by correlation and Cronbach's Alpha coefficient (P<.05). A Bland-Altman assessment for agreement was used to compare the two methods. RESULTS. Bland-Altman assessment showed that the mean of difference for marginal, absolute marginal, and axial gap was respectively -1.04 ㎛, -41.9 ㎛, and -29.53 ㎛ with limit of agreement (LOA) between -37.26 to 35.18 ㎛ for marginal, -105.85 to 22.05 ㎛ for absolute marginal and -80.52 to 22.02 ㎛ for axial gap. Positive correlation for repeatability (P<.05) in determining marginal and internal gaps by the two examiners in both techniques was revealed. Reliability of both techniques in all sites of measurements was at least good (0.8 ≤ α < 0.9). CONCLUSION. Both measuring techniques appeared highly reliable for evaluating fit of fixed dental restorations, while reference point matching provided higher values in axial and absolute marginal gap assessment.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2002년도 추계 학술발표회 논문집
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• pp.155-162
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• 2002

A technique for the seismic reliability evaluation of electric power transmission systems(EPTS) adapted to ground motion characteristics of Korea has been developed to evaluate reliability indices corresponding to the whole system and to each node within. A network model with nodes and links for EPTS has been established, and a seismic substation-fragility curve obtained from seismic fragilities of power system facilities has been derived. A point source model, the doubly truncated Gutenberg-Richter relationship, and earthquake intensity attenuation formula have been applied to simulate seismic events. Using Monte-Carlo simulation method, the seismic reliability of EPTS is evaluated and, it appeared that seismic effect on EPTS in low and moderate seismicity regions has to be considered.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.738-743
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• 1991

A multiobjective analysis technique was applied for the optimum operation of pumps and reservoirs in service water transmission systems. Three major objectives were identified and assessed on the normally operating service water transmission systems. They are, 1) stability of pump operation; 2) economic point of view in minimizing the energy cost for pumping; 3) reliability in meeting the stochasticaly varying demands. The measures of these objectives were required times of pump on-offs in stability, required total energy cost in economics, and minimum required storage during the operating horizon in reliability. In order to find the best meeting solution to the decision maker, a set of non-dominated solutions which show the tradeoff relationships between the considering objectives were generated. The DM selects the best solution from this explicit tradeoff relationships using his heuristic decision rules or experience. The theory was verified by applying to the Kumi Service Water System. A combined technique of the ${\varepsilon}-constraint$ and the weighting methods was used to generate the nondominated solutions, and the dynamic programming algorithm was applied to find the optimal solution for the discretized multi-objective analysis problems.

• 디지털산업정보학회논문지
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• 제11권3호
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• pp.69-77
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• 2015

MANET is composed of only the mobile nodes have a limited transmission range. The dynamic topology by the frequent movement of nodes makes routing difficult and is also cause exposed to security vulnerabilities. In this paper, we propose the security routing technique consisted of mechanism of two steps in order to respond effectively to attack by the modification of the routing information and transmit secure data. The hierarchical structure is used and the authentication node that issues the key of the nodes within each cluster is elected in this proposed method. The authentication node manages key issues and issued information for encrypting the routing information from the source node. The reliability value for each node is managed to routing trust table in order to secure data transmission. In the first step, the route discovery is performed using this after the routing information is encrypted using the key issued by the authentication node. In the second step, the average reliability value of the node in the found path is calculated. And the safety of the data transmission is improved after the average reliability value selects the highest path. The improved performance of the proposed method in this paper was confirmed through comparative experiments with CBSR and SEER. It was confirmed a better performance in the transmission delay, the amount of the control packet, and the packet transmission success ratio.

• 한국산학기술학회논문지
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• 제15권11호
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• pp.6838-6844
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• 2014

LTE-A 시스템은 고속 데이터 전송을 위해 다중안테나를 장착하고 있다. 일반적으로 공간다중화 다중안테나 시스템의 수신기 복잡도는 후보벡터의 개수에 따라 증가한다. 후보벡터의 개수가 증가함에 따라 연판정 값의 신뢰도가 향상된다. 많은 수의 후보벡터를 생성하는 최우도 신호검출방식을 사용하면 우수한 성능을 달성할 수 있다. 반면 적은 개수의 후보벡터를 생성하는 저복잡도 수신기는 신뢰도가 낮은 연판정 값을 생성한다. 본 논문에서는 적은 수의 후보벡터를 사용해서 얻게되는 연판정 값의 신뢰도를 향상시키는 새로운 기술을 제안하고 모의실험을 통해 개선된 성능을 확인한다.

• Earthquakes and Structures
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• 제14권5호
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• pp.425-436
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• 2018

The design of seismically isolated structures considering the stochastic nature of excitations, base isolators' design parameters, and superstructure properties requires robust reliability analysis methods to calculate the failure probability of the entire system. Here, by applying artificial neural networks, we proposed a robust technique to accelerate the estimation of failure probability of equipped isolated structures. A three-story isolated building with susceptible facilities is considered as the analytical model to evaluate our technique. First, we employed a sensitivity analysis method to identify the critical sources of uncertainty. Next, we calculated the probability of failure for a particular set of random variables, performing Monte Carlo simulations based on the dynamic nonlinear time-history analysis. Finally, using a set of designed neural networks as a surrogate model for the structural analysis, we assessed once again the probability of the failure. Comparing the obtained results demonstrates that the surrogate model can attain precise estimations of the probability of failure. Moreover, our proposed approach significantly increases the computational efficiency corresponding to the dynamic time-history analysis of the structure.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제31회 추계학술대회논문집
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• pp.55-59
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• 2008

액체로켓엔진의 성능 검증에 있어서 가장 큰 비중을 차지하는 것 중 하나는 정확한 추력 측정이다. 본 연구에서는 기존의 추력 측정 장치를 보완한 저추력 액체로켓엔진의 추력 측정 장치를 개발하여 작은 추력을 발생하는 로켓엔진의 보다 정확한 추력 측정을 가능하도록 하였다. 또한, 추력 측정 장치의 추력 측정 평가 시 고려되는 주요 인자들에 대한 연구를 수행하여 추력 측정 장치의 신뢰도 평가에 관한 기법 및 절차 수립의 기반을 마련하였다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2004년도 춘계 학술대회논문집
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• pp.9-16
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• 2004

This study presents results of aerodynamic wing optimization under uncertainties. To consider uncertainties, an alternative strategy for reliability-based design optimization(RBDO) is developed. The strategy utilizes a single loop algorithm and a sequential approximation optimization(SAO) technique. The SAO strategy relies on the trust region-SQP framework which validates approximated functions at every iteration. Further improvement in computational efficiency is achieved by applying the same sensitivity of limit state functions in the reliability analysis and in the equivalent deterministic constraint calculation. The framework is examined by solving an analytical test problem to show that the proposed framework has the computational efficiency over existing methods. The proposed strategy enables exploiting the RBDO technique in aerodynamic design. For the aerodynamic wing design problem, the solution converges to the reliable point satisfying the probabilistic constraints.

• Journal of Advanced Marine Engineering and Technology
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• 제28권7호
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• pp.1092-1100
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• 2004

This paper describes the application of fault tree technique to analyze of compressor failure. Fault tree analysis technique involves the decomposition of a system into the specific form of fault tree where certain basic events lead to a specified top event which signifies the total failure of the system. In this research. fault trees for failure analysis of screw type air compressor are made. This fault trees are used to obtain minimal cut sets from system failure and system failure rate for the top event occurrence can be calculated. It is Possible to estimate air compressor reliability by using constructed fault trees through compressor failure example. It is Proved that FTA is efficient to investigate the compressor failure modes and diagnose system.

• 한국재난정보학회 논문집
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• 제3권1호
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• pp.5-20
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• 2007

The role of a pavement means a social axis for the future as well as a function of road itself. To achieve its intended purposes, the maintenance technique of the pavement performance should be improved. For this, pavement investigators have dealt with the simulated pavement sites under actual environmental conditions. One of them is wandering device to improve the maintenance system of a pavement. The primary purpose of this research is to develop a portable wandering device using statistical analysis technique. It is noted that the new device using laser sensor demonstrates better field applications and reliability compare to the conventional one.