• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.1
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• pp.45-54
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• 2019

The damage detection method using the extended Kalman filter(EKF) technique has been continuously used since EKF can estimation the responses of the damaged building structure and the stiffness of the structure. However, in the use of EKF, the requirement of setting the initial paramters P, Q, and R has caused the divergence and instability of the state vector, and various researches have been conducted to determine theses parameters. In this paper, adaptive extended Kalman filter(AEKF) method is proposed to solve the problem of setting the values of P, Q, and R, which are important parameters determining the convergence performance of the EKF state vector. By using the AEKF method proposed in this study, the P, Q, and R parameters are updated every k steps. The proposed algorithm is applied for the estimation of stiffness and the damage detection of 3-DOF problem. Based of the verification, it can be found that the selection process for the values of P, Q, and R can improve the convergence performance of EKF.

• Journal of Dental Rehabilitation and Applied Science
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• v.34 no.2
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• pp.80-88
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• 2018

Purpose: Implant surface modification and implant design are the principle targets for achieving successful primary stability. The aim of this study was to measure implant stability quotient (ISQ) values of sandblasted, large-grit, acid-etched (SLA) implants with tapered straight body design during the healing period, and to determine the various factors affecting implant stability. Materials and Methods: To measure implant stability, resonance frequency analysis (RFA) was performed in 26 patients (13 women and 13 men) with 44 SLA implants with tapered straight body design. Implant stability (ISQ values) was evaluated at baseline and healing abutment connection (12 weeks), and the correlations between RFA and insertion torque (IT), bone quality, and jawbone were determined. Results: The mean ISQ value of the implants was $69.4{\pm}10.2$ at the time of implant placement (baseline) and $81.4{\pm}6.9$ at the time of healing abutment connection (P < 0.05). Significant differences were found between RFA and bone quality and between RFA and jawbone (P < 0.05). No significant differences were found between RFA and IT, insertion area, fixture diameter, and implant length (P > 0.05). Conclusion: ISQ values of SLA implants with tapered straight body design were high at baseline and healing abutment connection. It was concluded that SLA implants with tapered straight body design show improved primary and secondary stability, and that immediate or early loading may be applicable.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.3
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• pp.2263-2271
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• 2015

The thin cylindrical shell structure under compression should be checked with buckling stability. Initial imperfection effects on buckling strength has been investigated by many researchers. Even though there have been a number of these studies, more studies of buckling strength with various initial imperfections are still necessary. In Eurocode, there is a design parameter that is applicable only on specific imperfection by section thickness rather than on various initial imperfection. In this study, structural analyses, using geometry and material nonlinear analysis, of cylindrical buckling strength with various initial imperfection were performed and compared with Eurocode design strength and Finite Element Method (FEM) analysis results. Moreover, the modified design parameter, which gives more exact prediction result of buckling strength under bending with initial imperfection, is proposed for various initial imperfections.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.11
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• pp.761-767
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• 2019

In the present study, analyses of initial behavior of an air-launched projectile for varying initial conditions are performed by coupling computational fluid dynamics and 6 degrees of freedom calculations. Accuracy of the present numerical methods is validated by comparing the present result with the measured data. Launching safety analyses are carried out for various ejecting conditions by considering weight of the projectile and magnitude of front and rear ejector forces as the major parameters of initial behavior of the projectile. A response surface of the projectile launching safety is obtained in the range of the major parameters. In all the conditions of zero rear ejector force, unsafe launching behavior is observed. As the weight of the projectile decreases, the initial launching behavior becomes more unsafe.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.16.2-16.2
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• 2011

이산화탄소는 인체에 무해하지만 인간의 신진대사와 깊은 관련이 있기 때문에 인간의 정신적 육체적 행동을 제어하는 분야에 많이 응용되고 있다. 따라서 지능형 빌딩이나 고급 공동주택 등의 실내공기를 제어하는 시스템에 적용되어 효율적으로 환기시스템을 운용하는데 사용되어져 왔다. 앞으로 이는 에너지절감과 연동되어 자동차나 가전제품 등 앞으로 점점 밀폐되어가는 구조에 사용이 늘어날 것으로 전망된다. 그러나 종래는 이산화탄소가 특정파장(4.2 um)의 적외선을 흡수하는 성질을 이용하여 Lambert law에 의해 이산화탄소의 양을 측정하였다. 따라서 가격이나 크기가 비교적 경제적이지 못한 측면이 많았다. 이와 반대로 전기화학적인 방식은 가격이나 크기의 측면에서 장점이 있었으나, 초기동작시간이나 안정성, 수명 등에서 상용화되기에는 아직 소비자가 이해하기 힘든면이 많았다. 이에 고체전해질을 이용하여 수명이나 초기시간 및 안정성을 획기적으로 개선하여 상용화가 가능하도록 만든 이산화탄소 센서를 소개하고자 한다. 이 센서는 전자회로와 결합되어 사용이 편리하도록 모듈화 하였고 이 모듈을 사용하여 "airwatch"라는 응용제품으로 판매되고 있다.

• Journal of the Korean GEO-environmental Society
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• v.24 no.10
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• pp.15-23
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• 2023

In this study, the infiltration behavior of slopes composed of mixed soils with clay contents of 0%, 5%, and 10% in weathered Gneiss soil, which is a representative weathered soil in Korea, was investigated, and the stability of unsaturated slopes due to rainfall infiltration was examined. For this, in this study, the soil water characteristic curve was obtained through the water retention test, and the strength constant was obtained through the triaxial compression test. Based on the obtained results, the influence of clay content and antecedent rainfall effect (i.e., initial suction) on the formation of saturated zone (i.e., wetting band) and slope stability due to rainfall infiltration was examined through infiltration and stability analyses. As a result, it was found that the hig her the initial suction, the slower the formation of the saturated zone on the slope. In addition, it was found that as the clay content increases, the shear strength of the ground increases and the resistance to rainfall infiltration increases, and eventually the slope stability is greatly improved.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3A
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• pp.485-496
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• 2006

Practical stability design method of main members of cable-stayed bridges is proposed and discussed through a design example. For this purpose, initial tensions of stay cables and axial forces of main members are firstly determined using initial shaping analysis of bridges under dead loads. And then the effective buckling length using system elastic/inelastic buckling analysis and bending moments considering $P-{\delta}-{\Delta}$ effect by second-order elastic analysis are calculated for main girder and pylon members subjected to both axial forces and moments, respectively. Particularly, three load combinations of dead and live loads, in which maximum load effects due to live loads are obtained, are taken into account and effects of live loads on effective buckling lengths are investigated.

• Proceedings of the Korean Information Science Society Conference
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• 2000.04a
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• pp.92-94
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• 2000

자바는 이동성, 호환성, 안정성을 위해서 자바 가상 기계를 이용한 수행 방법을 사용한다. 이는 수행 속도를 저하 시키는 한 요인이다. 그래서, 정적 컴파일 모델과 동적 컴파일 모델과 같은 자바 가상 세계의 성능을 높이기 위한 여러 연구들이 진행되었다. 정적 컴파일 모델은 자바의 특성을 해치며, 동적 컴파일 모델은 초기화 시간이 증가하는 문제점이 있다. 본 논문에서는 디스크 캐쉬 기법을 이용하여 동적 컴파일 모델에서 발생하는 초기화 시간을 줄이는 자바 가상 기계를 구현하였다. SPEC JVM98[1]을 이용하여 Kaffe[2] 와 비교했을 때, 초기화 시간이 2배에서 5배 정도 줄었음을 알 수 있었다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.200.2-200.2
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• 2016

무전해 도금용 팔라듐 촉매액 중의 팔라듐 이온과 주석이온의 농도비($Sn^{2+}/Pd^{2+}$), 염산의 농도 및 첨가제의 농도 등은 촉매액의 안정성 및 흡착력에 영향을 미치는 것으로 알려져 있다. 무전해 도금용 콜로이드 타입 팔라듐 촉매액에 요구되어지는 특성으로는 1) 액 안정성이 양호하여 장시간 연속 사용에 있어서 나노입자의 응집 및 침전이 없을 것 2) 피도금체 표면에 흡착력이 양호할 것 3) 촉매활성이 충분하여 다음 공정인 무전해 도금피막의 초기석출성이 양호할 것 등이다. 본 연구에서는, 콜로이드 타입 팔라듐 촉매액 중의 염산 농도 및 금속이온의 농도비($Sn^{2+}/Pd^{2+}$), 첨가제를 변화시켜 촉매액의 안정성 및 촉매활성에 미치는 영향을 조사하였다. 그 결과를 시판의 팔라듐 촉매액과 비교하여 보고한다.

• Proceedings of the Korean Society of Computer Information Conference
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• 2021.01a
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• pp.1-3
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• 2021

서버 가상화 기술은 초기 하이퍼바이저 방식에서 비즈니스 민첩성을 높일 수 있는 컨테이너 기술로 진화하고 있다. 하지만, 컨테이너 기술은 운영체제를 공유하고 잦은 빌드와 배포로 보안과 안정성에 대한 문제가 제기되고 있다. 이에 따라 본 논문에서는 서버 가상화 기술인 하이퍼바이저와 컨테이너 기술을 비교분석하고 애플리케이션 특성을 분석한다. 하이퍼바이저 기술은 하드웨어 가상화를 통해 안정성이 높은 반면 복잡하고 무거우며 속도가 느린 단점이 있다. 컨테이너 기술은 하이퍼바이저에 비해 가볍고 성능이 향상되는 반면 보안 및 안정성에 문제가 발생할 수 있다는 단점이 있다. 이를 통해 미션 크리티컬 워크로드를 가진 애플리케이션은 안정성이 우수한 하이퍼바이저 기술이 적합하고, 자원 사용이 가변적인 애플리케이션은 서버 확장이 유연하고 성능이 우수한 컨테이너 기술이 적합하다고 제안한다.