• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.28 no.6
• /
• pp.635-643
• /
• 2015

In this study, the experimental test results are given to confirm the control efficiency of the linear control algorithm used for designing the active mass dampers(AMD) which are supposed to be installed at Incheon international airport control tower. The comparison between the results from test and numerical analysis is conducted and it was observed that the AMD showed the control performance expected by the numerical model. The effects of the gain scheduling and constant-velocity signal added to the control signal calculated by the algorithm is identified through the observation that the AMD always show behavior within the given stroke limit without any loss of the desired control performance. The phase difference between the accelerations of the structure and the AMD were almost close to 90 degree, which implies that the AMD absorbed the structural energy effectively.

• Journal of KSNVE
• /
• v.9 no.1
• /
• pp.206-213
• /
• 1999

In the beam-like ship vibration analysis. three-dimensional correction factor(J-factor) can be calculated by considering the three-dimensional effect of the two-dimensional added mass. However, existing method is time-consuming with low accuracy in respect of global vibration analyses for vessels with large breadth. In this paper, to improve the demerit of the previous method, a new method of the beam-like ship vibration analysis is introduced In this method. the three-dimensional fluid added mass of surrounding water is calculated directly by solving the velocity potential problem using the Boundary Element Method (BEM). Then the three-dimensional added mass is evaluated as the lumped mass for each strip. Also, the beam-like ship vibration analysis for the structural beam model if performed with the lumped mass considered. It was verified that this new method is useful for the beam-like ship vibration analysis by comparing results obtained from both the existing method and the new method with experimental measurements for the open top container model.

• The Journal of the Convergence on Culture Technology
• /
• v.6 no.3
• /
• pp.457-462
• /
• 2020

Osteoporosis is a disease that occurs mainly in the elderly and increases the risk of fractures due to structural deterioration of bone mass and tissues. The purpose of this study are to assess the relationship between nutritional components and osteoporosis and to evaluate models for predicting osteoporosis based on nutrient components. In experimental method, association was performed using binary logistic regression, and predictive models were generated using the naive Bayes algorithm and variable subset selection methods. The analysis results for single variables indicated that food intake and vitamin B2 showed the highest value of the area under the receiver operating characteristic curve (AUC) for predicting osteoporosis in men. In women, monounsaturated fatty acids showed the highest AUC value. In prediction model of female osteoporosis, the models generated by the correlation based feature subset and wrapper based variable subset methods showed an AUC value of 0.662. In men, the model by the full variable obtained an AUC of 0.626, and in other male models, the predictive performance was very low in sensitivity and 1-specificity. The results of these studies are expected to be used as the basic information for the treatment and prevention of osteoporosis.

• Proceedings of the Korean Vacuum Society Conference
• /
• 1999.07a
• /
• pp.44-44
• /
• 1999

저진공(1 kPa~ 100 kPa)은 대기압 측정, 비행고도, 기체의 온도 측정, 질량의 부력 보정, 레이저의 굴절률 측정등에 사용되는 영역으로 과학적 중요성을 갖고 있다. 또한 대기압 이상의 압력 측정과 고진공 측정의 경계적 역할도 수행하고 있어 압력 표준기의 국제 비교에 필수적으로 권장되는 역역이다. 이 영역에 주로 사용되는 압력 표준기는 수은 압력계(Mercury manometer)와 분동식 압력계(Deadweight piston gauge or Pressure)가 있다. 이들은 이동이 불편하거나 불가능하므로 표준기의 국제 비교에 사용되는 전달 표준기로는 보다 이동이 간편한 탄성 압력계인 CDG(Capacitance diaphragm Gauge)가 있다. 이 게이지는 반도체 산업의 공정 제어용으로도 많이 사용되고 있다. 그러나 게이지와 함께 사용되는 컨트롤러의 부피가 크고 무거우며 영점 이동이 커서 측정때 마다 재조정하여야 하는 단점이 있다. 본 논문에서는 이 같은 단점을 극복하기 위해 수정빔 진동형 진공 센서를 잔달 표준기로 사용하는 것에 대한 연구를 수행하였다. 수정빔 진동형 압력 센서는 수정빔으 공진주파수가 스트레인에 비례하는 것을 이용하여 제작된 센서로 주로 대기압 이상의 고압 측정에 많이 사용되고 있다. 먼저 수정빔의 압력과 주파수간의 관계를 측정하고 또한 내장된 수정 온도센서의 공진 주파수를 측정하여 온도 보상을 위한 자료로 사용하였다. 규격에 나와 있는 수정빔의 기하학적 형상으로부터 거동에 관한 이론 모델식을 구하고 압력교정 자료로부터 얻어진 데이터를 이 식과 비교 분석하여 적합한 특성식과 인자를 구하였으며 게이지의 불확도를 추정하였다.모델은 길이가 유한한 0-차원 실린더 모델로 가정하였고, 이에 대한 기하학적 성질 및 열역학적 성질은 유효계수를 고려하여 산출하였다. 진공용기 이중 벽 내부로 흐르는 질소가스의 유량과 온도의 계산은 진공용기 내벽과 외벽을 각각 독립적인 열전달 요소로 가정하여 구성한 모델을 이용하였다. 전체 해석에서 각 열전달 요소의 비열 값은 온도에 따라 변화하는 비열의 특성을 반영하였으며. 진공용기와 플라즈마 대향 부품의 방사율(emissivity)은 앞서 가정했던 각 온도 상승 곡선에 대해서 각각 0.1, 0.2, 1.3의 경우를 가정하여 계산하였다. 직선적으로 증가하는 온도 상승 곡선중 2$0^{\circ}C$/hr의 온도상승율을 갖는 경우가 다른 베이킹 시나리오 모델에 비해 효과적이라 생각되며 초대 필요 공급열량은 200kW 정도로 산출되었다. 실질적인 수치를 얻기 위해 보다 고차원 모델로의 해석이 필요하리라 생각된다. 끝으로 장기적인 관점에서 KSTAR 장치의 베이킹 계획도 살펴본다.습파라미터와 더불어, 본 연구에서 새롭게 제시된 주기분할층의 파라미터들이 모형의 학습성과를 높이기 위해 함께 고려된다. 한편, 이러한 학습과정에서 추가적으로 고려해야 할 파라미터 갯수가 증가함에 따라서, 본 모델의 학습성과가 local minimum에 빠지는 문제점이 발생될 수 있다. 즉, 웨이블릿분석과 인공신경망모형을 모두 전역적으로 최적화시켜야 하는 문제가 발생한다. 본 연구에서는 이 문제를 해결하기 위해서, 최근 local minimum의 가능성을 최소화하여 전역적인 학습성과를 높여 주는 인공지능기법으로서 유전자알고리즘기법을 본 연구이 통합모델에 반영하였다. 이에 대한 실

• Journal of Korean Society of Environmental Engineers
• /
• v.31 no.9
• /
• pp.825-830
• /
• 2009

Pharmaceutical compounds enter the water environment through the diverse pathways. Because their concentration in the water environment was frequently detected in the level of ppt to ppb, the monitoring system should be optimized as much as possible for finding appropriate management policies and technical solutions. One Factor At a Time (OFAT) approach approximating the response with a single variable has been preferred for the optimization of LC-MS/MS operational conditions. However, it is common that variables in analytical instruments are interdependent. Therefore, the best condition could be found by using the statistical optimization method changing multiple variables at a time. In this research, response surface analysis (RSA) was applied to the LC-MS/MS analysis of emerging antibiotic compound, sulfamethoxazole, for the best sensitivity. In the screening test, fragmentation energy and collision voltage were selected as independent variables. They were changed simultaneously for the statistical optimization and a polynomial equation was fit to the data set. The correlation coefficient, $R^2$ valuerepresented 0.9947 and the error between the predicted and observed value showed only 3.41% at the random condition, fragmentation energy of 60 and collision voltage of 17 eV. Therefore, it was concluded that the model derived by RSA successfully predict the response. The optimal conditions identified by the model were fragmentation energy of 116.6 and collision voltage of 10.9 eV. This RSA can be extensively utilized for optimizing conditions of solid-phase extraction and liquid chromatography.

• Journal of the Korea Concrete Institute
• /
• v.23 no.5
• /
• pp.551-558
• /
• 2011

The effect of the maximum aggregate size and substitution rate of natural sand on the mechanical properties of concrete is evaluated using 15 lightweight aggregate concrete mixes. For mechanical properties of concrete, compressive strength increase with respect to age, tensile resistance, elastic modulus, rupture modulus, and stress-strain relationship were measured. The experimental data were compared with the design equations specified in ACI 318-08, EC2, and/or CEB-FIP code provisions and empirical equations proposed by Slate et al., Yang et al., and Wang et al. The test results showed that compressive strength of lightweight concrete decreased with increase in maximum aggregate size and amount of lightweight fine aggregates. The parameters to predict the compressive strength development could be empirically formulated as a function of specific gravity of coarse aggregates and substitution rate of natural sand. The measured rupture modulus and tensile strength of concrete were commonly less than the prediction values obtained from code provisions or empirical equations, which can be attributed to the tensile resistance of lightweight aggregate concrete being significantly affected by its density as well as compressive strength.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.26 no.5
• /
• pp.513-518
• /
• 2008

The research of global-scale mass redistribution and it changed by Earth gravity filed variation observations, including Earth's oblateness $J_2$(also called low degree spherical harmonic coefficient $C_{20}$), is in continuous progress. Recently, the comparative analysis of geodetic observation SLR can be made by the development of GRACE and other time-variable gravity measurements. In this study, $C_{20}$ time series changes in the value of comparative analysis was got by GRACE monthly Gravity filed model (CSR RL04) for the period April 2002 to May 2008. And comparative analysis the harmonic coefficients of $C_{20}$ was obtained from SLR observations. Signal analysis for two time-series data was made by wavelet transform, CWT(continuous wavelet transform), XWT(cross wavelet transform) and WTC(wavelet coherence) methods. The results indicate that GRACE and SLR values for $C_{20}$ had both decreasing trend, as well as SLR data represent the annual frequencies, and GRACE was semiannual variations. In addition, the results of GRACE and SLR had a strong correlation with the XWT and WTC in an annual cycle.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.5 no.5
• /
• pp.73-83
• /
• 2001

The mass and stiffness of upper wall-lower frame system(mixed building structures) change sharply at transfer floor due to different structural system in upper and lower part. These mixed building structures generally show the stiffness, weight or geometric vertical irregularities. The purpose of this study is to investigate the response characteristics of these structures by push-over analysis and nonlinear time history analysis. For four types of analysed models, only the variation of upper wall stories was considered. The conclusions of this study are following; (1) In the push-over analysis, yielding hinges in beams and columns of lower frame occurred at the base shear of similar magnitude in all models. But as the number of stories of upper wall increases, yielding hinges at ends of coupling beams were observed in the small magnitude of base shear. (2) In the nonlinear time history analysis, yielding of lower frame occurred at beams with as small ground acceleration as 55gal, and in upper walls yielding was concentrated on coupling beams and shear walls near the transfer floor. (3) As the number of stories of upper walls decreases, the story stiffness of the lower frames decreased relatively and the occurrence of soft stories in the lower frame was observed.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.35 no.2
• /
• pp.83-91
• /
• 2022

Seismic design and analysis of nuclear power plant components are performed based on an decoupled model. However, this decoupled analysis has a limitation in that it generates inaccurate results compared to the coupled analysis because it cannot simulate actual phenomena such as the interaction between structures and components. Thus, this study performed seismic coupled and decoupled analysis on an existing nuclear containment structure and related components, considering the mass and natural frequency ratios. And based on these results, comparative analyses of responses of components were conducted. Consequently, the seismic coupled analysis result generally gave a smaller value than the decoupled analysis result. These results were similar to the analysis results for the simple coupled model, which was an existing study, but the difference in component responses was much more pronounced. Also, this was influenced by the installation location of the component rather than the influence of the input frequency of the input seismic motions. Finally, the difference between the decoupled and coupled seismic analysis occurred in the region where the mass ratio of the components was large, and the natural frequencies were almost similar due to the considerable dynamic interaction between the structure and the component in this realm.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.12 no.3
• /
• pp.551-560
• /
• 1988

Gas-particle two phase flow and heat transfer in a cavity receiving thermal radiation through selectively transparent walls have been analyzed by a finite difference method. Particles injected from the upper hole of the cavity are accelerated downward by gravity and exit through the lower hole while they absorb, emit and scatter the incident thermal radiation. Gas phase is heated through convection heat transfer from particles, and consequently buoyancy induced flow field is formed. Two-equation model with two-way coupling is adopted and interaction terms are treated as sources by PSI-Cell method. For the particulate phase, Lagrangian method is employed to describe velocities and temperatures of particles. As thermal radiation is incident upon horizontally, radiative heat transfer in the vertical direction is assumed negligible and two-flux model is used for the solution of radiative heat flus. Gas phase velocity and temperature distributions, and particle trajectories, velocities and temperatures are presented. The effects of particle inlet condition, particle size, injection velocity and particle mass rate are mainly investigated.