• Journal of the Earthquake Engineering Society of Korea
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• v.1 no.3
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• pp.29-35
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• 1997

The megastructure combined with the modular concept is an effcient structural system adequate for ultra-tail buildings for the future. An ingeneous structural control system can be developed by separating the internal subframe in one or many modules from the external megaframe, thus taking advantage of the effect of tuned mass dampers without adding any aditional mass. This so called mega-subcontrol system is generally modeled by a 20DF system for parametric study and for finding optimal values of the parameters. In this study the equation of motion for the system is obtained frist and the preconditions for the simplified modeling are investigated. Finally the optimal value for the subsreucture strffness is fomputed with given mass and damping ratios and transfer functions for responses are abtained for white noise ground exitation to verify the effectiveness of the mega-subcontrol system.

• Computational Structural Engineering
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• v.10 no.3
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• pp.125-131
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• 1997

Most dynamic systems have are known to various random properties in excitation and system parameters. In this paper, a procedure for response analysis is proposed for the linear dynamic system with random properties in both excitation and system parameters. The system parameters and responses with random properties are modeled by perturbation technique, and then response analysis is formulated by probabilistic and vibration theories. And probabilistic FEM is also used for the calculation of mean response which is difficult by the proposed response model. As an applicative example, the transient response is considered for systems of single degree of freedom with random mass and spring constant subjected to stationary white-noise excitation and the results are compared to those of numerical simulation.

• Computational Structural Engineering
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• v.10 no.3
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• pp.225-231
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• 1997

The dynamic characteristics of Control Element Drive Mechanism(CEDM) for Korea Standard Nuclear Power Plant are studied with the CEDM modeled as a secondary mass in a simplified two degree of freedom system, while the reactor vessel as a primary mass. The optimal .mu.-f curve is developed to reduce the response amplitudes of both primary and secondary masses. In order to improve a design it is proposed that the natural frequency ratio, f, should be converged to 0.93, the mass ratio, .mu., should not be reduced, and the result should be converged to the optimal .mu.-f curve. Optimal design for CEDM components has been carried out and the response amplitude ratios of reactor are reduced 10.5 - 19.7% while those of CEDM are reduced 6.3 - 3.4%.

• Composites Research
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• v.12 no.1
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• pp.47-58
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• 1999

This paper describes the results of experiments to analyze the free vibration of the laminated composite and hybrid composite plates with various shapes and boundary conditions. The materials of specimens were the carbon fiber reinforced plastic (CFRP), the glass fiber reinforced plastic (GFRP), the GFRP-Aluminum hybrid composite and the CFRP-CFRP hybrid composite. The natural frequencies and nodal patterns of plates with various shapes were experimentally obtained by impact exciting test using an impact hammer and an accelerometer. The experimental results were presented with normalized frequency parameters. The effects of composite material properties, fiber orientation angles, various geometrical shapes and boundary conditions on the vibration characteristics of composite plates were evaluated. To compare and verify these experimental results, the finite element analysis was carried out, and was well agreed with experimental results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.89-96
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• 2002

A two-degree of freedom model is suggested to understand the basic dynamical behaviors of the interaction between two masses of the friction induced vibration system. The two masses may be considered as the pad and the disk of the brake, The phase space analysis is performed to understand complicated dynamics of the non-linear model. Attractors in the phase space are examined for various conditions of the parameters of the model especially by emphasizing on the damping parameters. In certain conditions, the attractor becomes a limit cycle showing the stick-slip phenomena. In this paper, not only the existence of the limit cycle but also the size of the limit cycle is examined to demonstrate the non-linear dynamics that leads the unstable state. For the two different cases of the system frequency ((1)two masses with same natural frequencies, (2) with different natural frequencies), the propensity of limit cycle is discussed in detail. The results show an important fact that it may make the system worse when too much damping is present in the only one part of the masses.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.7
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• pp.502-509
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• 2002

A two-degree of freedom model Is suggested to understand the basic dynamical behaviors of the interaction between two masses of the friction induced vibration system. The two masses may be considered as the pad and the dusk of the brake. The phase space analysis is performed to understand complicated dynamics of the non-linear model. Attractors in the phase space are examined for various conditions of the parameters of the model especially by emphasizing on the damping parameters. In certain conditions, the attractor becomes a limit cycle showing the stick-slip phenomena. In this Paper, not only titre existence of the limit cycle but also the sloe of the limit cycle is examined to demonstrate the non-linear dynamics that leads the unstable state. For the two different cases of the system frequency[(1) Two masses with same natural frequencies, (2) with different natural frequencies] . the propensity of limit cycle Is discussed In detail. The results show an important fact that it may make the system worse when too much damping Is present in the only one part of the masses.

• Computational Structural Engineering
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• v.11 no.3
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• pp.173-185
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• 1998

본 연구에서는 자동차엔진 및 트랜스미션 성능시험을 위한 다이나모 베드구조물을 분석하고 설계하였다. 해석상에 고려된 베드구조물은 Ⅰ형강 구조물, 보강된 박스구조물 그리고 블록구조물로 제작되었으며, 시험을 위한 엔진 및 트랜스미션은 베드상판에 장착된다. 엔진구동시 회전에 의한 진동이 발생된다. 공진을 피하기 위해 베드구조는 충분한 구조적 일체성을 가져야 한다. 본 연구에서는 베드 구조물의 응력, 변위 그리고 자유진동해석이 ANSYS Code를 이용한 유한요소해석이 수행되었다. Ⅰ형강 구조형 베드 구조물에서 최대 응력은 23.2MPa에서 90.3MPa까지 나타났으며, 최대 처짐은 0.25㎜에서 0.92㎜까지 나타났다. 박스 구조형 베드 구조물에서 최대 응력은 0.028MPa에서 0.259MPa까지 나타났으며, 최대 처짐은 0.031㎜에서 0.413㎜까지 나타났다. 그리고 박스구조형 베드 구조물에서 최대 처짐은 0.92MPa에서 2.15MPa까지 나타났으며, 최대 처짐은 1.1㎜에서 2.7㎜까지 나타났다. 모든 구조물이 응력과 처짐 값에서 매우 안정적인 범위 내에서 발생됨을 볼 수 있었다. 구조진동해석에서 Ⅰ형강 베드구조물의 고유진동수는 112.03㎐에서 141.66㎐까지의 범위에 발생되었다. 박스 구조형 베드구조물에서의 고유진동수는 396.93㎐에서 755.11㎐까지의 범위에서 발생되었다. 마지막으로 블록구조형 베드구조물에서는 266.51㎐에서 244.67㎐까지의 고유진동수를 찾을 수 있었다. 모든 구조물에서 베드구조물의 무게증가에 따른 기본진동수는 증가된다. 베드시스템의 지지기초시스템은 2자유도계 시스템으로 설계되었으며, 다양한 질량변화 및 스프링상수 변화에 따른 진동해석을 수행하였다. 질량비가 증가될수록 고유진동수는 크게 감소되며, 스프링상수가 증가될수록 고유진동수는 감소된다.

• Journal of Preventive Medicine and Public Health
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• v.21 no.2 s.24
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• pp.340-350
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• 1988

This study was carried out to clarify the effect of dietary calcium, casein, and suet on the accumulation of cadmium in mice. It was performed for 30 days, from April 11 to May 10 1988.90 mice were divided into 4 experimental groups and control group with 6 mice each dietary group, and measured survival rate, body weight, and weight ratio of organ to body. The contents of cadmium in liver, kidney, spleen, muscle and skin with hair, and feces were analyzed by atomic absorption spectrophotometer after sacrifice by anesthesia. After 30 days, the survival rate of control group was loot,, but 66.7% in group IV(basal diet+Cd+Ca) with single dose of $100{\mu}g$ cadmium and with free-intake of water containing 50ppm cadmium, and group V(basal diet+Cd+suet) with free-intake of water containing 50ppm cadmium. The rate of weight gain in the case of single dose of $100{\mu}g$ cadmium was highest in group IV as 42.3% and lowest in group V as 26.0%, whereas in the cases of free intake group W was highest as 24.0% and group II(basal diet+Cd) was lowest as 11.6%. The body weight, in the case of single dose of $100{\mu}g$ cadmium showed no increase until 5th day after acute poisoning. But in the case of free intake group, it showed very slight increase through all the breeding period. The weight ratio of organ to body were lowest in the liver of group II in both occasions. The most of cadmium adminstered. were excreted through feces within 2 days after single dose of $100{\mu}g$ cadmium. The contents of cadmium in each group were significantly higher than those of control group. In the liver, kidney, spleen and muscle, group II showed the highest level in both occasions of $100{\mu}g$ single dose and free intake of water containing 50ppm cadmium. In the skin with hair, group ll of the occasion with single dose of $100{\mu}g$ and group V with free intake showed the highest level. And the contents of cadmium in tissue were markedly higher in the occasion of free intake of water containing 50ppm cadmium. From the above results I would conclude that the addition of casein and calcium are effective in the inhibition of intesitnal absorption of cadmium esp. by calcium.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.3
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• pp.125-130
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• 1992

A digital 6-dof motion measuring system is developed using 7 accelerometers following Miles'[1] method. A snoic wave height gauge is also developed to measure the relative wave height at the foremost end of the ship. By combining the time series of both 6-dof motions and relative wave height, we can estimate the time series of real sea wave. Results of model tests shows the validity of the developed system.

• The Journal of Engineering Geology
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• v.32 no.1
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• pp.143-155
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• 2022

In this study, the response acceleration amplification according to different conditions was analyzed by changing the boundary condition of the soil called LSB (Laminar Shear Box), which is placed on a 1 g shaking table for earthquake simulation experiments. Experiments were carried out with different boundary conditions by fixing both sides of the LSB, and two samples were tested by installing an accelerometer at the same location. In addition, using DEEPSOIL v7 program, a one-dimensional ground response analysis was performed to compare and analyze with the free field condition. As a result, it was confirmed that the acceleration was amplified as it went from the lower layer to the upper layer, and as a result of comparing it with the ground response analysis, it was confirmed that it appeared similar to the analysis under the free field condition. As a result of the SA (Spectrum acceleration) analysis, a result similar to that of the ground response analysis was obtained, and in the case of fixing, it was confirmed that the PSA (Peak Spectral Acceleration) was further amplified.