• Journal of the Earthquake Engineering Society of Korea
• /
• v.7 no.6
• /
• pp.81-91
• /
• 2003

Recently, many high-rise reinforced concrete(RC) bearing-wall structures of multiple uses have been constructed, which have the irregularities of weak(or soft) story and torsion at the lower stories simultaneously. The study stated herein was performed to investigate seismic performance of such a high-rise RC structure through a series of shaking table tests of a 1: 12 model. Based on the observations of the test results, the conclusions are drawn as follows: 1) Accidental torsion due to the uncertainty on the properties of structure can be reasonably predicted by using the dynamic analysis than by using lateral force procedure. 2) The mode coupled by translation and torsion induced the overturning moments not only in the direction of excitations but also in the perpendicular direction: The axial forces in columns due to this transverse overturning moment cannot be adequately predicted using the existing mode analysis technique, and 3) the hysteretic curve and the strength diagram between base shear and torque(BST) clearly reveal the predominant mode of vibrations and the failure mode.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.31 no.6
• /
• pp.17-22
• /
• 2003

An airship is statically unstable, because it has no wing, relatively small tails and a large hull. Hence, an accurate prediction of dynamic stability is critical. In this study, dynamic stability data of the 50m Length Airship were acquired through forced oscillation wind tunnel tests. The tests were done in Birhle Applied Research Inc's Lange Amplitude Multi-Purpose(BAR LAMP) Facility located in Germany. The tests were composed with 16 static runs and 26 dynamic runs. As results, it is obtained that dynamic characteristics of the airship depend on the sideslip angle, the angular rate and its direction as well as the angle of attack. Generally, three directional moments have damping, but the normal force, the side force, and the cross-derivatives are unstable. The dynamic derivatives are not sensitive to the control surfaces, but nonlinear to the sideslip angle.

• Journal of the Korea Convergence Society
• /
• v.11 no.11
• /
• pp.203-209
• /
• 2020

A hybrid mount featuring rubber element and piezoelectric actuator is devised to reduce vibration when starting a vehicle engine. As a first step, a passive mount adopting rubber element is manufactured and its dynamic characteristics are experimentally evaluated. After evaluating dynamic characteristics of the manufactured inertial piezoelectric actuator, the proposed hybrid mount is then established by integrating the piezoelectric actuator with the rubber element for performance improvement at non-resonant high frequencies. A mathematical model of the established active vibration control system is formulated and expressed in the state space form. Subsequently, sliding mode controller (SMC) is designed to attenuate the vibration transmitted from the base excitation. Finally, control performances of the proposed hybrid mount are evaluated such as transmissibility in frequency domain and time responses.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.13 no.6
• /
• pp.1128-1146
• /
• 1989

본 논문에서는 2상 횡유동의 진동 메카니즘을 규명하기 위한 실험계획의 일환으로 실시된 실험으로 부터 튜브집합체의 추가질량(hydrodynamic mass)과 감쇠 (damping)에 대해 고찰하였다. 실험은 튜브배열과 피치 대 직경비(pitch-over-di- ameter:.rho./ｄ)가 상이한 튜브집합체에 대해 2상 유체를 모의한 공기-물(air-water) 혼합물에서 수행하였다. 액체상태로부터 99%의 보이드율까지 변화된 2상 유체의 유량은 튜브가 유체탄성 불안정성 (fluidelastic instability)에 도달할 때까지 점진적으로 증가하였다.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2002.09a
• /
• pp.43-50
• /
• 2002

부지고유의 강지진동모사를 위해 한반도 남부의 지각감쇠(Q)에 대한 두 가지 특성을 비선형 역산을 통해 규명하였다. 한 특성은 한반도 남부의 주요 지체구조구 및 특정 주향각에 대한 Q의 이방성이고 다른 특성은 Q의 수평방향으로의 공간적 변화 특성이다. 0의 이방성은 주향에 평행한 Q와 이에 수직한 Q의 비로 정의되었다. 사용된 지진자료는 190개 지진에 대한 3,400개 기록의 푸리에스펙트럼으로서 기록의 파선 분포는 한반도 남부 대부분을 조밀하게 덮었다. 역산 방법은 Levenberg-Marquardt 비선형역산 방법을 보다 안정화시킨 수정된 Levenberg-Marquardt 방법이 사용되었으며 기존에 도출된 광역적인 지진동파라미터를 초기해로 활용하였다. 역산 결과 국내의 중요 지체구조구 중 소백산육괴와 경상분지는 서로 다른 방향의 강한 Q 이방성을 나타내었으며 Q의 공간적 분포는 지진발생위치와 매우 밀접한 상관관계를 보여주었다

• Proceedings of the Optical Society of Korea Conference
• /
• 2000.02a
• /
• pp.260-261
• /
• 2000

광결정(photonic crystal)은 빛의 파장 크기 정도의 격자 상수를 지닌 1차원, 2차원, 또는 3차원의 주기적인 구조이다. 광결정에는 광밴드갭(photonic bandgap)이라는 빛의 자발 방출이 억제된 진동수의 영역이 존재하는데, 이 영역을 이용하여 빛의 자발 방출을 조절하고 빛의 흐름을 제어할 수 있다. $^{[1]}$ 지난 10여년간 2차원, 3차원의 광결정 구조에 대한 연구가 많이 이루어져 왔는데, 최근에는 슬랩 도파관(slab waveguide)에 2차원 광결정을 만든 구조에 대한 연구가 활발하게 진행중이다. 이 구조는 평면 방향으로는 광밴드갭 효과로 광모드를 가둘 수 있고 수직 방향으로는 전반사를 이용하여 모드를 가둘 수 있어서 3차원적인 모드 confinement 효과를 얻을 수 있다. [그림 1]의 (a)에 air-bridge 형태의 2차원 광결정 슬랩(photonic crystal slab) 구조를 도식적으로 나타내었고, (b)에는 본 연구실에서 제작한 구조 표면의 scanning electron micrograph을 나타내었다. 현재 몇몇 연구 그룹에서 이와 같은 광결정 슬랩 구조를 이용한 반도체 레이저를 실현하는데 성공하였다.$^{[2,3]}$ (중략)

• Journal of the Korean Chemical Society
• /
• v.17 no.2
• /
• pp.80-84
• /
• 1973

In treating solid-liquid interfaces, it is assumed that the adsorbed layer consists of monolayer and the molecules of the adsorbed layer behave as two dimensional liquid and oscillate harmonically in the vertical direction to the adsorbent. Applying the transition state theory of significant liquid structure to the adsorbed molecules, the adsorption isotherm, entropy and heat of adsorption for cyclohexane-benzene solutions adsorbed on silica-gel G are calculated. The calculated values are in good agreements with those of the observed ones.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.20 no.1
• /
• pp.104-111
• /
• 2016

The steel frame modular housing of which the research and development has been actively carried out recently cannot be constructed through monolithic placement like the reinforced concrete deck of general structure due to the characteristics of construction method of production in the factory and assembly on the site. And floor vertical vibration and deflection caused by inhabitants' activities may become an important issue in the aspect of usability evaluation due to a decrease in the section size of member, a decrease in weight, and so on. Therefore, this study evaluated the vibration performance of deck by using formula of AISC Design Guide 11(hereinafter AISC formula) which was practically used in general for modules where a stud was and wasn't installed at the center of beam in the longitudinal direction in the modular housing to be studied, and examined the applicability of AISC formula through comparison with the results of analysis using a general-purpose analysis program. On the basis of this, a structural cause for an error to occur between analysis result and AISC formula in the deck of module in which a stud was installed was analysed, and measures for considering this were suggested. Besides, an analysis model with the variables of measures for improving the floor vibration performance of modular housing to be studied was established. And measures having excellent vibration performance and economic feasibility were suggested through vibration response analysis and economic evaluation.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.30 no.6
• /
• pp.469-477
• /
• 2017

In this paper, the floor vibration of an example concert hall building was measured and floor safety criteria were analytically checked through comparison between experimental and analytical results. The floor bottom plate model was constructed considering the composite effect and the analytical model was modified to have the natural frequency identical to the measured one. Also, time history analysis was conducted using the dynamic loads induced by human rhythmic movement during a musical performance, and the analytically calculated floor accelerations were similar to the measured one. Based on this model, the floor vibration level due to the group activities of about 400 persons, maximum available persons for the concert hall, was estimated. It was confirmed that the human induced dynamic loads applied to the column and beam would be much lower than the design strength. In addition, the horizontal acceleration level is just 2% of the design seismic load, so the concert hall is safe in both vertical and horizontal excitations by human rhythmic movements.

• Tunnel and Underground Space
• /
• v.11 no.4
• /
• pp.362-367
• /
• 2001

The stiff top layer in a soil profile, which can happen in winter, may change the isolation effect of the wave barrier. The research scope of this paper is the investigation of the propagation of surface waves in layered soil with a stiff layer on its top, and the isolation effect of the solid stiff wave barrier. The investigations have been performed numerically by the Boundary-Element Method as a two-dimensional problem. A strip foundation vibrated harmonically in vertical direction was considered as the vibration source. Three soil profiles, a homogeneous half-space, two profiles with different thickness of stiff top layer, with two different types of wave barriers were investigated. The profiles with a stiff top layer show considerable reductions of the amplitude of the vibration in comparison to the homogeneous soil profile. The layered soil profiles with a stiff top layer do not show wave propagation velocities as high as they are expected from the material properties. Furthermore the vibration amplitudes in a frozen soil are much smaller with distance than in a non-frozen soil.