• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.387-388
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• 2006

This article provides a dynamic analysis model for huge marine engine that examined analytically variation effects of frequency response by fitting of transverse stays such as hydraulic type. First, vibration analysis using the three dimensional finite element models for the huge marine engine has performed in order to find out the dynamic characteristics. Second, three dimensional finite elements model for the huge marine engine was modifued so that generate forcing nodes in crosshead part and top bracing nodes in cylinder frame part. Third, a system matrix and output matrix was derived for the general siso(single input single out) state space model. Finally, developed state space model for the three dimensional finite elements model for the huge marine engine without the additional modifying process.

• Smart Structures and Systems
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• 제13권2호
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• pp.281-303
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• 2014

In order to suppress the wind-induced vibrations of the Canton Tower, a pair of active mass driver (AMD) systems has been installed on the top of the main structure. The structural principal directions in which the bending modes of the structure are uncoupled are proposed and verified based on the orthogonal projection approach. For the vibration control design in the principal X direction, the simplified model of the structure is developed based on the finite element model and modified according to the field measurements under wind excitations. The AMD system driven by permanent magnet synchronous linear motors are adopted. The dynamical models of the AMD subsystems are determined according to the open-loop test results by using nonlinear least square fitting method. The continuous variable gain feedback (VGF) control strategy is adopted to make the AMD system adaptive to the variation in the intensity of wind excitations. Finally, the field tests of free vibration control are carried out. The field test results of AMD control show that the damping ratio of the first vibration mode increases up to 11 times of the original value without control.

• Smart Structures and Systems
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• 제23권6호
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• pp.669-682
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• 2019

Vibration mitigation of cables or hangers is one of the crucial problems for cable supported bridges. Previous research focused on the behaviors of cable with dampers or crossties, which could help engineering community apply these mitigation devices more efficiently. However, less studies are available for hybrid applied cross-ties and dampers, especially lack of both analytical and experimental verifications. This paper studied damping and frequency of two parallel identical cables with a connection cross-tie and an attached damper. The characteristic equation of system was derived based on transfer matrix method. The complex characteristic equation was numerically solved to find the solutions. Effects of non-dimensional spring stiffness and location on the maximum cable damping, the corresponding optimum damper constant and the corresponding frequency of lower vibration mode were further addressed. System with twin small-scale cables with a cross-link and a viscous damper were tested. The damping and frequency from the test were very close to the analytical ones. The two branches of solutions: in-phase modes and the out-of-phase modes, were identified; and the two branches of solutions were different for damping and frequency behaviors.

• Smart Structures and Systems
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• 제24권5호
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• pp.631-639
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• 2019

Finite element analysis is one of the important methods to study the structural performance. Due to the simplification, discretization and error of structural parameters, numerical model errors always exist. Besides, structural characteristics may also change because of material aging, structural damage, etc., making the initial finite element model cannot simulate the operational response of the structure accurately. Based on Bayesian methods, the initial model can be updated to obtain a more accurate numerical model. This paper presents the work on the field test, modal identification and model updating of a Chinese reinforced concrete pagoda. Based on the ambient vibration test, the acceleration response of the structure under operational environment was collected. The first six translational modes of the structure were identified by the enhanced frequency domain decomposition method. The initial finite element model of the pagoda was established, and the elastic modulus of columns, beams and slabs were selected as model parameters to be updated. Assuming the error between the measured mode and the calculated one follows a Gaussian distribution, the posterior probability density function (PDF) of the parameter to be updated is obtained and the uncertainty is quantitatively evaluated based on the Bayesian statistical theory and the Metropolis-Hastings algorithm, and then the optimal values of model parameters can be obtained. The results show that the difference between the calculated frequency of the finite element model and the measured one is reduced, and the modal correlation of the mode shape is improved. The updated numerical model can be used to evaluate the safety of the structure as a benchmark model for structural health monitoring (SHM).

• Journal of Electrical Engineering and Technology
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• 제1권1호
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• pp.101-105
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• 2006

In this paper, a disk-type ultrasonic motor using a combination of radial and bending vibration modes is newly designed and fabricated. The characteristics of the test motor are also measured. By means of traveling elastic wave induced at the surface of circumference of the elastic disk, a steel bar in contact with the surface of circumference of the elastic disk bonded onto the piezoelectric ceramic disks is driven in both directions by changing the sine and cosine voltage inputs. The stator of the motor is composed of two sheets of piezoelectric ceramic disks to bond onto both surfaces of an elastic disk, respectively. As a result, the diameter of the elastic body is increased and the resonant frequency is decreased. The resonant frequency of the stator is about 92 kHz, which is composed with piezoelectric ceramic disks of 28 mm in diameter and 2 mm in thickness, and an elastic body of 32 mm in diameter and 2 mm in thickness. A driving voltage of 20 VPP Produces 200 rpm with a torque of 1Nm and an efficiency of about 10%.

• 전산구조공학
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• 제3권2호
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• pp.77-88
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• 1990

환경조건 및 내부의 유공부 크기와 위치가 변화함에 따라 평판의 두개의 고유치(고유 진동수와 탄성 임계하중)는 어떻게 변화하며, 이들 고유치 상호간의 관계는 어떻게 되는지 검토 하기로 한다. 이상과 같은 검토 목적에는 수치 해석법이 적당한데 본 논문에서는 그 중의 하나인 유한 요소법을 채택하기로 한다. 유한 요소법에서 이용할 요소는 각 절점에서 자유도가 3, 따라서 요소 전체의 자유도가 12인 사각형 요소이다.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.II
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• pp.1538-1541
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• 2005

For reliability evaluation of AC-PDP, one of the most important factor is sealing property. In this paper, the reliability evaluation test method of the commercialized sealing glass frit in AC-PDP was studied. 6 inch AC-PDP panels were tested for evaluation of sealing glass frit by vibration shock test, thermal shock test, non -destructive X-ray inspection, residual stress inspection and residual gas detection. These test methods are proposed as a standard for testing the reliability of sealing glass frit. The main failure mode of sealing glass frit in AC-PDP seems to be the crack propagation from thermal cycling rather than mechanical factor.

• Bulletin of the Korean Chemical Society
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• 제21권10호
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• pp.1041-1043
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• 2000

We present the effects of temperature (between 10 K and 298 K) and of hole concentration on the frequency and intensity of characteristic phonons in polycrystalline $La_2CuO_4-related$ compounds using FT-IR spectros-copy. The influences of the concentration of carrier doped on the phonon modes are prominent in the IR spectra of $La_2CuO_4-related$ compounds. For $La_2-xSrxCuO_4({\chi}=$ 0.00, 0.03, 0.07, 0.10, and 0.15) and electrochemically (or chemically) oxidized $La_2CuO_4$, the intensities of the transverse oxygen mode around 680cm $-^1$ which cor-responds mainly to Cu-O(1) stretching vibration in the basal plane of CuO6 octahedron, are decreased and dis-appeared depending on the Sr-substitution rate and the amount of excess oxygen, while the longitudinal oxygen mode around 510 cm $-^1$ corresponding to the Cu-O(2) stretching in the basal plane of CuO6 octahedron are near-ly invariable. In particular, after two cycles of cooling-heating between 10 K and 298 K for these sample, the phonons around 680 cm $-^1$ are blue shif 13-15 cm $-^1$, while the phonons around 510 cm $-^1$ are nearly constant. The introduction of the charge carrier by doping would give rise to the small contraction of CuO6 oc-tahedron as Cu $^3+$ requires a smaller site than Cu $^2+$, which results in the shortening of the Cu-O(1) bond length and Cu-O(2) bond length with the increased La-O(2) bond length. These results in the frequency shift of the characteristic phonons. The IR spectra of $La_2Li0.5Cu0.5O_4$ which exhibits an insulator behavior despite the $Cu^3+$ of nearly 100%, corroborate our IR interpretations. The mode around 710 cm $-^1$ corresponding to Cu-O(1) stretching vibration is still strongly remained even at low temperature (10 K). Thus, we conclude that the con-duction electrons formed within $CuO_2$ planes of $La_2CuO_4-related$ superconductors screen more effectively the transverse oxygen breathing mode around 680 $cm-^1$ depending on the concentration of the doped charge carrier in $La_2CuO_4-related$ compounds, which might use as a superconductivity probe.

• 한국산학기술학회논문지
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• 제15권1호
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• pp.39-46
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• 2014

미얀마 Kayah산 녹색 투어말린의 특성을 X-선 형광분석, 자외선-가시광선 그리고 중적외선 분광분석을 통하여 타산지의 녹색 투어말린과 비교하였다. 화학성분 분류에 의해 미얀마 투어말린이 속한 그룹을 조사 하였다. 미얀마 투어말린은 V 원소를 많이 함유하고 있었고 X 사이트에 Ca 원소를 반 이상 함유한 Calcic 그룹에 속했고 우바이트 (Uvite)로 명명되었다. 자외선-가시광선 분석결과 $V^{3+}$ 이온에 의한 415와 611 nm에 강한 흡수밴드가 나타나 녹색 투어말린의 원인이 되었다. $Fe^{2+}$ 이나 $Cu^{2+}$ 이온에 의해 녹색이 나타나는 타산지의 녹색 투어말린과 차이가 있었다. 중적외선 분석에서는 수산기와 금속들 간의 진동에 의한 흡수가 일어났는데 1100 $cm^{-1}$ 근처에서 스트레칭 모드, 3500 $cm^{-1}$ 주변에서 벤딩 모드 그리고 4600과 4200 $cm^{-1}$ 사이에서 스트레칭과 벤딩 모드의 혼합 밴드가 나타났다.

• 한국산학기술학회논문지
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• 제22권3호
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• pp.777-783
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• 2021

항공기는 기동 중 다양한 진동의 영향을 받게 된다. 이러한 진동들은 상황에 따라서는 항공기 생존에 치명적인 영향을 미칠 수 있으므로 항공기에 적용되는 구성품들은 랜덤 진동해석을 통해 다양한 진동 조건에 대한 안전성이 입증되어야 한다. 본 연구에서는 상용 소프트웨어인 MSC.Random을 사용하여 랜덤진동 조건에서 군용항공기 외부연료탱크와 파일런에 대한 구조 강건성을 평가하였다. 랜덤 진동해석은 경계조건 지점에 단위하중을 부과하여 주파수 응답해석을 수행한 후 파워 스펙트럼 밀도 프로파일로 가진하게 되는데, 이 과정에서 필요한 모드 데이타는 모달해석 방법을 통해 추출하였다. 그리고, 랜덤진동 조건으로 미국 국방환경규격에서 규정하고 있는 랜덤 진동 프로파일을 적용하였고, G 단위로 주어진 파워 스펙트럼 밀도 프로파일을 중력가속도 단위로 변환하여 사용하였다. 수치해석 결과로, x축, y축 및 z축 방향에서의 랜덤 가진에 대해 수치해석 모델을 구성하는 빔 요소, 쉘 요소 그리고 솔리드 요소의 안전여유를 파악하여 본 논문에서 다루고 있는 군용 항공기에 장착되는 외부연료탱크와 파일런의 구조 강건성을 평가하였다.