• Wind and Structures
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• 제4권2호
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• pp.147-162
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• 2001

This paper presents an analytical method which takes into account the non-linearity of individual members, and discusses some case study results. It also discusses the relationship between member non-elastic behavior and excitation duration, and the relationship between member fracture and overall structure behavior. It is clearly demonstrated that the frame already shows almost unstable behavior due to long-columnization just before the occurrence of a column fracture. Then, a column fracture immediately induces a structural collapse mechanism.

• Advances in nano research
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• 제9권4호
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• pp.277-294
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• 2020

In current paper, nonlocal (NLT), nonlocal strain gradient (NSGT) and Gurtin-Murdoch surface/interface (GMSIT) theories with classical theory (CT) are utilized to investigate vibration and stability analysis of Double Walled Piezoelectric Nanosensor (DWPENS) based on cylindrical nanoshell. DWPENS simultaneously subjected to direct electrostatic voltage DC and harmonic excitations, structural damping, two piezoelectric layers and also nonlinear van der Waals force. For this purpose, Hamilton's principle, Galerkin technique, complex averaging and with arc-length continuation methods are used to analyze nonlinear behavior of DWPENS. For this work, three nonclassical theories compared with classical theory CT to investigate Dimensionless Natural Frequency (DNF), pull-in voltage, nonlinear frequency response and stability analysis of the DWPENS considering the nonlocal, material length scale, surface/interface (S/I) effects, electrostatic and harmonic excitation.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2005년도 학술발표회 논문집
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• pp.169-176
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• 2005

Many RC building structures of multiple uses constructed in Korea have the irregularities of torsion and soft story at bottom stories. A typical irregular building was selected as prototype and shaking table tests were performed to investigate the seismic performance of this building. The objective of this study is to evaluate the correlation between the experimental and analytical responses of this irregular building structure subjected to the earthquake excitation by using OpenSees(Open System for Earthquake Engineering Simulation). The results of analyses simulate well the effect of axial forces on the shear force of column and axial deformation. However, some discrepancy between analytical and experimental results in the distribution of shear forces and overturning deformation were observed.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.633-638
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• 2000

This paper reports an example of flow-induced vibration in a very large plant and the whole procedure of reducing the vibration. During the operation of flue gas desurfurization unit of the thermal power plant, serious vibration occurred at all around the unit. The worst vibration was recorded on the heat exchanger surface, which weighed 180 tones, as 17.8 m/$s^2$ in vibration amplitude at 34Hz. To identify the vibration, frequency analysis on the response vibration, the expected excitation force and the system resonance was executed. This investigation revealed that the cause of the vibration was vortex shedding from the circular pipes in the heat exchanger. Vortices from the pipes excited acoustic resonance in the heat exchanger room, which, in turn, made the structure vibrate. Through inserting the baffles between the pipes, which had an effect of cutting the acoustic wave at resonance frequency, the vibration was eliminated dramatically.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.1139-1146
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• 2000

The frequencies of principal noise in interior permanent motor originate form two sources. One is torque ripple that is composed of cogging torque, magnetic torque ripple and reluctance torque ripple. The other is induced by natural frequencies. In this paper, the torque ripple and its influence on noise was examined by theoretical analysis. Understanding relation of dynamic characteristics and noise, natural frequencies and mode shapes were obtained by experimentation and operational deflection shape was observed. Finally, the method of predicting frequencies of principal noise was proposed.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 춘계학술대회 논문집
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• pp.929-932
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• 2012

Beat map shows the distribution property of the beating sound in the bell structure. Using the beat map, beat control and beat estimation are available. To draw the beat map, mode pair parameters of the bell are required. However, in case of large bell which is struck by a heavy wooden hammer, it is very difficult to measure the excitation force and to obtain the mode pair parameters. In this paper, we determined the mode pair parameters of the bell from the transmissibility between the roving signal and reference signal, using ODS(operational deflection shape) method. The mode pair data are input to the theoretical model of the beat response and beating waves are generated on the bell circumference. All the numerical and beat map drawing procedures are automatized using Matlab. Finally, the reliability of the beat map generated by the program is verified.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 춘계학술대회 논문집
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• pp.686-690
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• 2012

The modal test has been carried out using the exciter machine to investigate the vibration characteristics of the hull and super structure of the ship. The conventional exciter acts only one(1) direction and the exciter should be reinstalled for different direction test, which consumes additional expense. The 3 axes exciter has been designed of which force acts three directions without reinstallation for efficient modal test of the ship. It consists of rotatable base frame structure and the clutch mechanism for the unbalances to excite three directions. And the 3 axes exciter for the local structure has been made in advance and its performance test was carried out in the laboratory. The developed 3 axes exciter shows the ability of three-directions excitation with simple operation and modal test for the various local structure of the ship will be performed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2015년도 제46회 하계학술대회
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• pp.748-749
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• 2015

본 논문에서는 권선사양에 따른 10kW급 동 다이캐스팅 고속 유도전동기의 전자기적 특성과 전기기기의 진동을 발생시키는 고정자 치의 가진력을 분석하였다. 회전자 모델과 코일의 점적률은 일정하게 유지하면서 턴 수, 코일단면적, 고정자 슬롯의 형상을 변경하였다. 이에 따라 1, 2차 측 저항과 누설리액턴스 성분이 변화함을 확인하였고, 저항과 누설리액턴스 성분의 변화가 유도전동기의 토크, 자속밀도, 효율 특성 및 고정자 치의 가진력에 미치는 영향에 대해 분석하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.481-486
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• 2000

This paper presents vibration control performance of a passenger vehicle installed with olectro-rheological(ER) engine mounts. As a first step, a mixed-mode ER engine mount is modeled and manufactured. After verifying the controllability of the dynamic stiffness by the intensity of the electric field, ER engine mounts are incorporated with a full-car model. The governing equation of motion is then formulated by considering engine excitation force. A skyhook controller to attenuate vibration motions is designed. The controller is implemented through hardware-in-the-loop simulation and control responses are presented in the both frequency and time domains.

• Applied Science and Convergence Technology
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• 제23권6호
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• pp.387-391
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• 2014

Self-assembled InAlAs/AlGaAs quantum dots (QDs) on GaAs substrates were grown by using modified molecular epitaxy beam in Stranski-Krastanov method. In order to study the structural and optical properties of InAlAs/AlGaAs QDs, atomic force microscopy (AFM) and photoluminescence (PL) measurements are conducted. The size and uniformity of QDs have been observed from the AFM images. The average widths and heights of QDs are increased as the deposition time increases. The PL spectra of QDs are composed of two peaks. The PL spectra of QDs were analyzed by the excitation laser power- and temperature-dependent PL, in which two PL peaks are attributed to two predominant sizes of QDs.