• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2007년도 춘계학술대회 논문집
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• pp.379-384
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• 2007

In this paper, a new method for detecting rotor vibrations in a squirrel-cage induction motor is proposed. The air-gap flux variation analysis was done using search coils inserted in stator slots when rotor vibration conditions occurs. An accurate modelling and analysis of air-gap flux variation in the induction motor are developed using finite-element (FE) software packages, and treasuring the flux are made using search coils. In the FE analysis and experiment, the three-phase squirrel-gage induction motor with 380 [V], 7.5 [kW], 4 Poles, 1,768 [rpm] ratings is used. The simulation and experiment results can be useful for detecting rotor vibration of the induction motors.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 전기설비
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• pp.52-54
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• 2005

In this paper, a new approach monitoring rotor vibrations in a squirrel-cage induction motor is proposed. The air-gap flux variation analysis was done using search coils inserted in stator slots when rotor vibration conditions occur. An accurate modelling and analysis of air-gap flux variation in the induction motor are developed using finite-element(FE) software packages, and measuring the flux are made using search coils. In the FE analysis, the three-phase squirrel-gage induction motor with 380 (V), 5 (HP), 4 Poles, 1,742 [rpm] ratings is used. The results of FE analysis can be useful for on-line vibration monitoring of the induction motors.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2004년도 전력전자학술대회 논문집(2)
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• pp.862-865
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• 2004

Faults such as broken rotor bars, static and dynamic eccentricity are often reported in induction motors. These faults increase the down-time of equipment, which causes major loss of earnings to the industry. This paper presents a result of the finite-element(FE) analysis of air-gap flux variation in induction motors when rotor vibration conditions occur, An accurate modelling and analysis of rotor vibration in the machine are developed using FE software packages, and measuring the flux are made using the search coils. In the FE analysis, an induction motor with 380 [V], 5[HP], 4 Poles, 1742 [rpm] ratings is used. The results of FE analysis can be used for on-line vibration monitoring of the induction motors.

• 한국포장학회지
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• 제15권1호
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• pp.1-6
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• 2009

The impact absorption materials made of synthetic organic chemical product like Expanded Polystyrene(EPS), Expanded Polyethylene(EPE), Expanded Polyurethane(EPU), etc. have been used with general packaging material until the present. But nowadays, the use of these materials is intended to be decreased and to be recycled in connection with environmental pollution. In addition, it has been tried to substitute these materials with non-pollution materials(natural materials) like pulp mould, paper protectors, etc. At the same time, it is required to evaluate and analyze these cushioning materials for cushioning properties based on impact and vibration, in order to make an efficiency on the overall packaging system because they are generally being used by a random choice regardless of the properties of contents and cushioning materials. Therefore, this study provides analyzed data on cushioning properties of various cushioning materials against impact and vibration, and is intended to provide more efficient model for packaging system by minimizing their using amount through choosing an optimal cushioning material as well as intended to lead to the use of nonpollution materials in case these cushioning materials have same cushioning properties.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1998년도 춘계학술대회논문집; 용평리조트 타워콘도, 21-22 May 1998
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• pp.432-437
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• 1998

This paper presents modal characteristics of bowl parts feeder featuring piezoelectric actuators. As wellknown, the piezoelectric materials develop an electric charge proportional to a mechanical stress and vice versa. This generic phenomenon allows us to use the piezoelectric materials as sensors and actuators. Using the actuating property, we can device effective bowl parts feeder. The parts feeder activated by the piezoceramic actuators provides a large degree of freedom of controlling excitation magnitude and frequency, and thus accurate and fast feeding of various parts. As a first phase to demonstrate these advantages, a finite clement model of the bowl parts feeder is constructed and analyzed using commercial software packages. In addition, the simulated modal characteristics are compared with the measured ones to validate the proposed model.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.439-449
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• 2002

This paper reviews our recent research works on the interconnection technologies in electronic packaging and assembly. At the aspect of advanced joining methods, laser-ultrasonic fluxless soldering technology was proposed. The characteristic of this technology is that the oxide film was removed through the vibration excitated by high frequency laser change in the molten solder droplet. Application researches of laser soldering technology on solder bumping of BGA packages were carried out. Furthermore, interfacial reaction between SnPb eutectic solder and Au/Ni/Cu pad during laser reflow was analyzed. At the aspect of soldered joints' reliability, the system for predicting and analyzing SMT solder joint shape and reliability(PSAR) has been designed. Optimization design method of soldered joints' structure was brought forward after the investigation of fatigue failure of RC chip devices and BGA packages under temperature cyclic conditions with FEM analysis and experimental study. At the aspect of solder alloy design, alloy design method based on quantum was proposed. The macroproperties such as melting point, wettability and strength were described by the electron parameters. In this way, a great deal of the experimental investigations was replaced, so as to realize the design and research of any kinds of solder alloys with low cost and high efficiency.

• Advances in aircraft and spacecraft science
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• 제6권6호
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• pp.479-495
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• 2019

Periodic cellular core structures included in sandwich panels possess good stiffness while saving weight and only lately their potential to act as passive vibration filters is increasingly being studied. Classical homogeneous honeycombs show poor vibracoustic performance and only by varying certain geometrical features, a shift and/or variation in bandgap frequency range occurs. This work aims to investigate the vibration filtering properties of the AUXHEX "hybrid" core, which is a cellular structure containing cells of different shapes. Numerical simulations are carried out using two different approaches. The first technique used is the harmonic analysis with commercially available software, and the second one, which has been proved to be computationally more efficient, consists in the Wave Finite Element Method (WFEM), which still makes use of finite elements (FEM) packages, but instead of working with large models, it exploits the periodicity of the structure by analysing only the unit cell, thanks to the Floquet-Bloch theorem. Both techniques allow to produce graphs such as frequency response plots (FRF's) and dispersion curves, which are powerful tools used to identify the spectral bandgap signature of the considered structure. The hybrid cellular core pattern AUXHEX is analysed and results are discussed, focusing the investigation on the possible spectral bandgap signature heritage that a hybrid core experiences from their "parents" homogeneous cell cores.

• 대한기계학회논문집A
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• 제38권1호
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• pp.45-50
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• 2014

인쇄회로기판 위에 9개의 PBGA (Plastic Ball Grid Array) 패키지를 SnPb 솔더로 실장하여 진동시편을 제작하고 랜덤진동시험을 수행하였다. 진동에 대한 각 패키지 솔더의 내구수명을 분석한 결과, 패키지의 인쇄회로기판 배치 위치에 따라 솔더의 내구수명이 결정됨을 보였다. 이 위치에 따른 내구수명 의존성을 규명하기 위하여 유한요소모델을 작성하고, 모델의 모든 요소에 대해서 응력응답함수로부터 정의되는 등가응력을 분석하였다. 분석결과로부터 랜덤진동시험에서 패키지를 연결하는 솔더 중 코너에 위치한 솔더에서 최대 등가응력이 발생함을 보였다. 마지막으로, 각 패키지별 코너 솔더의 최대 등가응력값을 파괴등가응력으로 정의하고 파괴등가응력과 각 패키지의 내구수명간에 직접적인 연관관계가 있음을 제시하였다.

• Advances in aircraft and spacecraft science
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• 제6권2호
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• pp.117-144
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• 2019

High Altitude and Long Endurance (HALE) aircraft are capable of providing intelligence, surveillance and reconnaissance (ISR) capabilities over vast geographic areas when equipped with advanced sensor packages. As their use becomes more widespread, the demand for additional range, endurance and payload capability will increase and designers are exploring non-conventional configurations to meet the increasing demands. One such configuration is the joined-wing concept. A joined-wing aircraft is one that typically connects a front and aft wings in a diamond shaped planform. One such example is the Boeing SensorCraft configuration. While the joined-wing configuration offers potential benefits regarding aerodynamic efficiency, structural weight, and sensing capabilities, structural design requires careful consideration of elastic buckling resulting from the aft wing supporting, in compression, part of the forward wing structural loading. It has been shown already that this is a nonlinear phenomenon, involving geometric nonlinearities and follower forces that tend to flatten the entire configuration, leading to structural overload due to the loss of the aft wing's ability to support the forward wing load. Severe gusts are likely to be the critical design condition, with flight control system interaction in the form of Gust Load Alleviation (GLA) playing a key role in minimizing the structural loads. The University of Victoria Center for Aerospace Research (UVic-CfAR) has built a 3-meter span scaled and flexible wing UAV based on the Boeing SensorCraft design. The goal is to validate the nonlinear structural behavior in flight. The main objective of this research work is to perform Ground Vibration Tests (GVT) to characterize the dynamic properties of the scaled flight vehicle. Results from the experimental tests are used to characterize the modal dynamics of the aircraft, and to validate the numerical models. The GVT results are an important step towards a safe flight test program.

• Steel and Composite Structures
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• 제42권5호
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• pp.591-598
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• 2022

The article deals with the possibilities of vibration stimulation. Based on the stability analysis, a multi-scale approach with a modified whole-building model is implemented. The motion equation is configured for a controlled bridge with a MDOF (multiple dynamic degrees of freedom) Tuned Mass Damper (M-TMD) system, and a combination of welding, excitation, and control effects is used with its advanced packages and commercial software submodel. Because the design of high-performance and efficient structural systems has been of interest to practical engineers, systematic methods of structural and functional synthesis of control systems must be used in many applications. The smart method can be stabilized by properly controlling the high frequency injection limits. The simulation results illustrate that the multiple modeling method used is consistent with the accuracy and high computational efficiency. The M-TMD system, even with moderate reductions in critical pressure, can significantly suppress overall feedback on an unregulated design.