• 소음진동
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• 제9권1호
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• pp.196-205
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• 1999

6승의 비선형 항을 가지는 두개의 질량으로 구성된 비선형 해밀톤계에 대해서, 비선형 정규모드인 주기운동의 존재성, 분기현상 및 궤도 안정성을 연구하였다. 운동방정식의 직접적분을 통해 4차원 위상공간에서의 운동궤적을 2차원 면으로 투영하는 푸앙카레 사상을 구하였고, 또한 버크 호프-구스타프슨 표준 변환을 통해 구한 운동적분을 이용하여 에너지가 작을때 푸앙카레 사상에 나타나는 불변 곡선들의 해석적인 표현을 유도하였다. 본 논문에서 연구한 진동계는 비선형 계수의 값에 따라 2개 또는 4개의 비선형 정규모드를 가짐이 밝혀졌다. 푸앙카레 사상은, 분기된 모드는 안정하고, 원래의 모드는 안정한 상태에서 불안정한 상태로 변한다는 것을 분명하게 보여주었다.

• 한국음향학회지
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• 제35권4호
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• pp.243-252
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• 2016

본 논문에서는 연성 모드 기반의 양상태 비상관 잔향음 모델을 제안한다. 거리종속 환경에서 단방향 연성모드 기반의 음파전달모델을 사용하여 음원에서의 산란체에 도달하는 음압과 산란체에서 수신원에 도달하는 음압을 계산한다. 계산의 편의 상 각 산란체와 음원 또는 수신기 사이의 음파전달은 산란체와 음원 또는 수신기를 잇는 2차원 평면에서만 일어난다고 가정한다. 모델의 타당성을 검증하기 위해, 미 해군 잔향음 모델링 워크숍 I, II에 제시된 문제에 대해 계산하고, 그 결과를 음선 이론 기반의 비상관 잔향음 결과와 비교했다.

• 한국해양공학회지
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• 제33권1호
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• pp.50-60
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• 2019

Recently, problems with excessive vibration of the radar masts of large bulk carriers and crude oil tankers have frequently been reported. This paper explores a design method to avoid the resonance of a radar mast installed on a large ship using various design of experiment (DOE) methods. A local vibration test was performed during an actual sea trial to determine the excitation sources of the vibration related to the resonant frequency of the radar mast. DOE methods such as the orthogonal array (OA) and Latin hypercube design (LHD) methods were used to analyze the Pareto effects on the radar mast vibration. In these DOE methods, the main vibration performances such as the natural frequency and weight of the radar mast were set as responses, while the shape and thickness of the main structural members of the radar mast were set as design factors. From the DOE-based Pareto effect results, we selected the significant structural members with the greatest influence on the vibration characteristics of the radar mast. Full factorial design (FFD) was applied to verify the Pareto effect results of the OA and LHD methods. The design of the main structural members of the radar mast to avoid resonance was reviewed, and a normal mode analysis was performed for each design using the finite element method. Based on the results of this normal mode analysis, we selected a design case that could avoid the resonance from the major excitation sources. In addition, a modal test was performed on the determined design to verify the normal mode analysis results.

• JSTS:Journal of Semiconductor Technology and Science
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• 제15권4호
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• pp.445-453
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• 2015

A fully integrated cost-effective and low-power single chip Lithium-Ion (Li-Ion) battery protection IC (BPIC) for portable devices is presented. The control unit of the battery protection system and the MOSFET switches are integrated in a single package to protect the battery from over-charge, over-discharge, and over-current. The proposed BPIC enters into low-power standby mode when the battery becomes over-discharged. A new auto release function (ARF) is adopted to release the BPIC from standby mode and safely return it to normal operation mode. A new delay shorten mode (DSM) is also proposed to reduce the test time without increasing pin counts. The BPIC implemented in a $0.18-{\mu}m$ CMOS process occupies an area of $750{\mu}m{\times}610{\mu}m$. With DSM enabled, the measured test time is dramatically reduced from 56.82 s to 0.15 s. The BPIC chip consumes $3{\mu}A$ under normal operating conditions and $0.45{\mu}A$ under standby mode.

• Smart Structures and Systems
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• 제17권3호
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• pp.413-429
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• 2016

The recent research on proper orthogonal decomposition (POD) has revealed the linkage between proper orthogonal modes and linear normal modes. This paper presents an investigation into the modal identifiability of an instrumented cable-stayed bridge using an adapted POD technique with a band-pass filtering scheme. The band-pass POD method is applied to the datasets available for this benchmark study, aiming to identify the vibration modes of the bridge and find out the so-called deficient modes which are unidentifiable under normal excitation conditions. It turns out that the second mode of the bridge cannot be stably identified under weak wind conditions and is therefore regarded as a deficient mode. To judge if the deficient mode is due to its low contribution to the structural response under weak wind conditions, modal coordinates are derived for different modes by the band-pass POD technique and an energy participation factor is defined to evaluate the energy participation of each vibration mode under different wind excitation conditions. From the non-blind datasets, it is found that the vibration modes can be reliably identified only when the energy participation factor exceeds a certain threshold value. With the identified threshold value, modal identifiability in use of the blind datasets from the same structure is examined.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.2
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• pp.1254-1257
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• 2004

This paper presents a built-in current sensor(BICS) that can detect defects in CMOS integrated circuits through current testing technique - Iddq test. Current test has recently been known to a complementary testing method because traditional voltage test cannot cover all kinds of bridging defects. So BICS is widely used for current testing. but there are some critical issues - a performance degradation, low speed test, area overhead, etc. The proposed BICS has a two operating mode- normal mode and test mode. Those methods minimize the performance degradation in normal mode. We also used a current-mode differential amplifier that has a input as a current, so we can realize higher speed current testing. Furthermore, only using 10 MOSFETS and 3 inverters, area overhead can be reduced by 6.9%. The circuit is verified by HSPICE simulation with 0.25 urn CMOS process parameter.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1994년도 추계학술대회논문집; 한국종합전시장, 18 Nov. 1994
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• pp.21-28
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• 1994

The forced vibration with the symmetric boundary condition in nonlinear structure is studied by utilizing the characteristic of the free vibration which have two modes with the similar natural frequency. Two linear modes exist to have no concern with the amplitude. It is found that the normal mode or elliptic orbit as the newly coupled modes is generated in accordance with changing the stability. It is also known that responses for forced vibration having the small external force and damping are near mode of free vibration and the stability for each response is determined according to the stability for each response is determined according to the stability in mode of free vibration. Finally the stability and bifurcation are analyzed in proportion to increment of external force and damping.

• 전기학회논문지
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• 제58권1호
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• pp.199-202
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• 2009

Scan design is currently the most widely used structured Design For Testability approach. In scan design, all storage elements are replaced with scan cells, which are then configured as one or more shift registers(also called scan chains) during the shift operation. As a result, all inputs to the combinational logic, including those driven by scan cells, can be controlled and all outputs from the combinational logic, including those driving scan cells, can be observed. The scan inserted design, called scan design, is operated in three modes: normal mode, shift mode, and capture mode. Circuit operations with associated clock cycles conducted in these three modes are referred to as normal operation, shift operation, and capture operation, respectively. In spite of these, scan design methodology has defects. They are power dissipation problem and test time during test application. We propose a new methodology about scan shift clock operation and present low power scan design and short test time.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 A
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• pp.363-365
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• 1999

800kV GIS(Gas Insulated Switchgear) was first developed by Hyosung Corporation in Korea at Dec. 1998 and is going to be installed first in the Dangjin Thermal Plant. We intoned to verify the structural safety of 800kV GIS under seismic load. The modal analysis of 800kV GIS has been carried out to obtain the natural frequency and mode shape. PATRAN was used for mode)ing exactly 800kV GIS Geometry. 800kV GIS FE(Finite Element) model was constructed of shell elements for the enclosures and beam elements for the conductors and the support insulators NASTRAN was used for analyzing the normal modes of 800kV GIS FE model.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 전력전자학술대회 논문집
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• pp.81-84
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• 2001

In the power system of a satellite, solar array and a battery have directly impact on the life time of the satellite, and their stable operation is decided by whether their states are in the steady state operation or not. In this study, solar array capacity and battery characteristics of proposed communication satellite are designed and simulation is conducted according to the operation mode. Each operation mode is classified as the normal and worst case modes, respectively. The normal mode is analyzed under daylight and the eclipse with the EHT burn, and the worst case modes which have solar cell circuit failure, and battery cell failure are analyzed too.