• Journal of Mechanical Science and Technology
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• 제18권7호
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• pp.1246-1257
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• 2004

The objective of this paper is to characterize dynamic pressure traces measured at self-excited combustion instabilities occurring in two combustion systems of different hardware. One system is a model lean premixed gas turbine combustor and the other a fullscale bipropellant liquid rocket thrust chamber. It is commonly observed in both systems that low frequency waves at around 300㎐ are first excited at the onset of combustion instabilities and after a short duration, the instability mode becomes coupled to the resonant acoustic modes of the combustion chamber, the first longitudinal mode for the lean premixed combustor and the first tangential mode for the rocket thrust chamber. Low frequency waves seem to get excited at first since flame shows the higher heat release response on the lower frequency perturbations with the smaller phase differences between heat release and pressure fluctuations. Nonlinear time series analysis of pressure traces reveals that even stable combustion might have chaotic behavior with the positive maximum Lyapunov exponent. Also, pressure fluctuations under combustion instabilities reach a limit cycle or quasi-periodic oscillations at the very similar run conditions, which manifest that a self-excited high frequency instability has strong nonlinear characteristics.

• 제어로봇시스템학회논문지
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• 제13권6호
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• pp.547-554
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• 2007

This thesis presents a kind of active noise control(ANC) algorithm for reducing noise due to engine inside a car. The proposed control algorithm is, by using WP(Wavelet Packet), a one improving the instability due to delay of noise transmission and the lack of response ability for the rapid change of noise, which are defects of the existing FXLMS(Filtered-X Least Mean Square) algorithm. The chief character of this system is a thing that faster operation than the FXLMS is implemented by inserting WP in the secondary path. In other words, WP implements parallel operation. Then, the weights of filter in the adaptive algorithm will be updated faster. In addition, because WP have so excellent a resolution, they can process very minute noise. The efficiency of this control algorithm will be demonstrated in the matlab simulation and in the actual experiments by using a Labview program and a car.

• Journal of Communications and Networks
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• 제17권2호
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• pp.118-125
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• 2015

In this paper, we propose a method to reduce mobile social network services (SNSs) traffic using a mobile integrated SNS gateway (MISG) to improve network communication performance between the mobile client and SNS servers. The gateway connects the client and SNS servers using the contents adapter and the web service adapter and helps to improve communication performance using its cache engine. An integrated SNS application, the user's client, communicates with the gateway server using integrated SNS protocol. In addition, the gateway can alert the client to new SNS contents because of the broker server implemented by the message queuing telemetry transport protocol. We design and develop the modules of the gateway server and the integrated SNS application. We then measure the performance of MISG in terms of content response time and describe the result of the experiment.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.155-158
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• 2005

Sub-frame is a key component to damp the vibration of engine-born and isolate the input force from a ground. To enhance the performance of the sub-frame of vehicle, its structure should be designed to be a high performing mechanical filter that exclude the low frequency vibration elements. In this paper, a contribution analysis based on the frequency response function(FRF) is introduced to detect a high sensitive position of the target sub-frame and its results are validated with a SDM(structural dynamic modification) analysis.

• 한국기계가공학회지
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• 제21권7호
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• pp.105-113
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• 2022

In this study, a variable displacement swash plate pump supplying high-pressure hydraulic oil to control the hydraulic system of a marine engine was developed. A structural analysis was performed on the main parts of the pump to ensure the structural safety in the design. Using a pump testing equipment, performance characteristics such as no-load flow rate, load flow rate, flow rate according to the swivel angle change, flow rate with lubrication orifice, and response time according to the swivel motion were tested. Consequently, the pump was confirmed to satisfy the required specifications.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2020년도 봄 학술논문 발표대회
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• pp.119-120
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• 2020

Recently, a building fire has occurred due to various influences. Accordingly, we are developing an public safety & security unmanned aerial vehicle for fire prevention and initial response to fire. The public safety & security unmanned aerial vehicle is used to grasp the traffic route to enter the fire engine in the event of a fire in a dense structure and to determine the scale of the fire and the area of danger of collapse around the fire site. In this study, an environmental test of the public safety & security unmanned aerial vehicle's heat resistance was performed in an environment simulating a fire scene.

• 한국항공우주학회지
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• 제43권7호
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• pp.619-625
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• 2015

스월 인젝터는 액체로켓 엔진에서의 연료 분사 장치로 널리 사용되고 있으며, 이에 따른 연구 또한 활발하게 진행되고 있다. 특히 연소 불안정 문제를 해결하는 것은 모든 종류의 액체로켓 엔진에서 필수적이다. 본 연구에서는 연소불안정을 해결하기 위한 기초 연구로 오픈형 스월 인젝터에 대한 수류실험을 수행하였다. 인젝터로 유입되는 작동유체에 압력 섭동을 발생시키고, 그에 따른 응답특성을 실험적으로 파악하였다. 또한, 인젝터 스월 챔버의 길이와 지름을 변화시킴으로써 인젝터 구조의 변화에 따른 응답 특성의 변화를 확인하였다.

• 한국멀티미디어학회논문지
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• 제20권3호
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• pp.520-532
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• 2017

Large-scale natural disasters such as typhoon and localized torrential downpour cause widespread human and property damages. Recently, management systems using GIS are being developed to manage such disasters from various angles. Integrated disaster management encompasses diverse areas such as prediction through the computation of disaster information and field support for response. The development of disaster information systems must also consider the installation of various computation modules. Furthermore, GIS is generally included for realistic description of the field situation and for spatial operations. This study aims to develop the core module of a visualization platform for the 3D GIS services of integrated disaster information using Unity engine This system will enable integrated disaster management from various angles, encompassing disaster prevention experts, field support personnel, and citizens.

• Journal of Advanced Marine Engineering and Technology
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• 제39권3호
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• pp.211-216
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• 2015

차체중량이 90 ton인 초대형 유압굴삭기에서는 유압시스템의 효율향상을 통한 연비개선을 위해서 유압펌프 구동용 기어박스(hydraulic pump driving gear box)를 사용하여 다수(3~6개)의 펌프를 병렬로 장착하여 사용한다. 펌프 구동 기어 박스는 굴삭기의 대형엔진과 연결되는 입력 축 1개로 기계적 동력인 회전수와 토크를 공급받아 고압펌프와 저압펌프에서로 다른 기계적 출력을 공급하게 된다. 따라서 펌프 구동 기어박스는 굴삭기의 대동맥과 같으며, 엔진이 가동되는 시간동안 지속적으로 펌프를 구동함으로서 장 수명이 요구된다. 본 연구에서는 큰 시험동력(600kw)이 요구되는 수명평가에서 에너지절감을 위한 전기 회생식 시험 장비를 구축하여 높은 에너지 절감과 수명시험을 수행하면서 기어박스의 마모 특성을 분석하는 방법으로 윤활유 오염 입자 분석과 기어파손 유무를 검증하는 방법으로 진동분석 방법을 사용하였다.

• 한국추진공학회지
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• 제18권2호
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• pp.35-41
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• 2014

베어링 하우징의 구조 유연성을 고려하여 7톤급 액체 로켓 엔진용 터보펌프의 회전체동역학 해석이 수행되었다. 볼 베어링과 펌프 비접촉 실의 강성 및 감쇠 특성이 회전체동역학 모델에 반영되었으며, 베어링 하우징의 동특성이 집중 질량 및 강성으로 모델링 되어 해석에 반영되었다. 동기 회전체 질량 불평형 응답 해석과 회전 속도에 따른 복소 고유치 해석으로부터 회전체의 임계속도와 불안정 운전 시작 속도를 예측하였다. 회전체동역학적 특성에 베어링 하우징이 미치는 영향이 베어링 부하 조건 및 무부하 조건에서 각각 검토되었다. 수치 해석 결과 베어링 하우징의 구조 유연성은 회전체의 임계속도와 불안정 운전 속도를 의미있게 감소시킬 수 있는 것으로 확인되었다.