• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.853-858
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• 2001

The knowledge of flame structure is essential for control of combustion instability phenomena. Some results of an experimental study on mechanism of naturally occurring combustion oscillations with a single dominant frequency are presented. Tests were conducted in a laboratory-scale dump combustor at atmospheric pressure. Sound level meter was used to track the pressure wave inside the combustor. The observed instability was a longitudinal mode with a frequency of $\sim341.8Hz$. Instability map was obtained at the condition of inlet temperature of $360^{\circ}C$, mean velocities of $8.5\sim10.8m/s$ and well premixed mixture. It showed that combustion instability was susceptible to occur in the lean conditions. In this study, unstable flame was observed from stoichiometric to 0.7 in overall equivalence ratio. At selected unstable conditions, phase-resolved OH chemiluminescence images were captured to investigate flame structure with various mean velocities. As mean velocity is increased, the flame grows and global heat release was changed. Due to these effects, combustion instability can be maintained at more lean air-fuel ratio. Also, these results give an insight to the controlling mechanism for an increasing heat release at maximum pressure.

• 대한기계학회논문집A
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• 제28권8호
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• pp.1116-1124
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• 2004

In these days, a vehicle simulator has been developed with a VR(Virtual Reality) system. A VR system must provide a vehicle simulator with natural interaction, sufficient immersion and realistic images. In addition, a VR system must present a driver with the realistic driving situation. To achieve these, it is important to obtain a fast and uniform rendering performance regardless of the complexity of virtual worlds. In this paper, the factors to improve the reality for the VR based vehicle simulator have been investigated. For the purpose, the modeling and the rendering methods which offer an improved performance for complex VR applications as the 3D road model have been implemented and verified. Then, we experiment on the influence of graphic and sound factors to the driver, and analyze each result for improving the reality such as the driver's viewport, the form of texture, the lateral distance of the side object, and the sound effect. These factors are evaluated on the driving system which is constructed for qualitative analysis. The research results could be used for improving the reality of the VR based vehicle simulator.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.1067-1071
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• 2004

In this paper, the characteristic of the regenerative pump is reviewed by the measurement and the analysis. The dominant noise sources are harmonic components of the rotating impeller frequency. The acoustic characteristics and the noise source position at the dump are identified. In order to reduce the high-level peak noise, the interior flow of the pump chamber is analyzed by CFD (Computational Fluid Dynamics). Acoustic pressure is calculated with Ffowscs Williams and Hawkings equation. As the result of the analysis new design of the pump chamber is recommended. The recommended pump is compared with original pump by evaluating the RMS value of a interior static pressure and the sound pressure level. The new pump chamber recommended by analysis results is proved by a process of the measurement. The overall SPL of a recommended pump is reduced about 3 dBA.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.1087-1092
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• 2006

Recently, traffic noise level is rapidly increasing, and it is crowed caused by recently overcrowded and overgrown cities, and increasing traffic volume is emerging as a major factor of disrupting the living and working environment. In this situation, citizens are increasingly complaining about the traffic noise. The noise level of in major cities in Korea is serious and affects on citizens physically and psychologically. Many people live in residential areas around crowed roads in major cities, such as Seoul. Accordingly, the purpose of this study is to predict outside noise distribution of building through survey and simulation to make better sound insulation performance research. The result of this study shows that the traffic noise is influenced from ground 50m and analyzed that form of building and arrangement type must be considered to the level of noise decrease.

• 한국산림과학회지
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• 제87권2호
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• pp.300-307
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• 1998

산림관리자에게 있어서 경영계획을 수립하거나 작업계획을 수립하기 위한 의사결정을 올바르게 한다는 것이 쉬운 일이 아니다. 이것은 산림자원관리에서 요구되는 공간자료나 시간의 흐름에 따라 변해가는 산림자료가 방대하며, 의사결정을 수행하는 과정이 복잡하기 때문이다. 그러나 지리정보체계는 이와 같은 산림자원의 자료 혹은 경영관리 조건을 폭넓게 이해하고, 산림자원을 해석하게 해줌으로써 산림관리자의 임무수행을 보다 수월하게 해줄 수 있다. 본 연구에서는 산림관리 현장에 적용할 수 있는 지리정보모델을 개발하였다. 이 모델에서는 MapInfo 4.0을 기본 엔진으로 장착하였고, 산림관리자들이 MapInfo를 쉽게 이용할 수 있도록 interface 모듈이 부착되어 있다. 이 모듈은 산림관리자가 산림자원조사 자료들을 관리하거나 임분 공간상의 분포조건을 해석할 수 있는 MapInfo 기능들을 쉽게 사용할 수 있도록 지원한다. 또한 이 모델의 적용성을 검토할 목적으로 춘천관리소 산하의 국우림 단지를 선정하고, 요구되는 자료를 수집하여 구축하였고, 임분속성자료 분석 및 주제도 작성을 통해 이 모델의 기능성을 검토하였다. 이 논문에는 개발된 모델의 구조와 분석기능 그리고 적용성 검토결과가 제시되어 있다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 춘계학술대회논문집
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• pp.535-540
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• 2005

In environmental impact assessment, noise impact assessment usually consists of three stages surveying the existing noise levels by measurements, predicting noise levels induced by construction works and predicting noise levels after the completion of project. When predicting noise level in urban area, this method does not consider acoustic phenomena like multi reflection, diffraction and absorption due to complex topographic configuration of building and terrains. For the purpose, a noise mapping tool is utilized to produce a series of noise maps, which are those for the present, for the works of construction and for the future. For accurate noise mapping, acoustical and topographic information is essential. Standard sound power levels and directivities of various construction equipments are required and scheduling of construction processes and locations of the equipments should be provided. In the case of exceeding legal limit, mitigation measures are applied to satisfy the legal limits and subsequent noise map is obtained and checked.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2006년도 춘계학술대회 논문집
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• pp.373-376
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• 2006

The ring rolling design for a large-scale Ti-6Al-4V alloy ring was performed with a calculation method and FEM simulation. The ring rolling design includes geometry design and optimization of process variables. The calculation method was to determine geometry design such as initial billet and blank size, and final rolled ring shape. A commercial FEM code, SHAPE was used to simulate the effect of process variables in ring rolling on the distribution of the internal state variables such as strain, strain rate and temperature. In order to predict the forming defects during ring rolling, the process-map approach based on Ziegler's instability criterion was used with FEM simulation. Finally, an optimum process design to obtain sound Ti-6Al-4V rings without forming defects was suggested through combined approach of Ziegler's instability map and FEM simulation results.

• 한국콘텐츠학회논문지
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• 제12권1호
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• pp.38-47
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• 2012

본 논문은 시각장애인들의 활동 범위를 확대하기 위해서 주변 시설물 검색서비스와 길안내 서비스를 제공하는 시각장애인을 위한 네비게이션 시스템을 설계하고 구현한다. 제안하는 네비게이션 시스템은 시각 장애인을 위한 경로 생성 모듈 및 저장 모듈로 구성된다. 특히, 제안하는 네비게이션 시스템은 시각 장애인을 위한 인터페이스로 TTS(Text-to-Speech) 프로그램을 이용하여 음성을 통한 안내서비스를 위한 음성 모듈과 촉각을 이용하여 점자를 출력하는 점자모듈을 통하여 구현한다. 또한 최신 지도정보를 서비스하기 위해서 구글 맵 API들을 사용한다.

• 한국소음진동공학회논문집
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• 제15권11호
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• pp.1311-1317
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• 2005

In environmental Impact assessment, noise impact assessment usually consists of three stages-surveying the existing noise levels by measurements, predicting noise levels induced by construction works and predicting noise levels after the completion of a project. The distance-attenuation relation of a point source, which has been used to predict the noise level due to its simplicity does not consider complex acoustic phenomena like multi-reflection, -diffraction and -absorption due to complex topographic configuration of buildings and terrains. For the consideration of such physical complexities. a noise mapping tool is adopted to produce a series of noise maps, which are those for the present, tot the works of construction and for the future. For accurate noise mapping, acoustical and topographic Information is used. Standard sound power levels and directivities of various construction equipments are need and scheduling of construction processes and locations of the equipments should be provided. In the case of exceeding legal limit, mitigation measures are applied to satisfy the legal limits and subsequent noise map is obtained and checked.

• Imaging Science in Dentistry
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• 제30권1호
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• pp.55-62
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• 2000

Purpose: This study was performed to develop the electronic textbook (CD-rom title) about preclinical practice of oral and maxillofacial radiology, using multimedia technology with interactive environment. Materials and Methods: After comparing the three authoring methods of multimedia, i.e. programming language, multimedia authoring tool and web authoring tool, we determined the web authoring tool as an authoring method of our electronic textbook. Intel Pentium II 350 MHz IBM-compatible personal computer with 128 Megabyte RAM, Umax Powerlook flatbed scanner with transparency unit, Olympus Camedia l400L digital camera, ESS 1686 sound card, Sony 8 mm Handycam, PC Vision 97 pro capture board, Namo web editor 3.0, Photoshop 3.0, ThumbNailer, RealPlayer 7 basic and RealProducer G2 were used for creating the text document, diagram, figure, X-ray image, video and sound files. We made use of javascripts for tree menu structure, moving text bar, link button and spread list menu and image map etc. After creating all files and hyperlinking them, we burned out the CD-rom title with all of the above multimedia data, Netscape communicator and plug in program as a prototype. Results and Conclusions : We developed the dental radiology electronic textbook which has 9 chapters and consists of 155 text documents, 26 figures, 150 X-ray image files, 20 video files, 20 sound files and 50 questions with answers. We expect that this CD-rom title can be used at the intranet and internet environments and continuous updates will be performed easily.