• 한국통신학회논문지
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• 제31권1B호
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• pp.26-38
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• 2006

효과적인 원격 헙업환경을 구축하기 위해서는 참가자들이 의도하는 바를 사실적으로 전달하여야 하며, 특히 손동작, 표정, 분위기와 같은 시각적인 감정전달 요소들은 고품질 영상 전달을 통해 상호간에 공유되어야 한다. 본 논문에서는 다자간 공동작업 환경으로 널리 사용되고 있는 액세스그리드(Access Grid, AG)에 기반을 둔 디지털 영상과 고선명 디지털 영상 지원하는 고화질 영상 서비스를 제안하여 협업 환경의 실감성 향상에 기여하고자 한다. 제안하는 영상 서비스는 다양한 영상 코덱과 영상 프로그램을 AG 환경에서 이용할 수 있도록 설계되었으며, AG 노드들에 다양한 영상 서비스를 송수신할 수 있는 세션 묘사 및 공지 프로토콜을 이용한다. 또한 급격한 네트워크 상황 변화에 따른 영상 품질 저하를 최소화하기 위하여 네트워크 적응형 전송 기법을 이용한 디지털 비디오 전송 기능을 제공한다. 이는 종단간 멀티캐스트 네트워크 성능을 지속적으로 감시하고, 네트워크 성능에 따른 송신측 프레임 전송률을 조절한다. 테스트베드에서의 구현 및 실험 결과는 제안하는 서비스가 AG 영상 서비스의 품질을 개선하고 네트워크 변화에 의한 품질저하 현상을 감소시킬 수 있음을 보여준다.

• 한국물환경학회지
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• 제28권1호
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• pp.26-37
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• 2012

Multi-dimensional hydrodynamic and water quality models are widely used to simulate the physical and biogeochemical processes in the surface water systems such as reservoirs and estuaries. Most of the models have adopted the Eulerian grid modeling framework, mainly because it can reasonably simulate physical dynamics and chemical species concentrations throughout the entire model domain. Determining the optimum grid cell size is important when using the Eulerian grid-based three-dimensional water quality models because the characteristics of species are assumed uniform in each of the grid cells and chemical species are represented by concentration (mass per volume). The objective of this study was to examine the effect of grid-size of a three dimensional hydrodynamic and water quality model (EFDC) on hydrodynamics and mass transport in the Saemangeum Reservoir. Three grid resolutions, respectively representing coarse (CG), medium (MG), and fine (FG) grid cell sizes, were used for a sensitivity analysis. The simulation results of numerical tracer showed that the grid resolution affects on the flow path, mass transport, and mixing zone of upstream inflow, and results in a bias of temporal and spatial distribution of the tracer. With the CG, in particular, the model overestimates diffusion in the mixing zone, and fails to identify the gradient of concentrations between the inflow and the ambient water.

• 한국ITS학회 논문지
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• 제11권3호
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• pp.48-54
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• 2012

텔레메틱스 기반의 VoIP 음성통화는 지연, 지터 그리고 패킷손실과 같은 네트워크 장애요소로 인해 품질저하가 발생된다. 본 논문에서는 이런 장애요소로 인한 통화품질 문제를 해결하기 위하여 수신단 기반의 통화품질 향상 알고리즘을 제안한다. 제안된 방식은 손실은닉, 역동적인 지터추정을 이용한 적응적인 플레이아웃 버퍼 스케줄링, 그리고 전이영역에 존재하는 두 신호간의 스무딩 방법으로 구성된 플레이아웃 콘트롤 및 신호합성부를 통해 고품질의 음성통화를 가능하게 한다. 성능 측정 결과, 제안된 알고리즘은 기존 알고리즘에 비해 높은 PESQ와 낮은 버퍼링 지연을 보여주었다.

• 한국대기환경학회:학술대회논문집
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• 한국대기환경학회 2005년도 추계학술대회 논문집
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• pp.129-130
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• 2005

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2009년도 IWAIT
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• pp.184-188
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• 2009

To interactively share High Definition (HD)-quality visualization over emerging ultra-high-speed network infrastructure, several lossless and low-delay real-time media (i.e., uncompressed HD video and audio) transport systems are being designed and prototyped. However, most of them still rely on expensive hardware components. As an effort to reduce the building cost of system, in this paper, we propose the integration of both transmitter and receiver machines into a single bi-directional transport system. After detailed bottleneck analysis and subsequent refinements of embedded software components, the proposed integration can provide Real-time Transport Protocol (RTP)-based bi-directional transport of uncompressed HD video and audio from a single machine. We also explain how to interface the Gbps-bandwidth display output of uncompressed HD media system to the networked tiled display of 10240 $\times$ 3200 super-high-resolution. Finally, to verify the feasibility of proposed integration, several prototype systems are built and evaluated by operating them in several different experiment scenarios.

• 보건의료산업학회지
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• 제11권4호
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• pp.189-202
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• 2017

Objectives : This study aims to present a new classification system using evaluation standards to ensure the safety of transport ventilators used in Korea. Due to the rapid advancement of technology, various types of ventilators have been developed and as the range of application increases, so does demand. With quick access to information and a growing economy, the technology used in Korean hospitals is equivalent to that of other countries; however, regulatory and safety consciousness are still lagging in Korea. Methods : Based on researching overseas cases, reference data and standards for improving the current system in Korea are proposed. Results : According to the review of transport ventilator use in Korea, it was found that concerns about safety is due to the absence of a standardized classification system for evaluating the safety and effectiveness of transport ventilators. Conclusions : In order to improve the safety of patients and the quality of medical care, it is essential to establish guidelines and assessment standards guaranteeing the safety of transport ventilators in Korea. Clear definitions and classifications for devices must precede the application of such standards. In addition, effective evaluation standards should be developed in order to resolve problems and improve upon the current system through continuous validation.

• 한국환경보건학회:학술대회논문집
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• 한국환경보건학회 2001년도 Proceedings of the 3rd Annual Meeting of Yellow Sea Environment
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• pp.49-63
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• 2001

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 E
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• pp.1752-1754
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• 1998

Recently the research about electron transport characteristic and energy distribute function in mixture gases within Helium, has been used and developed widely as industrial quality improvement of extinguish characteristic, electrical dielectric strength ability of application of each species high voltage apparatus, gas plasma etching progress of work to use manufacture of semiconductor, thin film molding by CVD, insulation film to use ultra LSI, etc. This paper analyze electron transport characteristic in the range E/N $1{\sim}60$[Td], pressure $0.1{\sim}6.0$[Torr] by MCS. It is necessary to seek electron drift velocity, diffusion coefficient, lonization coefficients, characteristic energy, mean energy and electron energy distribution function as electron transport characteristic.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2005년도 학술발표회 논문집
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• pp.1398-1402
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• 2005

Riverbank filtration is a natural process using alluvial aquifers to remove contaminants and pathogens in river water for the production of drinking water. In riverbank filtration, the understanding of contaminant transport is an important task for the production of high quality drinking water. This study investigates the transport behavior of hydrophobic organic contaminants when colloids (dissolved organic matter and bacteria) are present in the aquifer. A mathematical model for the transport of contaminants is developed and solved numerically for various situations. Results show that in the riverbank filtration the presence of DOM and bacteria enhances the mobility of contaminant significantly. Sensitivity analysis indicates that the distribution of the total aqueous Phase contaminant is significantly affected by distribution coefficients which account for affinity of solid or colloidal Phase to contaminant.

• 한국환경과학회:학술대회논문집
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• 한국환경과학회 2003년도 International Symposium on Clean Environment
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• pp.65-68
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• 2003

A quantitative study of the amount of air transported between the boundary layer and the free atmosphere is important for understanding air quality and upper tropospheric ozone, which is a greenhouse gas. Frontal systems are known to be an effective mechanism for the vertical transport of pollutants. Numerical experiments have been performed with a simple two-dimensional front model to simulate vertical transport of trace gases within developing cold fronts. Three different trace gases experiments have been done numerically according to the different initial fields of trace gases such as aerosol, ozone and $H_2O_2$. Trace gas field tilts to the east while the front tilts to the west. Aerosol simulation shows that pollutants can be transported out of the boundary to altitudes of about 10 km. The stratospheric ozone is brought downwards in a tropopause fold behind of the frontal surface. The meridional gradient in trace gas ($H_2O_2$) can cause a complicate structure in the trace field by the meridional advection.