• 한국유체기계학회 논문집
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• 제4권4호
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• pp.16-21
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• 2001

The field tests on the waterhammer were carried out for PalDang intake pumping station of the metropolitan water supply 5th stage project. The pumping station was equipped with the pump control valve as the main surge suppression device and the surge relief valve as auxiliary. However, the pump control valve had not been early controlled in the planned closing mode, and the slamming occurred to the valve which abruptly closed during the large reverse flow. Because the pressure wave caused by the pump failure was superposed on the slam surge, the upsurge increased so extremely that the shaft of the valve was damaged. It was desirable that the surge relief valve was installed in the pumping station or near the pump exit for the delay of response. After reforming the oil dashpot of the pump control valve, the sliming disappeared and the measured pressure was in fairly good agreement with the results of simulation. In case of three pumps for ${\phi}2,600$ pipeline being simultaneously tripped, the pressure head in the pumping station increased to 95.6 m, and the upsurge caused by the emergency stop of four pumps for ${\phi}2,800$ pipeline was 89.6m. We concluded that the pumping station acquired the safety and reliability for the pressure surge.

• 한국생산제조학회지
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• 제19권2호
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• pp.301-305
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• 2010

Cutting procedures where qualities are determined by various demand factors largely influences shipbuilding productivity. Particularly, defects in cutting shapes and cutting surface results in delay for post shipbuilding stages such as in welding and assemblage lines which could become factors for reduced economic viability of the project. Existing cutting procedures utilize fossil fuels such as propane or ethylene as the main fuel component and these methods applied particularly to ship plate cutting gives relatively slow cutting speed and generates large quantities of harmful and sometimes poisonous polluting fumes of which warrants an urgent need to look for alternative cutting methods. Recent introduction of hydrox gas generated by electrically dissociating water into hydrogen and oxygen components to be utilize as an alternative cutting fuel has resulted not just in visible improvement on cutting quality and speed over the existing methods but it has also been welcomed as an environmentally friendly clean fuel source. This paper has been prepared to serve as the basis for accommodating this environmentally friendly hydrox gas cutting method into actual working environment by observing and recording hydrox gas cutting thermal characteristics.

• 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.

• 인터넷정보학회논문지
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• 제3권3호
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• pp.39-53
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• 2002

도메인 모델은 객체 모델 개발과 소프트웨어 설계에 관한 결정에 큰 영향을 끼치고 있어, 오늘날 많은 객체 지향적 시스템과 컴포넌트 기반의 소프트웨어 개발 시 도메인 모델을 만들고 있다. 그러나 UML과 객체 지향적 방법론에서는 재사용을 위한 개발과 재사용을 수반한 개발의 지원이 부족하여 매번 새로이 모델을 개발하고 있으며 프로젝트 개발 기간 지연과 불충분한 모델 생성을 초래하고있다. 이러한 문제는 UML 표기의 확장과 재사용 처리방법을 통해 해결될 수 있다. 본 연구에서는 도메인 모델의 재사용을 위하여 UML 기반의 도메인 모델 템플리트를 설계하고 분석정보의 재사용을 위한 도메인 모델 개발 방법을 제안하였다. 아울러 제안된 표현을 인터넷 응용에 적용하여 도메인 모델과 도메인 템플리트를 생성할 수 있었다.

• 조명전기설비학회논문지
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• 제20권10호
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• pp.135-140
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• 2006

본 논문에서는 인터넷이나 멀티미디어 서비스 등 고속 패킷 전송에 있어서 전송 효율을 증대하기 위한 H-ARQ(Hybrid-Automatic Repeat reQuest) 기법에 대하여 고찰하였다. H-ARQ 기법의 성능 분석을 위하여 3GPP(3rd Generation Partnership Project) 시스템에서 WWW 트래픽 모델에 근거하여 각 타입별 성능에 대하여 고찰하였다. 또한 GPRS(General Packet Radio Service)에 대하여 링크 적응 기법과 H-ARQ Type II 방식에 대한 링크 성능을 전송 효율 및 패킷 지연 차원에서 비교 분석하였다. 분석 결과 링크 효율 측면에서 H-ARQ Type II 방식이 더 높은 효율을 나타냈으나 패킷 지연 시간은 링크 적응 기법이 조금 더 나은 것을 확인하였다.

• ETRI Journal
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• 제38권5호
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• pp.847-857
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• 2016

Broadcasting services such as multi/single channel HDTV and 3DTV/2DTV use a multi-channel encoder that changes the bitrate and composition of the video service depending on the time. However, this type of multi-channel encoder could cause a longer latency owing to the variable bitrate and relatively bigger size of the buffers, which results in the same delay as in 3DTV even for a conventional DTV service. On the other hand, systems built based on separate encoders, each of which is optimized for the target service, might not have such latency problems. Nevertheless, there might be a distortion problem in the image and sound at the time of a switchover between two encoders with different output bitrates and group of picture structures. This paper proposes a system that can realize a seamless video service conversion using two different video encoders optimized for each video service. An overall functional description of the video service change control server, which is a main control block for the proposed system, is also provided. The experiment results confirm the seamless switchover and reduced broadcasting latency of DTV services compared with a broadcasting system composed of a multi-channel encoder system.

• 한국조경학회지
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• 제31권3호
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• pp.114-124
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• 2003

The management methods of rooftop greening must be get ready without delay, Because rooftop greening has been generalized owing to the supporting project of The Seoul Metropolitan Government. Because most of the rooftop greening system is a recently-constructed low-management type, management methods should be made to suit it. This study is intended to set up a program for low-management rooftop greening based on "Choroktteul", the low management type of rooftop peening on the roof of one of the buildings in Seoul City Hall. Through monitoring, we found that most of the planted plants grew well but a few species needed physical management. We also found that invasive species(62 sp.) were 1.5 times as many as the planted plants. Most of the invasive plants were exotic species that need to be managed. The physical management methods were "pulling up" and "cutting". These methods should be carried out according to the growth stage. It was judged that a biological-ecological management program should be prepared through the long-period of monitoring and experiment. System methods such as guidelines of management program through monitoring was also required due to the emphasis on public ownership among the managers of the invasive species.

• 대한교통학회지
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• 제26권4호
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• pp.161-172
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• 2008

국토해양부는 신호교차로 서비스수준 분석에 도로용량편람이 제시하는 방법의 적용을 장려하고 있으며 실시간신호제어교차로는 지능형교통체계 구축사업으로 그 숫자가 현장에서 꾸준히 증가하고 있다. 도로용량편람은 정주기식 신호교차로 서비스수준 분석방법에 국한하여 제시하고 있어 현장 실무자들은 실시간신호제어교차로 서비스수준 분석에 어려움을 경험하고 있다. 본 연구는 도로용량편람 수준에서 실시간신호제어교차로 서비스수준 분석의 기초가 되는 방법론을 제안하며 향후 추가로 수행되어야 하는 개발방향을 검토한다. 한 개의 신호교차로를 표본으로 세부 요소모형들을 간이 개발하여 검증한 결과 제안된 방법은 실제 현장 자료와 유사한 수준의 서비스 수준을 추정할 수 있음을 확인하였다.

• 한국산학기술학회논문지
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• 제9권3호
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• pp.757-764
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• 2008

효율적인 공정이행관리를 통해서 건설공사 일정의 불필요한 공기지연을 사전에 예방하고, 나아가 품질확보를 위하여 각 공정의 내용을 정확하게 숙지하고 관리하는 일이 중요하다. 더욱 중요한 것은 공사계획에 따른 공정이 원활하게 진행될 수 있도록 각각의 공정에 필요한 선행작업들을 체계화하여 관리하는 것이다. 이를 위하여 본 연구에서는 아파트공사를 대상으로 이정표 중심, 작업공종 중심, 활동 중심, 작업 담당자 중심으로 구분하여 선행작업관리 시안을 제시하였다.

• 전자통신동향분석
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• 제34권6호
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• pp.51-60
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• 2019

As a way to further expand and enable the 5G ecosystem, the $3^{rd}$ Generation Partnership Project (3GPP) is considering the development of a 5G new radio (NR)-based non-terrestrial network (NTN). These NTNs are expected to provide ubiquitous 5G services to user's equipment (especially, in Internet of Things/machine-type communications (IoT/MTC) public safety, and critical communications) by extending service coverage to areas not covered by 5G terrestrial networks. To this end, this NTN is developing scenarios to provide 5G services using spaceborne vehicles, such as geosynchronous and low-Earth orbit satellites, and airborne vehicles, such as unmanned aircraft systems, including high-altitude pseudo-satellites. In addition, various technologies are being studied to satisfy new requirements not considered in 5G NR, such as long propagation delay time, large cell coverage, large Doppler effect, and base station movement. In this paper, we present the scenarios, requirements, technical issues and solutions, and standardization planning for NR-based NTN in 3GPP.