• The Journal of the Acoustical Society of Korea
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• v.19 no.1
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• pp.16-24
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• 2000

In this paper the performance of a closed-loop power control scheme using variable step size decision method for DS/CDMA based-low earth orbit(LEO) mobile satellite systems in which the long round trip delay is a dominant performance degradation factor is evaluated. Because there are fundamental differences in the characteristics between the LEO mobile satellite channel and terrestrial mobile channel, such as long round trip delay and different elevation angle, these factors are considered in channel modeling based on the European Space Agency(ESA) measurement data. Since the round trip delay (from the mobile terminal to the gateway station via satellite) is typically 10∼20ms in low altitude satellite channels, closed-loop power control is much less effective than it is on a terrestrial channel. Thus, the adaptive power control scheme using a variable step size control is essential for overcoming the long round trip delay and fading due to the elevation angle. It is shown that the standard deviation of signal to interference ratio(SIR) adopting a variable step size closed-loop power control scheme is much less than that of a fixed step size closed-loop power control. Furthermore, we have driven the conclusion that the measurement interval of power control commands is optimal choice when it is twice the round trip delay.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.3
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• pp.997-1005
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• 2010

Recently, there has been a growing interest in the use of WLAN technology due to its easy deployment, flexibility and so on. Examples of WLAN applications range from standard internet services such as Web access to real-time services with strict latency/throughput requirements such as multimedia video and voice over IP on wireless network environments. Fair and efficient distribution of the traffic loads among APs(Access Points) has become an important issue for improved utilization of WLAN. This paper focuses on an AP selection scheme for achieving better load balance, and hence increasing network resource utilization for each user on wireless network environments. This scheme makes use of active scan patterns and the network delay as main parameters of load measurement and AP selection. This scheme attempts to estimate the AP traffic loads by observing the up/down delay and utilize the results to maximize the link resource efficiency through load balancing. We compared the proposed scheme with the original SNR(Signal to Noise Ratio)-based scheme using the NS-2(Network Simulation.2). We found that the proposed scheme improves the throughput by 12.5% and lower the network up/down link delay by 36.84% and 60.42%, respectively. All in all, the new scheme can significantly increase overall network throughput and reduce up/down delay while providing excellent quality for voice and video services.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.3D
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• pp.363-369
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• 2008

Change is inevitable and is a reality of construction projects. Change adjustment includes the cost associated with materials, labor, etc. However, the actions of a contractor can cause a loss of productivity and furthermore can result in disruption of the whole project because of a cumulative or ripple effect. Because of its complicated nature, it becomes a complex issue to determine the cumulative impact (ripple effect) caused by single or multiple change orders. Furthermore, owners and contractors do not always agree on the adjusted contract price for the cumulative impact of the changes. What is needed is a reliable method to identify and quantify the loss of productivity caused by cumulative impact of change orders. This study survey the change orders data in domestic area for public construction and analyze to quantify change order impact. This study developed concepts of "%CO", "%Delta", "%T" to capture change order effect on project and search the relationships between them. Finally, this study find strong relationship between change order and loss.

• Journal of Cadastre & Land InformatiX
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• v.53 no.2
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• pp.67-77
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• 2023

As cities become overcrowded and concentrated, the demand for public services continues to increase due to the improvement of the living standards of urban residents. Among them, fire service can be seen as one of the important public services by reducing damage caused by accidents in emergency situations and affecting the improvement of access to medical services for urban residents. Rapid movement of patients and medical institutions within golden time and proper first aid are essential elements in emergency situations, and Seoul is a super-large city with a large population of about 10 million people and has a large number of emergency medical patients. Therefore, this study used spatial regression analysis to examine the factors affecting the delay factors of emergency dispatch in Seoul to secure golden time, and derived management priorities, and suggested implications for the management of emergency vehicle dispatch delay factors. As a result of the main analysis, land-use characteristics were the most influential factor in emergency vehicle dispatch time, and land-use mixing, commercial area density, average patient age, and average road length were found to affect emergency vehicle dispatch time in order. This study can be used as important basic data for an accurate understanding of the delay factors for emergency dispatch and preparing countermeasures according to priorities.

• Proceedings of the Korea Society of Environmental Toocicology Conference
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• 2003.05a
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• pp.164-164
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• 2003

전국 주요 산단 지역에서 현재 유통되고 있는 화학물질의 스크리닝 수준에서의 생태 위해성 평가를 수행하고, 체계적인 위해도 분석 시스템을 구축하기 위한 수생 및 육상 생태계가 통합된 생태 위해성 예측 모형을 개발하였다. 전국 118개 공단 중 시화반월, 전주, 대전, 대구, 청주, 울산, 구미, 여천공단 등 8개 주요 산단 지역을 program 개발을 위한 비교 대상 지역으로 선정하였고 이들 공단에서 사용되고 있는 약 1700여종의 화학물질의 물리 화학적 특성 자료와 생태 독성값의 문헌치, 추정치를 포함한 database를 구축하였다. 구축된 database를 활용하여 산단별, 화학물질별 생태 위해도를 상대적으로 비교한 결과 어류 만성의 위해도는 청주 공단>울산미포>여천 공단의 순이었고, 물벼룩 만성의 위해도는 시화반월>여천>울산미포 공단의 순이었다. 또한 산단별로 위해도 우선순위 물질을 선정하였으며 styrene, xylene 등의 위해도가 높게 나타났다. 이때 화학 물질의 수계 배출량은 TRI 자료와 사용량과의 상관관계로부터 구한 배출 계수를 적용하여 산정하였으며, 선정된 위해도 우선 순위 물질을 대상으로 실제 공단의 하천 시료를 채취, 분석하여 이 모형에 의해 예측된 생태 위해도의 타당성을 검증하고 보완하는 연구를 지속적으로 수행하여 예측 program의 신뢰도를 높이고자 한다.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2004.11a
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• pp.376-379
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• 2004

Building construction Is essential part that we get the enjoyment and promote the quality in human life. But construction process itself has an bad effect on environment: air Pollution, water Pollution, soil Pollution ,etc. These day, Air-environment management becomes very important part in Construction because Construction duration delay which is caused by civil petitions related air-environment occurs frequently. For developing the management-guideline of environment management, This study suggests an executive management-guideline based on surveying air-environmental related laws, regulations and literatures, making out important factors. With the management guideline, The Purpose of this study is to make an air-environmental management system through that Process.

• 정보화사회
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• s.185
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• pp.14-14
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• 2007

세계는 1990년대 중반 '정보화 혁명'에 이어 2000년대 중반 이후에는 '디지털 융합 혁명'이라는 새로운 물결에 직면해 있다. 디지털기술의 발전과 전송망의 광대역화에 따라 전통적으로 서로 다른 영역이었던 통신과 방송이 네트워크, 서비스, 단말기, 콘텐츠 차원에서 경계가 허물어지는 통신.방송 융합현상이 가속화되고 있다. 이에 따라 IPTV, DMB, 웹캐스팅, 데이터방송 등 기존의 통신과 방송의 속성을 모두 가진 서비스가 우리들의 실생활에 속속 등장하고 있다. 이러한 융합현상은 이용자에게는 새로운 융합서비스 이용을 통한 편익 증진뿐만 아니라 통신.방송 전반의 산업구조까지 근본적으로 변화시키고 국가 경쟁력을 높일 수 있는 좋은 기회가 될 것으로 보고 있다. 이미 세계 주요국은 IPTV서비스를 도입하고 있으나, 세계 최고의 정보통신 인프라를 보유하고 있는 우리나라는 안타깝게도 법제도 정비의 지연으로 아직 도입을 못하고 있다. 우리나라는 IPTV 도입뿐만 아니라, 디지털방송 활성화, 디지털콘텐츠 육성 등 풀어나가야 할 현안들이 산적해 있다. 또한 방송과 통신 전반에 걸쳐 정책과 규제체계를 융합환경에 맞추어 새롭게 설계해야 하는 과제도 있다. 이러한 과제를 순조롭게 해결하기 위해서는 우선적으로 정책과 규제기구를 융합환경에 맞게 개편하는 것이 시급하다. 이번호에서는 방송통신 융합의 주요 이슈 가운데 가장 시급하게 해결해야할 방송.통신 기구개편과 대표적인 방송통신융합서비스인 IPTV서비스 도입정책방안 그리고 방송통신융합법에 대해 전문가들의 특별기고를 통해 살펴보는 자리를 마련한다.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2008.04a
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• pp.298-302
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• 2008

In this study, we have carried out the test to examine the ignition characteristics, such as a relation of moisture content and combustibility, and ignition temperature using KRS-RG-9000 tester, living leaves and dead leaves of significant 7 species of Young Dong Provinces of Korea after and before the rainfall. After 144 hours at normal temperature, the percentage of water content of the needle-shaped leaves was less than 10%. So it is suppose to be ignite easily. On the other hand, the self-temperature to ignite of broadleaf is higher. So the retard time at lower temperature is more long than needle-shaped leaf. Consequently, the fire-resistant qualities of broadleaf is higher than needle-shaped leaf.

• Fire Science and Engineering
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• v.23 no.1
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• pp.21-32
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• 2009

In order to inspect the danger of forest fires, the thermal characteristics and the ignitability of the dead leaves and the living leaves for the main species of trees in Youngdong areas have been studied by the TG/DTA and the group flammability tester. From this work, the thermal delay has been increased with the increase of the heating rate. The fractions of the thermal weight loss for the dead leaves and the living leaves of the coniferous trees were higher than those of the broadleaf trees. Also, it was confirmed that the ignitable dangers of the dead leaves and the coniferous trees were higher than those of the living leaves and the broadleaf trees, due to the low auto ignition temperature and thermal resistance.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.153.1-153.1
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• 2012

조립 후 발사대로 이송된 추진기관(또는 발사체)는 지상시험 및 비행시험을 위한 충전을 하게 되는데, 추진제 및 고압가스 등 추진기관 구성품의 운용절차는 하드웨어의 설계 단계에서 그 개념이 수립되어야 한다. 다시 말해, 발사체 및 추진기관 설계 단계에서 연료와 산화제의 충전/배출, 시험 취소시의 운용절차 개념이 수립되어 있어야 추진기관 구성품들의 설계, 지상인터페이스 구성품의 설계에 그 내용이 반영될 수 있다. 따라서, 본 논문에서는 발사체 및 추진기관 운용와 관련된 일반적인 충전/배출 절차와 지연 또는 취소시의 작업절차의 주요개념을 다루었고, 추진기관 운용에 필요한 각종 지상설비에 요구되는 주요 기능을 검토하였다. 또한, 추진제 충전 이후 발사 대기시까지의 업무와 발사 전에 수행되어야 하는 추진기관 운용 업무(Pre-Launch Operation)도 다루었다. 특히 다단 발사체의 경우에는 운용과 관련된 준비 업무량이 단수에 비례하여 늘어나므로, 효율적으로 모든 시험 준비 업무를 마치기 위해, 지상에서의 추진기관 운용절차는 각 단별로 유기적으로 진행되어야 한다. 즉, 각 단별 하드웨어에 대한 사전 검사, 충전, 대기 등의 운용시간 설계 및 그 절차가 중요하다. 한국형 발사체 및 추진기관의 운용 개념설계를 수행하는데에는 기 확보된 운용기술을 활용하였다.