• 한국건설관리학회논문집
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• 제14권4호
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• pp.164-171
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• 2013

도시개발에 있어 도로의 건설은 교통의 목적 외에 전기, 가스, 통신, 난방, 하수, 상수, 오수 등의 도시 편의시설을 위한 공간으로도 활용되고 있다. 하지만 현재 도로 시공과정에서 각 기능에 따른 관련 주체들이 진행되는 공사수행일정에 대한 의사소통이 충분히 이루어지지 않아 재굴착 작업이 빈번히 이루어지고 있으며 이로 인해 예산의 중복투입, 공사기간 지연, 품질저하, 이용자의 불편 등 여러 가지 문제점들이 나타나고 있다. 본 연구에서는 신도시 개발과 같은 대규모의 프로젝트에서 도로 재굴착으로 인한 문제를 사전에 예방하기 위해 시간과 공간데이터를 활용한 재굴착 방지 프로세스 모델을 개발하였으며, 이를 활용하여 도시기반시설 건설주체간 원활한 협의를 돕기 위한 재굴착방지시스템을 개발하였다. 아울러, 개발된 시스템을 개발중인 신도시 건설사업에 활용하여 그 적용성을 검토하였다.

• 한국건설관리학회:학술대회논문집
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• 한국건설관리학회 2007년도 정기학술발표대회 논문집
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• pp.971-976
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• 2007

미국의 경우 지하지장물의 이설시 발생하는 시설물들의 손상, 간섭으로 인한 작업지연 등이 여전히 미국 건설업의 주요한 문제점 중 하나로 지적되고 있으며, 국내의 경우에도 전기, 통신, 가스, 상 ${\cdot}$ 하수도 등과 같은 지하지장물 이서에 따른 공기지연 및 추가비용 사례가 발생하고 있고, 이로 인해 발주자와 시공자간의 책임소재를 둘러싼 클레임의 제기가 증가하고 있는 실정이다. 하지만 국내의 경우 지하지장물 이설과 관련 공기지연 및 설계변경 등에 따른 추가 공사비 발생 등에 대한 현황 파악조차 제대로 이루어지고 있지 못한 실정이며, 원인 및 파급효과 분석 등 문제해결을 위한 체계�Ю� 연구가 매우 부족한 상황이다. 이에 본 연구는 미국의 FHWA, SHA 및 지하지장물 이설을 관리하는 유관 기관들의 모범사례 규명을 통한 최근 연구결과를 분석하여 보여줌과 동시에 FHWA가 제시한 문제해결 도구들 중에서 특히 신뢰성 있는 지하지장물의 위치 파악을 위한 SUE에 관한 기본적인 개념을 고찰하고, 국내 관련기술개발 현황 등을 살펴봄으로서, 향후 국내 건설업의 효율적인 지장물 이설작업을 위한 체계적인 연구를 제안하고자 한다.

• 한국경영과학회지
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• 제28권4호
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• pp.1-19
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• 2003

This paper studies power and rate control for data users on the forward link of CDMA system with two cells. The QoS for data users is specified by delay and error rate constraints as well as a family of utility functions representing system throughput and fairness among data users. Optimal power and rate allocation problem is mathematically formulated as a nonlinear programming problem, which is to maximize total utility under delay and error rate constraints, and optimal power and rate allocation scheme (OPRAS) is proposed to obtain a good solution in a fast time. Computational experiments show that the proposed scheme OPRAS works very well and increases total utility compared to the separate power and rate allocation scheme (SPARS) which considers each cell individually.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제5권3호
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• pp.542-559
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• 2011

Most game-theoretic works of Aloha have emphasized investigating Nash equilibria according to the system state represented by the number of network users and their decisions. In contrast, we focus on the possible change of nodes' utility state represented by delay constraint and decreasing utility over time. These foregone changes of nodes' state are more likely to instigate selfish behaviors in networking environments. For such environment, in this paper, we propose a repeated Bayesian slotted Aloha game model to analyze the selfish behavior of impatient users. We prove the existence of Nash equilibrium mathematically and empirically. The proposed model enables any type of transmission probability sequence to achieve Nash equilibrium without degrading its optimal throughput. Those Nash equilibria can be used as a solution concept to thwart the selfish behaviors of nodes and ensure the system stability.

• ETRI Journal
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• 제27권6호
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• pp.777-787
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• 2005

In this paper, we propose an urgency- and efficiency-based wireless packet scheduling (UEPS) algorithm that is able to schedule real-time (RT) and non-real-time (NRT) traffics at the same time while supporting multiple users simultaneously at any given scheduling time instant. The UEPS algorithm is designed to support wireless downlink packet scheduling in an orthogonal frequency division multiple access (OFDMA) system, which is a strong candidate as a wireless access method for the next generation of wireless communications. The UEPS algorithm uses the time-utility function as a scheduling urgency factor and the relative status of the current channel to the average channel status as an efficiency indicator of radio resource usage. The design goal of the UEPS algorithm is to maximize throughput of NRT traffics while satisfying quality-of-service (QoS) requirements of RT traffics. The simulation study shows that the UEPS algorithm is able to give better throughput performance than existing wireless packet scheduling algorithms such as proportional fair (PF) and modified-largest weighted delay first (M-LWDF), while satisfying the QoS requirements of RT traffics such as average delay and packet loss rate under various traffic loads.

• Journal of Communications and Networks
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• 제11권5호
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• pp.464-472
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• 2009

In this paper, we propose a packet scheduling algorithm for cellular relay networks by considering relay selection, variation of channel quality, and packet delay. In the networks, mobile users are equipped with not only cellular but also user relaying radio interfaces, where base station exploits adaptive high speed downlink channel. Our proposed algorithm selects a user with good cellular channel condition as a relay station for other users with bad cellular channel condition but can get access to relay link with good quality. This can achieve flexible packet scheduling by adjusting transmission rates of cellular link. Packets are scheduled for transmission depending on scheduling indexes which are calculated based on user's achieved transmission rate, packet utility, and proportional fairness of their throughput. The performance results obtained by using computer simulation show that the proposed scheduling algorithm is able to achieve high network capacity, low packet loss, and good fairness in terms of received throughput of mobile users.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제18권2호
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• pp.327-347
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• 2024

Edge computing is frequently employed in the Internet of Vehicles, although the computation and communication capabilities of roadside units with edge servers are limited. As a result, to perform distributed machine learning on resource-limited MEC systems, resources have to be allocated sensibly. This paper presents an Improved MADDPG algorithm to overcome the current IoV concerns of high delay and limited offloading utility. Firstly, we employ the MADDPG algorithm for task offloading. Secondly, the edge server aggregates the updated model and modifies the aggregation model parameters to achieve optimal policy learning. Finally, the new approach is contrasted with current reinforcement learning techniques. The simulation results show that compared with MADDPG and MAA2C algorithms, our algorithm improves offloading utility by 2% and 9%, and reduces delay by 29.6%.

• ETRI Journal
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• 제45권5호
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• pp.887-898
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• 2023

Aerial base stations (ABSs) seem promising to enhance the coverage and capacity of fifth-generation and upcoming networks. With the flexible mobility of ABSs, they can be positioned in air to maximize the number of users served with a guaranteed quality of service (QoS). However, ABSs may be overloaded or underutilized given inefficient placement, and user association has not been well addressed. Hence, we propose a three-dimensional ABS placement scheme with a delay-QoS-driven user association to balance loading among ABSs. First, a load balancing utility function is designed based on proportional fairness. Then, an optimization problem for joint ABS placement and user association is formulated to maximize the utility function subject to statistical delay QoS requirements and ABS collision avoidance constraints. To solve this problem, we introduce an efficient modified gray wolf optimizer for ABS placement with a greedy user association strategy. Simulation results demonstrate that the proposed scheme outperforms baselines in terms of load balancing and delay QoS provisioning.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1996년도 창립기념 전력전자학술발표회 논문집
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• pp.109-112
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• 1996

In this paper, we composed utility interactive photovoltaic generation system of current source inverter, and controlled that low harmonic and high power factor are hold by supposing control and compensation method which is concerned with synchronous signal distortion and modulation delay. And we put parallel resonant circuit into dc link, so, magnitude of direct reactance was reduce by restraining direct current pulsation which had accumulation of pulsating power in alternating electrolytic condenser. Also we controlled that modulation factor is operated around maximum output of solar cell.

• Nuclear Engineering and Technology
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• 제47권3호
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• pp.362-379
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• 2015

In this study, Nuclear Power Plant (NPP) construction schedule delay risk assessment methodology is developed and the construction delay risk is assessed for turnkey international NPP projects. Three levels of delay factors were selected through literature review and discussions with nuclear industry experts. A questionnaire survey was conducted on the basis of an analytic hierarchy process (AHP) and Relative Importance Index (RII) methods and the schedule delay risk is assessed qualitatively and quantitatively by severity and frequency of occurrence of delay factors. This study assigns four main delay factors to the first level: main contractor, utility, regulatory authority, and financial and country factor. The second and the third levels are designed with 12 sub-factors and 32 sub-sub-factors, respectively. This study finds the top five most important sub-sub-factors, which are as follows: policy changes, political instability and public intervention; uncompromising regulatory criteria and licensing documents conflicting with existing regulations; robust design document review procedures; redesign due to errors in design and design changes; and worldwide shortage of qualified and experienced nuclear specific equipment manufacturers. The proposed combined AHP-RII methodology is capable of assessing delay risk effectively and efficiently. Decision makers can apply risk informed decision making to avoid unexpected construction delays of NPPs.