• Proceedings of the Korea Information Processing Society Conference
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• 2007.05a
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• pp.1291-1293
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• 2007

Due to dense deployment and innumerable amount of traffic flow in wireless sensor networks (WSNs), congestion becomes more common phenomenon from simple periodic traffic to unpredictable bursts of messages triggered by external events. Even for simple network topology and periodic traffic, congestion is a likely event due to dynamically time varying wireless channel condition and contention caused due to interference by concurrent transmissions. In this paper, we have proposed three mechanisms: upstream source count and buffer based rate control and snoop based MAC level ACK scheme to avoid congestion. The simulation results show that our proposed mechanism achieves around 80% delivery ratio even under bursty traffic condition

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.10
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• pp.967-973
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• 2009

The model matching problem of asynchronous sequential machines is to design a corrective controller such that the stable-state behavior of the closed-loop system matches that of a prescribed model. In this paper, we address model matching when the external input set consists of controllable inputs and uncontrollable ones. Like in the frame of supervisory control of Discrete-Event Systems (DES), uncontrollable inputs cannot be disabled and must be transmitted to the plant without any change. We postulate necessary and sufficient conditions for the existence of a corrective controller that solves model matching despite the influence of uncontrollable events. Whenever a controller exists, the algorithm for its design is outlined. To illustrate the physical meaning of the proposed problem, the closed-loop system of an asynchronous machine with the proposed control scheme is implemented in VHDL code.

• BMB Reports
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• v.51 no.10
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• pp.493-499
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• 2018

Cellular senescence is a state of permanent cell-cycle arrest triggered by different internal and external stimuli. This phenomenon is considered to be both beneficial and detrimental depending on the cell types and biological contexts. During normal embryonic development and after tissue injury, cellular senescence is critical for tissue remodeling. In addition, this process is useful for arresting growth of tumor cells, particularly during early onset of tumorigenesis. However, accumulation of senescent cells decreases tissue regenerative capabilities and induces inflammation, which is responsible for cancer and organismal aging. Therefore cellular senescence has to be tightly regulated, and dysregulation might lead to the aging and human diseases. Among many regulators of cellular senescence, in this review, I will focus on microRNAs, small non-coding RNAs playing critical roles in diverse biological events including cellular senescence.

• Korean Management Science Review
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• v.33 no.2
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• pp.117-131
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• 2016

This study introduces the concepts on the phase-shifting phenomenon of financial markets, which was firstly used in econophysics area and explains how the phase-shifting behavior is studied in the fields of business management and finance. Specifically, we explain how the phases of financial markets are extremely changed under some external conditions, do an extensive literature review, and carry out case studies focusing on the 3 major financial crisis events including the 87 October crash, 97 Asian financial crisis, and 2007 global financial crisis. We also empirically examine the phase-shifting behavior of the Korean ELW products that has a similar payoff structure to the KOSPI200 options.

• The Korean Journal of Applied Statistics
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• v.16 no.2
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• pp.293-303
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• 2003

Under the case that we know the period and the reason of external events, we reviewed the method of model identification, parameter estimation and model diagnosis with the former papers that have been studied about the linear time series model with intervention, and compared with nonlinear time series model such as ARCH, GARCH model that it has been used widely in economic models, and also we compared with the combination prediction method that Tong(1990) introduced.

• Korean Security Journal
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• no.2
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• pp.33-60
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• 1999

I Study on the security measures of the World Cup Korea and Japan jointly in 2002. The paper, purporting to consider security counterplans, comprise five chapters. Chapter I which sets out purpose, scope and method, is followed by chapter II, dealing largely with the legislations and importance on the security measures of the 17th FIFA World Cup in 2002. Chapter III concerns the security environment -internal environment, external environment- and the highlights accidents and events of history on the FIFA World Cup. Chapter IV consider security measures of the World Cup Korea in 2002. It is followed by concluding observation made in chapter V. To be operated security systems effectively, these need to be regulated according to a security measures organizations, security facilities and equipments, security plan and protective force, security operations and so forth.

• Proceedings of the Korea Database Society Conference
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• 2008.05a
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• pp.477-486
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• 2008

This paper examines the evolution issues of regional tourism resources in complicated and networked industry the perspective of co-evolution types and dualism. Regional tourism structure has been changing more and faster according to various attractions and internal and external environment; natural resources, facilities, festivals and events, drama and movies, and public resources, etc. This paper approaches Olikowski's dualism perspective as a theoretical view about the alliance network between region's attractions and tourism industry in Korea. Exploratory analysis was explained the dualism cases performed on the matrix between resource characteristics and alliance complexity on human resources based on regional tourism industry.

• ETRI Journal
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• v.28 no.5
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• pp.555-560
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• 2006

A PIN photodiode having a low dark current of 1.35 nA and a high external quantum efficiency of 95.3% fabricated for a passive optical network receiver. As the current was increased under a high voltage of 38 V and a temperature of $190^{\circ}C$, it was observed that there is a threshold current at 11 mA which induces a junction failure. Experimental data suggest that the junction failure occurs due to the crystal breaking at the end facet as a result of thermal heat or energetic carriers. This threshold behavior of junction failure is a valuable observation for the safe treatment of photodiodes. As long as the current is limited below the threshold currents, we have not observed failure events of our photodiodes.

• JSTS:Journal of Semiconductor Technology and Science
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• v.5 no.4
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• pp.243-248
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• 2005

The UAV (Unmanned Aerial Vehicle) systems like unmanned autonomous helicopters are used in various missions of flight navigation and used to collect the environmental information of the surroundings. To realize the full functionalities of the UAV, the software part becomes a challenging problem. In this paper embedded real-time software architecture for unmanned autonomous helicopter is proposed that guarantee real-time performance of hard-real time tasks and re-configurability of soft-real time and non-real time tasks. The proposed software architecture has four layers: hardware, execution, service agent and remote user interface layer according to the reactiveness level for external events. In addition, the layered separation of concurrent tasks makes different kinds of mission reconfiguration possible in the system. An Unmanned autonomous helicopter system was implemented (Kyosho RC Helicopter) in our lab to test and evaluate the performance of the proposed system.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.3
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• pp.300-305
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• 2013

LOOP(Loss of Offsite Power) and SBO(Station Blackout) events have been occurring in nuclear power plants should be reviewed and be controlled on important electrical equipments by professional engineer to prevent and to safety improvement from safety assessment and reliability analysis report. LOOP and SBO occasionally happened by internal or external causes. This paper contained that LOOP frequency in the United States NPPs and in the domestic NPPs have compared and analyzed data by the past lessons and probabilistic statistics. Additionally will be installed MG(Mobile Generator) according to the lessons of Fukushima nuclear accident in Japan, which CDF(Core Damage Frequency) and LOOP frequency have reconsidered. And this paper proposed to reduce reliability criteria using PSA(Probabilistic Safety Analysis).