• 한국정보통신학회논문지
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• 제20권3호
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• pp.499-505
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• 2016

본 논문에서는 웨어러블 컴퓨터 시스템을 위한 WUSB over WBAN 프로토콜에서 요구되는 신체 영역 위치인식기술을 제안한다. 제안하는 위치인식기술은 웨어러블 컴퓨터의 주변 장치를 구성하는 WUSB over WBAN 프로토콜 기반 센서노드에서 실행된다. 웨어러블 컴퓨터 시스템에서 다양한 신체 모션을 통한 입력 정보의 정확성을 높이기위해서는, 높은 정밀도를 갖는 새로운 위치인식기술이 반드시 개발되어야 한다. 이러한 목적을 달성하기 위해, 본 논문은 신체에 부착된 WUSB over WBAN 디바이스들의 개수를 4개 이상으로 하는 TDoA/FDoA/AoA 복합 방식을 제안한다. 실험 결과에서는 제안하는 TDoA/FDoA/AoA의 복합 방식 알고리즘이 TDoA/FDoA 복합 알고리즘 보다 위치 추정 오차를 10mm 감소시킨다. 이 값은 다른 통신 시스템에서는 무시할 수 있는 작은 값이나, 신체 영역 내 통신에서는 위치 추정 성능을 향상시키는 결과를 나타낸다.

• 한국국방경영분석학회지
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• 제32권1호
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• pp.36-50
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• 2006

한국군은 전시 상당량의 전략물자를 미국으로부터 항공수송을 통해 도입하고자 한다. 이 연구는 항공수송 모델을 형성하고 전시 동원될 민간 항공기를 포함한 동원자원의 항공수송 능력을 평가하는 것이다. 전략 항공수송계획은 국군수송사령부에 의해 매년 조정 수립되고 있으나 항공수송 과정의 불확실성으로 인해 시뮬레이션을 통해 실현가능성을 평가할 필요가 있다. 불확실한 요인은 미국 공항에서의 전략물자 도착에 대한 불확실성, 적하역 시간, 동원령 발령시 항공기 최초 위치 지점 등이다. 시뮬레이션은 두 개의 시나리오 하에서 실행되었으며 결과에 대한 민감도 분석을 수행하였다. 시뮬레이션 결과, 항공수송 능력에 가장 큰 영향을 미치는 요인들은 미국 공항에서의 물자 도착 불규칙성과 항공기 동원 대수이었다.

• 대한수학회보
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• 제43권2호
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• pp.277-292
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• 2006

We consider a single-server queue with service time distribution of phase type where positive customers, negative customers and disasters arrive according to a Markovian arrival process with marked transitions (MMAP). We derive simple formulae for the stationary queue length distributions. The Laplace-Stieltjes transforms (LST's) of the sojourn time distributions under the combinations of removal policies and service disciplines are also obtained by using the absorption time distribution of a Markov chain.

• Journal of Information Technology Applications and Management
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• 제20권1호
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• pp.87-106
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• 2013

This study is to explore the airline network patterns of Incheon and Narita International Airports using passenger flight departure and arrival data of the two airports. The so-called Origin-Destination data is collected from the airports' websites and some of the important data items are flight number, city of origin, destination city, departure/arrival time, number of flights, and delay time. A snowflake schema dimensional model is proposed and implemented. Tableau Public, a well-known visual analytic tool, is used to connect the dimensional model and played an important role in navigating the data space to find interesting and visual patterns among corresponding airports and airlines. For the efficiency of analyzing this spacious data mart, data visualization method was used. Four types of visualization method proposed by Yau was used; visualizing patterns over time, visualizing proportions, visualizing relationships, and visualizing spatial relationships. The strength of connectivity of each flight segments is calculated to evaluate the degree of globalization of Seoul and Tokyo. We anticipate that various patterns and new findings produced by the data mart would provide airline managers, airport authorities, and policy makers in the field of travel and transportation with insightful information.

• 대한임베디드공학회논문지
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• 제5권3호
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• pp.152-156
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• 2010

Non-line-of-sight (NLOS) propagation is one of the challenges in radio positioning. Distinguishing the transmission status of the communication as line-of-sight (LOS) or NLOS is of great importance for the wireless communication systems. This paper focuses on the identification of NLOS based on time-of-arrival (TOA) distance estimates and the received signal strength (RSS) measurements. We set a path loss threshold based on the joint TOA and RSS based NLOS detection method to determine LOS or NLOS. Simulation results show that the proposed method ensures the correct of detection for the LOS condition and can improve the NLOS identification for the weak noise and long distance.

• Journal of applied mathematics & informatics
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• 제8권1호
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• pp.285-295
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• 2001

We consider a queueing system under overload control to support bursty traffic. The queueing system under overload control is modelled by MMBP/D1/K queue with two thresholds on buffer. Arrival of customer is assumed to be a Markov-modulated Bernoulli process (MMBP) by considering burstiness of traffic. Analysis is done in discrete-time case. Using the generating function method, we obtain the stationary queue length distribution. Finally, the loss probability and the waiting time distribution of a customer are given.

• 전기학회논문지
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• 제65권8호
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• pp.1392-1399
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• 2016

Blackout effect occurs when a driver misadapts to the changed lighting conditions upon entering a tunnel. This could lead to a decrease in visibility especially in the daylight, depending on the difference in the degree of brightness between inside and outside the tunnel. To alleviate such a problem, we decrease windshield transparency before the driver arrives at the tunnel entrance. Controlled amount of light inside the car can allow the drivers to adjust to the dark prior to entering. The windshield transparency coefficient is to be determined by the arrival time at the tunnel and difference in the level of brightness between inside and outside the tunnel. Navigation, road sign detection, and tunnel entrance detection provide the arrival time. We also designed an opto-electronic conversion function to estimate the level of brightness. The black-hole phenomenon alleviation method is verified by field experiments using an automobile camera and a navigation. The result shows that the adjusted windshield transparency is able to provide an environment with a comfortable level of brightness with which the drivers can enter tunnels without the visibility problem.

• 지질공학
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• 제25권1호
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• pp.103-113
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• 2015

본 연구에서는 신호 대 잡음비가 낮은 미소파괴음 신호에 대한 진원 위치표정 결과의 정확성 향상을 위하여 가변창문함수를 이용한 P파 도달시간 결정 알고리즘을 제안하였다. 제안된 알고리즘은 기존 P파 도달시간 결정알고리즘과 함께 신호 대 잡음비(SNR)가 각기 다른 가상의 미소파괴음 신호에 적용하여 정확성을 검토하였다. 실험결과 기존 P파 도달시간 결정알고리즘은 SNR이 낮아질수록 결과의 정확성이 낮아지며 특히 SNR이 2.14에서는 모든 알고리즘에서 오류가 발생하였다. 반면에, 제안된 알고리즘은 신호의 분산을 고려한 가변창문함수를 신호에 적용하기 때문에 신호의 주파수특성과 신호의 증폭을 동시에 고려하였다. 따라서 SNR 2.14 이하의 신호에서도 제시된 알고리즘은 정확한 결과를 제시하였다.

• 한국항해학회지
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• 제7권1호
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• pp.1-32
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• 1983

The delay due to congestion has recently attracted widespread attention with the analysis of over-all operation at the port. But, the complexity of the situation is evident in view of the large number of factors which impinge on the considerable end. Queueing theory is applicable to a large scale transportation system which is associated with arrivals of vessels in a large port. The attempt of this paper is to make an extensive analysis of the port transport system and its economic implications from the viewpoint that port is one of the physical distribution facilities and a kind of queueing system which includes ships and cargoes as port customer. By analyzing the real data on the Port of Pusan, it is known that this port can be represented as a set of multi-channel with identical setof Poisson arrival and Erlang service time, and also it is confirmed that the following formula is suitable to calculate the mean delay in this port, namely, $W_4={\frac{\rho}{\lambda(1-\rho)} {\frac{e_N(\rho{\cdot}N)}{D_{N-1}(\rho{\cdot}N)}$ where, ${\lambda}$: mean arrival rate $\mu$: mean servicing rate; N: number of servicing channel; ${\rho}$: utillization rate (${\lambda}/N{\mu}$) $e_N$: the Poisson function Coming to grips with the essentials of the cost of delay due to congestion, a simple ship journey cost model is adopted and the operating profit sensitivity to variation in port time is examined, and for purpose of a future development for port princing service the marginal cost is approximately calculated on the basis of queueing theory.

• 대한임상독성학회지
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• 제16권2호
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• pp.176-180
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• 2018

Drug abuse and its related problems are increasing continuously in Korea. One of the most frequently abused drugs is methamphetamine, but there are few medical report in Korea. This is the first report of the identification of methamphetamine in the blood of a patient who had a return of spontaneous circulation after cardiac arrest and survived discharge. A 33-year-old male arrived at the emergency department presenting with chest pain and dyspnea. He had ingested methamphetamine and alcohol approximately 7 hours before arrival. One hour after arrival, he had seizure followed by cardiac arrest. Spontaneous circulation was recovered after 4 minutes of CPR. An analysis of the National Forensic Service identified plasma methamphetamine with an estimated average concentration of plasma methamphetamine at the time of arrival of 0.6 mg/L, a lethal dose. He had rhabdomyolysis and acute kidney injury but survived after continuous renal replacement therapy. Since then, he has suffered chronic kidney disease, and he is being followed up at the out-patient department. In Korea, although drug abuse is still uncommon, it is on the increase. Therefore, emergency physicians should be aware of the clinical characteristics of methamphetamine poisoning.