• 대한수학회보
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• 제53권4호
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• pp.985-1004
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• 2016

We consider the MAP/PH/c/K queue in which blocked customers retry to get service and servers may take vacations. The time interval between retrials and vacation times are of phase type (PH) distributions. Using the method of mean drift, a sufficient condition of ergodicity is provided. A condition for the system to be unstable is also given by the stochastic comparison method.

• 한국통신학회논문지
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• 제30권3B호
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• pp.114-129
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• 2005

본 논문에서는 gigabit Ethernet-PON의 상향 트래픽 제어를 위해 제안 된 Interleaved Polling with Adaptive Cycle Time (IPACT) 방식을 살펴보고 IPACT의 gated service와 limited service에 관한 성능을 수학적으로 분석하였다. 성능분석 방법은 IPACT polling system으로 모델링하고, mean value analysis를 사용하였다. Arrival rate λ의 값을 크기에 따라 세 구간으로 나누곤 구간마다의 수학적 분석과정을 제시하였다. 분석결과 gated service와 limited service의 평균 패킷 지연시간, 평균 큐 사이즈, 평균 싸이클 시간 등을 구하고, 수학적 성능분석의 정확성을 검증하기 위해 시뮬레이션을 수행하여 수학적 분석결과와 시뮬레이션 결과가 상당히 일치함을 확인하였다. 기존에 IPACT의 성능평가는 시뮬레이션에만 의존하였는데, 이 방법은 시간과 노력이 많이 필요하였지만, 수학적 성능분석은 성능지표를 단시간 내에 다양하게 구할 수 있어서 시스템 설계에 널리 활용될 수 있을 것이다.

• 한국항만학회지
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• 제14권1호
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• pp.13-26
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• 2000

In this paper, we compare and analyze the current state of the productivity of the stevedoring work among several container terminals in 1999. Based on these results of analysis, we firstly classify several factors which impede the efficient operations of container terminal as follows ; late arrival of container beyond cargo closing time(CCT), change of port of destination, change of vessel, and return cargo. Such factors are major cause for the cargo rehandling on terminals, thus deteriorate the overall performance of transfer crane during the stevedoring work. In order to improve the productivity of container terminal, we suggest that it is necessary for establishing and operating the efficient logistics management system. Especially, we emphasize the importance of information exchange on the scheduled cargoes among the relevant parties such as shippers, shipping companies, and terminal operators, which is the most effective way to alleviate the cargo rehandling.

• 한국소음진동공학회논문집
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• 제26권1호
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• pp.89-96
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• 2016

TDOA(time delay of arrival) position estimate from acoustic measurement of artillery shell impact is studied in order to develop a targeting evaluation system. Impact position is calculated from the intersections of hyperbolic estimates based on the least square Taylor series method. The mathematical process of Taylor series estimation is known to be robust. However, the concern lays with the accuracy because it is sensitive to the bias caused by the randomness of measurement situation. The measurement error typically occurs from the distortion of waveform, change of travelling path, and sensor position error. For outdoor measurement, a consideration should be made on the atmospheric condition such as temperature and wind which can possibly change the trajectories of rays of sound. It produces wrong propagation time events accordingly. Ray tracing and optimization techniques are introduced in this study to minimize the bias induced by the ray of sound. The numerical simulation shows that the atmospheric correction improves the estimation accuracy.

• Korean Journal of Acupuncture
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• 제25권1호
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• pp.1-18
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• 2008

Objectives : The aim of this study is to investigate the properties of Meridian Gi in $\ulcorner$Huangdineijing(黃帝內經)$\lrcorner$, specially one of the movement properties like that comings and goings of Gi. Methods : Through searching concepts and properties of Meridian Gi in several chapters of $\ulcorner$Huangdineijing(黃帝內經)$\lrcorner$, many phrases concerned with that properties could be explained and reconstructed into new motional shape of Meridian Gi. Results : The basic characters of comings and goings of Meridian Gi or genuine Gi originate from food essence, and that are like a kind of waves. The most important moments of acupuncture treatment is such time of it's short passing the acupoints, carrying out tonifying and purging methods by controlling the spirit. Conclusions : The Meridian Gi consists of anti-pathogenic Gi so called genuine Gi and pathogenic Gi. Medical doctor must correctly knows the flow of Meridian Gi to operate tonifying and purging method of acupuncture treatments in order to get the desired results. Also maintaining very sensitive state in diagnostic process, the most important key points is to control the spirit and adjust mental activities of both doctors and patients. The motional properties of Meridian Gi are actually concerned with the arrival of Gi and reinforcement-reduction along and against Meridian Gi.

• Journal of Trauma and Injury
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• 제24권2호
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• pp.89-94
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• 2011

Purpose: A few studies have assessed the factors affecting the prognoses for major trauma patients and those improving the circumstances when dealing with the trauma system. In that light, we analyzed factors, such as pre-hospital factors, the time to admission, the length of stay in the emergency department (ED) and emergency operation, influencing the outcomes for trauma patients. Methods: The patients who visited our emergency department from April 1, 2009, to February 29, 2011, due to major trauma were enrolled in the study. The inclusion criterion was a revised trauma score (RTS) < 7 or injury severity score (ISS) ${\geq}$ 16. We used reviews of medical records, to analyze each step of emergency medical care with respect to patients' sex, age, visit time and visit date. Continuous variables were described as a median with an interquartile range, and we compared the variables between the survival and the mortality groups by using the Mann-Whitney U test. Fisher's exact test was used for nominal variables. Using the variables that showed statistical significance in univariate comparisons, we performed a logistic regression analysis, and we tested the model's adequacy by the using the Hosmer-Lemeshow method. Results: A total of 261 patients with major trauma satisfied either the RTS score criterion or the ISS score criterion. Excluding 12 patients with missing data, 249 patients were included in this study. The overall mortality rate was 16.9%. Time to ED arrival, time to admission, time of ED stay, RTS, ISS, and visit date being a holiday showed statistically significant differences between the survival and the mortality groups in the univariate analysis. RTS, ISS, length of ED stay, and visit date being a holiday showed statistical significance in the multivariate analysis. Conclusion: The mortality rate did not show a significant relationship with the time to ED arrival, use of 119, on time to admission. Rather, it elicited a quite significant correlation with the trauma scoring system (RTS and ISS), the time of ED stay, and the visit date being a holiday.

• 한국안전학회지
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• 제19권3호
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• pp.20-25
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• 2004

In order to obtain the flame Propagation speed in freely falling droplet suspension Produced by an ultrasonic atomizer, a light collecting probe named Multi-color Integrated Cassegrain Receiving Optics (MICRO) is applied to spark-ignited spherical spray flames. Two MICRO probes are used to monitor time-series signals of OH chemilumine-scence from two different locations in the flame. The flame propagation speed is calculated by detecting the arrival time difference of the propagating flame front. In addition, time-series images of OH chemiluminescence are simultaneously obtained by a high-speed digital CCD camera to ensure the validity of the MICRO system. Furthermore, relationship between the spray properties measured by phase Doppler anemometer (PDA) and the flame propagation speed are discussed with k different experimental conditions by changing the fuel injection rate. It was confirmed that the MICRO probe system was very useful and convenient to obtain the flame propagation speed and that the flame propagation speed was different depending on the spray properties.

• 대한산업공학회지
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• 제16권1호
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• pp.107-114
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• 1990

A queueing system with compound Poisson arrival and server vacation is analyzed by including supplementary variables. We consider a vacation system in which the server leaves for a vacation as soon as the system empties. When he returns, if no customer is waiting for service, he waits until a group of customers arrive and then begins to serve. We obtain the system size distribution and the waiting time distribution. Additional performance measures will be also considered.

• 한국통신학회논문지
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• 제28권9B호
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• pp.783-792
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• 2003

We consider a finite-buffer discrete-time queueing system with fixed-size bulk-service discipline: Geo/ $G^{B}$1/K＋B. The main purpose of this paper is to present a performance analysis of this system that has a wide range of applications in Asynchronous Transfer Mode (ATM) and other related telecommunication systems. For this purpose, we first derive the departure-epoch probabilities based on the embedded Markov chain method. Next, based on simple rate in and rate out argument, we present stable relationships for the steady-state probabilities of the queue length at different epochs: departure, random, and arrival. Finally, based on these relationships, we present various useful performance measures of interest such as the moments of number of packets in the system at three different epochs and the loss probability. The numerical results are presented for a deterministic service-time distribution - a case that has gained importance in recent years.s.

• 한국ITS학회 논문지
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• 제10권1호
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• pp.49-59
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• 2011

현재 목표기기(target node)의 위치를 측정하는 기술 중에 가장 정확도가 높다고 평가되는 방법은 ToA(Time of Arrival) 거리 측정(Ranging) 기술과 TDoA(Time Difference of Arrival) 거리 측정 기술을 이용한 위치 측정 방법이다. ToA와 TDoA는 시간을 기반으로 하는 거리 측정 기술이기 때문에 여러 개의 참조기기(Reference node)와 목표기기 사이의 시간 동기화와 오프셋이 중요시 된다. 참조기기와 목표기기 사이의 시간 동기화가 정확하게 이루어지지 않거나 참조기기 간 시간 오프셋이 발생할 경우 정확한 시점에서 신호를 검출할 수 없게 되어 거리오차가 발생하게 되고, 이러한 거리오차를 일반적인 위치 측정 알고리즘에 적용하게 되면 목표 기기의 정확한 위치를 측정할 수 없다. 따라서 본 논문에서는 참조기기와 목표기기 사이에 시간 동기화가 맞지 않을 경우와 참조기기와 참조기기 사이의 시간 오프셋이 발생할 경우에 위치 측정의 오차를 줄이는 ToA와 TDoA의 Hybrid 방식을 제안한다. 각각의 펄스가 직교성을 갖는 특징을 지닌 MHP(Modified Hermite Polynomial) 펄스를 이용하여 참조기기들이 각기 다른 MHP 펄스를 송수신하도록 하고 이를 통해 한 번의 MHP 펄스 송수신만으로 TDoA와 ToA 두 가지 방법을 모두 이용하여 각각의 거리를 측정하고 위치 계산을 할 수 있도록 한다. Hybrid 방식은 TDoA와 ToA 방법을 이용한 거리 측정을 반복적인 계산을 통해 실제 거리 오차가 적은 방법을 선택하여 목표기기의 위치를 좀 더 정확하게 측정할 수 있음을 시뮬레이션을 통해 보였다.