• Journal of the Korea Society for Simulation
• /
• v.20 no.2
• /
• pp.1-10
• /
• 2011

In queueing network analysis, arrival processes are usually modeled as renewal processes by matching mean and variance. The renewal approximation simplifies the analysis and provides reasonably good estimate for the performance measures of the queueing systems under moderate conditions. However, high variability in arrival process or in service process requires more sophisticated approximation procedures for the variability parameter of departure/arrival processes. In this paper, we propose an heuristic approach to refine Whitt's variability function with the k-interval squared coefficient of variation also known as the index of dispersion for intervals(IDI). Regression analysis is used to establish an empirical relationships between the IDI of arrival process and the IDI of departure process of a queueing system.

• Journal of Trauma and Injury
• /
• v.34 no.2
• /
• pp.105-111
• /
• 2021

Purpose: Open extremity fractures require prompt antibiotic medication and initial debridement surgery to reduce the infection rate and restore functional stabilization. We aimed to report the effects and positive outcomes of a trauma team approach on the management of open extremity fractures in polytrauma patients. Methods: This retrospective review included all polytrauma patients with open extremity fractures admitted between March 2009 and December 2019. Patients were divided into two groups according to whether they were treated before or after the implementation of the trauma team approach (March 2014). We analyzed the outcomes in each group with respect to the time interval until the doctor's arrival, total length of stay in the emergency department, the time interval until initial antibiotic treatment and operation, whether the initial operation was performed within 24 hours, and the rate of deep infections. Results: A total of 123 patients met the inclusion criteria. There were no statistically significant differences in demographic characteristics. The time interval until the doctor's arrival (64.12±49.2 minutes vs. 19.82±15.23 minutes; p=0.035) and initial antibiotic treatment (115.47±72.12 minutes vs. 48.78±30.12 minutes; p=0.023) significantly improved after implementing the trauma team approach. The union rate was not significantly different. However, the time interval until initial debridement, opportunity for initial debridement within 24 hours, and the rate of deep infections demonstrated better results. Conclusions: The reduced time interval until initial antibiotic treatment and debridement could be attributed to the positive effect of the trauma team approach on the management of open extremity fractures in polytrauma patients.

• Journal of applied mathematics & informatics
• /
• v.6 no.2
• /
• pp.553-568
• /
• 1999

This paper is of concern to queueing analysis of the dynamic rate leaky bucket(LB) scheme in which the token generation interval changes according to the buffer state at a token generation epoch. Cell arrivals are assumed to follow a Markovian arrival process (MAP) which is weakly dense in the class of the stationary point processes. By using the embedded Markov chain method we obtain the probability distribution of the system state at a token generation epoch and an arbitrary time. Some simple numerical examples also are provided to show the effects of the proposed LB scheme.

• Journal of the Korean Operations Research and Management Science Society
• /
• v.38 no.3
• /
• pp.13-22
• /
• 2013

Queueing system with scheduled arrivals is useful in many fields where both customers' waiting time and servers' operation time (utilization) are important, and arrival time of customers is possible to be controlled. In this paper, we analyzed the operation of ship maintenance with the queueing system with scheduled arrival. Based on the model presented by Pegden and Rosenshine [8], who dealt with exponential service time, we extended the service time distributions to phase-type distribution which is able to include a wide range of real stochastic phenomena. Since most activities in the military are carried out under tight control and schedule, scheduled arrival queue has quite good applicability in this area. In this context, we applied queue with scheduled arrival to the optimal booking time decision for the ship maintenance in the navy.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.8 no.3
• /
• pp.1-10
• /
• 2009

Bus delay time is occurred as the result of traffic condition and important factor to predict bus arrival time. In this paper, transition probability matrixes between bus stops are made by using Markov Chain and it is predicted bus delay time with them. As the results of study, it is confirmed a possibility of adapting the assumption which it has same bus transition probability between stops through paired-samples T-test and overcame the limitation of exiting studies in case there is no scheduled bus arrival time for each stops with using bus interval time. Therefore it will be possible to predict bus arrival time with Markov Chain.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.35 no.6B
• /
• pp.895-900
• /
• 2010

As the diverse telecommunication services have been developed, network designers need to prevent congestion which may be caused by properties of timecorrelation and burstiness, and unpredictable statistical fluctuation of traffic streams. This paper considers the leaky bucket scheme with combined control of arrival and token rates, in which the arrival rate and the token generation interval are controlled according to the queue length. By using the embedded Markov chain and the supplementary variable methods, we obtain the queue length distribution as well as the loss probability and the mean waiting time.

• Journal of Satellite, Information and Communications
• /
• v.10 no.4
• /
• pp.146-150
• /
• 2015

The COSPAS-SARSAT committee decides MEOSAR (Medium-Earth Orbit for search and rescue) service development for installing 406MHz SAR instruments on their respective MEO navigation satellite system of the United States, EU, and Russia, since 2000. The transmitted beacon signal is separately arrived by satellites with different FOA (Frequency of Arrival) and TOA (Time of Arrival). It is directly transferred to MEOLUT. In MEOLUT, a LUT track at least 3 or 4 satellites simultaneously and estimate location of beacon using time difference of arrival (TDOA) and frequency difference arrival (FDOA). But the transmitted distress signals may be overlapped each other because the distress beacons transmit signal on mean interval of 50 seconds in arbitrary time. It's difficult that simultaneously estimate location of beacon by current scheme for several overlapped distress signal. So we use cross ambiguity function (CAF) Map algorithm and present Multi-CAF MAP scheme in order to satisfy performance requirement of system. The performance is analyzed for COSAPS-SARSAT MEOSAR.

• Journal of Korean Public Health Nursing
• /
• v.13 no.2
• /
• pp.70-83
• /
• 1999

This study was designed to evaluate the prevalence and significant features of accidental patients and to evaluate the degree of satisfaction on emergency care who visited emergency room. The subject of this study was a total of 243 accidental patients and 249 patients with disease visiting emergency room of 4 university hospitals in Seoul. The data was collected from guestionnaire during the period of January to february 1999. The results were summarized as follows. 1. Distribution of the general characteristics (age, sex, educational status, marrital status and job) in the accidental patients were significantly different from that of the control group. The most common group of age was 20-30 years of age and males predominated over female. 2. CD Fourty two $\%$ of accidental patients arrived within 30 mins. (2) Fifty seven $\%$ of patients was first-aided one. (3) An ambulance was the most frequently used transportation. (4) The time interval from arrival to initial emergency care was 10 mins. (5) Admission rates of the patients after treatment was $72.0\%$. (6) Time interval from arrival to completion was 3-4 hours. 3. The Mean score of the accidental patents' degree of satisfaction on emergency services was $3.26\pm0.64$ which was not significantly different from that of control group.

• The Korean Journal of Emergency Medical Services
• /
• v.22 no.3
• /
• pp.47-54
• /
• 2018

Purpose: The purpose of this study was to present evidence for quality management based on analysis of patient transportation and response intervals among emergency medical squads. Methods: The chi-square test was used to determine whether mental status and patient assessment affected direct medical control and hospital destination. One way analysis of variance was used to compare response intervals depending on mental status and patient assessment using data drawn from 1172 prehospital care reports. Results: There was a statistically significant relationship between mental status and direct medical control (p<.001); there was a statistically significant relationship between patient assessment and hospital destination (p=.011). However, there was no statistically significant relationship between mental status and hospital destination. The interval from arrival at the patient's side to departure from the scene showed a statistically significant difference (p<.001, p<.001), however, it took the longest time (16.8 minutes) in unresponsive patients. It showed a statistically significant difference (p<.001) in the interval from arrival at patient's side to departure from the scene depending on patient assessment; however, it took the longest time (9.6 minutes) in emergency patients. Conclusion: There was call for direct medical control based on patient assessment; however, patient transportation and response intervals were not appropriate.

• Journal of Korean Port Research
• /
• v.9 no.1
• /
• pp.33-43
• /
• 1995

Korean economic and industrial structure has been seperated into some areas with the trend of the change to the bloc system of international economy: the Gyeongin including the capital area, the Middle-West, the South-West, the South-East, and the Eastern sea areas. Mokpo port has played a major role as the central one of the South-West area and the entrance of Yeong-san river of Jeonnam province gate. Some studies has been done on the Mokpo port, but there is no research of the analytical approach about it. In this paper, we analyze the data of 1994's on the domestic and oceangoing piers in the Mokpo port and simulate the transportation process of it through a queueing model. The results of the simulation are summarized as follows: The average arrival interval of the domestic vessel is 6.034 hours. The average service time and the berth utility rate are 24.056 hours and over 100%, respectively. The average arrival interval of the oceangoing vessel is 34.48 hours. The average service time and the berth utility rate are 120.04 hours and the 34.91%, respectively. The proposal to improving of the Mokpo port as follows: It is desirable to extend the capacity of domestic pier to about 50% for the optimal utility rate of 70% and in the case of oceangoing pier to be increase 65% of the vessel capacity for the optimal utility rate of 70%.