• Journal of the Korean Operations Research and Management Science Society
• /
• v.26 no.4
• /
• pp.47-53
• /
• 2001

We demonstrate that the arrival time approach of Chae et al. [4], originally proposed for continuous-time queues, is also useful for discrete-time queues. The approach serves as a simple alternative to finding the probability generating functions of the queue lengths for a variety of discrete-time single-server queues with bulk arrivals and bulk services.

• Journal of the Korean Mathematical Society
• /
• v.38 no.4
• /
• pp.807-842
• /
• 2001

This paper summarizes recent development of analytical and algorithmical results for stationary FIFO queues with multiple Markovian arrival streams, where service time distributions are general and they may differ for different arrival streams. While this kind of queues naturally arises in considering queues with a superposition of independent phase-type arrivals, the conventional approach based on the queue length dynamics (i.e., M/G/1 pradigm) is not applicable to this kind of queues. On the contrary, the workload process has a Markovian property, so that it is analytically tractable. This paper first reviews the results for the stationary distributions of the amount of work-in-system, actual waiting time and sojourn time, all of which were obtained in the last six years by the author. Further this paper shows an alternative approach, recently developed by the author, to analyze the joint queue length distribution based on the waiting time distribution. An emphasis is placed on how to construct a numerically feasible recursion to compute the stationary queue length mass function.

• Journal of Korean Institute of Industrial Engineers
• /
• v.28 no.1
• /
• pp.36-43
• /
• 2002

We analyze bulk service $M/G^{b}/1$ queues using the arrival time approach of Chae et al. (2001). As a result, the decomposition property of the M/G/1 queue with generalized vacations is extended to the $M/G^{b}/1$ queue in which the batch size is exactly a constant b. We also demonstrate that the arrival time approach is useful for relating the time-average queue length PGF to that of the departure time, both for the $M/G^{b}/1$queue in which the batch size is as big as possible but up to the maximum of constant b. The case that the batch size is a random variable is also briefly mentioned.

• Journal of the Korean Operations Research and Management Science Society
• /
• v.27 no.2
• /
• pp.51-61
• /
• 2002

By using the arrival time approach of Chae et at. [6], we derive various performance measures including the queue length distributions (in PGFs) and the waiting time distributions (in LST and PGF) for both M$^{x}$ /G/1 and Geo$^{x}$ /G/1 queueing systems, both under the assumption that the server, when it becomes idle, takes multiple vacations up to a random maximum number. This is an extension of both Choudhury[7] and Zhang and Tian [11]. A few mistakes in Zhang and Tian are corrected and meaningful interpretations are supplemented.

• Journal of Korean Institute of Industrial Engineers
• /
• v.38 no.1
• /
• pp.31-40
• /
• 2012

Distributed arrival time control (DATC) is a distributed feedback control algorithm for real-time scheduling problems in dynamic operational environment. Even though DATC has provided excellent performance for dynamic scheduling problems, it can be improved by considering the following considerations. First, the original DATC heavily depends on the quality of initial solution. In this paper, well-known dispatching rules are incorporated DATC algorithm to enhance its performance. Second, DATC improves its solution with adjusting virtual arrival times of jobs to be scheduled in proportion to the gap between completion time and due date iteratively. Since this approach assigns the same weight to all gaps generated with iterations, it fails to utilize significantly more the latest information (gap) than the previous ones. To overcome this issue we consider exponential smoothing which enable to assign different weight to different gaps. Using these two consideration This paper proposes A-DATC (Advanced-DATC). We demonstrate the effectiveness of the proposed scheduling algorithm through computational results.

• 한국지구물리탐사학회:학술대회논문집
• /
• 2007.06a
• /
• pp.64-68
• /
• 2007

The classic graphical method to determine the epicenter uses differences between the arrival times of P and S waves at each station. In this research, a robust approach is proposed, which provides a fast and intuitive estimation of earthquake epicenters. This method uses an empirical relationship between epicentral distance and traveltime of the first arrival P phase of local or regional earthquake. The relationship enables us to estimate epicentral distances and draw epicentral circles from each station with P-traveltimes counted from a probable origin time. As the assigned time is getting close to the origin time of the earthquake, epicentral circles begin to intersect each other at a possible location of the epicenter. Then the possibility of the epicenter can be expressed by a function of the time and the space. We choose the location which gives the minimum standard deviation of the origin time as an estimated epicenter. In this research, 918 P arrival times from 84 events occurring from 2005 to 2006 listed in the KMA earthquake catalog are used to determine the empirical P-traveltime function of epicentral distances.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.13 no.6
• /
• pp.87-92
• /
• 2013

This paper focuses on analyzing the effects of primary user (PU) signal arrival on the local spectrum sensing performance. The probability for signal arrival at a sample in the sensing time is uniformly distributed in the sensing time. We first analyze the main factor that causes the degradation in the detection results in the conventional energy detection (CED) under the uniformly random arrival of the PU-signal. Thus we propose an approach in order to enhance the detection performance, in which an estimator which detects the arrival of the PU signal cooperates with a composite energy detection. The mathematical analysis and numerical simulation has validated the outperformance of the proposed approach compared to the CED.

• The Journal of the Acoustical Society of Korea
• /
• v.43 no.2
• /
• pp.178-183
• /
• 2024

This study introduces an enhanced sound source localization technique, bolstered by a data-driven deep learning approach, to improve the precision and accuracy of direction of arrival estimation. Focused on refining Time Difference Of Arrival (TDOA) based sound source localization, the research hinges on accurately estimating TDOA from cross-correlation functions. Accurately estimating the TDOA still remains a limitation in this research field because the measured value from actual microphones are mixed with a lot of noise. Additionally, the digitization process of acoustic signals introduces quantization errors, associated with the sampling frequency of the measurement system, that limit the precision of TDOA estimation. A deep learning-based approach is designed to overcome these limitations in TDOA accuracy and precision. To validate the method, we conduct comprehensive evaluations using both two and three-microphone array configurations. Moreover, the feasibility and real-world applicability of the suggested method are further substantiated through experiments conducted in an anechoic chamber.

• Journal of the Korea Society for Simulation
• /
• v.28 no.4
• /
• pp.45-56
• /
• 2019

Literatures have considered mathematical model that change the job order of shipper for improving the operation time of yard crane. However, on the real site, it is impossible to change the job order decided according to the shipper's arrival order. Therefore, operation managers have been utilized the relatively simple strategy that job control is better but the process time of yard crane is longer due to the growth of yard crane's interference time and empty drive time. This study proposed a new yard-crane scheduling approach that decided the job order before the shipper's truck arrived the yard terminal. We utilize the Container Pre-Information Notice estimating the arrival time of truck. We developed the container terminal simulation model for validation of the effect of proposed scheduling approach. The results show that the proposed scheduling reduced the interference delay time and empty moving time of yard crane and shipper's truck delay time.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.17 no.4
• /
• pp.571-576
• /
• 2022

Due to the epochal development of the unmanned technology, the importance of LDT(: Location Detection Technology), which accurately estimates the location of a user or object, is dramatically increased. TOA(: Time of Arrival), which calculates a location by measuring the arrival time of signals, and TDOA(: Time Difference of Arrival) which calculates it by measuring the difference between two arrival times, are representative LDT methods. Based on the signals received from three or more base stations, TOA calculates an intersection point by drawing circles and TDOA calculates it by drawing hyperbolas. In order to improve the radio shadow area problem, a huge number of repeaters have been installed in the urban area, but the signals received through these repeaters may cause the serious error for estimating a location. In this paper, we propose an efficient location estimation technique using the signal received through the repeater. The proposed approach estimates the location of MS(: Mobile Station) employing TOA and TDOA methods, based on signals received from one repeater and two BS(: Base Station)s.