• Proceedings of the Korean Operations and Management Science Society Conference
• /
• 1993.04a
• /
• pp.229-229
• /
• 1993

• Journal of the Korean Operations Research and Management Science Society
• /
• v.18 no.3
• /
• pp.51-63
• /
• 1993

We consider a cyclid server system under N-policy. This system consists of multiple queues served in a cyclic order by a single server. In this paper, we consider the following control policy. Every time server polls one queue, the server inspects the state of the queue. If the total number of units is found to have reached or exceeded a pre-specified value, the server begins to serve the queue until it is empty. As soon as the queue becomes empty, the server polls next queue. An approximate analysis of this system is presented. Sever vacation model is used as an analytical tool. However, server vacation periods are considered to be dependent on the service times of respective queues. The results obtained from the approximate analysis are ompared with simulation results.

• Journal of applied mathematics & informatics
• /
• v.6 no.1
• /
• pp.309-320
• /
• 1999

Models of single-server queues with vacations have been widely used to study the performance of many computer communi-cation and production systems. In this paper we analyze an M/G/1 queue with generalized vacations and exhaustive service. This sys-tem has been shown to possess a stochastic decomposition property. That is the customer waiting time in this system is distributed as the sum of the waiting time in a regular M/G/1 queue with no va-cations and the additional delay due to vacations. Herein a general formula for the additional delay is derived for a wide class of vacation policies. The formula is also extended to cases with multiple types of vacations. Using these new formulas existing results for certain vacation models are easily re-derived and unified.

• International Journal of Reliability and Applications
• /
• v.11 no.2
• /
• pp.107-122
• /
• 2010

This paper deals with the reliability analysis of a complex system, which consists of two subsystems A and B connected in series. Subsystem A has only one unit and B has two units $B_1$ and $B_2$. Marked process has been applied to model the complex system. Present reliability model incorporated two repairmen: supervisor and novice to repair the failed units. Supervisor is always there and the novice remains in vacation and is called for repair as per demand. The repair rates for supervisor and novice follow general and exponential distributions respectively and the failure time for both the subsystems follows exponential distribution. The model is analyzed under "Head of line repair discipline". By employing supplementary variable technique, Laplace transformation and Gumbel-Hougaard family of copula various transition state probabilities, reliability, availability and cost analysis have been obtained along with the steady state behaviour of the system. At the end some special cases of the system have been taken.

• Journal of Engineering Education Research
• /
• v.24 no.2
• /
• pp.3-11
• /
• 2021

In the COVID-19 era, it was implemented to be used as a basic material for setting the direction of learning support and student guidance for university institutions and professors who are experiencing confusion. The purpose of this study is to compare the actual status of daily-routines of COVID-19 period, general semester period, and vacation period, and to examine whether there is a difference between the period of general semester and COVID-19 period, and whether there is a difference in daily use of COVID-19 period depending on grade. For this reason, a questionnaire survey was conducted from April 23 to 29, 2020, targeting students of University A, which is a small-scale technical centered university in the region, and 754 students answered. As a result of the study, first of all, when we looked at the trends in the use of daily-routines by period of general semester, vacation period, and COVID-19 period, the trends of the general semester period and COVID-19 period were similar in the areas of learning and self-development. Second, there were statistically significant differences in sleep, relaxation, learning and other areas between the period of the general semester and the duration of COVID-19. Third, there were statistically significant differences over grade in relaxation, learning, development, and other areas.

• Proceedings of the Korean Operations and Management Science Society Conference
• /
• 2005.05a
• /
• pp.1137-1140
• /
• 2005

We present the discrete-time version of the heuristic interpretation of the mean waiting time known well about the continuous-time version. The heuristic approach is mainly based on an arriving customer's viewpoint. We obtain the mean waiting time of $Geo^X/G/1$ queueing systems, including vacation queues.

• Journal of Korea Society of Industrial Information Systems
• /
• v.23 no.2
• /
• pp.29-39
• /
• 2018

In this paper, we discuss a discrete-time queueing system with dyadic server control policy that combines workload control and multiple vacations. Customers arrive at the system with Bernoulli arrival process. If there is no customer to serve in the system, an idle single server spends a vacation of discrete random variable V and returns. The server repeats the vacation until the total service time of waiting customers exceeds the predetermined workload threshold D. In this paper, we derived the steady-state workload distribution of a discrete-time queueing system which is operating under a more realistic and flexible server control policy. Mean workload is also derived as a performance measure. The results are basis for the analysis of system performance measures such as queue lengths, waiting time, and sojourn time.

• Journal of applied mathematics & informatics
• /
• v.29 no.1_2
• /
• pp.469-474
• /
• 2011

In a M/G/I queue where the server alternates between busy and idle periods, we assume that firstly customers arrive at the system according to a Poisson process and the arrival process and customer service times are mutually independent, secondly the system has infinite waiting room, thirdly the server utilization is less than 1 and the system has reached a steady state. With these assumptions, we analyze waiting times on the systems where some vacation policies are considered.

• ETRI Journal
• /
• v.19 no.4
• /
• pp.344-362
• /
• 1997

The delay which is one of the quality of service parameters is considered to be a crucial factor for the effective usage of real-time audio and video streams in interactive multimedia collaborations. Among the various causes of the delay, we focus in this paper on the local delay concerned with the schemes which handle continuous inflow of encoded data from constant or variable bit-rate audio and video encoders. We introduce two kinds of implementation approaches, pull model and push model. While the pull model periodically pumps out the incoming data from the system buffer, the push model receives events from the device drivers. From our experiments based on Windows NT 3.51, it is shown that the push model outperforms the other for both constant and variable bit-rate streams in terms of the local delay, when the system suffers reasonable loads. We interpret this experimental data with M/G/1 multiple vacation queuing theories, and show that it is consistent with the queuing theoretic interpretations.

• Korean Journal of Human Ecology
• /
• v.23 no.1
• /
• pp.149-161
• /
• 2014

The purpose of this study was to investigate the nutrition teachers' operation and demand of dietary life education in Jeonbuk Province. The study was carried out using a self administered questionnaire and the subjects were 190 nutrition teachers. The questions were general characteristics of the subjects, operating status as frequency, place, the main use time, and training demand on dietary life education by elementary school and middle & high school, teaching career, and training hours. The results are as follows. Most of the subjects were female(98.9%), more than half were 40's(52.1%) in their age, school work career was 13.2 years. Frequency of the dietary life education operation was once per month(56.8%), 2~3 times per month(27.9%), and place of education were dinning room (49.7%), classroom(25.9%). Almost of the subjects(90.4%) recognized the facilities for education was lack, 89.3% of them did the education materials was lack, also. The desirable frequency of dietary life education was once per month(48.9%), and once per week(35.3%.) The half of the subjects recognized the objects of the dietary life education was not only students but also their parents and teachers. The proper education time was dietary life education tim (34.2%), discretion activity time(31.1%). Most of the subjects(95.7%) had willing to get training, the proper training program was 30 hours, and they prefer summer vacation(61.0%) than winter vacation(30.5%) and semester(8.6%). Proper experimental practice ratio of environment : health : thanks were 30% : 43% : 27%. It is concluded that the demand of nutrition teachers is necessary for their education program in elementary and middle & high school.