• Journal of Korean Institute of Industrial Engineers
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• v.19 no.4
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• pp.137-146
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• 1993

We consider single server feedback queueing systems with priorities. In the model, there are J stations and job classes. Jobs of class i arrive at station i according to a Poisson process, and have a general service time distribution. We derive the generating functions of the number of jobs at each station just after a busy period and the formula for the mean sojourn time that a specific tagged job spends at station j from its arrival to departure from the system.

• Journal of the Korean Society for Railway
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• v.17 no.6
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• pp.402-409
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• 2014

Wireless local area network (WLAN) is a widely used wireless access method due to its easy usability and excellent performance. However, its performance degrades significantly as the number of users increases. In busy train stations, where the number of WLAN users are large and, more importantly the number of simultaneous packet transmission attempts is extremely large due to the time synchronization upon train arrival, the packet transmission delay problem is very severe and almost impossible for WLAN stations to initiate communication with WLAN networks. In this paper, a novel distributed WLAN access scheme for efficient WLAN communication in busy train stations is proposed. Using the proposed scheme, WLAN access delay can be significantly reduced under highly congested traffic environments. Therefore, a significant performance enhancement for the WLAN performance used in the Communication Based Train Control (CBTC) can be achieved.

• Korean Journal of Rural Living Science
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• v.7 no.1
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• pp.81-97
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• 1996

The purpose of this study was to analyze the structure of time use by housewives in rural households, and to compare the time use structure of housewives with that of their husbands. To attain this goals, we have selected 108 farmhouses considering agricultural area and size in L993. Data was collected by observing how (i. e., doing what kinds of work) housewives and husbands spend time, Time use was divided into four categories : physiological time, socio-cultural time, household work time and agricultural labor time. The results in this study present a valuable insight to assuage the overloaded works of rural housewives. The major results can be outlined as follows : 1. Rural housewives worked 1.2 times longer hours a day than their husbands did. 2, There existed a severe labour time imbalance between housewives and husbands during the busy farming season. 3. The time use patterns of housewives and husbands were significantly different across agricultural areas. Also, the education level of a housewife was associated with the length of her labor time.

• Journal of IKEEE
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• v.21 no.2
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• pp.115-122
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• 2017

In vehicular safety service, every vehicle broadcasts Basic Safety Message (BSM) periodically to inform neighbor vehicles of host vehicle information. However, this can cause network congestion in a region that is crowded with vehicles resulting in a reduction in the message delivery ratio and an increase in the end-to-end delay. Therefore, it could destabilize the vehicular safety service system. In this paper, in order to improve the congestion control and to consider the hidden node problem, we propose a congestion control scheme using entire network congestion level estimation combined with transmission power control, data rate control and time slot based transmission control algorithm. The performance of this scheme is evaluated using a Qualnet network simulator. The simulation result shows that our scheme mitigates network congestion in heavy traffic cases and enhances network capacity in light traffic cases, so that packet error rate is perfectly within 10% and entire network load level is maintained within 60~70%. Thus, it can be concluded that the proposed congestion control scheme has quite good performance.

• Korean Journal of Culture and Social Issue
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• v.27 no.4
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• pp.529-559
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• 2021

This study examines how people perceive and experience busyness, which is a great social pressure in the Korean society, and The socio-psychological motives that drive people's different paces of life, such as busyness or slowness, despite being in the same busy reality, were examined. Furthermore, an in-depth study was conducted on the adaptation factors in the real society according to the speed of individual life. The analysis of this study was based on an in-depth interview data of 21 unmarried men and women in their 20s and 30s, and was conducted using a phenomenological qualitative analysis method. As a result, the perception and experience of being busy had both positive and negative parts. The components of socio-psychological motivation that affect the speed of an individual's life are 'internalization of positive values of (busy/rest)', '(future/present) centric', 'selection & concentration/Inertial busyness', 'personality characteristics' were derived. In addition, 'self-selection', 'successful time management', and 'maintenance of psychological health' were derived as common factors among adaptation factors in real society, 'a sense of achievement' and 'understanding and accepting self-characteristics' were derived as discriminatory factors. became Based on these results, the value and meaning of being busy in Korean society was discussed from a social psychology perspective, and a new perspective was presented to existing studies and discussions related to the speed of life. In addition, several follow-up studies were proposed.

• Journal of Families and Better Life
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• v.27 no.6
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• pp.111-124
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• 2009

The purpose of this study is first to examine the tendency in what kinds of activities are carried out as family rituals; what kinds of obstacles there are; and why any problems, if any, tend to arise. Second, the study seeks to discern the relationship between family rituals and wives' marital satisfaction. For this purpose, the study surveyed 251 wives who had fourth, fifth, or sixth grade children and resided in Busan, and then analyzed the data obtained from the survey. The major findings of this study can be summarized as follows: (1) Regarding the dinner ritual, it turned out that a majority of subjects had a difficult time establishing a regular ritual due to 'their busy schedule at work' and 'children's studying at academies'. For the weekend leisure ritual, in the case of difficulty in spending this kind of time it tended to be because of the wives' 'busy schedules at work' and 'lack of mutually available time for all family members'. In birthday rituals, when wives reported having trouble with her family members regarding birthdays, they explained that this was most often' because family members forget their birthday'. Finally, when the subjects reported problems related to tradition rituals, it was mainly because of 'stress from the burden of housework (2) In every dimensions including occurrence, routine, deliberateness, attendance, affect, and symbolic significance, the top-ranked group showed a high degree of satisfaction in their marriage.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.10a
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• pp.201-204
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• 2017

People live in their everyday life busy with studies, part-time jobs, and searching for an ideal job. In their busy routine, they try to find time for themselves and expose their emotions through diverse social network services(SNS). We made a service that we can plant a virtual tree in places we daily visit and go by. You can keep note on the virtual tree and look through the past records. It is a reality based mobile application service that can be used like a diary.In this project we chose the tree as the metaphor and tried to express time passing in a specific place. As our memory is a part of our daily life, we emphasized the meaning of space important.

• Journal of Korean Institute of Industrial Engineers
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• v.28 no.2
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• pp.187-192
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• 2002

In this paper we consider an M/G/1 queueing system with vacation. The length of vacation period may be controlled by the waiting time of the first customer. The server goes on vacation as soon as the system is empty, and resumes service either when the waiting time of the leading customer reaches a predetermined value, or when the vacation period is expired, whichever comes first. We consider two types of vacation, say, multiple vacation type and N-policy type. We derive the steady-state distributions of the number of customers at arbitrary time and arbitrary customer's waiting time by means of decomposition property. Also, the mean lengths of busy period, idle period and a cycle time are given.

• Management Science and Financial Engineering
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• v.15 no.2
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• pp.1-21
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• 2009

We consider an $M^x/G/1$ queueing system with a random setup time under Bernoulli vacation schedule, where the service of the first unit at the completion of each busy period or a vacation period is preceded by a random setup time, on completion of which service starts. However, after each service completion, the server may take a vacation with probability p or remain in the system to provide next service, if any, with probability (1-p). This generalizes both the $M^x/G/1$ queueing system with a random setup time as well as the Bernoulli vacation model. We carryout an extensive analysis for the queue size distributions at various epochs. Further, attempts have been made to unify the results of related batch arrival vacation models.

• Journal of the Korean Mathematical Society
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• v.35 no.3
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• pp.503-525
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• 1998

In the theory of retrial queues it is usually assumed that the flow of primary customers is Poisson. This means that the number of independent sources, or potential customers, is infinite and each of them generates primary arrivals very seldom. We consider now retrial queueing systems with a homogeneous population, that is, we assume that a finite number K of identical sources generates the so called quasi-random input. We present a survey of the main results and mathematical tools for finite source retrial queues, concentrating on M/G/1//K and M/M/c//K systems with repeated attempts.