• Journal of the Korean Operations Research and Management Science Society
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• v.21 no.2
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• pp.49-58
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• 1996

The generalized Erlang loss function, extensively studied in the literature, is revisited. We study the steady state loss probability in M/M/s/s + c queueing system and prove that it satisfies the first and second order properties in integral number of servers as well as integral queue capacities. Also we study the problem of allocating integral number of servers and queue capacities, and develop an algorithm to obtian an optimal allocation of them individually and jointly with the small number of computations.

• Journal of Korean Society for Quality Management
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• v.19 no.2
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• pp.78-85
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• 1991

In this paper, an inspection and replacement policy in a redundant system is considered. It is assumed that the state of the redundant system is known by inspection. When the system is inspected, it is preventively replaced only if the number of failed units exceeds the predetermined limit. Otherwise, the system is inspected after a inspection interval which depends on the number of failed units. We obtain the optimal number of redundant units, inspection intervals and replacement limit minimizing the expected cost rate.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.47 no.6
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• pp.1037-1054
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• 2014

In this study, the status of coastal fisheries was examined based on the catch and number of fishing vessels of coastal fisheries in Korea. Comparing the status on coastal fisheries of the East Sea, Yellow Sea and South Sea in Korea, scientific evidence was made for fisheries management on coastal fisheries based on characteristics of each sea area. From 1990 to 2011, the catch of coastal fisheries in Korean waters ranged from 150,000 mt to 230,000 mt, with an average of 190,000 mt, and it accounted for 15% in average of total catch fished in adjacent waters of Korea. In order of catch by coastal fisheries, gillnet (36.7%) was the primary fishery, followed by coastal complex (24.7%), stow net (18.3%), trap (12.9%), lift net (3.9%), purse seine (3.0%) and beam trawl (0.4%) fisheries. In order of catch by species, anchovy (15.0%) had the largest proportion of total catch, followed by common squid (10.3%), akiami paste shrimp (5.2%), blue crab (3.9%) and octopus (3.7%). Of the average catch by sea area from 1990 to 2011, Yellow Sea, South Sea and East Sea were 37.4%, 34.6% and 28.0%, respectively. Since 2000s, however, the average catch of South Sea has accounted for the largest proportion. The number of permitted fishing vessels involved in 8 coastal fisheries was 55,336 vessels in average from 1997 to 2011. The number of vessels was about 47,000 vessels in 1997, and increased to 61,300 vessels until 2000, then has decreased to 44,000 vessels operating in 2011. In order of the number of permitted fishing vessels by fisheries, complex (52.4%) took the first place, followed by gillnet (31.5%), trap (13.4%), stow net (0.8%), beam trawl (0.8%), purse seine (0.6%), lift net (0.4%) and seine net (0.0%). In order of the number of permitted fishing vessels by sea area, South Sea (29,994 vessels) took the first place, followed by Yellow Sea (18,185 vessels) and East Sea (7,158 vessels). In order of the catch per unit effort (CPUE, mt/vessels) which was analyzed using catch and number of vessels in average by fishery, stow net is the highest followed by lift net, trap, purse seine, gill net, beam trawl and complex fisheries. In particular, the CPUE of complex and gill net fisheries, which accounted for the largest number of vessels were 4.0 mt/vessels and 1.6 mt/vessels, respectively. Since those are too low relative to other fisheries, it was judged to need systematical management on both fisheries.

• Journal of Advanced Information Technology and Convergence
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• v.10 no.2
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• pp.73-81
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• 2020

The number of mobile devices roaming into a ubiquitous city (u-city) continues to rise as wireless systems have been widely deployed. The number of mobile devices also varies with time, and they tend to frequently change their locations. In addition, the available wireless access networks may belong to different domains, administrations, management, and internet service providers (ISPs). A fusion of overlapping heterogeneous wireless access networks (e.g., WiMax, Wi-Fi, LTE, etc.) serves the u-city in order to reach different coverage. In this context, technical challenges arise in mobility management for heterogeneous networks to realize their potential coverage and capacity benefits. This paper deals with the analysis of a decentralized mobility management support for u-City wireless network infrastructure. This scheme takes advantage of the features of the fully-distributed model of networked-based mobility management protocol to alleviate and realize the ubiquitous requirements of a u-City.

• Health Policy and Management
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• v.17 no.2
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• pp.18-32
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• 2007

The purpose of this study was a quantitative analysis for the influence of physician's assistants on national health insurance revenue and number of patients in clinic. The data was derived from the Korean national health insurance. That was complete enumeration. Dependent variables were measured by national health insurance revenue and number of patients. Independent variables were reported physician's assistants that the number of nurse, nurse-aid, technologist of clinical laboratory, physical therapist and radiologist in clinic. Confounding variables were classified by demand(region, number of inhabitants, number of clinics, number of bed per a hundred thousand persons) and supply(sex and age of representative, number of bed, subjective of medical treatment). On the multiple regression analyses, the physician's assistants that nurse, nurse-aid, technologist of clinical laboratory and physical therapist were statistically significant for outputs. But radiologist was statistically significant only for number of patient.

• Journal of Korean Society for Quality Management
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• v.48 no.1
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• pp.201-214
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• 2020

Purpose: The purpose of this paper is to determine an optimal number of cycle times for the replacement under the circumstance where the system is replaced at the periodic time and the multiple number of working cycles whichever occurs first and the system is minimally repaired between the replacements if it fails. Methods: The system is replaced at periodic time () or cycle time, whichever occurs first, and is repaired minimally when it fails between successive replacements. To determine the optimal number of cycle times, the expected total cost rate is optimized with respect to the number of cycle times, where the expected total cost rate is defined as the ratio of the expected total cost between replacements to the expected time between replacements. Results: In this paper, we conduct a sensitivity analysis to find the following results. First, when the expected number of failures per unit time increases, the optimal number of cycle times decreases. Second, when the periodic time for replacement becomes longer, the optimal number of cycle times decreases. Third, when the expected value for exponential distribution of the cycle time increases, the optimal number of cycle times increases. Conclusion: A mathematical model is suggested to find the optimal number of cycle times and numerical examples are provided through the sensitivity analysis on the model parameters to see the patterns for changes of the optimal number of cycle times.

• Journal of Korean Institute of Industrial Engineers
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• v.34 no.4
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• pp.373-385
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• 2008

This paper presents an overview of inventory management. This includes a categorization, by a number of dimensions, of inventory problems and associated models. Relevant literature references are provided within the dimensions. The paper points out the continuing gap between theory and practice, followed by a number of suggested research topics to help bridge the gap.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.61-62
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• 2006

In this paper, using Bianchi's model with channel idle probability we analyze performance of power management scheme of IEEE 802.11 DCF according to ATIM window size and number of nodes for wireless ad hoc networks. The analytical results show that, when the number of nodes is given, the selected ATIM window size limits the performance.

• Journal of the Korea Safety Management & Science
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• v.17 no.3
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• pp.97-104
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• 2015

The study is conducted in order to identify whether there is difference in laboratory safety management committee and safety manager appointment for type of institutes(university, research institute, enterprise institute). The study conducted statistical analysis of 2484 institutes (university, research institute, enterprise institute) that attended 'current status of laboratory safety management' by year(number of current status participation). As a result, university showed increase in forming safety management committee as the number of current status(year) increases. The number of safety management committee held were the highest amongst all institutes being 2 held/2 year. Furthermore, period of safety management committee held at university and research institutes are decreasing stately. For 2014, the rate of hosting periodic committee and temporary committee simultaneously when necessary are increasing. The rate of appointing safety manager who is in charge of laboratory safety is increasing in university, but it is decreasing in research institute and enterprise institute. The work pattern of safety manager in university is increase in exclusive duties and decrease in adjunct duties, while work pattern in research institute and enterprise institute is more on the contract duties.

• Korean Management Science Review
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• v.34 no.2
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• pp.103-113
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• 2017

The artillery is a key element of the ground forces operation during wartime, and the military engineers support the artillery position development operation to support the smooth operation of the artillery. In establishing the artillery position development operation plan, the commander requires more than his intuition to find the best option reflecting a number of elements of the battlefield situation which changes every minute. Moreover, the number of available equipment is smaller than the number of required position developments, and the effective equipment operation becomes essential element of this issue. This study quantified the capability of the available engineering equipment, organized a number of teams enabling equipment to put out the maximum capacity based on the quantified figures, and formed the model which allocates the team to the developing points to minimize the developing time. The goal programming method was applied to resolve the problem. The developed model was applied to compare the total mission duration following the number of teams, the variable for commander's decision, and the result of this study can be used as the quantitative data for commander's decision making process in establishing the artillery position development support operation through effective equipment management.