• Journal of the Korean Mathematical Society
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• v.42 no.6
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• pp.1251-1264
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• 2005

Let D be an acyclic digraph. The competition graph of D has the same set of vertices as D and an edge between vertices u and v if and only if there is a vertex x in D such that (u, x) and (v, x) are arcs of D. The competition number of a graph G, denoted by k(G), is the smallest number k such that G together with k isolated vertices is the competition graph of an acyclic digraph. It is known to be difficult to compute the competition number of a graph in general. Even characterizing the graphs with competition number one looks hard. In this paper, we continue the work done by Cho and Kim[3] to characterize the graphs with one hole and competition number one. We give a sufficient condition for a graph with one hole to have competition number one. This generates a huge class of graphs with one hole and competition number one. Then we completely characterize the graphs with one hole and competition number one that do not have a vertex adjacent to all the vertices of the hole. Also we show that deleting pendant vertices from a connected graph does not change the competition number of the original graph as long as the resulting graph is not trivial, and this allows us to construct infinitely many graph having the same competition number. Finally we pose an interesting open problem.

• Journal of the Korean Mathematical Society
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• v.48 no.4
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• pp.691-702
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• 2011

The competition graph of a digraph D is a graph which has the same vertex set as D and has an edge between x and y if and only if there exists a vertex v in D such that (x, v) and (y, v) are arcs of D. For any graph G, G together with sufficiently many isolated vertices is the competition graph of some acyclic digraph. The competition number k(G) of a graph G is defined to be the smallest number of such isolated vertices. In general, it is hard to compute the competition number k(G) for a graph G and it has been one of important research problems in the study of competition graphs. In this paper, we compute the competition numbers of Hamming graphs with diameter at most three.

• Bulletin of the Korean Mathematical Society
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• v.37 no.4
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• pp.649-657
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• 2000

The 2-step competition graph of D has the same vertex set as D and an edge between vertices x and y if and only if there exist (x, z)-walk of length 2 and (y, z)-walk of length 2 for some vertex z in D. The 2-step competition number of a graph G is the smallest number k such that G together with k isolated vertices is the 2-step competition graph of an acyclic digraph. Cho, et al. showed that the 2-step competition number of a path of length at least two is two. In this paper, we characterize all the minimal acyclic digraphs whose 2-step competition graphs are paths of length n with two isolated vertices and construct all such digraphs.

• Journal of Distribution Science
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• v.17 no.3
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• pp.97-105
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• 2019

Purpose - The purpose of this study is to investigate the effect of the government support project on traditional market and the interaction effect between the government support project and the competition intensity. Therefore, this study focuses on the competition intensity of individual stores in traditional markets, unlike the traditional research flow, which is beyond the competitive structure of traditional markets and large retailers. Research design, data, and methodology - This study is based on the data of 'Statistics of Traditional Market in 2017'. In this study, a multiple regression equation was constructed using the number of government support projects as an independent variable, competition intensity as an interaction, and sales per store, number of customers per store as a dependent variable for analysis. A multiple regression equation was constructed for the main effect analysis. To investigate the effect of the interaction, cohen(1980)'s regression equation and two-way ANOVA were used. Results - First, according to this study, the traditional market participated in the government support project showed that the sales and the number of visitors per store in the traditional market were higher than those in the non-participation market. Second, the impact of government support projects on sales per store(also number of visiting customers per store) can be different depending on the competition intensity. More specifically, if the market is politically supported by a market with a high level of competition, it may be more effective than the market with no support. Conclusions - Based on the results of the study, we suggested academic and practical implications and suggested that competition intensity of stores in the traditional market should be considered in the future. The implications of this study are as follows. First, the effects of the government's traditional market support project were analyzed empirically. Second, this study is different from the previous studies in that it examined the competitive strengths and the effects of individual stores in traditional markets, away from competition between traditional market and large retailers. Third, it provided practical implications for the operation of government support projects.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.05a
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• pp.391-394
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• 2002

Number portability facilitates that a customer can keep their phone number when changing from one network operator to another. There are three types of NP, that is the operator portability, the service portability and the location portability. Political regulation is required, because number portability induces the transfer of benefits from suppliers to customers and activate the competition among firms. In this paper, we will examin the domestic trends of number portability and analysis the effort of number portability on the competition among firms.

• International conference on construction engineering and project management
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• 2022.06a
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• pp.18-24
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• 2022

State highway agencies (SHAs) typically apply a competitive procurement procedure to select contractors for their design-bid-build projects. Since the level of competition affects construction bid prices and project outcomes, the Federal Highway Agency (FHWA) suggests SHAs seek ways to improve competition among contractors continuously. However, they rarely conduct an empirical assessment of the current competition level necessary to identify room for improvement. Besides the number of bidders on a project, other factors such as winning or losing rates among the contractors in previous projects can also indicate the degree of competition; only a few contractors may have won the majority of the projects in a specific region. However, few studies have investigated such factors. This paper proposes a network analysis-based approach to evaluating contractor competition levels of highway projects using historical bid tabulation data. The proposed method provides insights into overall competition levels, the determination of competitive contractors, and winning rate distribution among contractors.

• Journal of Korea Technology Innovation Society
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• v.7 no.3
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• pp.555-580
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• 2004

We analyzed the effect of 6-month lagged number portability policy and introduction of common number among carriers on Korean mobile market. Our result shows that the policy change contributed to both the increase in number of mobile subscribers and decrease in dominant carrier's market share. We found that unified prefix among mobile operators is more effective than the lagged number portability policy. The carriers' profit, however, decreased a lot due to excessive marketing expenditure. We also estimated market shares of carriers up to year 2005 when full number portability policy is adopted. The results show that dominant carrier's monopolistic power will be recovered by the end of 2005 implying government's number policy itself cannot guarantee the effective competition in Korean mobile market.

• Journal of Korea Technology Innovation Society
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• v.9 no.4
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• pp.796-811
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• 2006

This paper aims to develop methodology and indicators to review effective competition in Korean mobile telecommunication market. After examining strengths and weaknesses of other countries' experiences, we proposed several indicators for the assessment of competition. Developed from criteria such as transparency, regulation cost, policy objectives, proposed indicators comprise market structure, behaviour of sellers and consumers, and consumer benefits. These indicators are applied to the Korean mobile market. During the period 2001-2004, 'the competition assessment index' increased steadily, meaning the state of competition was aggravated during this period.

• The Journal of the Korean dental association
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• v.54 no.12
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• pp.971-984
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• 2016

The increase rate of dentists' competition is very fast at metropolitan areas in South Korea. We compare metropolitan and rural parameters to investigate the relation between competition and revenue variation. The competition and revenue variables of 73 metropolitan and 75 rural areas were calculated from 2010 Census of Service Industry microdata which include non-insurance revenues of dental clinics. Independent sample t-test results showed that the level of competition among dental clinics in metropolitan areas is higher. The lowest and the low ranked revenues are higher in rural areas. The highest and the average revenues are higher in metropolitan areas. But, 25 percentile and median revenues has no significant difference between two areas. Simple log linear regression results showed that the number of clinics could explain the distribution of revenues in both areas better than the density of active dentists and Herfindahl-Hirschman index. In the areas with many clinics have high maximum and average revenues and low minimum revenues. The increasing rate of maximum revenues is higher in metropolitan areas though the decreasing rate of minimum revenues is higher in rural areas. Metropolitan areas have higher Gini coefficients than rural areas, but the increasing rate of Gini coefficients is lower than rural areas. Findings from this study are useful reference when the dentists select the opening areas. One is that the median revenues between metropolitan and rural areas have no significant difference. The other is that the rural areas ensure the more stable and uniform revenues. The results would help to relieve the consumptive competition among dentists and to achieve the distributional efficiency of dental human resources.

• Journal of Communications and Networks
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• v.13 no.5
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• pp.499-510
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• 2011

Any server offering a routing service in the Internet would naturally be in competition for clients, and clients may need to utilize service from a specific server in order to achieve a desired result. We study the various properties of this competition, such as the fraction of route requests handled by a routing service provider and the fraction of total revenue obtained. As the routing service providers (i.e., servers or routers in this context) compete, they may alter behavior in order to optimize one of the above properties. For example, a service provider may lower the price charged for its service, in order to increase the number of clients served. Our models are based on servers offering a routing service to clients within representative network topologies based on actual Internet sub-graphs. These models provide, a framework for evaluating competition in the Internet. We monitor key aspects of the service, as several variables are introduced into the models. The first variable is the fraction of client requests that will pay more for a better quality route. The remaining requests are normal client requests that are satisfied by the most economical route. The second variable is the fraction of servers who choose to lower service prices in order to maximize the number of client requests served. As this fraction increases, it is more likely that a server will lower the price. Finally, there are some resource constraints applied to the model, to increase the difficulty in providing a routing solution, i.e., to simulate a realistic scenario. We seek to understand the effect on the overall network, as service providers compete. In simple cases, we show that this competition could have a negative impact on the overall efficiency of a service. We show that the routing variety present in the larger models is unable to mask this tendency and the routing service performance is decreased due to competition.