• Journal of the Korean Operations Research and Management Science Society
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• v.15 no.2
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• pp.97-104
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• 1990

The problem is a variation of the weighted set-covering problem (SCP) which requires the minimum-cost cover to be self-covering. It is shown that direct extension of the well-known greedy heuristic for SCP can have an arbitrarily large error in the worst case. It remains an open question whther these exists a greedy heuristic with a finite error bound.

• Korean Journal of Mathematics
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• v.25 no.3
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• pp.437-453
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• 2017

A new class of sets, called generalized (${\Lambda}$, b)-closed sets, has been introduced and studied. Also, several properties of generalized (${\Lambda}$, b)-closed sets are investigated. Some characterizations of ${\Lambda}_b$-regular spaces and ${\Lambda}_b$-normal spaces are discussed.

• Communications of the Korean Mathematical Society
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• v.33 no.4
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• pp.1181-1203
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• 2018

In this paper, we are mainly devoted to find out the general meromorphic solution of some specific type of differential equation. We have also answered an open question posed by Banerjee-Chakraborty [4] by extending their results in a large extent. We have provided an example showing that the conclusion of the results of Zhang-Yang [16] is not general true. Some examples have been exhibited to show that certain claims are true in our main result. Finally some questions have been posed for the future research in this direction.

• Journal of Scientific & Technological Knowledge Infrastructure
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• s.9
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• pp.8-19
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• 2002

The Dublin Core element set has been developed over the past years as an open, consensus-building metadata from many user communities. Wider adoption in many countries made this metadata a major resource discovery standard on the internet. The version 1.1 of the Dublin Core element set was adopted as CEN Workshop Agreement 13874 in Europe, and also ratified under the auspices of the National Information Standards Organization in US as ANSI Standard Z39.85. This report summarizes the standardization activities that have taken place in the Dublin Core Metadata Initiative for the past years.

• Journal of the Korean Institute of Intelligent Systems
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• v.20 no.4
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• pp.569-573
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• 2010

We introduce the concept of fuzzy r-minimal preopen set on a fuzzy minimal space. We also introduce the concept of fuzzy r-M precontinuous mapping which is a generalization of fuzzy r-M continuous mapping, and investigate characterization of fuzzy r-M precontinuity.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1382-1383
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• 2011

결정질 실리콘 태양전지에서 전극 형성 공정은 Voc(Open-circuit voltage), Isc(Short-circuit current), Rser(Series resistance), Rshunt(Shunt resistance), FF(Fill factor) 특성에 영향을 주기 때문에 매우 중요하다. 하지만 paste와 선 공정에서의 조건에 따라 특성이 바뀌기 때문에 소성 공정을 최적화하기는 쉽지 않다. 본 연구에서는 Gravure Off-set printing 방식을 이용하여 결정질 실리콘 기판 표면에 미세 전극 형성 공정을 하고 소성 조건 최적화를 위해 peak 온도와 ramp-up 속도를 변화시켜 각 조건별 특성을 비교하였다. Peak 온도가 커질수록, contact resistance의 감소에 따라 Rser가 줄어들었다. 본 연구를 통해 Voc는 619mV, FF는 77.9%로 측정되는 Gravure Off-set 태양전지에 최적화된 소성 공정 조건을 확보하였다.

• Communications of the Korean Mathematical Society
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• v.11 no.3
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• pp.665-672
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• 1996

Let U denote the set of all Schwarzian derivatives $S_f$ of conformal function f in the unit disk D. We show that if $S_f$ is a local extreme point of U, then f cannot omit an open set. We also show that if $S_f \in U$ is an extreme point of the closed convex hull $\bar{co}U$ of U, then f cannot omit a set of positive area. The proof of this uses Nguyen's theorem.

• Bulletin of the Korean Mathematical Society
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• v.59 no.1
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• pp.167-177
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• 2022

A vertex v of a graph G = (V, E) is said to ve-dominate every edge incident to v, as well as every edge adjacent to these incident edges. A set S ⊆ V is called a double vertex-edge dominating set if every edge of E is ve-dominated by at least two vertices of S. The minimum cardinality of a double vertex-edge dominating set of G is the double vertex-edge domination number γ_dve(G). In this paper, we provide an upper bound on the double vertex-edge domination number of trees in terms of the order n, the number of leaves and support vertices, and we characterize the trees attaining the upper bound. Finally, we design a polynomial time algorithm for computing the value of γ_dve(T) for any trees. This gives an answer of an open problem posed in [4].

• Journal of Internet Computing and Services
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• v.18 no.2
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• pp.1-11
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• 2017

There are two kinds of wireless network access to a certain place by using smart devices - 1) open (anonymous) - access and 2) user-authorized access. The open-access is a non-authorization connection method which does not need to require Smart device's user authorized information. It means open-access use only user's SSID (Service Set Identifier) information to access the wireless AP devices following public wireless network standard. This access mechanism is not suitable to use all of public wireless networks because users have to get all wireless network information around them. As a result, huge data for smart devices should be one of the most critical overload problems for them. Secondly, the user-authorized access method uses wireless network information (SSID and password) chosen by the users. So, the users have to remember and use the network access information data manually whenever accessing the network. Like open-access, this access method also has the operational and inconvenient problem for the users - manually inputting access information whenever connecting to the network. To overcome this problem in both schemes, we propose two improved wireless network access methods: 1) the implementation of automatic AP connection mechanism using user-authorization and iBeacon messages, and 2) SSID registration form for public wireless networks.

• Journal of Information Technology Services
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• v.21 no.4
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• pp.1-26
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• 2022

Recently, the number of cases of purchasing food online has been increased, especially in the open market. Therefore, we examined the characteristics of status quo bias and switching costs in the open market. Also, in this study, the causal relationship between the characteristics of status quo bias and switching costs, switching costs and switching intention in the open market was investigated. The analysis result consists of four parts as follows. First, in the open market, rational decision making, which belongs to the characteristics of status quo bias, was found to have a positive (+) effect on time switching cost among switching costs, but did not have a positive (+) effect on economic and psychological switching cost. Second, cognitive misperceptions was consistent with the assumption that it have a positive (+) effect on all of the economic, time, and psychological switching cost, which are switching costs in the open market. Third, psychological commitment was found to have a positive (+) effect on economic and time switching cost among switching costs, but did not have a positive (+) effect on psychological switching cost. Fourth, psychological switching cost, which belongs to switching costs in the open market, was found to have a negative (-) effect like the hypothesis set in switching intention. However, it was found that economic and time switching cost did not have a negative (-) effect on switching intention. This study subdivided the switching costs into three dimensions and compared the degree of influence on the switching intention, and the degree of influence was different for each dimension. Therefore, it was found that when switching from the existing open market to the new open market, it is not possible to simply judge that the switching costs directly has a negative (-) effect on the switching intention or does not.