• The Mathematical Education
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• v.50 no.3
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• pp.337-354
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• 2011

The purpose of the study was to investigate how students understand multiplication and division of fractions and how their understanding influences the solutions of fractional word problems. Thirteen students from 5th to 6th grades were involved in the study. Students' understanding of operations with fractions was categorized into "a part of the parts", "multiplicative comparison", "equal groups", "area of a rectangular", and "computational procedures of fractional multiplication (e.g., multiply the numerators and denominators separately)" for multiplications, and "sharing", "measuring", "multiplicative inverse", and "computational procedures of fractional division (e.g., multiply by the reciprocal)" for divisions. Most students understood multiplications as a situation of multiplicative comparison, and divisions as a situation of measuring. In addition, some students understood operations of fractions as computational procedures without associating these operations with the particular situations (e.g., equal groups, sharing). Most students tended to solve the word problems based on their semantic structure of these operations. Students with the same understanding of multiplication and division of fractions showed some commonalities during solving word problems. Particularly, some students who understood operations on fractions as computational procedures without assigning meanings could not solve word problems with fractions successfully compared to other students.

• Journal of the Korean Operations Research and Management Science Society
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• v.39 no.2
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• pp.1-19
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• 2014

Recently, one of the core keywords in information technology (IT) as well as areas such as business management is big data. Big data is a term that includes technology, personnel, and organization required to gather/manage/analyze collection of data sets so large and complex that it becomes difficult to manage and analyze using traditional tools. The military has been accumulating data for a long period due to the organization's characteristic in placing emphasis on reporting and records. Considering such characteristic of the military, this study verifies the possibility of improving the performance of the military organization through use of big data and furthermore, create scientific development of operation, strategy, and support environment. For this purpose, the study organizes general status and case studies related to big data, traces back examples of data utilization by Korean's national defense sector through US military data collection and case studies, and proposes the possibility of using and applying big data in the national defense sector.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1994.04a
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• pp.13-20
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• 1994

We consider the satellite cluster scheduling problem which is one of the most interesting problems in satellite communication scheduling area. This problem is known to be NP-complete and a couple of heuristic algorithms had been developed. In this paper, we suggest another algorithm for this problem which has the same computational complexity as the best existing one and provides much better solution quality. Extensive computational simulation results are reported.

• Journal of the military operations research society of Korea
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• v.12 no.1
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• pp.38-49
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• 1986

Cryptography attempts to protect information by altering its form to make it unreadable to all but the authorized readers. DBMS is a most important computer application area requiring data security, but only a few cryptosystems are suggested for the database encryption. This research develops a new Residue-Coded Cryptosystem based on the Chinese Remainder Theorem, which is considered to be more efficient than the database encryption scheme introduced by Davida, Wells and Kam in 1981.

• Journal of the Korean Operations Research and Management Science Society
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• v.38 no.3
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• pp.13-22
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• 2013

Queueing system with scheduled arrivals is useful in many fields where both customers' waiting time and servers' operation time (utilization) are important, and arrival time of customers is possible to be controlled. In this paper, we analyzed the operation of ship maintenance with the queueing system with scheduled arrival. Based on the model presented by Pegden and Rosenshine [8], who dealt with exponential service time, we extended the service time distributions to phase-type distribution which is able to include a wide range of real stochastic phenomena. Since most activities in the military are carried out under tight control and schedule, scheduled arrival queue has quite good applicability in this area. In this context, we applied queue with scheduled arrival to the optimal booking time decision for the ship maintenance in the navy.

• Journal of the military operations research society of Korea
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• v.17 no.1
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• pp.159-176
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• 1991

The probability of target survival is the most important factor in the target assignment, Most of the studies about it have assumed the case of one target and ane weapon type. Therefore, they can not be applied to the real situation. In this paper. the quantity and type of enemy assets of the friendly force are considered simultaneously. Considered defense type is the coordinated defense with no impact point prediction. The objective function is to minimize the expected total survival value of targets which are scattered in the defense area. The rules of aircraft assignment are as follows : first, classify targets into several groups, each of those has the same desired damage level secondly. select the critical group which has the least survival value in accordance with the additional aircraft assignment, and finally. assign the same number of attack assets against each target in the critical group. In this paper, the attack assets, the escort assets, and the defense assets are considered. The model is useful to not only the simple aircraft assignment problem but also the complicated wargame models.

• Journal of the Korean Operations Research and Management Science Society
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• v.23 no.3
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• pp.169-184
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• 1998

Despite the adoption of advanced computer technologies by organizational makers, the actual use of E-mail by managers and professionals has tended to be lagging and the potential benefits of these technologies have not been fully realized. Much of the prior research in this area has focused on the utility or perceived usefulness of E-mail as the principal motivating factor in using them. Relatively little attention has been given to the recreational basis of E-mail usage. The limited research in this area indicates the use of E-mail can be stimulated by the intrinsic joy and enjoyment derived. The objective of this study is to integrate these perspectives on the reasons underlying the use of E-mail and to examine simultaneously the relative influence of motivators identified in the literature as affecting individuals' decision to use E-mail. The study focuses specifically on E-mail because of its ubiquitous usage.

• Journal of the Korean Society for Library and Information Science
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• v.34 no.3
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• pp.5-23
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• 2000

The purpose of this study is to explore ways to imporve bookmobile operations by investigating bookmobiles' operating status and users' behavior in DaeJeon City. Concerning the bookmobiles operated in 32 areas of DaeJeon City, the suitability of visiting area and staying hours, the correlation between users' circumstances and lending aspects, the effects of bookloan shop in the same area, etc. are analyzed, and for the improvement of bookmobile operations, the utilization of volunteers, the connection with the main libraries' collection, the development of service programs, the strengthening of publicity activities, etc. are proposed.

• IE interfaces
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• v.24 no.1
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• pp.51-57
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• 2011

The traveling purchaser problem (TPP) is a generalization of the well-known traveling salesman problem (TSP), which has many real-world applications such as purchasing the required raw materials for the manufacturing factories and the scheduling of a set of jobs over some machines, and many others. In the last decade, TPP has received some attention of the researchers in the operational research area. However, all of the past researches for TPP are restricted on a single purchaser (vehicle). It could be the limitation to solve the real world problem. The purpose of this paper is to suggest the capacitated multiple TPP (CMTPP). It could be used in inbound logistics optimization in supply chain management area and many others. Since TPP is known as NP-hard, we also developed the heuristic algorithm to solve the CMTPP.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2001.10a
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• pp.128-131
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• 2001

With the advent of the Internet, data centric computing applications, and e-business applications, virtually all network-stored data has become mission critical in nature. This increasing reliance on the access to enterprise data is challenging the limitations of traditional server-storage solutions. As a result, the ongoing need to add more storage, serve more users and back up more data has given rise to the concept of a SAN(Storage Area Network), “a network whose primary purpose is the transfer of data between computer systems and storage elements and among storage elements.” The purpose of this article is to help the managers and researchers make the understanding of a SAN as the possibility of new data repository in e-business era. This paper provides a thorough literature review on this new concept including its structure, its benefits and disadvantages, and its underlying issues.