• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.12
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• pp.59-70
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• 2003

Proposed CCRSVP (Candidate Casting RSVP) algorithm is a new fast handoff method which uses advanced multicasting method and RSVP for IEEE 802.11 Wireless LAN (WLAN) environments. The proposed algorithm shows good performance in the handoff latency and the B/W efficiency aspect and guarantees QoS because it uses L2 information (BSSID) of WLAN and starts to reserve resources and multicast packets before L2 handoff completes. We also propose a Markov chain performance analysis model in which we can analyze the handoff performance of various handoff algorithms. Using the model, we compare bandwidth efficiency of the proposed algorithm with existing handoff algorithms which use RSVP by analyzing blocking probability of session, resource usage, and the average number of ongoing session in a cell. The results show that the proposed algorithm shows better performance than the existing algorithms in the above three performance aspects.

• Journal of The Korean Association of Information Education
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• v.12 no.4
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• pp.375-384
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• 2008

Computer programming has educational effect on improving high-level thinking abilities. However, students initially have to spend too much effort in learning the basic grammar and the usage model of programming languages, which negatively affects their eagerness in learning. To remedy this problem, we propose to apply the Scratch to a Game Developing Programming Class; Scratch is an easy-to-learn and intuitive Educational Programming Language (EPL) that helps improving the Meta-cognition and Self-efficacy of middle school students. Also we used the Demonstration-Practice instruction model with self-questioning method for activating the Meta-cognition. In summary, a game developing programming class using Scratch was shown to significantly improve the Meta-cognition of middle school students. However it was shown to insignificantly improve the Self-efficacy of girl students group.

• The Journal of Korean Association of Computer Education
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• v.16 no.1
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• pp.11-22
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• 2013

Due to the advent of new smart devices, the new technology addiction problems have been much severer than the Internet addiction recently. A lot of research about each technology addiction has been proposed, but the research about the changes in the addictions has been rare. In this paper, we analyze how the environmental factors such as parents and friends affect the personal factors such as time perspectives and technology usage time. In addition, we get the relative importances among the factors which influence on the Internet and mobile phone addictions. As a result, we can analyze the relationships among the factors and the differences between the two addictions with time perspective. In order to achieve our goals, we surveyed on 1,420 primary and secondary school students. We also provided the results produced by structural equation model and Budescu's Dominance analysis. Based on these analyses, we described the differences between the Internet and mobile phone addictions and proposed an alternative to prevent new technology addictions.

• The Journal of Korean Association of Computer Education
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• v.10 no.1
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• pp.77-88
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• 2007

More flexible learning models are needed, and learning environments that operate through mobile technologies such as portable multimedia players(PMP) provide useful tools in implementing these learning models. The main attractant of PMP is often their versatility: being able to load and play different formats of video, audio, digital images, and interactive media. In this paper, we investigate the factors influencing the usage and acceptance of the PMP for study, based on the extended version of the Technology Acceptance Model (TAM). Based on data collected from online survey, we show that perceived usefulness, perceived ease of use, flow and perceived enjoyment are the major determinants for users to play PMP for study purpose. Factors, including ease of use, contents-credibility are shown to determine the level of perceived usefulness; additionally, perceived usefulness, ease of use and perceived enjoyment are shown to directly affect the level of flow. Based upon the statistical results, some useful guidelines for developing learning contents are also provided.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.1C
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• pp.18-24
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• 2004

Nowadays, the development of wireless communications provides a convenience for many people. On the other hand, the openness of wireless communications poses serious security threats and the security of wireless communications is necessary to support the secure communication channel. The common security method on wireless is the stream cipher that generates the pseudorandom number. In this paper, we propose the usage of the nonlinear function S-box and the mechanism according to it in stream cipher as the study to securely protect data transferred on wireless communications. Besides, it goes abreast a study on S-box with the best random characteristic among the used S-boxes on wireless communications. By means of test, we investigate the most appropriate S-box of DES on wireless communications environment and prove the efficiency of the proposed model by comparing and analysis of the randomness of the based stream cipher and the proposed model.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.5
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• pp.80-86
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• 2010

The conventional bus system architecture consists of masters, slaves, arbiter, decoder and so on in shared bus. As several masters can't use a bus concurrently, arbiter plays an role in arbitrating the bus. The efficiency of bus usage can be determined by the selection of arbitration method. Fixed Priority, Round-Robin, TDMA and Lottery arbitration policies are studied in the conventional arbitration method where the bus priority is primarily considered. In this paper, we propose the arbitration method that calculates the bus utilization of each master. Furthermore, we verify the performance compared with the other arbitration methods through TLM(Transaction Level Model). From the results of performance verification, the arbitration methods of Fixed Priority and Round-Robin can not set the bus utilization and those of TDMA and Lottery happen the error of 50% and 70% respectively compared with bus utilization set by user in more than 100,000 cycles. On the other hand, the bandwidth-award bus arbitration method remains the error of less than 1% since approximately 1000 cycles, compared with bus utilization set by user.

• Composites Research
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• v.29 no.5
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• pp.236-242
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• 2016

In this work, tensile and in-plane shear tests for thermoplastic glass fiber/polypropylene composites were performed at a thermo-forming temperature and their properties were characterized and mathematically expressed by using the non-orthogonal constitutive model. As for the thermo-forming test, half-dome experiments were carried out by varying the usage of a releasing agent and the weight of holders. As results, the optimum final shape having well-aligned symmetry and no wrinkle formation was obtained when the releasing agent was used, and it was found that the careful control of a holding force is crucial to manufacture the healthy product. Furthermore, FEM simulations based on the non-orthogonal model showed similar final shapes and tendency of wrinkle formation with experimental results, and confirmed that wrinkles increase with less holding force and higher punch force is required under high frictional condition.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.10
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• pp.1644-1652
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• 2003

The monitor product is packed by cushioning materials because the monitor can be broken during transportation. However, the addition of the cushioning material increased the volume of the product. Therefore, it is required that the usage of cushioning material be minimized. In practice, design engineers have followed the ad hoc design with experiences of predecessors. Automation of the design process is very important for the reduction of engineering cost, and can be achieved by an excellent design process and software development. According to Axiomatic design, a design flow is defined and a software system is developed for automated design. At first, a basic model is defined. A user can modify the model from menus and design is carried out according to the input from the user. Finite element models are automatically generated based on the design. A nonlinear finite element analysis program called LS/DYNA3D is linked for the impact analysis. The process of Design of Experiments using orthogonal array is installed to minimize the maximum acceleration in drop test. Therefore, a new design can be proposed by the system. The program is designed according to the Independence Axiom of Axiomatic design. FRs and DPs of the software system are defined and decomposed by zigzagging process. Independent modules can be generated by analysis of the full design matrix and each module is coded as class in Object Oriented Programming (OOP). Design results are discussed.

• Journal of Korea Port Economic Association
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• v.33 no.1
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• pp.61-74
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• 2017

The aim of this study is to analyze informatization competencies of the international ship supply companies at Busan port. This study comprehensively suggests certain issues attributed to the successful implementation of total information management system for ship supply. To achieve this objective, evaluation was undertaken based on the model of the National Competency Standards (NCS). This model consisted of three evaluation areas, including 20 items. Analysis of information competencies of ship supply companies was undertaken using the Importance-Performance Analysis (IPA) method. Survey data was collected from ship supply companies located in the ship supply center at Busan port. Results found that there were significant differences between importance and performance. In addition, overall informatization competency was very low. Thus, in order to ensure successful implementation of total information management system, re-education programs for ICT usage and dedicated support organization are necessary.

• Journal of Internet Computing and Services
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• v.15 no.1
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• pp.13-27
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• 2014

Agile methodologies have gained recognition as efficient development processes through their quick delivery of software, even under time constraints. However, like other agile methods such as Scrum, Extreme Programming (XP) and The Dynamic Systems Development Method (DSDM), Feature Driven Development (FDD) has been criticized due to the unavailability of security elements in its twelve practices. In order to examine this matter more closely, we conducted a systematic literature review (SLR) and studied literature for the years 2001-2012. Our findings highlight that, in its current form, the FDD model partially supports the development of secure software. However, there is little research on this topic, as detailed information about the usage of secure software is rarely published. Thus, we have been able to conclude that the existing five phases of FDD have not been enough to develop secure software until recently. For this reason, security-based phase and practices in FDD need to be proposed.