• Journal of the Korea Society of Computer and Information
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• v.20 no.6
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• pp.1-11
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• 2015

Recently, NAND flash memories are used for storage devices because of fast access speed and low-power. However, applications of FTL on low power computing devices lead to heavy workloads which result in a memory requirement and an implementation overhead. Consequently, studies of B+-Tree on embedded devices without the FTL have been proposed. The studies of B+-Tree are optimized for performance of inserting and updating records, considering to disadvantages of the NAND flash memory that it can not support in-place update. However, if a general garbage collection method is applied to the previous studies of B+-Tree, a performance of the B+-Tree is reduced, because it generates a rearrangement of the B+-Tree by changing of page positions on the NAND flash memory. Therefor, we propose a novel garbage collection method which can apply to the B+-Tree based on the NAND flash memory without the FTL. The proposed garbage collection method does not generate a rearrangement of the B+-Tree by using a block information table and a proxy block. We implemented the B+-Tree and ${\mu}$-Tree with the proposed garbage collection on physical devices with the NAND flash memory. In experiment results, the proposed garbage collection scheme compared to greedy algorithm garbage collection scheme increased the number of inserted keys by up to about 73% on B+-Tree and decreased elapsed time of garbage collection by up to about 39% on ${\mu}$-Tree.

• Journal of Digital Convergence
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• v.12 no.11
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• pp.289-298
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• 2014

Recently, the traditional paradigm in railroad technology is changing as more efficient and cost-effective electric vehicle (EV) technologies have emerged. The original concept of PRT (Personal Rapid Transit) proposed in the past has come to be regarded as unrealistic, but its feasibility is improving through the utilization of an EV platform. In particular, battery-powered vehicles pose difficult technical challenges in attempts to achieve reliable and efficient operation. However, based on the inductive power transfer (IPT) technology, the fast charging of supercapacitors with high energy density can contribute to overcoming this technical challenge and promote the transition to electric-powered ground transportation by improving the appearance of cities. This study discusses the development process of a power supply system for PRT, including concept design, numerical analysis, and device manufacturing, along with performance predictions and evaluations. In terms of results, the system was found to meet the performance requirements for power supply modules on a test-bed.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.146-149
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• 2013

For in recently years, global cellular network service is changing rapidly to 4G. However, the fast introducing of 4G has been going with not enough research about security threat, it could be many kind of vulnerability. Therefore the research about security threat on 4G network is ongoing in external countries, but not sufficient in domestic. particularly in domestic situation of rapidly increased subscribers, The security threats which are hindering stability and usability could make a fatal effect on many users. 4G network should be considered about the feature of mobile network to protect 4G network stable. Mobile network has limited radio resources, it releases the radio resource which is not used in selected time and reallocate when detected the data transmission. Many signaling messages are transferred in the network entities to allocate or release the radio resource. In this paper, it will be introduced the technology to detect signaling DoS traffic hindering the stability and usability of network entities managing the radio resources by huge signaling message from the repetitive wireless connection/release message.

• Korean Security Journal
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• no.15
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• pp.337-358
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• 2008

With the Japanese attacks on Pearl Harbor in 1941, approximately 2,500 people were killed. The terrorist attack on World Trade Center in the United States resulted in the heavy loss of people's lives, 2,749 in all. The 9.11 demonstrated that terrorist attack could be more serious problem than the war in our modern life. In addition, terrorist armed with new and high technologies have become more dangerous elements to the international community. Especially, the fact that the weapons of mass destruction are used by terrorist organizations is a matter of great concern. The strength of terrorist arsenal gives terrorist a decided advantage over us. The chances of success for terrorist have been increased due to the terrorist friendly environments. Terrorism has evolved without stopping from its birth, which is imposing a great burden on the authorities concerned. The counter-terrorism strategy and tactics used in the past have been useless in the fighting against new terrorism. To cope with the fast changing terrorism, comprehensive countermeasures should be developed. The purpose of this study is to know the enemy. To achieve the goal, the current situation on international terrorism as a whole is examined. Based on the result of the research, this paper also tried to give a perspectives on the future terrorism. At the same time, it provides a guidelines of the direction in the fighting against terrorism.

• The Journal of the Korea Contents Association
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• v.13 no.4
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• pp.481-496
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• 2013

The purpose of this study was to make a basic research on college cultural contents education in an effort to step up the manifestation of the creativity of cultural contents experts in line with the development of the fast-changing era of creative economy. It's basically meant to analyze the characteristics of cultural contents education in relation to creative idea to seek practical ways of improving that education. What problems there were with cultural contents education and how that education was actually provided were analyzed to suggest some of the right directions for client-centered cultural contents education. Earlier studies were analyzed, and the results of a survey that was conducted on students whose major was linked to cultural contents were analyzed as well. As a result, current cultural contents education was considered not to be satisfactory due to existing teaching methods, learning process and curriculums that were devoid of creativity. To rectify the situation, interdisciplinary attempts should be made such as multi-major, interdisciplinary programs or convergence education, and plenty of experiments, sufficient practice and an increase in the number of faculty members are all required. In terms of education, existing curriculums and courses should urgently be revamped to strengthen field placement and creative discussions. As for educational methods, the lecture method should be avoided, and specialized education should be offered instead, which should strike a balance between discussion, team play and project education. It is expected to produce good results if there are appropriate connection among different major fields of study and the harmonious implementation of diverse internship, convergence and field placement programs.

• Korean Business Review
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• v.19 no.2
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• pp.261-274
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• 2006

Airline business operates in the 21st century within fast changing market environment and fierce competition. Management of airline companies has faced the need for vast adaptation to new trends in the growth of world economy that are cardinal changes in marketing environment due to quick development of Internet and IT, transport price competition and, as a consequence, low profit margin, diversified customer wants and needs, lack of investment needed for new aircraft equipped with the latest high tech innovations, unpredictable oil price changes, and exchange rate fluctuations. This study is aimed to evaluate the quality performance of cabin service, to analyse, further, the issues that appeared to be the most significant among customers' answers to questionnaire, to explore the relationships between these issues and customer satisfaction, to highlight the essential questions to address, and to provide some practical suggestions. The five dimensions (such as tangible, reliability, responsiveness, assurance, and empathy) were adopted to examine the relationship between the service quality and customer satisfaction of Mongolian and non-Mongolian passengers travelling by the MIAT. According to findings of analysis made with use of the SERVPERF model, it can be concluded that Mongolian travellers' satisfaction was effected by 'Tangible' and 'Responsiveness' dimensions of service quality, whereas the 'Empathy' dimension has more impact on the satisfaction of non-Mongolian.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.42 no.6
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• pp.37-48
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• 2005

The efficiency of power supply circuits such as DC-DC converters and batteries varies on the trend of the power consumption because their efficiencies are not fixed. To analyze the efficiency of power supply circuits, we need the temporal behavior of the power consumption of the loads, which is dependent on the activity factors of the devices during the operation. Since it is not easy to model every detail of those factors, one of the most accurate power consumption analyses of power supply circuits is measurement of a real system, which is expensive and time consuming. In this paper, we introduce an active load emulator for embedded systems which is capable of power measurement, logging, replaying and synthesis. We adopt a pattern recognition technique for data compression in that long-term behaviors of power consumption consist of numbers of repetitions of short-term behaviors, and the number of short-term behaviors is generally limited to a small number. We also devise a heterogeneous structure of active load elements so that low-speed, high-current active load elements and high-speed, low-current active load elements may emulate large amount and fast changing power consumption of digital systems. For the performance evaluation of our load emulator, we demonstrate power measurement and emulation of a hard drive. As an application of our load emulator, it is used for the analysis of a DC-DC converter efficiency and for the verification of a low-power frequency scaling policy for a real-time task.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.45 no.1
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• pp.37-47
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• 2008

Exploitation of address generation units which are typically provided in DSPs plays an important role in DSP code generation since that perform fast address computation in parallel to the central data path. Offset assignment is optimization of memory layout for program variables by taking advantage of the capabilities of address generation units, consists of memory layout generation and address pointer assignment steps. In this paper, we propose an effective address pointer assignment method to minimize the number of address calculation instructions in DSP code generation. The proposed approach reduces the time complexity of a conventional address pointer assignment algorithm with fixed memory layouts by using minimum cost-nodes breaking. In order to contract memory size and processing time, we employ a powerful pruning technique. Moreover our proposed approach improves the initial solution iteratively by changing the memory layout for each iteration because the memory layout affects the result of the address pointer assignment algorithm. We applied the proposed approach to about 3,000 sequences of the OffsetStone benchmarks to demonstrate the effectiveness of the our approach. Experimental results with benchmarks show an average improvement of 25.9% in the address codes over previous works.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.44 no.5
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• pp.45-53
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• 2007

To recover transmitted signal perfectly at DTV receiver, we have to acquire carrier frequency synchronization to compensate pilot signal which located in wrong position and rotated phase. Also, we need a symbol timing synchronization to compensate sampling timing error. Conventionally, to synchronize symbol timing, we use Gardner's scheme which used in multi-level signal. Gardner's scheme is well known for its sampling the timing error signal from every symbol and it makes easy to detect and keep timing sync in multi-path channel. In this paper, to discuss the problem when the received power level is out of range and we cannot get synchronization information. With this problem, we use 2 step procedures. First, we put a received signal power compensation block before Garder's timing error detector. Second, adaptive loop filter to get a fast synchronization information and averaging loop filter's output value to reduce the amount of jitter after synchronization in PLL(Phased Locked Loop) circuit which is used to get a carrier frequency synchronization and symbol timing synchronization. Using the averaging value, we can estimate offset. Based on offset changing ratio, we can adapt adaptive loop filter to carrier frequency and symbol timing synchronization circuit.

• Journal of Korea Game Society
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• v.11 no.6
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• pp.127-138
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• 2011

The creation and interchange of information through the Internet network forms online community and makes Social Network Game (SNG) as a new entertainment by grafting it onto the most popular online games. SNG means the service which amalgamates social network service (e.g., Facebook, Twitter, etc) strong points and the fun of online game. It promotes the intimacy of relation between the friends above social network service and the gaming amusement for users. The domestic SNG market is currently fast changing according to the smart environment which is quickly shifted. The existing online game field will continuously maintain a market size. SNOG will be more developed because it is competitive from the business perspective of managing cost and production cost when compares with the existing online game. In relation to Facebook, Twitter, etc. overseas SNS platform base SNOG service, the domestic competition for launching SNG is expected to heat up as NHN, Daum and SK Communication introduce open type SNS. This study examines the successful factors and strategy for domestic SNOG by studying the case of MapleStory Adventures successful possibility. The possible successful factors are combing SNS on the existing popular online game, marketing through the existing users, and solving the platform problem of a failure factor of NexonStar. This case study is expected to contribute to the domestic SNOG industry development by providing several implications for the successful factors and strategy of SNOG which will be continuously developed.