• The Journal of the Acoustical Society of Korea
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• v.21 no.6
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• pp.566-575
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• 2002

Low-titrate audio coding enables a number of Internet and mobile multimedia streaming service more efficiently. For the help of next-generation mobile telephone technologies and digital audio/video compression algorithm, we can enjoy the real-time multimedia contents on our mobile devices (cellular phone, PDA notebook, etc). But the limited available bandwidth of mobile communication network prohibits transmitting high-qualify AV contents. In addition, most bandwidth is assigned to transmit video contents. In this paper, we design a novel and simple method for reproducing high frequency components. The spectrum of high frequency components, which are lost by down-sampling, are modeled by the energy rate with low frequency band in Bark scale, and these values are multiplexed with conventional coded bitstream. At the decoder side, the high frequency components are reconstructed by duplicating with low frequency band spectrum at a rate of decoded energy rates. As a result of segmental SNR and MOS test, we convinced that our proposed method enhances the subjective sound quality only 10%∼20% additional bits. In addition, this proposed method can apply all kinds of frequency domain audio compression algorithms, such as MPEG-1/2, AAC, AC-3, and etc.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.11 no.5
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• pp.38-45
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• 2012

Finding shortest paths on time dependent networks is an important task for scheduling and routing plan and real-time navigation system in ITS. In this research, one-to-one time dependent shortest path algorithms based on link flow speeds on urban networks are proposed. For this work, first we select three general shortest path algorithms such as Graph growth algorithm with two queues, Dijkstra's algorithm with approximate buckets and Dijkstra's algorithm with double buckets. These algorithms were developed to compute shortest distance paths from one node to all nodes in a network and have proven to be fast and efficient algorithms in real networks. These algorithms are extended to compute a time dependent shortest path from an origin node to a destination node in real urban networks. Three extended algorithms are implemented on a data set from real urban networks to test and evaluate three algorithms. A data set consists of 4 urban street networks for Anaheim, CA, Baltimore, MD, Chicago, IL, and Philadelphia, PA. Based on the computational results, among the three algorithms for TDSP, the extended Dijkstra's algorithm with double buckets is recommended to solve one-to-one time dependent shortest path for urban street networks.

• The Journal of the Korea Contents Association
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• v.20 no.4
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• pp.396-405
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• 2020

In this study, we used the big data of Voice of Customer (VOC) related to high-speed Internet products to look at the causes of perceived quality and the possibility of proactive service. In order to verify the possibility of proactive service, we collected VOC data from 13 facilities and equipment of a mobile communication service company, and then conducted 𝒙² test to verify that there was a statistically significant difference between the actual VOC observation values and expected values. We found statistical evidence that proactive service is possible through real-time monitoring for the six disability alarms among the 13 facilities and equipment, which are FTTH-R Equipment ON/OFF, FTTH-EV Line Error Detection, Port Faulty, FTTH-R Line Error Detection, Network Loop Detection, and Abnormal Limiting Traffic. Companies are able to adopt the proactive service to improve their market share and to reduce customer service costs. The results of this study are expected to contribute to the actual application of industry in that it has diagnosed the possibility of proactive service in the telecommunication service sector and further suggested suggestions on how to provide effective proactive service.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.25 no.5
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• pp.1043-1057
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• 2015

In order to recognize intelligent threats quickly and detect and respond to them actively, major public bodies and private institutions operate and administer an Intrusion Detection Systems (IDS), which plays a very important role in finding and detecting attacks. However, most IDS alerts have a problem that they generate false positives. In addition, in order to detect unknown malicious codes and recognize and respond to their threats in advance, APT response solutions or actions based systems are introduced and operated. These execute malicious codes directly using virtual technology and detect abnormal activities in virtual environments or unknown attacks with other methods. However, these, too, have weaknesses such as the avoidance of the virtual environments, the problem of performance about total inspection of traffic and errors in policy. Accordingly, for the effective detection of intrusion, it is very important to enhance security monitoring, consequentially. This study discusses a plan for the reduction of false positives as a plan for the enhancement of security monitoring. As a result of an experiment based on the empirical data of G, rules were drawn in three types and 11 kinds. As a result of a test following these rules, it was verified that the overall detection rate decreased by 30% to 50%, and the performance was improved by over 30%.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.6
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• pp.1-8
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• 2016

Current sensors are used widely in the fields of current control, monitoring, and measuring. They have become more popular with the increasing demand for smart grids in a power network, generation of renewable energy, electric cars, and hybrid cars. Although open loop Hall effect current sensors have merits, such as low cost, small size, and weight, they have low accuracy. This paper describes the design and fabrication of a 300A open loop current sensor that has high accuracy and temperature performance. The core of the current sensor was calculated numerically and the signal conditioning circuits were designed using circuit analysis software. The characteristics of the manufactured open loop current sensor of 300 A class was measured at currents up to 300 A. According to the test of the current sensor, the accuracy error and linearity error were 0.75% and 0.19%, respectively. When the temperature compensation was carried out with the relevant circuit, the temperature coefficients were less than $0.012%/^{\circ}C$ at temperatures between $-25^{\circ}C$ and $85^{\circ}C$.

• Journal of Korea Port Economic Association
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• v.24 no.4
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• pp.71-96
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• 2008

The purpose of this study is to suggest the new strategies for West coast ports, especially Mokpo Port development. This paper also analyzes the recently evolving change of shipping environment such as upsizing of vessels, horizontal and vertical integration strategies in the liner shipping industries through the mergers and acquisitions or strategic alliances, establishment of dedicated terminal and surging bunker charge. With shipping environment is rapidly changing, we examine how to cope with the current situation and suggest the solutions how to tackle shippers' and shipping companies' request. As a result of an empirical study, we found out that Mokpo Port suffers from the shortage of container cargo, container imbalance, insufficient forwarders and inland trucking service providers and hinterland transportation network system. With these obstacles settled, the number of container cargo can be induced to Mokpo Port and the regular container services between Mokpo and Chinese ports and Japanese ports loops were found to be competitive.

• International Commerce and Information Review
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• v.14 no.3
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• pp.539-558
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• 2012

The purpose of this study is examining the differences of mobile SNS's service quality, which consists data quality and system quality, among the groups that are classified by commitment and customer loyalty. For the experimental analysis, the frequency analysis was performed for general characteristics of sample. The variables were selected by factor analysis that also prove the validity of variables. The value of Cronbach's alpha was calculated to check the reliability of variables. In addition, the group was determined by the both hierarchical and hierarchical cluster analysis, then ANOVA was performed to test the hypotheses that there are differences of mobile SNS's service quality, among the groups that are classified by commitment and customer loyalty. The results of this study support that there are differences among the groups toward mobile SNS's service quality and also shows the more commitment and loyalty group is the higher recognition of mobile SNS's service quality. Thus, the companies have to realize that mobile SNS is very important key factor to success in rapidly changing business environment. In conclusion, the companies implement different customized strategy for the different group and develop the contents and the applications to maximize the commitment and loyalty of for the mobile SNS users.

• Journal of the Korean earth science society
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• v.33 no.2
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• pp.183-199
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• 2012

Previous Earth Science textbooks have mostly lacked the latest astronomical phenomena frequently being reported in mass media such as popular science magazines. One of the main directions in the revision of the 2009 National Curriculum of Korea is to actively include those phenomena. Furthermore, despite a close link between astronomy and physics, the concept of modern physics has not been actively introduced in Earth Science textbooks and at the same time the linkage of physics to astronomy has rarely been studies in physics textbooks. Therefore, the concept of integration among different fields in science is emphasized in the new National Curriculum. Transient phenomena in the high energy astrophysical objects are examples that reflect such issue. The purpose of this study is to introduce transferring a real-time data and making imaging of astronomical observations using e-Science. As a first step, we performed the first experiment for a large data transfer of astronomical observation between Korea and Japan using KOREN, a National Research and Education Test Network. We introduce actively on-going fields of e-Science in observational activities of astronomy and astrophysics, and their close interrelationship with scientific inquiry activities and public outreach activities. We discuss our experiment in the scientific and educational aspects to the primitive e-Science activity in the Korean astronomical society and, in turn, provide a prospective view for its application to the scientific inquiry activities and public outreach activities in the upcoming commercial Gbps-level internet environments.

• Journal of The Korean Astronomical Society
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• v.49 no.6
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• pp.295-306
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• 2016

We present the results of BV time-series photometry of the globular cluster NGC 288. Observations were carried out to search for variable stars using the Korea Microlensing Telescope Network (KMTNet) 1.6-m telescopes and a 4k pre-science CCD camera during a test observation from August to December, 2014. We found a new SX Phe star and confirmed twelve previously known variable stars in NGC 288. For the semi-regular variable star V1, we newly determined a period of 37.3 days from light curves spanning 137 days. The light-curve solution of the eclipsing binary V10 indicates that the system is probably a detached system. The pulsation properties of nine SX Phe stars were examined by applying multiple frequency analysis to their light curves. We derived a new Period-Luminosity (P-L) relation, ${\langle}M_V{\rangle}=-2.476({\pm}0.300){\log}P-0.354({\pm}0.385)$, from six SX Phe stars showing the fundamental mode. Additionally, the period ratios of three SX Phe stars that probably have a double-radial mode were investigated; $P_{FO}/P_F=0.779$ for V5, $P_{TO}/P_{FO}=0.685$ for V9, $P_{SO}/P_{FO}=0.811$ for V11. This paper is the first contribution in a series assessing the detections and properties of variable stars in six southern globular clusters with the KMTNet system.

• Journal of the Korean Society of Clothing and Textiles
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• v.31 no.12
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• pp.1772-1783
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• 2007

This study aimed to investigate differences in the purchasing patterns of and the levels of satisfaction with cosmetic products, and the method of disposing dissatisfied cosmetics for female university students among China, Japan and Korea. Survey was conducted with 1,200 female coeducational university students in Beijing, Tokyo and Seoul and 1,115 were used for the data analysis. Data were analysed by frequency analysis, Cronbach's ${\alpha}$, chi-square analysis, analysis of variance, Duncan's Multiple Range test. The results showed significant differences in purchasing behaviors in China, Japan and Korea. Japanese students mainly got information through objective sources, while Koreans did so through human network. Regrading the evaluative criteria for basic care items, function and effect were the most important criteria for Chinese and Korean consumers and skin compatibility for Japanese. For color make-up, Chinese, Japanese and Korean respondents respectively cared the most on brand image, convenience of purchase and the current trend. Chinese tended to shop cosmetics at department stores due to store reputation, Japanese preferred supermarkets and pharmacies and Koreans shopped at discount stores for low price. The most influential human sources were friends and colleagues for Chinese and Korean, and models on advertisements and magazines for Japanese. Korean respondents displayed the highest level of satisfaction with cosmetics followed by Japanese and Chinese. As for the methods of disposing dissatisfactory cosmetics, Chinese were the most active in exchanging for other product; Japanese and Korean were not likely to use or throw the products away.