• Journal of KIISE:Computer Systems and Theory
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• v.26 no.8
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• pp.957-965
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• 1999

그룹간 공동 작업이나 화상 회의와 같은 그룹 통신의 수요가 늘어나면서 멀티캐스팅을 이용한 효율적인 데이타 전송에 대한 요구가 증가하고 있다. 특히 오디오나 비디오 데이타와는 달리 공동 문서 작업이나 그룹간 문서 전송을 위한 데이타 처리를 위해서는 어느 정도의 시간 손실이 있더라도 신뢰성을 보장할 수 있는 멀티캐스트 프로토콜이 요구된다. 그러나 멀티캐스트 전송에서의 신뢰성을 보장하기 위하여 손실 패킷에 대한 재전송 패킷이 전체 그룹으로 멀티캐스트 되는 것은 네트워크 상에 트래픽을 폭증시키는 요인이 된다. 이에 본 논문에서는 지역 그룹에서의 오류 회복을 위한 재전송 제한 기법을 제안하여 손실 패킷의 재전송 과정에서 발생하는 트래픽의 폭주를 제어하고자 한다. 이것은 재전송 패킷이 중복없이 다중 수신자에게 전송될 수 있도록 하여 그룹 내의 재전송 패킷의 양을 줄이고 필요없는 중복 패킷이 네트워크의 효율을 저하시키는 것을 방지하고자 하는 데 그 목적이 있다. Abstract As the size and the geographic span of communication groups increases, efficient data transmission schemes using Multicast service become more and more essential. Especially, unlike audio and video applications, for some collaborative applications and other data delivery components which require ordered and lossless delivery of data, Reliable Multicast Service is needed to ensure consistent presentation across multiple views. Thus error recovery by retransmission of loss data is provided in order to guarantee the reliability of multicast transmission protocol. However, redundant retransmission packets by multicast may cause traffic implosion on the Internet and it can be aggravated with continuous retransmission.This paper describes a Restricted Retransmission Mechanism as an error recovery method of multicast service in a local group, which can handle traffic implosion in retransmission process. It reduces redundant retransmission packets flowing into a local group and supports reliable multicast transmission. The goal of this mechanism is to reduce retransmission packets and decrease the load for group members and networks.

• The Journal of Korean Association of Computer Education
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• v.7 no.3
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• pp.67-78
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• 2004

Since the 7th National Curriculum was established, ICT has emerged as an indispensable tool for teaching a variety of subjects in K-12 education systems. This paper develops the model for explaining the factors affecting students' satisfaction level in using web contents for science class. Based on data collected from a questionnaire survey from the students who evaluated the web sites providing the information related to the science subject, the structural equation model is presented. From this model, a following conclusion is provided : credibility and understandability/motivation are the most important factors affecting the level of satisfaction, but the presentation method, the screen design as well as contents itself has indirect impact on user satisfaction through understandability/motivation. Other interesting results are also provided. This result might provide the useful guidelines for designing the web-contents for science class in high school.

• Archives of design research
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• v.13 no.1
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• pp.157-166
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• 2000

Since the cognitive science developed as a brandl of academic researdl, studies on human brains have flourished. Emotional features have been centered on the field of design, and the development of the design process has been diversified that makes use of the factors. The purpose of this study is to reflect the current trend and to convert the results into a method for designing. The researdl is based on the mind map techniques which spread like a trendy fashion, and tries to supply a theoretical explanation of how to overcome the fixed idea. Recognizing the importance of learned information in approaching a problem, I regarded the roles of left and right brain as analogue and digital images interpreting them by freely crossing language(digital images) and visual thought (analogue images), using mapping tedlniques. I pursued the research goal of the techniques focusing on the idea of using mapping. As a result of this. I established a logic system [figure 8] in that a proposition which starts as a problem introduction goes on until a problem solution, which is visualized with concept presentation, using a brainstorming technique. According to the suggested concept. I concluded that idea proliferation as a design demand can be solved by applying mapping techniques like one shown in figure 12.

• Journal of Internet Computing and Services
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• v.11 no.4
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• pp.1-10
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• 2010

As recent fusion industry and ubiquitous technology have grown fast, network contents, which require high load, are provided in various infrastructures and facilities such as u-city and smart phones. Therefore, it is anticipated that the playback quality of multimedia compared to network loads degrades dramatically due to the drastic increment of real-time reference of conventional high load contents (eg. multimedia data). In this paper, we improved the method of the traffic assignment based on MPP which elevated the playback quality of multimedia by assigning discriminately the possible traffic of MMS with TP coefficients. When the TP coefficient which combines content preference with media preference was applied to a real-time traffic assignment scheduler, the simulation results showed that the multimedia playback stream was assigned within the possible traffic of a server. The real-time scheduling algorithm was improved by using the TP coefficient that combines the time-dependent image contents and the weighted value of media preference. It was observed from the experiment that the loss of the possible traffic decreases to 3.91% and 3.88% for three and four clients respectively.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.70.1-70.1
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• 2012

In-situ X-ray photoelectron spectroscopy (XPS) and infrared (IR) spectroscopy studies of SOFC cathode materials will be discussed in this presentation. The mixed conducting perovskites (ABO3) containing rare and alkaline earth metals on the A-site and a transition metal on the B-site are commonly used as cathodes for solid oxide fuel cells (SOFC). However, the details of the oxygen reduction reaction are still not clearly understood. The information about the type of adsorbed oxygen species and their concentration is important for a mechanistic understanding of the oxygen incorporation into these cathode materials. XPS has been widely used for the analysis of adsorbed species and surface structure. However, the conventional XPS experiments have the severe drawback to operate at room temperature and with the sample under ultrahigh vacuum (UHV) conditions, which is far from the relevant conditions of SOFC operation. The disadvantages of conventional XPS can be overcome to a large extent with a "high pressure" XPS setup installed at the BESSY II synchrotron. It allows sample depth profiling over 2 nm without sputtering by variation of the excitation energy, and most importantly measurements under a residual gas pressure in the mbar range. It is also well known that the catalytic activity for the oxygen reduction is very sensitive to their electrical conductivity and oxygen nonstoichiometry. Although the electrical conductivity of perovskite oxides has been intensively studied as a function of temperature or oxygen partial pressure (Po2), in-situ measurements of the conductivity of these materials in contact with the electrolyte as a SOFC configuration have little been reported. In order to measure the in-plane conductivity of an electrode film on the electrolyte, a substrate with high resistance is required for excluding the leakage current of the substrate. It is also hardly possible to measure the conductivity of cracked thin film by electrical methods. In this study, we report the electrical conductivity of perovskite $La_{0.6}Sr_{0.4}CoO_{3-{\delta}}$ (LSC) thin films on yttria-stabilized zirconia (YSZ) electrolyte quantitatively obtained by in-situ IR spectroscopy. This method enables a reliable measurement of the electronic conductivity of the electrodes as part of the SOFC configuration regardless of leakage current to the substrate and cracks in the film.

• Publications of The Korean Astronomical Society
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• v.36 no.2
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• pp.37-45
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• 2021

We have analyzed 42 research papers regarding on the solar astronomy written by North Korea scientists to investigate the current status of astronomical activities in North Korea. The papers are surveyed from the 'Bulletin of Astronomy', the 'Physics', the 'Bulletin of Academy of Science', and the 'Natural Science' in North Korea, and SCI journals. In addition, we refer to the presentation material announced in the 2015 IAU by director of Pyongyang Astronomical Observatory (PAO) and the 2013 OAD/IAU reports. We have analyzed the papers statistically according to three criteria such as research subject, research field, and research members. The main research subjects are the sunspot (28%), observation system (21%), and space environments (19%). The research fields are distributed with data analysis (50%), numerical method (29%), and instrument development (21%). There have been 25 and 9 researchers in the solar astronomy and space environment, respectively since 1995. North Korea's solar research activities were also investigated in three area: instrument, solar physics, and international research linkage. PAO has operated two of sunspot telescope and solar horizontal telescope for spectroscopy and polarimetry, but there is no specific information on solar radio telescopes. North Korea has cooperated in solar research with Europe and China. We expect that the results of this study will be used as useful resource in supporting astronomical cooperation between South and North Korea in the future.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.20 no.6
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• pp.214-227
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• 2021

The purpose of this study is to find the driving difficulty of automated vehicles in terms of road infrastructure operation. It was judged out of this study that the level of automated driving would be enhanced if the road situation recognition ability was advanced through the presentation of infrastructure information during the difficult driving situations. The difficulty evaluation index was divided into three stages, and a survey of experts and an AHP were conducted. The result of the AHP showed that the driving difficulty of the interrupted flow was much higher than that of the uninterrupted flow. The AHP results also showed that and the driving difficulty of unsignalized intersections and roundabouts under an interrupted flow was evaluated as the highest. The top six driving situations with high difficulty were also evaluated to occur under unsignalized intersections and roundabouts.

• Journal of Korea Water Resources Association
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• v.55 no.spc1
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• pp.1261-1270
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• 2022

The purpose of this study is to collect and analyze information related to water leaks that cannot be easily accessed, and utilized by using the news search results that people can easily access. We applied a web crawling technique for extracting big data news on water leakage accidents in the water supply system and presented an algorithm in a procedural way to obtain accurate leak accident news. In addition, a data analysis technique suitable for water leakage accident information analysis was developed so that additional information such as the date and time of occurrence, cause of occurrence, location of occurrence, damaged facilities, damage effect. The primary goal of value extraction through big data-based leak analysis proposed in this study is to extract a meaningful value through comparison with the existing waterworks statistical results. In addition, the proposed method can be used to effectively respond to consumers or determine the service level of water supply networks. In other words, the presentation of such analysis results suggests the need to inform the public of information such as accidents a little more, and can be used in conjunction to prepare a radio wave and response system that can quickly respond in case of an accident.

• Journal of Korean Library and Information Science Society
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• v.55 no.1
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• pp.193-214
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• 2024

This study aimed to propose a method for collecting and applying media platform based materials at the National Library of Korea. Firstly, we analyzed the current status and limitations of data collection based on domestic media platforms, including the National Library of Korea. Secondly, a literature review method was used to investigate the current status and types of digital content based on media platforms. Thirdly, we identified the types of materials based on media platforms that are not currently included in the National Central Library's online material collection guidelines through the examination of cases from major overseas libraries. Fourthly, after reviewing technical and legal elements such as the definition of collection targets and scope for each new media, and collection methods, we established collection criteria. Fifthly, based on the research results, the policies proposed in this study are as follows: 1) there is a need to establish a clear legal basis for the collection of media platform based materials; 2) the development and presentation of collection guidelines for media platform based materials is necessary; 3) the development of collection tools and infrastructure for media platform based materials is required; 4) for the collection of media platform based materials, it is necessary to obtain permission for collection from targeted social media organizations, and to cooperate in linkage with organizations that produce and service extended reality content; 5) for the service activation of media platform based materials, it is necessary to improve accessibility for the usage activation of these materials, to enhance the content extensibility and ease of use of the e-deposit system including extended reality content, and to advance and construct spaces for reproducing extended reality content.

• Journal of The Korean Association For Science Education
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• v.19 no.3
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• pp.461-470
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• 1999

The purpose of this study was to investigate teachers' perception about 'Science Field Trip(SFT) to Korean historical sites'. Ninety-seven teachers were asked to reply the questionnaire about SFT to Korean historical sites. This questionnaire was divided into three parts: educational value, teaching method, and difficulty of management. Firstly, teachers indicated that SFT to Korean historical sites had much educational value in that it could give students chances to understand Korean culture, to acquire investigative process skills, to experience divergent investigation and cooperative learning, to raise integrated thinking skill concerning science and other subjects, and to learn contents related with science curriculum. It also had advantages of caring for students out of school and giving the information for future occupation. Secondly, teachers suggested the desirable teaching method: teachers' explanation about SFT to Korean historical sites with worksheets before it, students' group work during it, and the presentation and discussion after it. Finally, the most frequent answer in the difficulty of management was the lack of teaching materialsfor SFT to Korean historical sites.