• Korean Journal of Agricultural and Forest Meteorology
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• v.5 no.2
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• pp.138-149
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• 2003

Korean regional network of tower flux sites, KoFlux, has been initiated to better understand $CO_2$, water and energy exchange between ecosystems and the atmosphere, and to contribute to regional, continental, and global observation networks such as FLUXNET and CEOP. Due to heterogeneous surface characteristics, most of KoFlux towers are located in non-ideal sites. In order to quantify carbon and energy exchange and to scale them up from plot scales to a region scale, applications of various methods combining measurement and modeling are needed. In an attempt to infer regional-scale flux, four methods (i.e., tower flux, convective boundary layer (CBL) budget method, MM5 mesoscale model, and NCAR/NCEP reanalysis data) were employed to estimate sensible heat flux representing different surface areas. Our preliminary results showed that (1) sensible heat flux from the tower in Haenam farmland revealed heterogeneous surface characteristics of the site; (2) sensible heat flux from CBL method was sensitive to the estimation of advection; and (3) MM5 mesoscale model produced regional fluxes that were comparable to tower fluxes. In view of the spatial heterogeneity of the site and inherent differences in spatial scale between the methods, however, the spatial representativeness of tower flux need to be quantified based on footprint climatology, geographic information system, and the patch scale analysis of satellite images of the study site.

• Journal of Digital Convergence
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• v.14 no.4
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• pp.111-128
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• 2016

The purpose of this study was to analyze domestic research trends of social learning in higher education, and find out educational implications with regard to the effectiveness of social learning. The 63 articles on social learning were finally analyzed, which were published in KCI journals. The results are as follows: Firstly, in respect of research contents, the research area of utilization and the survey methods were most frequently used in those studies. Secondly, as to the use of SNS, the analyzed studies were centralized on Facebook and Formal Structured Learning. Thirdly, as for the effectiveness of SNS, the experimental studies showed that social learning has an effective impact on the learning outcomes, learning processes, and learners' characteristics. In addition, survey studies most frequently set the independent variables as learners' characteristics and the dependent variables as participation, satisfaction, and academic achievement. This research has a significance in terms of verifying the educational implications of social learning, and providing the preliminary data to facilitate the performance for the effective social learning.

• Korean Journal of Social Welfare
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• v.62 no.1
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• pp.155-183
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• 2010

Despite the increase in the demands on collaboration between health and social welfare, the success of such schemes have been limited. The extant literatures tends to be dominated by explanations for needs or short-term outcomes of collaboration rather than systematic follow-up research to apply to the frontline. At the same time, there is no attempt to apply the theories related to collaboration in order to discuss the situation. This study explores the factors hindering such collaborative working in the frontline, through semi-structured interviews with practitioners involved in two pilot projects. A theoretical framework (Equilibrium Model-Sensemaking, E-S model) which combined Equilibrium Model of 'Interorganizational Network' of Benson(1975) and 'Sensmaking' of Weick(1995) for conceptualiing aspects of collaborations such as working atmosphere and agency was applied to the empirical study of the Public Health and Welfare Office(1995-1999) and the Social Welfare office(2004-2006) pilot projects. Data were collected over three months from 8 pilot project areas with practitioners and managers from health and social welfare. The findings show significant regional differences between pilot areas, such as the presence of active leaders and co-location, had a major impact on the ability of practitioners to effectively integrate services. In other words, active leaders tended to influence practitioners' motivation, while co-location encouraging communication between both practitioners, and thus seemed to influence the practices of collaborative working. Furthermore, through E-S model, it is interpreted that this kind of positive experiences about collaborations may impact on the current practitioners' comprehensive perspective towards health and social welfare services in general. The findings could help policy makers consider the practical ways to break down the barriers between health and social welfare.

• Journal of The Korean Astronomical Society
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• v.48 no.2
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• pp.125-137
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• 2015

We report results of the performance evaluation of a new hardware correlator in Korea, the Daejeon correlator, developed by the Korea Astronomy and Space Science Institute (KASI) and the National Astronomical Observatory of Japan (NAOJ). We conduct Very Long Baseline Interferometry (VLBI) observations at 22 GHz with the Korean VLBI Network (KVN) in Korea and the VLBI Exploration of Radio Astrometry (VERA) in Japan, and correlated the aquired data with the Daejeon correlator. For evaluating the performance of the new hardware correlator, we compare the correlation outputs from the Daejeon correlator for KVN observations with those from a software correlator, the Distributed FX (DiFX). We investigate the correlated flux densities and brightness distributions of extragalactic compact radio sources. The comparison of the two correlator outputs shows that they are consistent with each other within < 8%, which is comparable with the amplitude calibration uncertainties of KVN observations at 22 GHz. We also find that the 8% difference in flux density is caused mainly by (a) the difference in the way of fringe phase tracking between the DiFX software correlator and the Daejeon hardware correlator, and (b) an unusual pattern (a double-layer pattern) of the amplitude correlation output from the Daejeon correlator. The visibility amplitude loss by the double-layer pattern is as small as 3%. We conclude that the new hardware correlator produces reasonable correlation outputs for continuum observations, which are consistent with the outputs from the DiFX software correlator.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.11A
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• pp.1027-1034
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• 2005

IEEE802.15.4a, which is started to realize the PHY layer including high precision ranging/positioning and low data rate communication functions, requires a simple and low power consumable transceiver architecture. To satisfy this requirements, the simple noncoherent on-off keying (OOK) UWB transceiver with the parallel energy window banks (PEWB) giving high precision signal processing interface is proposed. The flexibility of the proposed system in multipath fading channel environments is acquired with the pulse and bit repetition method. To analyze the bit error rate (BER) performance of this proposed system, a noise model in receiver is derived with commonly used random variable distribution, chi-square. BER of $10^{-5}$ under the line-of-sight (LOS) residential channel is achieved with the integration time of 32 ns and signal to noise ratio (SNR) of 15.3 dB. For the non-line-of-sight (NLOS) outdoor channel, the integration time of 72 ns and SNR of 16.2 dB are needed. The integrated energy to total received energy (IRR) for the best BER performance is about $86\%$.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.10B
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• pp.1050-1061
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• 2009

The Tactical Internet(TI) managed by Infantry Brigades is used for the purpose of sharing information of Command Control and Situation Awareness. When there are more than two destinations to transmit data in the TI system, a multicasting is utilized based on pre-defined multicast groups. However even in the case when a source node needs to send some messages like weathercast and attack alarm etc to only a part of Battalion or Brigades in a specific geographical region (destination region), the current TI multicasting protocol is designed to transmit the messages to the pre-defined group or all of the Battalion/Brigade nodes, resulting in inefficiency in terms of end-to-end delay and overhead. In this paper, we propose more efficient protocol for such cases, named as "Tactical Internet Geocasting (TIG)". The proposed scheme firstly checks whether the destination region belongs to one Battalion region or more than two Battalion regions using location information, and then performs a greedy forwarding from the source node to the destination region, followed by a local flooding inside of the destination region. With performance analysis and simulations using NS-2, TIG is compared to the current TI multicasting protocol (i.e., Simplified MDP) and the LBM (Location-based Multicast). The simulation results show that the proposed TIG is more efficient than both in terms of delay and network overhead.

• Proceedings of the Korea Database Society Conference
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• 2008.05a
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• pp.389-403
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• 2008

As the information of web dramatically increase, the existing web reveals more and more limitations in information search because web pages are designed only for human consumption by mixing content with presentation. In order to improve this situation, the Semantic Web comes on the stage by W3C. Semantic web is based on ontology that defines relationships between resources and it is enough to bring a significant advancement in web search. But to do this, the Semantic Web must provide a novel search and visualization methods which can make users instantly and intuitively understand why and how the results are retrieved because ontology has formal explicit descriptions of meaning. In this paper, we propose a semantic association-based search methodology that consists of how to find relevant information for a given user's query in the ontology, that is, a semantic network of resources and properties and how to provide proper visualization and navigation methods on the results. From this work, users can search the semantically associated resources for their query and also navigate such associations between resources.

• Journal of the Korea Society of Computer and Information
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• v.25 no.8
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• pp.159-172
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• 2020

Social networking services (SNS) are developing significantly with the Internet and smartphones. It's a friendly social media, but if you think deeply about it, you'll find that it has a variety of faces. It is a communication tool between users, a medium for delivering information, an infrastructure for providing applications, and a community where people with common interests gather. In recent years, business tools, shopping and payment methods are also being swallowed. The influence of the spread of SNS on the real world is also expanding, and the work being dealt with from a sociological perspective is also increasing. Also, if you pay attention to the technical aspects of SNS, it is composed of various technical elements, such as infrastructure that handles large-scale access, user interface that supports comfortable use, and big data analysis to understand people's behavior more deeply. However, I usually use it as usual. However, if you look through SNS, you can see that the situation is surprisingly profound and multifaceted. This study began by looking at the history and current status of SNS and attempted to find its status through comparison with other media. From the point of view of relationship with society, it can be a risk and legal issue when using SNS, such as crimes using bad social media or social media. It is also necessary to comment on the activities on SNS or the guidelines established by the operators. Therefore, various legal issues on SNS will be discussed. Also, as an example of using SNS, I will introduce an example of using SNS in disaster response. From a more technical point of view, you will receive commentary on SNS's network-based technology and SNS's information use, and these articles will help you understand and use SNS safely and help you further utilize or develop SNS.

• Korean journal of communication and information
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• v.56
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• pp.48-70
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• 2011

Although many researchers propose that market-driven journalism is incurred by the worsening of financial situation as a result of intensifying competition in mass media industry, few studies investigated this claim with actual news data. This study analyzed the headline news of eight major newspapers and two terrestrial TV companies to find the weakening of 'orientating-journalism' function of Korean news media. The results revealed that the duplication rate of news items among ten news companies were decreasing, and the range of news subjects were broadened into diverse topics during last ten years. Therefore it seemed that the tendency of monopolization of a certain events or issues was weakening in news reporting. The financial situation of news companies is an important factor in explaining the change of news reporting. The companies with more worse financial situation have higher duplication rate of news topics along as the more amount of soft news items, leading to the gradual deterioration of their own voices in reporting. The rate of 'independent issue report' was also less than seven precent, thus their reporting is evaluated as having many limitations. In sum, the major newspapers and network broadcasting companies are still exerting strong influences in agenda-setting, but they(mostly newspapers) are suffering from the financial problems, resulting the deterioration of performing orientation journalism function. This study concluded with remarks about the role of major news media in current changing situation.

• Journal of Korea Water Resources Association
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• v.31 no.6
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• pp.727-739
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• 1998

The main objectives o reservoir optimal operation can be described as follows : maximization of the benefits through optimal allocation of the limited water resources for various purpose; minimization of t도 costs by the flood damage in potential damaging regions and risk of dam failure, etc. through safe drainage of a bulky volume of excessive water by a proper reservoir operation. Reviewing the past research works related to reservoir operation, we can find that the study on the matter of the former has been extensively carried out in last decades rather than the matter of the latter. This study is focused on developing a methodology of optimal reservoir operation for flood control, and a case study is performed on the Chungju multipurpose reservoir in Korea. The final goal of the study is to establish a reservoir optimal operation system which can search optimal policy to compromise two conflicting objectives: downstream flood damage and dam safety-upstream flood damage. In order to reach the final goal of the study, the following items were studied : (1)validation of hydrological data using HYMOS: (2)establishment of a downstream flood routing model coupling a rainfall-runoff model and SOBEK system for 1-D hydrodynamic flood routing; (3)replication of a flood damage estimation model by a neural network; (4)development of an integrated reservoir optimization module for an optimal operation policy.