• Geophysics and Geophysical Exploration
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• v.2 no.1
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• pp.17-25
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• 1999

A traveltime tomography has been carried out by transforming electromagnetic data in frequency domain to wave-like domain. The transform uniquely relates a field satisfying a diffusion equation to an integral of the corresponding wavefield. But direct transform of frequency domain magnetic fields to wave-field domain is ill-posed problem because the kernel of the integral transform is highly damped. In this study, instead of solving such an unstable problem, it is assumed that wave-fields in transformed domain can be approximated by sum of ray series. And for further simplicity, reflection and refraction energy compared to that of direct wave is weak enough to be neglected. Then first arrival can be approximated by calculating the traveltime of direct wave only. But these assumptions are valid when the conductivity contrast between background medium and the target anomalous body is low enough. So this approach can only be applied to the models with low conductivity contrast. To verify the algorithm, traveltime calculated by this approach was compared to that of direct transform method and exact traveltime, calculated analytically, for homogeneous whole space. The error in first arrival picked by this study was less than that of direct transformation method, especially when the number of frequency samples is less than 10, or when the data are noisy. Layered earth model with varying conductivity contrasts and inclined dyke model have been successfully imaged by applying nonlinear traveltime tomography in 30 iterations within three CPU minutes on a IBM Pentium Pro 200 MHz.

• Korean Journal of Remote Sensing
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• v.37 no.6_3
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• pp.1965-1974
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• 2021

Satellite remote sensing approach can be actively used for forest monitoring. Especially, it is much meaningful to utilize Korea multi-purpose satellites, an independently operated satellite in Korea, for forest monitoring of Korea, Recently, several studies have been performed to exploit meaningful information from satellite remote sensed data via machine learning approaches. The forest information produced through machine learning approaches can be used to support the efficiency of traditional forest monitoring methods, such as in-situ survey or qualitative analysis of aerial image. The performance of machine learning approaches is greatly depending on the characteristics of study area and data. Thus, it is very important to survey the best model among the various machine learning models. In this study, the performance of deep neural network to classify artificial or natural forests was analyzed in Samcheok, Korea. As a result, the pixel accuracy was about 0.857. F1 scores for natural and artificial forests were about 0.917 and 0.433 respectively. The F1 score of artificial forest was low. However, we can find that the artificial and natural forest classification performance improvement of about 0.06 and 0.10 in F1 scores, compared to the results from single layered sigmoid artificial neural network. Based on these results, it is necessary to find a more appropriate model for the forest type classification by applying additional models based on a convolutional neural network.

• Journal of The Korean Association For Science Education
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• v.41 no.3
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• pp.267-281
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• 2021

The shift in the perspective on learning as participation draws attention to learners' identity work. This manuscript foregrounds the ongoing and fluid processes of identity, and focuses on the structure surrounding learners where identity work occurs and the expression of individual agency. From the perspective of learning as participation, we introduce Holland et al. (1998) identity-in-practice theory, as the theoretical lens that dialectically describes structure, agency and identity. The concepts representing this theory are 'figured world', 'positionality' and 'authoring self'. The figured world is a web of meaning encompassing the continuous construct/reconstruct through human actions and also exerts as the social force that shapes human actions. 'Positionality' on the other hand, means an understanding of one's social position in the world. The notion of 'authoring self', is a dimension that synthesizes the above two concepts, which describes the improvisation of one's self through the orchestration and collaboration of various social voices. Next, we analyzed and described various cases of this theory that we found within the scope of science education. However, due to the nature of this theory, which takes a sociocultural approach, international research studies cannot be simply applied to the Korean context. Therefore, we sought to expand the applicability of this theory as a methodological tool, by discussing the directions in which this theory can be used in a domestic context. It is intended that the introduction of this theory, which emphasizes multi-layered, continuous and cumulative identity work, will be used as a resource to further expand the horizon of science education reform that is required for the times.

• Asia pacific journal of information systems
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• v.18 no.3
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• pp.147-165
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• 2008

IT education can be summarized as persuading the educatee to accept IT. The persuasion is made by delivering the messages for how-to-use and where-to-use to the educatee, which leads formulation of a belief structure for using IT. Therefore, message based persuasion theory, as well as IT acceptance theories such as technology acceptance model(TAM), would play a very important role for explaining IT education. According to elaboration likelihood model(ELM) that has been considered as one of the most influential persuasion theories, people change attitude or perception by two routes, central route and peripheral route. In central route, people would think critically about issue-related arguments in an informational message. In peripheral route, subjects rely on cues regarding the target behavior with less cognitive efforts. Moreover, such persuasion process is not a one-shot program but continuous repetition with feedbacks, which leads to changing a belief structure for using IT. An educatee would get more knowledge and experiences of using IT as following an education program, and be more dependent on a central route than a peripheral route. Such change would reformulate a belief structure which is different from the intial one. The objectives of this study are the following two: First, an identification of the relationship between ELM and belief structures for using IT. Especially, we analyze the effects of message interpretation through both of central and peripheral routes on perceived usefulness which is an important explaining variable in TAM and perceived use control which have perceived ease of use and perceived controllability as sub-dimensions. Second, a longitudinal analysis of the above effects. In other words, change of the relationship between interpretation of message delivered by IT education and beliefs of IT using is analyzed longitudinally. For achievement of our objectives, we suggest a research model, which is constructed as three-layered. While first layer has a dependent variable, use intention, second one has perceived usefulness and perceived use control that has two sub-concepts, perceived ease of use and perceived controllability. Finally, third one is related with two routes in ELM, source credibility and argument quality which are operationalization of peripheral route and central route respectively. By these variables, we suggest five hypotheses. In addition to relationship among variables, we suggest two additional hypotheses, moderation effects of time in the relationships between perceived usefulness and two routes. That is, source credibility's influence on perceived usefulness is decreased as time flows, and argument quality's influence is increased. For validation of it, our research model is tested empirically. With measurements which have been validated in the other studies, we survey students in an Excel class two times for longitudinal analysis. Data Analysis is done by partial least square(PLS), which is known as an appropriate approach for multi-group comparison analysis with a small sized sample as like this study. In result. all hypotheses are statistically supported. One of theoretical contributions in this study is an analysis of IT education based on ELM and TAM which are considered as important theories in psychology and IS theories respectively. A longitudinal analysis by comparison between two surveys based on PLS is also considered as a methodological contribution. In practice, finding the importance of peripheral route in early stage of IT education should be notable.

• Journal of the Korea Convergence Society
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• v.11 no.1
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• pp.1-7
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• 2020

Recently 5G technology is one of the technologies that has been receiving much positive responses from users as it is integrated with virtual technology. However, 5G's security issues have not been fully resolved and more security is soon required. In this paper, an approach technique is proposed as a probability-based hierarchy to provide personal privacy for 5G-based IoT users more safely. The proposed technique is aimed at not exposing the privacy of IoT users to third parties by using two random keys created personally by IoT users. In order to satisfy both safety and efficiency, the proposed technology divides the privacy of IoT users into two layers. In the first stage, IoT users will control access to intermediate media using anonymous keys generated by IoT users, and in the second stage, information of IoT users registered with servers will be darkened and replicated. The proposed technique has improved the accuracy of the privacy protection of IoT users as they assign weights to layered information after layering users' privacy information on a probabilistic basis.

• Korean Journal of Heritage: History & Science
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• v.52 no.1
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• pp.190-211
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• 2019

In March 2015, The Agency for Cultural Affairs of Japan implemented a project called "Japan Heritage," which aims to promote the unique narratives of cultural properties of the region by branding the locality for revitalization in preparation for the 2020 Tokyo Olympics and Paralympics. This bottom-up approach of cultural policy has been called a "Cool Japan Strategy of Cultural Heritage" in the 21st century, which effectively incorporates local cultural heritage and tourism. However, although a total of 67 Japan Heritage projects have been designated as of December 2018, almost none has been introduced in the academic forum in Korea. On the basis of this background and a lack of academic awareness in Korea on Japan's recent cultural policies, this research aims to focus on the three cases of Gunma Prefecture implemented in local, global, and glocal aspects. To specify, the cases are the "Gunma Silk Heritage" project, implemented in 2011, the "Tomioka Silk Mill and Related Sites" project that was included on the UNESCO World Heritage List in 2014, and "The Best Wife in the World - Silk Story of Gunma," case certified as the first project of "Japan Heritage" launched in 2015. Based on the questionnaire method conducted with the World Heritage Registration Promotion Division in Gunma Prefectural Government, as well as a literature view, the research revealed that the consecutive implementation of a series of cultural heritage projects in Gunma is not coincidental, but rather a strategy aiming to create a synergism where each project complements the others. Moreover, this paper demonstrates that Gunma Prefecture has been utilizing the local silk industry as a tangible and intangible cultural resource in multi-layered heritage projects, resulting in a "spiral synergy effect" and a "chain of the recognition process." In conclusion, it illustrates the recent trend of utilizing cultural heritage in the context of the Cool Japan strategy, which seeks to move away from the administration of maintaining the status quo cultural heritage protection to a proactive one with greater potential growth. This research may thus provide meaningful insight into the utilization of domestic historical and cultural resources as well as related policy-making, in that it will ultimately promote the chain effect of linking the multiple heritage policies and projects at the local, global, and glocal levels.