• Journal of the Korean Geotechnical Society
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• v.28 no.9
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• pp.97-106
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• 2012

In order to investigate mechanics of mixtures composed of sand and non-plastic silt, various specimens, with sand dominating the soil structure, and with varying fines content, fines content varying were produced. Isotropic consolidation tests were performed using high pressure triaxial test apparatus within high pressure levels where sand grain crushing happened. Experimental results showed that compressive curve of sand after yielding contracts to the NCL due to breakage of sand grains. Moreover, with the increase of fines content, coarse grains are surrounded by fines to form cushion effect, which made the breakage of coarse grains become difficult. Therefore, the maximum inclination of compressive curve became flatter and yield stress increased.

• Journal of the Korean earth science society
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• v.30 no.2
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• pp.176-184
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• 2009

The purpose of this study is to develop and apply the web contents about the optical characteristics of rock forming minerals. The web contents developed in this study are fundamentally made up so as to show clearly the learning objective and the teaching and learning contents, and to review one content easily and search for another content freely. In addition to the web contents, the photos and moving images of the optical characteristics of rock forming minerals cited in the middle and high school textbooks are demonstrated for the students to recognize the mineral characteristics on the screen. The analysis on the quality level and teaming effect of teaching and teaming materials based on the investigation of the MALSAM after the application of the web contents to the class, showed that most students evaluated were effective for understanding the optical characteristics of the rock-forming minerals. About 62% of the students who used the web contents were able to identify the rock-forming minerals on the thin section under the polarizing microscope.

• Journal of the Korean Institute of Intelligent Systems
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• v.25 no.2
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• pp.180-185
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• 2015

As the number of document resources is continuously increasing, automatically extracting keyphrases from a document becomes one of the main issues in recent days. However, most previous works have tried to extract keyphrases from words in documents, so they overlooked latent keyphrases which did not appear in documents. Although latent keyphrases do not appear in documents, they can undertake an important role in text summarization and information retrieval because they implicate meaningful concepts or contents of documents. Also, they cover more than one fourth of the entire keyphrases in the real-world datasets and they can be utilized in short articles such as SNS which rarely have explicit keyphrases. In this paper, we propose a new approach that selects candidate keyphrases from the keyphrases of neighbor documents which are similar to the given document and evaluates the importance of the candidates with the individual words in the candidates. Experiment result shows that latent keyphrases can be extracted at a reasonable level.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.4
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• pp.695-702
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• 2020

Recently, as research on smart farms has been actively conducted, indoor environment control, such as a green house, has reached a high level. However, In the field of forestry where cultivation is carried out in outdoor, the use of ICT is still insufficient. In this paper, we propose LPWA-based forest growth environment collection and big data analysis system using ICT technology. The proposed system collects and transmits the field cultivation environment data to the server using small solar power generation and LPWA technology based on the oneM2M architecture. The transmitted data is constructed as big data on the server and utilizes it to predict the production and quality of forest products. The proposed system is expected to contribute to the production of low-cost, high-quality crops through the fusion of renewable energy and smart farms. In addition, it can be applied to other industrial fields that utilize the oneM2M architecture and monitoring the growth environment of agricultural crops in the field.

• Journal of the Korean Data and Information Science Society
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• v.22 no.6
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• pp.1065-1074
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• 2011

During several decades, many researchers in the field of finance have studied Value at Risk (VaR) to measure the market risk. VaR indicates the worst loss over a target horizon such that there is a low, pre-specified probability that the actual loss will be larger (Jorion, 2006, p.106). In this paper, we compare conditional copula method with two conventional VaR forecasting methods based on simple moving average and exponentially weighted moving average for measuring the risk of the portfolio, consisting of two domestic stock indices. Through real data analysis, we conclude that the conditional copula method can improve the accuracy of portfolio VaR forecasting in the presence of high kurtosis and strong correlation in the data.

• Journal of the Korea Convergence Society
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• v.11 no.9
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• pp.203-217
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• 2020

The purpose of this study was to perform a convergence study for investigating main features and influencing factors in career development process, throughout the whole periods of education, that might influence their ultimate choice of majors. We collected data of career development process at the elementary, middle, high school, and college levels using career-o-grams, for the college students who majored in English Lang/Lit and Global Commerce, and we applied text mining techniques for qualitative data analysis. Two major factors influencing career goals were parents and teachers. In particular, teachers were most influential in the career decisions at the middle school level. Teachers, family situations, and peers showed a negative impact on career aspiration. The findings would serve as a guide for career consultants and education program developers.

• Journal of Korean Elementary Science Education
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• v.24 no.1
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• pp.77-85
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• 2005

This study organized a Science Improvement Activity Program designed for the excellent students in science in 5th and 6th grades. After application the effect of the program on science process skills was analyzed. The Science Improvement Activity Program was applied to the experimental group as a club activity after school during the semester. The results of this study were as follows: First, the students participated in the Science Improvement Activity showed an increase in the science process skills compared with those who didn't. Second, it was found have improved in enhancing their science process elements of observation, measurement, data analysis, forming hypotheses, and controlling variables. It is expected that the development of activity programs and their active application should be done in order for schools to provide science education according to each student's capacity from various angles.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.1
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• pp.179-189
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• 2000

Recently, due to the increasing interests in deep sea development, all possible efforts to the development of underwater unmanned working vehicles such as AUV(Autonomous Underwater Vehicle) or underwater robot are exerted. This paper proposes a new efficient acoustic-based underwater image data communication system, which ensures a certain level of maximum throughput regardless of the propagation delay of ultrasonic and allowsfast data transmission through the multiple ultrasonic communication channel. Proposed system consists of an acoustic transducer which operates at 136kHz center frequency and it's 10kHz bandwidth, pre-amplifier, $\pi/4 QPSK$(Quadrature Phase Shift Keying) modulation/demodu-lation method, image compressing method using JPEG technique and modified Stop & Wait protocol. The experimental result of the system make it possible to transfer the underwater image as a high throughput at the basin test. The results of test are also verified which allows to desirable transmission performance compared with the existing developed system and the possibility to put the practical use of survey and investigation in the water.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.3
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• pp.617-624
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• 2014

A campus network nowadays adapts the security policies in detail and even in variety, along with firewall based access control. Nevertheless, security threats, such as information hacking, intrusion and DoS, are not decreasing yet. This paper proposes an enabling method of discriminative security policies to enforce an adaptive security for security objects on basis of the security elements. The security level of a security devices is decided based on the mapping between the users and the objects. The proposed security policies could improve the security effect in terms of investment in creative campus environment, and aim to provide fast and stable services to users.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.2
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• pp.443-449
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• 2017

Opened platform is called that anybody can be a producer and consumer in some platform. And many opened platforms are using in various area such as general goods, smart phone application and contents. In this paper, we will propose the opened platform system for the problems for evaluation the level of learners. Any user can register problems as public or private-type in this system and use them. So our proposed system has the advantage in selecting the high quality problems by continuous reviews about that even after they have been registered. Proposed system has three different modules such as submit, evaluate and produce problems modules. A user can submit various kind of problems in the submit module. The evaluation module is a module that allows the user who is not the problem registrant to evaluate the registered problem. The production module can use the registered problems for online and offline evaluation.