• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2009.06a
• /
• pp.287-288
• /
• 2009

In this paper we developed positioning algorithm considering distributed energy resource of ocean side by load flow calculation using Newton-Rhapson method.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2009.06a
• /
• pp.289-290
• /
• 2009

In this paper we designed the sensor system that is based on the PT, CT and microprocessors for measuring power of distributed energy resource of ocean side.

• Proceedings of the KSRS Conference
• /
• 2003.11a
• /
• pp.1326-1328
• /
• 2003

An elliptical basis function (EBF) network is proposed in this study for the classification of remotely sensed images. Though similar in structure, the EBF network differs from the well-known radial basis function (RBF) network by incorporating full covariance matrices and uses the expectation-maximization (EM) algorithm to estimate the basis functions. Since remotely sensed data often take on mixture -density distributions in the feature space, the proposed network not only possesses the advantage of the RBF mechanism but also utilizes the EM algorithm to compute the maximum likelihood estimates of the mean vectors and covariance matrices of a Gaussian mixture distribution in the training phase. Experimental results show that the EM-based EBF network is faster in training, more accurate, and simpler in structure.

• Korean Journal of Materials Research
• /
• v.27 no.6
• /
• pp.301-306
• /
• 2017

The discovery of new luminescent materials for use in light-emitting diodes(LEDs) has been of great interest, since LED-based solid state lighting applications are attracting a lot of attention in the energy saving and environmental fields. Recent research trends have centered on the discovery of new luminescent materials rather than on fine changes in well-known luminescent materials. In a sense, the novelty of our study beyond simple modification or improvement of existing phosphors. A good strategy for the discovery of new fluorescent materials is to introduce activators that are appropriate for conventional inorganic compounds, that have well-defined structures in the crystal structure database, but have not been considered as phosphor hosts. Another strategy is to discover new host compounds with structures that cannot be found in any existing databases. We have pursued these two strategies at the same time using composite search technology with particle swarm optimization(PSO). In this study, using PSO, we have tracked down a search space composed of Sr-Al-Si-O-N and have discovered a new phosphor structure with yellow luminescence; this material is a potential candidate for UV-LED applications.

• Research in Mathematical Education
• /
• v.14 no.4
• /
• pp.361-380
• /
• 2010

Some 400 Secondary One (i.e. seventh-grade) students from 10 schools were provided with non-routine mathematical problems in their normal mathematics classes as exercises for one academic year. Their attitudes toward mathematics, their conceptions of mathematics and their problem-solving performance were measured both in the beginning and at the end of the year. Hierarchical regression analyses revealed that the introduction of an appropriate dose of non-routine problems would generate some effects on the students' conceptions of mathematics. A medium dose of non-routine problems (as reported by the teachers) would result in a change of the students' conception of mathematics to perceiving mathematics as less of "a subject of calculables." On the other hand, a high dose would lead students to perceive mathematics as more useful and more as a discipline involving thinking. However, with a low dose of non-routine problems, students found mathematics more "friendly" (free from fear). It is therefore proposed that the use of non-routine mathematical problems to an appropriate extent can induce changes in students' "lived space" of mathematics learning and broaden their conceptions of mathematics and mathematics learning.

• Structural Engineering and Mechanics
• /
• v.35 no.4
• /
• pp.459-478
• /
• 2010

This paper contains detailed descriptions of a dynamic time-history modal analysis to calculate deflection, inter-storey drift and storey shear demand in single-storey and multi-storey buildings using an EXCEL spreadsheet. The developed spreadsheets can be used to obtain estimates of the dynamic response parameters with minimum input information, and is therefore ideal for supporting the conceptual design of tall building structures, or any other structures, in the early stages of the design process. No commercial packages, when customised, could compete with spreadsheets in terms of simplicity, portability, versatility and transparency. An innovative method for developing the stiffness matrix for the lateral load resistant elements in medium-rise and high-rise buildings is also introduced. The method involves minimal use of memory space and computational time, and yet allows for variations in the sectional properties of the lateral load resisting elements up the height of the building and the coupling of moment frames with structural walls by diaphragm action. Numerical examples are used throughout the paper to illustrate the development and use of the spreadsheet programs.

• The Journal of the Convergence on Culture Technology
• /
• v.4 no.4
• /
• pp.161-166
• /
• 2018

Sojeon, Son Jaehyung(1903~1981) was interested in the composition of the classical writing style of Han-gul and its merits in the operation of the brush. And a genius, modern sense of sculpture and ingenious ideas applied to the calligraphy. Thus, he succeeded Tonggukjinche by sublimating it into a unique Handwriting pure and humorous. Sojeon Hangul Calligraphy is exaggerated in consideration of the change of direction, thickness and length of the stroke. There is nothing strange about law and organization and express the great beauty of the great art of harmony and change. Sojeon's contribution is significant in that it has not only become a model for the development of Han-gul calligraphy, but also created a new area of space in modern calligraphy.

• Biomedical Engineering Letters
• /
• v.8 no.4
• /
• pp.345-353
• /
• 2018

This study suggested a new EMG-signal-based evaluation method for knee rehabilitation that provides not only fragmentary information like muscle power but also in-depth information like muscle fatigue in the field of rehabilitation which it has not been applied to. In our experiment, nine healthy subjects performed straight leg raise exercises which are widely performed for knee rehabilitation. During the exercises, we recorded the joint angle of the leg and EMG signals from four prime movers of the leg: rectus femoris (RFM), vastus lateralis, vastus medialis, and biceps femoris (BFLH). We extracted two parameters to estimate muscle fatigue from the EMG signals, the zero-crossing rate (ZCR) and amplitude of muscle tension (AMT) that can quantitatively assess muscle fatigue from EMG signals. We found a decrease in the ZCR for the RFM and the BFLH in the muscle fatigue condition for most of the subjects. Also, we found increases in the AMT for the RFM and the BFLH. Based on the results, we quantitatively confirmed that in the state of muscle fatigue, the ZCR shows a decreasing trend whereas the AMT shows an increasing trend. Our results show that both the ZCR and AMT are useful parameters for characterizing the EMG signals in the muscle fatigue condition. In addition, our proposed methods are expected to be useful for developing a navigation system for knee rehabilitation exercises by evaluating the two parameters in two-dimensional parameter space.

• Journal of Information Science Theory and Practice
• /
• v.9 no.1
• /
• pp.35-53
• /
• 2021

The study reported in this paper aimed to evaluate the topics and opinions of COVID-19 discussion found on Twitter. It performed topic modeling and sentiment analysis of tweets posted during the COVID-19 outbreak, and compared these results over space and time. In addition, by covering a more recent and a longer period of the pandemic timeline, several patterns not previously reported in the literature were revealed. Author-pooled Latent Dirichlet Allocation (LDA) was used to generate twenty topics that discuss different aspects related to the pandemic. Time-series analysis of the distribution of tweets over topics was performed to explore how the discussion on each topic changed over time, and the potential reasons behind the change. In addition, spatial analysis of topics was performed by comparing the percentage of tweets in each topic among top tweeting countries. Afterward, sentiment analysis of tweets was performed at both temporal and spatial levels. Our intention was to analyze how the sentiment differs between countries and in response to certain events. The performance of the topic model was assessed by being compared with other alternative topic modeling techniques. The topic coherence was measured for the different techniques while changing the number of topics. Results showed that the pooling by author before performing LDA significantly improved the produced topic models.

• Journal of Information Science Theory and Practice
• /
• v.9 no.1
• /
• pp.68-78
• /
• 2021

Political weblogs are as diverse as political viewpoints are. In the period of Prime Minister Yingluck Shinawatra, several political crises occurred, such as opposition to the Amnesty Act, the constitutional amendment, and the anti-government protests. Remarkably, during this time, social media were used as a platform for political expressions. This study employed a content analysis method to explore twenty-nine Thai political weblogs established during the period of Prime Minister Yingluck Shinawatra's administration. At the time, the most prominent Thai political weblogger was Nidhi Eawsriwong. Not surprisingly, the Pheu Thai Party and the Democrat Party were the most frequently appearing political parties in these weblog's posts. Most contents in these posts were related to government protesters by the People's Democratic Reform Committee (PDRC) and the coup d'état. The purposes of writing such weblogs were to express feelings and thoughts about Thai politics and to provide political information to the general public. The findings from this investigation revealed two significant uses of Thai political weblogs: the communication media for political expressions and viewpoints (a safe online space for political engagement and participation), and vital sources for Thai political information and news (social narratives).