• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.8
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• pp.48-59
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• 2011

This paper presents a new gain scheduling speed controller of permanent magnet synchronous generators(PMSG) for MW-class direct-driven wind turbine systems. The proposed gain scheduling speed controller performs the speed tracking at more than one operating point, and the first-order torque observer estimates the turbine torque which is needed to precisely control the speed of PMSG. The proposed speed controller verifies that the PMSG can successfully follow the reference speed which is determined via the maximum power point tracking(MPPT) control and pitch control under turbulent wind conditions. The proposed speed control algorithm is simulated using Simulink and its performance is confirmed through comparison with the results by PI control method.

• Journal of Institute of Control, Robotics and Systems
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• v.2 no.4
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• pp.337-343
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• 1996

In this paper, we investigate the defect detection by making use of pre-made reference image data and classify the defects by using the artificial neural network. The approach is composed of three main parts. The first step consists of a proper generation of two reference image data by using a low level morphological technique. The second step proceeds by performing three times logical bit operations between two ready-made reference images and just captured image to be tested. This results in defects image only. In the third step, by extracting four features from each detected defect, followed by assigning them into the input nodes of an already trained artificial neural network we can obtain a defect class corresponding to the features. All of the image data are formed in a bit level for the reduction of data size as well as time saving. Experimental results show that proposed algorithms are found to be effective for flexible defect detection, robust classification, and high speed process by adopting a simple logic operation.

• Journal of applied mathematics & informatics
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• v.26 no.5_6
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• pp.1149-1159
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• 2008

Blind source extraction (BSE) is a special class of blind source separation (BSS) methods, which only extracts one or a subset of the sources at a time. Based on the time delay of the desired signal, a simple but important extraction algorithm (simplified " BC algorithm")was presented by Barros and Cichocki. However, the performance of this method is not satisfying in some cases for which it only carries out the constrained minimization of the mean squared error. To overcome these drawbacks, ICA with reference (ICA-R) based approach, which considers the higher-order statistics of sources, is added as the second stage for further source extraction. Specifically, BC algorithm is exploited to roughly extract the desired signal. Then the extracted signal in the first stage, as the reference signal of ICA-R method, is further used to extract the desired sources as cleanly as possible. Simulations on synthetic data and real-world data show its validity and usefulness.

• Korean Journal of Child Studies
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• v.9 no.2
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• pp.133-156
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• 1988

This study investigated developmental change with reference to continuity theory in the acquisition of concepts of kin relation, task difficulty with reference to cognitive complexity, and interrelationships in the performance of cognitive tasks of kinship concepts with reference to cognitive parallelism. The subjects consisted of 6-, 8-, 10, and 12-year-old randomly selected children attending kindergartens or elementary schools in Seoul. The schools were located in various residental areas regarded as either middle or lower class. The 81 boys and 80 girls participated in 3 experiments on classification, seriation, and grouping. The instrument for the classification, seriation, and grouping tasks was composed of 10 10cm black on white line drawings of the head and upper torso area of persons in kin relationship. The data was analyzed with MANOVA. A significant age effect was found in the 3 quasi- experiments. There were significant effects on task difficulty. The biosocial power distribution indirectly influenced children's acquisition of kin relational concepts; that is, children performed better in male-kin than in female-kin tasks. There was a high correlation in performance between the 3 cognitive tasks. These findings support the continuity theory (except for seriation), a model which arranges kin-names in order of cognitive load, the centric status of men in society, and the theory of cognitive developmental parallelism.

• Journal of Magnetics
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• v.21 no.4
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• pp.603-615
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• 2016

In this study, in order to determine the validity and accuracy of MR imaging of 3D gradient dual echo 2-point DIXON technique for measuring abdominal adipose tissue volume and distribution, the measurements obtained by CT were set as a reference for comparison and their correlations were evaluated. CT and MRI scans were performed on each subject (17 healthy male volunteers who were fully informed about this study) to measure abdominal adipose tissue volume. Two skilled investigators individually observed the images acquired by CT and MRI in an independent environment, and directly separated the total volume using region-based thresholding segmentation method, and based on this, the total adipose tissue volume, subcutaneous adipose tissue volume and visceral adipose tissue volume were respectively measured. The correlation of the adipose tissue volume measurements with respect to the observer was examined using the Spearman test and the inter-observer agreement was evaluated using the intra-class correlation test. The correlation of the adipose tissue volume measurements by CT and MRI imaging methods was examined by simple regression analysis. In addition, using the Bland-Altman plot, the degree of agreement between the two imaging methods was evaluated. All of the statistical analysis results showed highly statistically significant correlation (p<0.05) respectively from the results of each adipose tissue volume measurements. In conclusion, MR abdominal adipose volumetry using the technique of 3D gradient dual echo 2-point DIXON showed a very high level of concordance even when compared with the adipose tissue measuring method using CT as reference.

• Journal of Astronomy and Space Sciences
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• v.36 no.3
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• pp.213-223
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• 2019

This paper analyzes delta-Vs to maintain an extremely low altitude on the Moon and investigates the possibilities of performing a CubeSat mission. To formulate the station-keeping (SK) problem at an extremely low altitude, current work has utilized real-flight performance proven software, the Systems Tool Kit Astrogator by Analytical Graphics Inc. With a high-fidelity force model, properties of SK maneuver delta-Vs to maintain an extremely low altitude are successfully derived with respect to different sets of reference orbits; of different altitudes as well as deadband limits. The effect of the degree and order selection of lunar gravitational harmonics on the overall SK maneuver strategy is also analyzed. Based on the derived SK maneuver delta-V costs, the possibilities of performing a CubeSat mission are analyzed with the expected mission lifetime by applying the current flight-proven miniaturized propulsion system performances. Moreover, the lunar surface coverage as well as the orbital characteristics of a candidate reference orbit are discussed. As a result, it is concluded that an approximately 15-kg class CubeSat could maintain an orbit (30-50 km reference altitude having ${\pm}10km$ deadband limits) around the Moon for 1-6 months and provide almost full coverage of the lunar surface.

• Journal of The Korean Society of Integrative Medicine
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• v.2 no.2
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• pp.1-12
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• 2014

Purpose : The purpose of this study was to investigate the effect that the academic achievement of the students about the evidence based learning investigates the learning utility value about and the request. Method : The agreement of college students explaining the purpose of research for 12 weeks against 17 students and investigate through a questionnaire. The level of academic achievement according to the sex and claim showed a characteristic with a percentage. An utility investigate the descriptive epidemiologic characteristic about the class of the evidence based learning. Result : The most of college students the level of academic achievement and requests the expected grade of the students about the evidence based learning wanted the 'high' grade of 9 persons, 'middle' grade of 8 persons in the part and the expectation for the class taken so much was high(p<.05). There was the significant different in the utility aspect in the need of the evidence based learning, homework solution, learning synergy effect improvement, and reference search ability improvement(p<.05). Conclusion : These finding revealed that the evidence based learning the satisfaction with class raises the improvement and utility value, and provided the need and the has to develop the educational model which the college students contentment raises an improvement after this opportunity for the new recognition.

• Journal of Korean Elementary Science Education
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• v.29 no.1
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• pp.13-21
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• 2010

This study reflects the demand of content elements related to "Human Reproduction" in elementary school science curriculum, and verifies its effects by developing and applying sex education contents available to elementary science class. The developed contents is composed of three sections in reference to the contents guideline for teachers. The contents include anatomical knowledge related to human reproduction and reflect social and cultural context of sex ethics. The first section: "How was I born?", second section: "Amazing changes in my body" and third section: "Healthy body, healthy mind." In the result of analysis of changes in sex knowledge and attitude after applying the contents, it showed statistically significant differences between experimental and comparative class. Thus, the developed contents made positive influence on improvement in elementary students' knowledge and attitude of human reproduction. However, it showed little difference in the effects of sex education contents by the grade and gender. In conclusion, if the sex education contents developed through this study is actively applied, it is expected to provide the elementary students with knowledge of the anatomic difference between male and female, its social and cultural understanding and responsibility for sex ethics. In addition, it is considered to be used as effective education programs and materials in elementary school science curriculum.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.7 no.1
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• pp.1-6
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• 2007

The SVDD (support vector data description) is one of the most well-known one-class support vector learning methods, in which one tries the strategy of utilizing balls defined on the feature space in order to distinguish a set of normal data from all other possible abnormal objects. Recently, with the objective of generalizing the SVDD which treats all training data with equal importance, the so-called D-SVDD (density-induced support vector data description) was proposed incorporating the idea that the data in a higher density region are more significant than those in a lower density region. In this paper, we consider the problem of further improving the D-SVDD toward the use of a partial reference set for testing, and propose an LMI (linear matrix inequality)-based optimization approach to solve the improved version of the D-SVDD problems. Our approach utilizes a new class of density-induced distance measures based on the RSDE (reduced set density estimator) along with the LMI-based mathematical formulation in the form of the SDP (semi-definite programming) problems, which can be efficiently solved by interior point methods. The validity of the proposed approach is illustrated via numerical experiments using real data sets.

• Nuclear Engineering and Technology
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• v.51 no.8
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• pp.1951-1956
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• 2019

As a part of the preliminary decommissioning plan of KEPCO-NF fuel fabrication facility, DCGLs of three target radionuclides, ²³⁴U, ²³⁵U, and ²³⁸U, were derived using RESRAD-BUILD code and contaminated areas of the facility were classified based on contamination levels from the derived DCGLs. From code simulations, one-room modeling results showed that the grinding room in building #2 was the most restrictive (DCGL_gross = 10493.01 Bq/㎡). The DCGL_gross results in contaminated areas from one-room modeling were slightly more conservative than three-room modeling. Prior to the code simulation, field survey and measurements conducted by each survey unit. For a conservative approach, the most restrictive DCGL_gross in each survey unit was taken as a reference to classify the contaminated areas of the facility. Accordingly, seven rooms and 37 rooms in the nuclear-fuel buildings were classified as Class 1 and Class 2, respectively. As expected, fuel material handling and processing rooms such as the grinding room, sintering room, compressing room, and powder collecting room were included in the Class 1 area.