• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.501-502
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• 2007

This paper describes a distance relay that operates in conjunction with a current transformer (CT) compensation algorithm. A distance relay detects a fault based on the ratio of the voltage to the current. If a CT saturates, the calculated impedance becomes larger. This causes maloperation or operating time delay of the distance relay. A compensating algorithm estimates the correct secondary current from the severely distorted currents even when the measurement CTs are used. The correct current is estimated by adding the calculated magnetizing current to the measured secondary current. Test results show that the proposed distance relay can detect a fault without the operating time delay even when the secondary currents are extremely distorted because of use of measurement CTs.

• Journal of Navigation and Port Research
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• v.39 no.1
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• pp.15-21
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• 2015

In high precision positioning systems based on GNSS, ambiguity resolution is an important procedure. Correct ambiguity leads to positioning results which have high precision between millimeters and centimeters. However, when the ambiguity is determined incorrectly, ensuring accuracy and precision of the positioning result is impossible. An ambiguity validation test is required to obtain correct ambiguity when ambiguity resolution is performed based on the ILS (Integer Least Squares), which shows the best performance in point of theory and experiment when compared with other methods such as IR (Integer Rounding) and IB (Integer Bootstrapping). Comparison between the candidates of the validation test is needed to judge ambiguity correctly, because ILS searches for candidates of integer ambiguity, unlike other methods which calculate only one integer ambiguity. We analyzed the experimental performance of ambiguity validation tests. R-ratio, F-ratio and W-ratio were adopted for analysis. The performance of validation tests was evaluated by classifying normal operation, detection, missed detection and false alarm. As a result, strengths and weaknesses of validation tests was showed to experimental. we concluded that validation tests must be selected according to environment.

• Journal of the Korean Chemical Society
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• v.65 no.1
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• pp.25-36
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• 2021

This study aimed to analyze achievement characteristics of Korean students in the results of PISA 2018 science domain. To this end, the characteristics of PISA 2009 to PISA 2018 science were analyzed in terms of the percentage of each performance level and the ratio of male and female by achievement level; in addition, the percentage of correct answers by framework subscale was compared with PISA 2015. The results showed that Korea has a higher percentage of students at the lower level of achievement as compared to the high-ranking countries of PISA, and the ratio of students at the higher level of achievement was lower. On average, the difference in achievement between boys and girls was negligible; however, but at the higher achievement level, the ratio of boys continued to be higher than that of girls. In addition, in the PISA science framework, the percentage of correct answers of the questions corresponding to 'personal' of 'contexts', 'evaluate and design scientific enquiry' of 'competencies', 'epistemic' of 'knowledge', and 'high' of 'cognitive demand' increased; similarly, and achievement improved as compared to PISA 2015. Based on these results of the study, we propose a method for improving teaching and evaluation to foster Korean students' scientific competence.

• Journal of Korea Multimedia Society
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• v.9 no.2
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• pp.151-159
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• 2006

The ratio of a segmentation algorithm of compound nouns causes an effect a lot in nouns which are not in the dictionary. The structure of Korean compound nouns are mostly derived from the Chinese characters and it includes some preference ratio. So it will be able to use segmentation rule of compound nouns. This paper suggests a segmentation algorithm using some preference ratio of Korean compound nouns which are not in the dictionary. The experiment resulted in getting 88.49% of correct segmentation and showed effective result from the comparative experimentation with other algorithm.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.985-988
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• 2002

The Spindle-]fearing System is very important unit for geometrical accuracy in machine tools. To improve effectively the weak point of spindle system, it is necessary that the contribution ratio of spindle core parts to static and dynamic stiffness is clarified. In this paper, static contribution ratio of core parts is calculated by overlapping static deformation of basic spindle design with one flexible parts. The dynamic contribution ratio for natural frequency and dynamic deformation at spindle end is obtained by calculating correlation between original and basic spindle deformation, by curve fitting with regressive method. It is proved the validity of estimation result is correct.

• 대한예방의학회:학술대회논문집
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• 1994.02b
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• pp.158-163
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• 1994

Slightly elevated urinary albumin excretion rate (microalhuminuria) is a marker of early diabectic nephropathy, but it is unclear if the established definition of microalbuminuria ($20-200{\mu}g/min$) is correct for children and adolescents. We investigated th.: albumin excretion rate, albumin/creatinine ratio and urinary albumin concentration in 150 healthy schoolchildren and adolescents to (a) obtain a reterence value for albumin excretion rate, (b) relate albumin excretion to pubertal stages and (c) evaluate albumin/creatinine ratio and morning albumin concentration as screening methods for elevated albumin excretion rate. Albumin concentration was measured by immunoturbidimetry in timed overnight urine samples. The albumin excretion showed a skewed distribution (geometric mean $3.2{\mu}g/min$, 95 percentile ($15.1{\mu}g/min$). In girls. a peak in the albumin excretion rate was found at the pubertal stage 4 (Tanner) and in boys at stage 5. Albumin/creatinine ratio of 2.5 mg/mmol as a screening level for elevated albumin excretion ($15{\mu}g/min$) showed a high positive (0.88) and negative (0.99) predictive value.

• Journal of the Optical Society of Korea
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• v.15 no.3
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• pp.209-215
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• 2011

A new iterative algorithm is developed to estimate LIDAR ratio for a thin cirrus cloud over an aerosol layer. First, the thin cirrus cloud is screened out and replaced by a modeled LIDAR signal and the extinction coefficients of the aerosol layer are derived using the Fernald backward method. These aerosol coefficients are referred as the "actual values". Second, the original LIDAR signal which includes the thin cirrus cloud is also inverted by the Fernald backward method down to the aerosol layer but using different LIDAR ratio for the thin cirrus cloud. Depending on the different assumptions about the LIDAR ratio of the thin cirrus cloud, different sets of aerosol extinction can be derived. The "actual values" which are found in the first step can be used to constrain this iterative progress and the correct LIDAR ratio of the thin cirrus cloud can be found. The detailed description of this method and retrieval examples are given in the paper. The cases compared with other methods are presented and the statistical result is also shown and agrees well with other studies.

• Journal of the Korean Wood Science and Technology
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• v.43 no.2
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• pp.177-185
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• 2015

The goal of this study is to evaluate the limitation of ASTM D 198 bending and ASTM D 3044 in determination of elastic modulus and shear modulus. Different material properties and span to depth ratios were used to analyze the effects of material property and testing conditions. The ratio of true elastic modulus to apparent elastic modulus evaluated from ASTM D 198 bending sharply decreased with increment of span to depth ratio. Shear modulus evaluated from ASTM D 198 bending decreased with increment of depth, whereas shear modulus evaluated from ASTM D 3044 was hardly influenced by increment of depth. Poisson's ratio influenced shear modulus from ASTM D 198 bending but did not influence shear modulus from ASTM D 3044. Different shearing factor was obtained for different depths of beams to correct shear modulus obtained from ASTM D 198 bending equivalent to shear modulus from theory of elasticity. Equivalent shear modulus of materials could be obtained by applying different shearing factors associated with beam depth for ASTM D 198 bending and correction factor for ASTM D 3044.

• School Mathematics
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• v.15 no.1
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• pp.179-199
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• 2013

In this study we grasp what contents in the mathematics curriculum the students of multicultural and North Korean migrant families are vulnerable to and we would like to provide the bases to devise the appropriate teaching and learning methods for them. In order to this work we used the results of 2011 National Assessment Educational Achievement. We categorized students from multicultural and North Korean migrant families into children from international marriage family (born in country or immigrated), foreign family, and North Korean migrant family and compared each category with the whole students. First, for each school class we analyzed characteristics of academic achievement by ratio of achievement level, means of calibrated score, and percentages of correct answers in NAEA, mean percentages of correct answers by content domains, and percentages of correct answers by items. In addition to these we analysed items qualitatively and investigated study conditions in which the students of multicultural and North Korean migrant families have difficult times. In every subgroup the more ratio of advanced level decreases and ratio of below basic level increases the more school classes go up. Also these phenomena appear differently by each group and by content domain. For this reason by group, the supporting on learning will be needed.

• Journal of the Korean Chemical Society
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• v.57 no.1
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• pp.138-146
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• 2013

This study examined the characteristics of the National Assessment of Educational Achievement (NAEA) in Science according to gender. It investigated gender achievement differences in the science section of the 2010 NAEA, the ratio of gender difference in achievement, the ratio of correct answers within each content domain and behavioral domain, and the items which showed high differences between males and females. The results indicate first, that, for 9th graders, females outperformed males in academic achievement in science. Second, with respect to the ratio of correct answers, males outperformed females in the advanced and below basic level groups, but females outperformed males in intermediate level groups. Third, females outperformed males in knowledge and inquiry in the behavior domains, and in chemistry and biology in the content domains. Fourth, an analysis of the items showing the largest gender gap indicated that males outperformed females in interpreting data, while females outperformed males in the items concerned with daily life and items related to the memorization of rules. This research on gender differences in science will allow teachers to complement the weaknesses of students when they study science, and support improved instructional methods in science.