• Journal of The Korean Association For Science Education
• /
• v.22 no.2
• /
• pp.345-356
• /
• 2002

This study investigated the trends in the number of applicants and mean score and applicants' responses on the test items of 'science inquiry' of the College Scholastic Ability Test(CSAT) implemented for 3 years$(1999\;{\sim}2001)$. The results of this study were as follows: The percentage of applicants of science track for 1995 CSAT were 43.13%, but reduced to 29.5% for 2001 CSAT. And unlike other tracks, the percentage of male applicants, ranking above average, of science track was 65.58%, which is about twofold of female applicants(34.42%). The mean score of 'Science inquiry' was 58.6 in 1999, and 69.5 in 2001. And the score of the applicants, ranking above average, of humanity and social science course and science course, were 85.8 and 90.7 respectfully in 2001 CSAT. These high mean scores were caused by the policy of "easy CSAT" so called. Most of test items were developed to have difficulty 60-79% or above 80%. This easy CSAT provoked intense dispute about the discriminating power of CSAT. The mean score of male applicants was higher than that of female. But the difference decreases every year. Applicants were generally very good at solving tests focusing on process skills only but poor at solving tests related to physics or calling for two or more science concepts. Thus special measures to cope with the decrease in applicants, especially female applicants, for science track should be provided. To increase discriminating power of CSAT, it is recommended to develop test items with wider range of difficulty and to reduce test items which are focussing process skills and can be solved without any special science concepts. And special consideration should be given to teaching the content area with poor achievement and high actual difficulty compared to the expected.

• Journal of the Korean Society of Radiology
• /
• v.15 no.6
• /
• pp.771-779
• /
• 2021

It is necessary to overlap several peaks to form spread out Bragg peak (SOBP) in order to cover the tumor volume because a mono-energetic proton beam forms a narrow Bragg peak. The tumor density has been considered as a brain tissue and then the absorbed dose of the tumor is calculated using Monte Carlo simulations. However, densities of tumors were not a constant. In this study, the SOBP of proton beams was calculated according to changing density of tumors by using Geant4. Tumors were selected as 10 mm and 20 mm width which were the treatment range in the brain phantom. The energies and relative weights of the proton beams were calculated using mathematical formula to form the SOBP suitable for the location and size of the tumor. As the density of the tumor was increased, the 95% modulation range and the practical range were decreased, and average absorbed dose in the 95% modulation range was increased. The change of the tumor density affects the dose distribution of the proton beams, which results in short SOBP within the tumor volume. The consideration of the tumor density affects the determination of the range, so that the margin of the treatment volume can be minimized, and the advantages of proton therapy can be maximized.

• The Mathematical Education
• /
• v.59 no.2
• /
• pp.131-146
• /
• 2020

Regarding the formula for measuring the area of a circle, the Archimedes' constant is generally written in front of the square of radius length, but there were a few cases where the Archimedes' constant was written after that in Germany and France. In this study, two things are studied: First, how many students are writing the Archimedes' constant after that? Second, what do the students think about the written order of characters in the formula for measuring the area of a circle? In the online survey of 201 people aged 14 to 21 in Korea, there was a perception of more than 86% that both are possible or only after that are possible. In this study, it is suggested that there is a difference between the general written order of characters and the natural perception of students formed through school education. In addition, students aged 14 to 16 thought more that the Archimedes' constant should be written after that, and after that age, there was a greater perception that both are possible without confusion of meaning. It can be seen that the change in students' perception has emerged through school education on natural mathematical written order of characters after middle school courses. From this point of view, the most common perception can be that if there is no confusion in meaning, then both expressions are possible.

• Education of Primary School Mathematics
• /
• v.19 no.2
• /
• pp.127-142
• /
• 2016

The purpose of this study was to examine the students' problem solving ability according to numeric expression and the semantic types of addition and subtraction word problems. For this, a research was to analyze the addition and subtraction calculation ability, word problem solving ability of the selected $2^{nd}$ grade(118) and 3rd grade(109) students. We got the conclusion as follows: When the students took the survey to assess their ability to solve the numerical expression and the word problems, the correct answer rates of the result unknown problems was larger than those of the change unknown problems or the start unknown problems. the correct answer rates of the change add-into situation was larger than those of the part-part-whole situation in the result unknown addition word problems: they often presented in text books. And, in the cases of the result unknown subtraction word problems that often presented in text books, the correct answer rates of the change take-away situation was the largest. It seemed probably because the students frequently experienced similar situations in the textbooks. We know that the formal calculation ability of the students was a precondition for successful word problem solving, but that it was not a sufficient condition for that.

• Korean Journal of Cognitive Science
• /
• v.16 no.1
• /
• pp.53-67
• /
• 2005

Present study identified categorization pattern differences between experts and novices and examined whether categorization training has positive effects on problem solving. In experiment I, we examined categorization differences between groups according to expertise using mathematical equation problems. Experts classified problems based on deep structure related to problem solution methods whereas novices classified problems based on surface features. However, in the labeled categorization condition, novices' categorization pattern was not different from experts'. These results suggest that novices have difficulty identifying deep structure of problems. In experiment 2, we examined whether categorization training showing subjects deep structure of problems explicitly increases transfer performance. The results showed that solution training was more effective to expert group whereas categorization training was more effective to novice group. We have discussed that different training methods should be applied according to expertise.

• Journal of the Korean earth science society
• /
• v.23 no.6
• /
• pp.461-473
• /
• 2002

Concept mapping is a device for representing the conceptual structure of a subject discipline in a two dimensional form which is analogous to a road map. In the teaching and learning of earth science, each concept depends on its relationships to many others for meaning. Using concept mapping in teaching helps teachers and students to be more aware of the key concepts and relationships among them. The purpose of this study is to investigate the effect of the use of concept mapping on science achievement and the scientific attitude in ocean units of earth science. The results of this study are as follows; first, the science achievement of a group of concept mapping teaching is significantly higher than that of the group of traditional teaching. Also, when the achievement levels are compared among different cognitive ability groups, the effect is more significant in mid or lower level student groups than in high level groups. The use of concept mapping is more effective when the concepts have a distinct concept hierarchy. Second, the scores of the test of ‘attitude toward scientific inquiry’ and ‘application of scientific attitude’ of the group of concept mapping teaching are significantly higher than those of the group of traditional teaching, whereas the scores of the test of ‘interest in science learning’ of concept mapping teaching is not different from those of group of traditional teaching. Third, the survey on the use of concept mapping shows a positive response across the tested groups. The use of concept mapping is more beneficial in fostering the comprehension of the topic. A concept map of student's own construction facilitates the assessment of learning, thus promising the usefulness of concept mapping as a means of evaluation. In regard to retention aspect, concept mapping is considered to be more effective in confirming and remembering the topic, while less effective in the aspects of activity and interest. In conclusion, the use of concept maps makes learning an active meaningful process and improves student's academic achievement and scientific attitude. If the concept mapping is more effectively as an active teaching strategy, more meaningful learning will be attained.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.16 no.7
• /
• pp.1351-1362
• /
• 1992

Qualitative models in model-based expert system needs modeling paradigm which provides intelligent control of modeling assumptions and extracts robust inferences without quantitative information about the system to be modeled. Qualitative reasoning methodologies has proved the property of the completeness but not the soundness to the corresponding quantitative model. We propose new methodology of qualitative reasoning by introducing the concept of Centroid-Oriented Composite Interval to improve the soundness problem. Arithmetic operations and equivalence classes were composed using this definition. Qualitative simulation results were compared to Kuipers's results and the improvements in the soundness problem is verified.

• Bulletin of Food Technology
• /
• v.9 no.2
• /
• pp.111-127
• /
• 1996

Potassium Sorbate의 향균능력측정결과 효모(Saccharomyces cerevisiae)의 성장에 대하여 uncompetitive 기작으로 작용하였다. 열처리 실험의 결과 Potassium Sorbate는 가열온도에 대하여 Arrhenius, 또한 가열시간에 대하여 1차반응식관계로 향균능력을 잃었으며 따라서 보존제로 Potassium Sorbate를 식품에 첨가후 포장, 가열살균하는 일반 식품가공공정상에서 가열살균공정이 첨가 보존제의 잔류향균능력을 잃게 하는 것으로 나타났다. 플라스틱 film과 치즈안에서 Potassium Sorbate의 확산계수 및 확산에 의한 물질전달 현상을 수학적모델과 컴퓨터 simulation 그리고 실험에 의해 구하였다. 저밀도폴리에틸렌(LDPE)이 범용플라스틱중에서 가장 작은 확산계수를 가져 빠른 물질전달이 요구되는 film층 또는 약물저장층으로 적합한것으로 나타났다. 그외 고밀도 폴리에틸렌(HDPE)과 폴리프로필렌(PP), 폴리에스터(PET)는 느린 물질전달이 요구되는층 또는 복합다층 film에서 물질전달에 단방향성을 주는 고차단층으로 적합한것으로 나타났다. Potassium Sorbate분말과 LDPE resin분말을 섞은후 단일스크루 익스트루더로 항균성 포장 film을 제조한 결과 LDPE film의 tensile strength과 elongation, elastic modulus는 Potassium Sorbate를 3% 이상 포함할때까지 변화하지 않았다. 그러나 film의 투명도는 급격히 낮아졌다. 향균성LDPE film은 효모가 접종된 한천배지상에서 항균물질인 Potassium Sorbate를 배지위로 서서히 방출시켜 효모의 성장속도(growth rate)를 저하시키고 초기성장지체기(lag period)를 연장시킨다. 따라서 식품포장재로 적용시에 미생물의 오염을 막고 식품저장기간을 연장할것이라 여겨진다.

• The Journal of Natural Sciences
• /
• v.8 no.2
• /
• pp.175-179
• /
• 1996

The fruit soluble solids and acidity decreased during storage regardless of fruit size, fruit firmness decreased also, and the decreasing rate of the firmness in large fruit was higher than small. The ethylene production of fruit was increased during storage, and there was the peak of fruit respiration rate at 2 and 6 weeks after harvest. The calcium and magnesium content was the highest in peel, the lowest in flesh, and intermediate in core. Especially, the calcium content in the outer flesh was lower than in the inner flesh, and the magnesium content in the middle part of flesh was lower than in the other parts. The Ca/Mg ratio in the inner flesh and the K/Ca ratio in the outer flesh were higher than in the other parts.

• Journal of Navigation and Port Research
• /
• v.36 no.8
• /
• pp.613-618
• /
• 2012

For the tug-barge simulation, captive model test(Horizontal Planar Motion Mechanism) of the barge model is carried out. From the result of HPMM test, a resistance coefficient, maneuvering coefficients of the barge are obtained. A mathmatical model of the barge is validated by turning simulations with different angle of towing line applied a simple towing line model and the tactical diameter compared to sea trial data. As a result, the tactical diameter of the barge is smaller as the angle of towing line is bigger. The tactical diameter from simulations is smaller than that from sea trial data, may be caused by increased displacement of the barge.