• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.4
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• pp.307-314
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• 2008

Loading noise generated by steady aerodynamic force exerted on the rotating body surface is theoretically analyzed and its radiation characteristics is examined as a fundamental research of helicopter rotor noise. For simplicity, the force exerted on each blade is not distributed but concentrated at one point and the noise is evaluated by using Lowson' exact formula with a discussion of the physical meaning of each term in the formula. For a single point force rotating with various angular frequencies, we investigated the radiation characteristics and theoretically explained the physical behavior at near and far-field. By investigating the amplitude of acoustic pressure with various distances, we observed the different decreasing ratio at near- and far-field with the discussion of the effect of acceleration of angular frequency. Finally, the phenomenon that the noise level is reduced everywhere as the number of blade increases is explained with the suggestion of a noise reduction idea, the limitations of this study, and the future research topics.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.45 no.6
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• pp.33-44
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• 2008

Multipath routing protocols with load balance, fault tolerance, aggregated bandwidth in Ad-hoc Networks provide improved throughput and reliable route as compared with singlepath routing protocols. However, multipath routing protocols have not been explored thoroughly in the domain of overhead in Ad-hoc Networks. In this paper, we analyze and compare on-demand singlepath and multipath routing with IEEE 802.11 DCF in terms of Routing overhead and MAC overhead. The results reveals that in comparison with singlepath routing protocol, multipath routing mechanism creates more overheads but provides better performance in congestion and capacity provided that the route length is within a certain upper bound which is derivable. The analytical results are further confirmed by simulation.

• Korean Journal of Food Science and Technology
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• v.26 no.2
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• pp.103-109
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• 1994

Changes in the rheological properties and the linear viscoelasticity of fish protein gel upon the thermal processing were studied by using mathematical models with stress-relaxation data. The linear viscoelasticity of surimi gel was observed in the range of the true strain $0.105{\sim}0.693$ and cross-head speed $50{\sim}250\;mm/min$ applied in this study. The results of the generalized Maxwell analysis showed that the magnitudes of elastic elements $(E,\;E_e)$ were increased, but the viscous element $({\eta}) $was decreased, as the cross-head speeds and strain levels were increased. Compared to the protein gel heated directly at $90^{\circ}C$ without preheating, the protein gel pretreated at $4^{\circ}C$ and $40^{\circ}C$ showed the higher elastic modulus, but showed different trends in the viscous component, depending on the rheological model applied. Thus, the approaching methods and curve fitting of two mathematical models of stress-relaxation to describe the viscoelastic properties of fish protein gel were discussed.

• Journal of Educational Research in Mathematics
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• v.18 no.3
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• pp.353-372
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• 2008

This study looks around the goals of teaching statistical graphs that are introduced in the seventh Korean Curriculum for Elementary School and in the Principles and Standards for School Mathematics(NCTM, 2000), and these are compared. We compare how to transpose statistical graphs didactically between the Korean and MiC textbooks. For it, it examines the types of statistical graphs, the methods defining them, and the making connections and comparing among them, which are content components in the chapters on statistical graphs. The results show that in contrast to the Korean textbooks, NCTM(2000) has allowed students to develop their own expression for data, to compare results analysed within different graphs, and to consider a graph as a whole in the goals of teaching statistical graphs. MiC textbooks have introduced the number-line plot and the box plot more than Korean. Although both of Korean and MiC textbooks usually use extensive methods for defining individual graphs, the former use extensive methods together with synonymic methods and the latter use extensive methods with the characteristics of graphs. Also, the number-line plot is defined using operative method in the MiC textbooks. MiC textbooks contain various activities for connecting and comparing graphs, but there are comparatively few comparing activities in the Korean textbooks.

• School Mathematics
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• v.10 no.2
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• pp.155-179
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• 2008

Multiplication problems for the 7th curriculum focus on functional realms featuring the memorization and application of the multiplication table, exposing learners only to additive thinking characterized by simple counting and drawing. A diversity of research has yet to be conducted for the transition to multiplicative thinking that highlights the capability to solve problems by using multiplication and division in the expanded number scope like 'prime numbers', 'fractional numbers', and 'ratio/rates' and to describe accurately how they solved. This research was designed to develop and utilize teaching-learning materials for the transition of fifth graders' additive thinking to advanced multiplicative one and to analyze the application results in order to identify validity in material development. The following conclusions were made. First, the development and application of teaching-learning materials for multiplicative thinking cultivation facilitated the transition from additive thinking featuring simple counting and drawing to multiplicative thinking characterized by multiplication and accurate description in a more complicated and expanded number scope. Second, the development of materials featuring 'basic'-'intermediate'-'in-depth' courses by activity enabled learners to benefit from learning by level and expansion in number scope. Third, the use of topics and materials closely connected to daily lives stimulated learners' curiosity, helping them concentrate more on given problems. Fourth, communication between teachers and students or among learners themselves was promoted by continuously encouraging them to explain and by reviewing their documents identifying rules or patterns.

• School Mathematics
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• v.17 no.2
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• pp.241-255
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• 2015

The purpose of this study is to analyze teachers' understanding on generating random number in Monte Carlo simulation and to provide educational implications in school practice. The results showed that the 70% of the teachers selected wrong ideas from three types for random-number as strategies for problem solving a probability problem and also they make some errors to justify their opinion. The first kind of the errors was that the probability of a point or boundary was equal to the value of the probability density function in the continuous probability distribution. The second kind of the errors was that the teachers failed to recognize that the sample space has been changed by conditional probability. The third kind of the errors was that when two random variables X, Y are independence of each other, then only, joint probability distribution is satisfied $P(X=x,\;Y=y)=p(X=x){\times}P(Y=y{\mid}X=x)$.

• 한국정보교육학회:학술대회논문집
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• 2021.08a
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• pp.167-173
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• 2021

The purpose of this study is to discuss the types of algorithms and data categories in AI education for elementary school students. The study surveyed 11 pre-elementary teachers after providing education and practice on various data, artificial intelligence algorithm, and AI education platform for 15 weeks. The categories of data and algorithms considering the elementary school level, and educational tools were presented, and their suitability was analyzed. Through the questionnaire, it was concluded that it is most suitable for the teacher to select and preprocess data in advance according to the purpose of the class, and the classification and prediction algorithms are suitable for elementary AI education. In addition, it was confirmed that Entry is most suitable as an AI educational tool, and materials that explain mathematical knowledge are needed to educate the concept of learning of AI. This study is meaningful in that it specifically presents the categories of algorithms and data with in AI education for elementary school students, and analyzes the need for related mathematics education and appropriate AI educational tools.

• Proceedings of the Korean Society of Computer Information Conference
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• 2011.06a
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• pp.419-420
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• 2011

스마트폰을 이용한 학습용 앱을 개발하기 위해 본 연구는 기초학습인 덧셈의 기능을 완료하였다. 덧셈문제를 계속해서 풀 수 있는 구조로 설계하였고, 정답과 오답에 대한 설명 이벤트를 배치하여 학습효과를 높였다. 본 과정은 수학공식 및 다양한 학습으로 확장 가능하며, 사용자별, 날짜별 점수 DB를 저장한다면 본인의 실력 향상을 체크해 볼 수 도 있을 것이다. 본 학습앱을 안드로이드기반 스마트폰에 배포한 결과 정상적으로 풀이 됨을 확인하였다.

• ETRI Journal
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• v.10 no.4
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• pp.99-117
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• 1988

This paper has two main purposes, One is a scientific theory for the Hangul writing system. It is a mathematical model which is formulated a logical characteristics involved in the compositionality principle of Hun Min Jung Um[6], and is based on the traditional scientific methodology and theory. The other is an engineering model for the Hangul writing system. It has proven that the model is more theoretical and practical that the conventional models called Hangul automata. This paper also shows the reasons why Korean has a great national pride in Hangul[3]. Consequently, we suggest that Hangul writing system has a potential capability as an ultimate human interface connecting human, computer and information.

• The Journal of the Korea Contents Association
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• v.8 no.12
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• pp.1-9
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• 2008

Fuzzy Cognitive Map, one of ways to model, describe and infer reasoning relations, is widely used in the field of reasoning knowledge engineering. Despite of the natural and easy understanding of decision and smooth explanation of relation between front and rear, reasoning relation is organized with mathematical haziness and complex algorithm and rarely has an interactive user interface. This paper suggests an interactive Fuzzy Cognitive Map(FCM) construction support system. It builds a FCM increasingly concerning multiple experts' knowledge. Futhermore, it supports user-supportive environment by dynamically displaying the structure of Fuzzy Cognitive Map which is constructed by the interaction between experts and the system.