• Communications of Mathematical Education
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• v.24 no.3
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• pp.543-562
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• 2010

The purpose of this thesis is to analyze the error happening in the process of solving the simultaneous inequality with two unknown qualities and to propose the correct teaching method. We first introduce a problem about the simultaneous inequality with two unknown qualities. And we will see the solution which a student offers. Finally we propose the correct teaching method by analyzing the error happening in the process of solving the simultaneous inequality with two unknown qualities. The cause of the error are a wrong conception which started with the process of solving the simultaneous equality with two unknown qualities and an insufficient curriculum in connection with the simultaneous inequality with two unknown qualities. Especially we can find out the problem that the students don't look the interrelation between two valuables when they solve the simultaneous inequality with two unknown qualities. Therefore we insist that we must teach students looking the interrelation between two valuables when they solve the simultaneous inequality with two unknown qualities.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.5
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• pp.489-495
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• 2014

A micro-genetic algorithm (MGA) is one of the improved forms of a genetic algorithm. It is used to reduce the number of iterations and the computing resources required by using small populations. The efficiency of MGAs has been proved through many problems, especially problems with 3-5 design variables. This study proposes an optimization algorithm based on the sequential design of experiments (SDOE) and an MGA. In a previous study, the authors used the SDOE technique to reduce trial-and-error in the conventional approximate optimization method by using the statistical design of experiments (DOE) and response surface method (RSM) systematically. The proposed algorithm has been applied to various mathematical examples and a structural problem.

• Journal of KIISE:Software and Applications
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• v.33 no.8
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• pp.730-740
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• 2006

In recent years, bullied students and rogue groups in teenagers make many serious social problems. In this paper we propose a novel approach that more objectively analyzes peer relationships among students. As the data for objective analysis, we use communication history records that are collected from various communication tools such as telephones, e-mails, and messengers. We use the simple intuition that communication history records implicitly contain peer relationship information. And, we adopt data mining techniques for the more systematic analysis. The proposed peer relationship analysis consists of the following steps. First, we formally define the notion of degree of familiarity between friends, and present mathematical equations that compute the degree based on communication history records. In the proposed method, we use the intuition that the degree of familiarity from student x to student y becomes higher as x makes the more communications with y. Second, by using the degree of familiarity between students, we find out the students who are potentially bullied. This procedure is based on the assumption that a bullied student may have a very small number of history records from other students to him. Third, we adopt the clustering technique, one of the most representative data mining techniques, to find out meaningful student groups by using the degree of familiarity. To use the clustering technique, we formally define the notion of similarity between friends based on the degree of familiarity, and perform clustering using the notion. Last, to show the practicality of the proposed method, we have implemented the method and interpreted the meaning of the experimental results. Overall, we believe that our research result provides an effective framework that analyzes peer relationships more objectively and more systematically.

• Korean Journal of Logic
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• v.8 no.1
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• pp.23-46
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• 2005

The purpose of the paper Is to discuss and estimate early Popper's theory of probability, which is presented in his book, The Logic of of Scientific Discovery. For this, Von Mises' frequency theory shall be discussed in detail, which is regarded as the most systematic and sophisticated frequency theory among others. Von Mises developed his theory to response to various critical questions such as how finite and empirical collectives can be represented in terms of infinite and mathematical collectives, and how the axiom of randomness can be mathematically formulated. But his theory still has another difficulty, which is concerned with the inconsistency between the axiom of convergence and the axiom of randomness. Defending the objective theory of probability, Popper tries to present his own frequency theory, solving the difficulty. He suggests that the axiom of convergence be given up and that the axiom of randomness be modified to solve Von Mises' problem. That is, Popper introduces the notion of ordinal selection and neighborhood selection to modify the axiom of randomness. He then shows that Bernoulli's theorem is derived from the modified axiom. Consequently, it can be said that Popper solves the problem of inconsistency which is regarded as crucial to Von Mises' theory. However, Popper's suggestion has not drawn much attention. I think it is because his theory seems anti-intuitive in the sense that it gives up the axiom of convergence which is the basis of the frequency theory So for more persuasive frequency theory, it is necessary to formulate the axiom of randomness to be consistent with the axiom of convergence.

• Journal of Gifted/Talented Education
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• v.25 no.6
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• pp.857-879
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• 2015

This study investigated the relationships among middle school students' perceptions on the roles of online tutor, their deep learning, achievement, and overall evaluation of learning experiences in the context of inquiry based online gifted mathematics and science learning. For this purpose, 249 middle school students who took online course were surveyed about their perceptions on the degree to which their tutor performed the roles as an online tutor. The students were also asked about the activities which indicate deep learning approaches and overall course experiences such as the level of satisfaction, understanding and engagement in the course. The regression analyses were conducted to examine the relationships of students' perceptions on the roles of online tutor, deep learning, achievement, and overall course experiences. The results first showed that the roles of online tutor which affects students' deep learning approach such as high-order learning, integrative learning, reflective learning were the role as a subject matter and evaluation expert. Among the sub variables of deep learning approach the variable that was related to students' overall achievement was the use of high-order learning strategy. Second, the achievement in inquiry task was related to the role of tutor as a guide of learning process and method. Third, students' overall course evaluations such as the level of satisfaction, understanding and engagement were not related to any role of tutor.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.100-100
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• 2017

하천에 유입된 오염물질의 2차원 혼합거동은 하천 주흐름에 의한 이송현상과 유속 성분의 수심평균 값에 대한 공간적 편차로부터 야기되는 분산현상으로 설명 할 수 있다. 이는 3차원 이송확산 방정식으로부터 수심 적분된 2차원 이송-분산 방정식으로 수학적 유도가 가능하며, 수심방향으로 적분하는 과정에서 발생되는 농도의 분산항은 Taylor Dispersion 개념에 기초하여 종방향 및 횡방향의 2차원 분산계수로 표현된다. Fischer(1978)는 연직방향 유속분포로부터 2차원 분산계수를 추정하는 해석해를 수학적으로 유도하였으나, 실제 하천에서 정밀한 연직방향 유속분포를 계측하는 것은 많은 비용 및 노동력을 초래한다. 따라서 선행 연구자들은 2차원 혼합모형의 분산계수를 산정하고자 실험적 방법으로써 추적자실험을 수행하였다. 추적자실험은 추적자 물질을 수체에 주입한 후 농도의 변화를 관측함으로써 추적자물질이 하천에서 이송 및 분산되는 과정을 이해하는데 유용하다. 기존의 추적자실험은 고정된 위치에서 농도를 계측하여 시계열적인 농도의 변화를 관측한 후, 오염운 동결가정을 통해 종,횡방향 분산계수의 산정이 가능하지만, 오염물질 농도의 공간적 분포를 얻기에는 한계가 있다. 본 연구에서는 기존의 추적자실험법의 한계를 극복하고자 형광물질을 이용한 추적자실험을 수행함과 동시에 드론에 장착된 디지털카메라를 이용하여 항공영상을 취득 및 분석하여, 하천에 주입된 형광물질의 농도분포를 시공간적으로 추출하는 기법을 개발하고, 이를 바탕으로 오염물질의 2차원 혼합거동을 분석하였다. 본 실험은 한국건설기술연구원의 안동하천실험센터의 A3실험수로에서 수행되었으며, 실험수로는 평균 하폭 5 m, 평균 수심 0.44 m, 유량 $0.96m^3/s$의 실제 소규모 하천과 유사한 축척을 가지고 있다. 추적자물질은 Rhodamine WT 용액이 사용되었으며, 실험수로 내 설치된 15개의 형광광도계(YSI-600OMS)를 이용하여 농도를 측정하였다. 항공영상의 취득을 위해 이용된 드론은 DJI-Phantom 3 Professional 이며, 3840x2160의 해상도로 초당 30 frame의 동영상으로 취득되었다. 영상의 정합 및 좌표화를 위해 RTK-GPS를 이용하여 12개의 지상 기준점의 좌표를 취득한 후, 사영변환을 통해 영상좌표를 지상좌표로 변환하였다. 영상의 픽셀값을 농도장으로 변환하기 위해 각 RGB 밴드의 픽셀값을 통계적으로 분석하여 농도장으로 변환하였으며, 영상으로부터 얻은 농도장은 형광광도계에 의해 실측된 농도와 결정계수 0.9이상의 수준으로 정확도를 나타냈다.

• Aerospace Engineering and Technology
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• v.4 no.2
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• pp.27-35
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• 2005

In this study, a performance analysis code was developed for the off-design performance analysis of air turbo ramjet(ATR) engine, and the analyses were performed for the pre-designed ATR engine at several operating points in the envelope. Variable intake and thrust nozzle were assumed to cover the wide envelope. Mathematical models for each components were developed to calculate their off-design performance. Simple design formulas were introduced for some components to explore the performance variation versus the design parameters. As a result, the pre-defined engine couldn't cover the entire mission profile. And it was also found that the effect of the pre-cooler was not very great, especially in the region of low Mach number.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.12B
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• pp.1426-1434
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• 2009

RFID/USN is considered as a key convergence technology in future ubiquitous network. In RFID/USN, the power saving issue receives a great attention due to limited battery lifetime of sensor node. In this paper, we propose a new power saving algorithm, which takes advantage of long-term sleep period. To provide a full network connectivity and balance the battery consumption among sensor nodes, the proposed algorithm intelligently selects the long-term sleep sensor nodes. With mathematical analysis and simulations, we prove that the proposed algorithm can significantly reduce the power consumption of sensor nodes as compared to existing algorithms.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.11a
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• pp.35-38
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• 2007

Aiming at time-dependent performance prediction of Liquid Rocket Engine(LRE) system, Modular Program for Conceptual Design of LRE is reviewed, and a modeling and dynamic analysis of rocket engine system with reference to Rocket Engine Dynamic Simulator(REDS) is outlined. Component modeling is based on classical thermodynamic and inviscid theories, and were formulated mathematically in terms of essential parameters. Essential design parameters are addressed. The rocket engine is modeled as a system of pipes with various hydraulic elements, and then the operate characteristic of that elements are simulated by solving conservation equation sequentially.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.4
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• pp.34-40
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• 2012

In wireless communication system, fading is an unavoidable problem. Hence, errors in form of BER are introduced with the transmitted signal. It is necessary to recognize the behavior of these errors in different fading channels. To obtain the mathematical solution for the average bit error rate(BER) of coherent MPSK, some techniques are presented. In this paper, the impact of diversity is also analyzed over slow and flat Rician fading channel. In here, the value of modulation index, M is varied and the effects of its variation are also depicted. So, these performance curves with different diversity values and fading parameter are useful to design and evaluate the radio channel for faithful communication system.