• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.4
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• pp.1251-1262
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• 1996

In this paper, a mathematical model for a belt driven system is proposed to analyse the vibration characteristics of the driving units with belts and the free and forced vibraiton anlyses are carried out. The mathematical model for a belt-driven system includes belts, pulleys, spindle and bearings. By using Hamilton's principle, four nonlinear governing equations and twelve nonlinear boundary conditions are derived. To linearize and discretize the nonlinear governing equations and boundary conditions, the perturbation method and Galerkin method are used. Also, the free vibration analyses for various parameters of a belt driven system, which are the tension of a belt, the length of a belt, the material properties of belts, the velocity of a velt and the mass of pulley are made. The forced vibration analyses of the system are performed and the dynamic responses for main parameters are anlysed with a belt driven system.

• The Mathematical Education
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• v.49 no.3
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• pp.353-373
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• 2010

This research was to help slow learners to be motivated and to make their outcome productive, using GSP based on the mathematization theory for learning mathematics, as a way of encouraging the learner-centered approach. With 2 of the second graders in a high school, who had not yet understood trigonometric functions in their first grade period, 7 units of lesson plans were designed for the research. The results showed that first, understanding real life contexts and analyzing properties by observation, and experiment using GSP, to build the concept of trigonometric functions could be a foothold on which learner's organization and outcome from a horizontal mathematization led to vertical mathematization. Despite the delay during the level-up-stage for a while, the learners could attain the vertical mathematization stage and moreover the applicative mathematization through effective use of GSP and the interaction between the learners or a teacher and the learners. Second, using GSP was a vertical tool of connecting horizontal mathematization with vertical mathematization in forming the concept of trigonometric functions and its meaning could be understood by their verbalizing and presenting the outcomes through their active performance. Using GSP is helpful for slow learners to overcome learning difficulties, based on the instructional materials designed by Realistic Mathematics Education.

• Communications of the Korean Mathematical Society
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• v.16 no.3
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• pp.445-458
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• 2001

The shape and the distribution of material construction of the scatterer may be obtained from its scattered fields by the iterative inversion in the spectral domain. The illposedness, the resolution, and the uniqueness of the inversion are the key problems in the inversion and inter-related. The illposedness is shown to be caused by the evanescent modes which carries and amplifies exponentially the measurement errors in the back-propagation of the measured scattered fields. By filtering out all the evanescent modes in the cost functional defined as the squared difference between the measured and the calculated spatial spectrum of the scattered fields from the iteratively chosen medium parameters of the scatterer, one may regularize the illposedness of the inversion in the expense of the resolution. There exist many local minima of the cost functional for the inversion of the large and the high-contrast scatterer and the hybrid algorithm combining the genetic algorithm and the Levenberg-Marquardt algorithm is shown to find efficiently its global minimum. The resolution of reconstruction obtained by keeping all the propating modes and filtering out the evanescent modes for the regularization becomes 0.5 wavelength. The super resolution may be obtained by keeping the evanescent modes when the measurement error and instance, respectively, are small and near.

• Bulletin of the Korean Mathematical Society
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• v.49 no.1
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• pp.109-126
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• 2012

In 2003, Marques-Smith and Sullivan described the join ${\Omega}$ of the 'natural order' $\leq$ and the 'containment order' $\subseteq$ on P(X), the semigroup under composition of all partial transformations of a set X. And, in 2004, Pinto and Sullivan described all automorphisms of PS(q), the partial Baer-Levi semigroup consisting of all injective ${\alpha}{\in}P(X)$ such that ${\mid}X{\backslash}X{\alpha}\mid=q$, where $N_0{\leq}q{\leq}{\mid}X{\mid}$. In this paper, we describe the group of automorphisms of R(q), the largest regular subsemigroup of PS(q). In 2010, we studied some properties of $\leq$ and $\subseteq$ on PS(q). Here, we characterize the meet and join under those orders for elements of R(q) and PS(q). In addition, since $\leq$ does not equal ${\Omega}$ on I(X), the symmetric inverse semigroup on X, we formulate an algebraic version of ${\Omega}$ on arbitrary inverse semigroups and discuss some of its properties in an algebraic setting.

• Steel and Composite Structures
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• v.31 no.5
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• pp.489-502
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• 2019

This article presents a unified mathematical model to investigate free and forced vibration responses of perforated thin and thick beams. Analytical models of the equivalent geometrical and material characteristics for regularly squared perforated beam are developed. Because of the shear deformation regime increasing in perforated structures, the investigation of dynamical behaviors of these structures becomes more complicated and effects of rotary inertia and shear deformation should be considered. So, both Euler-Bernoulli and Timoshenko beam theories are proposed for thin and short (thick) beams, respectively. Mathematical closed forms for the eigenvalues and the corresponding eigenvectors as well as the forced vibration time response are derived. The validity of the developed analytical procedure is verified by comparing the obtained results with both analytical and numerical analyses and good agreement is detected. Numerical studies are presented to illustrate effects of beam slenderness ratio, filling ratio, as well as the number of holes on the dynamic behavior of perforated beams. The obtained results and concluding remarks are helpful in mechanical design and industrial applications of large devices and small systems (MEMS) based on perforated structure.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1993.10a
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• pp.922-931
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• 1993

Boundary element method was used to solve heat conduction problem for predicting temperature distribution in grain storage bin. Temperature of grain in storage is one of the three main abiotic factors, besides the intergranular gas composition and the grain moisture content, that determine the keeping quality and control measures used to protect grain from insects and damaging microflora. Collecting the temperature data at various points in the storage bins at different time of the day over a period of time is one way of finding the temperature distribution, this method requires a lot of time, cost and labour and less efficient. However data so collected serve useful purpose of being used to validate predicted temperature distribution using mathematical models. Mathematical models based on physical principles can potentially predict with accuracy the temperature distribution in a grain storage bin. Using the boundary element model the effect of bin wall material, ambient emperature, bin size etc. on temperature distribution can be studied. A knowledge of temperature distribution in stored grain not only helps in identifying active deterioration , but also gives an indication of potential for detection.

• Communications of Mathematical Education
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• v.30 no.2
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• pp.139-159
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• 2016

This study is the field of mathematics education on the assumption that they can extend outside the classroom. Recent mathematics education is increasing the importance of field experience and various activities based on real-life math education. Thus, it is necessary to consider this situation in pre-service teacher's education. The purpose of this study is to apply the 'Mathematics Field Trips Activities' in the pre-mathematics teacher education. So the specific case of 'Mathematics Field Trips Activities' was analyzed. Mathematics teachers conducted preliminary exploration activities on the historical cultural property which were effective in the following four aspects. First, cognitive effects and second, definitive effect. Third, cultural-mathematical effect. Fourth, the effect on improving math class. Finally they were summarized and divided into classes target content knowledge and teaching knowledge both sides. As a result, the 'Mathematics Field Trips Activities' were found to have significant effects on pre-service math teacher. Finally, ongoing research is needed to settle into a new teaching and learning methods.

• Journal for History of Mathematics
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• v.26 no.2_3
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• pp.131-148
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• 2013

Euler's formula provides the topological characteristics of geometrical objects including polyhedra, and so an important mathematical concept. Descriptions on Euler's formula had been in the textbooks according to the 3rd through 7th National Mathematics Curriculum. However, they are gone after that. In this study, we focus on Euler characteristic and Euler's formula as an educational material for educations for the gifted or after-school educations. We first look at the mathematical history and the applications of Euler's formula and national curriculums to search for its mathematical and educational meaning. We further make a suggestion for a learning environment which provides a better education relying on search activities, not just depending on memorization, illuminated from the education of Euler's formula.

• Communications of Mathematical Education
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• v.25 no.2
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• pp.361-379
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• 2011

The purposes of this research are to develop Engineering Mathematics materials using the relations between Engineering Mathematics contents and not only pre-study contents but also major contents and to find the effect of the mathematics study which is applying them for students majoring in electronics. To accomplish the goals, I made list of Engineering Mathematics contents which is necessary to study electronics. Based on the list, I researched relations between Engineering Mathematics contents and not only pre-study contents but also major contents. After research, I selected some subjects which are related each other, developed study materials and examined responses to the materials. Then I analysed the effects on study attitude after used developed materials in my class. As a result, the major contents which was described in the introduction of the materials helped students to be motivated to study Engineering Mathematics and Pre-study contents described before Engineering Mathematics contents helped them to concentrate on studying Engineering Mathematics. Also it showed that developed study materials were effective in increasing self-confidence which is one attitude in the subcategories for Mathematics study.

• Journal for History of Mathematics
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• v.22 no.3
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• pp.153-170
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• 2009

Zoltan, P. Dienes is a famous researcher and practitioner who has tried to teach mathematical structures to children for about 50 years. Even though his ideas of teaching mathematics and materials including MAB have been well known in Korea, they are only a part of his achievement he has developed for his whole life. So this article is designed for taking an overview of his whole life and achievement and getting some implications for today's mathematics education. In this article, his life story could be divided by five periods in terms of a scholastic career and his research achievement could be reorganized with respect to five theses: psychology of learning mathematics, mathematical curriculum, teacher education, games and material for mathematical learning. As a result, it is found that there is a deep connection between his personal life and his scholastic career.