• Education of Primary School Mathematics
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• v.13 no.1
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• pp.13-24
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• 2010

Mathematics educators oriented to reform-based curricular have asserted that mathematics teachers should lead instructions where all students in their classrooms are able to participated. In this paper, some practices for them to implement it are discussed. Before explaining them, some discussions are made about students ability to construct knowledge. One of them is that teachers should know different learners construct different understandings because of their differences of prior knowledge and reasoning ability. Also, it was discussed that teachers consider classroom environments, assigning children's sitting and tasks in the light of learning. The reason to state them is that perspectives of them should be changed. Finally, "Teacher's careful listening to learners' responses", "Why do think in that way?, How do you know?, What is it meant?", "accepting ideas from all learners", "no supporting a particular idea", "utilizing waiting time", and "teacher's responses to learner's errors and mistakes" are discussed as practices for letting all learners be participated in the mathematics instruction.

• Education of Primary School Mathematics
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• v.23 no.3
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• pp.117-134
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• 2020

Based on the current curriculum, students learn the concept of fraction in the 3rd grade for the first time. At that time, fraction is introduced as whole-part relationship. But as the idea of fraction expands to improper fraction and so on, fraction as measurement would be naturally appeared. In that situation where fraction as whole-part relationship and fraction as measurement are dealt together, it is necessary for students to get experiences of understanding and exploring unit and whole adequately in order to fully understand the concept of fractions. Therefore, the purpose of this study is to analyze how to deal with unit fractions, how to implement activities to find the standard of reference from the part, and what visual representations were used to help students to understand the concept of fractions in elementary mathematics textbooks from the 7th to the 2015 revised curriculum. And we analyzed 60 3rd graders' understanding of finding and drawing the whole by looking at the part. Several didactical implications for teaching the concept of fractions were derived from the discussion according to the analysis results.

• Journal of Korea Water Resources Association
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• v.31 no.1
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• pp.95-103
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• 1998

Dam sediment can be predicted from the two methods: the one is a physical analysis based on the hydrjulic mechanism and the other is an empirical approach using observed data as a design factor. The former can be used to estimate short-term phenomena by mathematical methods. the latter can be used for deriving long-term design parameters such as dead storage calculation. Monthly reservoir operation is possible with the sluicing efficiency curve based on empirical data. The optimal sediment management can be carried out using the information variable which traces deposit sediments corresponding to the reservoir storage. The idea can provide an optimal operation strategy to save effective storage varying with time. This study presents a methodology for the long-term sediment prediction using sluicing efficiency curve. An application is conducted for estimating accumulated sedment deposit and water supply capability ofr the Fenhe dam in the Yellow rever of China.

• Archives of design research
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• v.16 no.1
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• pp.15-24
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• 2003

In the latest date, vehicles are offered to the drivers, not only the skill for shifting but the pleasure for driving vehicles that are existing today can be a social problem because the amount of vehicles that are increasing give difficulty for the traffic facilities and parking expansion. these day 80% of four wheeled vehicle carriers single or double person the reducing car scale is an important thing about the financial good use resources of energy and the storage of environment. A solution for these problem is a new general idea vehicle development for one or two person to ride. For the sake of these reasons, first, the information is collected and analyzed about existing foreign countries production. Car external design is intended by mathematical modeling, simulation and model testing about frame system of new concept specially we would like to show three wheeled vehicle that has active tilt control(ATC) system. This car tilts actively by the center rotation wheel and frame when the vehicle turns.

• Journal of Elementary Mathematics Education in Korea
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• v.14 no.3
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• pp.843-863
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• 2010

The basic purpose of 2007 revision curriculum is content of activity oriented, management of differentiated instruction, communication, introduction of story mathematics, mathematical exploration and problem solving ability and so on. In this paper, we investigate some characteristics of number teaching in the primary school of New Zealand. Especially, focused on materials and methods and so on. So we've got the following results. First, there are no fundamental differences in materials and methods in teaching number between Korea and New Zealand but in New Zealand there are no national textbook like us so there is a possibility not to teach number systematically like our Korea. On the contrary, they divide number region from one to six level and are offering achievement objects, suggestive learning experiences, sample assessment activities for each level and also they do not guide activities itself in detail like us and so have learners themselves think about the given problems. Second, there is a strategy stage in getting knowledge about number in New Zealand and so children can take advantage of this steps according to the type of problems. Third, it must be developed some materials and idea to reach the learning purpose rousing interest of children.

• Journal of Educational Research in Mathematics
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• v.9 no.1
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• pp.263-278
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• 1999

Computer with various powerful functions has profound potential for mathematics instruction and learning. As computer technology progress, its applicability to mathematics education become more comprehensive. Not only its functional development but various psychological positions also changed the way computer technology utilized in mathematics education. In behaviorist's perspective, computer viewed as a teaching machine and constructivist viewed computer as microworld where students could explore various mathematical contents. Both theoretical positions emphasized individual aspect of learning because behaviorist tried to individualize learning using computer and constructivist focused on the process of individual construction. But learning is not only a individual event but also a social event. Therefore we must take social aspect into account. This is especially important when it comes to computer based learning. So far, mathematics loaming with computer weighed individual aspect of loaming. Even in microworld environment, learning should be mediated by teacher and collaborative learning activities. In this aspect, the roles of teacher and peers are very important and socio-cultural perspective sheds light on the computer based learning. In socio-cultural perspective, the idea of scaffold is very important in learning and students gradually internalize the social dimension and scaffolding is gradually faded. And in the zone of proximal development, teacher and more competent peers guide students to formulate their own understanding. In sum, we must take following points into account. First of all, computer should not be viewed as a medium for individualized teaming. That is, interaction with computer should be catalyst for collaborative activities with peers. So, exploration in computer environment has to be followed by small group activities including small group discussion. Secondly, regardless of the role that computer would play, teacher should play a crucial role in computer based learning. This does not mean teacher should direct every steps in learning process. Teacher's intervention should help student construct actively. Thirdly, it is needed to conceptualize computer in learning situation as medium. This would affect learning situation and result in the change of pre-service and in-service teacher training. Computer to be used effectively in mathematics classroom, researches on assessment of computer based learning are needed.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.4
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• pp.303-311
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• 2011

This study presents a new idea of liquid desiccant dehumidifier with extended surface to improve the compactness. Extended surface is inserted between vertical cooling tubes, and the liquid desiccant flows down along the tube walls and the extended surface as well. Though the extended surface contributes to the increase in the mass transfer area, the effect tends to be limited because less conductive non-metallic materials need to be applied due to the high corrosiveness of liquid desiccant. To analyze the effects of the extended surface insertion, mathematical modelling and numerical integration are performed for the heat and mass transfer in the liquid desiccant dehumidifier. The results show that, though the liquid desiccant on the extended surface is heated due to the moisture absorption, the temperature can be maintained by periodic mixing at the contact points between the tube and the extended surface with the liquid desiccant stream from the tube side at a relatively low temperature. This implies the absorption heat from the extended surface side can be removed effectively by mixing, which leads to a substantial improvement of the dehumidification in the liquid desiccant dehumidifier with extended surface. When the interval of the extended surface, $p_e/L$, is less than 0.1, the dehumidification is shown to increase by more than two times compared with that without extended surface.

• Journal of Adhesion and Interface
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• v.5 no.2
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• pp.14-26
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• 2004

For reliable determination of mechanical characteristics of adhesively bonded joints used e.g. as input data for computer-aided design of complex components, the thick-adherend tensile-shear test according to ISO 11003-2 is the most important material testing method. Although the total displacement of the joint is measured across the polymer layer directly in the overlap zone in order to minimize the influence of the stepped adherends, the substrate deformation must be taken into account within the framework of the evaluation of the shear modulus and the maximum shear strain, at least when high-strength adhesives are applied. In the standard ISO 11003-2 version of 1993, it was prescribed to perform the substrate deformation correction by means of testing a one-piece reference specimen. The authors, however, pointed to the excessive demands on the measuring accuracy of the extensometers connected with this technique in industrial practice and alternatively proposed a numerical deformation analysis of a dummy specimen. This idea of a mathematical correction was included in the revised ISO 11003-2 version of 2001 but in the simplified form of an analytical method based on Hooke's law of elasticity for small strains. In the present work, it is shown that both calculation techniques yield considerably discordant results. As experimental assessment would require high-precision distance determination (e.g. laser extensometer), finite element analyses of the deformation behavior of the bonded joint are performed in order to estimate the accuracy of the obtained substrate deformation corrections. These simulations reveal that the numerical correction technique based on the finite element deformation modeling of the reference specimen leads to considerably more realistic results.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.48 no.1
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• pp.55-60
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• 2011

The most basic algorithm in SLAM(Simultaneous Localization And Mapping) technique of mobile robots is EKF(Extended Kalman Filter) SLAM. However, it requires prior information of characteristics of the system and the noise model which cannot be estimated in accurate. By this limit, Kalman Filter shows the following behaviors in a highly uncertain environment: becomes too sensitive to internal parameters, mathematical consistency is not kept, or yields a wrong estimation result. In contrast, $H_{\infty}$ filter does not requires a prior information in detail. Thus, based on a idea that $H_{\infty}$ filter based SLAM will be more robust than the EKF-SLAM, we propose a framework of $H_{\infty}$ filter based SLAM and show that suggested algorithm shows slightly better result man me EKF-SLAM in a highly uncertain environment.

• Structural Engineering and Mechanics
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• v.53 no.2
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• pp.205-226
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• 2015

Finite element method (FEM) is an effective quantitative method to solve complex engineering problems. The basic idea of FEM for a complex problem is to be able to find a solution by reducing the problem made simple. If mathematical tools are inadequate to obtain precise result, even approximate result, FEM is the only method that can be used for structural analyses. In FEM, the domain is divided into a large number of simple, small and interconnected sub-regions called finite elements. FEM has been used commonly for linear and nonlinear analyses of different types of structures to give us accurate results of plane stress and plane strain problems in civil engineering area. In this paper, FEM is used to investigate stress analysis of a shear wall which is subjected to concentrated loads and fundamental principles of stress analysis of the shear wall are presented by using matrix displacement method in this paper. This study is consisting of two parts. In the first part, the shear wall is discretized with constant strain triangular finite elements and stiffness matrix and load vector which is attained from external effects are calculated for each of finite elements using matrix displacement method. As to second part of the study, finite element analysis of the shear wall is made by ANSYS software program. Results obtained in the second part are presented with tables and graphics, also results of each part is compared with each other, so the performance of the matrix displacement method is demonstrated. The solutions obtained by using the proposed method show excellent agreements with the results of ANSYS. The results show that this method is effective and preferable for the stress analysis of shell structures. Further studies should be carried out to be able to prove the efficiency of the matrix displacement method on the solution of plane stress problems using different types of structures.