• Research in Mathematical Education
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• v.16 no.1
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• pp.31-50
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• 2012

The present study explored whether the implementation of focused activities (intervention programme) can enhance 22 pre-service mathematics teachers' proficiency in solid geometry thinking level as well as change for the better their feelings in this discipline. Over a period of 6 weeks the pre-service teachers participated in activities and diversified experiences with 3D shapes, using illustration aids and actual experience of building 3D shapes in relation to the various spatial thinking levels. The research objectives were to investigate whether the intervention programme, comprising task-oriented activities of solid geometry, enhance mathematics pre-service teachers' mastery of their geometric thinking levels as well as examine their feelings towards this discipline before and after the intervention programme. The findings illustrate that learners' levels of geometric thinking can be promoted, entailing control on higher thinking levels as well as a more positive attitude towards this field.

• Journal of the Korea Fashion and Costume Design Association
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• v.13 no.2
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• pp.103-119
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• 2011

This study set out to analyze the solid shapes of knit flared skirts, which are best represented in a 3-dimensional shape for all knit skirts, according to the seamed and seamless production method and to estimate the silhouettes of knit flared skirts based on the results. It also aimed to help with the introduction and spread of seamless weaving by revising and supplementing potential problems and provide findings that would be put to active use as basic data, thus contributing to the development of original knitwear and offering fundamental materials for the development of the knitting industry. A number of experimental knit flared skirts were made according to skirt angle ($90^{\circ}$ and $180^{\circ}$), gauge (7G, 12G, and 15G), and grain (bias, wale, and radial), including 12 kinds of seamed knit flared skirts and 6 kinds of seamless knit flared skirts. Using a three-dimensional shape measurement system, the investigator measured the cross-sectional shapes of their hemlines. The SPSS 12 Version program was used for statistical processing, and descriptive statistics such as mean and standard deviation were used to compare the seamed and seamless knit flared skirts in the measurements (measurement items) of their solid shapes according to the width, gauges, and grain directions. The central grain direction of seamless knit flared skirts was in a radial form and even hemlines, thus presenting a beautiful appearance and solid shape. The 3-dimensional shapes show that seamless knit flared skirts are superior to seamed ones. The research findings are expected to open a door for Korea's knitting industry to quickly respond to small quantity batch production and additional orders.

• Journal of Powder Materials
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• v.1 no.1
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• pp.60-65
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• 1994

When a commercial prealloyed Fe-powder(Fe-5Cr-lMo-2Cu-0.5P-3C) is liquid phase sintered at 116$0^{\circ}C$, liquid precipitates with various shapes form within solid grains during the initial stage of sintering. The shape of a liquid precipitate changes pith the increment of their size from sphere(with radius<0.3$\mu\textrm{m}$), a transient polyhedron with more than 7 faces(1~2 $\mu\textrm{m}$), cuboid(3~5 $\mu\textrm{m}$), and finally to sphere(>5 $\mu\textrm{m}$). The shapes of liquid precipitates closely resemble the growth shapes predicted on the basis of solid-liquid interfacial energy and the coherency strain energy with anisotropic elastic constants in the diffusion zone around the precipitates.

• International Journal of Naval Architecture and Ocean Engineering
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• v.6 no.1
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• pp.132-150
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• 2014

In this study, the inertial properties of fully filled liquid in a tank were studied based on the potential theory. The analytic solution was obtained for the rectangular tank, and the numerical solutions using Green's 2nd identity were obtained for other shapes. The inertia of liquid behaves like solid in recti-linear acceleration. But under rotational acceleration, the moment of inertia of liquid becomes small compared to that of solid. The shapes of tank investigated in this study were ellipse, rectangle, hexagon, and octagon with various aspect ratios. The numerical solutions were compared with analytic solution, and an ad hoc semi-analytical approximate formula is proposed herein and this formula gives very good predictions for the moment of inertia of the liquid in a tank of several different geometrical shapes. The results of this study will be useful in analyzing of the motion of LNG/LPG tanker, liquid cargo ship, and damaged ship.

• Korean Journal of Computational Design and Engineering
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• v.13 no.5
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• pp.372-381
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• 2008

We developed a design automation system to reduce the lead time and help engineers in designing a solid fuel, or a grain, for rocket missiles. First, we analyzed design activities and shapes of a grain, which resulted in the standard of design process and shape. We decided development process which consisted of two typical activities such as constructing master library and implementing design system. We constructed some master models for typical external shapes and core shapes of grains which were used in modeling the shape of a designing grain. Also we implemented a design automation program to use the master models according to the pre-defined design process. It can calculate some design parameters such as mass, mass center, volume and combustion area that are used in analyzing a proposed grain. Finally, we could reduce the design time dramatically and increase design quality by automating many routine and difficult works.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.6
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• pp.98-104
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• 2010

Rapid Prototypes with internally colored objects are convenient by visualizing. A rapid prototyping method has been developed to fabricate mono-colored or multi-colored objects. In this work, a new process was proposed that can fabricate internally visible colored 3D objects in stereolithography parts. The process consists of projection stereolithography process using transparent photocurable resin for outer shapes and molten ink deposition process using molten solid ink for internal shapes. In molten ink deposition process, molten solid ink could be deposited uniformly in a designed pattern. To make molten solid ink uniform over a designed region, parametric study through a patterning solid ink was performed. By laminating resin and solid ink in sequence, the process can make colored 3D objects in StereoLithography(SL) parts. The practicality and effectiveness of the proposed process were verified through fabrication of colored basic 3D objects in SL parts.

• Smart Media Journal
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• v.13 no.5
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• pp.45-51
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• 2024

Recently, realistic contents such as virtual reality(VR) and augmented reality (AR) are widely used for education to provide beneficial learning environments with thee-dimensional(3D) information and interactive technology. Specially, AR technology will be helpful to intuitively understand by adding virtual objects registered in the real learning environment with effective ways. In this paper, we developed an AR learning system using 3D spatial information in the 2D based textbook for studying math related to geometry. In order to increase spatial learning effect, we applied to solid shapes such as prisms and pyramids in mathematics education process. Also, it allows participants to use various shapes and expression methods (e.g., wireframe mode) with interaction. We conducted the experiment with our AR system, evaluated achievement and interest. Our experimental study showed positive results, our results are expected to provide effective learning methods in various classes through realistic visualization and interaction methods.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.6
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• pp.44-49
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• 2013

This study investigates the surface discharge characteristics of solid insulators by varying their materials, their shapes, and the dew-point of dry-air. The methodology of this study is that a quasi-uniform field is first applied to a test chamber. Then, the chamber is filled with dry-air as an insulation gas which pressure is varied from 1 to 6atm while applying an AC voltage to the chamber. The used solid insulators are teflon, polycarbonate, and bakelite. As the dew-point is lower and the pressure of dry-air is higher, the flashover voltage of all solid insulators increases more. When each characteristic of the solid insulators is compared under the same gas pressure, the flashover voltage of teflon is the highest. Then, the flashover voltage of polycarbonate is higher than that of bakelite. Moreover, it is observed that the flashover voltage increases as the diameter and the thickness of each solid insulator become larger and thicker, respectively. However, the thickness of the solid insulators is more critical for increasing the flashover voltage than their diameter.

• Transactions of Materials Processing
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• v.19 no.1
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• pp.17-24
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• 2010

A stretch forming method has been widely used in sheet metal forming process. Especially, this process has been adopted in aircraft and high-speed train industries for skin structure forming having a variety of curvature. Until now, solid dies, which are designed with respect to the specific shapes and manufactured as a single piece, have been usually applied to stretch forming process. Therefore, a great number of solid dies has to be developed according to the shapes of the curved skin structure. Accordingly, a flexible die is proposed in this study. It replaces the conventional solid dies with a set of height adjustable punch array. A usefulness of the flexible die is verified through a formability comparison with the solid die using finite element method considering an elastic recovery and the stretch forming apparatus with the flexible die is developed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.9
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• pp.1337-1343
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• 2004

Shape optimization was performed to obtain a precise shape of cutouts including the internal shape of cutouts in a laminated composite plate by three dimensional modeling using solid element. Volume control of the growth-strain method was implemented and the distributed parameter chosen as Tsai-Hill fracture index for shape optimization. It makes Tsai-Hill failure index at each element uniform in laminated composites under the predetermined volume a designer requires. Shapes optimized by Tsai-Hill failure index were compared with those of the initial shapes for the various load conditions and cutouts. The following conclusions were obtained in this study; (1) It was found that growth-strain method was applied efficiently to shape optimization of three dimensional cutouts in a laminate composite, (2) The optimal shapes of the various load conditions and cutouts were obtained, (3) The maximum Tsai-Hill failure indices of the optimal shapes were remarkably reduced comparing with those of the initial shapes.