• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.749-752
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• 2005

In the industry, three-dimensional coloring has been needed for realistic prototype from rapid prototyping. Z-corporation developed a 3D printer which provides three-dimensional colored prototype. However, the existing process cannot be adopted to models from other rapid prototyping process. In addition, time and cost for manufacturing colored prototype still remain to be improved. In this study, a new coloring process using ink-jet head is proposed for color printing on three-dimensional prototype surface. Process parameters such as the angle and the distance between ink-jet nozzle and the three-dimensional surface should be investigated from experiments. The correction matrix according to sloped angle to minimize the distortion of 2D image was proposed by analysis of printing error. Therefore, approximated method for angle and discrete length according to the radius of curvature for printing on the curved surface was proposed. By printing image on the doubly curved surface, the method was verified. As a practical example, helmet was chosen for printing images on the curved surface. The character images were applied with approximated method for angle and discrete length and was printed on the helmet surface.

• Korean Institute of Interior Design Journal
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• no.19
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• pp.45-52
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• 1999

This study is on Buckminster Fuller, who is generally known as a structure engineering architect, and his influences. Fuller's radical and utopian ideas and designs were regarded as 'paper architecture'. But considering today's high cost of energy and the limited natural resources, Fuller's Dymaxion theory must be re-evaluated. Fuller's influences on the contemporary architecture are summarized as follows. 1) His idea of controlling the environment through the use of technology influenced today's 'High-Tech' architects. Architecture is no-longer designed purely by its formal character, but becomes a tool of investigating environmental significance of modern technology. 2) Through systemizing mechanical equipment, Dymaxion House prototype, and aggregation of high-tech mechanical equipments, influenced Archigram & Metabolist's capsule idea. It is expressed as a plug-in module equipment of 'High-Tech' architecture which has flexible interior with mechanical exterior image. 3) Megastructure. The Manhattan dome project gave an influence to many engineer/architects who tried to achieve an ideal artificial environment. This is in connection to 1960's utopian projects. Today's megastructures show new possibilities in urbanism and architecture. Fuller's comprehensive idea of humans living in harmony in the universe shows possibilities not only in structural engineering, but in solving various problems that confront today's architecture.

• Korean Journal of Materials Research
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• v.21 no.5
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• pp.263-267
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• 2011

The present study was carried out to evaluate the microstructural and mechanical properties of cross-roll rolled pure copper sheets, and the results were compared with those obtained for conventionally rolled sheets. For this work, pure copper (99.99 mass%) sheets with thickness of 5 mm were prepared as the starting material. The sheets were cold rolled to 90% thickness reduction and subsequently annealed at $400^{\circ}C$ for 30 min. Also, to analyze the grain boundary character distributions (GBCDs) on the materials, the electron back-scattered diffraction (EBSD) technique was introduced. The resulting cold-rolled and annealed sheets had considerably finer grains than the initial sheets with an average size of 100 ${\mu}M$. In particular, the average grain size became smaller by cross-roll rolling (6.5 ${\mu}M$) than by conventional rolling (9.8 ${\mu}M$). These grain refinements directly led to enhanced mechanical properties such as Vickers micro-hardness and tensile strength, and thus the values showed greater increases upon cross-roll rolling process than after conventional rolling. Furthermore, the texture development of <112>//ND in the cross-roll rolling processed material provided greater enhancement of mechanical properties relative to the case of the conventional rolling processed material. In the present study, we systematically discuss the enhancement of mechanical properties in terms of grain refinement and texture distribution developed by the different rolling processes.

• Design & Manufacturing
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• v.11 no.3
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• pp.41-45
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• 2017

Drones can be manipulated in a variety of ways. One of the most common controller is joystick method. But joystick controller uses both hands and takes a long time to learn. Particularly, in the case of 8-character flight, it is necessary to use both front and rear flight (pitch), left and right flight (Roll), and body rotation (Yaw). Joystick controller has limitations to intuitively control it. In particular, when the main body rotates, the viewpoint of the forward direction is changed between the drones and the user, thereby causing a mental rotation problem in which the user must control the rotating state of the drones. Therefore, we developed a motion matching controller that matches the motion of the drones and the controller. That is, the movement of the drone and the movement of the controller are the same. In this study, we used a gyro sensor and an acceleration sensor to map the controller's forward / backward, left / right and body rotation movements to drone's forward / backward, left / right, and rotational flight motion. The motor output is controlled by the throttle dial at the center of the controller. As the motions coincide with each other, it is expected that the first drone operator will be able to control more intuitively than the joystick manipulator with less learning.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.2
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• pp.95-105
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• 2002

In order to reduce the lead-time and cost, the technology of rapid prototyping (RP) has been widely used. However, RP technologies have disadvantageous characteristics according to their working principle: low building speed, high cost for introduction and maintenance of RP apparatus, stair-stepped surface and additional post processing. A new rapid prototyping process, as a transfer type of Variable Lamination Manufacturing by using expandable polystyrene room (VLM-ST), has been developed to reduce building lime. apparatus cost including the introduction and the maintenance and additional post-processing. The objective of this study is to propose a VLM-ST process and to develop an apparatus for implementation of the process. Design criteria of the apparatus are defined and the techniques arc proposed to satisfy the design criterion. In order to examine the efficiency and applicability of the developed process, various three-dimensional shapes, such as a world-cup logo. a knob shape, an extruded cross, a twisted shape, a character, Son-o-kong. a helical gear shaped and a scissor shape are fabricated on the apparatus in which unit shape layer (USL) was generated to build up each layer.

• Applied Chemistry
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• v.15 no.1
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• pp.17-20
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• 2011

A disposable light exposure detector kit has been developed by UV curing of a hydrogel material. The devised light exposure detector kit consisted of light sensitive structures, bottom plate, character sheet and sticky back plate. A light exposure detector kit has a serial light sensitive structures that contain various light sensitive dyes such as rhodamine and fluorescein. The light sensitive structure composed of UV curable hydrogel polymer material as a supporing material and photosensitive dye in a certain concentration. The fabrication procedure of the ligh exposure detector kit is very simple and fast due to UV curing procedure of a photopolymerizable hydrogel material such as poly(ethylene glycol) methyl ether acrylate (PEGMEA) and poly(ethylene glycol) diacrylate (PEGDA) with a photosensitive dye. By the proposed fabrication method, various size and shape of a light exposure detector kit could be fabricated using a flexible elastomer mold. Due to a fast and inexpensive fabrication method, the light exposure detector kit could be use a single use for various industrial applications. According to light irradation, the light sensitive structure on a light exposure detector kit could be lose its color by decomposition of a photosensitive dye chemical in the structure. Thus the amount of the exposed light on a substrate could easily be recognised by changing color or transparency of the structure.

• Polymer(Korea)
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• v.32 no.4
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• pp.305-312
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• 2008

A novel TPC-PEG-TPC with active end-groups was obtained from the end-groups of polyethylene glycol (PEG) modified by terephthaloyl chloride (TPC). These active end-groups can link up with a rare earth ion, which is a luminescent center of a rare earth fluorescent complex. Complexes of Eu-PEG with novel ligands (TPC-PEG-PTC) were synthesized by the coordination of the active reactant (as the first ligand) and phenanthroline (as the second ligand) with $Eu^{3+}$.IR, $^1H$-NMR, element analysis, DSC, WAXD, fluorescent spectroscopy, TGA, and SEM were used to characterize the structure and properties of these complexes. The results showed that this type of complex is a heat storage material with the phase change character of polyethylene glycol (PEG) and the luminescent properties of europium. There was no thermal decomposition of the complex of Eu-PEG until $300^{\circ}C$. SEM showed that the complex of Eu-PEG can be dispersed in PE.

• Journal of Korean Medicine Rehabilitation
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• v.19 no.1
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• pp.169-186
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• 2009

Obejectives : The electroacupuncture(EA) on regional fat is often used by oriental medicine doctors in Korea. However, there have been few studies about safety and biocompatibility of its application. Therefore we investigated the safety and change of mechanical character of electroacupuncture after its application on localized fat deposit. Methods : Online surveys were completed from Aug 21 2008 to Aug 28 2008, by email, the online survey data were obtained from nearly 10,002 Korean medical doctors who listed their email address on the website of association of korean oriental medicine. This study includes an experiment on the physical strength and biological property of long needles. We represent each method which were collected in advance survey, then sealed the needles off and did laboratory experiment, which includes surface observation, analysis, vickers hardness test, and also biocompatibility and toxicity test. Results : There was no considerable difference about the physical property after applying electric current, the cell survival rate did not change in comparison with controlled group either. Conclusions : Although it seems there are no considerable acupuncture-related problem, we still need additional studies about clinical effectiveness difference related operation condition. Besides, it will need research on the actual condition, standardization, and criteria about the comsumed needle in Korea.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.8
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• pp.1229-1240
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• 1997

The purpose of this study is to build up control scheme that promptly control pressure in a hydraulic cylinder having comparatively small control volume, using a PCV (proportional control valve) and a digital computer. Object pressure control system has the character to be unstable easily, because the displacement-flow gain of the PCV is too large considering the small volume of the hydraulic cylinder and the time delay of response of the PCV is comparatively long. Considering the above-mentioned characteristics of the object pressure control system, in this study, control system is designed with two degree of freedom control scheme that is composed by adding a feed-forward control path to I-PDD$^{2}$ control system, and a reference model is used on the decision of control parameters. And through some experiments on the control system with FF-I-PDD$^{2}$ controller, the validity of this control method has been confirmed.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.12
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• pp.101-106
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• 2000

As the rotational speed of optical disk drive is increasing nowadays, the reliability to vibration and shock becomes more important. For this, various of rubber vibration isolators are being developed by varying the shape and hardness. But it is difficult for the hardness of common used rubber to be lowered below Duro 30 degrees, and because of the shape complexity of rubber vibration isolator there are difficulties of analysis. Microcellular foamed vibration isolator has various cell densities and cell sizes, so it can vary the stiffness and damping coefficient. In addition, its hardness can be lowered below Duro 30 degrees. Axiomatic Approach is very useful design method for designing new product or new process. Axiomatic Approach's character is scientific and analytical method. In this paper, developing process of microcellular foamed vibration isolator for DVD is presented with Axiomatic Approach.