• Maxillofacial Plastic and Reconstructive Surgery
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• v.34 no.1
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• pp.41-52
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• 2012

Purpose: Triangulation is the process of determining the location of a point by measuring angles to it from known points at either end of a fixed baseline. This point can be fixed as the third point of a triangle with one known side and two known angles. The aim of this study was to find a clinically adaptable method for applying an optical tracking navigation system to orthognathic surgery and to estimate its accuracy of measuring the bone displacement by use of triangulation methods. Methods: In orthognathic surgery, the head position is not fixed as in neurosurgery, so that a head tracker is needed to establish the reference point on the head surface byusing an optical tracking system. However, the operation field is interfered by its bulkiness that makes its clinical use difficult. To solve this problem, we designed a method using an Aquaplast splinting material and a mini-screw in applying a head tracker on a patient's forehead. After that, we estimated the accuracy of measuring displacements of the ball marker by an optical tracking system with a conventional head tracker (Group A) and with a newly designed head tracker (Group B). Measured values of ball markers' displacements by each optical tracking system were compared with values obtained from fusion CT images for an estimation of accuracy. Results: The accuracy of the optical tracking system with a conventional head tracker (Group A) is not suitable for clinical usage. Measured and predictable errors are larger than 10 mm. The optical tracking system with a newly designed head tracker (Group B) shows 1.59 mm, 6.34 mm, and 9.52 mm errorsin threeclinical cases. Conclusion: Most errors were brought on mainly from a lack of reproducibility of the head tracker position. The accuracy of the optical tracking system with a newly designed head tracker can be a useful method in further orthognathic navigation surgery even though the average error is higher than 2.0 mm.

• Fire Science and Engineering
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• v.25 no.3
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• pp.119-124
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• 2011

In this study, we measured the smoke density characteristics to find the fire risk of Wood-Plastic composites (WPCs) which are one of spotlighting materials for landscape architecture and residential construction material with the cone calorimeter tester (by ISO 5660-2) and the smoke density tester (by ASTM E 662). In addition, the identical test was implemented to compare the smoke density characteristics between the red pine and the antiseptic wood. The result of cone calorimeter test showed that emissions of carbon monoxide, carbon dioxide and total smoke production rate of WPCs were higher than those of red pine and antiseptic wood. And the result of smoke density test showed that maximum specific optical smoke density(Dm) of WPCs was higher than that of red pine and antiseptic wood as well.

• Clean Technology
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• v.29 no.3
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• pp.172-177
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• 2023

Many studies have been conducted on the indiscriminate use of plastic due to the environment problems it has caused all over the world. This problem can be mitigated by using eco-friendly/biodegradable plastics that can be decomposed by microorganisms or enzymes. This study focused on addressing the plastic golf tees that are thrown away at golf courses. In order to replace conventional golf tees (ABS) with a more eco-friendly alternative, this study explored a biodegradable plastic and 3D printing method for producing golf tees. Among the biodegradable plastics, PLA (polylactic acid) was found to be a good candidate as an eco-friendly material because it is biodegradable by microorganisms. Thus, golf tees were prepared by using PLA via 3D printing, and the physical and chemical properties of the tees were evaluated. The amorphous region of PLA was confirmed through XRD. Also, FT-IR showed the unique peak of PLA without impurities. It was confirmed through an optical microscope that the specific surface area and roughness had increased. This structure plays a role in firmly fixing the golf tee when it is inserted into the ground. In addition, it was possible to improve the compressive load compared to ABS golf tees while also decreasing the compressive stretching.

• Macromolecular Research
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• v.12 no.6
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• pp.564-572
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• 2004

Modem applications could benefit from multifunctional materials having anisotropic optical, electrical, thermal, or mechanical properties, especially when coupled with locally controlled distribution of the directional response. Such materials are difficult to engineer by conventional methods, but the electric field-aided technology presented herein is able to locally tailor electroactive composites. Applying an electric field to a polymer in its liquid state allows the orientation of chain- or fiber-like inclusions or phases from what was originally an isotropic material. Such composites can be formed from liquid solutions, melts, or mixtures of pre-polymers and cross-linking agents. Upon curing, a 'created composite' results; it consists of these 'pseudofibers' embedded in a matrix. One can also create oriented composites from embedded spheres, flakes, or fiber-like shapes in a liquid plastic. Orientation of the externally applied electric field defines the orientation of the field-aided self-assembled composites. The strength and duration of exposure of the electric field control the degree of anisotropy created. Results of electromechanical testing of these modified materials, which are relevant to sensing and actuation applications, are presented. The materials' micro/nanostructures were analyzed using microscopy and X-ray diffraction techniques.

• Journal of the Korean Society of Industry Convergence
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• v.6 no.3
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• pp.171-176
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• 2003

The poly(triazine bissulfide) synthesized from 6-dibutylamino-1,3,5-triazine-2,4-dithiol with bis(4-chloro-3-nitrophenyl) sulfone in the presence of the phase transfer catalyst, the maximum algebra viscosity (0.57 dL/g) is stable at reaction temperature of $60^{\circ}C$ overall. We could not acquire the good result about solubility, thermal property, and molecular weight to make cast film, we made base for the synthesis of functionalization polymer material.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.509-514
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• 2001

The Fibre-optic Bragg grating (FBG) sensor is broadly accepted as a structural health monitoring device for Fibre reinforced plastic (FRP) materials by either embedding into or bonding onto the structures. The accuracy of the strain measured by using the FBG sensor is highly dependent on the bonding characteristics among the bare optical fibre, protective coating, adhesive layer and host material. In general, the signal extracted from the embedded FBG sensor should reflect the straining condition of the host structure. This paper presents a theoretical model to evaluate the differential strains between the bare fibre and host material with different adhesive thickness and modulus of the protective coating of the embedded FBG sensor.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.4
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• pp.386-390
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• 2006

Global consumption of aspheric lens will expand rapidly due to golbal transformation of the electronics based industry to optics based mechatronics. Especially, F-Theta lens is one of important parts in Laser Scanning Unit(LSU) because it affects the optical performance of LSU dominantly. Non axisymmetric machine based processing techologies are required to obtain high accuracy in utlra-precision aspheric core, the most important component in plastic injection molded F-Theta lens assembly. In this study, the core with non-axisymmetric aspheric shape which is used to emit the F-Theta lens was processed using the ultra precision processing technology and the shape accuracy of the core was measured. And the results there of were evaluated and compared with the emitted shape accuracy of F-Theta lens.

• Clean Technology
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• v.11 no.4
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• pp.205-211
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• 2005

There have been many technologies and materials proposed for realizing microlens array, and plastic injection is recognized as the most promising one because of several merits such as optical properties, impact resistance, formability, lightening and environmental adaptability. Since PR reflow for injection template fabrication enables the lens shape control easier, and the sample technology more effective for mass production, it lowers the cost, enhances integration, and reduces process steps, which leads to be environmentally benign. However injection of polymers may face the difficulty of formability depending on their properties. In order to overcome the difficulty, fast heating/cooling technology was introduced in this study, and microlenses were fabricated and evaluated. template obtained by PR reflow method was heated and cooled fast during injection to fabricate microlens array. PC and PMMA polymer materials were compared, and it was realized that PMMA showed much better formability due to its lower melting temperature. Injection parameters of pressures and velocities were driven out for injection optimization.

• Transactions of Materials Processing
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• v.32 no.4
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• pp.180-190
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• 2023

This study deals with residual stress prediction and hardness evaluation within cross ball grooved inner race fabricated by cold upsetting process consisted of upsetting and ejection steps. A raw workpiece material of AISI 5120H (SCr420H) is first spheroidized and annealed, then phosphophyllite coated to form solid lubricant layer on its outer surface. To investigate influences of the heat treatment, uni-axial compression tests and Vickers micro-hardness measurements are conducted. Three-dimensional elasto-plastic FE simulations on the upsetting step and the ejection one are performed to visualize the residual stress and the ductile (plastic deformation) damage. External feature of the fabricated inner race is fully captured by using an optical 3D scanner, and the micro-hardness is measured on internal cross-sections. Consequently, the dimensional compatibility between the simulated inner race and the fabricated one is ensured with a difference of under 0.243mm that satisfied permissible error range of ±0.50mm on the grooved surface, and the predicted residual stress is verified to have similar distribution tendency with the measured Vickers micro-hardness.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.38
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• pp.17.1-17.6
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• 2016

Background: The aim of this study is to verify the feasibility of using silk fibroin (SF) as a potential membrane for guided bone regeneration (GBR). Methods: Various cellular responses (i.e., cell attachment, viability, and proliferation) of osteoblast-like MG63 cells cultured on an SF membrane were quantified. After culturing on an SF membrane for 1, 5, and 7 days, the attachment and surface morphology of MG63 cells were examined by optical and scanning electron microscopy (SEM), cell viability was determined using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, and cell proliferation was quantified using 4',6-diamidino-2-phenylindole (DAPI) fluorescence staining. Results: Optical microscopy revealed that MG63 cells cultured on the SF membrane proliferated over the 7-day observation period. The viability of cells cultured on SF membranes (SF group) and on control surfaces (control group) increased over time (P < 0.05); however, at respective time points, cell viability was not significantly different between the two groups (P > 0.05). In contrast, cell proliferation was significantly higher in the SF membrane group than in the control group at 7 days (P < 0.05). Conclusions: These results suggest that silk fibroin is a biocompatible material that could be used as a suitable alternative barrier membrane for GBR.