• Transactions of Materials Processing
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• v.28 no.4
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• pp.183-189
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• 2019

Cylindrical worm reducers are generally used in various fields and forms throughout the industry, and demand is increasing due to their role as an integral part of the industry. Market trends require high-load, high-precision components, and small-sized reducers with large loads. When using a cylindrical worm reducer, a reducer designed with a reduced center distance while maintaining the same output torque results in gear wear. To overcome this difficulty, an enveloping worm gear reducer is introduced and studied. In this paper, three types of end mill tools are used to evaluate the tooth profile accuracy for each tool shape during machining of the tooth profile for a non-developed surface worm thread. The effect of the endmill shape on the accuracy of the tooth profile was analyzed by performing 3D modeling of the surrounding worm tooth profile based on the Hindley method. In this study, we analyzed tooth profile accuracy, tooth surface roughness, and tooth surface machining time, etc. Through the study, efficient machining conditions for the enveloping worm gears and the influence of parameters on the process were presented.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.192-193
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• 2000

We studied the characteristics and fabricated the plano-convex refractive microlenses using the thermal reflow method. The exposed resist was resolved in a standard developing process. The remaining resist of circle pattern was melted in an oven 12$0^{\circ}C$ to 15$0^{\circ}C$. The shape of the melted resist microlenses is ruled by surface tension. Diameter and hight of the fabricated microlenses were 250${\mu}{\textrm}{m}$ to 325${\mu}{\textrm}{m}$ and 15${\mu}{\textrm}{m}$ to 22${\mu}{\textrm}{m}$, respectively. The surface profile was calculated using data curve-fitting method with circle equation. The optical characteristics was analysed using optical simulation program.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.11
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• pp.1917-1924
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• 2003

This paper proposes a roughing path generation method fer machining impeller with 5-axis machining center. Traditional researches are focus on finishing for machining impeller. To achieve efficient machining, roughing method must be studied. The proposed method consists two steps : One is to select optimal tool size and tool attitude by dividing cutting area into two regions to reduce cutting time. The regions are automatically divided by character point on the geometry of impeller blade. After dividing, the tool of the optimal size is selected for each divided region. The other is avoidance of tool interference. Tool interference in cutting areas is avoided by checking the distance between tool axis vector and ruling line on blade surface or approximated plan between ruling line. Using this method, the cutting time is reduced efficiently.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.988-993
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• 2004

This paper considers corrosion problems in the bolt connection of weathering steel box girder bridge using the external electric type corrosion resistance method which resisted to local corrosion in coated steel surface with contacted air. The weathering steel was created a rust itself in the passive state. but a coated box girder type was easily dew form could be made galvanic cell that accelerated corrosion. so that it was ruled by protection coat with some paint. Therefore, it needed that can be applied the external electric type corrosion resistance method in coated surface. As a result of the test of polarization amount had measured that the weathering steel was higher currents than the general steel by about $5\~10\%$. Therefore. an external electric type corrosion resistance method can be used to protect local corrosion in the coated bolt connection of weathering steel box girders effectively.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.05a
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• pp.105-106
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• 2018

Cracks are typical defects that occur in concrete structures. When cracks occur in the structure, durability reduction, concrete neutralization, and steel corrosion cause functional safety problems. In order to prevent such cracks, surface repair method is performed for cracks smaller than 0.3 mm and rechargeable method is performed for cracks larger than 0.3 mm. However, even if it is applied by the surface repair method at less than 0.3 mm, re-leakage cracks continue to occur. Recently, the Supreme Court ruled that the rechargeable method should be applied to cracks less than 0.3mm in order to reduce the occurrence of defects. However, it was considered that the repair fees were too high relative to the observed defect rate, resulting in a necessitation of modifying the existing construction analysis administration standards. This study analyzes the differences in the subjective views on the durability degradation with regards to surface repair methods in concrete structures.

• Journal of the Korean Society of Safety
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• v.28 no.3
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• pp.74-79
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• 2013

As the feature of fire, it is hard for deep-seated fire to spread to the deeper site, and it also has danger for being re-ignited cause of recontacting with oxygen after being put off. Now it is ruled in the certification criteria of wetting agent used for extinguishing deep-seated fire that the criteria for surface tension is below 33[mN/m] in Korea. For figuring out how much water for fire-fighiting can permeate into combustibles, in this research, the permeating performance is analyzed by measuring the speed of permeating and transmission quantity released after that, by pouring solution whose surface tension is changed by adjusting concentration of surfactant BDG(Butyl Di Glycol) in column From this result, it is can be determined that transmission quantity becomes less and wet area goes wider as surface tension is lower, and it is also able to be analyzed as quantity of absorbed liquid and wet area is increased because fluid permeates into the core.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.7
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• pp.71-79
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• 2002

A new rapid prototyping process, Variable Lamination Manufacturing using a 4-axis-controlled hotwire cutter and expandable polystyrene foam sheet as a laminating material of the part (VLM-S), has been developed to reduce building time and to improve the surface finish of parts. The objective of this study is to reconstruct the surface of the original 3D CAD model in order to generate mid-slice data using the advancing front technique. The generation of 3D layers by a 4 axis-controlled hot-wire cutter requires a completely different procedure to generate toolpath data unlike the conventional RP CAD systems. The cutting path data for VLM-S are created by VLM-Slicer, which is a special CAD/CAM software with automatic generation of 3D toolpath. For the conventional sheet type system like LOM, the STL file would be sliced into 2D data only. However, because of using the thick layers and a sloping edge with the firstorder approximation between the top and bottom layers, VLM-Slicer requires surface reconstruction, mid-slice, and the toolpath data generation as well as 2D slicing. Surface reconstruction demands the connection between the two neighboring cross-sectional contours using the triangular facets. VLM-S employs thick layers with finite thickness, so that surface reconstruction is necessary to obtain a sloping angle of a side surface and the point data at a half of the sheet thickness. In the process of the toolpath data generation the surface reconstruction algorithm is expected to minimize the error between the ruled surface and the original parts..

• International Journal of CAD/CAM
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• v.4 no.1
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• pp.33-45
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• 2004

In this work, a rational procedure has been formulated for the selection of points approximating slice contours cut in LOM (Laminated Object manufacturing) with first order approximation. It is suggested that the number of points representing a slice contour can be 'minimised' or 'optmised' by equating the horizontal chordal deviation (HCD) to the user-defined surface form tolerance. It has been shown that such optimization leads to substantial reduction in slice height calculations and NC codes file size for cutting out the slices. Due to optimization, the number of contour points varies from layer to layer, so that points on successive layer contours have to be matched by four sided ruled surface patches and triangular patches. The technological problems associated with the cutting out of triangular patches have been addressed. A robust algorithm has been developed for the determination of slice height for optimum and arbitrary numbers of contour points with different strategies for error calculations. It has been shown that optimisation may even lead to detection and appropriate representation of elusive surface features. An index of optimisation has been defined and calculations of the same have been tabulated.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.4
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• pp.226-231
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• 2000

In this paper, we present new method to analyze the space charge effect on the electrical characteristics in polymer. It is new measurement system and analysis method that have not reported yet. By using this measurement system, we make observation to space charge accumulated on the surface of polymer at AC voltage, so it is examined to verify the correlation of space charge and partial discharge(PD). In the result of experiment, it can be known that PD pattern is related more closely to space charge accumulated on the surface of polymer than in the inner part, and applied voltage in the air is ruled by this dynamic partial discharge. Also, above critical voltage, the space charge accumulated on the surface of polymer have no effect to the magnitude of PD and the applied voltage in the air. It has been known that the electric power of the dissolution system is proportioned to the frequency and the magnitude of applied voltage, but we can know by this result of the experiment that the efficiency of the dissolution is not related to the rise of voltage above critical voltage.

• Journal of Periodontal and Implant Science
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• v.35 no.4
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• pp.863-875
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• 2005

Bovine bone-derived bone substitutes are widely used for treatment of bone defects in dental and orthopedic regenerative surgery. The purpose of this study was to evaluate the basic characteristics of deproteinized bovine bone mineral as a bone graft substitute. Commercially available products from three different bovine bone minerals-Bio-Oss(GeistlichPharma, Switzerland), BBP(Oscotec. Korea), Osteograf/N-300(Dentsply Friadent Ceramed, USA) - were investigated. They were evaluated by scanning electron microscopy(SEM), energy dispersive X-ray spectrometer(EDS), surface area analysis(BET), and Kjeldahl protein analysis. Cell viability on different products was evaluated by 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide(MTT) assay. The results of this study indicated that each bone substitute displayed distinct surface properties. Furthermore, Kjeldahl protein analysis indicated that residual crude proteins are present in deproteinized bovine bone mineral. BBP showed relatively large amount of residual protein, which indicated that the possibility of disease transmission can not be safely ruled out. Based on the results of this study, it is suggested that active quality management is strongly needed in operations that involve processing bovine bone tissue for medical use.