• Journal of the Korean Crystal Growth and Crystal Technology
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• v.22 no.6
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• pp.299-304
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• 2012

Geopolymer was made using magnetic separation fly ash with NaOH(Sodium Hydroxide) and the water glass as alkali activators in this study. Compressive strength of geopolymers ceramics was measured and analyzed according to the type of materials. Under the conditions of fly ash without magnetic separation and 28 day curing after molding, the compressive strength of the geopolymer reached up to 28 MPa.

• Korean Journal of Cleft Lip And Palate
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• v.10 no.1
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• pp.39-56
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• 2007

The bilateral cleft lip, a more severe form of clefting than unilateral cleft lip, involves separation of the lip along philtral lines, isolating the central segment (prolabium). Bilateral cleft lip may be either symmetrical or asymmetrical, in which case the cleft lip is split more on one side than on the other. The cleft affects the obvious facial form as an anatomic deformity and has functional consequences, affecting the child's ability to eat, speak, hear, and breathe. Although there would seem to be quite a variance in reported figures, ratios of cleft lip with or without cleft palate have gone as high as 1:500 and as low as 1:1000. It is known that less than 10% of cleft lips are bilateral. Although bilateral cleft lip is less common than unilateral cleft lip, the deformity is more severe, and the reconstructive technique is more complex. Surgery is the only treatment necessary for patients with bilateral cleft lip. Accompanying the evolution of surgical repair is the increasingly important role of orthodontic support with early presurgical alveolar and nasal molding. Repositioning the maxillary and alveolar segments into a more anatomic position allows the surgeon to repair the lip and associated nasal deformity under more optimal conditions. The purpose of this article is to review the related anatomy, presurgical management, and surgical management of bilateral cleft lip.

• 대한공업교육학회지
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• v.31 no.2
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• pp.350-363
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• 2006

Recently, the micro end-milling processing is demanded the high-precise technique with good surface roughness and rapid time in milli-structure parts, micro machine parts and molding industry. The cutting conditions of micro end-milling has an effect on surface roughness of cutting surface. Therefore this study was carried out to cut stainless steel using high revolution air bearing spindle and micro end-mill and analyze the cutting condition to get the optimum surface roughness by design of experiment. From this study, surface roughness have an much effect according to priority on depth of cut, revolution of spindle and feed.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.274.2-274.2
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• 2013

We described a simple and efficient fabrication method for generating microfluidic channels with a circular-cross sectional geometry by exploiting the reflow phenomenon of a thick positive photoresist. Initial rectangular shaped positive photoresist micropatterns on a silicon wafer, which were fabricated by a conventional photolithography process, were converted into a half-circular shape by tuning the temperature to around $105^{\circ}C$. Through optimization of the reflow conditions, we could obtain a perfect circular micropattern of the positive photoresist, and control the diameter in a range from 100 to 400 ${\mu}m$. The resultant convex half-circular photoresist was used as a template for fabricating a concave polydimethylsiloxane (PDMS) through a replica molding process, and a circular PDMS microchannel was produced by bonding two half-circular PDMS layers. A variety of channel dimensions and patterns can be easily prepared, including straight, S-curve, X-, Y-, and T-shapes to mimic an in vivo vascular network. To inform an endothelial cell layer, we cultured primary human umbilical vein endothelial cells (HUVECs) inside circular PDMS microchannels, and demonstrated successful cell adhesion, proliferation, and alignment along the channel.

• Journal of the Korean institute of surface engineering
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• v.36 no.6
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• pp.491-499
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• 2003

Copper-based leadframe sheets were oxidized in a hot alkaline solution to form brown-oxide layer on the surface and molded with epoxy molding compound (EMC). The brown-oxide-coated leadframe/EMC joints were machined to form sandwiched double-cantilever beam (SDCB) specimens and sandwiched Brazil-nut (SBN) specimens for the purpose of measuring the fracture toughness of leadframe/EMC interfaces. The SDCB and the SBN specimens were designed to measure the fracture toughness of the leadframe/EMC interfaces under nearly mode-I loading and mixed-mode (mode I ＋ mode II) loading conditions, respectively. Fracture surfaces were analyzed by various equipment such as glancing-angle XRD, SEM, AES, EDS and AFM to elucidate failure path. Results showed that failure occurred irregularly in the SDCB specimens, and oxidation time of 2 minutes divided the types of irregular failures into two classes. The failure in the SBN specimens was quite different from that in the SDCB specimens. The failure path in the SBN specimens was not dependent on the phase angle as well as the distance from tips of pre-cracks.

• Korean Journal of Metals and Materials
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• v.50 no.11
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• pp.809-815
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• 2012

Recently, as the interest in improving energy efficiency has grown, the demand for vehicle and machine parts that are resistant in high temperature corrosive conditions and abrasive environments has increased. Pack chromizing treatment of sintered steels is a profitable method that satisfies both corrosion resistance and low friction properties. Since austenitic stainless steels have good corrosion resistance but low mechanical hardness, if they are replaced by sintered steel parts with pack chromizing treatment, all the desirable properties such as low price, easy molding, high hardness, low frictional coefficient, and high corrosion resistance, can be obtained. The higher corrosion resistance of the chromized parts over that of the austenitic stainless steels was acquired by coating chromium carbides and a thin chromium oxides layer on the surface. Moreover, the surface morphology of chromized parts, which were composed of chromium rich phases and hardened chromium carbides by diffusing and alloying, had a peak-and-valley shape so that the dimple effect by the wrinkled morphology and high hardness induced a low friction coefficient.

• Journal of the Semiconductor & Display Technology
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• v.20 no.4
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• pp.177-181
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• 2021

Scaffolds protect the sensor in the body. Scaffolds are made of a bioabsorbable polymer. The polymer process is sensitive to humidity. Inside of the 3D printer has been improved to control the humidity. Specimens were produced by injection molding and 3D printer. 3D printed specimens were printed under various humidity conditions. We measured tensile strength of the injection-molded specimen and tensile strength of the 3d printing specimen. We compared tensile strength of the injection-molded specimen and tensile strength of the 3d printing specimen. Tensile strength of the injection-molded specimen is 557 kgf/cm². We confirmed tensile strength of the specimen was highest at 741 kgf/cm² when the humidity was 10 %. We confirmed lower the humidity, higher tensile strength of the polymer product.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.3
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• pp.213-218
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• 2019

In this study, a high-temperature vulcanizing (HTV) method was used to achieve a shore a hardness of 70. The basic base was composed of 60% silicon gum (GUM) which is a high-viscosity polymer, 30% fumed silica (FS), and 5% of plasticizer. The GUM and FS were mixed well with less than 1% silane to improve rubber strength. Expanded vermiculite was added as a filler at 10%, 15%, and 20%. The curing conditions were $170^{\circ}C$ for 10 min and a molding method was applied. We report herein, the results of inorganic analysis and flame-retardant and tracking tests on the expanded vermiculite. The flame retardance and tracking test outcomes for a shore a hardness of 70 were found to be optimal when the expanded vermiculite content was 10%.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.6
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• pp.98-104
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• 2018

Deflected 4-way panels of ceiling air conditioners produced by injection molding process have caused dew condensation at the edge of products. In order to prevent this drawback with reducing weight and deformation, this study proposed renovated process adopting microcellular foaming. According to results from 2-sample t-test and analysis of variance(ANOVA), the critical factors affecting weight were melt temperature and injection speed. In addition, the vital effects on deformation were structure at the edge, mold temperature and cooling time. Optimal conditions of these parameters were derived by regressive analysis with CAE and response surface method(RSM), and then applied to an actual design and process stage to analyze performance. As a results, it clearly showed that new process improved process capability as well as reduced both weight and deformation by 18.8% and 71.9% respectively compared to the conventional method.

• Design & Manufacturing
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• v.15 no.3
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• pp.13-18
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• 2021

In plate forming technology, cylindrical drawing process is widely used in industry due to technological development. In this study, we used stainless steel 3042B and stainless steel 304J1, which are the most commonly used materials in the production of cold and hot water tanks for water purifiers, among cylindrical drawing products. Under the same conditions, the thickness of the sidewall of the product formed by drawn experiment was studied. As a result of the experiment, the bottom thickness of stainless steel 304J1 was considered to be thick. It is judged that the defect rate can be reduced by changing the breaking phenomenon of the floor surface of the cold and hot water bottles to the material of stainless steel 304j1. Stainless steel 304 2B material shows a sharp change in thickness from punch corner R to sidewall position, while stainless steel 304J1 material showed a uniform change from punch corner R to sidewall position. Stainless steel 304J1 material is considered to improve the clamping of the product in the process of extracting the product after hand drawing. The appearance of stainless steel 3042B products is considered to produce more wrinkles in the flange, which exerts greater tensile force on the sidewall during molding, resulting in uneven sidewall thickness.