• 한국결정성장학회지
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• 제22권6호
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• pp.299-304
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• 2012

본 연구에서는 비산회를 자력선별한 후 알칼리 활성화제인 수산화나트륨과 물유리를 사용하여 지오폴리머를 제조하였다. 자력 선별전의 원료, 자력 선별된 두 가지 종류의 자력 및 비자력 원료를 사용한 지오폴리머 시편에 대한 압축강도를 측정하여 비교하였다. 비자력 비산회 원료를 사용한 지오폴리머 시편에서 가장 좋은 압축강도가 나올 것으로 예상하였으나, 실제로는 자력선별하지 않은 원재료 비산회와 고로슬래그를 사용한 경우에 재령 28일차 압축강도가 27.54 MPa로 가장 우수하였다. 이 결과에서, 자력선별 후 CaO 성분 농축으로 수화반응 증진에 의한 강도발현 증진 효과 보다는 자력선별에 의해 지오폴리머 형성반응에 필요한 실리카와 알루미나 성분이 오히려 줄어들어 지오폴리머 축합반응이 감소하여 오히려 압축강도 측면에서는 물성 개선효과가 없는 것으로 판명되었다.

• 대한구순구개열학회지
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• 제10권1호
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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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• 제31권2호
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• pp.350-363
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• 2006

최근 마이크로 엔드밀을 이용한 가공은 소형구조물이나 소형기계의 부품과 금형산업에서 양호한 표면 거칠기와 가공시간의 단축을 위해 고정도의 기술을 요구하고 있다. 마이크로 엔드밀을 이용한 가공에 있어서 가공조건은 절삭면의 표면거칠기에 커다란 영향을 미치게 된다. 따라서 본 연구에서는 마이크로 엔드밀을 이용하여 스테인리스 강(STS 304)의 표면을 가공하였고, 실험계획법에 의해 최적의 표면거칠기를 얻기 위한 가공조건에 대해 분산분석하였다. 본 연구를 통하여 마이크로 엔드밀에 의한 가공에서 가공조건은 절삭깊이, 스핀들의 회전수, 이송속도의 순서로 표면거칠기에 영향을 미치는 것을 알았다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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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.

• 한국표면공학회지
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• 제36권6호
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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.

• 대한금속재료학회지
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• 제50권11호
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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.

• 반도체디스플레이기술학회지
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• 제20권4호
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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.

• 한국전기전자재료학회논문지
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• 제32권3호
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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%.

• 한국기계가공학회지
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• 제17권6호
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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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• 제15권3호
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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.