• 대한치과보철학회지
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• 제42권6호
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• pp.654-663
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• 2004

Statement of problem. According to the fracture pattern in several reports, fractures most frequently occur in the interface between the ceromer and the substructure. Purpose. The aim of this in vitro study was to compare the macro shear bond strength and microshear bond strength of a ceromer bonded to a fiber reinforced composite (FRC) as well as metal alloys. Material and methods. Ten of the following substructures, type II gold alloy, Co-Cr alloy, Ni-Cr alloy, and FRC (Vectris) substructures with a 12 mm in diameter, were imbedded in acrylic resin and ground with 400, and 1, 000-grit sandpaper. The metal primer and wetting agent were applied to the sandblasted bonding area of the metal specimens and the FRC specimens, respectively. The ceromer was placed onto a 6 mm diameter and 3 mm height mold in the macro-shear test and 1 mm diameter and 2 mm height mold in the micro-shear test, and then polymerized. The macro- and micro-shear bond strength were measured using a universal testing machine and a micro-shear tester, respectively. The macro- and micro-shear strength were analyzed with ANOVA and a post-hoc Scheffe adjustment ($\alpha$ = .05). The fracture surfaces of the crowns were then examined by scanning electron microscopy to determine the mode of failure. Chi-square test was used to identify the differences in the failure mode. Results. The macro-shear strength and the micro-shear strength differed significantly with the types of substructure (P<.001). Although the ceromer/FRC group showed the highest macroand micro-shear strength, the micro-shear strength was not significantly different from that of the base metal alloy groups. The base metal alloy substructure groups showed the lowest mean macro-shear strength. However, the gold alloy substructure group exhibited the least micro-shear strength. The micro-shear strength was higher than the macro-shear strength excluding the gold alloy substructure group. Adhesive failure was most frequent type of fracture in the ceromer specimens bonded to the gold alloys. Cohesive failure at the ceromer layer was more common in the base metals and FRC substructures. Conclusion. The Vectris substructure had higher shear strength than the other substructures. Although the shear strength of the ceromer bonded to the base metals was lower than that of the gold alloy, the micro-shear strength of the base metals were superior to that of the gold alloy.

• Environmental Engineering Research
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• 제22권1호
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• pp.75-86
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• 2017

The aerosol content dynamics in a virtual system were investigated. The outcome was extended to monitor the mean concentration diffusion of aerosols in a predefined macro and micro scale. The data set used were wind data set from the automatic weather station; satellite data set from Total Ozone Mapping Spectrometer aerosol index and multi-angle imaging spectroradiometer; ground data set from Aerosol robotic network. The maximum speed of the macro scale (West Africa) was less than 4.4 m/s. This low speed enables the pollutants to acquire maximum range of about 15 km. The heterogeneous nature of aerosols layer in the West African atmosphere creates strange transport pattern caused by multiple refractivity. It is believed that the multiple refractive concepts inhibit aerosol optical depth data retrieval. It was also discovered that the build-up of the purported strange transport pattern with time has enormous potential to influence higher degrees of climatic change in the long term. Even when the African Easterly Jet drives the aerosols layer at about 10 m/s, the interacting layers of aerosols are compelled to mitigate its speed to about 4.2 m/s (macro scale level) and boost its speed to 30 m/s on the micro scale level. Mean concentration diffusion of aerosols was higher in the micro scale than the macro scale level. The minimum aerosol content dynamics for non-decaying, logarithmic decay and exponential decay particulates dispersion is given as 4, 1.4 and 0 respectively.

• 전자공학회논문지B
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• 제31B권9호
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• pp.47-56
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• 1994

In this paper, we demonstrate how to design a redundant robot which is suitable for the multiple task execution without any constraints on the work space. The implementation is possible by the rigid connection of a cacro-robot and a micro-robot. A 5 d.o.f. articulated robor designed for commercial purpose is utilized as a micro-robot which can perform a general task with the appropriate adjustment of its base location. The base of a micro-robot is located at a suitable position by the macro-robot designed and implemented through this research. A task assigned to this redundant robot is performed mainly by the micro-robot. However, when the micro-robot cannot perform the task by itself or when the micro-robot has difficulties in performing the task, the coordination of the macro-robot is requited. To monitor the task execution efficiency of the micro-robot, we used the 'Manipulability Measure' as a cost function. The coordination between the two robots are verified both by the simulation and the experiment.

• Corrosion Science and Technology
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• 제9권6호
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• pp.331-337
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• 2010

This study compared the macro and micro electrochemical characteristics at the local area of welding metal on dissimilar welding parts for type 304 stainless steel (SS) and type 316L SS. The materials are used for double wall gas pipe of duel fuel engine for a ship. The various potentiodynamic experiments were performed several times in 10% ${H_2C_2O_2}{\cdot}{H_2O}$ solution using macro and micro methods, respectively. The micro electrochemical experiments conducted to resolve at local area on cross-section of dissimilar welding materials by micro-droplet cell device. The micro-droplet cell techniques can be used almost electrochemical experiments to resolve corrosion characteristics of the limited electrode area of the metallic surface between wetted spot of working electrode and tip of sharpened capillary tube. The results of macro electrochemical experiments show that resistance of active dissolution reaction at welding zone was high due to low current density by formation of passivation protection film at passive region. According to the micro electrochemical experiment, the corrosion current density of welding zone and bond zone were relatively high.

• Computers and Concrete
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• 제4권1호
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• pp.19-32
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• 2007

This paper is concentrated on the behaviors of five different types of fiber reinforced concrete (FRC) in uniaxial tension and flexural impact. The complete stress-strain responses in tension were acquired through a systematic experimental program. It was found that the tensile peak strains of concrete with micro polyethylene (PEF) fiber are about 18-31% higher than that of matrix concrete, those for composite with macro polypropylene fiber is 40-83% higher than that of steel fiber reinforced concrete (SFRC). The fracture energy of composites with micro-fiber is 23-67% higher than that of matrix concrete; this for macro polypropylene fiber and steel fiber FRCs are about 150-210% and 270-320% larger than that of plain concrete respectively. Micro-fiber is more effective than macro-fiber for initial crack impact resistance; however, the failure impact resistance of macro-fiber is significantly larger than that of microfiber, especially macro-polypropylene-fiber.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.602-603
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• 2006

Micro-porous nickel (Ni) with an open cell structure was fabricated by powder metallurgy. The pore size of the micro-porous Ni approximated $30{\mu}m$ and $150{\mu}m$. For comparison, porous Ni with a macro-porous structure were also prepared by both powder metallurgy (pore size $800{\mu}m$) and the traditional chemical vapour deposition method (pore size $1300{\mu}m$). The mechanical properties of the micro-and macro-porous Ni samples were evaluated using compressive tests. Results indicate that the micro-porous Ni samples exhibited significantly enhanced mechanical properties, compared to those of the macro-porous Ni samples.

• Journal of the Korean Wood Science and Technology
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• 제36권6호
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• pp.13-22
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• 2008

보드의 기계적 성질에 영향을 미치는 공극에 대하여 공극을 두가지로 분류하고 밀도에 따른 오에스비의 내부 공극구조의 특성에 대하여 살펴보고자 하였다. 스트랜드보드의 내부공극을 X-ray 단층촬영기로 측정하고 이미지분석 소프트웨어를 사용하여 밀도에 따른 공극의 분포와 공극의 함유량을 조사하였다. 측정 전에 보드의 밀도를 밀도측정기와 전건법으로 측정하였으며 이 두 방법에 의해 측정된 결과는 아주 높은 상관관계를 보여주었다. X-ray를 서로 다른 배율로 조사하여 획득한 이미지를 바탕으로 분석한 결과, 저해상도에서는 스트랜드간의 공극(macro-void)의 측정이 가능하나 스트랜드내의 미세공극(micro-void)은 이미지획득이 불가능하였다. 중해상도에서는 두가지 형태 모두의 이미지 획득이 가능하였고, 고해상도에서는 대부분의 미세공극 이미지의 획득이 가능하였다. 저배율을 채택하여 스트랜드간의 공극을 측정하고 스트랜드내의 미세공극은 관련식을 이용하여 추정하였다. 이를 통해 보드내부에 존재하는 스트랜드간의 공극분포를 파악할 수 있었으며 그 공극의 함유비율을 정확하게 산정할 수 있었다.

• 한국융합학회논문지
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• 제13권2호
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• pp.13-20
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• 2022

본 연구는 딥러닝 기법을 활용하여 범죄 수사 도메인에 특화된 개체명 인식 모델을 개발하는 연구이다. 본 연구를 통해 비정형의 형사 판결문·수사 문서와 같은 텍스트 기반의 데이터에서 자동으로 범죄 수법과 범죄 관련 정보를 추출하고 유형화하여, 향후 데이터 분석기법을 활용한 범죄 예방 분석과 수사에 기여할 수 있는 시스템을 제안한다. 본 연구에서는 범죄 수사 도메인 텍스트를 수집하고 범죄 분석의 관점에서 필요한 개체명 분류를 새로 정의하였다. 또한 최근 자연어 처리에서 높은 성능을 보이고 있는 사전학습 언어모델인 KoELECTRA를 적용한 제안 모델은 본 연구에서 정의한 범죄 도메인 개체명 실험 데이터의 9종의 메인 카테고리 분류에서 micro average(이하 micro avg) F1-score 99%, macro average(이하 macro avg) F1-score 96%의 성능을 보이고, 56종의 서브 카테고리 분류에서 micro avg F1-score 98%, macro avg F1-score 62%의 성능을 보인다. 제안한 모델을 통해 향후 개선 가능성과 활용 가능성의 관점에서 분석한다.

• 소성∙가공
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• 제12권4호
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• pp.314-319
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• 2003

In the micro hole punching, the size and shape of burr and burnish zone are very important factors to evaluate quality of micro holes which depend on punch-die clearance, strain rate, workpiece material and etc. To get micro holes with small burr and wide burnish zone for industrial demands, not only the parametric study but also a study on fracture behavior in shear band are necessary. In this study, 100 $\mu$m, 25 $\mu$m micro holes in diameter were fabricated on brass (Cu63/Zn37) and SUS 316 foils as aspect ratio 1:1, and the characteristics of micro holes was investigated comparing with those of macro holes over several mm by scanning electron microscopic views and section views. Like macro hole, micro hole is also composed of 4 portions, rollover. burnish zone, fracture zone and burr, and it shows similar fracture behavior in shear band. But by high strain rate (10$^2$∼10$^3$s$^{-1}$ ) condition unlike that of macro hole fabrication and by the increment of relative grain size in the direction of the workpiece thickness, fracture zone is not observed.

• 디지털융복합연구
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• 제18권4호
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• pp.75-80
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• 2020

본 연구는 중국시장에서 미시 및 거시적 국가이미지가 브랜드태도에 영향을 미치는 영향관계에서 브랜드친숙도, 개방성의 조절효과를 검증하였다. 이를 위해 기존 문헌에 대한 고찰을 바탕으로 거시적 국가이미지의 하위 요인을 경제적 이미지로 사용하였다. 본 연구에서 사용된 연구 방법은 주로 선행 문헌 연구 방법과 실증 연구 방법을 포함하며, 선행연구 이론들을 바탕으로 연구 모형을 수립하고 관련 연구 가설을 설정하는 동시에 중국소비자를 설문 대상으로 선정하여 설문 조사 및 데이터 수집을 실시하고 모형의 적합성 테스트 및 연구 가설에 대해 검증하였다. 본 연구의 결과, 미시적 및 거시적 국가이미지는 브랜드 태도에 정(+)의 영향을 미치고 브랜드 친숙도와 개방성은 미시적 국가이미지에는 조절효과 없는 것으로 분석되었고 거시적 국가이미지(경제이미지)에는 조절효과가 있는 것으로 분석되었다. 본 연구의 결과는 중국시장에서 중국과 밀접한 관계를 맺고 있는 한국, 미국, 일본기업들의 다양한 비즈니스 전략을 활용하는데 시사점을 제공하고 있다.