• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1997년도 춘계학술대회논문집
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• pp.69-72
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• 1997

The indentation process in the Vickers hardness test is a kind of controlled local plastic deformation. Vickers hardness is defined as indenting force per unit area indented by a pyramid-shaped diamond at the hardness test. That is a measure of mechanical resistance against indentation of a rigid body into the deformable material. Therefore it is well known that Vickers hardness has a direct relation with the flow stress of the strain-hardened tmaterial. This relation is theoretically investigated and the result is given for use in practice.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.950-955
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• 2001

For the development of an ultra-precision CNC polishing system including on-machine measurement system, we study a corrective polishing algorithm. We analyze and test the unit removal profiles for a ball type polishing tool. Using these results we calculate dwell time distributions and residual errors for a target removal shape. We use the polishing simulation method and feed rate calculation method for the dwell time calculation. We test corrective polishing algorithm with an optical glass. The target removal shape is a sine wave that has amplitude 0.3 micro meters. We find this polishing process has a machining resolution of nanometer order and is effective for sub-micrometer order machining. This result will be used for the software development of the CNC polishing system.

• 한국지반신소재학회논문집
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• 제19권1호
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• pp.103-110
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• 2020

심층혼합공법은 오거를 사용하여 지반을 굴착한 후 지반안정재를 흙 재료와 혼합하여 연약지반에 개량체를 설치하는 공법으로, 지중에 설치되는 개량체는 흙 재료의 종류와 특성에 따라 압축강도가 다르게 발현되기도 한다. 이를 위해 기존의 연구에서는 순환유동층 보일러의 연소재를 고로슬래그의 알칼리 활성화 반응의 자극재로 활용하여 개발한 심층혼합공법용 지반안정재를 부산, 여수, 인천 지역의 점토와 혼합한 후 실내 배합시험을 실시하고, 결과를 분석하여 단위안정재량(γ_B)과 일축압축강도(q_u)의 상관관계를 도출하였다. 본 연구에서는 새만금 지역을 대상으로 채취한 흙 재료에 대해 동일한 실내시험을 실시하여 도출된 상관관계에 대한 비교검토를 실시하였고, 현장에서 수행한 시험시공 결과를 분석하여 현장에서의 안정성을 평가하였다. 연구결과, 실내시험에서는 기존의 연구를 통해 도출된 단위안정재량(γ_B)과 일축압축강도(q_u)의 상관관계를 만족하는 것으로 나타났고, 현장에서의 시험시공 결과는 현장의 기준강도에 비해 높은 일축압축강도를 보여 안정성 측면에서 우수한 것으로 나타났다.

• Nuclear Engineering and Technology
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• 제52권11호
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• pp.2652-2659
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• 2020

The methyl iodide (CH₃I) removal performance of tri-ethylene-di-amine impregnated activated carbon (TEDA-AC) used in the air cleaning unit of nuclear power plants (NPPs) should be maintained at least 99% between 24 month-performance test period. In order for evaluating the effectiveness of TEDA-AC on the removal performance of CH₃I in nuclear power plant during the operation of NPPs, the long-term test for up to 15 months was carried out under the simulated operating conditions (e.g., 25 ℃, RH 50%, ppb level poisoning gases injection) at nuclear power plants (NPPs). The TEDA-AC samples were analyzed with the Brunauer-Emmett-Teller (BET) specific surface area and TEDA content as well as CH₃I penetration test. It is clearly evident that more than 99% of CH₃I removal performance of TEDA-AC was observed in the TEDA-AC samples during 15 months of long-term operation under the simulated NPP operating conditions including the ppb level of organic and oxide form of poisoning gases. BET specific surface area and TEDA content that can affect the CH₃I removal performance of TEDA-AC were also maintained as those in new TEDA-AC during 15 months of long-term operation.

• 한국초등과학교육학회지:초등과학교육
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• 제28권3호
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• pp.321-330
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• 2009

This study investigated the effects of teaching-learning lesson plan using cognitive acceleration instructional strategies applied to the unit, 'The Light and Shadow' in elementary school. Two classes of the second grade elementary students (N=63) in Chungcheongbukdo districts were assigned to control and treatment groups each, and were taught about 'The Light and Shadow' for 8 class hours. For the treatment group, teaching-learning lesson plan using cognitive acceleration instructional strategies developed by this research was applied. The traditional instruction by textbook and teacher's guides was used for the control group. All students were tested with the test for concept of the shadow and the test for academic achievement about the unit. As the result of the post-test, the scores of the treatment group were higher than those of the control group. However, it was not statistically meaningful difference. The scores of the treatment group were significantly higher than those of the control group in the delayed-post-test for concept of the shadow. No significant interaction was observed with respect to the students' gender, instruction and pre-level for the concept of the shadow. Data analysis indicated that the scores of the treatment group were significantly higher than those of the control group in the post-test and delayed- post-test for the concept of the shadow in the area of object permanence. Our research work shows the effectiveness of the teaching-learning lesson using cognitive acceleration instructional strategies for the development for concept of the shadow for elementary school students, and suggests the necessity for this kind of teaching-learning program in the fields.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.982-989
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• 2005

In this study, a series of laboratory tests based on 'Unit-cell concept' are performed to investigate improvement characteristics of clay ground in sand compaction pile method. Settlement reduction characteristics of composite ground and improvement characteristics of clay part could be qualified. In these procedure, the new strain-compression index($C_{\epsilon}$) of composite ground are adopted to show compressibility of composite ground according to the area replacement ratio, which is similar to the compression index($C_c$) in pure clay ground. Also, using normalization of reduction of water content in composite ground to the initial water content, improvement characteristics of clay part are investigated.

• The Journal of Advanced Prosthodontics
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• 제9권6호
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• pp.463-469
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• 2017

PURPOSE. To evaluate the fit of a three-unit metal framework of fixed dental prostheses made by subtractive and additive manufacturing. MATERIALS AND METHODS. One master model of metal was fabricated. Twenty silicone impressions were made on the master die, working die of 10 poured with Type 4 stone, and working die of 10 made of scannable stone. Ten three-unit wax frameworks were fabricated by wax-up from Type IV working die. Stereolithography files of 10 three-unit frameworks were obtained using a model scanner and three-dimensional design software on a scannable working die. The three-unit wax framework was fabricated using subtractive manufacturing (SM) by applying the prepared stereolithography file, and the resin framework was fabricated by additive manufacturing (AM); both used metal alloy castings for metal frameworks. Marginal and internal gap were measured using silicone replica technique and digital microscope. Measurement data were analyzed by Kruskal-Wallis H test and Mann-Whitney U-test (${\alpha}=.05$). RESULTS. The lowest and highest gaps between premolar and molar margins were in the SM group and the AM group, respectively. There was a statistically significant difference in the marginal gap among the 3 groups (P<.001). In the marginal area where pontic was present, the largest gap was $149.39{\pm}42.30{\mu}m$ in the AM group, and the lowest gap was $24.40{\pm}11.92{\mu}m$ in the SM group. CONCLUSION. Three-unit metal frameworks made by subtractive manufacturing are clinically applicable. However, additive manufacturing requires more research to be applied clinically.

• 대한토목학회논문집
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• 제6권1호
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• pp.79-86
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• 1986

개념유출모형(槪念流出模型)인 모형(模型)의 매개변수(媒介變數) n, k는 유성면적(流城面積)이 $53.7{\sim}1,361km^2$의 범위에 있는 18개 유역의 강우(降雨)-유출자료(流出資料)로부터 모멘트방법에 의하여 추정(推定)된다. 이들 n, k는 F-test와 더불어 복합상관방법(複合相關方法)에 의하여 유성특성(流城特性) 인자(因子)들만의 함수로 유도된다. 유도된 매개변수(媒介變數)들은 한강(漢江), 금강(錦江) 및 낙동강유성(洛東江流城)에 적용하여 계산된 수문곡선(水文曲線)과 실제자료(實際資料)로부터 유도한 수문곡선(水文曲線)은 비교적 잘 맞았으며, 이는 유성특성(流城特性)만으로 미계측소유성(未計測小流城)의 강우(降雨)-유출자료(流出資料)의 가능(可能)함을 시사한다.

• 한국철도학회논문집
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• 제9권5호
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• pp.577-581
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• 2006

Urban transit operation corporations perform repetitive work to investigate the EMU, electric multiple unit, by some fixed maintenance cycle. The quality of maintenance work usually depends on workers' know-how. Though some information to support the maintenance work is digitalized and provided to workers, it is not great help to them because of its non systematic structure. The information includes drawings, manuals, work results, work history, fault history, etc. The maintenance workers want to access the information anytime anywhere, and make an effect to promote the efficiency of maintenance for EMU. But it is difficult to achieve that without some structured information system which is able to use in work area. So we develop maintenance information system for EMU for about 4 years from 2002 to 2005. In this paper we present the configuration and characteristics of this system, and the results of the evaluation test. We install the system in two depots, Changdong and Jichuk, belonged to SeoulMetro to evaluate its efficiency and estimate its economic benefits.

• 국제지역연구
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• 제22권3호
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• pp.67-84
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• 2018

본 연구는 BS(Balassa-Samuelson)효과가 장기 실질환율 변화를 설명할 수 있는지를 실증적으로 분석하는 데 있다. 이를 위해 1995년부터 2015년까지 OECD 25개 회원국(기준국 미국 제외)을 대상으로 패널자료를 구축하고 단위근 및 공적분검정을 통해 자료의 안정성을 검토하여 공적분 관계가 존재할 경우 추정모형을 설정하여 장기균형식을 추정하였다. 관련 변수들에 대한 패널 단위근 및 공적분검정을 실시한 결과 실질환율을 제외한 모든 변수들이 단위근을 가지고 있어 불안정적 시계열로 나타났으며 관련 변수들 간에 공적분 관계 즉 안정적인 균형관계가 존재하는 것으로 분석되었다. 동태최소자승법(Dynamic Ordinary Least Square, 이하 DOLS) 및 오차수정모형(Error-Correction Model, 이하 ECM)을 이용해 장기균형식을 추정한 결과 대체로 이론에서 예측하는 BS효과를 얻었으나 그 효과는 크지 않은 것으로 분석되었다. 특히 노동생산성이 실질환율에 직접 미치는 효과는 작았거나 통계적으로 유의하지 않았다. 그러나 교역재에 대한 비교역재 상대가격은 통계적으로 유의하게 실질환율에 영향을 미쳤으며 이론이 예측하는 바와 동일했다. 상대노동생산성이 상대가격에 미치는 효과는 분명하지 않았다. 한편 교역조건을 설명변수에 포함하여 추정한 결과 이론에서 예측하는 바와 동일한 결과를 얻었으며 모두 통계적으로 유의한 수준에서 교역조건이 실질환율 변화를 설명하는 데 중요한 변수라는 결과를 도출했다.