• Education of Primary School Mathematics
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• v.14 no.3
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• pp.303-316
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• 2011

The purpose of this study was to analyze a first grader's number sense in playing the searching complement of ten game. For this purpose, the researcher conducted the game with a first-year student and analyzed her number sense based on conversations in playing games. The results obtained in this study were as follows: First, the student had a very big interested in the game and it was easily converted into additional situations. Second, she fully understood the rules of the game and made the complement of the given number. However, she was not good at making complement of twelve. Third, she made new rules like using three or four cards. She easily made the number 10 with two cards, but she didn't easily understand how to make 10 with more than three cards.

• Magazine of the Korea Concrete Institute
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• v.8 no.1
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• pp.121-129
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• 1996

본 연구에서는 대기 습도변화에 의한 콘크리트 보수체(기층 콘크리트/보수 모르터)의 파괴현상을 조사하기 휘해서 보수체내의 비정상적인 습도분포를 계산하였다. 계산된 습도분포에 의해서 기층과 보수층 경계면 부위의 습도차이가 보수층 두께(0.5~2.5cm)와 보수작업전 기층 콘크리트 표면의 습윤처리시간(0~72hr)을 주요 변수로 하여 조사되었고, 이는 주로 시멘트 모르터로 보수된 접촉면이 없는 보수체에서 수행되었다. 계산 및 조사결과 보수층 두께가 감소하고 습윤 처리시간이 증가할수록 경계면 부위의 습도차이는 감소하는 경향을 보였고, 특히 보수후 습도차이가 음수값이 될 때의 시간을 하나의 수식으로 표시하였다.

• Journal of the Korean Society for Railway
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• v.14 no.3
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• pp.216-221
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• 2011

An important problem in reliability analysis for repairable systems is to model the maintenance effect. The most of researches have assumed two extreme cases; one is perfect maintenance and the other is minimal maintenance. However, many of maintenances performed by domestic subway operators are imperfect maintenances which have the effect between both of two extreme cases. This article deals with the problem determining the imperfect preventive maintenance intervals based on failure data in units of the PDS(passenger door system) in Metro EMU. This paper deals with a case study on determining imperfect maintenance interval by using the level of maintenance effect through reliability analysis of PDS.

• 전기의세계
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• v.37 no.10
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• pp.46-53
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• 1988

앞으로 보수관리를 효율적으로 대처하기 위하여, 또한 대용량화및 새로운 설비 증가에 따른 각종 정보처리, 기술의 진일보를 위하여 자동화 및 기계화 기술을 과감히 도입 적용하여야 설비의 수명을 극대화하고, 안정된 전력공급을 효율적으로 이룩할수 있을 것으로 생각한다.

• Composites Research
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• v.37 no.2
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• pp.76-85
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• 2024

In this paper, a composite maintenance robot using carbon fiber spray method was developed that automatically sprays mixture was created for repair to damaged areas to repair them. To develop a robot, a repair process was developed in which a mixture of milled carbon fiber, epoxy resin, and hardener is sprayed and consolidated on the damaged area. To automate the repair process, an EOAT based on a collaborative robot was developed that can automatically suction and spray the mixture onto the damaged area. To evaluate the repair performance of the robot, 0° and 90° unidirectional specimens were manufactured and tested in accordance with ASTM D3039. Tests were performed on undamaged specimen, damaged specimen, and repaired specimen by a robot after damaged. As a result of the specimen test, the tensile strength of the 0° and 90° specimens was recovered by 10% and 90% after repair. Based on the test results, the repair performance of the developed composite maintenance robot was verified.

• Applied Biological Chemistry
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• v.21 no.2
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• pp.109-111
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• 1978

This study was undertaken in order to observe the differences of the changes in the water-holding capacity (WHC), extractability of proteins (EP) and pH value of ovine muscle during storage. WHC decreased gradually after slaughter, reached to minimum at about 2-4hr after death as well as that of pH value and then these were recovered along with the progress of the storage. The same tendency was observed in EP but the degree of the changes in pH value up to 6hr after slaughter was more rapid this that of WHC and EP. After the fourth day, the rate of recovery in WHC, EP and pH value in ovine muscle during storage showed similar pattern.

• Magazine of the Korea Concrete Institute
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• v.10 no.4
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• pp.145-151
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• 1998

The vertical tensile stress, ${\sigma}_y$, in the contact zone between the overlay (mortar layer) and substratum (base concrete) can be the main cause of the failure phenomenon of overlaid concrete structures. The development of tensile stress, ${\sigma}_y$, due to external rainy condition was analytically investigated using finite element method. Rainfall intensity $(n_R\;=\;1/a,\;t_R\;=\;10min,\;60min)$, thickness of overlay (do=1,2,4,10 cm) and overlay material (CM,ECM,EM) were the main variables in the analyses. An equation was suggested with which the development of vertical tensile stress, ${\sigma}_y$, in the rainy condition could be determined. Using this equation, it is possible to select proper material properties and overlay thicknesses to prevent failure in the contact zone due to thermally transient condition caused by rainfall.

• Electronics and Telecommunications Trends
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• v.8 no.4
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• pp.13-22
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• 1993

이동통신 가입자는 통신망을 매우 많이 이용하면서 부단한 서비스를 요구하는 고객이므로 DCN은 고객에게 양질의 서비스를 제공할 수 있게 운용되어야 한다. 따라서 DCN 에서는 시스템 고장과 같은 이유로 통신망에 이상이 발생하지 말아야 하며, 만일 이상이 발생되었다 하더라도 신속한 복구가 이루어질 수 있도록 운용 체계가 구성되어야 한다. 본 고에서는 현재 개발되고 있는 DCN 에서 제어국을 구성하고 있는 한 서브시스템인 CCP 에서 수행되는 유지보수 기능과 이를 구현하는 과정을 보였다. 먼저 DCN 의 구조와 연관하여 제어국의 위치와 역할을 분석하고 제어국 내의 여러 서브 시스템의 기능을 살펴본 후 CCP 의 기능이 원활하게 수행될 수 있도록 CCP 의 유지 보수 기능은 어떻게 정의되어야 하는 가를 분석하고 이를 구현할 수 있는 설계 방향을 제시하였다.

• Magazine of the Korea Concrete Institute
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• v.9 no.3
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• pp.157-166
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• 1997

The object of this study was invest, igat, ing the failure phenomenon in the contact zone of rcpnired concrete structures due to the external climate change(hygral transient condition). This study was carrie out by calculating the non-stationary moisture and stress distribution in the repaired concrete structures with the cement mortar. In this analysis, main variables were the overlay thickness (Do=0.5-2.5cm). and the pre-wetting time(tc= l-5days). and the cxtcrnal 1.~1ative humidity(Ho=50-80%). The results show that the minimum overlay thickness and the minimum pre-wetting time are necessary to k e ~ p compressive stresses in the contact zone for a relative humidity.

• Journal of the Korea Concrete Institute
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• v.16 no.1 s.79
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• pp.88-93
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• 2004

The objective of this study was to investigate applicability of epoxy injection method to cracked RC beams and structural behavior of repaired RC beams considering pre-loading conditions. For this purpose, five test beams were fabricated under two experimental variables. The main variables of this experimental study were pre-loading conditions and repair methods. The two pre-loading conditions were selected as $70\%$ and $90\%$ of nominal strength and the repair methods were to repair the cracked RC beams under free loading after crack and sustained loading. The comparative study was executed to evaluate effects of pre-loading conditions on the structural behavior of the cracked RC beams after crack-repair. The strains of reinforcement and concrete and deflections of beams at each loading step were measured and evaluated. As the results of this study, repair methods have much influence on structural behavior of epoxy injected RC beams and epoxy injection method for cracks of RC structures is appeared to be efficient.