• Tribology and Lubricants
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• 제12권4호
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• pp.18-27
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• 1996

An interlaboratory wear testing was performed in order to understand the friction behaviors and the wear mechanisms of the sintered composites. The specimens were the sintered bronze matrix composites having various contents of friction additives, friction control agents and reinforcements. The variation of the wear characteristics according to the constituents of the composites as well as the wear conditions was investigated by SEM, EPMA, OM, the hardness testing and the measurement of friction. The specimen having glass fiber as the matrix reinforcement showed a remarkable increase in wear resistance as increasing the content of glass fiber. Graphite particles in the composites exhibited the lubricating effect and also resulted in the lowering strength of the matrix. Addition of Mo powder to the composites led to the deterioration of wear properties at the room temperature, however, an enhanced wear properties were obtained in the containing Mo at an elevated temperature.

• 한국농공학회논문집
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• 제52권4호
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• pp.73-81
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• 2010

The cemented sand and gravel (CSG) method is a construction technique that adds cement and water to rock-like materials, such as rivered gravel or excavation muck which can be obtained easily at areas adjacent to dam sites. This study was performed to evaluate the compaction and compressive strength properties of stress-strain, elastic modulus and fracture mode CSG materials reinforced polypropylene fiber. Polypropylene fiber widely used for concrete reinforcement is randomly distributed into cemented sand. The two types of polypropylene fiber (monofillament and fibrillated fiber) were used and fiber fraction ratio was 0, 0.2 %, 0.4 %, 0.6 % and 0.8 % by the weight of total dry soil. The effect of fiber fraction ratio and fiber shape on compaction and compressive strength were investigated. The optimum moisture contents (OMC) of CSG material increased as fiber fraction increased and the dry density of CSG material decreased as fiber fraction. Also, the maximum increase in compressive strength was obtained at 0.4 % content of monofillament and fibrillated fiber. CSG material behaviour was controlled not only by fiber fraction but also fiber distribution, fiber shape and fiber type.

• 한국분말재료학회지
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• 제23권3호
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• pp.213-220
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• 2016

In this study, bulk nickel-carbon nanotube (CNT) nanocomposites are synthesized by a novel method which includes a combination of ultrasonication, electrical explosion of wire in liquid and spark plasma sintering. The mechanical characteristics of the bulk Ni-CNT composites synthesized with CNT contents of 0.7, 1, 3 and 5 wt.% are investigated. X-ray diffraction, optical microscopy and field emission scanning electron microscopy techniques are used to observe the different phases, morphologies and structures of the composite powders as well as the sintered samples. The obtained results reveal that the as-synthesized composite exhibits substantial enhancement in the microhardness and values more than 140 HV are observed. However an empirical reinforcement limit of 3 wt.% is determined for the CNT content, beyond which, there is no significant improvement in the mechanical properties.

• 한국환경교육학회지:환경교육
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• 제9권1호
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• pp.90-99
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• 1996

This study focused on the investigation of objects and contents of environment-related chapters which were contained in the biology textbooks of middle school in the 5th curriculum, and in the 6th curriculum. As a result of objects analysis, cognitive domain such as the knowledge and information categories were allocated more than affective domain as skill, value and attitude, and behavior and participation. Compared with the 5th curriculum, the average-pages of environment-related chapters in the 6th curriculum were decreased. Environment-related chapters in the 6th curriculum also dealt negligibly with the real environmental problems in our country. Therefore the importance of the environment-related chapters of biology textbooks in the 6th curriculum was relatively deceased compared with that in the 5th curriculum. In considering the actual low optional rate of environment subject in middle school, it was thought that the reinforcing effect of environmental education can be hardly expected. Rather, the status of environment subject will grow weaker and weaker. Thus, in order to avoid the deterioration effect of its status and solve its problems, it is necessary to up-grade environment subject as obligatory course or needs strong reinforcement of environmental education.

• 한국사회복지학
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• 제61권4호
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• pp.217-241
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• 2009

본 연구는 사회복지사들의 실천지식의 생성과정과 내용 그리고 규범적 실천을 살펴보고 사회복지 지식의 재구조화에 시사점을 찾고자 하는 목적하에 수행되었다. 연구방법으로는 성찰적 내러티브 방법을 원용하였고 연구에는 6명의 현직 사회복지사가 참여했다. 연구결과 참여자들은 기존이론과 지식체계로 설명할 수 없는 현상에 직면했을 때 자기 성찰을 통해 지식을 만들었고 실천을 통해 이를 확인하고 재생산하는 경향을 보였다. 연구결과를 근거로 실천현장에서의 지식개발 방법론으로 귀추 추론 양식, 사회복지교육과정에서 인문학 교육의 강화, 네트워크의 지식공동체로의 재구조화를 제언했다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.461-464
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• 2008

본 연구는 섬유보강 콘크리트를 사용한 APT 공용부 무근 콘크리트 균열저감공법의 적용을 위하여 국내에서 판매되는 섬유 종류별 표준사용량을 사용한 콘크리트의 역학적 특성을 분석한 것으로써, 그 결과를 요약하면 다음과 같다. 굳지않은 콘크리트의 특성으로 슬럼프는 섬유 혼입 시 약간감소하는 것으로 나타났는데, 이는 섬유의 표면적 증가 및 섬유의 가교작용에 기인한 결과로 분석된다. 경화 콘크리트의 특성으로 섬유 혼합 시 압축강도는 섬유와 시멘트 페이스트와의 부착력 저하에 의해 약간 감소하는 것으로 나타났고, 인장강도는 섬유의 가교작용에 의해 약간 증가하는 것으로 나타났으며, 휨강도 및 건조수축 길이변화는 큰 차이가 없는 것으로 판단된다.

• 한국산업보건학회지
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• 제23권4호
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• pp.374-383
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• 2013

Objectives: The major objective of this study is to review overall and in detail the Corporate Manslaughter and Corporate Homicide Act 2007 in the U.K.and the principal contents of this act. Methods: A variety of articles related to the background and circumstances under which the legistration was enacted and the details of this act were investigated and analyzed. Results: In enacting Corporate Manslaughter and Corporate Homicide Act 2007, legislators mainly took elements of legal culture into account and focused on seeking to broaden the law on corporate manslaughter. An indictable offence is considered to have been committed if the way in which an organization's activities are managed or organised causes a person's death and amounts to a gross breach of the relevant duty of care owed by the organization to the deceased. The way in which its activities are managed or organized by its senior management is a substantial element in the breach. Upon conviction, a corporation may be ordered to remedy any breach, publicize its failures, or be given an unlimited fine. Conclusions: The enactment background and details of Corporate Manslaughter and Corporate Homicide Act 2007 is understood accurately. On the basis of the findings, it is necessary to heighten effectiveness of punishment.for senior management or corporations that cause a person's death in Korea.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 추계학술발표대회 논문집
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• pp.153-156
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• 2005

Nondestructive sensing of electrospun PYDF web and multi-wall carbon nanotube (MWCNT)/epoxy composites were investigated using electro-micromechanical technique. Electrospinning is a technique used to produce micron to submicron diameter polymeric fibers. Electrospun PVDF web was also evaluated for the sensing properties by micromechanical test and by measurement electrical resistance. CNT composite was especially prepared for high volume contents, 50 vol% of reinforcement. Electrical contact resistivity on humidity sensing was a good indicator for monitoring as for multifunctional applications. Work of adhesion using contact angle measurement was studied to correlate acid-base surface energy between carbon fiber and CNF composites, and will study furher for interfacial adhesion force by micromechanical test.

• Computers and Concrete
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• 제21권1호
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• pp.1-9
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• 2018

Electrical resistivity is a property associated with both the physical and chemical characteristics of concrete. It allows the evaluation of the greater or lesser difficulty with which aggressive substances penetrate the concrete's core before the dissolution of the passive film process and the consequent reinforcement's corrosion begin. This work addresses the steel fiber addition to concrete with two types and various contents from 0% to 1.3%, correlating it with its electrical resistivity. To that effect, 9 different mixes of steel fiber reinforced concrete (SFRC) were produced. The electrical resistivity was evaluated on the on six years aged SFRC by direct measurement at different frequency from 0.1 kHz to 100 kHz. The results indicate that steel fiber content is strongly conditioned by the type and quantity of the additions used. It was also found that long type of fibers has more effect on decreasing the electrical resistivity of concrete than short fibers. Therefore, they increase the corrosion risk of concrete depending on fiber volume fraction and moisture percentage.

• 한국가구학회지
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• 제24권4호
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• pp.379-388
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• 2013

In this study, the effect of various glass fiber (GF) contents in a shell layer and shell thickness changes on the flexural property of coextruded wood plastic composites (WPCs) in combination with three core systems (weak, moderate, and strong) was investigated. GF behaved as an effective reinforcement for the whole coextruded WPCs and GF alignments in the shell layer played an important role in determining the flexural property of the coextruded WPCs. At a given shell thickness, the flexural property of the whole coextruded WPCs was improved with the increase of GF content in shell. For core quality, when the core is weak, increase of GF content in shell led to improved flexural property of the whole composites and increase of shell thickness helped it. On the other hand, when the core is strong, the flexural property of the whole composites showed reduced features at low GF content in shell and increase of shell thickness aggravated it. This approach provides a method for optimizing performance of the coextruded WPCs with various combinations of core-shell structure and properties.