• Composites Research
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• 제36권4호
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• pp.264-269
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• 2023

Spent coffee grounds (SCG) are a ubiquitous byproduct of coffee consumption, representing a significant waste management challenge, as well as an untapped resource for economic development and sustainability. Improper disposal of SCG can result in environmental problems such as methane emissions and leachate production. This study aims to investigate the physicochemical properties of SCG and their potential as a reinforcement material in polypropylene (PP) to fabricate an eco-friendly composite via extrusion and injection molding, with SCG filler ratios ranging from 5-20%. To evaluate the effect of SCG on the morphological and mechanical properties of the bio- composite, thermogravimetric analysis, SEM, tensile, flexural, and impact tests were conducted. The results demonstrated that the addition of SCG lead to a slight increase in brittleness of the composite but did not significantly affect its mechanical properties. Impressively, the presence of a significant organic component in SCG contributed to the enhanced thermal performance of PP/SCG composites. This improvement was evident in terms of increased thermal stability, delayed onset of degradation, and higher maximum degradation temperature as compared to pure PP. These findings suggest that SCG has potential as a filler material for PP composites, with the ability to enhance the material's properties without compromising overall performance.

• 한국지반환경공학회 논문집
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• 제8권3호
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• pp.19-25
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• 2007

쇄석말뚝은 느슨한 사질토지반이나 점토지반에 치환법에 의해 다져진 자갈이나 쇄석을 연약한 지반에 삽입하여 개량하는 공법이다. 쇄석말뚝 공법은 흙과 말뚝 접촉면에서 압밀거동이 다양한 인자에 의해 영향을 받게 되어 정량적인 해석에 많은 어려움이 있다. 본 연구에서는 재하시험을 통해 선단지지 군말뚝의 거동에 대한 다양한 인자의 영향을 조사하였다. 궁극적으로 연약지반의 개량 특성과 설계인자의 영향력을 PR값을 사용하여 평가하였다. 실험결과와 계산된 PR 값으로부터 쇄석말뚝의 침하거동이 근입비나 매트의 설치여부 보다는 말뚝의 직경이나 복합지반의 치환율에 의해 영향을 받고 있음을 알 수 있다.

• Steel and Composite Structures
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• 제19권3호
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• pp.697-711
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• 2015

It is well known the importance of considering hysteretic energy demands for the seismic assessment and design of structures. In such a way that it is necessary to establish new parameters of the earthquake ground motion potential able to predict energy demands in structures. In this paper, several alternative vector-valued ground motion intensity measures (IMs) are used to estimate hysteretic energy demands in steel framed buildings under long duration narrow-band ground motions. The vectors are based on the spectral acceleration at first mode of the structure Sa($T_1$) as first component. As the second component, IMs related to peak, integral and spectral shape parameters are selected. The aim of the study is to provide new parameters or vector-valued ground motion intensities with the capacity of predicting energy demands in structures. It is concluded that spectral-shape-based vector-valued IMs have the best relation with hysteretic energy demands in steel frames subjected to narrow-band earthquake ground motions.

• 펄프종이기술
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• 제48권2호
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• pp.83-90
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• 2016

Increasing the amount of filler in paper is of high interest for paper industry while maintaining its key sheet quality properties. In this study, a MFC-GCC composite, made through a co-grinding NBSK (Northern bleached softwood kraft) pulp with a ground calcium carbonate (Intracarb 60), was used as a strength aid in paper in order to evaluate a potential cost reduction through filler increase without sacrificing paper quality. Hand-sheets were made of NBSK and/or eucalyptus pulp by using white water recirculation in a Tappi sheet former and was compared its properties without or with MFC additions at different filler levels. It was found that the MFC-GCC composite has a large surface area compared to the fiber, allowing the formation of more hydrogen bonds in the web, thus giving natural strength to the paper. Overall results are encouraging that the MFC-GCC composite allows papermaker to reduce basis weight and maintain critical sheet properties.

• 한국통신학회논문지
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• 제10권2호
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• pp.88-92
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• 1985

複合클러터에 대한 MTI信號處理器의 性能은 클러터스펙트럼의 電力密度函數뿐 아니라 各 클러터의 平均 레이다平面的 및 平均 도플러周波數에 따라서도 달라진다. 본 論文에서는 地上클러터나 氣象클러터와 같이 서로 다른 特性을 갖는 클러터에 의해서 複合的으로 MTI信號處理器의 性能에 미치는 影響을 MTI改善因子로 比較, 平價할 수 있는 方法을 提示하였다.

• Restorative Dentistry and Endodontics
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• 제5권1호
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• pp.7-12
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• 1979

After applying three types of composite resins - Hi-Pol composite with Enamel bond, Hi-Pol composite without Enamel bond, Restodent - to the intact and the ground surface of tooth that had been acid etched for one or two minutes, the author observed the penetration of these resins into the acid etched enamel surface with scanning electron microscope. The results were as follows. 1. All the experimented materials showed the penetration into the acid etched enamel surface, and the average depth of penetration was 7 microns. 2. There was no significant difference in the penetration of these three resins despite different etching, time. 3. The grinding of the Enamel surface before acid - etching was not effective in altering the depth of penetration of these materials.

• International Journal of Aerospace System Engineering
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• 제6권1호
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• pp.1-7
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• 2019

In the present study, structural safety and stability on the main wing and tail planes of the 1.2 ton WIG(Wing in Ground Effect) flight vehicle, which will be a high speed maritime transportation system for the next generation, was performed. The carbon-epoxy composite material was used in design of wing structure. The skin-spar with skin-stressed structural type was adopted for improvement of lightness and structural stability. As a design procedure for this study, the design load was estimated with maximum flight load. From static strength analysis results using finite element method of the commercial codes. From the stress analysis results of the main wing, it was confirmed that the upper skin structure between the second rib and the third rib was unstable for the buckling load. Therefore in order to solve this problem, three stiffeners at the buckled region were added. After design modification, even though the weight of the wing was a little bit heavier than the target weight, the structural safety and stability was satisfied for design requirements.

• 대한토목학회논문집
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• 제29권5C호
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• pp.199-206
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• 2009

본 연구에서는 수평하중을 받는 강관합성 말뚝의 역학적 특성을 평가하기 위하여 서로 다른 단면 특성을 가진 모형 말뚝에 대하여 실내 모형 실험을 수행하였다. 지반 반력의 효율적인 모사를 위하여 스프링 장치를 이용한 지반 반력 시스템을 개발하였으며, 축하중 및 수평하중을 독립적으로 재하할 수 있는 하중 재하 시스템을 적용하여 사용하중 상태에서의 말뚝의 수평방향 거동 특성을 평가하였다. 강관합성 말뚝은 기존의 현장타설 말뚝에 비하여 증가된 수평저항 특성을 보여주며, 강관 합성 효과에 의하여 강관 및 철근 콘크리트의 수치합 보다 큰 수평 극한강도를 발휘하는 것을 확인하였다. 또한, 전단 연결재의 사용에 따른 강관-콘크리트의 일체화 거동을 검토하였으며, 고강도 콘크리트의 사용에 따른 강관합성 말뚝의 하중 지지성능을 평가하였다. 이와 함께, 강관합성 말뚝의 강관에 의한 내부 철근망의 대체 가능성 여부를 평가하였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1997년도 가을 학술발표회 논문집
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• pp.89-96
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• 1997

• 한국지반환경공학회 논문집
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• 제21권9호
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• pp.15-24
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• 2020

본 연구에서는 저유동성 몰탈 주입공법의 개량체에 관한 응력분담비를 복합지반법, 지반아칭이론, 소성각법 및 2차원과 3차원 수치해석, 3차원 모형실험을 통해 평가하였다. 복합지반법으로 계산된 응력분담비는 89.3, 3차원 지반아칭이론을 적용할 경우 3.75~59.0, 3차원 소성각법의 경우 82.8로 이론별 응력분담비의 차이가 나타났다. 2차원 수치해석 결과 응력분담비는 63.0~77.0으로 개량율이 증가할수록 증가하는 것으로 나타났고, 3차원 수치해석 결과 50.0~56.0으로 2차원 해석 결과 대비 작게 예측되었다. 대형 삼축압축셀을 이용한 특수 모형 실험의 경우 하중단계별 응력분담비는 53.0~60.0으로 나타났고, 실험으로 평가한 응력분담비는 2차원과 3차원 수치해석적 예측치 내에서 측정되었다. 본 연구에서는 저유동성 몰탈 주입 공법의 개량체에 대하여 해석 및 실험값을 바탕으로 개량율에 따른 응력분담비에 대한 예측식을 제안하였다.