• Composites Research
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• 제26권3호
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• pp.160-164
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• 2013

In this study, the effect of phosphoric acid (PA) as a fiber spinning aid on the strength increase of polyacrylonitrile (PAN) nano-fibers by using modified mechano-electrospinning technologies has been analyzed. The medium carbonization temperature of $800^{\circ}C$ has been selected for the future economic production of these new materials. The concentration of PAN in dimethyl sulfoxide (DMSO) was fixed as 5 wt%. The weight fraction of PA was selected as being 2%, 4%, 6%, and 8% in comparison to PAN. These solutions have been used to make the nanofibers. The mechano-electrospinning apparatus installed in KRICT was made by our own design. By using this apparatus the continous and highly aligned precursor nano-fibers have been obtained. The bundle of 50 well aligned nano diameter continuous fibers with the diametr of 10 microns with 6 wt% phosphoric acid for addition showed maximum mechanical properties of 1.6 GPa as tensile strength and 300 GPa as Young's modulus. The weight of final product can be increased 19%, which can improve the economical benefits for the application of these new materials.

• 한국가스학회지
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• 제28권1호
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• pp.1-10
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• 2024

본 연구에서는 농업 분야 에너지 자립 시스템 기술도입의 일환으로 농산부산물 기반 SOFC 열병합발전 시스템의 공정 모사 모델을 구축하고 열교환망 최적화를 진행하였다. 0.3 ton/d급 농산부산물 반탄화 연료 가스화기 실험 결과를 기반 농산부산물 SOFC 열병합발전 시스템 모델을 구축하여 4~20 kW급 SOFC 발전 용량별 열교환망 최적화를 진행하였다. 현재 시스템상에서 8 kW급 농산부산물 기반 SOFC 열병합발전 시스템이 최적으로 도출되었으며, 본 연구 결과를 기반으로 추후 상용 설비 설계 시 기초자료로 활용이 가능할 것으로 판단된다.

• 한국분말재료학회지
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• 제31권2호
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• pp.163-168
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• 2024

As the demand for lithium-ion batteries for electric vehicles is increasing, it is important to recover valuable metals from waste lithium-ion batteries. In this study, the effects of gas flow rate and hydrogen partial pressure on hydrogen reduction of NCM-based lithium-ion battery cathode materials were investigated. As the gas flow rate and hydrogen partial pressure increased, the weight loss rate increased significantly from the beginning of the reaction due to the reduction of NiO and CoO by hydrogen. At 700 ℃ and hydrogen partial pressure above 0.5 atm, Ni and Li₂O were produced by hydrogen reduction. From the reduction product and Li recovery rate, the hydrogen reduction of NCM-based cathode materials was significantly affected by hydrogen partial pressure. The Li compounds recovered from the solution after water leaching of the reduction products were LiOH, LiOH·H₂O, and Li₂CO₃, with about 0.02 wt% Al as an impurity.

• Computers and Concrete
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• 제31권4호
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• pp.327-335
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• 2023

The most popular building material, concrete, is intrinsically linked to the advancement of humanity. Due to the ever-increasing complexity of cementitious systems, concrete formulation for desired qualities remains a difficult undertaking despite conceptual and methodological advancement in the field of concrete science. Recognising the significant pollution caused by the traditional cement industry, construction of civil engineering structures has been carried out successfully using Geopolymer Concrete (GPC), also known as High Performance Concrete (HPC). These are concretes formed by the reaction of inorganic materials with a high content of Silicon and Aluminium (Pozzolans) with alkalis to achieve cementitious properties. These supplementary cementitious materials include Ground Granulated Blast Furnace Slag (GGBFS), a waste material generated in the steel manufacturing industry; Fly Ash, which is a fine waste product produced by coal-fired power stations and Silica Fume, a by-product of producing silicon metal or ferrosilicon alloys. This result demonstrated that GPC/HPC can be utilised as a substitute for traditional Portland cement-based concrete, resulting in improvements in concrete properties in addition to environmental and economic benefits. This study explores utilising experimental data to train artificial neural networks, which are then used to determine the effect of supplementary cementitious material replacement, namely fly ash, Ground Granulated Blast Furnace Slag (GGBFS) and silica fume, on the compressive strength, tensile strength, and modulus of elasticity of concrete and to predict these values accordingly.

• 한국재료학회지
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• 제12권10호
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• pp.771-775
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• 2002

$Gd_2$$O_3$:Eu phosphor particles with nano-sized and non-aggregation characteristics were prepared by spray pyrolysis using the spray solution containing polymeric precursor and $Li_2$$CO_3$ flux material. Nano-sized $Gd_2$$O_3$:Eu phosphor particles had higher brightness than the commercial $Y_2$$O_3$:Eu phosphor particles. The $Gd_2$$O_3$:Eu phosphor particles had nano-size and non-aggregation characteristics after heat-treatment at $1000^{\circ}C$ when the addition amount of $Li_2$$CO_3$ flux was 1 wt.% and 3 wt.%. The mean size of particles were 200 nm and 400 nm when the amount of flux was 1 wt.% and 3 wt.%, respectively. The prepared phosphor particles had higher photoluminescence intensity than that of the commercial product regardless of the content of$ Li_2$$CO_3$ flux and had the maximum brightness when the content of flux was 5 wt %. The photoluminescence intensity of the nano-sized $Gd_2$$O_3$:Eu phosphor particles containing 3 wt.% $Li_2$$CO_3$ flux was 125% in comparison with that of the micron-sized $Y_2$$O_3$:Eu commercial product.

• 자원리싸이클링
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• 제30권6호
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• pp.68-75
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• 2021

본 연구에서는 석회석, 임의의 산업부산물, 국내산 석탄재 및 시멘트 킬른더스트를 활용해 원료배합특성 및 소성조건에 따른 CCA 특수시멘트 제조특성을 조사하였다. 소성조건에 따른 CCA 특수시멘트 제조특성결과, 소성온도 1200℃에서 CCA 광물상(C₁₂A₇·CaCl₂) 합성량이 최대치를 나타내는 것을 확인할 수 있었다. 소성온도 1300℃에서는 CCA 광물상 합성량이 감소하는 것을 알 수 있었는데, 이는 염소성분 휘발에 의한 현상으로 보여지며, CCA 광물상 합성에 기여했던 CaO-Al₂O₃ 화합물은 SO₃와 결합하여 yeelimite가 형성된 것으로 판단된다. 소성유지시간에 따른 CCA 특수시멘트 제조특성 결과, 대체로 소성시간이 길어짐에 따라 CCA 합성량이 증가하는 경향을 나타내었으나 소성시간 30 min 이상에서는 클링커의 용융현상이 확인되며, 클링커링 공정을 위해서는 소성시간 20 min 이내가 적당한 것으로 사료된다. 이로 미루어볼 때 CCA 특수시멘트 제조를 위한 최적 소성조건은 승온속도 10℃/mim, 소성온도 1200℃, 유지시간 20 min으로 판단되며, 고염소 함유 시멘트 킬른 더스트를 활용한 CCA 특수시멘트 제조가 용이한 것을 알 수 있었다.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 2017년도 춘계공동학술대회
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• pp.108-108
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• 2017

In this study, biocomposite filaments with agricultural by-products can be used in extrusion-based 3D (Three-dimensional) printing. Extrusion-based 3D printing stands as a promising technique owing to its versatility. We hypothesized that bio-filament composite consisted of something derived from agricultural by-products could be used as 3D printing materials that could overcome the drawbacks of PCL (poly-caprolactone). Bio-filament mixed with PCL and agricultural by-products was defined as r-PCL in this study. In order to find it out the optimal mixing ratio of filaments, we had investigated PCL, r-PCL 10%, r-PCL 20%, r-PCL 50% separately. The morphological and chemical characteristics of the filaments were analyzed by FE-SEM (Field emission scanning electron microscope) and EDX (Energy-dispersive X-Ray spectroscopy), and the mechanical properties were evaluated by stress-strain curve, water contact angle, and cytotoxicity analysis. Results of this study have been shown as a promising way to produce eco-friendly bio-filaments composite for FDM (Fused deposition modeling) method based 3D printing technology. Thus, we could establish biomimetic scaffolds based on bio-printer filaments mixed with agricultural by-product.

• 융합정보논문지
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• 제9권9호
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• pp.20-26
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• 2019

ICT 기술의 발전과 스마트폰 보급의 활성화로 온라인 마켓을 통해 다양한 제품을 구매하는 구매 서비스가 활성화되고 있다. 특히 보관 및 배송 기술의 발전으로 인하여 보관기관이 짧은 식자재의 경우도 온라인을 통해 구매가 가능함으로써 오프라인 판매만을 수행하는 상가의 경우 매출이 감소되고 있는 추세이다. 따라서 본 논문에서는 기존 오프라인 판매만 수행이 가능한 소규모 상가에서 전문적인 판매 지식 및 판매망이 없어도 구매 서비스를 통해 광고 효과 및 주문, 배달이 가능한 통합 솔루션을 제안한다. 제안하는 시스템은 사용자가 원하는 제품에 대한 이미지 검색을 통해 효율적으로 제품에 대한 정보를 카테고리별로 볼 수 있으며, 이로 인해 등록된 제품 판매처가 추가적인 광고가 없어도 효율적으로 판매가 가능하다는 장점이 있다.

• 한국의류학회지
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• 제47권1호
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• pp.35-51
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• 2023

This study used text mining to extract 2,842 keywords from 7,397 product names and organized them into categories in order to analyze the characteristics of keywords appearing in the product names of jeans after 2020. The item category included denim and Chungbaji [청바지], and Ilja [일자], while the silhouette category included wide and bootcut. In addition, high-waist and banding comprised the making sector, and the materials category consisted of napping, spandex, and soft blue. Denim surpassed the others in frequency, co-occurrence frequency, and centrality, and co-appeared with various other keywords. Also, the co-appearance of item and silhouette was prominent, and there were many keyword combinations that showed characteristics related to (a) high waist; (b) hemline detail; (c) rubber band; and (d) partial tearing. Furthermore, idiom expressions such as 'slim fit' and 'back tearing', which were not highlighted in the co-occurrence frequency, were additionally confirmed through correlation. Therefore, the product name analysis effectively identified the detailed characteristics of the silhouette and the making of jeans preferred by consumers.

• 산업기술연구
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• 제21권B호
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• pp.281-286
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• 2001

In this study, product design and prototype manufacturing of a plastic water-pump pulley has been tried. The designed model is supposed to be made of 33 % glass reinforced resin of which the tensile strength is 180 MPa, and has 24 ribs on each side to increase its structural strength. Structural analysis under a static load of 300 kgf acting on both edges of the belt has been carried out using a commercial finite element code, MARC. The analysis result showed the maximum effective stress near a rib of designed model would be at most 35 MPa (less than 20% of the tensile strength), therefore, the plastic product would be sufficiently safe under that loading condition. On the basis of the structural analysis, a prototype of the designed model has been manufactured by using the fused deposition modelling (FDM) method which is one of the rapid prototyping (RP) methods, using ABS resin and support materials. The CAD data exported to the RP system in STL format was prepared by a commercial solid modeling software, SolidWorks. It has been proved that the plastic pulley can successfully replace the existing flow-formed steel product.