• Composites Research
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• v.33 no.6
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• pp.371-376
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• 2020

The adhesive strength can be improved through surface treatment. The most common method is to improve physical bonding by varying the surface conditions. This study presents the effect of laser surface treatment on the adhesive strength of CFRP. The surface roughness was patterned using a 1064 nm laser. The effects of the number of laser shots and the direction and length of the pattern on the adhesion of the CFRP/CFRP single joint were investigated through tensile tests. Tests according to ASTM D5868 were performed, and the bonding mechanism was determined by analyzing the damaged surface after a fracture. The optimized number of the laser shots and the optimized depth of the roughness should be required to increase the bonding strength on the CFRP surface. When considering the shear stress in the tensile direction, the roughness pattern in the direction of 45° that increases the length of the fracture path in the adhesive layer resulted in an increase of the adhesive strength. The surface treatment of the bonding surface using a laser is a suitable method to acquire a mechanical bonding mechanism and improve the bonding strength of the CFRP bonding joint. The study on the optimized laser process parameters is required for utilizing the benefits of laser surface processing.

• Composites Research
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• v.31 no.5
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• pp.251-259
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• 2018

In this paper, statistical volume element modeling method was developed for multi-scale progressive failure analysis of fiber reinforced composite materials. Big-size statistical volume elements (BSVEs) was considered to minimize the size effect in the micro-scale, by including as many fibers as possible. For that purpose, a mesh cutting method is suggested and adapted into the fiber model generator that creates finite element domain rapidly. The fiber defect model was also developed based on the experimental distribution of the fiber strength. The size effects from the local load sharing (LLS) are evaluated by increasing the fiber inclusion in the micro-scale model. Finally, continuum damage mechanics (CDM) model to the fiber direction was extracted from numerical analysis on BSVEs. And it was compared with strength prediction from typical representative volume element (RVE) model.

• Composites Research
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• v.26 no.2
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• pp.85-90
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• 2013

This paper presents the fabrication and 3-point flexion testing of carbon fiber reinforced polymer (CFRP) composite face/aluminum honeycomb core sandwich panels. Specimen sandwich panels were fabricated with three honeycomb types (3.18 mm, 4.76 mm, and 6.35 mm cell size) and three panel radii (flat, r = 1.6 m, r = 1.3 m). The curved sandwiches were fabricated normally with the core in the W-direction. The tensile mechanical properties of the CFRP $2{\times}2$ twill fabric face laminate were evaluated (modulus, strength, Poisson's ratio). The measured values are comparable to other CFRP fabric laminates. The flat sandwich 3-point flexion test core shear strength results were 11-30% lower than the manufacturer published data; the test set-up used may be the cause. With a limited sample size, the 1.3 meter panel curvature appeared to cause a 0.8-3.8% reduction in ultimate core shear strength compared to a flat panel.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.11
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• pp.927-933
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• 2016

In a solid propulsion system, the rocket nozzle is exposed to high temperature combustion gas. Hence, choosing an appropriate material that could demonstrate adequate performance at high temperature is important. As advanced materials, carbon/silicon carbide composites (C/SiC) have been studied with the aim of using them for the rocket nozzle throat. However, when compared with typical structural materials, C/SiC composites are relatively weak in terms of both strength and toughness, owing to their quasi-brittle behavior and oxidation at high temperatures. Therefore, it is important to evaluate the thermal and mechanical properties of this material before using it in this application. This study presents an experimental method to investigate the fracture behavior of C/SiC composite material manufactured using liquid silicon infiltration (LSI) method at elevated temperatures. In particular, the effects of major parameters, such as temperature, loading, oxidation conditions, and fiber direction on strength and fracture characteristics were investigated. Fractography analysis of the fractured specimens was performed using an SEM.

• Journal of Life Science
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• v.30 no.10
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• pp.919-929
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• 2020

Aromatic compounds are widely used in the chemical, food, polymer, cosmetic, and pharmaceutical industries and are produced by mainly chemical synthesis using benzene, toluene, and xylene or by plant extraction methods. Due to many rising threats, including the depletion of fossil fuels, global warming, the strengthening of international environmental regulations, and the excessive harvesting of plant resources, the microbial production of aromatic compounds using renewable biomass is regarded as a promising alternative. By integrating metabolic engineering with synthetic and systems biology, artificial biosynthetic pathways have been reconstituted from L-tryptophan biosynthetic pathway in relevant microorganisms, such as Escherichia coli and Corynebacterium glutamicum, enabling the production of a variety of value-added aromatic compounds, such as 5-hydroxytryptophan, serotonin, melatonin, 7-chloro-L-tryptophan, 7-bromo-L-tryptophan, indigo, indirubin, indole-3-acetic acid, violacein, and dexoyviolacein. In this review, we summarize the characteristics, usage, and biosynthetic pathways of these aromatic compounds and highlight the latest metabolic engineering strategies for the microbial production of aromatic compounds and suitable solution strategies to overcome problems in increasing production titers. It is expected that strain development based on systems metabolic engineering and the optimization of media and bioprocesses using renewable biomass will enable the development of commercially viable technologies for the microbial production of many aromatic compounds.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• autumn
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• pp.323-326
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• 2002

Facing the rapid changes in business environment, construction companies have been required to improve their structures to reinforce the competitiveness. Construction companies have attempted the various management innovation and taken measures to enhance the productivity through the information systems. But compared to the efforts made in restructuring and process improvement, organization issues have not been considered sufficiently. So this study was executed to discuss the organization changes due to the innovation occurring in construction organization. This study was focused on the organization controlling the activities directly in construction site and the work process improvement in management.

• Composites Research
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• v.31 no.5
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• pp.192-201
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• 2018

The use of 3D printing for rapid tooling and manufacturing has promised to produce components with complex geometries according to computer designs and it is emerging as the next generation key of manufacturing. Due to the intrinsically limited mechanical/electrical properties and functionalities of printed pure polymer parts, there is a critical need to develop 3D printable polymer composites with high performance. This article gives a review on 3D printing techniques of polymer composite materials and the properties and performance of 3D printed composite parts as well as their potential applications in the various fields.

• Journal of Korean Society of Forest Science
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• v.90 no.3
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• pp.346-354
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• 2001

This study was conducted to investigate the status and problems, and suggest the proper improvement of provincial rotation hunting system in Korea. There were many problems in recently provincial rotation hunting system, such as, difficulty of budget interiority, low participation rate of hunters, low specialization degree of officers on their job, and extremity of illegal capture of wildlife by the absence of wildlife manager. The municipal hunting system, which have many merits, such as, increase of hunters' participation and income of municipality, creation of engagement, and prohibit of illegal capture of wildlife would be suggest for the improvement of hunting system.

• Journal of Korea Foundry Society
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• v.27 no.5
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• pp.209-211
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• 2007

최근에는 탄소섬유강화복합재료(CFRP)는 우수한 기계적인 물성치와 수월한 설계특성으로 인해 우주.민간 항공산업분야 뿐만 아니라 여러분야에 응용성이 매우 높다. 그러나 CFRP 복합적층판으로 제작된 구조물은 충격손상을 받을 시에는 50-75%치 강도가 낮아지는 취약성을 가지고 있다. 따라서 본 연구에는 CFRP복합재의 구조건전성 및 결함여부를 비파괴적으로 검사 및 탐상을 하기 위해서 시도하였다. 특히, C-scanner의 수침조에서 충격손상을 받은 시험편을 집어넣어 자동 데이터 획득 시스템을 구동하여 현장응용성이 가장 높은 일 방향 초음파측정 (one-sided ultrasonic measurement) 방법인 평가기법을 제안하였다. 본 연구에서 제안한 일방향 초음파 피치캐치방법이 CFRP 복합적층판내에서 일반 수직 초음파 탐상기법보다 훨씬 민감함을 알 수 있었다.

• Korean Architects
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• s.653
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• pp.32-36
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• 2023

지난 3월 권영걸 위원장이 국가건축정책위원장으로 취임하며 국가건축정책위원회(이하 국건위)가 새롭게 거듭났다. 제7기 국건위는 자연친화적인 국토환경, 건강한 생태도시 구현을 목적으로 '공원같은 나라, 정원같은 도시'를 슬로건으로 내걸고, 스마트 기술을 기반으로 도시의 쾌적성을 높여 국민 삶의 질을 높이고자 한다. 국가와 사회의 과제를 건축공간적 해법으로 풀겠다는 목표다. 이를 위해 국가상징공간 조성, ESG+Art 기반 선진 생태도시 모델 제시, ICT 융·복합 기반 '한국형 건축도시' 개발, 지방소멸에 대응한 도시건축 사업 추진 등 네 가지 중핵과제를 설정, 불철주야 노력하고 있다. 지난 7월 28일 권영걸 위원장을 직접 만나 정책 방향을 물어봤다. 한편 권영걸 위원장은 이날 인터뷰에서 "8월 3일부터 협회 의무가입제도가 도입된 것을 축하드린다. 이를 계기로 건축계 의견을 하나로 모으고, 건축사들의 직업윤리를 강화할 수 있게 됐다는 점에서 건축산업 발전에 크게 기여하게 될 것으로 기대한다"고 말했다. 그러면서 "건축사들의 직업적 권위가 보호되고 스스로 국가 디자이너이자 신문명 디자이너라는 시각을 갖고 일할 수 있도록 제반환경이 조성돼야 한다"며 "협회가 그런 길을 인도할 수 있는 역할을 해주시길 바란다. 국건위도 열심히 돕겠다"고 밝혔다.