• Bulletin of the Korean Chemical Society
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• 제32권9호
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• pp.3219-3222
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• 2011

Three types of ${\beta}$-ketoacyl acyl carrier protein synthase (KAS) are important for overcoming the bacterial resistance problem. Recently, we reported the discovery of a antimicrobial flavonoid, YKAF01 (3,6-dihydroxyflavone), which exhibits antibacterial activity against Gram-positive bacteria through inhibition of ${\beta}$-ketoacyl acyl carrier protein synthase III (KAS III). In this report, we suggested that YKAF01 can be an inhibitor ${\beta}$-ketoacyl acyl carrier protein synthase I (KAS I) with dual inhibitory activity for KAS I as well as KAS III. KAS I is related to the elongation of unsaturated fatty acids in bacterial fatty acid synthesis and can be a good therapeutic target of designing novel antibiotics. We performed docking study of Escherichia coli KAS I (ecKAS I) and YKAF01, and determined their binding model. YKAF01 binds to KAS I with high binding affinity ($2.12{\times}10^6$) and exhibited an antimicrobial activity against the multidrug-resistant E. coli with minimal inhibitory concentration (MIC) value of 512 ${\mu}g$/mL. Further optimization of this compound will be carried out to improve its antimicrobial activity and membrane permeability against bacterial cell membrane.

• 한국주조공학회지
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• 제19권1호
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• pp.24-32
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• 1999

A series of investigations for Austempered Ductile Iron (ADI) castings were carried out by using the specimens with various chemical compositions and heat treatment conditions. The rolling wear characteristics of alloyed austempered ductile irons under an unlubricated dry rolling condition was evaluated by the Amsler type test with 9.09% sliding ratio. Generally, the wear amount was increased with the austempering temperature and decreased when the hardness of the matrix was higher. The alloying elements also influenced the austempering reaction, the microstructure and the mechanical properties. In this study, the mechanical properties (i.e.) ultimate tensile strength (UTS), hardness, elongation) and the wear resistance are analysed to show the relationship between the alloying elements and the austempering temperatures. Mo, Cu and Ni are alloyed individually or in combination. It has been found that when Cu and Ni alloyed individually to a casting, the wear amount is increased than others with elements alloyed in combination. The amount of rolling wear loss was decreased when Mo was alloyed in cast iron, individually or in combination.

• The Journal of the Acoustical Society of Korea
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• 제13권2E호
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• pp.5-13
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• 1994

능동소나에서 표적에 의해 산란된 표적신호를 합성하기 위해서는 반사점(Highlight, 이하 HL)에서의 산란현상의 이해가 선행되어야 한다. 본 논문에서는 음향수조실험에서 얻어진 자료를 분석하여 표적신호를 특징지우고, HL 모델의 기본 가정의 타당성을 검토한다. 수조실험결과는 산란신호가 시간영역에서 신장되고, 도플러효과가 나타나며, 표적의 내부 구조형상이 표적산한신호에 직접반사 이상의 영향을 미침을 보여준다. 이는 표적산란 신호의 합성에 있어서 사용되는 충격응답 또는 그린 함수(Green's function)가 단순한 델타함수가 아닌 필터역할을 하도록 시뮬레이션해야 함을 보여 준다.

• 한국작물학회지
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• 제26권2호
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• pp.121-124
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• 1981

출수 후 수확할 때까지 이삭이 전혀 추출하지 않고 엽초에 싸여 등숙되는 특성을 가진 Nepal의 수도품종 GAMADI를 포장 및 벽실 양조건의 8시간, 자연일장 및 24시간 일장하에서 생육시켜 일장조건이 GAMADI 품종의 이삭 추출에 미치는 영향을 검토하었다. 그 결과를 요약하면 다음과 같다. 1. 8시간과 자연일장 조건에서는 이삭이 전혀 추출되지 않았으며 24시간 일장조건에서 생육된 경우에만 전체 이삭 길이의 71% 정도가 추출되었다. 2. 24시간 일장조건에서는 상위 제일절간신장 정도가 8시간과 자연일장에 비하여 현저하여 이삭추출과 유의한 관계에 있는 것으로 나타났다. 3. 제3 및 제4절간신장 정도는 자연일장에 비하여 8시간 및 24시간 일장조건에서 유의하게 낮게 나타났다. 4. GAMADI 품종의 수장, 수당입수는 일장에 영향하지 않았다. 5. 수원의 자연상태에서의 GAMADI 품종의 임실율은 Nepal에서 보다 현저하게 낮았다.

• 한국분말재료학회지
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• 제29권4호
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• pp.309-313
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• 2022

In this study, additive manufacturing of a functionally graded material (FGM) as an alternative to joining dissimilar metals is investigated using directed energy deposition (DED). FGM consists of five different layers, which are mixtures of austenitic stainless steel (type 316 L) and low-alloy steel (LAS, ferritic steel) at ratios of 100:0 (A layer), 75:25 (B layer), 50:50 (C layer), 25:75 (D layer), and 0:100 (E layer), respectively, in each deposition layer. The FGM samples are successfully fabricated without cracks or delamination using the DED method, and specimens are characterized using optical and scanning electron microscopy to monitor their microstructures. In layers C and D of the sample, the tensile strength is determined to be very high owing to the formation of ferrite and martensite structures. However, the elongation is high in layers A and B, which contain a large fraction of austenite.

• 열처리공학회지
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• 제24권5호
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• pp.277-286
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• 2011

The spot weldability of metal joints between SD35 and SD30A steel was investigated. This study was aimed to determine the spot welding parameters (i.e. welding current and time) for reinforcement bar joint and to evaluate the weldability, mechanical strength, hardness and microstructure. The results indicated that shear strength and elongation of the welding joints at 12.5kA and 1000 ms were 26.7 $kgf/mm^2$ and 22%, respectively. And fracture distribution of them by using shear and tensile test showed 100% necking mode and 100% ductile mode, respectively.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
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• pp.208-211
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• 2003

In this paper, mechanical property of electric epoxy with water aging was discussed. We studied mechanical property of elastic resin after absorption in water from 0 to 484 hour. As a result, diffusion factor of elastic epoxy showed $20-21{\times}10^{-4}mm^2/s$ and general epoxy showed $9.5{\times}10^{-4}mm^2/s$. Elastic property increased linearly according to amount of addictives and decreased elastic property according to amount of water absorption. Tensile strength was reduced to add to addictives. It was effected by water absorption of micro-void of elastic epoxy. Hardness inclined to decrease after increasing according to absorbed time.

• 소성∙가공
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• 제30권3호
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• pp.134-141
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• 2021

In order to improve excessive spring-back behavior as a result of the roll forming process using ultra high strength steel (UHSS) sheet, local softening in region of a partial area expected to be deformed on an initial blank is considered in this study. With SPFC1470 UHSS sheet with initial blank thickness of 1.20mm, the local softening is performed with the following conditions: temperatures of 500℃, 550℃, 600℃ and 650℃, and holding time of 20s, 40s, 80s and 160s. Mechanical properties, such as yield stress and tensile strength, as well as elongation, are evaluated through uniaxial tensile tests, while the microstructural characteristics as a result of local softening are also investigated using the heat-treated specimens. As a result, it is shown that the spring-back behavior of the roll-formed prototype was reduced about by 78.9%, when the local softening at about 500℃ was performed for 160s considering the practical manufacturing condition.

• 한국재료학회지
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• 제23권8호
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• pp.423-429
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• 2013

Recently, steel structures have increasingly been required to have sufficient deformability because they are subjected to progressive or abrupt displacement arising from structure loading itself, earthquake, and ground movement in their service environment. In this study, high-strength low-carbon bainitic steel specimens with enhanced deformability were fabricated by varying thermo-mechanical control process conditions consisting of controlled rolling and accelerated cooling, and then tensile and Charpy V-notch impact tests were conducted to investigate the correlation between microstructure and mechanical properties such as strength, deformability, and low-temperature toughness. Low-temperature transformation phases, i.e. granular bainite (GB), degenerate upper bainite(DUB), lower bainite(LB) and lath martensite(LM), together with fine polygonal ferrite(PF) were well developed, and the microstructural evolution was more critically affected by start and finish cooling temperatures than by finish rolling temperature. The steel specimens start-cooled at higher temperature had the best combination of strength and deformability because of the appropriate mixture of fine PF and low-temperature transformation phases such as GB, DUB, and LB/LM. On the other hand, the steel specimens start-cooled at lower temperature and finish-cooled at higher temperature exhibited a good low-temperature toughness because the interphase boundaries between the low-temperature transformation phases and/or PF act as beneficial barriers to cleavage crack propagation.

• 패션비즈니스
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• 제18권3호
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• pp.134-147
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• 2014

The aim of this study is to create smart wear that brings out the perspective person's individuality and creativity wearing these garments through various interactions. It is intended to build a prototype for a "Shape-folding Dress", which is length-adjustable skirt that responses with the environment of the wearer. In this process, four basic physical properties can be identified with fabric samples selected which are relatively stiff, including fusible interlining, organdy, silk, and ramie. In addition, two types of folding pattern specimens, "Basic Pattern" and "Diamond Pattern", and heat-steam were used to make the specimens so that the correlation could be calculated by recovery rate among flexing, stiffness and tensile properties. As a result, compared to other fabrics, the silk showed low stress to repeat folding and unfolding process, and its recovery rate of elongation deformation was stable without being affected by the different folding types and twice repeated process. In this study, forming a circuit using an Arduino, illuminance sensor, motors, and pulley, the prototype was created with a silk fabric.