• 대한방사성의약품학회지
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• 제3권1호
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• pp.15-17
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• 2017

In carbon-11 labeling, $[^{11}C]$methyltriflate (methyltrifluoromethanesulfonate, MeOTf) is the most widely used through mild reaction condition with high yield. Strong inorganic bases, KOH, NaH and so on, were chosen to activate precursors that have phenolic alcohol as a nucleophilic moiety, because of its poor nucleophilicity. However, these catalyst can also react with radioactive intermediate, $[^{11}C]$MeOTf to afford side products. We will briefly discuss the history of the effort to increase the yield of $[^{11}C]$raclopride and suggest the alternate method for better radiochemical yield and consistency.

• 에너지공학
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• 제27권2호
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• pp.70-80
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• 2018

Natural organic matter (NOM) is among the most common pollutant in underground and surface waters. It comprises of humic substances which contains anionic macromolecules such as aliphatic and aromatic compounds of a wide range of molecular weights along with carboxylic, phenolic functional groups. Although the concentration of NOM in potable water usually lies in the range of 1-10 ppm. Conventional treatment technologies are facing challenge in removing NOM effectively. The main issues are concentrated to low efficiency, membrane fouling, and harmful by-product formation. Ion-exchangers can be considered as an efficient and economic pretreatment technology for the removal of NOM. It not only consumes less time for pretreatment but also resist formation of trihalomethanes (THMs), an unwanted harmful by-product. This article provides a comprehensive review of ion exchange processes for the removal of NOM.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2004년도 추계학술발표대회 논문집
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• pp.139-142
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• 2004

The fabric composite rings for nozzle parts of solid rocket motors should be thick to endure high temperature and pressure of combustion gas. Since the thermal residual stresses developed during manufacturing of the axi-symmetric composite structures increase as the thickness increases and eventually induce failures during storage and operation, the estimation of the residual stresses is indispensable for design and manufacture of the thick composite nozzle parts. In this paper, thick fabric rings made of carbon fabric phenolic composites were fabricated in a hydroclave and in an autoclave using a multi-step pre-compaction process to minimize draping. The residual stresses distributed in the rings were measured by the radial-cut method and it was found that the compaction reduces the residual stresses in the composite ring.

• Preventive Nutrition and Food Science
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• 제21권4호
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• pp.398-405
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• 2016

The objective of this study was to evaluate the characteristics of melanoidins formed from black garlic (BG) after different thermal processing steps. The melanoidins formed from BG during thermal processing were produced in large amounts, and the initial (280 nm), intermediate (360 nm), and final stage product (420 nm) had similar tendencies. Compounds like degraded proteins, peptides, and phenolic acids were present in the melanoidins during thermal processing. All the melanoidin samples showed different absorptions in the UV-visible spectra, although these had similar shapes. Moreover, the carbon, hydrogen, and oxygen content of melanoidins formed from BG during thermal processing decreased initially, and then increased. However, the nitrogen content increased during thermal processing. As thermal processing progressed, the molecular weight of all the melanoidin samples showed increasing intensities, whereas the major peaks of each melanoidin sample had different retention times. Furthermore, the melanoidins formed from BG after different thermal processing steps contained -OH, -CH, amide I, and III groups. The crystallinity of the melanoidins was majorly formed at $31.58^{\circ}$ and $43.62^{\circ}$ ($2{\theta}$).

• Steel and Composite Structures
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• 제26권5호
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• pp.649-662
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• 2018

In this study, based on the three-dimensional theory of elasticity, free vibration characteristics of sandwich sectorial plates with multiwalled carbon nanotube-(MWCNT)-reinforced composite core are considered. Modified Halpin-Tsai equation is used to evaluate the Young's modulus of the MWCNT/epoxy composite samples by the incorporation of an orientation as well as an exponential shape factor in the equation. The exponential shape factor modifies the Halpin-Tsai equation from expressing a straight line to a nonlinear one in the MWCNTs wt% range considered. In this paper, free vibration of thick functionally graded sandwich annular sectorial plates with simply supported radial edges and different circular edge conditions including simply supported-clamped, clamped-clamped, and free-clamped is investigated. A semi-analytical approach composed of two-dimensional differential quadrature method and series solution are adopted to solve the equations of motion. The material properties change continuously through the core thickness of the plate, which can vary according to a power-law, exponentially, or any other formulations in this direction. This study serves as a benchmark for assessing the validity of numerical methods or two-dimensional theories used to analysis of laminated sectorial plates.

• International Journal of Aeronautical and Space Sciences
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• 제17권2호
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• pp.175-183
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• 2016

A poroelastic composite material, containing different material phases and filled with fluids, serves as a model to formulate the overall ablative behaviors of such materials. This article deals with the assessment of variation in nondeterministic poroelastic properties of two-phase composite materials using micromechanical representative volume element (RVE) models. Considering the configuration and arrangement of pores in a matrix phase, various RVEs are modeled and analyzed according to their porosity. In order to quantitatively investigate the effects of microstructure, changes in effective elastic moduli and poroelastic parameters are measured via finite element (FE) analysis. The poroelastic parameters are calculated from the effective elastic moduli and the pore-pressure-induced strains. The reliability of the numerical results is verified through image-based FE models with the actual shape of pores in carbon-phenolic ablative materials. Additionally, the variation of strain energy density is measured, which can possibly be used to evaluate microstress concentrations.

• Journal of Microbiology and Biotechnology
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• 제28권8호
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• pp.1225-1232
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• 2018

Phenylethanoids, including 2-phenylethanol, tyrosol, and salidroside are a group of phenolic compounds with a C6-C2 carbon skeleton synthesized by plants. Phenylethanoids display a variety of biological activities, including antibacterial, anticancer, anti-inflammatory, neuroprotective, and anti-asthmatic activities. Recently, successful microbial synthesis of phenylethanoids through metabolic engineering and synthetic biology approaches has been reported and could allow phenylethanoid production from alternative microbial sources. Here, we review the recent achievements in the synthesis of phenylethanoids by microorganisms. The work done so far will contribute to the production of diverse phenylethanoids using various microbial systems and facilitate exploration of further diverse biological activities of phenylethanoids.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2004년도 춘계학술발표대회 논문집
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• pp.51-54
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• 2004

Testing methods for mechanical properties of the advanced composites were introduced. The mechanical properties, such as tensile properties, compressive properties, in-plane shear properties, flexural properties, and interlaminar shear properties, were evaluated along the warp and the fill directions. The CF3327 of the carbon fabric, the HG1581 of the glass fabric, and the HK285 of the aramid fabric were considered as reinforcements. Epoxy and phenolic resin were used as resin. The experimental results obtained in this study would be applicable in the design and structural analysis for the manufacture of the carbody of the tilting train.

• 연구논문집
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• 통권24호
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• pp.81-96
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• 1994

To investigate failure mechanisms observed in carbon-phenolic thermal insulators, differential equations which govern the decomposition process in a deformable anisotropic porous solid are derived for three-dimensional axisymmetric constructions. The governing equations not only couple the material deformation with pore pressure, but also couple pressure and temperature, which means that heat convected by the pyrolysis gases is properly accounted for. Then the Bubnov-Galerkin finite element method is applied to these equations to transform them into a semidescrete finite element system. A thermal insulation liner in the cowl region under typical operating conditions is analyzed to find a mechanism for plylift. The results from the structural analysis show across-ply failure in the cowl zone. The mechanism for plylift is hypothesized as a sequential procedure : 1) the across-ply failure which is the precursor to plylift and 2) the local fiber buckling caused by generation of excessive in-plane compressive stress. To prevent plylift, the across-ply stress can be reduced by using appropriate material ply angles in cowl zone design.

• 공업화학
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• 제32권2호
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• pp.174-179
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• 2021

인조흑연 제조용 바인더로 주로 이용되는 콜타르 핏치와 페놀 레진은 soft carbon 및 hard carbon의 초기 탄소화합물 구조에 차이가 있다. 따라서 탄화 온도에 따른 열분해 거동, 미세조직, 결정성의 변화 과정도 다를 것으로 예상할 수 있다. 본 연구에서는 콜타르 핏치 및 페놀 레진의 열분해 거동, 미세조직, 결정성 변화에 관하여 비교 분석하였다. 콜타르 핏치는 액상을 경유한 탄화 과정을 거치며, 탄화 온도가 증가함에 따라 미세조직이 점차 변화되는 것을 확인할 수 있었다. 탄화 온도가 증가함에 따라 콜타르 핏치 및 페놀 레진 모두 결정성은 증가하는 경향을 나타냈지만, 콜타르 핏치는 미세조직이 급변하는 500 및 600 ℃ 구간에서 결정성도 급격히 변화는 것을 확인할 수 있었다. 또한 미세조직과 결정성은 서로 밀접한 연관성이 있었다.