• 한국환경과학회지
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• 제13권4호
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• pp.403-412
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• 2004

Waste water-soluble cutting oil was treated with WI type #1 and WI type #2. The properties of the original water-soluble cutting oil were pH=l0.4, viscosity=1.4cP, CODcr=44,750 ppm, and TOC=10,569 ppm. However, the properties of the oil used for more than 3 months were changed to pH=7.82, viscosity=2.1cP, CODcr=151,000 ppm, and TOC=74,556 ppm. It might be attributed to the fact that molecular chains were cut due to thermal oxidation and impurities such as metal chips were incorporated in to the oil during the operation processes. To prevent the putrefaction of oil, the sterilization effect of ozone and UV on the microorganism in the oil was investigated. Ozone treatment showed that 99.99% of the microorganism was annihilated with 30 minutes contact time and 60 minutes were necessary for the same effect when UV was used. Ozone treatment could cut molecular chains of the oil due to strong sterilization power, which was evidenced by the increase of TOC from 25,132 ppm at instantaneous contact to 28,888 ppm at 30 minutes contact time. However, UV treatment didn't show severe changes in TOC values and thus, seemed to cause of severe cut of molecular chains. When the activated carbon was used to treat the waste water-soluble cutting oil, TOC decreased to 25,417 ppm with 0.lg carbon and to 15,946 ppm with 5.0g carbon. This results indicated that the waste oil of small molecular chains could be eliminated by adsorption. From the results, it could be concluded that these treatment techniques could be proposed to remove the waste oil of small molecular chains resulting in the degradation of the oil properties. In addition, these experimental results could be used for the correlation with future works such as investigation of the molecular distribution according to the sizes, lengths, and molecular weight of the chains.

• Composites Research
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• 제32권3호
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• pp.163-169
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• 2019

본 연구에서 우리는 자유 라디칼 중합에 기반한 열가소성 고분자의 동적 분자동역학 중합 알고리즘을 이용하여 95%의 변환률을 갖는 PMMA의 고분자 모델을 구성하였다. 본 알고리즘에서는 계산 수행에 필요한 시간을 줄이기 위해 PCFF 포텐셜 함수의 결합 항들 TraPPE-UA 포텐셜 함수의 비결합 항을 조합한 united-atom level의 coarse-grained 포텐셜 함수를 도입하였다. 자유 라디칼 중합 시뮬레이션을 통해 생성된 각 사슬을 분석하여 고분자의 분자량 분포와 평균 분자량을 계산하였고, 고분자의 분자량은 초기 상태에 존재하는 개시제 라디칼의 수를 이용하여 조절하였으며, 유리전이온도, 기계적 물성에 미치는 분자량의 효과에 대해 연구되었다.

• Bulletin of the Korean Chemical Society
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• 제33권5호
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• pp.1703-1706
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• 2012

Rice blast is the most serious disease of rice due to its harmfulness and its world wide distribution. $Magnaporthe$ $grisea$ is the cause of rice blast disease and destroys rice enough to feed several tens of millions of people each year. Fungicides are commonly used to control rice blast. But $M.$ $grisea$ acquires resistance to chemical treatments by genetic mutations. 2-Phenylimino-1,3-thiazolines were proposed as a novel class of fungicides against $M.$ $grisea$ in the previous study. To develop compounds with a higher biological activity, a new series of 2-phenylimino-1,3-thiazolines was synthesized and its fungicidal activity was determined against $M.$ $grisea$. The QSAR analysis was carried out on a series of 2-phenylimino-1,3-thiazolines. The QSAR results showed the dependence of fungicidal activity on the structural and physicochemical features of 2-phenylimino-1,3-thiazolines. Our results could be used as guidelines for the study of the mode of action and further design of optimal fungicides.

• BMB Reports
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• 제42권4호
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• pp.206-211
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• 2009

Proopiomelanocortin (POMC) plays an essential role in the stress response of the hypothalamic-pituitary-adrenal axis, and is the precursor of biologically active peptides such as adrenocorticotropin (ACTH), $\alpha$-melanocyte-stimulating hormone ($\alpha$-MSH), $\beta$-melanocyte-stimulation hormone ($\beta$-MSH) and $\beta$-endorphin. We have synthesized two different forms of POMC cDNA clones, POMC-I and POMC-II, from a pituitary cDNA library for Paralichthys olivaceus, or Japanese flounder. jfPOMC-I cDNA consists of 954bp and encodes a polypeptide of 216 amino acid residues, whereas jfPOMC-II consists of 971bp which encode a polypeptide of 194 amino acid residues. The high levels of jfPOMC-I and -II mRNAs detected in the pituitary tissue and moderate levels detected in the brain tissue plus our quantitative RT-PCR analysis, which showed there to be no significant difference between the levels of jfPOMC-I and -II mRNAs, indicate that there may be no functional separation between these two mRNAs in the flounder.

• Current Photovoltaic Research
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• 제3권2호
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• pp.61-64
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• 2015

In solar industry, numerous researchers reported about cold spray method among various electrode formation technic, but there are no known a bonding mechanism of metal powder. In this study, a cross-section of copper electrode formed by cold spray method was observed and heterogeneous phase between silicon substrate and copper electrode was analyzed using morphology observation technic. SEM and TEM analysis were performed to analyze a crystallinity and distribution shape of heterogeneous copper phase. Molecular dynamics simulation was performed to calculate glass transition temperature of copper metal. In the result, amorphous copper phase was observed near interface between silicon substrate and metal electrode. The results of the molecular dynamics simulation show that an amorphous copper phase could be formed at a temperature below the melting point of copper because cold spraying resulted in a lower glass transition temperature.

• Journal of Microbiology and Biotechnology
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• 제19권3호
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• pp.299-306
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• 2009

Dissolved oxygen (DO) has a significant effect on the molecular weight of hyaluronic acid (HA) during the fermentation of Streptococcus zooepidemicus. Therefore, to further investigate the effect of DO on the yield and molecular weight of HA, this study compared the metabolic flux distribution of S. zooepidemicus under aerobic conditions at various DO levels. The metabolic flux analysis demonstrated that the HA synthesis pathway, considered a dependent network, was little affected by the DO level. In contrast, the fluxes of lactate and acetate were greatly influenced, and more ATP was generated concomitant with acetate at a high DO level. Furthermore, the has gene expression and HA synthase activity were both repressed under anaerobic conditions, yet not obviously affected under aerobic conditions at various DO levels. Therefore, it was concluded that the HA molecular weight would seem to depend on the concomitant effect of the generation of ATP and reactive oxygen species. It is expected that this work will contribute to a better understanding of the effect of the DO level on the mechanism of the elongation of HA chains.

• 천문학회보
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• 제41권2호
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• pp.40.1-40.1
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• 2016

We present the far-ultraviolet fluorescent molecular hydrogen ($H_2$) emission map observed with FIMS/SPEAR for ~76% of the sky. The fluorescent $H_2$ emission is found to be saturated by strong dust extinction at the optically thick, Galactic plane region. However, the extinction-corrected intensity of fluorescent $H_2$ emission is found to have strong linear correlations with the well-known tracers of the cold interstellar medium, such as the E(B-V) color excess, neutral hydrogen column density N(HI), $H{\alpha}$ emission, and CO $J=1{\rightarrow}0$ emission. The all-sky molecular hydrogen column density map is also obtained using a photodissociation region model. We also derive the gas-to-dust ratio, hydrogen molecular fraction ($f_{H2}$), and $CO-to-H_2$ conversion factor ($X_{CO}$) of the diffuse interstellar medium. The gas-to-dust ratio is consistent with the standard value $5.8{\times}10^{21}atoms\;cm^{-2}mag^{-1}$, and the $X_{CO}$ tends to increase with E(B-V), but converges to the Galactic mean value $1.8{\times}10^{20}cm^{-2}K^{-1}km^{-1}s$ at optically thick regions with E(B-V)>2.0.

• 한국세라믹학회지
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• 제42권8호
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• pp.593-598
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• 2005

Polycarbosilane was synthesized by the Kumada rearrangement of polydimethylsilane in the presence of zeolite (ZSM-5) as a catalyst at $350^{\circ}C$. The prepared polycarbosilane had very low molecular weight ($M_w=500$), so that it was not suitable to fabricate SiC fiber by melt spinning. Further polymerization of PCS was conducted around $400^{\circ}C$ to obtain spinnable polycarbosilane. After polymerization, the polycarbosilanes were isolated by distillation according to the molecular weight distributions. The PCS with a controlled molecular weight distribution was spun into continuous polycarbosilane green fibers. The PCS green fiber was successfully transformed into silicon oxycarbide fiber. The room temperature strength of the SiC fiber was around 1.5 - 1.8 GPa. The oxidation behavior and the tensile strength after oxidation were also evaluated.

• Fibers and Polymers
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• 제5권2호
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• pp.89-94
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• 2004

N-Vinylcarbazole (VCZ) was solution-polymerized in tetrahydrofuran (THF) at 25, 35, and $45^{\circ}C$ using a room temperature initiator, 2,2'-azobis(2,4-dimethylvaleronitrile) (ADMVN); the effects of amount of solvent, polymerization temperature, and initiator concentration were investigated. On the whole, the experimental results corresponded to predicted ones. Room polymerization temperature using ADMVN proved to be successful in obtaining poly(N-vinylcarbazole) (PVCZ) of high molecular weight with small temperature rise during polymerization, nevertheless of free radical polymerization by azoinitiator. The polymerization rate of VCZ in THF was proportional to the 0.47 power of ADMVN concentration. The molecular weight was higher and the molecular weight distribution was narrower with PVCZ polymerized at lower temperatures. For PVCZ prepared in THF at $25^{\circ}C$ using ADMVN concentration of 0.00005 mol/mol of VCZ, weight-average molecular weight of 221,000 was obtained, with polydispersity index of 2.05, and degree of lightness converged to about 99%.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 학술대회
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• pp.208-214
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• 2008

The equilibrium molecular-dynamic simulations have been performed to estimate the properties of the three kinds of fluids (the Lennard-Jones fluid, water and aqueous sodium-chloride solution) confined between two plates that are separated by 1.086 nm; included in the equilibrium properties are the density distribution and the static structure, and the diffusivity in the dynamic property. Three kinds of fluids considered in this study are. The water molecules are modeled by using the SPC/E model and the ions by the charged Lennard-Jones particle model. To treat the water molecules, we combined the quaternion coordinates with Euler angles. We also proposed a plausible algorithm to assign the initial position and direction of molecules. The influence of polarization of water molecules as well as the presence of ions in the solution on the properties will be addressed in this study. In addition, we performed the non-equilibrium molecular-dynamic simulation to compute the flow velocity for the case with the gravitational force acting on molecules.