• Bulletin of the Korean Chemical Society
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• 제32권1호
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• pp.41-48
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• 2011

The wettabilities of the partially fluorinated polymers (ethylene-tetrafluoroethylene copolymer (ETFE), ethylenechlorotrifluoroethylene copolymer (ECTFE), and poly(vinylidene fluoride) (PVDF)) were investigated by contact angle measurements. Zisman plots for ETFE and ECTFE exhibited linear relationships, while the Zisman plot for PVDF showed a slight curvature, which was interpreted to indicate strong non-dispersive interactions between the surface and the contacting liquids. The Lifshitz-van der Waals forces of the fluoropolymers were estimated to increase in the order of ETFE < PVDF $\ll$ ECTFE. An evaluation of the polar or "acid-base" interaction energies showed that PVDF, which possesses the most acidic hydrogens among the examined fluoropolymers, has the strongest acid-base interactions.

• 한국정밀공학회지
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• 제21권9호
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• pp.158-166
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• 2004

A new method to measure residual unbalance of rotor - bearing system was proposed. The method which determine residual unbalance based on polar plot and an analytical method which calculates the residual unbalance of the rotor from the vibration response of the Jeffcott rotor are proposed in this study with respect to a real rotor system of which the residual unbalance is unknown. The unbalance eccentricity of the produced experimental model is 3.78 mil, developing the measurement method of the residual unbalance more convenient than the proposed method of ISO and API standard. The proposed method was experimentally compared with the ISO standard, and the two methods were exactly correspondent to each other within an error of 1%.

• 폴리머
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• 제34권1호
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• pp.32-37
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• 2010

액정표시소자의 광배향막으로 적용하기 위하여 올리고머 신나메이트와 폴리(비닐 신나메이트) (PVCi)의 블렌드를 이용하여 그루브 패턴을 형성하고 광배향 특성을 관찰하였다. UV-vis 스펙트럼 분광계를 이용하여 자외선 조사 시간에 따른 광반응 속도를 평가한 결과 올리고머 신나메이트는 폴리(비닐 신나메이트)에 비해 빠른 반응속도를 나타내었다. 폴리(비닐 신나메이트)를 주성분으로 하여 올리고머 신나메이트를 블렌드한 경우 반응속도가 약간 향상되는 특성을 확인하였다. 올리고머 신나메이트는 높은 결정성으로 인해 표면 그루브 패턴을 단독으로 형성할 수 없었지만 폴리(비닐 신나메이트)와의 블렌드를 통하여 그루브 패턴을 형성할 수 있었으며 그루브 패턴에서도 polar plot에 의해 분자 배향성을 나타냄을 확인하였다. 올리고머 신나메이트와 고분자계 신나메이트의 블렌드를 통하여 반응속도의 향상과 박막 구조의 패턴을 형성하기에 적합함의 확인을 통해 새로운 광배향막 재료로 적용 가능함을 알 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제28권12호
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• pp.2377-2381
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• 2007

Solvolyses of 3,4-dimethoxybenzenesulfonyl chloride (DSC) in water, D2O, CH3OD, and in aqueous binary mixtures of acetone, acetonitrile, 1,4-dioxane, ethanol, methanol, and 2,2,2-trifluoroethanol (TFE) have been investigated at 25.0 oC. Kinetic solvent isotope effects (KSIE) in water and in methanol and product selectivities in alcohol-water mixtures are also reported. The Grunwald-Winstein plot of first-order rate constants for the solvolyic reaction of DSC with YCl shows marked dispersions into separated lines for various aqueous mixtures. With use of the extended Grunwald-Winstein equation, the l and m values obtained are 1.12 and 0.58 respectively for the solvolyses of DSC. The relatively large magnitude of l is consistent with substantial nucleophilic solvent assistance. From Grunwald-Winstein plots the rate data are dissected approximately into contributions from two competing reaction channels. This interpretation is supported for alcohol-water mixtures by the trends of product selectivities, which show a maximum for ethanol-water mixtures. From the KSIE of 1.45 in methanol, it is proposed that the reaction channel favored in methanolwater mixtures and in all less polar media is general-base catalysed and/or is possibly (but less likely) an addition-elimination pathway. Also, the KISE value of 1.35 for DSC in water is expected for SN2-SN1 processes, with minimal general base catalysis, and this mechanism is proposed for solvolyses in the most polar media.

• Bulletin of the Korean Chemical Society
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• 제24권8호
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• pp.1207-1210
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• 2003

The effect of solvent structure on the slope in the plot of ln K vs. solute carbon number was examined. It was found that the free energy of methylene group transfer from the gas phase into a solvent was always negative and that the absolute magnitude of interaction free energy between the methylene group and the solvent was always larger than the absolute magnitude of cavity formation free energy of the methylene group in the solvent. Thus, the slope in the plot of ln K vs. solute carbon number was always positive and its value decreases with increase of solvent polarity since the cavity formation energy of the CH₂ unit increases with increase of solvent polarity while the dispersive interaction energy of the CH₂ unit is virtually invariant. We also examined the effect of sequential addition of CH₂ unit to a solvent molecule upon ln K for three homologous series of solvents: n-alkanes, n-alcohols, and n-nitriles. Characteristic trends in the plots of ln K vs. solvent carbon number were observed for individual solvent groups. A decrease of ln K with solvent carbon number was observed for n-alkanes. An abrupt increase in ln K followed by levelling off was observed for n-alcohols while a final slight decrease in ln K after an abrupt increase followed by rapid levelling off was noted for n-nitriles. All of theses phenomena were found related to variation in cavity formation energy. It was clearly shown that a structural change of a polar solvent by sequential addition of CH₂ units causes an abrupt polarity decrease initially, then gradual levelling off, and finally, conversion to a virtually nonpolar solvent if enough CH₂ units are added.

• 대한화학회지
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• 제36권1호
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• pp.131-136
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• 1992

$Ce^{4+}$ ion을 개시제로 사용하여 폴리비닐알코올에 2,2,2-trifluoroethyl methacrylate를 그라프트중합 반응시켜 새로은 PVA/perfluoroalkylmethacrylate 그라프트 공중합체들을 합성하였다. 수소 결합능이 큰 폴리비닐알코올에 여러 가지 그라프트율을 갖는 공중합체의 표면 자유에너지를 이 고체 표면들과 여러가지 액체와의 접촉각을 측정하여 구하였다. Perfluoroalkyl group이 그라프팅이 커짐에 따라 고체의 표면 자유에너지는 감소하며, 그 고체들은 극성 부분에 의해 기여되는 힘이 크므로 극성 고체의 분자 특성을 고려한 식으로부터 ${\gamma}_{si}$을 구하여 임계 표면 에너지 ${\gamma}_c$를 계산하였다.

• Journal of Positioning, Navigation, and Timing
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• 제7권4호
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• pp.267-275
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• 2018

The reference stations in a satellite-based augmentation system (SBAS) collect raw data from global navigation satellite system (GNSS) to generate correction and integrity information. The multipath signals degrade GNSS raw data quality and have adverse effects on the SBAS performance. The currently operating SBASs (WAAS and EGNOS, etc.) survey existing commercial equipment to perform multipath assessment around the antennas. For the multi-path assessment, signal power of GNSS and multipath at the MEDLL receiver of NovAtel were estimated and the results were replicated by a ratio of signal power estimated at NovAtel Multipath Assessment Tool (MAT). However, the same experiment environment used in existing systems cannot be configured in reference stations in Korean augmentation satellite system (KASS) due to the discontinued model of MAT and MEDLL receivers used in the existing systems. This paper proposes a test environment for multipath assessment around the antennas in KASS Multipath Assessment Tool (K-MAT) for multipath assessment. K-MAT estimates a multipath error contained in the code pseudorange using linear combination between the measurements and replicates the results through polar plot and histogram for multipath assessment using the estimated values.

• 원예과학기술지
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• 제32권1호
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• pp.123-128
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• 2014

This study investigated the exercise intensity and energy expenditure involved in two gardening activities (planting transplants and sowing seeds in a garden plot) and four common physical activities (running, skipping rope, walking, and throwing a ball) in children. Eighteen children aged 11 to 13 years (mean age, $12.3{\pm}0.7$ years) participated in this study. The children made two visits to a high tunnel in Cheongju, Chungbuk, South Korea and performed randomly selected activities. Each activity was performed for 10 min, with a 5-min rest period between activities. The children wore a Cosmed $K4b^2$ (Cosmed $K4b^2$; Cosmed, Rome, Italy), which is a portable calorimetric monitoring system, to measure indicators of metabolic cost such as oxygen uptake and energy expenditure. The children's heart rates during the activities were measured by radiotelemetry (Polar T 31; FitMed, Kempele, Finland). We found that the two gardening and four physical activities performed by the 11-13 years old children in this study were moderate-to high-intensity physical activities [i.e.,$5.4{\pm}0.7$ to $9.1{\pm}1.4$ metabolic equivalents (METs)]. Running ($9.1{\pm}1.4$ METs) and skipping rope ($8.8{\pm}1.1$ METs) were high-intensity physical activities, whereas walking ($6.1{\pm}0.9$ METs), planting transplants ($5.8{\pm}1.1$ METs), throwing a ball ($5.6{\pm}1.1$ METs), and sowing seeds ($5.4{\pm}0.7$ METs) were moderate intensity physical activities. Running and skipping rope were significantly more intense than the other activities (P < 0.0001). The gardening tasks such as planting transplants and sowing seeds in a garden plot showed similar exercise intensities and energy costs as walking and throwing a ball. This study indicates that gardening can be used as a physical activity intervention to provide health benefits similar to more common physical activities such as walking and running.

• 한국염색가공학회지
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• 제1권1호
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• pp.7-18
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• 1989

The distinguishing characteristic of the glow discharge is that chemical reaction induced by partially ionized gases are limited only to the substrate surface. Most studies have been done on the plasma etching and polymerization. The graft polymerization in vapour phase by cold plasma has been rarely investigated. In this study the system of tub3ar reaction chamber with capacitively coupled electrode of alternative current of 60 Hz was employed for the graft polymerization. The graft polymerization of Acylic Acid(AA) onto the poly (ethylene terephthalate) (PET) was carried out by treatment of PET film and fabric by cold plasma (glow discharge of argon gas), followed by the supply of AA vapour. The graft yield was about 1 wt%. The surface property was determined by contact angle, the surface tension was evaluated by zisman’s plot and equation of surface tension mesurement. The results were as follows: 1. In order to obtain lower contact angle, it was effective to avoid the vicinity of electrodes for a setting position of substrate. 2. Contact angle affected on the monomer pressure and its duration of exposure to the acid vapour. 3. Polymer radical formation was influenced by the changes of the value of current density and plasma treatment time. 4. Total surface tension of plasma grafted PET film increased. With an increase in the carboxylic acid content, the dispersion force decreased, while, the polar force and hydrogen bonding force increased. 5. The contact angle decreased from $75^\circ$ to around $30^\circ$ by plasma grafting. There was no ageing effect on the contact angle after 4 months.

• Asian Pacific Journal of Cancer Prevention
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• 제14권12호
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• pp.7473-7482
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• 2013

The G-protein coupled receptor 87 (GPR87) is a recently discovered orphan GPCR which means that the search of their endogenous ligands has been a novel challenge. GPR87 has been shown to be overexpressed in squamous cell carcinomas (SCCs) or adenocarcinomas in lungs and bladder. The 3D structure of GPR87 was here modeled using two templates (2VT4 and 2ZIY) by a threading method. Functional assignment of GPR87 by SVM revealed that along with transporter activity, various novel functions were predicted. The 3D structure was further validated by comparison with structural features of the templates through Verify-3D, ProSA and ERRAT for determining correct stereochemical parameters. The resulting model was evaluated by Ramachandran plot and good 3D structure compatibility was evidenced by DOPE score. Molecular dynamics simulation and solvation of protein were studied through explicit spherical boundaries with a harmonic restraint membrane water system. A DRY-motif (Asp-Arg-Tyr sequence) was found at the end of transmembrane helix3, where GPCR binds and thus activation of signals is transduced. In a search for better inhibitors of GPR87, in silico modification of some substrate ligands was carried out to form polar interactions with Arg115 and Lys296. Thus, this study provides early insights into the structure of a major drug target for SCCs.