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폴리비닐리덴플루오라이드-테트라플루오로에틸렌과 폴리비닐 리덴플루오라이드-헥사플로오로아세톤의 블렌드의 압전성
조재환,김상용,궁전청,Jo, Jae-Hwan,Kim, Sang-Yong,Gung, Jeon-Cheong The Korean Fiber Society 1989 한국섬유공학회지 Vol.26 No.2
Poly(vinylidenefluoride-tetrafluoroethylene), P(VDF-TFE)and poly(vinylidenefluoride-hexafluoroacetone), P(VDF-HFA) were blended, both of which were crystalline polymers. The crystal structures of the blends were investigated using X-ray diffraction. The samples containing the rich P(VDF-TEE) showed the crystal structure of only the polar phase, whereas those containing the rich P(VDF-HFA) showed the mixed crystal structure of $\alpha$ and $\beta$ phases. The piezoelectric properties of the blends were measured to investigate the origin of piezoelectricity and the mechanism of dipole reorientation. The piezoelectricity may be originated from the residual polarization and the internal strain of the samples. The 180$^{\circ}$rotation of dipoles was supported by the fact that the measured value of the maximum polarization agrees with the calculated value using the frozen dipole model.
Vinylidene Fluoride-Trifluoroethylene 공중합체의 상전이촉매작용에 의한 탈불화수소화
조재환,송하율,국윤환,Jo, Jae-Hwan,Song, Ha-Yul,Guk, Yun-Hwan 한국섬유공학회 1995 한국섬유공학회지 Vol.32 No.1
Films of vinylidene fluoride - trifluoroethylene (VDF-TrFE ) copolymer were dehydrofluorinated in aqueous sodium hydroxide solutions by phase transfer catalysis(PTC). Conjugated C=C double bonds in the polymer back-bone were bonds in the dehydrofluorination of VDF-TrFE copolymer. The color of film became brown and finally black with rigid double bonds during the PTC reaction. It was found from UV/VIS spectroscopic measurements that the length of conjugated double bonds of dehydrofluorinated VDF-TrFE copolymer was longer than that of dehydrofluorinated poly(vinylidene fluoride) . It was ascribed to the reaction activity due to the difference of solubility parameter between the sample and reaction solution. Thermal behavior by DSC analysis showed that the dehydrofluorination occurred at least in the crystal surfaces as well as in the amorphous chains.
연신조건이 저온에서의 PET 필라멘트사의 점탄성적 성질에 미치는 영향
조재환,조원호,김상용,Jo, Jae-Hwan,Jo, Won-Ho,Kim, Sang-Yong 한국섬유공학회 1981 한국섬유공학회지 Vol.18 No.1
Dynamic mechanical measurements were made in order to investigate effects of the drawing conditions on the viscoelastic properties of PET filament yarns at low temperatures(-100$^{\circ}$C∼-0$^{\circ}$C). The tan$\delta$-temperature relations of the Maxwell and the Zener model were theoretically plotted and compared with the experimental data. It was shown that the experimental results nearly coincided with the Maxwell model at temperatures below the ${\beta}$ peak and with the Zener model in the neighbor of the ${\beta}$ peak. Maximum tan$\delta$ at the ${\beta}$ peak decreased with the increase of the drawing temperature but was not affected by the draw ratio. On the other hand maximum tan$\delta$ temperature at the ${\beta}$ peak was not significantly affected by the drawing temperature and the draw ratio.
Structure and Physical Property of the Blends of Ultra-high Molecular Weight Polyethylene
조재환,국윤환,황윤언,Jo, Jae-Hwan,Guk, Yun-Hwan,Hwang, Yun-Eon The Korean Fiber Society 1989 한국섬유공학회지 Vol.26 No.2
Gel films were prepared from the mixtures of ultra-high molecular weight polyethylene(UHME PE) and high density polyethylene (HDPE) in a decalin solution. To investigate the formation of mixed crystals in the blends, i.e.cocrystallization, melting behaviors of the gel films and the slowly cooled films from melt were analyzed by differential scanning calorimetry. The slowly cooled films from melt as well as gel films showed the single melting peaks and this was ascribed to the formation of mixed crystals. The heat of fusion of the slowly cooled films from melt was nearly linear to the weight percent of UHMW PE and HDPE but gel films showed a minimum value. However, no significant lattice changes were found in the X-ray diffraction of gel films. The tensile moduli of gel films decreased with the increase of weight percent of HDPE and the yield stresses were almost constant in the intermediate weight percent of UHMW PE and HDPE.
건설현장에서의 산업안전교육이 재해 및 사고방지에 미치는 효과 연구
조재환,Jo, Jae-Hwan 한국건설안전협회 2009 建設 安全技術 Vol.50 No.-
Construction companies economic to lighten the restrictions on safety education and training due to the domestic recession as long as the global downturn. With this, the Korean government restrictions, but the incidents are being sharply increased nowadays. The construction industry hazardous than any others, so, they insist to reinforce the training for incidents prevention, to be disregarded at the subcontractors of the bigger construction companies problems. According to these matters, this study hereby surveyed regarding their suggestions for the improvements of the training concepts through questionnaires below.
Zone 연신된 폴리비닐리덴 플루오라이드의 결정구조와 점탄성적 성질
조재환,지병철,김상용,Jo, Jae-Hwan,Ji, Byeong-Cheol,Kim, Sang-Yong 한국섬유공학회 1985 한국섬유공학회지 Vol.22 No.6
Zone drawing of PVDF of Form II crystal was carried out by changing the zone drawing temperature and stress. Form I crystal of PVDF was obtained by this method and was confirmed by IR spectroscoty and X-ray diffraction. Form I and II crystals were transformed to Form II and III crystals, respectively, after they were annealed at the temperatures above 160$^{\circ}C$, but were not transformed at the temperatures below 160$^{\circ}C$. Tan$\delta$ and complex modulus were decreased by stretching the specimens at very high stresses.
산업안전교육이 건설현장에 미치는 영향에 관한 실증적 연구
조재환,Jo, Jae-Hwan 한국건설안전협회 2010 建設 安全技術 Vol.51 No.-
In terms of deregulation requests from business, incidents at construction sites are rapidly increasing after reducing the regular safety training hours. Especially, to prevent incidents through safety trainings for construction site workers, who have lots of hazardous tasks than general manufacturing, is not only to protect property of both the companies and the country but also to increase their profits. That is why there are loud voices regarding that the safety training is a core mandatory to prevent industrial incidents. But, most companies, as soon as the deregulation for safety training is implemented, mitigated conducting safety trainings to prevent incidents. With this, theincidents are currently to be increased and caught in a vicious circle of many incidents at the smaller companies because of their absentmindedness regarding safety training due to their poorness as subcontractors of major companies, comparing to major companies. This study explains that incident factors are roughly divided into technical factor, managerial factor, and educational factor. And, we confirmed that the educational factor led by deficiency safety awareness and knowledge was the major factor.
조재환 ( Jae Hwan Cho ),이정환 ( Jung Hwan Lee ),조영득 ( Young Deuk Jo ) 한국농업경제학회 2011 農業經濟硏究 Vol.52 No.3
A Linear Approximated Inverse Almost Ideal Demand System suggested by Eales and Unnevehr was estimated using monthly data of beef carcass grades in Korea. LA/IAIDS consists of 5 demand equations of Korean beef carcass for Hanwoo 1 and over, 1, 2, 3 grades and Beef Cattle. The results showed that price flexibility and scale flexibility are both negative, as we expected. The responses of Korean beef price to 1% increase in imported beef quantity were 0.04~0.2% decline in low-grade beefs while 0.02~0.08% increase in Hanwoo high-grade beef. We also found that both own-price flexibility and scale flexibility of high-grade beef are much greater than those of low-grade beef. This implies that Hanwoo cattle farmer might be in the face of deficit operation due to long-term fattening with high-grade beef price plummeted, if the number of Hanwoo cattle continues to increase much faster than before.
연신비가 초고분자량 폴리에틸렌과 고밀도 폴리에틸렌 블렌드 겔 필름의 열적 및 역학적 성질에 미치는 영향
김창경,조재환,김진사,Kim, Chang-Gyeong,Jo, Jae-Hwan,Kim, Jin-Sa 한국섬유공학회 1990 한국섬유공학회지 Vol.27 No.10
Blend films of ultra-high molecular weight polyethylene (UHMW PE) and high density polyethylene(HDPE) were prepared by gelation/crystallization from p-xylene solution and they were drawn at various draw ratios in order to investigate thermal and mechanical properties of drawn samples. High draw ratio above 100 could be obtained from drawing the blend films of 70/30 and 50/50 weight percent of UHMW PE/HDPE as well as UHMW PE gel film. Melting temperatures of drawn samples were initially decreased with the increase of draw ratio but above a certain draw ratio, were increased. For the samples having the same draw ratio, melting temperatures were decreased with the increase of weight percent of HDPE. Tensile modulus and tenacity of drawn samples were dependent on the blend composition. Modulus and tenacity were decreased with the increase of weight percent of HDPE. Modulus of samples was almost linearly increased with the increase of draw ratio for all the blend compositions. Tenacity was increased with the increase of draw ratio but the rate of increase was lessened for the high draw ratios.