• Polymer(Korea)
• /
• v.35 no.6
• /
• pp.505-512
• /
• 2011

Effects of structural features of 4 dinuclear constrained geometry catalysts having paraxylene derivative bridge (DCGC) on copolymerization of ethylene and 1-hexene were investigated. The bridges of three catalysts have para-xylene backbone with a different substituent at benzene ring. The substituents were hydrogen (Catalyst 1), isopropyl (Catalyst 2), n-hexyl (Catalyst 3) and 1-octyl (Catalyst 4). It was found that Catalyst 1 having hydrogen as a substituent exhibited the greatest activity among the four dinuclear CGCs. On the other hand, Catalyst 2 containing isopropyl as a substituent showed the smallest activity. Very interestingly, Catalyst 2 was able to produce about 6 times higher molecular weight polymer than Catalyst 3 and 4. Catalyst 3 and 4 having a long alkyl chain substituent revealed the biggest comonomer response to generate polyethylene copolymer containing more than 40% 1-hexene contents. These results suggest that the control of the substituent of para-xylene bridge of dinuclear CGC can provide a proper method to adjust the microstructure of polyethylene copolymers.

• Product Safety
• /
• s.54
• /
• pp.22-27
• /
• 1997

FPLMTS란 단어 그대로 미래 공중 육상이동통신시스템 (Future Public Land Mobile Telecommunication System)을 말한다. 그러나 단순히 육상이동통신의 의미만이 아닌 육상, 해상, 공중에 이르는 모든 상황의 통신을 포함, 지상과 위성간 상호보완적인 망 구성으로 이동, 고정통신 이용자에게 광범위하고 다양한 서비스를 제공할 이동통신시스템을 의미한다.

• Defense and Technology
• /
• no.1 s.287
• /
• pp.86-93
• /
• 2003

Objective Force의 모든 측면에서 볼 때, 육군항공은 절대 필요한 구성요소이다. 통합개념팀(Intergrated Concept Team)은 현재 Alabama주 Fort Rucker에서 미래 항공력에 대한 작전적 및 조직적(O & O : Operational and Organizational) 개념을 개발하고 있는 중이다. 이러한 노력은 무인항공기, 공중기동수송기, Loitering Attack Munition – Aviation, 새로운 군수 및 공중수송서비스 등과 같은 최근에 생겨난 개념과 시스템들을 획득하는데 목적이 있다.

• Korea Information Processing Society Review
• /
• v.11 no.1
• /
• pp.20-28
• /
• 2004

영화 '스타워즈'를 보면 적들과 대치하고 있는 일촉즉발의 위기 상황에서 '해결사'가 나타나 공주의 메시지를 공중에 홀로그램으로 재생시켜 모면책을 알려주고 순식간에 사라지는 장면이 나온다. 그리고, 영화 '마이너리티 리포트'에서는 주인공 톰크루즈가 가족과 찍은 동영상을 일반적인 디스플레이가 아닌 공중에다 홀로그램을 펼쳐놓고 3차원 입체영상을 만들어 회상하는 장면이 나온다.(중략)

• 대한방사선방어학회:학술대회논문집
• /
• 2009.04a
• /
• pp.190-191
• /
• 2009

• 정보화사회
• /
• s.25
• /
• pp.38-44
• /
• 1989

공중전기통신 사업에의 경쟁체제 돌입에 대비한 공중전기통신사업법과 전기통신공사 민영화를 대비한 한국전기통신공사법 개정법률이 국회에 상정, 심의중에 있다. 본고에서는 올해내로 확정, 고시될 것으로 보이는 이들 법률안들을 게재한다. 단, 게재된 내용은 심의결과에 따라 수정 또는 보완될 수도 있다.

• Journal of Bio-Environment Control
• /
• v.19 no.4
• /
• pp.305-310
• /
• 2010

This study was carried out to investigate the effect of air humidity and water content of medium on the growth and physiological disorder of paprika in summer hydroponics. Treatments were composed of air humidity of control (over 90%) and dehumidification (low 90%) and water content of 80% and 50%. Time domain reflectometry (TDR) sensors and dehumidifier were used in a drip irrigation system and control system of air humidity, respectively. The early growth of paprika was not affected by air humidity but increased by high water content (80%) of medium. Mean fruit weight was reduced at high air humidity and low water content (50%) of medium, but the fruit number per plant and yield were increased at low air humidity. The incidence of brown fruit stem increased with increasing air humidity and water content of medium. Rate of blossom end rot increased in the low water content medium compared with the high water content medium. The nitrogen (N) was higher content in brown fruit stem than normal stem, but calcium (Ca) was lower.

• Korean Chemical Engineering Research
• /
• v.49 no.1
• /
• pp.62-68
• /
• 2011

In the study, acrylate copolymer as MMA-co-GMA-co-AA with a high hardness and flexibility was synthesized for applying to the clear protection film, where GMA was used as a mediator to enhance polymerization-efficiency between MMA and AA. With an increase of GMA content, molecular weight and hardness of acrylate copolymer increased, however, flexibility decreased. With an increase of AA content, its molecular weight and hardness decreased, however, flexibility increased. Molar ratio of GMA/MMA and AA/GMA were optimized as 1.6 and 1.8, respectively, at 30 g of MMA to enhance hardness and flexibility of acrylate copolymer film. Molecular weight and Tg of the acrylate copoylmer were 13,300 g/mol and 136.5 $^{\circ}C$, respectively. Hardness of the coated film at 1.4 g/$m^2$ of spread was 1 H and no crack was observed at expansion ratio of 5% and 15%, respectively. Hardness of film was improved to 3 H by increasing spread of 4.1-4.6 g/$m^2$.

• Journal of the Korea Concrete Institute
• /
• v.18 no.4 s.94
• /
• pp.569-576
• /
• 2006

PC-type copolymers were synthesized using MPEG(polyethylene glycol methyl ether methacrylate, Mn=2080) to different mole ratios of mono-carboxylic acid(AA : acylic acid). The mole ratios of AA were 2, 3, 4 and PC-type terpolymers were synthesized using mono-, dicarboxylic acid(ITA : itaconic acid MAL : maleic acid) with the same graft chain. To investigate effects of PC-type co-, ter-polymers on the hydration of cement experiments involving FT-IR, XRD, DSC, SEM have been analysed with cement paste specimens to 1, 3, 28 day. The hydration reaction rate of cement paste was slightly delayed at 1 day, due to increase in molar ratio of [AA]/[MPEG], it was recovered in the days after and the copolymer was more active than the terpolymer, because of low carboxylic acid content PC-type copolymers applied 2AA-type were fastest copolymer on hydration reaction of cement paste to 3 day and the more AA mole ratios increased, the more hydration was retarded.

• Applied Chemistry for Engineering
• /
• v.18 no.5
• /
• pp.516-521
• /
• 2007

The copolymerization characteristics of a newly-synthesized catalyst, $rac-Me_2Si(2-p-tolylindenyl)_2ZrCl_2$, and its analogue, $rac-Me_2Si(Ind)_2ZrCl_2$, were examined in the ethylene/1-octene copolymerization while varying the concentration of 1-octene in the reaction mixture. The activity of $rac-Me_2Si(2-p-tolylindenyl)_2ZrCl_2$ catalyst was decreased with increase of comonomer concentration, which is different from the usual comonomer effect of the metallocene catalysts with a bridge structure. The contents of 1-octene in the copolymer from the catalyst with 2-p-tolyl substituent were higher than those from the catalyst without that substituent. The melting point, crystallinity, and molecular weight decreased with comonomer content which was more apparent for $rac-Me_2Si(2-p-tolylindenyl)_2ZrCl_2$ catalyst.