• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.7A
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• pp.951-958
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• 2000

In wavelength-routed all-optical networks, signals are transmitted on a direct optical path, or a lightpath, in a single-hop manner without opto-electronic/electro-optic(OE/EO) conversion at intermediate nodes. However, due to the physical constraints of optical elements such as ASE noise and crosstalk signals can be degraded un a long path. To establish a connection under such impairments, the optical signal may need to be regenerated at intermediate nodes, dividing a lightpath into two or more fragments. However, since signal regeneration at intermediate nodes requires additional network resources, the selection of these nodes should be made carefully to minimize blocking of other lightpaths. In this paper, we deal with the problem of establishing a lightpath in a multihop manner under physical constraints. We provide both minimal-cost and heuristic algorithms for locating signal regeneration nodes(SRNs). For a minimal-cost algorithm, we formulate the problem using dynamic programming(DP) such that blocking of other lightpaths due to the lack of transmitters/receivers(TXs/RXs) and wavelengths is minimized throughout the network.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1394-1399
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• 2007

Recently, Study of 3D freeform fabrication method was working in the various applications. For example, in the powder base, it's laminated using a binding method or laser sintering method. However, these methods are not suitable in the office environments because it dust with powder that is bad for health. In this paper, we introduce a method of 3D freeform fabrication using a curing of photo-polymer resin and construct a system has multi printing head. A photo-polymer curing method has simply fabrication process and high strength of manufacturing part. However, this method has a problem on the multi print-head system. Because multi-printing system has a other printing method compare with a single printing system. Therefore, we experiment a single head 3D printing and proposed a 3D printing method using a multi-piezo head.

• Applied Chemistry for Engineering
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• v.16 no.3
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• pp.342-347
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• 2005

Photocurable hyperbranched acrylates were prepared from acrylic acid and hyperbranched polyol (HBP-16, 32, 64). Physical properties of three kinds of photocurable hyperbranched acrylated were investigated. Thermal stability of UV cured film measured by TGA shifted to higher temperature with increasing of functionality. Hardness, abrasion resistance, and tensile strength of UV cured film also increased with increasing functionality of acrylate. Weathering test for UV cured film showed the value of yellow index increased with increasing functionality of acrylate.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2003.05a
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• pp.433-440
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• 2003

통신시스템의 발전과 더불어 WDM 전송기술의 등장은 미래의 다양한 광대역 서비스의 제공이 가능하게 되었다. 하지만, 개별 수요들이 요구하는 대역폭이 광파장의 대역폭에 비해 매우 작으므로. 개별 수요들을 다중화하여 하나의 광경로를 통해 전송하는 수요집적(traffic grooming)에 관한 연구들이 많은 관심을 받고. 있다 본 연구는 mesh 구조의 WDM 통신망에서의 수요집적 및 광경로 설정에 관한 문제를 다루고 있다. 주어진 네트워크 상에 하나의 가상노드와 아크를 추가하여 새로운 네트워크를 구성하고 이를 대상으로 목적함수를 사용되는 광파장의 수를 최소화하는 혼합정수계획 모형을 수립하였다. 아울러. NP-Complete로 알려진 본 문제의 해를 효과적으로 구하기 위한 발견적 해법을 제안하며, 실제 다양한 실험을 통해 제안된 알고리즘의 효율성을 보인다.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2008.10a
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• pp.135-136
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• 2008

EU-Reach Regulation 대비 유해물질 대체약품 개발 프로그램인 SVHC(Substance of very high concern)로부터 환경친화적인 방염제의 스크리닝으로 LOI 30이상의 Halogen-free 유기계 Organo-Phosphonate 화합물들이 유력한 후보로 선별되었으며 여기에 반응형 저에너지 타입 아(메타)크릴계 광기능성기를 도입하여 에너지 절감형이면서 친환경적인 가공약제를 개발 하였다. 먼저 열경화형 타입중에서도 면섬유에 취급이 용이한 DMP(dimethylphosphite)를 출발물질로한 N-Methylol type의 열경화형 인/질소 타입 알코올 함유 면섬유용 방염제를 제조한후 -OH기에 광반응형 아크릴 기능성기를 도입하여 개시제와 함께 광경화 방염가공 후 물성에 관한 특성를 관찰 하였다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.5
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• pp.475-479
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• 2012

We present a novel polymer fabrication process involving direct UV patterning of a hyperbranched polymer, AEO3000. Compared to PDMS, which is the most widely used polymer in bioMEMS devices, the present polymer has advantages with regard to electrode integration and fast fabrication. We designed a four-chip microelectrofluidic bench having three electrical pads and two fluidic I/O ports. We integrated a microfluidic mixer and a cell separator on the bench to characterize the interconnection performance and sample manipulation. Electrical and fluidic characterization of the microfluidic bench was performed. The measured electrical contact resistance was $0.75{\pm}0.44{\Omega}$, which is small enough for electrical applications, and the pressure drop was 8.3 kPa, which was 39.3% of the value in the tubing method. By performing yeast mixing and a separation test in the integrated module on the bench, we successfully showed that the interconnected chips could be used for bio-sample manipulation.

• Polymer(Korea)
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• v.38 no.6
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• pp.801-808
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• 2014

Ion diffusion and chemical binding to acrylic polymer were investigated in a solid film. The composition of acrylic monomers containing amino group and carboxylic acid was adjusted for rapid ion migration in the film. p-Methylred (PMR) and phenolphthalein derivatives were optically sensitive to the concentration of proton and hydroxyl anion, respectively and verified the ion migration through the film layers. A rapid proton migration was observed in the film of a high amino content. On the other hand, $OH^-$ migration occurred rapidly in a high content of carboxylic acid group. The proton migration occurred through the internal layer as well as surface layer of a film and was reversible during 50 repetition examination. Copper(II) ion migration was examined with a Rhodamine-containing polymer film. The light absorption and emission spectra of a Rhodamine-Cu complex showed the key contribution of carboxylic acid group to the Cu(II) migration in a film.

• Polymer(Korea)
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• v.34 no.6
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• pp.574-578
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• 2010

In this study, the caprolactone modified hydroxy acrylates (CHAs) were synthesized by ring-opening reaction of caprolactone and 2-hydroxyethyl acrylate (2-HEA) as initiator. Also, the caprolactone modified urethane acrylate (UA) oligomers were synthesized by condensation reaction of previously synthesized CHAs, 2-hydroxyethyl acrylate (2-HEA) and hexamethylene diisocyanate trimer (HDT). Using the hydroxy number of CHAs, the molecular weights of the CHAs were calculated easily and their molecular weight was similar to the theoretical molecular weight of them. The viscosity of UA oligomers decreased as increasing a content of CHA in the UA oligomer. Cure films were prepared from UA oligomer, reactive diluents, and UV initiator to investigate their physical properties. The thermal stability and color difference on high temperature for the cured film were improved as increasing the crosslinking density. Their surface hardness was also increased as increasing crosslinking density of the cured films, but their elongation at break was decreased.

• Polymer(Korea)
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• v.35 no.2
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• pp.183-188
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• 2011

Pentaerytritol triacrylate (PETA) was synthesized by a condensation reaction between pentaerytritol and acrylic acid. The highest yield of PETA was obtained when heptane was used as a solvent under the 1:4 mole ratio of pentaerytritol and acrylic acid. The 6-functional urethane acrylates(UA) were also synthesized by a condensation reaction between PETA and diisocyanate. Cured films were prepared from the mixtures of UA oligomer, reactive diluents and UV initiator to investigate their physical properties. The thermal stability of the aliphatic urethane acrylate was better than that of the aromatic urethane acrylate. The UA-2 showed good hardness and scratch resistance properties while the UA-l with a high degree of curing density exhibited a better chemical resistance. All the UA oligomers showed fairly good adhesion strengths but the other physical properties of UA-3 were poor due to its low curing density.

• Polymer(Korea)
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• v.37 no.1
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• pp.1-4
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• 2013

We proposed a new process to fabricate a high-aspect-ratio microhair having surface wrinkles using the contact-and-tension of a microstamp. Through this work, we observed that regular surface wrinkles were generated on the hair with a diameter of around $20{\mu}m$ due to the uni-directional compressive stress during the photocuring process by ultraviolet light. To do this, we conducted an experimental system setup for contact-and-tension process. From the preliminary test results, we believed that the proposed method can be applied to make a long polymer hair having surface wrinkles for special applications to biomimetics, and some research fields related on surface area such as heat transfer and catalyst enhancement.