• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.111-114
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• 2002

We propose and fabricate a vertically integrated waveguide thermo-optic switch. It controls the optical path between two vertically stacked waveguide. As a first step, we fabricate polymeric waveguides. The measured propagation loss is ranged from 0.3 db/cm to 0.4 dB/cm at the wavelength of 1.55 $\mu\textrm{m}$. We fabricate the proposed vertically integrated waveguide thermo-optic switch to demonstrate its preliminary feasibility. The measured crosstalk is better than -10 db. The power consumption is about 500 mW. Further effort is necessary to improve its performance.

• Proceedings of the Korea Crystallographic Association Conference
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• 2002.11a
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• pp.31-31
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• 2002

The hydrothermal reaction of Zn(NO₃)₂6H₂O with benzene-1,3-dicarboxylic acid (or isophthalic acid, 1,3-BDCH₂) and pyridine led to the formation of a 1-dimensional coordination polymer with the empirical formula of [Zn₄(1,3-BDC)₃(Py)₂(O/sup 2-/)] (1). On the other hand, the hydrothermal reaction of Tb(NO₃)₃5H₂O with benzene-1,3-dicarboxylic acid (or isophthalic acid, 1,3-BDCH₂) and pyridine gave a 3-D compound [Tb₃(1,3-BDC)₂(H₂O₃] (2). The structures of both compounds have been determined by X-ray diffraction. 1 crystallizes in the monoclinlc space group P2₁/n, a = 10.344(3) Å, b = 18.030(3) Å, c = 18.033(3) Å, = 90.46(2)°, V = 3363.1(13) ,ų, Z = 4. 2 crystallizes in the monoclinic space group C2/n, a = 22.253(5) Å, b = 18.672(4) Å, c = 11.5812 Å, = 101.40(2)°, V = 4717.3(21) ų, Z = 8.

• Bulletin of the Korean Chemical Society
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• v.25 no.12
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• pp.1955-1958
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• 2004

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.265.2-265.2
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• 2013

We fabricate poly(3,4-ethylenedioxythiopene patterns using liquid-bridge-mediated nanotransfer (LB-nTM) printing via vapor phase polymerization (VPP). LB-nTM printing method can simultaneously enable the synthesis, alignment and patterning of the nanowires from molecular ink solutions. Two- or three-dimensional complex structures of VPP-PEDOT were directly fabricated over a large area using many types of molecular inks. VPP method is a versatile technique that can be used to obtain highly conducting coatings of conjugated polymer on both conducting and non-conducting substrates. The PEDOT patterns has analyzed crystallinity from X-ray diffraction pattern and select-area diffraction patterns. In addition, the PEDOT pattern has high conductivity compared other conducting polymers.

• Journal of Radiation Industry
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• v.7 no.2_3
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• pp.167-170
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• 2013

Lignin can be a valuable natural chemical resource. Structurally, lignin is a three-dimensional polymer made up of condensed C-C bonds and some ether linkages, most of which are not readily degraded. In this study, lignin carbonization under various electron beam pretreatment conditions was characterized through a thermogravimetric analysis (TGA), X-ray diffraction (XRD) and Raman spectroscopy. Lignin stabilization was controlled by various doses of electron beam irradiation corresponding to 50, 100, 200, 500 and 1,000 kGy; the carbonization process was performed under a nitrogen gas atmosphere at $1000^{\circ}C$ for 1 h. The TGA results showed that a 1,000 kGy lignin dose increased the residue weight from 39.96% to 45.23%, compared to non-irradiated lignin. This observation is in agreement with the XRD and Raman spectroscopy results, in which the two theta degrees and the degree of crystallization were improved by increasing the electron beam irradiation.

• Polymer(Korea)
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• v.36 no.2
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• pp.229-234
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• 2012

This paper studied the effects of the content and the orientation of the disk shape fillers on the modulus of PP composites. The experimental results were compared with the theoretical calculations which included the three dimensional ellipsoids and analyzed by two aspect ratios, ${\rho}_{\alpha}=a_1/a_3$and ${\rho}_{\beta}=a_1/a_2$proposed by Lee and his researchers. Mica and talc were used as disk shape fillers in the composites. The shapes of mica and talc were observed by SEM and aspect ratios were statistically calculated. For the case of mica, the average aspect ratios were ${\rho}_{\alpha}=13.5$ and ${\rho}_{\beta}=1.8$, and for the case of talc, they were ${\rho}_{\alpha}=3.8$ and ${\rho}_{\beta}=1.4$. Also, the effects of two aspect ratios and the content of filler on the mechanical properties were studied: For 30 wt% of mica, $E_{11}$ increased up to about 2.7 times, and for the other case of talc, $E_{11}$ increased up to about 2.3 times, respectively.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.4
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• pp.15-20
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• 2022

Aerogel is a material having a nanopore structure based on a high porosity. Due to this high porosity, it has excellent properties not found in conventional materials, but its application has been limited due to low mechanical strength. Therefore, to improve the mechanical strength of the aerogel, polyurea crosslinking was introduced and a precursor having an amine group essential for polyurea polymer formation was selected to synthesize a polyurea crosslinked aerogel composite. In addition, the crosslinking of polyurea was adjusted according to the number of amine groups present in aminosilane. It was confirmed through various analyses that the nanopore structure of the aerogel was maintained to have mesopores. The aerogel thus formed was able to improve the mechanical strength by about two times, and it was confirmed through field emission scanning electron microscope analysis that a one-dimensional polymer was formed on the silica aerogel surface through the introduction of ethylene diamine. The one-dimensional polymer thus formed has improved mechanical properties, resulting in securing an elastic modulus of about 2.66 MPa.

• Korea-Australia Rheology Journal
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• v.12 no.3_4
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• pp.165-173
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• 2000

Three-dimensional numerical simulation of isothermal/nonisothermal coextrusion process of two immiscible polymers through a rectangular channel has been done using the finite element method. The encapsulation phenomenon with the less viscous layer encapsulating the more viscous layer was investigated with the generalized Newtonian fluids. The interface position around the symmetric plane obtained by numerical simulation nearly coincided with the one observed in experiments, but the degree of encapsulation was less than the one observed experimentally. Open boundary condition method was found to be applied to the simulation of nonisothermal coextrusion process, however, the results are not far from those using the fully developed boundary condition, because the temperature development along the downstream direction is very slow in the case of convection dominated flow. When the inlet velocity is increased, the interface profile does not change in isothermal flow, while it moves upward in nonisothermal situation. The degree of encapsulation decreases along the downstream direction in nonisothermal flow. When the inlet temperature increases compared to the wall temperature, the outlet interface moves downward and the degree of encapsulation increases. The difference of degree of encapsulation between the simulation and the experiments seems to arise from the viscoelastic effect of the materials. It was concluded that the nonisothermal effect alone does not explain the complex coextrusion process and the viscoelastic effect needs to be considered.

• Steel and Composite Structures
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• v.38 no.5
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• pp.477-496
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• 2021

The main objective of this paper is to study vibration of sandwich open cylindrical panel with damaged core and FG face sheets based on three-dimensional theory of elasticity. The structures are made of a damaged isotropic core and two external face sheets. These skins are strengthened at the nanoscale level by randomly oriented Carbon nanotubes (CNTs) and are reinforced at the microscale stage by oriented straight fibers. These reinforcing phases are included in a polymer matrix and a three-phase approach based on the Eshelby-Mori-Tanaka scheme and on the Halpin-Tsai approach, which is developed to compute the overall mechanical properties of the composite material. Three complicated equations of motion for the panel under consideration are semi-analytically solved by using 2-D differential quadrature method. Several parametric analyses are carried out to investigate the mechanical behavior of these multi-layered structures depending on the damage features, through-the-thickness distribution and boundary conditions. It is seen that for the large amount of power-law index "P", increasing this parameter does not have significant effect on the non-dimensional natural frequency parameters of the FG sandwich curved panel. Results indicate that by increasing the value of isotropic damage parameter "D" up to the unity (fully damaged core) the frequency would tend to become zero. One can dictate the fiber variation profile through the radial direction of the sandwich panel via the amount of "P", "b" and "c" parameters. It should be noticed that with increase of volume fraction of fibers, the frequency parameter of the panels does not increase necessarily, so by considering suitable amounts of power-law index "P" and the parameters "b" and "c", one can get dynamic characteristics similar or better than the isotropic limit case for laminated FG curved panels.

• Korean Journal of Crystallography
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• v.16 no.2
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• pp.107-127
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• 2005

Five Cu(II) compounds were obtained from different copper salts with btp ligands, and their structures were determined by X-ray crystallography. The structure of coordination polymer 2 contains btp-bridged tetranuclear Cu(II) units weakly connected by nitrate ions, and the structure of a discrete Cu(II) molecule 1 contains acetates and btp ligands. With perchlorate anions, two btp ligands bridge Cu(II) ions to form a double zigzag chain 3, while a single zigzag chain 4 is created with sulfate anions. The reaction of $Cu(NO_{3})_{2}$ containing $NH_{4}PF_{6}$ with btp ligands also produced a polymeric compound 5 containing $Cu(H_{2}O)_{2}^{2+}$ and $Cu(NO_{3})_{2}$ units alternatively bridged by btp ligands with H-bonds between copper bonded water and nitrate oxygen atoms. Five Zn(II) compounds were obtained from different zinc salts with btp ligands, and the structures of polymeric compounds (6, 7 and 8) and monomeric compounds (9 and 10) were determined by X-ray crystallography. With nitrate, chloride and bromide anions, btp ligands bridge Zn(II) ions to form polymeric compounds (6, 7 and 8), but btp ligands coordinate to a Zn(II) ion to form monomeric complexes (9 and 10) with $PF_{6}^{-}$ and perchlorate anions. Four silver salts and btp ligands produced two kinds of structures, dinuclear 20-membered rings and one-dimensional zigzag chain depending on different anions. For $ClO_{4}^{-}$ and OTf anions, weak interactions between Ag(I) and anions make dinuclear 20-membered rings construct polymeric compounds (11 and 13). For $PF_{6}^{-}$ anion, there are also weak interactions between Ag(I) and $F(PF_{6}^{-})(12)$, but they do not construct a polymeric compound. For $O_{2}CCF_{3}^{-}$ anion, btp ligands bridge Ag(I) atoms to make one-dimensional zigzag chain (14), and there are also interactions between Ag(I) and anions.