• Bulletin of the Korean Chemical Society
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• v.28 no.6
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• pp.999-1004
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• 2007

Spherical porous silica supports modified with titanium or zirconium alkoxides were prepared, and allyl groups were chemically attached to the titanized or zirconized silica supports, and the product was cross-polymerized with a double bond containing cellulose derivative to yield new CSPs (chiral stationary phases). Magic angle spinning 13C solid state NMR and elemental analysis were used to characterize the CSPs. The performances of the chiral stationary phases were examined in comparison with a conventional chiral stationary phase. Spherical porous silica particles modified with 3,5-dimethylphenylcarbamate of cellulose were prepared and used as the conventional chiral stationary phase. Chromatographic data were collected for a few pairs of enantionmers in heptane/2-propanol mixed solvents of various compositions with the three chiral columns and the results were comparatively studied. The separation performance of the chrial phase made of the titanized silica was better than the others, and the separation performance of the chiral phase of the zirconized silica was comparable to that of the conventional chiral phase. The superiority of titanized silica over bare or zirconized silica in chiral separation seemed to be owing to the better yield of crosslinking (monitored by increase of carbon load) for titanized silica than for the others.

• Journal of the Korean Chemical Society
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• v.29 no.3
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• pp.213-219
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• 1985

The relative stability as a function of geometry in rigid cyclopropylcarbinyl cations was examined by $^{19}$F-nmr spectroscopy. 8-p-Fluorophenyl-tricyclo[3.3.1.0$^{2,7}$]octane-8-yl-(I), 9-p-fluorophenyl-tricyclo[3.3.1.0$^{2,8}$]nonane-9-yl (II), and 10-p-fluorophenyl-tricyclo[4.3.1.0$^{2,9}$]decane-10-yl cation(Ⅲ) were prepared from the corresponding carbinols in FSO$_3$H-SO$_2$ClF solution at -120$^{\circ}C$. $^{19}$F-nmr data indicate that the symmetrical bisected geometry of cyclopropane ring for ${\sigma}$-conjugation is a very impotant factor in charge delocalization. However, varied orientation of the bond angle ${\theta}$ within the bisected conformation does not affect the charge delocalization into the cyclopropane ring.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.11 s.114
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• pp.1105-1111
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• 2006

In this paper, using low-temperature co-fired ceramic(LTCC) based system-in-package(SiP) technology, a very compact power amplifier LTCC module was designed, fabricated, and then characterized for 60 GHz wireless transmitter applications. In order to reduce the interconnection loss between a LTCC board and power amplifier monolithic microwave integrated circuits(MMIC), bond-wire transitions were optimized and high-isolated module structure was proposed to integrate the power amplifier MMIC into LTCC board. In the case of wire-bonding transition, a matching circuit was designed on the LTCC substrate and interconnection space between wires was optimized in terms of their angle. In addition, the wire-bonding structure of coplanar waveguide type was used to reduce radiation of EM-fields due to interconnection discontinuity. For high-isolated module structure, DC bias lines were fully embedded into the LTCC substrate and shielded with vias. Using 5-layer LTCC dielectrics, the power amplifier LTCC module was fabricated and its size is $4.6{\times}4.9{\times}0.5mm^3$. The fabricated module shows the gain of 10 dB and the output power of 11 dBm at P1dB compression point from 60 to 65 GHz.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.6
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• pp.130-137
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• 2018

Many constitutive models for concrete have been developed to predict the nonlinear behavior of concrete members considerably. The constitutive model for reinforcing bar that include the tension stiffening effect due to the bond characteristics between steel bars and concrete is being studied but the bilinear model is generally used. It was found that the buckling of the longitudinal reinforcing bars is controlled the nonlinear behavior of hybrid precast concrete panel, which is being developed for core wall. In this study, the constitutive models that can consider the embedding and buckling effects of reinforcing bar are investigated and a new model combing these constitutive models is proposed. In order to verify the proposed model, the analysis results are compared with experimental results of the concrete wall and hybrid precast concrete panel. The analysis of embedding-effect-only modeling predicted that the deformation increases continually without the decrease in the load carrying capacity. However, the analysis results of proposed model showed good agreement with some experimental results, thus verifying the proposed computational model.

• Bulletin of the Korean Chemical Society
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• v.18 no.1
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• pp.14-18
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• 1997

Sulconazole nitrate, C18H16Cl3N3O3S, crystallizes in monoclinic, space group C2/c, with a=14.401(1), b=8.051(1), c=34.861(2) Å, β=95.9(1)°, g=0.58 mm-1, Dc=1.523 g/cm3, Dm=1.522 g/cm3, F(000)=1888.0, and z=8. Intensities for 2460 unique reflections were measured on a CAD4 diffractometer with graphited-monochromated Mo-Kα radiation. The structure was solved by direct method and refined by full matrix least squares to a final R=0.071 for 2182 reflections (Io > 2σIo). The bond lengths and angles are comparable with the values found in the analogues imidazole derivatives. The 2,4-dichlorophenyl ring(A) and the p-chlorophenyl ring(B) are almost planar with different heights [dihedral angle 17.3°] while the imidazole ring(C) is nearly perpendicular to the two phenyl rings[dihedral angles about the two rings A, B are 110.8° and 96.1° respectively]. In order to understand the overall conformation we calculated the selected distances (l1, l2, l3) among the center of the three rings and considered the imaginary plan D[C(7), C(9) and C(16)]. The two polar group S(8) and N(19) do not have gauche conformation and l2 value (4.47 Å) is shorter than the other imidazole derivatives. One -NO3 group are hydrogen bonded the two neighbored sulconazole molecules. The molecular crystal packing is also formed by two hydrogen bondings and van der Waals forces.

• Advances in nano research
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• v.7 no.4
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• pp.233-240
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• 2019

The present research work reports in-vitro anti-cancer activity of biologically synthesized ZnO nanoparticles (ZnO NPs) against human carcinoma cells viz SCC-40, SK-MEL-2 and SCC-29B using Sulforhodamine-B (SRB) Assay. ZnO NPs were synthesized by a unique and novel biological route using Temperature-gradient phenomenon where the extract of combination of Catharanthus roseus (L.) G. Don (C. roseus), Azadirachta indica (A. indica), Ficus religiosa (F. religiosa) and NaOH solution were used as synthesis medium. The morphology of the ZnO NPs was characterized by Transmission Electron Microscopy (TEM). TEM images reveal that particle size of the samples reduces from 76 nm to 53 nm with the increase in reaction temperature and 68 nm to 38 nm with the increase in molar concentration of NaOH respectively. XRD study confirms the presence of elements and reduction in crystallite size with increase in reaction temperature and NaOH concentration. The diffraction peaks show broadening and a slight shift towards lower Bragg angle ($2{\theta}$) which represents the reduction in crystallite size as well as presence of uniform strain. The FTIR spectra of the extract show transmittance peak fingerprint of Zn-O bond and presence of bioactive molecules These NPs exhibit inhibition greater than 50% for SCC-40, SK-MEL-2 and SCC-29B cell lines and more than 50% cell kill for SCC-29B cells at concentrations < $80{\mu}g/ml$. Nanoparticles with smallest size have shown better anti-cancer activity and peculiar cell-selectivity. The combination of extracts of these plants with ZnO NPs can be used in targeted drug delivery as an effective anti-cancer agent, a potential application in cancer treatment.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.2
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• pp.1-6
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• 2019

With the increase in number of the athletic population and elderly demographic, the demand for orthopedic splints, which are used to support a damaged body, has rapidly increased. Current splints mainly consist of inner and outer parts, which are multiple fabrics covered with polyurethane and nonwoven fabrics, respectively. However, the laminated materials with directly applied pre-polymer coating lead to a high defect rate because of the uneven thickness on the surface. Thus, this study proposes an indirect coating method using a precise clearance controller, which enables the even application of the coating material on multiple inner parts while maintaining a constant thickness. In addition, a roll-to-roll (R2R) technique is applied instead of the sewing mechanism to bond the inner and outer materials together and enhance the productivity in the final stage. In the advanced methods, there is a storage tank that contains polyurethane, a clearance controller, and pairs of rollers in the upper and lower rows. To improve the quality of the products and optimize the equipment, three controllable factors are determined: the viscosity of polyurethane, angle of the gap controller and number of pairs of rollers in the R2R system.

• Bulletin of the Korean Chemical Society
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• v.6 no.4
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• pp.202-206
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• 1985

The crystal structure of The crystal structure of $Ag^+$-Exchanged Zeolite A, $Ag_{4.6}Na_{7.4}-A$, dehydrated, treated with $H_2$, and evacuated, all at $350^{\circ}C$, has been determined by single crystal x-ray diffraction methods in the cubic space group Pm3m at $24(1)^{\circ}C;$ a = $12.208(2)\AA.$ The structure was refined to the final error indices R1 = 0.088 and R2 (weighted) = 0.069 using 194 independent reflections for which II_0$ > $3{\sigma}(I_0)$. On threefold axes near the centers of 6-oxygen rings, $7.4 Na^+$ ions and $0.6 Ag^+$ ions are found. Two non-equivalent 8-ring $Ag^+$ ions are found off the 8-ring planes, each containing about $0.6 Ag^+$ ions. Three non-equivalent Ag atom positions are found in the large cavity, each containing about 0.6 Ag atoms. This crystallographic analysis may be interpreted to indicate that $0.6 (Ag_6)^{3+}$ clusters are present in each large cavity. This cluster may be viewed as a nearly linear trisilver molecule $(Ag_3)^0$ (bond lengths, 2.92 and 2.94 $\AA;$ angle, $153^{\circ})$ stabilized by the coordination of each atom to a Ag^+$ ion at 3.30, 3.33, and 3.43 $\AA$, respectively. In addition, one of the silver atoms approaches all of the 0(1) oxygens of a 4-ring at $2.76\AA.$ Altogether $7.4 Na^+$ ions, $1.8 Ag^+$ ions, and 1.8 Ag atoms are located per unit cell. The remaining $1.0 Ag^+$ ion has been reduced and has migrated out of the zeolite framework to form silver crystallites on the surface of the zeolite single crystal.

• Journal of the Korean Wood Science and Technology
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• v.50 no.3
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• pp.149-158
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• 2022

To realize the infinite possibilities of materials derived from wood, it is necessary to overcome the weak moisture stability of wood. Thus, the development of an eco-friendly hydrophobic coating agent is essential, and of these, woody biomass-based materials are strongly attractive as coatings. In this study, eco-friendly hydrophobic wood coatings were prepared using carnauba wax purified from palm leaves and sprouts, and kraft lignin. The physicochemical properties of the carnauba wax/lignin blends according to the ratio of carnauba wax and lignin were observed by morphology and functional group change. In addition, the coating performance of carnauba wax/lignin blend coatings was confirmed by measuring the contact angle change. It was found that the addition of lignin could accelerate the atomization of wax particles, and that micro-roughness can be realized when applied to the actual wood surface, to ensure that the coating effect over time lasts longer. In addition, it was confirmed that the addition of lignin increases the hydrogen-bond-based interaction with the wood of the coating, thereby providing better coating stability and increasing the durability of the coating solvent under friction. The carnauba wax/lignin paint developed in this way is eco-friendly because all components are made of wood-based raw materials and have an excellent affinity with wood surfaces. Therefore, it is expected to be applicable to the coating process of wood-plastic composites and timber composites.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.4A
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• pp.267-279
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• 2009

A numerical model that can simulate the nonlinear behavior of ultra high strength fiber reinforced concrete (UHSFRC) structures subjected to monotonic loading is introduced. The material properties of UHSFRC, such as compressive and tensile strength or elastic modulus, are different from normal strength reinforced concrete. The uniaxial compressive stress-strain relationship of UHSFRC is designed on the basis of experimental result, and the equivalent uniaxial stress-strain relationship is introduced for proper estimation of UHSFRC structures. The steel is uniformly distributed over the concrete matrix with particular orientation angle. In advance, this paper introduces a numerical model that can simulate the tension-stiffening behavior of tension part of the axial member on the basis of the bond-slip relationship. The reaction of steel fiber is considered for the numerical model after cracks of the concrete matrix with steel fibers are formed. Finally, the introduced numerical model is validated by comparison with test results for idealized UHSFRC beams.