• Polymer(Korea)
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• 제26권6호
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• pp.759-766
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• 2002

Regular, spherical and isotropic open-microcellular foams having low density were prepared by the high internal phase emulsion (HIPE) polymerization mainly composed of styrene monomer and water The effects of Polymerization conditions. such as the content of water, divinylbenzene as a crosslinking agent and dodecane as a chain transfer agent, were investigated based on the tell size and foam properties. The microstructural morphology was observed using scanning electron microscopy (SEM) and the compression modulus of the foam was evaluated using compression test. The dropwise feeding of the aqueous phase into the oil phase was more effective than the batch feeding in producing the uniform and stable foam. Agitation speed and surfactant strongly influenced on the cell size and the window size between water droplets. Introduction of chain transfer agent increased the cell size, whereas it decreased the window size. Compression modulus increased with the crosslinking agent, but decreased with the chain transfer agent.

• Journal of the Korean Applied Science and Technology
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• 제36권3호
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• pp.813-820
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• 2019

The influence of cholesterol on the physicochemical properties of the oleic acid was clarified through the measurements of density, viscosity, IR, $^1H$ NMR, self-diffusion coefficient for the oleic acid samples containing a small amount of additives such as cholesterol, cholestanol, cholestane, cholesteryl oleate, benzene, and ethanol. Cholesterol, possessing one OH group and one double bond in its molecular structure, largely increased the viscosity and reduced the self-diffusion coefficient and the intramolecular movement of oleic acid. Oleic acid forms a complex with cholesterol as well as with ethanol. On the basis of these complex formations and the existence of the clusters composed of oleic acid dimers, it was known the role and the fundamental mechanism of cholesterol to the intermolercular and intramolecular movements of oleic acid in the liquid state.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• 제23권6호
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• pp.691-699
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• 2012

In this paper, we present a Vt-DRO with a low phase noise, which is achieved by improving the coupling structure between the dielectric resonator and microstrip line. The Vt-DRO is a closed-loop type and is composed of 3 blocks; dielectric resonator, phase shifter, and amplifier. We propose a mathematical estimation method of phase noise, using the group delay of the resonator. By modifying the coupling structure between the dielectric resonator and microstrip line, we achieved a group delay of 53 nsec. For convenience of measurement, wafer probes were inserted at each stage to measure the S-parameters of each block. The measured S-parameter of the Vt-DRO satisfies the open-loop oscillation condition. The Vt-DRO was implemented by connecting the input and output of the designed open-loop to form a closed-loop. As a result, the phase noise of the Vt-DRO was measured as -132.7 dBc/Hz(@ 100 kHz offset frequency), which approximates the predicted result at the center frequency of 5.3 GHz. The tuning-range of the Vt-DRO is about 5 MHz for tuning voltage of 0~10 V and the power is 4.5 dBm. PFTN-FOM is -31 dBm.

• Journal of the Korean Chemical Society
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• 제55권2호
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• pp.199-203
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• 2011

The title one-dimensional hydrogen-bonded coordination compound $[Cu^{II}(C_{13}H_{17}N_3OBr)(C_8H_5O_4)]{\cdot}2H_2O.CH_3OH$ has been synthesized and characterized by single crystal X-ray diffraction study. The monomeric unit contains a square-planar $Cu^{II}$ centre. The four coordination sites are occupied by a tridentate anionic Schiff base ligand (4-bromo-2-[(2-piperazin-1-yl-ethylimino)-methyl]-phenol) which furnishes an $N_2O$-donor set, with the fourth position being occupied by the oxygen atom of an adjacent terephthalate unit. Two adjacent neutral molecules are linked through intermolecular N-H---O and O-H---N hydrogen bonds and generate a dimeric pair. Each dimeric pair is connected with each other via discrete water and methanol molecules by hydrogen bonding to form a one-dimensional supramolecular network.

• KSBB Journal
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• 제19권6호
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• pp.489-493
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• 2004

The hydrolysis characteristics of various fatty acids composing the fish oil was investigated for function of acyl chain specificities using Lipase-OF 360,000 from Candida cylindracea. The hydrolysis of fatty acids decreased with the increase of the number of carbon and double bond in the fatty acids, in case that the number of double bond and the position of the first double bond from the methyl group of fatty acids were the same. The position of the first double bond was found to be an acyl chain specificity of Lipase-OF 360,000 for the hydrolysis of fish oil. Lipase-OF 360,000 also showed the another acyl chain specificity that the increase of double bond of fatty acids, having the same number of carbon and the position of double bond, brought about the decrease of hydrolysis.

• Resources Recycling
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• 제23권4호
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• pp.37-46
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• 2014

Carbon dioxide generated from construction materials and construction material industry among the fields of construction is approximately 67 million tons. It is about 30% of the carbon dioxide generated in the fields of construction. In order to reduce carbon dioxide in the fields of construction, it is necessary to control the use of fossil fuel consumed and decrease carbon emission by reducing the secondary and tertiary curing generating carbon dioxide in construction material industry. Therefore, this study manufactured mortar by having cement as the Plain and substituting three binding materials up to 50% and then adopted different curing methods to analyze congelation and strength characteristics. Test results for strength property by changing binding materials showed that specimens with blast furnace slag, CSA 15% and CAMC 5% resulted in positive effect for strength.

• The Korean Journal of Pharmacology
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• 제23권2호
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• pp.101-111
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• 1987

We investigated the binding properties of $(^3H)$ QNB and $(^3H)$ NMS to mAchR to elucidate the characterstics of mAchR in rat brain by using two different preparations (homogemates & intact brain cell aggregates). The binding properties of both ligands demonstrated high affinity and saturability in both experiments, however $(^3H)$ QNB showed a significantly higher maximal binding capacity than tha ot $(^3H)$ NMS 1. In rat brain homogenates; Displacement of both lignands with several mAchR antagonists resulted in competition curves in accoradnce with the law of massaction for QNB, atropine & scopolamine in thie preparation, also a similar profile was found for the quaternary ammonium analogs of atropine & scopolamine (methyl atropine & methylscopolamine) when $(^3H)$ NMS was used to label the receptors in rat brain. But when these hydrophillic antagonists were used to displace $(^3H)$ QNB, they showed interaction with high- and low-affinity binding sites in brain homogenates. Pirenzepine, the nonclassical mAchR antagonist, was able to displace both ligands from binding sites in this preparation. 2. In intact rat brain cell aggregates; Intact bain cell aggregates were used to elucidate the binding characteristics of $(^3H)$ NMS to mAchR in rat. The magnitude of binding of this ligand was related linearly to the amount of cell protein in the binding assay with a high ratio of total to nonspecific binding. mAchR antagonists displaced specific $(^3H)$ NMS binding according to the law of mass-action, while it was possible to resolve displacement curves using mAchR agonist into high-& low-affinity component. 3. Our results indicate that more hydrophilic receptor ligand $(^3H)$ QNB, displacement experiments in both tissues demonstrated that the lipid solubility of a particulr mAchR ligand might play an important role in determining its profile of binding to the mAchR, and the concentrations of mAchR in rat brain are both on the cell surface (membrane-bound receptor) and in the intracelluar membrane (intermembrane-bound receptor). 4. The results are discussed in terms of the usefulness of dissociated intact rat brain cells in studying mAchR in central nervous system.

• Tunnel and Underground Space
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• 제22권2호
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• pp.157-161
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• 2012

ZnO-98% and $Ga_2O_3$-2% powder were consolidated by shock compaction technique, which uses a high performance explosive. The microstructural and electrical characteristics of $ZnOGa_2O_3$ compact with density of 97% and hardness of 220~250 $H_v$ were investigated using SEM (Scanning Electron Microscope) and X-ray diffraction analysis, respectively. In the microstructures of the compact, there were no visible cracks at most of the surface areas, and interparticle bonding between powder particles was confirmed. The broadened peaks were detected due to deformation of crystallited size and high electric resistances were confirmed due to increased grains because of shock energy with a high pressure and high velocity.

• Journal of the Korean Chemical Society
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• 제39권5호
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• pp.338-343
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• 1995

The electronic structure of photoskinsensitizing 8-azapsoralen and 4,4',5'-trimethyl-8-azapsoralen has been investigated by the semiempirical (PM3-CI-UHF, etc) methods. The formation of molecular complexes between ground thymine and excited azapsoralen is discussed in terms of charge transfer interaction. The results indicated that the most probable orientation through C4-cycloaddition of 3,4-double bond of azapsoralen and 5,6-double bond of thymine bases, expecially photoadducts were inferred to be a trans-anti azapsoralen(3,4) < > Thymine(5,6) and trans-anti 4,4',5'-trimethyl-8-azapsoralen (3,4) < > Thymine(5,6).

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• 제19권7호
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• pp.713-718
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• 2008

A modified broad-band ring hybrid balun with additional two shorted $\lambda$/4 stubs is proposed. The proposed balun is a modified version which has additional two shorted $\lambda$/4 stubs to compensate phase and amplitude imbalances of conventional ring hybrid coupler. To demonstrate the validity of the proposed balun, a balanced Schottky-diode frequency doubler is designed and measured. Measurement data show that the proposed frequency doubler has around 10 dB conversion loss and more than 30 dB fundamental suppression over an input range of $1.6{\sim}2.35\;GHz$.