• Applied Chemistry for Engineering
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• v.3 no.4
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• pp.639-648
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• 1992

For recycling cement hydrate(CH) as waterproofers for mortar and concrete or a filler for rubber & plastics, the cement hydrates were treated with stearic acid(SA). And the bonding characteristics and the water repellency of the CH-SA compounds were investigated by using FT-IR, TGA, SEM, XRD, and contact angle measuring apparatus. Water tightness of the remitars used CH-SA compounds was also tested. The results are summarized as follows : 1) If the cement hydrates are treated with over 2.0% of stearic acid, the CH-SA compounds show very strong water repellency. 2) The stearic acids are solidified on the surfaces of cement hydrate in calcium stearate and aluminium stearate. 3) If CH-SA compounds which is cement hydrate treated with 5~10% of stearic acid are used 3%~6% in remitar, water absorption ratio and water permeatility ratio of remitar are decreased in below 30% of those of the ordinary remitar.

• Bulletin of the Korean Chemical Society
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• v.27 no.10
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• pp.1587-1592
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• 2006

We report the preparation, structure and magnetic properties of a new pillared complex, copper(II) hydroxy-1,4-butanedisulfonate, $Cu_2(OH)_3(O_3SC_4H_8SO_3)_{1/2}$. The titled compound was obtained by anion exchange, using copper hydroxyl nitrate $(Cu_2(OH)_3NO_3)$ as the starting material. According to the XRD data, this compound exhibits a pillared layered structure with organic layers tilted between the copper hydroxide layers with a tilt angle of $21.8^{\circ}$. FTIR spectroscopy confirms total exchange of nitrate by the sulfonate and indicates that the sulfonate functions are linked to the copper(II) ions with each aliphatic chain bridging the adjacent hydroxide layers. According to the dc and ac magnetic measurements, the title compound is a metamagnet consisting of spin-canted antiferromagnetic layers, with a Neel temperature of 11.8 K.

• Journal of Fashion Business
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• v.7 no.2
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• pp.69-81
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• 2003

Among the various properties of textile fabrics, the moisture-related properties are important for the textile processes or the apparel comfort characteristics. Alkaline hydrolysis results in pitting on the surface of fibers and increases the amount of hydroxyl and carboxyl end groups of the PET molecules on the fiber surface. The purpose of this study is to investigate the moisture-related properties of PET fabrics treated with quaternary ammonium compound/alkaline solution. The wetting and wicking properties of the PET fabrics were measured using the following experiments: contact angle, surface free energy, work of adhesion, vertical wicking height, moisture regain, and frictional static voltage. It was concluded that by the alkaline hydrolysis process, surface hydrophilicity and reactivity were considerably improved especially at lower levels of weight loss% and that the pitting of the fiber surface resulted in at higher levels of weight loss% was disadvantageous in moisture-related properties of PET.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.05a
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• pp.15-17
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• 2001

A new possibility of our atmospheric cold plasma torch has been examined on the surface treatment of an air-exposed vulcanized rubber compound. The plasma treatment effect was evaluated by the bondability with another rubber compound using a polyurethane adhesive.

• Journal of the Microelectronics and Packaging Society
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• v.5 no.2
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• pp.37-48
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• 1998

The popcorn cracking phenomena in plastic IC packages during reflow soldering are investigated by considering the heat transfer and moisture diffusion through the epoxy molding compound(EMC) along with the mechanics of interface delamination. Heat transfer and moisture diffusion through EMC under die pad are analyzed by finite difference method (FDM)during the pre-conditioning and subsequent reflow soldiering pro-cess and the amounts of moisture mass and vapor pressure at delaminated die pad/ EMC interface are calculated as a function of the reflow soldering time. The energy release rate stress intensity factor and phase angle were obtained under various loading conditions which are thermal crack face vapor pressure and mixed loadings. It was shown that thermal loading was the main driving force for the crack propagation for small crack lengths but vapor pressure loading played more significant role as crack grew.

• Journal of the Korean Society of Industry Convergence
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• v.4 no.4
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• pp.395-401
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• 2001

The characteristics of heat transfer and pressure drop through tubes has been investigated experimentally for a compound heat transfer enhancement. The test tubes were spirally indented tubes with wire coil inserts which had a various combinations of pitch and helix angles. Pure water was used as working fluids for the experiments, Heat transfer coefficients and friction factors of the test tubes were evaluated from the values of measured temperatures, flow rates and pressure drops. An performance evaluation was performed to find an optimal combination of spirally indented tubes with wire coil inserts. When the helix angle of wire coil insert are $71^{\circ}-72^{\circ}$, the best heat transfer enhancement was shown. The friction factor was 9 - 13 times higher than those in smooth tubes, and the heat transfer was enhanced a maximum of 500%.

• Bulletin of the Korean Chemical Society
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• v.29 no.5
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• pp.963-968
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• 2008

For the [$Cr_2(H_2tmp)_2Cl_4$] compound, simplified models with two bridging methoxo ligands have been studied. The influence of the bridging Cr-O-Cr bond angles on the exchange coupling between metal atoms in the model compound has been analyzed by means of density functional calculations with the broken-symmetry approach. Coupling constant calculated for the full structure is in good agreement with the experimentally reported value, confirming the validity of the computational strategy used in this work to predict the exchange coupling in a family of related dinuclear Cr(III) compounds. The calculations indicate a good correlation between the calculated coupling constant and the sum of the squared energy gap of three pairs of metal $t_{2g}$ OMSOs with a limited variation of the Cr-O-Cr angle. The spin density distribution and the mechanism of magnetic coupling interactions are discussed.

• Transactions on Electrical and Electronic Materials
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• v.2 no.4
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• pp.7-10
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• 2001

A new possibility of our atmospheric cold plasma torch has been examined on the surface treatment of an air-exposed vulcanized rubber compound. The plasma treatment effect was evaluated by the bondability with another rubber compound using a polyurethane adhesive. The adhesion property was improved by the treatment with plasma containing oxygen radicals. The oxygen radical generation from the plasma was verified and its efficiency was found to be dependent on the cathode material.

• Bulletin of the Korean Chemical Society
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• v.17 no.8
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• pp.730-735
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• 1996

The layered perovskite oxide, KSr2Nb3O10, was synthesized. The interlayer potassium cations were readily exchanged by protons in hydrochloric acid solution to give the protonation compound, HSr2Nb3O10·0.5H2O. The intercalation compounds, [NH3(CH2)nNH3]xSr2Nb3O10, were also obtained by acid-base reactions between the protonation compound and organic bases, 1,n-alkyldiamines. The interlayer distances in the intercalation compounds were linearly increased with the increase of the number of carbon (Δc/Δn=1.05 Å) in 1,n-alkyldiamines. The intercalated alkyldiammonium ions formed a paraffin-like monolayer with average tilting angle (θ) of ca. 56°. The intercalation reactions occurred stoichiometrically. The thermal decomposition process of the intercalation compounds showed distinct three steps due to the desorption of hydrated water, the decomposition of organic moiety, and the decomposition of Sr-related compounds.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.8
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• pp.615-623
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• 2018

The probability density function(PDF) for the amplitude of the reflectivity of low-grazing-angle sea clutter has generally been modeled by a compound-Gaussian distribution, rather than by the Rayleigh distribution, owing to the intensity variation of each clutter patch over time. The texture component forming the reflectivity has been simulated by combining Gamma distribution and memory-less nonlinear transformation(MNLT). On the other hand, there is no typical method available that can be used to simulate the speckle component. We first review Watt's method, wherein the speckle is simulated starting from the Doppler spectrum of the received echoes that is modeled as having a Gaussian shape. Then, we introduce a newly proposed method. The proposed method simulates the speckle by manipulating a clutter covariance matrix through the Cholesky decomposition after minimizing the effect of adjacent clutter patches using an equalizer. The feasibility of the proposed method is validated through simulation, wherein the results from two methods are compared in terms of the Doppler spectrum and the correlation function.