• Applied Chemistry for Engineering
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• v.21 no.3
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• pp.317-322
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• 2010

In this study, poly(methyl methacrylate) (PMMA) was treated with changing mixing ratios of $F_2$ and $O_2$ using oxyfluorination method for hydrophilic modification of PMMA film. For the characterizations of oxyfluorinated PMMA surface, contact angle, surface free energy, X-ray photoelectron spectroscopy (XPS) and optical transmittance (UV-vis) were carried out. After the oxyfluorination, PMMA surface became more hydrophilic showing the decrease of water contact angle from $69^{\circ}$ to $44^{\circ}$. So, surface free energy of oxyfluorinated PMMA film was increased from 46 to $58\;mN\;m^{-1}$. These results are attributed to hydrophilic functional groups such as hydroxyl group formed oxyfluorination method on the PMMA surface. From XPS results, it was confirmed that O/C concentration ratio on the surface of PMMA was increased, the amount of C-OH bonding which shows hydrophilicity was also largely increased from 6.7 to 24.8% with increasing fluorine partial-pressure via the oxyfluorination, The oxyfluorination conditions, room temperature, 1 bar with one mixture ratio of $F_2$ to $O_2$ had little influence on optical transmittance properties of PMMA film but enhanced its surface hydrophilicity. This result suggests that oxyfluorination method could be useful to change hydrophobic PMMA surface to hydrophilic.

• Journal of the Korean Society for Marine Environment & Energy
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• v.12 no.3
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• pp.151-156
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• 2009

The purpose of this study is to evaluate the affecting factors on Oil-Mineral Aggregates(OMA) for stranded oil on intertidal flat, because the OMA formation enhances the oil dispersion and biodegradation rates. We choose the affecting factors such as spilled oil concentrations(50, 100, 200, 300, 400, 500 mg/L), mineral concentration(100, 200, 500, 1,000, 2,000, 4,000 mg/L), salinity(10, 20, 30, 40 psu), shaking time(1, 2, 4, 8, 12, 24 hr) and applied dispersant volume(0, 5, 10, 15, 20%). Major conclusions derived from this study are as follows. It was observed that the kaolinite interacts three times strongly with crude oil than quartz. OMA formation was enhanced with increasing of spilled oil concentrations, whereas the increase of salinity rarely affected the OMA formation. The shaking time for OMA formation affected positively with kaolinite, but quartz was irrespective the shaking time. The applied dispersant enhanced the OMA formation by 13% in kaolinite and 56% in quartz experimental condition.

• Journal of Energy Engineering
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• v.24 no.4
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• pp.124-129
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• 2015

An experimental study was performed estimating COP(Coefficient of Performance) of air-conditioning cycle using inverter scroll compressor with and without $Al_2O_3$ nano particle. All experiments were done for various compressor speeds from 1000~4000 rpm and used the inverter controller called CANDY to change the compressor rpm. The air-conditioning cycle components in the apparatus were used as same with components of YF hybrid car. To estimate the COP, this study measured the temperature and pressure at inlets and outlets of compressor, condenser, and evaporator. And also measured the compressor input power using Powermeter. Through the experiments, the maximum error to estimate COP was shown about ${\pm}6.09%$ at 3500rpm. The COP of refrigeration cycle with $Al_2O_3$ nano-particle was similar with that of the base cycle without nano-particle between 1000~3000 rpm of the compressor speed. But, This study showed that the COP of the cycle with $Al_2O_3$ over 3000 rpm of the compressor speed was higher than that of the base cycle due to the higher heat transfer rate increased in the evaporator from the higher oil flow rate inside the cycle as well known. Those results can be used the basic and fundamental data to design the air-conditioning cycle using inverter scroll compressor with $Al_2O_3$ nano particle.

• Journal of Radiation Protection and Research
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• v.39 no.4
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• pp.159-167
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• 2014

In Korea, July 2012, the law as called 'Act on Safety Control of Radioactive Rays Around Living Environment' was implemented to control the consumer product containing Naturally Occurring Radioactive Material (NORM), but, there are no appropriate database and effective dose calculation system. The aim of this study was to develop evaluation technique of the exposure dose with the use of the consumer products containing NORM and to understand the characteristics of the exposed dose according to the radiation type and energy. For the evaluate of exposure dose, the ICRP reference phantom was simulated by the MCNPX code based on Monte Carlo method, and the minimum, medium, maximum energy of alphas, betas, gammas from the representative NORM of Uranium decay series were used as the source term in the simulation. The annual effective doses were calculated by the exposure scenario of the consumer product usage time and position. Short range of the alpha and beta rays are mostly delivered the dose to the skin. On the other hand, the gamma rays mostly delivered the similar dose to all of the organs. The results of the annual effective dose with $1Bq{\cdot}g^{-1}$ radioactive stone-bed and 10% radioactive concentration were employed with the usage time of 7 hours 50 minute per day, the maximum annual effective dose of alphas, betas, gammas were calculated 0.0222, 0.0836, $0.0101mSv{\cdot}y^{-1}$, respectively.

• Korean journal of applied entomology
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• v.29 no.1
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• pp.31-42
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• 1990

Storage ecosystems of rough rice, brown rice and polished rice were analyzed form Feb. 1987 to Nov. 1988 to investigate structures and ecological successions in the arthropod communities as well as changes in energy of the systems. The changes in temperature of stored rice showed high degree dependence on the temperature of storage room with time lag of about four weeks. Moisture content of rough rice, brown rice and polished rice during the period were in the range of 12.7$\pm$0.4, 13.1$\pm$0.4 and 13.5$\pm$0.3%, respectively. The arthropod communities in rough rice, brown rice and polished rice were qualitatively and quantitatively different. In rough rice, dominant species changed from Leptinotus reticulatus Endlein to Liposcelisentomophilus Endlein, while in brown rice from Pyralis farinalis L. to Sitophilus oryze (L.), unidentified parasitic wasps, Anisopteromalus calandrae Howard and Tribolium castaneum Herbst and finally to S. oryzae. In polished rice, the arthropod community showed an ecological succession similar to that in brown rice except for a transient dominance of two psocidspecies. Thearthropod community in rough rice was rather simple and unstable in comparison with those in brown rice and polished rice. The 1000 kernel weight of brown rice decreased slightly during the period when the arthropods were active (summer season), while that of rough rice and polished rice remained at the similar level. However, the ash content per unit volume of brown rice as well as rough rice and polished rice showed no increase during the period.

• Journal of the Korean Ceramic Society
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• v.41 no.11
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• pp.858-863
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• 2004

The thermoelectric power, dc conductivity and magnetic properties of the cubic L $a_{2}$ 3/Ti $O_{2.84}$ were investigated. The thermoelectric power was negative below 350 K. The measured thermoelectric power of L $a_{2}$ 3/Ti $O_{2.84}$ increased linearly with temperature, in agreement with model proposed by Emin and Wood, and was represented by A+BT. Temperature dependence indicates that the charge carrier in this material is a small polaron. L $a_{2}$ 3/Ti $O_{2.84}$ exhibited a cross over from variable range hopping to small polaron hopping conduction at a characteristic temperature well below room temperature. The low temperature do conduction mechanism in L $a_{2}$ 3/Ti $O_{2.84}$ was analyzed using Mott's approach. Mott parameter analysis gave values for the density of state at Fermi level [N( $E_{F}$)] = 3.18${\times}$10$^{20}$ c $m^{-3}$ e $V^{-1}$ . The disorder energy ( $W_{d}$) was found to be 0.93 eV, However, it was noted that the value of the disorder energy was much higher than the high temperature activation energy. The exist linear relation between log($\sigma$T)와 1/T in the range of 200 to 300 K, the activation energy for small polaron hopping was 0.15 eV.

• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.2
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• pp.41-54
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• 1999

Because of relatively heavy dead weight of concrete itself and unavoidable heat of massive concrete in bridge piers, circular hollow columns are widely used in Korean highway bridges. Since the occurrence of 1995 Kobe earthquake, there have been much concerns about seismic design for various infrastructures, inclusive of bridge structures. It is, however, understood that there are not much research works for nonlinear behavior of circular hollow columns subjected to eqrthquake motions. The objective of this experimental research is to investigate nonlinear behavior of circular hollow reinforced concrete bridge piers under the quasi-static cyclic load, and then to enhance their ductility by strengthening the plastic hinge region with glassfiber sheets. Particularly for this test, constant 10 cyclic loads have been repeatedly actuated to investigate the magnitude of strength degradation for the displacement ductility factor. Important test parameters are seismic design, confinement steel ratio, axial force and load pattern. It is observed from quasi-static tests for 7 bridge piers that the seismically designed columns and the retrofitted columns show better performance than the nonseismically designed colums, i.e. about 20% higher for energy dissipation capacity and about 70% higher for curvatures.

• Journal of the Korean Society for Marine Environment & Energy
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• v.9 no.4
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• pp.225-234
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• 2006

Using the data from the sea water monitoring system installed at the Ieodo Ocean Research Station, we have analyzed the water properties around the station as well as the characteristics of the fresh water from the Changjiang River and the influence of typhoons on the sea water. In general, the accuracy and stability of the temperature data are high, but those of the salinity data are worse than the specification of the instruments. The daily variation of temperature and salinity is mainly controlled by the vertical motion of a water column due to semi-diurnal tide and diurnal change in the solar insolation. Seasonal change is prominent in temperature data. The freshwater from the Changjiang River is the main cause of large salinity variation. In August 2003 and August 2004, about 10 days before fresh water was observed near the Jeju Island, low salinity water was observed at the Ieodo Station. On the other hand, in July 2005 fresh water was observed at the station but not at around the Jeju Island. In other words, the fresh water observed at the Ieodo Station does not always expand to the Jeju Island. Two strong typhoons passed by the station in September 2003 and August 2004. The effects of the typhoons were lasted for 3 to 4 days.

• Solar Energy
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• v.11 no.2
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• pp.41-50
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• 1991

Heat transfer phenomena and temperature characteristics in heat storage and release process in the heat storage system using PCM(Phase Change material) were studied experimentally. The melting points of Octacosane paraffin($C_{28}H_{58}$) and sodium pyrophosphate decahydrate ($Na_4P_2O_7{\cdot}10H_2O$) used for phase change materials are $62^{\circ}C$ and $79^{\circ}C$ respectively. Experiments were performed in order to investigate temperature distributions, the heat storage quantity and the release quantity on octacosane paraffin and sodium pyrophosphate decahydrate for heat storage and release in the heat storage system. Furthermore the comparison of these characteristics between paraffin and $Na_4P_2O_7{\cdot}10H_2O$ were evaluated. In case of the paraffin, temperature slowly increased at early heat storage process by natural convection, while temperature of $Na_4P_2O_7{\cdot}10H_2O$ rapidly increased the dominant role played by conduction at early heat storage processing Also, during the heat storage and release process in case of the paraffin, it was observed that the variation of temperature of the neighborhood of wall and center in the top and bottom of the tube exhibited a great difference, however in $Na_4P_2O_7{\cdot}10H_2O$, it was observed that the variation of temperature exhibited a little difference. And heat storage quantity of each PCM of identity mass in heat storage process was shown that $Na_4P_2O_7{\cdot}10H_2O$ exhibited more by 16 percents than paraffin.

• Solar Energy
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• v.13 no.1
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• pp.11-21
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• 1993

The purpose of this study was to investigate the enhancement of heat transfer without additional external power in the case of rectangular impingement air jet vertically on the flat heating surface. The technique used in the present study was placement of square rod bundles as a turbulence promoter in front of the heat transfer surface. The results obtained through this study were summerized as follws. High heat transfer enhancement was achieved by inserting rods in front of the heating flat plate. According to visulaization, it was examined because of flow acceleration and separation and disturbance of boundary layer. The smaller clerance between rod and heating plate was, the larger heat transfer effect became at each H/B. Arverage Nusselt number reached maximum at H/B=10 and the local augmentation rate of heat transfer became maximum at H/B=2. The maximum average heat transfer enhancement rate increase about 43% for the case of X/B=2 and C=1mm, compared to a flat plate without rods. The correlating equation of average Nusselt number and Reynolds number was obatined. As follws : ${\overline{Nu}}_0=1.249Re^{0.465}(C/A)^{-0.033}(H/B)^{0.013}$.