• Korean Journal of Fisheries and Aquatic Sciences
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• v.10 no.4
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• pp.205-212
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• 1977

The properties of sea water in deep-sea are still quite poorly understood, even though those of the surface water have been sufficiently investigated. In this study, the specific conductance of sea water was measured under the circumstances : pressure of 1 to 2,000 bars and temperature 10 to $35^{\circ}C$ as well as over the concentration of 6.228 to 19.372 per mil chloronity. The specific conductance gave the linearity with the given pressure. The initial slope, ${\triangle}k/{\triangle}P$ of the specific conductance n versus the pressure P over the pressure 1 to 1,000 bars showed a large positive value, but the second slope over the pressure 1,000 to 2,000 bars was relatively less positive value. And our equations were comparable with the empirical formular obtained by Horns et al. (1963).

• Asian-Australasian Journal of Animal Sciences
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• v.12 no.8
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• pp.1273-1276
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• 1999

Several reports have indicated that a rectal temperature of buffaloes is easily influenced by their surroundings. To clarify an effect of changing environmental temperature on thermoregulatory responses of buffaloes, an environment with diurnal temperature changes of $25^{\circ}C$ to $35^{\circ}C$ was created using an artificial climate laboratory. Three swamp buffaloes and three Friesian cows were exposed to three different experimental periods as follows: Period 1 (constant temperature of $30^{\circ}C$, Period 2 (diurnally changing temperature) and Period 3 (diurnally changing temperature and fasting). Heat production, rectal temperature, respiration rate, heart rate and respiration volume were measured during each period. Rectal temperature of the buffaloes fluctuated diurnally with the changing temperature (Periods 2 and 3), but remained constant in cows. Mean heat production was significantly lower in buffaloes than in cows in Period 2 and 3. However, the maximum rectal temperature and the increment of heat production were not always lower in buffaloes than in cows during Period 2. These results show that a rectal temperature and heat production in buffaloes are markedly influenced by the diurnal changes in temperature. Compared with Bos Taurus cows, the differences may be attributed to the physiological features of buffaloes including a high heat conductivity of their bodies and an lower heat production.

• Journal of Powder Materials
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• v.18 no.6
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• pp.568-574
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• 2011

As operating temperatures of engines or turbines continually increase for higher efficiency, significant amounts of researches have been focused on finding new materials, which would be alternatives to conventional yttria-stabilized zirconia (YSZ) for thermal barrier coatings (TBCs). In this study, phase evolution and thermo-physical properties of $La_2(Zr_{1-x}Hf_x)_2O_7$ pyrochlore systems are investigated for TBC applications. $La_2(Zr_{1-x}Hf_x)_2O_7$ systems are comprised by selecting $La^{3+}$ as A-site ions and $Zr^{4+}/Hf^{4+}$ as B-site ions in $A_2B_2O_7$ pyrochlore structures. For the developed phases in $La_2(Zr_{1-x}Hf_x)_2O_7$ compositions, thermo-physical properties such as thermal conductivity, thermal expansion coefficient are examined. The potential of these $La_2(Zr_{1-x}Hf_x)_2O_7$ compositions for TBC application is also discussed.

• Journal of Korean Ophthalmic Optics Society
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• v.6 no.2
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• pp.23-29
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• 2001

In the SP series of glasses, the formation of droplet is well done with increasing PbO. But in the case SP-1, droplet could not be observed in low concentration PbO. These results are considered that PbO does the role of a network modifier, so the crosslinking break down by $SiO_2$. But, in the glasses contained PbO above 50 mol%, glasses are formeddue to $Pb^{4+}$ ion does the role of a network former. As a result of electrical conductivity analysis for SP series of glasses, the electrical conduction is due to bipolaron at high temperature, and it is due to single polaron hopping at low temperature. In the SP series of glasses, electrical conduction mechanism coincide with the correlated-barrier hopping(CBH) model.

• Ocean and Polar Research
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• v.26 no.2
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• pp.299-309
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• 2004

Conductivity-temperature-depth (CTD) data obtained along a meridional section in the eastern tropical Pacific in July 2003 have been analyzed to identify various water masses, and to examine the hydrographic structure and zonal geostrophic currents in the upper 1000 m. Water mass analysis shows the existence of subtropical and intermediate waters, characterized by layers of subsurface salinity maximum and minimum, originating from both hemispheres of the Pacific. Vertical section of temperature in the upper 200 m shows the typical trough-ridge structure associated with the zonal current system for most of the tropical Pacific. Water with the lowest salinity of less than 33.6 was found in the upper 30 m between $8.5^{\circ}N$ and $10.5^{\circ}N$ in a boundary zone between the North Equatorial Current and North Equatorial Countercurrent. Temporal changes in water properties observed at $10.5^{\circ}N$ over a period of 9 days suggest both the local rainfall and horizontal advection is responsible for the presence of the low-salinity water. Development of a barrier layer was also observed at $10.5^{\circ}N$. In the North Equatorial Current region a local upwelling was observed at $15^{\circ}N$, which brings high salinity and cooler subtropical water to the sea surface. A band of countercurrent occurs in the upwelling region between $13^{\circ}N$ and $15^{\circ}N$.

• Korean Chemical Engineering Research
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• v.48 no.3
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• pp.292-299
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• 2010

Graphene is a two-dimensional nanosheet consisting of honeycomb lattices of $sp^2$ carbon atoms. It is one of promising active materials for the anode of lithium-ion battery and the electrode of supercapacitor, due to its large specific surface area(theoretically $2600m^2\;g^{-1}$), high electric conductivity(typically $8{\times}10^5S\;cm^{-1}$), and mechanical strength. In this review, the synthetic methods of graphene nanosheet and graphene-based nanocomposite are introduced. Also, the electrochemical properties obtainable when the graphene-based materials are adopted to the electrodes of lithium-ion battery and supercapacitor are discussed along with their nanostructures.

• Korean Journal of Materials Research
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• v.20 no.9
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• pp.472-477
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• 2010

$Al_2O_3$ has received wide attention with established use as a catalyst and growing application in structural or functional ceramic materials. On the other hand, the boehmite (AlO(OH)) obtained by sol-gel process has exhibited a decrease in surface area during phase transformation due to a decline in surface active site at high temperature. In this work, $Al_2O_3$-CuO/ZnO (ACZ) and $Al_2O_3$-CuO/CeO (ACC) composite materials were synthesized with aluminum isopropoxide, copper (II) nitrate hemi (pentahydrate), and cerium (III) nitrate hexahydrate or zinc (II) nitrate hexahydrate. Moreover, the Span 80 as the template block copolymer was added to the ACZ/ACC composition to make nano size particles and to keep increasing the surface area. The ACZ/ACC synthesized powders were characterized by Thermogravimetry-Differential Thermal analysis (TG/DTA), X-ray Diffractometer (XRD), Field-Emmision Scanning Electron Microscope (FE-SEM), Bruner-Emmett-Teller (BET) surface analysis and thermal electrical conductivity (ZEM-2:M8/L). An enhancement of surface area with the addition to Span 80 surfactant was observed in the ACZ powders from 105 $m^2$/g to 142 $m^2$/g, and the ACC powders from 103 $m^2$/g to 140 $m^2$/g, respectively.

• Polymer(Korea)
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• v.31 no.6
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• pp.543-549
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• 2007

We synthesized various polyurethanes(PU) haying different hard segments with different molecular weights of the soft segment to explore the effect of structure on the dispersion of silver particle in the phase of synthesized polyurethanes matrix. The thermal stability was increased by increasing the number of aromatic compound, while the degree of dispersion for silver particle was decreased. Silver particles showed better dispersion in the PU matrix having aromatic compounds when the soft segments were held constant. On the contrary, when the hard segment was held constant, silver particles on the PU matrix haying low $M_w$ of soft segment showed better dispersion than high $M_w$ of soft segment because poor chain mobility of low $M_w$ of soft segment restricted re-aggregation of silver particle. A sheet resistance of composite materials showed different aspects. In this case, the inter connection between silver particles was more important than its dispersion. In this study, the NDI-PEG 900/silver particle composite film showed the best thermal stability and electro conductivity.

• Polymer(Korea)
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• v.34 no.5
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• pp.424-429
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• 2010

The hybrid composites of aliphatic polyester-silica were prepared via a sol-gel reaction and their potential application using as a buffer coating layer in the thermoelectric device were investigated. When aliphatic polyesters were thermally treated at a high temperature of $240^{\circ}C$, the polymer showed an increases in thermal degradation temperature by $30{\sim}90^{\circ}C$ according to the thermal treatment time. The polyester-silica composites showed an increases in thermal degradation temperature by $30{\sim}50^{\circ}C$ according to the content of the added silica. Polyester-silica composite showed neither discoloration nor change in optical properties because Knoevenagel condensation reaction was hindered by silica structure. The thermal conductivity of the composites increased linearly according to the content of added silica.

• Polymer(Korea)
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• v.38 no.4
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• pp.502-509
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• 2014

Carbon-based nanoplatelets such as graphene oxide (GO) sheets and graphite nanoplatelets (GNPs) are frequently used as conductive nanofillers for polymer nanocomposites. In this study, polystyrene (PS)/GO and PS/GNP nanocomposites were prepared through a latex technology and investigated to compare the effect of nanofillers on rheological and electrical properties of the PS nanocomposites. PS particles were prepared by emulsifier-free emulsion polymerization and GO was synthesized by using the modified Hummers' method from graphite. Hydrophilic GO was dispersed in aqueous PS suspension, but hydrophobic GNPs were dispersed with the help of a surfactant. In comparison with PS/GO nanocomposites, the rheological properties of PS/GNP counterparts were not too high because GNP existed in aggregates of graphene layers. Conducting pathways of PS/GO and PS/GNP nanocomposites were achieved at the electrical percolation threshold of 0.50 and 5.82 wt%, respectively. The reason for enhanced electrical conductivity in PS/GO nanocomposites is that GO was thermally reduced during molding.