• Journal of the Korean Wood Science and Technology
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• v.23 no.4
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• pp.46-53
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• 1995

The anatomy of Korean diffuse-porous woods, 36 families, 75 genera, 145 species, 215 specimens was described and analyzed. Sixteen wood anatomical characters, habit and phenology factors were determined by simple correlation and principal component analysis. Strong positive correlations were found between vessel element length and fiber length, ray width and ray height, simple pits of fiber wall and paratracheal parenchyma distribution. The results of principal component analysis (PCA) disclose the primitive characteristics and the direction of xylem evolution of Korean diffuse-porous woods. The xylem evolution scenario for Korean dicotyledonous woods is considered to be developed in the direction of decreasing trends of vessel frequency, vessel element length, and length/diameter(L/D) ratio of vessel element but increasing trends of vessel diameter, fiber length/vessel element length(F/V) ratio, libriform wood fibers, simple perforation, and homogeneous ray composition. Increase of vessel diameter and decrease of vessel frequency seem to be related to the improvement of conductive efficiency, and increase of the vessel element length and occurrence of scalariform perforation in vessel element may be related to enhanced of conductive safety. Also the libriform wood fibers and ray features appear to have relationship with mechanical support and nutrient metabolism, respectively.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.9 s.102
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• pp.1077-1083
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• 2005

Electro-Active Paper (EAPap) is one of attractive electro-active polymer (EAP) materials for artificial muscles due to its many advantages such as light weight, biologically degradable, low cost, large displacement output, low actuation voltage and low power consumption. However, drawbacks of EAPap actuators include low force output and humidity dependence. To enhance the performance of EAPap, conductive polymer (PPy) and SWNT/conductive polymer (PANI) are coated on EAPap PPy as conductive polymer is coated on cellulose EAPap by means of electrochemical deposition. Two different dopants are used in PPy through conducting polymer processing. SWNTS are mixed with PANI in emeraldine base along with different dopants. The compound materials are coated on cellulose EAPap using spin coating system. The performance of PPy/EAPap and SWNT/PANI/EAPap are evaluated in terms of bending displacement, blocked force, and the effects of dopants, humidity, coaling time, voltage and frequency are investigated. Comparing with EAPap actuators, SWNT/PANI/EAPap actuators show $200\%$ improvement of bending displacement and $300\%$ increment of blocked force.

• Nuclear Engineering and Technology
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• v.51 no.7
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• pp.1853-1859
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• 2019

The two-thermocouple method was investigated experimentally to evaluate its accuracy for the measurement of local wall temperature and heat flux on a heat transfer tube with an electric heater rod installed in an annulus channel. This work revealed that a thermocouple flush-mounted in a surface groove serves as a good reference method for the accurate measurement of the wall temperature, whereas two thermocouples installed at different depths in the tube wall yield large bias errors in the calculation of local heat flux and wall temperature. These errors result from conductive and convective changes due to the fin effect of the thermocouple sheath. To eliminate the bias errors, we proposed a calibration method based on both the local heat flux and Reynolds number of the cooling water. The calibration method was validated with the measurement of local heat flux and wall temperature against experimental data obtained for single-phase convection and two-phase condensation flows inside the tube. In the manuscript, Section 1 introduces the importance of local heat flux and wall temperature measurement, Section 2 explains the experimental setup, and Section 3 provides the measured data, causes of measurement errors, and the developed calibration method.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.16 no.2
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• pp.194-203
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• 1987

A numerical study has been conducted on the combined radiation-natural convection heat transfer characteristics in a square cavity with a selectively transparent wall. The fluid in the cavity is assumed to be transparent to the thermal radiation. The effect of the wall emissivity is mainly considered in view of the temperature and flow fields. The comparison of the radiative heat flux and conductive heat flux variations along the isothermal wall is presented as well. The results show that the Nusselt number distribution is fairly uniform due to the com-pensative interaction of the radiation and convection heat transfer.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.06a
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• pp.677-678
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• 2007

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08b
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• pp.1257-1260
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• 2007

A single-wall carbon nanotube (SWNT) transparent conductive film (TCF) was fabricated using a simple inkjet printing method. The TCF could be selectively patterned by controlling the dot size to diameters as small as $34\;{\mu}m$. In this repeatable and scalable process, we achieved 71% film transmittance and a resistance of 900 ohm/sq sheet with an excellent uniformity, about ${\pm}\;5%$ deviation overall. Inkjet printing of SWNT is substrate friendly and the TCF is printed on a flexible substrate. This method of fabrication using direct printing permits mass production of TCF in a large area process, reducing processing steps and yielding low-cost TCF fabrications on a designated area using simple printing.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.10 no.1
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• pp.1-11
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• 1981

In this paper, a new performance equation of bath tubs has been derived, which is very characteristically illuminating and in good agreement with experiments : $$T=T_{\infty}+(T_0-T_{\infty})e-\frac{k(A'_f+A_0)}{Mc_{P{\Delta}x}t$$, where $T_{\infty}$ is the temperature of the bathroom, $T_0$ that of the bathwater at t=0, k the overall heat conductivity of the tub- wall, $A'_f$ the equivalent surface area to the wall, $A_0$ the submerged area of the tub-wall, M mass of the bath-water, $C_p$ the specific heat of the bathwater and ${\Delta}x$ the thickness of the tub-wall. Here the equivalent-free surface area is written as $$A'_f=mA_f,\;m=const.(1-{\phi})^{0.88}$$ : where m is a numerical factor which is determined by a simple experiment and some calculation, {\phi}$ the relative humidity and $A_f$ the real free-surface area. From this study, it has been clarified that cooling of bath-water is mainly due to mass-transfer through evaporation from the free surface and conductive heat loss through the tub-wall is minor, which rather gaily mock at common sense. The effect of keeping bathwater warn by increase of the tub-wall thickness is also analyzed by a new idea of the thickness gain factor.

• Journal of Sensor Science and Technology
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• v.14 no.6
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• pp.374-380
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• 2005

Vibration sensors have a wide scope of applications in the field of monitoring systems that needs to perceive an undesirable physical vibration before a critical failure occurs in a system, and then costly unplanned repairs can be avoided. The conventional vibration sensors developed so far have many disadvantages, such as complex manufacturing process, bulkiness, high cost, less reliability and so on. This paper reports a simple-structured vibration sensor, which has been developed using a commercialized conductive ball and silicon bulk-micromachining technology. The sensor consists of a conductive ball placed in $600{\mu}m$-deep micromachined silicon groove, in which Au thin film has been patterned using a shadow mask technique. Prior to the formation of the Au thin film, the sharp convex corner was rounded for smooth meatl deposition on the non-planar surface at the edge of the groove. The measurement results of the fabricated vibration sensor demonstrate a stable response characteristic to low-frequency vibration range ($1{\sim}30{\;}Hz$).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.205-206
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• 2008

The transparent conductive film was prepared by bar coating method of poly (3, 4-ethylenedioxythiophene) (PEDOT) and poly (sodium 4-stylenesulfonate) grafted multi-walled carbon nanotubes (MWNT-PSS) nanocomposites solution on the polyethylene terephthalate (PET) film. In this case, multi-wall carbon nanotubes was treated by chemical methods to obtain water soluble MWNT-PSS and then blending with PEDOT. The non-covalent bonding of polymer to the MWNT surface was confirmed by Fourier transform infrared (FT-IR), thermal gravimetric analysis (TGA) and Transmission electro microscope (TEM) investigation also showed a polymer-wrapped MWNT structure. Furthermore, the electrical, transmission properties of the transparent conductive film were investigated and compared with control samples are raw PEDOT films.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.10a
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• pp.20-21
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• 2016

In this study, the shielding properties of concrete with conductive materials as shielding material for electromagne- tic pulse(EMP) within 10kHz~18GHz were investigated. The shielding effectiveness of specimens were compared with different entrained materials. The shielding effectiveness were determined according to MIL-STD-188-125-1, IEEE-STD-299 at 28 days of concrete curing. The results of shielding effectiveness did not meet the criteria(80dB) severely.