• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.2
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• pp.191-199
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• 2005

Double pane window system, in which an air layer with a finite width is filled between glasses, is used in order to increase the insulation efficiency. In the present study, a conjugate heat transfer problem of a double pane window system has been studied numerically in order to investigate the effect of an air layer on the heat transmittance of the double pane window system using a finite element method based on P2P1 basis function. In this study on the conjugate heat transfer of a double pane window system, numerically predicted Nusselt numbers with or without conjugate heat transfer effect have been compared with an available existing empirical formula. It has been found that a Nusselt number from an existing formula for an enclosed space is different from that obtained from the present conjugate heat transfer analysis mainly due to the effects of a very high aspect ratio and conjugate heat transfer mechanism. Furthermore, it has been shown that the numerically estimated optimal air thickness of the double pane window system with conjugate heat transfer effect is a little bit longer than that obtained without considering conjugate heat transfer effect.

• Journal of the Korean Society of Clothing and Textiles
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• v.19 no.1
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• pp.142-148
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• 1995

In this study, FVM (Finite Volume Method) which is one of the 2-dimensional numerical approach has been conducted to anticipate the temperature distribution between skin and clothes by the change of air temperature and fabric characteristics including fabric thickness. Several experimental works have been done to understand the thermal insulation effect (If fabrics on a human body by measuring the averaged temperature in the air layer between skin and clothes or by measuring the thermal resistance of fabrics. However, the formal method is inconvenient to measure the temperature distribution in the air layer to evaluate the insulation rate of the clothes on the skin because the real size of the clearance between skin and the clothes is too small to place the temperature sensor, and in the Tatter method the relationship between human body and the fabrics are ignored. However, the numerical method will be very effective and economical way to evaluate the insulation efficiency of clothes when the computational result is in the reliable range. As the result of this study, the temperature change in the sir layer between skin and clothes was linear to the fabric thickness and this result coincides with many previous experimental results. Moreover, it is possible to predict the optimum fabric thickness for the best thermal insulation in the air layer between skin and clothes.

• Journal of the Korean institute of surface engineering
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• v.25 no.3
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• pp.107-116
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• 1992

The optimum thickness of Pd-Ni plated layers used as an electrical contact film was investigated by evaluating mechanical, thermal and environmental characteristics. The variations of morphologies and chemical compositions were studied by using SEM, EDS and ESCA. As a result of wear test, the wear resistance behavior of the gold plated layers was not changed with the sliding velocity changes. The palladium-nickel plated layer showed better wear resistance than the gold plated layer at low sliding velocity, but it showed poor wear resistance at high sliding velocity. Under the thermal condition of $400^{\circ}C$ in air, the gold thickness of $2\mu\textrm{m}$ without underplate on phosphorous bronze formed copper oxide on the surface layer by rapid diffusion of copper whereas the gold thickness of $0.8\mu\textrm{m}$ deposited on nickel and palladium-nickel underplate was stable at $400^{\circ}C$. Under the sulfur dioxide environments, the gold thickness of $0.3\mu\textrm{m}$ deposited on the nickel thickness of$ 3\mu\textrm{m}$ and the palladium-nickel thickness of $2\mu\textrm{m}$ underplate was more corrosion-resistant than the gold thickness of $2\mu\textrm{m}$ without underplate on phosphorous bronze. Under the nitric acid vapor environment, corrosion resistance of the gold film was superior to an equivalent thickness of the palladium-nickel film.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.633-636
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• 2005

Imprint lithography is a promising method for high-resolution and high-throughput lithography using low-cost equipment. As with other nanoimprint methods, ultraviolet-nanoimprint lithography (UV-NIL) resolution appears to be limited only by template resolution, and offers a significant cost of ownership reduction when compared to other next generation lithography (NGL) methods such as EUVL and 157 nm lithography. The purpose of this paper is to suggest optimum values of control parameters of Imprio 100 manufactured by Molecular Imprint, Inc., which is the first commercially available UV-NIL tool, for sound nanoimprint. UV-NIL experiments were performed on Imprio 100 to find dispensing recipe for avoiding air entrapment. Dispensing recipe related to residual layer thickness and uniformity was optimized and 40 nm thick residual layer was achieved.

• Korean Journal of Materials Research
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• v.14 no.2
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• pp.152-156
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• 2004

We have studied the effective optical absorption power of Si solar cell with $SiO_2$-antireflection layer based on a mathematical modelling of AM(air mass)1 spectrum and Si refractive index in the wavelength range(0.4 $\mu\textrm{m}\leq$λ$\leq$$0.97\mu\textrm{m}$). The effective optical absorption power obtained from the theoretical calculation was 450 and 520 W/$\m^2$ for the Si solar cells with $SiO_2$-antireflection layer of 500$\AA$ and 1000$\AA$, respectively. The optimum thickness of $SiO_2$-antireflection layer showing the minimum reflection loss was about 1000$\AA$ in the computer simulation. Two kinds of Si solar cells named EBS(500$\AA$) and EBS(l000$\AA$) were fabricated to evaluate the effect of $SiO_2$-antireflection layer thickness on the optical absorption. The epitaxial base Si cell with $SiO_2$-antireflection layer of 1000$\AA$ [EBS(l000$\AA$)] showed the output power improvement of about 15% upon the EBS(500$\AA$) cell due to larger absorption of effective optical power under illumination of AM1, 1 sun.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.06a
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• pp.7-13
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• 1999

An experimental study was performed to discover the effect of silver coating on the frictional behavior of SM45C steel at sliding surfaces. Pure silver was coated the SM45C disk surfaces by a thermal evaporation method. Experiments using a pin-on-disk test-rig was performed under dry air and various humidity conditions. Friction coefficients increased to a high and unstable value after failure of coating, and friction coefficients increased with increasing the thickness of silver coated layer. But optimum coating thickness was not observed.

• Journal of the Korean institute of surface engineering
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• v.31 no.2
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• pp.91-100
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• 1998

NiCrAlY/YSZ(8wt%$Y_2O_3-ZrO_2$) functionally graded thermal barrier coating (FGC) layers on a Co-base superalloy (HAYNESS 188) substrate were fabstrate were fabicated using Ar shielded single torch air plasma spraying method. Functional grading with the stepwise compositional change throughout layer thickness. Microstructural observation trvealed a successful fabrication of NiCrAlY/YSZ FGC. From the results of the curvature measurement, adhesive strength measurement and thermal shock test for the FGC, it was concluded that the optimum conditions of functionally graded coating layer thinkness and compositional pattern exit to enhance the properties of FGC, which is closely related to the internal residual stess distribution witin it.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.111-114
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• 1999

Electroluminescence(EL) devices based on organic thin films have been attracted lots of interests in large-area light-emitting display. In this stuffy, an emissive layer was fabricated using Langmuir-Blodgett(LB) technique in organic light-emitting (OLEDs). This emissive organic material was synthesized and named PECCP[poly(3.6-N-2-ethylhexyl carbazolyl cyanoterephthalidene)] which has a strong electron donor group and an electron acceptor group in main chain repeated unit. This material has good solubility in common organic solvents such as chloroform. THF, etc, and has a good stability in air. The Langmuir-Blodgett(LB) technique has the advantage of precise control of the thickness down to the molecular scale, In particular, by varying the film thickness it is possible to investigate the metal/polymer interface. Optimum conditions for the LB film deposition are usually determined by investigating a relationship between a surface pressure $\pi$ and an effective are A occupied by one molecule on the subphase. The LB films were deposited on an indium-tin-oxide(ITO) glass at a surface pressure of 10 mN/m and dipping speed of 12 mm/min after spreading PECCP solution on distilled water surphase at room temperature, Cell structure was ITO/PECCP LB film/Alq$_3$/Al. We considered PECCP as a hole -transport layer inserted between the emissive layer and ITO. We also used Alq$_3$ as an emissive layer and an electron transport layer. We measured current-voltage(I-V) characteristics, UV/visible absorption, PL spectrum and EL spectrum of the OLEDs.

• Journal of the Korean institute of surface engineering
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• v.35 no.1
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• pp.17-32
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• 2002

Electroplating methods by molten salts and non-aqueous melts were employed for aluminium coating on STS 316L stainless steel. After coated with Ni or non-coated surface on stainless steel, Al pulse plating was carried out in two different types of electrolytes at room temperature. The Al layer from $AlCl_3$-TMPAC melts could not obtain appreciable thickness for engineering application due to chemical reactions between deposits and moisture of air. However, The Al coating by pulse plating in the Ethylbenzene-Toluene-$AlBr_3$ systems was found to be solid coating layer with a few $\mu\textrm{m}$ scale. The conductivity of Ethylbenzene-Toluene-$AlBr_3$ electrolyte was as functions of time and agitation. By seven days exposure after mixing of the electrolyte, Al-deposited layer shows uniform and near by pore-free with high current density (higher than 30mA/$\textrm{cm}^2$). The roughness and imperfection of coating layer were decreased with a increasing agitation speed. It was found that the optimum condition for the Al pulse plating on the 316L stainless steel was a 400mA peak current, duty cycle, $t_{on}$ $t_{ off}$=3ms/1ms, and a current density of 30mA/$\textrm{cm}^2$.

• Journal of the Korean institute of surface engineering
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• v.48 no.2
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• pp.33-37
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• 2015

High efficiency LED device is being concerned due to its high heat loss, and such heat loss will cause a shorter lifespan and lower efficiency. Since there is a demand for the materials that can release heat quickly into the external air, the organic insulating layer was required to be replaced with high thermal conductive materials such as metal or ceramics. Through anodizing the upper layer of Al, the Breakdown Voltage of 3kV was obtained by using an uniform thickness of $60{\mu}M$ aluminum oxide($Al_2O_3$) and was carried out to determine the optimum process conditions when thermal cracking does not occur. Two Ni layers were formed above the layer of $Al_2O_3$ by sputtering deposition and electroplating process, and saccharin was added for the purpose of minimizing the remain stress in electroplating process. The results presented that the 3-layer film including the Ni layer has an adhesive force of 10N and the thermal conductivity for heat dissipation is achieved by 150W/mK level, and leads to improvement about 7 times or above in thermal conductivity, as opposed to the organic insulation layer.