• 한국화재소방학회논문지
• /
• 제30권4호
• /
• pp.73-81
• /
• 2016

정온전선은 평형 도체 사이에 반도전성 폴리머를 연속 압출 방식으로 충전시킨 후 양 도체 사이에 전기를 흐르게 함으로써 고분자에 의한 전열을 이용한 전기 발열체이다. 정온전선은 가격이 저렴하고 시공이 편리하기 때문에 겨울철 수배관의 동파방지용 열선으로 주로 사용되고 있다. 하지만 이러한 유용함에도 불구하고 구조적인 문제로 인하여 두 평형 도체의 절연이 파괴되는 경우에는 화재로 이어질 수도 있는 위험성이 존재하고 있다. 본 논문은 정온전선에 의한 화재현장을 조사하여 원인을 도출하는 방식으로 직접적인 원인을 추론하고자 하였으며, 결함수 분석을 통해 근본적인 문제를 파악해 보고자 하였다. 실제 냉동창고 화재현장을 조사하여 정온전선에 의한 화재원인을 추론한 결과 전선 말단 절연처리 결함에 의한 절연파괴인 것으로 판단되었다. 향후 이 결과는 안전활동 및 유사 화재원인조사 시에도 활용될 수 있을 것이다

• Journal of Electrical Engineering and Technology
• /
• 제8권1호
• /
• pp.163-167
• /
• 2013

Aluminum doped zinc oxide (AZO) thin films have been prepared on the glass substrates (Corning 1737) by sol-gel dip-coating method employing zinc acetate and aluminum chloride hexahydrate for the transparent conducting oxide (TCO) applications. 1 at% Al was doped to the ZnO thin films. The effects of post-heating temperature on the crystallization, optical and electrical properties of the AZO films have been investigated. Experimental results showed that post-heating temperature affected the microstructure, electrical resistance, and optical transmittance of the AZO films. From the X-ray diffraction analysis, all films have hexagonal wurtzite crystal structure. Optical transmittance spectra of the AZO films exhibited transmittance higher than about 80% within the visible wavelength region and the optical direct band gap ($E_g$) of these films was increased with increasing post-heating temperature. A minimum resistivity of $2.5{\times}10^{-3}{\Omega}cm$ was observed at $650^{\circ}C$.

• 설비공학논문집
• /
• 제16권11호
• /
• pp.1021-1027
• /
• 2004

Design performances of various configurations of hybrid systems combining an atmospheric pressure molten carbonate fuel cell and a gas turbine have been analyzed. Two different fuel reforming methods (internal and external reforming) were considered. Influences of turbine inflow heating method, location of fuel combustor and associated component arrangements were investigated. In general, internal reforming leads to higher system efficiencies. The optimum design pressure ratio varies among different system configurations. In particular, the design point selection is closely related to the allowable turbine inlet temperature. Configurations with direct heating of turbine inlet flow may realize both higher efficiency and higher specific power than those with indirect heating.

• 한국세라믹학회지
• /
• 제27권1호
• /
• pp.136-146
• /
• 1990

Whiskers of SiC were grown from the mixture of silica and graphite powders by Acheson method(direct heating method). The structrua, morphological and chemical characterizations have been performed by X-ray diffractometer(XRD), transmission electron microscopy(TEM), optical microscopy(OM), scanning electron microscopy(SEM), X-ray photoelectron spectroscopy(XPS) and energy dispersive spectrometer(EDS). The growth mechanism of SiC whiskers is also discussed.

• 대한기계학회논문집B
• /
• 제28권12호
• /
• pp.1494-1500
• /
• 2004

A zero-dimensional direct simulation Monte Carlo(DSMC) model is developed for simulating diatomic gas including vibrational kinetics. The method is applied to the simulation of two systems: vibrational relaxation of a simple harmonic oscillator and translational-rotational-vibrational energy exchange process under heating and cooling. In the present DSMC method, the variable hard sphere molecular model and no time counter technique are used to simulate the molecular collision kinetics. For simulation of diatomic gas flows, the Borgnakke-Larsen phenomenological model is adopted to redistribute the translational and internal energies.

• 한국기계가공학회지
• /
• 제19권10호
• /
• pp.8-15
• /
• 2020

The diffusion cell method is the main technique employed for the in vitro diffusion test of transdermal drug delivery preparations. Most existing transdermal diffusion devices use a water bath heating structure and direct current motor magnetic stirrer. However, these devices are confronted with problems, such as large volume, incompatible vertical and horizontal diffusion cells, few diffusion cell sets, and poor reliability. To overcome these deficiencies, the system adopts a dry heating method and uses a rotating magnetic field generated by the electromagnetic stirrer to drive the magnetic stirrer. Accordingly, the resulting device is characterized by a simple structure and small volume, convenient operation, compatible vertical and horizontal diffusion cells, and numerous diffusion cell sets. The reliability and practicability of the system is verified by the in vitro percutaneous permeability test of the bisoprolol patch.

• 한국정밀공학회지
• /
• 제27권12호
• /
• pp.67-74
• /
• 2010

The fabrication method of aspheric lens is changed from machining to press molding so as to improve the productivity. In the case of the press molding method, the temperature control of the molding die is most impotent, because the temperature of each molding die determines the quality of lens. But any practical method for direct measuring of the lens temperature and the die internal temperature is yet unknown. Besides, in the case of the press molding system in which the heating and pressing and cooing of a die is done at one work station, the cycle time for the system is yet too long. The paper shows an improved structure of radiant sequential system in which the heating and pressing and cooing of dies is done at individual work station so as to cut down the cycle time. To know the die internal temperature, numerical results are given using ANSYS. An experimental radiant sequential system is developed and tested. Finally, the Taguchi method is applied in order to optimize the setting conditions of individual work station.

• Elastomers and Composites
• /
• 제50권2호
• /
• pp.138-145
• /
• 2015

A series of wholly aromatic poly(hydroxyamide)s(PHAs), containing varying amounts of 2,6-dimethylphenoxy group and quinoxaline ring in the main chain, were synthesized by a direct polycondensation method. The inherent viscosities of the PHAs in either DMAc or DMAc/LiCl solution at $35^{\circ}C$ were found to be in the range of 1.02~1.90 dL/g. In the solubility study, we observed that PHA 1, PHA 2, and PHA 3 were dissolved in aprotic solvents such as DMAc, NMP, DMF, and DMSO with LiCl on heating; however, PHA 4, PHA 5, and PHA 6 could be dissolved in aprotic solvents on heating without LiCl. For poly(benzoxazole)s(PBOs), the 10% and maximum weight loss temperatures were in the range of $582{\sim}622^{\circ}C$ and $630{\sim}659^{\circ}C$, respectively. Residues of PBOs at $900^{\circ}C$ were found to be relatively high, which were in the range of 65.3~70.8%.

• 한국의류산업학회지
• /
• 제9권3호
• /
• pp.341-346
• /
• 2007

This research is the hair damage as treating a perm before and after that is compared the change of surface characteristics of human hair. On the basis of this, we would to show a basic data for hair damage prevention and hair improvement to keep the beautiful and healthy hair. Results are as follows; For the change of formational characteristics of hair surface, untreated hair before the perm treatment had smooth appearance overall and undamaged scale that is in pattern and finely folded was observed but damaged hair and extremely hair had uneven edge and damages throughout along with the dissolution of scale which the border of epidermal gap is unclear. Hair after a perm treatment caused cortical exposures due to extensive loss of scale during the treatment and even bubble effect. Protein perm, regular perm, soft perm, and direct heating perm, in that order, had the most damages to the hair.

• 설비공학논문집
• /
• 제14권1호
• /
• pp.38-45
• /
• 2002

Evaporative heat transfer characteristics of carbon dioxide have been investi- gated by experiment. The experiments have been carried out for a seamless stainless steel tube of the outer diameter of 9.55 mm, the inner diameter of 7.75 mm and the length of 5.0 m. Direct heating method was used for supplying heat to the refrigerant where the test tube was uniformly heated by electric current which was applied to the tube wall. Experiments were conducted with$CO_2$of purity 99.99% at saturation temperatures of 0.0 to 10.5$^{\circ}C$, heat fluxes of 12 to 27kW/$m^2$s and mass fluxes of 212 to 530 kg/$m^2$s. The heat transfer coefficients of $CO_2$are decreased as the vapor quality increases and these phenomena are explained by dimensionless Weber and Bond numbers. The heat transfer coefficients of$CO_2$increase when the heat and mass fluxes increase, and the saturation temperature effects are minor in the test range of this study. The present experimental data are compared with six renowned correlations with root-mean-squared deviations ranging from 23.0 to 94.9% respectively.