• Journal of the Korean Ceramic Society
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• v.43 no.2 s.285
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• pp.85-91
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• 2006

Electron Beam Physical Vapor Deposition (EB-PVD) was applied to fabricate a thin film YSZ electrolyte with large area on the porous NiO-YSZ anode substrate. Microstructural and thermal stability of the as-deposited electrolyte film was investigated via SEM and XRD analysis. In order to obtain an optimized YSZ film with high stability, both temperature and surface roughness of substrate were varied. A structurally homogeneous YSZ film with large area of $12\times12\;cm^2$ and high thermal stability up to $900^{\circ}C$ was fabricated at the substrate temperature of $T_s/T_m$ higher than 0.4. The smoother surface was proved to give the better film quality. Precise control of heating and cooling rate of the anode substrate was necessary to obtain a very dense YSZ electrolyte with high thermal stability, which affords to survive after post heat treatment for fabrication a cathode layer on it as well as after long time operation of solid oxide fuel cell at high temperature.

• Korean Journal of Optics and Photonics
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• v.21 no.5
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• pp.200-205
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• 2010

We report temperature and strain sensing characteristics of two kinds of in-line fiber interferometers. One interferometer consists of a section of Hollow Optical Fiber(HOF) spliced between two Photonic Bandgap Fibers(PBGF) and the other is built by splicing a section of HOF between two Large Mode Area-Photonic Crystal Fibers(LMA-PCF). To minimize the splice losses, we carefully optimized the heating time and arc current of the splicer so as not to collapse the air holes of the fiber. It is found that the first interferometer has a temperature sensitivity of 15.4 pm/$^{\circ}C$ and a strain sensitivity of 0.24 pm/${\mu}\varepsilon$. The other interferometer exhibits a temperature sensitivity of 17.4 pm/$^{\circ}C$ and a strain sensitivity of 0.2 pm/${\mu}\varepsilon$.

• Transactions of the Korean hydrogen and new energy society
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• v.19 no.6
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• pp.514-519
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• 2008

In the present study, biomass pyrolysis was done using five different kinds of catalysts with change in the support species and their compositions. Ni was loaded on alumina, ceria and alumina-ceria supports using co-precipitation method. In all the catalysts, 30wt% of nickel was loaded on the support materials. The paper used in daily writing purposes was taken into account as biomass sample. In the experiment, 19 of biomass was mixed with o.1g of each catalyst separately. Thermogravimetric analysis (TGA) was performed with all the catalysts diminished the initial degradation temperature of paper biomass sample considerably. During the pyrolysis process, the temperature was raised from room temperature to $800^{\circ}C$ with the heating rate of $10^{\circ}C$/min in the furnace. The cumulative $H_2$ volume had reached the best value of l4.02ml with the Ni/$Al_2O_3-CeO_2$ 30wt%/(50wt%-50wt%) catalysts. In presence of all the catalysts, the highest amount of $H_2$ was produced at $800^{\circ}C$, 10min. of residence time.

• Journal of Ocean Engineering and Technology
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• v.24 no.6
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• pp.86-91
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• 2010

Superconductor material $Bi_2Sr_2Ca_2Cu_3O_x$(Bi-2223) powders were synthesized by ultrasonic spray pyrolysis method. It is clear that Bi-2223 phase more than Bi-2212 phase was acquired at sufficient synthesized time. Best condition for Bi-2223 phase was synthesizing temperature at $860^{\circ}C$. We also investigated the effects for concentrations and viscosities of starting liquid precursor as well as temperature distribution of reacting furnace. The size of synthesized powder was decreased by decreasing the concentration of starting liquid precursor. Modified reacting furnace with four different temperature heating zones gave us successful results for desirable nano-powder including $Bi_2Sr_2Ca_2Cu_3O_x$ phase. Citric acid addition to starting liquid precursor showed increasing of the size for synthesized powder. Bi-2223 single phase was acquired from Bi2223 and Bi-2212 mixed phases through heat treatment in box furnace at 24 hours.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.32 no.5
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• pp.205-211
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• 2022

The Granule Spray in Vacuum (GSV) process is a method of forming a dense nanostructured ceramic coating film by spraying ceramic granules on a substrate at room temperature in a vacuum. In the Granule Spray, the granules made by agglomerating particles with the size from submicrometer to micrometer can be sprayed into the substrate. Once the granules were squashed upon collision with the substrate, they become several dozens of nanometer-sized crystals in vacuum process. The zirconia of the monoclinic phase transform into tetragonal phase at 1150℃. At this time, its volume is changed by about 6.5 %. For this reason, it is widely held that it is difficult to acquire a compact of monoclinic zirconia sinter. In this study, the effect of particle treatment temperature and standoff distance on the substrate of zirconia granules were investigated in GSV. Also, particle treatment temperature, standoff distance, coating efficiency, and microstructure of the film were considered in forming the monoclinic zirconia coating film in GSV without any heating process. The deposited films exhibited monoclinic zirconia phase without any other detectable phase by X-ray diffractometer (XRD).

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.7
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• pp.571-579
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• 2014

A series of field tests on hybrid desiccant cooling systems were conducted in July-August, 2013. The temperature and humidity of the supply and return air, power, and heat consumption were monitored and transferred in real time through the Internet. The performance parameters of the cooling system, namely, cooling capacity and COP (coefficient of performance), were evaluated from the measured data and their variations under outdoor conditions was analyzed. It was found that with increase in the outdoor temperature, the total energy decreases and cooling capacity increases whereas the latter decreases with increase in the outdoor humidity. The COP was also found to increase with the increase in outdoor temperature.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.6
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• pp.1163-1168
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• 2011

Most transformers use insulating and cooling fluids derived from petroleum crude oil, but mineral oil has some possibility of environmental pollution and fire with explosion. vegetable oil fluids extracted from seed has superior biodegradation and fire-resistant properties including an exceptionally high fire point enhancing fire safety. In this study, it is aimed at the practicality of substituting natural ester dielectric fluid for mineral oil in liquid insulation system of transformers. As a rise in coil winding temperature has a direct influence on transformer life time, it is important to evaluate the temperature rise of coil winding in vegetable oil in comparison with mineral oil. Four transformers for the test are designed with 10KVA, 13.2KV, one phase unit. The temperature are directly measured in insulating oil of these transformers with the two sorts of natural ester and mineral oil dielectric fluid respectively. Experiment for aging carry out two means. First means remained $120^{\circ}C$ that transformer of mineral oil were operated at 185% load. Second means is that insulating oils of two natural ester and mineral oil were aged by thermal cycles repeating from $30^{\circ}C$ to $120^{\circ}C$. For the heating, Transformers were operated at 185% load. For the cooling, cooling system was operated in the chamber. Samples were analyzed at 42, 63, 93, 143, 190, 240 300cycles. Analysis contents are dielectric strength, total acid value. Mineral oils compared results of first means with results of second means. And compared two sort natural esters respectively with mineral oil in second means.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.4
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• pp.475-480
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• 2010

The thermal barrier coating of a gas turbine blade was degraded by isothermal heating in a furnace and by varying the exposure time and temperature. Then, a micro-Vickers hardness test was conducted on the cross section of the bond coat and Ni-based superalloy substrate. Further, the thickness of TGO(Thermally Grown Oxide) was measured by using an image analyzer, and the changes in the microstructure and element contents in the coating were analyzed by using an optical microscope and by performing SEM-EDX analysis. No significant change was observed in the Vickers hardness of the bond coat when the coated specimen was degraded at a high temperature; delamination was observed between the top coat and the bond coat when the coating was degraded for 50 h at a temperature $1,151^{\circ}C$.

• The Journal of the Acoustical Society of Korea
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• v.37 no.5
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• pp.338-342
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• 2018

In order to solve the floor impact sound problem in the upper and lower floors, the Ministry of Land, Transport and Maritime Affairs also notifies the physical properties of the resilient material affecting the floor impact sound level. The dynamic modulus of elasticity and the loss factor before and after heating are most related to the floor impact noise, especially for the cushioning material. Therefore, in this study, the rate of change with respect to the dynamic modulus and loss factor with temperature change was examined by increasing $10^{\circ}C$ by $10^{\circ}C$ from the temperature condition of $70^{\circ}C$ specified in the standard. The dynamic modulus of elasticity and the loss modulus were measured by using the pulse excitation method for eight kinds of samples. The calculation method was calculated by the time series analysis method using the damped vibration waveform.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.869-872
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• 2008

Recently, the effects of high temperature on compressive strength, elastic modulus and strain at peak stress of high strength concrete were experimentally investigated. The present study is aimed to study the effect of elevated temperatures ranging from 20 to $700^{\circ}C$ on the material mechanical properties of high-strength concrete of 40, 60, 80MPa grade. In this study, the types of test were the stressed test and stressed residual test that the specimens are subjected to a 25% of ultimate compressive strength at room temperature and sustained during heating and when target temperature is reached, the specimens are loaded to failure. Or specimens are loaded to failure after 24hour cooling time. tests were conducted at various temperatures ($20{\sim}700^{\circ}C$) for concretes made with W/B ratios 46%, 32% and 25%. Test results showed that the relative values of compressive strength and elastic modulus decreased with increasing compressive strength grade of specimen.