• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.1 s.232
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• pp.151-158
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• 2005

A characteristic of discharge for a foam spray nozzle with various parameters was investigated. The discharge patterns from a fire foam spray nozzle are important to evenly spray over a maximum possible floor area. Two parameters of a foam spray nozzle were chosen, and compared with those from the standard one. Also, in order to evaluate the performance of discharged foam agents used to protect structures from heat and fire damages, the thermal characteristics of fire-protection foams were experimentally investigated. A simple repeatable test for fire-protection foams subjected to fire radiation was developed. This test involves foam generation equipment, a fire source for heat generation, and data acquisition techniques. Results show that the bubble size of foam is increased by large inside diameter of orifice or closed air hole, but phenomenon of discharge angle and expansion ratio is opposite. For the case of the open air hole, liquid film of a circular cone discharges with formation, growth, split and fine grain. In case of the closed air hole, a pillar of foam solution discharges with that. Though the temperature gradient in the foam increases with increased foam expansion ratio. it is not change with increased intensity of heat flux.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.7
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• pp.8-14
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• 2021

Even welds that have passed non-destructive testing in the case of brittle crack arrest steel materials will actually have very fine weld defects. Based on studies showing that these defects adversely affect the structure if subjected to a certain period of load, the following conclusions were obtained by conducting CTOD tests on welding joints of high-strength BCA materials, structures comprising the upper decks of a large container vessel. First of all, the fatigue pre-cracking in the weld metal and heat affected areas was tested and the behavior was identified. Both parts of the welding joint are allowable range for the class regulations. In addition, CTOD results showed that the CTOD value in the heat affected area was more than 0.5 times higher than in the weld metal area.

• Journal of Ginseng Research
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• v.4 no.2
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• pp.165-174
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• 1980

The concentrated red ginseng extract (RGE) which was prepared from water extract of red ginseng tails was investigated for its changes in color intensity, sugar contents and during storage at various temperatures. In order to evaluate the color of RCE, a spectrophotometric measurement in ultraviolet and visible range was applied. The concentrated RGE was divided into three fractions of aqueous, butanol and benzene layers. It was found that : (1) Increase in RCE color during heat treatment was considered to be due to nonezymatic browning reaction. Water soluble layer showed approximately 100 times higher color intensity than those of organic solvent layers (2) The RCE stored at 8$0^{\circ}C$ showed an increase in fructose and glucose content while a rapid decrease was resulted at 10$0^{\circ}C$. (3) A rapid increase in absorbances at 400 and 460nm was shown at 90 and 10$0^{\circ}C$ after an initial induction period and slowed down after 50 hours . (4) A significant relationship was found between decrease in sugar content and increase in color intensity. (5) Absorbance ratio of 400nm/460nm indicated that benzene layer has about two times higher value in violet color than those of butanol and aqueous layers.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.6
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• pp.544-551
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• 2008

We have studied the dielectric characteristics of low-k interlayer dielectric materials fabricated by PECVD for various precursor's flow rates. BTMSM precursor was introduced with the flow rates from 42 sccm to 60 sccm by 2 sccm step in the constant flow rate of 60 sccm $O_2$. The absorption intensities of Si-O-$CH_x$ bonding group and Si-$CH_x$ bonding group changed synchronously for the variation of precursor flow rate, but the intensity of Si-O-Si(C) responded asynchronously with the $CH_x$ combined bonds. The heat treatment reduced the FTIR absorption intensity of Si-O-$CH_x$ bonding group and Si-$CH_x$ bonding group but increased the intensity of Si-O-Si(C). The nanopore and free space formed by the increasement of caged link mode and cross link mode of Si-O-Si(C) group implied the origin of low-k SiOCH films.

• Composites Research
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• v.27 no.1
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• pp.14-18
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• 2014

Carbon Fiber Reinforced Plastic (CFRP) has strong and superb material properties, especially in mechanical and heat-resisting aspects, but the drawback is its high price. In this study, we made a hybrid composite using carbon fiber and basalt fiber, which is expected to attribute to its strong material properties and its financial benefits. We found out that the higher the content of basalt fiber included, the lower the intensity, and carbon's intensity contents of 80% showed the similar intensity level as that of CFRP. Besides it was possible to get a better mechanical properties using the composite that included the mixed fiber, instead of using a composition of separate fibers filed.

• 한국연소학회:학술대회논문집
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• 2006.04a
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• pp.19-25
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• 2006

Energy efficient and low pollution combustion systems the use gaseous fuels have been in great demand in recent year. Radiant burner in many different forms are emerging as very desirable combustion systems for same reason. Porous radiant burners are used in drying, preheating and curing, and in other type of materials processing and manufacturing processes. However, little knowledge is available about the operating characteristics and the structure of flames in porous ceramic fiber radiant burners. The objective of the present work is to investigate the global performance characteristics of the ceramic fiber burner. A detailed study which includes the spectral intensity, gas temperature, radiation efficiency and global pollutant emissions. Another objective is to study the flame structure of the ceramic fiber burner by measuring the local gas temperature. The results indicate that ceramic fiber burner do offer a 19-44% gain in radiant efficiency. The ceramic fiber burner exhibit significant spectral intensity peaks in the band at $2.0-2.5{\mu}m$. The local temperature distribution inside the mat and near the mat surface as a function of the equivalence ratio can be reasonably interpreted by the relation of the heat balance in the mat and movement of the reaction zone. Nox emission from ceramic fiber burner is less than 25ppm throughout the operating range.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.1
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• pp.57-63
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• 2015

Recently, LED is widely used in the kinds of display devices or lighting. In this paper, we fabricated LED chamber light for naval vessels to replace to conventional chamber light using incandescent lamp. The LED package of chamber light was designed with luminous intensity of 5.5 cd, color temperature of $6,000{\pm}500K$, forward voltage of 3~3.2 V and input current of 60 mA. A LED module was composed of 36 LED packages and metal PCB. The VF and luminous intensity of LED package were getting down when temperature increased. The temperature of LED chamber light was measured by changing the number of LED package and applied current for one hour when an electric current flow. The heat transfer capability have been improved by using metal PCB. The power consumption of LED chamber light reduced by 86% compared to the conventional chamber light using incandescent lamp.

• Nuclear Engineering and Technology
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• v.48 no.6
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• pp.1412-1422
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• 2016

Austenitic stainless steels (ASSs) are widely used for nuclear pipes as they exhibit a good combination of mechanical properties and corrosion resistance. However, high tensile residual stresses may occur in ASS welds because postweld heat treatment is not generally conducted in order to avoid sensitization, which causes a stress corrosion crack. In this study, round robin analyses on stress intensity factors (SIFs) were carried out to examine the appropriateness of structural integrity assessment methods for ASS pipe welds with two types of circumferential cracks. Typical stress profiles were generated from finite element analyses by considering residual stresses and normal operating conditions. Then, SIFs of cracked ASS pipes were determined by analytical equations represented in fitness-for-service assessment codes as well as reference finite element analyses. The discrepancies of estimated SIFs among round robin participants were confirmed due to different assessment procedures and relevant considerations, as well as the mistakes of participants. The effects of uncertainty factors on SIFs were deducted from sensitivity analyses and, based on the similarity and conservatism compared with detailed finite element analysis results, the R6 code, taking into account the applied internal pressure and combination of stress components, was recommended as the optimum procedure for SIF estimation.

• Coupled systems mechanics
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• v.11 no.2
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• pp.151-166
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• 2022

Peltier cells have low efficiency, but they are becoming attractive alternatives for affordable and environmentally clean cooling. In this line, the current article develops closed-form and semianalytical solutions to improve the temperature distribution of Bi₂Te₃ thermoelements. From the distribution, the main objective of the current work-the optimal electric intensity to maximize cooling-is inferred. The general one-dimensional differential coupled equation is integrated for linear and quadratic geometry of thermoelements, under temperature constant properties. For a general shape, a piece-wise solution based on heat flux continuity among virtual layers gives accurate analytical solutions. For variable properties, another piece-wise solution is developed but solved iteratively. Taking advantage of the formulae, the optimal intensity is directly derived with a minimal computational cost; its value will be of utility for more advanced designs. Finally, a parametric study including straight, two linear, barrel, hourglass and vase geometries is presented, drawing conclusions on how the shape of the thermoelement affects the coupled phenomena. A specially developed coupled and non-linear finite element research code is run taking into account all the materials of the cell and using symmetries and repetitions. These accurate results are used to validate the analytical ones.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.1
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• pp.81-88
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• 2014

An experimental study is performed to obtain an average heat transfer coefficient around the perimeter of a near horizontal tube. For the test a stainless steel tube of 50.8 mm diameter submerged in water at atmospheric pressure is used. Both subcooled and saturated pool boiling conditions are considered and the inclination angle of the tube is changed from the horizontal position to $9^{\circ}$ in steps of $3^{\circ}$. In saturated water, the local boiling heat transfer coefficient at the azimuthal angle of $90^{\circ}$ from the tube bottom can be regarded as the average of the coefficients regardless of the tube inclination angles. However, when the water is subcooled the location for the average heat transfer coefficient depends on the inclination angle and the heat flux. It is explained that the major mechanisms changing the heat transfer are closely related with the intensity of the liquid agitation and the generation of big size bubbles through bubble coalescence.