• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.8 no.3
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• pp.131-150
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• 1979

Recently only a few correlations between various factors due to the different grades of surface roughness for the nucleate pool boiling have been proposed. The main purpose of this work is to test the validity of these types of correlations between related factors to nucleate pool boiling phenomena. The boiling experiments using distilled water were carried out at the heat flux ranging from $7.4\times10^4\;to\;2.4\times10^5kcal/m^2h$ on the sintered porous metal surface with the cavity diameter of 10, n, 40, 70, $100{\mu}$, respectively, at the atmospheric pressure, To determine the bubble sizes, number of nucleation sites, delay and growth time, frequency of bubble emission and rising velocities of bubbles, the high speed motion picture technique was employed. In the correlation $f{\propto}D_b^n$, where f denotes frequency of bubble emission and $D_b$ departure diameter, n, the power factor of $D_b$, have been found to be from -2 to -10/3. The correlation C in the correlation between heat flux q and density of nucleation sites $\frac{N}{A}$, $q=C(\frac{N}{A})^n$, was appeared to be more crucial than the power factor n. The correlation of the heat flux q to the temperature difference ${\Delta}T$ and the density of nucleation sites$\frac{N}{A}$, was proposed to be $$q-460{\Delta}T^{\frac{5}{4}}=K{\Delta}T{\frac{5}{3}}(\frac{N}{A})^{\frac{2}{3}}$$. The values of heat transfer coefficient obtained in this experiments for the porous sintered metal surface appeared to be very high in comparison with the formerly obtained results for the other surfaces.

• Journal of Powder Materials
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• v.22 no.5
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• pp.356-361
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• 2015

Fe-30 wt% TiC composite powders are fabricated by in situ reaction synthesis after planetary ball milling of (Fe, $TiH_2$, Carbon) powder mixture. Two sintering methods of a pressureless sintering and a spark-plasma sintering are tested to densify the Fe-30 wt% TiC composite powder compacts. Pressureless sintering is performed at 1100, 1200 and $1300^{\circ}C$ for 1-3 hours in a tube furnace under flowing argon gas atmosphere. Spark-plasma sintering is carried out under the following condition: sintering temperature of $1050^{\circ}C$, soaking time of 10 min, sintering pressure of 50 MPa, heating rate of $50^{\circ}C/min$, and in a vacuum of 0.1 Pa. The curves of shrinkage and its derivative (shrinkage rate) are obtained from the data stored automatically during sintering process. The densification behaviors are investigated from the observation of fracture surface and cross-section of the sintered compacts. The pressureless-sintered powder compacts are not densified even after sintering at $1300^{\circ}C$ for 3 h, which shows a relative denstiy of 66.9%. Spark-plasma sintering at $1050^{\circ}C$ for 10 min exhibits nearly full densification of 99.6% relative density under the sintering pressure of 50 MPa.

• Asian-Australasian Journal of Animal Sciences
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• v.25 no.2
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• pp.286-290
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• 2012

The majority of laboratory animals were transported from commercial breeders to a research facility by ground transportation. During the transportation, many biological functions and systems can be affected by stress. In this experiment, the change of body weight during the transportation was measured and the recovery periods from the transportation stress established based on the body weight changes. Total 676 laboratory animals which were aged between 3 to 9 wk old were studied. The transportation time taken from container packing to unpacking the container was approximately 24 h. The temperature of animal container was constantly maintained by air-conditioning and heating equipment. Rats were found to be more sensitive than mice. The body weight of rats was significantly decreased 3.71% (p<0.05) compared to the body weight of mice which decreased 0.9% There was no significant difference between the strains in the same species. When the changes of body weights were compared between delivery days, C57BL/6 mice showed the most variable changes compared to other species and strains. Consequently, C57BL/6 was more sensitive to stress than the other strains and the transportation process needs to be standardized to reduce between day variability. To establish the recovery periods from transportation stress, the body weight changes were measured during the acclimation period. Although the body weight of animals decreased during transportation, animals recovered their weight loss after the next day.

• Journal of Korean Society of Steel Construction
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• v.19 no.3
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• pp.335-344
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• 2007

The steel-concrete composite column (i.e., the SC composite column) supports large-gravity loads and simplifies the installation and removal of the work in pouring the concrete. The column takes advantage of the in-plant prefabrication of steel, the speed of erection of a steel structure, and the fire resistance of steel. This paper presents the results of a parametric study using heat transfer analysis and a P-M interaction curve, and compares these results with the experimental results to check the accuracy of the proposed parametric studies. The parametric studies, such as the study of the concrete ratio of an area and the fire protection thickness, provide information on the fire resistance of SC composite columns.

• Journal of the Society of Naval Architects of Korea
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• v.34 no.1
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• pp.68-76
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• 1997

The welding-induced initial imperfections such as residual stresses and initial strains in plated structures of ships and offshore structures can be effectively evaluated by the thermal elasto-plastic analysis method proposed in this paper. In the analysis of heat conduction of plate structures, both the analytical method and the numerical method are used. For the thermal elasto-plastic analysis of plates, the finite element analysis is performed, based on the initial strain method. In the plastic domain during incremental process, the 2nd order terms of stress increments and yield stress increments were considered, so that time increment could be controlled for more stable solution. To measure temperature distribution and angular distortion of plates during welding, bead-on-plate experiment are perform with various heat input and plate thickness. Measured data show good agreement with the calculated results.

• Journal of Advanced Marine Engineering and Technology
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• v.14 no.4
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• pp.57-66
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• 1990

In the design of an electric power plant, the capacity to meet the peak load demand is one of the important factors to be considered. This peak load usually occurs when the most of the cooling air conditioning systems are being operated during daytime in summer season, which inevitably entails the construction of an additional electric power plant. This study is aimed to carry out a basic experiment for the development of a cooling air conditioning system using the ice energy by the surplus electric power during the night-time. The experimental apparatus consists of four major parts; (1) the heating section consisting of the air duct and I.D. fan, (2) the cold section with the ice chamber, (3) the bundle of heat pipes made in a form of the staggered arrangement with ${C_y}/{d_o}$=2.0 and ${C_x}/{d_o}$=1.73, (4) the refrigerator system to cool down the ice chamber. This study involves an intensive experiment concerning the convective heat transfer of the air flow surrounding the bundle of heat pipes. This major experimental parameters are the amount of working fluid, the velocity of air and the working temperature. The major findings of the present study are as follows; (1) The optimum amount of the working fluid necessary for the horizontal heat pipes is much more than that for the vertical type. (2) The convective heat transfer coefficients of the air are coincided with the empirical equations of Grimson and ${\breve{Z}ukauskas}$. (3) The equation of the mean heat transfer coefficient obtained in the present study is ${N_um}=0.32 {Re_max^{0.63}}$.

• Korean Journal of Materials Research
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• v.9 no.2
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• pp.149-154
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• 1999

Alumina substrate was sealed by PbO-ZnO-$B_2O_3$glass using microwave heating. The crystallization behaviour of sealing glass and the state of sealing joint were investigated and were compared with those of conventionally sealed one. Compared to the conventional one, the microwave heat-treated sample had well-grown $\textrm{PbTiO}_3$ crystals and high degree of crystallinity even though it had shorter heat-treatment time and lower heat-treatment temperature. Also, the microwave sealed sample exhibited relatively a good sealing state and almost same bending strength.

• Journal of Food Hygiene and Safety
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• v.13 no.3
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• pp.278-293
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• 1998

The purposes of this study were to develop Hazard Analysis Critical Control Point-based standardized recipe applicable to cook/chilled Broiled Spanish Mackerel in school foodservice operations and to establish reasonable shelf-life limits by assessing food quality during chilled storage period of 5 days. HACCP for the production of menu items was identified in simulation study. At each critical control point, time-temperature profile was recorded and microbiological analysis was done. Also chemical analyses and sensory evaluation were conducted for 5 days of chilled storage. The results of time-temperature measurement of Broiled Spanish Mackerel by each production phase showed satisfactory condition that met the standards. Broiled Spanish Mackerel showed excellent microbiological quality from raw ingredient phase ($TPC:2.58{\pm}0.12\;Log\;CFU/g$) to holding phase ($TPC:2.70{\pm}0.42\;Log\;CFU/g$). Coliform (0.84 Log MPN/g) and fecal coliform (0.84 Log MPN/g) were detected from marinating phase ($TPC:3.82{\pm}0.52\;Log\;CFU/g$). After heating, only few mesophiles were detected ($TPC:1.83{\pm}0.49\;Log\;CFU/g$). No psychrophiles, coliforms and fecal coliforms were detected. In the phases after rapid chilling, during chilled storage and after reheating and distribution, almost none of the above microbes were detected. Salmonella and Listeria monocytogenes were not detected in all production phases. The pH immediately after cooking was 6.65 and then increased significantly to 6.81 on the third day of chilled storage (p<0.001). Acid value did not show significant changes while total volatile based nitrogen (TVBN) dramatitically increased during storage periods (p<0.01). In the result of sensory evaluation, general acceptability points had been rated high in the first day of storage, and then, the points were decreased significantly on the third day (p<0.05). General acceptability points ranged from 8.86 to 10.68. Accordingly, Broiled Spanish Mackerel is highly recommendable cook/chill system. Considering the DHSS standards for storage, the ideal shelf-life recommended for Broiled Spanish Mackerel is within 4 days excluding cooking day. For Broiled Spanish Mackerel, critical control points were purchasing and receiving of frozen Spanish Mackerel, heating, chilling, chilled storage, reheating and distribution.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.84.1-84.1
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• 2015

Recent years in particular in Korea see intensive interests in a deep geothermal engineering and its application in different uses as far as from direct uses to power generation sectors, that are achieved by harnessing hot energy sources from the earth. For instance widespread interest has been generated because the geothermal energy is the source that one extracts it for more than 20 hours per day and for about 30 years of an operation of the plant, which enables to give base load as for heating as well as an electric generation. In retrospect, shallow geothermal energy using heat pumps is commonplace in Korea while the deep geothermal is in the early stage of the development. Geothermal energies in view of the way of extracting heat are mainly categorized into several types such as a single well system, a hydrothermal system, an enhanced geothermal system (EGS) etc. In this talk, this speaker focuses on the thermo-fluid engineering of the single well system by introducing the modeling in order to harness hot fluid that is thermally balanced with the fluid of an injection well, which provides a challenge to assess the life time of the well. To avoid the loss of the temperature in producing the hot fluid, a specialized pipe or a borehole heat exchanger has been designed, and its concept is introduced. On the other hand, a binary system or an organic Rankine cycle, which provides the methodology to convert the heat into an electricity, is briefly introduced. Some experimental results of the binary system which has been constructed in our lab will be presented. Lastly as for the future direction, some comments for the industrialization of the deep geothermal energy in this country will be discussed.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.1
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• pp.118-123
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• 1987

In relation to the dust detonatians which have imposed severe damages on the industry, the ignitability of various dusts has been investigated on a horizontal shock tube in this study. By using a newly designed air injector, very well-distributed clouds could be obtained. The proper reflected shock conditions have been generated by placing a reflector 1.5cm behind the air injector, which reflected the incident shock wave. The incident shock waves in the range of Mach number 2.8-3.3 created the postreflected shock temperature of 1200-1600K. Experimentally the ignition delay was defined as the time interval between the arrival of a reflected shock wave at dusts and the detection of visible light. Measured ignition delays of dusts investigated were located lower than 1msec under the above conditions. These values are one-order higher than those in the incident shock wave condition. In this type of ignitiion process the following three processes are considered to play important roles; heating of a particle, generation of volatile gas by endothermic devolatilization process, and its diffusion from the particle surface and the formation of stoichiometric mixture with oxidizer.