• Journal of Mechanical Science and Technology
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• v.17 no.11
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• pp.1739-1745
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• 2003

The boiling heat transfer characteristics of two-phase closed thermosyphons with internal grooves are studied experimentally and a simple mathematical model is developed to predict the performance of such thermosyphons. The study focuses on the boiling heat transfer characteristics of a two-phase closed thermosyphons with copper tubes having 50, 60, 70, 80, 90 internal grooves. A two-phase closed thermosyphon with plain copper tube having the same inner and outer diameter as those of grooved tube is also tested for comparison. Methanol is used as working fluid. The effects of the number of grooves, the operating temperature, the heat flux are investigated experimentally. From these experimental results, a simple mathematical model is developed. In the present model, boiling of liquid pool in the evaporator is considered for the heat transfer mechanism of the thermosyphon. And also the effects of the number of grooves, the operating temperature, the heat flux are brought into consideration. A good agreement between the boiling heat transfer coefficient of the thermosyphon estimated from experimental results and the predictions from the present mathematical model is obtained. The experimental results show that the number of grooves and the amount of the working fluid are very important factors for the operation of thermosyphons. The two-phase closed thermosyphon with copper tubes having 60 internal grooves shows the best boiling heat transfer performance.

• The Korean Journal of Nuclear Medicine
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• v.14 no.1
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• pp.9-16
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• 1980

A 2-site immunoradiometric assay for serum ferritin was evaluated with commercially available kit. The assay required 6 hours. The slope of the standard curve kept up ideal range with the calculation of maxium binding instead of total dose until expire date. The stage II washing was more important than the stage I washing on the modified washing procedure as the bead keeping to remain in the tube. With this modified mothod, three times of tube. washing was sufficient to reduce the significant errors The measured values of serially diluted sample with standard diluting buffer was proportional to the predicted values. In the experiment of serum effect on the assay. a linear relationship from 5 to 50% serum, but beyond 50% there was reduction in measured ferritin concentration. It has a sensitivity of 2.77 ng/ml, within-assay precision (CV) of 8.0%, and between-assay reproducibility(CV) of 7.4% (mean 174.8 ng/ml).

• Journal of the Korea Institute of Military Science and Technology
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• v.15 no.2
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• pp.224-230
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• 2012

Thermal batteries have excellent mechanical robustness, reliability, and long shelf life. Due to these characteristics as well as their unique activation mechanism, thermal batteries are widely adopted as military power sources. Li(Si)/$FeS_2$ thermal batteries, which are used mostly in these days, use LiCl-KCl and LiBr-LiCl-LiF as molten salt electrolyte. However, it is known that Li(Si)/$FeS_2$ thermal batteries have high internal resistance. Especially, $FeS_2$ cathode accounts for the greater part of internal resistance in unit cell. Many efforts have been put into to decrease the internal resistance of thermal batteries, which result in the development of new electrode material and new electrode manufacturing processes. But the applications of these new materials and processes are in some cases very expensive and need complicated additional processes. In this study, internal resistance study was conducted by adding carbon black and carbon nano-tube, which has high electron conductivity, into the $FeS_2$ cathode. As a results, it was found that the decrease of internal resistance of $FeS_2$ cathode by the addition of carbon black and carbon nano-tube.

• Journal of the Korean Society of Radiology
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• v.12 no.1
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• pp.39-46
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• 2018

The purpose of this study was to determine suitable angle of Tibia-foot and the X-ray tube for scaphoid in foot X-ray examination. A total of twenty patients(mean age $32.12{\pm}years)$ are participated in this study. In the positions of Foot AP, internal and external oblique, tibia-foot angle was defined as $90^{\circ}$ and $135^{\circ}$, and x-ray tube angle was defined as $0^{\circ}$, $5^{\circ}$, $10^{\circ}$, $15^{\circ}$ and $20^{\circ}$ respectively. The image quality was evaluated with blind test yielding scores ranging from 0 to 5 by the evaluation team consisted of 2 radiogical technologists, 2 radiologists, and 2 orthopedic surgeons. In case of Foot AP position, the degree of overlap between cuneiform and navicular was 3% and the blind test result was 4.89 at tibia-foot angle of $90^{\circ}$ and $15^{\circ}$ X-ray tube angle. When the tibia-foot angle is $135^{\circ}$, the degree of overlap was 5%, also the blind test result was 4.30 at $15^{\circ}$ X-ray tube angle. The degree of overlap and blind test result were 30% and 3.75 respectively at $0^{\circ}$ X-ray tube angle. In case of internal oblique position, at tibia-foot angle of $90^{\circ}$ and $0^{\circ}$ X-ray tube angle, the degree of overlap was 4% and the blind test result was 4.70. The 5% overlapping and highest score as 4.55 were obtained on tibia-foot angle of $135^{\circ}$ and $0^{\circ}$ X-ray tube angle. In case of external oblique position, at tibia-foot angle of $90^{\circ}$ and $15^{\circ}$ X-ray tube angle, the degree of overlap was 4% and the blind test score was 4.85. The 5% overlapping and highest score as 4.75 were obtained on tibia-foot angle of $135^{\circ}$ and $15^{\circ}$ X-ray tube angle. In conclusion, we confirmed suitable angle of tibia-foot and X-ray tube for scaph46oid in foot X-ray examination in this study. These findings will be helpful for us to reading for navicular fracture.

• Journal of Korean Society of Steel Construction
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• v.12 no.6
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• pp.759-767
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• 2000

In this study, the time dependent internal stress changes of a Concrete Filled Steel Tube(CFT) column during a fire test were quantitatively analyzed. The strain ratio of a CFT column on the different loads was measured by tensile strength tests in terms of yield strength, tensile strength average extensibility and elasticity modulus. To understand the internal material properties change of concrete in CFT column damaged due to a fire, the compressive strength and elastic modulus tests were measured on a core sample from the center of the steel tube after the fire test. The elastic modulus test measured the strain from the stress. To determine the fire temperature of the test material, a differential thermal analysis was done. From the tested result, the gained data were conducted and an analysis method was suggested. The purpose of this work is to suggest a basic data for structure regulation enactments of the internal fire design of CFT.

• Plant Journal
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• v.15 no.2
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• pp.56-61
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• 2019

In this study, the failure analysis of the internal tube occurred in the high pressure feedwater heater for power generation boiler of 500 MW supercritical pressure coal fired power plant was investigated. I suggested a prediction model that can diagnose internal tube failure by changing the position of level control valve on the shell side and the suction flow rate of the boiler feedwater pump. The suggested prediction model is demonstrated through additional cases of feedwater system unbalance. The simultaneous comparison of the shell side level control valve position and the suction flow rate of the boiler feedwater pump compared to the normal operating state value, even in the case of the high pressure feedwater heater for the power boiler, It can be a powerful prediction diagnosis.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.9 no.2
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• pp.189-197
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• 1997

The vaporizing characteristics of LNG(liquefied natural gas) via heat exchanger with sea water are analytically studied for an open rack vaporizer(ORV). This study is intended to supply the design data for the domestic fabrication of the corrosion-resistant vaporizer tube. A computational program is developed to predict the exit temperature of LNG for various conditions. In the program, thesimple and justifiable heat transfer models are selected for fully-developed internal flow of LNG, the star-shaped finned-tube, and the external falling films of sea water, as well as the possible ice formation and the fouling on the tube walls. It is found that the enongh corrugation inside of the tube wall is the most significant in the vaporizer performance for the current operating conditions. the effects of other design parameters on the heat exchanger between LNG and sea water are quantitatively presented.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.10a
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• pp.149-152
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• 2000

By using a three-dimensional finite element program HydroFORM-3D based on a rigid-plastic model, the hydroforming process for automobile subfrmae is analyzed in this study. The goal of this study is to accomplish preform design and determine the level of internal pressure for producing final hydroformed subframe component. Prior to hydroforming, the initial tube blank must be bent to the approximate centerline of the final part to enable the tube to be placed in the die cavity, After then, a preforming operation like stamping is carried out to the prebent tube. Finally, hydroforming process is performed to the preformed tube to get the final production. And through ductile fracture theory, the failure, bursting, is predicted during hydroforming process for tube blank with different diameter.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.05a
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• pp.194-197
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• 2004

In the tube hydroforming process, a tube is placed into the die cavity and the ends of the tube are sealed by fixing the axial cylinder piston into the ends. Then the tube is pressurized with a hydraulic fluid and simultaneously the axial cylinders move to feed the material into the expansion zone. Therefore, the quantitative relationship between process parameters such as internal pressure and feeding amount and hydroformabillity, is hard to establish because of their high complexity and many unknown factors. In this study, the empirical and the quantitative relationship between process parameters and hydroformabillity are analyzed by fuzzy rules. Fuzzy expert system is an advanced expert system which uses fuzzy rule and approximate reasoning. Many process parameters are converted to the quantitative relationship by use of approximate reasoning of fuzzy expert system. The comparison between experimentally measured hydroformabillity from hydroforming experiments and the predicted values by fuzzy expert system shows a good agreement.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2008.11a
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• pp.117-120
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• 2008

The Purpose of this is properties of CFT filled with expansion concrete. CFT(concrete filled steel tube) is the structure that circle shape steel column filled with concrete. 3 kinds of expansive additives and variation of replacement rate. we changed expansive additive from 0%, 10%, 20%, 30% of ratio of addition rate are selected for this experiment. Merits of CFT are concrete internal force rising influenced by steel shape restriction, reinforcing the local buckling, excellent resistance to transformation. Generally, High rise building using CFT utilize the high strength and fluidity concrete for packing the tube inside. As the result a steel tube charged expensive concrete has stiffness 1.5times more than a steel tube not charged concrete. Increase of resisting power about compressive stress by binding expansion of expansive concrete affects strength increase and softness.