• Proceedings of the KSME Conference
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• 2000.04b
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• pp.57-64
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• 2000

The present work investigates the heat transfer characteristics for laminar fully developed forced convection in an internally finned tube with axially uniform heat flux and peripherally uniform temperature through analytical models of convection in a porous medium. Using the Brinkman-extended Darcy flow model and the two equation model fur heat transfer, analytical solutions fur fluid flow and heat transfer are obtained and compared with the exact solution for fluid flow and the numerical solutions for conjugate heat transfer to validate the porous medium approach. Using the analytical solutions, parameters of engineering importance are identified and their effects on fluid flow and heat transfer are studied. Also, the expression fur total thermal resistance is derived from the analytical solutions and minimized in order to optimize the thermal performance of the internally finned tubes.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.52-56
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• 2011

Recently, KARI(Korea Aerospace Research Institute) has been developing a modern 11.5m diameter four bladed bearingless main rotor system, and this rotor system can be used for 7,000lb class helicopter. Flexbeam and torque tube can be considered as the key structural components, and large elastic twist of flexbeam induced by pitch control motion of torque tube can influence the nonlinear aeroelastic behavior. In this paper, the dynamic characteristic analysis results of bearingless rotor system were presented. In order to construct a input model and validate the analysis procedures, calculated results using the comprehensive helicopter analysis program CAMRAD II were compared with the measured natural frequencies and lag damping data from small-scale wind tunnel test. Next, the analysis model was extended to a full-scale model, and the dynamic analysis results were presented.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.2
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• pp.187-192
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• 2012

Recently, KARI(Korea Aerospace Research Institute) has been developing a modern 11.5 m diameter four bladed bearingless main rotor system, and this rotor system can be used for 7,000 lb class helicopter. Flexbeam and torque tube can be considered as key structural components, and large elastic twist of flexbeam induced by pitch control motion of torque tube can influence the nonlinear aeroelastic behavior. In this paper, the dynamic characteristic analysis results of bearingless rotor system were presented. In order to construct a input model and validate the analysis procedures, calculated results using the comprehensive helicopter analysis program CAMRAD II were compared with the measured natural frequencies and lag damping data from small-scale wind tunnel test. Next, the analysis model was extended to a full-scale model, and the dynamic analysis results were presented.

• Journal of the Korean Society of Combustion
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• v.18 no.2
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• pp.23-31
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• 2013

Compact steam boiler is a useful heat exchanger in a space-intensive system. There are some constraints in terms of sizing and designing the space confined in the system which is usually used in vessels. In this study, design considerations for heavy duty heat exchangers of compact steam boilers are presented and evaluated. Especially, evaporator tubes of marine boiler which are exposed to a high temperature environment are considered. Also, extended surface designs with a high temperature are examined. In order to determine the criteria with considerations of both heat transfer rate and pressure drop in the heat exchanger, they are evaluated with major variables, such as the tube diameter, the number of tubes, and the tube length. Finally, the design parameters are estimated as the bare tubes are installed instead of the finned tubes.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.240-243
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• 2003

Finite element analyses for bursting failure prediction in bulge forming under combined internal pressure and independent axial feeding are carried out. By means of the FEM combined with Oyane's ductile fracture criterion based on Hills quadratic plastic potential, the forming limit and bursting pressure level are investigated for a seamed tube that comprises of weldment, heat affected zone(HAZ) and base material parts. Especially, in order to determine the material property of HAZ tensile tests for the base material and the weld metal are executed based on iso-strain approach. Finally, through a series of bulge forming simulations with consideration of the weldment and HAZ it is concluded that the proposed method would be able to predict the bursting pressure and fracture initiation site more realistically, so the approach can be extended to a wide range of practical bulge forming processes.

• Korean Journal of Clinical Laboratory Science
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• v.39 no.3
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• pp.161-166
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• 2007

To develop a rapid and reliable single-tube-based PCR technique for detection simultaneously the quinolone resistance qnrA, qnrB and qnrS genes. After multiple alignment, primers were designed to detect known qnr variants. I was used for A total of 43 extented-spectrum ${\beta}$-lactamases (ESBLs) producing Escherichia coli and Klebsiella pneumoniae isolated from university hospital were tested for screening, as with qnr genes. In optimized conditions, all positive controls confirmed the specificity of the PCR primers. Out of 43 isolates, qnrA genes were detected 19 (44.2%), qnrB genes 5 (11.7%), qnrS genes 15 (34.9%) and 8 (18.6%) isolates were not detected. I report here a fast and reliable technique for rapid screening of qnr positive strains to be used for epidemiological surveys.

• Journal of Veterinary Clinics
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• v.17 no.1
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• pp.138-144
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• 2000

The studies were carried out to investigate the effects of esophageal thermal tube for rewarming in the hypothermia in rabbits. Thiry-one rabbits were continuously cooled with femoral arterio-venous bypass circulation to 25.0${\pm}$0.3$^{\circ}C$(profound hypothermia) of rectal temperature. The experiment was consisted with 3 esophageal thermal tube groups perfused with circulation water at 38${\pm}$1$^{\circ}C$(low, n=12), 42${\pm}$1$^{\circ}C$(medium, n=12), and 45${\pm}$1$^{\circ}C$(high, n=7). Esophageal thermla tube specially constructed double-lumen esophageal tube with circulating warm water at respective htermal grade. With this device, rewarming of the rabbits as follows; High-esophageal thermal tube group(45${\pm}$1$^{\circ}C$)had a more effect on mean arterial pressure(MAP), heart rate(HR), esophageal temperature, and rectal temperature than others groups, but the circulation water at 45$\pm$1$^{\circ}C$ may cause thermal injuries in the esophagus because esophageal temperature increased to 41.1$^{\circ}C$. Medium-esophageal thermal tube group(42${\pm}$1$^{\circ}C$) had a more effect on RR than others groups, but the circulation water at 42${\pm}$1$^{\circ}C$ may also cause thermal injuries in the esophagus if the temperature exceeds 42$^{\circ}C$ for an extended period of time because its esophageal temperature increased to 39.4$^{\circ}C$. Low-esophageal thermal tube group(38${\pm}$1$^{\circ}C$) had a more effect on MAP, RR, and esophageal temperature than others groups. In conclusion, rewarming of the central core in the treatment of profound hypothermia using the esophageal thermal tube perfused with circulation water at 38${\pm}$1$^{\circ}C$ appears to be a ideal alternative safety zone of the temperature of circulation water avoiding thermal injury in esophagus causing by out of order or lower precise thermostat of water bath to that of others groups.

• The Journal of the Acoustical Society of Korea
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• v.19 no.6
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• pp.3-9
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• 2000

The Bell King Songdok the Great tolls magnificient sound that would be a great vehicle which brings all beings to the Sutras. Since 693, there was a magic flute, MANPASIKJUK, which was in existence in Shilla Dynasty that could lull all the evil-wawes, such an plaques, storms, Droughts, Famines and even Enemies. Thus, a sound tube, MANPASIKJUK, was erected in the crown of the Bell Songdok the Great so as to be effective to emit the nominal frequency tone whenever the Bell tolls for the national prosperity and welfare the People. Therefore, the Bell makers tried to fine the transmissibility condition through the sound tubr, several times during 34 years, However, it seems to be unfinished. Ever since, all of the korean Brahman Bell have the sound tubes of MANPASIKJUK, but none is performed their own functions. Here, one of the way to let the function of the sound tube of MANPASIKJUK out in the Bell Songdok the Great is proposed. There are two steps: the 1st is to elongate 18cm to the present length 77cm to fulfill the transmissibility condition for the nominal frequency of sound is emitted through the corrected sound tybe. 2nd step is to rise to 95% of the emission of the tone of nominal frequency, so that an exponential hem with the flare constant 2.8m-1, length 2.259m and the radius of the mouth 1.772m is to be extended to the corrected sound tube.

• Steel and Composite Structures
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• v.3 no.1
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• pp.47-64
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• 2003

In a nonlinear finite element study on the mechanical behavior of simple beam connections to continuous concrete-filled steel tube columns, two principally different connection types were analyzed: one with plates attached to the outside of the tube wall, relying on shear transfer, and one with an extended plate inserted through the steel section to ensure bearing on the concrete core. The load was applied partly at the connection within the column length and partly at the top, representing the load from upper stories of a multistory building. The primary focus was on the increased demand for load transfer to ensure composite action when concrete with higher compressive strength is used. The results obtained from the analyses showed that the design bond strength derived from push tests is very conservative, mainly due to the high frictional shear resistance offered by pinching and contraction effects caused by connection rotation. However, with higher concrete strength the demand for load transfer increases, and is hard to fulfill for higher loads when connections are attached only to the steel section. Instead, the connection should penetrate into the concrete core to distribute load to the concrete by direct bearing.

• Proceedings of the Korean Nuclear Society Conference
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• 1999.10a
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• pp.355.2-355
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• 1999

The spnng back phenomena occurring in the coiling process of a steam generator tube induces the dimensional inaccuracy and makes the coiling procedure difficult. In this research, an analytical model was developed to evaluate the amount of the spring back for SMART steam generator tubes. The model was developed on the basis of beam theory and elastic-perfectly plastic material property. This model was extended to consider the effect of plastic hardening and the effect of the tensile force on the spring back phenomena. Parametric studies were performed for various design variables of steam generator tubes in order to minimize the spring back in the design stage. A sensitivity analysis has shown that the low yield strength, the high elastic modulus, the small helix diameter, and the large tube diameter result in a small amount of the spring back. The amount of the spring back can be controlled by the selection of adequate design values in the basic design stage and reduced to an allowable limit by the application of the tensile force to the tube during the coiling process.rocess.