• Journal of Korean Neurosurgical Society
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• v.49 no.2
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• pp.107-111
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• 2011

Objective : The aim of this study was to evaluate the utility of volume-rendered helical computerized tomography (CT) angiography focusing tracheostomy tube and innominate artery for prevention of tracheoinnominate artery fistula. Methods : The authors retrospectively analyzed 22 patients with tracheostomy who had checked CT angiography. To evaluate the relationship between tracheostomy tube and innominate artery, we divided into three categories. First proximal tube position based on cervical vertebra, named "tracheostomy tube departure level (TTDL)". Second, distal tube position and course of innominate artery, named "tracheostomy tube-innominate artery configuration (TTIC)". Third, the gap between the tube and innominate artery, named "tracheostomy tube to innominate artery gap (TTIG)". The TTDL/TTIC and TTIG are based on 3-dimensional (3D) reconstruction around tracheostomy and enhanced axial slices of upper chest, respectively. Results : First, mean TTDL was $6.8{\pm}0.6$. Five cases (23%) were lower than C7 vertebra. Second, TTIC were remote to innominate artery (2 cases; 9.1 %), matched with it (14 cases; 63.6%) or crossed it (6 cases; 27.3%). Only 9% of cases were definitely free from innominate artery injury. Third, average TTIG was $4.3{\pm}4.6$ mm. Surprisingly, in 6 cases (27.3%), innominate artery, trachea wall and tracheostomy tube were tightly attached all together, thus have much higher probability of erosion. Conclusion : If low TTDL, match or crossing type TTIC with reverse-L shaped innominate artery, small trachea and thin TTIG are accompanied all together, we may seriously consider early plugging and tube removal.

• Journal of Biomedical Engineering Research
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• v.5 no.1
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• pp.47-54
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• 1984

In order to research the flow in the thin wall compliant tube, this present study is attempt to measure the cross sectional area according to change of external pressure and flow by ultrasonic method different from willy used impedance technique for flow analysis about one dimensional Steads flow. The experimental results are as follows. 1) Measurement of cross sectional area ratio by ultrasonic method by comparison with experimental results of impedance technique & theoretical results were well consent. 2) Pressure difference of upstream and down stream is alwap's maximum range at 0.4 < $\alpha$ <0.5, and have no connection with changing external pressure. 3) when the external pressure is fixed and resistance is varied, Self excited oscillation occurs in the region at 0.5 < $\alpha$ <0.6, and oscillation disappear almost at R2>=1.2

• Nuclear Engineering and Technology
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• v.36 no.4
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• pp.316-326
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• 2004

The $40\%$ of wall criterion, which is generally used for the plugging of steam generator tubes, is applied only to a single crack. In a previous study, a total number of 9 failure models were proposed to estimate the local failure of the ligament between cracks, and the optimum coalescence model of multiple collinear cracks was determined among these models. It is, however known that parallel axial cracks are more frequently detected than collinear axial cracks during an in-service inspection. The objective of this study is to determine the plastic collapse model that can be applied to steam generator tubes containing two parallel axial through-wall cracks. Three previously proposed local failure models were selected as the candidates. Subsequently, the interaction effects between two adjacent cracks were evaluated to screen them. Plastic collapse tests for the plate with two parallel through-wall cracks and finite element analyses were performed to determine the optimum plastic collapse model. By comparing the test results with the prediction results obtained from the candidate models, a COD base model was selected as an optimum model.

• Steel and Composite Structures
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• v.52 no.2
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• pp.183-197
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• 2024

Not all structural columns maintain a vertical orientation. Several contemporary building structures have inclined columns, introducing distinct challenges, particularly in buckling behavior. This study examines the buckling behavior of inclined, thin-walled steel bundled columns, differing from typical vertical columns. Using specimens with three tubes welded to plates linearly aligned at the top and triangularly at the bottom, tests indicated that buckling capacity increases with tube wall thickness and diameter but decreases with column height. Inclined tubes in bundled columns showed improved buckling resistance over vertical ones. Results were verified against standard steel design guidelines to assess their predictive accuracy.

• Journal of the Korean Geotechnical Society
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• v.35 no.12
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• pp.91-100
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• 2019

Hollow prestressed concrete-filled steel tube (HCFT) piles, which combines PHC piles inside thin-wall steel tubes, were developed to increase the flexural strength of the pile with respect to the lateral load. Since P-M curves are needed for evaluating the structural safety of piles when applying HCFT piles to fields, equations for plotting P-M curves of HCFT piles in limit states were proposed. When the yield strength is applied to the steel tube and PC steel bar of HCFT piles, the proposed equations significantly underestimated the flexural strength of HCFT piles. Unlike the flexural strength test results, the proposed equations also provide greater flexural strengths for 12 mm thick steel pipe piles with the same diameter than for HCFT piles. However, when the ultimate strengths are used instead of the yield strengths for the steel tube and PC steel bar, the proposed equations provide the flexural strengths very close to the flexural strength test results.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.1
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• pp.114-120
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• 2020

In this study, the process of freezing around two consecutively arranged channel tubes used for evaporator heat exchange was numerically investigated. Numerical results confirmed that the vortex occurred between the front channel and the rear channel and also that the vortex occurred due to the rapid change of the channel at the rear of the rear channel. These vortices were found to play a role in reducing the ice layer to some extent by the growth of the ice layer at the front and rear of the channel tube. The freezing layer showed a tendency to gradually increase as it passed through the channel pipe. As the wall temperature in the channel pipe decreased, the thickness of the freezing layer increased. As the flow rate of water slowed, the thickness of the freezing layer became thicker. In particular, in the case of a slow flow rate of 0.03 m/s, the freezing layers of the front channel pipe and the rear channel pipe were connected to each other. The narrower the channel, the thinner the freezing layer was in both the front and rear channel tubes. It is found that these thin freezing layers are caused by the low thickness of the temperature boundary layer formed around the channel tube.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.1
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• pp.11-19
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• 2015

We present the results of a multi-material numerical investigation of the propagation of a combustible gas mixture detonation in narrow metal tubes. We use an experimentally tuned one step Arrhenius chemical reaction and ideal gas equation of state (EOS) to describe stoichiometric $H_2-O_2$ and $C_2H_4-O_2$ detonations. The purely plastic deformations of copper and steel tubes are modeled using the Mie-Gruneisen EOS and Johnson-Cook strength model. To precisely track the interface motion between the detonating gas and the deforming wall, we use the hybrid particle level-sets within the ghost fluid framework. The calculated results are validated against the experimental data because the results explain the process of the generation and subsequent interaction of the expansion wave with the high-strain-rate deformation of the walls.

• Nuclear Engineering and Technology
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• v.29 no.2
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• pp.175-180
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• 1997

It has been known that eater-side corrosion of fuel rods in nuclear reactor is accompanied with the metallic loss of wall thickness and hydrogen pickup in the fuel dadding tube. The fuel dad corrosion is one of the major factors to be controlled to maintain the fuel integrity during reactor operation. An oxide later thickness measuring device equipped with ECT probe system was developed by KAERI, and whose performance test was carried out in NDT(Non-destructive Test) hot-cell or PIE(Post Irradiation Examination) Facility. At first, the calibration/performance test was executed for the unirradiated standard specimen rod fabricated with several kinds of plastic thin films whose thickness ore predetermined, and the result of which showed a good precision within 10% of discrepancy. And then, hot test us peformed for the irradiated fuel rod selectively extracted from J44 fuel assembly discharged from Kori Unit-2. The data obtained with this device were compared with the metallographic result obtained from destructive examination in PIEF hot-cell on the same fuel rod to verify the validity of the measurement data.

• Journal of Korean Society of Steel Construction
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• v.15 no.1
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• pp.1-8
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• 2003

In locations where the cost of concrete is relatively high or in situations where the weight of concrete members has to be kept to a minimum, it may be more economical to use hollow reinforced concrete vertic al members. Hollow reinforced concrete colun-ms with a low axial load, a moderate longitudinal steel percentage and a reasonably thick wall were found to perform in a ductile manner at the flexural strength, similar to solid columns. Hollow reinforced concrete columns with a high axial load, a high longitudinal steel percentage, and a thin wall were found, however, to behave in a brittle manner at the flexural strength, since the neutral axis is forced to occur away from the inside face of the tube towards the section centroid and, as a result, crushing of concrete occurs near the unconfined inside face of the section. If, however, a steel tube is placed near the inside face of a circular hollow column, the column can be expected not to fail in a brittle manner through the disintegration of the concrete in the compression zone. A design recommendation and example through the moment-curvature analysis program for curvature ductility are herein presented. A theoretical moment-curvature analysis for reinforced concrete columns, indicating the available flexural strength and ductility, can be conducted, providing that the stress-strain relation for the concrete and steel are known. In this paper, a unified stress-stain model for confined concrete by Mander is developed foi members with circular sections.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.5
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• pp.407-415
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• 2008

The tubes in heat exchanger are typically made from copper alloy, stainless steel, carbon steel, titanium alloy material. type-439 ferritic stainless steel is ferromagnetic material, and furnish higher heat transfer rates than austenitic stainless steels and higher resistance to corrosion-induced flaws. Ferritic stainless steel can typically be found in low-pressure(LP) feedwater heaters and moisture separator reheaters(MSRs). LP feedwater heaters generally utilize thin wall type-439 stainless steel tubing, whereas MSRs typically employ a heavier wall tubing with integral fins. Service-induced damage can occur on the OD(outside diameter) surface of type-439 ferritic stainless steel tubing which is employed for MSRs tubing, and the most typical damage mechanism is vibration-induced tube-to-TSP(tube support plate) wear and fatigue cracking. The wear has been reported that occurs mainly on the OD surface. Accordingly, in this study, we have evaluated the flaw sizing capability of magnetic saturation eddy current technique using magnetic saturation probe and flawed specimen.