• Steel and Composite Structures
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• v.10 no.2
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• pp.109-128
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• 2010

The expediency of using tubular composite steel and concrete columns of annular cross-sections in construction is discussed. The new type space framework with tubular composite columns of multi-storey buildings and its rigid beam-column joints are demonstrated. The features of interaction between the circular steel tube and spun concrete stress-strain states during the concentrical and eccentrical loading of tubular composite members are considered. The modeling of the bearing capacity of beam-columns of composite annular cross-sections is based on the concepts of bending with a concentrical force and compression with a bending moment. The comparison of modeling results for the composite cross-sections of beam-columns is analysed. The expediency of using these concepts for the limit state verification of beam-columns in the methods of the partial safety factors design (PSFD) legitimated in Europe and the load and resistance factors design (LRFD) used in other countries is presented and illustrated by a numerical example.

• Journal of Magnetics
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• v.16 no.1
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• pp.46-50
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• 2011

This paper presents size reduction of primary iron core for tubular linear induction motor by improved winding configuration. Using one-ampere conductor method, magnetic field analysis of tubular linear induction motor for size reduction is conducted. Size reduction and improvement of air gap flux distribution is achieved by improved winding configuration, and analysis results are verified by finite element analysis (FEA) and experiments.

• Journal of the Korea Institute of Military Science and Technology
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• v.25 no.4
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• pp.355-363
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• 2022

Development of supersonic flying vehicle is one of the most latest issue in modern military technology. Specifically, structural integrity of supersonic flying vehicle can be verified by high temperature structural test. High temperature structural test is required to consider thermal load caused by aerodynamic heating while applying structural load simultaneously. Tubular quartz lamps are generally used to generate thermal load by emitting infrared radiation. In this study, modified heat flux model of tubular quartz lamp is proposed based on existing model. Parameters of the proposed model are optimized upon measured heat flux in three dimensions. Finally, thermal load of plate specimen is designed by the heat flux model. In conclusion, it is possible to predict heat flux applied on plate specimen and desired thermal load of high temperature structural test can be obtained.

• Kyungpook Mathematical Journal
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• v.62 no.3
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• pp.497-507
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• 2022

In this study, we define tubular surfaces in Pseudo Galilean 3-space as type-1 or type-2. Using the X(s, t) position vectors of the surfaces and G(s, t) Gaussian transformations, we obtain equations for the two types of tubular surfaces that satisfy the conditions ∆X(s, t) = 0, ∆X(s, t) = AX(s, t), ∆X(s, t) = λX(s, t), ∆X(s, t) = ∆G(s, t), ∆G(s, t) = 0, ∆G(s, t) = AG(s, t) and ∆G(s, t) = λG(s, t).

• Proceedings of the KIEE Conference
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• 1986.07a
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• pp.28-30
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• 1986

• Journal for History of Mathematics
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• v.11 no.1
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• pp.42-46
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• 1998

Using Fermi coordinates and the principle curvature on the tubula hypersurfaces, we characterize space of constant sectional curvature by analysing the shape operator on the tubular hypersurfaces.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2007.11a
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• pp.193-198
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• 2007

KIER has been developing the anode supported flat tubular SOFC stack for the intermediate temperature $(700{\sim}800^{\circ}C)$ operation. for this purpose, we have first fabricated anode supported flat tubular cells by the optimization between the current collecting method and the induction brazing process. After that we designed the compact fuel & air manifold by adopting the simulation technique to uniformly supply fuel & air gas and the unique seal & insulation method to make the more compact stack. For making stack, the prepared anode-supported flat tubular cells with effective electrode area of $90cm^2$ of connected in series with 12 modules, in which one module consists of two cells connected in parallel. The performance of stack in 3 % humidified $H_2$ and air at $800^{\circ}C$ shows maximum power of 507 W. Through these experiments, we obtained basic & advanced technology of the anode-supported flat tubular cell and established the proprietary concept of the anode-supported flat tubular SOFC stack in KIER.

• Journal of Sensor Science and Technology
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• v.23 no.3
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• pp.211-215
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• 2014

The Pt-, Ni- and Cr-decorated tubular $SnO_2$ nanofibers for gas sensors were prepared by the electrospinning of polyvinylpyrrolidone (PVP) nanofibers containing Pt, Ni, and Cr precursors, the sputtering of $SnO_2$ on the electrospun PVP nanofibers, and the removal of sacrificial PVP parts by heat treatment at $600^{\circ}C$ for 2 h. Pt-decorated tubular $SnO_2$ nanofibers showed high response ($R_a/R_g=210.5$, $R_g$: resistance in gas, $R_a$: resistance in air) to 5 ppm $C_2H_5OH$ at $350^{\circ}C$ with negligible cross-responses to other interference gases (5 ppm trimethylamine, $NH_3$, HCHO, p-xylene, toluene and benzene). Cr-decorated tubular $SnO_2$nanofibers showed the selective detection of p-xylene at $400^{\circ}C$. In contrast, no significant selectivity to a specific gas was found in Ni-decorated tubular $SnO_2$ nanofibers. The selective and sensitive detection of gases using Pt-decorated and Cr-decorated tubular $SnO_2$ nanofibers were discussed in relation to the catalytic promotion of gas sensing reaction.

• Steel and Composite Structures
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• v.33 no.4
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• pp.615-627
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• 2019

This paper aims to study the compressive behavior of circular hollow and concrete-filled steel tubular stub columns under simulated marine atmospheric corrosion. The specimens after salt spray corrosion were tested under axial compressive load. Steel grade and corrosion level were mainly considered in the study. The mechanical behavior of circular CFST specimens is compared with that of the corresponding hollow ones. Design methods for circular hollow and concrete-filled steel tubular stub columns are modified to consider the effect of marine atmospheric corrosion. The results show that linear fitting curves could be used to present the relationship between corrosion rate and the mechanical properties of steel after simulated marine atmospheric corrosion. The ultimate strength of hollow steel tubular and CFST columns decrease with the increase of corrosion rate while the ultimate displacement of those are hardly affected by corrosion rate. Increasing corrosion rate would change the failure of CFST stub column from ductile failure to brittle failure. Corrosion rate would decrease the ductility indexes of CFST columns, rather than those of hollow steel tubular columns. The confinement factor ${\xi}$ of CFST columns decreases with the increase of corrosion rate while the ratio between test value and nominal value shows an opposite trend. With considering marine atmospheric corrosion, the predicted axial strength of hollow steel tubular and CFST columns by Chinese standard agree well with the tested values while the predictions by Japanese standard seem conservative.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.127-132
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• 2002

Recent deepwater offshore structures in Gulf of Mexico utilize butt welded tubular joints. Application of welded tubular joint includes tendons, production risers, and steel catenary risers. Fatigue life assessment of these joints becomes more critical because the structures to which they are attached are allowed to undergo cyclic and sometimes large displacements around an anchored position. Estimating the fatigue behavior of these tubular members in the design stage is generally conducted by using S-N curves specified in the codes and standards. Applying the stress concentration factor of the welded structure to S-N approach often results in very conservative assessment because the stress field acting on the tubular has a non-uniform distribution through the thickness. Fracture mechanics and fitness for service (FFS) technology have been applied in the design of the catenary risers. This technology enables the engineer to establish proper requirements on weld quality and inspection acceptance criteria to assure satisfactory structural integrity during its design life. It also provides guidance on proper design curves to be used and a methodology for accounting for the effects of non-uniform stress distribution through the wall thickness. An attempt was made to develop set of S-N curves based on fracture mechanics approach by considering non-uniform stress distribution and a threshold stress intensity factor. Series of S-N curves generated from this approach were compared to the existing S-N curves. For flat plate butt joint, the S-N curve generated from fracture mechanics matches with the IIW class 100 curve when initial crack depth was 0.5 mm (0.02"). Similar comparison with API X′ was made for tubular joint.. These initial crack depths are larger than the limits of inspection by current Non-destructive examination (NDE) means, such as Automatic Ultrasonic Inspection (AUT). Thus a safe approach can be taken by specifying acceptance criteria that are close to limits of sizing capability of the selected NDE method. The comparison illustrates conservatism built into the S-N design curve.