• Journal of the Korean GEO-environmental Society
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• v.15 no.11
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• pp.29-42
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• 2014

This paper investigates the effects of micro-tunneling on buried pipelines parametrically. A simplified numerical approach was developed and various parametric studies have been conducted to evaluate the effects of ground settlements on the response of buried pipelines. The controlled parameters included the pipe stiffness, ground loss magnitude, and pipe location with respect to a micro-tunnel. Maximum settlement and curvature along a pipeline have been investigated and compared among others for different conditions. In addition, the numerical results have been compared with a theoretical method by Attewell et al. (1986), which is based on a Winkler type linear-elastic solution. The comparison indicated that the response of buried pipes to micro-tunneling-induced ground settlements highly depends on the soil-pipe interaction including the separation and slippage of pipe from soil with the effects of the investigated parameters. Therefore, rather than using the theoretical method directly, it would be a better assessment of the response of buried pipelines to consider the soil-pipe interaction in more realistic conditions.

• Journal of the Korean Ceramic Society
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• v.25 no.6
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• pp.665-670
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• 1988

The behavior of mechanical properties of ion exchanged glasses was investigated in this study. The used glasses were soda-lime-silica glasses that were produced by float process. The maximum values of the bending strength and the curvature depth are 45Kg/$\textrm{mm}^2$ and 8.6mm respectively treated at 45$0^{\circ}C$ for 6h, which are 4.4 times and 3.3 times higher than parent glass. In the case, the thermalshock resistance ΔT is 335$^{\circ}C$ that is 205$^{\circ}C$ higher than parent glass, which is the maximum values in this study. The maximum values of the surface microhardness is 490Kg/$\textrm{mm}^2$ in case of 43$0^{\circ}C$ for 4h. It is also found out that annealing points are increased linearly with increasing the amount of K+ ion exchange independent of treatment temperature. Furthermore, the present work shows that the ion exchange strengthened glasses are more effective than the physical tempering glasses ; the bending strength and the curvature depth are 1.8 times and twice higher respectively.

• Geotechnical Engineering
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• v.12 no.6
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• pp.79-86
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• 1996

This study develops a new method for interpreting the yield load from load tests on drilled shaft foundations ended on general soils, which is defined as a point where the maximum curvature on the hyperbolic-approximated load-settlement curve occurs. How ever, the point of maximum curvature is a variable depending on the units and scales of the load and settlement. Therefore, to obtain a unique maximum curvature point, both the load and settlement must be normalized by proper parameters, respectively, and be expressed on the same scaled arses(1:1). Normalization has been processed so that the yield load by the new interpretation is to be close to the average of yield loads interpreted by other methods investigated in this study. The quantitative comparison between the new criterion and other conventitonal methods is presented.

• Journal of the Korea Concrete Institute
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• v.26 no.2
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• pp.159-169
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• 2014

This study generalizes the lateral load-displacement relationship of reinforced concrete shear walls from the section analysis for moment-curvature response to straightforwardly evaluate the flexural capacity and ductility of such members. Moment and curvature at different selected points including the first flexural crack, yielding of tensile reinforcing bar, maximum strength, 80% of the maximum strength at descending branch, and fracture of tensile reinforcing bar are calculated based on the strain compatibility and equilibrium of internal forces. The strain at extreme compressive fiber to determine the curvature at the descending branch is formulated as a function of reduction factor of maximum stress of concrete and volumetric index of lateral reinforcement using the stress-strain model of confined concrete proposed by Razvi and Saatcioglu. The moment prediction models are simply formulated as a function of tensile reinforcement index, vertical reinforcement index, and axial load index from an extensive parametric study. Lateral displacement is calculated by using the moment area method of idealized curvature distribution along the wall height. The generalized lateral load-displacement relationship is in good agreement with test result, even at the descending branch after ultimate strength of shear walls.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.11a
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• pp.35-38
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• 2005

The Objective of this work was to design Composite Antenna Structures (CAS) and investigate impact behavior of CAS which was various curvature. This term, CAS, indicates that structural surface becomes antenna. Constituent materials were selected considering electrical properties, dielectric constants and tangent loss as well as mechanical properties. For the antenna performance, microstrip antenna layers inserted into structural layers were designed for satellite communication at the resonant frequency of 12.5 GHz and final demonstration article was. After making five kinds of curved CAS, which radii of curvature are flat, 200, 150, 100, 50 mm. The antenna performance changed in accordance with variation of curvature. The Reflection coefficient was independent of curvature but the gain decreased with the radius of curvature. The impact test equipment was Dyna-8250 drop weight tester. The impact characteristic in accordance with curvature is maximum absorb energy is same each other. The impact energy was 8.5 J. For various Impact energy test, five energy levels 3 J, 5 J, 7 J, 10 J, 20 J were used. The performance of impact damaged antenna was estimated by measuring the return loss and the radiation pattern. It was revealed that the performance of antenna was not related to the impact damage. Because the impactor did not damage the patch directly. CAS have good impact stability for the antenna performance.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.4
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• pp.1510-1520
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• 1996

An experimental study on the flow over the axisymmetric backward-facing step was carried out. The purpose of the present study is to investigate the effect of the separating streamline curvature on the reattachment length and to understand the structure of recirculating flows. Local mean and fluctuating velocity components were measured in the separating and reattaching axisymmetric region of turbulent boundary layer on the wall of convex cylinder placed in a water tunnel by using 2-color 4-beam fiber optics laser Doppler velocimetry. The study demonstrates that the reattachment length increases with increasing separating streamline curvature. It is also observed that the reverse flow velocity and turbulent kinetic energy increase with an increase in the separating streamline curvature. In addition, the behavior of maximum turbulent stresses show that the effect of separating streamline curvature is larger in the region of recirculating zone(X/H<2) than in the region of reattachment point.

• Journal of Ocean Engineering and Technology
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• v.20 no.4 s.71
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• pp.24-30
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• 2006

Different methods exist for the estimation of thermaldeformation of plates in the line heating process. These are based on the assumption of residual strains in the heat-affected zone, known as the method of inherent strains, or simulated relations between heating conditions and residual deformations. The purpose of this paper is to develop a simulator of thermal deformation in the line heating, using the artificial neural network. Curvature deformations for the plate-forming are investigated, which can be used as a prime deformation parameter in the process. The curvature of plates are calculated using the approximation of plate surface by NURBS. Line heating experiments for 11 specimens of different thickness and heating conditions were performed. Two neural networks predicting the maximum temperature and curvature deformations at the heating line are studied. It was concluded that the thermal deformations predicted by the neural network can be used in a line heating simulator, which is considered an attractive and practical alternative to the existing methods.

• Korean Journal of Optics and Photonics
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• v.18 no.2
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• pp.130-134
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• 2007

I present a novel curvature profilometer devised fur the profile measurement of aspheric and free-form surfaces on the nanometer scale. A profile is reconstructed from measuring the curvature of a test part of the surface at several locations along a line. For profile measurement of free-farm surfaces, methods based on local part curvature sensing have strong appeal. Unlike full-aperture interferometry they do not require customized null optics. The measurement accuracy of the curvature profilometer was assessed by comparison with a well-calibrated interferometer in NIST. Experimental results prove that the maximum discrepancy turns out to be 37 nm on the 28 mm measurement range for the spherical mirror.

• Structural Engineering and Mechanics
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• v.52 no.2
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• pp.307-322
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• 2014

A two-step procedure to detect and quantify damages in structures from changes in curvature mode shapes is presented here. In the first step the maximum difference in curvature mode shapes of the undamaged and damaged structure are used for visual identification of the damaged internal-substructure. In the next step, the identified substructures are searched using unified particle swarm optimization technique for exact identification of damage location and amount. Efficiency of the developed procedure is demonstrated using beam like structures. This methodology may be extended for identifying damages in general frame structures.

• Journal of the Korean Mathematical Society
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• v.55 no.3
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• pp.749-761
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• 2018

Here, we calculate the evolution equation of the reduced hh-curvature and the Ricci scalar along the Finslerian Ricci flow. We prove that Finsler Ricci flow preserves positivity of the reduced hh-curvature on finite time. Next, it is shown that evolution of Ricci scalar is a parabolic-type equation and moreover if the initial Finsler metric is of positive flag curvature, then the flag curvature, as well as the Ricci scalar, remain positive as long as the solution exists. Finally, we present a lower bound for Ricci scalar along Ricci flow.