• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.211-216
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• 2007

The objective of this paper is to present the results of an experimental and a finite-element investigation into the behavior of X80 grade pipes subjected to bending. For the pipe specimens comprising the test series, different D/t is applied to be representative of those that can be expected in the field. Results from the numerical models are checked against the observations in the testing program and the ability of numerical solutions to predict pipe moment capacity. curvatures. and buckling modes is established. A finite-element model was developed using the finite-element simulator to predict the local buckling behavior of pipes. The comparison between the numerical and the experimental results demonstrates the ability of the analytical model to predict the local buckling behavior of pipes when deformed well into the post-yield range.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.5
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• pp.158-165
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• 2004

Up to now, many crack repair techniques have been developed for inhibiting crack growth in structural components. However, the simplest way for inhibiting crack growth is to apply a indentation at the crack tip or at some distance ahead of the expected crack growth path so as to produce residual compressive stresses that can reduce the effective stresses around the crack tip. In spite of its importance to the aerospace industry, little attention has been devoted to evaluation of the indentation residual stress effect on the fatigue crack initiation life quantitatively. Therefore, in the present work, the magnitude and distribution of the indentation residual stresses were investigated in order to estimate the beneficial effect on fatigue crack initiation by using finite element method. Furthermore, to examine the validity of finite element analysis results, residual stress distribution in the indented specimen was measured by using X-ray diffraction technique, and fatigue crack behavior at fastener hole in aluminum alloy 7075-T6 before and after indentation processes was investigated.

• Communications of the Korean Mathematical Society
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• v.38 no.1
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• pp.1-9
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• 2023

An le-module M over a commutative ring R is a complete lattice ordered additive monoid (M, ⩽, +) having the greatest element e together with a module like action of R. This article characterizes the le-modules _RM such that the pseudo-prime spectrum X_M endowed with the Zariski topology is a Noetherian topological space. If the ring R is Noetherian and the pseudo-prime radical of every submodule elements of _RM coincides with its Zariski radical, then X_M is a Noetherian topological space. Also we prove that if R is Noetherian and for every submodule element n of M there is an ideal I of R such that V (n) = V (Ie), then the topological space X_M is spectral.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.1
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• pp.34-39
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• 2002

Most X-ray generator had been used do rectifier type transformer high tension generator which is supplied in a clinical diagnosis. But it is difficult to miniaturize and become light weight. Also, because the ripple rate of tube voltage is high, X-ray generating efficiency is very low. Therefore, it is supplied gradually from abroad being developed high tension generator for inverter type X-ray generator which use semi-conductor switching element for electric power that have high speed switching ability to solved these problem. But, semi-conductor element of big capacity are used by X-ray tube's big consumption power and diffusion is difficult in the small size hospital because production cost is ascending by doing digital control through DSP and product price becomes expensive. Therefore, in this paper, design and manufactured CR type voltage divider for feedback control of tube voltage of high frequency resonance type inverter and high tension transformer for high frequency to apply economical diffusion type X-ray generator which have wide output voltage and load extent. It is Proved do X-ray generator and stability of X-ray tube's output characteristics through an experiment.

• Journal of radiological science and technology
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• v.24 no.2
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• pp.5-11
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• 2001

Most of X-ray generator had used rectifier type transformer with high tension generator which is supplied in a clinical diagnosis. Because the ripple rate of tube voltage is high, X-ray generating efficiency is very low. In these days, high tension generator for inverter type X-ray generator is being supplied from a broad which uses semi-conductor switching element for the electric power that have a high speed switching ability to solve these problem. But, semi-conductor element with large capacity is used with X-ray tube's large consumption power and diffusion is difficult in the small size hospital because production cost is going up by doing digital control through DSP. Therefore, this paper designed and manufactured CR type voltage divider for feedback control of tube voltage with high frequency resonance type inverter and for high tension transformer with high frequency. It was to make economical diffusion type X-ray generator which has wide output voltage and load extent. It was preyed that the X-ray generator had the stability of X-ray tube's output characteristics.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1696-1701
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• 2007

This paper presents a micro-mechanical model of ductile fracture for the API X65 steel using the Gurson-Tvergaard-Needleman (GTN) model. Experimental tests and FE damage simulations using the GTN model are performed for smooth and notched tensile bars, from which the parameters in the GTN model are calibrated. As application, the developed GTN model is applied to simulate small-sized, single-edge-cracked tensile and bend bars, via three-dimensional FE damage analyses. Comparison of FE damage analysis results with experimental test data shows overall good agreements.

• Tunnel and Underground Space
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• v.1 no.2
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• pp.168-180
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• 1991

Through field measurements, it was shown that the shear stresses along a fully grouted rock blot were proportional to the differences between the displacement of a bolt rod and that of surrounding rock. Accordingly the theoretical equation for the displacement along a rock bolt, R(x), can be proposed as differential form; $ \frac{d^2R(x)}{dx^2}-aR(x)=-a^2U(x)$ where U(x) is the displacement of surrounding rock and α is a constant. In this study above equation was applied to the boundary element analysis which can simulate the supporting behavior of each rock bolt around a tunnel and the results of the implementation of boundary element technique were shown.

• Journal of the Korean Institute of Intelligent Systems
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• v.19 no.3
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• pp.425-431
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• 2009

By using the notion of interval-valued fuzzy relations, we forms the poset (IVFR (X), $\leq$) of interval-valued fuzzy relations on a given set X. In particular, we forms the subposet (IVFE (X), $\leq$) of interval-valued fuzzy equivalence relations on a given set X and prove that the poset (IVFE(X), $\leq$) is a complete lattice with the least element and greatest element.

• Journal of the Korean Institute of Intelligent Systems
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• v.21 no.1
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• pp.145-152
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• 2011

By using the notion of interval-valued intuitionistic fuzzy relations, we form the poset (IVIR(X), $\leq$) of interval-valued intuitionistic fuzzy relations on a given set X. In particular, we form the subposet (IVIE(X), $\leq$) of interval-valued intuitionistic fuzzy equivalence relations on a given set X and prove that the poset (IVIE(X), $\leq$) is a complete lattice with the least element and greatest element.

• Bulletin of the Korean Mathematical Society
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• v.28 no.2
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• pp.243-254
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• 1991

For a given function f.mem.F and a set of functions J.subeq.F, the problem of isotonic optimization is to determine an element in the set nearest to f in some sense. Specifically, let X be a partially ordered finite set with a partial order << and, let F"=F(X) be the linear space of all bounded real valued functions on X. A function g.mem.F is said to be an isotonic function if g(x).leq.g(y) whenever x,y.mem.X and x << y.<< y.