• Transactions of Materials Processing
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• v.33 no.2
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• pp.87-95
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• 2024

The current study aims to prove that high-speed forming has better formability than conventional low-speed forming. Experimentally, the quasi-static forming limit diagram was obtained by Nakajima test, and the dynamic forming limit diagram was measured by electrohydraulic forming. For the experiments, the LS-DYNA was used to create the optimal specimen for electrohydraulic forming. The strain measurement was performed using the ARGUS, and comparison of the forming limit diagrams confirmed that EHF showed better formability than quasi-static forming. Theoretically, the Marciniak-Kuczynski model was used to calculate the theoretical forming limit. Swift hardening function and Cowper Symonds model were applied to predict the forming limits in quasi-static and dynamic status numerically.

• Honam Mathematical Journal
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• v.19 no.1
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• pp.139-144
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• 1997

In this paper, we make some results on the direct limit of the locally nilpotent direct system. We study the ($T^{**}$) - properties of the above direct limit and homotopy equivalence of the direct limits.

• Journal of the Chungcheong Mathematical Society
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• v.19 no.4
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• pp.409-415
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• 2006

In this paper, we study the condition that a given homeomorphism has a square root and give an example of a wandering homeomorphism without square roots.

• Journal of the Korean Statistical Society
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• v.24 no.1
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• pp.219-224
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• 1995

A central limit theorem with random indices is obtained for stattionary martingale difference sequences.

• Communications of the Korean Mathematical Society
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• v.12 no.4
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• pp.1033-1038
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• 1997

A functional central limit theorem for a class of nonlinear stationary Markov processes which are geometrically Harris ergodic is derived.

• Communications of the Korean Mathematical Society
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• v.10 no.4
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• pp.963-974
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• 1995

We formulate central limit theorems for non-linear functionals of stationary Gaussian vector processes with long-range dependence.

• Journal of applied mathematics & informatics
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• v.22 no.1_2
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• pp.569-575
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• 2006

In this paper, we define the positive and negative limit sets in the hemicompact space and establish their dynamical properties.

• Communications of the Korean Mathematical Society
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• v.15 no.3
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• pp.541-547
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• 2000

In this paper, we discuss various limit sets of projectively flat manifolds and relationship between them.

• Journal of the Chungcheong Mathematical Society
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• v.35 no.1
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• pp.69-76
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• 2022

In this article, we investigate minimality, transitivity and mixing property for a shift map on the orbital inverse limit systems.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.2
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• pp.135-140
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• 2010

A new treatment is proposed to handle a deflection limit in the open-loop-onset-point (OLOP), which is commonly used in the prediction of pilot in-the-loop oscillation (PIO) due to a rate saturation. The new approach is motivated by the frequency response of a stand-alone actuator in that, unlike the suggestion by the original OLOP procedure, the rate limit onset is not delayed to a higher frequency by a deflection limit. Indeed, if a feedback control loop is closed, the rate limit onset can be shifted to a lower frequency since the controller tends to react with larger commands when deflection limited. The amplitude of the command at this onset frequency is combined with the deflection limit to estimate the associated gain reduction in the open-loop-onset-point in the final step of the OLOP process. The comparison of the new approach with the previous method reveals that an inaccurate optimism which can occur in the previous method is corrected by the proposed treatment.