• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.5
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• pp.76-81
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• 2012

The continuing demand for increasingly slimmer and brighter liquid crystal display(LCD) panels has led to an increased focus on the role of the light guide panels(LGPs) or optical films that are used to obtain diffuse, uniform light from the backlight unit(BLU). And the most basic process in the production of such BLU components is the micromachining. LCD BLUs comprise various optical elements such as a LGP, diffuser sheet, prism sheet, and protector sheet with micro patterns. High aspect ratio patterns are required to reduce the number of sheets and enhance light efficiency, but there is a limit to the aspect ratio achievable for a given material and cutting tool. Therefore, this study comprised a series of experimental evaluations conducted to determine the machining feasibility in microcutting various aspect ratio patterns on electroless nickel plated die materials when using single-crystal diamond tools. Cutting performance was evaluated at various cutting speeds and depths of cut using different machining methods and machine tools.

• Journal of Korean Society for Quality Management
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• v.20 no.2
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• pp.11-20
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• 1992

We discuss the feed back control of the on-line QC in the Taguchi method. Taguchi(1982) used the assumptions that the quality characteristics follow an uniform distribution and the Brownian motion to draw the loss function and proposed ${\Delta}/3$ or ${\Delta}$ for the initial control limit. Adams and Woodall(1989) also proposed a different procedure but using the same loss function. We propose, in this paper the new loss function under the assumption of mainly Brownian motion and compare the results with the results of the above.

• Geomechanics and Engineering
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• v.33 no.1
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• pp.53-63
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• 2023

Rock disturbance caused by blasting and stress relaxation is commonly observed during excavation. As the distance from the source of disturbance increases, the degree of disturbance decreases, and rock at a large depth does not experience disturbance. However, in stability analyses, a single value of disturbance is often applied to the entire rock mass, which leads to underestimated results. In this study, this modeling mistake is addressed by considering realistically varying rock disturbance. The safety of infinite slopes in a disturbed rock mass with a strength governed by the Hoek-Brown failure criterion is investigated based on the kinematic approach of limit analysis. The maximum disturbance is assigned to the outermost slope face because it is directly exposed to blasting damage and dilation, and the disturbance progressively decays with distance in the rock mass. The safety analysis results indicate that the assumption of uniform disturbance in the entire rock mass leads to underestimation of the rock strength and safety on infinite rock slopes. A critical slip surface appears to be within the disturbed rock layer as well as the interface between the disturbed upper rock and undisturbed lower rock.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.5
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• pp.182-189
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• 2002

This paper is concerned with a collapse behavior analysis for a thin-walled structure considering farming effects. Numerical simulation is carried out with a finite element limit analysis in order to identify forming effects on collapse behavior of a thin-walled structure such as an S-rail. The formed S-rail contains fabrication histories such as residual stress, work hardening, non-uniform thickness distribution and geometric changes resulted from the forming process. The collapse behavior analysis of an S-rail with forming effects leads to different results from that without such effects. The present study deals with the collapse analysis of the S-rail fabricated with the typical forming, trimming and springback processes. Collapse properties such as the collapse load, the collapse mode and the energy absorption are calculated and investigated In order to identify forming effects. It is fully demonstrated that the design of thin-walled structures needs to consider the forming effects for a proper assessment of the load-carrying capacity and the deformation of the formed structures.

• Geomechanics and Engineering
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• v.15 no.3
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• pp.879-888
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• 2018

Probability-based design codes have been developed to sufficiently confirm the safety level of structures. One of the most acceptable probability-based approaches is Load Resistance Factor Design (LRFD), which measures the safety level of the structures in terms of the reliability index. The main contribution of this paper is to calibrate the load and resistance factors of the design code for tunnels. The load and resistance factors are calculated using the available statistical models and probability-based procedures. The major steps include selection of representative structures, consideration of the limit state functions, calculation of reliability for the selected structures, selection of the target reliability index and calculation of load factors and resistance factors. The load and resistance models are reviewed. Statistical models of resistance (load carrying capacity) are summarized for strength limit state in bending, shear and compression. The reliability indices are calculated for several segments of a selected circular tunnel designed according to the tunnel manual report (Tunnel Manual). The novelty of this paper is the selection of the target reliability. In doing so, the uniform spectrum of reliability indices is proposed based on the probability paper. The final recommendation is proposed based on the closeness to the target reliability index.

• Bulletin of the Korean Mathematical Society
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• v.59 no.1
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• pp.241-263
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• 2022

We consider a nonlinear Schrödinger equation with critical frequency, (P_𝜀) : 𝜀²∆v(x) - V(x)v(x) + |v(x)|^p-1v(x) = 0, x ∈ ℝ^N, and v(x) → 0 as |x| → +∞, for the infinite case as described by Byeon and Wang. Critical means that 0 ≤ V ∈ C(ℝ^N) verifies Ƶ = {V = 0} ≠ ∅. Infinite means that Ƶ = {x₀} and that, grossly speaking, the potential V decays at an exponential rate as x → x₀. For the semiclassical limit, 𝜀 → 0, the infinite case has a characteristic limit problem, (P_inf) : ∆u(x)-P(x)u(x) + |u(x)|^p-1u(x) = 0, x ∈ Ω, with u(x) = 0 as x ∈ Ω, where Ω ⊆ ℝ^N is a smooth bounded strictly star-shaped region related to the potential V. We prove the existence of an infinite number of solutions for both the original and the limit problem via a Ljusternik-Schnirelman scheme for even functionals. Fixed a topological level k we show that v_k,𝜀, a solution of (P_𝜀), subconverges, up to a scaling, to a corresponding solution of (P_inf ), and that v_k,𝜀 exponentially decays out of Ω. Finally, uniform estimates on ∂Ω for scaled solutions of (P_𝜀) are obtained.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2004.04a
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• pp.359-362
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• 2004

Using the idea of intuitionistic fuzzy set due to Atanassov, we define the notion of intuitionistic fuzzy metric spaces as a natural generalization of fuzzy metric spaces due to George and Veeramani and prove some known results of metric spaces including Baire's theorem and the Uniform limit theorem for intuitionistic fuzzy metric spaces.

• The Pure and Applied Mathematics
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• v.12 no.3 s.29
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• pp.169-178
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• 2005

In this paper we study the existence and local asymptotic limit of the topological Chern-Simons vortices of the CP(1) model in $\mathbb{R}^2$. After reducing to semilinear elliptic partial differential equations, we show the existence of topological solutions using iteration and variational arguments & prove that there is a sequence of topological solutions which converges locally uniformly to a constant as the Chern­Simons coupling constant goes to zero and the convergence is exponentially fast.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.295-299
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• 2006

The inner-structure bonded(ISB) sheet metal is defined as a composite sheet metal which has middle layer of truss-structure between two skin sheets. The characteristics such as ultra-light weight, high rigidity, high strength, etc are required especially for automobile parts. The characteristic of ISB sheet metal depends on inner-structure pattern or method of bonding. Pyramid type of crimped expanded metal is used for inner-structure and both of resistance welding and adhesive bonding are applied to make a specimen. As a result of compression test, it is appeared that forming limit is 10% reduction in thickness under a load of 8kgf per unit element(one inner-structure). In case of uniaxial tensile test the non-uniform surface integrity rather than the buckling of inner-structure happened at a load of 450kgf, which indicates elongation of 7.2% and thickness reduction of 13%. The eye-inspection method was applied to examine the defects occurring on the specimen during stretch forming. In case of biaxial stretch forming only the non-uniform deformation on the surface of a skin sheet could be observed. The forming limit in stretching of ISB sheet metal with the hemi-spherical punch of 150mm in diameter was 3mm in forming depth and 5% reduction in thickness.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.3
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• pp.725-733
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• 1990

An analysis of laminar mixed convection flow adjacent to the inclined flat surface which is subjected to a uniform temperature in a uniform free stream is performed. Nonsimilar boundary layed equation are derived by using the mixed convection parameters such that smooth transition from the purely forced convection limit to the purely free convection limit is possible. The governing equations are solved by a finite difference method using the coupled box scheme of sixth order. Numerical results are presented for prandtl numbers of 0.7 and 7 with the angle of inclination ranging from 0 to 90 degree from the vertical. The velocity distributions for the buoyancy assisting flow exhibit a significant overshoot above the free stream value in the region of intense mixed convection and the velocity field is found to be more sensitive to the buoyancy effect than the temperature field. The separation point near the wall was obtained for the buoyancy opposing flow. The local Nusselt number increases for buoyancy assisting flow and decreases for opposing flow with increasing value of the local Grashoff number in the mixed convection parameter. For large Prandtl number, the Nusselt number and the friction factor decrease significantly near the separation point. Present numerical predictions are in good agreement with recent experimental results by Ramachandran.