• Journal of the Korean Society for Precision Engineering
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• v.12 no.10
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• pp.40-49
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• 1995

This paper presents the performance and problems in analysis method and testing system of Electronic Speckle Pattern Interferometry (ESPI) method, in measuring two - dimensional in-plane displacement. The anyalysis result of measurement by ESPE is quite comparable to that tof measurement by strain gauge method. This implies that the method of ESPE is a very effective tool in non-contact two-dimensional in-plane strain analysis. But there is a controversal point, measurment error. This error is discussed to be affected not by ESPE method itself, but by its analysis scheme of the interference fringe, where the first-order interpolation has been applied to the points of strain measured. In this case, it is turned out that the more errors would be occurred in the large interval of fringe. And so this paper describes a computer method for drawing when the height is available only for some arbitrary collection of points. The method is based on a distance-weighted, last- squares approximation technique with the weight varying with the distance of the data points.

• Journal of Hydrospace Technology
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• v.2 no.1
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• pp.1-9
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• 1996

We consider the following two questions mainly in this study. First one is how the free surface hayes affect the lift of a shallowly submerged moving body. For this matte., we reinterpret the theoretical results of Kochin(1936), and point out that the high Froude number approximation is not always on the safer side. Second one is what sort of dimensionless parameters determine the occurrence of wave breaking behind a moving submerged body. Temporarily before getting a better answer, we propose that the two-parameter-plane, namely, the plane of the Froude number and the square root of the ratio of the submerged depth and the body length, may be used for predicting the possibility of wave breaking behind the submerged body. A region in the parameter plane is put forth as that of wave breaking, and the validity of this proposal is shown by its agreement with the existing experimental data of Parkin et al(1955) and those of Duncan(1983). Finally, linear and nonlinear numerical results are compared with the existing experimental data to see in what range of the parameters the linear and nonlinear theory case predict the wave field and the pressure on the body with reasonable accuracy. However, since the experimental data, which offer both the pressure and wave elevation for a submerged moving body, are very scarce, much cannot be attained through this comparative study. Hence, it is strongly recommended to carry out well planned experiments to get such data.

• Journal of the Korean Institute of Telematics and Electronics
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• v.22 no.5
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• pp.93-101
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• 1985

A two-dimensional numerical analysis progranl, called SOMOS ( simulation of MO5 transistors), has been developed for the simulation of MOSFET's with various channel lengths and bias conditions. The finite difference approximation of the fundamental equa-tions are formulated using Newton's method for Poisson's equation and the divergence theorem for the continuity equation. For the solution of the lincariBed equations, SOR (successive over relaxation) method and Gummel's algorithm have been employed, The total simulation time for oar operating point is varying between 30 sec. and 4 min. on VAX 11/780 depending on bias conditions, The nonuniform mesh was generated and refined automatically to account for various bias values and the potential distributions.

• Journal of Ocean Engineering and Technology
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• v.7 no.1
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• pp.13-24
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• 1993

The dispersion in the oscillatory flow generated by gravitational waves above the spatially periodic repples is studied. The steady parts of equations describing the orbit of the passive particle in a two dimensional field are assumed to be simply trigonometric functions. From the view point of nonlinear dynamics, the motion of the particle is chaotic under externally time-periodic perturbations which come from the wave motion. Two cases considered here are; (i) shallow water, and (ii) deep water approximation.

• Journal of Korean Port Research
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• v.14 no.4
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• pp.451-461
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• 2000

The design and maintenance of navigation channel and water facilities of an harbor which is located at the mouth of river or at the estuary area are difficult due to the complexity of estuarial water and sediment circulation. Effects of deepening navigable waterways, of changing coastline configurations, or of discharging dredged material to the open sea are necessary to be investigated and predicted in terms of water quality and possible physical changes to the coastal environment. A borad analysis of the transport mechanism in the estuary area was made in terms of sediment property, falling velocity, concentration and flow characteristics. In order to simulate the transport processes, a two-dimensional finite element model is developed, which includes erosion, transport and deposition mechanism of suspended sediments. Galerkin’s weighted residual method is used to solve the transient convection-diffusion equation. The fluid domain is subdivided into a series of triangular elements in which a quadratic approximation is made for suspended sediment concentration. Model could deal with a continuous aggregation by stipulating the settling velocity of the flocs in each element. The model provides suspended sediment concentration, bed shear stress, erosion versus deposition rate and bed profile at the given time step.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.41 no.4
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• pp.123-130
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• 2018

Triangulation is one of the fundamental problems in computational geometry and computer graphics community, and it has huge application areas such as 3D printing, computer-aided engineering, surface reconstruction, surface visualization, and so on. The Delaunay refinement algorithm is a well-known method to generate quality triangular meshes when point cloud and/or constrained edges are given in two- or three-dimensional space. In this paper, we propose a simple but efficient algorithm to triangulate Voronoi surfaces of Voronoi diagram of spheres in 3-dimensional Euclidean space. The proposed algorithm is based on the Ruppert's Delaunay refinement algorithm, and we modified the algorithm to be applied to the triangulation of Voronoi surfaces in two ways. First, a new method to deciding the location of a newly added vertex on the surface in 3-dimensional space is proposed. Second, a new efficient but effective way of estimating approximation error between Voronoi surface and triangulation. Because the proposed algorithm generates a triangular mesh for Voronoi surfaces with guaranteed quality, users can control the level of quality of the resulting triangulation that their application problems require. We have implemented and tested the proposed algorithm for random non-intersecting spheres, and the experimental result shows the proposed algorithm produces quality triangulations on Voronoi surfaces satisfying the quality criterion.

• Korean Journal of Mathematics
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• v.32 no.1
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• pp.137-162
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• 2024

This paper consists of two significant aims. The first aim of this paper is to establish the criteria for the existence of solutions to nonlinear Volterra-Fredholm (V-F) fractional integral equations on [0, L], where 0 < L < ∞. The fractional integral is described here in the sense of the Katugampola fractional integral of order λ > 0 and with the parameter β > 0. The concepts of the fixed point theorem and the measure of noncompactness are used as the main tools to prove the existence of solutions. The second aim of this paper is to introduce a computational method to obtain approximate numerical solutions to the considered problem. This method is based on the Fibonacci wavelets with collocation technique. Besides, the results of the error analysis and discussions of the accuracy of the solutions are also presented. To the best knowledge of the authors, this is the first computational method for this generalized problem to obtain approximate solutions. Finally, two examples are discussed with the computational tables and convergence graphs to interpret the efficiency and applicability of the presented method.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.3
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• pp.185-196
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• 2006

Fracture toughness is a material property for crack initiation and propagation in fracture mechanics. For mode I fracture toughness measurement in concrete, RILEM committees 89-FMT proposed three-point bend tests based on the two-parameter fracture model. But, there is no proposed test method as a standard for mixed mode test for now. And RILEM three-point bend test procedure is complicate. Therefore, in this study, brazilian disks of various size were designed as the concrete with a similar specified concrete strength and maximum size of coarse aggregate($G_{max}$) were respectively 20mm and 40mm. And mode I fracture toughness of brazilian disks was compared with that of RILEM three-point bend test. As a result, it was suggested appropriate size(thickness, diameter) and notch length ratio of brazilan disk on the $G_{max}$. And it was verified that stress intensity factors for mixed mode can be easily calculated with the disk specimen. Stress intensity factors of a concrete brazilian disk were evaluated with finite element analysis and five terms approximation for comparison.

• Journal of Korea Water Resources Association
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• v.33 no.6
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• pp.815-825
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• 2000

In the present work Einstein's(l942) suspended load equation IS refined in vanous aspects. After checking the flow characteristics a new method is presented for the estimation of zero velocity point at the condition of smooth turbulent flow, and non-dimensional number of suspended load is introduced for the clear representation of suspended load equation. And a recent equation of bed load is employed in order to calculate accurately the sediment concentration at a reference point. Several approximation equations are also developed to compute directly or explicitly two integrals introduced in the equations. The refined equation has been tested against the measurement data collected by Brownlie(l981) in comparison with Einstein's original equation.uation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.1
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• pp.17-27
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• 2014

As the importance of Cooperative Engagement Capability and network-centric warfare has been dramatically increasing, it is necessary to develop distributed tracking systems. Under the development of distributed tracking systems, it requires tracking filters and data fusion theory for nonlinear systems. Therefore, in this paper, the problem of nonlinear track fusion, which is suitable for distributed networks, is formulated, four algorithms to solve the problem of nonlinear track fusion are introduced, and performance of introduced algorithms are analyzed. It is a main problem of nonlinear track fusion that cross-covarinaces among multiple platforms are unknown. Thus, in order to solve the problem, two techniques are introduced; a simplification technique and a approximation technique. The simplification technique that help to ignore cross-covariances includes two algorithms, i.e. the sample mean algorithm and the Millman formula algorithm, and the approximation technique to obtain approximated cross-covariances utilizes two approaches, by using analytical linearization and statistical linearization based on the sigma point approach. In simulations, BCS fusion is the most efficient scheme because it reduces RMSE by approximating cross-covariances with low complexity.