• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.7
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• pp.1783-1788
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• 1994

A comparison of the temperature distributions along the wall and center of the fin and the heat loss from the fin, computed assuming the fin tip is insulated and assuming it is not insulated in a triangular fin, is performed by the two-dimensional forced analytic method. When the fin tip is not insulated, a comparison between forced analytic method and analytic method is made in the heat loss and temperature along the fin wall. The value of Biot number varies from 0.01 to 1.0. The root temperature and surrounding convection coefficients of the fin are assumed as a constant. The results are (1) the analysis on the triangular fin assuming the fin tip is insulated does not produce a good value as compared to that of not-insulated case as the non-dimensional fin length decreases and as the value of Biot number increases and (2) the errors between forced analytic method and analytic method are very small, but the former method is better for computer running time and accuracy.

• Journal of Korean Society for Quality Management
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• v.18 no.1
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• pp.48-54
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• 1990

The purpose of this study is to design effective working systems which adapt to change in human needs by developing an method which forms into optimal groups using the measure of cohesion. Two main results can be derived from the study as follows : First, the clustering method based on the entropic measure of cohesion is predominant with respect to any other methods proposed in designing the work groups, since this clustering criterion includes symmetrical relations of total work groups and the dissimilarity as well as the similarity relations of predicate value, the clustering method based on this criterion is suitable for designing the new work structure. Second, total work group is clustered as the workers who have the equal predicate value and then clustering results are produced through the combinatorial agglomerative hierarchical clustering method. This clustering method present more economic results than the method that clustering the total work group do.

• Bulletin of the Society of Naval Architects of Korea
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• v.16 no.4
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• pp.3-11
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• 1979

This paper deals with Guilloton's method for wave-making resistance calculation. Ship is considered as slender in this paper. Guillotin's method requires a large and fast computer, while mini-computer is good enough for the present method. Present method is practical as well, as prismatic curves along with other principal particulars are requirements for the calculation. Unless the ship is thin, Z-transformation is difficult to carry out, but this can be done smoothly in the present method by considering the flow around the bottom of the ship. As an example of this method, corresponding real hulls of Maruo's least wave-making resistance ship forms are calculated.

• Proceedings of the Korean Nuclear Society Conference
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• 1998.05a
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• pp.87-92
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• 1998

A nonlinear iterative scheme developed to reduce the computing time of the AFEN method was tested and applied to two benchmark problems. The new nonlinear method for the AFEN method is based on solving two-node problems and use of two nonlinear correction factors at every interface instead of one factor in the conventional scheme. The use of two correction factors provides higher-order accurate interface noes as well as currents which are used as the boundary conditions of the two-node problem. The numerical results show that this new method gives exactly the same solution as that of the original AEFEN method and the computing time is significantly reduced in comparison with the original AFEN method.

• 유체기계공업학회:학술대회논문집
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• 1999.12a
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• pp.221-226
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• 1999

Three-dimensional flow analysis and numerical optimization methods are presented for the design of an axial-flow fan. Steady, Incompressible, three-dimensional Reynolds-averaged Wavier-Stokes equations are used as governing equations, and standard k-$\epsilon$ turbulence model is chosen as a turbulence model. Governing equations are discretized using finite volume method. Steepest descent method, conjugate gradient method and BFGS method are compared to determine the searching directions. Golden section method and quadratic fit-sectioning method are tested for one dimensional search. Objective function is defined as a ratio of generation rate of the turbulent kinetic energy to pressure head. Sweep angle distributions are used as design variables.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.639-642
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• 1999

Pullout test known as Lok test among the test methods to evaluate concrete strength strength is a test method which is used to decide the form removal time by assessing the early strength of concrete in a new construction, or to control the quality of newly placed concrete. This method has inconvenience to place inserts on the form work in advance, however, the placing work is quite simple and it has advantage that the strength can be measured at field as long as the inserts are placed. In this study, the first step is to investigate the properties of test method itself, by performing the laboratory test which covers deviation of the method and factors affecting the results, etc. The second step is to correlate the result with cylinder strength and other NDT methods such as rebound hammer, ultrasonic method, etc. And that, the results are compared with foreign results to find the differences between the two. In this research, new factors such as moisture content, area of aggregate failure cross section and area of aggregate separation cross section, etc as well as wate-cement ratio and age are investigated.

• Journal of KSNVE
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• v.6 no.6
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• pp.835-842
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• 1996

To identify the locations and strengths of acoustic sources, one may use a microphone line array. Apparent advantage of the source identification method utilizing a line array is that it requires less measurement points than intensity method and holography. This method is based on the information of magnitude and phase difference between pressure signals at each microphone. Since those differences are dependent on the source model, we have to assume them such as plane, monopole, etc. In this paper the conventional source identification methods such as beamforming method and MUSIC method are briefly reviewed by modeling a source as plane and spherical wave, then a modified method is introduced. This can be applied to sound field which may by either coherent or incoherent. Typical simulations and experiment are performed to confirm this identification method.

• Journal of applied mathematics & informatics
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• v.7 no.3
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• pp.905-915
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• 2000

In this article we discuss some aspects of operational Tau Method on delay differential equations and then we apply this method on the differential delay equation defined by $\omega(u)\;=\frac{1}{u}\;for\;1\lequ\leq2$ and $(u\omega(u))'\;=\omega(u-1)\;foru\geq2$, which was introduced by Buchstab. As Khajah et al.[1] applied the Recursive Tau Method on this problem, they had to apply that Method under the Mathematica software to get reasonable accuracy. We present very good results obtained just by applying the Operational Tau Method using a Fortran code. The results show that we can obtain as much accuracy as is allowed by the Fortran compiler and the machine-limitations. The easy applications and reported results concerning the Operational Tau are again confirming the numerical capabilities of this Method to handle problems in different applications.

• Journal of Information Technology Applications and Management
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• v.24 no.1
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• pp.25-32
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• 2017

For repairable software systems, the Mean Time Between Failure (MTBF) is used as a measure of software system stability. Therefore, the evaluation of software reliability requirements or reliability characteristics can be applied MTBF. In this paper, we want to compare MTBF in terms of parameter estimation using Makeham life distribution. The parameter estimates used the least square method which is regression analyzer method and the maximum likelihood method. As a result, the MTBF using the least square method shows a non-decreased pattern and case of the maximum likelihood method shows a non-increased form as the failure time increases. In comparison with the observed MTBF, MTBF using the maximum likelihood estimation is smallerd about difference of interval than the least square estimation which is regression analyzer method. Thus, In terms of MTBF, the maximum likelihood estimation has efficient than the regression analyzer method. In terms of coefficient of determination, the mean square error and mean error of prediction, the maximum likelihood method can be judged as an efficient method.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.456-456
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• 2000

The back projection histogram method has been proposed as the method to construct an image from waves reflected from a buried object for subsurface radar. This method is compose of two phases, i.e., a back projection image construction process and a back projection image superposition process. A simulation analysis of this method has been studied. In this paper, an experimental study is demonstrated in air as the homogeneous Held using three cylinders as buried objects.