• Ocean Systems Engineering
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• v.9 no.3
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• pp.287-328
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• 2019

Comprehensive understanding of the flood risk assessments via frequency analysis often demands multivariate designs under the different notations of return periods. Flood is a tri-variate random consequence, which often pointing the unreliability of univariate return period and demands for the joint dependency construction by accounting its multiple intercorrelated flood vectors i.e., flood peak, volume & durations. Selecting the most parsimonious probability functions for demonstrating univariate flood marginals distributions is often a mandatory pre-processing desire before the establishment of joint dependency. Especially under copulas methodology, which often allows the practitioner to model univariate marginals separately from their joint constructions. Parametric density approximations often hypothesized that the random samples must follow some specific or predefine probability density functions, which usually defines different estimates especially in the tail of distributions. Concentrations of the upper tail often seem interesting during flood modelling also, no evidence exhibited in favours of any fixed distributions, which often characterized through the trial and error procedure based on goodness-of-fit measures. On another side, model performance evaluations and selections of best-fitted distributions often demand precise investigations via comparing the relative sample reproducing capabilities otherwise, inconsistencies might reveal uncertainty. Also, the strength & weakness of different fitness statistics usually vary and having different extent during demonstrating gaps and dispensary among fitted distributions. In this literature, selections efforts of marginal distributions of flood variables are incorporated by employing an interactive set of parametric functions for event-based (or Block annual maxima) samples over the 50-years continuously-distributed streamflow characteristics for the Kelantan River basin at Gulliemard Bridge, Malaysia. Model fitness criteria are examined based on the degree of agreements between cumulative empirical and theoretical probabilities. Both the analytical as well as graphically visual inspections are undertaken to strengthen much decisive evidence in favour of best-fitted probability density.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.06a
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• pp.303-309
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• 1999

The fretting wear behaviour of Zircaloy-4 tube used as the fuel rod cladding in PWR nuclear power plants has been investigated at the different test environment, in light water and in air as a function of slip amplitude, normal load, test duration and frequency. Zircaloy-4 tubes were used for both of oscillating and stationary specimens. A fretting wear tester was designed to be suitable for this fretting test. The wear volume and specific wear rate of Zircaloy-4 tube in water were greater than those in air under various slip amplitude. It was found that delaminate debris and surface cracks were observed at low slip amplitude and high load in water Experimental results showed that the light water accelerated the wear of Zircaloy-4 tube at low slip amplitude in fretting.

• Resources Recycling
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• v.9 no.5
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• pp.11-15
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• 2000

The sample made of $Mn_3O_4$ indicated an excellent frequency dependency for intial permeability and core loss. Moreover the homogeneity of cation configuration in he spinel structure was confirmed by X-ray diffraction analysis. The result of homogeneity of the spinel structural coincided with the analytical results of temperature dependence of magnetization. Furthermore, the influence of manganese oxide as starting material, on homogeneity of spinel structure was examined by using thermogravimetry-differential thermal analysis. It may be concluded that the reaction between $Mn_3O_4$ and Fe-Zn oxide mixture proceeds at fist in all combination of manganese oxide and oxie mixture, and then Mn-Zn-Fe spinel was formed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.641-645
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• 2008

In this paper, vibration sources of the BLOC motor are identified and the motor vibrations are reduced by structural modification. For vibration characteristic identification, vibration signals measured by an accelerometer when the BLOC motor is moving. These signals are presented in a waterfall plot in order to find the dependency of frequency components on the motor speed. It is found that main vibration source is BLOC motor test rig. From finite element analyses and some experiments, it is also found that resonances occur because the natural frequencies of the test rig exist in usual driving speed rang. To shift the natural frequencies outside the driving rang, the test rig is modified increase stiffness. It is verified that considerable amount of vibration are reduced by the structural modification.

• Journal of the Korean Operations Research and Management Science Society
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• v.30 no.2
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• pp.63-71
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• 2005

In the field of nuclear reactor safety study, common cause failures (CCFs) became significant contributors to system failure probability and core damage frequency in most Probabilistic risk assessments. However, it is hard to estimate the reliability of such a system, because of the dependency of components caused by CCFs. In order to analyze the system, we propose an analytic method that can find the parameters with lack of raw data. This study adopts the shock model in which the failure probability increases as the shock is cumulated. We use two-step Expectation and Maximization (EM) algorithm to find the unknown parameters. In order to verify the analysis result, we perform the simulation under same environment. This approach might be helpful to build the defensive strategy for the CCFs.

• Proceedings of the Korea Multimedia Society Conference
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• 2000.04a
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• pp.449-452
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• 2000

This paper proposes a new, adaptive Dead Reckoning model, called Dynamic Dead Reckoning , for Distributed Interactive Simulation and humanoid avatar systems. The proposed model can overcome the weak points of traditional Dead Reckoning caused by a fixed threshold and strong dependency on rotation event. This paper introduces new criteria for update message filtering , named as Update lifetime. The Dynamic Dead Reckoning keeps the balance between extrapolation fidelity and filtering performance by two component models, Variable Threshold Mechanism and Rotation Event model. The experimental results show that the proposed model can lower the increment rate of update traffic to the increase of rotation frequency without any significant loss of accuracy.

• New & Renewable Energy
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• v.6 no.2
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• pp.5-11
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• 2010

This paper reviews three commercial softwares for wind climate data analysis in wind resource assessment; WAsP/Observed Wind Climate, WindRose and Windographer. Windographer is evaluated as the best software because of its variety of input data format, analysis functions, easiness of user interface, etc. For a quantitative understanding of uncertainty depending on software selection, a benchmark is carried out with the met-mast observation dataset at the Gimnyeong Wind Turbine Performance Test Site. It is found that Weibull parameter calculation and air density correction have a dependency on the software so that such uncertainty should be considered when an analysis software is selected. It is confirmed that annual energy production calculated by WAsP using a statistical table of frequency of occurrence may have some error compared to a time-series calculation method used by the other softwares.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2003.11a
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• pp.57-60
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• 2003

As the business dependency to information systems and the frequency of the large scale disasters increase, implementing the disaster recovery center has been a common practice. However, since there has been little quantitative decision method for the distance between the data center and the disaster recovery center, the distance decision has been commonly made by qualitative guidelines. In this research, the decision method for the optimal distance between the data center and the disaster recovery center is developed, using the cost analysis including the operation cost and the expected disaster cost. An illustrative numerical example is provided.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.12 s.255
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• pp.1155-1163
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• 2006

Calculation was carried out for phase velocity and deformation wave decay in a layer of viscoelastic material fixed tightly on the solid substrate. Analysis has been performed regarding the inner structure of the wave, i.e., the proportions between the vertical and horizontal displacements and their profiles. The wave characteristics depend strongly on media compressibility factor. The effect of viscous losses on parameters of the main oscillation mode was studied in detail. Results were compared with the model of coating with local deformation. A new experimental approach was made in order to measure such wave properties of a compliant coating as the dependency of deformation wave velocity on frequency and decay factor was made. The method for estimation of coating parameters enabling the drag reduction in turbulent flow was then refined.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.255-258
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• 2001

In this paper, DC and small signal characteristics with different physical parameters are expected for p-HEMTs (Pseudomorphic High Electron Mobility Transistors) with different temperatures ranging from 300K to 623K which are widely used for a low noise and/or ultra high frequency device. A device of 0.2$\times$200 ${\mu}{\textrm}{m}$$^2$dimension having very low noise has been chosen to extract the experimental data. Theoretical prediction has been obtained using a simulaor(HELENA) which needs experimental input data extracted from reverse engineering process. From the results, relation between structural parameters and temperature dependency of electrical characteristics are qualitatively explained to use in the design of descrete and integrated circuits to guarantee the optimal operation of the system.