• Proceedings of the Korea Contents Association Conference
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• 2016.05a
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• pp.241-242
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• 2016

Recent abnormal climate change induces localized heavy rainfall and extreme disasters such as debris flow near urban area. Thus many researches have been conducted to estimate and prevent, especially in focus of physical behavior of debris flow. Even though it is hardly to consider overall related parameters to estimate the extent and degree of directly or indirectly damages due to debris flow. Those analytic restraint would be caused by the diversity and complexity of regional topographic and hydrodynamic characteristics of debris flow inside. We have utilized the Bayesian method to compensate the uncertainty due to the complex characteristics of it after analyzing the numerical results from FLO-2D and field measurement data. Revised values by field measurements will enhance the numerical results and the missing parameters during numerical simulation will be supplemented with this methodology. As a final outcome in this study, the risk index of debris flow damage will be suggested to provide quantitative estimation in terms of hazard protection including the impact on buildings, especially in inner and outer of urban area.

• Geomechanics and Engineering
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• v.13 no.6
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• pp.1045-1055
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• 2017

Tensile strength is considered key properties for characterizing rock material in engineering project. It is determined by direct and indirect methods. Point load test is a useful testing method to estimate the tensile strengths of rocks. In this paper, the effects of rock shape on the point load index of gypsum are investigated by PFC2D simulation. For PFC simulating, initially calibration of PFC was performed with respect to the Brazilian experimental data to ensure the conformity of the simulated numerical models response. In second step, nineteen models with different shape were prepared and tested under point load test. According to the obtained results, as the size of the models increases, the point load strength index increases. It is also found that the shape of particles has no major effect on its tensile strength. Our findings show that the dominant failure pattern for numerical models is breaking the model into two pieces. Also a criterion was rendered numerically for determination of tensile strength of gypsum. The proposed criteria were cross checked with the results of experimental point load test.

• Korean Journal of Microbiology
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• v.30 no.6
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• pp.444-449
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• 1992

A total of 858 heterotrohic bacteria were isolated and analyzed hy numerical method to investigate the heterotrophic hacterial community structure in Naktong Estuary. Although the values of H' (Shannon's diversity index). ranged between 1.54 and 3.49. were similar with those of the data hefore the construction of Naktong River barrage, however J' (evenness index. 0.31-0.80) was reduced. Physiological tolerance index for water temperature ($P_{s}$) was high at St.l and 2 whose depthes arc shallower than the other stations. and indices for pH ($P_{h}$) and salinity ($P_{s}$) were high at St. 2. 3. 4 where freshwater and seawater arc mixed. The predominant clusters were identified as Aeromonas. Vihrio. Pseudomonas. Acinelobacter-Morexella. Alcaligenes. Flavobacterium. Micrococcaccae. and Enterohacteriaceae. The kinds nf the isolates were similar with the previous result. hut the dominant genus was changed. These results suggest that the environmental changes in Naktong Estuary affect the hacterial physiological adaptation rather than the composition of heterotrophic hactcrial community.

• Kyungpook Mathematical Journal
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• v.48 no.3
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• pp.387-393
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• 2008

In this note, we present some inequalities for the norm and numerical radius of 2-homogeneous polynomials from the 2-dimensional real space $l_p^2$, (1 < p < $\infty$) to itself in terms of their coefficients. We also give an upper bound for n^{(k)}(l_p^2), (k = 2, 3, $\cdots$).

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1274-1279
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• 2004

We performed the numerical study on the comparison of thermal comport performance indices for cooling loads in the classroom when the 4-way cassette air-conditioner is mounted on the ceiling. We investigated the velocity and the temperature distribution of the classroom as with respect to the variation of the air diffusion angle of the air-conditioner. Air diffusion performance index and Predicted mean vote were used for analyzing the characteristics of the thermal comport in the classroom and comparing their values each other. From the numerical results, we knew that the thermal comport is largely affected by the air diffusion angle and velocity of the air-conditioner. And we also found out that the qualitative tendency of the distribution between Air diffusion performance index and Predicted mean vote is very similar in all occupied zone.

• International Journal of Fluid Machinery and Systems
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• v.3 no.3
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• pp.227-234
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• 2010

Numerical analyses have been performed to investigate the effects of geometric parameters of a straight groove micromixer on mixing performance and pressure drop. Three-dimensional Navier-Stokes equations with two working fluids, water and ethanol have been used to calculate mixing index and pressure drop. A parametric study has been carried out to find the effects of the number of grooves per cycle, arrangement of patterned walls, and additional grooves in triangular dead zones between half cycles of grooves. The three arrangements of patterned walls in a micromixer, i.e., single wall patterned, both walls patterned symmetrically, and both walls patterned asymmetrically, have been tested. The results indicate that as the number of grooves per cycle increases the mixing index increases and the pressure drop decreases. The microchannel with both walls patterned asymmetrically shows the best mixing performance among the three different arrangements of patterned walls. Additional grooves confirm the better mixing performance and lower pressure drop.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.167-174
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• 2006

In this paper, the applicability of strain data to a strain-energy-based damage evaluation methodology in detecting damage in a beam-like structure is demonstrated. For the purpose of this study, one of the premier damage evaluation methodology based on modal amplitudes, the damage index method, is expanded to accomodate strain data, and the numerical and experimental verifications are conducted using numerical and experimental data. To compare the relative performance of damage detection, the damage evaluation using acceleration data is also performed for the same damage scenarios. The experimental strain and acceleration data are extracted from laboratory static and dynamic tests. The numerical and experimental studies show that the strain data as well as acceleration data can be utilized in detecting damage.

• Journal of applied mathematics & informatics
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• v.30 no.5_6
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• pp.951-969
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• 2012

In this paper, we propose a class of meshless collocation approaches for the solution of time dependent partial differential algebraic equations (PDAEs) in terms of a radial basis function interpolation numerical scheme. Kansa's method and the Hermite collocation method (HCM) for PDAEs are given. A sensitivity analysis of the solutions from different shape parameter c is obtained by numerical experiments. With use of the random collocation points, we have obtain the more accurate solution by the methods than those by the finite difference method for the PDAEs with index-2, i.e, we avoid the influence from an index jump of PDAEs in some degree. Several numerical experiments show that the methods are efficient.

• Structural Engineering and Mechanics
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• v.67 no.4
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• pp.327-336
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• 2018

In this study, an efficient damage index is proposed to identify multiple damage cases in structural systems using the concepts of frequency response function (FRF) matrix and strain energy of a structure. The index is defined based on the change of strain energy of an element due to damage. For obtaining the strain energy stored in elements, the columnar coefficients of the FRF matrix is used. The new indicator is named here as frequency response function strain energy based index (FRFSEBI). In order to assess the performance of the proposed index for structural damage detection, some benchmark structures having a number of damage scenarios are considered. Numerical results demonstrate that the proposed index even with considering noise can accurately identify the actual location and approximate severity of the damage. In order to demonstrate the high efficiency of the proposed damage index, its performance is also compared with that of the flexibility strain energy based index (FSEBI) provided in the literature.

• Journal of Power System Engineering
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• v.11 no.3
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• pp.66-72
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• 2007

This study proposed new method to decide the reference model necessary for design PID controller. In generally, control design problems using the reference model have the following two factors. One factor is that numerical model of the controlled system can be obtained extremely, and the other is that specification for the closed-loop dynamic performance is pure moderate. Therefore, the control design procedure is essentially based on the partial reference model matching which offers a reasonable method to simplify the design and the controller configuration under the controlled system uncertainty. ITAE(Integral of time-multiplied absolute error) performance index and Kitamori method etc. which were used a reference model method had a limit to settling time and rising time of reference model that it arrived to steady state response according to the controlled system. On this study, if it only knew peak time of overshoot and settling time by measurement signal of the controlled system, it can be made the reference model easily. We proposed new method to improve performance index of the reference model superior to existing reference model index and illustrate the numerical simulation results to show the effectiveness of proposed control method design.