Hk Valve Co. and Korea Water Resources Corporation | Date: 2011-11-10
The ozone-resistant polyurethane composition according to the present invention, which is for the linings of valves, pipes or ozone contactors used in advanced water-treatment plants, comprises: 100 parts by weight of a polyurethane prepolymer consisting of toluene diisocyanate and poly(tetramethylene ether)glycol; from 8 to 14 parts by weight of 6-methyl-2,4-bis(methylthio)phenylene-1,3-diamine; and from 0.8 to 2.8 parts by weight of benzophenone or benzotriazole. Also, the production method for the ozone-resistant polyurethane composition according to the present invention, which is for the linings of valves, pipes or ozone contactors used in advanced water treatment plants, comprises the steps of: mixing from 0.8 to 2.8 parts by weight of benzophenone or benzotriazole in 100 parts by weight of a polyurethane prepolymer consisting of toluene diisocyanate and poly(tetramethylene ether)glycol, and stirring for between 25 and 35 minutes at between 90 and 100 C.; and mixing from 8 to 14 parts by weight of 6-methyl-2,4-bis(methylthio)phenylene-1,3-diamine into the stirred liquid.
Cho S.E.,Korea Water Resources Corporation
Journal of Geotechnical and Geoenvironmental Engineering | Year: 2010
In this paper, a numerical procedure for probabilistic slope stability analysis is presented. This procedure extends the traditional limit equilibrium method of slices to a probabilistic approach that accounts for the uncertainties and spatial variation of the soil strength parameters. In this study, two-dimensional random fields were generated based on a Karhunen-Loève expansion in a fashion consistent with a specified marginal distribution function and an autocorrelation function. A Monte Carlo simulation was then used to determine the statistical response based on the generated random fields. This approach makes no assumption about the critical failure surface. Rather, the critical failure surface corresponding to the input random fields of soil properties is searched during the process of analysis. A series of analyses was performed to verify the application potential of the proposed method and to study the effects of uncertainty due to the spatial heterogeneity on the stability of slope. The results show that the proposed method can efficiently consider the various failure mechanisms caused by the spatial variability of soil property in the probabilistic slope stability assessment. © 2010 ASCE.
Hong Y.H.,Seoul National University |
Lee S.G.,Korea Water Resources Corporation |
Lee H.S.,Seoul National University
Mechanical Systems and Signal Processing | Year: 2013
This paper presents a displacement reconstruction scheme using acceleration measured at a high sampling rate and displacement measured at a considerably low sampling rate. The governing equation and the boundary conditions for the reconstruction are derived using the variational statement of an inverse problem to minimize the errors between measured and reconstructed responses. The transfer function of the governing equation is identically 1 over whole frequency domain, and the proposed scheme would not result in any reconstruction error. A finite impulse response filter (FIR filter) is formulated through the finite element discretization of the governing equation. The Hermitian shape function is adopted to interpolate the displacement in a finite element. The transfer functions of the FIR filter are derived, and their characteristics are thoroughly discussed. It is recommended that the displacement sampling rate should be higher than the Nyquist rate of the target frequency, which is the lowest physically meaningful frequency in measured acceleration. In case the displacement sampling rate is lower than the recommended rate, the use of a higher target accuracy, which is the predefined accuracy at the target frequency, is required. The reconstruction of velocity with the proposed scheme is also presented. The validity of the proposed scheme is demonstrated with a numerical simulation study and a field test on a simply-supported railway bridge. © 2013 Elsevier Ltd.
Cho Y.,Korea Water Resources Corporation |
Yun R.,Hanbat National University
Energy and Buildings | Year: 2011
Raw water source is one of the promising new heat sources that researchers are looking into along with various others water-based sources such as ground, lake, river and sewage water. Generally, the water that is taken from the environment and supplied to a water treatment facility is called raw water. In this study, the heating and cooling performance of a heat pump utilizing the heat energy of raw water supplied to a water treatment facility is investigated. The two heat pumps being investigated have a heating capacity of 65.2 kW and were installed at the site for the heating and cooling of the central control room. A brazed plate heat exchanger was used for obtaining heat energy from the raw water. The raw water source provides a favorable heat source compared to the ambient air source except in spring. In the seasons of spring and autumn, the heating and cooling load are extremely low, this is the main reason for the poor performance of the raw-water heat pump system for those seasons. The average unit COP during the heating season is 3.3, and the average unit COP for the cooling season is 7.2. © 2011 Elsevier B.V. All rights reserved.
Choi D.Y.,Korea Water Resources Corporation |
International Journal for Numerical Methods in Fluids | Year: 2012
A horizontally curvilinear non-hydrostatic free surface model that embeds the second-order projection method, the so-called θ scheme, in fractional time stepping is developed to simulate nonlinear wave motion in curved boundaries. The model solves the unsteady, Navier-Stokes equations in a three-dimensional curvilinear domain by incorporating the kinematic free surface boundary condition with a top-layer boundary condition, which has been developed to improve the numerical accuracy and efficiency of the non-hydrostatic model in the standard staggered grid layout. The second-order Adams-Bashforth scheme with the third-order spatial upwind method is implemented in discretizing advection terms. Numerical accuracy in terms of nonlinear phase speed and amplitude is verified against the nonlinear Stokes wave theory over varying wave steepness in a two-dimensional numerical wave tank. The model is then applied to investigate the nonlinear wave characteristics in the presence of dispersion caused by reflection and diffraction in a semicircular channel. The model results agree quantitatively with superimposed analytical solutions. Finally, the model is applied to simulate nonlinear wave run-ups caused by wave-body interaction around a bottom-mounted cylinder. The numerical results exhibit good agreement with experimental data and the second-order diffraction theory. Overall, it is shown that the developed model, with only three vertical layers, is capable of accurately simulating nonlinear waves interacting within curved boundaries. © 2011 John Wiley & Sons, Ltd.