• 한국유체기계학회 논문집
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• 제10권4호
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• pp.55-60
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• 2007

This paper describes an evaluation method of pressure drop in a circular pipe of waste collection piping system. Accurate pressure drop in a piping system is very important to determine the capacity of turbo blower, which is one of the main elements in the system. Three-dimensional Navier-Stokes analysis is introduced to analyze the pressure drop in the piping system. Organic waste is selected and modeled using the result of site survey performed in an apartment area. Evaluation method of pressure drop used In the present numerical simulation is performed in the shortened pipe line prior to the calculation of the real system. Throughout the numerical simulation, pressure drop in a waste pipe is obtained and compared to the value determined by analytical method. The pressure drop obtained by numerical simulation has a good agreement with that of the analytic method. It is noted that present evaluation method is effective to determine a pressure drop in the piping system. Detailed flow characteristics inside the pipe line are also analyzed and discussed.

• Computers and Concrete
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• 제18권3호
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• pp.367-388
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• 2016

In this paper, a simple practical method is introduced in which a simple weight measurement of concrete and finite element numerical analysis are used to determine the moisture transfer coefficient of concrete with a satisfactory accuracy. Six concrete mixtures with different water-to-cementitious material (w/cm) ratios and two pozzolanic materials including silica fume and zeolite were examined to validate the proposed method. The comparison between the distribution of the moisture content obtained from the model and the one from the experimental data during both the wetting and drying process properly validated the performance of the method.With the proposed method, it was also shown that the concrete moisture transfer coefficient considerably depends on the pore water saturation degree. The use of pozzolanic materials and also lowering w/cm ratio increased the moisture transfer coefficient during the initial sorption, and then, it significantly decreased with an increase in the water saturation degree.

• Smart Structures and Systems
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• 제12권6호
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• pp.679-694
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• 2013

In this paper the application of the Interpolation Damage Detection Method to the numerical model of a suspension bridge instrumented with a network of Micro-Electro-Mechanical System sensors is presented. The method, which, in its present formulation, belongs to Level II damage identification method, can identify the presence and the location of damage from responses recorded on the structure before and after a seismic damaging event. The application of the method does not require knowledge of the modal properties of the structure nor a numerical model of it. Emphasis is placed herein on the influence of recorded signals noise on the reliability of the results given by the Interpolation Damage Detection Method. The response of a suspension bridge to seismic excitation is computed from a numerical model and artificially corrupted with random noise characteristic of two families of Micro-Electro-Mechanical System accelerometers. The reliability of the results is checked for different damage scenarios.

• 대한수학회지
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• 제46권5호
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• pp.1105-1117
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• 2009

In this paper a parameter identification problem for a damped sine-Gordon equation is studied from the theoretical and numerical perspectives. A spectral method is developed for the solution of the state and the adjoint equations. The Powell's minimization method is used for the numerical parameter identification. The necessary conditions for the optimization problem are shown to yield the bang-bang control law. Numerical results are discussed and the applicability of the necessary conditions is examined.

• Smart Structures and Systems
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• 제28권6호
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• pp.727-735
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• 2021

Recently, non-destructive health monitoring methods such as magnetic flux leakage (MFL) method, have become popular due to their advantages over destructive methods. Currently, numerical study on this field has been limited to simplified studies by only obtaining MFL instead of induced voltage inside coil sensor. In this study, it was proposed to perform a novel numerical simulation of MFL's coil sensor by considering vital parameters including specimen's motion with constant velocity and saturation status of specimen in time domain. A steel-rod specimen with two stepwise cross-sectional changes (i.e., 21% and 16%) was fabricated using low carbon steel. In order to evaluate the results of numerical simulation, an experimental test was also conducted using a magnetic probe, with same size specimen and test parameters, exclusively. According to comparative results of numerical simulation and experimental test, similar signal amplitude and signal pattern were observed. Thus, proposed numerical simulation method can be used as a reliable source to check efficiency of sensor probe when different size specimens with different defects should be inspected.

• Earthquakes and Structures
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• 제7권2호
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• pp.159-178
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• 2014

Although the family methods with unconditional stability and numerical dissipation have been developed for structural dynamics they all are implicit methods and thus an iterative procedure is generally involved for each time step. In this work, a new family method is proposed. It involves no nonlinear iterations in addition to unconditional stability and favorable numerical dissipation, which can be continuously controlled. In particular, it can have a zero damping ratio. The most important improvement of this family method is that it involves no nonlinear iterations for each time step and thus it can save many computationally efforts when compared to the currently available dissipative implicit integration methods.

• Structural Engineering and Mechanics
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• 제66권5호
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• pp.649-663
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• 2018

The scaled boundary finite element method is extended to evaluate the dynamic stress intensity factors and T-stress with a numerical procedure based on the improved continued-fraction. The improved continued-fraction approach for the dynamic stiffness matrix is introduced to represent the inertial effect at high frequencies, which leads to numerically better conditioned matrices. After separating the singular stress term from other high order terms, the internal displacements can be obtained by numerical integration and no mesh refinement is needed around the crack tip. The condition numbers of coefficient matrix of the improved method are much smaller than that of the original method, which shows that the improved algorithm can obtain well-conditioned coefficient matrices, and the efficiency of the solution process and its stability can be significantly improved. Several numerical examples are presented to demonstrate the increased robustness and efficiency of the proposed method in both homogeneous and bimaterial crack problems.

• 대한기계학회논문집B
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• 제24권10호
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• pp.1317-1325
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• 2000

A new efficient numerical method for computing three-dimensional, unsteady, incompressible flows is presented. To eliminate the restriction of CFL condition, a fully-implicit time advancement in which the Crank-Nicolson method is used for both the diffusion and convection terms, is adopted. Based on an approximate block LU decomposition method, the velocity -pressure decoupling is achieved. The additional decoupling of the intermediate velocity components in the convection term is made for the fully -implicit time advancement scheme. Since the iterative procedures for the momentum equations are not required, the velocity components decouplings bring forth the reduction of computational cost. The second-order accuracy in time of the present numerical algorithm is ascertained by computing decaying vortices. The present decoupling method is applied to minimal channel flow unit with DNS (Direct Numerical Simulation).

• 한국철도학회논문집
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• 제9권2호
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• pp.174-179
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• 2006

Recently, the crossing tunnel has been constructed frequently to connect the separated area by highway and railroad. The construction of crossing tunnel must be progressed while maintaining the existing traffic of the highway as well as railroad. There are many cross funnelling methods such as NTR, TRCM, Messer Shield, Front Jacking, and Pipe Roof Method. The advantages of adopting RPS(Roof Panel Shield) method in crossing tunnel construction with comparing other existing cross funnelling methods are needed a little volume of concrete and easy to change the direction of cutting shoe during the construction of pipe roof, The 3-dimensional numerical analysis of RPS to consider the arching effect was performed for the application in the crossing tunnel under railroad. The earth pressure distribution and settlement were predicted when the RPS method was applied during the excavation for crossing railroad tunnel construction.

• 한국수학교육학회지시리즈B:순수및응용수학
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• 제28권4호
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• pp.329-341
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• 2021

In this study, we consider an efficient and accurate finite difference method for the four underlying asset equity-linked securities (ELS). The numerical method is based on the operator splitting method with non-uniform grids for the underlying assets. Even though the numerical scheme is implicit, we solve the system of discrete equations in explicit manner using the Thomas algorithm for the tri-diagonal matrix resulting from the system of discrete equations. Therefore, we can use a relatively large time step and the computation of the ELS option pricing is fast. We perform characteristic computational test. The numerical test confirm the usefulness of the proposed method for pricing the four underlying asset equity-linked securities.