• Proceedings of the KIEE Conference
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• 1995.07b
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• pp.667-669
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• 1995

This paper presents a method to design Kalman filter on continuous stochastic dynamical systems via BPFT(block pulse functions transformation). When we design Kalman filter, minimum error valiance matrix is appeared as a form of nonlinear matrix differential equations. Such equations are very difficult to obtain the solutions. Therefore, in this paper, we simply obtain the solutions of nonlinear matrix differential equations from recursive algebraic equations using BPFT. We believe that the presented method is very attractive and proper for the evaluation of Kalman gain on continuous stochastic dynamical systems.

• Computers and Concrete
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• v.2 no.1
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• pp.55-77
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• 2005

The closed form solution of the equilibrium equations in the ultimate design of reinforced concrete sections under biaxial bending is presented. The stresses in the materials are described by the Model Code 1990 equations. Computation of the integral equations is performed generally in terms of all variables. The deformed shape of the section in the ultimate conditions is defined by Heaviside functions. The procedure is convenient for the use of mathematical manipulation programs and the results are easily included into nonlinear analysis codes. The equations developed for rectangular sections can be applied for other sections, such as T, L, I for instance, by decomposition into rectangles. Numerical examples of the developed model for rectangular sections and composed sections are included.

• Research in Mathematical Education
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• v.6 no.2
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• pp.159-170
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• 2002

The undergraduate curriculum in differential equations has undergone important changes in favor of the visual and numerical aspects of the course primarily because of recent technological advances. Yet, research findings that have analyzed students' thinking and understanding in a reformed setting are still lacking. This paper discusses an ongoing developmental research effort to adapt the instructional design perspective of Realistic Mathematics Education (RME) to the teaching and learning of differential equations at Ewha Womans University. The RME theory based on the design heuristic using context problems and modeling was developed for primary school mathematics. However, the analysis of this study indicates that a RME design for a differential equations course can be successfully adapted to the university level.

• Proceedings of the KSR Conference
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• 1999.11a
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• pp.542-549
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• 1999

The purpose of this study is to investigate stability of a high speed train and to propose optimal design using sensitivity analysis of suspension design parameters. A form of equations of motion in tangent track and curve track is obtained based on each creep force. Tangent track and curve track equations include lateral, rolling and yawing motions of wheel sets, bogies, and carbodies. Three track cases have been chosen to stability assesment of a high speed train analysis. Sensitivity equations are set up by directly differentiating the equations of motion. This study def'.led Stability performance index of a high speed train in tangent track and curve track. The relative magnitude of the effect of suspension parameters on the critical speed is computed, and by adjusting these parameters, the increase of the critical speed is achieved.

• Computers and Concrete
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• v.26 no.4
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• pp.317-325
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• 2020

A precise estimation of the natural time period of buildings improves design quality, causes a significant reduction of the buildings' weight, and eventually leads to a cost-effective design. In this study, in order to optimise the reinforced concrete frames design, some symmetrical and unsymmetrical buildings composed of solid and hollow members have been simulated using finite element software SAP 2000. In numerical models, different parameters such as overturning moment, story drift, deflection, base reactions, and stiffness of the buildings were investigated and the results have been compared with strength and serviceability limit criteria proposed by Australian Standard (AS 3600 2018). Comparing the results of the numerical modelling with existing standards and performing a cost analysis proved the merits of hollow box sections compared to solid sections. Finally, based on numerical simulation results, two equations for natural time period of moment resisting reinforced concrete buildings have been presented. Both derived equations reflected higher degree of correlation and reliability with different complexities of building when compared with existing standards and relationships provided by other scholars. Therefore, these equations will assist practicing engineers to predict elastic behaivour of structures more precisely.

• Smart Structures and Systems
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• v.2 no.1
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• pp.81-100
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• 2006

To calculate the shear capacity of concrete beams reinforced with fibre-reinforced polymer (FRP), current shear design provisions use slightly modified versions of existing semi-empirical shear design equations that were primarily derived from experimental data generated on concrete beams having steel reinforcement. However, FRP materials have different mechanical properties and mode of failure than steel, and extending existing shear design equations for steel reinforced beams to cover concrete beams reinforced with FRP is questionable. This paper investigates the feasibility of using artificial neural networks (ANNs) to estimate the nominal shear capacity, Vn of concrete beams reinforced with FRP bars. Experimental data on 150 FRP-reinforced beams were retrieved from published literature. The resulting database was used to evaluate the validity of several existing shear design methods for FRP reinforced beams, namely the ACI 440-03, CSA S806-02, JSCE-97, and ISIS Canada-01. The database was also used to develop an ANN model to predict the shear capacity of FRP reinforced concrete beams. Results show that current guidelines are either inadequate or very conservative in estimating the shear strength of FRP reinforced concrete beams. Based on ANN predictions, modified equations are proposed for the shear design of FRP reinforced concrete beams and proved to be more accurate than existing equations.

• Journal of the Korean Society of Safety
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• v.27 no.2
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• pp.57-64
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• 2012

For the vibration control of earthquake-excited buildings, an optimal design method of integrated control system considering soil-structure interaction is studied in this paper. Interaction between soils and the base of the building is simply modeled as lumped parameters and equations of motion are derived. The equations of motion are transformed into the state space equations and the probabilistic excitations such as Kanai-Tajumi power spectral density function is introduced. Then an optimization problem is formulated as finding hybrid or integrated control systems which minimizes the stochastic responses of the building structure for given constraints. In order to investigate the feasibility of the optimization method, an example design and numerical simulations are performed with tenstory building. Finally, numerical results are compared with a conventional design case that soil-structure interaction is not considered.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.684-689
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• 2001

In this study, three-dimensional viscous flow analysis and optimization are presented for the design of a mixed-flow fan. Steady, imcompressible, three-dimensional Reynolds averaged Navier-Stokes equations are used as governing equations, and standard $k-{\varepsilon}$ turbulence model is chosen as a turbulence model. Governimg equations are discretized using finite volume method. Upwind difference scheme is used for the discretization of the convective term and SIMPLEC algorithm is used as a velocity-pressure correction procedure. The computational results are compared with the results obtained by TASCflow. For the numerical optimization of the design, objective function is defined as a ratio of generation of the turbulent energy to pressure head. Sweep angles are used as design variables.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.833-838
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• 2001

The objectives of this study are to investigate effective stiffness of circular reinforced bridge columns and to provide reasonable effective stiffness equations for seismic design to the current Korean Bridge Design Standard. The material nonlinear analysis was conducted for 5184 columns of which variables were the concrete compressive stress, the steel yielding stress, the longitudinal steel location parameter, the longitudinal steel ratio, the axial load level, and the diameter of section. The current Korean Bridge Design Standard generally used the gross section stiffness because of unclear provision, it may be non-conservative because of being evaluated greater design seismic force and less design displacement than those of the abroad provision. Therefore, the proposed effective stiffness equations include three variables such as : the longitudinal steel location parameter, the longitudinal steel ratio, and the axial load ratio. Two equations of effective stiffness are proposed which may be used for earthquake force estimation and for earthquake displacement estimation, respectively.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.5
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• pp.128-137
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• 1998

A numerical approach for performing kinematic design sensitivity analysis of vehicle suspension systems is presented. Compared with the conventional analytical methods, which require explicit derivation of sensitivity equations, the proposed numerical method can be applied to any type of suspension systems without obtaining sensitivity equations, once any kinematic analysis procedure is established. To obtain sensitivity equations, a numerical differentiation algorithm that uses the third order Lagrange polynomial is developed. The algorithm efficiently and accurately computes the sensitivity of various vehicle static design factors with respect to kinematic design variables. Through a suspension design problem, the validity and usefulness of the method is demonstrated.