• Proceedings of the KSME Conference
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• 2001.11a
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• pp.9-15
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• 2001

In the case of a crack propagation, a portion of the work of inelastic deformation near the crack tip is dissipated as heat. In order to understand the thermal effect on fracture toughness, tensile test was carried out using thermocouples to monitor the variation of temperature with SA516 Gr70. The experimental results show that the temperature of specimen was increased $3.6^{\circ}C$ at static load condition. And the thermal effect was investigated connected with the steady-state stress in the vicinity of a crack propagation in the elastic-plastic C-T specimen theoretically. And fracture toughness, the energy to make crack surfaces, presented correctively. The fracture toughness with considering heat at the blunting of the crack tip ws lower about 19.3% than that of ignoring heat. So, it is resonable to apply the fracture toughness with considering thermal energy and it would be good explanation for constraint effect depending on the configuration in the presence of excessive plasticity.

• Journal of Power System Engineering
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• v.3 no.2
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• pp.84-88
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• 1999

In this paper, systems described by state-space models are considered. For these systems, author studies the decoupling of linear systems and gives a sufficient condition for a system to be made feedback decouplable. Especially, the condition is given by LMI(Linear Matrix Inequality) form. Based on this condition, it is guaranteed that the system decoupling problem is achieved and the $H_{\infty}$ constraint is satisfied simultaneously. This result can be easily extended to the robust decoupling control system design problems.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.3
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• pp.235-244
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• 2014

This article introduces recent trends in RHC (Receding Horizon Control), also known as MPC (Model Predictive Control), that has been well recognized in industry and academy as a systematic approach for optimal design and constraint management. Constrained and robust RHCs will be briefly reviewed with milestone results. Among the diverse developments and achievements of RHCs, implementation issues will be focused on, together with the latest applications. In particular, this article introduces results on how to solve a finite horizon open-loop optimal control problem in an efficient way, together with code generation for real-time execution and easy implementation. Instead of traditional applications such as refineries and petrochemical plants, this article highlights some selected emerging applications, such as energy management systems and mechatronics, that have resulted from state-of-the-art high performance computing power and advanced numerical schemes.

• Steel and Composite Structures
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• v.7 no.6
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• pp.421-440
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• 2007

An optimal design method in cooperated with nonlinear inelastic analysis is presented. The proposed nonlinear inelastic method overcomes the difficulties due to incompatibility between the elastic global analysis and the limit state member design in the conventional LRFD method. The genetic algorithm used is a procedure based on Darwinian notions of survival of the fittest, where selection, crossover, and mutation operators are used to look for high performance ones among sections in the database. They are satisfied with the constraint functions and give the lightest weight to the structure. The objective function taken is the total weight of the steel structure and the constraint functions are load-carrying capacity, serviceability, and ductility requirement. Case studies of a planar portal frame, a space two-story frame, and a three-dimensional steel arch bridge are presented.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2004.04a
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• pp.135-140
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• 2004

In this paper, we study the posture control of an underwater vehicle with nonholonomic constraint. Generally, systems with nonholnomic constraints cannot be stabilized to an equilibrium points by smooth state feedback control. Therefore, we proposed a control strategy for posture control of the underwater vehicle using backstepping control. The proposed control scheme is applied to the posture control of an underwater vehicle and verified the effectiveness of control strategy by numerical simulation.

• KIEE International Transaction on Systems and Control
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• v.2D no.2
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• pp.108-114
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• 2002

This paper describes the design of a robust adaptive controller for a nonlinear dynamical system with unknown nonlinearities. These unknown nonlinearities are approximated by multilayered neural networks (MNNs) whose parameters are adjusted on-line, according to some adaptive laws far controlling the output of the nonlinear system, to track a given trajectory. The main contribution of this paper is a method for considering input constraint with a rigorous stability proof. The Lyapunov synthesis approach is used to develop a state-feedback adaptive control algorithm based on the adaptive MNN model. An overall control system guarantees that the tracking error converges at about zero and that all signals involved are uniformly bounded even in the presence of input saturation. Theoretical results are illustrated through a simulation example.

• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.253-255
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• 1999

In this paper, a shape optimization algorithm of superconducting magnet using finite element method is presented. Since the superconductor loses its superconductivity over the critical magnetic field and critical current density, this material property should be taken into account in the design process. Trial and error approach of repeating the change of the design variables costs much time and it sometimes does not guarantee an optimal design. This paper presents a systematic and efficient design algorithm for the superconducting magnet. We employ the sensitivity analysis based on finite element formulation. As for optimization algorithm, the inequality constraint for the superconducting state is removed by modifying the objective function and the nonlinear equality constraint of constant volume is satisfied by the gradient projection method. This design algorithm is applied to an optimal design problem of a solenoid air-cored superconducting magnet that has a design objective of the maximum energy storage.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.10a
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• pp.145-152
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• 2003

An optimal design method in cooperated with nonlinear inelastic analysis method is presented. The proposed nonlinear inelastic method overcomes the difficulties due to incompatibility between the elastic global analysis and the limit state member design in the conventional LRFD method. The genetic algorithm uses a procedure based on Darwinian notions of survival of the fittest, where selection, crossover, and mutation operators are used among sections in the database to look for high performance ones. They satisfy the constraint functions and give the lightest weight to the structure. The objective function is set to the total weight of the steel structure and the constraint functions are load-carrying capacities, serviceability, and ductility requirement. Case studies of a three-dimensional frame and a three-dimensional steel arch bridge are presented.

• Bulletin of the Korean Chemical Society
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• v.34 no.1
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• pp.197-200
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• 2013

The bound state wave functions for all the known exactly solvable potentials can be expressed in terms of orthogonal polynomials because the polynomials always satisfy the boundary conditions with a proper weight function. The orthogonality of polynomials is of great importance because the orthogonality characterizes the wave functions and consequently the quantum system. Though the orthogonality of orthogonal polynomials has been known for hundred years, the known orthogonality is found to be inadequate for polynomials appearing in some exactly solvable potentials, for example, Ginocchio potential. For those potentials a more general orthogonality is defined and algebraically derived. It is found that the general orthogonality is valid with a certain constraint and the constraint is very useful in understanding the system.

• Journal of the Korean Society of Safety
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• v.16 no.2
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• pp.1-6
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• 2001

In the case of a crack propagation a portion of the work of inelastic deformation near the crack tip is dissipated as heat. In order to understand the thermal effect on fracture toughness, tensile tests were carried out using thermocouples to monitor the variation of temperature. The experimental results show that the temperature of specimen was increased $5.4^{\circ}C$ at static load condition. And the thermal effect is investigated connected with the steady-state stress in the vicinity of a crack propagation in the elastic-plastic C-T specimen theoretically. And fracture toughness, the energy to make crack surfaces, presented correctively. The fracture toughness with considering heat at the blunting of the crack tip is lower about 16.9％ than that of ignoring heat. So, it is resonable to apply the fracture toughness with considering thermal energy and it would be good explanation for constraint effect depending on the configuration in the presence of excessive plasticity.