• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.275-276
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• 2010

In this study, using experimental results on the autogenous expansion of concrete containing MgO, autogenous expansion model which considers water-binder ratio, amount of MgO and curing temperature was suggested. The results predicted by autogenous expansion model agreed well with experiment results.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.80-82
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• 1996

This paper deals with the effects of the volume of thermal expansion chamber on the interrupting performance in thermal expansion type 25.8kV 25kA gas circuit breaker. Model interrupters with 5 type thermal expansion chamber were designed and manufactured. Short-circuit tests were carried out for those model interrupters with 25kA breaking current. Pressure rise in the expansion chamber were measured and compared with the calculated one which was obtained from a self-developed program in our team. The analysis on the interrupting performance of each model interrupter has been done on the base of the short-circuit test results.

• Smart Media Journal
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• v.5 no.1
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• pp.137-142
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• 2016

In this paper, a multi-scale model is applied to the simulation of thrombus growth. This model includes macroscale model and microscale model. The former is used to model the plasma flow with Navier-Stokes equations, and the latter is used to model the platelets adhesion and aggregation, thrombus motion, and the surface expansion of thrombus. The force acting on platelets and thrombus from plasma is modeled by the drag force, and the forces from biochemical reactions are modeled by the adhesion force and the aggregation force. As more platelets are merged into the thrombus, the thrombus surface expands. We proposed a thrombus growth model for simulating the expansion of thrombus surface and tracking the surface by Level Set Methods. We implemented the computational model. The model performs well, and the experimental results show that the shape of thrombus in level set expansion form is similar with the thrombus in clinical test.

• Smart Structures and Systems
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• v.10 no.4_5
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• pp.485-499
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• 2012

Mode shape expansion is useful in structural dynamic studies such as vibration based structural health monitoring; however most existing expansion methods can not consider the modelling errors in the finite element model and the measurement uncertainty in the modal properties identified from vibration data. This paper presents a reliable approach for expanding mode shapes with consideration of both the errors in analytical model and noise in measured modal data. The proposed approach takes the perturbed force as an unknown vector that contains the discrepancies in structural parameters between the analytical model and tested structure. A regularisation algorithm based on the Tikhonov solution incorporating the L-curve criterion is adopted to reduce the influence of measurement uncertainties and to produce smooth and optimised expansion estimates in the least squares sense. The Canton Tower benchmark problem established by the Hong Kong Polytechnic University is then utilised to demonstrate the applicability of the proposed expansion approach to the actual structure. The results from the benchmark problem studies show that the proposed approach can provide reliable predictions of mode shape expansion using only limited information on the operational modal data identified from the recorded ambient vibration measurements.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.7
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• pp.957-965
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• 2012

Korean government has been preparing the introduction of Emission Trading as part of the framework convention on Climate Change as a relief of negative downstream effect over electricity industry. This paper develops a mathematical model amenable to analyzing the economic impact of introduced emission trading system on the national generation expansion planning. The developed model was also employed with a case study to verify its applicability.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.3
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• pp.481-490
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• 2007

WASP which is used to plan generation expansion has disadvantages that can't manage environmental factors and regional supply-demand planning. But with the effectuation of the United Nations Framework Convention on Climate Change (UNFCCC) and Kyoto Protocol, it is expected that reducing greenhouse gases affects power system in its long-term generation expansion planning. Therefore national countermeasures is needed. This paper formulates a mathematical model considering CO2 emission constraints and Emission Trading that will be enforced. This model is based on the MEFISET (Model for Economic Feasibility of Interstate Electrical Ties) which was made by Korea Energy Economics Institute and Hong-ik university and manages generation expansion planning. And this mathematical model is verified by studying a case system.

• Proceedings of the KIEE Conference
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• 2008.11a
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• pp.74-76
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• 2008

The power expansion planning is large and capital intensive capacity planning. In the past the expansion planning was established with the proper supply reliability in order to minimize social cost. However, the planning not used cost minimizing objective function in the power markets with many market participants. This paper proposed the power expansion planning process in the power markets. This system is composed of Regulator and GENCO's model. Regulator model used multi-criteria decision making rule. GENCO model is very complex problem. Thus, this system transacted the part by several scenario assuming GENCO model.

• International Journal of Air-Conditioning and Refrigeration
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• v.7
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• pp.11-21
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• 1999

The capillary tube and short tube orifice have been widely used as an expansion device in the refrigeration and air-conditioning system. To improve the system performance, expansion devices need to be optimized with the components of a refrigeration system. In the present study, a numerical model for a capillary, which could predict the flow rate and properties along a tube, was developed by assuming homogeneous two-phase flow. A semi-empirical flow model for evaluation of the flow rate through a short tube orifice was also developed by using the experimental data. Finally, the results of the numerical model for a capillary was compared with those of the semi-empirical model for a short tube orifice to identify the dominant flow factors for the expansion devices.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.1
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• pp.118-128
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• 1998

Capillary and short tube orifice have been widely used as an expansion device in refrigeration and air-conditioning system. To improve the system performance, expansion devices need to be optimized with the components of a refrigeration system. In the present study, a numerical model for a capillary, which can predict properties along a tube and flow rate through a tube, was developed by assuming homogeneous two-phase flow, A semi-empirical flow model that can be used to evaluate the flow rate through a short tube orifice was also developed by summarizing the experimental data. Finally, the results of the numerical model for capillaries were compared with those of the semi-empirical model for short tube orifices to verify dominant flow factors for the expansion devices.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.59 no.1
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• pp.44-54
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• 2023

In this study, the second-order Nomoto's nonlinear expansion model was implemented as a Tagaki-Sugeno fuzzy model based on the heading angular velocity to design the automatic steering system of a ship considering nonlinear elements. A Tagaki-Sugeno fuzzy PID controller was designed using the applied fuzzy membership functions from the Tagaki-Sugeno fuzzy model. The linear models and fuzzy membership functions of each operating point of a given nonlinear expansion model were simultaneously tuned using a genetic algorithm. It was confirmed that the implemented Tagaki-Sugeno fuzzy model could accurately describe the given nonlinear expansion model through the Zig-Zag experiment. The optimal parameters of the sub-PID controller for each operating point of the Tagaki-Sugeno fuzzy model were searched using a genetic algorithm. The evaluation function for searching the optimal parameters considered the route extension due to course deviation and the resistance component of the ship by steering. By adding a penalty function to the evaluation function, the performance of the automatic steering system of the ship could be evaluated to track the set course without overshooting when changing the course. It was confirmed that the sub-PID controller for each operating point followed the set course to minimize the evaluation function without overshoot when changing the course. The outputs of the tuned sub-PID controllers were combined in a weighted average method using the membership functions of the Tagaki-Sugeno fuzzy model. The proposed Tagaki-Sugeno fuzzy PID controller was applied to the second-order Nomoto's nonlinear expansion model. As a result of examining the transient response characteristics for the set course change, it was confirmed that the set course tracking was satisfactorily performed.