• Journal of the Korean Solar Energy Society
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• v.30 no.3
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• pp.39-46
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• 2010

This study is focused on the effect of thermal load according to the various plan types in tower-type apartment in Korea. So, we chose the '』' type model in order to analyze the shading effect of the plan type. The main results are as follows. In chosen model, cooling energy demands are more sensitive than heating ones when is compared with the two methods. And there are about 10% deviations between new and conventional method. Because new method considers more detailed than conventional one about the building geometries. We also found that this building type affects to the about 3 floors from the top and it doesn't affect to the thermal load in lower floors. From these facts, we suggest new modeling method to the similar researches that will be analyzed the thermal load on the tower type apartment in Korea. Also there is no difference of the thermal load in each azimuth between simple and detailed modeling method. Consequently, we judge that this new method considered the shading effect will be used a lot to the similar analysis in tower type apartment in Korea.

• Journal of the Korean Institute of Intelligent Systems
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• v.8 no.6
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• pp.1-11
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• 1998

In this work, we propose a modeling method based on an artifical intelligence technique for a stem generator in a nuclear power plant. Modeling the steam generator is known to be difficult due to several facts; especially, the dynamics of the steam generator is nonminimum phase which is mainly caused by the swell and shrink phenomena from thermal effects. In order to overcome this difficulty, we adopt so-called logic processor whose structure itself has a logical meaning to be easily established and also efficiently learned. Such a manner, we could derive an useful model simulating the dynamics of the steam generator in a nuclear power plant.

• Journal of the Korean Chemical Society
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• v.67 no.1
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• pp.42-53
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• 2023

The purpose of this study is to obtain basic data for constructing a modeling practice program integrated with meta-modeling knowledge by analyzing the cognition level for each meta-modeling knowledge components through modeling practice in the context of the chemistry discipline content. A chemistry teacher conducted inquiry-based modeling practice including anomalous phenomena for 16 students in the second year of a science gifted school, and in order to analyze the cognition level for each of the three meta-modeling knowledge components such as model variability, model multiplicity, and modeling process, the inquiry notes recorded by the students and observation note recorded by the researcher were used for analysis. The recognition level was classified from 0 to 3 levels. As a result of the analysis, it was found that the cognition level of the modeling process was the highest and the cognition level of the multiplicity of the model was the lowest. The cause of the low recognitive level of model variability is closely related to students' perception of conceptual models as objective facts. The cause of the low cognitive level of model multiplicity has to do with the belief that there can only be one correct model for a given phenomenon. Students elaborated conceptual models using symbolic models such as chemical symbols, but lacked recognition of the importance of data interpretation affecting the entire modeling process. It is necessary to introduce preliminary activities that can explicitly guide the nature of the model, and guide the importance of data interpretation through specific examples. Training to consider and verify the acceptability of the proposed model from a different point of view than mine should be done through a modeling practice program.

• Journal of Educational Research in Mathematics
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• v.15 no.4
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• pp.505-522
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• 2005

In this article we studied the role of spreadsheet in teaching function and modeling activity by some examples and students' activity performed by the six 10th graders. We especially focused the role of spreadsheet in understanding of various kinds of functions and the families of functions, and in the explanation of the given modeling problem situations. The functions of automatic copy, graphic and the cell reference of spreadsheet can be used to make students observe the causes and effects of changes of the various kind of mathematical representations of functions such as algebraic formulas, tables and graphs. Especially those functions give students a chance to identify family of functions by changing the parameters and this may lead them to the discovery of mathematical facts. In modeling activities they play a key role in the stages of the analysis of the model, explanation of the results of model and conjecture of the real world situations. As well as they make students find the rules underlying in the real world by making spreadsheet as simulation environments, which are almost impossible to make in paper and pencil environments, and give them a chance to justify their findings using mathematics.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.5
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• pp.53-60
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• 2002

This paper presents exact autotransformer-fed AC electric railroad system modeling using constant current mode, and single-phase STATCOM(Static Synchronous Compensator) which has an effect on electric railroad system. An AC electric railroad is rapidly changing single-phase feeding electric power. To avoid voltage fluctuation under single phase loads, electric power should be received from a large source. The system modeling theory is based on the solution of algebraic. The AC electric railroad load model is nonlinear. Therefore this paper is considered nonlinear load using PSCAD/EMTDC. And the proposed modeling method is considered the line self-impedances and mutual-impedances that techniques for the AC electric railroad system modeling analysis, and that single-phase STATCOM can reliably compensate the voltage drop. In the case study, the allowance range of feeding voltage is 22.5∼27.5 kV, AT-fed AC electric railroad system circuit is analyzed by loop equation both normal and extension modes. The simulation objectives are to calculate the catenary and rail voltages with respect to ground, as the train moves along a section of line between two adjacent ATs. The results show that single-phase STATCOM can reduce the voltage drop in the feeding circuit and improve the power quality at AC electric railroad system by compensating the reactive power.

• Proceedings of the KIEE Conference
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• 2000.11a
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• pp.217-219
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• 2000

Recently a static var compensator(SVC) is installed at Seo-deagu Substation. It is a power system controller using power electronics commonly called Flexible AC Transmission Systems(FACTS). This paper presents the characteristics and configuration of the Seo-deagu SVC. This paper discusses the modeling aspect of the Seo-deagu SVC systems. EMTDC simulation model of the Seo-deagu SVC is developed and verified.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.3
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• pp.495-501
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• 2001

In this paper, a new technique which models the joints characteristics through reduction of DOFs of structures with joints using component mode synthesis (CMS) method is proposed. Bolt joints are modeled by mass-spring systems. Also generalized mass and stiffness matrices for this models are introduced. Because bolt joints have influence on eigenvalues of structures, exact eigenvalues from modal test are used. The results show that the behaviors of structures with bolt joints depend to a large extent on the translational DOFs and not on rotational DOFs of mass and stiffness matrices of bolts. Furthermore it is confirmed that lumped mass-spring systems as models of bolt joints are effective models considering the facts that joint characteristics converged to constant values in some iterations and eignevalues from proposed method are in good agreement with ones from modal test.

• Proceedings of the KIPE Conference
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• 1998.07a
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• pp.447-454
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• 1998

This paper describes a modeling and current control techniques of Distribution static condenser (D-STATCON) for power factor compensation. The current control is based on the predictive and the space vector PWM scheme. The predictive current controlled PWM D-STATCON can maintain its performance with power factor compensation and fixed switching frequency. By using the space vector control low ripple and offset in the current and the voltage as well as fast dynamic responses are achieved with a small DC link capacitance employed.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.49 no.6
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• pp.272-279
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• 2000

This paper describes a controller design and dynamic performance analysis of UPFC based on 3-level inverters. Major attention is focused on the controller design for both shunt and series inverters, including regulator design for the dc link voltage sharing across the dc capacitors. An energy-based approach was investigated for effectively designing the controller. A detailed UPFC model has been developed with EMTP using 24-pulse 3-level inverters to verify this approach. Simulation results about dynamic performance of UPFC confirm effects for increasing transmission capacity and damping low-frequency oscillation. The developed simulation model would be very effective to analyze the dynamic performance of UPFC.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.1
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• pp.48-55
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• 2003

Hidden Markov Model(HMM) has a doubly embedded stochastic process with an underlying stochastic process that can be observed through another set of stochastic processes. This structure of HMM is useful for modeling vector sequence that doesn't look like a stochastic process but has a hidden stochastic process. So, HMM approach has become popular in various areas in last decade. The increasing popularity of HMM is based on two facts : rich mathematical structure and proven accuracy on critical application. In this paper, we applied continuous HMM (CHMM) approach with AR coefficient to detect and predict the chatter of lathe bite and to diagnose the wear of oil Journal bearing using rotor shaft displacement. Our examples show that CHMM approach is very efficient method for machine health monitoring and prediction.