• Journal of Power Electronics
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• v.18 no.2
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• pp.627-639
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• 2018

The fact that the reliability of IGBTs has become a more and more significant aspect of power converters has resulted in an increase in the research on the open circuit (OC) fault location of IGBTs. When an OC fault occurs, a zero-current phenomena exists and frequently appears, which can be found in a lot of the existing literature. In fact, fault variables have a very high correlation with the zero-current interval. In some cases, zero-current interval actually decides the most significant fault feature. However, very few of the previous studies really explain or prove the zero-current phenomena of the fault current. In this paper, the zero-current phenomena is explained and verified through mathematical derivation, based on two-level and three-level NPC static var generators (SVGs). Mathematical models of single OC fault are deduced and it is concluded that a zero-current interval with a certain length follows the OC faults for both two-level and NPC three-level SVGs. Both inductive and capacitive reactive power situations are considered. The unbalanced load situation is discussed. In addition, simulation and experimental results are presented to verify the correctness of the theoretical analysis.

• Proceedings of the KSRS Conference
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• v.1
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• pp.90-93
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• 2006

The first Geostationary Ocean Color Imager (GOCI) onboard its Communication Ocean and Meteorological Satellite (COMS) is scheduled for launch in 2008. GOCI includes the eight visible-to-near-infrared (NIR) bands, 0.5km pixel resolution, and a coverage region of 2500 ${\times}$ 2500km centered at 36N and 130E. GOCI has had the scope of its objectives broadened to understand the role of the oceans and ocean productivity in the climate system, biogeochemical variables, geological and biological response to physical dynamics and to detect and monitor toxic algal blooms of notable extension through observations of ocean color. The special feature with GOCI is that like MODIS, MERIS and GLI, it will include the band triplets 660-680-745 for the measurements of sun-induced chlorophyll-a fluorescence signal from the ocean. The GOCI will provide SeaWiFS quality observations with frequencies of image acquisition 8 times during daytime and 2 times during nighttime. With all the above features, GOCI is considered to be a remote sensing tool with great potential to contribute to better understanding of coastal oceanic ecosystem dynamics and processes by addressing environmental features in a multidisciplinary way. To achieve the objectives of the GOCI mission, we develop the GOCI Data Processing System (GDPS) which integrates all necessary basic and advanced techniques to process the GOCI data and deliver the desired biological and geophysical products to its user community. Several useful ocean parameters estimated by in-water and other optical algorithms included in the GDPS will be used for monitoring the ocean environment of Korea and neighbouring countries and input into the models for climate change prediction.

• Journal of Science of Art and Design
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• v.12
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• pp.125-143
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• 2007

The politics penetrating through the contemporary art since modernism to postmodernism is to accomplish the 'Non-representation' in the artworks. This study argues that postmodernism did not put an end to the formalistic feature of modernism but intended to accomplish it. Modernist art aimed at purity, i.e. self-referential and self-definition art advocated by Clement Greenberg, and it carne to the end by accomplishing flatness and materiality. It was an 'evasion to the matter' which allocated the object from visuality of outer object to the psychic image of the subject. It failed being 'non-representational' as what it really achieved was transition of object. Jean Baudrillard's theory tried to overcome the representational quality by 'being simulacre'. In the representative artworks of the past, the meaning of artworks was reverted under the outer context or object. The meaning again failed being 'Non-representational' as it was restored to the psychic image of the subject in modernist artworks where the definite illusion was demolished Meanwhile, artwork advocating simulacre acquired Non-representational quality by liberating from both models. It did not deconstruct the self-referential tendency of modernism but maximized the Non-representational modernistic principle. After creating 'Non-representation' through simulacre, the existential status and function of an artwork is the inclination and moral of contemporary art as 'Non-representation'. The image theory of Henri Bergson sets the existential status of 'image' as it does not belong to either subject nor object. It provides significant foundation for arguing the existential status of simulacre. Moreover, though an artwork as a fragment forming a movement image in the world cannot represent the object, it can however sustain certain kind of fractal resemblance with the world by letting the two parties communicate. The theory of sense by Gilles Deleuze is of profound significance as it specifically indicated way how the stage of absorption through the unity of subject and object is realized in forms of artworks, and configured the latent and invisible energy.

• Nuclear Engineering and Technology
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• v.19 no.4
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• pp.233-241
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• 1987

Difficulties are encountered when the behavior of complex systems (i.e., fuel failure probability) that have unreliable deterministic models is predicted. For more realistic prediction of the behavior of complex systems with limited observational data, the present study was undertaken to devise an approach of combining predictions from the deterministic model and actual observational data. Predictions by this method of combining are inferred to be of higher reliability than separate predictions made by either model taken independently. A systematic method of hierarchical pattern discovery based on the method developed in the SPEAR was used for systematic search of weighting factors and pattern boundaries for the present method. A sample calculation was performed for prediction of CANDU fuel failures that had occurred due to power ramp during refuelling process. It was demonstrated by this sample calculation that there exists a region of feature space in which fuel failure probability from the PROFIT model nearly agree with that from observational data.

• Journal of Korean Society of Transportation
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• v.17 no.3
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• pp.117-130
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• 1999

Earthquakes damage roadway bridges and structures, resulting in significant impacts on transportation system Performance and regional economy. Seismic risk analysis (SRA) procedures establish retrofit priorities for vulnerable highway bridges. SRA procedures use average daily traffic volumes to determine the relative importance of a bridge. This research develops a cost-effective transportation network analysis (TAN) procedure for evaluating numerous traffic flow analyses in terms of the additional system cost due to failure. An important feature of the TNA Procedure is the use of an associative memory (AM) approach in the artificial intelligence held. A simple seven-zone network is developed and used to evaluate the TNA procedure. A subset of link failure system states is randomly selected to simulate synthetic post-earthquake network flows. The performance of different AM model is evaluated. Results from numerous link-failure scenarios demonstrate the applicability of the AM models to traffic flow estimation.

• Journal of Broadcast Engineering
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• v.11 no.4 s.33
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• pp.458-470
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• 2006

This paper describes issues and consideration on authoring of interactive multi-view visual content based on MPEG-4. The issues include types of multi-view visual content; scene composition for rendering; functionalities for user-interaction; and multi-view visual content file format. The MPEG-4 standard, which aims to provide an object based audiovisual coding tool, has been developed to address the emerging needs from communications, interactive broadcasting as well as from mixed service models resulting from technological convergence. Due to the feature of object based coding, the use of MPEG-4 can resolve the format diversity problem of multi-view visual contents while providing high interactivity to users. Throughout this paper, we will present which issues need to be determined and how they can be realized by means of MPEG-4 Systems.

• Spatial Information Research
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• v.22 no.2
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• pp.31-44
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• 2014

According to the purpose of applications, the application program will utilize the most suitable data model and 3D modeling data would be generated based on the selected data model. In these reasons, there are various data sets to represent the same geographical features. The duplicated data sets bring serious problems in system interoperability and data compatibility issues, as well in finance issues of geo-spatial information industries. In order to overcome the problems, this study proposes a spatial data fusion method using topological relationships among spatial objects in the feature classes, called Topological Relation Model (TRM). The TRM is a spatial data fusion method implemented in application-level, which means that the geometric data generated by two different data models are used directly without any data exchange or conversion processes in an application system to provide indoor LBSs. The topological relationships are defined and described by the basic concepts of IndoorGML. After describing the concepts of TRM, experimental implementations of the proposed data fusion method in 3D GIS are presented. In the final section, the limitations of this study and further research are summarized.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.590-593
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• 2009

To identify the detailed 3D flow characteristics of a model scramjet engine, a unified 3D numerical analysis was performed. The numerical domain of concern includes the entire flow path of the model scramjet engine extending from the intake to the nozzle exhaust. Turbulent models($k-{\omega}$ SST and low Reynolds number k-e with Sarkar model) were applied with comparison of experiment result. Intake side wall's effect on flow characteristics was analyzed in view points of flow quality at inlet duct and near the flame holder as well. The code is paralleled with multi-block feature using MPI(Massage Passing Interface) library to speed up the 3D calculation.

• Journal of IKEEE
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• v.1 no.1 s.1
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• pp.101-110
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• 1997

SVLIW processor architectures can resolve resource collisions and data dependencies between the instructions while scheduling VLIW instructions at run-time. As a result, long NOP word instructions can be removed from the object code produced for the processor. Thus, the occurrence of cache misses on the SVLIW processor would be lesser than that on the same cache size VLIW processor. Less frequent cache misses on the SVLIW processor would incur less frequent memory access, and thus, the total execution cycles to complete an application would be shortened compared with cases on the VLIW processor. Such a feature eventually compromises effects of longer instruction pipeline stages than those of the VLIW processor. In this paper, we formulate and compare two execution cycle models of the two architectures. A simulation results show that the longer memory access cycles when cache miss occurs, the total execution cycles of SVLIW processor would be shorter than those of VLIW processor.

• International Journal of Control, Automation, and Systems
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• v.1 no.2
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• pp.194-202
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• 2003

In this paper, we introduce a category of Multi-FNN (Fuzzy-Neural Networks) models, analyze the underlying architectures and propose a comprehensive identification framework. The proposed Multi-FNNs dwell on a concept of fuzzy rule-based FNNs based on HCM clustering and evolutionary fuzzy granulation, and exploit linear inference being treated as a generic inference mechanism. By this nature, this FNN model is geared toward capturing relationships between information granules known as fuzzy sets. The form of the information granules themselves (in particular their distribution and a type of membership function) becomes an important design feature of the FNN model contributing to its structural as well as parametric optimization. The identification environment uses clustering techniques (Hard C - Means, HCM) and exploits genetic optimization as a vehicle of global optimization. The global optimization is augmented by more refined gradient-based learning mechanisms such as standard back-propagation. The HCM algorithm, whose role is to carry out preprocessing of the process data for system modeling, is utilized to determine the structure of Multi-FNNs. The detailed parameters of the Multi-FNN (such as apexes of membership functions, learning rates and momentum coefficients) are adjusted using genetic algorithms. An aggregate performance index with a weighting factor is proposed in order to achieve a sound balance between approximation and generalization (predictive) abilities of the model. To evaluate the performance of the proposed model, two numeric data sets are experimented with. One is the numerical data coming from a description of a certain nonlinear function and the other is NOx emission process data from a gas turbine power plant.