• Proceedings of the KIEE Conference
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• 1998.07f
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• pp.1963-1965
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• 1998

In this paper, a new simplified configuration for a multi-level PWM inverter is proposed. The proposed inverter consists of an auxiliary circuit with one switching device, and 3 phase full-bridge inverter. The proposed inverter, in spite of reduction of the switching devices, offers characteristics similar to the NPC(Neutral - point - clamped)- PWM inverter. Also, since the reduction of the switching devices, the control strategy is simplified. And switching loss is reduced. In addition to, it is possible that reliable DC level voltage than former multi-level inverter. And load power application is same to conventional NPC-PWM inverter. The performance of the system is verified by simulation. In this paper, show the simulation result of the single phase full bridge inverter application.

• Proceeding of Spring/Autumn Annual Conference of KHA
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• 2005.11a
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• pp.269-272
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• 2005

The purpose of this study is to analyze the relation between the dwelling location and the satisfaction level, and suggest a proposal to increase the quality of the livability space. A first of this study began from public surveys conducted to gather the information of satisfaction level from 4 multi-family housing sites in Gwang-ju. The plan was to the characteristics of the LS(livability space). The poll and the observation investigation was run concurrently. The cross analysis and the frequency analysis were used to analyze the data from the questionnaires. The validity of fixed quantitative index was got through the correlation analysis between the result of former analysis and index of livability space. The result said that the dwelling location have relations with the satisfaction level. In the conclusion, this will be a suggestion of the methods to enhance equal-quality of the livability space.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.1178-1183
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• 2008

This paper is about a study of atomizing characteristics of a Multi-Nozzle, which is an important part in a flooding water mist system for extinguishing fires broke out in ships. Comparing the results of experiments for the Single-Nozzle to that of numerical analyses, characteristics of a Multi-Nozzle can be found out. In situation of a Single-Nozzle’s, the atomizing angle was $34^{\circ}$. And in situation of Multi-Nozzle that combined with 5 single-nozzles, the atomizing angle increase to $125^{\circ}$. The effective area is 3.7 times of the former. The quality factor will reduce, if the diameter of the atomizing region of the nozzle reduces. Although the atomizing angle is reduced because of the atomizing property, the value of SMD still shows a good result.

• Journal of Korea Society of Digital Industry and Information Management
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• v.5 no.4
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• pp.87-97
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• 2009

Internet network routing system is used to prevent spread and distribution of malicious data traffic. This study is based on analysis of diagnostic weakness structure in the network security domain. We propose an improved integrated multi-level protection domain for in the internal route of groupware. This paper's protection domain is designed to handle the malicious data traffic in the groupware and finally leads to lighten the load of data traffic and improve network security in the groupware. Infrastructure of protection domain is transformed into five-stage blocking domain from two or three-stage blocking. Filtering and protections are executed for the entire server at the gateway level and internet traffic route ensures differentiated protection by dividing into five-stage. Five-stage multi-level network security domain's malicious data traffic protection performance is better than former one. In this paper, we use a trust evaluation metric for measuring the security domain's performance and suggested algorithm.

• Journal of the Society of Naval Architects of Korea
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• v.48 no.6
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• pp.552-559
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• 2011

An interest in Arbitrary Lagrangian Eulerian (ALE) finite element methods has been increased due to more accurate responses in Fluid-Structure Interaction(FSI) problems. The multi-material ALE approach was applied to the prediction of the acceleration response of free-fall lifeboat, and its responses were compared to those of the single-material ALE one. It could be found that even though there was no big difference in the simulation responses of two methods, the single-material and multi-material ALE ones, the latter multi-material ALE method showed a little bit more close response to those of experimental results compared to the former single-material ALE one, especially in the x- and z-direction acceleration responses. Through this study, it could be found that several parameters in the ALE algorithms have to be examined more carefully for a good structural safety assessment of FSI problems.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.4
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• pp.1933-1939
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• 2011

The former people who made musical instruments used touch devices for sound control. As the first multi-touch system appeared in 1982, the performance of the system has been improved rapidly by many researches. In spite of such performance improvement, the popularization of multi-touch interface was looked difficult. However, in 2007, multi-touch interfaces have become popular with Apple Iphone and people have been able to experience easily multi-touch interface using smart phones. In this paper we propose a general-purpose multi-touch interaction system for multi-touch content producer and market invigoration of multi-touch interface. We show by real field tests that the proposed method has benefits in the aspects of price and performance compared with other techniques.

• Korean Journal of Computational Design and Engineering
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• v.10 no.6
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• pp.444-454
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• 2005

Recently, the requirements of multi-resolution models of a solid model, which represent an object at multiple levels of feature detail, are increasing for engineering tasks such as analysis, network-based collaborative design, and virtual prototyping and manufacturing. The research on this area has focused on several topics: topological frameworks for representing multi-resolution solid models, criteria for the level of detail (LOD), and generation of valid models after rearrangement of features. As a solution to the feature rearrangement problem, the new concept of the effective zone of a feature is introduced in the former part of the paper. In this paper, we propose a feature-based non-manifold modeling system to provide multi-resolution models of a feature-based solid or non-manifold model on the basis of the effective feature zones. To facilitate the implementation, we introduce the class of the multi-resolution feature whose attributes contain all necessary information to build a multi-resolution solid model and extract LOD models from it. In addition, two methods are introduced to accelerate the extraction of LOD models from the multi-resolution modeling database: the one is using an NMT model, known as a merged set, to represent multi-resolution models, and the other is storing differences between adjacent LOD models to accelerate the transition to the other LOD. We also suggest the volume of the feature, regardless of feature type, as a criterion for the LOD. This criterion can be used in a wide range of applications, since there is no distinction between additive and subtractive features unlike the previous method.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.1
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• pp.33-41
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• 2010

This study was aimed at the design of the dies for the unified pipe joint of the intermediate shaft using the computer simulation to shorten the period of production, on the basis of the process planning which was designed by the field experts. In the computer simulation, 'Deform-3d' and 'eesy-DieOpt' have been used, which are the commercial process analysis and die design program. Through the process analysis, we could know the propriety of the forming process, the inner pressure of the die and the suitable fitting pressure between the insert and the sleeve which was not showing any positive tangential stresses in the insert. Through the simulation of die design, we could know the number of the stress ring, the diameter ratios, the stresses of the die, the shrink fitting tolerance and temperature in the condition of the already determined maximum outer die diameter of the multi-stage former. The validity of the die design using the computer simulation was analyzed by the experiments and the results were satisfactory. As the results of this study, the new and easy die design system for multi-forging has been developed.

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.116-119
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• 2005

As to the synthetical estimation of land covering parameters or the compounded land covering classification for multi-resolution satellite data, former researches mainly adopted linear or nonlinear regression models to describe the regression relationship of land covering parameters caused by the degradation of spatial resolution, in order to improve the retrieval accuracy of global land covering parameters based on 1;he lower resolution satellite data. However, these methods can't authentically represent the complementary characteristics of spatial resolutions among different satellite data at arithmetic level. To resolve the problem above, a new compounded land covering classification method at arithmetic level for multi-resolution satellite data is proposed in this .paper. Firstly, on the basis of unsupervised clustering analysis of the higher resolution satellite data, the likelihood distribution scatterplot of each cover type is obtained according to multiple-to-single spatial correspondence between the higher and lower resolution satellite data in some local test regions, then Parzen window approach is adopted to derive the real likelihood functions from the scatterplots, and finally the likelihood functions are extended from the local test regions to the full covering area of the lower resolution satellite data and the global covering area of the lower resolution satellite is classified under the maximum likelihood rule. Some experimental results indicate that this proposed compounded method can improve the classification accuracy of large-scale lower resolution satellite data with the support of some local-area higher resolution satellite data.

• 한국전산유체공학회:학술대회논문집
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• 2005.10a
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• pp.55-59
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• 2005

CFD analysis has been conducted to find the two stage impeller configuration which is the most suitable for a stirred tank with an internal helical cooling coil and a cooling jacket, which is frequently used in chemical industries for highly exothermic reactions ranged from low to medium viscosity. Two typical types of impellers are considered; pitched paddle impellers and Rushton turbine impellers. Interestingly, pitched paddle impellers show a good mixing performance for multi-species, whereas Rushton turbine impellers achieve a good mixing performance for multi-phases. Besides the type of an impeller, the location of an impeller is another important factor to be considered in order to accomplish an effective mixing. The best set of types and locations of two impellers is recommended based on the coefficient of variation(CoV) value and the heat removal capability obtained from CFD results. The former is a measure to quantify the degree of mixing.