• Journal of Power Electronics
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• v.9 no.3
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• pp.481-490
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• 2009

This paper describes a SVPWM overmodulation scheme of NPC type three-level inverter for traction drives which extends the modulation index from MI=0.907 to unity. SVPWM strategy is organized by two operation modes of under-modulation and over-modulation. The switching states under the under-modulation modes are determined by dividing them with two linear regions and one hybrid region the same as the conventional three-level inverter. On the other hand, under the over-modulation mode, they are generated by doing it with two over-modulation regions the same as the conventional over-modulation strategy of a two level inverter. Following the description of over-modulation scheme of a three-level inverter, the system description of a vector controlled induction motor for traction drives has been discussed. Finally, the validity of the proposed modulation algorithm has been verified through simulation and experimental results.

• Journal of Advanced Marine Engineering and Technology
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• v.19 no.1
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• pp.71-81
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• 1995

In this paper, a new speed control scheme for induction motor drives that regular sampled PWM and harmonic elimination switching pattern over the full range of output speed is presented. The proposed scheme(hybrid scheme) provides three mode and guarantees smooth voltage boost. A detailed description of the scheme, along with the relalization aspect, is described. Moreover, methods of compensating for dead time and optical transmission system of drive signal are proposed and investigated. Finally, experimental investigation of hybrid scheme is presented.

• Knowledge Management Research
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• v.20 no.3
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• pp.139-154
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• 2019

With the increasing use of smartphone apps, many apps are coming out in various fields. In order to analyze the current status and trends of apps in a specific field, it is necessary to establish a classification scheme. Various schemes considering users' behavior and characteristics of apps have been proposed, but there is a problem in that many apps are released and a fixed classification scheme must be updated according to the passage of time. Although it is necessary to consider many aspects in establishing classification scheme, it is possible to grasp the trend of the app through the proposal of a classification scheme according to the characteristic of the app. This research proposes a method of establishing an app classification scheme through the description of the app written by the app developers. For this purpose, we collected explanations about apps in the tourism field and identified major categories through topic modeling. Using only the apps corresponding to the topic, we construct a network of words contained in the explanatory text and identify subcategories based on the networks of words. Six topics were selected, and Clauset Newman Moore algorithm was applied to each topic to identify subcategories. Four or five subcategories were identified for each topic.

• Journal of Broadcast Engineering
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• v.5 no.1
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• pp.82-93
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• 2000

Recently, the capability of efficient access to the desired video content is of growing importance because more digital video data are available at an increasing rate. A video summary abstracting the gist from the entirety enables the efficient browsing as well as the fast skimming of the video contents. In this paper, we discuss a novel dynamic summarization method based on the detection of highlights which represent semantically significant content and the description scheme (DS) proposed to MPEG-7 aiming to provide summary description. The summary DS proposed to MPEG-7 allows for efficient navigation and browsing to the contents of interest through the functionalities of multi-level highlights, hierarchical browsing and user-customized summarization. In this paper, we also show the validation and the usefulness of the methodology for dynamic summarization and the summary DS in real applications with soccer video sequences.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.9C
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• pp.840-848
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• 2007

A multiple description coding (MDC) scheme for 3-D Data is presented. First, a plane-based 3-D data is split into two descriptions, each of which has identical contribution in 3-D surface reconstruction. In order to maximize the visual quality of reconstructed 3-D data, then, plane parameters are modified according to channel error condition. Finally, these descriptions are compressed and transmitted over distinct channels. In decoder, if two descriptions are available, we reconstruct a high quality 3-D data. If only one description is transmitted, however, 3-D surface recovery scheme reduces artifacts on erroneous 3-D surface, yielding a smooth 3-D surface. Therefore, the proposed algorithm guarantees acceptable quality reconstruction of 3-D data even though one channel is totally lost.

• Transactions of Materials Processing
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• v.5 no.1
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• pp.47-54
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• 1996

An improved nonparametric tool description based on successive refined nonparametric patches is proposed and the related criterion for refinement is also discussed. In the proposed scheme any required order of tool surface conformity can be achieved by employing successive refinements according to the suggested criterion. By using the suggested adaptive tool refinement technique based on the nonparametric patch tool description the locally refined nonparametric tool surface with economic memory size and sufficient accuracy as well as with favorable characteristics for contact treatment can be obtained directly from the parametric patch related with commercial CAD system. Computation is carried out for a chosen complex sheet forming example of an actual autobody panel in order to verify the validity and the efficiency of the developed tool surface description.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.3
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• pp.1140-1154
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• 2015

Multiple Description (MD) coding is a promising alternative for the robust transmission of information over error-prone channels. Lattice vector quantization (LVQ) is a significant version of MD techniques to design an MD image coder. However, different from the traditional 2D texture image, the 3D depth image has its own special characteristics, which should be taken into account for efficient compression. In this paper, an optimized MDLVQ scheme is proposed in view of the characteristics of 3D depth image. First, due to the sparsity of depth image, the image blocks can be classified into edge blocks and smooth blocks, which are encoded by different modes. Furthermore, according to the boundary contents in edge blocks, the step size of LVQ can be regulated adaptively for each block. Experimental results validate the effectiveness of the proposed scheme, which show better rate distortion performance compared with the conventional MDLVQ.

• Transactions of Materials Processing
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• v.4 no.1
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• pp.69-78
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• 1995

The arbitrary Lagrangian-Eulerian(ALE) finite element analysis is applied to the axisymmetric hot extrusion through continuous dies. In order to simulate hot forming problems, an ALE scheme for temperature analysis is proposed. The computed results are compared with experimental results as with those by pure Lagrangian method. In the present study mesh control is accomplished by the use of isoparametric mapping of quadrilaterals.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.91.3-91
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• 2001

A sensor fusion scheme for mobile robot environment recognition that incorporates range data and contour data is proposed. Ultrasonic sensor provides coarse spatial description but guarantees open space with no obstacle within sonic cone with relatively high belief. Laser structured light system provides detailed contour description of environment but prone to light noise and is easily affected by surface reflectivity. Overall fusion process is composed of two stages: Noise elimination and belief updates. Dempster Shafer´s evidential reasoning is applied at each stage. Open space estimation from sonar range measurements brings elimination of noisy lines from laser sensor. Comparing actual sonar data to the simulated sonar data enables ...

• Journal of KIISE
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• v.42 no.3
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• pp.413-418
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• 2015

In this paper, we design new video metadata schema for searching video segments to create UEC (User Edited Contents). The proposed video metadata schema employs hierarchically structured units of 'Title-Event-Place(Scene)-Shot', and defines the fields of the semantic information as structured form in each segment unit. Since this video metadata schema is defined by analyzing the structure of existing UECs and by experimenting the tagging and searching the video segment units for creating the UECs, it helps the users to search useful video segments for UEC easily than MPEG-7 MDS (Multimedia Description Scheme) which is a general purpose international standard for video metadata schema.