• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.201-205
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• 1998

In this paper, the charge control with the input voltage feed forward is proposed for the input series-output parallel connected converter configuration for high voltage power conversion applications. This control scheme accomplishes the output current sharing for the output-parallel connected modules as well as the input voltage sharing for the input-series connected modules for all operating conditions including the transients. It also offers the robustness for the component value mismatches among the modules.

• Journal of Power Electronics
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• v.18 no.3
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• pp.746-756
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• 2018

Harmonic resonance exists in grid-connected inverter systems. In order to determine the network components that contribute to harmonic resonance and the composition of the resonant circuit, sensitivity theory is applied to the resonance characteristic analysis. Based on the modal analysis, the theory of sensitivity is applied to derive a formula for determining the sensitivities of each network component parameter under a resonance circumstance that reflects the participation of the network component. The solving formula is derived for both parallel harmonic resonance and series harmonic resonance. This formula is adopted to a 4-node grid-connected test system. The analysis results reveal that for a certain frequency, the participation of parallel resonance and series resonance are not the same. Finally, experimental results demonstrate that the solving formula for sensitivity is feasible for grid-connected systems.

• Journal of KIISE:Software and Applications
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• v.32 no.7
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• pp.625-635
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• 2005

In this paper, we propose a hybrid approach for segmenting the lungs efficiently and automatically in chest CT images. The proposed method consists of the following three steps. first, lungs and airways are extracted by two- and three-dimensional automatic seeded region growing and connected component labeling in low-resolution. Second, trachea and large airways are delineated from the lungs by two-dimensional morphological operations, and the left and right lungs are identified by connected component labeling in low-resolution. Third, smooth and accurate lung region borders are obtained by refinement based on image subtraction. In experiments, we evaluate our method in aspects of accuracy and efficiency using 10 chest CT images obtained from 5 patients. To evaluate the accuracy, we Present results comparing our automatic method to manually traced borders from radiologists. Experimental results show that proposed method which use connected component labeling in low-resolution reduce processing time by 31.4 seconds and maximum memory usage by 196.75 MB on average. Our method extracts lung surfaces efficiently and automatically without additional processing like hole-filling.

• Journal of the Semiconductor & Display Technology
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• v.10 no.3
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• pp.53-59
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• 2011

This paper proposes a new method of traffic signal detection and recognition in an RGB color model. The proposed method firstly processes RGB-filtering in order to detect traffic signal candidates. Secondly, it performs adaptive threshold processing and then analyzes connected components of the binary image. The connected component of a traffic signal has to be satisfied with both a bounding box rate and an area rate that are defined in this paper. The traffic signal recognition system is implemented using C language in an embedded Linux system for a high-speed real-time image processing. Experiment results show that the proposed algorithms are quite successful.

• International Journal of Contents
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• v.13 no.3
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• pp.1-8
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• 2017

Rice plant numbers and density are key factors for yield and quality of rice grains. Precise and properly estimated rice plant numbers and density can assure high yield from rice fields. The main objective of this study was to automatically detect and count rice plants using images of usual field condition from an unmanned aerial vehicle (UAV). We proposed an automatic image processing method based on morphological operation and boundaries of the connected component to count rice plant numbers after transplanting. We converted RGB images to binary images and applied adaptive median filter to remove distortion and noises. Then we applied a morphological operation to the binary image and draw boundaries to the connected component to count rice plants using those images. The result reveals the algorithm can conduct a performance of 89% by the F-measure, corresponding to a Precision of 87% and a Recall of 91%. The best fit image gives a performance of 93% by the F-measure, corresponding to a Precision of 91% and a Recall of 96%. Comparison between the numbers of rice plants detected and counted by the naked eye and the numbers of rice plants found by the proposed method provided viable and acceptable results. The $R^2$ value was approximately 0.893.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.5
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• pp.778-785
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• 2017

This paper presents a control method for reducing the distortion of the grid current at a grid-connected three-level neutral point clamped (NPC) inverter. The grid current is distorted from the 5th and 7th harmonic components in the stationary frame current also the 6th harmonic component in the synchronous frame current. In this paper, the 6th harmonic component on synchronous frame is controlled by using all-pass filters (APFs) and proportional integral (PI) controllers for distortion of the grid side. When transformed the 6th harmonic component is controlled, the 5th and 7th harmonic components are reduced. The validity of the proposed control method is verified by simulation and experiment results using a 25kW three-level NPC inverter.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.41 no.6
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• pp.175-186
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• 2004

We present a hybrid approach of texture-based method and connected component (CC)-based method for text extraction in complex images. Two primary methods, which are mainly utilized in this area, are sequentially merged for compensating for their weak points. An automatically constructed MLP-based texture classifier can increase recall rates for complex images with small amount of user intervention and without explicit feature extraction. CC-based filtering based on the shape information using NMF enhances the precision rate without affecting overall performance. As a result, a combination of texture and CC-based methods leads to not only robust but also efficient text extraction. We also enhance the processing speed by adopting appropriate region marking methods for each input image category.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.11
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• pp.68-76
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• 2014

This paper presents an offset error compensation algorithm for the accurate phase angle of the grid voltage in single-phase grid-connected inverters. The offset error generated from the grid voltage measurement process cause the fundamental harmonic component with grid frequency in the synchronous reference frame phase lock loop (PLL). As a result, the grid angle is distorted and the power quality in power systems is degraded. In addition, the dq-axis currents in the synchronous reference frame and phase current have the dc component, first and second order ripples compared with the grid frequency under the distorted grid angle. In this paper, the effects of the offset and scaling errors are analyzed based on the synchronous reference frame PLL. Particularly, the offset error can be estimated from the integrator output of the synchronous reference frame PLL and compensated by using proportional-integral controller. Moreover, the RMS (Root Mean Square) function is proposed to detect the offset error component. The effectiveness of the proposed algorithm is verified through simulation and experiment results.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.8
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• pp.1883-1897
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• 1993

Interactive computer-aided analysis of mechanical systems has recently been undergoing an evolution due to highly efficient computer graphics. The industrial implementation of state-of-the-art analytical developments in mechanisms has been facilitated by computer-aided design packages because these rigid-body mechanism analysis programs dramatically reduce the time required for linkage design. This paper proposes a component modular approach to computeraided kinematic motion analysis for general planar multiloop mechanisms. Most multiloop mechanisms can be decomposed into serveral components. The kinematic properties (position, velocity, and acceleration) of every node can then be determined from the kinematic analysis of the corresponding component modules by a closed-form solution procedure. In this paper, 8 types of modules are defined and formulations for kinematic analysis of the component modules are derived. Then a computer-aided kinematic analysis program is developed using the proposed approach and the solution procedure of an example shows the effectiveness and accuracy on the approach.

• Communications of the Korean Mathematical Society
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• v.14 no.2
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• pp.295-299
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• 1999

Every quasi-random graph G(n) on n vertices consists of a giant component plus o(n) vertices, and every quasi-random graph G(n) with minimum degree (1+o(1))\ulcorner is connected.