• Journal of Power Electronics
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• v.16 no.2
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• pp.425-435
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• 2016

This paper presents a comprehensive theoretical analysis and an accurate calculation method of the dead-time required to achieve zero-voltage-switching (ZVS) in a battery charger with the phase-shifted full-bridge (PSFB) topology. Compared to previous studies, this is the first time that the effects of nonlinear output filter inductance, varied Miller Plateau length, and blocking capacitors have been considered. It has been found that the output filter inductance and the Miller Plateau have a significant influence on the dead-time for ZVS when the load current varies a lot in battery charger applications. In addition, the blocking capacitor, which is widely used to prevent saturation, reduces the circulating current and consequently affects the setting of the dead-time. In consideration of these effects, accurate analytical equations of the dead-time range for ZVS are deduced. Experimental results from a 1.5kW PSFB battery charger prototype shows that, with the proposed analysis, an optimal dead-time can be selected to meet the specific requirements of a system while achieving ZVS over wide load range.

• KIEE International Transactions on Electrophysics and Applications
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• v.12C no.4
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• pp.220-224
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• 2002

The electromagnetic properties and thermal behavior of Mn-Zn ferrite cores for the blocking filter of PLC application were investigated as the function of additives. The highest density and permeability were 4.98 g/㎤ and 8,221, respectively and were obtained to the specimen with composition of MnO 24 mol%, ZnO 25 mol% and Fe$_2$O$_3$51 mol%, added MoO$_3$ of 400 ppm, SiO$_2$ of 100 ppm, and CaO of 200 ppm. The uniform grains were organized, and the microstructures were compacted due to reduction of pores in the specimen. The permeability was increased up to 13,904 as the temperature of specimen increased to 110。C. However, it was decreased precipitously under 100 over 110。C. The exothermic behavior was observed in the frequency range from 1 kHz to 1 MHz, and the maximum temperature of specimen was 102。C at 1 MHz. In the consequence, the Mn-Zn ferrite core developed in this research will maintain the stable electromagnetic properties since the temperature of ferrite core rose to 93 。C in the range of 100 kHz to 450 kHz bandwidth qualified for PLC. The blocking filters were designed for single phase and three phases using the in-line and non-contact core. The best attenuation ratios of -46.46 dB and -73.9 dB were measured in the range of 100 kHz to 450 kHz bandwidth, respectively.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.39 no.4
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• pp.399-407
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• 2002

In this paper, a novel algorithm is proposed to reduce the blocking artifacts of block-based coded images by using block classification and MLP. In the proposed algorithm, we classify the block into four classes based on a characteristic of DCT coefficients. And then, according to the class information of neighborhood block, adaptive neural network filter is performed in horizontal and vertical block boundary. That is, for smooth region, horizontal edge region, vertical edge region, and complex region, we use a different two-layer neural network filter to remove blocking artifacts. Experimental results show that the proposed algorithm gives better results than the conventional algorithms both subjectively and objectively.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.1102-1107
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• 2005

In this study, a specification for the filter system of plastic board drain using in korea. When PBDs was installed in the soft ground, bridging, blocking, blinding and clogging phenomena could be appeared near the PBD. Especially, clogging phenomena near the filter of PBD is very important factor to determine the life span of the vertical drainage system. Therefore, in this study, we proposed the specification on the filter of PBD considering the size of soil particle. To verify the proposed specification, model tests were conducted by using filter seepage tester. From the model test, newly proposed specification which considered the size of soil particle maintained the ability of seepage of the filter system of PBD.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.48 no.5
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• pp.84-95
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• 2011

In this paper, we present a deblocking algorithm that removes grid and staircase noises, which are called "blocking artifacts", occurred in the compressed satellite images. Particularly, the given satellite images are compressed with equal quantization coefficients in row according to region complexity, and more complicated regions are compressed more. However, this approach has a problem that relatively less complicated regions within the same row of complicated regions have blocking artifacts. Removing these artifacts with a general deblocking algorithm can blur complex and undesired regions as well. Additionally, the general filter lacks in preserving the curved edges. Therefore, the proposed algorithm presents an adaptive filtering scheme for removing blocking artifacts while preserving the image details including curved edges using the given quantization step size and content analysis. Particularly, WLFPCA (weighted lowpass filter using principle component analysis) is employed to reduce the artifacts around edges. Experimental results showed that the proposed method outperforms SA-DCT in terms of subjective image quality.

• Journal of Broadcast Engineering
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• v.17 no.6
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• pp.1048-1060
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• 2012

In this paper, an adaptive temporal and spatial filter (ATSF) based on mean square error (MSE) estimation is proposed. ATSF is a block based de-noising algorithm. Each noisy block is selectively filtered by a temporal filter or a spatial filter. Multi-hypothesis motion compensated filter (MHMCF) and bilateral filter are chosen as the temporal filter and the spatial filter, respectively. Although there is no original video, we mathematically derivate a formular to estimate the real MSE between a block de-noised by MHMCF and its original block and a linear model is proposed to estimate the real MSE between a block de-noised by bilateral filter and its original block. Finally, each noisy block is processed by the filter with a smaller estimated MSE. Simulation results show that our proposed algorithm achieves substantial improvements in terms of both visual quality and PSNR as compared with the conventional de-noising algorithms.

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.403-406
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• 2000

본 논문에서는 저비트율 영상통신에서 발생되는 블록화현상과 컬러 번짐 현상을 효과적으로 줄임으로써, 주관적 화질을 개선하는 후처리 필터를 제안한다. 저비트율 영상통신에서 8*8 블록 단위의 DCT 수행은 블록화 및 컬러 번짐 현상과 같은 화질 열화를 초래한다. 이러한 화질 열화를 개선하기 위하여 밝기 영역과 컬러 영역에서 각기 다른 후처리 필터를 본 논문에서 제안한다. 밝기 부분의 후처리 필터에서는 일률적인 후처리 필터에서 발생하게 되는 새로운 artifact 인 geometric pattern 을 방지하기 위해 각 화소의 공간영역에서 블록 경계 좌우로 filtering range 를 다르게 수행하고, 컬러부분의 후처리 필터에서는 컬러번짐 현상을 최대한 억제하기 위해 블록간 컬러 값의 차이에 따라 다르게 수행되는 후처리 필터를 제안한다. 제안된 실험을 통하여 후처리 필터를 수행한 영상화질이 H.263 baseline 에 비해 월등히 나아짐을 확인할 수 있었으며, H.263 Annex J의 deblocking filter mode에 비해서도 떨어지지 않는 화질을 얻을 수 있었다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.12
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• pp.47-56
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• 2010

For a human being's smooth activity, the clean air and comfortable lighting environment are needed. The suitable lighting environment is obtained generally by making it available for being formed the bright situation easy for seeing object and the visually comfortable atmosphere. In this way, even the lighting environment was changed along with economic development. Even a light source was diversified. Thus, several kinds of new light sources such as LED, OLED, PLS, and CNT came to appear. Halogen lamp, which has low efficiency due to high color rendering among lamps of being used now, is being much used yet. However, owing to radiation of UV and IR, there are many limitations to the subject in general exhibition lighting, museum, and art museum. Accordingly, a research was performed on filter that is blocked UV and IR at the same time, by using halogen lamp that is excellent in color rendering and in life.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.2
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• pp.151-154
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• 2020

Radiation noise due to EMI noise generated by the driving circuits of LED lighting devices in a medical imaging room was reduced by decreasing the noise source in the driving circuits and changing the number of corrections in EMI filters. Noise attenuation and filter changes enabled driving circuits that reduced the electromagnetic waves. Such circuits were efficiently designed by using capacitors and inverters in a given space. Therefore, the malfunction of radiation devices can be minimized by using EMI-reduction filter circuits, and reliable operation of medical devices can be expected by blocking electromagnetic waves.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.06a
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• pp.1035-1040
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• 2005

This paper deals with the design rule and performance results of the surge protective devices (SPDs) for low-voltage mains on shipboard. The proposed SPDs consists of a metal oxide varistors (MOV) and a L-C filter to improve noise-elimination performance. Three kinds of SPDs are fabricated and tested by using a combination surge generator which produce the standard impulse current of 8/20${\mu}s$ 2.1kA. As a results, the proposed SPDs with series L-C filter have more excellent transient blocking and noise reduction performance than the conventional ones.