• Journal of Power Electronics
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• v.16 no.6
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• pp.1991-2004
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• 2016

An LC filter is required to reduce the output current ripple in the auxiliary resonant snubber inverter (ARSI) for high-performance applications. However, if the traditional control method is used in the ARSI with LC filter, then unnecessary current flows in the auxiliary circuit. In addressing this problem, a novel load-adaptive control that fully uses the filter inductor current ripple to realize the soft-switching of the main switches is proposed. Compared with the traditional control implemented in the ARSI with LC filter, the proposed control can reduce the required auxiliary current, contributing to higher efficiency and DC-link voltage utilization. In this study, the detailed circuit operation in the light load mode (LLM) and the heavy load mode (HLM) considering the inductor current ripple is described. The characteristics of the improved ARSI are expressed mathematically. A prototype with 200 kHz switching frequency, 80 V DC voltage, and 8 A maximum output current was developed to verify the effectiveness of the improved ARSI. The proposed ARSI was found to successfully operate in the LLM and HLM, achieving zero-voltage switching (ZVS) of the main switches and zero-current switching (ZCS) of the auxiliary switches from zero load to full load. The DC-link voltage utilization of the proposed control is 0.758, which is 0.022 higher than that of the traditional control. The peak efficiency is 91.75% at 8 A output current for the proposed control, higher than 89.73% for the traditional control. Meanwhile, the carrier harmonics is reduced from -44 dB to -66 dB through the addition of the LC filter.

• Proceedings of the KSAR Conference
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• 2003.06a
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• pp.78-78
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• 2003

Embryonic stem (ES) cells, derived from preimplantation embryo, are able to differentiate into various types of cells consisting the whole body, or pluripotency. In contrast, terminally differentiated cells do not usually alter their nature but frequently die or transform if they are exposed to inappropriate external stimulations. In addition to the plasticity, ES cells are expected to be different from terminally differentiated cells in very many ways, such as patterns of gene expressions, ability and response of the cells in confronting environmental stimulations, metabolism, and growth rate. As a model system to differentiate these two types of cells, human ES cells (MB03) and terminally differentiated cells (HeLa), we examined the ability of these two types of cells in confronting a severe oxidative insult, that is $H_2O$$_2$. Approximately 1$\times$10$^4$ cells were plated in 96 well plate and serum starved for overnight. The conditioned cells were exposed to a various concentration of $H_2O$$_2$ fur 24 hrs and loaded with neutral red (50$\mu\textrm{g}$/ml) for 4 hrs, washed with PBS for 2 min three times, and entrapped dye was dissolved out using acetic ethanol. Cytotoxicity was determined by reading the amount of dye in the medium using microplate reader. equipped with 575 nm filter. Relative amount of the dye entrapped within MB03 or HeLa were not significantly different when cells were exposed up to 0.4 mM $H_2O$$_2$. However, this sharply decreased down to 0.12% in HeLa cells when the cells were exposed to 0.8 mM $H_2O$$_2$, while it was approximately 54% in MB03 suggesting that this concentration of $H_2O$$_2$ is the defensive threshold for HeLa cells. The resistance to oxidative stimulation reversed, however, when cells were co-treated with BSO (L-buthionine- 〔S, R〕-sulfoximine) which chelates intracellular GSH. This result suggests that cellular GSH is the major defensive mechanism of human ES cells. Induction of enzymes involved in GSH metabolism and type of cell death is currently being studied.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.7 no.4
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• pp.187-194
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• 1974

When rearing fish at recirculating filter systems, some pesticides are often used for controling various fish diseases. In this case, the pesticides are usually applied after stopping the filteration, from a view point of affecting the filtering ability of oxidation and decomposition by killing the decomposing bacteria in the filter system. Therefore, a great inconvenience is usually net. The authors carried out a series of experiments, and the influence of 3 kinds of treatments of pesticides, formalin 33 ppm+matachite green 0.15 ppm, dipterex 0.25 ppm, and furanace 0.1 ppm, to the filtering ability expressed as the consumption rate of dissolved oxygen and depletion of ammonia-nitrogen during the passing time through the filter layer was investigated, and it was found out that these pesticides with above mentioned concentrations which is normally used for controling several kinds of diseases and parasites during the time of eel culture, did not affect the filtering ability. Consequently, it can be said that these pesticides with above mentioned concentrations can he used without stopping filteration.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.42 no.2 s.302
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• pp.19-26
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• 2005

After various video coding standards such as H.263, MPEG-4, and H.264 have been introduced, there has bun strong need to support the multiple standards with limited resources efficiently. In terms of deblocking Inter which plays an important role in improving visual quality, K264 deblocking filter implementation has different aspects as compared with traditional $8\times8$ block-based post-filter implementation. Analyzing the differences, this paper proposes a H.264 deblocking filter implementation method that supports $8\times8$ block-based post-filtering for the traditional video coding systems. In the proposed implementation method the block boundaries to he filtered are adaptively chosen for $8\times8$ and $4\times4$ block boundary filtering. Since the filtered result is selectively used for motion compensation or not, both loop-filtering and post-filtering can be achieved. A quantization parameter conversion unit that converts H.263 quantization parameters to H.264 quantization parameters is utilized by examining the $8\times8$ block boundary errors based on human visual system. Since the original nature of the H.264 deblocking filter is well expanded to the $8\times8$ block-based post-filter with minor modifications, the proposed implementation method is suitable to implement the deblocking function of the multiple video standards such as H.263, MPEG-4, and K264, efficiently.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.14 no.4
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• pp.423-434
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• 1989

In this paper, a PRS transmission system using TMRCP as the unit pulse is proposed, which solves the problems occur when the PRS method will be applied to the digital transmultiplexer for each channel. And a design technique which uses this PRS method for the FFT polyphase filter transmultiplexer concept is given. TMRCP-PRS signal require a bandwidth about 2.5KHz(including some guard-band) for a 4-KHz bandlimited voice channel. Therefore, in he 24 channel transmission line, it gives the same advantages as he ordinary PRS system and sloves the inter-channel interference problems. And its good speed-tolerance reduces the time-errors by the environments and the power loss, so it makes the system to be stable. The total system, however, attaces the filters for PCM-PRS, PRS-PCM conversion before and after the transmultiplexer respectively.

• 유체기계공업학회:학술대회논문집
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• 1999.12a
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• pp.81-89
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• 1999

The major source of noise in the process of transporting liquids is related to the cavitation phenomenon. The control valve noise is mostly dominated by bubble dynamics under cavitating conditions. In this investigation, an orifice configuration is set-up to correlate its flow-field and acoustic signatures with those from a control valve device. The performance and noise characteristics form the orifice configuration in anechoic surroundings were measured to reveal the noise sources depending on pressure differences across the orifice configuration. The sound powers from the orifice configuration are effectively normalized using proposed scaling parameters. Flow-excited dynamic systems for which there is no strong coupling between the flow and the system response can be described using a linear source-filter model. On this assumption, the normalized sound powers can be decomposed of noise source function and a response function. To find noise sources, pressure spectra measured over a range of pressure differences are transformed into the product of two non-dimensional frequency function : $P_{ss}(He,f_{ca},x/D) = F(f_{ca})\;G(He,x/D)$. This scheme of finding noise sources is shown to be applicable to the cavitation noise from the control valve effectively Two kinds of cavitating modes based on our experimental data are found and discussed.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.2
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• pp.61-66
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• 2003

The electromagnetic properties and thermal behavior of Mn-Zn ferrite cores used for the blocking filter in he Power Line Communication(PLC) application were investigated as the function of additives. The highest density and permeability of 4.98 g/㎤) and 8,221 respectively were obtained to the specimen with composition of MnO 24 mol%, ZnO 25 mol% and Fe$_2$O$_3$ 51 mol% added MnO$_3$ 400 ppm, SiO$_2$ 100 ppm and CaO 200 ppm since the uniform grains were organized and the microstructures were compacted through reduction of pores. The permeability was increased up to 13,904 as temperature of specimen increased to 11$0^{\circ}C$, however, it was decreased precipitously under 100 over 11$0^{\circ}C$. The exothermic behavior was observed in the frequency range from 1 kHz to 1 MHz that the maximum temperature of specimens became 102$^{\circ}C$ at 1 MHz. In the consequence, the Mn-Zn ferrite core developed by this research will maintain the stable electromagnetic properties since the temperature of ferrite core rose to 93$^{\circ}C$ in the range of 10 kHz to 450 kHz bandwidth qualified for PLC.

• IEIE Transactions on Smart Processing and Computing
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• v.1 no.1
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• pp.8-16
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• 2012

An image obtained from a low light environment results in a low-exposure problem caused by non-ideal camera settings, i.e. aperture size and shutter speed. Of particular note, the multiple color-filter aperture (MCA) system inherently suffers from low-exposure problems and performance degradation in its image classification and registration processes due to its finite size of the apertures. In this context, this paper presents a novel method for the color enhancement of low-exposure images and its application to color shift model-based MCA system for image refocusing. Although various histogram equalization (HE) approaches have been proposed, they tend to distort the color information of the processed image due to the range limits of the histogram. The proposed color enhancement algorithm enhances the global brightness by analyzing the basic cause of the low-exposure phenomenon, and then compensates for the contrast degradation artifacts by using an adaptive histogram specification. We also apply the proposed algorithm to the preprocessing step of the refocusing technique in the MCA system to enhance the color image. The experimental results confirm that the proposed method can enhance the contrast of any low-exposure color image acquired by a conventional camera, and is suitable for commercial low-cost, high-quality imaging devices, such as consumer-grade camcorders, real-time 3D reconstruction systems, digital, and computational cameras.

• Structural Engineering and Mechanics
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• v.54 no.2
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• pp.291-304
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• 2015

Compared with the identification of linear structures, it is more challenging to conduct identification of nonlinear structure systems, especially when the locations of structural nonlinearities are not clear in structural systems. Moreover, it is highly desirable to develop methods of parametric identification using partial measurements of structural responses for practical application. To cope with these issues, an identification method is proposed in this paper for the detection and parametric identification of structural nonlinear restoring forces using only partial measurements of structural responses. First, an equivalent linear structural system is proposed for a nonlinear structure and the locations of structural nonlinearities are detected. Then, the parameters of structural nonlinear restoring forces at the locations of identified structural nonlinearities together with the linear part structural parameters are identified by the extended Kalman filter. The proposed method simplifies the identification of nonlinear structures. Numerical examples of the identification of two nonlinear multi-story shear frames and a planar nonlinear truss with different nonlinear models and locations are used to validate the proposed method.

• Smart Structures and Systems
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• v.15 no.1
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• pp.169-189
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• 2015

Convergence difficulty and available complete measurement information have been considered as two primary challenges for the identification of large-scale engineering structures. In this paper, a time domain substructural identification approach by combining a weighted adaptive iteration (WAI) algorithm and an extended Kalman filter method with a weighted global iteration (EFK-WGI) algorithm was proposed for simultaneous identification of physical parameters of concerned substructures and unknown external excitations applied on it with limited response measurements. In the proposed approach, according to the location of the unknown dynamic loadings and the partially available structural response measurements, part of structural parameters of the concerned substructure and the unknown loadings were first identified with the WAI approach. The remaining physical parameters of the concerned substructure were then determined by EFK-WGI basing on the previously identified loadings and substructural parameters. The efficiency and accuracy of the proposed approach was demonstrated via a 20-story shear building structure and 23 degrees of freedom (DOFs) planar truss model with unknown external excitation and limited observations. Results show that the proposed approach is capable of satisfactorily identifying both the substructural parameters and unknown loading within limited iterations when both the excitation and dynamic response are partially unknown.