• Journal of Power Electronics
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• 제16권3호
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• pp.960-969
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• 2016

High-power three-level voltage-source converters are widely utilized in high-performance AC drive systems. In several ultra-power instances, the harmonics on the grid side should be reduced through multiple rectifications. A combined harmonic elimination method that includes a dual primary-side series-connected winding transformer and selective harmonic elimination pulse-width modulation is proposed to eliminate low-order current harmonics on the primary and secondary sides of transformers. Through an analysis of the harmonic influence caused by dead time and DC magnetic bias, a synthetic compensation control strategy is presented to minimize the grid-side harmonics in the dual primary side series-connected winding transformer application. Both simulation and experimental results demonstrate that the proposed control strategy can significantly reduce the converter input current harmonics and eliminates the DC magnetic bias in the transformer.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 C
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• pp.1096-1098
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• 1999

The performance of as plasma display panels (PDP) is influenced strongly by the surface glow discharge characteristics on the MgO thin films. This paper deals with the optimum preparation conditions of MgO Protecting layer by RF unbalanced magnetron sputtering(UBMS) in surface discharge type AC PDP. The samples prepared with the do bias voltage of -10V showed lower discharge voltage, lower erosion rate as a consequence of ion bombardment, higher optic transparency and higher crack resistance in annealing process than those samples prepared by conventional magnetron sputtering or E-beam eraporation.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.69-71
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• 2014

MLCCs are used broadly in electronic industry like smart phone and TV. Although they are fabricated in small size and have high capacitance, there are acoustic noise problems to reduce comfort of user. Acoustic noise results from linear piezoelectricity and nonlinear electrostriction of $BaTiO_3$ in MLCC and there are some researches on MLCC vibration under AC electric field. When only AC electric field without DC bias is applied to MLCC, fundamental frequency response is affected by piezoelectricity and second-harmonic frequency response shows electrostrictive vibration. In this study we get vibration shape of MLCC under AC electric field for each frequency and analysis on the mechanism of MLCC vibration affected by piezoelectricity and electrostriction.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.I
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• pp.639-642
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• 2005

A new dual-slope ramp (DSR) reset waveform is proposed to improve the dark room contrast ratio in AC-PDPs. The proposed reset waveform has two different voltage slopes during a ramp-up period. The first voltage slope is lower than the conventional ramp voltage slope, causing a reduction in the background luminance, whereas the second voltage slope is higher than the conventional ramp voltage slope, causing an increase in the background luminance. Thus, a bias voltage is also applied during the second voltage-slope period to adjust the background luminance and address discharge characteristics. As a result, the proposed dual-slope reset waveform can lower the background luminance, thereby improving the high dark room contrast ratio of an AC-PDP without reducing the address voltage margin

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 춘계학술대회 논문집
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• pp.379-382
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• 1999

In this paper, we investigated the characteristics of MgO thin film prepared by unbalanced magnetron sputtering(UBMS) in surface discharge type AC PDP The minimum discharge voltage is obtained for the sample of substrate bias voltage-10V. Moreover the anti-sputtering characteristics of MgO thin film by UBMS is improved about 40% than one of balanced magnetron sputtering(BMS)

• 반도체디스플레이기술학회지
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• 제8권1호
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• pp.27-31
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• 2009

A characteristic of new waveform, called a negative waveform, was studied during reset and address periods. IR distribution, black luminance and time delay were measured to compare the negative waveform with the conventional positive waveform. Based on the analysis of IR measurement, the negative waveform could accumulate more wall charges than the positive waveform. Also the black luminance of negative waveform was lower than that of positive waveform under the same bias and ramp-slope conditions. During address period, the discharge time lag was measured. The negative waveform was showed 0.25 us faster formative time lag and 0.1 us faster average time lag than those of positive waveform.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제51권4호
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• pp.147-151
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• 2002

The resistances of metal2 contact to metall and poly Si are checked by various RF etch conditions in terms of pre-cleaning. The changes of resistance are evaluated by statistical analysis method(SAS) for the AC bias power, coil power and RF target. The contact area on poly Si is shown by TEM image and the distributions of contact resistance according to ar etch target and RTP are investigated. The RTP groups have larger variations than normal RF etch targets. When the RF etch target becomes lower and coil power becomes higher, the resistances of metal2 contact to metals and poly Si have lower contact resistance. But the condition of AC bias power did not satisfied low meta12 contacts resistance for metall and poly Si simultaneously. The R-square of ststistical analysis was 0.98 for resistances of meta12 contact to poly Si and 0.87 for resistances of meta12 contact to metall.

• Journal of Power Electronics
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• 제14권3호
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• pp.564-571
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• 2014

Rotor initial position is an important factor affecting the control performance of electrically excited synchronous motors. This study presents a novel method for estimating rotor initial position based on sliding discrete Fourier transform (sDFT). By injecting an ac excitation into the rotor winding, an induced voltage is generated in stator windings. Through this voltage, the stator flux can be obtained using a pure integral voltage model. Considering the influence from a dc bias and an integral initial value, we adopt the sDFT to extract the fundamental flux component. A quadrant identification model is designed to realize the accurate estimation of the rotor initial position. The sDFT and high-pass filter, DFT, are compared in detail, and the contrast between dc excitation and ac injection is determined. Simulation and experimental results verify that this type of novel method can eliminate the influence of dc bias and other adverse factors, as well as provide a basis for the control of motor drives.

• 대한한방부인과학회지
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• 제36권3호
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• pp.154-172
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• 2023

Objectives: This study aimed to assess the clinical evidence supporting the use of acupuncture (AC) for premenstrual syndrome (PMS). Methods: We searched randomized controlled trials (RCTs) that used AC for PMS in 9 databases (PubMed, EMBASE, Cochrane Library, CINAHL, CNKI, CiNii, SCIENCE ON, KoreaMed, OASIS) from their inception to July 2022. Results: We identified 1,168 studies, of which 15 RCTs met the inclusion criteria. The risk of bias in the included studies was relatively unclear or high. Meta-analysis of 3 RCTs showed that the AC group had a significantly higher effective rate than the Medroxyprogesterone group (RR 1.48, 95% CI (1.23, 1.78), p<0.0001). Meta-analysis of 2 RCTs showed that there was no statistically significant difference between the AC group and the Sham AC group in the effective rate (RR 4.72, 95% CI (0.88, 25.36), p=0.07). In a review of individual studies, the AC group was more effective than the control group in terms of the effective rate, symptom scale, quality of life, adverse events, and recurrence rate. Conclusions: The AC group was more effective than general treatments groups such as sham AC, western medicine, and dietary supplements, and there were no serious adverse events. However, the evidence on the effectiveness and safety of acupuncture for PMS was inconclusive due to the small number of included studies and low quality. Therefore, systematic reviews based on more rigorously designed randomized clinical trials are needed in the future to properly evaluate the effect of AC on PMS.

• Progress in Superconductivity
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• 제9권1호
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• pp.18-22
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• 2007

For interlayer tunneling spectroscopy using a small stack of $Bi_2Sr_2CaCu_2O_{8+x}$ (Bi-2212) intrinsic junctions in a high-bias range, large self-heating takes place due to the poor thermal conductivity of Bi-2212. In this study, we numerically estimate the self-heating around a Bi-2212 sample stack for I-V or dI/dV-V measurements. Our results show that the temperature discrepancy between the Bi-2212 sample stack and top Au electrodes due to bias-induced self-heating is small enough along the c-axis direction of Bi-2212. On the other hand, the lateral temperature discrepancy between the sample stack and the Bi-2212 on-chip thermometer stack can be as large as ${\sim}20\;K$ for the highest bias required to observe the pseudogap hump structure. We thus suggest a new in-situ ac thermometry, employing the Au current-bias electrode itself deposited on top of the sample stack as the resistive thermometer layer, which is supposed to allow safe temperature measurements for the interlayer tunneling spectroscopy.