• Journal of Plant Biology
• /
• v.29 no.1
• /
• pp.1-10
• /
• 1986

Intra- and inter-specific protoplast fusion of tobacco (Nicotiana tabacum cv. Virginia 115) and pea (Pisum sativum cv. Sparkle) were carried out in highly inhomogeneous alternating electric fields. Under the electric field of alternating current (AC, sine wave), 600 V/cm and 800 kHz for tobacco protoplast, and 600 V/cm and 700 kHz for pea protoplasts, the protoplasts were aggregated in pearl chains. Intra-specific protoplast fusions were most effectively induced within the aggregates of tobacco and pea, respectively, by the additional application of a single high field pulse of direct current (DC, square wave) at 1 kV/cm for 50 $mutextrm{s}$. Inter-specific fusions between protoplasts of the two plants were most effectively induced in the electric field of 600 V/cm and 700 kHz, and square wave pulse at 1 kV/cm for 50 $mutextrm{s}$. The duration of the pulse over the electrical breakdown voltages was simulated from 1 to 100 $mutextrm{s}$ in both tobacco and pea protoplast. The yield of the electrofusion products was significantly high (above 60%), compared with that (20%) of the standard fusion method by polyethylene glycol (PEG) 4,000, and the viability of electrofused protoplasts was above 70%, but that of PEG-fused protoplasts 8~16%, when determined by Evan's blue staining method.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.49 no.3
• /
• pp.131-137
• /
• 2000

2 phase 8 pole HB-type(flat-type) Linear Pulse Motor can be used as the high precision position actuator because of its many advantages (simple control circuit, high stiffness characteristics, etc). Also, using the microstep drive, its noise and vibration can be reduced considerably and positional resolution may be increased further. But, $20^{\circ}$tapered tooth shape to reduce the normal force have an much effect on the static thrust force characteristics. And, because of hybrid-type LPM, interaction between the permanent magnet and the excitation current have an effect on the various characteristics of LPM. Hence, in this paper, the effect of tooth shape on static thrust force characteristics was analyzed using the air gap permeance by finite element method. For analyzing the effect of unbalance between the m.m.f of permanent magnet and the m.m.f of excitation current, unbalanced m.m.f coefficient $\sigma$ were introduced with the permenace matrix and switching matrix.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.12 no.1
• /
• pp.45-50
• /
• 1998

In recent year, inverters and cycloconverters system are widely used for fed induction motor drives. Motor drives by cycloconverter is possible to frequency have been directly changed without AC/DC converter, so that circuits is simpler than inverter. A aims of this paper is the control strategy and hardware design for vector control system by cycloconverter fed induction motor drives. In this paper, Algorithm of vector control is derivlid from the model of controlled current source-fed induction motor. Vector control system is implemented using these algorithm and a pulse width controled cycloconverter using a SCR. Cycloconverter of vector control system is controlled by pulse width of SCR's trigger signal. pulse width is controlled primary command current $li_1l$ and frequency TEX>$\omega_1$..

• Nuclear Engineering and Technology
• /
• v.54 no.3
• /
• pp.781-789
• /
• 2022

KHNP had licensed Dynamic Control rod Reactivity Measurement (DCRM) method using detector current signals of PWRs in 2006. The method has been applied to all PWRs in Korea for about 15 years successfully. However, the original method was inapplicable to PWRs using low-sensitivity integral fission chamber as ex-core detectors because of their pulse pile-up and the nonlinearity of the mean-square voltage at low power region. Therefore, to overcome this disadvantage, a modified method, DCRM-EK, was developed using kinetics behavior after equilibrium condition where the pulse counts maintain the maximum value before pulse pile-up. Overall measurement, analysis procedure, and related computer codes were changed slightly to reflect the site test condition. The new method was applied to a total of 15 control rods of 1000 MWe and 1400 MWe PWRs in Korea with worths in the range of 200 pcm -1200 pcm. The results show the average difference of -0.4% and the maximum difference of 7.1% compared to the design values. Therefore, the new DCRM-EK will be applied to PWRs using low sensitivity integral fission chambers, and also can replace the original DCRM when the evaluation fails by big noises present in current or voltage signals of uncompensated/compensated ion chambers.

• Journal of Electrochemical Science and Technology
• /
• v.14 no.4
• /
• pp.326-332
• /
• 2023

The high cost of Si-based solar cells remains a substantial challenge to their widespread adoption. To address this issue, it is essential to reduce the production cost of solar-grade Si, which is used as raw material. One approach to achieve this is Si electrodeposition in molten salts containing Si sources, such as SiO₂. In this study, we present the pulse electrodeposition of Si in molten CaCl₂ containing SiO₂ nanoparticles. Theoretically, SiO₂ nanoparticles with a diameter of less than 20 nm in molten CaCl₂ at 850℃ have a comparable diffusion coefficient with that of ions in aqueous solutions at room temperature. However, we observed a slower-than-expected diffusion of the SiO₂ nanoparticles, probably because of their tendency to aggregate in the molten CaCl₂. This led to the formation of a non-uniform Si film with low current efficiency during direct current electrodeposition. We overcome this issue using pulse electrodeposition, which enabled the facile supplementation of SiO₂ nanoparticles to the substrate. This approach produced a uniform and thick electrodeposited Si film. Our results demonstrate an efficient method for Si electrodeposition in molten CaCl₂ containing SiO₂ nanoparticles, which can contribute to a reduction in production cost of solar-grade Si.

• Progress in Superconductivity and Cryogenics
• /
• v.20 no.1
• /
• pp.19-22
• /
• 2018

The thermal and electrical properties of the conductor are critical parametersfor the design and optimization of the superconducting magnet. This paper presents simulation code to analyze electrical and thermal stability characteristics of the second generation (2G) high-temperature superconductor (HTS) by varying copper stabilizer thickness. Two types of commercial 2G HTS coated conductor tapes, YBCO and GdBCO were used in this study. These samples were cooled by Liquid Nitrogen ($LN_2$) having boiling at 77.3 K and an equivalent electrical circuit model for them is choosen and analysed in details. Also, an over-current pulse test in which a current exceeding a critical current was performed. From the simulation results, the influences of the copper stabilizer thickness on the stability characteristics of these samples are presented.

• Journal of Electrical Engineering and Technology
• /
• v.12 no.5
• /
• pp.1872-1882
• /
• 2017

Medium voltage drive systems driven by high-power multi-level inverters operating at low switching frequency can reduce the switching losses of the power device and increase the output power. Employing subsection synchronous current harmonic minimum pulse width modulation (CHMPWM) technique can maintain the total harmonic distortion of current at a very low level. It can also reduce the losses of the system, improve the system control performance and increase the efficiency of DC-link voltage accordingly. This paper proposes a subsection synchronous CHMPWM approach of active neutral point clamped five-level (ANPC-5L) inverter under low switching frequency operation. The subsection synchronous scheme is obtained by theoretical calculation based on the allowed maximum switching frequency. The genetic algorithm (GA) is adopted to get the high-precision initial values. So the expected switching angles can be achieved with the help of sequential quadratic programming (SQP) algorithm. The selection principle of multiple sets of the switching angles is also presented. Finally, the validity of the theoretical analysis and the superiority of the CHMPWM are verified through both the simulation results and experimental results.

• Journal of Power Electronics
• /
• v.17 no.1
• /
• pp.41-55
• /
• 2017

This study proposes a novel zero voltage transition (ZVT) pulse width modulation (PWM) DC-DC interleaved boost converter with an active snubber cell. All the semiconductor devices in the converter turn on and off with soft switching to reduce the switching power losses and improve the overall efficiency. Through the interleaved approach, the current stresses of the main devices and the ripple of the output voltage and input current are reduced. The main switches turn on with ZVT and turn off with zero voltage switching (ZVS). The auxiliary switch turns on with zero current switching (ZCS) and turns off with ZVS. In addition, the snubber cell does not create additional current or voltage stress on the main switches and main diodes. The proposed converter can smoothly achieve soft switching characteristics even under light load conditions. The theoretical analysis and operating stages of the proposed converter are made for the D > 50% and D < 50% modes. Finally, a prototype of the proposed converter is implemented, and the experimental results are given in detail for 500 W and 50 kHz. The overall efficiency of the proposed converter reached 95.5% at nominal output power.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2018.06a
• /
• pp.29.1-29.1
• /
• 2018

양극산화 표면처리 방법의 일종인 플라즈마 전해산화(PEO, Plasma electrolytic oxidation)는 금속 소재에 양극 전압을 인가하여 고경도의 산화 피막을 금속 표면에 형성시키는 표면처리 기술이다. PEO 공정은 피막의 국부적 유전체 파괴에 의한 아크의 발생을 동반하며, 형성된 산화 피막이 아크 발생에 의한 높은 열에 의해 결정화 되어 일반적인 양극산화 피막보다 우수한 경도와 내마모성을 가진다. 하지만 PEO 공정은 고전압을 필요로 하여 일반적인 양극산화 처리보다 소모되는 전력량이 많으며, 아크 발생에 의해 형성된 피막의 표면 거칠기가 높기 때문에 활용 분야가 제한되거나 후속 연마 공정을 필요로 하는 단점이 존재한다. 본 연구에서는 전류 파형이 알루미늄 합금의 플라즈마 전해산화 피막의 형성 거동에 미치는 영향을 직류 및 펄스전류를 사용하여 연구하였다. NaOH 및 $Na_2SiO_3$가 혼합된 전해액에서 직류 전류 밀도, 전압, 펄스폭을 달리하여 알루미늄 합금에 전류를 인가할 때 발생되는 아크의 거동, 형성된 산화 피막의 두께, 거칠기, 경도, 표면 및 단면 구조를 비교 분석하였다.

• Korean Journal of Materials Research
• /
• v.18 no.3
• /
• pp.117-122
• /
• 2008

Micro-sized bumps on a multi-layered build-up PCB were fabricated by pulse-reverse copper electroplating. The values of the current density and brightener content for the electroplating were optimized for suitable performance with maximum efficiency. The micro-bumps thus electroplated were characterized using a range of analytical tools that included an optical microscope, a scanning electron microscope, an atomic force microscope and a hydraulic bulge tester. The optical microscope and scanning electron microscope analyses results showed that the uniformity of the electroplating was viable in the current density range of $2-4\;A/dm^2$; however, the uniformity was slightly degraded as the current density increased. To study the effect of the brightener concentration, the concentration was varied from zero to 1.2 ml/L. The optimum concentration for micro-bump electroplating was found to be 0.6 ml/L based on an examination of the electroplating properties, including the roughness, yield strength and grain size.