• Journal of the Korean Society of Clothing and Textiles
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• v.21 no.2
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• pp.471-481
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• 1997

Denims were treated with neutral cellulase, acid cellulase, stone, and stone-neutral cellulase respectively at different cellulase concentrations varying treatment times in rotary washer. The effect of washing on denim was estimated by the changes in weight, color, back staining, tear strength, flex stiffness, and surface characteristics. Also the comparison of neutral cellulase, acid cellulase, stone, and stone-neutral cellulase washings was studied. Washing removes surface fibers and provides weight loss, color difference, back staining, and a decrease in tear strength and in flex stiffness. Stone-neutral cellulase washing and acid cellulase washing have a larger washing effect than neutral cellulase washing and stone washing.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.5
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• pp.67-72
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• 2011

In this study we investigate the background of UPS output transformer(${\Delta}-Y$) operation on neutral ungrounded system, and perform field experiment of neutral floating-phenomenon for the inter-locked securing of electric facilities and improvement of neutral floating-phenomenon. Experiment results show that a floating-phenomenon occurs when four-pole input-breaker trip and the neutral to earth voltage occurring concurrently is identified as phantom voltage. And the measures for the transient overvoltage that can occur in floating-state also are investigated. As a result, the risk elements of neutral ungrounded method as well as neutral floating-phenomenon are removed by installation of separate solidly-grounded transformer and switching four-pole input-breaker to three-pole input breaker.

• Journal of Electrical Engineering and Technology
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• v.10 no.1
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• pp.75-82
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• 2015

This paper presents a new technique for enhancing power quality by reducing harmonics in the neutral conductor. Three-Phase Four-Wire (3P4W) system is commonly used where single and three phase loads are connected to Point of Common Coupling (PCC). Due to unbalance loads, the 3P4W distribution system becomes unbalance and current flows in the neutral conductor. If loads are non-linear, then the harmonic content of current will flow in neutral conductor. The neutral current that may flow towards transformer neutral point is compensated by using a series active filter. In order to reduce the harmonic content, the series active filter is connected in series with the neutral conductor by which neutral and phase current harmonics are reduced significantly. In this paper, solar PV based inverter circuit is proposed for compensating neutral current harmonics. The simulation is carried out in MATLAB/SIMULINK and also an experimental setup is developed to verify the effectiveness of the proposed method.

• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.5
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• pp.385-393
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• 2020

This study introduces an analysis and control method for the variation of neutral point current in a grid-tied three-level neutral point clamped (NPC) converter under various grid imbalance operating conditions. Various fault cases with unbalanced amplitude and phase are systematically categorized and described using a unified metric called the imbalance factor. The fundamental component of neutral point current is generated under grid imbalance cases. The pattern and behavior of this fundamental component of neutral point current highly depend on the imbalance factor regardless of the particular type of grid fault cases. The control scheme for regulating the negative sequential component of AC input current effectively reduces the size of the fundamental component of neutral point current under a wide range of grid imbalance cases. The control scheme will enable a grid-tied three-level NPC converter to operate reliably and stably under various types of grid faults.

• Journal of Life Science
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• v.8 no.3
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• pp.305-311
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• 1998

These studies were undertaken to investigate changes of neutral lipid content and fatty acid composition were determined. Also accumulation process of monoglyceride, diglyceride and triglyceride content, and fatty acid composition were investigated during the development. The results were summarized as follows ; Changes of lipid during development sesame seeds, glycolipid contents which showed the highest in the early ripening stage and after that rapidly decreased, and phospholipid contents showed a similar pattern as glycolipid occurred. In contrast, the content of neutral lipid was rapidly increased by 29.21% 10 days after flowering(DAF), and showed the highest value by 91.84% at 40th day after flower. The neutral lipid, triglyceride content was rapidly increased as the seeds developed, and consisted of over 60% of the neutral lipid since 30 DAF. In the changes of neutral lipid, phospholipid and glycolipid, stearic acid and palmitic acid decreased during the seed ripening. However, oleic acid and linoleic acid increased during the same periods. Linolenic acid, which showed relatively higher value in the early ripening stage, but rapidly decreased as much as 1% at the later ripening stage.

• Journal of the Korean Society of Food Science and Nutrition
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• v.27 no.6
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• pp.1041-1046
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• 1998

This study was carried out to investigate the changes and composition of the non-cellulosic neutral sugars in cell wall of soybean sprouts during growth. The composition of non-cellulosic neutral sugars in cell of soybean sprouts was rhamnose, fucose, xylose, arabinose, mannose, galactose and glucose. The galactose content of cell wall was higher than other non-cellulosic neutral sugars, and was remarkably decreased during growth. The major non-cellulosic sugars of pectic substances were rhamnose, arabinose, and galactose. The arabinose content of pectic substance was increased in cotyledon and hypocotyl during growth. The contents of non-cellulosic neutral sugars were decreased in hypocotyl during growth. The galactose content of pectic substance was higher in cotyledon than those in hypocotyl, and was increased in cotyledon. The content of rhamnose was higher in ionically associated pectic substance than that in covalently bounded pectic substance. The major non-cellulosic neutral sugars of hemicellulose were glucose, rhamnose, arabinose and galactose. The galactose of hemicellulose was decreased remarkably during growth.

• Proceedings of the KIPE Conference
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• 2017.11a
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• pp.95-96
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• 2017

A three-level inverter is widely used thanks to its excellent performances, but the voltage may fluctuate at the neutral point of the split DC-Link. Neutral point voltage fluctuations cause inverter performance degradation and switching element damage, so the neutral point voltage control is essential. However, the neutral point control can be also limited by modulation index and power factor. This paper analyzes the limitation of the neutral point voltage control due to the limitation of zero-sequence voltage, and suggests a method to determine the region where the PWM has to be changed for a better neutral point control.

• Proceedings of the KIPE Conference
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• 2015.07a
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• pp.177-178
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• 2015

This paper presents a neutral point deviation compensating control algorithm applied to a 3-level NPC converter. The neutral point deviation is analyzed with a focus on the current flowing out of or into the neutral point of the dc link. Based on the zero sequence components of the reference voltages, this paper analyzes the neutral point deviation and balancing control for 3-level NPC converter. An analytical method is proposed to calculate the injected zero sequence voltage for NP balancing based on average neutral current. This paper also proposes a control scheme compensating for the neutral point deviation under generalized unbalanced grid operating conditions. The positive and negative sequence components of the pole voltages and ac input currents are employed to accurately explain the behavior of 3-level NPC converter. Simulation and experimental results for a test set up of 30kW are shown to verify the validity of the proposed algorithm.

• Journal of Power Electronics
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• v.18 no.6
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• pp.1866-1878
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• 2018

This paper presents a neutral point deviation and ripple compensation control method for application to 3-level NPC converters. The neutral point deviation and its harmonic components are analyzed with a focus on the average current flowing through the neutral point of the dc-link. This paper also proposes a control scheme to compensate for the neutral point deviation and dominant harmonic components under generalized unbalanced grid operating conditions. The positive and negative sequence components of the pole voltages and ac input currents are employed to accurately explain the behavior of 3-level NPC converters. Simulation and experimental results are presented to verify the validity of the proposed method.

• East Asian mathematical journal
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• v.21 no.1
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• pp.49-60
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• 2005

In this paper we introduced Semi-neutral BCK-algebra and investigate some of its properties. The notions of ideals and subalgebras coincide in Semi-neutral BCK-algebras. We also show that if the number of nonzero elements in a Semi-neutral BCK-algebra is n, then the number of ideals/subalgebras in it is $2^n$. Further, we solved an open problem posed by W.A. Dudek in [2].