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High precision Automatic Voltage Regulator by using series transformer
Zhang Lei(장뢰),Hwa-Chun Lee(이화춘),Tae-Uk Jung(정태욱),Hae-Kon Nam(남해곤),Soon-Ryul Nam(남순열),Sung-Jun Park(박성준) 전력전자학회 2008 전력전자학술대회 논문집 Vol.- No.-
Now there are two types Non-contact compensation AC automatic voltage regulator (A.V.R). One is transformer compensation regulator, whose principle is the combination of multiple compensation transformers, do the compensation by turning on and off the connections of the transformer through the multi-full bridge circuit. This method removed the mechanical drive and contacts, which increases the life and the dynamic performance of the A.V.R. However, the compensation is multilevel, and it needs many compensation transformers and switches, the circuit is complex, the compensation precision is low. Another type is PWM switch AC regulator, whose principle is getting the AC voltage from the input, then induce the AC compensation voltage through commutating and high frequency PWM transforming, and phase tracking. Here the compensation is step-less, the compensation precision is high, and the response is fast. But the circuit is complex, and it needs an inverse compensation transformer, which is difficult to realize high-power applications. In this paper, it shows an Automatic Voltage Regulator which use high frequency PWM inverter do compensation. This A.V.R has the function as the custom-power, which make the performance of the power supply in a high level.
장성욱(Zhang, Sung-Uk) 대한전기학회 2022 전기의 세계 Vol.71 No.12
전 세계에서 환경 보호를 위해서 탄소 배출을 저감할 수 있는 정책이 진행 중에 있다. 이중 하나의 정책은 전기자동차 보급 장려이다. 전기 자동차 수요의 증가는 자동차용 전력반도체의 수요 증가로 나타나게 되었다. 전력반도체를 차량용 부품으로 만들기 위해서는 신뢰성 규격을 관장하는 AEC(Automotive Electronic Council)에 의해 제정된 신뢰성 평가 절차에 따라 평가 및 인증이 필요하다. 본 고에서는 AEC에서 제정한 여러 가지 표준 중 하나인 AEC-Q101에 대해서 간략히 소개하고 이를 표로 정리하였다. 이 신뢰성 실험과 관련한 전력반도체의 불량들을 간략히 소개하고 고신뢰성 자동차용 전력반도체 만들기 위한 연구에 대해서 고찰하도록 한다. In order to protect the environment around the world, policies to reduce carbon emissions are in progress. One of these policies is the dissemination of electric vehicles. The increase in the demand for electric vehicles is due to the increase in the demand for electric power semiconductors for automobiles. In order to make power semiconductors into automotive parts, evaluation and certification are required according to the reliability evaluation procedure established by the Automotive Electronic Council (AEC), which is in charge of reliability standards. This paper briefly introduces AEC-Q101, one of the various standards established by AEC, and summarizes them in tables. The paper introduces the defects of power semiconductors related to this reliability test and considers research for making high-reliability power semiconductors for automobiles.
Fundamental effects in nanoscale thermocapillary flow
Hun Jin, Sung,Song, Jizhou,Uk Chung, Ha,Zhang, Chenxi,Dunham, Simon N.,Xie, Xu,Du, Frank,Kim, Tae-il,Lee, Jong-Ho,Huang, Yonggang,Rogers, John A. American Institute of Physics 2014 Journal of Applied Physics Vol.115 No.5
When implemented on the nanoscale, material flows driven by gradients in temperature, sometimes known as thermocapillary flows, can be exploited for various purposes, including nanopatterning, device fabrication, and purification of arrays of single walled carbon nanotubes (SWNTs). Systematic experimental and theoretical studies on thermocapillary flow in thin polymer films driven by heating in individual metallic SWNT over a range of conditions and molecular weights reveal the underlying physics of this process. The findings suggest that the zero-shear viscosity is a critical parameter that dominates the dependence on substrate temperature and heating power. The experimentally validated analytical models in this study allow assessment of sensitivity to other parameters, such as the temperature coefficient of surface tension, the thermal interface conductance, and the characteristic length scale of the heated zone. (c) 2014 AIP Publishing LLC.
Park, Young-Uk,Bai, Jianming,Wang, Liping,Yoon, Gabin,Zhang, Wei,Kim, Hyungsub,Lee, Seongsu,Kim, Sung-Wook,Looney, J. Patrick,Kang, Kisuk,Wang, Feng American Chemical Society 2017 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.139 No.36
<P>Ion exchange is a ubiquitous phenomenon central to wide industrial applications, ranging from traditional (bio)chemical separation to the emerging chimie douce synthesis of materials with metastable structure for batteries and other energy applications. The exchange process is complex, involving substitution and transport of different dons under non-equilibrium conditions, and thus difficult to probe, leaving a gap in mechanistic understanding of kinetic exchange pathways toward final products. Herein, we report in situ tracking kinetic pathways of Li+/Na+ substitution during solvothermal ion-exchange synthesis of LixNa1.5-xVOPO4F0.5 (0 <= x <= 1.5), a promising multi-Li polyanionic cathode for batteries. The real-time observation, corroborated by first-principles calculations, reveals a selective replacement of Na+ by Li+, leading to peculiar Na+/Li+/vacancy orderings in the intermediates. Contradicting the traditional belief of facile topotactic substitution via solid solution reaction, an abrupt two-phase transformation occurs and predominantly governs the kinetics of ion exchange and transport in the ID polyanionic framework, consequently leading to significant difference of Li stoichiometry and electrochemical properties in the exchanged products. The findings may help to pave the way for rational design of ion exchange synthesis for making new materials.</P>
국내 스마트하우스 연구사례를 활용한 층간소음 문제해결 방안
김민지(Minji Kim),장성욱(Sung-Uk Zhang) 대한기계학회 2020 대한기계학회 춘추학술대회 Vol.2020 No.12
We would like to come up with a solution to the problem by utilizing domestic smart house research cases of noise between floors, which has become an issue in society. Among the various research cases, we want to create a plan by attaching sensors to slabs and ceilings to alert mobile phones when noise occurs.
Big Data Analysis on Oyster Growth and FLUPSY Environment
Hyun-Joo Yoo(유현주),Sung-Uk Zhang(장성욱),Sun-Jin Jung(정선진) 한국기계가공학회 2020 한국기계가공학회지 Vol.19 No.7
In the era of the fourth industrial revolution, the application of big data analysis technology is crucial in various industries. In this regard, considerable research is necessary to improve aquafarming productivity, particularly in fish culture, which is one of the primary industries in the world. In this study, a sample experiment using a flop was conducted to improve oyster productivity in fish farms, and a flush was installed in an environment similar to aquaculture farms. Thereafter, the temperature data of the water environment where the formation of burrows considerably improved were collected; the growth rate of burrow seeds was also measured. The gathered experimental data were examined by time series data analysis. Finally, a system that visualizes the analysis results based on big data is proposed. In accord with the results of this study, it is expected that more advanced research on the productivity improvement of oyster aquafarming will be performed.
High field MREIT: setup and tissue phantom imaging at 11 T
Sadleir, Rosalind,Grant, Samuel,Zhang, Sung Uk,Oh, Suk Hoon,Lee, Byung Il,Woo, Eung Je IOP Pub 2006 Physiological measurement Vol.27 No.5
<P>Magnetic resonance electrical impedance tomography (MREIT) has the potential to provide conductivity and current density images with high spatial resolution and accuracy. Recent experimental studies at a field strength of 3 T showed that the spatial resolution of conductivity and current density images may be similar to that of conventional MR images as long as enough current is injected, at least 20 mA when the object being imaged has a size similar to the human head. To apply the MREIT technique to image small conductivity changes using less injection current, we performed MREIT studies at 11 T field strength, where noise levels in measured magnetic flux density data are significantly lower. In this paper we present the experimental results of imaging biological tissues with different conductivity values using MREIT at 11 T. We describe technical difficulties encountered in using high-field MREIT systems and possible solutions. High-field MREIT is suggested as a research tool for obtaining accurate conductivity data from tissue samples and animal subjects.</P>