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인버터 구동 유도전동기의 가창소음 저감을 위한 새로운 펄스폭 변조기법
최규하,신우석,함연창 建國大學校 附設 産業技術硏究所 1992 논문집 Vol.17 No.-
The PWM inverter system are widely used to control the induction motor, and their switching frequency rises to the higher for better performances. But the upper should be limited for safe operation as well as switching loss reduction in the power transistor inverters. This makes the level of the audible noise much increased. In order to overcome such noise problem, a new PWM control technique is proposed in the power transistor inverters, of which carrier frequency is to change a according to the slope of the sine wave reference signal. As a result the frequency spectra are improved and hence the audible noise couble be reduced greatly.
주우석,박경희,유승열,최병석 明知大學校 産業技術硏究所 1995 産業技術硏究所論文集 Vol.14 No.-
We propose a new architecture of multicast ATM switch which has input and output buffers and uses Multicast Ring Reservation Algorithm to resolve output port contention. This new algorithm eliminates internal cell loss due to contention, and reduces the hardware complexity. We can dynamically control the number of cells routed to a specific output port during one cell time with this contention resolution algorithm. The computer simulation is performed under bursty traffic condition to show the performance of this proposed multicast ATM switch.
신우석,최규하,정만규 건국대학교 산업기술연구원 1994 건국기술연구논문지 Vol.19 No.-
This paper describes voltage-controlled delta-modulation scheme for active power filters, which is to control the harmonic-compensating current indirectly by adjusting the capacitor voltage to be sinusoidal. The overall control system has two feedback loops : one is the outer proportional feedback for loop regulating the de current of the active filter and the other is the inner feedback loop for maintaining the ac current waveform to be sinusoidal, and to have zero power factor angle(i. e. unity power factor). The characteristics of the proposed scheme are investigated by digital simulation using ACSL.
GaAs/AIGaAs 양자우물구조 검출기의 구속-연속상태 전이연구
황형준,최정우,최우석 慶熙大學校 材料科學技術硏究所 1997 材料科學技術硏究論集 Vol.10 No.-
We study the methods to calculate the bound-to-continuum transition amplitudes in a biased GaAs/AlGaAs quantum well detector structure. First we apply the complex energy method to evaluate the energy levels of meta-stable states. We also present how the coefficients of the travelling waves change with the complex value of energy. Transition amplitudes to each continuous scattering states are also calculated. The transition peaks evaluated agree well with the energy levels of the meta-stable states found using the complex energy method.
한석우(Seok-Woo Han),전윤석(Ywun-Seok Jeon),최규하(Gyu-Ha Choe),목형수(Hyung-Soo Mok) 전력전자학회 1999 전력전자학술대회 논문집 Vol.1999 No.7
This paper presents design of controllers for battery energy storage system The proposed battery energy storage system can be controlled to operate in the power conditioning mode or the inverter mode,<br/> The operation of this mode further divided into three cases: (a) m the peak load period, the load power supplied from the utility is minimized as far as possible; (b) in the off-peak load period, the utility supplies power to the load and characteristics the battery bank with automatic charging control, (c) m the medium load period, to save battery energy the real power flow out of the battery energy storage system is minimized, Besides, m all cases, the proposed battery energy storage system also automabcally compensates the harmonics, subharmonics and reactive power factor in the utility side are much improved,<br/> Simulation results are presented by the effectiveness of the proposed controllers for battery energy storage system,
UPS용 인버터의 LC필터 출력 전압제어를 위한 디지털 제어기 설계
조준석(Jun-Seok Cho),이승요(Seung-Yo Lee),최규하(Gyu-Ha Choe),목형수(Hyung-Soo Mok),신우석(Woo-Seok Shin),한석우(Seok-Woo Han) 전력전자학회 1998 전력전자학술대회 논문집 Vol.- No.-
This paper presents an observer filter algorithm to estimate the load currents in the output voltage control of 3-phase uninterruptible power supply with deadbeat controller As the result of the proposed algorithm, the sensors to measure the<br/> load currents is not required The comparison of output voltage controls according to the methods of measuring the load currents is also presented in this paper The results of comparison are shown by the simulation.<br/> <br/>
Minimum Current Control for PWM Inverter-Mounted Drive System
Woo-Seok Shin,Gyu-Ha Choe 전력전자학회 1998 ICPE(ISPE)논문집 Vol.- No.-
This paper describes minimum current control method for size reduction and performances improvement at unified inverter-induction motor system This control method is based on V'f without speed sensor Through the use of mimimum stator current points at required torque during V'f operation it is possible to minimize the size of heat-sink related with the losses of power circuit and to improve overall efficiency compared to conventional V'f control Using this proposed scheme, it is so much more useful to apply to some fields such as electric vehicles, air conditioning system and textile mills where the limited space is given and required low cost.<br/>
A New Scoring Method of the Mini-Mental Status Examination to Screen for Dementia
Choe, Jin Yeong,Han, Ji Won,Kim, Tae Hui,Kim, Jeong Lan,Moon, Seok Woo,Park, Joon Hyuk,Kim, Shin Gyeom,Kim, Bong-Jo,Kwak, Kyung-Phil,Ryu, Seung-Ho,Yoon, Jong Chul,Lee, Dong Young,Lee, Dong Woo,Lee, Se Karger 2014 DEMENTIA AND GERIATRIC COGNITIVE DISORDERS Vol.37 No.5
<P>Abstract</P><P><B><I>Background:</I></B> Although the Mini-Mental Status Examination (MMSE) is the most widely used screening instrument for dementia, it has several limitations. <B><I>Methods:</I></B> We developed and validated a new scoring method of the MMSE, namely the short form of the MMSE (MMSE-S). <B><I>Results:</I></B> The MMSE-S was more robust to demographic influences than the MMSE. The influence of education, in particular, was smaller in the MMSE-S compared to the MMSE (p < 0.01). The diagnostic accuracy of the MMSE-S for very mild to mild dementia was also better than that of the original MMSE (p < 0.0001). Its specificity, in particular, was higher than that of the original MMSE. In Korea, we could improve the post-test probability for dementia from 46.88 to 64.76% by employing the MMSE-S instead of the MMSE. We also provided optimal cut-off scores for dementia stratified by age, education, and gender, which may further improve the diagnostic accuracy of the MMSE-S for dementia. <B><I>Conclusion:</I></B> Due to its good accuracy and brevity, the MMSE-S may contribute to enhancing the cost-effectiveness of and accessibility to dementia screening as well as early diagnosis and treatment of dementia, particularly in low- and middle-income countries.</P><P>© 2014 S. Karger AG, Basel</P>