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Sungkyu Jung,Jungwoo Lee IEEE 2012 IEEE transactions on signal processing Vol.60 No.11
<P>This paper analyzes the linear degrees of freedom (LDoF) for <I>K</I>-user <I>M</I> ×<I>N</I> MIMO interference channels with constant channel coefficients. In this correspondence, we interpret the interference alignment problem as a multivariate polynomial system in terms of properness. The properness provides a LDoF upperbound for interference alignment. With this approach, we propose a method to obtain the upperbound for total LDoF achievable by linear interference alignment. The LDoF upperbound for properness condition results have two different cases which depend on the number of users, the number of transmit antennas, and the number of receive antennas. A key contribution of this paper is that it provides a closed-form LDoF upperbound for <I>M</I> ×<I>N</I> MIMO interference channels where the LDoF of each user may be different.</P>
낮은 복잡도를 갖는 Sample Matrix Inversion (SMI) 기법
정성규(Sungkyu Jung),이정우(Jungwoo Lee) 한국방송·미디어공학회 2010 한국방송공학회 학술발표대회 논문집 Vol.2010 No.7
적응 어레이(adaptive array) 기법은 이동통신 시스템에서 발생하는 동일채널 간섭신호를 제거하는 데에 효과적인 기술이다. 적응 어레이 기법 중 가장 널리 이용되는 SMI 기법은 높은 성능을 보이는 데 반해 상대적으로 많은 계산량을 필요로 한다. 본 논문에서는 역행렬의 크기를 줄임으로써 SMI 기법의 복잡도를 줄이는 방법을 제안한다. 제안하는 기법은 안테나 어레이 중 받은 신호의 파워가 가장 작은 안테나를 사용하지 않음으로써 안테나 어레이의 개수를 하나 줄이는 방식을 사용한다. 시뮬레이션 결과는 제안하는 방법의 복잡도가 낮음에도 불구하고 우수한 성능을 갖는다는 것을 입증한다.
Continuum directions for supervised dimension reduction
Elsevier 2018 Computational statistics & data analysis Vol.125 No.-
<P><B>Abstract</B></P> <P>Dimension reduction of multivariate data supervised by auxiliary information is considered. A series of basis for dimension reduction is obtained as minimizers of a novel criterion. The proposed method is akin to continuum regression, and the resulting basis is called continuum directions. With a presence of binary supervision data, these directions continuously bridge the principal component, mean difference and linear discriminant directions, thus ranging from unsupervised to fully supervised dimension reduction. High-dimensional asymptotic studies of continuum directions for binary supervision reveal several interesting facts. The conditions under which the sample continuum directions are inconsistent, but their classification performance is good, are specified. While the proposed method can be directly used for binary and multi-category classification, its generalizations to incorporate any form of auxiliary data are also presented. The proposed method enjoys fast computation, and the performance is better or on par with more computer-intensive alternatives.</P>
Near - field photocurrent measurements on GaAs / AlGaAs multiple quantum wells
Jung Gyu Shin,Joo In Lee,Jae-Yong Leem,Sungkyu Yu 한국진공학회(ASCT) 2000 Journal of Korean Vacuum Science & Technology Vol.4 No.2
Near-field photocurrent experiments were performed for GaAs/AlGaAs MQWs at room temperature. Heavy hole and light hole related peaks are clearly resolved even under extremely low power of near-field excitation. By scanning laterally 2 ㎛×2 ㎛ area on the surface, minority carrier diffusion process in the well region was qualitatively studied.
Power module stray inductance extraction: Theoretical and experimental analysis
Jung, Dong Yun,Jang, Hyun Gyu,Cho, Doohyung,Kwon, Sungkyu,Won, Jong Il,Lee, Seong Hyun,Park, Kun Sik,Lim, Jong-Won,Bae, Joung Hwan,Choi, Yun Hwa Electronics and Telecommunications Research Instit 2021 ETRI Journal Vol.43 No.5
We propose a stray inductance extraction method on power modules of the few-kilovolts/several-hundred-amperes class using only low voltages and low currents. The method incorporates a double-pulse generator, a level shifter, a switching device, and a load inductor. The conventional approach generally requires a high voltage of more than half the power module's rated voltage and a high current of around half the rated current. In contrast, the proposed method requires a low voltage and low current environment regardless of the power module's rated voltage because the module is measured in a turn-off state. Both theoretical and experimental results are provided. A physical circuit board was fabricated, and the method was applied to three commercial power modules with EconoDUAL3 cases. The obtained stray inductance values differed from the manufacturer-provided values by less than 1.65 nH, thus demonstrating the method's accuracy. The greatest advantage of the proposed approach is that high voltages or high currents are not required.
PI(Power Integrity)해석을 통한 HPCU (Hybrid Power Control Unit) 전자파 성능 향상
김성규(Sungkyu Kim),정태환(Taehwan Chung),정진환(Jinhwan Jung),이기상(Kisang Lee) 한국자동차공학회 2010 한국자동차공학회 학술대회 및 전시회 Vol.2010 No.11
Power Integrity(PI) means a quality of the power and ground planes in an electric circuit board. This is closely bound up with the EMC performance of the circuit board. The electric potential actually fluctuates because of the influx of return-current circulating in the power and ground planes, which causes abnormal signals or EMC problems. This paper suggests a practical PI simulation method for analyzing EMC performance in design stage. With using this method, a proper countermeasure for any EMC problem can be taken before manufacturing an electric circuit board
진동 파워 흐름 측정을 이용한 승용차 부우밍 소음원 규명에 관한 연구
고성규(Sungkyu Koh),이상권(Sangkwon Lee),최병욱(Byunguk Choi),도종구(Jonggu Do),정승균(Seongkyun Jung) 한국자동차공학회 2003 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Reduction of structure-borne noise of the compartment in a car is an important task in automotive engineering. Many methods which analyze noise transfer path have been generally used for structure-borne noise. These methods<br/> are useful in solving particular problem but do not quantify the effectiveness of vibration isolation of each isolator of<br/> a vehicle. To quantify the effectiveness of vibration isolation, the vibrational power flow measurement has been used for a simple isolation system or a laboratory based isolation system. This paper identifies transfer path of booming noise of a car with in-line 3 cylinder diesel engine using the vibrational power flow measurement and vibro-acoustic transfer function. It is found that the main source of noise is the rear roll mount.