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Seog Geun Kang,Zhenxing Chen,Ju Yeong Kim,Jin Sub Bae,Jong-Soo Lim IEEE 2011 IEEE transactions on signal processing Vol.59 No.12
<P>A simple and straightforward method of constructing higher-level three-dimensional (3-D) signal constellations for a reliable digital communication system is proposed in this paper. The new method expands basic 8-ary constellation into 3-D signal space systematically so that it produces lattice configurations. We also derive accurate closed-form symbol error probability (SEP) of cross-lattice constellations in additive white Gaussian noise (AWGN). It is verified that the theoretical SEPs are almost the same as simulation results. Minimum Euclidean distance (MED) of the higher-level 3-D constellations is increased at least 49% in comparison with quadrature amplitude modulation (QAM). When the number of symbols is 256, the 3-D constellation has around 105% longer MED than the 2-D QAM. Due to increase in MED, the 3-D constellations have much improved error performance compared to the QAM configurations. It is, therefore, considered that the higher-level 3-D constellations are appropriate for high-quality digital communications.</P>
Seog Geun Kang,Dong Min Kim,Eon Kyeong Joo 한국정보과학회 1999 Journal of Electrical Engineering and Information Vol.4 No.3
In this paper, a channel estimation algorithm for efficient transmission of orthogonal frequency division multiplexing signals in multipath channel is presented and analyzed. To increase transmission efficiency, known reference signals instead of the cyclic prefix are inserted into the guard interval. Estimation coefficients are obtained according to one-to-one correspondence between the received reference signals and the known ones in frequency domain and used to compensate the effect of channel on each subband. Computer simulation shows that bit error rate of the presented algorithm is slightly higher than that of the conventional one. However, the transmission efficiency of the system has been increased up to 20% when the length of guard interval is 1/4 the data block. Thus, the presented estimation algorithm is expected to be suitable for high speed transmission systems such as digital terrestrial broadcasting.
단일표본관측을 이용한 직교진폭변조 신호의 최우 변조분류 성능
강석근 ( Seog Geun Kang ) 한국정보처리학회 2005 정보처리학회논문지 C : 정보통신,정보보안 Vol.12 No.1
In this paper, performance of a maximum-likelihood modulation classification for quadrature amplitude modulation (QAM) is studied. Unlike previous works, the relative classification performance with respect to the available modulations and performance limit with single-sample observation are presented. For those purpose, all constellations are set to have the same minimum. Education distance between symbols so that a smaller constellation is a subset of the larger ones. And only one sample of received waveform is used for multiple hypothesis test. As a result, classification performance is improved with increase in signal-to-noise ratio in all the experiments. Especially, when the true modulation format used in the transmitter is 4 QAM, almost perfect classification can be achieved without any additional information or observation samples. Though the possibility of false classification due to the symbols shared by subset constellations always exists, correct classification ratio of 80% can be obtained with the single-sample observation when the true modulation formats are 16 and QAM.
가압유동층에서 기체-고체의 Chaotic 흐름 거동 해석
강석환 ( Kang Seog Hwan ),강용 ( Kang Yong ),한근희 ( Han Geun Hui ),진경태 ( Jin Gyeong Tae ) 한국공업화학회 2003 공업화학 Vol.14 No.6
최소유동화속도 부근의 가압유동층에서 기체-고체의 흐름 거동을 chaos이론을 도입하여 연구하였다. 압력 변동을 계를 해석하기 위한 상태 변수로 사용하였으며, 유동층에서 기체와 고체의 불규칙적이고 chaotic 흐름에 기인된 압력변동 신호는 상공간투영, kolmogorov 엔트로피 그리고 상관차원과 같은 chaos 파라메타들에 의해 해석하였다. 기체-고체 가압유동층에서 기체-고체 흐름의 비선형적 거동을 묘사하고 설명하는데 chaos 파라메타들은 효과적으로 사용될 수 있었다. 또한, 이들 chaos 파라메타들은 복잡한 기체-고체 흐름에 기인하여 발생하는 동역학적 거동의 정량적인 정보를 제공할 수 있었다. 본 연구의 실험범위에서 압력요동의 kolmogorov 엔트로피와 상관차원의 값들은 실험변수들과 좋은 상관관계를 나타내었다. In a pressurized fluidized bed, chaotic flow behavior of gas-solid in the vicinity of minimum fluidization velocity condition has been investigated by adopting the concept of chaos theory. Pressure fluctuation has been chosen as a state variable for the analysis of the system. The pressure fluctuation signals due to the irregular and chaotic flow of gas and solid. in the bed, have been interpreted by means of chaotic parameters such as phase space portraits, Kolmogorov entropy and correlation dimension. It was found that the chaotic parameters can be utilized effectively to describe and explain the non-linear dynamic behaviors of gas-solid flow in a pressurized gas-solid fluidized bed. Also, they can provide quantitative measures of dynamic behavior arising from the complex gas-solid flow. The values of Kolmogorov entropy and correlation dimension of pressure fluctuations have been well correlated with operating variables within experimental conditions.
Kang, Byeong-Mo,Lim, Yeong-Seog,Jeong, Woon-Jo,Kang, Byung-Woo,Ahn, Ho-Geun The Korean Institute of Electrical and Electronic 2014 Transactions on Electrical and Electronic Material Vol.15 No.5
We deposited TiAgN and ZrAgN nanocomposite coatings on pure Titanium specimens, by using arc ion plating (AIP) with single alloy targets. TiAg ZrAg alloy targets of 5 wt.%, 10 wt.% silver content by vacuum arc remelting (VAR), followed by homogenization for 2 hours at $1,100^{\circ}C$ in non-active Ar gas atmosphere and characterized these samples for morphology and chemical composition. We investigated the biocompatibility of TiAg and ZrAg alloys by examining the proliferation of L929 fibroblast cells by MTT test assay, after culturing the cells ($4{\times}10^4cells/cm^2$) for 24 hours; and exploring the antibacterial properties of thin films by culturing Streptococus Mutans (KCTC3065), using paper disk techniques. Our results showed no cytotoxic effects in any of the specimens, but the antibacterial effects against Streptococus Mutans appeared only in the 10 wt.% silver content specimens.