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ML Symbol Detection for MIMO Systems in the Presence of Channel Estimation Errors
( Namsik Yoo ),( Jong-hyen Back ),( Hyeon-yeong Choi ),( Kyungchun Lee ) 한국인터넷정보학회 2016 KSII Transactions on Internet and Information Syst Vol.10 No.11
In wireless communication, the multiple-input multiple-output (MIMO) system is a well-known approach to improve the reliability as well as the data rate. In MIMO systems, channel state information (CSI) is typically required at the receiver to detect transmitted signals; however, in practical systems, the CSI is imperfect and contains errors, which affect the overall system performance. In this paper, we propose a novel maximum likelihood (ML) scheme for MIMO systems that is robust to the CSI errors. We apply an optimization method to estimate an instantaneous covariance matrix of the CSI errors in order to improve the detection performance. Furthermore, we propose the employment of the list sphere decoding (LSD) scheme to reduce the computational complexity, which is capable of efficiently finding a reduced set of the candidate symbol vectors for the computation of the covariance matrix of the CSI errors. An iterative detection scheme is also proposed to further improve the detection performance.
김관주(Kim Kwanju),유남식(Yoo Namsik) 한국철도학회 1998 한국철도학회 학술발표대회논문집 Vol.- No.-
In this study, system analysis for a train vehicle with an articulated bogie frame adopted in TGV and TGV-K system is performed. System analysis is carried out as follows. First, modal analysis of each subsystem is performed to obtain the natural frequencies and mode shapes. Then modal analysis of a whole vehicle is performed to obtain the potential interaction between the subsystems. Finallyforced response analysis, such as driving point mobility, is performed to obtain the dynamic response of specific points.
이은석(Eunseok Lee),김관주(Kwanju Kim),유남식(Namsik Yoo),이범주(Beomjoo Lee),나선주(Sunjoo Na),나종태(Jongtae Na) Korean Society for Precision Engineering 2022 한국정밀공학회지 Vol.39 No.5
The brake squeal noise is a high-frequency noise over 1 kHz range generated by the contact between the brake pad and the disk. The purpose of this paper was to investigate the behavior of the squeal noise characteristics of the brake system from an instability point of view, according to the variation of major parameters such as friction coefficient between the flexible pad and the disk, brake pressure, and Young’s modulus of disk. Full nonlinear perturbed modal analysis using commercial finite element analysis program was performed to derive complex eigenvalue results of the model. And the sensitivity behavior was observed. Increasing the coefficient of friction or Young’s modulus of disk tended to make the squeal mode of the model more unstable. However, the change in brake pressure has a complicated nonlinear relationship with the squeal mode of the model. The judgment technique conducted in this study should be considered to be used in the design of the vibration point of the disk and pad of railway vehicles in the future.
Circulating IL-8 levels in heart failure patients with and without metabolic syndrome
Shin, Min-Jeong,Lee, Kyung Hye,Chung, Ji Hyung,Park, Yoo Kyoung,Choi, Mi Kyung,Oh, Jaewon,Choi, Ji Won,Lee, Sang-Hak,Chung, Namsik,Kang, Seok-Min Elsevier 2009 Clinica chimica acta Vol.405 No.1
<P><B>Abstract</B></P><P><B>Background</B></P><P>It has been suggested that the metabolic syndrome (MetS) is associated with increased risk for heart failure (HF) and progression of HF. However, the underlying mechanisms are unclear. We tested whether the presence of the MetS would be associated with the increased degree of inflammatory state in HF.</P><P><B>Methods</B></P><P>Ninety-one eligible consecutive stable HF patients participated in this cross-sectional study. Anthropometric measurements were carried out and serum concentrations of lipoproteins, apolipoproteins (apoB, apoAI) and high sensitivity C-reactive protein (hsCRP) were measured. The simultaneous measurement of 17 cytokines using bioplex analysis was used.</P><P><B>Result</B></P><P>Thirty-five subjects (39% of total, 48% of males and 31% of females) were classified as having the MetS in total HF patients. Serum concentrations of apoB (<I>p</I><0.005) were significantly higher and the ratio of apoAI and apoB was significantly lower (<I>p</I><0.01) in HF patients with MetS than those without MetS. Plasma levels of IL-8 (<I>p</I><0.05) were significantly higher in HF patients with MetS than those without MetS. In addition, serum concentrations of hsCRP (<I>p</I><0.005) were significantly higher in HF patients with MetS compared to those without MetS.</P><P><B>Conclusions</B></P><P>The MetS in HF is associated with increased degree of inflammation, which provides information regarding the relationship between inflammation and HF with MetS.</P>
Song, Heesang,Chang, Woochul,Lim, Soyeon,Seo, Hye-Sun,Shim, Chi Young,Park, Sungha,Yoo, Kyung-Jong,Kim, Byung-Soo,Min, Byoung-Hyun,Lee, Hakbae,Jang, Yangsoo,Chung, Namsik,Hwang, Ki-Chul Wiley (John WileySons) 2007 Stem Cells Vol.25 No.6
<P>Autologous mesenchymal stem cell (MSC) transplantation therapy for repair of myocardial injury has inherent limitations due to the poor viability of the stem cells after cell transplantation. Adhesion is a prerequisite for cell survival and also a key factor for the differentiation of MSCs. As a novel prosurvival modification strategy, we genetically engineered MSCs to overexpress tissue transglutaminase (tTG), with intention to enhance adhesion and ultimately cell survival after implantation. tTG-transfected MSCs (tTG-MSCs) showed a 2.7-fold and greater than a twofold increase of tTG expression and surface tTG activity, respectively, leading to a 20% increased adhesion of MSCs on fibronectin (Fn). Spreading and migration of tTG-MSCs were increased 4.75% and 2.52%, respectively. Adhesion of tTG-MSCs on cardiogel, a cardiac fibroblast-derived three-dimensional matrix, showed a 33.1% increase. Downregulation of tTG by transfection of small interfering RNA specific to the tTG resulted in markedly decreased adhesion and spread of MSCs on Fn or cardiogel. tTG-MSCs on Fn significantly increased phosphorylation of focal adhesion related kinases FAK, Src, and PI3K. tTG-MSCs showed significant retention in infarcted myocardium by forming a focal adhesion complex and developed into cardiac myocyte-like cells by the expression of cardiac-specific proteins. Transplantation of 1 x 10(6) MSCs transduced with tTG into the ischemic rat myocardium restored normalized systolic and diastolic cardiac function. tTG-MSCs further restored cardiac function of infarcted myocardium as compared with MSC transplantation alone. These findings suggested that tTG may play an important role in integrin-mediated adhesion of MSCs in implanted tissues. Disclosure of potential conflicts of interest is found at the end of this article.</P>