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심부정맥 혈전증의 도관유도 혈전용해술 또는 약물기계적 혈전제거술 후에 하대정맥 여과기 제거율과 임상적인 특징
노효근(Hyo Keun No),김중석(Joong Suck Kim),김장용(Jang Yong Kim),김경래(Kyung Rae Kim),신석환(Seok-Hwan Shin),안승익(Seung-Ik Ahn),조영업(Young Up Cho),김세중(Sei Joong Kim),이건영(Keon-Young Lee),허윤석(Yoon-Seok Hur),최선근(Sun Keu 대한외과학회 2010 Annals of Surgical Treatment and Research(ASRT) Vol.79 No.6
Purpose: Inferior vena cava (IVC) filter is commonly practiced to prevent pulmonary embolism during endovascular therapy of deep vein thrombosis (EndoDVT). When the thrombus is trapped inside the filter during intervention, its removal is quite challenging. The purpose of this study is to determine retrieval rates of IVC filter after EndoDVT and its characteristics. Methods: Patients who underwent EndoDVT in Inha Unversity Hospital from June 2004 to May 2009 were reviewed retrospectively. Retrievable IVC filter was inserted before EndoDVT. EndoDVT was done by catheter directed thrombolysis or pharmacomechanical thrombectomy using urokinase. IVC filter retrieval was decided according to computed tomography after 2 weeks. Results: 126 patients were treated with EndoDVT. Optease (n=101) and Tulip (n=25) IVC filters were inserted. IVC filters were retrieved in 42.9% (54/126). There was no IVC filter related complication during its insertion and removal. IVC filter was not retrieved in 72 patients. Reasons for its failure include residual thrombosis in IVC filter (n=28), high risk for recurrent DVT (n=34), massive pulmonary embolism (n=8), and death (n=2). Residual thrombus inside IVC filter disappeared in 5 patients during 6-month follow up. Conclusion: IVC filters retrieval rate after EndoDVT was 42.9%. This can be improved by thorough patient follow up and extended retrievability.
Opportunistic Power Control for Successive Interference Cancellation
Yong-Up Jang,Eui-Rim Jeong IEEE 2011 IEEE COMMUNICATIONS LETTERS Vol.15 No.3
<P>This letter proposes an opportunistic power control for increasing the transmission rate of a secondary transmitter (ST) in frequency reused scenario. The environments considered herein have multiple primary transmitter/receiver pairs and one secondary transmitter/receiver pair using the same frequency band. In this scenario, we develop the opportunistic power control method for assisting successive interference cancellation (SIC) and optimal SIC order. Simulation results show that the proposed method improves the ST transmission rate significantly when compared to the method with no power control, and it exhibits a small throughput loss compared to the optimal technique while offering simpler implementation and using less transmission power.</P>
On the Multiuser Diversity of Relay-Aided Downlink Systems Using Reduced Feedback
Jang, Yong-Up,Shin, Won-Yong Hindawi Publishing Corporation 2014 The Scientific World Journal Vol.2014 No.-
<P>We introduce an efficient multiuser scheduling method using amplify-and-forward relaying in relay-aided downlink systems, consisting of one base station (BS), one relay station, and multiple mobile stations (MSs). In our scheme, the BS opportunistically selects both the transmission mode, that is, either one- or two-hop transmission, and the desired user (i.e., the desired MS). Closed-form expressions for the average achievable rates are derived for the two transmission modes with multiuser scheduling, and its asymptotic solutions are also analyzed in the limit of large number of MSs. Based on the analysis, we propose a <I>feedback-efficient</I> two-step multiuser scheduling algorithm: the transmission mode selection followed by the user selection that only needs a partial feedback for instantaneous signal-to-noise ratios (SNRs) to the BS. We also analyze the <I>average SNR</I> condition such that the multiuser diversity gain is fully exploited for two-hop transmission. The proposed two-step scheduling algorithm exhibits the quite comparable achievable rates to those of the optimal one using full feedback information, while its required feedback information is reduced by half of the optimal one.</P>
Performance Analysis of User Selection for Multiuser Two-Way Amplify-and-Forward Relay
Yong-Up Jang,Lee, Yong H IEEE 2010 IEEE communications letters Vol.14 No.11
<P>This paper considers a multiuser two-way relay channel (MU-TWRC) in which a base-station and a selected mobile-station (MS) among K number of MSs exchange messages during two time slots with the help of a half-duplex amplify-and-forward relay. We analyze the performances of a MU-TWRC. The closed-form expressions of the lower bound of the average rates are derived. The asymptotic expressions of the average rates are also analyzed in the limit of large K. Analysis and simulation results indicate that the former matches well to the latter, and the performance of a MU-TWRC can increase as K increases or be bounded to some constant according to the channel conditions.</P>
Frame Design and Throughput Evaluation for Practical Multiuser MIMO OFDMA Systems
Yong-Up Jang,Jingon Joung,Won-Yong Shin,Eui-Rim Jeong IEEE 2011 IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY Vol.60 No.7
<P>This paper describes the design of a time-division duplexing frame with a variety of pilots for multiuser multiple-input-multiple-output orthogonal frequency-division multiple access (MU-MIMO OFDMA) systems, where the base station and users are equipped with four and two transmitting and receiving antennas, respectively. In addition, a simplified scheduling algorithm for the MU-MIMO OFDMA is proposed, and its computational complexity is analyzed. The proposed scheduling algorithm shows comparable sum achievable rates to the optimal MU-MIMO OFDMA scheduling that searches for user pairs in an exhaustive manner, whereas its complexity is fairly reduced. Furthermore, to verify the performance of MU-MIMO OFDMA systems that employ the proposed frame structure and scheduling algorithm, a system-level comparison of the average cell throughputs between the proposed MU-MIMO and the conventional MIMO OFDMA systems is numerically performed in a practical cellular environment. As a result, vital information on how we can apply MU-MIMO OFDMA schemes in cellular environments is provided.</P>
A Two-Step Approach to Power Allocation for OFDM Signals Over Two-Way Amplify-and-Forward Relay
Yong-Up Jang,Eui-Rim Jeong,Lee, Y.H. IEEE 2010 IEEE transactions on signal processing Vol.58 No.4
<P>A two-way relay channel (TWRC) in which two terminals <I>T</I> <SUB>1</SUB> and <I>T</I> <SUB>2</SUB> exchange orthogonal frequency division multiplexing (OFDM) signals with the help of an amplify-and-forward (AF) relay <I>T</I> <SUB>3</SUB> is considered here, and an efficient technique for allocating powers to <I>N</I> parallel tones of OFDM is developed. A sum rate maximization problem is formulated by replacing the individual power constraints of the conventional sum rate maximization problem, which limit the power of each terminal, with the total power constraint limiting the sum of powers of all terminals. The maximization problem with the total power constraint yields a more efficient power allocation policy than the conventional problem with individual power constraints. It is shown that the closed-form solution of the maximization problem under the total power constraint can be obtained for a single-tone system (<I>N</I>=1). Based on this result, a two-step suboptimal approach is proposed in which the power is optimally assigned to each tone first, and then at each tone the assigned power is distributed to the three terminals. The proposed method is shown to assign 50% of the total power to relay <I>T</I> <SUB>3</SUB> irrespective of the channels. It is demonstrated that the proposed method is considerably simpler to implement than the conventional dual-decomposition method (DDM), yet the performance of the former is almost identical to that of the latter.</P>