• 제목/요약/키워드: Iterative technique

검색결과 570건 처리시간 0.029초

A Comparative Quantitative Analysis of IDEAL (Iterative Decomposition of Water and Fat with Echo Asymmetry and Least Squares Estimation) and CHESS (Chemical Shift Selection Suppression) Technique in 3.0T Musculoskeletal MRI

  • Kim, Myoung-Hoon;Cho, Jae-Hwan;Shin, Seong-Gyu;Dong, Kyung-Rae;Chung, Woon-Kwan;Park, Tae-Hyun;Ahn, Jae-Ouk;Park, Cheol-Soo;Jang, Hyon-Chol;Kim, Yoon-Shin
    • Journal of Magnetics
    • /
    • 제17권2호
    • /
    • pp.145-152
    • /
    • 2012
  • Patients who underwent hip arthroplasty using the conventional fat suppression technique (CHESS) and a new technique (IDEAL) were compared quantitatively to assess the effectiveness and usefulness of the IDEAL technique. In 20 patients who underwent hip arthroplasty from March 2009 to December 2010, fat suppression T2 and T1 weighted images were obtained on a 3.0T MR scanner using the CHESS and IDEAL techniques. The level of distortion in the area of interest, the level of the development of susceptibility artifacts, and homogeneous fat suppression were analyzed from the acquired images. Quantitative analysis revealed the IDEAL technique to produce a lower level of image distortion caused by the development of susceptibility artifacts due to metal on the acquired images compared to the CHESS technique. Qualitative analysis of the anterior area revealed the IDEAL technique to generate fewer susceptibility artifacts than the CHESS technique but with homogeneous fat suppression. In the middle area, the IDEAL technique generated fewer susceptibility artifacts than the CHESS technique but with homogeneous fat suppression. In the posterior area, the IDEAL technique generated fewer susceptibility artifacts than the CHESS technique. Fat suppression was not statistically different, and the two techniques achieved homogeneous fat suppression. In conclusion, the IDEAL technique generated fewer susceptibility artifacts caused by metals and less image distortion than the CHESS technique. In addition, homogeneous fat suppression was feasible. In conclusion, the IDEAL technique generates high quality images, and can provide good information for diagnosis.

심볼 기반 빔포밍을 위한 제한 피드백 기법 (Limited Feedback Technique for Symbol-Based Beamforming)

  • 이현호;고영채
    • 한국방송∙미디어공학회:학술대회논문집
    • /
    • 한국방송공학회 2010년도 추계학술대회
    • /
    • pp.214-216
    • /
    • 2010
  • 본 논문에서는, 다중송수신안테나 직교주파수분할다중화 (MIMO-OFDM) 시스템에서 심볼 기반 빔포밍을 위한 제한 피드백 기법을 고려하였다. 공간적 상관도가 존재하는 다중전달경로 채널에서, 심볼 기반 빔포밍을 위한 제한 피드백 기법과 코드북을 제안하였다. 모의실험 결과를 통해 제안한 기법이 낮은 복잡도를 가짐에도 불구하고 기존의 iterative 알고리즘을 기반으로 하는 심볼 기반 빔포밍을 이용한 제한 피드백 기법보다 우수한 성능을 보임을 확인하였다. 또한, 제안한 코드북이 랜덤 벡터 양자화 코드북보다 우수한 성능을 보임을 확인하였다.

  • PDF

부착과 비부착된 프리스트레스트 콘크리트보의 휨 모델 (Flexural Modeling of Bonded and Unbonded Prestressed Concrete Beam)

  • 김민경;이차돈
    • 한국콘크리트학회:학술대회논문집
    • /
    • 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
    • /
    • pp.467-470
    • /
    • 1999
  • An analytical method based on the nonlinear layered finite element method is developed to simulate overall load-deflection behavior of bonded and unbonded prestressed concrete beams. The model which uses rather advanced numerical technique for iterative convergence to equilibrium can be regarded as superior one compared to the models mainly based on either load control or displacement control methods. Model predictions were compared with preceding experimental results and it was observed that there were good agreements between them.

  • PDF

Piecewise Phase Recovery Algorithm Using Block Turbo Codes for Next Generation Mobile Communications

  • Ryoo, Sun-Heui;Kim, Soo-Young;Ahn, Do-Seob
    • ETRI Journal
    • /
    • 제28권4호
    • /
    • pp.435-443
    • /
    • 2006
  • This paper presents an efficient carrier recovery algorithm combined with a turbo-coding technique in a mobile communication system. By using a block turbo code made up of independently decodable block codes, we can efficiently recover the fast time-varying carrier phase as well as correct channel errors. Our simulation results reveal that the proposed scheme can accommodate mobiles with high speed, and at the same time can reduce the number of iterations to lock the phase.

  • PDF

$H_\infty$ 최적제어기의 이산화 구현 (Digital Implementation of $H_\infty$ Optimal Controller)

  • 김광우;오도창;박홍배
    • 제어로봇시스템학회:학술대회논문집
    • /
    • 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국내학술편); Seoul National University, Seoul; 20-22 Oct. 1993
    • /
    • pp.471-476
    • /
    • 1993
  • In this paper we proposed the digital implementation of an $H^{\infty}$-optimal controller using lifting technique and $H^{\infty}$-control theory. The discrete controller is obtained through iterative adjustment of sampling time and weighting function, which can ber performed by computing the L$_{2}$-induced input to output norm of the sampled-data system with bandlimited exogenous input. The resulting sampled-data bandlimited exogenous input. The resulting sampled-data system is stable and the performance including inter-sampling behaviour of the hybrid system can be also optimized.d.

  • PDF

A SYSTEM OF NONLINEAR VARIATIONAL INCLUSIONS WITH (A, $\eta$)-MONOTONE MAPPINGS IN HILBERT SPACES

  • Shang, Meijuan;Qin, Xiaolong
    • East Asian mathematical journal
    • /
    • 제24권1호
    • /
    • pp.1-6
    • /
    • 2008
  • In this paper, we introduce a system of nonlinear variational inclusions involving (A, $\eta$)-monotone mappings in the framework of Hilbert spaces. Based on the generalized resolvent operator technique associated with (A, $\eta$)-monotonicity, the approximation solvability of solutions using an iterative algorithm is investigated. Our results improve and extend the recent ones announced by many others.

  • PDF

ITERATIVE ALGORITHMS FOR A SYSTEM OF RANDOM NONLINEAR EQUATIONS WITH FUZZY MAPPINGS

  • Kim, Jong Kyu;Salahuddin, Salahuddin
    • East Asian mathematical journal
    • /
    • 제34권3호
    • /
    • pp.265-285
    • /
    • 2018
  • The main purpose of this paper, by using the resolvent operator technique associated with randomly (A, ${\eta}$, m)-accretive operator is to establish an existence and convergence theorem for a class of system of random nonlinear equations with fuzzy mappings in Banach spaces. Our works are improvements and generalizations of the corresponding well-known results.