Browsing by Author "Lee, YM"

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A robust generalized sidelobe canceller against multipath induced perturbations in wireless communications
(2005)
Lee, YM
;
Wu, WR
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電信工程研究所
;
Institute of Communications Engineering
Conventional generalized sidelobe canceller (GSC) is sensitive to coherent multipath disturbance in wireless communication environments. Such disturbance, including coherent interference and local scattering, causes signal cancellation in the GSC. In this paper, we propose a new decision feedback (DF) technique to overcome this problem. The proposed algorithm introduces a feedback filter with one tap weight in the GSC structure. We analyze the robustness of this algorithm and the result shows that the problem of signal cancellation can be avoided. Simulations demonstrate that the DF-GSC has greatly improved robustness as compared to the conventional GSC.
An LMS-based adaptive generalized sidelobe canceller with decision feedback
(2005)
Lee, YM
;
Wu, WR
;
電信工程研究所
;
Institute of Communications Engineering
Conventional least-mean-square (LMS) based adaptive generalized sidelobe canceller (GSC) suffers from the slow convergence problem. When the environment is fast varying, the conventional GSC cannot perform satisfactorily. In this paper, we propose a new decision feedback (DF) technique to overcome this problem. The proposed algorithm introduces a feedback filter with one tap weight in the GSC structure. The Wiener solution for the proposed structure is derived and the convergence behavior of the adaptive DF-GSC is also analyzed. Simulation results show that the proposed structure can significantly accelerate the convergence and enhance the overall performance.
HiPRIME: Hierarchical and passivity preserved interconnect macromodeling engine for RLKC power delivery
(2005-06-01)
Lee, YM
;
Cao, YH
;
Chen, TH
;
Wang, JML
;
Chen, CCP
This paper proposes a general hierarchical analysis methodology, HiPRIME, to efficiently analyze RLKC power delivery systems. After partitioning the circuits into blocks, we develop and apply the IEKS (Improved Extended Krylov Subspace) method to build the multiport Norton equivalent circuits which transform all the internal sources to Norton current sources at ports. Since there are no active elements inside the Norton circuits, passive or realizable model order reduction techniques such as PRIMA can be applied. The significant speed improvement, 700 times faster than Spice with less than 0.2% error and 7 times faster than a state-of-the-art solver, InductWise, is observed. To further reduce the top-level hierarchy runtime, we develop a second-level model reduction algorithm and prove its passivity.
Parallel implementation of molecular dynamics simulation for short-ranged interaction
(2005-08-01)
Wu, JS
;
Hsu, YL
;
Lee, YM
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機械工程學系
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Department of Mechanical Engineering
A parallel molecular dynamics simulation method, designed for large-scale problems, employing dynamic spatial domain decomposition for short-ranged molecular interactions is proposed. In this parallel cellular molecular dynamics (PCMD) simulation method, the link-cell data structure is used to reduce the searching time required for forming the cut-off neighbor list as well as for domain decomposition, which utilizes the multi-level graph-partitioning technique. A simple threshold scheme (STS), in which workload imbalance is monitored and compared with some threshold value during the runtime, is proposed to decide the proper time for repartitioning the domain. The simulation code is implemented and tested on the memory-distributed parallel machine, e.g., PC-cluster system. Parallel performance is studied using approximately one million L-J atoms in the condensed, vaporized and supercritical states. Results show that fairly good parallel efficiency at 49 processors can be obtained for the condensed and supercritical states (similar to 60%), while it is comparably lower for the vaporized state (-40%). (c) 2005 Elsevier B.V. All rights reserved.
Solubilization of hydrophilic compounds in 1,1,1,2-tetrafluoroethane with a cationic surfactant
(2000-03-15)
Li, JR
;
Lee, YM
;
Yu, T
;
應用化學系
;
Department of Applied Chemistry
Solubilization of hydrophilic compounds was examined in liquid 1,1,1,2-tetrafluoroethane (R134a) in the presence of the cationic surfactant trioctylmethylammonium chloride (TOMAC). The absorption spectra of methyl orange in the TOMAC-containing R134a solutions were obtained. Significant blue shifts were observed in comparison with the spectrum of methyl orange in aqueous solution. The shifts decreased as the water-to-surfactant ratio, Wb, increased. In addition, spectral measurements confirmed the dissolution of cytochrome c in R134a in the presence of TOMAC. R134a remains as a liquid under mild applied pressure and becomes gas under ambient conditions; it therefore separates from analytes of interest directly without further concentration when used as an extraction solvent. Accordingly, it may be applied to recover valuable hydrophilic substances of low concentration from aqueous solutions.
The power grid transient simulation in linear time based on 3-D alternating-direction-implicit method
(2003-11-01)
Lee, YM
;
Chen, CCP
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The rising power consumption and clock frequency of very large scale integration technology demand robust and stable power delivery. Extensive transient simulations on large-scale power delivery structures are required to analyze power delivery fluctuation caused by dynamic IR drop and Ldi/dt drop as well as package and on-chip resonance. In this paper, we develop a novel and efficient transient simulation algorithm for the power distribution networks. Our algorithm, three-dimensional (3-D) transmission-line-modeling alternating-direction-implicit (TLM-ADI) method, first models the power delivery structure as 3-D transmission line shunt-node structure and transfer those equations to the telegraph equation. Finally, we solve it by the alternating direction implicit method. The 3-D TLM-ADI method, with linear runtime and memory requirement, is also unconditionally stable, which ensures that the time steps are not limited by any stability requirement. Extensive numerical simulation results show that the proposed algorithm is not only over 300000 times faster than SPICE but also extremely memory saving and accurate.