Adaptive Algorithms (adaptive + algorithms)

Distribution by Scientific Domains


Selected Abstracts


An adaptive non-conforming finite-element method for Reissner,Mindlin plates

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 15 2003
Carsten Carstensen
Abstract Adaptive algorithms are important tools for efficient finite-element mesh design. In this paper, an error controlled adaptive mesh-refining algorithm is proposed for a non-conforming low-order finite-element method for the Reissner,Mindlin plate model. The algorithm is controlled by a reliable and efficient residual-based a posteriori error estimate, which is robust with respect to the plate's thickness. Numerical evidence for this and the efficiency of the new algorithm is provided in the sense that non-optimal convergence rates are optimally improved in our numerical experiments. Copyright 2003 John Wiley & Sons, Ltd. [source]


A variationally consistent mesh adaptation method for triangular elements in explicit Lagrangian dynamics

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 9 2010
Sudeep K. Lahiri
Abstract In this paper a variational formulation for mesh adaptation procedures, involving local mesh changes for triangular meshes, is presented. Such local adaptive changes are very well suited for explicit methods as they do not involve significant computational expense. They also greatly simplify the projection of field variables from the old to the new meshes. Crucially, the variational nature of the formulation used to derive the equilibrium equations at steps where adaptation takes place ensures that conservation of linear and angular momentum is obtained (Int. J. Numer. Meth. Engng 2000; 49:1295,1325). Several examples in 2-D showing the application of the proposed adaptive algorithms are used to demonstrate the validity of the methodology proposed. Copyright 2009 John Wiley & Sons, Ltd. [source]


Fixed-point steady-state analysis of adaptive filters

INTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 3 2003
Nabil R. Yousef
Abstract The steady-state performance of adaptive filters can vary significantly when they are implemented in finite precision arithmetic, which makes it vital to analyse their performance in a quantized environment. Such analyses can become difficult for adaptive algorithms with non-linear update equations. This paper develops a feedback and energy-conservation approach to the steady-state analysis of quantized adaptive algorithms that bypasses some of the difficulties encountered by traditional approaches. Copyright 2003 John Wiley & Sons, Ltd. [source]


Adaptive joint beamforming and B-MMSE detection for CDMA signal reception under multipath interference

INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 7 2004
Hsiao-Hwa Chen
Abstract The combination of antenna array beamforming with multiuser detection can effectively improve the detection efficiency of a wireless system under multipath interference, especially in a fast-fading channel. This paper studies the performance of an adaptive beamformer incorporated with a block-wise minimum mean square error(B-MMSE) detector, which works on a unique signal frame characterized by training sequence preamble and data blocks segmented by zero-bits. Both beam-former weights updating and B-MMSE detection are carried out by either least mean square (LMS) or recursive least square (RLS) algorithm. The comparison of the two adaptive algorithms applied to both beamformer and B-MMSE detector will be made in terms of convergence behaviour and estimation mean square error. Various multipath patterns are considered to test the receiver's responding rapidity to changing multipath interference. The performance of the adaptive B-MMSE detector is also compared with that of non-adaptive version (i.e. through direct matrix inversion). The final performance in error probability simulation reveals that the RLS/B-MMSE scheme outperforms non-adaptive B-MMSE by 1,5 dB, depending on the multipath channel delay profiles of concern. The obtained results also suggest that adaptive beamformer should use RLS algorithm for its fast and robust convergence property; while the B-MMSE filter can choose either LMS or RLS algorithm depending on antenna array size, multipath severity and implementation complexity. Copyright 2004 John Wiley & Sons, Ltd. [source]


Adaptive beam search lookahead algorithms for the circular packing problem

INTERNATIONAL TRANSACTIONS IN OPERATIONAL RESEARCH, Issue 5 2010
Hakim Akeb
Abstract This paper addresses the circular packing problem (CPP), which consists in packing n circles Ci, each of known radius ri, i,N={1, ,, n}, into the smallest containing circle C. The objective is to determine the radius r of C as well as the coordinates (xi, yi) of the center of Ci, i,N. CPP is solved using two adaptive algorithms that adopt a binary search to determine r, and a beam search to check the feasibility of packing n circles into C when the radius is fixed at r. A node of level ,, ,=1, ,, n, of the beam search tree corresponds to a partial packing of , circles of N into C. The potential of each node of the tree is assessed using a lookahead strategy that, starting with the partial packing of the current node, assigns each unpacked circle to its maximum hole degree position. The beam search stops either when the lookahead strategy identifies a feasible packing or when it has fathomed all nodes. The computational tests on a set of benchmark instances show the effectiveness of the proposed adaptive algorithms. [source]