This paper presents the possibilities of active noise control techniques to reduce repetitive transient noise. Although there is a significant difference in nature between periodic and transient noise, up till now no ...
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This paper presents the possibilities of active noise control techniques to reduce repetitive transient noise. Although there is a significant difference in nature between periodic and transient noise, up till now no specific research on active noise control of transient noise was reported. The presented research focuses on the development of control algorithms, dedicated for the control of repetitive transient noise. The effectiveness of the control algorithms is demonstrated for the reduction of impulse noise in a duct by a secondary loudspeaker. A linear time-invariant feedback controller is developed to drive this loudspeaker. The performance of this time-invariant controller is limited for several reasons: time variance of the system parameters, limited controller bandwidth, nonlinearities, etc. However, when the noise consists of successive impulsive sounds that exhibit a repetitive character, it is possible to extend the developed time-invariant feedback controller with a learning behaviour, based on the additional information about the repetitiveness. At each pulse, the control signal for the secondary loudspeaker can be adapted on the basis of the residual noise at the previous pulses, such that the radiated noise is reduced. This latter control technique, called iterative learning control, can significantly increase the performance of a feedback active noise control system. (C) 2007 Elsevier Ltd. All rights reserved.
The performance improvement imparted by routing and spectrum assignment on flexible grid optical networks is a subject of current extensive investigation. Proposed is an efficient spectrum-assignment algorithm based o...
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The performance improvement imparted by routing and spectrum assignment on flexible grid optical networks is a subject of current extensive investigation. Proposed is an efficient spectrum-assignment algorithm based on reducing the loss of capacity of future bandwidth-variable path requests. In all scenarios analysed the proposed algorithm outperformed currently investigated slot assignment algorithms.
Recently, a variable step-size affine projection (VSS-AP) algorithm has been introduced. The algorithm provides faster convergence rate and lower misadjustment but has heavy computational complexity. Proposed is a new...
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Recently, a variable step-size affine projection (VSS-AP) algorithm has been introduced. The algorithm provides faster convergence rate and lower misadjustment but has heavy computational complexity. Proposed is a new variable step-size pseudo affine projection (VSS-PAP) algorithm, which not only has a much lower complexity than the VSS-AP algorithm but also provides performance comparable with the conventional algorithm. Simulation results confirm fast convergence rate and small misalignment of the proposed algorithm with less computational complexity.
The paper presents parts of the development of a spatial query language for building information models. Such a query language enables the spatial analysis of building information models and the extraction of partial ...
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The paper presents parts of the development of a spatial query language for building information models. Such a query language enables the spatial analysis of building information models and the extraction of partial models that fulfill certain spatial constraints. Among other features, it includes topological operators, i.e. operators that reflect the topological relationships between 3D spatial objects. The paper presents definitions of the semantics of the topological operators within, contain, touch, overlap, disjoint and equal in 3D space by using the 9-intersection model. It further describes a possible implementation of the topological operators by means of an octree-based algorithm. The recursive algorithm presented in this article relies on a breadth-first traversal of the operands' octree representations and the application of rules that are based on the color of the octants under examination. Because it successively increases the discrete resolution of the spatial objects employed, the algorithm enables the user on the one hand to handle topological relationships in a fuzzy manner and on the other hand to trade-off between computational effort and the required accuracy. The article also presents detailed investigations on the run-time performance of the developed algorithm. (C) 2009 Elsevier Ltd. All rights reserved.
The applicability of the accommodating function, a relatively new measure for the quality of on-line algorithms, is extended. The standard quality measure for on-line algorithms is the competitive ratio, which is, rou...
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The applicability of the accommodating function, a relatively new measure for the quality of on-line algorithms, is extended. The standard quality measure for on-line algorithms is the competitive ratio, which is, roughly speaking, the worst case ratio of the on-line performance to the optimal off-line performance. However, for many on-line problems, the competitive ratio gives overly pessimistic results and/or fails to distinguish between algorithms that are known to perform very differently in practice. Many researchers have proposed variations on the competitive ratio to obtain more realistic results. These variations are often tailor-made for specific on-line problems. The concept of the accommodating function applies to any on-line problem with some limited resource, such as bins, seats in a train, or pages in a cache. If a limited amount n of some resource is available, the accommodating function A(alpha) is the competitive ratio when input sequences are restricted to those for which the amount alphan of resources suffices for an optimal off-line algorithm. For all resource bounded problems, the standard competitive ratio is lim(alpha-->infinity) A(alpha). The accommodating function was originally used only for alpha greater than or equal to 1. We focus on alpha < 1, observe that the function now appears interesting for a greater variety of problems, and use it to make new distinctions between known algorithms and to find new ones.
The higher goal of rehabilitation robot is to aid a person to achieve a desired functional task (e. g., tracking trajectory) based on assisted-as-needed principle. To this goal, a new adaptive inverse optimal hybrid c...
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The higher goal of rehabilitation robot is to aid a person to achieve a desired functional task (e. g., tracking trajectory) based on assisted-as-needed principle. To this goal, a new adaptive inverse optimal hybrid control (AHC) combining inverse optimal control and actor-critic learning is proposed. Specifically, an uncertain nonlinear rehabilitation robot model is firstly developed that includes human motor behavior dynamics. Then, based on this model, an open-loop error system is formed;thereafter, an inverse optimal control input is designed to minimize the cost functional and a NN-based actor-critic feedforward signal is responsible for the nonlinear dynamic part contaminated by uncertainties. Finally, the AHC controller is proven (through a Lyapunov-based stability analysis) to yield a global uniformly ultimately bounded stability result, and the resulting cost functional is meaningful. Simulation and experiment on rehabilitation robot demonstrate the effectiveness of the proposed control scheme.
A digital closed-loop driving technique is presented in this paper that uses the PFD- (phase frequency detector-) based CORDIC (coordinate rotation digital computer) algorithm for a biaxial resonant microaccelerometer...
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A digital closed-loop driving technique is presented in this paper that uses the PFD- (phase frequency detector-) based CORDIC (coordinate rotation digital computer) algorithm for a biaxial resonant microaccelerometer. A conventional digital closed-loop self-oscillation system based on the CORDIC algorithm is implemented and simulated using Simulink software to verify the system performance. The system performance simulations reveal that the incompatibility between the sampling frequency and effective bits of AD and DA convertors limits further performance improvements. Therefore, digital, closed-loop self-oscillation using the PFD-based CORDIC algorithm is designed to further optimize the system performance. The system experimental results illustrate that the optimized system using the PFD-based CORDIC improves the bias stability of the resonant micro accelerometer by more than 5.320 times compared to the conventional system. This demonstrates that the optimized digital closed-loop driving technique using the PFD-based CORDIC for the biaxial resonant microaccelerometer is effective.
Most fast block matching algorithms ignore the efficiency in motion compensation within each checking step. In order to achieve better-compensated performance, the limited computational complexity should be allocated ...
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Most fast block matching algorithms ignore the efficiency in motion compensation within each checking step. In order to achieve better-compensated performance, the limited computational complexity should be allocated more carefully into each block. It means that the fast block matching algorithm can be viewed as a kind of rate-distortion optimization problem. The complexity-distortion optimal fast block matching algorithm should find the maximized quality of the compensated image under a target computational complexity. In order to approach the optimal complexity-distortion solution, some strategies are developed. For example, a domination-based motion vector prediction technique is developed to set the initial motion vector for each block. A predictive complexity-distortion benefit list is established to predict the compensated benefit for each block. Also, a three-level pattern searching is employed to check the candidate motion vector. Experimental results show that our proposed algorithm outperforms significantly the three-step search. For example, in "Salesman," the average checkpoints for one block is 33 by using the three-step search. The average checkpoint is 1.75 by using our proposal algorithm under the same average PSNR condition. (C) 2002 Wiley Periodicals, Inc.
This paper solves the robust control problem of a plant with distributed delay using a reference model. The plant is subjected to bounded exogenous disturbances and the parameters of its mathematical model appear unkn...
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This paper solves the robust control problem of a plant with distributed delay using a reference model. The plant is subjected to bounded exogenous disturbances and the parameters of its mathematical model appear unknown. The author suggests a control algorithm for compensating the a priori parametric uncertainty and the bounded exogenous disturbances with a desired accuracy. A numerical example with corresponding simulation results is provided.
For the model of joint servicing of the real-time service and data traffics, numerical study of the demand servicing indices vs. the model input parameters was carried out. Solution of the problem of estimating the mi...
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For the model of joint servicing of the real-time service and data traffics, numerical study of the demand servicing indices vs. the model input parameters was carried out. Solution of the problem of estimating the minimal channel resource sufficient to service the demand inflow with the desired performance was considered. Approximate algorithms to calculate the model were constructed, and their accuracy was analyzed numerically.
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