With the growing popularity of the MPEG-1 Audio Layer 3 (MP3) format, handheld devices such as personal digital assistants (PDAs) and mobile phones have become important entertainment platforms. Unlike conventional au...
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With the growing popularity of the MPEG-1 Audio Layer 3 (MP3) format, handheld devices such as personal digital assistants (PDAs) and mobile phones have become important entertainment platforms. Unlike conventional audio equipment, mobile devices are characterized by limited processing power, battery life, and memory, as well as other constraints. Therefore, music-processing tasks like beat detection must be implemented using low-complexity algorithms to cope with the constraints of these mobile devices.
Two optimization algorithms are presented that are capable of finding a global optimum in a computationally efficient manner: a gradient-based multistart algorithm based on Sobol sampling and a hybrid optimizer combin...
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Two optimization algorithms are presented that are capable of finding a global optimum in a computationally efficient manner: a gradient-based multistart algorithm based on Sobol sampling and a hybrid optimizer combining a genetic algorithm with a gradient-based algorithm. The optimizers are used to investigate multimodality in aerodynamic-shape-optimization problems. The performance of each algorithm is tested on an analytical test function as well as several aerodynamic-shape-optimization problems in two and three dimensions. In each problem the primary objectives are to classify the problem according to the degree of multimodality and to identify the preferred optimization algorithm for the problem. The results show that multimodality should not always be assumed in aerodynamic-shape-optimization problems. Typical two-dimensional airfoil-optimization problems are unimodal. Three-dimensional shape-optimization problems may contain local optima. The number of local optima tends to increase with increasing geometric degrees of freedom and design space bounds. For problems with a modest number of local optima, which we term somewhat multimodal, the gradient-based multistart Sobol algorithm is the most efficient method.
We formulate a new approach for evaluating a prefetching algorithm. We first carry out a profiling run of a program to identify all of the misses and corresponding locations in the program where prefetches for the mis...
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We formulate a new approach for evaluating a prefetching algorithm. We first carry out a profiling run of a program to identify all of the misses and corresponding locations in the program where prefetches for the misses can be initiated. We then systematically control the number of misses that are prefetched, the timeliness of these prefetches, and the number of umused prefetches. We validate the accuracy of our approach by comparing it to one based on a Markov prefetch algorithm. This allows us to measure the potential benefit that any application can receive from prefetching and to analyzed application behaviour under conditions that cannot be explored with any known prefetching algorithm. Next, we analyze a system parameter that is vital to prefetching performance, the line transfer interval, whish is the number of processor cycles required to transfer a cache line. This interval is determined by technology and bandwidth. We show that under ideal conditions, prefetching can remove nearly all of the stalls associated with cache misses. Unfortunately, real processor implementations are less than ideal. In particular, the trend in processor frequency is outrunning on-chip and off-chip bandwidths. Today, it is not uncommon for processor frequency to be three or four times bus frequency. Under these conditions, we show that nearly all of the performance benefits derived from prefetching are eroded, and in many cases prefetching actually degrades performance. We carry out quantitative and qualitative analyses of these tradeoffs and show that there is a linear relationship between overall performance and three metrics: percentages of misses prefetched, percentage of unused prefetches, and bandwidth.
The peculiarities of fractal characteristics' calculations for time series are described in this article. An algorithm for calculation of fractal dimension is suggested. it has been proved that the suggested metho...
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The peculiarities of fractal characteristics' calculations for time series are described in this article. An algorithm for calculation of fractal dimension is suggested. it has been proved that the suggested method possesses high accuracy and the rapidity of convergence on the limited number of measurements compared to the methods of covering. The criteria of early diagnosis for changes in the condition of hydrodynamic processes, which do not vary by fractal dimension, have been recommended. The presented method is applicable for practical engineering calculations with self-affine, chaotic data, usually with relatively limited number of measurements. It is quite a simple method for calculation of fractal dimension, algorithm can be easily realized and it should be useful for engineers. The applicability of the proposed algorithm for fractal dimension calculation and early diagnosis criteria of qualitative changes in the behaviour of various dynamic systems has been tested both on simulated as well as practical examples of oil and gas production. (C) 2008 Elsevier Ltd. All rights reserved.
This paper addresses the problem of designing robust tracking controls for a class of switched fuzzy (SF) systems with time delay. A switched fuzzy system, which differs from existing ones, is firstly employed to desc...
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This paper addresses the problem of designing robust tracking controls for a class of switched fuzzy (SF) systems with time delay. A switched fuzzy system, which differs from existing ones, is firstly employed to describe a nonlinear system. Next, a fast switching controller consisting of a number of simple subcontrollers is proposed. The smooth transition is governed by using the fast switching controller. Tracking hybrid control schemes which are based upon a combination of the H-infinity tracking theory, fast switching control algorithm, and switching law design are developed such that the H-infinity model referent tracking performance is guaranteed. Since convex combination techniques are used to derive the delay independent criteria, some subsystems are allowed to be unstable. Finally, various comparisons of the elaborated examples are conducted to demonstrate the effectiveness of the proposed control design approach. All results illustrate good control performances as desired.
This article describes an analytic study of the process used by John Chowning for the composition of Stria. This article is intended to complete the description of the compositional process given in a previous work (M...
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This article describes an analytic study of the process used by John Chowning for the composition of Stria. This article is intended to complete the description of the compositional process given in a previous work (Meneghini 2003), largely restated by Bossis in a subsequent paper (Bossis 2005). Stria was composed in 1977 and was fully generated by means of computer algorithms (Chowning 1977c) and the corresponding input files (Chowning 1977a, b): all the parameters of the sounds generated in Stria are determined and calculated by these algorithms on the basis of specific mathematical rules and of numerical parameters chosen by Mr. Chowning as input for the programs. For this reason, an accurate analysis of these algorithms is fundamental for a complete comprehension of the compositional process.
Detecting communities within networks is of great importance to understand the structure and organizations of real-world systems. To this end, one of the major challenges is to find the local community from a given no...
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Detecting communities within networks is of great importance to understand the structure and organizations of real-world systems. To this end, one of the major challenges is to find the local community from a given node with limited knowledge of the global network. Most of the existing methods largely depend on the starting node and require predefined parameters to control the agglomeration procedure, which may cause disturbing inference to the results of local community detection. In this work, we propose a parameter-free local community detecting algorithm, which uses two self-adaptive phases in detecting the local community, thus comprehensively considering the external and internal link similarity of neighborhood nodes in each clustering iteration. Based on boundary nodes identification, our self-adaptive method can effectively control the scale and scope of the local community. Experimental results show that our algorithm is efficient and well-behaved in both computer-generated and real-world networks, greatly improving the performance of local community detection in terms of stability and accuracy.
Large-scale inversion methods have been recently developed and permitted now to considerably reduce the computation time and memory needed for inversions of models with a large amount of parameters and data. In this w...
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Large-scale inversion methods have been recently developed and permitted now to considerably reduce the computation time and memory needed for inversions of models with a large amount of parameters and data. In this work, we have applied a deterministic geostatistical inversion algorithm to a hydraulic tomography investigation conducted in an experimental field site situated within an alluvial aquifer in Southern France. This application aims to achieve a 2-D large-scale modeling of the spatial transmissivity distribution of the site. The inversion algorithm uses a quasi-Newton iterative process based on a Bayesian approach. We compared the results obtained by using three different methodologies for sensitivity analysis: an adjoint-state method, a finite-difference method, and a principal component geostatistical approach (PCGA). The PCGA is a large-scale adapted method which was developed for inversions with a large number of parameters by using an approximation of the covariance matrix, and by avoiding the calculation of the full Jacobian sensitivity matrix. We reconstructed high-resolution transmissivity fields (composed of up to 25,600 cells) which generated good correlations between the measured and computed hydraulic heads. In particular, we show that, by combining the PCGA inversion method and the hydraulic tomography method, we are able to substantially reduce the computation time of the inversions, while still producing high-quality inversion results as those obtained from the other sensitivity analysis methodologies.
There are usually larger uncertainties in the atmosphere density of Mars and the aerodynamic parameters of entry vehicles, which inevitably degrades the performance of entry guidance and control algorithms. This paper...
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There are usually larger uncertainties in the atmosphere density of Mars and the aerodynamic parameters of entry vehicles, which inevitably degrades the performance of entry guidance and control algorithms. This paper studies the robust Mars atmospheric entry guidance design based on the radial basis function neural network (RBF-NN) and second-order sliding mode control (SOSMC). First, second-order sliding mode guidance (SOSMG) law is developed to robustly follow the pre-designed nominal trajectory under larger uncertainties and effectively reduce the longitudinal error. Then, the RBF neural network is included into the second-order sliding surface guidance law to online approximate the bounded uncertain terms and further improve the guidance accuracy. Finally, the effectiveness of the guidance algorithm proposed in this paper is confirmed by Monte Carlo simulations. (C) 2015 Elsevier Masson SAS. All rights reserved.
Type 1 diabetes mellitus is a disease affecting millions of people worldwide and causing the expenditure of millions of euros every year for health care. One of the most promising therapies derives from the use of an ...
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Type 1 diabetes mellitus is a disease affecting millions of people worldwide and causing the expenditure of millions of euros every year for health care. One of the most promising therapies derives from the use of an artificial pancreas, based on a control system able to maintain the normoglycaemia in the subject affected by diabetes. A dynamic simulation model of the glucose-insulin system can be useful in several circumstances for diabetes care, including testing of glucose sensors, insulin infusion algorithms, and decision support systems for diabetes. This paper considers the problem of the identification of single individual parameters in detailed dynamic models of glucose homeostasis. Optimal model-based design of experiment techniques are used to design a set of clinical tests that allow the model parameters to be estimated in a statistically sound way, while meeting constraints related to safety of the subject and ease of implementation. The model with the estimated set of parameters represents a specific subject and can thus be used for customized diabetes care solutions. Simulated results demonstrate how such an approach can improve the effectiveness of clinical tests and serve as a tool to devise safer and more efficient clinical protocols, thus providing a contribution to the development of an artificial pancreas.
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