- Informacje o czasopiśmie
- Format
- Czasopismo
- eISSN
- 2083-8492
- Pierwsze wydanie
- 05 Apr 2007
- Częstotliwość wydawania
- 4 razy w roku
- Języki
- Angielski

#### Wyszukiwanie

- Otwarty dostęp

Maintaining the Feasibility of Hard Real–Time Systems with a Reduced Number of Priority Levels

Zakres stron: 709 - 722

#### Abstrakt

When there is a mismatch between the cardinality of a periodic task set and the priority levels supported by the underlying hardware systems, multiple tasks are grouped into one class so as to maintain a specific level of confidence in their accuracy. However, such a transformation is achieved at the expense of the loss of schedulability of the original task set. We further investigate the aforementioned problem and report the following contributions: (i) a novel technique for mapping unlimited priority tasks into a reduced number of classes that do not violate the schedulability of the original task set and (ii) an efficient feasibility test that eliminates insufficient points during the feasibility analysis. The theoretical correctness of both contributions is checked through formal verifications. Moreover, the experimental results reveal the superiority of our work over the existing feasibility tests by reducing the number of scheduling points that are needed otherwise.

#### Słowa kluczowe

- real-time systems
- feasibility analysis
- fixed-priority scheduling
- rate monotonic algorithm
- online scheduling

- Otwarty dostęp

Torus–Connected Cycles: A Simple and Scalable Topology for Interconnection Networks

Zakres stron: 723 - 735

#### Abstrakt

Supercomputers are today made up of hundreds of thousands of nodes. The interconnection network is responsible for connecting all these nodes to each other. Different interconnection networks have been proposed; high performance topologies have been introduced as a replacement for the conventional topologies of recent decades. A high order, a low degree and a small diameter are the usual properties aimed for by such topologies. However, this is not sufficient to lead to actual hardware implementations. Network scalability and topology simplicity are two critical parameters, and they are two of the reasons why modern supercomputers are often based on torus interconnection networks (e.g., Fujitsu K, IBM Sequoia). In this paper we first describe a new topology, torus-connected cycles (TCCs), realizing a combination of a torus and a ring, thus retaining interesting properties of torus networks in addition to those of hierarchical interconnection networks (HINs). Then, we formally establish the diameter of a TCC, and deduce a point-to-point routing algorithm. Next, we propose routing algorithms solving the Hamiltonian cycle problem, and, in a two dimensional TCC, the Hamiltonian path one. Correctness and complexities are formally proved. The proposed algorithms are time-optimal.

#### Słowa kluczowe

- algorithm
- routing
- Hamiltonian
- supercomputer
- parallel

- Otwarty dostęp

Decentralized Job Scheduling in the Cloud Based on a Spatially Generalized Prisoner’s Dilemma Game

Zakres stron: 737 - 751

#### Abstrakt

We present in this paper a novel distributed solution to a security-aware job scheduling problem in cloud computing infrastructures. We assume that the assignment of the available resources is governed exclusively by the specialized brokers assigned to individual users submitting their jobs to the system. The goal of this scheme is allocating a limited quantity of resources to a specific number of jobs minimizing their execution failure probability and total completion time. Our approach is based on the Pareto dominance relationship and implemented at an individual user level. To select the best scheduling strategies from the resulting Pareto frontiers and construct a global scheduling solution, we developed a decision-making mechanism based on the game-theoretic model of

#### Słowa kluczowe

- job scheduling
- multiobjective optimization
- genetic algorithm
- cellular automata

- Otwarty dostęp

The Give and Take Game: Analysis of a Resource Sharing Game

Zakres stron: 753 - 767

#### Abstrakt

We analyse

#### Słowa kluczowe

- two player game
- cooperation agreements
- social behaviours
- resource model

- Otwarty dostęp

The Non–Symmetric s –Step Lanczos Algorithm: Derivation of Efficient Recurrences and Synchronization–Reducing Variants of BiCG and QMR

Zakres stron: 769 - 785

#### Abstrakt

The Lanczos algorithm is among the most frequently used iterative techniques for computing a few dominant eigenvalues of a large sparse non-symmetric matrix. At the same time, it serves as a building block within biconjugate gradient (BiCG) and quasi-minimal residual (QMR) methods for solving large sparse non-symmetric systems of linear equations. It is well known that, when implemented on distributed-memory computers with a huge number of processes, the synchronization time spent on computing dot products increasingly limits the parallel scalability. Therefore, we propose synchronization-reducing variants of the Lanczos, as well as BiCG and QMR methods, in an attempt to mitigate these negative performance effects. These so-called

#### Słowa kluczowe

- synchronization-reducing
- -step Lanczos
- -step BiCG
- -step QMR
- efficient recurrences

- Otwarty dostęp

Ergodicity and Perturbation Bounds for Inhomogeneous Birth and Death Processes with Additional Transitions from and to the Origin

Zakres stron: 787 - 802

#### Abstrakt

Service life of many real-life systems cannot be considered infinite, and thus the systems will be eventually stopped or will break down. Some of them may be re-launched after possible maintenance under likely new initial conditions. In such systems, which are often modelled by birth and death processes, the assumption of stationarity may be too strong and performance characteristics obtained under this assumption may not make much sense. In such circumstances, time-dependent analysis is more meaningful. In this paper, transient analysis of one class of Markov processes defined on non-negative integers, specifically, inhomogeneous birth and death processes allowing special transitions from and to the origin, is carried out. Whenever the process is at the origin, transition can occur to any state, not necessarily a neighbouring one. Being in any other state, besides ordinary transitions to neighbouring states, a transition to the origin can occur. All possible transition intensities are assumed to be non-random functions of time and may depend (except for transition to the origin) on the process state. To the best of our knowledge, first ergodicity and perturbation bounds for this class of processes are obtained. Extensive numerical results are also provided.

#### Słowa kluczowe

- inhomogeneous birth and death processes
- ergodicity bounds
- perturbation bounds

- Otwarty dostęp

Observability and Controllability Analysis for Sandwich Systems with Backlash

Zakres stron: 803 - 814

#### Abstrakt

In this paper, an approach to analyze the observability and controllability of sandwich systems with backlash is proposed. In this method, a non-smooth state-space function is used to describe the sandwich systems with backlash which are also non-smooth non-linear systems. Then, a linearization method based on non-smooth optimization is proposed to derive a linearized state-space function to approximate the non-smooth sandwich systems within a bounded region around the equilibrium point that we are interested in. Afterwards, both observability and controllability matrices are constructed and the methods to analyze the observability as well as controllability of sandwich system with backlash are derived. Finally, numerical examples are presented to validate the proposed method.

#### Słowa kluczowe

- backlash
- sandwich systems
- non-smooth systems
- state-space equations
- observability
- controllability

- Otwarty dostęp

Exponential Estimates of a Class of Time–Delay Nonlinear Systems with Convex Representations

Zakres stron: 815 - 826

#### Abstrakt

This work introduces a novel approach to stability and stabilization of nonlinear systems with delayed multivariable inputs; it provides exponential estimates as well as a guaranteed cost of the system solutions. The result is based on an exact convex representation of the nonlinear system which allows a Lyapunov–Krasovskii functional to be applied in order to obtain sufficient conditions in the form of linear matrix inequalities. These are efficiently solved via convex optimization techniques. A real-time implementation of the developed approach on the twin rotor MIMO system is included.

#### Słowa kluczowe

- exponential estimates
- time delay systems
- TS model
- guaranteed cost
- convex representations

- Otwarty dostęp

Positivity and Linearization of a Class of Nonlinear Continuous–Time Systems by State Feedbacks

Zakres stron: 827 - 831

#### Abstrakt

The positivity and linearization of a class of nonlinear continuous-time system by nonlinear state feedbacks are addressed. Necessary and sufficient conditions for the positivity of the class of nonlinear systems are established. A method for linearization of nonlinear systems by nonlinear state feedbacks is presented. It is shown that by a suitable choice of the state feedback it is possible to obtain an asymptotically stable and controllable linear system, and if the closed-loop system is positive then it is unstable.

#### Słowa kluczowe

- positive
- nonlinear
- system
- linearization
- state feedback

- Otwarty dostęp

Nonlinear State–Space Predictive Control with On–Line Linearisation and State Estimation

Zakres stron: 833 - 847

#### Abstrakt

This paper describes computationally efficient model predictive control (MPC) algorithms for nonlinear dynamic systems represented by discrete-time state-space models. Two approaches are detailed: in the first one the model is successively linearised on-line and used for prediction, while in the second one a linear approximation of the future process trajectory is directly found on-line. In both the cases, as a result of linearisation, the future control policy is calculated by means of quadratic optimisation. For state estimation, the extended Kalman filter is used. The discussed MPC algorithms, although disturbance state observers are not used, are able to compensate for deterministic constant-type external and internal disturbances. In order to illustrate implementation steps and compare the efficiency of the algorithms, a polymerisation reactor benchmark system is considered. In particular, the described MPC algorithms with on-line linearisation are compared with a truly nonlinear MPC approach with nonlinear optimisation repeated at each sampling instant.

#### Słowa kluczowe

- process control
- model predictive control
- nonlinear state-space models
- extended Kalman filter
- on-line linearisation

- Otwarty dostęp

Towards Robust Predictive Fault–Tolerant Control for a Battery Assembly System

Zakres stron: 849 - 862

#### Abstrakt

The paper deals with the modeling and fault-tolerant control of a real battery assembly system which is under implementation at the RAFI GmbH company (one of the leading electronic manufacturing service providers in Germany). To model and control the battery assembly system, a unified max-plus algebra and model predictive control framework is introduced. Subsequently, the control strategy is enhanced with fault-tolerance features that increase the overall performance of the production system being considered. In particular, it enables tolerating (up to some degree) mobile robot, processing and transportation faults. The paper discusses also robustness issues, which are inevitable in real production systems. As a result, a novel robust predictive fault-tolerant strategy is developed that is applied to the battery assembly system. The last part of the paper shows illustrative examples, which clearly exhibit the performance of the proposed approach.

#### Słowa kluczowe

- max-plus algebra
- interval analysis
- battery assembly
- model predictive control
- fault-tolerant control

- Otwarty dostęp

Nonlinear System Identification with a Real–Coded Genetic Algorithm (RCGA)

Zakres stron: 863 - 875

#### Abstrakt

This paper is devoted to the blind identification problem of a special class of nonlinear systems, namely, Volterra models, using a real-coded genetic algorithm (RCGA). The model input is assumed to be a stationary Gaussian sequence or an independent identically distributed (i.i.d.) process. The order of the Volterra series is assumed to be known. The fitness function is defined as the difference between the calculated cumulant values and analytical equations in which the kernels and the input variances are considered. Simulation results and a comparative study for the proposed method and some existing techniques are given. They clearly show that the RCGA identification method performs better in terms of precision, time of convergence and simplicity of programming.

#### Słowa kluczowe

- blind nonlinear identification
- Volterra series
- higher order cumulants
- real-coded genetic algorithm

- Otwarty dostęp

A Comparative and Experimental Study on Gradient and Genetic Optimization Algorithms for Parameter Identification of Linear MIMO Models of a Drilling Vessel

Zakres stron: 877 - 893

#### Abstrakt

The paper presents algorithms for parameter identification of linear vessel models being in force for the current operating point of a ship. Advantages and disadvantages of gradient and genetic algorithms in identifying the model parameters are discussed. The study is supported by presentation of identification results for a nonlinear model of a drilling vessel.

#### Słowa kluczowe

- MIMO dynamic plant
- identification
- nonlinear system

- Otwarty dostęp

Optimization of the Maximum Likelihood Estimator for Determining the Intrinsic Dimensionality of High–Dimensional Data

Zakres stron: 895 - 913

#### Abstrakt

One of the problems in the analysis of the set of images of a moving object is to evaluate the degree of freedom of motion and the angle of rotation. Here the intrinsic dimensionality of multidimensional data, characterizing the set of images, can be used. Usually, the image may be represented by a high-dimensional point whose dimensionality depends on the number of pixels in the image. The knowledge of the intrinsic dimensionality of a data set is very useful information in exploratory data analysis, because it is possible to reduce the dimensionality of the data without losing much information. In this paper, the maximum likelihood estimator (MLE) of the intrinsic dimensionality is explored experimentally. In contrast to the previous works, the radius of a hypersphere, which covers neighbours of the analysed points, is fixed instead of the number of the nearest neighbours in the MLE. A way of choosing the radius in this method is proposed. We explore which metric—Euclidean or geodesic—must be evaluated in the MLE algorithm in order to get the true estimate of the intrinsic dimensionality. The MLE method is examined using a number of artificial and real (images) data sets.

#### Słowa kluczowe

- multidimensional data
- intrinsic dimensionality
- maximum likelihood estimator
- manifold learning methods
- image understanding

- Otwarty dostęp

Statistical Testing of Segment Homogeneity in Classification of Piecewise–Regular Objects

Zakres stron: 915 - 925

#### Abstrakt

The paper is focused on the problem of multi-class classification of composite (piecewise-regular) objects (e.g., speech signals, complex images, etc.). We propose a mathematical model of composite object representation as a sequence of independent segments. Each segment is represented as a random sample of independent identically distributed feature vectors. Based on this model and a statistical approach, we reduce the task to a problem of composite hypothesis testing of segment homogeneity. Several nearest-neighbor criteria are implemented, and for some of them the well-known special cases (e.g., the Kullback–Leibler minimum information discrimination principle, the probabilistic neural network) are highlighted. It is experimentally shown that the proposed approach improves the accuracy when compared with contemporary classifiers.

#### Słowa kluczowe

- statistical pattern recognition
- classification
- testing of segment homogeneity
- probabilistic neural network

- Otwarty dostęp

Application of Cubic Box Spline Wavelets in the Analysis of Signal Singularities

Zakres stron: 927 - 941

#### Abstrakt

In the subject literature, wavelets such as the Mexican hat (the second derivative of a Gaussian) or the quadratic box spline are commonly used for the task of singularity detection. The disadvantage of the Mexican hat, however, is its unlimited support; the disadvantage of the quadratic box spline is a phase shift introduced by the wavelet, making it difficult to locate singular points. The paper deals with the construction and properties of wavelets in the form of cubic box splines which have compact and short support and which do not introduce a phase shift. The digital filters associated with cubic box wavelets that are applied in implementing the discrete dyadic wavelet transform are defined. The filters and the

#### Słowa kluczowe

- cubic box splines
- wavelets
- dyadic wavelet transform
- singularity detection

- Otwarty dostęp

High Dynamic Range Imaging by Perceptual Logarithmic Exposure Merging

Zakres stron: 943 - 954

#### Abstrakt

In this paper we emphasize a similarity between the logarithmic type image processing (LTIP) model and the Naka–Rushton model of the human visual system (HVS). LTIP is a derivation of logarithmic image processing (LIP), which further replaces the logarithmic function with a ratio of polynomial functions. Based on this similarity, we show that it is possible to present a unifying framework for the high dynamic range (HDR) imaging problem, namely, that performing exposure merging under the LTIP model is equivalent to standard irradiance map fusion. The resulting HDR algorithm is shown to provide high quality in both subjective and objective evaluations.

#### Słowa kluczowe

- logarithmic image processing
- human visual system
- high dynamic range

- Otwarty dostęp

Neural Networks as a Tool for Georadar Data Processing

Zakres stron: 955 - 960

#### Abstrakt

In this article a new neural network based method for automatic classification of ground penetrating radar (GPR) traces is proposed. The presented approach is based on a new representation of GPR signals by polynomials approximation. The coefficients of the polynomial (the feature vector) are neural network inputs for automatic classification of a special kind of geologic structure—a sinkhole. The analysis and results show that the classifier can effectively distinguish sinkholes from other geologic structures.

#### Słowa kluczowe

- neural networks
- artificial neural networks
- ground penetrating radar
- classification of a geological structure
- sinkhole

- Otwarty dostęp

Symbolic Computing in Probabilistic and Stochastic Analysis

Zakres stron: 961 - 973

#### Abstrakt

The main aim is to present recent developments in applications of symbolic computing in probabilistic and stochastic analysis, and this is done using the example of the well-known MAPLE system. The key theoretical methods discussed are (i) analytical derivations, (ii) the classical Monte-Carlo simulation approach, (iii) the stochastic perturbation technique, as well as (iv) some semi-analytical approaches. It is demonstrated in particular how to engage the basic symbolic tools implemented in any system to derive the basic equations for the stochastic perturbation technique and how to make an efficient implementation of the semi-analytical methods using an automatic differentiation and integration provided by the computer algebra program itself. The second important illustration is probabilistic extension of the finite element and finite difference methods coded in MAPLE, showing how to solve boundary value problems with random parameters in the environment of symbolic computing. The response function method belongs to the third group, where interference of classical deterministic software with the non-linear fitting numerical techniques available in various symbolic environments is displayed. We recover in this context the probabilistic structural response in engineering systems and show how to solve partial differential equations including Gaussian randomness in their coefficients.

#### Słowa kluczowe

- probabilistic analysis
- stochastic computer methods
- symbolic computation