Next Issue
Previous Issue

Table of Contents

Algorithms, Volume 2, Issue 3 (September 2009), Pages 879-1262

  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Readerexternal link to open them.
View options order results:
result details:
Displaying articles 1-17
Export citation of selected articles as:

Research

Jump to: Review

Open AccessArticle Open Problems in Universal Induction & Intelligence
Algorithms 2009, 2(3), 879-906; doi:10.3390/a2030879
Received: 8 April 2009 / Revised: 15 June 2009 / Accepted: 16 June 2009 / Published: 2 July 2009
Cited by 7 | PDF Full-text (255 KB) | HTML Full-text | XML Full-text
Abstract
Specialized intelligent systems can be found everywhere: finger print, handwriting, speech, and face recognition, spam filtering, chess and other game programs, robots, et al. This decade the first presumably complete mathematical theory of artificial intelligence based on universal induction-prediction-decision-action has been proposed. [...] Read more.
Specialized intelligent systems can be found everywhere: finger print, handwriting, speech, and face recognition, spam filtering, chess and other game programs, robots, et al. This decade the first presumably complete mathematical theory of artificial intelligence based on universal induction-prediction-decision-action has been proposed. This informationtheoretic approach solidifies the foundations of inductive inference and artificial intelligence. Getting the foundations right usually marks a significant progress and maturing of a field. The theory provides a gold standard and guidance for researchers working on intelligent algorithms. The roots of universal induction have been laid exactly half-a-century ago and the roots of universal intelligence exactly one decade ago. So it is timely to take stock of what has been achieved and what remains to be done. Since there are already good recent surveys, I describe the state-of-the-art only in passing and refer the reader to the literature. This article concentrates on the open problems in universal induction and its extension to universal intelligence. Full article
Figures

Open AccessArticle Classification of Echolocation Calls from 14 Species of Bat by Support Vector Machines and Ensembles of Neural Networks
Algorithms 2009, 2(3), 907-924; doi:10.3390/a2030907
Received: 16 June 2009 / Accepted: 1 July 2009 / Published: 9 July 2009
Cited by 21 | PDF Full-text (83 KB) | HTML Full-text | XML Full-text
Abstract
Calls from 14 species of bat were classified to genus and species using discriminant function analysis (DFA), support vector machines (SVM) and ensembles of neural networks (ENN). Both SVMs and ENNs outperformed DFA for every species while ENNs (mean identification rate – [...] Read more.
Calls from 14 species of bat were classified to genus and species using discriminant function analysis (DFA), support vector machines (SVM) and ensembles of neural networks (ENN). Both SVMs and ENNs outperformed DFA for every species while ENNs (mean identification rate – 97%) consistently outperformed SVMs (mean identification rate – 87%). Correct classification rates produced by the ENNs varied from 91% to 100%; calls from six species were correctly identified with 100% accuracy. Calls from the five species of Myotis, a genus whose species are considered difficult to distinguish acoustically, had correct identification rates that varied from 91 – 100%. Five parameters were most important for classifying calls correctly while seven others contributed little to classification performance. Full article
(This article belongs to the Special Issue Neural Networks and Sensors)
Open AccessArticle Improving the Competitive Ratio of the Online OVSF Code Assignment Problem
Algorithms 2009, 2(3), 953-972; doi:10.3390/a2030953
Received: 7 May 2009 / Revised: 14 July 2009 / Accepted: 14 July 2009 / Published: 17 July 2009
Cited by 2 | PDF Full-text (349 KB) | HTML Full-text | XML Full-text
Abstract
Online OVSF code assignment has an important application to wireless communications. Recently, this problem was formally modeled as an online problem, and performances of online algorithms have been analyzed by the competitive analysis. The previous best upper and lower bounds on the [...] Read more.
Online OVSF code assignment has an important application to wireless communications. Recently, this problem was formally modeled as an online problem, and performances of online algorithms have been analyzed by the competitive analysis. The previous best upper and lower bounds on the competitive ratio were 10 and 5/3, respectively. In this paper, we improve them to 7 and 2, respectively. We also show that our analysis for the upper bound is tight by giving an input sequence for which the competitive ratio of our algorithm is 7 ― ε for an arbitrary constant ε > 0. Full article
Figures

Open AccessArticle Automated Modelling of Evolving Discontinuities
Algorithms 2009, 2(3), 1008-1030; doi:10.3390/a2031008
Received: 7 May 2009 / Accepted: 7 August 2009 / Published: 18 August 2009
Cited by 3 | PDF Full-text (1395 KB) | HTML Full-text | XML Full-text
Abstract
The automated approximation of solutions to differential equations which involve discontinuities across evolving surfaces is addressed. Finite element technology has developed to the point where it is now possible to model evolving discontinuities independently of the underlying mesh, which is particularly useful [...] Read more.
The automated approximation of solutions to differential equations which involve discontinuities across evolving surfaces is addressed. Finite element technology has developed to the point where it is now possible to model evolving discontinuities independently of the underlying mesh, which is particularly useful in simulating failure of solids. However, the approach remains tedious to program, particularly in the case of coupled problems where a variety of finite element bases are employed and where a mixture of continuous and discontinuous fields may be used. We tackle this point by exploring the scope for employing automated code generation techniques for modelling discontinuities. Function spaces and variational forms are defined in a language that resembles mathematical notation, and computer code for modelling discontinuities is automatically generated. Principles underlying the approach are elucidated and a number of two- and three-dimensional examples for different equations are presented. Full article
(This article belongs to the Special Issue Numerical Simulation of Discontinuities in Mechanics)
Open AccessArticle Graph Compression by BFS
Algorithms 2009, 2(3), 1031-1044; doi:10.3390/a2031031
Received: 30 June 2009 / Revised: 20 August 2009 / Accepted: 21 August 2009 / Published: 25 August 2009
Cited by 24 | PDF Full-text (261 KB) | HTML Full-text | XML Full-text
Abstract
The Web Graph is a large-scale graph that does not fit in main memory, so that lossless compression methods have been proposed for it. This paper introduces a compression scheme that combines efficient storage with fast retrieval for the information in a [...] Read more.
The Web Graph is a large-scale graph that does not fit in main memory, so that lossless compression methods have been proposed for it. This paper introduces a compression scheme that combines efficient storage with fast retrieval for the information in a node. The scheme exploits the properties of the Web Graph without assuming an ordering of the URLs, so that it may be applied to more general graphs. Tests on some datasets of use achieve space savings of about 10% over existing methods. Full article
(This article belongs to the Special Issue Data Compression)
Open AccessArticle Radial Basis Function Cascade Correlation Networks
Algorithms 2009, 2(3), 1045-1068; doi:10.3390/a2031045
Received: 1 July 2009 / Revised: 31 July 2009 / Accepted: 21 August 2009 / Published: 27 August 2009
PDF Full-text (386 KB) | HTML Full-text | XML Full-text
Abstract
A cascade correlation learning architecture has been devised for the first time for radial basis function processing units. The proposed algorithm was evaluated with two synthetic data sets and two chemical data sets by comparison with six other standard classifiers. The ability [...] Read more.
A cascade correlation learning architecture has been devised for the first time for radial basis function processing units. The proposed algorithm was evaluated with two synthetic data sets and two chemical data sets by comparison with six other standard classifiers. The ability to detect a novel class and an imbalanced class were demonstrated with synthetic data. In the chemical data sets, the growth regions of Italian olive oils were identified by their fatty acid profiles; mass spectra of polychlorobiphenyl compounds were classified by chlorine number. The prediction results by bootstrap Latin partition indicate that the proposed neural network is useful for pattern recognition. Full article
(This article belongs to the Special Issue Algorithms and Molecular Sciences)
Open AccessArticle How Many Lions Are Needed to Clear a Grid?
Algorithms 2009, 2(3), 1069-1086; doi:10.3390/a2031069
Received: 30 July 2009 / Revised: 3 September 2009 / Accepted: 4 September 2009 / Published: 7 September 2009
Cited by 4 | PDF Full-text (251 KB) | HTML Full-text | XML Full-text
Abstract
We consider a pursuit-evasion problem where some lions have the task to clear a grid graph whose nodes are initially contaminated. The contamination spreads one step per time unit in each direction not blocked by a lion. A vertex is cleared from [...] Read more.
We consider a pursuit-evasion problem where some lions have the task to clear a grid graph whose nodes are initially contaminated. The contamination spreads one step per time unit in each direction not blocked by a lion. A vertex is cleared from its contamination whenever a lion moves to it. Brass et al. [5] showed that n/2 lions are not enough to clear the n x n-grid. In this paper, we consider the same problem in dimension d > 2 and prove that Θ(nd-1/√d) lions are necessary and sufficient to clear the nd-grid. Furthermore, we analyze a problem variant where the lions are also allowed to jump from grid vertices to non-adjacent grid vertices. Full article
(This article belongs to the Special Issue Computational Geometry)
Open AccessArticle Featured-Based Algorithm for the Automated Registration of Multisensorial / Multitemporal Oceanographic Satellite Imagery
Algorithms 2009, 2(3), 1087-1104; doi:10.3390/a2031087
Received: 11 June 2009 / Revised: 31 August 2009 / Accepted: 3 September 2009 / Published: 8 September 2009
Cited by 3 | PDF Full-text (709 KB) | HTML Full-text | XML Full-text
Abstract
Spatial registration of multidate or multisensorial images is required for many applications in remote sensing. Automatic image registration, which has been extensively studied in other areas of image processing, is still a complex problem in the framework of remote sensing. In this [...] Read more.
Spatial registration of multidate or multisensorial images is required for many applications in remote sensing. Automatic image registration, which has been extensively studied in other areas of image processing, is still a complex problem in the framework of remote sensing. In this work we explore an alternative strategy for a fully automatic and operational registration system capable of registering multitemporal and multisensorial remote sensing satellite images with high accuracy and avoiding the use of ground control points, exploiting the maximum reliable information in both images (coastlines not occluded by clouds), which have been coarsely geometrically corrected only using an orbital prediction model. The automatic feature-based approach is summarized as follows: i) Reference image coastline extraction; ii) Sensed image gradient energy map estimation and iii) Contour matching, mapping function estimation and transformation of the sensed images. Several experimental results for single sensor imagery (AVHRR/3) and multisensorial imagery (AVHRR/3-SeaWiFS-MODIS-ATSR) from different viewpoints and dates have verified the robustness and accuracy of the proposed automatic registration algorithm, demonstrating its capability of registering satellite images of coastal areas within one pixel. Full article
(This article belongs to the Special Issue Sensor Algorithms)
Open AccessArticle Approximate String Matching with Compressed Indexes
Algorithms 2009, 2(3), 1105-1136; doi:10.3390/a2031105
Received: 9 July 2009 / Revised: 8 September 2009 / Accepted: 9 September 2009 / Published: 10 September 2009
Cited by 15 | PDF Full-text (334 KB) | HTML Full-text | XML Full-text
Abstract
A compressed full-text self-index for a text T is a data structure requiring reduced space and able to search for patterns P in T. It can also reproduce any substring of T, thus actually replacing T. Despite the recent [...] Read more.
A compressed full-text self-index for a text T is a data structure requiring reduced space and able to search for patterns P in T. It can also reproduce any substring of T, thus actually replacing T. Despite the recent explosion of interest on compressed indexes, there has not been much progress on functionalities beyond the basic exact search. In this paper we focus on indexed approximate string matching (ASM), which is of great interest, say, in bioinformatics. We study ASM algorithms for Lempel-Ziv compressed indexes and for compressed suffix trees/arrays. Most compressed self-indexes belong to one of these classes. We start by adapting the classical method of partitioning into exact search to self-indexes, and optimize it over a representative of either class of self-index. Then, we show that a Lempel- Ziv index can be seen as an extension of the classical q-samples index. We give new insights on this type of index, which can be of independent interest, and then apply them to a Lempel- Ziv index. Finally, we improve hierarchical verification, a successful technique for sequential searching, so as to extend the matches of pattern pieces to the left or right. Most compressed suffix trees/arrays support the required bidirectionality, thus enabling the implementation of the improved technique. In turn, the improved verification largely reduces the accesses to the text, which are expensive in self-indexes. We show experimentally that our algorithms are competitive and provide useful space-time tradeoffs compared to classical indexes. Full article
(This article belongs to the Special Issue Data Compression)
Open AccessArticle Optimal 2-Coverage of a Polygonal Region in a Sensor Network
Algorithms 2009, 2(3), 1137-1154; doi:10.3390/a2031137
Received: 19 July 2009 / Accepted: 25 August 2009 / Published: 14 September 2009
Cited by 3 | PDF Full-text (1896 KB)
Abstract
Wireless sensor networks are a relatively new area where technology is developing fast and are used to solve a great diversity of problems that range from museums’ security to wildlife protection. The geometric optimisation problem solved in this paper is aimed at [...] Read more.
Wireless sensor networks are a relatively new area where technology is developing fast and are used to solve a great diversity of problems that range from museums’ security to wildlife protection. The geometric optimisation problem solved in this paper is aimed at minimising the sensors’ range so that every point on a polygonal region R is within the range of at least two sensors. Moreover, it is also shown how to minimise the sensors’ range to assure the existence of a path within R that stays as close to two sensors as possible. Full article
(This article belongs to the Special Issue Computational Geometry)
Open AccessArticle Stefan Problem through Extended Finite Elements: Review and Further Investigations
Algorithms 2009, 2(3), 1177-1220; doi:10.3390/a2031177
Received: 2 August 2009 / Revised: 16 September 2009 / Accepted: 17 September 2009 / Published: 21 September 2009
Cited by 4 | PDF Full-text (366 KB) | HTML Full-text | XML Full-text
Abstract
A general review of the extended finite element method and its application to the simulation of first-order phase transitions is provided. Detailed numerical investigations are then performed by focusing on the one-dimensional case and studying: (i) spatial and temporal discretisations, (ii) different [...] Read more.
A general review of the extended finite element method and its application to the simulation of first-order phase transitions is provided. Detailed numerical investigations are then performed by focusing on the one-dimensional case and studying: (i) spatial and temporal discretisations, (ii) different numerical techniques for the interface-condition enforcement, and (iii) different treatments for the blending elements. An embeddeddiscontinuity finite element approach is also developed and compared with the extended finite element method, so that a clearer insight of the latter can be given. Numerical examples for melting/solidification in planar, cylindrical, and spherical symmetry are presented and the results are compared with analytical solutions. Full article
(This article belongs to the Special Issue Numerical Simulation of Discontinuities in Mechanics)
Figures

Open AccessArticle Multiplication Symmetric Convolution Property for Discrete Trigonometric Transforms
Algorithms 2009, 2(3), 1221-1231; doi:10.3390/a2031221
Received: 25 June 2009 / Revised: 31 August 2009 / Accepted: 15 September 2009 / Published: 22 September 2009
PDF Full-text (303 KB) | HTML Full-text | XML Full-text
Abstract The symmetric-convolution multiplication (SCM) property of discrete trigonometric transforms (DTTs) based on unitary transform matrices is developed. Then as the reciprocity of this property, the novel multiplication symmetric-convolution (MSC) property of discrete trigonometric transforms, is developed. Full article
(This article belongs to the Special Issue Data Compression)
Open AccessArticle Classification of Sperm Whale Clicks (Physeter Macrocephalus) with Gaussian-Kernel-Based Networks
Algorithms 2009, 2(3), 1232-1247; doi:10.3390/a2031232
Received: 9 July 2009 / Revised: 31 August 2009 / Accepted: 15 September 2009 / Published: 22 September 2009
Cited by 2 | PDF Full-text (488 KB) | HTML Full-text | XML Full-text
Abstract
With the aim of classifying sperm whales, this report compares two methods that can use Gaussian functions, a radial basis function network, and support vector machines which were trained with two different approaches known as C-SVM and ν-SVM. The methods [...] Read more.
With the aim of classifying sperm whales, this report compares two methods that can use Gaussian functions, a radial basis function network, and support vector machines which were trained with two different approaches known as C-SVM and ν-SVM. The methods were tested on data recordings from seven different male sperm whales, six containing single click trains and the seventh containing a complete dive. Both types of classifiers could distinguish between the clicks of the seven different whales, but the SVM seemed to have better generalisation towards unknown data, at the cost of needing more information and slower performance. Full article
(This article belongs to the Special Issue Algorithms for Sound Localization and Sound Classification)
Figures

Open AccessArticle RFI Mitigation in Microwave Radiometry Using Wavelets
Algorithms 2009, 2(3), 1248-1262; doi:10.3390/a2031248
Received: 2 August 2009 / Revised: 2 September 2009 / Accepted: 16 September 2009 / Published: 23 September 2009
Cited by 17 | PDF Full-text (381 KB) | HTML Full-text | XML Full-text
Abstract
The performance of microwave radiometers can be seriously degraded by the presence of radio-frequency interference (RFI). Spurious signals and harmonics from lower frequency bands, spread-spectrum signals overlapping the “protected” band of operation, or out-of-band emissions not properly rejected by the pre-detection filters [...] Read more.
The performance of microwave radiometers can be seriously degraded by the presence of radio-frequency interference (RFI). Spurious signals and harmonics from lower frequency bands, spread-spectrum signals overlapping the “protected” band of operation, or out-of-band emissions not properly rejected by the pre-detection filters due to the finite rejection modify the detected power and the estimated antenna temperature from which the geophysical parameters will be retrieved. In recent years, techniques to detect the presence of RFI have been developed. They include time- and/or frequency domain analyses, or statistical analysis of the received signal which, in the absence of RFI, must be a zero-mean Gaussian process. Current mitigation techniques are mostly based on blanking in the time and/or frequency domains where RFI has been detected. However, in some geographical areas, RFI is so persistent in time that is not possible to acquire RFI-free radiometric data. In other applications such as sea surface salinity retrieval, where the sensitivity of the brightness temperature to salinity is weak, small amounts of RFI are also very difficult to detect and mitigate. In this work a wavelet-based technique is proposed to mitigate RFI (cancel RFI as much as possible). The interfering signal is estimated by using the powerful denoising capabilities of the wavelet transform. The estimated RFI signal is then subtracted from the received signal and a “cleaned” noise signal is obtained, from which the power is estimated later. The algorithm performance as a function of the threshold type, and the threshold selection method, the decomposition level, the wavelet type and the interferenceto-noise ratio is presented. Computational requirements are evaluated in terms of quantization levels, number of operations, memory requirements (sequence length). Even though they are high for today’s technology, the algorithms presented can be applied to recorded data. The results show that even RFI much larger than the noise signal can be very effectively mitigated, well below the noise level. Full article
(This article belongs to the Special Issue Sensor Algorithms)

Review

Jump to: Research

Open AccessReview Computer-Aided Diagnosis Systems for Brain Diseases in Magnetic Resonance Images
Algorithms 2009, 2(3), 925-952; doi:10.3390/a2030925
Received: 27 March 2009 / Revised: 6 June 2009 / Accepted: 2 July 2009 / Published: 10 July 2009
Cited by 19 | PDF Full-text (2489 KB) | HTML Full-text | XML Full-text
Abstract
This paper reviews the basics and recent researches of computer-aided diagnosis (CAD) systems for assisting neuroradiologists in detection of brain diseases, e.g., asymptomatic unruptured aneurysms, Alzheimer's disease, vascular dementia, and multiple sclerosis (MS), in magnetic resonance (MR) images. The CAD systems [...] Read more.
This paper reviews the basics and recent researches of computer-aided diagnosis (CAD) systems for assisting neuroradiologists in detection of brain diseases, e.g., asymptomatic unruptured aneurysms, Alzheimer's disease, vascular dementia, and multiple sclerosis (MS), in magnetic resonance (MR) images. The CAD systems consist of image feature extraction based on image processing techniques and machine learning classifiers such as linear discriminant analysis, artificial neural networks, and support vector machines. We introduce useful examples of the CAD systems in the neuroradiology, and conclude with possibilities in the future of the CAD systems for brain diseases in MR images. Full article
(This article belongs to the Special Issue Machine Learning for Medical Imaging)
Open AccessReview Advances in Artificial Neural Networks – Methodological Development and Application
Algorithms 2009, 2(3), 973-1007; doi:10.3390/algor2030973
Received: 1 July 2009 / Revised: 24 July 2009 / Accepted: 28 July 2009 / Published: 3 August 2009
Cited by 29 | PDF Full-text (622 KB) | HTML Full-text | XML Full-text
Abstract
Artificial neural networks as a major soft-computing technology have been extensively studied and applied during the last three decades. Research on backpropagation training algorithms for multilayer perceptron networks has spurred development of other neural network training algorithms for other networks such as [...] Read more.
Artificial neural networks as a major soft-computing technology have been extensively studied and applied during the last three decades. Research on backpropagation training algorithms for multilayer perceptron networks has spurred development of other neural network training algorithms for other networks such as radial basis function, recurrent network, feedback network, and unsupervised Kohonen self-organizing network. These networks, especially the multilayer perceptron network with a backpropagation training algorithm, have gained recognition in research and applications in various scientific and engineering areas. In order to accelerate the training process and overcome data over-fitting, research has been conducted to improve the backpropagation algorithm. Further, artificial neural networks have been integrated with other advanced methods such as fuzzy logic and wavelet analysis, to enhance the ability of data interpretation and modeling and to avoid subjectivity in the operation of the training algorithm. In recent years, support vector machines have emerged as a set of high-performance supervised generalized linear classifiers in parallel with artificial neural networks. A review on development history of artificial neural networks is presented and the standard architectures and algorithms of artificial neural networks are described. Furthermore, advanced artificial neural networks will be introduced with support vector machines, and limitations of ANNs will be identified. The future of artificial neural network development in tandem with support vector machines will be discussed in conjunction with further applications to food science and engineering, soil and water relationship for crop management, and decision support for precision agriculture. Along with the network structures and training algorithms, the applications of artificial neural networks will be reviewed as well, especially in the fields of agricultural and biological engineering. Full article
(This article belongs to the Special Issue Neural Networks and Sensors)
Open AccessReview Algorithm for the Analysis of Tryptophan Fluorescence Spectra and Their Correlation with Protein Structural Parameters
Algorithms 2009, 2(3), 1155-1176; doi:10.3390/a2031155
Received: 15 July 2009 / Revised: 20 August 2009 / Accepted: 10 September 2009 / Published: 16 September 2009
Cited by 7 | PDF Full-text (173 KB) | HTML Full-text | XML Full-text
Abstract
The fluorescence properties of tryptophan residues are sensitive to the microenvironment of fluorophores in proteins. Therefore, fluorescence characteristics are widely used to study structural transitions in proteins. However, the decoding of the structural information from spectroscopic data is challenging. Here we present [...] Read more.
The fluorescence properties of tryptophan residues are sensitive to the microenvironment of fluorophores in proteins. Therefore, fluorescence characteristics are widely used to study structural transitions in proteins. However, the decoding of the structural information from spectroscopic data is challenging. Here we present a review of approaches developed for the decomposition of multi-component protein tryptophan fluorescence spectra and correlation of these spectral parameters with protein structural properties. Full article
(This article belongs to the Special Issue Algorithms and Molecular Sciences)

Journal Contact

MDPI AG
Algorithms Editorial Office
St. Alban-Anlage 66, 4052 Basel, Switzerland
algorithms@mdpi.com
Tel. +41 61 683 77 34
Fax: +41 61 302 89 18
Editorial Board
Contact Details Submit to Algorithms
Back to Top