Impulse invariance-based method for the computation of fractional integral of order

This paper presents a simple and efficient method for the design of recursive digital fractional order integrator when the order of integration is a real number between 0 and 1. The proposed method is based on the impulse invariance method. First the initial value theorem is used for the selection of the initial value of the impulse response and then any of the well-established signal modeling techniques can be employed for the parameterization of the discrete impulse response by pole-zero models. For a given model order, the approximation accuracy greatly depends on the initial value selected. Illustrative examples are presented to demonstrate the effectiveness and usefulness of the proposed method.     

Parallel cycle-based branch-and-bound method for Bayesian network learning

Pattern Analysis and Applications - Bayesian networks (BNs) are one of the most commonly used models for representing uncertainty in medical diagnosis. Learning the exact structure of a BN is a...     

Indoor navigation of a non-holonomic mobile robot using a visual memory

When navigating in an unknown environment for the first time, a natural behavior consists on memorizing some key views along the performed path, in order to use these references as checkpoints for a future navigation mission. The navigation framework for wheeled mobile robots presented in this paper is based on this assumption. During a human-guided learning step, the robot performs paths which are sampled and stored as a set of ordered key images, acquired by an embedded camera. The set of these obtained visual paths is topologically organized and provides a visual memory of the environment. Given an image of one of the visual paths as a target, the robot navigation mission is defined as a concatenation of visual path subsets, called visual route. When running autonomously, the robot is controlled by a visual servoing law adapted to its nonholonomic constraint. Based on the regulation of successive homographies, this control guides the robot along the reference visual route without explicitly planning any trajectory. The proposed framework has been designed for the entire class of central catadioptric cameras (including conventional cameras). It has been validated onto two architectures. In the first one, algorithms have been implemented onto a dedicated hardware and the robot is equipped with a standard perspective camera. In the second one, they have been implemented on a standard PC and an omnidirectional camera is considered.

Reverse engineering relational databases to identify and specify basic Web services with respect to service oriented computing

Service-oriented computing (SOC) is the computing paradigm that utilizes services as a fundamental building block. Services are self-describing, open components intended to support composition of distributed applications. Currently, Web services provide a standard-based realization of SOC due to: (1) the machine-readable format (XML) of their functional and nonfunctional specifications, and (2) their messaging protocols built on top of the Internet. However, how to methodologically identify, specify, design, deploy and manage a sound and complete set of Web services to move to a service-oriented architecture (SOA) is still an issue. This paper describes a process for reverse engineering relational database applications architecture into SOA architecture, where SQL statements are insulated from the applications, factored, implemented, and registered as Web services to be discovered, selected, and reused in composing e-business solutions. The process is based on two types of design patterns: schema transformation pattern and CRUD operations pattern. First, the schema transformation pattern allows an identification of the services. Then the CRUD operations pattern allows a specification of the abstract part of the identified services, namely their port types. This process is implemented as a CASE tool, which assists analysts specifying services that implement common, reusable, basic business logic and data manipulation.

Electrical and optical characterisation of CuInS2 crystals and polycrystalline coevaporated thin films

Single crystals CuInS₂ were grown by iodine vapour transport method, whereas polycrystalline thin films were obtained by coevaporation technique from three sources. The temperature dependence of the hole mobility in valence band is analysed by taking into account contributions from several scattering mechanisms of the charge carriers. To account for the temperature dependant conductivity of polycrystalline CuInS₂ thin films, grainboundary conduction process was suggested. In the low temperature region, we interpret the data in terms of the Mott law and the analysis is very consistent with the variable range hopping. However, thermionic emission is predominant at high temperatures. Photoluminescence measurements have been performed on CuInS₂ crystals and the analysis has revealed that the emission is mainly due to free-to-bound and donor–acceptor pair transitions. The band gap of that compound is derived from the excitonic emission line at 1.53 eV.     

Segmentation and recognition system for unknown-length handwritten digit strings

The segmentation of handwritten digit strings into isolated digits remains a challenging task. The difficulty for recognizing handwritten digit strings is related to several factors such as sloping, overlapping, connecting and unknown length of the digit string. Hence, this paper aims to propose a segmentation and recognition system for unknown-length handwritten digit strings by combining several explicit segmentation methods depending on the configuration link between digits. Three segmentation methods are combined based on histogram of the vertical projection, the contour analysis and the sliding window Radon transform. A recognition and verification module based on support vector machine classifiers allows analyzing and deciding the rejection or acceptance each segmented digit image. Moreover, various submodules are included leading to enhance the robustness of the proposed system. Experimental results conducted on the benchmark dataset show that the proposed system is effective for segmenting handwritten digit strings without prior knowledge of their length comparatively to the state of the art.     

Robust feature points extraction for image registration based on the nonsubsampled contourlet transform

In this letter, a new feature points extraction method based on the nonsubsampled contourlet transform (NSCT) is proposed for image registration. The primary motivation of this work is to determine the effectiveness of the NSCT transform in extracting feature points for image registration. Preliminary experimental results show that the registration accuracy and robustness of the proposed algorithm is acceptable and very promising, and confirm the success of the proposed NSCT-based feature points extraction approach.     

Friction and wear properties of MoAlB against Al2O3 and 100Cr6 steel counterparts

The present work investigates, for the first time, the dry sliding friction and wear behaviour of fully dense, predominantly single-phase MoAlB ceramics against alumina (Al₂O₃) and 100Cr6 steel counterparts. Against Al₂O₃, the friction coefficient (μ) increased with increasing load and the wear was highly dependent on the load applied. A transition from mild wear under 1 N and 4 N to severe wear at 10 N occurred. Scanning electron microscopy revealed that abrasion is the dominant wear mechanism. Against steel, μ decreased with increasing load and the wear rates were low, under all applied loads. The morphologies of the worn surfaces against steel were characterized by the appearance of a rippled layers. Atomic force microscopy and Raman spectroscopy were used to propose a possible formation mechanism of such patterns. X-ray photoelectron spectroscopy revealed the rippled surfaces to be composed of Fe₂O₃ and a mixture of MoO_x.