Stable feature selection based on instance learning,redundancy elimination and efficient subsets fusion

Neural Computing and Applications - Feature selection is frequently used as a preprocessing step to data mining and is attracting growing attention due to the increasing amounts of data emerging...     

Consistency requirements in business process modeling: a thorough overview

Software and Systems Modeling - The field of business process modeling has been beset by inter-model consistency problems which are mainly due to the existence of multiple variants of the same...     

Stereoscopic video watermarking: a comparative study

Despite the sound theoretical, methodological, and experimental background inherited from 2D video, the stereoscopic video watermarking imposed itself as an open research topic. Paving the way towards practical deployment of such copyright protection mechanisms, the present paper is structured as a comparative study on the main classes of 2D watermarking methods (spread spectrum, side information, hybrid) and on their related optimal stereoscopic insertion domains (view or disparity based). The performances are evaluated in terms of transparency, robustness, and computational cost. First, the watermarked content transparency is assessed by both subjective protocols (according to ITU-R BT 500-12 and BT 1438 recommendations) and objective quality measures (five metrics based on differences between pixels and on correlation). Secondly, the robustness is objectively expressed by means of the watermark detection bit error rate against several classes of attacks, such as linear and nonlinear filtering, compression, and geometric transformations. Thirdly, the computational cost is estimated for each processing step involved in the watermarking chain. All the quantitative results are obtained out of processing two corpora of stereoscopic visual content: (1) the 3DLive corpus, summing up about 2 h of 3D TV content captured by French professionals, and (2) the MPEG 3D video reference corpus, composed of 17 min provided by both academic communities and industrials. It was thus established that for a fixed size of the mark, a hybrid watermark insertion performed into a new disparity map representation is the only solution jointly featuring imperceptibility (according to the subjective tests), robustness against the three classes of attacks, and nonprohibitive computational cost.     

A fault tolerant tracking control for a quadrotor UAV subject to simultaneous actuator faults and exogenous disturbances

ABSTRACT

An observer-based robust adaptive Fault Tolerant Control approach is proposed in this paper to tackle the problem of trajectory tracking for a quadrotor unmanned aerial vehicle (UAV) suffering simultaneous actuator faults, exogenous disturbances and actuator saturation limits. An adaptive fuzzy state observer is proposed to estimate the immeasurable states by using fuzzy logic systems to approximate the unknown nonlinear functions of the uncertain system model. Based on the estimates of the fuzzy observer, an Integral Terminal Sliding Mode Controller that guarantees finite time convergence of the states to a small neighbourhood of zero, even under impaired conditions, is developed. Stability analysis was carried over using the Lyapunov method. The proposed approach was implemented to a quadrotor UAV and its performance was assessed under nominal conditions, and by subjecting the quadrotor to disturbances, simultaneously occurring actuator faults and input saturation limits. Excellent tracking performance and robustness even under worst-case scenarios are among the positive features of the proposed approach.     

Finite element analysis of countersinking process

In this work, countersinking which is the manufacturing operation used to enlarge the side of an existing hole is studied. A finite element model is built in order to get the normalized dimensions of the countersink. The obtained countersink allows to the head of screws or rivets to sit flush with the surface with the surrounding material. A case study is detailed in order to show the effect of the pertinent parameters. The procedure is summarized by the construction of a single diagram in which the coupled effects of the different parameters are shown. A fully automatic procedure can be built in the light of this analysis.     

Method for reliable isolation of Lactobacillus sakei strains originating from Tunisian seafood and meat products

In Tunisia, several food products derived from meat or seafood are naturally processed, without any addition of bacterial starters. Such fermented, dried-cured, salted, or marinated products, as well as the raw meat or fish may thus provide a source to isolate the natural microflora colonizing such environments. We isolated lactic acid bacteria from a representative range of flesh-foods sold or manufactured in different parts of Tunisia, and selectively searched for Lactobacillus sakei, a lactic acid bacterium potentially useful as starter or protective culture. Eighty six (86) strains were isolated from various seafood (anchovy, sardine, sole, mullet, and octopus), or meat (pork, veal, beef, sheep, chicken, and turkey) products that were either fresh, or transformed by different traditional processes. Several methods were used in order to develop a rapid and reliable protocol for the direct identification of L. sakei. Amplified ribosomal DNA restriction analysis (ARDRA) classified the various isolates into 9 distinct groups. Search for the presence of the L. sakei specific katA gene indicated that all positive isolates were grouped in the same ARDRA group. Sequencing of 16S rDNA confirmed those isolates as L. sakei. Those 22 different L. sakei strains represent 25.6% of the total isolates, while other isolates found in the different ARDRA groups were tentatively ascribed to Lactobacillus plantarum, Lactococcus lactis/garviae, Enterococcus avium, Streptococcus parauberis, Hafnia alvei, Pediococcus pentosaceus, and Lactobacillus curvatus through 16S rDNA sequencing. A fast and reliable method to isolate and discriminate L. sakei from complex food environments is proposed.