Numerical analysis of the patch shape effects on the performances of bonded composite repair in aircraft structures

In this study, the three-dimensional finite element method is used to analyze the effects of the patch shape on the efficiency end the durability of bonded composite repairs of aircraft structures. The stress intensity factor at the crack tip is used as fracture criteria. The determination of this factor allows us to estimate the repair efficiency. The analysis of the stresses distribution in the adhesive layer allows us to estimate the durability of the adhesion between the damaged plate and the composite patch. The obtained results show that the repair performances are closely related to the patch shape. It was demonstrated that the rectangular shape of the patch could be improved using an “H” shape of the patch. This last shape could also be improved using an arrow shape.     

An effective heuristic algorithm for the maximum satisfiability problem

Stochastic local search algorithms (SLS) have been increasingly applied to approximate solutions of the weighted maximum satisfiability problem (MAXSAT), a model for solutions of major problems in AI and combinatorial optimization. While MAXSAT instances have generally a strong intrinsic dependency between their variables, most of SLS algorithms start the search process with a random initial solution where the value of each variable is generated independently with the same uniform distribution. In this paper, we propose a new SLS algorithm for MAXSAT based on an unconventional distribution known as the Bose-Einstein distribution in quantum physics. It provides a stochastic initialization scheme to an efficient and very simple heuristic inspired by the co-evolution process of natural species and called Extremal Optimization (EO). This heuristic was introduced for finding high quality solutions to hard optimization problems such as colouring and partitioning. We examine the effectiveness of the resulting algorithm by computational experiments on a large set of test instances and compare it with some of the most powerful existing algorithms. Our results are remarkable and show that this approach is appropriate for this class of problems.     

Disbond effect on the stress intensity factor for repairing cracks with bonded composite patch

It is well known that the stress intensity factor is considerably reduced by the bonded composite repair. The finite element method is used to compute the stress intensity factor for repairing cracks with bonded composite patch taking account of the disbond. In the case of a disbond, the increase of patch thickness reduce the negative effects of disbond. The curves plotted show the concordance with the model [Thermal residual stresses in composite repairs on cracked metal structures, Ph.D. Thesis, University of British Columbia, 1998].     

Variabilité saisonnière et interannuelle de la concentration de la chlorophylle dans la zone côtière du golfe de Guinée à partir des images SeaWiFS

La variabilité saisonnière et interannuelle de la concentration de chlorophylle dans le golfe de Guinée est analysée pour la période de 1997 à 2004 en utilisant une série d'images SeaWiFS auxquelles ont été associées des images de température de surface de la mer. Les résultats montrent que la zone côtière du golfe de Guinée est caractérisée par une forte variabilité spatiale et temporelle de ses propriétés physiques et biologiques. Ainsi, seules les zones côtières de la Guinée-Bissau et de la Côte d'Ivoire et dans une moindre mesure celle du Ghana montrent un comportement classique reliant la présence de résurgences côtières à de plus fortes concentrations de chlorophylle. La zone côtière du Liberia est caractérisée par une variabilité interannuelle quasi-nulle de la chlorophylle alors que celles du Nigéria et du Gabon ne montrent aucune relation entre la chlorophylle et la température. Plusieurs processus physiques apparaissent jouer un rôle important dans la réponse biologique des régions; à savoir la position latitudinale de la Zone de Convergence Inter-Tropicale qui modifie considérablement les patrons de vent dans l'ensemble du golfe de Guinée et le El-Niño Atlantique qui modifie les masses d'eaux dans l'est équatorial.     

The Influence of the Color Model on the Performance of a CBIR System Based on Color Moments

In this paper, we evaluate the influence of color models on the performance of a CBIR system based on color moments signature. The color models considered are： RGB （red, green, blue）, HSV （hue, saturation, value） and the mixture RGB-HSV. We specifically investigate also the effect of the moment＇s degree （0： mean, 1： variance, 2： skewness） and their conjunction on the system relevance. Practically, many scenarios have been checked： three, six, nine, twelve and eighteen values extracted from moments over the three color models. For the evaluation, we use the precision recall curves on the Wang database. We also employ the utility concept in the evaluation of the ranking quality of the returned images. Results show that the combination （RGB-HSV, mean） is the best configuration. In addition, results show also that the mean （three values） is the best signature regardless of the color space and the HSV color model is the best regardless of the number of values to consider.     

Impact of preprocessing on medical data classification

The significance of the preprocessing stage in any data mining task is well known. Before attempting medical data classification, characteristics ofmedical datasets, including noise, incompleteness, and the existence of multiple and possibly irrelevant features, need to be addressed. In this paper, we show that selecting the right combination of preprocessing methods has a considerable impact on the classification potential of a dataset. The preprocessing operations considered include the discretization of numeric attributes, the selection of attribute subset(s), and the handling of missing values. The classification is performed by an ant colony optimization algorithm as a case study. Experimental results on 25 real-world medical datasets show that a significant relative improvement in predictive accuracy, exceeding 60% in some cases, is obtained.     

Disruption of Redox Homeostasis by Alterations in Nitric Oxide Synthase Activity and Tetrahydrobiopterin along with Melanoma Progression

Cutaneous melanoma emerges from the malignant transformation of melanocytes and is the most aggressive type of skin cancer. The progression can occur in different stages: radial growth phase (RGP), vertical growth phase (VGP), and metastasis. Reactive oxygen species contribute to all phases of melanomagenesis through the modulation of oncogenic signaling pathways. Tetrahydrobiopterin (BH4) is an important cofactor for NOS coupling, and an uncoupled enzyme is a source of superoxide anion (O₂^•−) rather than nitric oxide (NO), altering the redox homeostasis and contributing to melanoma progression. In the present work, we showed that the BH4 amount varies between different cell lines corresponding to distinct stages of melanoma progression; however, they all presented higher O₂^•− levels and lower NO levels compared to melanocytes. Our results showed increased NOS expression in melanoma cells, contributing to NOS uncoupling. BH4 supplementation of RGP cells, and the DAHP treatment of metastatic melanoma cells reduced cell growth. Finally, Western blot analysis indicated that both treatments act on the PI3K/AKT and MAPK pathways of these melanoma cells in different ways. Disruption of cellular redox homeostasis by the altered BH4 concentration can be explored as a therapeutic strategy according to the stage of melanoma.     

Microwave shielding performance of TiO2/Co/GF containing high structure carbon fiber alternate laminate composite

Journal of Materials Science: Materials in Electronics - Recently, the design of low cost, lightweight, and flexible electromagnetic interference (EMI) shielding fabrics mitigation is a great...     

Characterization of the Illilten earth flow (Algeria)

Bulletin of Engineering Geology and the Environment - Located at the summits of the mountains of Djurdjura, the mudflow of Illilten has damaged the two villages, Ait Aïssa Ouyahia and El-Had,...