Showing papers by "Tunis University published in 2012"
TL;DR: In this paper, the authors introduce a new concept of α - ψ -contractive type mappings and establish fixed point theorems for such mappings in complete metric spaces.
Abstract: In this paper, we introduce a new concept of α – ψ -contractive type mappings and establish fixed point theorems for such mappings in complete metric spaces. Starting from the Banach contraction principle, the presented theorems extend, generalize and improve many existing results in the literature. Moreover, some examples and applications to ordinary differential equations are given here to illustrate the usability of the obtained results.
749 citations
TL;DR: In this article, the authors investigated the relationship between carbon dioxide emissions, energy consumption, and real GDP for 12 Middle East and North African Countries (MENA) over the period 1981-2005.
676 citations
TL;DR: In this paper, a sensor fault detection and isolation (FDI) algorithm for electrical systems is proposed, keeping system performances unchanged under certain faulty sensor conditions when reconfigurations are available.
Abstract: This paper focuses on sensor fault detection and isolation (FDI) for electrical systems. A new, easy and fast FDI algorithm is proposed, keeping system performances unchanged under certain faulty sensor conditions when reconfigurations are available. The proposed FDI algorithm is derived from a parity space approach and is based on temporal redundancies. It is insensitive to parameter variations since no model knowledge is required. Also, it is available for a large class of electrical systems such as single- or three-phase power converters, dc or ac electrical drives, etc. Moreover, the residual threshold used for FDI is accurately defined and is suitable for the whole operating range. Simulations results are presented to illustrate the good functionality of theoretical developments. Numerous experimental results are also shown to validate the effectiveness of the proposed FDI algorithm and to highlight its advantages for the control of electrical systems.
171 citations
TL;DR: In this paper, the authors investigated the effects of oil price shocks on stock market returns in emerging countries and found that oil price risk is significantly priced in emerging markets, and that the oil impact is asymmetric with respect to market phases.
156 citations
TL;DR: Coupled fixed point theorems for mixed monotone mappings satisfying nonlinear contraction involving two altering distance functions in ordered partial metric spaces are established.
141 citations
TL;DR: This review presents an interesting field for application for MRM concept, i.e. the microbial communities associated with arthropods and nematodes, and prospect further studies aimed to verify, improve and apply MRM by using the insect–symbiont ecosystem as a model.
Abstract: Microorganisms establish with their animal hosts close interactions. They are involved in many aspects of the host life, physiology and evolution, including nutrition, reproduction, immune homeostasis, defence and speciation. Thus, the manipulation and the exploitation the microbiota could result in important practical applications for the development of strategies for the management of insect-related problems. This approach, defined as Microbial Resource Management (MRM), has been applied successfully in various environments and ecosystems, as wastewater treatments, prebiotics in humans, anaerobic digestion and so on. MRM foresees the proper management of the microbial resource present in a given ecosystem in order to solve practical problems through the use of microorganisms. In this review we present an interesting field for application for MRM concept, i.e. the microbial communities associated with arthropods and nematodes. Several examples related to this field of applications are presented. Insect microbiota can be manipulated: (i) to control insect pests for agriculture; (ii) to control pathogens transmitted by insects to humans, animals and plants; (iii) to protect beneficial insects from diseases and stresses. Besides, we prospect further studies aimed to verify, improve and apply MRM by using the insectsymbiont ecosystem as a model.
118 citations
TL;DR: The prevalence of COPD in this region seems to be lower than that reported in industrialised countries, and under-reporting and risk factors other than smoking may contribute to this difference.
111 citations
TL;DR: In this article, the authors prove the local well-posedness of three-dimensional incompressible inhomogeneous Navier-Stokes equations with initial data in the critical Besov spaces, without assumptions of small density variation.
Abstract: We prove the local wellposedness of three-dimensional incompressible inhomogeneous Navier–Stokes equations with initial data in the critical Besov spaces, without assumptions of small density variation. Furthermore, if the initial velocity field is small enough in the critical Besov space \({\dot B^{1/2}_{2,1}(\mathbb{R}^3)}\) , this system has a unique global solution.
107 citations
TL;DR: In this article, the elastic moduli obtained through ultrasonic wave propagation method, thermal conductivity, porosity and the mechanical strength in flexure and compression were compared to those of an ordinary cement concrete.
101 citations
TL;DR: The objective of this investigation was to analyse the carriage rate of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli in faecal samples of healthy humans in Tunisia and to characterise the recovered isolates.
Abstract: The objective of this investigation was to analyse the carriage rate of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli in faecal samples of healthy humans in Tunisia and to characterise the recovered isolates. One hundred and fifty samples were inoculated on MacConkey agar plates supplemented with cefotaxime (2 μg/ml) for ESBL-positive E. coli recovery. The characterisation of ESBL genes and their genetic environments, detection of associated resistance genes, multilocus sequence typing (MLST) and phylogroup typing were performed by polymerase chain reaction (PCR) and sequencing. The presence and characterisation of integrons and virulence factors were studied by PCR and sequencing. ESBL-positive E. coli isolates were detected in 11 of 150 faecal samples (7.3%) and one isolate/sample was further characterised. These isolates contained the blaCTX-M-1 (ten isolates) and blaTEM-52c genes (one isolate). The ISEcp1 (truncated by IS10 in four strains) and orf477 sequences were found upstream and downstream, respectively, of all blaCTX-M-1 genes. Seven different sequence types (STs) and three phylogroups were identified among CTX-M-1-producing isolates [ST/phylogroup (number of isolates)]: ST58/B1 (3), ST57/D (2), ST165/A (1), ST155/B1 (1), ST10/A (1), ST398/A (1) and ST48/B1 (1). The TEM-52-producing isolate was typed as ST219 and phylogroup B2. Six ESBL isolates contained class 1 integrons with the gene cassettes dfrA17-aadA5 (five isolates) and dfrA1-aadA1 (one). Healthy humans in the studied country could be a reservoir of CTX-M-1-producing E. coli.
98 citations
TL;DR: In this paper, the authors studied coupled coincidence and coupled common fixed point theorems in ordered generalized metric spaces for nonlinear contraction condition related to a pair of altering distance functions.
Abstract: In this article, we study coupled coincidence and coupled common fixed point theorems in ordered generalized metric spaces for nonlinear contraction condition related to a pair of altering distance functions. Our results generalize and modify several comparable results in the literature. 2000 MSC: 54H25; 47H10; 54E50.
TL;DR: Because BDI is a rare event, it is difficult to generate evidence for prevention, diagnosis, or the management of BDI from clinical studies, Nevertheless, an international expert panel has formulated recommendations.
Abstract: Background
Laparoscopic cholecystectomy is one of the most common surgical procedures in Europe (and the world) and has become the standard procedure for the management of symptomatic cholelithiasis or acute cholecystitis in patients without specific contraindications. Bile duct injuries (BDI) are rare but serious complications that can occur during a laparoscopic cholecystectomy. Prevention and management of BDI has given rise to a host of publications but very few recommendations, especially in Europe.
TL;DR: In this paper, the authors developed a mathematical model to study the opportunity provided by the extended warranty for the buyer as well as for the manufacturer, and the total average cost incurred by each side during the product's life cycle is expressed in order to determine the maximum extra cost the consumer should pay and the minimum price at which the manufacturer should sell the Extended Warranty.
TL;DR: In this article, the stability analysis of a water-saturated rock slope by means of the kinematic approach of limit analysis theory is presented, with particular emphasis on the effects of pore water pressure on the global stability of geotechnical structures.
TL;DR: Nares of healthy sheep could be a reservoir of PVL-positive community-associated-MRSA and also of TSST-positive S. aureus isolates, with potential implications in public health.
13 Jun 2012
TL;DR: The results of the DBSCAN-GM method show that it is efficient even for large data sets especially data with large dimension and capable to handle noises, contrary to partitioning algorithms such as K-means or Gaussian-Means.
Abstract: Clustering is one of the most useful methods of intelligent engineering domain, in which a set of similar objects are categorized into clusters. Almost all of the well-known clustering algorithms require input parameters which are hard to determine but have a significant influence on the clustering result. Furthermore, the majority is not robust enough towards noisy data. This paper presents an efficient and effective clustering technique, named DBSCAN-GM that combines Gaussian-Means and DBSCAN algorithms. The idea of DBSCAN-GM is to cover the limitations of DBSCAN, by exploring the benefits of Gaussian-Means: it runs Gaussian-Means to generate small clusters with determined cluster centers, in purpose to estimate the values of DBSAN's parameters. The results of our method show that it is efficient even for large data sets especially data with large dimension and capable to handle noises, contrary to partitioning algorithms such as K-Means or Gaussian-Means. Additionally, DBSCAN-GM does not necessitate any priori information, in contrast to the density clustering DBSCAN obliging two input parameters which are hard to guess, namely Eps (the radius that bounds the neighborhood region of an object) and MinP ts (the minimum number of objects that must exist in the objects neighborhood region). Simulative experiments are carried out on a variety of datasets, which highlight the DBSCAN-GM's effectiveness and cluster validity to check the good quality of clustering results.
TL;DR: In this paper, a new approach based on a dynamic coherence function (DCF) was applied to study the interactions bringing together different real estate markets (the securitized market, the commercial market and the residential market).
TL;DR: In this article, the authors investigated the effect of different TiO 2 compositions on the stability of tellurite glass with different FTIR results and showed that the Te-O-Te inter-chain linkages are progressively substituted by stronger TeO-Ti bridges that are at the origin of the increase of the thermal stability of the glass.
TL;DR: The concept of fixed point of N-order for mappings F:X^N->X, where N>=2 and X is an ordered set endowed with a metric d, is introduced.
Abstract: We introduce the concept of fixed point of N-order for mappings F:X^N->X, where N>=2 and X is an ordered set endowed with a metric d. We establish fixed point results for such mappings satisfying a given contractive condition. Presented theorems extend and generalize the coupled fixed point results of Bhaskar and Lakshmikantham [T. Gnana Bhaskar, V. Lakshmikantham, Fixed point theorems in partially ordered metric spaces and applications, Nonlinear Anal. 65 (7) (2006) 1379-1393] and the tripled fixed point results of Berinde and Borcut [V. Berinde, M. Borcut, Tripled fixed point theorems for contractive type mappings in partially ordered metric spaces, Nonlinear Anal. 74 (2011) 4889-4897]. Some applications to integral equations and to matrix equations are also presented in this work.
TL;DR: This work introduces the robust plug and play chaotic circuit designed to be easily realized using standard components in a rigorous, fast and inexpensive way and finds that experimental results display periodicity, bifurcations and chaos that match with high accuracy the corresponding theoretical values.
Abstract: Long run growth of the US national economic system, for example, reveals a strong oscillatory behavior due to complex interactions of aggregates. However, modelizations of such dynamics often assume that instability is the outcome of linear and additive cycles determined by exogenous shocks. In this work, a modelization of endogenous nonlinear and inseparable cycles is retained to explain the highly complex business cycle phenomenon. Bouali’s system is built to this scope. Its numerical simulations exhibit a rich repertoire of nonlinear dynamical phenomena, but this paper introduces its electronic implementation. The robust plug and play chaotic circuit is designed to be easily realized using standard components in a rigorous, fast and inexpensive way. We find that experimental results display periodicity, bifurcations and chaos that match with high accuracy the corresponding theoretical values.
TL;DR: E. coli isolates of the CTX-M-1 and CMY-2 types that potentially could be transmitted to humans via the food chain or by direct contact are studied in food-producing animals at the farm level in Tunisia and recovered isolates were characterized for the presence of other resistance genes and integrons.
Abstract: The prevalence of extended-spectrum beta-lactamase (ESBL)– and plasmidic AmpC–beta-lactamase (pAmpC-BL)–producing Escherichia coli isolates has been studied in food-producing animals at the farm level in Tunisia, and recovered isolates were characterized for the presence of other resistance genes and integrons. Eighty fecal samples of food-producing animals (23 sheep, 22 chickens, 22 cattle, six horses, five rabbits, and two dromedaries) were obtained from 35 different farms in Tunisia in 2011. Samples were inoculated onto MacConkey agar plates supplemented with cefotaxime (2 mg/L) for cefotaxime-resistant (CTXR) E. coli recovery. CTXR E. coli isolates were detected in 11 out of 80 samples (13.8%), and one isolate per sample was further characterized (10 from chickens and one from a dromedary). The 11 CTXR isolates were distributed into phylogroups: B1 (five isolates), A (two isolates), D (three isolates), and B2 (one isolate). The following beta-lactamase genes were detected: blaCTX-M-1 (seven i...
TL;DR: The findings suggest that vitamin D is an important promoter of T cell regulation in vivo in young asthmatics, and even in a southern Mediterranean country, hypovitaminosis D is frequent in children with asthma.
Abstract: Background
Vitamin D exerts profound effects on both adaptive and innate immune functions involved in the development and course of autoimmune and inflammatory diseases. As the incidence of vitamin D insufficiency is surprisingly high in the general population, experimental studies have started to investigate whether vitamin D levels (measured as serum 25 hydroxy vitamin D-25[OH]D) are correlated with immune cells and clinical parameters.
TL;DR: Different experiences of menopause are linked to social class and to the degree of male domination, and the distribution of types of experiences according to social but not geographic or national factors indicates that the differences in symptoms are not biologically determined.
TL;DR: The findings suggest that the short questionnaire of fatigue could be a practical and a sensitive tool for monitoring changes in training load and strain in team-sport athletes.
Abstract: Purpose: Trainers and physical fitness coaches’ need a useful tool to assess training loads to avoid overtraining. However, perceived scales or questionnaires were required. Therefore, the purpose of this study was to assess whether a short 8-item questionnaire of fatigue could be a useful tool for monitoring changes in perceived training load and strain among elite rugby Sevens (7s) players during preparation for a major competition. Methods: Sixteen elite rugby 7s players completed an 8-week training program composed of 6-week intense training (IT) and 2-week reduced training (RT). They were tested before (T0), after the IT (T1) and after the RT (T2). The quantification of the perceived training load and strain were performed by the session-RPE (rating of perceived exertion) method and concomitantly the 8-item questionnaire of fatigue was administered. Results: Training load (TL) and strain (TS) and total score of fatigue (TSF from the 8-item questionnaire) increased during IT and decreased during RT. Simultaneously, physical performances decreased during IT and were improved after LT. The changes in TL, TS and TSF correlated significantly over the training period (r=0.63-0.83). Conclusions: These findings suggest that the short questionnaire of fatigue could be a practical and a sensitive tool for monitoring changes in training load and strain in team-sport athletes. Accordingly, the simultaneous use of the short questionnaire of fatigue along with the session-RPE method for perceived changes in training load and strain during training could provide additional information on the athletes’ status, allowing coaches to prevent eventual states of overreaching or overtraining.
TL;DR: In this paper, the Boubaker Polynomials Expansion Scheme (BPES) was applied to obtain analytical-numerical solutions to two separate Lane-Emden problems, the first kind describing the gravitational potential of a self-gravitating spherically symmetric polytropic gas and the second kind describing isothermal gas spheres embedded in a pressurized medium at the maximum possible mass allowing for hydrostatic equilibrium.
TL;DR: An integrated approach for the joint optimization of production-inventory control and preventive maintenance policy for a manufacturing cell comprising an imperfect process where the ‘in-control’ period has a general deterioration distribution is dealt with.
TL;DR: In this paper, the Lipschitz constant of the nonlinear term in the system and the disturbance attenuation level are maximized simultaneously through convex multiobjective optimization.
Abstract: This paper presents a new approach for the design of robust H∞ sliding mode observer (SMO) for a class of Lipschitz nonlinear systems where both faults and uncertainties are considered. A sufficient condition using linear matrix inequality (LMI) optimization is derived to guarantee the asymptotically stability of the estimation error dynamics and compute the observer gains. A fault estimation scheme is presented where the estimation signal can approximate the fault to some degree of accuracy. Our design approach has some advantages. The Lipschitz constant of the nonlinear term in the system and the disturbance attenuation level are maximized simultaneously through convex multiobjective optimization. For this reason, the Lipschitz constant is suitable to a large class of uncertain nonlinear systems. Moreover, the fault estimation is much more robust against disturbances and nonlinear uncertainty and can preserve the fault signal shape effectively. Finally, a simulation study on a robotic arm system is presented to show the effectiveness of this approach.
TL;DR: In this paper, a numerical approach was developed to predict the near surface residual stresses and plastic strain resulting from turning in orthogonal cutting configuration using the commercial finite element code Abaqus-Explicit.
TL;DR: In this paper, the bending fatigue resistance of the nitrided 42CrMo4 steel improvement by shot-peening is analyzed by methods of fracture mechanisms, and the gains, expressed in term of endurance limit, brought by these treatments are established by three-points bending fatigue tests and discussed in relation to the residual stresses evolution under the cyclic loading conditions.
TL;DR: A new color image segmentation method, based on multilevel thresholding and data fusion techniques which aim at combining different data sources associated to the same color image in order to increase the information quality and to get a more reliable and accurate segmentation result.
Abstract: In this article, we present a new color image segmentation method, based on multilevel thresholding and data fusion techniques which aim at combining different data sources associated to the same color image in order to increase the information quality and to get a more reliable and accurate segmentation result. The proposed segmentation approach is conceptually different and explores a new strategy. In fact, instead of considering only one image for each application, our technique consists in combining many realizations of the same image, together, in order to increase the information quality and to get an optimal segmented image. For segmentation, we proceed in two steps. In the first step, we begin by identifying the most significant peaks of the histogram. For this purpose, an optimal multi-level thresholding is used based on the two-stage Otsu optimization approach. In the second step, the evidence theory is employed to merge several images represented in different color spaces, in order to get a final reliable and accurate segmentation result. The notion of mass functions, in the Dempster-Shafer (DS) evidence theory, is linked to the Gaussian distribution, and the final segmentation is achieved, on an input image, expressed in different color spaces, by using the DS combination rule and decision. The algorithm is demonstrated through the segmentation of medical color images. The classification accuracy of the proposed method is evaluated and a comparative study versus existing techniques is presented. The experiments were conducted on an extensive set of color images. Satisfactory segmentation results have been obtained showing the effectiveness and superiority of the proposed method.