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Purpose This paper provides an effective study to detect and locate the inter-turn short-circuit faults (ITSC) in a three-phase induction motor (IM) using the support vector machine (SVM). The characteristics extracted from the analysis of the phase shifts between the stator currents and their corresponding voltages are used as inputs to train the SVM. The latter automatically decides on the IM state, either a healthy motor or a short-circuit fault on one of its three phases. Design/methodology/approach To evaluate the performance of the SVM, three supervised algorithms of machine learning, namely, multi-layer perceptron neural networks (MLPNNs), radial basis function neural networks (RBFNNs) and extreme learning machine (ELM) are used along with the SVM in this study. Thus, all classifiers (SVM, MLPNN, RBFNN and ELM) are tested and the results are compared with the same data set. Findings The obtained results showed that the SVM outperforms MLPNN, RBFNNs and ELM to diagnose the health status of the IM. Especially, this technique (SVM) provides an excellent performance because it is able to detect a fault of two short-circuited turns (early detection) when the IM is operating under a low load. Originality/value The original of this work is to use the SVM algorithm based on the phase shift between the stator currents and their voltages as inputs to detect and locate the ITSC fault.

The present work is conducted for studying the natural convection in a circular enclosure that contains three equal-sized cylinders in tandem arrangement. The outer cylinder has a cold surface and the enclosure internals have hot surfaces. The relation between the density of the fluid and the temperature is treated by the Boussinesq approximation. The fluid used for the investigation is Newtonian and incompressible. The results present the roles of some non-dimensional parameters (Rayleigh (Ra) and Prandtl (Pr) numbers) on the buoyancy-driven flow and the convective heat transfer. The obtained results revealed an intensification of the v-velocity component in the annular space and an enhancement in the heat transfer rates with the rise of Rayleigh number.

Hybrid systems are complex systems where a software controller interacts with a physical environment, usually named a plant, through sensors and actuators. The specification and design of such systems usually rely on the description of both continuous and discrete behaviours. From complex embedded systems to autonomous vehicles, these systems became quite common, including in safety critical domains. However, their formal verification and validation as a whole is still a challenge. To address this challenge, this article contributes to the definition of a reusable and tool supported formal framework handling the design and verification of hybrid system models that integrate both discrete (the controller part) and continuous (the plant part) behaviours. This framework includes the development of a process for defining a class of basic theories and developing domain theories and then the use of these theories to develop a generic model and system-specific models. To realise this framework, we present a formal proof tool chain, based on the Event-B correct-by-construction method and its integrated development environment Rodin, to develop a set of theories, a generic model, proof processes, and the required properties for designing hybrid systems in Event-B. Our approach relies on hybrid automata as basic models for such systems. Discrete and continuous variables model system states and behaviours are given using discrete state changes and continuous evolution following a differential equation. The proposed approach is based on refinement and proof using the Event-B method and the Rodin toolset. Two case studies borrowed from the literature are used to illustrate our approach. An assessment of the proposed approach is provided for evaluating its extensibility, effectiveness, scalability, and usability.

Bioremediation is among the most basic and reliable way to eliminate pollutants by transforming the toxic petroleum components into less toxic metabolites. In order to compare the change of bacteri...

System substitution can be defined as the capability to replace a system by another one that preserves the specification of the original one. It may be used for reconfiguration in various situations like failure management, maintenance or Web services compensation. When substituting a system at runtime, a key requirement is to correctly restore the state of the substituted one. This paper proposes a correct-by-construction generic model for system reconfiguration defined using formal methods, based on a system substitution operator we define. This model provides a formal semantics for Web services compensation seen as a particular case of system substitution. The originality of the proposed approach relies on the fact that it is defined on a family of systems and it provides instantiation mechanisms for particular systems using witnesses. Systems are seen as state transition systems, and the system substitution operation is formalized as a state recovery operation. This proposal is supported by a formal model relying on stepwise refinements and proofs. A generic formal model is developed using Event-B. Specific systems instantiate this generic model using a particular use of refinement based on the definition of witnesses for existential proof obligations. A specific case study, borrowed from an electronic commerce application, is used as a particular instance of the defined generic model.

The approach presented in this paper addresses the machining process optimization problem through realistic modeling of multi-pass operations. It is designed to determine, at the same time, the number of passes and the cutting conditions of each. This is a multi-objective optimization model that simultaneously minimizes the production rate and the used tool life under all technological and organizational constraints based on fundamental cutting laws. The posterior selection of a solution is made from a Pareto front generated by a multi-objective particle swarm algorithm based on the concept of dynamic neighborhood. In an example application which consists in determining the cutting conditions for a turning operation, using this approach has provided a rich set of Pareto optimal solutions that represents all possible compromises. This set offers, normally, all the information needed for the optimal selection of cutting conditions. Despite the complexity of treated problem, the analysis of the obtained results demonstrates the effectiveness of the developed approach. Thus, it presents the possibility of using this approach for other problems from industry.

Solar energy is the most renewable energy widely spread on the globe with several applications such as power generation and thermal comfort amelioration inside buildings. In the present study, one of the multiple solar energy techniques is discussed. New, simple and low-cost solar chimney (SC) made of polyvinyl chloride (PVC) tube with internal PVC obstacles was investigated experimentally. Heat transfer of air passing through the new device were studied and results show SC ability of increasing air temperature from 25°C to 48°C and reducing relative humidity from 40% to 10%. Internal PVC obstacles were responsible for increasing outlet air temperature by more than 7°C in 63% of compared cases with simple PVC tube SC without internal obstacles. In the last part of the study, the new system was compared with three conventional square glazed SCs found in the literature. The new system outlet’s air temperature was higher by 12°C than the first two models and 2°C with the third model, which increase the kinetic energy of air leaving the building and increase the internal airflow, ameliorating the air quality and reducing the age of air inside the dwellings. Obtained results encourage building designers and people to widely use SCs.

The aim of this paper is to investigate the impact of Brexit on the dependence between European financial markets. We use the Diebold and Yilmaz (2009, 2012) approach to better map the relationship between the three main European markets and we propose an Optimal portfolio weighting to gain insights into the portfolio design dynamics in the period between 2013 and 2019, in particular any changes due to uncertainty surrounding Brexit. First, the findings show that between September 2015 and September 2016, the high level of volatility and spillover confirms the strong degree of market integration, with uncertainty surrounding the referendum outcome having a clear impact on the three main European markets. Second, the direction of spillover in the pre-Brexit period was from the UK market to the French and German markets in anticipation of uncertainty regarding the outcome of the referendum and the period immediately following it. Third, only the conditional correlation between the pair (CAC40-FTSE100) is characterized by an asymmetric effect.

Geometrical configurations of tubes and vortex generators have been optimized in order to improve the hydrothermal characteristics of fin-and-tube heat exchangers. The work is divided into two part...

This manuscript reports computational fluid dynamic simulations of turbulent air forced-convection and friction loss in a horizontal-duct air-heat exchanger. Epsilon-shaped baffles are inserted on the bottom wall of the channel to augment its thermal efficiency. The working fluid is flowing under Reynolds numbers (Re) within the range [17,000–32,000]. The presence of the epsilon-shaped vortex generator (VG) in the duct heat exchanger forced a considerable increase of the convective thermal transfer in the domain, but it caused also significant friction losses. For all Re numbers used, the heat transfer rate in epsilon-shaped baffle case was upper than that in no-baffle case, which indicates that the epsilon-baffled exchanger is more efficient than the simple exchanger with no VG.

This paper presents a formal development approach for designing interactive applications using a correct-by-construction approach. In this work, we propose a refinement strategy using model-view-controller (MVC) to structure and design Event-B formal models of the interactive application. The proposed MVC-based refinement strategy facilitates the development of an abstract model and a series of refined models by introducing the possible modes, controller’s behaviour and visual components of the interactive application while preserving the required interaction-related safety properties. To demonstrate the effectiveness, scalability, reliability and feasibility of our approach, we use a small example (from automotive domain) and real-life industrial case studies (from aviation). The entire development is realized in Event-B and the associated Rodin tool is used to analyse and verify the correctness of the formalized model. Finally, the developed Event-B models are used to generate source code using EB2ALL tool for going from the specification to the implementation of the interactive application.

This paper reports a numerical study of laminar fluid flow and thermal performances along a solar collector. This technique is used to improve the heat transfer in outlet of the system. The numerical model based on the finite volume method and the SIMPLE Algorithm is applied for the solution of the mass, momentum and energy governing equations. In our mathematical formulation, the terms of convection and diffusion are discretized respectively by center and quick schemes. In this work, we consider that the working fluid is transparent, at most the upper solid surface contributes to radiation exchanges and lower solid is assumed to be insulated. Results are analyzed in terms of velocity, temperature fields, average Nusselt numbers and friction factor for various positions of the shoulder in the solar collector.

Ni-TiO2 nanocomposite coatings were fabricated on mild steel surface by pulsed direct current (PC) electrodeposition. This process was carried out in pulsed current at (1, 10, 50) Hz and a duty cycle (25%, 50%, 75%) respectively, at a minimum current density of 0 & high current density of 4 A/dm2. In this work the properties of nanocomposite films were investigated using scanning electron microscopy (SEM), Vickers microhardness measurements and Tafel polarization tests. The composition of the electrodeposits was analyzed by energy dispersive X-ray analysis (EDX). It was found that the coated surface contained at maximum 16.30 % Ti and 35.48 % O. XRD studies revealed [111] preferred orientation. Hardness increased from 560.4 Hv for Ni-TiO2 (F=10 Hz, DC=75 %) nanocomposite coating to 645.7 Hv for Ni-TiO2 (F=10 Hz, DC=25 %) nanocomposite coating. The corrosion resistance of Ni-TiO2 coatings was evaluated by potentiodynamic polarization studies in 3.5 % NaCl solutions. The Pulsed current offer composite coatings with uniform surface, high microhardness and enhanced corrosion resistance significantly for F=10Hz and DC=25 %.

The present paper is a numerical investigation on the performance of perforated baffles in a plate-fin heat exchanger. Two types of perforations are studied, namely the circular and elliptical shapes. Values of heat transfer coefficient, pressure drop, and thermal performance factor are determined for both cases and compared with those for a smooth channel. Also, the flow fields and heat transfer characteristics are determined for different fluids and various Reynolds numbers. The working fluids are complex, non-Newtonian and have an inelastic shear thinning behavior. The obtained results showed a good enhancement in the thermal performance factor by the suggested design in baffles. In the case of low viscous fluids, the elliptical perforated baffle performs better (by about 63.4%) than the circular one for all values of Reynolds number. But for highly viscous fluids, the elliptical perforation shows higher thermal performance than the circular hole by about 25% for low Reynolds numbers and 27% for high Reynolds numbers. The overall thermal performance factors are about 1.55 and 1.74 for the circular and elliptical perforations, respectively.

The turbulent convective thermal transfer in channel heat exchangers (CHEs) is studied numerically via the CFD (Computational Fluid Dynamics) method. Deflectors are inserted on the hot bottom walls of the heat channel to enhance the hydrothermal characteristics. Various shapes of in-line deflectors are considered, namely: rectangular (a/b = 0.00), cascaded rectangular-triangular (a/b = 0.25, 0.50, and 0.75), and triangular (a/b = 1.00) shapes. From the obtained results, the inclusion of in-line deflectors with a/b = 0.75 has given the most significant thermal enhancement factor, which was higher than that for a/b = 0.00, 0.25, 0.50, and 1.00 by about 5.36, 5.06, 67.27, and 3.88%, respectively. Also, the in-line cascaded deflector’ case (a/b = 0.75) shows an increase in the enhancement factor (η) from 4 to 15.44% over the cases of one deflector (corrugated, rectangular, triangular, trapezoidal, arc, (+), S, 45° V, 45° W, T, Γ, and ε-shaped) or two deflectors (staggered corrugated). This highlights the effectiveness of in-line cascaded rectangular-triangular deflectors with a/b = 0.75 in improving the performance of the proposed exchanger for the conditions adopted.

International audience; Cyber-Physical Systems (CPSs) are multi-component systems that interact with the real world. Their heterogeneous nature makes them particularly difficult to model and prove. Our work proposes a framework allowing to design complex hybrid systems based on decomposition using formally verified architectural patterns. It relies on a proof and refinement-based, correct-by-construction approach with Event-B. In particular, the generic model developed in our previous work is used as a base for defining different patterns, for modelling different architectures of systems. Three architectural patterns are presented, corresponding to simple, centralised and distributed control: one controller controlling one plant, one controller controlling several plants and several controllers controlling several plants. The progressive development of the proposed patterns and their application to specific hybrid systems allows to prove the required safety properties by introducing invariants, decomposing and balancing the proof effort at every step of the development. An assessment of the proposed architectural patterns is undertaken: different designs of the same case study are used to demonstrate the feasibility, reliability and extensibility of our approach to model and designing different classes of controllers.

An attempt is made to improve the overall performances of channel heat exchangers. The techniques of baffles and nanofluids are combined to enhance the dynamic and thermal behaviors within the chan...

This study aims to measure the risk dependence between the two most important energy markets, oil and gas, to analyze their risk spillovers. To this end, we apply different extreme risk measures (the value at risk, conditional value at risk, delta conditional value at risk, and copula) to high-frequency energy data to capture the intraday dynamic dependence between oil and gas prices (using, in particular, a 5-min intraday sample data from November 2014 to October 2017). Our analysis shows two interesting findings. First, while we highlight an extreme risk dependence between oil and gas markets, the risk spillover from the oil to the gas market is higher than that from the gas to the oil market. Second, the upward and downward risk spillovers exhibit asymmetry, as extreme negative shocks produce a stronger spillover effect than do extreme positive shocks. The exploration of these systemic risk forms provides significant insights for policymakers and investors in terms of risk management and portfolio diversification.

The ternary (ABX2) semiconductors have wide optical band gaps range and motilities of carrier, has led to their appearance importance device materials, including solar cells of photovoltaic and lig...

An attempt is made to enhance the thermal hydrodynamic performance of a solar channel by using vortex generators including attached fins and detached bars. Hydrogen gas is used as a working fluid under turbulent flow conditions. The computational fluid dynamics method is used to achieve the investigations. Governing equations among fluid and solid sections are determined and solved by the computational finite volume method. The hydrodynamic characteristics, dynamic pressure, turbulent kinetic energy, turbulent viscosity, Nusselt number, skin friction, and the thermal enhancement factor (TEF) are investigated for a range of Reynolds number (Re) from 5000 to 20,000. The obtained results revealed that the TEF values are important (TEF > 1) for all Re values under investigation. The TEF values are between 1.2 and 3.5. An increase in the TEF values was observed with increased Reynolds number, where the maximum value of TEF of about 3.5 was achieved at Re = 20,000. At this value of Re, the normalized heat transfer value (Nu/Nu0) is the highest, while the normalized friction values (f/f0) are the lowest. This demonstrates the usefulness of the suggested vortex generators combined with the fluid (H2) for the successful thermal and dynamic performance within the smooth channels.

The wind catcher or wind tower is a natural ventilation technique that has been employed in the Middle East region and still until nowadays. The present paper aims to study the effect of the one-sided position of a wind catcher device against the ventilated space or building geometry and its natural ventilation performance. Four models based on the traditional design of a one-sided wind catcher are studied and compared. The study is achieved under the climatic conditions of the South-west of Algeria (arid region). The obtained results showed that the front and Takhtabush’s models were able to create the maximum pressure difference (ΔP) between the windward and leeward of the tower-house system. Internal airflow velocities increased with the increase of wind speed in all studied models. For example, at Vwind = 2 m/s, the internal flow velocities were 1.7, 1.8, 1.3, and 2.5 m/s for model 1, 2, 3, and 4, respectively. However, at Vwind = 6 m/s, the internal flow velocities were 5.6, 5.5, 2.5, and 7 m/s for model 1, 2, 3, and 4, respectively. The higher internal airflow velocities are given by Takhtabush, traditional, front and middle tower models, respectively, with a reduction rate between the tower outlet and occupied space by 72, 42, 36, and 33% for the middle tower, Takhtabush, traditional tower, and the front model tower, respectively. This reduction is due to the due to internal flow resistance. The third part of the study investigates the effect of window (exist opening) position on the opposite wall. The upper, middle and lower window positions are studied and compared. The air stagnation or recirculation zone inside the ventilated space reduced from 55% with the lower window to 46% for the middle window and reached 35% for the upper window position. The Front and Takhtabush models for the one-sided wind catcher with an upper window position are highly recommended for the wind-driven natural ventilation in residential houses that are located in arid regions.

In the present study, two-phase flow and forced-convection heat transfer of hydrogen gas (H2) in a solar finned and baffled channel heat exchanger (SFBCHE) is studied numerically. The effect of different obstacles in the channel is addressed. A H2 heat transfer fluid (HTF) having a high thermal conductivity with the baffling technique is implemented to enhance the overall performance of a solar channel. In the initial step, the results from the proposed numerical model were compared with the experimental data of a smooth channel, and then against data with a baffled channel. After checking the validity of our model, the same numerical approach was used for studying thermal-fluid characteristics of the channel with the new fluid. A hydrothermal analysis is presented for a range of Reynolds number (Re) from 5000 to 25,000. At the lowest Re = 5000, the thermal enhancement factor (TEF) is about 1.25. This value increases to 2.16, or 73.46%, when Re = 10,000. This increase in the TEF values continues as Re increases. The largest Re = 25,000 gives the highest TEF value, as it is about 4.18, which is 2.75 times greater than that given for the case of using the conventional gaseous fluid (air). Therefore, our proposed structure for the SFBCHE with high H2 HTF flow velocity leads to improve the values of dynamic pressure (Pd) and heat transfer (Nu), while reducing the skin friction (f) values, which increases the overall TEF of the channel. In addition, all performance values are greater than unity (or 1.00). This reflects the importance of the H2 HTF baffling and finning technique in improving the hydrodynamic thermal-energy performance of solar heat exchangers. The suggested model of SFBCHE filled with an H2 HTF having a high thermal conductivity allows a considerable enhancement in the overall thermal performances which can be employed in various thermal types of equipment, such as solar energy receivers, automotive radiators, and cooling in chemical industries.

International audience; The aim of the present study is to investigate the mechanical behavior of carbon/flax hybrid composites under static and fatigue tensile loading. The failure characteristics and parameters used in the fatigue tests were deduced from the static ones. The effect of the applied stress level, hybridization and stacking sequences on the stiffness, hysteresis loops, dissipated energy and damping, were studied for a various number of cycles during fatigue tests. The Wohler S-N curves were constructed to investigate the effect of hybridization on the fatigue behavior. The results obtained show that the fatigue performance as well as the fatigue resistance increase with the increase of the volume fraction of carbon fiber. Nevertheless, the damping ratio and the fatigue life increase with the increase of the flax fiber volume fraction.

The industrial and academic interest of the research on mobile service recommendation systems based on a wide range of potential applications has significantly increased, owing to the rapid progress of mobile technologies. These systems aim to recommend the right product, service or information to the right mobile users at anytime and anywhere. In smart cities, recommending such services becomes more interesting but also more challenging due to the wide range of information that can be obtained on the user and his surrounding. This quantity and variety of information create problems in terms of processing as well as the problem of choosing the right information to use to offer services. We consider that to provide personalized mobile services in a smart city and know which information is relevant for the recommendation process, identifying and understanding the context of the mobile user is the key.This paper aims to address the issue of recommending personalized mobile services in smart cities by considering two steps: defining the context of the mobile user and designing an architecture of a system that can collect and process context data. Firstly, we propose an UML-based context model to show the contextual parameters to consider in recommending mobile services in a smart city. The model is based on three main classes from which others are divided: the user, his device and the environment. Secondly, we describe a general architecture based on the proposed context model for the collection and processing of context data.

Data hiding is the discipline of hiding information into digital media. A reversible steganographic method allows to extract data from the stego file as well as to retrieve the cover file. This paper proposes a reversible steganographic method based on interpolation by linear box-splines on the three directional mesh. Secret data is hidden in the error between the cover and interpolated pixels. To have better imperceptibility, we search for the nearest value to the cover pixel that can dissimulate data; this was achieved with two techniques: Optimal Pixel Adjustment Procedure and Message Adaptive Error. The proposed method is tested through experiments on a variety of images and compared to prior works. Results indicate a large capacity of hiding and good values of PSNR. The proposed work was also tested by steganalysis attacks; results show a low detectability rate. We find in the comparison that the proposed work surpasses the literature in the capacity of hiding with an equivalent level of imperceptibility.

The water jet at high pressure is used in the manufacturing processes of machines, especially that of cutting. This technique, which is encountered in many industrial applications, is known for its complexity when using the experimental approach. From this viewpoint, an accessible and less expensive method is used, aiming to provide further knowledge on this machining process. The numerical approach is employed, taking into account the fluid flow before the abrasive jet of water in the atmosphere, i.e., in the focusing tube, as well as the free jet itself. Calculations have been achieved for different working conditions. The validation was performed by comparing our results with other available data, and a satisfactory agreement was found. The obtained results revealed a reduction in the fluid velocity during the first moments of the jet due to the carrier abrasives, resulting thus in an increase in the speed of abrasive particles in the same space and time. According to the predicted findings, the shooting distances are commended to be between 1 and 5 mm from the entrance of the jet.

Improving the hydrodynamic characteristics of STHECs (Shell-and-Tube Heat Exchanger Channels) by using BVGs (Baffle-type Vortex Generators) is among the common passive methods due to their proved efficiency. In this computational investigation, the same method is used to enhance the hydrodynamic behavior of STHECs, by inserting W-shaped Baffle-type Vortex Generators. The numerical model represented by the computational FVM (Finite Volume Method) is used to simulate and analyzed the considered physical model. The fluid used is air, its thermal physical properties are constant, turbulent, incompressible, and its temperature is 300 K at the inlet section of the STHEC. The flow velocity ( Uin ) and atmospheric pressure ( Patm ) are considered as boundary conditions at the entrance (x = 0) and exit (x = L) of the channel, respectively. The results showed that the friction coefficients were related to the pressure, velocity, and Reynolds number values. High values of Re yielded an acceleration of the fluid, resulting thus in increased pressure on the solid walls and augmented friction values.

Text Categorization is an important task in the area of Natural Language Processing (NLP). Its goal is to learn a model that can accurately classify any textual document for a given language into one of a set of predefined categories. In the context of the Arabic language, several approaches have been proposed to tackle this problem, many of which are based on the bag-of-words assumption. Even though these methods usually produce good results for the classification task, they often fail to capture contextual dependencies from textual data. On the other hand, deep learning architectures that are usually based on Recurrent Neural Networks (RNNs) or Convolutional Neural Networks (CNNs) do not suffer from such a limitation and have recently shown very promising results in various NLP applications. In this work, we use deep learning models that combine RNN and CNN for the task of Arabic text categorization using static, dynamic, and fine-tuned word embeddings. The experimental results reported on the Open Source Arabic Corpora (OSAC) dataset have shown the effectiveness and high performance of our proposed models.

Arid regions around the world are characterized by hard summer and winter seasons, which leads to thermal discomfort. The southwest of Algeria is classified as an arid region, where the temperature in the summer season passes sometimes 50 °C in the shade and reaches negative values in the winter season. In addition, the yearly relative humidity is below 50%. The hard thermal and hygrometric situation requires actions to fulfill the thermal comfort requirements. Air-conditioning systems are a solution, but at the same time, they are responsible for a big amount of energy consumption in the building sector. In the present paper, an experimental investigation is conducted on the performance of a coupled system: earth-to-air heat exchanger and a solar chimney. The main purpose is to reduce costs and maximize the direct effect between the two techniques. The obtained results showed that the new system was able to create two main thermal regimes in the same day. The first one is a ‘heating’ by increasing the outlet air temperature passing through the buried pipe and solar chimney to reach a maximum gain of 14 °C in day 3. The second thermal regime is the ‘cooling’ that is made by reducing the air temperature at the EAHE outlet by 11.6 °C on day 5. It is also observed that the system increases the outlet air relative humidity by 46% due to the condensation phenomena and reduces it sometimes by 45%. The recent model made of the two techniques was able to produce between 3 and 20 Watts of heating/cooling capacity at the outlet of the system.

Near-stoichiometric CuInSe2 thin films were synthesized by one-step electrodeposition on molybdenum-coated glass substrates. Cyclic voltammetry measurements were firstly used to investigate the electrodeposition mechanisms. The electrochemical, structural, composition and nucleation properties of these films were investigated by cyclic voltammetry, scanning electron microscopy (SEM) and x-ray diffraction (XRD) using an energy dispersive x-ray spectrometer. Analysis of the nucleation mechanisms indicated that the electrodeposition of CuInSe2 from a single bath solution involved an instantaneous 3-D nucleation. An appropriate deposition-imposed potential range of −700 to −400 mV/SCE was determined, although the reduction peak of indium occurred around −960 mV/SCE. The most suitable deposition potential for film preparation was determined to be −500 mV/SCE. The XRD results showed that the films exhibit a polycrystalline tetragonal CuInSe2 phase with (112) orientation. The composition of the film deposited at −500 mV/SCE is very close to the stoichiometric ratio of 1:1:2 according to energy-dispersive x-ray spectroscopy measurements. We discuss the results obtained for the SEM and structural properties of the latter films, which were subjected to a post-annealing process under vacuum at temperatures of 300, 400 and 500°C for 30 min.

The main aim of this research work is to show the simultaneous effects of ferro-particles ( Fe 3 O 4 {\text{Fe}_{3}}{\text{O}_{4}} ) and thermal radiation on the natural convection of non-Newtonian nanofluid flow between two vertical flat plates. The studied nanofluid is created by dispersing ferro-particles ( Fe 3 O 4 {\text{Fe}_{3}}{\text{O}_{4}} ) in sodium alginate (SA), which is considered as a non-Newtonian base fluid. Resolution of the resulting set of coupled non-linear second order differential equations characterizing dynamic and thermal distributions (velocity/temperature) is ensured via the Adomian decomposition method (ADM). Thereafter the obtained ADM results are compared to the Runge–Kutta–Feldberg based shooting data. In this investigation, a parametric study was conducted showing the influence of varying physical parameters, such as volumic fraction of Fe 3 O 4 {\text{Fe}_{3}}{\text{O}_{4}} nanoparticles, Eckert number ( E c {E_{c}} ) and thermal radiation parameter (N), on the velocity distribution, the skin friction coefficient, the heat transfer rate and the temperature distribution. Results obtained also show the advantages of ferro-particles over other types of standard nanoparticles. On the other hand, this investigation demonstrates the accuracy of the adopted analytical ADM technique.

In this work, we present a new method of synthesis of a polymer-MnO2 composite. A film of poly [4-(pyrrol-1-yl methyl) benzoic acid] denoted PPy-B is deposited on the surface of a vitreous carbon electrode by electrochemical oxidation of the corresponding monomer in acetonitrile solution. The carbon modified electrode was immersed in MnSO4 aqueous solution to obtain the Mn2+-polymer complex. The oxidation of the complex in Na2SO4 aqueous solution leads to the formation of MnO2 micro-particles within the polymer matrix. The effect of the pH, the concentration of MnSO4 solution and the thickness of the polymer film on the amount of MnO2 incorporated in the polymer film were studied. The presence of MnO2 particles was confirmed by scanning electronic microscopy and energy dispersive X-ray spectroscopy. The electrical properties of the composite material were investigated by electrochemical impedance spectroscopy.

Magnetic resonance imaging (MRI) has emerged as the golden reference for cardiac examination. This modality allows the assessment of human cardiovascular morphology, functioning, and perfusion. Although a couple of challenging issues, such as the cardiac magnetic resonance (MR) image's features and the large variability of images among several patients, still influences the cardiac cavities’ segmentation and needs to be carried out. In this study, the authors have profoundly reviewed and fully compared semi-automated segmentation methods performed on cardiac cine-MR short-axis images for the evaluation of the left ventricular functions. However, the number of parameters handled by the synthesised works is limited if not null. For the sake of ensuring the highest coverage of the left ventricle parameters computing, they have introduced a parallel watershed-based approach to segment the left ventricular allowing hence the computation of six parameters (end-diastolic volume, end-systolic volume, ejection fraction, cardiac output, stroke volume, and left ventricular mass). An algorithm is associated with the main considered measurements. The experimental results that were obtained through studying 20 patients’ MRI data base demonstrate their approach's accuracy in estimating real values of the parameters’ set thanks to a faithful segmentation of the myocardium.

Histogram of oriented gradients (HOG) descriptor and support vector machine (SVM) classifier have been considered as a very efficient and robust tools used in the development of pedestrian detection systems. However, the enormous calculations make it difficult to meet real-time requirement specifically for advanced driver assistance system applications. The latter requires higher frame rate and resolution. In the present work, efficient pipelined architecture founded on cell-based scanning and simultaneous linear SVM classification is highlighted. The proposed real-time pedestrian detection architecture performs without external memories, and only 3 × 3 pixels are processed using two line buffers. Indeed, intermediate results will contribute directly to build the cell histograms. Consequently, it allows to reduce the required memory and to speed up the HOG feature extraction procedure. The implementation results on a heterogeneous platform show that the proposed architecture achieves an efficient pedestrian detection for full-HD video recordings (1080 × 1920 pixels) at 60 fps with reduced hardware resource consumption. Using the same hardware resources at 444 MHz, the proposed system turns out to handle a HD video at 180 fps.

Improving the wellbeing of the occupants is the main challenge in the building design field. This work aims optimizing the design of a free-running residential building located in northern Morocco according to the bioclimatic architecture concept. In the first stage, an analysis of the bioclimatic chart has been done to find the best passive design strategies for the northern Morocco climate. Based on the results of the analysis, a set of passive design parameters has been selected to be considered in a building thermal and lighting energy performance optimization. A case study of a family detached residential building is considered for this purpose. The optimization problem is multi-objective, so the Pareto front approach was used to select the best design solution. Finally, a monthly assessment of the thermal and lighting energy performance of the chosen design solution is presented. The main results show that applying exterior insulation with a thick thermal mass layer is best for thermal performance enhancement. A wider glazed area with small overhang depth is more suitable for the south facade. For the east facade, the best solution is to limit the glazed area and increase the overhang depth. The importance of natural night ventilation for summer cooling has been also confirmed. This study can serve as a reference for building designers in northern Morocco while developing their projects.

Purpose The purpose of this paper is to carry out a hydrodynamic and thermal analysis of turbulent forced-convection flows of pure water, pure ethylene glycol and water-ethylene glycol mixture, as base fluids dispersed by Al2O3 nano-sized solid particles, through a constant temperature-surfaced rectangular cross-section channel with detached and attached obstacles, using a computational fluid dynamics (CFD) technique. Effects of various base fluids and different Al2O3 nano-sized solid particle solid volume fractions with Reynolds numbers ranging from 5,000 to 50,000 were analyzed. The contour plots of dynamic pressure, stream-function, velocity-magnitude, axial velocity, transverse velocity, turbulent intensity, turbulent kinetic energy, turbulent viscosity and temperature fields, the axial velocity profiles, the local and average Nusselt numbers, as well as the local and average coefficients of skin friction, were obtained and investigated numerically. Design/methodology/approach The fluid flow and temperature fields were simulated using the Commercial CFD Software FLUENT. The same package included a preprocessor GAMBIT which was used to create the mesh needed for the solver. The RANS equations, along with the standard k-epsilon turbulence model and the energy equation were used to control the channel flow model. All the equations were discretized by the finite volume method using a two-dimensional formulation, using the semi-implicit method for pressure-linked equations pressure-velocity coupling algorithm. With regard to the flow characteristics, the interpolation QUICK scheme was applied, and a second-order upwind scheme was used for the pressure terms. The under-relaxation was changed between the values 0.3 and 1.0 to control the update of the computed variables at each iteration. Moreover, various grid systems were tested to analyze the effect of the grid size on the numerical solution. Then, the solutions are said to be converging when the normalized residuals are smaller than 10-12 and 10-9 for the energy equation and the other variables, respectively. The equations were iterated by the solver till it reached the needed residuals or when it stabilized at a fixed value. Findings The result analysis showed that the pure ethylene glycol with Al2O3 nanoparticles showed a significant heat transfer enhancement, in terms of local and average Nusselt numbers, compared with other pure or mixed fluid-based nanofluids, with low-pressure losses in terms of local and average skin friction coefficients. Originality/value The present research ended up at interesting results which constitute a valuable contribution to the improvement of the knowledge basis of professional work through research related to turbulent flow forced-convection within channels supplied with obstacles, and especially inside heat exchangers and solar flat plate collectors.

This analysis intends to simulate the forced-convection and oil flow characteristics in the turbulent regime (Re = 5000-25000) through rectangular-shaped ducts with staggered, transverse, solid, and flat baffle plates. The study is achieved by using a calculation software based on the finite volume method (FLUENT) with selected SIMPLE, Quick, and k-? model. Two various models of baffled ducts are simulated in this analysis under steady flow conditions. In the first model (Case A), a duct with one upper fin and two lower baffles is examined. However and in the second model (Case B), a duct with two upper fins and one lower baffle is treated. The con?tour plots of stream-function, number of Nusselt, and coefficient of skin friction are addressed. As expected, the heat transfer rates raised in the second case (Case B), due to the presence of the lower second obstacle that directs the entire oil current towards the hot upper part of the second duct at very high velocities, resulting thus in enhanced heat transfer rates, especially in the case of high Reynolds number values.

The baffling technique is well-known for its efficiency in terms of enhancement of heat transfer rates throught channels. However, the baffles insert is accompanied by an increase in the friction factor. This issue remains a great challenge for the designers of heat exchangers. To overcome this issue, we suggest in the present paper a new design of baffles which is here called graded baffle-design. The baffles have an up- or down-graded height along the channel length. This geometry is characterized by two ratios: up-graded baffle ratio and down-graded baffle ratio which are varied from 0-0.08. For a range of Reynolds number varying from 104 to 2 ? 104, the turbulent flow and heat transfer characteristics of a heat exchanger channel are numerically studied by the computer code FLUENT. The obtained results revealed an enhancement in the thermohydraulic performance offered by the new suggested design. For the channel with a down-graded baffle ratio equal to 0.08, the friction factors decreased by 4-8%

Network comparison is an essential issue in the analysis of biological, social, and communication networks, and recent network comparisons have required the simultaneous mining of several networks on a similar vertex set. In this work, we study the case where the input consists of a directed acyclic graph D and an undirected graph G on the same vertex set. The goal is then to find the longest path P in D whose vertices induce a connected subgraph of G . This problem is known to be NP -hard and has immediate applications in the analysis of biological networks and foreseeable applications in the analysis of social, information, and communication networks. We propose hereinafter improvements to an existing branch-and-bound method and different resolution approaches based on Integer Linear Programming. We also experimentally evaluate both simulated and real data.

Non-orthogonal multiple access schemes with grant free access have been recently highlighted as a prominent solution to meet the stringent requirements of massive machine-type communications (mMTCs). In particular, the multi-user shared access (MUSA) scheme has shown great potential to grant free access to the available resources. For the sake of simplicity, MUSA is generally conducted with the successive interference cancellation (SIC) receiver, which offers a low decoding complexity. However, this family of receivers requires sufficiently diversified received user powers in order to ensure the best performance and avoid the error propagation phenomenon. The power allocation has been considered as a complicated issue especially for a decentralized decision with a minimum signaling overhead. In this paper, we propose a novel algorithm for an autonomous power decision with a minimal overhead based on a tight approximation of the bit error probability (BEP) while considering the error propagation phenomenon. We investigate the efficiency of multi-armed bandit (MAB) approaches for this problem in two different reward scenarios: (i) in Scenario 1, each user reward only informs about whether its own packet was successfully transmitted or not, (ii) in Scenario 2, each user reward may carry information about the other interfering user packets. The performances of the proposed algorithm and the MAB techniques are compared in terms of the successful transmission rate. The simulation results prove that the MAB algorithms show a better performance in the second scenario compared to the first one. However, in both scenarios, the proposed algorithm outperforms the MAB techniques with a lower complexity at user equipment.

International audience; Few studies have reported the performance of Polylactic acid (PLA) flax feedstock composite for additive manufacturing. In this work, we report a set of experiments conducted by fused filament technology on PLA and PLA-flax with the aim of drawing a clear picture of the potential of PLA-flax as a feedstock material. Nozzle and bed temperatures are both combined with the printing angle to investigate their influence on structural and mechanical properties. The study shows a low sensitivity of PLA-flax to process parameters compared to PLA. A varied balance between shearing and uniaxial deformation is found consistent with tensile results where filament crossing at −45/+45° provides the optimal load-bearing capabilities. However, Scanning Electron Microscopy (SEM) and high-speed camera recording shows a limiting reinforcing effect of flax fibre due to the presence of intra-filament porosity and a significant amount of fibre pull-out resulting from the tensile loading. These results suggest that the quality of the bond between PLA matrix and flax fibre, intra-filament porosity, and surface roughness should receive more attention as well as the need for more continuous fibre reinforcement in PLA filaments to optimise the performance of PLA-flax printed materials.

International audience; Latent heat thermal energy storage systems incorporate phase change materials (PCMs) as storage materials. The high energy density of PCMs, their ability to store at nearly constant temperature, and the diversity of available materials make latent heat storage systems particularly competitive technologies for reducing energy consumption in buildings. This work reviews recent experimental and numerical studies on the integration of PCMs in building envelopes for passive energy storage. The results of the different studies show that the use of PCMs can reduce the peak temperature and smooth the thermal load. The integration of PCMs can be done on the entire building envelope (walls, roofs, windows). Despite many advances, some aspects remain to be studied, notably the long-term stability of buildings incorporating PCMs, the issues of moisture and mass transfer, and the consideration of the actual use of the building. Based on this review, we have identified possible contributions to improve the efficiency of passive systems incorporating PCMs. Thus, fatty acids and their eutectic mixtures, combined with natural insulators, such as vegetable fibers, were chosen to make shape-stabilized PCMs composites. These composites can be integrated in buildings as a passive thermal energy storage material.

We investigate the linear viscoelasticity of polymer gels produced by the dispersion of gluten proteins in water:ethanol binary mixtures with various ethanol contents, from pure water to 60% v/v ethanol. We show that the complex viscoelasticity of the gels exhibits a time/solvent composition superposition principle, demonstrating the self-similarity of the gels produced in different binary solvents. All gels can be regarded as near critical gels with characteristic rheological parameters, elastic plateau and characteristic relaxation time, which are related one to another, as a consequence of self-similarity, and span several orders of magnitude when changing the solvent composition. Thanks to calorimetry and neutron scattering experiments, we evidencea co-solvency effect with a better solvation of the complex polymer-like chains of the gluten proteins as the amount of ethanol increases. Overall the gel viscoelasticity can be accounted for by a unique characteristic length characterizing the crosslink density of the supramolecular network, which is solvent composition-dependent. On a molecular level, these findings could be interpreted as a transition of the supramolecular interactions, mainly H-bonds, from intra- to interchains, which would be facilitated by the disruption of hydrophobic interactions by ethanol molecules. This work provides new insight for tailoring the gelation process of complex polymer gels., Comment: Macromolecules. In press 2020

International audience

International audience; Checking the conformance of a system design to a standard is a central activity in the system engineering life cycle, a fortiori when the concerned system is deemed critical. Standard conformance checking entails ensuring that a system or a model of a system faithfully meets the requirements of a specification of a standard improving the robustness and trustworthiness of the system model. In this paper, we present a formal framework based on the correct-by-construction Event-B method and related theories for formally checking the conformance of a formal system model to a formalised standard specification by construction. This framework facilitates the formalization of standard concepts and rules as an ontology, as well as the formalization of an engineering domain, using an Event-B theory consisting of data types and a collection of operators and properties. Conformance checking is accomplished by annotating the system model with typing conditions. We address an industrial case study borrowed from the aircraft cockpit engineering domain to demonstrate the feasibility and strengths of our approach. The ARINC 661 standard is formalised as an Event-B theory. This theory formally models and annotates the safety-critical real-world application of a weather radar system for certification purposes.

This paper presents the influence of mineral additions in blended cement, or ‘green’ concrete, on the divalent ions of the cement paste pore solution. Because of the lack of data concerning the direct comparison between the pore solution of cement and mineral additions-based material, six types of hardened cement pastes were tested. For this purpose, Portland cement (CEM I or CEM V) and mineral additions (limestone filler, fly ash, blast-furnace slag and silica fume) were used. Results from chemical analyses by ionic chromatography show significant concentrations of divalent ions, such as sulfates and calcium, in the pore solution. In fact, the reference cement paste based on CEM I contains about 1.8 mmol/l of calcium and 1.6 mmol/l of sulfates. However, the use of mineral addition significantly modifies the pore solution. In particular, a substitution of cement by 10% of silica fume increases the calcium and sulfates concentrations to 12.2 mmol/l and 6.7 mmol/l, respectively. This change in the chemical composition, the pH and the ionic strength should be taken into account in multispecies transfer modelling and the thermodynamic equilibrium. The time evolution of the chemical composition, pH and ionic strength of the pore solutions was also investigated.

International audience; When a drop of fluid hits a small solid target of comparable size, it expands radially until reaching a maximum diameter and subsequently recedes. In this work, we show that the expansion process of liquid sheets is controlled by a combination of shear (on the target) and biaxial extensional (in the air) deformations. We propose an approach toward a rational description of the phenomenon for Newtonian and viscoelastic fluids by evaluating the viscous dissipation due to shear and extensional deformations, yielding a prediction of the maximum expansion factor of the sheet as a function of the relevant viscosity. For Newtonian systems, biaxial extensional and shear viscous dissipation are of the same order of magnitude. On the contrary, for thinning solutions of supramolecular polymers, shear dissipation is negligible compared to biaxial extensional dissipation and the biaxial thinning extensional viscosity is the appropriate quantity to describe the maximum expansion of the sheets. Moreover, we show that the rate-dependent biaxial extensional viscosities deduced from drop impact experiments are in good quantitative agreement with previous experimental data and theoretical predictions for various viscoelastic liquids.

In the catadioptric images, the neighborhood topology is usually modified by the mirror shape which consists of significant radial distortions and low non-uniform resolution because of its convexity geometry. Consequently, conventional compression approaches (i.e. H.264 intra-frame coding or JPEG standard) based on rectangular block partitioning cannot be applied directly to catadioptric images because they inevitably produce significant block effects. In this investigation, we propose a new coding scheme based on an adaptive block partitioning. Particularly, to reduce the blocking artifacts, we propose the shape-adaptive discrete cosine transform (SA-DCT) and adapted neighborhood. The adapted neighborhood is obtained from the equivalence between the catadioptric image and the scene point’s projection on the unit sphere. The adapted blocks shape correctly follows the geometric context and varies according to the resolution of the catadioptric images. Such changes improve considerably the compression efficiency using the block partitioning in catadioptric images. Experimental results figured out that our proposal scheme outperforms the JPEG standard and the Intra-frame coder H264. Moreover the proposed coding scheme based on SA-DCT transform and the suitable partitioning for catadioptric images provides high PSNR and a considerable reduction of block effects compared to conventional approaches, especially in the case of low bit rate.

This paper presents an output feedback control for the multicellular converter using hybrid systems theory. First, we study the observability of the continuous state of the converter under predetermined finite switching sequence. Using some dynamical properties of the converter, a time independent necessary and sufficient condition is given for the continuous state observability. This interesting condition allows the avoidance of the usual matrix exponential computations for the observability analysis and leads to major notes on the multicellular converter observability. Second, as an application of the above results, we consider the case of the 2-cell converter where we establish a new switching control scheme that guarantees the existence and the finite-time stability of a limit cycle. The corresponding repetitive switching sequence of the limit cycle is used to prove the continuous state observability. We next design a super twisting sliding mode observer that guarantees the finite continuous state convergence. Simulation results confirm the effectiveness and the robustness of the output control scheme under different perturbations: variations of the input voltage and load resistance.

In this paper, we report an electrochemical study using cyclic voltammetry and chronoamperometry on the kinetic and nucleation mechanisms of electrodeposited copper on indium-doped tin oxide-coated glass substrates from sulfate solutions. The present investigation has been carried out in an acid solution at pH = 5. The Scharifker–Hills model was used to analyze current transients. At relatively low overpotentials, copper deposition is observed to follow a model that involves instantaneous nucleation and diffusion-controlled 3D growth. The diffusion coefficient for Cu2+ for various applied potentials is determined. Atomic force microscopy (AFM) has been used to check the surface morphology of the electrodeposited thin films.