Dirac Fermions in Blue Phosphorene Monolayer

2D materials beyond graphene and in particular 2D semiconductors have raised interest due to their unprecedented electronic properties, such as high carrier mobility or tunable bandgap. Blue phosphorene is an allotrope of black phosphorene that resembles graphene as it presents a honeycomb structure. However, it is known to have semiconductor character and the crucial point is to determine whether this hexagonal phase of phosphorene presents Dirac fermions as in graphene. Here, the first compelling experimental evidence of Dirac fermions in blue phosphorene layer grown on Cu(111) surface is presented. The results highlight the formation of a highly ordered blue phosphorene sheet with a clear Dirac cone at the high symmetry points of the Brillouin Zone. The charge carriers behave as massless relativistic particles. Therefore, all the expectations held for graphene, such as high-speed electronic devices based on ballistic transport at room temperature, may also be applied to blue phosphorene.     

Hybrid models based on biological approaches for speech recognition

This paper aims to adapt the Clonal Selection Algorithm (CSA) which is usually used to explain the basic features of artificial immune systems to the learning of Neural Networks, instead of Back Propagation. The CSA was first applied to a real world problem (IRIS database) then compared with an artificial immune network. CSA performance was contrasted with other versions of genetic algorithms such as: Differential Evolution (DE), Multiple Populations Genetic Algorithms (MPGA). The tested application in the simulation studies were IRIS (vegetal database) and TIMIT (phonetic database). The results obtained show that DE convergence speeds were faster than the ones of multiple population genetic algorithm and genetic algorithms, therefore DE algorithm seems to be a promising approach to engineering optimization problems. On the other hand, CSA demonstrated good performance at the level of pattern recognition, since the recognition rate was equal to 99.11% for IRIS database and 76.11% for TIMIT. Finally, the MPGA succeeded in generalizing all phonetic classes in a homogeneous way: 60% for the vowels and 63% for the fricatives, 68% for the plosives.     

Soft Computing Techniques for Classification of Voiced/Unvoiced Phonemes

A method that uses fuzzy logic to classify two simple speech features for the automatic classification of voiced and unvoiced phonemes is proposed. In addition, two variants, in which soft computing techniques are used to enhance the performance of fuzzy logic by tuning the parameters of the membership functions, are also presented. The three methods, manually constructed fuzzy logic (VUFL), fuzzy logic optimized with genetic algorithm (VUFL-GA), and fuzzy logic with optimized particle swarm optimization (VUFL-PSO), are implemented and then evaluated using the TIMIT speech corpus. Performance is evaluated using the TIMIT database in both clean and noisy environments. Four different noise types from the AURORA database—babble, white, restaurant, and car noise—at six different signal-to-noise ratios (SNRs) are used. In all cases, the optimized fuzzy logic methods (VUFLGA and VUFL-PSO) outperformed manual fuzzy logic (VUFL). The proposed method and variants are suitable for applications featuring the presence of highly noisy environments. In addition, classification accuracy by gender is also studied.     

Assessment and biomonitoring of aquatic pollution by heavy metals (Cd,Cr, Cu,Pb and Zn) in Hammam Grouz Dam of Mila (Algeria)

Concentrations of Cd, Cr, Cu, Pb and Zn were determined in water, sediment and tissues of fish (Cyprinus carpio and Barbus setivimensis) from November 2014 to August 2015, in order to estimate the aquatic pollution in Hammam Grouz dam, by the technique of atomic absorption spectrophotometry. The concentrations of heavy metals in the water and sediment were higher than the WHO standards. The calculation of Bioconcentration factor showed that all fish species studied have accumulated heavy metals in their tissues (gill, liver, muscle and kidney). The concentrations of metals in B. setivimensis were higher than those in C. carpio. The highest concentration of heavy metals was recorded in the gill while the lowest was recorded in the muscle and kidney. Our study reveals that these fish species can be used as bioindicators in the biomonitoring of metallic pollution in aquatic ecosystem.     

Analysis of intermetallic swelling on the behavior of a hybrid solution for compressed hydrogen storage – Part I: Analytical modeling

This study focuses on the mechanical response of a hybrid solution dedicated to gaseous hydrogen storage. This solution is made of a carbon/epoxy composite overwrapped on a metal liner first coated with intermetallic material. The composite helps to reinforce the structure, while the liner prevents it from any leakage. In case of deficiency, the intermetallic material behaves as a sponge and interrupts the leakage by absorption and micro-cracks reduction. This hybrid solution or this specific use of intermetallic material has never been presented before. The laminate composite is anisotropic, whereas the liner is an elastic–plastic material. The intermetallic is purely thermo elastic and its study is limited to its mechanical contribution. Using these hypotheses, the suggested analytical model provides an exact solution for stresses and strains on the cylindrical section of the hybrid solution submitted to thermomechanical static loading and hydrogen leakage. The swelling effect of the intermetallic on the behavior of the structure is then investigated.     

The Effect of a Number of Baffles on the Performance of Shell-and-Tube Heat Exchangers

The number of baffles has an impact on the thermal-hydraulic performance of a shell-and-tube heat exchanger (STHX), thus a model was developed using Engineering Equations Solver software to solve the governing equations. The program uses Kern, Bell-Delaware, and flow-stream analysis (Wills Johnston) methods to predict both the heat-transfer coefficient and pressure drop on the shell side of an STHX. It was found that Bell-Delaware method is the most accurate method when compared with the experimental results. The effect of a number of baffles, mass flow rate, tube layout, fluid properties and baffle cut were investigated. The analysis revealed that an increase in the number of baffles increases both the heat-transfer coefficient and pressure drop on the shell-side. Increasing the mass flow rate, the heat transfer coefficient increases; however, the pressure drop increases at a higher rate. For a large number of baffles, the pressure drop decreases with an increase in the baffle cut. It also shows that the heat transfer coefficient increases at a higher rate with the square tube layout, whereas the rotated square and triangular layouts have approximately the same behavior.     

Electrical properties of Al-doped oxyapatites at intermediate temperature

In order to obtain acceptable performances in SOFC, relatively high operating temperatures (∼850–1000 °C) are required. That is mainly due to the low ionic conductivity of YSZ electrolyte. These temperature conditions are at the origin of the cell degradation, which justify the search for alternative electrolytes presenting the same performances but at lower temperature (∼800 °C). It is in this context that the oxyapatites of general formula La_10−xSi_6−yAl_yO_{27−3x/2−y/2} (x = 0, 0.67; y = 0.25, 0.50, 0.75) are studied in this work. The solid solutions are prepared by sintering the oxide powders at 1600 °C. All samples have shown a hexagonal structure with an increase in the cell parameters with the aluminium content. Electrical properties are determined by impedance spectroscopy between 169 and 790 °C. The results are treated by separating the bulk and grain boundary conductivities between 169 and 500 °C and in the form of total (bulk + grain boundary) conductivity between 500 and 790 °C. The respective influences of the activation energy and the pre-exponential factor on conductivity are analyzed. Activation energies are about 0.65 eV suggesting an interstitial mechanism. No variation of conductivity is observed with the oxygen partial pressure. Finally, La₁₀Si_5.5Al_0.5O_26.75 shows conductivity higher than that of YSZ at intermediate temperature.     

Cold adaptation of Escherichia coli: microbiological and proteomic approaches

The aim of this work was to use two approaches (microbiological and proteomic) to study the effect of cold adaptation (3 h at 4 degrees C) on the survival of two Escherichia coli strains, I2 and R3, following freezing at -20 degrees C for 24 h and thawing for 45 min at 37 degrees C. The effect of cold adaptation on cell survival after freezing was determined by measuring viable counts on selective (PTX) and nonselective media (TSA). The beneficial effect of the cold treatment was more pronounced for the freezing-sensitive R3 strain: Prior to adaptation, differences between the two media were 3.5 log10 for R3 and 0.4 log10 for I2. After adaptation, the differences were 2.5 log10 and 0.1 log10 for R3 and I2, respectively. The proteins from two cell compartments, cytoplasm and outer membrane, were separated by two-dimensional electrophoresis and identified by mass spectrometry or Edman sequencing. The adaptation resulted in changes in the expression of certain proteins. Among the principal changes to protein profiles in strain R3 following cold adaptation, we observed an over-expression of the EF-TU elongation factor in the outer membrane, and an under-expression of flagellin (FLIC) in the cytoplasm. Very few changes were observed in strain I2.     

Propagation d’impulsions électromagnétiques au-dessus d’un terrain irrégulier ou non homogène

This paper presents an analysis of the propagation of electromagnetic pulses over a ground which can be irregular or inhomogeneous. For this type of terrain the profile is given in a vertical plan containing the transmitter and the receiver, and an integral formalism supplying numerical solutions is used. The experimental results of the vertical component of the electric field, coming from natural or triggered lightnings are presented together with results of theoretical simulation.