Development of a simulation model for a three-dimensional wind velocity field using Ténès Algeria as a case study

A mathematical simulation model was developed that can determine the three-dimensional wind velocity field over a complex terrain. The Ténès area in the Valley of Cheliff in Algeria was used as a case study. This region is exposed to south-west circulation that makes it favorable to the use of wind energy. Knowledge of wind fields is crucial for predicting the dispersion of pollutants, for forecasting meteorological weather, for fire spread prediction and in the design and implementation of wind turbines. By means of a mass consistent model, an in-house program was developed to calculate the three-dimensional wind velocity field in the study region. The model was supported by a numerical box in which flow through is allowed for in the upper and lateral boundaries. The bottom boundary through which no flow through occurs was determined by the topographic relief at the surface. From measured wind velocities, observed values were calculated by interpolation-extrapolation. Using an optimization method, the adjusted velocities were obtained from constraints, observed velocities and the continuity equation. The model was verified with wind point data, the relative error did not exceed 6%.     

Study of Proton Leakage at Interface of Anion-Exchange Membrane in Solutions of Acids,Salts, and Solvents Using Current/Voltage Characteristics

Water dissociation and proton leakage using the anionic exchange membrane (AMH) are studied by means of current/voltage characteristics and confirmed by simulation of transport number using Hittorf's method. The acids used are HCl, HNO₃, and H₂SO₄ and the salts are NaCl, ZnCl₂, and NaNO₃. Concentration polarization of such membrane is accompanied by a change in the electrolyte concentration/solution interface due hydrolysis reactions. The results show that when the concentration of the electrolyte increases, the limiting current density increases linearly and the transmembrane resistance decreases systematically. The thickness of the diffusion layer is always higher in presence of acid than salt, making in evidence the proton leakage through the membrane. Besides, when the membrane is selectively permeable to chloride anion in the case of ZnCl₂, the thickness of the double layer is rather bigger and far exceeds that of the membrane. The voltamperometry method seems reliable and offers some advantages over that of Hittorf because it shows the effects of some parameters on the value of limiting current: concentration, counter-ion types (Cl^?, NO₃^? SO₄^2?), and the gradient of concentration in the anode and cathode compartments. It can, therefore, allow to optimize the value of the current which should be used in electrodialysis in any form and without a great consumption of energy. Moreover, the simulation carried out for transport number of proton, shows its sensitivity toward the variation in concentration in the receiving compartment. In effect, a small decrease in concentration implies an enormous decrease in its value.     

Experimental and theoretical investigations of the adhesion time of Penicillium spores to cedar wood surface

In this study, the adhesion of 4 Penicillium strains (Penicillium granulatum, Penicillium crustosum, Penicillium commune and Penicillium chrysogenum) on cedar wood was examined qualitatively and quantitatively by using the extended DLVO (XDLVO) approach and the environmental scanning electronic microscopy (ESEM) technique. A comparison between the XDLVO theories and the ESEM technique was also investigated. The adhesion tests revealed that P. chrysogenum was not able to adhere on the cedar wood substrata, as predicted by the XDLVO approach. We have also found by ESEM that the three Penicillium strains (P. granulatum, P. crustosum, P. commune) adhered on wood, as not predicted theoretically.Moreover, the time of adhesion (3 h and 24 h) was used not only to compare the capacity of adhesion according to contact time but also to explain the discrepancies between the XDLVO approach prediction and the adhesion experiments. A positive relationship between the XDLVO approach and adhesion experiments has been observed after 3 h of adhesion. In contrast, a contradiction between the XDLVO predictions and the adhesion test results has been noted after 24 h of adhesion of Penicillium strains to the wood surface.     

A Taguchi design approach for the enhancement of a detergent-biocompatible alkaline thermostable protease production by Streptomyces mutabilis strain TN-X30

The ability of microorganisms to grow at high temperature, alkaline pH, and high salinity makes them an attractive target for enzyme-production with several industrial applications. One strain TN-X30 has been selected as protease producer and identified as Streptomyces mutabilis after a phenotypic and molecular study. Its production of protease was improved using Taguchi L27 design. The strategy was carried out to identify the optimum levels and the interaction of the screened factors. Following this step, maximum protease activity (10,895 U/ml) was achieved after 6-days of incubation. The TN-X30 protease activity had an optimum of pH and temperature of 10 and 65°C, respectively. Thermodynamic parameters at 60°C were enthalpy 14.26 kJ/mol, entropy −220 J/mol/K, and Gibbs free energy 90.53 kJ/mol. TN-X30 protease production displayed a 16-fold increase reaching 175,000 U/ml in a 100-L fermentor. Furthermore, the lyophilization in presence of sorbitol enhanced the stability of the TN-X30 protease which remained active at 75% after 24-months of storage. The lyophilized TN-X30 protease exhibited exceptional stability indexes in presence of some known commercialized detergent components as NEODOL® 25-7, Dehydol® LT 7, Na₂ CMC, Galaxy LAS, Galaxy LES 70, Galaxy 110, Galaxy CAPB Plus, and Sulfacid K. The lyophilized enzyme also displayed high stability with respect to both solid and liquid detergents. Finally, TN-X30 protease exhibited remarkable destaining of blood, egg, and chocolate stained cloth pieces. These findings may promote TN-X30 protease for use as bioadditive in detergent formulation, thereby reducing environmental chemical threat.     

Maintainability defects detection and correction: a multi-objective approach

Software defects often lead to bugs, runtime errors and software maintenance difficulties. They should be systematically prevented, found, removed or fixed all along the software lifecycle. However, detecting and fixing these defects is still, to some extent, a difficult, time-consuming and manual process. In this paper, we propose a two-step automated approach to detect and then to correct various types of maintainability defects in source code. Using Genetic Programming, our approach allows automatic generation of rules to detect defects, thus relieving the designer from a fastidious manual rule definition task. Then, we correct the detected defects while minimizing the correction effort. A correction solution is defined as the combination of refactoring operations that should maximize as much as possible the number of corrected defects with minimal code modification effort. We use the Non-dominated Sorting Genetic Algorithm (NSGA-II) to find the best compromise. For six open source projects, we succeeded in detecting the majority of known defects, and the proposed corrections fixed most of them with minimal effort.     

Optical limiting in hydrogenated amorphous silicon-selenium thin films

Hydrogenated amorphous silicon-selenium alloy thin films grown by capacitively coupled radio-frequency glow-discharge are investigated. Nonlinear absorptive effects are evaluated with the help of open aperture z-scan technique in the 525 to 580 nm spectral range. The nonlinear absorption coefficient is found to be very large and reaching the value of 5.14 × 10^− 3 cm/W at 525 nm. The origin of the optical nonlinearities is studied and found to be due mainly to two photon absorption in the case of pulsed excitation, whereas thermal effects are thought to be dominant when the sample is excited with a continuous wave laser. Optical limiting potentialities of the thin film are experimentally observed and their thresholds are found to be very low.     

Hygrothermal effects on structural stiffness and structural damping of laminated composites

In this paper the hygrothermal effects on structural stiffness and damping of laminated composites are investigated. Since the hygrothermal influence on properties of composite materials is primarily matrix dominated, we first determine experimentally the effects of temperature and moisture on the storage modulus, Poisson's ratio and material damping of the epoxy matrix. With the experimentally determined properties of the epoxy material, we then determine the complex moduli (E _L ^* ,E _T ^* ,G _LT ^* andv _LT ^* ) of unidirectional glass-epoxy and graphite-epoxy composites. The structural stiffness (extensional and flexural) and damping of symmetric angle-ply laminates of glass-epoxy and graphite-epoxy are then investigated both analytically and experimentally for temperatues of 20° C and 80° C, respectively. Three moisture contents which are the dry, saturated and a non-uniform moisture gradient states corresponding to each temperature case are considered. Numerical and limited experimental results show that the effects of moisture on the real part ofA ₁₁ ^* ,A ₆₆ ^* ,D ₁₁ ^* andD ₆₆ ^* at room temperature, 20° C, are negligible for all the considered cases. But as temperature increases, the moisture and temperature combined influence induces significant changes in the complex stiffnessA ₁₁ ^* A ₆₆ ^* ,D ₁₁ ^* , andD ₆₆ ^* especially for the matrix dominated terms.     

Advances of nanofluids in heat exchangers—A review

Recently, many researchers have focused on their studies on the analysis of nanofluid flows due to their participation in the enhancement of heat transfer rates in industrial processes. The ordinary fluids, such as water, mineral oils, and so on, are known for their low thermal conductivity in heat transfer processes. A significant enhancement in the thermal properties of ordinary fluid may be obtained by adding nanoparticles having a diameter of less than 100 nm or suspension of fibers. Better spreading, wetting, dispersion, and stability and with acceptable viscosity are the main advantageous properties of nanofluids on a solid surface. The nanofluids are encountered in various thermal engineering systems such as in heat exchangers, refrigeration, thermal management of fuel cells, cooling of nuclear reactors, microelectromechanical systems, and others. In particular, the thermal conversion is known as a great application of nanotechnology, and many studies have been achieved with such fluids in heat exchangers. Therefore, this paper aims to present a global insight into the different applications of nanofluids in various heat exchangers, that is, heat pipe and plate-fin heat exchangers. All research works have been summarized into three main parts: laminar, transition, and turbulent nanofluid flow regimes.     

The Capability Assessment of the Spectrum Decomposition Technique for Measurements of the Group Velocity of Lamb Waves

The ultrasonic guided waves are dispersive waves characterized by the phase and group velocities dispersion curves. In order to use guided waves in various industrial applications, their parameters must be known. Since these guided wave velocities depend on the frequency and thickness of the material, they propagate differently comparing to bulk ultrasonic waves. Therefore, to analyze the parameters of such waves, new measurement techniques should be proposed and possibilities of their application have to be investigated. In this paper possibilities to measure the group velocity based on the spectrum decomposition approach are presented. The investigations are carried out using the simulated and experimental signals of Lamb wave propagating in a 2 mm thickness aluminium plate. The two fundamental modes \(\hbox {A}_{0}\) and \(\hbox {S}_{0}\) are selected. Using the proposed technique, segments of the group velocity dispersion curves have been reconstructed and compared with the dispersion curves calculated by the SAFE method to estimate errors. Accordingly to the obtained lower absolute and relative errors, an optimal set of narrowband filters with bandwidth from 20 kHz up to 100 kHz for the \(\hbox {A}_{0}\) mode and from 80 kHz up to 160 kHz for the \(\hbox {S}_{0}\) mode are proposed. Applying the proposed optimal frequency sets of narrowband filters for the experimental signals, segments of the group velocity dispersion curves for both modes are reconstructed. The average relative error for the \(\hbox {A}_{0}\) mode is 1.7–2.2% (expanded relative uncertainty ± (2.2–2.8)%) and 0.78–1.2% (expanded relative uncertainty ± (0.5–0.8)%) for the \(\hbox {S}_{0}\) mode.     

Effect of vegetable and synthetic fibers on mechanical performance and durability of Metakaolin-based mortars

The use of vegetable fibers has regained interest in different fields. In fact, fibers may represent an alternative to traditional fibers incorporated in building materials, such as polypropylene fibers. Sustainable development requires the adoption of ecofriendly and natural materials. In this approach, using vegetable fibers as reinforcement for cementitious materials represents an interesting option for concrete industry. Thus, this article studies mechanical performances and transfer properties of cementitious mortars reinforced with vegetable fibers. The used fibers were Dis (DS), Alfa (AF), Date palm (DP) and Hemp (HE). They were subjected to prior treatment with calcium hydroxide. The results show that reinforced mortars with vegetable fibers represent a better deformation capacity than the control mortar without fibers; the best bending strength was recorded for hemp and date palm mortars; the addition of vegetable fibers leads to thermal conductivity decrease by 15% for a content of 0.1%. However, greater carbonation depths were recorded for vegetable fibers based mixes. These findings, for us, are promising for the use of vegetable fibers in cementitious materials.