Comparative simulation of wind park design and siting in Algeria

In this paper, five typical regions of Algeria where wind is strong enough are selected. These regions usually intended for traditional agriculture are, centred around the towns of Guelma, El Oued, Tindouf, Touggourt and Tamanrasset. To make wind energy conversion available as an alternative energy source for the populations living in such countries, nine types of small and medium wind turbines constructed by American and European manufacturers are studied for their suitability. To account for the wind variations with height, four possible heights of the pylon holding the turbines are considered: 10, 20, 40 and 60 m. In each of the five locations and at each pylon height, wind energy converted by the turbines, is cumulated over the year and computed. Depending on the site and their size, most of these turbines are found to produce about 1000–10,000 MWh of electricity per year at 60 m of altitude and can easily satisfy the electricity need in irrigation and its household applications in rustic and arid regions. A quick glance of the results of the above computation shows that the choice of pylons of 20 m height yields a trade-off between the production of electrical energy and the requirements of economy. Owing to the sporadic wind variations, wind energy conversion systems can only be used as an auxiliary source. In particular, these systems can advantageously be coupled to stand-alone photovoltaic conversion systems in remote locations or connected to the electric mains in urban zones.     

Impulse invariance-based method for the computation of fractional integral of order

This paper presents a simple and efficient method for the design of recursive digital fractional order integrator when the order of integration is a real number between 0 and 1. The proposed method is based on the impulse invariance method. First the initial value theorem is used for the selection of the initial value of the impulse response and then any of the well-established signal modeling techniques can be employed for the parameterization of the discrete impulse response by pole-zero models. For a given model order, the approximation accuracy greatly depends on the initial value selected. Illustrative examples are presented to demonstrate the effectiveness and usefulness of the proposed method.     

The drag force on a particle approaching a solidifying interface

Lubrication theory is applied to derive an expression for the drag force on a particle approaching a directionally solidified interface. To the leading order in the Peclet number, the thermal and hydrodynamic problems are uncoupled. The former yields an equation for the front’s curvature, the solution of which gives the interface profile. The drag force is obtained by solving the lubrication equations in the gap between the particle and the interface. In the absence of shrinkage flow, the force is due solely to the particle’s movement. The dependence of the drag on the parameters, such as the thermal gradient, the latent heat of fusion, and the ratio of the particle’s thermal conductance to that of the melt. α, is explicitly depicted. We find that the drag increases with α, so that perfectly insulated particles experience less drag than highly conducting particles. The variation of the drag force with the thermal gradient also depends on the thermal conductance ratio α. Furthermore, it is noted that the fluid drag force derived here resembles the Taylor’s lubrication force that resists the approach between two rigid surfaces.     

Resonant-cavity infrared optoelectronic devices

The Cd_xHg_1−xTe compounds are well suited to the design of resonant microcavity devices. Indeed these compounds display a wide variation of bandgap and refractive index with composition, while the lattice parameter remains practically unchanged. Microcavities resonating in the 3–5 μm range have been prepared by molecular beam epitaxy. Light emitting diodes (LEDs) are obtained by stacking a lower Bragg mirror (10.5 periods) which is doped n-type and a nominally undoped cavity medium containing a 50 nm active layer (CdTe-HgTe pseudo-alloy). The upper mirror is a gold layer deposited on the cavity, which is partly p-type doped. The diode emission is observed under direct bias, up to room temperature, in coincidence with the cavity resonance mode (linewidth 8 meV). It is much narrower than the inhomogeneous linewidth of the active layer (60 meV at 300K). The directivity is also much better. The diode properties are only very slightly dependent on temperature. A similar device can also be designed to make an infrared detector whose active layer thickness is reduced with respect to conventional detectors. The detector efficiency at the resonance wavelength may be increased by a factor close to the cavity finesse. With 16.5 periods in the lower mirror and a dielectric mirror as upper mirror (seven periods of ZnS/YF₃), it has been possible to make a cavity resonating at 3.06 μm whose quality factor reaches 350. By photopumping the cavity across the dielectric mirror with a YAG microlaser, a laser emission occurred at the cavity resonance. At 10K, the laser threshold is 45 kW/cm₂ and the linewidth is only 1.7 meV. These results demonstrate the usefulness of the microcavity concept for designing new devices such as LED or lasers which could be the basis for new applications of CdHgTe compounds.     

Influence of some factors affecting antibacterial activity of PVA/Chitosan based hydrogels synthesized by gamma irradiation

Poly (vinyl alcohol) hydrogels containing different concentrations of chitosan with molecular weight of 471 and 101 kDa were crosslinked by gamma irradiation at a dose of 25 kGy. The swelling behavior, gel content and morphological structure of the blend were investigated. The antibacterial effect, as a function of chitosan content and molecular weight in the hydrogel, was investigated against Escherichia coli and Bacillus subtilis. With increasing chitosan content the equilibrium degree of swelling of the blend increased and the gel fraction decreased. Results of antibacterial activity of chitosan revealed that chitosan was more effective in inhibiting growth of gram positive bacteria than that of gram negative ones. It was observed that, the chitosan content as well as its molecular weight has a direct influence on bacteria growth inhibition. The higher the chitosan content in the blend and the higher its initial molecular weight, the larger was the inhibition zone diameter. The bacteria growth inhibition was attributed to the diffusion of entrapped chitosan from the hydrogel blend to the culture medium.     

Microstructural and Mechanical Properties of Ni-Base Thermal Spray Coatings Deposited by Flame Spraying

In this work, two different Ni-base powders, namely, ProXon 21021 (P21) and ProXon 21031 (P31), were sprayed onto a steel substrate 35CrMo4 using a thermal flame spray technique. The morphology and chemical composition of the phases that are present in the powders and coatings were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The hardness and wear resistance of the coatings were investigated. The XRD analysis revealed that the phases present in the coatings are different from the initial powders. In addition, some inhomogeneities such as oxides, porosity, and unmelted particles were observed by SEM. It was found that the P31 spray-coated exhibited higher microhardness, higher wear resistance, and significantly lower friction coefficient in comparison with those of P21 coatings.     

Aryloxy Triester Phosphoramidates as Phosphoserine Prodrugs: A Proof of Concept Study

The specific targeting of protein-protein interactions by phosphoserine-containing small molecules has been scarce due to the dephosphorylation of phosphoserine and its charged nature at physiological pH, which hinder its uptake into cells. To address these issues, we herein report the synthesis of phosphoserine aryloxy triester phosphoramidates as phosphoserine prodrugs that are enzymatically metabolized to release phosphoserine. This phosphoserine-masking approach was applied to a phosphoserine-containing inhibitor of 14-3-3 dimerization, and the generated prodrugs exhibited improved pharmacological activity. Collectively, this provided a proof of concept that the masking of phosphoserine with biocleavable aryloxy triester phosphoramidate masking groups is a viable intracellular delivery system for phosphoserine-containing molecules. Ultimately, this will facilitate the discovery of phosphoserine-containing small-molecule therapeutics.     

Equilibrium Studies on the Synergic Liquid‐Liquid Extraction Process of Copper(II) from Sulphate Media with Mixtures of some Bidentate Mono‐Schiff Bases and Acyclic Polyether Non‐ionic Surfactant in Chloroform

The liquid‐liquid extraction of copper(II) with bidentate mono‐Schiff base extractants(HL), namely, N‐salicylideneaniline (SA), N‐(2‐hydroxy‐1‐naphthalidene)aniline (HNA), N‐salicylidene‐1‐naphthylamine (SN), and N‐(2‐hydroxy‐1‐naphthalidene)‐1‐naphthylamine (HNN), from a weakly acidic sulphate media into chloroform was studied in both the absence and the presence of acyclic polyether non‐ionic surfactant (S). In the absence of the non‐ionic surfactant, the extractability of copper(II) was 92.6% with SA, 89% with HNA, 81% with SN, and 80% with HNN. The estimated extraction constants, (log K_ex) of the four extractants revealed that the extraction efficiency increased in the order HNN< SN< HNA<SA. Besides, it was found that copper(II) was extracted as CuL₂ (HL) with SA and HNA, and as CuL₂ with SN and HNN. The extraction of copper(II) was significantly enhanced with HL into chloroform upon the addition of a non‐ionic surfactant. An extractability of 100% was reached. The stoichiometry of the extracted complexes was CuL₂S. The synergic extraction ability of extractants changed in the order SA>HNA>SN～HNN, whereas, the synergic effect fell in the order HNN>SN>HNA～SA.     

A privacy-preserving code-based authentication protocol for Internet of Things

The Journal of Supercomputing - The Internet of Things (IoT) is an upcoming technology that permits to interconnect different devices and machines using heterogeneous networks. One of the most...     

The ProTides Boom

The masking of nucleoside phosphate and phosphonate groups by an aryl motif and an amino acid ester, nowadays known as the ‘ProTide’ technology, has proven to be effective in the discovery of nucleotide therapeutics. Indeed, this technology, which was invented by Chris McGuigan in the early 1990s, has inspired the discovery of two FDA‐approved antiviral nucleotide drugs, and many more are currently undergoing (pre)clinical development. The usefulness of this technology in the discovery of nucleotide therapeutics is showcased in this Highlight by discussing the ProTides development and the various ProTides that have reached clinical trials.