Gonflement du nickel irradie par des ions Ni+ de moyenne energie

After briefly summarising the advantages and drawbacks of bombardment with heavy ions, we describe the experimental apparatus we used for studying swelling in nickel. Next we discuss the problems connected with the determination of the number of atoms displaced during ion-bombardment.We studied the influence of the following parameters on the swelling of nickel: temperature, gas content, fluence, ion energy. Swelling varied with temperature and increases to a maximum at 620°C for 500 keV nickel ions. Prior helium-loading of the samples (10ppm) reduces swelling and the mean void size and increases the number of cavities. Swelling grows linearly with fluence up to 25 displacements per atom. The number and size of voids grows rapidly in the early stages of irradiation.We explain how helium reduces swelling in our experiments, and we determine how far the fluences calculated for ion-bombardments need to be corrected to allow valid comparisons with in-pile results.     

Clusters identification and characterization in a gas–solid fluidized bed by the wavelet analysis

The local solid flow structure of the bubbling fluidized bed of sand particles was investigated in order to identify and characterize the clusters. Extensive experiments were carried out using an optical fibre probe, measuring the velocity and the diameter of clusters. Under all operating conditions, ascending and descending clusters co‐existed at all measurement locations. The locus of the inversion point at which the directions of cluster motion changed was determined. The velocity of the ascending clusters was a function of both superficial gas velocity and the radial and axial position. With increasing superficial gas velocity, both the velocity and the diameter of ascending clusters decreased near the wall. However, the velocity of descending clusters depended mainly on superficial gas velocity and the largest clusters existed closer to the wall. The results of this study help to explain cluster hydrodynamics in fluidized beds.     

Engineering characteristics of a glacio-lacustrine clay deposit in a semi-arid climate

Parent material composition, particle disintegration by glaciers and lacustrine environment govern the geological development and engineering characteristics of clay deposits in southern Saskatchewan. The pre-existing expansive clay minerals were preserved due to the restrained leaching in the Regina Lake and the prevalent aridity in the area. The main objective of this paper was to develop a fundamental understanding of the clay deposit for the use in the design and construction of civil infrastructure. The results indicated the presence of expansive clay minerals in the deposit, with smectite accounting for 35% of the material. The major exchangeable cation was found to be Ca²⁺ which accounted for more than half of the total measured cation exchange capacity of 40 (cmol(+)/kg). The most likely exchange complex governing water adsorption of the clay was determined to be Ca²⁺-smectite. Alongside a high initial saturation (86%), this complex resulted in moderate volume changes in the clay. The swelling pressure was fully developed within the first hour of the constant volume test. The corrected swelling pressure was determined to be 120 kPa leading to an estimated heave of 36 mm in the surface layer of the deposit. The compression index and the swelling index were found to be 0.25 and 0.08, respectively.     

Preparation of binary and hybrid epoxy nanocomposites containing graphene oxide and rubber nanoparticles: Fracture toughness and mechanical properties

Binary and hybrid epoxy nanocomposites modified with graphene oxide (GO) and core–shell rubbers (CSR) were synthesized via the solvent-exchange method. X-ray diffraction analysis and scanning electron microscopy of the samples showed a homogeneous dispersion of GO and CSR in the epoxy matrix. The tensile modulus and tensile strength of the samples modified with CSR decreased continuously with increasing CSR content; however, with the addition of only 0.05 phr GO to the neat epoxy and rubber-modified epoxy, these properties significantly increased. The use of GO and CSR individually improved the fracture toughness, but the impact of GO was greater. The simultaneous use of GO and CSR improved both the fracture toughness and the mechanical properties. Our investigation of the toughening mechanism indicated that crack deflection–bifurcation, crack pinning, and particle debonding–pullout in the presence of GO nanosheets and limited rubber particle cavitation contributed to fracture toughness improvement in the hybrid systems. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46988.     

A high capacity tunable retransmission type frequency coded chipless radio frequency identification system

This article presents a 12‐bit frequency coded chipless RFID system in the frequency range of 3 to 6 GHz. The system consists of a fully printable chipless tag and a pair of high‐gain reader antennas. The tag also incorporates its own antennas to improve the read range. Information is encoded into frequency spectrum using a multi‐resonant circuit. The circuit consists of multiple microstrip U and L‐shaped open stub resonators patterned in a unique configuration. The proposed configuration aids in capturing more data in a reduced space as well as tunable frequency operation. Tag and reader antennas utilize techniques such as stepped impedance feeding line, defective partial ground plane, and stair‐step patch structure to achieve wide‐band impedance bandwidth in miniature size. The results of the wireless measurements in the non‐anechoic environment show that the proposed system has a reading range of more than 20 cm. The presented system possesses great potential for low‐cost short‐range inventory tracking.     

Nigella arvensis leaf extract mediated green synthesis of silver nanoparticles: Their characteristic properties and biological efficacy

In the present study, the potential of aqueous leaf extract of Nigella arevensis for biosynthesis of silver nanoparticles (AgNPs) was evaluated. The formation of AgNPs was confirmed by color changes and UV–visible spectroscopy, which showed absorbance maxima peak at 416?nm. The transmission electron microscope (TEM) image showed the AgNPs to be anisotropic and mostly spherical with sizes in the range of 5–100?nm. Fourier transform infrared (FTIR) analysis indicated that the flavonoids, alkaloids and phenolic groups present in leaf extract were involved in the reduction and capping of phytogenic AgNPs. These nanoparticles showed the cytotoxic effects against H1229 and MCF-7 cancer cell lines with an IC₅₀ value of 10?μg/mL. AgNPs showed insignificant antioxidant properties compared to the crude extract, and it was effective against clinical isolated bacterial strains. Furthermore, the bioderived AgNPs displayed significant catalytic activity against methylene blue. These results confirmed the advantages and applications of these phytogenic AgNPs using the green method in various fields.     

Synthesis of undoped and Fe nanoparticles doped SnO<Subscript>2</Subscript> nanostructure: study of structural,optical and electrocatalytic properties

In this study, undoped and nano Fe doped SnO₂ nanostructures were synthesized by hydrothermal method. Characterization of the synthesized nanostructures was performed by X-ray diffraction and scanning electron microscopy. For investigation of optical properties, photo luminescence and UV–Vis spectrum were taken. The electrochemical response of the carbon paste electrode modified with synthesized nanostructures toward levodopa (L-Dopa) was studied. Cyclic voltammetry studies using prepared modified electrodes showed outstanding electrocatalytic properties towards electro-oxidation of L-Dopa and a significant reduction was observed in anodic over voltage compared to the bare electrode. Obtained results indicated the effective role of the employed dopant. Best response in terms of the current enhancement, overvoltage reduction, and reversibility improvement of the L-Dopa oxidation reaction under experimental conditions was obtained by modified electrode with Fe doped SnO₂ nanoparticles.     

An efficient double exponentially weighted moving average Benjamini‐Hochberg control chart to control false discovery rate

A control chart based on double exponentially weighted moving average and Benjamini‐Hochberg multiple testing procedure is proposed that controls the false discovery rate (FDR). The proposed control chart is based on probabilities (or P values) to accept or reject the null hypothesis of the underlying process is in control. To make a decision, instead of using only the current probability, previous “m” probabilities are considered. The performance of the control chart is evaluated in terms of average run length (ARL) using Monte Carlo simulations. Procedure for estimation of parameters used in the control chart is also discussed. The proposed control chart is compared with previous control charts and found to be more efficient in controlling the false discovery rate.     

Secure and Trust-Aware Routing Scheme in Wireless Sensor Networks

Wireless Personal Communications - Secure and trustable routing is one of the remarkable challenges in wireless sensor networks (WSNs). In this paper, we proposed a secure, trustable and...     

Morphology Development via Static Crosslinking of (Polylactic Acid/Acrylic Rubber) as an Immiscible Polymer Blend

The interrelation between crosslinking and morphology is investigated for an immiscible blend of polylactic acid (PLA) and acrylic rubber (ACM). The blends are prepared by solution mixing and static crosslinking is used to avoid the simultaneous effect of the flow field that occurs in dynamic vulcanization. It is carried out at different temperatures, times, and curing agent contents. Scanning force microscopy (SFM) and polarized optical microscopy are used to determine the morphology of the blends. The chemical interactions and viscoelastic properties of the blends after crosslinking are also studied using infrared spectroscopy and rheological tests, respectively. Before crosslinking, SFM shows matrix‐droplet morphology for the samples that it is retained after that for the blend with 30 wt% ACM; however, it is changed to cocontinuous one in the blend with 50 wt% ACM. Partially, grafting of PLA on the crosslinked ACM is confirmed by Fourier transform infrared spectroscopy. The rheological results show that the incorporation of ACM to the PLA slows down the chain relaxation and vulcanization intensifies this effect. A model is proposed to explain the morphology evolution during static crosslinking of an immiscible blend.