Effect of Al Doping on Structural, Electrical, Optical and Photoluminescence Properties of Nano-Structural ZnO Thin Films

The nano-structural Al-doped ZnO thin films of different morphologies deposited on glass substrate were successfully fabricated at substrate temperature of 350 C by an inexpensive spray pyrolysis method. The structural, electrical, optical and photoluminescence properties were investigated. X-ray diffraction study revealed the crystalline wurtzite (hexagonal) structure of the films with nano-grains. Scanning electron mi- croscopy (SEM) micrographs indicated the formation of a large variety of nano-structures during film growth. The spectral absorption of the films occurred at the absorption edge of ～410 nm. In the present study, the optical band gap energy 3.28 eV of ZnO decreased gradually to 3.05 eV for 4 mol% of Al doping. The deep level activation energy decreased and carrier concentrations increased substantially with increasing doping. Exciting with the energy 3.543 eV (λ=350 nm), a narrow and a broad characteristic photoluminescence peaks that correspond to the near band edge (NBE) and deep level emissions (DLE), respectively emerged.     

Correction to: Security analysis of an audio data encryption scheme based on key chaining and DNA encoding

Multimedia Tools and Applications - A Correction to this paper has been published: https://doi.org/10.1007/s11042-021-10592-x     

Electronic structure and optical properties of complex hydrides LiBH4 and NaAlH4 compounds

The properties of the complex hydrides LiBH₄ and NaAlH₄ such as structural, electronic, and optical properties were calculated using the augmented plane wave plus local orbitals (APW + lo) method. The three phases α, β, and γ of LiBH₄ and NaAlH₄ hydrides are studied, the β‐phase is transformed at the high‐pressure to γ phase for the compound LiBH₄ with the generalized gradient approximation (GGA) with a 16% volume decrease. However, NaAlH₄ compound did not show any phase transition. The interaction between the boron (aluminum) atoms and the hydrogen atoms in the [AlH₄]^? ([BH₄]^? ) complexes is strongly covalent, and between the complexes [AlH₄]^? and the lithium Li⁺ cations for the LiBH₄ compound and between the complexes [AlH₄]^? and the sodium Na⁺ cations for the NaAlH₄ compound, the bond is ionic. For the most stable phases of the two complex hydrides, different optical parameters have been calculated as a function of the photon energy. The plasma frequency ω_p is calculated from the mean peak of the energy loss function. Therefore, by way of example, the plasma energy ?ω_p of its peak position is 13.23 (12.93) eV for α‐NaAlH₄ (α‐LiBH₄).     

Electrical properties of an insulating varnish

A systematic dielectric study was carried out over a frequency range 60 Hz–300 kHz and at temperatures between 5 and 90°C on dehydrated castor oil mixed with different concentrations of styrene monomer to produce an insulating varnish. The volume resistivity was also studied. The results show that, when dehydrated castor oil is mixed with 10% styrene content by weight of the oil, epoxidised and then chemically treated with melamine resin and other additives, a varnish is produced with favourable electrical insulation properties.     

Assessment of Equity and Adequacy of Water Delivery in Irrigation Systems Using Remote Sensing-Based Indicators in Semi-Arid Region, Morocco

The irrigation performance criteria of equity and adequacy are of primary concern for irrigation managers. The input data required at various scales to assess irrigation performance, often not available, need costly intensive field campaigns. Remote sensing techniques, used to directly estimate crop evapotranspiration (ETc), became recently an attractive option to assess irrigation performance from individual fields to irrigation scheme or river basin scale. In this study, ETc maps were obtained by combining the FAO-56 dual approach with relationships between crop biophysical variables and NDVI (Normalized Difference Vegetation Index), using high spatial resolution time series of SPOT and Landsat images. This approach was applied for 2002/2003 growing season in Haouz plain, Morocco. Remote sensing-based indicators, reflecting equity and adequacy of the irrigation water delivery were estimated. Adequacy was determined according to Relative Irrigation supply (RIS), Depleted Fraction (DF) and Relative Evapotranspiration (RET) and equity according to the coefficient of variation of ETc. The analysis of these indicators exhibits a great variability among fields. Variability in irrigation performance at all levels, associated factors and possible improvements are discussed. This study demonstrates how remote sensing-based estimates of water consumption provide better estimates of irrigation performance at different scales than the traditional field survey methods.     

Linear and quadratic solid–shell finite elements SHB8PSE and SHB20E for the modeling of piezoelectric sandwich structures

In this article, hexahedral piezoelectric solid–shell finite element formulations with linear and quadratic interpolation, denoted by SHB8PSE and SHB20E, respectively, are proposed for the modeling of piezoelectric sandwich structures. Compared to conventional solid and shell elements, the solid–shell concept reveals to be very attractive, due to a number of well-established advantages and computational capabilities. More specifically, the present study is devoted to the modeling and analysis of multilayer structures that incorporate piezoelectric materials in the form of layers or patches. The interest in this solid–shell approach is shown through a set of selective and representative benchmark problems. These include numerical tests applied to various configurations of beam, plate and shell structures, both in static and vibration analysis. The results yielded by the proposed formulations are compared with those given by state-of-the-art piezoelectric elements available in ABAQUS, in particular, the C3D20E quadratic hexahedral finite element with piezoelectric degrees of freedom.     

PLA/SiO2 composites: Influence of the filler modifications on the morphology,crystallization behavior,and mechanical properties

Films of an architecturally modified poly(lactic acid) (PLA_REx) with three different types of fumed silica nanofillers (SiO₂) were processed through reactive extrusion‐calendering in a pilot plant. The effects of the SiO₂ type on both the dispersion and the crystallization behavior under dynamic and isothermal conditions are investigated using transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). The mechanical properties are assessed by tensile testing. TEM micrographs showed that the improved chemical affinity of both surface‐treated SiO₂ toward PLA_REx end groups did not improve particle dispersion. DSC results revealed that untreated SiO₂ nucleated PLA_REx more efficiently than both surface‐modified silicas. The activation energy for the isothermal crystallization process, as determined by an Arrhenius method, suggests that addition of untreated SiO₂ enhances the crystallization rate of PLA_REx. However, it seems that the tensile behavior remained unchanged whether silicas were added or not. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45367.     

Application of practical fuzzy arithmetic to fuzzy internal model control

This paper applies a new fuzzy arithmetic of interval calculus and fuzzy quantities to automatic control. Practical results are obtained which overcome those based on the extension principle or α-cuts. The proposed approach is based on a different representation of fuzzy numbers, though most common arithmetic operators cannot be directly applied for designing a fuzzy controller due to the unjustified overestimation effect. To avoid this phenomenon, a procedure based on an “exact” resolution calculus is proposed, whose solutions allow creating a fuzzy internal model control scheme. The validity of the new method is illustrated by a real-time educational engineering application on classical control design: a coupled tanks system.