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Present work reports the synthesis of RE3+ (La3+, and Ce3+) and Co2+ co-doped Zn0.75Cu0.25Fe2O4 samples powder using sol-gel auto combustion process. Rietveld refinement established the spinel matrix with the space group (F d -3 m) and suggests that the uniform distribution of cations at the tetrahedral and octahedral lattice sites. The comparative study of crystallite size (D) was found using the Scherrer's relation, Scherrer's plot, Williamson-Hall (W–H), and Size-Strain (SS) plot methods for the as-prepared ferrites. The absorption band analysis confirmed the characteristic band absorptions lie in the frequency range of (577.82–418.84) 102 × m−1. Moreover, the electrical resistivity (ρ) measurements showed that the Co–Ce doped ZCF sample is highly resistive as compared to the other samples. The dielectric measurements revealed a dispersion pattern at lower frequencies and an almost frequency-independent pattern at higher frequencies. The field dependence of the dM/dH curve shows a magnetically well stable state and good crystallization cubic matrix of all the samples.

Due to their low cost, easy preparation, and outstanding electrical, dielectric, and magnetic properties, spinel ferrites are of enormous scientific and technological importance. Moreover, graphene nanoplatelets (GNPs) are an excellent supporting material for the construction of a wide range of composites. The sol-gel auto combustion (SGAC) route was used to prepare Ni0.5Co0.5Fe1.97Nd0.03O4 (NCNF) ferrite and their composites with GNPs. Single-phase structures were found by X-ray diffraction (XRD) analysis and the crystallite size increased with the insertion of GNPs into the NCNF sample. Raman spectra also confirmed the spinel structure of the ferrites and supported the existence of graphene in the composite. Micrographs indicate that agglomeration decreased in all the samples. It was found for the NCNF/2.5 wt%GNPs composite, the energy bandgap was 1.90 eV, while the temperature coefficient of resistance (TCR) had a value of -4.27 K-1 and the values of the dielectric constant and quality (Q) factor were a maximum. Moreover, the dielectric tangent loss was minimum, and magnetic tangent loss was maximum for the NCNF/2.5 wt%GNPs composite. A saturation magnetization of 108.83 emu/g and 24.06 GHz microwave frequency were observed for NCNF/2.5 wt%GNPs composite. Therefore, the composite NCNF/2.5 wt%GNPs had improved dielectric characteristics making them a promising material for a variety of applications, including microwave frequency operating devices, bolometric devices, and microwave absorbing materials.

Multi-criteria decision approaches are preferred for achieving multidimensional sustainable renewable energy goals. A more critical issue faced by the wind power industry is the selection of a location to tap prospective energy, which needs to be evaluated on multiple measures. In this paper, the aim is to assess and rank alternative wind power plant locations in Saudi Arabia. The approach presented here takes multiple criteria into consideration, such as wind speed, wind availability, site advantages, terrain details, risk and uncertainty, technology used, third party support, projected demand, types of customers, and government policies. A comparative analysis of feasible alternatives that satisfy all multi-criteria objectives is carried out. The results obtained are subjected to sensitivity analysis. Concepts such as 'threshold values' and 'attribute weights' make the approach more sensitive. Multikriteria besluitnemingsbenaderings word verkies om multi-dimensionele, volhoubare en hernubare energie doelstellings te bereik. 'n Belangrike kwessie vir die windkragindustrie is die identifisering van 'n geskikte ligging wat onderhewig is aan verskeie kriteria. Hierdie artikel assesseer en rangskik verskeie potensiële windkragopwekking liggings in Saoedi-Arabië. Die voorgestelde benadering neem meervoudige kriteria, onder andere wind spoed en wind beskikbaarheid, ligging voordele, terrein detail, risiko en onsekerheid, die tegnologie wat gebruik word, derdeparty ondersteuning, geprojekteerde vraag, die tipe kliënte en regeringsbeleide, in ag. 'n Vergelykende analise van uitvoerbare alternatiewe wat aan al die kriteria doelstellings voldoen is uitgevoer. Die daaropvolgende resultate is dan aan 'n sensitiwiteitsanalise onderwerp. Konsepte soos drempelwaardes en eienskapgewigte maak die benadering meer sensitief.

Repeating structures in the form of multiple‐bladed rotors are used widely in turbomachinery. Mistuning in turbomachinery is caused by small differences in individual blade properties because of inevitable material and manufacturing variations, resulting in the splitting of vibration modes of the tuned system. Modal characteristics of the blades are quite sensitive to the level of mistuning present inside the structure. In addition, the existence of damage also results in changed dynamics of the complete system. This paper introduces a modal assurance criterion (MAC)‐based approach for the investigation of small defects such as cracks in a repeating structure. In order to understand the key issues involved, initial work involved a numerical study of a simple comb‐like repeating structure, followed by a detailed numerical and experimental investigation of a tuned and mistuned bladed disc. Changes to the system mode shapes and mode order arising from damage are related to the location and severity of damage. Damage, in the form of small, open cracks, is modelled using different techniques such as follows: material removal, monotonic reduction in the modulus of elasticity of selected elements at the required location and mass modification. Damage indices based on differences in the MAC that give a measure of the change in the mode shapes are introduced. MAC matrices are obtained using a reduced number of data points. The damage index is obtained from the Frobenius norm of the MAC matrix subtracted from the AutoMAC of a reference tuned model without crack. A clear correlation between the damage indices and the crack depth/location is shown. Application of this approach to the limited data obtainable from developing techniques such as blade tip timing is also explained.