Prediction of effect of natural antioxidant compounds on hazelnut oil oxidation by adaptive neuro-fuzzy inference system and artificial neural network

In this study, natural compounds including gallic acid, ellagic acid, quercetin, β-carotene, and retinol were used as antioxidant agents in order to prevent and decrease oxidation in hazelnut oil. Quercetin showed the strongest antioxidative effect among the antioxidative agents, during storage. The accuracy of adaptive neuro-fuzzy inference system (ANFIS) and artificial neural network (ANN) models was studied to estimate the oil samples' peroxide value (PV), free fatty acid (FFA), and iodine values (IV). The root mean square error (RMSE), mean absolute error (MAE), and determination coefficient (R(2)) statistics were used to evaluate the models' accuracy. Comparison of the models showed that the ANFIS model performed better than the ANN and multiple linear regressions (MLR) models for estimating the PV, FFA, and IV. The values of R(2) and RMSE were found to be 0.9966 and 2.51, 0.6269 and 88.55, 0.5120 and 101.8 for the ANFIS, ANN, and MLR models for PV in testing period, respectively. The MLR was found to be insufficient for estimating various properties of the oil samples.     

Deep-collapse operation of capacitive micromachined ultrasonic transducers

Capacitive micromachined ultrasonic transducers (CMUTs) have been introduced as a promising technology for ultrasound imaging and therapeutic ultrasound applications which require high transmitted pressures for increased penetration, high signal-to-noise ratio, and fast heating. However, output power limitation of CMUTs compared with piezoelectrics has been a major drawback. In this work, we show that the output pressure of CMUTs can be significantly increased by deep-collapse operation, which utilizes an electrical pulse excitation much higher than the collapse voltage. We extend the analyses made for CMUTs working in the conventional (uncollapsed) region to the collapsed region and experimentally verify the findings. The static deflection profile of a collapsed membrane is calculated by an analytical approach within 0.6% error when compared with static, electromechanical finite element method (FEM) simulations. The electrical and mechanical restoring forces acting on a collapsed membrane are calculated. It is demonstrated that the stored mechanical energy and the electrical energy increase nonlinearly with increasing pulse amplitude if the membrane has a full-coverage top electrode. Utilizing higher restoring and electrical forces in the deep-collapsed region, we measure 3.5 MPa peak-to-peak pressure centered at 6.8 MHz with a 106% fractional bandwidth at the surface of the transducer with a collapse voltage of 35 V, when the pulse amplitude is 160 V. The experimental results are verified using transient FEM simulations.     

Sol-gel synthesis of silver/titanium dioxide (Ag/TiO2) core-shell nanowires for photocatalytic applications

Silver/titanium dioxide (Ag/TiO₂) core-shell nanowires were synthesized by direct coating of TiO₂ shells on the surface of silver nanowires (AgNWs) through a simple sol-gel process. TEM image and EDX elemental analysis had confirmed the presence of TiO₂ coating on the surface of AgNWs. The thickness of titanium dioxide coating was about 10 nm. These Ag/TiO₂ core-shell nanowires showed good photocatalytic activities in the decomposition of methylene blue as a model organic dye in aqueous solution under UV light irradiation. Ag/TiO₂ core-shell nanowires are potentially useful in photocatalytic applications.     

Phonon engineering in carbon nanotubes by controlling defect concentration

Outstanding thermal transport properties of carbon nanotubes (CNTs) qualify them as possible candidates to be used as thermal management units in electronic devices. However, significant variations in the thermal conductivity (κ) measurements of individual CNTs restrict their utilizations for this purpose. In order to address the possible sources of this large deviation and to propose a route to solve this discrepancy, we systematically investigate the effects of varying concentrations of randomly distributed multiple defects (single and double vacancies, Stone-Wales defects) on the phonon transport properties of armchair and zigzag CNTs with lengths ranging between a few hundred nanometers to several micrometers, using both nonequilibrium molecular dynamics and atomistic Green's function methods. Our results show that, for both armchair and zigzag CNTs, κ converges nearly to the same values with different types of defects, at all lengths considered in this study. On the basis of the detailed mean free path analysis, this behavior is explained with the fact that intermediate and high frequency phonons are filtered out by defect scattering, while low frequency phonons are transmitted quasi-ballistically even for several micrometer long CNTs. Furthermore, an analysis of variances in κ for different defect concentrations indicates that defect scattering at low defect concentrations could be the source of large experimental variances, and by taking advantage of the possibility to create a controlled concentration of defects by electron or ion irradiation, it is possible to standardize κ with minimizing the variance. Our results imply the possibility of phonon engineering in nanostructured graphene based materials by controlling the defect concentration.     

Determination of the Principal Volatile Compounds of Turkish Raki

Turkish Raki is a type of traditional aniseed spirit produced in different areas of Turkey. The amounts and the repartition of the alcoholic fermentation products (fusel alcohols, esters, and aldehydes) are mainly responsible for the flavours and quality of the spirit. Previous studies have been carried out on the quantification of the volatiles of the different aniseed spirits using GC and GC‐MS. In this study of 20 different commercial brands of bottled Raki and 5 homemade Turkish Raki products, the major volatiles and methanol were determined using direct injection with GC‐MS. SPME extraction was also used as a confirmation method for the separation of Raki volatiles. Eight different substances were successfully identified using SPME extraction. The results indicated that some homemade Turkish Raki products from the different regions contained slightly higher concentrations of the most studied compounds. The toxic compound methanol was detected only at a level far below the acceptable legal limit.     

An Automated Ultrasonic NDT System for In-Situ Inspection of Wind Turbine Blades

It is crucial to maintain wind turbine blades regularly, due to the high stress leading to defects or damage. Conventional methods require shipping the blades to a workshop for off-site inspection, which is extremely time-consuming and very costly. This work investigates the use of pulse-echo ultrasound to detect internal damages in wind turbine blades without the necessity to ship the blades off-site. A prototype 2D ultrasonic NDT （non-destructive testing） system has been developed and optimised for in-situ wind turbine blade inspection. The system is designed to be light weight so it can be easily carried by an inspector onto the wind turbine blade for in-situ inspection. It can be operated in 1D A-scan, 2D C-scan or 3D volume scan. A software system has been developed to control the automated scanning and show the damage areas in a 2D/3D map with different colours so that the inspector can easily identify the defective areas. Experiments on GFRP （glass fibre reinforced plastics） and wind turbine blades （made of GFRP） samples showed that internal defects can be detected. The main advantages of this system are fully automated 2D spatial scanning and the ability to alert the user to the damage of the inspected sample. It is intended to be used for in-situ inspection to save maintenance time and hence considered to be economically beneficial for the wind energy industry.     

A frequency domain boundary element formulation for dynamic interaction problems in poroviscoelastic media

A unified formulation is presented, based on the boundary element method, to perform the interaction analysis for the problems involving poroviscoelastic media. The proposed formulation permits the evaluation of all the elements of impedance and input motion matrices at a single step in terms of system matrices of boundary element method without solving any special problem, such as, unit displacement or load problem, as required by conventional methods. It further eliminates the complicated procedure and the need for using scattering analysis in the evaluation of input motion functions. The formulation is explained by considering a simple interaction problem involving an inclusion embedded in an infinite poroviscoelastic medium, which is under the influence of a dynamic excitation induced by seismic waves. In the formulation, an impedance relation is established for this interaction problem, suitable for performing the interaction analysis by substructure method, which permits carrying out the analysis for inclusion and its surrounding medium separately. The inclusion is first treated as poroviscoelastic, then viscoelastic and finally rigid, where the formulation in each of these cases is obtained consecutively as a special case of the previous one. It is remarkable to note that, a cavity problem where there is a hole in place of inclusion can be also considered within the framework of the present formulation. The formulation is assessed by applying it to some sample problems. The extension of the formulation to other types of interaction problems, such as, multi-inclusion problems, the analyses of foundations supported by a poroviscoelastic medium, etc., will be the subject of a separate study.     

A spin wave resonance study on reentrant Au77Fe23 films

Thin films prepared by both flash and slow evaporation of the bulk Au₇₇Fe₂₃ alloy have been studied by electron spin resonance (ESR) technique at the temperature range between 77–300 K. A series of spin wave resonance (SWR) peaks were observed at all temperatures when the external de magnetic field is applied along the directions lying in a small angular interval with respect to the film normal. The classical spin wave model has been used to analyze the experimental data. The magnetic parameters, such as exchange stiffness constant, the effective bulk and the surface anisotropy energy parameters of the system have been derived as a function of temperature. While the easy plane surface anisotropy almost remains constant, considerable increments were found in the exchange parameter, the magnetization and the linewidth with decreasing temperature. The SWR linewidths for the films obtained by slow evaporation at higher substrate temperatures are noticeably smaller compared to those of the film prepared by flash evaporation technique.     

On the Volta potential measured by SKPFM – fundamental and practical aspects with relevance to corrosion science

ABSTRACT

The Volta potential is an electron-sensitive parameter and describes the thermodynamic propensity of a metal to take part in electrochemical reactions. It has found widespread acceptance among corrosion researchers due to its connection to the corrosion potential and its easy measurability in local scale, being often used to study localised corrosion phenomena and micro-galvanic activities. The principle object of this paper is to provide a comprehensive, fundamental insight into the meaning of the Volta potential and to define a polarity convention of measured potentials by the scanning Kelvin probe force microscopy (SKPFM) in order to assess local nobilities in microstructures. Conditions to relate the Volta potential with the mixed-potential theory are discussed and a possible connection to corrosion phenomena explained. The limitations of the Volta potential as well as the SKPFM technique are also aimed to be explained, with some practical information to maximise the output of high quality data.     

Recovery of phenolic compounds from peach pomace using conventional solvent extraction and different emerging techniques

The study compared high-pressure, microwave, ultrasonic, and traditional extraction techniques. The following extraction conditions were implemented: microwave-assisted extraction (MAE) at 900 W power for durations of 30, 60, and 90 s; ultrasonic-assisted extraction (UAE) at 100% amplitude for periods of 5, 10, and 15 min; and high-pressure processing (HPP) at pressures of 400 and 500 MPa for durations of 1, 5, and 10 min. The highest yield in terms of total phenolic content (PC) was obtained in UAE with a value of 45.13 ± 1.09 mg gallic acid equivalent (GAE)/100 g fresh weight (FW). The highest PC content was determined using HPP-500 MPa for 10 min, resulting in 40 mg GAE/100 g, and MAE for 90 s, yielding 34.40 mg GAE/100 g FW. The highest value of antioxidant activity (AA) was obtained by UAE in 51.9% ± 0.71%. The PCs were identified through the utilization of Fourier transform infrared (FTIR) spectroscopy and high-performance liquid chromatography (HPLC). Utilizing multivariate analysis, the construction of chemometric models were executed to predict AA or total PC of the extracts, leveraging the information from IR spectra. The FTIR spectrum revealed bands associated with apigenin, and the application of HPP resulted in concentrations of 5.41 ± 0.25 mg/100 g FW for apigenin and 1.30 ± 0.15 mg/100 g FW for protocatechuic acid. Furthermore, HPLC analysis detected the presence of protocatechuic acid, caffeic acid, p-coumaric acid, and apigenin in both green extraction methods and the classical method. Apigenin emerged as the predominant phenolic compound in peach extracts. The highest concentrations of apigenin, p-coumaric acid, and protocatechuic acid were observed under HPP treatment, measuring 5.41 ± 0.25, 0.21 ± 0.04, and 1.30 ± 0.15 mg/kg FW, respectively.