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Article
Publication date: 2 October 2017

Reza Ebrahimi, Mostafa Ghayour and Heshmatallah Mohammad Khanlo

This paper aims to present bifurcation analysis of a magnetically supported coaxial rotor model in auxiliary bearings, which includes gyroscopic moments of disks and geometric…

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Abstract

Purpose

This paper aims to present bifurcation analysis of a magnetically supported coaxial rotor model in auxiliary bearings, which includes gyroscopic moments of disks and geometric coupling of the magnetic actuators.

Design/methodology/approach

Ten nonlinear equations of motion were solved using the Runge–Kutta method. The vibration responses were analyzed using dynamic trajectories, power spectra, Poincaré maps, bifurcation diagrams and the maximum Lyapunov exponent. The analysis was carried out for different system parameters, namely, the inner shaft stiffness, inter-rotor bearing stiffness, auxiliary bearing stiffness and disk position.

Findings

It was shown that dynamics of the system could be significantly affected by varying these parameters, so that the system responses displayed a rich variety of nonlinear dynamical phenomena, including quasi-periodicity, chaos and jump. Next, some threshold values were provided with regard to the design of appropriate parameters for this system. Therefore, the proposed work can provide an effective means of gaining insights into the nonlinear dynamics of coaxial rotor–active magnetic bearing systems with auxiliary bearings in the future.

Originality/value

This paper considered the influences of the inner shaft stiffness, inter-rotor bearing stiffness, auxiliary bearing stiffness and disk position on the bifurcation behavior of a magnetically supported coaxial rotor system in auxiliary bearings.

Details

Engineering Computations, vol. 34 no. 7
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 5 December 2024

Parisa Rousta, Mozhgan Shahamirian, Sedigheh Yazdanpanah and Alireza Shirazinejad

This study investigated the production of free and encapsulated nanoemulsions using Cordia myxa fruit peel (CMFP) extract and vitamin D3.

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Abstract

Purpose

This study investigated the production of free and encapsulated nanoemulsions using Cordia myxa fruit peel (CMFP) extract and vitamin D3.

Design/methodology/approach

The CMFP extract was obtained using an ultrasonic technique, and its characteristics such as total phenolic content (TPC), antioxidant activity, cytotoxicity and gas chromatography-mass spectrometry (GC/MS) analysis were assessed. CMFP was encapsulated in vitamin D3 oil droplets of nanoemulsion prepared by ultra-homogenization using calcium alginate polymer. The nanoemulsions were evaluated for 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity, antimicrobial activity, morphology, Fourier transform infrared (FTIR) analysis and release rate in a simulated gastrointestinal model.

Findings

The GC/MS results revealed that pyrocatechol, cholestanoids and propionaldehyde were the predominant compounds in the extract. The highest cytotoxicity effect of CMFP was observed at concentrations of 6.25 and 12.5 ppm of the extract. Encapsulated nanoemulsions exhibited the highest antimicrobial activity against Escherichia coli (ATCC 35218). The antioxidant activity of the free and encapsulated nanoemulsions ranged from 25.81 to 36.08 mg/100g and 49.25–55.7 mg/100g, respectively. Free nanoemulsions showed a higher release rate in the simulated gastric model compared to encapsulated ones. The FTIR spectrum allowed for the identification of functional groups responsible for antioxidant and antibacterial properties, indicating that these properties of the nanoemulsions were maintained.

Originality/value

This study demonstrates the successful co-encapsulation of CMFP extract and vitamin D3 in nanoemulsions, which significantly enhanced the stability, bioavailability and functional properties of both compounds. Encapsulated nanoemulsions exhibited higher antioxidant and antimicrobial activities compared to their free counterparts, with controlled release in simulated gastrointestinal conditions. These findings confirm that nanoemulsion-based encapsulation is an effective strategy to protect and enhance the bioactivity of plant extracts and vitamins, supporting their potential use in functional food products and therapeutic application.

Details

British Food Journal, vol. 127 no. 2
Type: Research Article
ISSN: 0007-070X

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