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    Dynamic stability and vibration responses of a volleyball game ball
    (2025-04-25)
    Zhao Daichang
    ;
    Li Aiyun
    ;
    HABIBI, MOSTAFA  
    ;
    Zhiqiang, Song
    ;
    Albaijan, Ibrahim
    This study investigates the vibrational response of a graphene oxide-reinforced volleyball under impact loading, aiming to enhance its dynamic stability. Employing Hamilton’s principle and spherical shell coordinates, we derive the governing equations for the ball’s motion under internal loading. These equations are solved using the generalized differential quadrature (GDQ) method and analytical techniques to analyze the vibrational modes. The results demonstrate a significant correlation between the ball’s radius and its dynamic stability, with variations in radius substantially affecting vibrational characteristics. Notably, we find that increased ball mass, independent of size, contributes to enhanced stability upon ground impact. This observation suggests that heavier balls exhibit improved resistance to deformation and vibration, leading to more predictable trajectories. The findings provide a quantitative basis for optimizing volleyball design by elucidating the interplay between material reinforcement, geometry, and impact dynamics, thereby facilitating the development of volleyballs with improved stability and performance.
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    Comparison of Gamma-Oryzanol Nanoemulsions Fabricated by Different High Energy Techniques
    (MDPI AG, 2024-07-17)
    Rodrigo Jaime-Báez
    ;
    Jordi Saldo
    ;
    Rosalía América González-Soto
    Gamma-oryzanol (GO) is a bioactive compound that, due to its biological characteristics, can be added to a food matrix. However, the bioactive compound is difficult to incorporate due to its low solubility and stability. A nanoemulsion allows substances to be packaged in nanometric sizes, improving their bioavailability. In this work, a GO nanoemulsion was developed using high-energy techniques. The methodological process began with the formulation of the coarse emulsion, where the emulsifiers (sodium caseinate and citrus pectin), diluent (rice bran oil), and pH were varied to find the most stable formulation. The coarse emulsion was subjected to four high-energy techniques (conventional homogenization, high-pressure homogenization, ultra-high-pressure homogenization, and ultrasonication) to reduce the droplet size. A physical-stability test, rheological-behavior test, image analysis, and particle-size-and-distribution test were conducted to determine which was the best technique. The formulation with the highest stability (pH 5.3) was composed of 87% water, 6.1% sodium caseinate, 0.6% citrus pectin, 6.1% rice bran oil, and 0.2% GO. The ultrasonic treatment obtains the smallest particle size (30.1 ± 1 nm), and the high-pressure treatment obtains the greatest stability (TSI < 0.3), both at 0 and 7 days of storage. High-energy treatments significantly reduce the droplet size of the emulsion, with important differences between each technique.