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169 results on '"Song, ChunFang"'

26. Effects of freeze–thaw pre‐treatment with different freezing methods on the microwave freeze drying of carrots.

Author

Li, Linlin, Chen, Xinyi, Cao, Weiwei, Liu, Wenchao, Duan, Xu, Ren, Guangyue, and Song, Chunfang

Subjects
MICROWAVE drying, FOOD dehydration, PRODUCT attributes, PRODUCT quality, CELL anatomy, CARROTS
Abstract

Summary: Three freeze–thaw (FT) pre‐treatments using different freezing methods that freezing at −80 °C (FT‐80), freezing at −25 °C (FT‐25) and vacuum freezing (VFT) were used for carrot slices, the effects and mechanisms of FT pre‐treatment on the drying characteristics and product quality of carrots during microwave freeze drying (MFD) were studied. The results showed that FT pre‐treatment under different freezing methods affected the water state of carrots, resulting in varying degrees of moisture loss and shortening drying time by 14.3% to 42.8%. VFT treatment caused the greatest water loss (35.33%) during FT and significantly increased the effective moisture diffusivity in the MFD process. FT treatments did not cause any significant degradation in the colour of the carrots. The VFT and FT‐80 treatments resulted in an elevated rehydration ratio, increased crispiness of MFD carrots and products with a porous microstructure and higher porosity. In contrast, the FT‐25 treatment led to a decrease in porosity due to destructive damage to the carrot cell structure. However, this damage favoured the extractability of carotenoids, resulting in a higher carotenoid content than the other treatments. This study provides a theoretical foundation for the practical implementation of FT pre‐treatment using various freezing methods on fresh foods prior to drying. It is recommended to employ VFT pre‐treatment before MFD due to its efficiency and effectiveness. [ABSTRACT FROM AUTHOR]

Published
2024
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41. Dynamic characteristics of two degree-of-freedom quasi-zero stiffness vibration isolation system with nonlinear springs.

Author

Liu, Yanqi, Ji, Wen, Deng, Erjie, Wang, Xin, and Song, Chunfang

Subjects
VIBRATION isolation, NONLINEAR systems, LINEAR systems, NONLINEAR equations, ANALYTICAL solutions, DEGREES of freedom, VIBRATION tests
Abstract

Based on the anti-resonance characteristics of multi-degree-of-freedom system, negative stiffness structures containing nonlinear inclined springs (NIS) are introduced to form a two degree-of-freedom (DOF) quasi-zero stiffness (QZS) vibration isolator. The remarkable feature of this system is the use of nonlinear springs to achieve the nonlinear stiffness. The restoring force generated by the NIS includes both linear stiffness term and cubic stiffness term. First, through static characteristic analysis, the relation between parameters is derived when the system meets QZS conditions. Influences of mechanical and structural parameters on stiffness characteristics are studied. Then, nonlinear dynamic equations of the two DOF vibration isolation system with QZS are established. Using the harmonic balance method, the frequency-domain analytical solutions and expression of force transmissibility are deduced. Effects of damping ratio, vertical stiffness ratio, mass ratio and excitation amplitude on the dynamic response and force transmissibility are numerically discussed. The isolation performance of the system is in comparison with single DOF QZS system and two DOF QZS system with linear inclined springs (LIS). The results indicate that smaller structural parameter E and nonlinear inclined springs with softening stiffness are conducive to obtain smaller system stiffness and larger low-stiffness interval near equilibrium position. Furthermore, by selecting suitable parameters, the system has advantages of achieving the lower initial isolation frequency and wider isolation frequency band. In addition, the attenuation rate of force transmissibility in a certain frequency region is able to be obviously accelerated and the low-frequency isolation performance of the system can be dramatically improved. [ABSTRACT FROM AUTHOR]

Published
2023
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