Proposal of Acoustic Liners Combined with Fine-Perforated-Film

This paper deals with a resonant type liner panel with a special surface structure. A typical resonant type liner panel generally consists of a perforated face plate, cells, and a back rigid plate. One of the technical challenges of the acoustic liners applied to the future ultra-high bypass ratio engines is to increase the sound absorption efficiency under grazing conditions because the nacelle, covering of the engine, tends to reduce its length and the lined area. It is known that the sound absorption of the conventional liners tends to deteriorate as grazing flow increases. The authors introduced a special thin acoustically transparent film over the face plate of the acoustic liner. The film, a fine perforated film (FPF), is expected to prevent the interaction of the grazing flow with the opening of the liner face plate. An experimental result with a flow duct rig in JAXA confirmed that the proposed combination of the acoustic liner and the FPF improved the absorption in acoustic energy under grazing conditions, compared with the sole acoustic liner and simple treatment of the FPF.

Growth Potential of Salmonella and Listeria monocytogenes in Ready-to-Eat Lettuce and Collard Greens Packaged under Modified Atmosphere and in Perforated Film

This study was aimed at determining the effects of different storage scenarios on the growth potential of Salmonella strains and Listeria monocytogenes in ready-to-eat (RTE) mixes of iceberg and crisp lettuces (Lactuca sativa) and collard greens (Brassica oleracea). Vegetables were submitted to minimal processing, experimentally contaminated to achieve 101 and 102 CFU/g, packed under modified atmosphere and in perforated film, and submitted to the following storage scenarios: I = 100% of the shelf life (6 days) at 7°C; II = 70% of shelf life at 7°C and 30% at 15°C; III = 30% at 7°C and 70% at 15°C; IV = 100% at 15°C. Higher populations of Salmonella were observed in lettuce mixes than in collard greens; the opposite occurred with L. monocytogenes. Keeping the RTE vegetables at 15°C during the whole shelf life (scenario IV) or part of it (scenarios II and III) markedly influenced the growth of both pathogens in most of the scenarios studied (P < 0.05). Growth potentials of strains of Salmonella and L. monocytogenes were significantly different depending on the scenarios in samples packed with perforated film in comparison to those stored under modified atmosphere (P < 0.05). The findings indicate that even contamination as low as 101 CFU/g can lead to high populations if there is temperature abuse during storage (15°C). This study of the behavior of Salmonella and L. monocytogenes in RTE vegetables provides insights that may be useful in the development of strategies to control pathogen growth in these products.

Quality Evaluation of Strawberries Packed with Perforated Film

Strawberries were stored in perforated film packages with different number and diameter of perforation for 5 days at 18°C simulating the ordinary logistics in Hefei. The non-perforated film packages were used as the control. Several quality parameters of strawberries were determined and analyzed everyday during storage. The principal component analysis was applied to the comprehensive assessment of strawberry quality. The results showed that suitable diameter and number of perforation could maintain strawberry quality. The comprehensive quality of strawberries packed in perforated film with 36 perforations of diameter 0.5mm was the best, followed by the ones packed in non-perforated film with internal atmosphere of low oxygen and high carbon dioxide concentration.