为了探讨冻融过程中羊肉保水性的变化规律,用低场核磁共振(Nuclear magnetic resonance,NMR)技术研究了羊肉冻融过程中水的T2驰豫性质变化,同时用解冻汁液流失率、加压失水率、蒸煮损失率指标测定保水性变化。结果表明:随着冻融次数增加...为了探讨冻融过程中羊肉保水性的变化规律,用低场核磁共振(Nuclear magnetic resonance,NMR)技术研究了羊肉冻融过程中水的T2驰豫性质变化,同时用解冻汁液流失率、加压失水率、蒸煮损失率指标测定保水性变化。结果表明:随着冻融次数增加,解冻汁液流失率先显著增加,后保持较小变化,加压失水率和蒸煮损失率先显著下降再上升最后再显著下降。NMRT2驰豫测定结果显示,肌肉中有结合水、不易流动水和自由流动水3个组分,对应的横向弛豫时间分别是T2b、T21、T22,T21和冻融次数、蒸煮损失、加压失水率显著相关;T22与保水性的变化趋势一致。羊肉冻融后持水力显著下降,因此在流通过程中,尽可能避免冻融现象的出现,T21可以做为考察冻融后肉品质持水能力的一个重要指标。展开更多
The active Lamb wave and piezoelectric transducer （PZT）-based structural health monitoring （SHM） technology is a kind of efficient approach to estimate the health state of aircraft structure. In practical applicat...The active Lamb wave and piezoelectric transducer （PZT）-based structural health monitoring （SHM） technology is a kind of efficient approach to estimate the health state of aircraft structure. In practical applications, PZT networks are needed to monitor large scale structures. Scanning many of the different PZT actuator-sensor channels within these PZT networks to achieve on-line SHM task is important. Based on a peripheral component interconnect extensions for instrumentation （PXI） platform, an active Lamb wave and PZT network-based integrated multi-channel scanning system （PXI-ISS） is developed for the purpose of practical applications of SHM, which is compact and portable, and can scan large numbers of actuator-sensor channels and perform damage assessing automatically. A PXI-based 4 channels gain-programmable charge amplifier, an external scanning module with 276 actuator-sensor channels and integrated SHM software are proposed and discussed in detail. The experimental research on a carbon fiber composite wing box of an unmanned aerial vehicle （UAV） for verifying the functions of the PXI-ISS is mainly discussed, including the design of PZTs layer, the method of excitation frequency selection, functional test of damage imaging, stability test of the PXI-ISS, and the loading effect on signals. The experimental results have verified the stability and damage functions of this system.展开更多
文摘为了探讨冻融过程中羊肉保水性的变化规律,用低场核磁共振(Nuclear magnetic resonance,NMR)技术研究了羊肉冻融过程中水的T2驰豫性质变化,同时用解冻汁液流失率、加压失水率、蒸煮损失率指标测定保水性变化。结果表明:随着冻融次数增加,解冻汁液流失率先显著增加,后保持较小变化,加压失水率和蒸煮损失率先显著下降再上升最后再显著下降。NMRT2驰豫测定结果显示,肌肉中有结合水、不易流动水和自由流动水3个组分,对应的横向弛豫时间分别是T2b、T21、T22,T21和冻融次数、蒸煮损失、加压失水率显著相关;T22与保水性的变化趋势一致。羊肉冻融后持水力显著下降,因此在流通过程中,尽可能避免冻融现象的出现,T21可以做为考察冻融后肉品质持水能力的一个重要指标。
基金Foundation items： National High-tech Research and Development Program of China （2007AA03Z117） National Natural Science Foundation of China （50830201） Graduate Education Innovation Project of Nanjing University of Aeronautics and Astronautics of China （BCXJ09-01）.
文摘The active Lamb wave and piezoelectric transducer （PZT）-based structural health monitoring （SHM） technology is a kind of efficient approach to estimate the health state of aircraft structure. In practical applications, PZT networks are needed to monitor large scale structures. Scanning many of the different PZT actuator-sensor channels within these PZT networks to achieve on-line SHM task is important. Based on a peripheral component interconnect extensions for instrumentation （PXI） platform, an active Lamb wave and PZT network-based integrated multi-channel scanning system （PXI-ISS） is developed for the purpose of practical applications of SHM, which is compact and portable, and can scan large numbers of actuator-sensor channels and perform damage assessing automatically. A PXI-based 4 channels gain-programmable charge amplifier, an external scanning module with 276 actuator-sensor channels and integrated SHM software are proposed and discussed in detail. The experimental research on a carbon fiber composite wing box of an unmanned aerial vehicle （UAV） for verifying the functions of the PXI-ISS is mainly discussed, including the design of PZTs layer, the method of excitation frequency selection, functional test of damage imaging, stability test of the PXI-ISS, and the loading effect on signals. The experimental results have verified the stability and damage functions of this system.
