为研究不同干燥方式对低盐腌制鲍鱼复水品质的影响,本研究采用真空冷冻干燥、冷风干燥与热风干燥对其进行干燥处理,研究其复水过程的质量体积和复水率,并通过低场核磁共振(low field nuclear magnetic resonance,LF-NMR)和磁共振成像(ma...为研究不同干燥方式对低盐腌制鲍鱼复水品质的影响,本研究采用真空冷冻干燥、冷风干燥与热风干燥对其进行干燥处理,研究其复水过程的质量体积和复水率,并通过低场核磁共振(low field nuclear magnetic resonance,LF-NMR)和磁共振成像(magnetic resonance imaging,MRI)研究复水过程的水分分布以及复水后的色差、质构、组织形态、游离氨基酸等变化情况。结果表明,在72 h时真空冷冻干鲍的复水率为278.73%,显著高于冷风干鲍和热风干鲍的复水率(P<0.05)。由LF-NMR和MRI结果分析得出,不易流动水和自由水含量是三种干鲍水分含量增加的主要因素。真空冷冻干鲍、冷风干燥和热风干鲍分别在72、48和24 h时复水完成。不同的干燥方式影响复水后的质构,结果显示,三种干燥方式的鲍鱼样品硬度与咀嚼性均有显著差异(P<0.05),真空冷冻干燥鲍鱼复水后硬度和咀嚼性最低,分别为954.01和708.59 g;热风干燥鲍鱼复水后硬度与咀嚼性最高,分别为1230.14和920.02 g。组织学染色与扫描电镜结果显示,真空冷冻干鲍的肌肉组织为较疏松的多孔结构;冷风干鲍和热风干鲍的组织为较细长和致密的结构。综上,真空冷冻干燥鲍鱼的复水率最高,硬度和咀嚼性最低,口感最好,但滋味不及热风干燥鲍鱼。本研究结果可为了解不同干燥方法对低盐腌制鲍鱼产品品质的影响提供理论参考。展开更多
A vibration energy harvester can harvest vibration energy in the environment and convert it into electrical energy to power the sensors in the Internet of Things.Human walking contains high-quality vibration energy,wh...A vibration energy harvester can harvest vibration energy in the environment and convert it into electrical energy to power the sensors in the Internet of Things.Human walking contains high-quality vibration energy,which serves as the energy source for vibration energy harvesters due to its abundant availability,high energy conversion efficiency,and environmental friendliness.It is difficult to harvest human walking vibration due to its low frequency.Converting the low-frequency vibration of human walking into high-frequency vibration has attracted attention.In previous studies,vibration energy harvesters typically increase frequency by raising excitation frequency or inducing free vibration.When walking frequency changes,the up-frequency method of raising the excitation frequency changes the voltage frequency,resulting in the best load resistance change and reducing the output power.The up-frequency method of inducing free vibration does not increase the external excitation frequency,which has relatively low output power.This paper designs a magnetostrictive vibration energy harvester with a rotating up-frequency structure.It consists of a rotating up-frequency structure,a magnetostrictive structure,coils,and bias magnets.The main body of the rotating up-frequency structure comprises a torsion bar and a flywheel with a dumbbell-shaped hole.The magnetostrictive structure includes four magnetostrictive metal sheets spliced by Galfenol and steel sheets.The torsion bar and flywheel interact to convert low-frequency linear vibration into rotating high-frequency excitation vibration of the flywheel.The flywheel plucks the magnetostrictive metal sheet with a high excitation frequency to generate free vibration.The vibration energy harvester increases the excitation frequency while inducing free vibration,which can effectively improve the output power.To characterize the excitation vibration and free vibration,based on the theory of Euler-Bernoulli beam theory,the vibration equation of the magnetostrictive metal sheet after being excited is given.According to the classical machine-magnetic coupling model and the Jiles-Atherton physical model,the relationship between stress and magnetization strength is derived.Combined with Faraday's law of electromagnetic induction,the distributed dynamic output voltage model is established.This model can predict the output voltage at different excitation frequencies.Based on this model,the mechanical-magnetic structural parameter optimization design is carried out.The parameters of the magnetostrictive metal sheet,the bias magnet,and the rotating up-frequency structure are determined.A comprehensive experimental system is established to test the device.The peak-to-peak voltage and output voltage signal by the proposed model are compared.The average relative deviation of the peak-to-peak voltage and the output voltage signal is 4.9%and 8.2%,respectively.The experimental results show that the output power is proportional to the excitation frequency.The optimum load resistance is always 800Ωas the excitation frequency changes,simplifying the impedance-matching process.The maximum peak-to-peak voltage of the device is 58.60 V,the maximum root mean square(RMS)voltage is 9.53 V,and the maximum RMS power is 56.20 mW.The magnetostrictive vibration energy harvester with a rotating up-frequency structure solves the problem of impedance matching,which improves the output power.The proposed distributed dynamic output voltage model can effectively predict the output characteristics.This study can provide structural and theoretical guidance for up-frequency structure vibration energy harvesters for human walking vibration.展开更多
为提高磁致伸缩位移传感器的测试量程,需要对传感器的输出特性进行研究,以期获得更大的检测信号。针对应力波在传播过程中的衰减直接影响检测信号幅值的问题,从声压强度与声波峰值的关系出发建立了含有传播距离的输出电压模型,确定了输...为提高磁致伸缩位移传感器的测试量程,需要对传感器的输出特性进行研究,以期获得更大的检测信号。针对应力波在传播过程中的衰减直接影响检测信号幅值的问题,从声压强度与声波峰值的关系出发建立了含有传播距离的输出电压模型,确定了输出电压随传播距离呈指数衰减的规律。为了测试输出电压随传播距离变化的关系,提出通过应力波来回多次反射来得到衰减后的电压幅值的方法,去掉波导丝两端阻尼,永磁体和检测线圈的位置不变,可以避免波导丝的不均匀性对输出电压的影响以及较长波导丝所需激励电压过高的问题。搭建了传感器输出信号衰减测试平台,对线径为0.5 mm,应力波衰减系数为0.132 3 Np·m^（-1）的Fe-Ga丝进行测试,基于所提实验方法,测得应力波传播距离为0.312~4.266 m时,偏置磁场分别为7.5和10 k A/m对应的输出电压的变化范围分别为138~79.6 m V和172~99.5 m V。从实验上验证了输出模型的准确性,应用此模型可以对传感器的输出电压值和量程进行预测。展开更多
基金supported by the National Natural Science Foundation of China(51777053,52077052)。
文摘A vibration energy harvester can harvest vibration energy in the environment and convert it into electrical energy to power the sensors in the Internet of Things.Human walking contains high-quality vibration energy,which serves as the energy source for vibration energy harvesters due to its abundant availability,high energy conversion efficiency,and environmental friendliness.It is difficult to harvest human walking vibration due to its low frequency.Converting the low-frequency vibration of human walking into high-frequency vibration has attracted attention.In previous studies,vibration energy harvesters typically increase frequency by raising excitation frequency or inducing free vibration.When walking frequency changes,the up-frequency method of raising the excitation frequency changes the voltage frequency,resulting in the best load resistance change and reducing the output power.The up-frequency method of inducing free vibration does not increase the external excitation frequency,which has relatively low output power.This paper designs a magnetostrictive vibration energy harvester with a rotating up-frequency structure.It consists of a rotating up-frequency structure,a magnetostrictive structure,coils,and bias magnets.The main body of the rotating up-frequency structure comprises a torsion bar and a flywheel with a dumbbell-shaped hole.The magnetostrictive structure includes four magnetostrictive metal sheets spliced by Galfenol and steel sheets.The torsion bar and flywheel interact to convert low-frequency linear vibration into rotating high-frequency excitation vibration of the flywheel.The flywheel plucks the magnetostrictive metal sheet with a high excitation frequency to generate free vibration.The vibration energy harvester increases the excitation frequency while inducing free vibration,which can effectively improve the output power.To characterize the excitation vibration and free vibration,based on the theory of Euler-Bernoulli beam theory,the vibration equation of the magnetostrictive metal sheet after being excited is given.According to the classical machine-magnetic coupling model and the Jiles-Atherton physical model,the relationship between stress and magnetization strength is derived.Combined with Faraday's law of electromagnetic induction,the distributed dynamic output voltage model is established.This model can predict the output voltage at different excitation frequencies.Based on this model,the mechanical-magnetic structural parameter optimization design is carried out.The parameters of the magnetostrictive metal sheet,the bias magnet,and the rotating up-frequency structure are determined.A comprehensive experimental system is established to test the device.The peak-to-peak voltage and output voltage signal by the proposed model are compared.The average relative deviation of the peak-to-peak voltage and the output voltage signal is 4.9%and 8.2%,respectively.The experimental results show that the output power is proportional to the excitation frequency.The optimum load resistance is always 800Ωas the excitation frequency changes,simplifying the impedance-matching process.The maximum peak-to-peak voltage of the device is 58.60 V,the maximum root mean square(RMS)voltage is 9.53 V,and the maximum RMS power is 56.20 mW.The magnetostrictive vibration energy harvester with a rotating up-frequency structure solves the problem of impedance matching,which improves the output power.The proposed distributed dynamic output voltage model can effectively predict the output characteristics.This study can provide structural and theoretical guidance for up-frequency structure vibration energy harvesters for human walking vibration.
文摘为提高磁致伸缩位移传感器的测试量程,需要对传感器的输出特性进行研究,以期获得更大的检测信号。针对应力波在传播过程中的衰减直接影响检测信号幅值的问题,从声压强度与声波峰值的关系出发建立了含有传播距离的输出电压模型,确定了输出电压随传播距离呈指数衰减的规律。为了测试输出电压随传播距离变化的关系,提出通过应力波来回多次反射来得到衰减后的电压幅值的方法,去掉波导丝两端阻尼,永磁体和检测线圈的位置不变,可以避免波导丝的不均匀性对输出电压的影响以及较长波导丝所需激励电压过高的问题。搭建了传感器输出信号衰减测试平台,对线径为0.5 mm,应力波衰减系数为0.132 3 Np·m^（-1）的Fe-Ga丝进行测试,基于所提实验方法,测得应力波传播距离为0.312~4.266 m时,偏置磁场分别为7.5和10 k A/m对应的输出电压的变化范围分别为138~79.6 m V和172~99.5 m V。从实验上验证了输出模型的准确性,应用此模型可以对传感器的输出电压值和量程进行预测。
