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This study aims to address the issue of high-precision measurement of AC electric field. An electro-optical sensor with high sensitivity is proposed for this purpose.

The proposed sensor combines electromagnetic induction and fiber Bragg grating (FBG) sensing techniques. It is composed of a sensing probe, a piece or stack of piezoelectric ceramics (PZT) and an FBG. A signal processing circuit is designed to rectify and amplify the induced voltage. The processed signal is applied to the PZT and the deformation of PZT is detected by FBG. Theoretical calculation and simulation are conducted to verify the working principle of the probe. The sensor prototype is fabricated and its performance is tested.

The results of this study show that the sensor has good linearity and repeatability. The sensor sensitivity is 0.061 pm/Vm⁻¹ in the range from 250 to 17,500 V/m, enabling a measurement resolution of electric field strength of 16.3 V/m. The PZT stack is used to enhance the sensor sensitivity and the resolution can be improved up to 3.15 V/m.

A flexure hinge lever mechanism is used to amplify the deformation of PZT for further enhancement of sensitivity. The results show that the proposed sensor has high sensitivity and can be used for the accurate measurement of an electric field. The proposed sensor could have potential use for electric field measurement in the power industry.

This study aims to elaborate on the microencapsulation of the plant extract (PE, from Camellia sinensis leaf, clover flower and cocoa flower) and the preparation of a slow-release lining fabric loading the PE microcapsule.

PE was microencapsulated into polyvinyl alcohol (PVA) shells through interfacial polymerization. The morphology, thermal stability, slow-release property and drug loading ratio of the PVA/PE microcapsules were characterized to ensure the availability in coating finishing. To find the optimum parameters, the composite fabrics were prepared from non-woven fabrics coated by calcium alginate hydrogel, which glued mass fractions of microcapsules and dried in different ways. To evaluate the effectiveness, a lipase enzyme activity test was conducted.

Under optimal conditions, the PVA/PE microcapsules with smooth surface have an average particle size of 14.5 um, and they are expected to reach a loading ratio of 38.5 per cent while remaining stable under 220°C. Given a microcapsule of 4 per cent (of the mass), the composite fabric has a good hand feeling, being prepared through calcium chloride coating. It is shown that the inhibition ratios of the microcapsules and composite fabrics on lipase are 31.3 and 21.0 per cent, respectively.

The composite fabric could be prepared through the other finishing methods such as padding and printing. In addition, the release mechanism of the composite could be studied.

This study provided a simple and effective way to prolong the duration of PE. This way was conductive to protect environmental sensitive PEs from being destroyed in compositing processes.

Preparing composite fabrics for transdermal delivery system was novel and other kind of plant extracts could be used in this way.