[Show abstract][Hide abstract] ABSTRACT: Microcapsule-based self-healing polymer materials are highly desirable because it can heal large-volume cracks without changing the original chemical structures of polymers. However, it's limited by processing difficulties and inhomogeneous distributions of two components. Herein, we report a one-component photo-responsive self-healing polymer composites with photo-absorbing hybrid microcapsules (PAHM), which gives the microcapsules photo-absorbing properties by introducing nano-TiO2 particles as photo-absorbing and emulsified agent in the poly(urea-formaldehyde)/TiO2 hybrid shells. Upon mechanical damages and then exposed to light, the photo-responsive healing agents in the cracks will be solidified to allow for self-healing, while the healing agents in the unbroken PAHM will be protected and remain unreacted, which endows this photo-responsive microcapsule-based self-healing composite with self-healing properties like the conventional two-component microcapsule-based systems do. Given the universality of this hybrid polymerization method, incorporation of the photo-absorbing particles to conventional polymer shells may further broaden the scope of applications of these widely used materials.
[Show abstract][Hide abstract] ABSTRACT: In this paper, we report on the new design of an electric field sensor based on piezoelectric bending effect in a capacitive-sensing method. The bipolar electric field sensor with a range from −22 to 22 kV/cm concentrates on a bending structure to enlarge the piezoelectric effect and to control its bending orientation. It performs with a much higher sensitivity of 0.448 pF/(kV/cm) or 5.78%/(kV/cm) and has a better resolution of 7.0 V/cm at $E=0$. Factors influencing the capacitance response are also discussed, which might further optimize the sensitivity. Moreover, the analytical model and experimental results make an agreement on the reasonability of this electric field sensor, gaining an insightful guide to the potential capacitive-sensing electric field chip sensor widely distributed in sensor networks.
[Show abstract][Hide abstract] ABSTRACT: Hepatitis B virus (HBV) chronically infects approximately 350 million people worldwide. The replication of HBV which genome is only 3.2 kb long relies heavily on host factors. Previous studies demonstrated that a highly expressed liver-specific microRNA (miRNA) miR-122 suppresses HBV expression and replication in multiple ways. In this study, we found that the miR-122 response elements in viral genome facilitate HBV expression and replication in miR-122 highly-expressed hepatocytes. Moreover, mutations in miR-122 response elements are correlated with viral loads and disease progression in HBV-infected patients. We next found that HBV mRNA with miR-122 response elements alone could lead to altered expression of multiple host genes by whole genome expression analysis. HBV mRNA-mediated miR-122 down-regulation plays a major role in HBV mRNA-induced differential gene expression. HBV mRNA could enhance viral replication via miR-122 degradation and the up-regulation of its target cyclin G1. Our study thereby reveals that under the unique condition of high abundance of miR-122 and viral mRNAs and much lower level of miR-122 target in HBV infection, HBV may have evolved to employ the miRNA-mediated virus and host mRNAs network for optimal fitness within hepatocytes.
[Show abstract][Hide abstract] ABSTRACT: In the fabrication of linear MTJ sensors, the utilization of magnetic bias field along the easy-axis direction makes the response of MTJ nonlinear, and the Neel and magnetostatic coupling usually induces a strong interlayer coupling field along the hard-axis direction. In this paper, we investigated the influence of hard-axis and easy-axis bias field on the linearity of MTJ magnetic sensor. The prediction and optimization of linearity were done by applying an appropriate hard-axis bias field in the specific easy-axis bias field and practical TMR ratio, and the model was verified by experiments. This work can give guidance to improve the linearity and to maximize the practical TMR ratio of the MTJ sensors under a given linearity requirement.
IEEE Transactions on Magnetics 07/2015; DOI:10.1109/TMAG.2015.2439152 · 1.39 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: An advanced metering and monitoring system based on autonomous, ubiquitous and maintenance-free wireless sensor networks is of great significance to the smart grid. However, the power supply for sensor nodes (especially those installed on high-voltage side) remains one of the most challenging issues. To date, miniaturized, reliable, low-cost and flexible designs catering the massive application of self-powered sensor nodes in the smart grid are still limited. This paper presents a nonintrusive design of power supply to support the sensor network applied in the smart grid. Using a cantilever-structured magnetoelectric (ME) composite, the energy harvester is able to scavenge energy from the power-frequency (50 Hz) magnetic field distributed around the transmission line. Design considerations for this specific type of scavenger have been discussed, and optimized energy harvester prototypes have been fabricated, which are further tested on a power line platform. Experimental results show that the single-cell and double-cell energy harvesters are capable of producing 0.62 mW and 1.12 mW at 10 A, respectively, while corresponding power outputs are enhanced to 4.11 mW and 9.40 mW at 40 A. The good energy harvesting ability of this particular ME composite indicates its great potential to make a nonintrusive, miniaturized, flexible and cost-effective power supply, which possesses great application prospects in the smart grid.
[Show abstract][Hide abstract] ABSTRACT: To improve the direct and converse magnetoelectric effects, a magnetic bias field is essential to first excite the magnetization and then determine its sensitivity to a large extent. Based on the minimum energy principle, a ferromagnetic phase model is constructed and amorphous and nanocrystalline alloys are then adopted as example materials to perform numerical calculations to optimize the magnetoelectric effect. Experimental verification of the model showed that the mechanical tensile strain determines the optimum bias in a nonlinear but bijection-type correlation. To improve the magnetoelectric effect in general terms, different ranges of induced strain require a specific optimum bias that can be precisely calculated using the model solution derived in this letter.
[Show abstract][Hide abstract] ABSTRACT: This experimental study reported electrical properties of linear low density polyethylene (LLDPE)/MgO nanocomposites, which were prepared by melt blending methods. The effects of surface modified MgO nanoparticles on the microstructure, space charge distribution, thermally stimulated current and DC breakdown strength of the nanocomposites were investigated. The addition of surface modified nanoparticles increases the amount of spherulites and decreases their sizes. It is found that the LDPE/MgO interface shows significant influence on electrical properties of nanocomposites. The addition of MgO nanoparticles is available to suppress the production of space charges and enhance the DC breakdown strength, depending on the loading levels of nanoparticles. Thermally stimulated currents of nanocomposites reveal strong correlation between the traps and electrical properties of nanocomposites. It is believed that this study would provide important hint to design and develop advanced polymer nanocomposites for dielectric applications, in particular the HVDC applications.
IEEE Transactions on Dielectrics and Electrical Insulation 06/2015; 22(3):1512-1519. DOI:10.1109/TDEI.2015.7116346 · 1.28 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The application of giant magnetoresistance
sensors in power grid and other industrial fields has a great prospect benefitting from their wide bands, high sensitivity, and good linearity. This paper studies the influence of mobile ions on current measurement of GMR
sensor under high external electric field. The R-H curves of GMR multilayer sensor were depicted when the external electric and magnetic fields were both changed under three orthogonal electric field orientations. The experiment results indicate slightly varying resistances of GMR
sensor when the external electric field was changed, and simulation analysis reveals that the resistance variation is attributed to the movement of surface ions under high external electric field. Therefore, a Faraday box is essential for GMR
sensors to avoid interferences under high-strength field conditions, which is especially significant for their application as current
sensors of the power grid.
[Show abstract][Hide abstract] ABSTRACT: Wireless sensors capable of scavenging energy from ambient environment have been increasingly attractive for their outstanding merits of self-sufficient and maintenance-free. This paper presents a specific design of magnetic energy harvester based on a piezoelectric/magnet composite and a magnetic concentrator. With the employment of concentrator, the energy harvesting properties have been greatly improved, which is theoretically analyzed and experimentally demonstrated with the 35 times power enlargement. The fabricated prototype with a 3 cm air-gap concentrator harvests 326 μW power at 10 Arms, which enables sufficient and reliable power supply for a wide range of low-power sensors.
[Show abstract][Hide abstract] ABSTRACT: A magnetoelectric (ME) composite cantilever consisting of two shear-mode Pb(Zr,Ti)O3 unimorphs and a tip NdFeB permanent magnet has been demonstrated to exhibit strong ME coupling based on the superior d
15 shear response of the piezoelectric phase. The static ME coefficient and the power density under resonance condition of the fabricated samples reach 300 mV/cm·Oe and 2.25 μW/cm3·Oe2, respectively, without demand for DC bias field, which make it outperform previous designs of shear-mode ME composites. These good properties of the ME composite cantilever promise its prospects as a miniature device for sensing, transducing, and energy harvesting applications.
[Show abstract][Hide abstract] ABSTRACT: An analytic approach, aimed at characterizing the degradation properties of the double-Schottky barrier formed at the grain boundary in various electroceramics, is exhaustively described. Migration and neutralization behavior of charged defect ions is portrayed during the degradation of electrostatic potential under electrical stress. By comparing simulation results with experimental data from the aging test performed on fabricated [0 0 0 1] ZnO bicrystals, Zni2+ from VO0-Zni2+ complex donor defect is identified as the optimum candidate for the mobile ion responsible for degradation phenomena of ZnO electroceramics.
Scripta Materialia 04/2015; 104. DOI:10.1016/j.scriptamat.2015.03.019 · 3.22 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This paper evaluates the microstructure and properties of polypropylene/polyolefin elastomer (PP/POE) blends for potential recyclable HVDC cable insulation applications. PP/POE blends with different POE content were prepared by melt mixing. The introduction of POE results in a slight decrease of the melting points but improves the flexibility of PP. Compared with PP, the volume resistivity of the blends shows a decrease at low loading of POE and starts to increase when the POE loading is higher than 15 wt%. After the introduction of POE, the DC breakdown strength is slightly decreased and the hetero space charge accumulation is enhanced. Although the electrical properties of the PP/POE blends are inferior to those of the pure PP, the enhanced flexibility, high volume resistivity, high breakdown strength as well as the excellent thermal properties make the PP/POE blends have the potential for HVDC cable application. The hetero space charge accumulation is still an issue, and further modification of the blends should be considered for suppressing the space charges.
IEEE Transactions on Dielectrics and Electrical Insulation 04/2015; 22(2):673-681. DOI:10.1109/TDEI.2015.7076762 · 1.28 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The converse magnetoelectric (CME) effect, a coupling effect resulted from compositing piezoelectric phase and piezomagnetic phase, is explored insightfully concerned with applying chip-scale CME composite into extensive electric field
measurement. To establish the in-plane longitudinal CME effect, comparable mathematical models elastomechanical tensile model and elastomechanical flexural model are proposed. Grounded on generalized theoretical frameworks, the models utilized some classical magnetoelectric modeling methods. Furthermore, groups of CME composite are taken as examples to simulate and experiment for consistency verification. What highlights in the proposed models is for the purpose of forecasting and evaluating the most favorable composite and structure for CME effect applied in sensing wide range electric field.