Design of a two-degree-of-freedom magnetic levitation vibration energy harvester for bridge vibration response analysis.

For bridges with high automobile traffic, a large amount of vibration is generated daily due to cars driving over imperfectly level roads, and a vibration energy harvester can convert this energy into electrical energy, thus providing energy for devices such as bridge health sensors. However, the traditional single degree of freedom magnetic levitation vibration energy harvester (SMEH) has the disadvantage of low output power, so this research designs an improved dual degree of freedom magnetic levitation vibration energy harvester (DMEH), and a mathematical model of the energy harvester is built for simulation tests and an optimization model based on NSGA-II algorithm is developed for optimizing the structural parameters of the energy harvester. The experimental results show that the maximum total output power of DMEH and SMEH on CSSBB1, CSSBB2 and CSSBB3 are 48.7 mW, 36.8 mW, 25.4 mW and 27.2 mW, 21.5 mW, 14.9 mW, respectively, and the minimum total magnet volumes of both on CSSBB1, CSSBB2 and CSSBB3 are 268 cm3, 132 cm3, 219 cm3, 214 cm3, 86.2 cm3, 156 cm3. Based on the experimental data, it is found that the maximum output power of the optimal solution of DMEH is larger than that of SMEH for the selected simply supported girder bridge project, and the volume of the former is also larger than that of the latter, but the degree of increase can still be adapted to the application environment. The research results have some reference significance for improving the energy harvesting efficiency of bridge vibration energy harvesters.

Preparation and characterization of novel fluorescent nanocomposite particles: CdSe/ZnS core-shell quantum dots loaded solid lipid nanoparticles.

Fluorescent quantum dots (QDs, semiconductor nanocrystals) have gained increasing attention in the past decade due to their unique optical properties. In this work, we synthesized highly luminescent lipophilic CdSe/ZnS core-shell QDs under mild conditions, and encapsulated the QDs into solid lipid nanoparticles (SLNs) to prepare fluorescent nanocomposite particles. The transmission electron microscopy image showed that the QDs were nearly monodispersed and uniform with an average diameter of about 4 nm. The fluorescence spectrum of the QDs was symmetric and narrow with an emission maximum at 556 nm. Characterized by photon correlation spectroscopy (PCS) and zeta potential measurement, the nanocomposite particles (QDs-loaded SLNs) exhibit an average particle size of about 90 nm and zeta potential of about -28 mV. Fluorescence measurements showed that the encapsulated QDs maintain their high fluorescence and narrow/symmetric emission spectra. Assembling many QDs in single nanocomposite particle significantly increases the fluorescence signal and the signal-to-background ratio compared to individual QDs. In vitro and in vivo imaging indicated that QDs-loaded SLNs were stable and slow to photobleach. These fluorescent QDs-loaded SLNs were biocompatible with fluorescence stability and had good potential in biological imaging applications. The approaches could also be used to encapsulate other optical nanocrystals or magnetic nanoparticles, and allow them to be used under aqueous biological conditions.