37 research outputs found
Down-regulation of BTG1 by miR-454-3p enhances cellular radiosensitivity in renal carcinoma cells
Modelling of a cantilevered energy harvester with partial piezoelectric coverage and shunted to practical interface circuits
Effects of Nano-Graphene Oxide on the Growth and Reproductive Dynamics of Spodoptera frugiperda Based on an Age-Stage, Two-Sex Life Table
The development and reproduction of the fall armyworm (FAW), Spodoptera frugiperda, which were reared on artificial diets containing nano-graphene oxide (GO), were determined based on age-stage, two-sex life table analysis. The results showed that GO had adverse effects on FAWs. Compared with the control, the duration of the egg stage and first, second, and sixth instar larval stages increased with increasing GO concentrations; however, the lifespan of male and female adults decreased with increasing GO concentrations. Weights of FAW pupae that were supplied with GO-amended diets increased by 0.17–15.20% compared to the control. Intrinsic growth, limited growth, and net reproductive rates of FAWs feeding on GO supplemented diets were significantly lower than the control, while mean generational periods (0.5 mg/g: 38.47; 1 mg/g: 40.38; 2 mg/g: 38.42) were significantly longer than the control. The expression of genes encoding vitellogenin (Vg) and vitellogenin receptor (VgR) expression was abnormal in female FAW adults feeding on GO-amended diets; the number of eggs laid decreased relative to the control, but Vg expression increased. In conclusion, GO prolonged the developmental period of FAWs, decreased fecundity, and led to a decline in the population size. The study provides a basis for the rational use of GO as a pesticide synergist for FAW control
Frequency Up-Conversion for Vibration Energy Harvesting: A Review
A considerable amount of ambient vibration energy spreads over an ultra-low frequency spectrum. However, conventional resonant-type linear energy harvesters usually operate within high and narrow frequency bands, which cannot match the frequencies of many vibration sources. If the excitation frequency deviates a bit from the natural frequency of an energy harvester, the energy harvesting performance will deteriorate drastically. Because of the ultra-low frequency characteristic, it is challenging to reliably harvest energy from the ambient vibrations. To address this mismatching issue, the ultra-low frequency ambient vibrations are converted into high-frequency oscillations using certain mechanical mechanisms, which are termed frequency up-conversion techniques. This paper reviews the existing approaches that can realize frequency up-conversion for enhancing energy harvesting from low-frequency vibration sources. According to their working mechanisms, the existing methods are classified into three categories: impact-based, plucking-based, and snap-through-based approaches. The working principles of the three approaches are explained in detail. Representative designs from all categories are reviewed. This overview on the state-of-the-art frequency up-conversion technology would guide the better design of future kinetic energy harvesting systems
Frequency Up-Conversion for Vibration Energy Harvesting: A Review
A considerable amount of ambient vibration energy spreads over an ultra-low frequency spectrum. However, conventional resonant-type linear energy harvesters usually operate within high and narrow frequency bands, which cannot match the frequencies of many vibration sources. If the excitation frequency deviates a bit from the natural frequency of an energy harvester, the energy harvesting performance will deteriorate drastically. Because of the ultra-low frequency characteristic, it is challenging to reliably harvest energy from the ambient vibrations. To address this mismatching issue, the ultra-low frequency ambient vibrations are converted into high-frequency oscillations using certain mechanical mechanisms, which are termed frequency up-conversion techniques. This paper reviews the existing approaches that can realize frequency up-conversion for enhancing energy harvesting from low-frequency vibration sources. According to their working mechanisms, the existing methods are classified into three categories: impact-based, plucking-based, and snap-through-based approaches. The working principles of the three approaches are explained in detail. Representative designs from all categories are reviewed. This overview on the state-of-the-art frequency up-conversion technology would guide the better design of future kinetic energy harvesting systems
Time-sharing Orbit Jump and Energy Harvesting in Nonlinear Piezoelectric Energy Harvesters Using a Synchronous Switch Circuit
Nonlinearity has enabled energy harvesting to advance towards higher power
output and broader bandwidth in monostable, bistable, and multistable systems.
However, challenges in operating in the high energy orbit (HEO) rather than low
energy orbit (LEO) have restricted their applications. Based on a monostable
nonlinear system, this paper proposes a self-contained solution for
time-sharing orbit jump and energy harvesting. The joint dynamics of an
electromechanical assembly consisting of a nonlinear energy harvester and a
switch-mode piezoelectric interface circuit is studied for high-capability
energy harvesting. The proposed solution is carried out by utilizing a
cutting-edge switch-mode bidirectional energy conversion circuit (BECC), which
enables time-sharing dual functions of energy harvesting and vibration
exciting. A theoretical model is established based on impedance analysis and
multiple time scales method to analyze the stability, frequency response, and
phase evolution of the autonomous and nonautonomous nonlinear energy harvesting
systems. Particularly, the detailed dynamics for the orbit jumps with vibration
exciting mode of BECC are studied. Experiments are performed to validate the
full-range orbit jumps with the monostable nonlinear energy harvester. The
harvested power after orbit jumps yields a nine-fold increase, compensating for
the energy consumption under vibration exciting mode quickly. The proposed
solution also refrains the system from extra mechanical or electrical energy
sources for orbit jumps, which leads to the first self-contained solution for
simultaneous energy harvesting and orbit jump in nonlinear piezoelectric energy
harvesting. This work enhances the practical utility of nonlinear energy
harvesting technologies toward engineering applications