108 research outputs found
The Loading Control Strategy of the Mobile Dynamometer Vehicle Based on Neural Network PID
To solve the problems of low loading precision, slow response speed, and poor adaptive ability of a mobile dynamometer in a tractor traction test, a PID control strategy based on a radial basis function neural network with self-learning and adaptive ability is proposed. The mathematical model of the loading system is established, the algorithm of adaptive control is described, and the loading control method is simulated with MATLAB software. The system, which uses the NN-PID (neural network PID) control strategy, is used to test a YTO-MF554 tractor. Then, the proposed control strategy is validated. Results show that when the traction increases from 0 to 10 kN, the response time of the test system is 1.5 s, the average traction force in the stability range is 10.13 kN, and the maximum relative error of traction force is 2.2%. This control strategy can improve the response speed and steady-state accuracy and enhance the adaptive ability of the mobile dynamometer vehicle loading system. This study provides a reference for designing the adaptive controller of the mobile dynamometer vehicle loading system
Accelerated Carrier Recombination by Grain Boundary/Edge Defects in MBE Grown Transition Metal Dichalcogenides
Defect-carrier interaction in transition metal dichalcogenides (TMDs) play
important roles in carrier relaxation dynamics and carrier transport, which
determines the performance of electronic devices. With femtosecond laser
time-resolved spectroscopy, we investigated the effect of grain boundary/edge
defects on the ultrafast dynamics of photoexcited carrier in MBE grown MoTe2
and MoSe2. We found that, comparing with exfoliated samples, carrier
recombination rate in MBE grown samples accelerates by about 50 times. We
attribute this striking difference to the existence of abundant grain
boundary/edge defects in MBE grown samples, which can serve as effective
recombination centers for the photoexcited carriers. We also observed coherent
acoustic phonons in both exfoliated and MBE grown MoTe2, indicating strong
electron-phonon coupling in this materials. Our measured sound velocity agrees
well with previously reported result of theoretical calculation. Our findings
provide useful reference for the fundamental parameters: carrier lifetime and
sound velocity, reveal the undiscovered carrier recombination effect of grain
boundary/edge defects, both of which will facilitate the defect engineering in
TMD materials for high speed opto-electronics
Carrier Trapping by Oxygen Impurities in Molybdenum Diselenide
Understanding defect effect on carrier dynamics is essential for both
fundamental physics and potential applications of transition metal
dichalcogenides. Here, the phenomenon of oxygen impurities trapping
photo-excited carriers has been studied with ultrafast pump-probe spectroscopy.
Oxygen impurities are intentionally created in exfoliated multilayer MoSe2 with
Ar+ plasma irradiation and air exposure. After plasma treatment, the signal of
transient absorption first increases and then decreases, which is a signature
of defect capturing carriers. With larger density of oxygen defects, the
trapping effect becomes more prominent. The trapping defect densities are
estimated from the transient absorption signal, and its increasing trend in the
longer-irradiated sample agrees with the results from X-ray photoelectron
spectroscopy. First principle calculations with density functional theory
reveal that oxygen atoms occupying Mo vacancies create mid-gap defect states,
which are responsible for the carrier trapping. Our findings shed light on the
important role of oxygen defects as carrier trappers in transition metal
dichalcogenides, and facilitates defect engineering in relevant material and
device applications
Ascorbic Acid Facilitates Neural Regeneration After Sciatic Nerve Crush Injury
Ascorbic acid (AA) is an essential micronutrient that has been safely used in the clinic for many years. The present study indicates that AA has an unexpected function in facilitating nerve regeneration. Using a mouse model of sciatic nerve crush injury, we found that AA can significantly accelerate axonal regrowth in the early stage [3 days post-injury (dpi)], a finding that was revealed by immunostaining and Western blotting for antibodies against GAP-43 and SCG10. On day 28 post-injury, histomorphometric assessments demonstrated that AA treatment increased the density, size, and remyelination of regenerated axons in the injured nerve and alleviated myoatrophy in the gastrocnemius. Moreover, the results from various behavioral tests and electrophysiological assays revealed that nerve injury-derived functional defects in motor and sensory behavior as well as in nerve conduction were significantly attenuated by treatment with AA. The potential mechanisms of AA in nerve regeneration were further explored by investigating the effects of AA on three types of cells involved in this process [neurons, Schwann cells (SCs) and macrophages] through a series of experiments. Overall, the data illustrated that AA treatment in cultured dorsal root ganglionic neurons resulted in increased neurite growth and lower expression of RhoA, which is an important inhibitory factor in neural regeneration. In SCs, proliferation, phagocytosis, and neurotrophin expression were all enhanced by AA. Meanwhile, AA treatment also improved proliferation, migration, phagocytosis, and anti-inflammatory polarization in macrophages. In conclusion, this study demonstrated that treatment with AA can promote the morphological and functional recovery of injured peripheral nerves and that this effect is potentially due to AA’s bioeffects on neurons, SCs and macrophages, three of most important types of cells involved in nerve injury and regeneration
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