A low-power circuit for piezoelectric vibration control by synchronized switching on voltage sources

In the paper, a vibration damping system powered by harvested energy with implementation of the so-called SSDV (synchronized switch damping on voltage source) technique is designed and investigated. In the semi-passive approach, the piezoelectric element is intermittently switched from open-circuit to specific impedance synchronously with the structural vibration. Due to this switching procedure, a phase difference appears between the strain induced by vibration and the resulting voltage, thus creating energy dissipation. By supplying the energy collected from the piezoelectric materials to the switching circuit, a new low-power device using the SSDV technique is proposed. Compared with the original self-powered SSDI (synchronized switch damping on inductor), such a device can significantly improve its performance of vibration control. Its effectiveness in the single-mode resonant damping of a composite beam is validated by the experimental results.Comment: 11 page

A New Open Loop Approach for Identifying the Initial Rotor Position of a Permanent Magnet Synchronous Motor

The precision of initial rotor position detection is critical for the start and running performance of permanent magnet synchronous motor (PMSM). This work describes a new open loop approach for identifying the initial position of a PMSM with an incremental encoder, even when a constant load torque is being applied. By giving a testing current with high frequency to the stator winding, the initial rotor position of a PMSM can be detected with reasonable accuracy. The rotor almost does not move during the process of identification. The FFT algorithms are used to remove the phase bias effects in identification. Our approach is quicker and simpler than the conventional approaches

Sb-, Dy-, and Eu-doped oxyfluoride silicate glasses for light emitting diodes

International audienceA series of Sb-, Dy-, and Eu-doped oxyfluoride silicate glasses for light emitting diodes (LEDs) applications were prepared via the melt-quenching method, and studied by a) photoluminescence emission and excitation spectra, b) decay curves, c) Commission Internationale de L'Eclairage (CIE) chromaticity coordinates, and d) correlated color temperatures (CCTs). We discover the energy transfer from Sb3+ to Dy3+ ions occurs in Sb/Dy co-doped glass. We also find the emission behavior of Sb3+ single doped glass is dependent on the excitation wavelength. Furthermore, the white light emission can be achieved in Sb/Dy/Eu co-doped oxyfluoride silicate glasses under ultraviolet (UV) light excitation. The results presented here demonstrate that the as-prepared Sb/Dy/Eu doped oxyfluoride silicate glasses may serve as a potential candidate for LEDs-based lightin

Research And Application On The Coupled Method Of Remote-Sensing And Ground-Monitoring Of Reservoir Storage Capacity

Reservoir storage capacity monitoring is the basis of reservoir operation. The relationship curves of reservoir water level-area and water level-capacity are the significant parameters of storage capacity calculation. With the long-term operation, both on the bottom and bank of the reservoir have erosion and deposition, causing the relationship of water level-area and level-storage changes, which leads to inaccuracy of reservoir storage capacity calculation with the original curves. It is costly to revise the curves of reservoir water level-area and water level-capacity by ground measurement termly. A coupled Method of Remote-sensing and Ground-monitoring of Reservoir Storage Capacity is proposed in this paper. Based on coupled data of satellite image of the reservoir water-area monitoring and the ground water-level monitoring on the same day, the relationship curves of reservoir water level-area and water level-capacity are updated, the calculation accuracy of reservoir storage capacity is improved. The Gangnan Reservoir is taken as an example for this research. 10 HJ-satellite images are used for revising the curve of reservoir water level-area and water level-capacity. The reservoir storage capacity differences between original and revised curves are analyzed and turned out to be reasonable

The Analysis of the Difficult Points on Developing E-Commerce of the Western Region in China

From 1999, China started to the project of “Development of Western Region of China” and many preferential policies were issued by the central government. However, after almost 5 years, compared with eastern region, the development of infrastructure is still relatively lower. As to the development of E-commerce, the most typical phenomenon is unbalance which means that the eastern region is much faster than the western because of territorial and economic factors. So it is necessary to get a whole picture and get a clear understanding of problems of current situation of E-commerce in west part of China in order to accelerate it. In this article, the difficult points of E-commerce development in west region are discussed, such as the law issue, infrastructure, information service providers and talents people and some strategies will be given finally based on the current situation of E-commerce in west part of China

STROBE-GnRHa pretreatment in frozen-embryo transfer cycles improves clinical outcomes for patients with persistent thin endometrium: A case-control study.

The well-prepared endometrium with appropriate thickness plays a critical role in successful embryo implantation. The thin endometrium is the main factor of frozen-embryo transfer (FET), resulting in the failure of implantation undergoing FET. Hormone treatment is suggested to improve endometrium thickness; however, among the larger numbers of cases, it cannot reach the sufficient thickness, which leads to a high cancelation rate of embryo transfer as well as waste high-quality embryos. Thus, it increases the burden to patients in both economic and psychological perspectives. We performed a retrospective observational study, which was composed with 2 cohorts, either with the conventional hormone replacement therapy (HRT) protocol or HRT with gonadotrophin-releasing hormone agonist (GnRHa) pretreatment to prepare the endometrium before FET. The measurements of endometrium thickness, hormone level, transfer cycle cancelation rate, pregnancy rate, and implantation rate were retrieved from the medical records during the routine clinic visits until 1 month after embryo transfer. The comparisons between 2 cohorts were performed by t-test or Mann-Whitney U test depending on the different attributions of data. In total, 49 cycles were under HRT with GnRHa pretreatment and 84 cycles were under the conventional HRT protocol. HRT with GnRHa pretreatment group improved the endometrial thickness (8.13 ± 1.79 vs 7.51 ± 1.45, P = .031), decreased the transfer cancelation rate (P = .003), and increased clinical pregnancy rate and implantation rate significantly (both P = .001). Additionally, luteinizing hormone level in pretreatment group was consistently lower than conventional HRT group (P < .05). Our study revealed HRT with GnRHa pretreatment efficiently improved the endometrial thickness, therefore, decreased the FET cycle cancelation. It also elevated the embryo implantation rate and clinical pregnancy rate by improving endometrial receptivity

Comparative analysis of the secretomes of Schizophyllum commune and other wood-decay basidiomycetes during solid-state fermentation reveals its unique lignocellulose-degrading enzyme system

Additional file 3: Table S2. Identified proteins in the secretomes of four fungi during SSF on Jerusalem artichoke stalk

Stable Li Metal Anode Enabled by Space Confinement and Uniform Curvature through Lithiophilic Nanotube Arrays

The application of lithium (Li) metal anodes in rechargeable batteries is primarily restricted by Li dendrite growth on the metal’s surface, which leads to shortened cycle life and safety concerns. Herein, well‐spaced nanotubes with ultrauniform surface curvature are introduced as a Li metal anode structure. The ultrauniform nanotubular surface generates uniform local electric fields that evenly attract Li‐ions to the surface, thereby inducing even current density distribution. Moreover, the well‐defined nanotube spacing offers Li diffusion pathways to the electroactive areas as well as the confined spaces to host deposited Li. These structural attributes create a unique electrodeposition manner; i.e., Li metal homogenously deposits on the nanotubular wall, causing each Li nanotube to grow in circumference without obvious sign of dendritic formation. Thus, the full‐cell battery with the spaced Li nanotubes exhibits a high specific capacity of 132 mA h g−1 at 1 C and an excellent coulombic efficiency of ≈99.85% over 400 cycles.This work presents a technique for suppressing lithium dendrite formation through ultrauniform curvature and space confinement. Lithium uniformly deposits/dissolves on the nanotube surfaces where the local current distribution is uniform due to the ultrauniform curvature. The nanotube spacing provides confined spaces to host deposited lithium. Thus, a full‐cell battery with spaced lithium nanotubes shows excellent specific capacity at high rates.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/153606/1/aenm201902819_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/153606/2/aenm201902819-sup-0001-SuppMat.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/153606/3/aenm201902819.pd

Enhanced Interfacial Electronic Transfer of BiVO4 Coupled with 2D g‐C3N4 for Visible‐light Photocatalytic Performance

A BiVO4/2D g‐C3N4 direct dual semiconductor photocatalytic system has been fabricated via electrostatic self‐assembly method of BiVO4 microparticle and g‐C3N4 nanosheet. According to experimental measurements and first‐principle calculations, the formation of built‐in electric field and the opposite band bending around the interface region in BiVO4/2D g‐C3N4 as well as the intimate contact between BiVO4 and 2D g‐C3N4 will lead to high separation efficiency of charge carriers. More importantly, the intensity of bulid‐in electric field is greatly enhanced due to the ultrathin nanosheet structure of 2D g‐C3N4. As a result, BiVO4/2D g‐C3N4 exhibits excellent photocatalytic performance with the 93.0% Rhodamine B (RhB) removal after 40 min visible light irradiation, and the photocatalytic reaction rate is about 22.7 and 10.3 times as high as that of BiVO4 and 2D g‐C3N4, respectively. In addition, BiVO4/2D g‐C3N4 also displays enhanced photocatalytic performance in the degradation of tetracycline (TC). It is expected that this work may provide insights into the understanding the significant role of built‐in electric field in heterostructure and fabricating highly efficient direct dual semiconductor systems