Harmonic distortion is one of the dominant factors limiting the overall signal-to-noise and distortion ratio of seismic-grade sigma-delta MEMS accelerometers. This study investigates harmonic distortion based on the multiple degree-of-freedom model (MDM) established in our previous study. The main advantage of using an MDM is that the effect of finger flexibility on harmonic distortion is considered. Initially, the nonlinear relationship between the input acceleration and output signal is derived using the MDM. Then, harmonic distortion is simulated and described in terms of the nonlinear input-output relationship. It is found that finger flexibility and parasitic capacitance mismatch both decrease harmonic distortion. Finally, the experimental testing of harmonic distortion is implemented. By reducing the finger length to realize a higher stiffness and compensating for the parasitic capacitance mismatch, the total harmonic distortion decreases from -66.8 dB to -86.9 dB.
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http://dx.doi.org/10.3390/s23198222 | DOI Listing |
Sci Rep
December 2024
Department of Theoretical Electrical Engineering and Diagnostics of Electrical Equipment, Institute of Electrodynamics, National Academy of Sciences of Ukraine, Beresteyskiy, 56, Kyiv-57, Kyiv, 03680, Ukraine.
In this paper, an improved voltage control strategy for microgrids (MG) is proposed, using an artificial neural network (ANN)-based adaptive proportional-integral (PI) controller combined with droop control and virtual impedance techniques (VIT). The control strategy is developed to improve voltage control, power sharing and total harmonic distortion (THD) reduction in the MG systems with renewable and distributed generation (DG) sources. The VIT is used to decouple active and reactive power, reduce negative power interactions between DG's and improve the robustness of the system under varying load and generation conditions.
View Article and Find Full Text PDFPhys Rev Lett
December 2024
Departments of Physics, Chemistry, and Earth and Environmental Sciences, University of Illinois Chicago, Chicago, Illinois 60607, USA.
We study ferroelectricity in the classic perovskite ferroelectric PbTiO_{3} to high pressures with density functional theory (DFT) and experimental diamond-anvil techniques. We use second harmonic generation spectroscopy to detect lack of inversion symmetry. Consistent with early understanding and experiments, we find that ferroelectricity disappears at moderate pressures.
View Article and Find Full Text PDFACS Omega
December 2024
Institut für Theoretische Physik and Center for Materials Research (LaMa), Justus-Liebig-Universität Gießen, 35392 Gießen, Germany.
The second harmonic generation (SHG) properties of adamantane-based tetraphenyl clusters are predicted from first principles and analyzed on the basis of the involved electronic transitions. In particular, the effect of a tetrel substitution in the cluster core on the nonlinear optical response is investigated. Electronic transitions spatially localized at the substituents are found to be responsible for the optical nonlinearities.
View Article and Find Full Text PDFSci Adv
December 2024
Beijing Key Laboratory of Micro-Nano Energy and Sensor, Center for High-Entropy Energy and Systems, Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing 101400, P. R. China.
Tissue imaging is usually captured by hospital-based nuclear magnetic resonance. Here, we present a wearable triboelectric impedance tomography (TIT) system for noninvasive imaging of various biological tissues. The imaging mechanism relies on the obtained impedance information from the different soft human tissues.
View Article and Find Full Text PDFInorg Chem
December 2024
Guangxi Key Laboratory of Electrochemical Energy Materials, School of Chemistry and Chemical Engineering, Guangxi University, Nanning, Guangxi 530004, China.
As nonlinear optical (NLO) crystals, sulfates have the superiority of transparency for ultraviolet (UV) light, but they are often troubled by small nonlinear coefficients and birefringence owing to the high symmetry of the [SO] group. By introducing two neutral diethylenetriamine (DETA) molecules to replace the six coordinated water molecules of the [Zn(HO)] complex cation in [Zn(HO)](SO)(HO), a new sulfate with an acentric structure, namely, [Zn(DETA)](SO)(HO), has been designed and synthesized. Structural investigation reveals that the coordination modification of Zn ion tremendously enhances its intraoctahedral distortion.
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