232 research outputs found

    A switched reluctance motor torque ripple reduction strategy with deadbeat current control and active thermal management

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    This paper presents a switched reluctance motor (SRM) torque ripple reduction strategy with deadbeat current control and active thermal management. In this method, the SRM torque is indirectly controlled by the phase current. A deadbeat current control method is used to improve the SRM phase current control accuracy, so that SRM torque control error can be reduced significantly. According to the online measurement of the power switching device temperature, the switching frequency will be reduced to prevent the SRM power converter from being damaged by over-temperature. The feasibility and effectiveness of the proposed strategy have been verified in both simulation and experimental studies

    A switched reluctance motor torque ripple reduction strategy with deadbeat current control

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    This paper presents a switched reluctance motor (SRM) torque ripple reduction strategy with deadbeat current control. In this method, the SRM torque is indirectly controlled by the phase current. The deadbeat control method can predict the duty cycle of the switching signal for the next control period according to current error, and achieve an accurate current tracking. Thus, SRM torque control error can be reduced significantly. The feasibility and effectiveness of the proposed strategy have been verified in both simulation and experimental studies

    Excited-State Deactivation Pathways in Uracil versus Hydrated Uracil: Solvatochromatic Shift in the <sup>1</sup><i>n</i>Ï€* State is the Key

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    Excited-state deactivation mechanisms of uracil are investigated using spin-flip time-dependent density functional theory. Two important minimum-energy crossing points are located, for both gas-phase and hydrated uracil, and optimized relaxation pathways connecting the most important critical points on the <sup>1</sup><i>n</i>π* and <sup>1</sup>ππ* potential energy surfaces are determined. An ultrafast decay time constant, measured via femtosecond spectroscopy, is assigned to direct <sup>1</sup>ππ* → <i>S</i><sub>0</sub> deactivation, while a slower decay component is assigned to indirect <sup>1</sup>ππ* → <sup>1</sup><i>n</i>π* → <i>S</i><sub>0</sub> deactivation. The shorter lifetime of the dark <sup>1</sup><i>n</i>π* state in aqueous solution is attributed to a decrease in the energy barrier along the pathway connecting the <sup>1</sup><i>n</i>π* minimum to a <sup>1</sup>ππ*/<i>S</i><sub>0</sub> conical intersection. This barrier arises due to hydrogen bonding between uracil and water, leading to a blue-shift in the <i>S</i><sub>0</sub> → <sup>1</sup><i>n</i>π* excitation energy and considerable modification of energy barriers on the <sup>1</sup><i>n</i>π* potential surface. These results illustrate how hydrogen bonding to the chromophore can significantly impact excited-state dynamics and also highlight that relaxation pathways can be elucidated using low-cost methods based on density functional theory

    Hierarchical PbZr<sub><i>x</i></sub>Ti<sub>1–<i>x</i></sub>O<sub>3</sub> Nanowires for Vibrational Energy Harvesting

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    Perovskite piezoelectric material nanostructures have gained immense interest in the energy harvesting community due to their ability of converting mechanical energy into electric power in a much more efficient manner. In this paper, we first successfully synthesized PbZr<sub><i>x</i></sub>Ti<sub>1–<i>x</i></sub>O<sub>3</sub> (PZT) nanowires with unique hierarchical nanostructures that are ∼100 nm in diameter and 6 μm in length by using a facile hydrothermal process. Then, a unimorph cantilever energy harvester was fabricated by bonding mixed hierarchical PZT nanowires with a polydimethylsiloxane (PDMS) polymer matrix to a brass substrate. The measured open-circuit voltage from this harvester was 2.7 V at its fundamental resonance (25.2 Hz) under a 0.1<i>g</i> root-mean-square (RMS) acceleration input, and the measured power density was 51.8 μW cm<sup>–3</sup> with an optimal load resistance of 2 MΩ, which is approximately 8 times larger than that of the commercial BaTiO<sub>3</sub> nanoparticle energy harvester on the same scale but driven by a much higher acceleration level

    Fluorescence Turn-on Enantioselective Recognition of both Chiral Acidic Compounds and α‑Amino Acids by a Chiral Tetraphenylethylene Macrocycle Amine

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    New chiral tetraphenylethylene (TPE) macrocycles bearing optically pure amine groups were synthesized and found to have a discriminating ability between the two enantiomers of not only chiral acidic compounds but also α-amino acids by enantioselective aggregation and aggregation-induced emission (AIE) effects. NMR spectra, including 2D-NOESY, disclosed that the host–guest interaction of the macrocycle receptor played a key role in addition to the acid–base interactions

    Moderated mediating effect analysis results.

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    Innovation has emerged as a crucial factor in the sustenance and growth of enterprises. Nonetheless, small and medium-sized enterprises (SMEs) confront numerous challenges in their pursuit of innovation, owing to constraints in capital, expertise, and knowledge resources. Drawing on the resource-based theory and the input-process-output (IPO) model, this study devises a mechanism model to assess the impact of knowledge heterogeneity and innovation performance on small and medium-sized manufacturing enterprises in Guizhou Province, China. The objective is to offer recommendations for the advancement and innovation of enterprises with relative knowledge resource deficiencies. A total of 324 valid questionnaires were gathered, and the acquired data were analyzed employing SPSS 23.0 and Amos 26.0. The findings reveal that knowledge heterogeneity exerts a significantly positive influence on innovation performance. Task conflict and relationship conflict serve as partial mediators in the effects of knowledge heterogeneity on innovation performance. By capitalizing on the heterogeneity of internal and external knowledge, enterprises can effectively enhance their innovation outcomes. Furthermore, the study demonstrates that knowledge sharing possesses a moderating effect on the impact of knowledge heterogeneity on task conflict, relationship conflict, and innovation performance. In a conducive sharing environment, the ultimate effect of knowledge heterogeneity on innovation is subject to alteration.</div

    The distribution of neighboring Lys pairs in different lipid-free apo A-I models and their consistency to the CCL/MS experiment.

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    <p>The relative distance of Cβ in Lys residues in the output structure of the simulation is measured by VMD. Hollow circles indicate experimental CCL/MS data (Davison et al [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0120233#pone.0120233.ref040" target="_blank">40</a>]). The cut-off distance between two Cβ in Lys residues chosen for the calculation was 20 Å. Gray circles present the experimental data from CCL/MS method. The X and Y axes of the plot indicate the residue number of apo A-I (1–243). The cross linking data is shown through Lys pairs with a CCL link distance of 20 Å (grey circles), and compared to the CCL/MS, MD, and CMD PDB models (red plus signs). Circles with a red plus sign mean the generated model Lys distance agrees with the CCL experimental data, consequently a circle without a plus sign means the CCL data did not match the model.</p

    Alternative conformation of local structure in the MD model.

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    <p>A) The variable position of H5 and H6. The backbone of apo A-I C-terminus is presented in ribbons. Structures were aligned by backbone of residue 170 to 185. B) The changeable center angle in H2. The backbone of apo A-I is presented in ribbons. Structures were aligned by the backbone of residues 51 to 62. The ribbon is colored by index from red to blue. C) Surface hydrophobicity representation of MD model (only helix 1 and 2 are displayed). Hydrophobic surface is represented in orange, while hydrophilic surface is represented in blue. D) RMSDs of multiple simulations with the MD model. RMSDs of all protein atoms were measured over the entire trajectory of over seven simulations of the MD model (MD1 to MD7 indicate seven simulations, respectively).</p

    Salt bridge distribution of lipid-free apo A-I MD model.

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    <p>The backbone of apo A-I is presented by ribbons and colored by residue index from red (N-terminus) to blue (C-terminus). Inter-helix salt bridges (listed on the right) are presented with atomic bond. Acidic amino acids are colored by yellow and basic amino acids are colored by green.</p

    Nonisocyanate Biobased Poly(ester urethanes) with Tunable Properties Synthesized via an Environment-Friendly Route

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    The objective of this study was to explore an environment-friendly route to synthesize nonisocyanate based poly­(ester urethanes) of poly­(1,10-bis­(hydroxyethyloxycarbonylamino) decane-<i>co</i>-dicarboxylic acid) (PBDA) from renewable materials/resources. In specific, 1,10-bis­(hydroxyethyloxycarbonylamino)­decane (BHD) was first synthesized from ethylene carbonate and decamethylene diamine via the melt ring-opening reaction. Subsequently, the PBDAs with tunable properties were synthesized from BHD and five dicarboxylic acids (including three biobased ones of oxalic acid, sebacic acid, and itaconic acid) via the melt polycondensation reaction. The structural, physical, and mechanical properties of PBDAs were characterized by FTIR, NMR, XRD, GPC, TGA, and mechanical testing machine; additionally, the environmental stability was evaluated upon measuring the water absorption amount in deionized water and the degradation percentage in phosphate buffer saline. The results indicated that the PBDAs possessed reasonably good properties and thus could potentially be used for engineering applications; moreover, because their macromolecular chains/backbones contained ester and urethane groups (which would usually result in excellent cytocompatibility), it was envisioned that these PBDAs might also be suitable for some biological and/or biomedical applications
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