This paper proposes a three-vector-based low-complexity model predictive direct power control (LC-MPDPC) strategy for doubly fed induction generators (DFIGs) in wind energy applications. Previous ...studies have applied one- and two-vector-based LC-MPDPC strategies for ac/dc converters with a satisfactory control performance. In this paper, an elaborated analysis of the DFIG mathematical model is made and then the feasibility of one- and two-vector-based LC-MPDPC strategies for DFIG are analyzed. However, using these approaches, the steady-state errors cannot be eliminated completely. Thus, a three-vector-based LC-MPDPC is further proposed to eliminate the power error. Both simulation and experimental results indicate that the proposed three-vector-based LC-MPDPC can significantly improve the steady-state performance and achieve an error-free control. In addition, its dynamic performance remains satisfactory compared with one- and two-vector-based LC-MPDPC.
Heavy metal pollution has pervaded many parts of the world, especially in developing countries. The purpose of this study was to determine the concentrations and health risks of heavy metals in urban ...soils around an electronics manufacturing site in the Hubei Province of China. Soils samples were collected from commercial, roadside, farmland, and residential areas around the electronics manufacturing facility. A total of 136 topsoil samples were collected, and these samples were analyzed for Cr, Cu, Zn, As, Cd, Ni, and Pb. The geoaccumulation index (Igeo), pollution index (PI), and potential ecological risk index (PER) were calculated to assess the soil pollution levels. The hazard index (HI) was used to assess the human health risks posed by the presence of heavy metals. The total concentrations of the seven congeners (∑metals) ranged from 3738.86 to 5173.25mgkg−1, and the concentrations were highest in the commercial area followed (in decreasing order) by the roadside, farmland, and residential areas. The HI for children and adults descended in the order of Cr>As>Pb>Cd>Cu>Ni>Zn. The carcinogenic risks of two metals, namely, Cr and As, for children and adults were higher than 10−4, and children faced greater health risks.
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•Metal contamination was detected in soils near an electronics manufacturing facility.•Chromium, zinc, and lead were the most abundant metals detected.•Risks assessment results indicate that these soils may pose health risks.
This paper proposes a low-complexity model predictive direct power control (LC-MPDPC) strategy for doubly fed induction generator (DFIG) under both balanced and unbalanced grid conditions. Based on ...the elaborated analysis of the mathematical model of DFIG, proper formulas for the LC-MPDPC strategy are obtained. A unified power compensation strategy is proposed to achieve various control targets flexibly during unbalanced grid condition. Comparative experimental studies of lookup table-based direct power control and LC-MPDPC for DFIG are conducted to validate the superior steady-state and dynamic performance of the LC-MPDPC under balanced grid condition. Furthermore, the experimental results also prove that the proposed LC-MPDPC with power compensation can satisfy different operation requirements of the DFIG system under unbalanced grid condition, and the dynamic response is satisfactory when the control target changes.
Polyaniline, polyaniline/graphene composites were synthesized by a novel in situ chemical oxidative polymerization method including two oxidants. The morphology and structure of the material were ...characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). The electrochemical performance of polyaniline (PANI)-based composites was tested by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) testing, and constant current charge and discharge (GCD) tests. At 0.2 C of constant current, the discharge specific capacities of PANI/graphene oxide (PANI/GO) and PANI/GO-sodium borohydride (graphene oxide is reduced by sodium borohydride, named PANI/GO-NaBH
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) were as high as 183 mAh/g and 192 mAh/g, respectively, which was nearly twice as high as that of PANI (100 mAh/g). After 100 charge and discharge cycles, the capacity retention rates of PANI, PANI/GO, and PANI/GO-NaBH
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were 80.4%, 89.4%, and 95.05%, respectively; the cycle performance was greatly improved before the modification. These results indicate that the composite has exciting potentials for the cathode material of zinc-rechargeable battery.
Abstract
Rechargeable aqueous zinc-ion batteries are a promising candidate for next-generation energy storage devices. However, their practical application is limited by the severe safety issue ...caused by uncontrollable dendrite growth on zinc anodes. Here we develop faceted titanium dioxide with relatively low zinc affinity, which can restrict dendrite formation and homogenize zinc deposition when served as the protective layer on zinc anodes. The as-prepared zinc anodes can be stripped and plated steadily for more than 460 h with low voltage hysteresis and flat voltage plateau in symmetric cells. This work reveals the key role of crystal orientation in zinc affinity and its internal mechanism is suitable for various crystal materials applied in the surface modification of other metal anodes such as lithium and sodium.
Smart cities improve services for businesses, among many other benefits. A comprehensive understanding and effective utilization of these advantages is crucial for promoting business development. ...Using panel data from Chinese listed companies (2010-2020), this study employs a multi-stage DiD model to investigate the impact of smart cities on corporate earnings management. The findings indicate that the smart city pilot policy has significantly reduced corporate earnings management. Further analysis suggests that smart cities primarily reduce earnings management by improving firms' external information environments. Additionally, the results show that the policy impact of smart cities is more significant in regions with lower regulatory intensity or higher marketization levels, compared to regions with higher regulatory intensity or lower marketization levels. Similarly, firms in less concentrated markets or those more closely related to smart city development tend to experience greater reductions in earnings management due to smart city construction, unlike firms in more concentrated markets or those less involved. Finally, this paper offers several brief suggestions.
Reversible post-translational modifications represent a mechanism to control tumor metabolism. Here we show that mitochondrial Sirtuin5 (SIRT5), which mediates lysine desuccinylation, ...deglutarylation, and demalonylation, plays a role in colorectal cancer (CRC) glutamine metabolic rewiring. Metabolic profiling identifies that deletion of SIRT5 causes a marked decrease in
C-glutamine incorporation into tricarboxylic-acid (TCA) cycle intermediates and glutamine-derived non-essential amino acids. This reduces the building blocks required for rapid growth. Mechanistically, the direct interaction between SIRT5 and glutamate dehydrogenase 1 (GLUD1) causes deglutarylation and functional activation of GLUD1, a critical regulator of cellular glutaminolysis. Consistently, GLUD1 knockdown diminishes SIRT5-induced proliferation, both in vivo and in vitro. Clinically, overexpression of SIRT5 is significantly correlated with poor prognosis in CRC. Thus, SIRT5 supports the anaplerotic entry of glutamine into the TCA cycle in malignant phenotypes of CRC via activating GLUD1.
News dissemination plays a vital role in supporting people to incorporate beneficial actions during public health emergencies, thereby significantly reducing the adverse influences of events. Based ...on big data from YouTube, this research study takes the declaration of COVID-19 National Public Health Emergency (PHE) as the event impact and employs a DiD model to investigate the effect of PHE on the news dissemination strength of relevant videos. The study findings indicate that the views, comments, and likes on relevant videos significantly increased during the COVID-19 public health emergency. Moreover, the public's response to PHE has been rapid, with the highest growth in comments and views on videos observed within the first week of the public health emergency, followed by a gradual decline and returning to normal levels within four weeks. In addition, during the COVID-19 public health emergency, in the context of different types of media, lifestyle bloggers, local media, and institutional media demonstrated higher growth in the news dissemination strength of relevant videos as compared to news & political bloggers, foreign media, and personal media, respectively. Further, the audience attracted by related news tends to display a certain level of stickiness, therefore this audience may subscribe to these channels during public health emergencies, which confirms the incentive mechanisms of social media platforms to foster relevant news dissemination during public health emergencies. The proposed findings provide essential insights into effective news dissemination in potential future public health events.
This letter proposes a unified space vector pulse width modulation (SVPWM) for a dual two-level inverter system with two isolated dc voltage sources. The gate pluses for the dual inverter are ...generated by the concept of one unified SVPWM in accordance with the voltage-second integral principle and the ratio of the two dc-link voltages can be an arbitrary positive value. This proposed technique also simplifies the region identification in sectors and reduces total switching frequency of the dual inverter. The beneficial performance of this proposed technique is verified experimentally.
This paper presents a sort of nonlinear backstepping-based algorithm combining with direct power control (DPC) to a wind turbine-driven doubly fed induction generator (DFIG) under normal and ...especially harmonic grid voltage. First, the power control objectives are analyzed and designed under normal and harmonic grid voltage for the purpose of harmonic stator current suppression; second, a unified mathematic model of a DFIG under normal and harmonic grid voltage is founded, exploring its power model in detail; finally, the backstepping algorithm is introduced briefly and the backstepping-based DPC (BS-DPC) algorithm of the DFIG is developed under normal and harmonic grid voltage. The comparative simulation results between vector control (VC) with resonant controller, look-up table DPC (LUT-DPC) and BS-DPC under normal grid voltage verify that the proposed BS-DPC realizes the decoupling control of active and reactive power of DFIG, with better dynamic performance than VC, as well as with better steady performance than LUT-DPC. Under the harmonic grid voltage, further simulation results verify the effectiveness of BS-DPC for suppressing the harmonic stator current of the DFIG in contrast to VC with a resonant controller and LUT-DPC with improved control objectives proposed by this paper; meanwhile, the adaptability of BS-DPC to minute frequency derivation, harmonic component order and distorted degree of the grid voltage under harmonic conditions are verified as well.
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