A Variable Step Size INC MPPT Method for PV Systems Fangrui Liu, Fangrui Liu; Shanxu Duan, Shanxu Duan; Fei Liu, Fei Liu ...
IEEE transactions on industrial electronics (1982),
07/2008, Volume:
55, Issue:
7
Journal Article
Peer reviewed
Maximum power point tracking (MPPT) techniques are employed in photovoltaic (PV) systems to make full utilization of PV array output power which depends on solar irradiation and ambient temperature. ...Among all the MPPT strategies, the incremental conductance (INC) algorithm is widely used due to the high tracking accuracy at steady state and good adaptability to the rapidly changing atmospheric conditions. In this paper, a modified variable step size INC MPPT algorithm is proposed, which automatically adjusts the step size to track the PV array maximum power point. Compared with the conventional fixed step size method, the proposed approach can effectively improve the MPPT speed and accuracy simultaneously. Furthermore, it is simple and can be easily implemented in digital signal processors. A theoretical analysis and the design principle of the proposed method are provided and its feasibility is also verified by simulation and experimental results.
Layered transition-metal oxides have attracted intensive interest for cathode materials of sodium-ion batteries. However, they are hindered by the limited capacity and inferior phase transition due ...to the gliding of transition-metal layers upon Na
extraction and insertion in the cathode materials. Here, we report that the large-sized K
is riveted in the prismatic Na
sites of P2-Na
K
MnO
to enable more thermodynamically favorable Na
vacancies. The Mn-O bonds are reinforced to reduce phase transition during charge and discharge. 0.901 Na
per formula are reversibly extracted and inserted, in which only the two-phase transition of P2 ↔ P'2 occurs at low voltages. It exhibits the highest specific capacity of 240.5 mAh g
and energy density of 654 Wh kg
based on the redox of Mn
/Mn
, and a capacity retention of 98.2% after 100 cycles. This investigation will shed lights on the tuneable chemical environments of transition-metal oxides for advanced cathode materials and promote the development of sodium-ion batteries.
Appropriate autophagy has protective effects on ischemic nerve tissue, while excessive autophagy may cause cell death. The inflammatory response plays an important role in the survival of nerve cells ...and the recovery of neural tissue after ischemia. Many studies have found an interaction between autophagy and inflammation in the pathogenesis of ischemic stroke. This study outlines recent advances regarding the role of autophagy in the post-stroke inflammatory response as follows. (1) Autophagy inhibits inflammatory responses caused by ischemic stimulation through mTOR, the AMPK pathway, and inhibition of inflammasome activation. (2) Activation of inflammation triggers the formation of autophagosomes, and the upregulation of autophagy levels is marked by a significant increase in the autophagy-forming markers LC3-II and Beclin-1. Lipopolysaccharide stimulates microglia and inhibits ULK1 activity by direct phosphorylation of p38 MAPK, reducing the flux and autophagy level, thereby inducing inflammatory activity. (3) By blocking the activation of autophagy, the activation of inflammasomes can alleviate cerebral ischemic injury. Autophagy can also regulate the phenotypic alternation of microglia through the nuclear factor-κB pathway, which is beneficial to the recovery of neural tissue after ischemia. Studies have shown that some drugs such as resveratrol can exert neuroprotective effects by regulating the autophagy-inflammatory pathway. These studies suggest that the autophagy-inflammatory pathway may provide a new direction for the treatment of ischemic stroke.
Owing to the low‐cost, safety, dendrite‐free formation, and two‐electron redox properties of magnesium (Mg), rechargeable Mg batteries are considered as promising next‐generation secondary batteries ...with high specific capacity and energy density. However, the clumsy Mg2+ with high polarity inclines to sluggish Mg insertion/deinsertion, leading to inadequate reversible capacity and rate performance. Herein, 2D VOPO4 nanosheets with expanded interlayer spacing (1.42 nm) are prepared and applied in rechargeable magnesium batteries for the first time. The interlayer expansion provides enough diffusion space for fast kinetics of MgCl+ ion flux with low polarization. Benefiting from the structural configuration, the Mg battery exhibits a remarkable reversible capacity of 310 mAh g−1 at 50 mA g−1, excellent rate capability, and good cycling stability (192 mAh g−1 at 100 mA g−1 even after 500 cycles). In addition, density functional theory (DFT) computations are conducted to understand the electrode behavior with decreased MgCl+ migration energy barrier compared with Mg2+. This approach, based on the regulation of interlayer distance to control cation insertion, represents a promising guideline for electrode material design on the development of advanced secondary multivalent‐ion batteries.
VOPO4 nanosheets with expanded interlayer spacing endow the architecture with MgCl+ insertion, featuring decreased polarization compared with Mg2+ and substantially enhancing ion‐diffusion dynamics. Benefiting from the dominant configuration, the VOPO4 nanosheets deliver a reversible capacity of 192 mAh g−1 at 100 mA g−1 even after 500 cycles and remarkable rate capability.
Sodium‐ion batteries (SIBs) reflect a strategic move for scalable and sustainable energy storage. The focus on high‐entropy (HE) cathode materials, particularly layered oxides, has ignited scientific ...interest due to the unique characteristics and effects to tackle their shortcomings, such as inferior structural stability, sluggish reaction kinetics, severe Jahn‐Teller effects induced lattice distortion, and poor oxygen reversibility at high voltage. This review focuses on high‐entropy oxide materials, highlighting their fundamentals, design principles, and application in layered oxide cathodes for SIBs. It delves into the growth mechanism, composition‐properties correlations, and the functional roles of high‐entropy design in enhancing the performance of layered oxide cathodes. Furthermore, it furnishes a comprehensive survey of recent advancements and persisting challenges within the domain of layered high‐entropy cathode materials, as well as offers insights into potential future research directions in line with the current state of knowledge.
Highly intriguing, high‐entropy layered oxides showcase distinctive characteristics, drawing scientific curiosity. This review explores fundamentals, design principles for sodium‐ion batteries, and applications in layered cathodes. It delves into growth mechanisms, composition‐properties correlations, and the significance of high‐entropy design. The overview also covers recent progress, challenges, and prospects in layered high‐entropy cathode materials for sodium‐ion batteries.
The mechanical properties of the constituent minerals in shale rock are fundamental to a better knowledge of multi-scale shale behaviors. It benefits the engineering applications and predictive ...physics modeling of the shale formation. In this work, nanoindentation testing combined with scanning electron microscopy - energy dispersive spectroscopy (SEM-EDS) were used to obtain the in situ mechanical properties of individual mineral phases in four shale samples. Engraved cross-marks were employed to locate the indented areas on a micron scale for subsequent SEM-EDS measurements and analysis. The elastic moduli and hardness of the quartz, iron-type minerals, muscovite, clinochlore, organic matter, and the mineral assortments in the matrix were analyzed and relevant deformative behaviors were compared. Results show that the identified mineral groups exhibit a diverse set of mechanical properties at the nanoscale. The iron-type minerals have the highest elastic modulus (104.7 GPa), then followed by quartz, muscovite, clinochlore, and organic matter. Quartz shows the highest hardness (10.2 GPa). The identified minerals demonstrated different elasto-plastic characteristics to the indentation loads. Quartz exhibits the lowest plastic behavior, while phyllosilicates exhibited large plastic behavior owing to the layered structure. Organic matter showed both elastic-dominant and plastic-dominant behaviors, which may be related to the chemical compositional differences and various thermal maturity of kerogen in the shale samples. The mechanical properties of three mineral assortments in shale matrices vary significantly due to the wide variety of the mineral compositions. Radial cracks were observed on the boundary of brittle minerals and relatively weak minerals, while shear cracks were observed on strength-weak minerals such as layered silicates and organic matters. The mechanism of the induced cracks was discussed. This study obtains a basic understanding of shale behavior on nano-scale and provides reliable basic data for multi-scale modeling of shale reservoirs without the need for large-scale mechanical tests.
Long and thin: SnO2 nanowires with tetragonal structure were successfully synthesized by a thermal evaporation method without any conventional metal catalysts. The enhanced electrochemical ...performance of SnO2 nanowires is believed to result from the combination of unique nanostructures with a high length/diameter ratio and the absence of traditional metal catalysts.
Animal studies implicate meningeal lymphatic dysfunction in the pathogenesis of neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease (PD). However, there is no direct ...evidence in humans to support this role
. In this study, we used dynamic contrast-enhanced magnetic resonance imaging to assess meningeal lymphatic flow in cognitively normal controls and patients with idiopathic PD (iPD) or atypical Parkinsonian (AP) disorders. We found that patients with iPD exhibited significantly reduced flow through the meningeal lymphatic vessels (mLVs) along the superior sagittal sinus and sigmoid sinus, as well as a notable delay in deep cervical lymph node perfusion, compared to patients with AP. There was no significant difference in the size (cross-sectional area) of mLVs in patients with iPD or AP versus controls. In mice injected with α-synuclein (α-syn) preformed fibrils, we showed that the emergence of α-syn pathology was followed by delayed meningeal lymphatic drainage, loss of tight junctions among meningeal lymphatic endothelial cells and increased inflammation of the meninges. Finally, blocking flow through the mLVs in mice treated with α-syn preformed fibrils increased α-syn pathology and exacerbated motor and memory deficits. These results suggest that meningeal lymphatic drainage dysfunction aggravates α-syn pathology and contributes to the progression of PD.
Fe‐Mn based layered oxides are recognized as promising cathode materials for sodium‐ion batteries (SIBs) with high capacities and earth‐abundant ingredients. However, their real‐world applications ...are still constrained by fast capacity decay accompanied with the requirements of deeper insights into the principles behind. Herein, taking O3‐NaxFe1/2Mn1/2O2 as a classic sample, the capacity fading mechanism of Fe‐Mn based layered oxides is comprehensively investigated through combined techniques. For the first time, it is revealed that Fe migration is merely triggered after the oxidation of ≈0.3 mol Fe3+ based on solid proofs from ex situ X‐ray absorption spectroscopy and Mössbauer spectroscopy, which implies the crucial role of the accumulated structural distortion induced by Jahn–Teller active Fe4+. O3‐P3 phase transition during cycling is obviously constrained along with Fe migration as evidenced by in situ/ex situ X‐ray diffraction, well interpreting the intensified polarization and the resulting large capacity loss. More importantly, within the desodiation depth (≈80% of sodium extraction) where Fe migration is almost absent, the capacity fading is dominantly rooted in the Fe4+ activated and Mn‐dissolution aggravated surface passivation as confirmed by mass/X‐ray spectroscopies and electrochemical analysis. These renewed understandings of the fast capacity decay in Fe‐Mn based layered oxides offer clearer clues for designing desirable cathodes for SIBs.
This work presents a comprehensive study of the capacity fading in O3‐NaxFe1/2Mn1/2O2. The key finding is the triggering of Fe migration at ≈4.2 V corresponding to oxidation of ≈0.3 mol Fe3+, clarifying the blurry correlations between capacity decay and Fe migration. Within the Fe‐migration‐free region, Fe4+‐activated and Mn‐dissolution aggravated surficial passivation is proved as the main origin of capacity loss.
The electrochemical performances of 1D SnO2 nanomaterials, nanotubes, nanowires, and nanopowders, are compared to define the most favorable morphology when SnO2 nanomaterials are adopted as the ...electrode material for lithium‐ion batteries. Changes in the morphology of SnO2 are closely related with its electrochemical performance. Some SnO2 nanomaterials feature not only an increased energy density but also enhanced Li+ transfer. The correlation between the morphological characteristics and the electrochemical properties of SnO2 nanomaterials is discussed. The interesting electrochemical results obtained here on SnO2 nanomaterials indicate the possibility of designing and fabricating attractive nanostructured materials for lithium‐ion batteries.
The electrochemical performance of 1D SnO2 nanomaterials (nanotubes, nanowires, and nanopowders) can be used to define the most favorable morphology when SnO2 nanomaterials are adopted as the electrode material for lithium‐ion batteries. Changes in the morphology of SnO2 (see figure) are found to be closely related to the electrochemical performance.
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