•Compared with the conventional control methods, a new control freedom i.e., the independent control of HBSM and FBSM output voltage enabling the flexible regulation of the charging and discharging ...behaviors of HBSMs and FBSMs, is proposed.•The optimal charging and discharging behaviors of HBSMs which can reduce the loss of the bottom IGBT in HBSMs, are derived in detail. When the modulation index is 0.827 and a unity power factor, the total loss of T2 can be reduced by 8.9 percent.•For the unidirectional power flow requirements e.g., off-shore HVDC and on-shore HVDC where the renewable energy sources distribute in the Gobi Deserts, the proposed method can save the bottom diode（IGBT） of HBSMs for the inverter (rectifier), which can reduce the converter’ cost.
Power losses on the upper and bottom IGBTs in half-bridge submodules (HBSMs) are not even when hybrid modular multilevel converters (MMCs) work as inverters, which results in a large difference in their lifetimes. Since the system reliability depends on the device with the lowest lifetime, the safe and reliable operation of the converter will be seriously threatened by the reliability of the devices. To address this issue, the power device loss distribution problem is studied, and the effect of forward voltage drops and on-state resistances on device conduction loss are analysed. Furthermore, a control method based on the targeted charging behaviours of HBSMs is proposed to decrease the loss of bottom IGBTs. The optimal charging behaviours of HBSMs are explored by increasing the HBSM charge, changing its average switching function, and decreasing the variation number of the inserted HBSMs, sequentially. Moreover, the natural balancing mechanism between HBSM and FBSM capacitor voltages is analysed, and the potential change in HBSM topology is explored. Simulation and experimental results demonstrate the feasibility and validity of the proposed method.
The present study investigated the anti-hyperglycemic properties and mechanisms of fucoidan, isolated from Cucumaria frondosa (Cf-FUC), in insulin resistant mice. Male C57BL/6J mice were fed regular ...diet or high-fat/high-sucrose diet for 19 weeks. Model animals were dietary administrated either rosiglitazone (RSG, 1 mg/kg·bw), fucoidan (Cf-FUC, 80 mg/kg·bw) or their combinations. Results showed that Cf-FUC significantly reduced fasting blood glucose and insulin levels, and enhanced glucose tolerance and insulin tolerance in insulin-resistant mice. Quantitative real-time PCR analysis showed that Cf-FUC increased the mRNA expressions of insulin receptors (IR), insulin receptor substrate 1 (IRS-1), phosphatidylinositol 3 kinase (PI3K), protein kinase B (PKB), and glucose transporter 4 (GLUT4). Western blot assays demonstrated that Cf-FUC showed no effect on total protein expression but nevertheless enhanced the phosphorylation of proteins listed above and increased translocation of GLUT4 to the cell membrane. Furthermore, Cf-FUC enhanced the effects of RSG. These results indicated that Cf-FUC exhibited significant anti-hyperglycemic effects via activating PI3K/PKB pathway and GLUT4 in skeletal muscle and adipose tissue.
Objective . We aimed to examine the benefits of catheter ablation on left heart structure and function in patients with persistent atrial fibrillation (AF) accompanied by heart failure (HF) with ...preserved ejection fraction (HFpEF), in comparison with the benefits in patients with AF accompanied by HF with reduced ejection fraction (HFrEF) or patients with no HF. Methods . A total of 399 patients with nonvalvular persistent AF who underwent catheter ablation from 2015 to 2021 were retrospectively included sixty‐seven patients with recurrence of AF within 1 year were excluded, as well as 53 patients who failed to be followed up at (12 ± 1) months after the procedure. Finally, 279 patients who fulfilled the criteria were included and divided into these groups: the HFpEF group (left ventricular ejection fraction (LVEF) ≥50% and N‐Terminal Pro‐Brain Natriuretic Peptide (NT‐proBNP) ≥125 pg/ml or E/e′ ≥15, n = 116), HFrEF group (LVEF <50%, n = 48), and no HF group (NT‐proBNP <125 pg/ml, n = 115). The endpoints were changes in image‐based functional status from baseline to 1 year, including echocardiogram and speckle‐tracking echocardiography. Results . The left atrial structure of patients with HFpEF decreased significantly 1 year after catheter ablation (left atrial anteroposterior dimension: 41.48 ± 4.53 mm vs. 38.64 ± 4.40; left atrial mediolateral dimension: 41.99 ± 5.52 vs. 38.24 ± 4.63 mm; left atrial superoinferior dimension: 61.36 ± 6.73 vs. 56.44 ± 6.97 mm). The left atrial and left ventricular volumes were significantly reduced and the ejection fraction was increased in all three groups, with HFrEF patients benefiting more. In the speckle‐tracking echocardiography indexes, significant improvements were observed in left atrial strain (16.83 ± 6.91 vs. 28.05 ± 9.92), left atrial storage function (0.97 ± 0.38 vs. 1.49 ± 0.58), and left atrial pump function (−1.15 ± 0.55 vs. −1.68 ± 0.75) among HFpEF patients after 1 year, with no changes in left atrial conduit function (−1.55 ± 0.62 vs. −1.50 ± 0.54). In addition to the above improvements in left atrial structure and function, there was no significant improvement in left ventricular diastolic function in patients with HFpEF (E/e′, 14.11 ± 5.52 vs. 14.30 ± 7.25, P = 0.85). Conclusion . Catheter ablation is beneficial in restoring sinus rhythm in patients with persistent AF with coexisting HFpEF, significantly decreasing the left atrial size, improving left atrial storage function and left atrial pump function, and increasing left atrial and left ventricular ejection fraction.
Prechamber jet ignition is a promising technology that enables stable ignition and fast combustion by combining thermal effects, chemical kinetics, and turbulent disturbance. The development and ...application of the prechamber ignition require a comprehensive and in-depth understanding of the operating characteristics of the prechamber ignition in the real engine working cycle. Therefore, numerical simulations are conducted to explore the operating performance of the prechamber ignition applied to a large-bore natural gas engine in this study. The differences between the passive prechamber (PPRE) and active prechamber (APRE) near the lean burn limit are compared. The results show that the jet ignition performance of the PPRE is hampered by the high residual gas coefficient and lean mixture in the prechamber under lean burn conditions. The ignition mode of the PPRE is similar to torch ignition, and the combustion process in the main chamber is mainly turbulent flame propagation. The ignition mechanism of the APRE is flame jet ignition. The main chamber combustion process presents a two-stage heat release characteristic, which can be subdivided into three phases: the initial flame development phase, the rapid combustion phase, and the late combustion phase. The heat release rate during the initial flame development phase depends on the physical and chemical properties of the prechamber jet and the mixture conditions in the main chamber. During the rapid combustion phase, the flame propagation along the radial direction of the jet largely depends on the time scale of the chemical reaction. The heat release rate depends on the coverage area of the jet, the jet residual momentum, and the turbulent flame speed. During the late combustion phase, the flame propagation is mainly affected by the turbulent flame speed. These results provide theoretical guidance for the subsequent application of prechamber ignition systems in various powertrains.
High-impedance faults (HIFs) in distribution networks may result in fires or electric shocks. However, considerable difficulties exist in HIF detection due to low-resolution measurements and the ...considerably weaker time-frequency characteristics. This paper presents a novel HIF detection method using synchronized current information. The method consists of two stages. In the first stage, joint key characteristics of the system are extracted with the minimal system prior knowledge to identify the global optimal micro-phase measurement unit (µPMU) placement. In the second stage, the HIF is detected through a multivariate Jensen-Shannon divergence similarity measurement using high-resolution time-synchronized data in µPMUs in a high-noise environment. l2,1principal component analysis (PCA), i.e., PCA based on the l2,1 norm, is applied to an extracted system state and fault features derived from different resolution data in both stages. An economic observability index and HIF criteria are employed to evaluate the performance of placement method and to identify HIFs. Simulation results show that the method can reliably detect HIFs with reasonable detection accuracy in noisy environments.
A novel selenadiazole-fused pyrene derivative PySe was successfully synthesized and characterized. Its single structure is almost planar and adopts a sandwich-herringbone packing model. The ...self-assembly behaviors based on compound PySe and its analogue thiadiazole-fused pyrene derivative PyS were studied in detail and the as-formed nanostructures were fully characterized by means of UV-vis absorption, emission spectra, X-ray diffraction, field emission SEM and TEM. We attribute the bathochromic shift absorption and emission spectra of PyS and PySe in aqueous solution to the formation of J-type aggregation. In addition, our investigation demonstrated that the shape and size of the as-prepared nanostructures could be tuned by different chalcogen analogues and the volume ratio of water to organic solvent.
Multi-microgrid collaborative scheduling can promote the local consumption of renewable energy in the smart grid and reduce the operating costs of the power grid park. At the same time, the access of ...the distributed energy storage (ES) system provides an opportunity to further enhance the park’s peak shaving and valley filling capacity, thereby reducing costs. However, the uncertainty of photovoltaic (PV) power generation and load demand seriously affects the profit maximization of the microgrid in the park. To address this challenge, this paper proposes a stochastic optimal scheduling strategy for industrial park smart microgrids with multiple transformers based on the information gap decision theory (IGDT). We first introduce a revenue maximization model for industrial parks, incorporating a two-part tariff system and distributed ES. Subsequently, we employ an envelope constraint model to accurately represent the uncertainty associated with PV generation and load demand. By integrating these components, we establish the IGDT stochastic optimization scheduling model for industrial parks with multiple transformers. Finally, we simulate and analyze the performance of the proposed IGDT model under various cost deviation factors during typical spring and summer days. The simulation results demonstrate the effectiveness of the proposed control strategy in mitigating the impact of PV generation and load uncertainty on industrial parks. The IGDT-based scheduling approach provides an efficient solution for maximizing revenue and enhancing the operational stability of industrial park microgrids.
TC21 titanium alloy was hot compressed isothermally at temperatures ranging from 880
°C to 950
°C and strain rates ranging from 0.01 to 10
s
−1. Microstructures were investigated by electron ...backscatter diffraction (EBSD) technique and transmission electron microscopy (TEM), and processing maps were developed at different strains. It is found that strain rate is a key factor for the formation of hot deformation microstructure. The stress–strain curves were exhibited flow softening behavior at high strain rate above 1
s
−1, while equiaxed grains were found at lower strain rates. There is no large instability zone besides two peak-areas of 880–900
°C, 1–10
s
−1 and 925–950
°C, 10
−0.5 to 10
s
−1.
•Anti-osteoporotic activity of Ca-SGP is reported for the first time.•Ca-SGP promoted osteogenesis.•Ca-SGP increased OPG/RANKL ratio in MC3T3-E1 cells and bilateral ovariectomized rats.•Ca-SGP ...improved tibia BMD of osteoporotic rats induced by bilateral ovariectomy.•Ca-SGP is a novel and significant functional factor for the treatment of osteoporosis.
The anti-osteoporotic activities of a sialoglycoprotein isolated from the eggs of Carassius auratus (Ca-SGP). Ca-SGP was composed of 14.33% protein, 62.81% hexose, and 19.72% N-acetylneuraminic acid (Neu5Ac). In vitro experimental results showed that Ca-SGP significantly increased MC3T3-E1 pre-osteoblastic cells' proliferation activities, promoted cell differentiation and mineralization as evidenced by increasing the contents or activities of major markers, i.e. collagen type I (COL I), osteocalcin (OCN), alkaline phosphatase (ALP) and bone nodules. Ca-SGP significantly augmented protein expressions and secretions of bone morphogenetic protein 2 (BMP-2) and osteoprotegerin (OPG), meanwhile, decreased that of receptor activator of nuclear factor κB ligand (RANKL). In vivo experimental data further revealed that Ca-SGP significantly reduced bone turnover rates, increased serum OPG/RANKL ratio and enhanced tibia bone mineral density (BMD) in the model rats of ovariectomized (OVX)-induced osteoporosis. These results suggest that Ca-SGP could improve osteoporosis by promoting osteogenesis and inhibiting bone resorption via increasing OPG/RANKL ratio, which indicates that Ca-SGP is a potential candidate functional factor for osteoporosis prevention.
Time-delay systems disturbed by white noise have been comprehensively modelled as stochastic functional differential equations in the existing literature. However, in some specific situations, they ...cannot always precisely describe the dynamic character of time-delay systems subject to non-white noise disturbances. In this paper, colour noises with finite two-order moments are introduced to time-delay systems (such systems are referred to as random ones). First, we present some general conditions to guarantee the existence and uniqueness of solutions to random time-delay systems. Next, in light of these results and the Lyapunov function approach, the noise-to-state stability and eλt-weighted integral noise-to-state stability are analysed, respectively. One example is given to illustrate the effectiveness of the obtained results.
