Chapter Tidal Turbine Generators

Recently, tidal stream turbines have become a preferable mode of harvesting tidal energy. The main issue for low utilization of tidal energy is the high levelized cost of energy (LCoE) from tidal stream turbines. A major reason for this is the high operation and maintenance costs for submerged installations. A possible way of minimizing the LCoE and improving the availability is to use a flooded (or a wetgap) generator rather than a conventional airgap generator. Inside flooded generators, the gap between the stator and rotor is filled with the seawater. This architecture has the potential to improve cooling and reduce reliance on ancillary systems (e.g., bilge system), thereby improving reliability. The chapter begins with a brief description of the generator systems used in current tidal stream turbines. The focus of the chapter is, however, to give a basic insight into the design aspects of the flooded generators, and compares it with the currently used sealed airgap generators in tidal turbine systems

A comparative study of Quasi-FEA technique on iron losses prediction for permanent magnet synchronous machines

The paper presents an advanced quasi-FEA technique on the iron losses prediction using Bertotti’s iron loss separation models, in which a curve fitting is taken into account for coefficients calculation of each model. Moreover, the skin effect and saturation consideration are applied in order to check the accuracy through the relative error distribution in the frequency domain of each model from low up to high frequencies 50 to 700 (Hz). Additionally, this comparative study presents a torquespeed-flux density computation that is discussed and presented. The iron loss characteristics of a radial flux permanent magnet synchronous machine (PMSM) with closed-slots and outer rotor topology are also discussed. The quasi-finite-element (FE) analysis was performed using a 2-D and 3-D FEA, where the employed quasi-2-D FEA is proposed and compared with 3-D FEA, and along with experimental verifications. Finally, all the iron-loss models under realistic and non-ideal magnetization conditions are verified experimentally on a surface-mounted PMSG for wind generation application.Peer ReviewedPostprint (published version

A Variable-Frequency ZVS Modulation for Four-Switch Buck+Boost Converters with Seamless Step-up/down Mode Transition

This paper introduces variable-frequency zero voltage switching (ZVS) modulation strategy for the four-switch buck+boost converter with one operating pattern for the inductor current, i.e., three-segment inductor current modulation control. The proposed modulation scheme guarantees a smooth transition from step-up to step-down or from step-down to step-up operating modes without abrupt duty cycle or switching frequency change. Triangular current mode (TCM) ZVS control could be derived from this three-segment inductor current modulation strategy. Moreover, the controller design can be simplified compared with other multi-mode control methods. Experimental results were given to validate the modulation control strategy based on a 300−600 V input, 400 V output, 3.3 kW prototype

The level of circulating endothelial progenitor cells may be associated with the occurrence and recurrence of chronic subdural hematoma

OBJECTIVES: The onset of chronic subdural hematoma may be associated with direct or indirect minor injuries to the head or a poorly repaired vascular injury. Endothelial progenitor cells happen to be one of the key factors involved in hemostasis and vascular repair. This study was designed to observe the levels of endothelial progenitor cells, white blood cells, platelets, and other indicators in the peripheral blood of patients diagnosed with chronic subdural hematoma to determine the possible relationship between the endothelial progenitor cells and the occurrence, development, and outcomes of chronic subdural hematoma. METHOD: We enrolled 30 patients with diagnosed chronic subdural hematoma by computer tomography scanning and operating procedure at Tianjin Medical University General Hospital from July 2009 to July 2011. Meanwhile, we collected 30 cases of peripheral blood samples from healthy volunteers over the age of 50. Approximately 2 ml of blood was taken from veins of the elbow to test the peripheral blood routine and coagulation function. The content of endothelial progenitor cells in peripheral blood mononuclear cells was determined by flow cytometry. RESULTS: The level of endothelial progenitor cells in peripheral blood was significantly lower in preoperational patients with chronic subdural hematomas than in controls. There were no significant differences between the two groups regarding the blood routine and coagulation function. However, the levels of circulating endothelial progenitor cells were significantly different between the recurrent group and the non-recurrent group. CONCLUSIONS: The level of circulating endothelial progenitor cells in chronic subdural hematoma patients was significantly lower than the level in healthy controls. Meanwhile, the level of endothelial progenitor cells in recurrent patients was significantly lower than the level in patients without recurrence. Endothelial progenitor cells may be related to the occurrence and recurrence of chronic subdural hematoma

LAMOST observations in the Kepler field. Analysis of the stellar parameters measured with the LASP based on the low-resolution spectra

All of the 14 subfields of the Kepler field have been observed at least once with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST, Xinglong Observatory, China) during the 2012-2014 observation seasons. There are 88,628 reduced spectra with SNR$_g$ (signal-to-noise ratio in g band) $\geq$ 6 after the first round (2012-2014) of observations for the LAMOST-Kepler project (LK-project). By adopting the upgraded version of the LAMOST Stellar Parameter pipeline (LASP), we have determined the atmospheric parameters ($T_{\rm eff}$ , $\log g$, and $\rm [Fe/H]$) and heliocentric radial velocity $v_{\rm rad}$ for 51,406 stars with 61,226 spectra. Compared with atmospheric parameters derived from both high-resolution spectroscopy and asteroseismology method for common stars in Huber et al. (2014), an external calibration of LASP atmospheric parameters was made, leading to the determination of external errors for the giants and dwarfs, respectively. Multiple spectroscopic observations for the same objects of the LK-project were used to estimate the internal uncertainties of the atmospheric parameters as a function of SNR$_g$ with the unbiased estimation method. The LASP atmospheric parameters were calibrated based on both the external and internal uncertainties for the giants and dwarfs, respectively. A general statistical analysis of the stellar parameters leads to discovery of 106 candidate metal-poor stars, 9 candidate very metal-poor stars, and 18 candidate high-velocity stars. Fitting formulae were obtained segmentally for both the calibrated atmospheric parameters of the LK-project and the KIC parameters with the common stars. The calibrated atmospheric parameters and radial velocities of the LK-project will be useful for studying stars in the Kepler field.Comment: 53 pages, 21 figures, 5 tables, Accepted for publication by ApJ

LncRNA ADAMTS9-AS1 knockdown suppresses cell proliferation and migration in glioma through downregulating Wnt/β-catenin signaling pathway

The long non‐coding RNA antisense 1 ADAMTS9-AS1 has been reported to serve as an oncogene or tumor suppressor in several tumors, including colorectal cancer and hepatocellular carcinoma. Nevertheless, the clinical significance and biological behaviors of ADAMTS9-AS1 in glioma still remain unclear. Therefore, the goal of this study was to evaluate the functional roles and potential mechanisms of ADAMTS9-AS1 in glioma cells. Using quantitative real-time PCR analysis, we found that ADAMTS9-AS1 was upregulated in glioma tissues and cells in comparison to corresponding controls. ADAMTS9-AS1 expression level was correlated to tumor size (p=0.005) and WHO grade (p=0.002). Kaplan-Meier analysis and Cox multivariate analysis showed that ADAMTS9-AS1 could serve as an independent prognostic factor affecting the overall survival of glioma patients. Functionally, depletion of ADAMTS9-AS1 significantly suppressed the proliferation, migration and invasion in glioma cell lines (U251 and U87), as shown via CCK-8 assay, Edu corporation assay, wound healing assay and transwell assay. Furthermore, we demonstrated that knockdown of ADAMTS9-AS1 suppressed Wnt1, β-catenin, c-myc and PCNA, while upregulating E-cadherin expression. In conclusion, our data revealed that ADAMTS9-AS1 confers oncogenic function in the progression of glioma, thus targeting ADAMTS9-AS1 might be a promising therapeutic strategy for this disease

Berberine Could Ameliorate Cardiac Dysfunction via Interfering Myocardial Lipidomic Profiles in the Rat Model of Diabetic Cardiomyopathy

Background: Diabetic cardiomyopathy (DCM) is considered to be a distinct clinical entity independent of concomitant macro- and microvascular disorders, which is initiated partly by disturbances in energy substrates. This study was to observe the dynamic modulations of berberine in DCM rats and explore the changes of lipidomic profiles of myocardial tissue.Methods: Sprague-Dawley (SD) rats were fed high-sucrose and high-fat diet (HSHFD) for totally 22 weeks and intraperitoneally (i.p.) injected with 30 mg/kg of streptozotocin (STZ) at the fifth week to induce DCM. Seventy-two hours after STZ injection, the rats were orally given with berberine at 10, 30 mg/kg and metformin at 200 mg/kg, respectively. Dynamic changes of cardiac function, heart mass ratios and blood lipids were observed at f 4, 10, 16, and 22, respectively. Furthermore, lipid metabolites in myocardial tissue at week 16 were profiled by the ultra-high-performance liquid chromatography coupled to a quadruple time of flight mass spectrometer (UPLC/Q-TOF/MS) approach.Results: Berberine could protect against cardiac diastolic and systolic dysfunctions, as well as cardiac hypertrophy, and the most effective duration is with 16-week of administration. Meanwhile, 17 potential biomarkers of phosphatidylcholines (PCs), phosphatidylethanolamines (PEs) and sphingolipids (SMs) of DCM induced by HSFD/STZ were identified. The perturbations of lipidomic profiles could be partly reversed with berberine intervention, i.e., PC (16:0/20:4), PC (18:2/0:0), PC (18:0/18:2), PC (18:0/22:5), PC (20:4/0:0), PC (20:4/18:0), PC (20:4/18:1), PC (20:4/20:2), PE (18:2/0:0), and SM (d18:0/16:0).Conclusions: These results indicated a close relationship between PCs, PEs and SMs and cardiac damage mechanisms during development of DCM. The therapeutic effects of berberine on DCM are partly caused by interferences with PCs, PEs, and SMs metabolisms

Extracellular mitochondria released from traumatized brains induced platelet procoagulant activity

Coagulopathy often develops soon after acute traumatic brain injury and its cause remains poorly understood. We have shown that injured brains release cellular microvesicles that disrupt the endothelial barrier and induce consumptive coagulopathy. Morphologically intact extracellular mitochondria accounted for 55.2% of these microvesicles, leading to the hypothesis that these extracellular mitochondria are metabolically active and serve as a source of oxidative stress that activates platelets and renders them procoagulant. In testing this hypothesis experimentally, we found that the extracellular mitochondria purified from brain trauma mice and those released from brains subjected to freeze-thaw injury remained metabolically active and produced reactive oxygen species. These extracellular mitochondria bound platelets through the phospholipid-CD36 interaction and induced α-granule secretion, microvesiculation, and procoagulant activity in an oxidant-dependent manner, but failed to induce aggregation. These results define an extracellular mitochondria-induced and redox-dependent intermediate phenotype of platelets that contribute to the pathogenesis of traumatic brain injury-induced coagulopathy and inflammation

Wind turbine drivetrains:State-of-the-art technologies and future development trends

This paper presents the state-of-the-art technologies and development trends of wind turbine drivetrains – the system that converts kinetic energy of the wind to electrical energy – in different stages of their life cycle: design, manufacturing, installation, operation, lifetime extension, decommissioning and recycling. Offshore development and digitalization are also a focal point in this study. Drivetrain in this context includes the whole power conversion system: main bearing, shafts, gearbox, generator and power converter. The main aim of this article is to review the drivetrain technology development as well as to identify future challenges and research gaps. The main challenges in drivetrain research identified in this paper include drivetrain dynamic responses in large or floating turbines, aerodynamic and farm control effects, use of rare-earth material in generators, improving reliability through prognostics, and use of advances in digitalization. These challenges illustrate the multidisciplinary aspect of wind turbine drivetrains, which emphasizes the need for more interdisciplinary research and collaboration