Passive cyclic pitch control for horizontal axis wind turbines

A flexible rotor concept, called the balanced pitch rotor, is described. The system provides passive adjustment of cyclic pitch in response to unbalanced pitching moments across the rotor disk. Various applications are described and performance predictions are made for wind shear and cross wind operating conditions. Comparisons with the teetered hub are made and significant cost savings are predicted

Small-signal Analysis of Active Loads and Large-signal Analysis of Faults in Inverter Interfaced Microgrid Applications

Rectifiers and voltage regulators that have characteristics of constant power loads may form a significant percentage of a microgrid's total loads. The real part of the input impedance of a constant power load is negative and it may have control loop dynamics in a similar frequency range to the inverters that are supplying the microgrid. This thesis examines the interactions between an active constant power load and a microgrid for the impact on stability. Participation analysis of the eigenvalues that result from the model of the combined microgrid and active load identified that the low-frequency modes are associated with the voltage controller of the active rectifier and the droop-controllers of the inverters. The analysis also revealed that when the active load dc-voltage controller is designed with large gains, the voltage controller of the inverter becomes unstable but the low frequency modes associated with the droop controller of the inverter remain stable. The transient stability of a microgrid may require that the inverter-interfaced generation remain connected during a fault and return to normal power export once a fault is cleared. For an inverter to supply fault current, the controller of the inverter must current-limit the output and the fault strategy chosen must ensure that the current and voltage limiter do not latch-up and that the controller integrators do not wind-up. This thesis analyses different limiting and reset strategies and concluded that that it is not possible to successfully reset a limiter when using a reset signal from a closed-loop controller within the inverter. In a system where there are cascaded limiters, successful operation is obtained when the inner limit is a saturation limiter and the output limiter is a set-reset limiter. It was found that the transient stability of an inverter interfaced microgrid using a droop control algorithm is dependent on the current limiter and inductance of the network.Open Acces

The Role Of Pdgf C And Its Splice Variant In Breast Cancer

The PDGF family consists of four members; while PDGF A and B are secreted as active dimers, PDGF C and D are secreted as latent dimers that undergo serine protease-mediated extracellular proteolytic activation. Gene expression analysis of breast cancer cell lines showed that PDGF C expression is associated with Basal B subtype breast cancer cells which have cancer stem cell-like characteristics. Furthermore, PDGF C expression is associated with triple-negative (estrogen receptor-, progesterone receptor- and HER2/neu-negative) breast cancer cells, a challenging type of breast cancer to treat. During the course of our study, we discovered a splice variant of PDGF C encoding the truncated PDGF C protein (t-PDGF C). Specific aims of this dissertation are to determine the role of full-length PDGF C (FL-PDGF C) and t-PDGF C in breast cancer and to characterize their subcellular localizations. This study found that although t-PDGF C presumably lacks the signal peptide, it is secreted as a heterodimer with FL-PDGF C which can undergo extracellular proteolytic activation. Furthermore, PDGF C was found in the nuclear fraction of breast cancer cells, suggesting an uncharacterized function in breast cancer. A putative nuclear localization sequence in PDGF C showed little effect on its nuclear localization as determined by the point mutagenesis assay. Interestingly, we found that the serine protease cleavage site in the hinge region plays a critical role for both extracellular proteolytic processing and nuclear accumulation of PDGF C, suggesting that the biochemical processing and the subcellular localization are co-regulated. For the functional study, we established in vitro cell models engineered to overexpress PDGF C isoforms or inhibit its expression. This study found that PDGF C expression correlates with cell proliferation, invasive phenotype and anchorage-independent growth in vitro. Importantly, t-PDGF C expression further promoted PDGF C-induced phenotypic transformation. PDGF C downregulation decreased tumor growth and metastatic potential in vivo. Taken together, this study identified PDGF C and its splice variant as key signaling molecules in breast cancer. In addition, once thought of as primarily an extracellular signaling molecule, nuclear localization marks a potentially important paradigm shift in PDGF C biology

Bulge plus disc and S\'ersic decomposition catalogues for 16,908 galaxies in the SDSS Stripe 82 co-adds: A detailed study of the ugrizugriz structural measurements

Quantitative characterization of galaxy morphology is vital in enabling comparison of observations to predictions from galaxy formation theory. However, without significant overlap between the observational footprints of deep and shallow galaxy surveys, the extent to which structural measurements for large galaxy samples are robust to image quality (e.g., depth, spatial resolution) cannot be established. Deep images from the Sloan Digital Sky Survey (SDSS) Stripe 82 co-adds provide a unique solution to this problem - offering $1.6-1.8$ magnitudes improvement in depth with respect to SDSS Legacy images. Having similar spatial resolution to Legacy, the co-adds make it possible to examine the sensitivity of parametric morphologies to depth alone. Using the Gim2D surface-brightness decomposition software, we provide public morphology catalogs for 16,908 galaxies in the Stripe 82 $ugriz$ co-adds. Our methods and selection are completely consistent with the Simard et al. (2011) and Mendel et al. (2014) photometric decompositions. We rigorously compare measurements in the deep and shallow images. We find no systematics in total magnitudes and sizes except for faint galaxies in the $u$-band and the brightest galaxies in each band. However, characterization of bulge-to-total fractions is significantly improved in the deep images. Furthermore, statistics used to determine whether single-S\'ersic or two-component (e.g., bulge+disc) models are required become more bimodal in the deep images. Lastly, we show that asymmetries are enhanced in the deep images and that the enhancement is positively correlated with the asymmetries measured in Legacy images.Comment: 27 pages, 14 figures. MNRAS accepted. Our catalogs are available in TXT and SQL formats at http://orca.phys.uvic.ca/~cbottrel/share/Stripe82/Catalogs

Geochemistry of reduced inorganic sulfur, reactive iron, and organic carbon in fluvial and marine surface sediment in the Laizhou Bay region, China

Understanding the geochemical cycling of sulfur in sediments is important because it can have implications for both modern environments (e.g., deterioration of water quality) and interpretation of the ancient past (e.g., sediment C/S ratios can be used as indicators of palaeodepositional environment). This study investigates the geochemical characteristics of sulfur, iron, and organic carbon in fluvial and coastal surface sediments of the Laizhou Bay region, China. A total of 63 sediment samples were taken across the whole Laizhou Bay marine region and the 14 major tidal rivers draining into it. Acid volatile sulfur, chromium (II)-reducible sulfur and elemental sulfur, total organic carbon, and total nitrogen were present in higher concentrations in the fluvial sediment than in the marine sediment of Laizhou Bay. The composition of reduced inorganic sulfur in surface sediments was dominated by acid volatile sulfur and chromium (II)-reducible sulfur. In fluvial sediments, sulfate reduction and formation of reduced inorganic sulfur were controlled by TOC and reactive iron synchronously. High C/S ratios in the marine sediments indicate that the diagenetic processes in Laizhou Bay have been affected by rapid deposition of sediment from the Yellow River in recent decades

Accident denominators relative to age groups in heavy industries of the Port Hedland region of Western Australia

The aim of this research is to investigate characteristics of accident denominators across age groups in mining and associated process industries in the Port Hedland region of Western Australia. Emphasis has been focussed on comparing young, inexperienced groups with older, more experienced groups. A literature review revealed some key contributors to accidents among younger workers, in particular, those who had only recently entered the workforce. The review also revealed contributors impacting accidents regarding other age groups over a wide range of industry types. From these findings an accident construct model and questionnaire were designed to identify contributing and mitigating denominators which input to accidents occurring across the defined age groups

Bacterially mediated removal of phosphorus and cycling of nitrate and sulfate in the waste stream of a "zero-discharge" recirculating mariculture system

Simultaneous removal of nitrogen and phosphorus by microbial biofilters has been used in a variety of water treatment systems including treatment systems in aquaculture. In this study, phosphorus, nitrate and sulfate cycling in the anaerobic loop of a zero-discharge, recirculating mariculture system was investigated using detailed geochemical measurements in the sludge layer of the digestion basin. High concentrations of nitrate and sulfate, circulating in the overlying water (~15 mM), were removed by microbial respiration in the sludge resulting in a sulfide accumulation of up to 3 mM. Modelling of the observed S and O isotopic ratios in the surface sludge suggested that, with time, major respiration processes shifted from heterotrophic nitrate and sulfate reduction to autotrophic nitrate reduction. The much higher inorganic P content of the sludge relative to the fish feces is attributed to conversion of organic P to authigenic apatite. This conclusion is supported by: (a) X-ray diffraction analyses, which pointed to an accumulation of a calcium phosphate mineral phase that was different from P phases found in the feces, (b) the calculation that the pore waters of the sludge were highly oversaturated with respect to hydroxyapatite (saturation index = 4.87) and (c) there was a decrease in phosphate (and in the Ca/Na molar ratio) in the pore waters simultaneous with an increase in ammonia showing there had to be an additional P removal process at the same time as the heterotrophic breakdown of organic matter