Submodule power losses balancing algorithms for the modular multilevel converter

Tolerance and component aging can cause signif¬icant differences in the capacitance values of the submodules (SMs) in a modular multilevel converter (MMC). Depending on the modulation technique, capacitance mismatches may produce uneven switching transitions of the SMs, hence imbalances in the power losses that can lead to reliability problems. In this paper, a new algorithm that helps to achieve evenly distributed switching and conduction losses within the converter SMs is presented. The proposed algorithm is based on a modification of the common voltage balancing algorithms, balancing a weighted function of voltage and losses. Even distribution of power losses is achieved at the cost of slightly increasing the capacitor voltage ripples. The effectiveness of the strategy has been demonstrated by simulation results of a high-power grid-connected MMC

Surface modification of HVOF thermal sprayed WC–CoCr coatings by laser treatment

In this work the affects of laser characteristics on microstructure and microhardness of high velocity oxygen fuel sprayed (HVOF) WC–CoCr coatings were investigated. The coating was deposited with a Sulzer Metco WokaJet™-400 kerosene fuel and the laser surface treatments were applied using CO2 laser with 10.6 μm wavelength. Large variations in surface properties were produced from variation in the laser processing parameters. In total, four levels of peak power (100, 200, 300 and 350 W), four levels of spot diameter (0.2, 0.4, 0.6 and 1 mm) and three levels of pulse repetition frequency (PRF) were investigated. An initial set of tests were followed by a more detailed 33 factorial design of experiments. Pulse repetition frequency and duty cycle were set in order to maintain the same overlap in the x and y directions for the raster scanned sample spot impact dimensions. Overlaps of 30% were used in the initial tests and 10% in the more detailed trials. The results have shown that care must be taken to keep the irradiance at a relatively low level compared to uncoated surfaces. High irradiance can in this case result in rough and porous surfaces. Lower levels of irradiance are shown to provide more uniform microstructures, reduced porosity and increased microhardness

Progressive Structural Defects in Canine Centronuclear Myopathy Indicate a Role for HACD1 in Maintaining Skeletal Muscle Membrane Systems

Mutations in HACD1/PTPLA cause recessive congenital myopathies in humans and dogs. Hydroxyacyl-coA dehydratases are required for elongation of very long chain fatty acids, and HACD1 has a role in early myogenesis, but the functions of this striated muscle-specific enzyme in more differentiated skeletal muscle remain unknown. Canine HACD1 deficiency is histopathologically classified as a centronuclear myopathy (CNM). We investigated the hypothesis that muscle from HACD1-deficient dogs has membrane abnormalities in common with CNMs with different genetic causes. We found progressive changes in tubuloreticular and sarcolemmal membranes and mislocalized triads and mitochondria in skeletal muscle from animals deficient in HACD1. Furthermore, comparable membranous abnormalities in cultured HACD1-deficient myotubes provide additional evidence that these defects are a primary consequence of altered HACD1 expression. Our novel findings, including T-tubule dilatation and disorganization, associated with defects in this additional CNM-associated gene provide a definitive pathophysiologic link with these disorders, confirm that dogs deficient in HACD1 are relevant models, and strengthen the evidence for a unifying pathogenesis in CNMs via defective membrane trafficking and excitation-contraction coupling in muscle. These results build on previous work by determining further functional roles of HACD1 in muscle and provide new insight into the pathology and pathogenetic mechanisms of HACD1 CNM. Consequently, alterations in membrane properties associated with HACD1 mutations should be investigated in humans with related phenotypes

HVOF-Deposited WCCoCr as Replacement for Hard Cr in Landing Gear Actuators

WCCoCr coatings deposited by HVOF can replace hard Cr on landing gear components. Powders with two different WC particle sizes (micro and nano-) and geometries have been employed to study the effects on the coating’s properties. Moreover, coatings produced employing two sets of parameters resulting in high and low flame temperatures have been evaluated. Minor differences in microstructure and morphology were observed for the two powders employing the same spraying parameters, but the nano-sized powder exhibited a higher spraying efficiency. However, more significant microstructural changes result when the low- and high-energy spray parameters are used. Moreover, results of various tests which include adhesion, wear, salt fog corrosion resistance, liquid immersion, and axial fatigue strength, indicate that the coatings produced with high-energy flame are similar in behavior. On the other hand, the nanostructured low-energy flame coating exhibited a significantly lower salt fog corrosion resistanc

Effect of particle and carbide grain sizes on a HVOAF WC-Co-Cr coating for the future application on internal surfaces: microstructure and wear

The use of nanoscale WC grain or finer feedstock particles are possible methods of improving the performance of WC-Co-Cr coatings. Finer powders are being pursued for the development of coating internal surfaces, as less thermal energy is required to melt the finer powder compared to coarse powders, permitting spraying at smaller stand - off distances. Three WC-0Co-4Cr coatings, with two different powder particle sizes and two different carbide grain sizes, were sprayed using a high velocity oxy-air fuel (HVOAF) thermal spray system developed by Castolin Eutectic - Monitor Coatings Ltd., UK. Powder and coating microstructures were characterised using XRD and SEM. Fracture toughness and dry sliding wear performance at three loads were investigated using a ball–on-disc tribometer with a WC–Co counter body. It was found that the finer powder produced the coating with the highest microhardness, but its fracture toughness was reduced due to increased decarburisation compared to the other powders. The sprayed nanostructured powder had the lowest microhardness and fracture toughness of all materials tested. Unlubricated sliding wear testing at the lowest load showed the nanostructured coating performed best; however at the highest load this coating showed the highest specific wear rates with the other two powders performing to a similar, better standard

Towards an integrated set of surface meteorological observations for climate science and applications

Observations are the foundation for understanding the climate system. Yet, currently available land meteorological data are highly fractured into various global, regional and national holdings for different variables and timescales, from a variety of sources, and in a mixture of formats. Added to this, many data are still inaccessible for analysis and usage. To meet modern scientific and societal demands as well as emerging needs such as the provision of climate services, it is essential that we improve the management and curation of available land-based meteorological holdings. We need a comprehensive global set of data holdings, of known provenance, that is truly integrated both across Essential Climate Variables (ECVs) and across timescales to meet the broad range of stakeholder needs. These holdings must be easily discoverable, made available in accessible formats, and backed up by multi-tiered user support. The present paper provides a high level overview, based upon broad community input, of the steps that are required to bring about this integration. The significant challenge is to find a sustained means to realize this vision. This requires a long-term international program. The database that results will transform our collective ability to provide societally relevant research, analysis and predictions in many weather and climate related application areas across much of the globe

COMUNICA Project: a commitment for strategic communication on Earth Sciences

The Institute of Earth Sciences Jaume Almera (ICTJA-CSIC) has just celebrated its 50-year anniversary last year. It is a reference research center on Earth Sciences both national and international level. The Institute includes 4 research groups which focus their scientific activity on the structure and dynamics of the Earth, the environmental changes in the geological record, geophysical and geochemical modelling and crystallography and optical properties. Only when large geological disasters happens, mainly earthquakes and volcanic eruptions, some interaction between ICTJA-CSIC researchers and traditional media occurs, which is limited by the fact that the aim of the Institute is the scientific research and it has no responsibilities in the area of civil protection. This relationship reduces the knowledge of our activity to the general public. To overcome this situation, the ICTJA-CSIC has decided to take an active role in the social dissemination of geological and geophysical knowledge. Thus, the ICTJA-CSIC has launched the COMUNICA Project. The project is aimed to increase the social visibility of the ICTJA-CSIC and to promote the outreach of researchers. Therefore ICTJA-CSIC has created the Communication Unit, which is in charge of designing communication strategies to give to different audiences (media, students of secondary and higher education, general public) an overview of the scientific and institutional activity of the ICTJA-CSIC. A global communication plan is being designed to define the strategic actions, both internal and external. An important role has been reserved for digital channels, to promote ICTJA-CSIC activity on social networks such as Twitter, Facebook or Youtube, besides making a major effort in the renovation and maintenance of the corporate website. A strong effort will be done to collect and spread through press releases the major scientific milestones achieved by the researchers, to promote the interest of mass media. Communication plan includes also institutional participation in scientific dissemination events, talks addressed to general public, and workshops and seminars for students of secondary and higher educationPeer Reviewe