Wind turbine design through evolutionary algorithms based on surrogate CFD methods

An automatic design environment using evolutionary techniques has been developed for the design of Horizontal Axis Wind Turbine (HAWT) blades taking into account both the aerodynamics and the structural constraints of the blades. This design environment is based on a simple, fast, and robust aerodynamic simulator intended for the prediction of the performance of any turbine blade produced as an intermediate individual of the evolutionary search process. In order to reduce the computational costs, the results obtained by this simple simulator have been corrected through the application of Artificial Neural Network (ANN) based approximations. An additional stress analysis stage has been introduced in order to take into account the structural resistance of the blades as a constraint throughout the optimization process. Results of the simulations obtained using this technique, of the application of the automatic design procedure and of the performance of the wind turbines thus produced are presented. In a first test case the rotor designed through the proposed method is compared to the one obtained analytically for a given air speed. This comparison to an analytical optimum provides a good index in order to evaluate the performance of the method. In a second case the rotor is optimized for a typical wind speed distribution, which is a more realistic scenario where the cost performance of the resulting turbines needs to be evaluated.     

Recent progress in research on tungsten materials for nuclear fusion applications in Europe

The current magnetic confinement nuclear fusion power reactor concepts going beyond ITER are based on assumptions about the availability of materials with extreme mechanical, heat, and neutron load capacity. In Europe, the development of such structural and armour materials together with the necessary production, machining, and fabrication technologies is pursued within the EFDA long-term fusion materials programme. This paper reviews the progress of work within the programme in the area of tungsten and tungsten alloys. Results, conclusions, and future projections are summarized for each of the programme’s main subtopics, which are: (1) fabrication, (2) structural W materials, (3) W armour materials, and (4) materials science and modelling. It gives a detailed overview of the latest results on materials research, fabrication processes, joining options, high heat flux testing, plasticity studies, modelling, and validation experiments.     

About the origin of low wafer performance and crystal defect generation on seed‐cast growth of industrial mono‐like silicon ingots

The era of the seed‐cast grown monocrystalline‐based silicon ingots is coming. Mono‐like, pseudomono or quasimono wafers are product labels that can be nowadays found in the market, as a critical innovation for the photovoltaic industry. They integrate some of the most favorable features of the conventional silicon substrates for solar cells, so far, such as the high solar cell efficiency offered by the monocrystalline Czochralski‐Si (Cz‐Si) wafers and the lower cost, high productivity and full square‐shape that characterize the well‐known multicrystalline casting growth method. Nevertheless, this innovative crystal growth approach still faces a number of mass scale problems that need to be resolved, in order to gain a deep, 100% reliable and worldwide market: (i) extended defects formation during the growth process; (ii) optimization of the seed recycling; and (iii) parts of the ingots giving low solar cells performance, which directly affect the production costs and yield of this approach. Therefore, this paper presents a series of casting crystal growth experiments and characterization studies from ingots, wafers and cells manufactured in an industrial approach, showing the main sources of crystal defect formation, impurity enrichment and potential consequences at solar cell level. The previously mentioned technological drawbacks are directly addressed, proposing industrial actions to pave the way of this new wafer technology to high efficiency solar cells. Copyright © 2012 John Wiley & Sons, Ltd.     

The linkage between cell wall metabolism and fruit softening: looking to the future

The softening that accompanies ripening of commercially important fruits exacerbates damage incurred during shipping and handling and increases pathogen susceptibility. Thus, postharvest biologists have studied fruit softening to identify ways to manage ripening and optimise fruit quality. Studies, generally based on the premise that cell wall polysaccharide breakdown causes ripening‐associated softening, have not provided the insights needed to genetically engineer, or selectively breed for, fruits whose softening can be adequately controlled. Herein it is argued that a more holistic view of fruit softening is required. Polysaccharide metabolism is undoubtedly important, but understanding this requires a full appreciation of wall structure and how wall components interact to provide strength. Consideration must be given to wall assembly as well as to wall disassembly. Furthermore, the apoplast must be considered as a developmentally and biochemically distinct, dynamic ‘compartment’, not just the location of the cell wall structural matrix. New analytical approaches for enhancing the ability to understand wall structure and metabolism are discussed. Fruit cells regulate their turgor pressure as well as cell wall integrity as they ripen, and it is proposed that future studies of fruit softening should include attempts to understand the bases of cell‐ and tissue‐level turgor regulation if the goal of optimising softening control is to be reached. Finally, recent studies show that cell wall breakdown provides sugar substrates that fuel other important cellular pathways and processes. These connections must be explored so that optimisation of softening does not lead to decreases in other aspects of fruit quality. Copyright © 2007 Society of Chemical Industry     

Effect of dietary supplementation with either red wine extract or vitamin E on the volatile profile of lamb meat fed with omega-3 sources

The effect of dietary supplementation with either vitamin E (300 ppm) or a red wine extract rich in polyphenols (900 ppm) in an omega-3 enriched concentrate on the volatile fraction of lamb meat was assessed. The effect of refrigerated storage (0 and 6 days) under high-oxygen atmospheres (70% O₂/30% CO₂) was also studied. Extraction and analysis of the volatile compounds was carried out by headspace solid-phase microextraction (HS-SPME) and GC–MS, respectively. Vitamin E supplementation led to lower levels of lipo-oxidation compounds, such as 2-heptanone and 1-penten-3-ol. The red wine extract was less efficient against lipid oxidation than vitamin E but more efficient than the control (no added antioxidants). The levels of numerous lipid-derived compounds were found to be lower after 6 days of storage which could be due to further interactions with protein-related compounds.     

Experimental study on pressure drops in a dividing wall distillation column

Previous studies in the fields of process design and process control [1] have shown the potential benefits that can be achieved through the implementation of thermally coupled distillation sequences, in particular, the dividing wall distillation column. The dividing wall distillation column meets important goals of process intensification, including energy savings, reduction in carbon dioxide emissions and miniaturization. In this paper, an experimental study on the hydrodynamic behavior of a dividing wall distillation column is presented. Several different values for gas and liquid velocities were tested in order to measure pressure drops and identify operational regions; the air/water system was used as the basis for the experimental setup. Results regarding pressure drops (fitted to the model of Stichlmair et al.) provide operational limits for the operation of the packed dividing wall distillation column. According to the results, the experimental dividing wall column can be operated at turbulent regime that is associated to proper mass transfer.     

Monte Carlo simulation of the homogeneous cooling state for a granular mixture

 The Direct Simulation Monte Carlo (DSMC) method is used to numerically solve the Enskog equation for a granular binary mixture in the homogeneous cooling state (HCS). The fourth velocity moments, the temperature ratio, and also the velocity distribution functions are obtained and compared with approximate analytical results derived recently from a Sonine polynomial expansion [V. Garzó and J. W. Dufty, Phys. Rev. E 60, 5706 (1999)]. The comparison shows an excellent agreement between both approaches, even for strong dissipation or disparate values of the mechanical parameters of the mixture. In contrast to previous studies, the partial temperatures of each species are clearly different, so that the total energy is not equally distributed between both species. Finally, in the same way as in the one-component case, the simulation as well as the theory show a high energy tail of the distribution functions. Received: 9 May 2001     

An examination of the antecedents and moderator influences of climate strength.

The authors tested 3 hypotheses regarding the antecedents and moderator influences of climate strength (CS; the degree of within-unit agreement of climate perceptions). The sample consisted of 197 work units. Social interaction among unit members showed positive, statistically significant correlations with CS in goals orientation and innovation climate. Work-unit leaders' informing behavior was positively correlated with CS in the 3 climate facets measured (i.e., support, goals orientation, and innovation). CS in innovation moderated the impact of work units' innovation climate on average satisfaction and commitment. CS in goals orientation moderated the influence of work units' goal orientation on average commitment. The moderator influences showed the expected direction: CS fostered the influence of work units' climate on the criterion variables. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Volume 21

Volume Contents

Volume 21