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A letter from Sandy Speed to Dr. Hector P. Garcia.
No full textA letter from Sandy Speed, General Chairman of Corpus Christi State University and Leadership Corpus Christi, to Dr. Hector P. Garcia, inviting him to serve on the Advisory Committee
Predictive control of wind turbines by considering wind speed forecasting techniques
No full textA wind turbine system is operated such that the points of wind rotor curve and electrical generator curve coincide. In order to obtain maximum power output of a wind turbine generator system, it is necessary to drive the wind turbine at an optimal rotor speed for a particular wind speed. A Maximum Power Point Tracking (MPPT) controller is used for this purpose. In fixed-pitch variable-speed wind turbines, wind-rotor parameters are fixed and the restoring torque of the generator needs to be adjusted to maintain optimum rotor speed at a particular wind speed for optimum power output. In turbulent wind environment, control of variable-speed fixed-pitch wind turbine systems to continuously operate at the maximum power points becomes difficult due to fluctuation of wind speeds. In this paper, wind speed forecasting techniques will be considered for predictive optimum control system of wind turbines
Structural analysis and parametric study ballasted track in sandy regions
No full textThe sand intrusion in railway tracks in sandy regions can significantly change the mechanical behaviour of tracks and thus threaten the safety of train operation. This paper presents substantial field tests on both sandy and clean railway tracks to study the effect of sand intrusion on the longitudinal resistance of ballast bed and the vibration behaviour of track structures. After that, a 3D multi-scale the discrete element model is developed to study the micro-contact between ballast particles and the vibration behaviour of sandy tracks during train passing in detail. Also, the effect of train speeds and axle loads on the mechanical behaviour of sandy tracks is discussed. The results show that the sand intrusion increases the vibration acceleration amplitude of rail and sleeper by 11.3% and 50.3%, while ballast bed decreases by 44.9%. Besides, the sand intrusion significantly changes the energy distribution in the track, wherein the frequencies of the highest energy of rail and sleeper are increased while that of the ballast bed is decreased. The parametric study shows the high train speed can cause the increase in overall acceleration of the ballast bed and high axle load can cause an increase in the micro-contact forces between ballast particles, diffusion angle of the contact force chain, displacements of ballast particles, acceleration of ballast particles, and sleeper displacements.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Mechanics and Physics of Structure
Non-discursive knowledge and the construction of identity. Potters, potting and performance at the bronze age tell of Százhalombatta, Hungary
No full textThis article explores the relationship between the making of things and the making of people at the Bronze Age tell at Százhalombatta, Hungary. Focusing on potters and potting, we explore how the performance of non-discursive knowledge was critical to the construction of social categories. Potters literally came into being as potters through repeated bodily enactment of potting skills. Potters also gained their identity in the social sphere through the connection between their potting performance and their audience. We trace degrees of skill in the ceramic record to reveal the material articulation of non-discursive knowledge and consider the ramifications of the differential acquisition of non-discursive knowledge for the expression of different kinds of potter's identities. The creation of potters as a social category was essential to the ongoing creation of specific forms of material culture. We examine the implications of altered potters' performances and the role of non-discursive knowledge in the construction of social models of the Bronze Ag
Seed ecology in dry sandy grasslands - an approach to patterns and mechanisms
No full textDry sandy grasslands occur throughout Central Europe and Southern Germany, and they host many rare and endangered plant species. To date, insufficient data on seed ecological aspects of this endangered vegetation type exist. Seed ecological studies attempt to develop ecological knowledge by identifying patterns and underlying mechanisms. To bring all results together, it can be pointed out that environmental factors strongly shape seed ecological patterns. Species with special mechanisms like those creating persistent seed banks for small sized seeds, faster germination speed and the development of physiological dormancy may tolerate sandy grasslands habitat conditions. Filtering effect of aluminum toxicity for germination of species from calcareous soil indicates the importance of regeneration niches in community assembly. Developing seed ecological traits as easy measurable traits would help to elucidate community assembly rules. Different factors like habitat conditions and seed responses to these environmental factors, seed reserves and germination limitations should be considered in restoration ecology and conservation issues. Seed ecological studies can help in habitat restoration planning and species reintroduction design making
Crushed rock and clay amelioration of a nutrient decifient, sandy soil of Maputaland
No full textBibliography: leaves 57-62.Various studies have suggested the possibility that food derived through subsistence agriculture in the Mseleni region of Maputaland contributes to malnutrition within the local community, particularfy within the high proportion of the population which suffers from a severe, disabling form of osteoarthritis. This study was conducted to determine if the application of local crushed rock or black clay to these nutrient deficient, sandy soils would increase available nutrient concentrations and improve the growth of plants in the ameliorated soil
Nowcasting extreme rain and extreme wind speed with machine learning techniques applied to different input datasets
No full textPredicting extreme weather events in a short time period and their developing in localized areas is a challenge. The nowcasting of severe and extreme weather events is an issue for air traffic management and control because it affects aviation safety, and determines delays and diversions. This work is part of a larger study devoted to nowcasting rain and wind speed in the area of Malpensa airport by merging different datasets. We use as reference the weather station of Novara to develop a nowcasting machine learning model which could be reusable in other locations. In this location we have the availability of ground-based weather sensors, a Global Navigation Satellite System (GNSS) receiver, a C-band radar and lightning detectors. Our analysis shows that the Long Short-Term Memory Encoder Decoder (LSTM E/D) approach is well suited for the nowcasting of meteo- rological variables. The predictions are based on 4 different datasets configurations providing rain and wind speed nowcast for 1 h with a time step of 10 min. The results are very promising with the extreme wind speed probability of detection higher than 90%, the false alarms lower than 2%, and a good performance in extreme rain detection for the first 30 min. The configuration using just weather stations and GNSS data in input provides excellent performances and should be preferred to the other ones, since it refers to the pre-convective envi- ronment, and thus can be adaptable to any weather conditions
Experimental measurement of the nearfield longitudinal wake profiles of a high-speed prismatic planing hull
No full textThis study details an extensive investigation into the nearfield longitudinal wake profiles of a high-speed planing hull. Developing understanding this flow is benaficial to the designers of stepped hulls in determining how the forebody’s wake intersects with the afterbody. As no experimental data was available, a novel small-scale model-testing programme was undertaken, measuring Centreline (CL) and Quarter Beam (QB) nearfield longitudinal wake profiles, as well as the forces. The nearfield wake profile was found to exhibit trends in agreement with the findings of studies investigating the mid and far-field wake. The results of this experimental work are provided in full as validation data. Savitsky’s Wake Equations and the Linear Wake Assumption are then assessed to determine the level of confidence with which they may be used to model this flow. Savitsky’s Wake Equations displayed a surprising level of accuracy whereas the Linear Wake Assumption was invalid for the conditions investigated
Sandy coastlines under threat of erosion
No full textSandy beaches occupy more than one-third of the global coastline1 and have high socioeconomic value related to recreation, tourism and ecosystem services2. Beaches are the interface between land and ocean, providing coastal protection from marine storms and cyclones3. However the presence of sandy beaches cannot be taken for granted, as they are under constant change, driven by meteorological4,5, geological6 and anthropogenic factors1,7. A substantial proportion of the world’s sandy coastline is already eroding1,7, a situation that could be exacerbated by climate change8,9. Here, we show that ambient trends in shoreline dynamics, combined with coastal recession driven by sea level rise, could result in the near extinction of almost half of the world’s sandy beaches by the end of the century. Moderate GHG emission mitigation could prevent 40% of shoreline retreat. Projected shoreline dynamics are dominated by sea level rise for the majority of sandy beaches, but in certain regions the erosive trend is counteracted by accretive ambient shoreline changes; for example, in the Amazon, East and Southeast Asia and the north tropical Pacific. A substantial proportion of the threatened sandy shorelines are in densely populated areas, underlining the need for the design and implementation of effective adaptive measures.Accepted Author ManuscriptCoastal Engineerin
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