Aerodynamic Optimization of High-Speed Trains Nose using a Genetic Algorithm and Artificial Neural Network

An aerodynamic optimization of the train aerodynamic characteristics in term of front wind action sensitivity is carried out in this paper. In particular, a genetic algorithm (GA) is used to perform a shape optimization study of a high-speed train nose. The nose is parametrically defined via Bézier Curves, including a wider range of geometries in the design space as possible optimal solutions. Using a GA, the main disadvantage to deal with is the large number of evaluations need before finding such optimal. Here it is proposed the use of metamodels to replace Navier-Stokes solver. Among all the posibilities, Rsponse Surface Models and Artificial Neural Networks (ANN) are considered. Best results of prediction and generalization are obtained with ANN and those are applied in GA code. The paper shows the feasibility of using GA in combination with ANN for this problem, and solutions achieved are included

Combined hydro-wind generation bids in a pool-based electricity market

Present regulatory trends are promoting the irect participation of wind energy in electricity markets. The final result of these markets sets the production scheduling for the operation time, including a power commitment from the wind generators. However, wind resources are uncertain, and the final power delivered usually differs from the initial power committed. This imbalance produces an overcost in the system, which must be paid by those who produce it, e.g., wind generators among others. As a result, wind farm revenue decreases, but it could increase by allowing wind farms to submit their bids to the markets together with a hydro generating unit, which may easily modify its production according to the expected imbalance. This paper presents a stochastic optimization technique that maximizes the joint profit of hydro and wind generators in a pool-based electricity market, taking into account the uncertainty of wind power prediction.En prens

Optimal security-constrained power scheduling by Benders decomposition

This paper presents a Benders decomposition approach to determine the optimal day-ahead power scheduling in a pool-organized power system, taking into account dispatch, network and security constraints. The study model considers the daily market and the technical constraints resolution as two different and consecutive processes. The daily market is solved in a first stage subject to economical criteria exclusively and then, the constraints solution algorithm is applied to this initial dispatch through the redispatching method. The Benders partitioning algorithm is applied to this constraints solution process to obtain an optimal secure power scheduling. The constraints solution includes a full AC network and security model to incorporate voltages magnitudes as they are a critical factor in some real power systems. The algorithm determines the active power committed to each generator so as to minimize the energy redispatch cost subject to dispatch, network and security constraints. The solution also provides the reactive power output of the generators, the value of the transformers taps and the committed voltage control devices. The model has been tested in the IEEE 24-bus Reliability Test System and in an adapted IEEE 118-bus Test System. It is programmed in GAMS mathematical modeling language. Some relevant results are reported.Publicad

Slide-Down Prevention for Wheeled Mobile Robots on Slopes

Wheeled mobile robots on inclined terrain can slide down due to loss of traction and gravity. This type of instability, which is different from tip-over, can provoke uncontrolled motion or get the vehicle stuck. This paper proposes slide-down prevention by real-time computation of a straightforward stability margin for a given ground-wheel friction coefficient. This margin is applied to the case study of Lazaro, a hybrid skid-steer mobile robot with caster-leg mechanism that allows tests with four or five wheel contact points. Experimental results for both ADAMS simulations and the actual vehicle demonstrate the effectiveness of the proposed approach.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Graphene growth on h-BN by Van der Waals MBE

García Martínez, Jorge Manuel et al.Comunicación presentada en el PDI Topical Workshop on MBE-Grown Graphene 2013, celebrado en Berlín el 19 y 20 de septiembre de 2013.Graphene growth on dielectric substrates has potential to enable new kinds of devices and applications. We explore graphene growth via direct depositing carbon in a MBE environment on different dielectric substrates, such as h-BN and sapphire. The growth of single layer graphene nanometer size domains by solid carbon source molecular beam epitaxy on hexagonal boron nitride (h-BN) flakes is demonstrated. These results are consistent with a Van der Waals growth mode of graphene on dielectric substrates. Atomic-force microscope images and Raman maps reveal that the graphene grown depends on the surface morphology of the h-BN substrates. On h-BN substrates, high quality single layer growth occurs as nano-domains. The growth is governed by a high mobility of the carbon atoms on the h-BN surface, in a manner that is consistent with van der Waals epitaxy. The successful growth of graphene layers depends on the substrate temperature, but is fairly independent of the incident flux of carbon atoms. Formation of single-layer graphene is clearly apparent in Raman spectra that display sharp optical phonon bands. We will show also results of graphene growth by MBE on sapphire, where large area growth occurs with monolayer thickness fluctuations. The successful growth of graphene on hexagonal boron-nitride flakes distributed over a large area allows the exploration of arrange of growth parameters and suggests the capability for large area growth.Work supported by ONR (N000140610138 and Graphene MURI), AFOSR (FA9550-11-1-0010), EFRC Cente fo Re-De_ning Photovoltaic E_ciency through Molecule Scale Control (award DE-SC0001085), NSF (CHE-0641523), NYSTAR, CSIC-PIF (200950I154), Spanish CAM (Q&C Light (S2009ESP-1503), Numancia 2 (S2009/ENE-1477)) and Spanish MEC (ENE2009-14481-C02-02, TEC2011-29120-C05-04, MAT2011-26534).Peer Reviewe

Graphene growth on h‐BN by Molecular Beam Epitaxy

Jorge M. Garcia...et al.The growth of single layer graphene nanometer size domains by solid carbon source molecular beam epitaxy on hexagonal boron nitride (h‐BN) flakes is demonstrated. Formation of single‐layer graphene is clearly apparent in Raman spectra which display sharp optical phonon bands. Atomic‐force microscope images and Raman maps reveal that the graphene grown depends on the surface morphology of the h‐BN substrates. The growth is governed by the high mobility of the carbon atoms on the h‐BN surface, in a manner that is consistent with van der Waals epitaxy. The successful growth of graphene layers depends on the substrate temperature, but is independent of the incident flux of carbon atoms.This work is supported by ONR (N000140610138 and Graphene MURI), AFOSR (FA9550‐11‐1‐ 0010), EFRC Center for Re‐Defining Photovoltaic Efficiency through Molecule Scale Control (award DE‐SC0001085), NSF (CHE‐0641523), NYSTAR, CSIC‐PIF (200950I154), Spanish CAM (Q&C Light (S2009ESP‐1503), Numancia 2 (S2009/ENE‐1477)) and Spanish MEC (ENE2009‐14481‐C02‐02, TEC2011‐29120‐C05‐04, MAT2011‐26534).Peer reviewe

Graphene growth on h-BN by molecular beam epitaxy

García Martínez, Jorge Manuel et al.Comunicación presentada en el 17th European Molecular Beam Epitaxy Workshop (EUROMBE), celebrado en Levi (Finlandia) del 10 al 13 de marzo de 2013.Graphene growth on dielectric substrates has potential to enable new kinds of devices and applications. We explore graphene growth via direct depositing carbon in a MBE environment on different dielectric substrates, such as h-BN and sapphire. The growth of single layer graphene nanometer size domains by solid carbon source molecular beam epitaxy on hexagonal boron nitride (h-BN) flakes is demonstrated [1]. Formation of single-layer graphene is clearly apparent in Raman spectra which display sharp optical phonon bands (see Fig. 1 (a)). Atomic-force microscope images and Raman maps (Fig. 2) reveal that the graphene grown depends on the surface morphology of the h-BN substrates. On h-BN substrates, high quality single layer growth occurs as nano-domains. The growth is governed by the high mobility of the carbon atoms on the h-BN surface, in a manner that is consistent with van der Waals epitaxy. The successful growth of graphene layers depends on the substrate temperature, but is independent of the incident flux of carbon atoms. We will show also results of graphene growth by MBE on sapphire, where large area growth occurs with monolayer thickness fluctuations.This work is supported by ONR (N000140610138 and Graphene MURI), AFOSR (FA9550-11-1-0010), EFRC Center for Re-Defining Photovoltaic Efficiency through Molecule Scale Control (award DE-SC0001085), NSF (CHE-0641523), NYSTAR, CSIC-PIF (200950I154), Spanish CAM (Q&C Light (S2009ESP-1503), Numancia 2 (S2009/ENE-1477)) and Spanish MEC (ENE2009-14481-C02-02, TEC2011-29120-C05-04, MAT2011-26534).Peer Reviewe

New trends in education: the use of ICT in different ways

In the 21st century and due to the exponential growth of the Internet and Information and Communication Technologies (ICT), people live in a technological age, in all areas and in all contexts, we have daily contact with technology, with access to Information. This dynamic requires a constant update of the services and technological tools that change the method that we study, work, communicate and socialize on an unprecedented scale. These constant changes force everyone, regardless of age, gender or profession, to possess a range of functional and critical thinking skills, such as information literacy, media literacy and technological literacy. The evolution of technologies, forces the promoters of education, to always be aware of the changes that society is introducing outside the classroom. Today, students don't have the same pattern as before, regardless of age, they are very active and are no longer the same introverted child who studied a few years ago in the classroom. According to this, students are eager for different forms of motivation inside and outside the classroom, they need the learning and teaching process to move along with changes in society and ICT. To ensure the success of today's students, it is important to provide them with the technological skills to make the correct use of ICTs, to perform tasks essential to their learning process, such as researching and selecting information, creating content, information sharing, use of collaboration tools or environment simulation tools. The main objective of this chapter is to show how ICT tools that can be used in educational environments to help students, helping them develop key skills in their training process, is also relevant to show how these tools can help teachers achieve these goals in daily activities with their students

Government revenue in the wake of the pandemic: tax residuals and inflation

Rationale Following the COVID-19 pandemic, tax revenue has shown strong dynamism, increasing as a proportion of GDP by 3.7 percentage points since 2019. Understanding the nature of this dynamism is key to assessing Spanish fiscal policy. Takeaways • This article breaks down revenue growth into four explanatory factors: real economic activity, price growth, the effect of fiscal measures and an unexplained component or tax residual. • The effect of prices (inflation) has been gaining weight and appears to account for somewhat more than half of the revenue growth observed in 2022, especially from VAT and personal income tax. • It is estimated that 2.6 percentage points of the 3.7 percentage point increase in the revenue-to-GDP ratio cannot be explained by the changes in economic activity, prices or the fiscal measures approved. In the absence of an explanation about the permanent or temporary nature of this phenomenon, the principle of prudence would advise against considering this increase in revenue to be permanent