Wake deviation of yawed wind turbine by Large-Eddy Simulation

International audienceKeywords: Large Eddy Simulation, yaw and wake interaction According to the current energetic and environmental challenges, maximizing the electric power generated in windfarms is a societal concern. New strategies such as involving wind turbine yaw angle seem relevant to reduce wake interaction and associated power losses [1]. Therefore, yawed turbine aerodynamics is modified and remains a challenging investigation topic. Since experimental data on actual windfarm scales are not affordable and given the constant growth of computational resources, high order numerical simulations tend to be a promising approach [2]. The goal of this study is to evaluate a highly resolved numerical model under yaw condition in a wind tunnel before applying it to actual windfarm. The blade modeling is performed using an Actuator Line Method [3] (ALM), coupled to the low Mach-number massively-parallel finite-volume Large-Eddy Simulation (LES) flow solver on unstructured meshes, called YALES2 [4] [5]. The Blind Test 5 experimental configuration led at NTNU [6], gathering numerous experimental data, is reproduced in this study. After the study of a yawed turbine wake interaction with downstream turbine the study of a single yawed turbine (+30 o and 0 o) will be presented. The computational domain of these cases will be the NTNU wind tunnel, involving a turbulence grid aiming to create a fully turbulent sheared inflow [6]. The grid will be modeled using multiple Actuator Lines (to mimic the turbine blades) with dedicated polars [7] [8]. Each computational case is performed on a unstructured mesh with around 150.10 6 tetrahedra. An instantaneous velocity field of the yawed turbine wake interaction is presented on Figure 1. Figure 1: Instantaneous streamwise velocity field of wake interaction between two turbines in the NTNU wind tunnel with unstructured mes

Hyper high NA achromatic interferometer for immersion lithography at 193nm

International audienceAn apparatus for immersion interferometric lithography is described here where the interfering beams are created by illuminating a first diffraction grating followed by a second diffraction grating recombining the diffracted beams onto the photo-resist plane. The main advantage of this system is to be achromatic: thus it is possible to use a basic commercial ArF excimer laser as the exposure source. We present here the calculations made to evaluate the different parameters that can influence the depth-of-focus in the immersion configuration. As the set-up is mainly based on the two diffraction gratings, it matters to properly design it. The purpose of this paper is to show the optimization made on the diffraction gratings in taking into account their fabrication process since they are fabricated using the capabilities of the silicon line available in our laboratory. On one hand, calculations have been done to determine the second grating period as a function of the first grating period and the ”immersion NA”. By simply adding a fluid to a “dry” system, we will indeed be able to improve the depth of focus but not the resolution. In playing with the diffraction grating periods, we are able to benefit from the introduction of the immersion fluid. We have performed simulations in order to optimize the grating diffraction efficiency as a function of the etch depth and the fractional linewidth. Finally we report on first results obtained with the achromatic immersion interferometer. The apparatus was used with a 193 nm GAM excimer laser to print resist patterns having a period of 100 nm with excellent contrast

Surface decoration of catanionic vesicles with superparamagnetic iron oxide nanoparticles: a model system for triggered release under moderate temperature conditions

International audienceWe report the design of new catanionic vesicles decorated with iron oxide nanoparticles, which could be used as a model system to illustrate controlled delivery of small solutes under mild hyperthermia. Efficient release of fluorescent dye rhodamine 6G was observed when samples were exposed to an oscillating magnetic field. Our system provides direct evidence for reversible permeability upon magnetic stimulation

Combined geochemical and electrochemical methodology to quantify corrosion of carbon steel by bacterial activity.

International audienceThe availability of respiratory substrates, such as H2 and Fe(II,III) solid corrosion products within nuclear waste repository, will sustain the activities of hydrogen-oxidizing bacteria (HOB) and iron-reducing bacteria (IRB). This may have a direct effect on the rate of carbon steel corrosion. This study investigates the effects of Shewanella oneidensis (an HOB and IRB model organism) on the corrosion rate by looking at carbon steel dissolution in the presence of H2 as the sole electron donor. Bacterial effect is evaluated by means of geochemical and electrochemical techniques. Both showed that the corrosion rate is enhanced by a factor of 2-3 in the presence of bacteria. The geochemical experiments indicated that the composition and crystallinity of the solid corrosion products (magnetite and vivianite) are modified by bacteria. Moreover, the electrochemical experiments evidenced that the bacterial activity can be stimulated when H2 is generated in a small confinement volume. In this case, a higher corrosion rate and mineralization (vivianite) on the carbon steel surface were observed. The results suggest that the mechanism likely to influence the corrosion rate is the bioreduction of Fe(III) from magnetite coupled to the H2 oxidation

Low-temperature anomalies in muon spin relaxation of solid and hollow nanoparticles: a pathway to detect unusual local spin dynamics

By means of muon spin relaxation measurements we unraveled the temperature spin dynamics in monodisperse maghemite spherical nanoparticles with different surface to volume ratio, in two samples with a full core (diameter D∼4 and D∼5nm) and one with a hollow core (external diameter D∼7.4nm). The behavior of the muon longitudinal relaxation rates as a function of temperature allowed us to identify two distinct spin dynamics. The first is well witnessed by the presence of a characteristic peak for all the samples around the so-called muon blocking temperature T$_{B}^{μ+}$. A Bloembergen-Purcell-Pound (BPP)-like model reproduces the experimental data around the peak and at higher temperatures (20<T<100K) by assuming the Néel reversal time of the magnetization as the dominating correlation time. An additional dynamic emerges in the samples with higher surface to volume ratio, namely, full 4 nm and hollow samples. This is witnessed by a shoulder of the main peak for T<20K at low longitudinal field (μ$_{0}$H≈15mT), followed by an abrupt increase of the relaxation rate at T<10K, which is more evident for the hollow sample. These unusual anomalies of the longitudinal relaxation rate for T<T$_{B}^{μ+}$ are suggested to be due to the surface spins’ dynamical behavior. Furthermore, for weak applied longitudinal magnetic field (μ$_{0}$H≈15mT) and T<T$_{B}^{μ+}$ we observed damped coherent oscillations of the muon asymmetry, which are a signature of a quasistatic local field at the muon site as probed by muons implanted in the inner magnetic core of the nanoparticles. The muon spin relaxation technique turns out to be very successful to study the magnetic behavior of maghemite nanoparticles and to detect their unusual local spin dynamics in low magnetic field conditions

El trabajo final para acceder al título de Ingeniero Agrónomo en la carrera de Ingeniería Agronómica de la Universidad Nacional de San Luis (UNSL) : I- Temáticas - Modalidad

El Plan de Estudio de la Carrera de Ingeniería Agronómica, UNSL, establece dentro de actividades complementarias obligatorias realizar un Trabajo Final, con un crédito horario de 200 horas. Esta instancia culminante de la intensidad de la formación práctica, con temática de libre elección para el alumno, estaba orientada a dos modalidades en el marco de proyectos desarrollados en la Unidad Académica: (1) extensión y transferencia, (2) investigación. El objetivo del presente trabajo fue analizar las temáticas y modalidades desde el año de su implementación en 1999 hasta 2009, cuando se amplían las modalidades; y que posteriormente será objeto de un análisis comparativo. Los trabajos finales se clasificaron considerando áreas y núcleos temáticos del Plan de Estudio, según Resolución Ministerial 334/03. Los resultados muestran que: el 5% corresponden al área de las Ciencias Básicas (4% al núcleo Botánica y 1% al núcleo Química). Al área Básicas Agronómicas le corresponde el 57%, (núcleos Protección Vegetal 22%, Genética-Mejoramiento 18% y Suelos y Aguas 11%). Al área de las Aplicadas Agronómicas pertenece el 38% (20% para el núcleo Producción Vegetal, 15% para Producción Animal y 3% para Socio-Economía). Todos los Trabajos Finales para el período analizado se enmarcaron en la modalidad investigaciónEje temático 1: Problemáticas y alternativas de mejora de la enseñanza e - Los enfoques y modalidades de integración curricularFacultad de Ciencias Agrarias y Forestale

Constructing large DNA segments by iterative clone recombination

Methods for constructing large contiguous segments of DNA will be enabling for Synthetic Biology, where the assembly of genes encoding circuits, biosynthetic pathways or even whole microbial organisms is of interest. Currently, in vitro approaches to DNA synthesis are adequate for generating DNAs that are up to 10s of kbp in length, and in vivo recombination strategies are more suitable for building DNA constructs that are 100 kbp or larger. We have developed a vector system for efficient assembly of large DNA molecules by iterative in vivo recombination of fosmid clones. Two custom fosmid vectors have been built, pFOSAMP and pFOSKAN, that support antibiotic switching. Using this technique we rebuilt two non-contiguous regions of the Haemophilus influenzae genome as episomes in recombinogenic Escherichia coli host cells. These regions together comprise190 kbp, or 10.4% of the H. influenze genome