Influence of model errors on some spatial analysis methods

The purpose of this article is ta study the influence of model errors on the performances of some spatial analysis methods. We present a unification of both the concerned methods and perturbations . This leads to a general expression of the estimation error on the sources bearings as a functon of both the perturbation and the method. This expression, calculated at the first order and in the non-asymptotic case, is then derived for each method and each perturbation .Nous étudions dans cet article l'influence d'erreurs de modèle sur le performances de certaines méthodes d'analyse spatiale. Une unification de methodes ainsi que des perturbations considérés nous permet de donner une formule générale pour l'erreur d'estimation des directions d'arrivées, en fonction de la perturbation et de la méthode utilisée. Cette formule, obtenue au premier ordre et dans le cas non-asymptotique, est ensuite dérivée pour chaque méthode et pour chaque perturbatio

Comparison of both the propagator and the Weiss-Friedlander methods

The purpose of this article is to compare two methods for the self-calibration of a distorted array. These methods allow to estimate both the array shape and the bearing angles. The first one uses the properties of the propagator The second one uses successive projections, on the bearing angles subspace and then on the array geometrical parameters subspace ; it is based on the MD-Music algorithm . We take a particular interest in the validity domains and in the limitations of both methods.Nous comparons dans cet article deux methodes pour l'auto-calibration d'une antenne déformée. Il s'agit de deux méthodes qui permettent d'estimer conjointement la forme de l'antenne et les directions d'arrivée des fronts d'ondes. La première utilise les propriétés du propagateur. La seconde utilise des projections successives tantôt sur le sous-espace des directions d'arrivées, tantôt sur le sous-espace des paramètres géométriques de l'antenne; elle repose sur l'algorithme MD-Music. Nous méttons notamment en évidence les domaines d'application et les limitations de ces deux méthode

Estudio estático y dinámico del ángulo Q mediante videofotogrametría 3D

OBJETIVOS: Se estudia la evolución del ángulo Q (Q dinámico) en bipedestación y en una marcha frontal, para obtener los valores de normalidad para futuros estudios dónde la clínica femoropatelar es más acentuada (bajar escaleras y descenso de rampa). MATERIAL Y MÉTODOS: Participaron 20 individuos sanos (10 hombres y 10 mujeres) con edad media de 22,7 años + 3,02 (20-25 años), a los que se realizó un análisis tridimensional del movimiento mediante el sistema de videofotogrametría en 3D Orthobio, en la bipedestación y durante la marcha en terreno llano. RESULTADOS: Hemos observado que durante la bipedestación el ángulo Q estático medio tiene un valor de 16,12º. Los datos obtenidos muestran que el ángulo Q dinámico oscila 8,13º (6,03º-14,16º), produciéndose el valor máximo en el momento del choque de talón y el mínimo poco después del despegue. La media del ángulo Q dinámico en un ciclo de marcha ha sido de 11,47º. En los datos por sexos corresponde a las mujeres es de 12,46º, y el de los hombres de 10,48º. CONCLUSIONES: Durante la marcha el ángulo Q dinámico disminuye con respecto al estático.OBJECTIVES: In this paper we study the evolution of the dynamic Q-angle in bipedal standing and forward gait to obtain values of normality for future studies in which femoropatellar problems are more pronounced (e.g. descending stairs or ramps). MATERIALS AND METHODS: Twenty healthy individuals (10 men and 10 women), with an average age of 22.7 + 3.02 years (i.e. 20–25 years), took part in this study. In these individuals, a tridimensional analysis of movement of bipedal standing and gait on flat terrain was conducted using 3D Orthobio videophotogrammetry. RESULTS: During bipedal standing, the average static Q angle was 16.12º. The dynamic Q angle fluctuated by 8.13º (between 6.03º and 14.16º), the maximum dynamic Q angle was reached as the heel contacted the ground and the minimum was reached just after leaving the ground. The average dynamic Q angle in a gait cycle was 11.47º (12.46º for women and 10.48º for men). CONCLUSIONS: During the cycle, the dynamic Q angle is lower than the static Q angle

Improving the modeling of geomagnetically induced currents in Spain

Vulnerability assessments of the risk posed by geomagnetically induced currents (GICs) to power transmission grids benefit from accurate knowledge of the geomagnetic field variations at each node of the grid, the Earth's geoelectrical structures beneath them, and the topology and relative resistances of the grid elements in the precise instant of a storm. The results of previous analyses on the threat posed by GICs to the Spanish 400 kV grid are improved in this study by resorting to different strategies to progress in the three aspects identified above. First, although at midlatitude regions the source fields are rather uniform, we have investigated the effect of their spatial changes by interpolating the field from the records of several close observatories with different techniques. Second, we have performed a magnetotelluric (MT) sounding in the vicinity of one of the transformers where GICs are measured to determine the geoelectrical structure of the Earth, and we have identified the importance of estimating the MT impedance tensor when predicting GIC, especially where the effect of lateral heterogeneities is important. Finally, a sensitivity analysis to network changes has allowed us to assess the reliability of both the information about the network topology and resistances, and the assumptions made when all the details or the network status are not available. In our case, the most essential issue to improve the coincidence between model predictions and actual observations came from the use of realistic geoelectric information involving local MT measurements

Validating GIC modeling in the Spanish power grid by differential magnetometry

series of experiences and recommendations are presented concerning the derivation of geomagnetically induced currents (GIC) by use of the differential magnetometry method (DMM) under power lines. This indirect technique, intended to obtain observations to validate GIC models, is an alternative to measuring the current flow in the transformer neutrals. It is a non-intrusive and autonomous technique, as the procedure does not depend on the grid operator. In contrast, the selection of suitable sites devoid of human interferences, the need for power to supply the magnetometer, the data acquisition and transmission system, along with the choice of the appropriate instrumentation are difficulties that make not just any site suitable for installation and often require costly solutions. We focus on the methodology followed to estimate the GIC flowing in several transmission lines of the Spanish power grid with the aim of validating our GIC models, and we share our experience on the installation of the measuring points. Uncertainty inherent in the DMM is assessed, showing that noise is the main handicap, although it can be minimized with appropriate filtering. According to such experience, on some occasions only total DC currents above a significant fraction of 1 A give magnetic signatures well above the noise level, so this figure can roughly be considered as the threshold limit for detection. The low solar activity, combined with the mid-latitude condition of Spain, limited the significance of available recorded data, but we can already report and analyze the results for several minor geomagnetic storms

Engineering of hybrid nanoporous anodic alumina photonic crystals by heterogeneous pulse anodization

In this study, we present an advanced nanofabrication approach, so-called ‘heterogeneous pulse anodization’ (HPA), in which galvanostatic stepwise and apodized sinusoidal pulse anodizations are combined in a single process. This novel anodization method enables the precise optical engineering of the characteristic photonic stopbands (PSBs) of nanoporous anodic alumina photonic crystals (NAA-PCs). The resulting structures are hybrid PCs (Hy-NAA-PCs) composed of distributed Bragg reflectors (DBRs) and apodized gradient-index filters (APO-GIFs) embedded within the same PC structure. The modification of various anodization parameters such as anodization period, relative and total anodization time, structural arrangement of PCs within Hy-NAA-PCs, and pore widening time allows the fine-tuning of the PSBs’ features (i.e. number, position and bandwidth of central wavelength) across the spectral regions. The effects of these fabrication parameters are systematically assessed, revealing that the positions of the characteristic transmission bands of Hy-NAA-PCs are highly controllable. Our study provides a comprehensive rationale towards the development of unique Hy-NAA-PCs with controllable optical properties, which could open new opportunities for a plethora of applications.Siew Yee Lim, Cheryl Suwen Law, Lluis F. Marsal and Abel Santo

A major population of mucosal memory CD4⁺ T cells, coexpressing IL-18Rα and DR3, display innate lymphocyte functionality

Mucosal tissues contain large numbers of memory CD4(+) T cells that, through T-cell receptor-dependent interactions with antigen-presenting cells, are believed to have a key role in barrier defense and maintenance of tissue integrity. Here we identify a major subset of memory CD4(+) T cells at barrier surfaces that coexpress interleukin-18 receptor alpha (IL-18Rα) and death receptor-3 (DR3), and display innate lymphocyte functionality. The cytokines IL-15 or the DR3 ligand tumor necrosis factor (TNF)-like cytokine 1A (TL1a) induced memory IL-18Rα(+)DR3(+)CD4(+) T cells to produce interferon-γ, TNF-α, IL-6, IL-5, IL-13, granulocyte-macrophage colony-stimulating factor (GM-CSF), and IL-22 in the presence of IL-12/IL-18. TL1a synergized with IL-15 to enhance this response, while suppressing IL-15-induced IL-10 production. TL1a- and IL-15-mediated cytokine induction required the presence of IL-18, whereas induction of IL-5, IL-13, GM-CSF, and IL-22 was IL-12 independent. IL-18Rα(+)DR3(+)CD4(+) T cells with similar functionality were present in human skin, nasal polyps, and, in particular, the intestine, where in chronic inflammation they localized with IL-18-producing cells in lymphoid aggregates. Collectively, these results suggest that human memory IL-18Rα(+)DR3(+) CD4(+) T cells may contribute to antigen-independent innate responses at barrier surfaces.Mucosal Immunology advance online publication, 1 October 2014; doi:10.1038/mi.2014.87