Reformulation du problème d'estimation des paramètres d'un réseau électrique

L’estimateur d’état est un outil pour la gestion de grands réseaux électriques. Il est formulé sous forme de problème d’optimisation aux moindres carrés pondérés. Il permet d’estimer les phaseurs de tension à partir des mesures redondantes et bruitées recueillies par les appareils de télémétrie. Ces valeurs de phaseurs sont par la suite utilisées dans plusieurs fonctions avancées de la conduite de réseau, comme par exemple : l’analyse de contingence, la surveillance des limites de sécurité, l’écoulement de puissance optimal, etc. L’une des hypothèses de l’estimateur d’état est que le modèle et les paramètres du réseau sont parfaitement connus. Cependant, des erreurs sont introduites dans la base de données pour une multitude de raisons. L’estimation des paramètres est une fonction complémentaire de l’estimateur d’état nécessaire afin d’en assurer sa robustesse et sa fiabilité. Bien que certaines méthodes aient déjà été étudiées dans la littérature, elles reposent toutes sur une fonction objectif aux moindres carrés pondérés. Or, les poids utilisés peuvent également être erronés. L’objectif de cette recherche est de développer un outil de diagnostic hors-ligne pour le réseau de TransÉnergie basé sur une nouvelle formulation du problème d’estimation des paramètres. Dans cette formulation, la fonction objectif reste quadratique, mais elle est non pondérée. Les écarts-types sont plutôt utilisés sous forme de variables qui s’ajoutent aux mesures. De plus, des variables binaires sont intégrées afin de détecter les paramètres erronés. Un algorithme glouton basé sur l’amélioration de la fonction objectif est proposé pour aider à la résolution de ce problème à variables mixtes. Tout d’abord, la formulation est testée sur le réseau IEEE 30 barres avec du bruit de 3% et une redondance des mesures de 3.6. Des erreurs allant de 5% à 100% des valeurs initiales des paramètres sont introduites et correctement identifiées. Même dans des cas où les erreurs de susceptances et de ratios de transformateurs sont adjacentes, les paramètres arrivent à être détectés et estimés avec une précision de 0.01-5%. Sur le réseau de transport, le bruit sur les mesures de puissances réactives atteint jusqu’à 20%. Dans ces conditions, la formulation arrive à identifier les erreurs dans les paramètres jusqu’à 30% de leur valeur initiale avec une précision d’environ 10%. Les tests permettent de tirer certaines conclusions. L’identification et l’estimation dépendent fortement du flux de puissance réactive à travers la branche où le paramètre est erroné. Les sous-réseaux et échantillons de temps sélectionnés pour estimer les paramètres doivent en tenir compte.----------Abstract State Estimator is a tool used in power systems to monitor its operating conditions. It is based on a weighted least square optimization problem. With noisy redundant measurements collected by equipment over the network, State Estimator estimates complex voltage phasors at each bus. Those variables are then used in multiple functions as: contingency analysis, overseeing line limits, optimal power flow, etc. An important hypothesis of State Estimator is that model and network parameters are well known. However, databases might contain errors for many reasons. Parameter Estimation is a necessary function for a robust and reliable State Estimator. Some methods have been explored in the literature. They’re all based on the same weighted least square objective function. Weights are based on standard deviations, which can also be erroneous in the database. The purpose of this research is to develop a new off-line diagnostic tool for TransÉnergie parameter network. The objective function is still quadratic, but standard deviations are no longer used as weights. Instead, they’re introduced as variables and added to measurements in the power flow equations directly. Binary variables are used for identifying erroneous parameters. A greedy algorithm with a decrease of the objective function as criteria is developed to help solve this mixed-integer non-linear optimization problem. This new formulation is tested on IEEE 30 buses network with 3% random noise and a redundancy of 3.6. Errors ranging from 5 to 100% of parameters initial values are introduced and successfully identified. Other cases with errors in adjacent branches susceptances and transformer tap ratios shows that the formulation is able to detect and estimate those parameters. Precision in general is around 0.01 to 5% which is pretty accurate. Transmissions power systems are prone to important noise in reactive power injections and flows. A test with a 20% level of noise shows that parameter errors are identified until 30% of their initial values with a precision of 10-20%. It is still a great improvement in those conditions. Other conclusions can be drawn from tests. Reactive power flow is really important for identification and estimation of erroneous parameters. If a part of the network stands out by having higher magnitude of flow, it might cause false detection. Subnetworks and scans should be taken according to branches having around the same magnitude and mean values. Also, if another parameter is erroneous but not estimated, it causes a great degradation of the solution and may even lead to false detection of an adjacent parameter

J/Psi mass shift in nuclear matter

The $J/\Psi$ mass shift in cold nuclear matter is computed using an effective Lagrangian approach. The mass shift is computed by evaluating $D$ and $D^*$ meson loop contributions to the $J/\Psi$ self-energy employing medium-modified meson masses. The modification of the $D$ and $D^*$ masses in nuclear matter is obtained using the quark-meson coupling model. The loop integrals are regularized with dipole form factors and the sensitivity of the results to the values of form-factor cutoff masses is investigated. The $J/\Psi$ mass shift arising from the modification of the $D$ and $D^*$ loops at normal nuclear matter density is found to range from -16 MeV to -24 MeV under a wide variation of values of the cutoff masses. Experimental perspectives for the formation of a bound state of $J/\Psi$ to a nucleus are investigated.Comment: 9 pages, latex file, 6 figures. Version published in Phys. Lett.

Analysis of the Human Mucosal Response to Cholera Reveals Sustained Activation of Innate Immune Signaling Pathways

To better understand the innate immune response to Vibrio cholerae infection, we tracked gene expression in the duodenal mucosa of 11 Bangladeshi adults with cholera, using biopsy specimens obtained immediately after rehydration and 30 and 180 days later. We identified differentially expressed genes and performed an analysis to predict differentially regulated pathways and upstream regulators. During acute cholera, there was a broad increase in the expression of genes associated with innate immunity, including activation of the NF-kappaB, mitogen-activated protein kinase (MAPK), and Toll-like receptor (TLR)-mediated signaling pathways, which, unexpectedly, persisted even 30 days after infection. Focusing on early differences in gene expression, we identified 37 genes that were differentially expressed on days 2 and 30 across the 11 participants. These genes included the endosomal Toll-like receptor gene TLR8, which was expressed in lamina propria cells. Underscoring a potential role for endosomal TLR-mediated signaling in vivo, our pathway analysis found that interferon regulatory factor 7 and beta 1 and alpha 2 interferons were among the top upstream regulators activated during cholera. Among the innate immune effectors, we found that the gene for DUOX2, an NADPH oxidase involved in the maintenance of intestinal homeostasis, was upregulated in intestinal epithelial cells during cholera. Notably, the observed increases in DUOX2 and TLR8 expression were also modeled in vitro when Caco-2 or THP-1 cells, respectively, were stimulated with live V. cholerae but not with heat-killed organisms or cholera toxin alone. These previously unidentified features of the innate immune response to V. cholerae extend our understanding of the mucosal immune signaling pathways and effectors activated in vivo following cholera

Analysis of the Human Mucosal Response to Cholera Reveals Sustained Activation of Innate Immune Signaling Pathways

To better understand the innate immune response to Vibrio cholerae infection, we tracked gene expression in the duodenal mucosa of 11 Bangladeshi adults with cholera, using biopsy specimens obtained immediately after rehydration and 30 and 180 days later. We identified differentially expressed genes and performed an analysis to predict differentially regulated pathways and upstream regulators. During acute cholera, there was a broad increase in the expression of genes associated with innate immunity, including activation of the NF-kappaB, mitogen-activated protein kinase (MAPK), and Toll-like receptor (TLR)-mediated signaling pathways, which, unexpectedly, persisted even 30 days after infection. Focusing on early differences in gene expression, we identified 37 genes that were differentially expressed on days 2 and 30 across the 11 participants. These genes included the endosomal Toll-like receptor gene TLR8, which was expressed in lamina propria cells. Underscoring a potential role for endosomal TLR-mediated signaling in vivo, our pathway analysis found that interferon regulatory factor 7 and beta 1 and alpha 2 interferons were among the top upstream regulators activated during cholera. Among the innate immune effectors, we found that the gene for DUOX2, an NADPH oxidase involved in the maintenance of intestinal homeostasis, was upregulated in intestinal epithelial cells during cholera. Notably, the observed increases in DUOX2 and TLR8 expression were also modeled in vitro when Caco-2 or THP-1 cells, respectively, were stimulated with live V. cholerae but not with heat-killed organisms or cholera toxin alone. These previously unidentified features of the innate immune response to V. cholerae extend our understanding of the mucosal immune signaling pathways and effectors activated in vivo following cholera

Spatially Extended Low Ionization Emission Regions (LIERs) at z∼0.9z\sim0.9

We present spatially resolved emission diagnostics for eight $z\sim0.9$ galaxies that demonstrate extended low ionization emission-line regions (LIERs) over kpc scales. Eight candidates are selected based on their spatial extent and emission line fluxes from slitless spectroscopic observations with the HST/WFC3 G141 and G800L grisms in the well-studied GOODS survey fields. Five of the candidates (62.5%) are matched to X-ray counterparts in the \textit{Chandra X-Ray Observatory} Deep Fields. We modify the traditional Baldwin-Philips-Terlevich (BPT) emission line diagnostic diagram to use [SII]/(H$\alpha$+[NII]) instead of [NII]/H$\alpha$ to overcome the blending of [NII] and H$\alpha$+[NII] in the low resolution slitless grism spectra. We construct emission line ratio maps and place the individual pixels in the modified BPT. The extended LINER-like emission present in all of our candidates, coupled with X-Ray properties consistent with star-forming galaxies and weak [OIII]$\lambda$5007\AA\ detections, is inconsistent with purely nuclear sources (LINERs) driven by active galactic nuclei. While recent ground-based integral field unit spectroscopic surveys have revealed significant evidence for diffuse LINER-like emission in galaxies within the local universe $(z\sim0.04)$, this work provides the first evidence for the non-AGN origin of LINER-like emission out to high redshifts.Comment: 11 pages, 1 table, 6 figures, accepted for publication in the Astrophysics Journal (ApJ

Arithmetical properties of Multiple Ramanujan sums

In the present paper, we introduce a multiple Ramanujan sum for arithmetic functions, which gives a multivariable extension of the generalized Ramanujan sum studied by D. R. Anderson and T. M. Apostol. We then find fundamental arithmetic properties of the multiple Ramanujan sum and study several types of Dirichlet series involving the multiple Ramanujan sum. As an application, we evaluate higher-dimensional determinants of higher-dimensional matrices, the entries of which are given by values of the multiple Ramanujan sum.Comment: 19 page

Economic choices can be made using only stimulus values

Decision-making often involves choices between different stimuli, each of which is associated with a different physical action. A growing consensus suggests that the brain makes such decisions by assigning a value to each available option and then comparing them to make a choice. An open question in decision neuroscience is whether the brain computes these choices by comparing the values of stimuli directly in goods space or instead by first assigning values to the associated actions and then making a choice over actions. We used a functional MRI paradigm in which human subjects made choices between different stimuli with and without knowledge of the actions required to obtain the different stimuli. We found neural correlates of the value of the chosen stimulus (a postdecision signal) in ventromedial prefrontal cortex before the actual stimulus–action pairing was revealed. These findings provide support for the hypothesis that the brain is capable of making choices in the space of goods without first transferring values into action space

Idea-caution before exploitation:the use of cybersecurity domain knowledge to educate software engineers against software vulnerabilities

The transfer of cybersecurity domain knowledge from security experts (‘Ethical Hackers’) to software engineers is discussed in terms of desirability and feasibility. Possible mechanisms for the transfer are critically examined. Software engineering methodologies do not make use of security domain knowledge in its form of vulnerability databases (e.g. CWE, CVE, Exploit DB), which are therefore not appropriate for this purpose. An approach based upon the improved use of pattern languages that encompasses security domain knowledge is proposed