Measurement based method for online characterization of generator dynamic behaviour in systems with renewable generation

This paper introduces a hybrid-methodology for online identification and clustering of generator oscillatory behavior, based on measured responses. The dominant modes in generator measured responses are initially identified using a mode identification technique and then introduced, in the next step, as input into a clustering algorithm. Critical groups of generators that exhibit poorly or negatively damped oscillations are identified, in order to enable corrective control actions and stabilize the system. The uncertainties associated with operation of modern power systems, including Renewable Energy Sources (RES) are investigated, with emphasis on the impact of the dynamic behavior of power electronic interfaced RES

Designing an Experimental and a Reference Robot to Test and Evaluate the Impact of Cultural Competence in Socially Assistive Robotics

The article focusses on the work performed in preparation for an experimental trial aimed at evaluating the impact of a culturally competent robot for care home assistance. Indeed, it has been estabilished that the user's cultural identity plays an important role during the interaction with a robotic system and cultural competence may be one of the key elements for increasing capabilities of socially assistive robots. Specifically, the paper describes part of the work carried out for the definition and implementation of two different robotic systems for the care of older adults: a culturally competent robot, that shows its awareness of the user's cultural identity, and a reference robot, non culturally competent, but with the same functionalities of the former. The design of both robots is here described in detail, together with the key elements that make a socially assistive robot culturally competent, which should be absent in the non-culturally competent counterpart. Examples of the experimental phase of the CARESSES project, with a fictional user are reported, giving a hint of the validness of the proposed approach

The prevalence of domestic violence among pregnant women in Nigeria: a systematic review.

To identify, appraise, and synthesize research evidence on the prevalence of domestic violence (DV) among pregnant women in Nigeria. We conducted a systematic review of all published studies between April 2004 and June 2016. Comprehensive searches were conducted on electronic databases such as PubMed, CINAHL, Global Health, MEDLINE, PsycINFO, Directory of Open Access Journals, Google Scholar, and electronic libraries of the authors' institution. Identified articles were screened in two stages against the inclusion criteria with titles and abstract screened first followed by full-text screening. Selected articles were assessed using the "guidelines for evaluating prevalence studies," and findings were synthesized narratively. Among 19 studies that met the inclusion criteria, two articles were excluded due to low methodological quality and 17 articles were included in the review. The prevalence of DV during pregnancy in Nigeria ranged between 2.3% and 44.6% with lifetime prevalence rates ranging between 33.1% and 63.2%. Physical, sexual, psychological, and verbal abuses were the most frequent types of DV reported in this review. The most common perpetrators were husbands, as reported in 11 of the 17 studies. Pregnant women between the ages of 20 and 30 years were the most common victims of DV. Our review suggests high prevalence of DV in pregnancy among women in Nigeria and higher lifetime prevalence. However, determining an overall, synthesized accurate prevalence rate of DV within this population based on existing evidence presents a challenge. The findings have important implications for stakeholders such as planners, policy makers, maternity care providers, and researchers in public health and social policy at national, regional, and international levels toward combating the issue. OBJECTIVE METHOD RESULTS CONCLUSIO

Using SHAP values and machine learning to understand trends in the transient stability limit

Machine learning (ML) for transient stability assessment has gained traction due to the significant increase in computational requirements as renewables connect to power systems. To achieve a high degree of accuracy; black-box ML models are often required - inhibiting interpretation of predictions and consequently reducing confidence in the use of such methods. This paper proposes the use of SHapley Additive exPlanations (SHAP) - a unifying interpretability framework based on Shapley values from cooperative game theory - to provide insights into ML models that are trained to predict critical clearing time (CCT). We use SHAP to obtain explanations of location-specific ML models trained to predict CCT at each busbar on the network. This can provide unique insights into power system variables influencing the entire stability boundary under increasing system complexity and uncertainty. Subsequently, the covariance between a variable of interest and the corresponding SHAP values from each location-specific ML model - can reveal how a change in that variable impacts the stability boundary throughout the network. Such insights can inform planning and/or operational decisions. The case study provided demonstrates the method using a highly accurate opaque ML algorithm in the IEEE 39-bus test network with Type IV wind generation

Limb-Shaking Transient Ischemic Attacks Successfully Treated with External Carotid Artery Stenting

The external carotid artery (ECA) is one of the most important extracranial-to-intracranial sources of collateral circulation, contributing significantly to the cerebral blood flow especially when perfusion through the internal carotid artery (ICA) is compromised. Most of the endovascular studies so far have been dedicated to ICA, with little focus on the ECA. Limb-shaking transient ischemic attacks (TIAs) are a relatively rare manifestation of carotid artery disease that may present with repetitive shaking movements of the affected limbs. We report a case of an 80-year-old male with bilateral internal and contralateral external carotid artery occlusion who developed limb-shaking TIAs as a result of significant stenosis of the right ECA. Percutaneous revascularization of the ECA was performed by angioplasty and stenting. At the follow-up 12 months later, the patient remained neurologically intact with complete resolution of his symptoms. Stenting of the ECA should be considered as a reasonable alternative to conventional open repair especially in patients with contralateral carotid stenosis, insufficient circle of Willis, and significant comorbidities

Matter flows around black holes and gravitational radiation

We develop and calibrate a new method for estimating the gravitational radiation emitted by complex motions of matter sources in the vicinity of black holes. We compute numerically the linearized curvature perturbations induced by matter fields evolving in fixed black hole backgrounds, whose evolution we obtain using the equations of relativistic hydrodynamics. The current implementation of the proposal concerns non-rotating holes and axisymmetric hydrodynamical motions. As first applications we study i) dust shells falling onto the black hole isotropically from finite distance, ii) initially spherical layers of material falling onto a moving black hole, and iii) anisotropic collapse of shells. We focus on the dependence of the total gravitational wave energy emission on the flow parameters, in particular shell thickness, velocity and degree of anisotropy. The gradual excitation of the black hole quasi-normal mode frequency by sufficiently compact shells is demonstrated and discussed. A new prescription for generating physically reasonable initial data is discussed, along with a range of technical issues relevant to numerical relativity.Comment: 27 pages, 12 encapsulated figures, revtex, amsfonts, submitted to Phys. Rev.

Criticality, Fractality and Intermittency in Strong Interactions

Assuming a second-order phase transition for the hadronization process, we attempt to associate intermittency patterns in high-energy hadronic collisions to fractal structures in configuration space and corresponding intermittency indices to the isothermal critical exponent at the transition temperature. In this approach, the most general multidimensional intermittency pattern, associated to a second-order phase transition of the strongly interacting system, is determined, and its relevance to present and future experiments is discussed.Comment: 15 pages + 2 figures (available on request), CERN-TH.6990/93, UA/NPPS-5-9

Power-law singularities in string theory and M-theory

We extend the definition of the Szekeres-Iyer power-law singularities to supergravity, string and M-theory backgrounds, and find that are characterized by Kasner type exponents. The near singularity geometries of brane and some intersecting brane backgrounds are investigated and the exponents are computed. The Penrose limits of some of these power-law singularities have profiles $A\sim {\rm u}^{-\gamma}$ for $\gamma\geq 2$. We find the range of the exponents for which $\gamma=2$ and the frequency squares are bounded by 1/4. We propose some qualitative tests for deciding whether a null or timelike spacetime singularity can be resolved within string theory and M-theory based on the near singularity geometry and its Penrose limits.Comment: 32 page