Model Reduction for Nonlinear Systems by Balanced Truncation of State and Gradient Covariance

Data-driven reduced-order models often fail to make accurate forecasts of high-dimensional nonlinear dynamical systems that are sensitive along coordinates with low-variance because such coordinates are often truncated, e.g., by proper orthogonal decomposition, kernel principal component analysis, and autoencoders. Such systems are encountered frequently in shear-dominated fluid flows where non-normality plays a significant role in the growth of disturbances. In order to address these issues, we employ ideas from active subspaces to find low-dimensional systems of coordinates for model reduction that balance adjoint-based information about the system's sensitivity with the variance of states along trajectories. The resulting method, which we refer to as covariance balancing reduction using adjoint snapshots (CoBRAS), is analogous to balanced truncation with state and adjoint-based gradient covariance matrices replacing the system Gramians and obeying the same key transformation laws. Here, the extracted coordinates are associated with an oblique projection that can be used to construct Petrov-Galerkin reduced-order models. We provide an efficient snapshot-based computational method analogous to balanced proper orthogonal decomposition. This also leads to the observation that the reduced coordinates can be computed relying on inner products of state and gradient samples alone, allowing us to find rich nonlinear coordinates by replacing the inner product with a kernel function. In these coordinates, reduced-order models can be learned using regression. We demonstrate these techniques and compare to a variety of other methods on a simple, yet challenging three-dimensional system and a nonlinear axisymmetric jet flow simulation with $10^5$ state variables

Analysis of amplification mechanisms and cross-frequency interactions in nonlinear flows via the harmonic resolvent

We propose a framework that elucidates the input-output characteristics of flows with complex dynamics arising from nonlinear interactions between different time scales. More specifically, we consider a periodically time-varying base flow, and perform a frequency-domain analysis of periodic perturbations about this base flow; the response of these perturbations is governed by the harmonic resolvent, which is a linear operator similar to the harmonic transfer function introduced by Wereley (1991). This approach makes it possible to explicitly capture the triadic interactions that are responsible for the energy transfer between different time scales in the flow. For instance, perturbations at frequency $\alpha$ are coupled with perturbations at frequency $\omega$ through the base flow at frequency $\omega-\alpha$. We draw a connection with resolvent analsyis, which is a special case of the harmonic resolvent when evaluated about a steady base flow. We show that the left and right singular vectors of the harmonic resolvent are the optimal response and forcing modes, which can be understood as full spatio-temporal signals that reveal space-time amplification characteristics of the flow. We illustrate the method on examples, including a three-dimensional system of ordinary differential equations and the flow over an airfoil at near-stall angle of attack

Morphing Wing Aircraft Using Piezoelectric Actuators

Using macro-fiber composites as aircraft control surfaces, rather than the hinged flaps of current aircraft, decreases energy and fuel consumption, and can increase wing versatility along with the aircraft\u27s range and endurance. The purpose of this project is to design and fabricate these morphing-wing aircraft control surfaces using piezoelectric actuators. In the first phase of our project, we are fabricating the horizontal stabilizer control surfaces of our aircraft, and testing them under unloaded and loaded conditions. By this process, we will calibrate the control of the actuators, so that the pilot experiences the same reaction from the morphing wing as he would from a normal, hinged-flap wing. This, along with hysteresis analysis of the actuators, will remedy many of the problems experienced by other morphing-wing aircraft, which caused them to be almost impossible to control. By the conclusion of the project, we will have constructed and conducted flight tests with a fully morphing-wing aircraft

Multi-domain analysis and prediction of the light emitted by an inductively coupled plasma jet

Inductively coupled plasma wind tunnels are crucial for replicating hypersonic flight conditions in ground testing. Achieving the desired conditions (e.g., stagnation-point heat fluxes and enthalpies during atmospheric reentry) requires a careful selection of operating inputs, such as mass flow, gas composition, nozzle geometry, torch power, chamber pressure, and probing location along the plasma jet. The study presented herein focuses on the influence of the torch power and chamber pressure on the plasma jet dynamics within the 350 kW Plasmatron X ICP facility at the University of Illinois at Urbana-Champaign. A multi-domain analysis of the jet behavior under selected power-pressure conditions is presented in terms of emitted light measurements collected using high-speed imaging. We then use Gaussian Process Regression to develop a data-informed learning framework for predicting Plasmatron X jet profiles at unseen pressure and power test conditions. Understanding the physics behind the dynamics of high-enthalpy flows, particularly plasma jets, is the key to properly design material testing, perform diagnostics, and develop accurate simulation modelsComment: 22 pages (including figures, appendix, and references); 13 figure

Improved pregnancy outcome in patients with Rheumatoid Arthritis who followed an ideal clinical pathway

Among women with rheumatoid arthritis (RA) we aimed to assess the effect of optimal management of pregnancy, on a composite outcome of miscarriage and complicated birth

Idosos atendidos em um Serviço de Urgência e Emergência Psiquiátrica

Objective: characterize the elderly treated in a Psychiatric Emergency and Urgency Serviceregarding their sociodemographic profile, psychiatric diagnosis, prescription of medication and medical conduct and evaluate their associations with sex. Method: a cross-sectional, quantitative study in which data was obtained from the medical records of patients seen in the referred service, between July/2015 and June/2016. The independent variable was gender and dependents were: age; origin; informant; previous psychiatric treatment;  diagnosis; prescribed drugs and conduct. Results: in the 152 medical records analyzed, the prevailing age is between 60 and 69 years old, most of them women, coming from the local municipality and attending with a companion. The prevalent diagnoses are schizophrenia and mental and behavioral disorders resulting from the use of psychoactive substances. The most frequently prescribed medications are in the class of antipsychotics and antihistamines, followed by anxiolytics/sedatives. Beers’ criteria considerthe prescription of benzodiazepine, antipsychotic and antihistamine medications inappropriate forthe elderly. The main conduct was discharge, without referral to another service. Conclusion: although there is encouragement from the Ministry of Health, with the creation of new mental health policies, many professionals maintain the model of care based on complaint and conduct, hindering the psychosocial rehabilitation of patients.Objetivo: caracterizar os idosos atendidos em um Serviço de Urgência e Emergência Psiquiátrica quanto ao perfil  sociodemográfico, diagnóstico psiquiátrico, prescrição de medicamentos e conduta médica e avaliar suas associações com o sexo. Método: estudo transversal, quantitativo, em que os dados foram obtidos a partir dos prontuários de pacientes atendidos no referido serviço, entre julho/2015 e junho/2016. A variável independente foi o sexo e as dependentes foram: idade; procedência; informante; tratamento psiquiátrico anterior; diagnóstico; medicamentos prescritos e conduta. Resultados: nos 152 prontuários analisados, observam-se idade prevalente entre 60 a 69 anos, maioria de mulheres, procedência do município local e comparecimento com acompanhante. Os diagnósticos prevalentes são a esquizofrenia e os transtornos mentais e comportamentais decorrentes do uso de substâncias psicoativas. As medicações prescritas com maior frequência são da classe dos antipsicóticos e anti-histamínicos, seguidas dos ansiolíticos/sedativos. O critério de Beers considera a prescrição de medicamentos do grupo dos benzodiazepínicos, antipsicóticos e anti-histamínicos inapropriada para idosos. A principal conduta foi a alta, sem encaminhamento a outro serviço. Conclusão: embora haja incentivo do Ministério da Saúde, com a criação de novas políticas de saúde mental, muitos profissionais mantêm o modelo de atendimento baseado na queixa e conduta, dificultando a reabilitação  psicossocial dos pacientes.Objetivo: caracterizar a los ancianos atendidos en un servicio psiquiátrico de emergencia y urgencia en relación con el perfil sociodemográfico, el diagnóstico psiquiátrico, la prescripción de medicamentos y la conducta médica; y evaluar sus asociaciones con el sexo. Método: un estudio cuantitativo y transversal en el que se obtuvieron datos de los registros médicos de los pacientes tratados en el citado servicio, del 2015 al 2016 de julio. La variable independiente era el sexo y los dependientes eran: edad, procedencia, informante, tratamiento psiquiátrico previo, diagnóstico, medicamentos recetados y conducta. Resultados: de los 152 registros médicos analizados, se observa que: la edad predominante es de 60 a 69 años, la mayoría de ellos son mujeres, desde el municipio local y atendido a la atención de un acompañante. Los diagnósticos prevalentes son la esquizofrenia y los trastornos mentales y conductuales resultantes del uso de sustancias psicoactivas. Los medicamentos recetados con mayor frecuencia son la clase antipsicótica y anti-histamina, seguida de ansiolíticos/sedantes. El criterio de Beers considera que la prescripción de fármacos del grupo de benzodiazepinas, antipsicóticos y antihistaminas, es inadecuada para los ancianos. La conducta principal era alta, sin remisión a otro servicio. Conclusión: aunque hay aliento del Ministerio de salud ..

Estudo e implementação de técnicas para identificação de anuros em imagem

This paper describes the process used in extracting characteristics of Anurans in pictures and it makes a comparison between J48, Random Tree and Random Forest classification algorithms. Two scenarios for evaluation were defined: in the first one we used two classes to represent objects in the image and in the second scenario five classes were used. The Random Forest algorithm obtained best result in the classification of data in relation to J48 algorithms and Random Tree.XIV Workshop Computación Gráfica, Imágenes y Visualización (WCGIV).Red de Universidades con Carreras en Informática (RedUNCI

Comportamento quimiometabólico do músculo sóleo na fase aguda da imobilização articular

The purpose of this study was to outline a physiological profile of the soleus muscle during the acute phase of joint immobilization at a 90º position. Male Wistar rats were divided into four groups (n=6): Control (C), immobilised for 1 (Im1), 2 (Im2), and 3 (Im3) days. After the experimental period, the soleus muscle was obtained in order to assess: glycogen content, muscle weight, hydration index, and protein-DNA interactions. Data were statistically analysed and significance level set at pO objetivo foi avaliar o perfil fisiológico do músculo sóleo na fase aguda da imobilização articular na posição de 90o. Ratos Wistar foram divididos em 4 grupos (n=6 cada): controle (C), imobilizado por 1 (Im1), 2 (Im2) e 3 dias (Im3). Após o período experimental, o músculo sóleo foi retirado e foram mensurados: o peso muscular, o índice de hidratação, a concentração de glicogênio e a concentração de DNA/proteínas totais. Os dados foram submetidos a análise estatística, com nível de significância fixado em