Image-based tracking technique assessment and application to a fluid–structure interaction experiment

This work analyses the accuracy and capabilities of two image-based tracking techniques related to digital image correlation and the Lucas–Kanade optical flow method, with the subsequent quantification of body motion in a fluid–structure interaction experiment. A computer-controlled shaker was used as a benchmark case to create a one-dimensional oscillatory target motion. Three target frequencies were recorded. The measurements obtained with a low-cost digital camera were compared to a high-precision motion tracking system. The comparison was performed under changes in image resolution, target motion and sampling frequency. The results show that, with a correct selection of the processing parameters, both tracking techniques were able to track the main motion and frequency of the target even after a reduction of four and five times the sampling frequency and image resolution, respectively. Within this good agreement, the Lucas–Kanade technique shows better accuracy under tested conditions, achieving up to 15.6% of lower tracking error. Nevertheless, the achievement of this higher accuracy is highly dependent on the position of the selected initial target point. These considerations are addressed to satisfactorily track the response of a wall-mounted cylinder subjected to a range of turbulent flows using a single camera as the measuring device

Dungeons and Data: A Large-Scale NetHack Dataset

Recent breakthroughs in the development of agents to solve challenging sequential decision making problems such as Go [50], StarCraft [58], or DOTA [3], have relied on both simulated environments and large-scale datasets. However, progress on this research has been hindered by the scarcity of open-sourced datasets and the prohibitive computational cost to work with them. Here we present the NetHack Learning Dataset (NLD), a large and highly-scalable dataset of trajectories from the popular game of NetHack, which is both extremely challenging for current methods and very fast to run [23]. NLD consists of three parts: 10 billion state transitions from 1.5 million human trajectories collected on the NAO public NetHack server from 2009 to 2020; 3 billion state-action-score transitions from 100,000 trajectories collected from the symbolic bot winner of the NetHack Challenge 2021; and, accompanying code for users to record, load and stream any collection of such trajectories in a highly compressed form. We evaluate a wide range of existing algorithms including online and offline RL, as well as learning from demonstrations, showing that significant research advances are needed to fully leverage large-scale datasets for challenging sequential decision making tasks

Renal function and volume of infants born with a very low birth-weight: a preliminary cross-sectional study.

AIM: The aim of our study was to compare the function and volumes of kidneys of very low birth-weight (VLBW) and of extremely low birth-weight (ELBW) infants at pre-school ages.PATIENTS AND METHODS: We did a revision of the neonatal records of infants born in our hospital that weighed < or =1500 g at birth. The children were divided into two groups according to their weight at birth: ELBW (<1000 g) and VLBW (1000-1500 g). At the age of 5.7 +/- 1.4 years, the children underwent clinical, laboratory and ultrasound renal assessments.RESULTS: Sixty-nine children fulfilled the requirements for the study. The rate of neonatal treatment with aminoglycosides was higher in ELBW preterms. Renal function parameters, i.e. estimated glomerular filtration rate and albuminuria, did not differ between the two groups of children. Urinary alpha1-microglobulin excretion was significantly higher and kidneys were significantly smaller in the ELBW group than in the VLBW group.CONCLUSION: No impairment or differences in renal parameters were found in pre-school children born ELBW compared with those born with VLBW, except for differences in kidney volume, renal cortical thickness and urinary alpha1-microglobulin excretion. Thus, patients born with ELBW would require a longer follow-up period

Ecología y biodiversidad de un arrecife formado por Phragmatopoma caudata Krøyer in Mörch (Canalipalpata: Sabellariidae) en República Dominicana

Se evaluó un arrecife formado por Phragmatopoma caudata (Canalipalpata: Sabellariidae), ubicado en Barco Viejo o Playa Desembarco, provincia Samaná, República Dominicana. Este tipo de arrecife está compuesto por los restos de sedimentos y rocas que son gradualmente depositados a través del tiempo por estos gusanos sabeláridos. El arrecife tiene una longitud de 115 m en total, 1.59 m de altura máxima y 19.58 m de ancho máximo, formando dos peldaños. La arena colectada en el arrecife y la playa presentaba granulometría variada, en la que los granos de arena de la playa se encontraron más pequeños que los granos de la arena de arrecife. Los diámetros de los tubos de gusano no superaron los 4 mm de ancho y 5.5 cm de altura. Hubo una disminución en la población de gusanos durante el tiempo abarcado por este estudio. Se registraron 19 especies de diferentes filos en el arrecife. El índice de Margalef fue de 5.04, el cual está por encima del máximo común. El índice de Shannon fue valorado en 0.54, el cual se considera extremadamente bajo. En base a estos resultados se infiere que la morfología de este arrecife proporciona arena a la playa y la protege de las condiciones ambientales adversas. Este arrecife es un foco de biodiversidad en la zona

WHAT DOES STUDYING OCCUPATIONAL THERAPY MEANS? THE PERSPECTIVE OF STUDENTS OF THE UNIVERSITY OF CHILE

The main goal of this work is to analyze the attributed perception of studying occupational therapy according to the students of University of Chile. A qualitative and phenomenological methodology was used, as this investigation tries to study the subjective dimension of a particular phenomenon, such as studying Occupational Therapy. Data recollection was made with open-semistructured interviews. Data analysis initiated with a previous categorization according to meaning, sense and purpose, as described in the AOTA’s framework; subcategories and codes were included from the interviews. Results show that in the Meaning category, external opinion makes reference to “studying occupational therapy” and “studying in a university”, mainly finding ignorance and a positive perception of the career. At the sense dimension, factors that give positive and/or negative values that influence self-efficacy, importance, motivation, interest and enjoyment are identified; these factors included the biopsychosocial approach and working with people. Finally, in the purpose dimension, goals and utilities are identified, both in a personal and professional aspects. These results prompt reflection around the perception of the career and the value given to professional studies

Image-based tracking technique assessment and application to a fluid-structure interaction experiment

This work analyses the accuracy and capabilities of two image-based tracking techniques related to digital image correlation and the Lucas–Kanade optical flow method, with the subsequent quantification of body motion in a fluid–structure interaction experiment. A computer-controlled shaker was used as a benchmark case to create a one-dimensional oscillatory target motion. Three target frequencies were recorded. The measurements obtained with a low-cost digital camera were compared to a high-precision motion tracking system. The comparison was performed under changes in image resolution, target motion and sampling frequency. The results show that, with a correct selection of the processing parameters, both tracking techniques were able to track the main motion and frequency of the target even after a reduction of four and five times the sampling frequency and image resolution, respectively. Within this good agreement, the Lucas–Kanade technique shows better accuracy under tested conditions, achieving up to 15.6% of lower tracking error. Nevertheless, the achievement of this higher accuracy is highly dependent on the position of the selected initial target point. These considerations are addressed to satisfactorily track the response of a wall-mounted cylinder subjected to a range of turbulent flows using a single camera as the measuring device

Interacting Kasner-type cosmologies

It is well known that Kasner-type cosmologies provide a useful framework for analyzing the three-dimensional anisotropic expansion because of the simplification of the anisotropic dynamics. In this paper relativistic multi-fluid Kasner-type scenarios are studied. We first consider the general case of a superposition of two ideal cosmic fluids, as well as the particular cases of non-interacting and interacting ones, by introducing a phenomenological coupling function $q(t)$. For two-fluid cosmological scenarios there exist only cosmological scaling solutions, while for three-fluid configurations there exist not only cosmological scaling ones, but also more general solutions. In the case of triply interacting cosmic fluids we can have energy transfer from two fluids to a third one, or energy transfer from one cosmic fluid to the other two. It is shown that by requiring the positivity of energy densities there always is a matter component which violates the dominant energy condition in this kind of anisotropic cosmological scenarios.Comment: Accepted for publication in Astrophysics &Space Science, 8 page

Four lectures on secant varieties

This paper is based on the first author's lectures at the 2012 University of Regina Workshop "Connections Between Algebra and Geometry". Its aim is to provide an introduction to the theory of higher secant varieties and their applications. Several references and solved exercises are also included.Comment: Lectures notes to appear in PROMS (Springer Proceedings in Mathematics & Statistics), Springer/Birkhause

Disposición al estudio, autoeficacia y atribuciones causales en estudiantes universitarios chilenos

The aim of this study is to analyze the relationship between (1) willingness to study strategies, (2) causal attributions (to effort, ability and external causes) and (3) student´s perception of self-efficacy about their ability to self-regulate their processes of willingness to study. Method: An instrument built by the researchers called Willingness to the Study Self-Regulation Questionnaire was applied to a non probabilistic convenience sample of 695 Chilean university students from 5 universities of the Province of Concepción. Outcomes: Strong correlations were found between selfefficacy for the willingness to study self-regulation and the willingness to study strategies (r=0.54 to r =0.55). the willingness to study strategies had positive and moderate correlations (r=0.38 to r=0.42) with causal attributions for success to effort, weak correlations (r=0.15 to r=0.28) with causal attributions for success to ability and to external factors, and negative weak to moderate correlations (r=-0.19 to r =-0.38) with causal attributions for failure to effort, ability, and external factors. Conclusions: Students with high levels of willingness to study strategies show positive beliefs about their own ability to self-regulate their processes of willingness to study, they make causal attributions for their success mainly to effort, and they attribute their academic failure less and less to ability and external factors.The aim of this study is to analyze the relationship between (1) willingness to study strategies, (2) causal attributions (to effort, ability and external causes) and (3) student´s perception of self-efficacy about their ability to self-regulate their processes of willingness to study. Method: An instrument built by the researchers called Willingness to the Study Self-Regulation Questionnaire was applied to a non probabilistic convenience sample of 695 Chilean university students from 5 universities of the Province of Concepción. Outcomes: Strong correlations were found between selfefficacy for the willingness to study self-regulation and the willingness to study strategies (r=0.54 to r =0.55). the willingness to study strategies had positive and moderate correlations (r=0.38 to r=0.42) with causal attributions for success to effort, weak correlations (r=0.15 to r=0.28) with causal attributions for success to ability and to external factors, and negative weak to moderate correlations (r=-0.19 to r =-0.38) with causal attributions for failure to effort, ability, and external factors. Conclusions: Students with high levels of willingness to study strategies show positive beliefs about their own ability to self-regulate their processes of willingness to study, they make causal attributions for their success mainly to effort, and they attribute their academic failure less and less to ability and external factors.El objetivo de este estudio es: analizar la relación entre (1) Las estrategias disposición al estudio, (2) atribuciones causales (al esfuerzo, capacidad y causas externas) y (3) la percepción de autoeficacia que tienen los estudiantes sobre su capacidad de autorregular sus procesos de disposición al estudio. Método: Se aplicó un instrumento construido por los investigadores denominado Cuestionario de Autorregulación de la Disposición al Estudio a una muestra no probabilística por conveniencia de 695 estudiantes universitarios chilenos de 5 universidades de la provincia de Concepción. Resultados: Se encontraron correlaciones fuertes entre la autoeficacia para la autorregulación de la disposición al estudio y las estrategias de disposición al estudio (r=0.54 a r=0.55). Las estrategias de disposición al estudio presentan correlaciones positivas y moderadas (r=0.38 a r= 0.42) con las atribuciones causales de éxito al esfuerzo, débiles (r=0.15 a r= 0.28) con las atribuciones causales de éxito a la habilidad como a las atribuciones causales de éxito a causas externas, y correlaciones negativas, de débiles a moderadas (r=-0.19 a  r= -0.38), con las atribuciones causales de fracaso al esfuerzo, a la habilidad y a causas externas. Conclusiones: Los estudiantes con altos niveles de estrategias de disposición al estudio presentan creencias positivas acerca de la propia capacidad para autorregular sus procesos de disposición al estudio, realizan atribuciones causales de sus éxitos principalmente al esfuerzo y disminuyen las explicaciones de fracasos académicos a su esfuerzo, su capacidad y a causas externas.