Nodo de recolección y procesamiento de datos basado en GNU/Linux.

Proyecto de Graduación (Licenciatura en Ingeniería en Electrónica. Instituto Tecnológico de Costa Rica. Escuela de Electrónica, 2012.En la actualidad, han surgido problemas en varias infraestructuras de obras públicas en Costa Rica, entre estos inconvenientes se encuentran los daños estructurales en puentes. Se requieren proyectos enfocados en la monitorización de estas estructuras que permitan la lectura de variables físicas por parte de los encargados, para determinar el estado actual del puente. De esta manera, permitir así la resolución de los problemas con suficiente antelación para evitar daños materiales e inclusive pérdidas humanas. Varias escuelas del Tecnológico de Costa Rica se encuentran desarrollando en conjunto, bajo el nombre de grupo de investigación eBridge, el proyecto Predicción Remota de Fallas Estructurales en Puentes. El proyecto de eBridge consiste en una red de sensores colocados en varios puntos estratégicos de un puente. Consecuentemente, un sistema ubicado a no más de 100 metros del puente, se encuentra recolectando, fusionando y procesando los datos de los sensores, los cuales se envían al servidor de ese grupo. El sistema actual que realiza tales funciones es un PC, el cual desperdicia recursos, el consumo energético es alto y no es práctica la instalación cerca del puente. Por lo tanto, el objetivo de este documento es detallar cada paso del desarrollo de un sistema empotrado para la recolección, fusión y procesamiento de datos provenientes de sensores inalámbricos colocados en un puente y el envío posterior de éstos a un servidor de internet. El sistema diseñado se le instaló un Sistema Operativo, el cual maneja los diferentes módulos que se le acopla. Además, la conexión a Internet se da por medio de la red inalámbrica de telefonía móvil. ____________________________________________________________________ Abtract: Nowadays, several problems have arisen in public works infrastructure in Costa Rica; among these problems are structural damages in bridges. Specifics systems are needed to monitor these structures so the administrators can read the physical variables obtained by these systems. Hence, it allows the early resolution of problems avoiding any kind of damage and even loss of humans lifes. Several Tecnológicos de Costa Rica’s schools are developing together (the investigation group is named eBridge) the project Remote Prediction for Bridges’s Structural Failures, which is network of sensors placed in several strategic points under a bridge. Consequently, a system placed within 100 meters of the bridge, is collecting, joining and processing the sensors data, which are sent to the eBridge’s server. Currently, a Personal Computer is performing these functions, which is a waste of resources, has high energy consumption and is not practical to install near the bridge. Therefore, the purpose of this paper is to detail every step of the development of an embedded system for collection, fusion and processing of data from wireless sensors placed on a bridge and later sending them to an internet server

Tuning Rules for a Class of Passivity-Based Controllers for Mechanical Systems

In this paper, we propose several rules to tune the gains for a class of passivity-based controllers for nonlinear mechanical systems. Such tuning rules prescribe a desired local transient response behavior to the closed-loop system. To establish the tuning rules, we implement a PID passivity-based controller. Then, we linearize the closed-loop system, and we transform the matrix of the resulting system into a class of saddle point matrices to analyze the influence of the control gains, in terms of the oscillations and the rise time, on the transient response of the closed-loop system. Hence, the resulting controllers stabilize the plant and simultaneously address the performance of the closed-loop system. Moreover, our analysis provides a clear insight into how the kinetic energy, the potential energy, and the damping of the mechanical system are related to its transient response, endowing in this way the tuning rules with a physical interpretation. Additionally, we corroborate the analytical results through the practical implementation of a controller that stabilizes a two degrees-of-freedom (DoF) planar manipulator, where the control gains are tuned following the proposed rules.Comment: Final submission for journal: IEEE Control Systems Letter

Vibration-Controlled Transient Elastography Scores to Predict Liver-Related Events in Steatotic Liver Disease

Importance Metabolic dysfunction–associated steatotic liver disease (MASLD) is currently the most common chronic liver disease worldwide. It is important to develop noninvasive tests to assess the disease severity and prognosis.Objective To study the prognostic implications of baseline levels and dynamic changes of the vibration-controlled transient elastography (VCTE)–based scores developed for the diagnosis of advanced fibrosis (Agile 3+) and cirrhosis (Agile 4) in patients with MASLD.Design, Setting, and Participants This cohort study included data from a natural history cohort of patients with MASLD who underwent VCTE examination at 16 tertiary referral centers in the US, Europe, and Asia from February 2004 to January 2023, of which the data were collected prospectively at 14 centers. Eligible patients were adults aged at least 18 years with hepatic steatosis diagnosed by histologic methods (steatosis in ≥5% of hepatocytes) or imaging studies (ultrasonography, computed tomography or magnetic resonance imaging, or controlled attenuation parameter ≥248 dB/m by VCTE).Main Outcomes and Measures The primary outcome was liver-related events (LREs), defined as hepatocellular carcinoma or hepatic decompensation (ascites, variceal hemorrhage, hepatic encephalopathy, or hepatorenal syndrome), liver transplant, and liver-related deaths. The Agile scores were compared with histologic and 8 other noninvasive tests.Results A total of 16 603 patients underwent VCTE examination at baseline (mean [SD] age, 52.5 [13.7] years; 9600 [57.8%] were male). At a median follow-up of 51.7 (IQR, 25.2-85.2) months, 316 patients (1.9%) developed LREs. Both Agile 3+ and Agile 4 scores classified fewer patients between the low and high cutoffs than most fibrosis scores and achieved the highest discriminatory power in predicting LREs (integrated area under the time-dependent receiver-operating characteristic curve, 0.89). A total of 10 920 patients (65.8%) had repeated VCTE examination at a median interval of 15 (IQR, 11.3-27.7) months and were included in the serial analysis. A total of 81.9% of patients (7208 of 8810) had stable Agile 3+ scores and 92.6% of patients (8163 of 8810) had stable Agile 4 scores (same risk categories at both assessments). The incidence of LREs was 0.6 per 1000 person-years in patients with persistently low Agile 3+ scores and 30.1 per 1000 person-years in patients with persistently high Agile 3+ scores. In patients with high Agile 3+ score at baseline, a decrease in the score by more than 20% was associated with substantial reduction in the risk of LREs. A similar trend was observed for the Agile 4 score, although it missed more LREs in the low-risk group.Conclusions and Relevance Findings of this study suggest that single or serial Agile scores are highly accurate in predicting LREs in patients with MASLD, making them suitable alternatives to liver biopsy in routine clinical practice and in phase 2b and 3 clinical trials for steatohepatitis