502 research outputs found

    Nodo de recolecci贸n y procesamiento de datos basado en GNU/Linux.

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    Proyecto de Graduaci贸n (Licenciatura en Ingenier铆a en Electr贸nica. Instituto Tecnol贸gico de Costa Rica. Escuela de Electr贸nica, 2012.En la actualidad, han surgido problemas en varias infraestructuras de obras p煤blicas en Costa Rica, entre estos inconvenientes se encuentran los da帽os estructurales en puentes. Se requieren proyectos enfocados en la monitorizaci贸n de estas estructuras que permitan la lectura de variables f铆sicas por parte de los encargados, para determinar el estado actual del puente. De esta manera, permitir as铆 la resoluci贸n de los problemas con suficiente antelaci贸n para evitar da帽os materiales e inclusive p茅rdidas humanas. Varias escuelas del Tecnol贸gico de Costa Rica se encuentran desarrollando en conjunto, bajo el nombre de grupo de investigaci贸n eBridge, el proyecto Predicci贸n Remota de Fallas Estructurales en Puentes. El proyecto de eBridge consiste en una red de sensores colocados en varios puntos estrat茅gicos de un puente. Consecuentemente, un sistema ubicado a no m谩s de 100 metros del puente, se encuentra recolectando, fusionando y procesando los datos de los sensores, los cuales se env铆an al servidor de ese grupo. El sistema actual que realiza tales funciones es un PC, el cual desperdicia recursos, el consumo energ茅tico es alto y no es pr谩ctica la instalaci贸n cerca del puente. Por lo tanto, el objetivo de este documento es detallar cada paso del desarrollo de un sistema empotrado para la recolecci贸n, fusi贸n y procesamiento de datos provenientes de sensores inal谩mbricos colocados en un puente y el env铆o posterior de 茅stos a un servidor de internet. El sistema dise帽ado se le instal贸 un Sistema Operativo, el cual maneja los diferentes m贸dulos que se le acopla. Adem谩s, la conexi贸n a Internet se da por medio de la red inal谩mbrica de telefon铆a m贸vil. ____________________________________________________________________ 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 Tecnol贸gicos de Costa Rica鈥檚 schools are developing together (the investigation group is named eBridge) the project Remote Prediction for Bridges鈥檚 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鈥檚 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

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    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

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    Importance Metabolic dysfunction鈥揳ssociated 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)鈥揵ased 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 鈮5% of hepatocytes) or imaging studies (ultrasonography, computed tomography or magnetic resonance imaging, or controlled attenuation parameter 鈮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鈥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鈥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
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