1,721,021 research outputs found
Temperature Monitoring with Fiber Bragg Grating Sensors in Non-Uniform Conditions
No full textFiber optics is the elective technology for sensing temperatures in harsh environments. Among the possible exploitable working principles, fiber Bragg gratings are the most widespread implementation for their excellent balance between system complexity and performance. However, despite they are well known and established, so far metrological investigations have been limited to cases in which the sensor is used in uniform temperature conditions. This paper analyzes the response of commercial fiber Bragg gratings employed as temperature sensors in applications that imply large temperature gradients, such as in laser based thermal treatments of solid tumors. A theoretical model of the sensor is implemented first and then used to evaluate its response in non-uniform temperature distributions. The model results are experimentally validated by means of a liver phantom and comparisons between different grating configurations, such as single or multiplexed with different lengths, are made
Experimental qualification of fiber bragg grating sensors for temperature monitoring in laser ablation
No full textThe paper discusses the main issues related
to the usage of Fiber Bragg Grating as temperature
sensors when they are employed to monitor
percutaneous laser ablation of tumors. After a
description of the main problems related to this specific
application, two different setups for the
characterization and the qualification of these sensors
are described and preliminary results are presented
Development and Validation of an Algorithm for the Digitization of ECG Paper Images
Full text linkThe electrocardiogram (ECG) signal describes the heart’s electrical activity, allowing it to detect several health conditions, including cardiac system abnormalities and dysfunctions. Nowadays, most patient medical records are still paper-based, especially those made in past decades. The importance of collecting digitized ECGs is twofold: firstly, all medical applications can be easily implemented with an engineering approach if the ECGs are treated as signals; secondly, paper ECGs can deteriorate over time, therefore a correct evaluation of the patient’s clinical evolution is not always guaranteed. The goal of this paper is the realization of an automatic conversion algorithm from paper-based ECGs (images) to digital ECG signals. The algorithm involves a digitization process tested on an image set of 16 subjects, also with pathologies. The quantitative analysis of the digitization method is carried out by evaluating the repeatability and reproducibility of the algorithm. The digitization accuracy is evaluated both on the entire signal and on six ECG time parameters (R-R peak distance, QRS complex duration, QT interval, PQ interval, P-wave duration, and heart rate). Results demonstrate the algorithm efficiency has an average Pearson correlation coefficient of 0.94 and measurement errors of the ECG time parameters are always less than 1 mm. Due to the promising experimental results, the algorithm could be embedded into a graphical interface, becoming a measurement and collection tool for cardiologists
Internet calibration: an innovative approach for the dissemination of the measurement units
No full textNoninvasive Arterial Blood Pressure Estimation using ABPNet and VITAL-ECG
Full text linkArterial Blood Pressure (ABP) is an important physiological parameter that should be properly monitored for the purposes of prevention and detection of cardiovascular diseases, which represent one of the leading causes of death in the world. Currently, the most common adopted noninvasive blood pressure measurement system is sphygmomanometer, which works by inflating and deflating a cuff around the arm. This work presents ABPNet, a new prediction technique, based on a multilayer perceptron (MLP), which uses ECG and PPG to estimate both systolic and diastolic blood pressure. To train the neural network, signals are gathered from the Physionet MIMIC database. The proposed architecture performances are evaluated w.r.t. both the invasive blood pressure signal and the noninvasive sphygmomanometer measurements. The experimental results are quite promising; they are compliant with the ANSI/AAMI/ ISO 81060-2:2013 for sphygmomanometer certification because the network predicted values are within +/-5 mmHg w.r.t. real invasive measurements, as imposed by the legislation. Finally, it is shown how ABPNet can be used to improve the VITAL-ECG, a wearable device designed to acquire vital parameters, such as electrocardiographic (ECG) and photoplethysmographic (PLETH/PPG) signals; indeed, by embedding the ABPNet neural network, VITAL-ECG can be upgraded to estimate, also, ABP. As a consequence, the device could be used to fight cardiovascular diseases and prevent their dangerous effects
Minimally Invasive Temperature Mapping for Laser Ablation: A Preliminary Study on Ex-vivo Livers
Full text linkThe optimization of laser ablation surgical procedures - specifically for the treatment of tumors - requires evaluating the temperature distribution across the entire area under treatment (e.g., the tumor volume). However, minimally invasive temperature sensors can only provide information in a limited number of points. Therefore, an effective prediction algorithm is required to reconstruct the temperature map for the entire heat affected tissue from as few temperature measurements as possible. This work presents an approach for predicting the temperature around the laser delivery fiber, based on the thermal Green's function, where patient-specific tissue thermal parameters are obtained through a fitting procedure using measurement of the temperature evolution at known locations. The proposed method is independent of the specific temperature sensor used; in the experiments reported, temperature was measured both at the prediction points and at validation points using quasi-distributed sensor composed of dense fiber Bragg grating (FBG) arrays, written with a femtosecond laser. A preliminary validation under ideal conditions, represented by ex-vivo cases, has been performed through a series of experiments on bovine liver samples. The obtained results demonstrate that it is possible to predict the temperature distribution across the entire ablated area, with errors well below the commonly accepted uncertainty for treatments of this type
Cross-Talk Effects in the Uncertainty Estimation of Multiplexed Data Acquisition Systems
Full text linkThis paper deals with the analysis of multi-channel data-acquisition systems with the aim of identifying and combining the main uncertainty contributions according to the GUM framework. Particular attention has been paid towards cross-talk effect, which could be an important uncertainty contribution in multiplexed data-acquisition systems. The uncertainty analysis is described for three commercial data acquisition devices highlighting that cross-talk specifications are often not suitable for a reliable uncertainty estimation in operating conditions. For this reason, an experimental set-up has been arranged to fully characterize the inter-channel effects of the investigated devices. The obtained results have highlighted that a proper characterization of a data-acquisition system is effective in estimating the actual performance at the frequency of interest and in the operating conditions for the source resistance and the input-channel configuration. Eventually, a customized procedure has been proposed that is effective in correcting the cross-talk effects also in very severe conditions of inter-channel disturbance
In-field monitoring of eight photovoltaic plants: Degradation rate over seven years of continuous operation
Full text linkThe results of more than seven years (October 2010-December 2017) of continuous monitoring are presented in this paper that refer to eight outdoors PhotoVoltaic (PV) plants. The monitored plants are based on different technologies: mono-crystalline silicon (m-Si), poli-crystalline silicon (p-Si), string ribbon silicon, Copper Indium Gallium Selenide (CIGS) thin film and Cadmium Telluride (CdTe) thin film. Thin-film and m-Si modules are used both in fixed installation and on x-y tracking systems. The results are expressed in terms of degradation rate of the efficiency of each PV plant, which is estimated from the measurements provided by a multi-channel data-acquisition system that senses both electrical and environmental quantities. A comparison with the electrical characterization of each plant obtained by means of the transient charge of a capacitive load is also proposed. In addition, three of the monitored plants have been characterized at module level and the estimated degradation rates have been compared to the values obtained with the monitoring system. The main outcome of this work can be summarized in a higher degradation rate of thin-film based PV modules with respect to silicon-based PV modules
E-learning in instrumentation and measurement courses
No full textE-learning is the one possible evolution of traditional teaching techniques and is becoming a mature technology. Several commercial suites are available to author multimedia courses either to be distributed in physical form (e.g. on CD or DVD) or to be used on-line. However the application of these suites to the instrumentation and measurement courses and in general to courses that require students to learn the use of real devices is difficult and sometime useless. In this paper, some peculiar aspects of the instrumentation and measurement courses are discussed, focusing on the impact of e-learning techniques in laboratory activities. Practical hints coming from the authors' experience in several years of in-the-field trials are reported and discussed
Thermal comfort evaluation: Which sensors for the most accurate assessment?
No full textIn the field of thermal comfort of garments, the importance of the small air gap between skin and garment, called microclimate, is recognized by predictive models and experimental works. However, accurate measurements of microclimate is complex because its volume is small and variable. Moreover, due to body movement, involuntary contact between sensors and skin/garment strongly affects the measurement. In this work, a wearable device designed for measuring microclimate and skin temperature and humidity is presented and validated through tests in a controlled climatic chamber
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