1,721,016 research outputs found
Performance characteristic determination of a roller pump for extracorporeal circulation for different working conditions
No full textA novel method for the simultaneous measurement of temperature and strain using a three wire connection
No full textA novel methodology to simultaneously measure strain and temperature by
means of an electrical resistance strain gauge powered by an ac signal and
connected to a strain indicator by means of thermocouple wires is proposed.
The experimental validation of the viability of this method is conducted by
means of a purely electrical simulation of both strain and temperature
signals, respectively from −2000 to 2000 μm m−1 and −250 to 230 ◦C. The
results obtained showed that strain measurement is affected by an error
always less than ±2 μm m−1 for the whole range of simulated strains, while
the error in temperature evaluation is always less than 0.6 ◦C. The effect of
cross-talk between the two signals was determined to be insignificant
Evaluation of error causes in the measurement of respiratory parameters during controlled ventilation: influence of the breathing circuit
No full textDesign of a novel PWV-Varying Arterial Simulator for biomedical applications: a preliminary study
No full textThe increasing trend of cardiovascular diseases recently led to a growing interest in evaluating methods and systems to diagnose and prevent them. Nowadays, one of the key indexes used to assess the health status of the cardiovascular tree is the Pulse Wave Velocity (PWV) which is strictly related to the mechanical and geometrical characteristics of blood vessels. It is currently measured as the ratio between the distance of two transducers located on the human body and the time the pulse takes to travel along the two chosen sites. Unfortunately, to date, the current measurement devices employed show a limited accuracy in PWV assessment, especially due to distance inaccuracy. The development of arterial simulators could potentially improve the current measurement systems accuracy by means of a better calibration. Despite the fact that many systems have been developed through time, they mainly focus on different aspects regarding the relationship between PWV and meaningful hemodynamic quantities rather than trying to provide a PWV measurement reference to test currently available devices. This results in a lack of information on the design of an in vitro experimental set-up specifically able to vary PWV according to different adjustable mechanical characteristics. In such a context, the present study aims at providing a numerical simulation, based on a previously developed mathematical model, as a next step for the design of a novel experimental set-up, constituted by an elastic tube as aortic surrogate (AS), able to simulate a desired PWV range according to different AS inner and outer pressures conditions
Comparative evaluation of three image analysis methods for angular displacement measurement in a MEMS microgripper prototype: A preliminary study
Full text linkThe functional characterization of MEMS devices is relevant today since it aims at verifying the behavior of these devices, as well as improving their design. In this regard, this study focused on the functional characterization of a MEMS microgripper prototype suitable in biomedical applications: The measurement of the angular displacement of the microgripper comb-drive is carried out by means of two novel automatic procedures, based on an image analysis method, SURF-based (Angular Displacement Measurement based on Speeded Up Robust Features, ADMSURF) and FFT-based (Angular Displacement Measurement based on Fast Fourier Transform, ADMFFT) method, respectively. Moreover, the measurement results are compared with a Semi-Automatic Method (SAM), to evaluate which of them is the most suitable for the functional characterization of the device. The curve fitting of the outcomes from SAM and ADMSURF, showed a quadratic trend in agreement with the analytical model. Moreover, the ADMSURF measurements below 1° are affected by an uncertainty of about 0.08° for voltages less than 14 V, confirming its suitability for microgripper characterization. It was also evaluated that the ADMFFT is more suitable for measurement of rotations greater than 1° (up to 30°), with a measurement uncertainty of 0.02°, at 95% of confidence level
Image quality comparison of two different experimental setups for MEMS actuators functional evaluation: a preliminary study
No full textThe high interest of scientists and industries in the application of MEMS micro-actuators to several fields requires effective and robust measurement methods and systems for their quality assessment, focusing on their functional characterization, usually carried out through image analysis-based methods. In this study, a comparison of two experimental setups for image acquisition is proposed, aiming at establishing which setup collects images with higher quality for MEMS microgripper functional evaluation. The proposed work describes an experimental approach based on the evaluation of five parameters, i.e., brightness, saturation, contrast, sharpness, and signal-to-noise ratio, applied to 24 regions of interest in two sets of images of a same micro-actuator acquired from different optical setups at three magnification levels. Measurement results have been assessed following an objective approach by processing the acquired data through an in-house algorithm and a subjective approach by showing the acquired images to six observers and collecting their preferences
Feature classification in ultrasound textures for image quality assessment: A preliminary study on the characterization and selection of haralick parameters by means of correlation matrices
No full textThis paper describes a preliminary study on feature selection from the gray level co-occurrence matrix (GLCM) among the 14 features proposed by R.M. Haralick (1979) with the aim to apply them to ultrasound image classification and Quality Assessment. In particular4 main-classes of images with different patterns (Lines, Chess, alternates Row and Circles)have been implemented and different levels ofspeckle noisehave been added to simulate ultrasound images with different textures.With the aim to characterize therelationship betweenHaralickfeatures and the pattern type, size, contrastand noise, someCorrelation Matrices have been implemented. Preliminary results are explained and discussed
A comparison among three different image analysis methods for the displacement measurement in a novel MEMS device
No full textThe functional characterization of MEMS devices is of great importance today, since it has the purpose both of verifying the behavior of these devices and of improving their future design. In this regard, the main topic of this study is the functional characterization of a microgripper prototype, a MEMS suitable in biomedical applications: to this aim, the measurement of the angular displacement of its comb-drive (capacitive electrostatic actuator that allows its movement) is provided by means of two novel automatic procedures, based on an image analysis software, the SURF-based (Speeded Up Robust Features) and the FFT-based (Fast Fourier Transform) method respectively. A preliminary comparison has been made, also with a previous semiautomatic method, to evaluate which of them is the best suitable for the functional characterization of the microgripper, highlighting their main advantages and limitations. The results obtained from the SURF-based method are promising; the curve obtained from the data showed a quadratic trend in agreement with both the analytical model and with the results obtained through the semiautomatic method. Moreover, the measurement obtained by the SURF-based method are affected by less than 0.2° uncertainty, that is less than one half of the measurement uncertainty due to the FFT-based algorithm
Ultrasound image uniformity assessment by means of sparse matrices: Algorithm implementation and first results
No full textThe current study is focused on an image segmentation algorithm for Uniformity Quality assessment in Diagnostic Ultrasounds.In particular a mathematical definition of the uniformity in ultrasound images is introducedand a split and merge algorithm performed on sparse matricesto measure uniformity is described. The algorithm is based on the Gray-Level Co-occurrence Matrices and the relativedescriptors,i.e. the Haralick features Entropy, Energy, Maximal CorrelationCoefficientand InformationMeasures of Correlation.Results on2 differentdatasetsof test images with different non-uniformities have been carried on. Several outcomesshow a goodsensitivity and agreement with the mean judgment by 7 human observers, i.e. differences are below 40% in most of the cases.On the basis of previousstudies, the latest developments and results are proposed and commented
A novel experimental set-up for Young Modulus Assessment through Transit Time measurements in Biomedical applications
No full textYoung Modulus estimation in arteries is a relevant issue, since such parameter is characteristic of their mechanical and structural properties. It is well-known that human arteries undergo modifications due to physiological aging and/or cardiovascular pathologies resulting in Young Modulus variations through time. In literature, the validation of specific techniques for in vivo monitoring of arterial stiffness is carried out through vessel phantoms that reproduce the pressure waves propagation for different stiffness conditions. A physical model widely used in the current state of the art is based on the well-known Moens-Korteweg equation which correlates the Young Modulus to the Pulse Wave Velocity (PWV). In the present work a novel experimental set-up has been designed and tested to simulate Young Modulus variation of a natural rubber (NR) tube through the application of different tensioning states. Such variation has been estimated by transit time measurements on the pressure waves acquired through Linear Variable Differential Transformer (LVDT) sensors. The relevance of the present study lies in the possibility to simulate human vessel stiffness increase and to provide a testing device for the validation of in vivo techniques able to assess arterial stiffness
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