1,721,046 research outputs found
Engineering-aided inventive surgery
Full text linkThis Editorial presents a new Special Issue dedicated to some old and new interdisciplinary areas of cooperation between engineering and surgery. The first two sections offer some food for thought, in terms of a brief introductory and general review of the past, present, future and visionary perspectives of the synergy between engineering and surgery. The last section presents a very short and reasoned review of the contributions that have been included in the present Special Issue. Given the vastness of the topic that this Special Issue deals with, we hope that our effort may have offered a stimulus, albeit small, to the development of cooperation between engineering and surgery
A novel method for automatic evaluation of the effective dynamic range of medical ultrasound scanners
No full textQuality of imaging in medical ultrasound system can be described by means of parameters such as spatial resolution, accuracy in distance measurements and depth of penetration: despite of their importance, it must be pointed out that the information which can be obtained from an ultrasound image is determined also by the dynamic range of signal levels displayed (gray scale characteristic) and by the minimum detectable changes in echo signal amplitude. Moreover, the knowledge the relationship between echo amplitude and gray level on the image (Gray Scale Mapping Function or GSMF) allows to evaluate the other parameters, like low contrast spatial resolution and depth of penetration, referring to the echo strength and so to the sensitivity of the diagnostic system. If system control settings are carefully selected, the echo range between lower and upper saturation of the GSMF determines the effective dynamic Range (EDR), that is the echo range (in dB) that corresponds to the "useful" gray levels spanned on the image: also EDR can be used as a performance indicator of ultrasound systems. Tissue equivalent test objects (ultrasound phantoms) are today available for direct determination of the gray scale characteristic and minimum detectable echo signal changes: they are usually embedded with large targets of different size and image contrast (contrast target in a background matrix). Contrast target provide a gray scale reference with uncertainty on echo level difference with respect to the background usually over ±1dB and a few points of contrast, moreover they are very expensive. The aim of the present study is the implementation of a novel and less expensive method for the automatic determination of the GSMF and EDR on medical ultrasound scanners: by means of a general purpose ultrasound phantom, the method allows the evaluation of the GSMF by a least squares estimation on the results of the analysis and processing of a series of uncompressed bi-dimensional ultrasound images directly produced by the scanner. Finally EDR has been investigated on 3 medical ultrasound scanners of different technologies and results are proposed and explained. © 2009 Springer Berlin Heidelberg
Design 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
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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
Accuracy Characterization of a MEMS Accelerometer for Vibration Monitoring in a Rotating Framework
Full text linkActive and passive vibration control systems are of paramount importance in many engineering applications. If an external load excites a structure’s resonance and the damping is too low, detrimental events, such as crack initiation, growth and, in the worst case, fatigue failure, can be entailed. Damping systems can be commonly found in applications such as industrial machines, vehicles, buildings, turbomachinery blades, and so forth. Active control systems usually achieve higher damping effectiveness than passive ones, but they need a sensor to detect the working conditions that require damping system activation. Recently, the development of such systems in rotating structures has received considerable interest among designers. As a result, the development of vibration monitoring equipment in rotating structures is also a topic of particular interest. In this respect, a reliable, inexpensive and wireless monitoring system is of utmost importance. Typically, optical systems are used to measure vibrations, but they are expensive and require rather complex processing algorithms. In this paper, a wireless system based on a commercial MEMS accelerometer is developed for rotating blade vibration monitoring. The proposed system measurement accuracy was assessed by means of comparison with a reference wired measurement setup based on a mini integrated circuit piezoelectric (ICP) accelerometer adapted for data acquisition in a rotating frame. Both the accelerometers were mounted on the tip of the blade and, in order to test the structure under different conditions, the first four blade resonances were excited by means of piezoelectric actuators, embedded in a novel experimental setup. The frequency and amplitude of acceleration, simultaneously measured by the reference and MEMS sensors, were compared with each other in order to investigate the viability and accuracy of the proposed wireless monitoring system. The rotor angular speed was varied from 0 to 300 rpm, and the data acquisitions were repeated six times for each considered condition. The outcomes reveal that the wireless measurement system may be successfully used for vibration monitoring in rotating blades
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