1,720,973 research outputs found
Design and Testing of a 3-DOF Robot for Studying the Human Response to Vibration
Full text linkThis work describes the design and validation of an electro-mechanical excitation system for characterization of the response of the human body to multiaxial vibrations. The presented system is based on the linear delta configuration and is designed to expose standing subjects to vibration along three perpendicular axes, with an excitation bandwidth of at least 30 Hz and a maximum vibration amplitude of±30 mm along the vertical direction and±20 mm along the horizontal directions. The shaker characteristic dimensions are the result of numerical optimization of the inverse manipulability index; the motors and transmissions have been selected using a multibody dynamic simulation. Finite element simulations were performed to ensure that the structural resonances were outside the excitation bandwidth. Once the shaker had been manufactured, experiments were performed to verify the capability of the system in real testing conditions. The mean quadratic error between the modulus of the imposed acceleration and the measured one is between 5.7× 10− 3 and 1.4× 10− 2 m/s 2 in the frequency range between 1 and 50 Hz, proving the good outcome of the design process
Measurement of the force exchanged by orthodontic masks and patients
No full textOne of the key factors for the success of the orthodontic treatments is the patients’ compliance to the prescriptions of the doctors, especially when removable appliances are used. However, at the current state of the art, there are no standard techniques for measuring for how long the patients use the prescribed appliance. Moreover, also the force exerted by the orthodontic appliance on patient is not directly measured. This paper describes two different sensors prototypes, based on pressure resistive transducers and on strain gauges respectively, that measure the traction force in the range between 5 and 30 N. The two prototypes have been calibrated with a purposely designed experimental setup. Results show the higher accuracy of the strain-gauge device in force measurements, that has a standard uncertainty of 0,23 N in the case of half bridge configuration, against a value of 6,7 N for the force sensitive resistors. The time in which the orthodontic mask is worn can be successfully measured also with the pressure-based setup, although the location and the positioning of the setup must be carefully chosen
Automatic measurement of the hand dimensions using consumer 3D cameras
Full text linkThis article describes the metrological characterisation of two prototypes that use the point clouds acquired by consumer 3D cameras for the measurement of the human hand geometrical parameters. The initial part of the work is focused on the general description of algorithms that allow for the derivation of dimensional parameters of the hand. Algorithms were tested on data acquired using Microsoft Kinect v2 and Intel RealSense D400 series sensors. The accuracy of the proposed measurement methods has been evaluated in different tests aiming to identify bias errors deriving from point-cloud inaccuracy and at the identification of the effect of the hand pressure and the wrist flexion/extension. Results evidenced an accuracy better than 1 mm in the identification of the hand’s linear dimension and better than 20 cm3 for hand volume measurements. The relative uncertainty of linear dimensions, areas, and volumes was in the range of 1-10 %. Measurements performed with the Intel RealSense D400 were, on average, more repeatable than those performed with Microsoft Kinect. The uncertainty values limit the use of these devices to applications where the requested accuracy is larger than 5 % (volume measurements), 3 % (area measurements), and 1 mm (hands’ linear dimensions and thickness)
Using real-time feedback of L5/S1 compression force based on markerless optical motion capture to improve the lifting technique in manual materials handling
Full text linkChallenges in manual materials handling (MMH) are posed in particular by the requirements for continuous repetition and individual feedback. Low effort in MMH instructions is accordingly a relevant factor. The combination of a markerless motion capture system with a biomechanical model providing visual MMH instructions by individual real-time feedback of the compression force of the intervertebral disc in L5/S1 (CF) could tackle these challenges. However, this raises the question of whether this approach provides appropriate MMH instructions to improve the lifting technique in MMH. Results of an experiment with 22 young male participants indicate that visual MMH instructions with such individual real-time feedback have significant advantages in improving the lifting technique by reducing those factors associated with lower back pain compared to instructions with a reference paper-based tutorial or a baseline without instructions. Thus, peak and mean CF and peak trunk flexion, for example, were significantly lower when lifting with individual real-time feedback of CF compared to other conditions tested. Hence, the results suggest that it may be sensible to improve the lifting technique by such an approach of MMH instructions and integrate it in MMH training programs or on-the-job training in order to reduce or prevent lower back pain. Relevance to industry: Using real-time feedback of the compression force of the intervertebral disc of L5/S1 based on markerless optical motion capture can improve the lifting technique in manual materials handling. This may be integrated into MMH training programs or on-the-job training to reduce or prevent low back pain
A prototype for the automatic measurement of the hand dimensions using the Microsoft Kinect V2
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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
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
Trajectory identification of a reciprocating drill for geological inspections
No full textLAUREA MAGISTRALEViene studiata la fattibilità di un nuovo strumento per le esplorazioni geologiche, tenendo in considerazione le difficili condizioni ambientali tipiche di questo settore. Questa particolare tecnologia è stata determinata dopo un esteso studio dello stato dell'arte dei sistemi di scavo, ed è stato proposto un progetto di massima del meccanismo. La tesi è quindi incentrata sulla validazione del sistema di misura atto a calcolare la traiettoria della trivella. Prima di tutto il metodo Monte Carlo è utilizzato per confrontare la robustezza di tre diversi algoritmi agli errori degli strumenti di misura, quindi il sistema di misura è stato progettato nel dettaglio. Infine due componenti principali di questo sistema, l'accelerometro ADXL206 e la scheda di aquisizione CN0365, creati da Analog Devices è stato testato per verificarne la stabilità a diverse temperature.The feasibility of a new kind of instrument for geological exploration, based on the dual reciprocating drilling technology, is studied in respect to the harsh environmental conditions typical of this field. This technology has been chosen after a survey of the state of the art of geological drilling and the mechanism has been outlined. The focus of this thesis is the validation of the measurement system through which the trajectory of the drill is computed. The Monte Carlo method is first used to conduct a statistical analysis and assess the robustness of three different algorithms to compute the trajectory, taking into account the measurement errors. On the basis of this simulation the measurement system has been designed and its principal component, the accelerometer ADXL206 and the acquisition board CN0365 from Analog Devices have been tested to assess their stability at different temperatures
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