O melhor de dois mundos: uma perspetiva motivacional dos árbitros de futebol

O presente trabalho constitui uma investigação no contexto da arbitragem nacional,procurando identificar e avaliar as características motivacionais dos árbitros de futebol.Neste projeto de trabalho procurou-se responder a três questões principais: Quais osprincipais motivos para ser árbitro de futebol? Quais as principais motivações dos árbitros?Que gratificações encontram na sua atividade?Para desenvolver o processo de investigação foram utilizados dois instrumentos detrabalho: um criado especificamente para esta problemática pelo autor da dissertação (eque se designou como "Questionário de Motivos para Ingressar no Mundo da Arbitragem")e um outro instrumento baseado na Sports Motivation Scale (Pelletier et al., 1995)utilizando a versão portuguesa de Bara Filho et al. (2011), designada como Escala deMotivação Desportiva.Os resultados obtidos mostraram que os principais motivos que levam as pessoas aingressar no mundo da arbitragem são a paixão que sentem pelo futebol, a procura denovas experiências, o gosto e a curiosidade sobre o mundo da arbitragem bem como avalorização pelo exercício físico. A aplicação da Escala de Motivação Desportiva (BaraFilho et al., 2011), revelou como principais características motivacionais dos árbitros, amotivação intrínseca para a estimulação da experiência e a motivação intrínseca para arealização. Finalmente os dados obtidos permitiram também confirmar que os árbitros queexperimentam um determinado tipo de paixão - a paixão harmoniosa - desfrutam do jogo,abstraindo-se de interferências externas, num estado de flow feeling (Csikszentmihalyi) oque os ajuda na tomada de decisão e na reação ao erro

Methodology to analyze the accuracy of 3D objects reconstructed with collaborative robot based monocular LSD-SLAM

SLAM systems are mainly applied for robot navigation while research on feasibility for motion planning with SLAM for tasks like bin-picking, is scarce. Accurate 3D reconstruction of objects and environments is important for planning motion and computing optimal gripper pose to grasp objects. In this work, we propose the methods to analyze the accuracy of a 3D environment reconstructed using a LSD-SLAM system with a monocular camera mounted onto the gripper of a collaborative robot. We discuss and propose a solution to the pose space conversion problem. Finally, we present several criteria to analyze the 3D reconstruction accuracy. These could be used as guidelines to improve the accuracy of 3D reconstructions with monocular LSD-SLAM and other SLAM based solutions.Comment: 5 pages, 5 figures, 2018 International Conference on Intelligent Autonomous Systems (ICoIAS 2018

Development of a cost effective three-dimensional posture analysis tool: validity and reliability

BACKGROUND: The lack of clear understanding of the association between sitting posture and adolescent musculoskeletal pain, might reflect invalid and/or unreliable posture measurement instruments. The psychometric properties of any new measurement instrument should be demonstrated prior to use for research or clinical purposes. This paper describes psychometric testing of a new three-dimensional (3D), portable, non-invasive posture analysis tool (3D-PAT), from sequential studies using a mannequin and high school students. METHODS: The first study compared the 3D-(X-, Y- and Z-) coordinates of reflective markers placed on a mannequin using the 3D-PAT, and the Vicon motion analysis system. This study also tested the reliability of taking repeated measures of the 3D-coordinates of the reflective markers. The second study determined the concurrent validity and test-retest reliability of the 3D-PAT measurements of nine sitting postural angles of high school students undertaking a standard computing task. In both studies, concordance correlation coefficients and Intraclass correlation coefficients described test-retest reliability, whilst Pearson product moment correlation coefficients and Bland-Altman plots demonstrated concurrent validity. RESULTS: The 3D-PAT provides reliable and valid 3D measurements of five of the nine postural angles i.e. head flexion, neck flexion, cranio-cervical angle, trunk flexion and head lateral bending in adolescents undertaking a standard task. CONCLUSIONS: The 3D-PAT is appropriate for research and clinical settings to measure five upper quadrant postural angles in three dimensions. As a measurement instrument it can provide further understanding of the relationship between sitting posture, changes to sitting posture and adolescent musculoskeletal pain.Web of Scienc

Photographic measurement of upper-body sitting posture of high school students: A reliability and validity study

<p>Abstract</p> <p>Background</p> <p>All the reported measures of sitting posture, as well as photographs, have one flaw, as these measures are external to the body. These measures use calculations from external bony landmarks to estimate spinal posture, on the understanding that what is being measured externally reflects the shape, health and performance of structures of the underlying spine. Without a comparative measure of the relative position of the structures of the spine, the validity of any external spinal posture measure cannot be established. This paper reports on a study which tests the validity of photographs to measure adolescent sitting posture.</p> <p>Methods</p> <p>The study was conducted in a laboratory at the Department of Human Biology, University of Cape Town. A random sample of 40 adolescents were recruited from the Cape metropolitan schools, to detect differences of three degrees or more between the repeated measures of upright, normal or slouched posture (photographs) and between the posture photographs and LODOX measures. Eligible participants were healthy male and female subjects aged 15 or 16 years old, in Grade 10, and who were undertaking Computer or Computype studies at their schools. Two posture measurement tools were used in the study, namely: Photographs were taken using the Photographic Posture Analysis Method (PPAM) and Radiograph<it>s </it>were taken using the LODOX (LODOX (Pty) Ltd) system. Subjects' posture was assessed in simulated computer workstations. The following angles were measured: the sagittal head angle, cervical angle, protraction/retraction angle, arm angle and the thoracic angle.</p> <p>Results</p> <p>Data from 39 subjects (19 males, 20 females) was used for analysis (17 15-year-olds (7 boys and 10 girls), 22 16-year-olds (12 boys and 10 girls)). All but one photographic angle showed moderate to good correlation with the LODOX angles (Pearson r values 0.67–0.95) with the exception being the shoulder protraction/retraction angle Pearson r values. Bland Altman limits of agreement illustrated a slight bias for all angles. The reliability study findings from repeated photographs demonstrated moderate to good correlation of all angles (ICC values 0.78–0.99).</p> <p>Conclusion</p> <p>The findings of this study suggest that photographs provide valid and reliable indicators of the position of the underlying spine in sitting. Clinically it is important to know whether a patient is showing true progression in relation to a postural intervention. Based on the results of this study, the PPAM can be used in practice as a valid measure of sitting posture.</p

Edge scanning and swept surface approximation in reverse engineering

Thesis (PhD)--University of Stellenbosch, 2001.ENGLISH ABSTRACT: Broadly speaking Reverse Engineering is the process of digitising a physical object and creating a computer model of the object. If sharp edges formed by two surfaces can be extracted from a point cloud (which is the set of measured points) it can speed up the segmentation of the point cloud and the edges may also be used to construct swept surfaces (or various other types of surface that best captures the design intent). A strategy is presented to "scan" edges. The strategy simulates a CMM (Coordinate Measurement Machine) as it would scan a sequence of short lines straddling the edge. Rather than measuring on a physical object, the algorithm developed in this dissertation "scans" on the points in the point cloud. Each line is divided in two parts, or line sections, belonging to the surfaces fanning the edge. The points of the line sections are then approximated with polynomials. Each edge point is the intersection of two such polynomials. In many engineering components sharp edges are replaced with fillet radii or the edges become worn or damaged. This algorithm is capable of reconstructing the original sharp edge without prior segmentation. A simple analytical model was developed to determine the theoretically achievable accuracy. This Analytical accuracy was compared with the accuracy of edges extracted from point clouds. A series of experiments were done on point clouds. The input parameters of the experiments were chosen using the technique of Design of Experiments. Using the experimental results the parameters that most significantly influences the accuracy of the algorithm was determined. From the Analytical and experimental analysis guidelines were developed which will help a designer to specify sensible input parameters for the algorithm. With these guidelines it is possible to find an edge with an accuracy comparably with an edge found with the traditional method of finding the edges with NURBS surface intersections. Finally the algorithm was combined with a swept surface fitting algorithm. The scanned edges are used as rails and profile curves for the swept surfaces. The algorithms were demonstrated by reverse engineering part of another core box for an inlet manifold. If the edge detection parameters are specified according to the guidelines developed here, this algorithm can successfully detect edges. The maximum gap size in the point cloud is an important limiting factor, but its effect has also been quantified.AFRIKAANSE OPSOMMING: In Truwaartse Ingenieurswese word 'n fisiese voorwerp opgemeet en 'n rekenaar model word daarvan geskep. Die segmentering van die puntewolk (dit is die versameling gemete punte) sal aansienlik vergemaklik word indien dit moontlik is om skerp rante in die puntewolk te identifiseer. Die rante sal dan gebruik kan word om veegvlakke (swept surfaces), of enige ander tipe oppervalk wat die ontwerp die beste beskryf, te konstrueer. Hierdie proefskrif beskryf 'n strategie wat die rante kan opmeet. Dit simuleer die manier waarvolgens 'n Koërdinaatmeetmasjien 'n reeks lyne, wat oor die rant lê, sou meet. In plaas van op 'n fisiese voorwerp op te meet, "meet" die algoritme op 'n puntwolk. Elke lyn word dan in twee dele verdeel (elke deel word 'n meetlynseksie genoem). Elke meetlynseksie behoort aan een van die twee oppervlaktes wat die rant vorm. Die rant punte word bereken as die interseksie van twee polinome wat deur die punte van die meetlynseksie gepas is. Dit is dikwels die geval met meganiese onderdele dat skerp rante vervang word met 'n vulstraal of dit kan ook gebeur dat die rant verweer het of beskadig is. Die algoritme, wat hier beskryf word, kan selfs die oorspronklike skerp rant in sulke gevalle herkonstrueer. 'n Eenvoudige analitiese model is ontwikkelom die teoretiese akkuraatheid van die algoritme te bepaal. Die teoretiese akkuraatheid is vergelyk met die akkuraatheid van rante wat uit puntewolke bepaal is. 'n Reeks eksperimente is op puntwolke gedoen. Die parameters vir die eksperimente is gekies deur van Eksperimentele Ontwerp gebruik te maak. Met behulp van hierdie tegniek kon bepaal word watter meetparameters die grootste invloed op die akkuraatheid van die gemete punte het. Die teoretiese en eksperimentele resultate is gebruik om riglyne daar te stel waarmee die intreeparameters van die algoritme gekies kan word. Met hierdie riglyne is dit moontlik om 'n rant te vind met 'n akkuraatheid vergelykbaar met die tradisionele metode om die rante te vind met behulp van NURBS oppervlakte interseksies. Laastens is die algoritme gekombineer met 'n algoritme wat veegvlakke deur punte kan pas. Die gemete rante word gebruik as spore en profiele vir die veegvlakke. Die tegnieke is gebruik om 'n CAD model van 'n sandkernvorm (vir die giet van 'n inlaatspruitstuk) te maak. Deur die riglyne te gebruik om die intreeparameters vir die algoritme te spesifiseer, kan rante suksesvol uit puntewolke bepaal word. Die maksimum afstand tussen naburige punte in die puntewolk beperk die gebruik van die algoritme, maar die effek hiervan is ook vasgevat in die riglyne wat ontwikkel is vir die algoritme

Cost estimating welded assemblies produced in batches

One copy microfiche.Thesis (M. Ing.) -- University of Stellenbosch, 1997.Full text to be digitised and attached to bibliographic record

Wayne Swart A Video-Oculography Based Telemedicine System for Automated Nystagmus Identification

This paper presents the research and results for an automated jerk-type nystagmus identification system that makes use of an efficient, low cost video-oculography (VOG) device, designed for telemedicine applications. The pupil position is estimated by a hybrid tracking algorithm from the captured VOG images. It is also shown that wavelet analysis with an appropriate mother wavelet, coupled with well-defined geometric constraints can provide a reliable and robust nystagmus identification algorithm. Some original research regarding robust analysis for signals with mixed content is also presented

Localisation accuracy of semi-dense monocular SLAM

Understanding the factors that influence the accuracy of visual SLAM algorithms is very important for the future development of these algorithms. So far very few studies have done this. In this paper, a simulation model is presented and used to investigate the effect of the number of scene points tracked, the effect of the baseline length in triangulation and the influence of image point location uncertainty. It is shown that the latter is very critical, while the other all play important roles. Experiments with a well known semi-dense visual SLAM approach are also presented, when used in a monocular visual odometry mode. The experiments show that not including sensor bias and scale factor uncertainty is very detrimental to the accuracy of the simulation results