Erscheinungsbasierte statistische Objekterkennung

Zusammenfassung.   Die automatische Erkennung und Lokalisation von Objekten in digitalen Bildern ist ein wesentlicher Bestandteil vieler praktisch relevanter Anwendungen. In diesem Artikel wird ein erscheinungsbasiertes Verfahren zur Erkennung starrer zwei- oder dreidimensionaler Objekte vorgestellt, dem eine statistische Modellierung zugrundeliegt. Im Gegensatz zu segmentierungsbasierten Verfahren, wie sie vor allem im Bereich der 3D-Objekterkennung eingesetzt werden, erm?glicht der erscheinungsbasierte Ansatz aufgrund der Modellierung der Intensit?tswerte oder davon abgeleiteter lokaler Merkmale eines Bildes die Erkennung komplexer Objekte. Die statistische Formulierung der Problemstellung bildet den mathematischen Kontext zur Bestimmung optimaler L?sungen. Die Form der Modellierung erlaubt neben der Einzelobjekterkennung auch die Berücksichtigung von heterogenem Bildhintergrund und Mehrobjektszenen. Die dazu ben?tigten lokalen Merkmale entstehen durch r?umlich begrenzte Transformationen des Bildes, wie beispielsweise Gabor- oder Wavelet-Transformationen. Die statistische Modellierung beschreibt die Verteilung dieser lokalen Merkmale anhand einer Dichtefunktion, die sich bei der Hintergrund- und Mehrobjektmodellierung als Mischungsverteilung der Einzelobjektverteilungen ergibt. Die Aufgabenstellungen des Erlernens und Erkennens von Objekten sind damit als Parametersch?tzprobleme formal darstellbar. Dabei werden im einen Fall die Modellparameter und im anderen Fall die Lageparameter beziehungsweise die Klassen von Objekten gesch?tzt. Die experimentelle überprüfung des Ansatzes anhand realer Objektaufnahmen durch CCD-Kameras zeigt seine Brauchbarkeit zur Erkennung von 2D- und 3D-Objekten bei homogenem und heterogenem Hintergrund. Eingegangen am 5. April 2000 / Angenommen am 20. Juli 2001     

Grundlagen des Burrows-Wheeler-Kompressionsalgorithmus

Der Burrows-Wheeler-Kompressionsalgorithmus hat als ein universelles Kompressionsverfahren in den letzten Jahren aufgrund seiner hervorragenden Kompressionsraten und hohen Verarbeitungsgeschwindigkeiten eine bemerkenswerte Beachtung erfahren. Das Herzstück des Algorithmus stellt die sogenannte Burrows-Wheeler-Transformation dar. Es handelt sich bei dieser Transformation um eine Permutation der Eingabedaten, welche Zeichen mit ähnlichem Kontext nahe beieinander anordnet. Die Transformation sowie die zugehörige Rücktransformation werden zusammen mit den weiteren Stufen des Algorithmus in einer gegenüber der Standardversion verbesserten Variante vorgestellt und die Ergebnisse mit denen anderer Datenkompressionsalgorithmen verglichen.     

Direct skeletal attachment prosthesis for the amputee athlete: the unknown potential

Lower limb amputees often experience complications with the use of conventional socket-type prostheses, which further reduce their already compromised ability to perform the activities of daily living, or to participate in sporting activities. During the last two decades, a new technology of direct skeletal attachment (osseointegration) of prosthesis to the femoral residuum has been developed. The aim of this research was to assess the implant design, surgery protocols, and functional testing of this new technology on the first 100 patients using the Integral Leg Prosthesis procedure. This new knowledge can guide future engineering developments of osseointegration within the sporting arena. Between 1999 and 2013, direct skeletal implantation was performed on 112 amputees, from two centres in Germany and Australia. From the experience of the surgical team, modifications were made to the implant design. This re-engineering of the implant has reduced the surgical revisions due to infection from 29 % with the early implant design down to 7 %. The functional testing of the 34 Australian cases were assessed pre- and 12 months post-implant with significant improvements of one complete K-scale; the Q-TFA measures increased (50.9–86.7), whilst the Timed Up and Go decreased significantly (12.43 s ± 3.89 to 8.03 s ± 2.80), and the 6 min walk increased (304.0–383.9 m). From these findings, osseointegration technology is realistically the way of the future for amputee athletes. Further refinement of the implant design and sports-specific functional testing are required to define the potential of this technology.     

Leg amputation side determines performance in curve sprinting: a case study on a Paralympic medalist

The lower limb kinetics of curve sprinting in amputees are not well described in the literature, particularly with respect to the effect of the side of amputation. This is an issue due to the importance of the knowledge for prosthetic design and classification of athletes. Thus, the aim of this study was to investigate the influence of side of amputation on curve sprinting performance in athletes with a unilateral leg amputation. A three-dimensional motion analysis system (Vicon), four force plates (Kistler) and a modified mathematical human model (ALASKA) were used to compare clockwise and counter clockwise curve sprinting lower limb kinematics and kinetics of a Paralympic medalist with a left-sided knee exarticular amputation. Results reveal that vertical ground reaction force application and total vertical impulse were lower when the affected limb was at the inside of the curve. The unaffected limb showed joint mechanics different to those established for non-amputee athletes and might contribute better to propulsion when being the inside limb. Curve sprinting biomechanics and the ability to attain high radial velocities are directly dependent on the side of amputation relative to the curve direction in a unilateral amputee athlete of highest performance level.     

Retracking on a grand scale: policy and pedagogy in the reform of eastern German secondary schools after the fall of socialism

This article reports on a multi‐year study of changes in eastern German schools after the fall of the Berlin Wall. In the wake of national unification, the traditional three‐track structure of the West German educational syatem was re‐institutionalized in eastern German secondary schools. The article explores how teachers respond to this shift from the untracked socialist common school to the new track system. The study found that influences of state policies on teachers’ tracking pedagogy varied. The new institutions have forcefully shaped many teachers’ assumptions about students’ ability and career paths. Value orientations are characterized by ambivalence; while organizational goals and values are very exclusion‐oriented, the role of schools in society is defined in more inclusive terms. Contrary to exclusion‐oriented sentiments, instructional routines changed little; they flow, to a large extent, from the previous inclusive curriculum that was geared to the average or ‘normal’ student during socialist times. The study underlines the importance of examining multiple layers of beliefs and practices for an adequate understanding of the relationship between policy and practice.     

Identifying teaching groups as a basis for academic development

Academic development recognizes the strengths of communities, such as communities of practice or learning communities, in providing academics with supportive environments for the development of teaching. The problem academic development faces is that not enough academics are involved in these communities. Instead of trying to interest academics in joining communities, this research looks at the existing contexts around academics, which it refers to as ‘teaching groups’. It is proposed that every academic involved in teaching belongs to at least one teaching group, formed by colleagues teaching in the same course, degree or subject and that teaching groups form relevant contexts for engagement with teaching. The research investigates how teaching groups compare to communities and finds that less than half of teaching groups named by participants have strong community characteristics, indicating large space for improvement in the remaining majority of groups. The suggestion is made that identifying teaching groups across an institution might provide a promising starting point for engaging a majority of academics and working with these academics towards increased interaction on teaching in open and trusting collegial atmospheres.