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1.
Leg amputation side determines performance in curve sprinting: a case study on a Paralympic medalist
Johannes Funken Kai Heinrich Steffen Willwacher Ralf Müller Jonas Böcker Hiroaki Hobara 《Sports biomechanics / International Society of Biomechanics in Sports》2019,18(1):75-87
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. 相似文献
2.
Steffen E. Seufert 《Informatik - Forschung und Entwicklung》2002,17(1):1-11
Zusammenfassung. In diesem Beitrag wird ein formaler Ansatz zur Ableitung von Zugriffsrechten auf der Basis eines formalen Organisationsmodells
vorgestellt. Hierzu wird der Ansatz der rollenbasierten Zugriffskontrolle (engl. Role-Based Access Control, kurz RBAC) um die M?glichkeit erweitert, Aufbauorganisationen zu modellieren. Der Vorteil gegenüber rollenbasierten Ans?tzen mit einfachen
Rollenhierarchien ist die klare Struktur, die einem Zugriffskontrollmodell durch die Organisationsform aufgepr?gt wird. Des
Weiteren k?nnen organisatorische Regelungen, wie z.B. Urlaubsvertretung oder Weisungsbefugnis, direkt im Modell hinterlegt
werden. Aufwendig zu pflegende und h?ufig inkonsistente Rollenkataloge werden obsolet. Sicherheitsstrategien mit unpr?zisen
Vorgaben lassen sich mittels der vorgestellten Technik der sog. `Kompetenzerweiterung' umsetzen. Das zugrundeliegende Paradigma
des vorgestellten Ansatzes unterscheidet sich stark von anderen Ans?tzen mit statischer Autorisation. Nutzer k?nnen sich Zugriffsrechte
in fest definierten Grenzen selbstverantwortlich zuteilen, wobei jedoch eine nachtr?gliche Kontrolle stark vereinfacht und
damit praktikabel wird.
Eingegangen am 22. Februar 2001 / Angenommen am 22. Mai 2001 相似文献
3.
Instructional Science - Digital drawing can foster learning, but only if the drawing is of sufficient quality. Hence, the focus of the present study was to investigate whether and how two types of... 相似文献
4.
C. E. Kennedy D. G. Danskin S. K. Edelman J. D. Steffen 《Counselor Education & Supervision》1970,9(4):272-276
This paper identifies several kinds of counselor activity for which practicum experiences have been or are being designed. These include individual and group counseling, outreach consultation, supervision of practicum students, and the study of student development. The SSD practicum is seen as sensitizing and predisposing the personnel worker to view action research as a relevant and crucial part of counselor education. 相似文献
5.
Steffen Pacholak Stefan Hochstein Alexander Rudert Christoph Brücker 《Sports biomechanics / International Society of Biomechanics in Sports》2014,13(2):176-194
The undulatory underwater sequence is one of the most important phases in competitive swimming. An understanding of the recurrent vortex dynamics around the human body and their generation could therefore be used to improve swimming techniques. In order to produce a dynamic model, we applied human joint kinematics to three-dimensional (3D) body scans of a female swimmer. The flow around this dynamic model was then calculated using computational fluid dynamics with the aid of moving 3D meshes. Evaluation of the numerical results delivered by the various motion cycles identified characteristic vortex structures for each of the cycles, which exhibited increasing intensity and drag influence. At maximum thrust, drag forces appear to be 12 times higher than those of a passive gliding swimmer. As far as we know, this is the first disclosure of vortex rings merging into vortex tubes in the wake after vortex recapturing. All unsteady structures were visualized using a modified Q-criterion also incorporated into our methods. At the very least, our approach is likely to be suited to further studies examining swimmers engaging in undulatory swimming during training or competition. 相似文献
6.
Mark H. Zmudy Matthew D. Curtner-Smith Jeff Steffen 《Sport, Education and Society》2013,18(4):465-480
Sport pedagogy researchers have contributed much to the literature on physical education teaching by describing the participation styles of children, youth and young adults in various settings. The purpose of this study was to describe the participation styles of children enrolled in two consecutive week-long summer adventure camps. Primary participants were 31 elementary and middle school students. Secondary participants were the two adventure educators (AEs) responsible for carrying out all the instruction at the camps. Data were collected using a variety of qualitative techniques and analysed using standard interpretive methods. Nine participation styles were identified indicating that the children in the camps had differing experiences of adventure education and varying degrees of success. Some of the participation styles had similar characteristics to those discovered previously in middle school physical education. Despite these similarities and unlike the middle school setting, there was no indication that a hierarchy of participation styles existed and, consequently, there was no sign of any bullying. Reasons for this difference may well have been the heavy focus on affective objectives within adventure education, much lower student–teacher ratios, higher levels of supervision and management, and greater instructional intent and skill. 相似文献
7.
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9.
Conventionally, isotachophoresis (ITP) is used for separation of ionic samples according to their electrophoretic mobilities. We demonstrate that the scope of ITP applications may be extended toward particle concentration and separation. Owing to the distributions of electrolyte concentration and electric field inside a transition zone between two electrolytes, a number of different forces act on a small particle. As far as possible, we provide estimates for the order of magnitude of these forces and analyze their scaling with the particle size and the electric-field strength. Furthermore, we experimentally demonstrate that polymer beads of 5 μm diameter dispersed in a high mobility “leading” electrolyte are picked up and carried along by an ITP transition zone which is formed with a low mobility “trailing” electrolyte. By studying the particle positions and trajectories, we show that impurities in the electrolytes play a significant role in the experiments. Additionally, it is experimentally shown that different types of beads can be separated at an ITP transition zone. In particular, beads of 1 μm diameter are not carried along with the transition zone, in contrast to the 5 μm beads. The presented technique thus adds to the portfolio of electrokinetic transport, concentration, and separation methods in microfluidics. 相似文献
10.
Steffen Hillmert 《Zeitschrift für Erziehungswissenschaft》2014,17(2):73-94
This paper describes mutual links between educational attainment and social inequality from a life course perspective. Analytically we distinguish between aspects of inequality with regard to access to education, consequences of education, and social reproduction through education. A special emphasis is put on the role institutions play in these processes. The paper presents selected empirical findings, discusses theoretical mechanisms, and draws some conclusions for the conceptualisation of education systems. 相似文献