Dynamics of a bouncing dimer

We investigate the dynamics of a dimer bouncing on a vertically oscillated plate. The dimer, composed of two spheres rigidly connected by a light rod, exhibits several modes depending on initial and driving conditions. The first excited mode has a novel horizontal drift in which one end of the dimer stays on the plate during most of the cycle, while the other end bounces in phase with the plate. The speed and direction of the drift depend on the aspect ratio of the dimer. We employ event-driven simulations based on a detailed treatment of frictional interactions between the dimer and the plate in order to elucidate the nature of the transport mechanism in the drift mode.Comment: 4 pages, 5 figures, Movies: http://physics.clarku.edu/~akudrolli/dime

Simple model of bouncing ball dynamics. Displacement of the limiter assumed as a cubic function of time

Nonlinear dynamics of a bouncing ball moving vertically in a gravitational field and colliding with a moving limiter is considered and the Poincare map, describing evolution from an impact to the next impact, is described. Displacement of the limiter is assumed as periodic, cubic function of time. Due to simplicity of this function analytical computations are possible. Several dynamical modes, such as fixed points, 2 - cycles and chaotic bands are studied analytically and numerically. It is shown that chaotic bands are created from fixed points after first period doubling in a corner-type bifurcation. Equation for the time of the next impact is solved exactly for the case of two subsequent impacts occurring in the same period of limiter's motion making analysis of chattering possible.Comment: 8 pages, 1 figure, presented at the DSTA 2011 conference, Lodz, Polan

Simple model of bouncing ball dynamics: displacement of the table assumed as quadratic function of time

Nonlinear dynamics of a bouncing ball moving in gravitational field and colliding with a moving limiter is considered. Displacement of the limiter is a quadratic function of time. Several dynamical modes, such as fixed points, 2 - cycles and chaotic bands are studied analytically and numerically. It is shown that chaotic bands appear due to homoclinic structures created from unstable 2 - cycles in a corner-type bifurcation.Comment: 11 pages, 6 figure

Dynamic buckling and fragmentation in brittle rods

We present experiments on the dynamic buckling and fragmentation of slender rods axially impacted by a projectile. By combining the results of Saint-Venant and elastic beam theory, we derive a preferred wavelength lambda for the buckling instability, and experimentally verify the resulting scaling law for a range of materials including teflon, dry pasta, glass, and steel. For brittle materials, buckling leads to the fragmentation of the rod. Measured fragment length distributions show two clear peaks near lambda/2 and lambda/4. The non-monotonic nature of the distributions reflect the influence of the deterministic buckling process on the more random fragmentation processes.Comment: 4 pages, 5 figures, submitted to Physical Review Letter

Platforming Equality: Policy Challenges for the Digital Economy

This is the final version. Available from Autonomy via the link in this recordWelcome to Autonomy’s ‘Platforming Equality’ document: a collection of papers on the challenges that the digital economy poses to policymakers, activists and researchers. We’ve invited a range of contributors to probe deeper into under-examined topics in the digital economy and to shed light on how they operate. Another aim of the collection is to explore policy options for alleviating a range of new challenges that have emerged within the digital economy. Contributors move beyond theoretical discussion of the problems themselves and turn towards an analysis of responses that are open to activists, municipal authorities and government policy makers. Articles suggest a range of policy recommendations and discuss the strengths and weaknesses of different approaches. Each contributor examines a specific issue based on their own research and an analysis of the existing literature. They then provide their own perspective on the policies and approaches that would be most suitable to tackling the issue

Impact testing to determine the mechanical properties of articular cartilage in isolation and on bone

The original publication is available at www.springerlink.comNon peer reviewedPostprin

Simulation for the oblique impact of a lattice system

The oblique collision between an elastic disk and an elastic wall is numerically studied. We investigate the dependency of the tangential coefficient of restitution on the incident angle of impact. From the results of simulation, our model reproduces experimental results and can be explained by a phenomenological theory of the oblique impact.Comment: 30 pages, 9 figures, submitted to J. Phys. Soc. Japa

The Political Attitudes and Subjective Wellbeing of the One Percent

In capitalist societies, individuals who occupy the highest positions in the economic hierarchy feature prominently in the political discourse under the moniker of the One Percent. However, little is known about how the psychology of One Percent might differ from that of the average person. Using a large, nationally representative sample in New Zealand (N = 14,650), we aimed to fill this gap examining the political attitudes and subjective wellbeing of the top one percent of the income distribution. We found that, compared to general public, the One Percent more strongly legitimize the political and economic systems in society, and express lower support for redistributive taxation. They also report higher life satisfaction, self-esteem and belongingness compared to everyone else. Thus, the One Percent benefit not only economically and politically from the current system, but also psychologically. Moreover, their political beliefs serve to bolster the inequality from which they benefit

Speaking with things: Encoded researchers, social data, and other posthuman concoctions

We apply our heuristics for ‘interviewing’ nonhuman research participants (Adams and Thompson 2011) to the digital things of qualitative research itself: recording devices, data analysis software, and other sociomaterial concoctions recruited at different stages of contemporary research projects. We suggest that these ‘inorganic organized’ entities participate as co-researchers that inevitably extend but also disrupt research practice and knowledge construction, introducing new tensions and contradictions. Counterpointing phenomenology and Actor Network Theory, we usher some of the hidden and coded materialities of research practice into view, and glimpse unexpected realities co-enacted. Such immersive entanglements raise ethical questions about the posthumanist fluencies now demanded in social science research practice and we outline several considerations

Evaluating teaching effectiveness in nursing education:An Iranian perspective

BACKGROUND: The main objective of this study was to determine the perceptions of Iranian nurse educators and students regarding the evaluation of teaching effectiveness in university-based programs. METHODS: An exploratory descriptive design was employed. 143 nurse educators in nursing faculties from the three universities in Tehran, 40 undergraduate, and 30 graduate students from Tehran University composed the study sample. In addition, deans from the three nursing faculties were interviewed. A researcher-developed questionnaire was used to determine the perceptions of both faculty and students about evaluating the teaching effectiveness of nurse educators, and an interview guide was employed to elicit the views of deans of faculties of nursing regarding evaluation policies and procedures. Data were analyzed using parametric and nonparametric statistics to identify similarities and differences in perceptions within the Iranian nurse educator group and the student group, and between these two groups of respondents. RESULTS: While faculty evaluation has always been a major part of university based nursing programs, faculty evaluation must be approached more analytically, objectively, and comprehensively to ensure that all nursing educators receive the fairest treatment possible and that the teaching-learning process is enhanced. CONCLUSION: Educators and students stressed that systematic and continuous evaluation as well as staff development should be the primary goals for the faculty evaluation process. The ultimate goals is the improvement of teaching by nurse educators