Design of a scanning laser radar for spaceborne applications, phase 3

Design of scanning laser radar for spaceborne application

Construction and testing of a Scanning Laser Radar (SLR), phase 2

The scanning laser radar overall system is described. Block diagrams and photographs of the hardware are included with the system description. Detailed descriptions of all the subsystems that make up the scanning laser radar system are included. Block diagrams, photographs, and detailed optical and electronic schematics are used to help describe such subsystem hardware as the laser, beam steerer, receiver optics and detector, control and processing electronics, visual data displays, and the equipment used on the target. Tests were performed on the scanning laser radar to determine its acquisition and tracking performance and to determine its range and angle accuracies while tracking a moving target. The tests and test results are described

Biogeomorphology in the Anthropocene: a hierarchical, traits-based approach

The complex web of interactions between ecological communities and the physical landscape (biogeomorphology) is being affected by the global scale environmental changes of the Anthropocene. Climate change, habitat destruction, invasions and extinctions are having profound impacts on biogeomorphological process regimes through changes in the composition and activity of ecological communities. However, on the other hand, deliberately-targeted human interventions to biogeomorphic systems have the potential to help mitigate against, and adapt to, the Anthropocene, by managing biogeomorphic processes to enhance resilience. To evaluate these relationships, we propose a conceptual framework based on the ecological concept of functional traits. We review how the Anthropocene is causing changes in species composition, abundance and the prevalence of functional traits to produce changes to biogeomorphic processes and functions that are, as yet, only partly understood. We use examples of fluvial, dryland and coastal biogeomorphic systems to illustrate how purposeful manipulation of biogeomorphic systems (as a type of Nature-based solution) can conserve, enhance or add biogeomorphic functions that are capable of enhancing geomorphic resilience. By focussing on function, this approach offers a range of advantages/avenues for biogeomorphological research. This includes the detection and prediction of human impacts, and an improved understanding of how biogeomorphology can contribute to tackling environmental challenges in the Anthropocene

Bumps and rings in a two-dimensional neural field: splitting and rotational instabilities

In this paper we consider instabilities of localised solutions in planar neural field firing rate models of Wilson-Cowan or Amari type. Importantly we show that angular perturbations can destabilise spatially localised solutions. For a scalar model with Heaviside firing rate function we calculate symmetric one-bump and ring solutions explicitly and use an Evans function approach to predict the point of instability and the shapes of the dominant growing modes. Our predictions are shown to be in excellent agreement with direct numerical simulations. Moreover, beyond the instability our simulations demonstrate the emergence of multi-bump and labyrinthine patterns. With the addition of spike-frequency adaptation, numerical simulations of the resulting vector model show that it is possible for structures without rotational symmetry, and in particular multi-bumps, to undergo an instability to a rotating wave. We use a general argument, valid for smooth firing rate functions, to establish the conditions necessary to generate such a rotational instability. Numerical continuation of the rotating wave is used to quantify the emergent angular velocity as a bifurcation parameter is varied. Wave stability is found via the numerical evaluation of an associated eigenvalue problem

Period-adding bifurcations and chaos in a periodically stimulated excitable neural relaxation oscillator

The response of an excitable neuron to trains of electrical spikes is relevant to the understanding of the neural code. In this paper we study a neurobiologically motivated relaxation oscillator, with appropriately identified fast and slow coordinates, that admits an explicit mathematical analysis. An application of geometric singular perturbation theory shows the existence of an attracting invariant manifold which is used to construct the Fenichel normal form for the system. This facilitates the calculation of the response of the system to pulsatile stimulation and allows the construction of a so-called extended isochronal map. The isochronal map is shown to have a single discontinuity and be of a type that can admit three types of response: mode-locked, quasi-periodic and chaotic. The bifurcation structure of the system is seen to be extremely rich and supports period-adding bifurcations separated by windows of both chaos and periodicity. A bifurcation analysis of the isochronal map is presented in conjunction with a description of the various routes to chaos in this system

Assessing Individual-level Factors Supporting Student Intrinsic Motivation in Online Discussions: A Qualitative Study

Research has established that intrinsic motivation has a positive effect on learning and academic achievement. However, little is known about the impact of different technology-supported learning activities on student intrinsic motivation or whether such learning activities significantly enhance student intrinsic motivation compared to traditional classroom environments without technological support. In order to investigate the phenomenon of intrinsic motivation in technology-supported learning environments, this paper examines factors that support individual student intrinsic motivation in online discussions. A research model is presented based on research into motivation, and the specific areas of self-determination and curiosity provide a framework for the model. A qualitative research methodology is used to validate the model. Results from the study indicate that five factors; perceived competence, perceived challenge, feedback, perceived interest and perceived curiosity, were strongly supported, with partial support for the construct of perceived choice

Robustness and Enhancement of Neural Synchronization by Activity-Dependent Coupling

We study the synchronization of two model neurons coupled through a synapse having an activity-dependent strength. Our synapse follows the rules of Spike-Timing Dependent Plasticity (STDP). We show that this plasticity of the coupling between neurons produces enlarged frequency locking zones and results in synchronization that is more rapid and much more robust against noise than classical synchronization arising from connections with constant strength. We also present a simple discrete map model that demonstrates the generality of the phenomenon.Comment: 4 pages, accepted for publication in PR

Student E-Learning Intrinsic Motivation: A Qualitative Analysis

In the age of life-long learning and increased competition for time, motivation becomes a salient issue. Students need to be more intrinsically motivated in the absence of more formal structure. This is especially true in online learning environments where direct instructor influence is mitigated. Online learning environments typically embrace many choices in ways in which learning material is presented and interaction with students is supported in both individual and collaborative contexts. As such, it is imperative that we better understand the implications of various learning activities and associated technologies on aspects of intrinsic motivation in e-learning. In this paper we examine these effects through qualitative analysis of semi-structured interviews with students in an online MBA program. Results encourage use of a pedagogically driven portfolio of learning activities supported by well-selected and integrated audio, video, and data technologies. Extension to use of mobile devices in ubiquitous e-learning contexts is explored