Mobile phones, tablet computers, laptops, desktops, and large screen displays are increasingly available to individuals for information access, often simultaneously. Dominant content access protocols, such as HTTP/1.1, do not take advantage of this device multiplicity and support information access from single devices only. Changing devices means restarting an information session. Using devices in conjunction with each other poses several challenges, which include the presentation of content on devices with diverse form factors and propagation of the content changes across these devices. In this dissertation, I report on the design and implementation of MIDAS - architecture and a prototype system for multi-device presentations. I propose a framework, called 12C, for characterizing multi-device systems and evaluate MIDAS within this framework. MIDAS is designed as a middleware that can work with multiple client-server architectures, such as the Web and context-aware Trellis, a non-Web hypertext system. It presents information content simultaneously on devices with diverse characteristics without requiring sensor-enhanced environments. The system adapts content elements for optimal presentation on the target device while also striving to retain fidelity with the original form from a human perceptual perspective. MIDAS reconfigures its presentation in response to user actions, availability of devices, and environmental context, such as a user's location or the time of day. I conducted a pilot study that explored human perception of similarity when image attributes such as size and color depth are modified in the process of presenting images on different devices. The results indicated that users tend to prefer scaling of images to color-depth reduction but gray scaling of images is preferable to either modification. Not all images scale equally gracefully; those dominated by natural elements or manmade structures scale exceptionally well. Images that depict recognizable human faces or textual elements should be scaled only to an extent that these features retain their integrity. Attributes of the 12C framework describe aspects of multi-device systems that include infrastructure, presentation, interaction, interface, and security. Based on these criteria, MIDAS is a flexible infrastructure, which lends itself to several content distribution and interaction strategies by separating client- and server-side configuration.

No description available.

The connection between phase shifts and the ANC has been explored in the frame of the effective range theory. The main result is that, in practice and under rather simple requirements, scattering states (phases shifts) can be correctly described and connected with bound states via the effective range function, and therefore, ANCs can be accurately determined thanks to the analytic properties of this function. This result has an important impact in stellar evolution due to the ANC and phases shifts are directly connected with capture cross sections which, for instance, determine partially the stage and evolution of stars.<p><p>As a first step, the effective range function is approximated via the effective range expansion which shows that a successful phase-shift description depends on how precise the effective range parameters are determined. Thus, a technique to compute accurately these parameters is developed here. Its construction is based on a set of recurrence relations at low energy, that allows a compact and general description of the truncated<p>effective range expansion. Several potential models are used to illustrate the effectiveness<p>of this technique and to discuss its numerical limitations. The results shows that a very good precision of the effective-range parameters can be achieved; nevertheless, to describe experimental phase shifts several effective-range parameters can be needed, which shows a limitation for practical applications.<p><p>As a second step, the effective range function is analyzed theoretically in an arbitrary energy range. This analysis shows that this function can be decomposed in such a way that contributions of bound states, resonances and background can be separated in a similar way as in the phenomenological R-matrix. In this new form experimental data can be better fitted because the free parameter space is reduced considerably,<p>and therefore, extrapolations are better handled. By construction, the method agrees with the scattering matrix properties which allows a simple calculation of resonances (locations and widths) and asymptotic normalization constants (ANCs). Several tests are successfully performed via potential models. Phase shifts for the 2 + partial wave of the 12C+α are analyzed with this method. They are correctly described including both<p>resonances at Ec.m. = 2.7 and 4.4 MeV. For the 6.92 MeV (2+) exited state of 16O, the ANC estimation 112(8) × 10 3 fm^−1/2 is obtained taking into account statistical errors. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished