Improving perceptual multimedia quality with an adaptable communication protocol

Copyrights @ 2005 University Computing Centre ZagrebInnovations and developments in networking technology have been driven by technical considerations with little analysis of the benefit to the user. In this paper we argue that network parameters that define the network Quality of Service (QoS) must be driven by user-centric parameters such as user expectations and requirements for multimedia transmitted over a network. To this end a mechanism for mapping user-oriented parameters to network QoS parameters is outlined. The paper surveys existing methods for mapping user requirements to the network. An adaptable communication system is implemented to validate the mapping. The architecture adapts to varying network conditions caused by congestion so as to maintain user expectations and requirements. The paper also surveys research in the area of adaptable communications architectures and protocols. Our results show that such a user-biased approach to networking does bring tangible benefits to the user

QoS impact on user perception and understanding of multimedia video clips

The widespread and increasing advent of multimedia technologies means that there must be a departure from the viewpoint that users expect a Quality of Service (QoS) which will only satisfy them perceptually. What should be expected of multimedia clips is that the QoS with which they are shown is such that it will enable the users to assimilate and understand the informational content of such clips. In this paper we present experimental results Iinking users’ understanding andperception of multimedia clips with the presentation QoS. Results show that the quality of video clips can be severely degraded without the user having to perceive any significant loss of informational content

Quality of perception: User quality of service in multimedia presentations

We define quality of perception (QoP) as representing the user side of the more technical and traditional quality of service. QoP encompasses not only a user’s satisfaction with the quality of multimedia presentations, but also his/her ability to analyze, synthesise and assimilate the informational content of multimedia displays.We found that significant reductions in frame rate and color depth does not result in a significant QoP degradation

Quantum spill out in few-nanometer metal gaps: Effect on gap plasmons and reflectance from ultrasharp groove arrays

Plasmons in ultranarrow metal gaps are highly sensitive to the electron density profile at the metal surfaces. Using a fully quantum mechanical approach, we study the effects of electron spill-out on gap plasmons and reflectance from ultrasharp metal grooves. We demonstrate that the mode index of ultranarrow gap plasmons converges to the bulk refractive index in the limit of vanishing gap and, thereby, rectify the unphysical divergence found in classical models. Surprisingly, spill-out also significantly increases the plasmonic absorption for few-nanometer gaps and lowers the reflectance from arrays of ultrasharp metal grooves. These findings are explained in terms of enhanced gap plasmon absorption taking place inside the gap 1-2 {\AA} from the walls and delocalization near the groove bottom. Reflectance calculations taking spill-out into account are shown to be in much better agreement with measurements compared with classical models

Quantum spill-out in nanometer-thin gold slabs: Effect on plasmon mode index and plasmonic absorption

A quantum mechanical approach and local response theory are applied to study plasmons propagating in nanometer-thin gold slabs sandwiched between different dielectrics. The metal slab supports two different kinds of modes, classified as long-range and short-range plasmons. Quantum spill-out is found to significantly increase the imaginary part of their mode indices, and, surprisingly, even for slabs wide enough to approach bulk the increase is 20%. This is explained in terms of enhanced plasmonic absorption, which mainly takes place at narrow peaks located near the slab surface

Defects in Jackiw-Teitelboim Quantum Gravity

We classify and study defects in 2d Jackiw-Teitelboim gravity. We show these are holographically described by a deformation of the Schwarzian theory where the reparametrization mode is integrated over different coadjoint orbits of the Virasoro group. We show that the quantization of each coadjoint orbit is connected to 2d Liouville CFT between branes with insertions of Verlinde loop operators. We also propose an interpretation for the exceptional orbits. We use this perspective to solve these deformations of the Schwarzian theory, computing their partition function and correlators. In the process, we define two geometric observables: the horizon area operator $\Phi_h$ and the geodesic length operator $L(\gamma)$. We show this procedure is structurally related to the deformation of the particle-on-a-group quantum mechanics by the addition of a chemical potential. As an example, we solve the low-energy theory of complex SYK with a U(1) symmetry and generalize to the non-abelian case.Comment: 66 pages, v4: clarifications added, typos corrected, matches published versio

Introduction to Library Trends 44 (2) Fall 1995: The Library and Undergraduate Education

published or submitted for publicatio

Multiwavelength optical pyrometer for shock compression experiments

A system for measurement of the spectral radiance of materials shocked to high pressures (~100 GPa) by impact using a light gas gun is described. Thermal radiation from the sample is sampled at six wavelength bands in the visible spectrum, and each signal is separately detected by solid-state photodiodes, and recorded with a time resolution of ~10 ns. Interpretation of the records in terms of temperature of transparent sample materials is discussed. Results of a series of exploratory experiments with metals are also given. Shock temperatures in the range 4000–8000 K have been reliably measured. Spectral radiance and temperatures have been determined with uncertainties of 2%