Multimedia information broadcasting using digital TV channels

The structure of a new system used to broadcast multimedia information within a digital TV channel is outlined. The proposed scheme is based on the the Digital Storage Media Command and Control (DSM-CC) functions, and uses a newly developed protocol that allows to efficiently convey multimedia information. Such information has the same characteristics of HTML files used in WWW environments, as it may contain text, images, sounds and animation organized as an hypertext. The transport structure used is the MPEG-2 Transport Stream, which is the most standardized platform for the development of new digital TV services. A prototype software was developed to encode the file system by means of DSM-CC operations and include it in a MPEG-2 compatible Transport Stream     

Challenges of future multimedia QoE monitoring for internet service providers

Multimedia Tools and Applications - The ever-increasing network traffic and user expectations at reduced cost make the delivery of high Quality of Experience (QoE) for multimedia services more...     

JPEG2000-coded image error concealment exploiting convex sets projections.

Transmission errors in JPEG2000 can be grouped into three main classes, depending on the affected area: LL, high frequencies at the lower decomposition levels, and high frequencies at the higher decomposition levels. The first type of errors are the most annoying but can be concealed exploiting the signal spatial correlation like in a number of techniques proposed in the past; the second are less annoying but more difficult to address; the latter are often imperceptible. In this paper, we address the problem of concealing the second class or errors when high bit-planes are damaged by proposing a new approach based on the theory of projections onto convex sets. Accordingly, the error effects are masked by iteratively applying two procedures: low-pass (LP) filtering in the spatial domain and restoration of the uncorrupted wavelet coefficients in the transform domain. It has been observed that a uniform LP filtering brought to some undesired side effects that negatively compensated the advantages. This problem has been overcome by applying an adaptive solution, which exploits an edge map to choose the optimal filter mask size. Simulation results demonstrated the efficiency of the proposed approach.     

Characterization and catalytic activity of soft-templated NiO-CeO2 mixed oxides for CO and CO2 co-methanation

Nanosized NiO,CeO₂ and NiO-CeO₂ mixed oxides with different Ni/Ce molar ratios were prepared by the soft template method.All the samples were characterized by different techniques as to their chemical composition,structure,morphology and texture.On the catalysts submitted to the same reduction pretreatment adopted for the activity tests the surface basic properties and specific metal surface area were also determined.NiO and CeO₂ nanocrystals of about 4 nm in size were obtained,regardless of the Ni/Ce molar ratio.The Raman and X-ray photoelectron spectroscopy results proved the formation of defective sites at the NiO-CeO₂ interface,where Ni species are in strong interaction with the support.The microcalorimetric and Fourier transform infrared analyses of the reduced samples highlighted that,unlike metallic nickel,CeO₂ is able to effectively adsorb CO₂,forming carbonates and hydrogen carbonates.After reduction in H2 at 400°C for 1 h,the catalytic performance was studied in the CO and CO₂ co-methanation reaction.Catalytic tests were performed at atmospheric pressure and 300°C,using CO/CO₂/H₂ molar compositions of 1/1/7 or 1/1/5,and space velocities equal to 72000 or 450000 cm³?h^-1?gcat^-1.Whereas CO was almost completely hydrogenated in any investigated experimental conditions,CO₂ conversion was strongly affected by both the CO/CO₂/H₂ ratio and the space velocity.The faster and definitely preferred CO hydrogenation was explained in the light of the different mechanisms of CO and CO₂ methanation.On a selected sample,the influence of the reaction temperature and of a higher number of space velocity values,as well as the stability,were also studied.Provided that the Ni content is optimized,the NiCe system investigated was very promising,being highly active for the CO_x co-methanation reaction in a wide range of operating conditions and stable(up to 50 h)also when submitted to thermal stress.     

Notch and mean stress effect in fatigue as phenomena of elasto-plastic inherent multiaxiality

The present paper summarises an attempt of estimating fatigue lifetime of notched metallic materials by directly accounting for the degree of multiaxiality of the local elasto-plastic stress/strain-fields acting on the fatigue process zone. In more detail, the proposed approach takes as its starting point the assumption that Stage I is the most important stage to be modelled to accurately estimate fatigue damage, and this holds true independently of the sharpness of the assessed geometrical feature. According to this initial idea, and by taking full advantage of the so-called Modified Manson-Coffin Curve Method (MMCCM), the hypothesis is then formed that the crack initiation plane is always coincident with that material plane experiencing the maximum shear strain amplitude. Subsequently, to devise an efficient design method capable of taking into account the detrimental effect of stress/strain gradients arising also from severe stress/strain concentration phenomena, the MMCCM is suggested here as being applied in terms of the Theory of Critical Distances (TCD), the latter being used in the form of the Point Method (PM). Further, in light of the well-known fact that the value of the mean stress/strain components in the vicinity of the stress/strain raisers’ apices can be different from the corresponding nominal values due to the actual elasto-plastic behaviour of the material being assessed, it is shown, through the MMCCM itself, that also the mean stress effect can directly and accurately be treated as a problem of inherent multiaxiality. Finally, as a preliminary validation, the accuracy and reliability of the proposed approach is checked through several experimental results taken from the literature and generated by testing, under uniaxial fatigue loading, samples containing a variety of geometrical features, the effect of different nominal load ratios being investigated as well.     

High-frequency error concealment in wavelet-based image coding

A new algorithm for high-frequency subband error concealment in wavelet-based picture coding is presented. It is based on a wavelet patch repetition approach: the LBG algorithm, given by Linde et al., is used to generate a codebook of patches and, according to a boundary distance measure, one of these patches is selected to mask the damaged area. Experiments show noteworthy results.     

Performance analysis of fractal modulation transmission over fast-fading wireless channels

Fractal modulation schemes have been under investigation for signal transmission over time-varying channels because of their advantages in data transmission at different frequency bands. This also allows efficient reception when channel conditions are varying by selecting the optimal frequency/time resolution based on the current channel condition. We present a performance analysis of fractal modulation transmission over Rician fast-fading channels in the presence of AWGN. A quadrature transmission scheme is simulated and compared, in terms of error robustness, to a QAM transmission system. Other papers analysing fractal modulation system performance do not consider time-varying channels, which are important as they represent the main configuration for communication systems based on this modulation technique. The novelty of our paper lies in the comparison of a fractal modulation system to a QAM one (core of the OFDM modulation technology, extensively used in broadcasting) using a testbed simulation environment where additive noise and fast fading are considered as typical error sources for transmission over wireless channels. Several wavelet families for a fractal modulation scheme have been considered and performance for each one measured; results reported show the effectiveness of the fractal modulation paradigm and confirm its effective utilization in data broadcasting.