Playout buffering of speech packets based on a quality maximization approach

To combat jitter problems in voice streaming over packet networks, playout buffering algorithms are used at the receiver side. Most of the proposed solutions rely on two main operations: prediction of delay statistics for future packets; setting of the end-to-end delay so as to limit or avoid packet losses. In recent years, a new approach has been presented, which is based on using a quality model to evaluate the impact of both packet loss and delay on the voice quality. Such a model is used to find the buffer setting that maximizes the expected quality. In this paper, we present a playout buffering algorithm whose main contribution is the extension of the new quality-based approach to the case of voice communications affected by bursty packet losses. This work is motivated by two main considerations: most of IP telephony applications are characterized by bursty losses instead of random ones; the human perception of the speech quality is significantly affected by the temporal correlation of losses. To this purpose, we make use of the extensions proposed in the ETSI Tiphon for the ITU-T E-Model so as to incorporate the effects of loss burstiness on the perceived quality. The resulting playout algorithm estimates the characteristics of the loss process varying the end-to-end delay, weights the loss and the delay effects on the perceived quality, and maximizes the overall quality to find the optimal setting for the playout buffer. The experimental results prove the effectiveness of the proposed technique.     

CO2 methanation on hard-templated NiOCeO2 mixed oxides

Mesostructured NiOCeO₂ mixed oxides, with Ni loadings in the range 5–35 wt% (g_Ni/g_CeO2), were synthesized by the hard template procedure using SBA-15 as the template. A hard-templated CeO₂ was also prepared and used as the support for depositing Ni (5–35 wt%) by impregnation. Two NiOAl₂O₃ catalysts were synthesized for comparison, by impregnating nickel on a commercial γ-alumina. All the samples were characterized by different techniques as to their chemical composition, structure, morphology, texture, and redox features. The catalytic performance was investigated in the CO₂ methanation reaction after mild reduction pretreatment (H₂ at 400 °C for 1 h). Catalytic testing was performed under atmospheric pressure, 300 °C, 72,000 cm³ h^?1 g_cat^?1, and stoichiometric H₂/CO₂ molar ratio. High catalytic activity, with CH₄ selectivity values ≥ 93 mol%, was obtained with the NiOCeO₂ mixed oxides (CO₂ conversions up to 76 mol%). When γ-Al₂O₃ was used as the support, catalysts with low activity (CO₂ conversion ≤ 20 mol%) were obtained. On selected samples, additional catalytic runs were also performed for reaction times up to 30 h or with a higher space velocity value. The catalytic results were explained by taking into account the role of the nickel-ceria interactions both during the reduction of NiO and in the reactants activation.     

Estimating Reduced-Reference Video Quality for Quality-Based Streaming Video

Reduced-reference (RR) video-quality estimators send a small signature to the receiver. This signature comprises the original video content as well as the video stream. RR quality estimation provides reliability and involves a small data payload. While significant in theory, RR estimators have only recently been used in practice for quality monitoring and adaptive system control in streaming-video frameworks. In this paper, we classify RR algorithms according to whether they are based on a) modeling the signal distortion, b) modeling the human visual system, or c) analyzing the video signal source. We review proposed RR techniques for monitoring and controlling quality in streaming video systems.     

Simple, efficient mixed solid element for accurate analysis of local effects in laminated and sandwich composites

A mixed, eight-node solid element is developed with the aim to accurately and efficiently capture local stresses in composites. The nodal degrees of freedom are the three displacements and the three interlaminar stresses. Characteristic features, C⁰, tri-linear, serendipity shape functions are used to interpolate these quantities across the element volume. With this choice, the intraelement stress fields satisfy the equilibrium equations in integral form. Integration is exact. It is carried out by a symbolic calculus tool. To test the element performances, the intricate stress fields of thick sandwich composites with undamaged and damaged face layers, piezoelectrically actuated beams, thermally loaded laminates and close to a two-material wedge singularity are investigated. The element appears robust, stable and rather accurate using reasonably fine meshes. Compared to displacement-based counterpart elements, the computational effort is not larger.     

Fatigue strength assessment of welded joints: From the integration of Paris’ law to a synthesis based on the notch stress intensity factors of the uncracked geometries

In the welded joints, the conventional welding procedures result in a small value of the weld toe and the weld root radius. By assuming such a radius equal to zero, the paper demonstrates the effectiveness of the Notch-stress intensity factor approach in summarising a number of experimental data from failures occurring at the weld toe. Then it is shown that fatigue data from failures originated from both weld roots and weld toes can be summarised in a single scatter band by using the mean value of the strain energy density in a well defined volume (area) surrounding the critical points. Finally, a simplified application of the NSIF approach based on finite element analyses carried out with coarse meshes is presented.     

Cycle-Based Rate Control for One-Way and Interactive Video Communications Over Wireless Channels

We propose a joint source-rate/channel-code control scheme for streaming video over a wireless channel. The scheme is designed to maximize the achievable source rate while guaranteeing an upper bound on the probability of starvation at the playback buffer. It can be applied to both one-way and interactive video communications. Rate control is performed adaptively on a per-cycle basis, where a cycle consists of a "good" channel period and the ensuing "bad" period. This cycle-based approach has two advantages. First, it reduces the fluctuations in the source bit rate, ensuring smooth variations in video quality. Second, it makes it possible to derive simple expressions for the starvation probability at the playback buffer, which we use to determine the optimal source rate and channel code for the good and bad periods of the subsequent cycle     

Current in vitro culture systems for Pneumocystis

Under oxidative stress normal hemoglobin (HbA) can trigger oxidation of low density lipoproteins (LDL) in the presence of hydrogen peroxide. Hb variants like isolated HbA chains possess higher peroxidative reactivity than the normal tetramer HbA. Because isolated Hb chains undergo fast autoxidation, a process yielding peroxidants, we studied the relative peroxidative activity of alpha- and beta-chains as well as of HbA without additional peroxidant. The descending order to relative oxidation of LDL protein ApoB (assessed by its crosslinking) and lipids (determined as formation of conjungated diens) was: alpha-chains > beta-chains > HbA. The results of our study indicate that extracellular chains may be the trigger of lipoproteins alterations observed in beta-thalassemia.     

The Peak Stress Method applied to fatigue assessments of steel tubular welded joints subject to mode-I loading

The paper presents the practical aspects involved in structural design of tubular joints mainly employed in roller coasters manufacturing. Different design standards, commonly adopted in fatigue assessments, are considered and compared. Then some constant amplitude fatigue test results concerning typical tubular welded joints are presented. Finally the experimental results and additional test data taken from the literature are compared with the theoretical estimations based on the Peak Stress Method, which has been recently conceived and proposed as a simplified, application-oriented version of the well known Notch-Stress Intensity Factor approach. The results indicate that the Peak Stress Method is suitable to estimate the fatigue life up to crack initiation of tubular welded joints subject to mode-I loading.     

A spatio-temporal concealment technique using boundary matchingalgorithm and mesh-based warping (BMA-MBW)

The transmission of block-coded visual information over packet networks introduces fidelity problems in terms of data losses, which result in wrong reconstruction of block sequences at the decoder. Concealment techniques aim at masking the visual effect of these errors, by exploiting either spatial or temporal available information. Both temporal and spatial approaches present drawbacks: the first is in general inefficient in handling complex or fast objects' motion, while the second is computationally expensive and is not able to recover high-frequency contents and small details. In this paper, a new solution is proposed that combines temporal and spatial approaches. The technique first replaces the lost block with the best matching pattern in a previously decoded frame (BMA), using the border information, and then applies a mesh-based warping (MBW) that reduces the artifacts caused by fast movements, rotations or deformations. The first step is achieved by a fast matching algorithm, for a high precision is not needed, while the second step uses an affine transform applied to a deformable mesh structure. Experimental results show that significant improvements can be achieved in comparison with traditional spatial or temporal concealment approaches, in terms of both subjective and objective reconstruction quality