Evalvid-RA: trace driven simulation of rate adaptive MPEG-4 VBR video

Due to the increasing deployment of conversational real-time applications like VoIP and videoconferencing, the Internet is today facing new challenges. Low end-to-end delay is a vital QoS requirement for these applications, and the best effort Internet architecture does not support this natively. The delay and packet loss statistics are directly coupled to the aggregated traffic characteristics when link utilization is close to saturation. In order to investigate the behavior and quality of such applications under heavy network load, it is therefore necessary to create genuine traffic patterns. Trace files of real compressed video and audio are text files containing the number of bytes per video and audio frame. These can serve as material to construct mathematical traffic models. They can also serve as traffic generators in network simulators since they determine the packet sizes and their time schedule. However, to inspect perceived quality, the compressed binary content is needed to ensure decoding of received media. The EvalVid streaming video tool-set enables this using a sophisticated reassembly engine. Nevertheless, there has been a lack of research solutions for rate adaptive media content. The Internet community fears a congestion collapse if the usage of non-adaptive media content continues to grow. This paper presents a solution named Evalvid-RA for the simulation of true rate adaptive video. The solution generates real rate adaptive MPEG-4 streaming traffic, using the quantizer scale for adjusting the sending rate. A feedback based VBR rate controller is used at simulation time, supporting TFRC and a proprietary congestion control system named P-AQM. Example ns-2 simulations of TFRC and P-AQM demonstrate Evalvid-RA’s capabilities in performing close-to-true rate adaptive codec operation with low complexity to enable the simulation of large networks with many adaptive media sources on a single computer.     

Mass Transport in Shallow Turbulent Wake Flow by Planar Concentration Analysis Technique

A planar concentration analysis (PCA) system is used for observing the transport and mixing of a tracer mass in a shallow turbulent free-surface wake flow of a large cylindrical obstacle. The nonintrusive, fieldwise PCA measuring technique is applied to evaluate depth-averaged mass concentrations by making use of light attenuation due to absorption and scattering processes related to a dissolved tracer mass. The scalar fields are decomposed into a low-frequency quasiperiodic part, the coherent flow, and a randomly fluctuating part. From accompanying near-surface velocity measurements, large-scale coherent structures are identified and related to the coherent mass fields. This allows one to assess the role of the large-scale vortices for advection and diffusion in shallow wake flows. The time–mean wake flow displays a self-similar spanwise distribution both for mass and velocity. The longitudinal development of shallow wakes initially shows the growth of unbounded wakes; in the wake far field an attenuated behavior applies.     

Examinations of Dimethyl Sulfoxide-Phase Equilibrium Acidities of Selected Polycyclic Aromatic Compounds

Comparisons of dimethyl sulibxide (DMSO)-phase pK _a's (in parentheses) for 10-cyano-9-methoxymethy-lanthracene (17.35), 10-cyano-9-phenoxymethylanthracene (14.9), 9-cyanomethoxymethylanthracene (20.4), and (α-methoxy) phenylacetonitrile (23.0) with literature DMSO-phase pK _a's for 9-methylanth-racene, 9-methoxymethylanthracene, 9-phenoxymethylanthracene, 9-cyanomethylanthracene, 10-cyano-9-methylanthracene, and phenylacetonitrile (31.1, 30.6, 30.2, 19.7, 20.0, and 21.9, respectively), indicate that: (a) α-methoxy and α-phenoxy substituents acidify 10-cyano-9-methylanthracene; (b) an α-methoxy moiety deacidifies 9-cyanomethylanthracene and phenylacetonitrile; and (c) 10-cyano substituents acidify 9-methylanthracene, 9-methoxymethylanthracene, and 9-phenoxymethylanthracene by 11.1, 13.25, and 15.3 pK _a units, respectively. These data are indicative of steric inhibition of resonance, resonance saturation, and effects due to cross conjugation, in carbanions derived from variously substituted 9-methylanthracenes. DMSO-phase pK _a for phenalene (18.2) and benzanthrene (20.2) have also been determined. In DMSO, phenalene is therefore 4.4 pK units more acidic than its isomeric analogue fluorene (22.6), while benzanthrene is 0.5 pK units less acidic than its isomeric analogue 1,2-benzofluorene (19.7). Specific solvation of the allylic-like phenalenide anion is a likely reason for its enhanced acidity, relative to benzanthrene.     

Estimation of mass transfer velocity based on measured turbulence parameters

The aim of this study is to quantify the mass transfer velocity using turbulence parameters from simultaneous measurements of oxygen concentration fields and velocity fields. The surface divergence model was considered in more detail, using data obtained for the lower range of β (surface divergence). It is shown that the existing models that use the divergence concept furnish good predictions for the transfer velocity also for low values of β, in the range of this study. Additionally, traditional conceptual models, such as the film model, the penetration‐renewal model, and the large eddy model, were tested using the simultaneous information of concentration and velocity fields. It is shown that the film and the surface divergence models predicted the mass transfer velocity for all the range of the equipment Reynolds number used here. The velocity measurements showed viscosity effects close to the surface, which indicates that the surface was contaminated with some surfactant. Considering the results, this contamination can be considered slight for the mass transfer predictions. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

A method for electrochemical growth of homogeneous nanocrystalline ZnO thin films at room temperature

We report the electrodeposition at room temperature (25 °C), in a potentiostatic mode, of cohesive nanocrystalline ZnO thin films from an oxygenated zinc chloride bath. It is shown that the bath saturation by molecular oxygen precursor is a key parameter to grow the oxide at low temperature. After low O₂ bubbling the solution is not saturated and the surface is more or less passivated by an amorphous Zn(OH)₂ veil-like thin layer. After intense and long molecular oxygen bubbling, the current density rapidly increases after an induction period of about 800 s. At the foot of the current onset, crystallized ZnO seeds appear entrapped in the initial amorphous layer. The film nucleation is a delayed process. The electrode is subsequently covered by a homogeneous ZnO film with structures of several hundreds of nanometers in length composed of nanocrystals with size of about 17 nm. The room-temperature photoluminescence spectrum of the film is dominated by a strong UV emission at 3.25 eV due to the recombination of excitons. The visible emission centered at 2.36 eV, due to deep defects, is less intense than the UV one showing the good structural quality of the ZnO nanocrystallized film. The films have interesting properties to be used as a seed layer for instance.     

Relationships between the normalised difference vegetation index and temperature fluctuations in post-mining sites

The effects of age, vegetation density (normalised difference vegetation index [NDVI]) and vegetation type on temperature fluctuations were studied in post-coal-mining sites in the Czech Republic. NDVI and surface temperature were obtained from an airborne multispectral aerial photograph and FLIR infrared camera. The difference between morning and afternoon temperature was assumed as a measure of the temperature buffering ability of the ecosystem. Buffering increased with increasing NDVI but also depended on the type of vegetation, reclaimed sites have significantly higher buffering than unreclaimed sites. In contrary to grasslands, woody vegetation gradually increased temperature buffering capacity with plot age. Topsoil application substantially increased buffering capacity.     

Positioning narratives of wine tourism websites: a lexical analysis across two different regions

Wine tourism is becoming an increasingly important tourism niche with various regions competing for tourism dollars. It is often assumed that differentiation in the sector is region based. This research investigates the positioning narratives from websites of a sample of top wine tour service firms across the US and Australia. Analysis is undertaken using an innovative methodology that combines computer-based lexical analysis followed by hierarchical clustering on principal components. The research seeks to determine the extent to which identified clusters are region based and whether the positioning narratives on websites can provides useful clusters across regions. Results are reported, implications are discussed, limitations are noted and possible areas for further research are indicated.     

On the role of Nb-related sites of an oxidized β-TiNb alloy surface in its interaction with osteoblast-like MG-63 cells

β-Stabilized titanium (Ti) alloys containing non-toxic elements, particularly niobium (Nb), are promising materials for the construction of bone implants. Their biocompatibility can be further increased by oxidation of their surface. Therefore, in this study, the adhesion, growth and viability of human osteoblast-like MG 63 cells in cultures on oxidized surfaces of a β-TiNb alloy were investigated and compared with the cell behavior on thermally oxidized Ti, i.e. a metal commonly used for constructing bone implants. Four experimental groups of samples were prepared: Ti or TiNb samples annealed to 600 °C for 60 min in a stream of dry air, and Ti and TiNb samples treated in Piranha solution prior to annealing. We found that on all TiNb-based samples, the cell population densities on days 1, 3 and 7 after seeding were higher than on the corresponding Ti-based samples. As revealed by XPS and Raman spectroscopy, and also by isoelectric point measurements, these results can be attributed to the presence of T-Nb₂O₅ oxide phase in the surface of the alloy sample, which decreased its negative zeta (ζ)-potential in comparison with zeta (ζ)-potential of the Ti sample at physiological pH. This effect was tentatively explained by the presence of positively charged defects acting as Lewis sites of the surface Nb₂O₅ phase. Piranha treatment slightly decreases the biocompatibility of the samples, which for the alloy samples may be explained by a decrease in the number of defective sites with this treatment. Thus, the presence of Nb and thermal oxidation of β-stabilized Ti alloys play a significant role in the increased biocompatibility of TiNb alloys.     

Linear Fresnel lenses, their design and use

A linear Fresnel lens (LFL) designed according to Fermat's principle is slightly modified with respect to used technology for mass production from glass. Manufactured Fresnel lenses are used in a fully tracking concentrating collector with aperture about 36 m² and in a collector with stationary concentrator and movable absorber, which may serve as solar collector with temperature and illumination control. A combination of linear Fresnel lenses with PV cells may reduce cost of autonomous solar installations.