Robust non-blind color video watermarking using QR decomposition and entropy analysis

Issues such as content identification, document and image security, audience measurement, ownership and copyright among others can be settled by the use of digital watermarking. Many recent video watermarking methods show drops in visual quality of the sequences. The present work addresses the aforementioned issue by introducing a robust and imperceptible non-blind color video frame watermarking algorithm. The method divides frames into moving and non-moving parts. The non-moving part of each color channel is processed separately using a block-based watermarking scheme. Blocks with an entropy lower than the average entropy of all blocks are subject to a further process for embedding the watermark image. Finally a watermarked frame is generated by adding moving parts to it. Several signal processing attacks are applied to each watermarked frame in order to perform experiments and are compared with some recent algorithms. Experimental results show that the proposed scheme is imperceptible and robust against common signal processing attacks.     

Spatial quality index based rate perceptual-distortion optimization for video coding

Spatial Quality Index (SQI) is a recently proposed video quality assessment metric that can predict video quality much close to subjective judgments. Since current video coding still has much redundancy in the sense of visual perception, in this paper, we incorporate SQI into video coding to further improve compression ratio without visual quality loss. Firstly, contributions of different human visual system (HVS) properties used in SQI are analyzed. Then two most important HVS properties, i.e. contrast masking effect (CME) and motion masking effect (MME), are extracted to measure perceptual-distortion D_p in video coding. Finally, based on D_p, a rate perceptual-distortion optimization (RpDO) algorithm is presented by adopting a suitable Lagrange multiplier from previous study. Experimental results show that, RpDO can averagely achieve 14% bitrate reduction when compared to HM14.0 under the same visual quality. At the same time, there is no significant change in the encoding time.     

Modeling ball impact on the wet mill liners and its application in predicting mill magnetic liner performance

Numerous studies have been conducted in the past and models have been developed to simulate ball motions in horizontal mills. Equations and computer programs have been published to calculate falling velocity of the grinding media upon impacting the mill shell (liner). However, these equations and programs are only suitable for dry mill applications.To accurately simulate the impact of falling balls on the liners in wet mills, the authors have developed models to determine the ball impact location and velocity as the ball contacts the mill liner. Drag and buoyancy forces are considered when the ball submerges in the pulp inside the mill. Models can be used to enhance mill liner design and optimize the operation of horizontal wet mills such as horizontal ball mills.The models are applied to calculate the falling ball impact on the metal magnetic mill liners. Various scenarios are simulated and results are used to predict the performance of magnetic mill liners in various ball mill applications.     

Use of computational fluid dynamics to model reservoir mixing and destratification

Destratification of reservoirs by the use of artificial mixing is a method of improving the impounded water quality. In order to design a destratification device at Stocks Reservoir, NW England, a Computational Fluid Dynamics model was used to trial different types and sizes of mixing device. It was found that a perforated pipe bubble mixing device performed far better than a large banana blade mixer at destratifying Stocks Reservoir. Two important criteria for the effective operation of a mixing device were established. These were a minimum upflow velocity of entrained water through the reservoir, and the need for a reverse flow along the surface of the reservoir away from the abstraction point. These criteria have been incorporated into design equations which can be extended to use at other reservoirs. A bubble mixer was installed at Stocks Reservoir, and has been shown to fully destratify the reservoir and to reduce the levels of dissolved manganese in the water by more than 50%.     

Tertiary creep in nickel-base superalloys: analysis of experimental data and theoretical synthesis

It has recently been established that the extended period of tertiary creep of nickelbase superalloys with good ductility is not primarily a consequence of the thermal instability of the particulate microstructure: rather it is believed to be caused by a strain-induced instability of the dislocation substructure. The instability appears to be intrinsic to this class of alloy and the resulting isotropicallyaccelerating creep rate can be represented by a scalar parameter in constitutive laws. Evidence is presented to suggest that a similar strain-induced instability operates in certain low alloy ferritic steels and precipitation-hardened aluminium alloys. The micromechanism responsible for this intrinsic instability is still a matter for speculation, but recently it was suggested that, for NiCr alloys hardened with aluminium and titanium, the acceleration in strain accumulation may be influenced by the volume fraction of γ′ particles and by the magnitude of their lattice-parameter mismatch with the matrix. In this paper, a more substantial range of data for alloys of this type is presented and it is concluded that ductility in creep is the most significant parameter correlating differences in rates of strain-accumulation in the tertiary stage: thus, the lower the ductility the greater the rate of strain-accumulation. The various shapes of uniaxial creep curve found in nickel-base superalloys have been synthesised quantitatively by developing a model with two internal state-variables: one represents damage caused by the intrinsic instability while the other represents damage caused by cavitation. The model accounts for the engineering classification of alloys into so-called “von-Mises type” and “maximum principal stress type” and also rationalises the previously unexplained fact that there is no unique correlation between this classification and uniaxial ductility in creep.     

The effect of external stress on the discontinuous precipitation in an AlZn alloy at high and low temperatures

The effect of external tensile stress on continuous precipitation (DP) has been investigated in an Al21.8 at.% Zn alloy at high (215°C) and low (75 and 50°C) temperatures. The ratio of the macroscopic lattice diffusivity, D, to the DP boundary velocity, v, (D/v) is estimated to be larger than the interatomic spacing, λ, at the high temperature, and smaller than λ at the low temperatures. Under tensile stresses, the DP rates are enhanced at the grain boundary segments oriented transverse to the stress direction and suppressed at those oriented parallel to it at both high and low temperatures. Furthermore, Yi and Park show the DP rate changing continuously with temperature over the range where D/v increased from values much smaller than λ to those much larger. These results show that the diffusional coherency strain is the major driving force for DP even at low temperatures where, with D/v < λ, no solute diffusion is usually assumed to occur in front of the moving DP boundaries.     

Visualization of CFD results in immersive virtual environments

An object-oriented event-driven immersive virtual environment (VE) is described for the visualization of computational fluid dynamics (CFD) results. The VE incorporates the following types of primitive software objects: interface objects, support objects, geometric entities, and finite elements. The fluid domain is discretized using either a multi-block structured grid or an unstructured finite element mesh. The VE allows natural ‘fly-through’ visualization of the model, the CFD grid, and the model's surroundings. In order to help visualize the flow and its effects on the model, the VE incorporates the following objects: stream objects (lines, surface-restricted lines, ribbons, and volumes); colored surfaces; elevation surfaces; surface arrows; global and local iso-surfaces; vortex cores; and separation/attachment surfaces and lines. Most of these objects can be used for dynamically probing the flow. Particles and arrow animations can be displayed on top of stream objects. Primitive response quantities as well as derived quantities can be used. A recursive tree search algorithm is used for real-time point and value search in the CFD grid.