Composite spectral shape descriptor

Effective spectral representations of shape region are proposed in literature. On the other hand, a significant spatial characteristic of shape region is shape contour because human beings discriminate shapes mainly by their contour features. It is proposed that a descriptor is obtained by complementing the spectral representation of shape region with the spectral representation of shape contour. Such a descriptor, obtained by explicitly combining two (or more) descriptors is termed composite descriptor. A composite descriptor is proposed; the effectiveness of the composite descriptor to represent shape region is evaluated.

Tracking single bubble in Hall-Héroult aluminium cell : an experimental and numerical study

In simulations of the hydrodynamics of the multiphase flow in gas– liquid systems with finite sizes of bubbles, the important thing is to compute explicitly the time evolution of the gas–liquid interface in many engineering applications. The most commonly used methods representing this approach are: the volume of fluid and the phase field methods. The later has gained significant interest because of its capability of performing numerical computations on a fixed Cartesian grid without having to parametrise these objects (Eulerian approach) and at the same time it allows to follow the interface ( for example bubble’s shape) that change the topology. In this paper, both numerical (phase field method) and experimental results for the bubble shapes underneath a downward facing plane is presented. Experiments are carried out to see the bubble sliding motion underneath a horizontal and inclined anode. It is assumed that the bubble formed under the anode surface is deformed (flattened) due to buoyant field before it goes around the anode corner. The bubble elongates to form a tail-like shape. The change in shape of the bubble is almost instantaneous and has a significant effect on the localised hydrodynamics around the bubble, which could influence the dynamics of the flow patterns in the Hall–Héroult cell. This deformation is the main cause of the bubble wake and the induced flow field in the aluminium cell. Various parameters such as bubble size, deformation and its sliding mechanism at different surface tensions are discussed and compared with experimental results.

Temperature variations at nano-scale level in phase transformed nanocrystalline NiTi shape memory alloys adjacent to graphene layers

The detection and control of the temperature variation at the nano-scale level of thermo-mechanical materials during a compression process have been challenging issues. In this paper, an empirical method is proposed to predict the temperature at the nano-scale level during the solid-state phase transition phenomenon in NiTi shape memory alloys. Isothermal data was used as a reference to determine the temperature change at different loading rates. The temperature of the phase transformed zone underneath the tip increased by _3 to 40 _C as the loading rate increased. The temperature approached a constant with further increase in indentation depth. A few layers of graphene were used to enhance the cooling process at different loading rates. Due to the presence of graphene layers the temperature beneath the tip decreased by a further _3 to 10 _C depending on the loading rate. Compared with highly polished NiTi, deeper indentation depths were also observed during the solidstate phase transition, especially at the rate dependent zones. Larger superelastic deformations confirmed that the latent heat transfer through the deposited graphene layers allowed a larger phase transition volume and, therefore, more stress relaxation and penetration depth.

On anomalous depth-dependency of the hardness of NiTi shape memory alloys in spherical nanoindentation

An experimental study on the indentation hardness of NiTi shape memory alloys (SMAs) by using a spherical indenter tip and a finite element investigation to understand the experimental results are presented in this paper. It is shown that the spherical indentation hardness of NiTi SMAs increases with the indentation depth. The finding is contrary to the recent study on the hardness of NiTi SMAs using a sharp Berkovich indenter tip, where the interfacial energy plays a dominant role at small indentation depths. Our numerical investigation indicates that the influence of the interfacial energy is not significant on the spherical indentation hardness of SMAs. Furthermore, the depth dependency of SMA hardness under a spherical indenter is explained by the elastic spherical contact theory incorporating the deformation effect of phase transformation of SMAs. Hertz theory for purely elastic contact shows that the spherical hardness increases with the square root of the indentation depth. The phase transformation beneath the spherical tip weakens the depth effect of a purely elastic spherical hardness. This study enriches our knowledge on the basic concept of hardness for SMAs under spherical indentation at micro- and nanoscales.

Shape evolution of silver nanoplates through heating and photoinduction

Shape conversions of silver nanoplates were realized by heating and subsequent light irradiation. The initial silver nanoprisms were transformed into silver nanodisks gradually in the process of heating, which was possibly achieved through dissolving and readsorption of silver atoms on the surface of silver nanoplates. Subsequently, under light irradiation, the heating induced silver nanodisks were reversed to silver nanoprisms in the same solution. The dissolved oxygen was found to play a pivotal role in the shape conversion from nanoprism to nanodisk. In addition to heating, deionized water could induce the shape conversion of silver nanoplates when it was added to precipitate of the initial silver nanoprisms after centrifugation. Citrate in solution is essential to the photoinduced shape conversion process. Transmission electron microscopy (TEM) and extinction spectroscopy results demonstrated that localized surface plasmon resonance (LSPR) properties of silver nanoplates were effectively tuned through shape conversion.

Face Recognition from Video Using the Generic Shape-Illumination Manifold

In spite of over two decades of intense research, illumination and pose invariance remain prohibitively challenging aspects of face recognition for most practical applications. The objective of this work is to recognize faces using video sequences both for training and recognition input, in a realistic, unconstrained setup in which lighting, pose and user motion pattern have a wide variability and face images are of low resolution. In particular there are three areas of novelty: (i) we show how a photometric model of image formation can be combined with a statistical model of generic face appearance variation, learnt offline, to generalize in the presence of extreme illumination changes; (ii) we use the smoothness of geodesically local appearance manifold structure and a robust same-identity likelihood to achieve invariance to unseen head poses; and (iii) we introduce an accurate video sequence “reillumination” algorithm to achieve robustness to face motion patterns in video. We describe a fully automatic recognition system based on the proposed method and an extensive evaluation on 171 individuals and over 1300 video sequences with extreme illumination, pose and head motion variation. On this challenging data set our system consistently demonstrated a nearly perfect recognition rate (over 99.7%), significantly outperforming state-of-the-art commercial software and methods from the literature