Photo Sequencing

A group of people taking pictures of a dynamic event with their mobile phones is a popular sight. The set of still images obtained this way is rich in dynamic content but lacks accurate temporal information. We propose a method for photo-sequencing—temporally ordering a set of still images taken asynchronously by a set of uncalibrated cameras. Photo-sequencing is an essential tool in analyzing (or visualizing) a dynamic scene captured by still images. The first step of the method detects sets of corresponding static and dynamic feature points across images. The static features are used to determine the epipolar geometry between pairs of images, and each dynamic feature votes for the temporal order of the images in which it appears. The partial orders provided by the dynamic features are not necessarily consistent, and we use rank aggregation to combine them into a globally consistent temporal order of images. We demonstrate successful photo-sequencing on several challenging collections of images taken using a number of mobile phones.     

Threading fundamental matrices

We present a new function that operates on fundamental matrices across a sequence of views. The operation, we call “threading”, connects two consecutive fundamental matrices using the trifocal tensor as the connecting thread. The threading operation guarantees that consecutive camera matrices are consistent with a unique 3D model, without ever recovering a 3D model. Applications include recovery of camera ego-motion from a sequence of views, image stabilization across a sequence, and multi-view image based rendering     

Attachment theory and rections to others' needs: Evidence that activiation of the sense of attachment security promotes empathic responses.

Five studies examined the effects of chronic and contextual activation of attachment security on reactions to others' needs. The sense of attachment security was contextually primed by asking participants to recollect personal memories, read a story, or look at a picture of supportive others or by subliminally exposing them to proximity-related words. This condition was compared against the priming of neutral themes, positive affect, or attachment-insecurity schemas. Then reports of empathy and personal distress or the accessibility of empathy and personal-distress memories were assessed. Attachment-security priming strengthened empathic reactions and inhibited personal distress. Self-reports of attachment anxiety and avoidance were inversely related to empathy, and attachment anxiety was positively related to personal distress. The discussion emphasizes the relevance of attachment theory for explaining reactions to others' needs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Bed expansion in high velocity fluidization

Bed expansion of fine powders was investigated in two high aspect ratio fluid beds, an expanded top bed and a circulating system. The range of gas velocities (0.07 – 8 m/s) spanned the bubbling/slugging, turbulent, fast, and dense conveying fluidization regimes. The two-phase theory was shown generally not to apply in the slugging and the higher velocity fluidization regimes. A modified Richardson-Zaki approach, using an ‘effective’ cluster terminal velocity, was shown to adequately describe bed expansion. Changes in slope of the expansion curve were associated with regime changes, and can prove useful for the analysis of large diameter fluid beds. The effect of particle size distribution was shown to be considerable.     

Trajectory triangulation: 3D reconstruction of moving points from amonocular image sequence

We consider the problem of reconstructing the 3D coordinates of a moving point seen from a monocular moving camera, i.e., to reconstruct moving objects from line-of-sight measurements only. The task is feasible only when some constraints are placed on the shape of the trajectory of the moving point. We coin the family of such tasks as “trajectory triangulation.” We investigate the solutions for points moving along a straight-line and along conic-section trajectories, We show that if the point is moving along a straight line, then the parameters of the line (and, hence, the 3D position of the point at each time instant) can be uniquely recovered, and by linear methods, from at least five views. For the case of conic-shaped trajectory, we show that generally nine views are sufficient for a unique reconstruction of the moving point and fewer views when the conic is of a known type (like a circle in 3D Euclidean space for which seven views are sufficient). The paradigm of trajectory triangulation, in general, pushes the envelope of processing dynamic scenes forward. Thus static scenes become a particular case of a more general task of reconstructing scenes rich with moving objects (where an object could be a single point)     

Probably Approximately Symmetric: Fast Rigid Symmetry Detection With Global Guarantees

We present a fast algorithm for global rigid symmetry detection with approximation guarantees. The algorithm is guaranteed to find the best approximate symmetry of a given shape, to within a user‐specified threshold, with very high probability. Our method uses a carefully designed sampling of the transformation space, where each transformation is efficiently evaluated using a sublinear algorithm. We prove that the density of the sampling depends on the total variation of the shape, allowing us to derive formal bounds on the algorithm's complexity and approximation quality. We further investigate different volumetric shape representations (in the form of truncated distance transforms), and in such a way control the total variation of the shape and hence the sampling density and the runtime of the algorithm. A comprehensive set of experiments assesses the proposed method, including an evaluation on the eight categories of the COSEG data set. This is the first large‐scale evaluation of any symmetry detection technique that we are aware of.     

Large blue shift of the biexciton state in tellurium doped CdSe colloidal quantum dots

The exciton-exciton interaction energy of tellurium doped CdSe colloidal quantum dots is experimentally investigated. The dots exhibit a strong Coulomb repulsion between the two excitons, which results in a huge measured biexciton blue shift of up to 300 meV. Such a strong Coulomb repulsion implies a very narrow hole wave function localized around the defect, which is manifested by a large Stokes shift. Moreover, we show that the biexciton blue shift increases linearly with the Stokes shift. This result is highly relevant for the use of colloidal QDs as optical gain media, where a large biexciton blue shift is required to obtain gain in the single exciton regime.     

Novel view synthesis by cascading trilinear tensors

Presents a new method for synthesizing novel views of a 3D scene from two or three reference images in full correspondence. The core of this work is the use and manipulation of an algebraic entity, termed the “trilinear tensor”, that links point correspondences across three images. For a given virtual camera position and orientation, a new trilinear tensor can be computed based on the original tensor of the reference images. The desired view can then be created using this new trilinear tensor and point correspondences across two of the reference images