Fast Bayesian Optimal Experimental Design for Seismic Source Inversion

We develop a fast method for optimally designing experiments in the context of statistical seismic source inversion. In particular, we efficiently compute the optimal number and locations of the receivers or seismographs. The seismic source is modeled by a point moment tensor multiplied by a time-dependent function. The parameters include the source location, moment tensor components, and start time and frequency in the time function. The forward problem is modeled by elastodynamic wave equations. We show that the Hessian of the cost functional, which is usually defined as the square of the weighted L2 norm of the difference between the experimental data and the simulated data, is proportional to the measurement time and the number of receivers. Consequently, the posterior distribution of the parameters, in a Bayesian setting, concentrates around the "true" parameters, and we can employ Laplace approximation and speed up the estimation of the expected Kullback-Leibler divergence (expected information gain), the optimality criterion in the experimental design procedure. Since the source parameters span several magnitudes, we use a scaling matrix for efficient control of the condition number of the original Hessian matrix. We use a second-order accurate finite difference method to compute the Hessian matrix and either sparse quadrature or Monte Carlo sampling to carry out numerical integration. We demonstrate the efficiency, accuracy, and applicability of our method on a two-dimensional seismic source inversion problem

Low-rank SIFT: An Affine Invariant Feature for Place Recognition

In this paper, we present a novel affine-invariant feature based on SIFT, leveraging the regular appearance of man-made objects. The feature achieves full affine invariance without needing to simulate over affine parameter space. Low-rank SIFT, as we name the feature, is based on our observation that local tilt, which are caused by changes of camera axis orientation, could be normalized by converting local patches to standard low-rank forms. Rotation, translation and scaling invariance could be achieved in ways similar to SIFT. As an extension of SIFT, our method seeks to add prior to solve the ill-posed affine parameter estimation problem and normalizes them directly, and is applicable to objects with regular structures. Furthermore, owing to recent breakthrough in convex optimization, such parameter could be computed efficiently. We will demonstrate its effectiveness in place recognition as our major application. As extra contributions, we also describe our pipeline of constructing geotagged building database from the ground up, as well as an efficient scheme for automatic feature selection

Live streaming viewing as functional alternatives to interpersonal interaction: who do you think he/she is?

Master of ScienceDepartment of Journalism and Mass CommunicationsAlec C. TefertillerBased on the Uses and Gratifications (U&G) approach and Parasocial Interaction (PSI) theory, this study examined how people use live streaming platforms in China. Uniquely, it sought to understand the effect of romantic relationships on how and why people watch Host Live Shows (HLSs) and explored the relationships between Chinese audiences and live- streamers. Through an online survey, four viewing motivations were identified: Community Building, Ego-boost, Escape, and Bandwagon. Ego-boost is a relatively new motivation of media use, which means audiences watch and interact with HLSs to get compliments, self-confidence, self- validation, and ego-boosts. This study found audiences’ perceived realism and PSI were both very neutral. However, emotion projection of audiences onto streamers was observed – most viewers highly agree that streamers are their friends. Moreover, this study found the quality of interpersonal communication is affecting audiences’ HLS dependence and the degree of PSI, while the quantity of interpersonal communication might not be – the more satisfied a person is about his/her interpersonal communication, the heavier he/she depends on HLSs and the stronger his/her PSI is. As expected, the degrees of both romantic relationship status and romantic relationship satisfaction influence people’s HLS use. While compared with females, males are affected by romantic relationships more, both the status and satisfaction level. Lastly, when it comes to people’s romantic lives and social lives, HLSs are more likely to be used as alternatives to meet their unsatisfied needs from their “real partners.

Two-copy Quantum Teleportation

We investigate two-copy scenario of quantum teleportation based on Bell measurements. The detailed protocol is presented and the general expression of the corresponding optimal teleportation delity is derived, which is given by the two-copy fully entangled fraction that is invariant under local unitary transformations. We prove that under a speci c case of the protocol, which is signi cant for improving the optimal delity, the set of states with their two-copy fully entangled fractions bounded by a threshold value that required for useful two-copy teleportation is convex and compact. Hence the witness operators exist to separate states that are useful for two-copy teleportation from the rest ones. Moreover, we show that the optimal delity of two-copy teleportation surpasses that of the original one copy teleportation.Comment: 8 pages, 2 figure

Path Planning Problems with Side Observations-When Colonels Play Hide-and-Seek

Resource allocation games such as the famous Colonel Blotto (CB) and Hide-and-Seek (HS) games are often used to model a large variety of practical problems, but only in their one-shot versions. Indeed, due to their extremely large strategy space, it remains an open question how one can efficiently learn in these games. In this work, we show that the online CB and HS games can be cast as path planning problems with side-observations (SOPPP): at each stage, a learner chooses a path on a directed acyclic graph and suffers the sum of losses that are adversarially assigned to the corresponding edges; and she then receives semi-bandit feedback with side-observations (i.e., she observes the losses on the chosen edges plus some others). We propose a novel algorithm, EXP3-OE, the first-of-its-kind with guaranteed efficient running time for SOPPP without requiring any auxiliary oracle. We provide an expected-regret bound of EXP3-OE in SOPPP matching the order of the best benchmark in the literature. Moreover, we introduce additional assumptions on the observability model under which we can further improve the regret bounds of EXP3-OE. We illustrate the benefit of using EXP3-OE in SOPPP by applying it to the online CB and HS games.Comment: Previously, this work appeared as arXiv:1911.09023 which was mistakenly submitted as a new article (has been submitted to be withdrawn). This is a preprint of the work published in Proceedings of the 34th AAAI Conference on Artificial Intelligence (AAAI

Reconstruction quasi-dense et modèles 3D à partir d'une séquence d'images

National audienceCe papier propose une reconstruction quasi-dense à partir d'une séquence d'images non calibrées ainsi qu'un système associé de reconstruction de modèles 3D. La principale innovation est que toute la géométrie est calculée à partir de mises en correspondances quasi-denses sous-échantillonnées au lieu des points d'intérets épars usuels. Cela produit non seulement une reconstruction plus précise (au sens des incertitudes) et plus robuste grace à des mises en correspondances bien redondantes et réparties dans les images, mais aussi une reconstruction plus adéquate (car plus dense) pour l'application de la reconstruction de surface. Des expériences sur des séquences réelles montrent de meilleures performances des reconstructions quasi-denses par rapport aux reconstructions éparses à la fois en robustesse et incertitudes. De plus, les surfaces des nombreux objets ont été obtenues à partir des points quasi-denses reconstruits

Atom Interferometry with up to 24-Photon-Momentum-Transfer Beam Splitters

We present up to 24-photon Bragg diffraction as a beam splitter in light-pulse atom interferometers to achieve the largest splitting in momentum space so far. Relative to the 2-photon processes used in the most sensitive present interferometers, these large momentum transfer beam splitters increase the phase shift 12-fold for Mach-Zehnder (MZ-) and 144-fold for Ramsey-Borde (RB-) geometries. We achieve a high visibility of the interference fringes (up to 52% for MZ or 36% for RB) and long pulse separation times that are possible only in atomic fountain setups. As the atom's internal state is not changed, important systematic effects can cancel.Comment: New introduction. 4 pages, 4 figure