Hierarchical structure-and-motion recovery from uncalibrated images

This paper addresses the structure-and-motion problem, that requires to find camera motion and 3D struc- ture from point matches. A new pipeline, dubbed Samantha, is presented, that departs from the prevailing sequential paradigm and embraces instead a hierarchical approach. This method has several advantages, like a provably lower computational complexity, which is necessary to achieve true scalability, and better error containment, leading to more stability and less drift. Moreover, a practical autocalibration procedure allows to process images without ancillary information. Experiments with real data assess the accuracy and the computational efficiency of the method.Comment: Accepted for publication in CVI

Method for 3D modelling based on structure from motion processing of sparse 2D images

A method based on Structure from Motion for processing a plurality of sparse images acquired by one or more acquisition devices to generate a sparse 3D points cloud and of a plurality of internal and external parameters of the acquisition devices includes the steps of collecting the images; extracting keypoints therefrom and generating keypoint descriptors; organizing the images in a proximity graph; pairwise image matching and generating keypoints connecting tracks according maximum proximity between keypoints; performing an autocalibration between image clusters to extract internal and external parameters of the acquisition devices, wherein calibration groups are defined that contain a plurality of image clusters and wherein a clustering algorithm iteratively merges the clusters in a model expressed in a common local reference system starting from clusters belonging to the same calibration group; and performing a Euclidean reconstruction of the object as a sparse 3D point cloud based on the extracted parameters

Contribuição ao Estudo dos Sedimentos da Região Estreito de Brainsfield (Antártica)

Com o propósito de contribuir para um melhor conhecimento da sedimentação glacial e glacio-marinha na região próxima a Estação Brasileira “Comandante Ferraz”, amostras superficiais e de testemunhos, obtidas durante a Operação “Deep Freeze 82” (USA) e “Antártica IV” (Brasil), foram analisadas. Depósitos não selecionados produzidos por ação direta do gelo (ortotil) gelo flutuante e ação de correntes (paratil), fluxos gravitacionais (fluxos de massa, fluxo de fragmentos e correntes de turbidez) constituem os principais depósitos ocorrentes ao longo da plataforma, declive e elevação continentais. Lamas e vasas biogênicas silicosas, lamas terrígenas laminadas e sedimentos vulcanoclásticos são igualmente importantes entre os depósitos identificados na margem continental Antártica

Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition)

In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. For example, a key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process versus those that measure fl ux through the autophagy pathway (i.e., the complete process including the amount and rate of cargo sequestered and degraded). In particular, a block in macroautophagy that results in autophagosome accumulation must be differentiated from stimuli that increase autophagic activity, defi ned as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (inmost higher eukaryotes and some protists such as Dictyostelium ) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the fi eld understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. It is worth emphasizing here that lysosomal digestion is a stage of autophagy and evaluating its competence is a crucial part of the evaluation of autophagic flux, or complete autophagy. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. Along these lines, because of the potential for pleiotropic effects due to blocking autophagy through genetic manipulation it is imperative to delete or knock down more than one autophagy-related gene. In addition, some individual Atg proteins, or groups of proteins, are involved in other cellular pathways so not all Atg proteins can be used as a specific marker for an autophagic process. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field

Efficient coverage optimization in energy-constrained Wireless Sensor Networks

We consider the problem of optimizing the area coverage of a wireless sensor network under energy consumption constraints. Following existing approaches, we use a mixed integer linear program formulation. We then show how to use partitioning techniques, developed in the context of VLSI place and route, to decompose the problem into separate sub-problems, overcoming the exponential complexity typical of integer linear programming, while minimizing the loss in optimality. In addition, we are able to evaluate the achieved degree of optimality by computing relatively tight bounds with respect to the optimal solution. Finally, we employ simple but effective heuristics to further improve our solution. The results show that our procedure is very efficient and is able to find solutions that are very close to optimal

Towards automatic acquisition of high-level 3D models from images

Nei tempi recenti abbiamo assistito a un crescente interesse nella modellazione automatica da immagine. Mentre gli studi recenti nell'ambito della ricostruzione tridimensionale si sono concentrata soprattutto sull'estrazione di rappresentazioni dense e accurate di oggetti catturati tramite foto o video, il sostenuto interesse verso software di modellazione accessibile \ue8 una forte riprova del grande bisogno di rappresentazioni astratte e compatte degli oggetti. In questa tesi, il problema dell'estrazione di modelli di alto livello a partire dalle immagini viene discusso in dettaglio. Nella prima parte viene introdotta una pipeline di "Structure from Motion". A partire dai risultati di tale pipeline, vengono studiati due differenti approcci per la generazione di modelli di alto livello. Nel primo approccio viene innanzitutto introdotto un nuovo algoritmo di stereo multivista per produrre una nuvola di punti densa e accurata. Successivamente viene presentato un sistema di ricerca e reperimento di mesh, basato su segmentazione e un algoritmo di tipo "Bag of Words". Nel secondo approccio, la nuvola di punti sparsa proveniente dalla pipeline di "Structure from Motion" viene descritta da piani e aree planari convesse. Le aree planari sono una rappresentazione compatta e intermedia della scena. Entrambe le parti della tesi mirano ad assottigliare il divario tra acquisizione e interpretazione di una scena, attraverso la definizione di rappresentazioni ad alto livello ottenute tramite strategie molto diverse tra loro.In recent years there has been a surge of interest in automatic modeling from images. While the current state of the art in three-dimensional reconstruction has focused on the recovery of dense and accurate representations of objects imaged through pictures or video, the sustained interest in accessible modeling software is a strong evidence of an untapped general need for compact, abstract representations of objects. In this thesis, the problem of producing high level models starting from images is discussed in details. In the first part, an automatic uncalibrated Structure from Motion pipeline is presented. Starting from the output of the pipeline, two different approaches of generating high-level renditions are studied. The first approach employs a novel Multiple view Stereo algorithm to produce a dense and accurate point cloud. A retrieval system for meshes, based on segmentation and Bag of Words, is then introduced. In the latter approach, the sparse Structure from Motion point cloud is fitted by planes and planar patches. Planar patches are a compact, intermediate representation of the scene. Both branches of the thesis aim to narrow the gap between scene acquisition and interpretation, through the definition of high level renditions produced by very different strategies

Real-time Incremental J-linkage for Robust Multiple Structures Estimation

This paper describes an incremental, real-time implementation of J-linkage, a procedure that can detect multiple instances of a model from data corrupted by noise and outliers. The method is incremental, as it exploits the information extracted in the previous steps and processes the data as they become available. It works in real-time, thanks to several approximations that have been introduced to get around the quadratic complexity of the original algorithm. Tests have been carried out both with synthetic data and real data. 1