Search results for "projection"
showing 10 items of 378 documents
Design of Asymmetric Shift Operators for Efficient Decentralized Subspace Projection
2021
A large number of applications in decentralized signal processing includes projecting a vector of noisy observations onto a subspace dictated by prior information about the field being monitored. Accomplishing such a task in a centralized fashion in networks is prone to a number of issues such as large power consumption, congestion at certain nodes and suffers from robustness issues against possible node failures. Decentralized subspace projection is an alternative method to address those issues. Recently, it has been shown that graph filters (GFs) can be implemented to perform decentralized subspace projection. However, most of the existing methods have focused on designing GFs for symmetr…
Reservoir computing model of prefrontal cortex creates novel combinations of previous navigation sequences from hippocampal place-cell replay with sp…
2019
As rats learn to search for multiple sources of food or water in a complex environment, they generate increasingly efficient trajectories between reward sites. Such spatial navigation capacity involves the replay of hippocampal place-cells during awake states, generating small sequences of spatially related place-cell activity that we call “snippets”. These snippets occur primarily during sharp-wave-ripples (SWRs). Here we focus on the role of such replay events, as the animal is learning a traveling salesperson task (TSP) across multiple trials. We hypothesize that snippet replay generates synthetic data that can substantially expand and restructure the experience available and make learni…
Salient Pixels and Dimensionality Reduction for Display of Multi/Hyperspectral Images
2012
International audience; Dimensionality Reduction (DR) of spectral images is a common approach to different purposes such as visualization, noise removal or compression. Most methods such as PCA or band selection use either the entire population of pixels or a uniformly sampled subset in order to compute a projection matrix. By doing so, spatial information is not accurately handled and all the objects contained in the scene are given the same emphasis. Nonetheless, it is possible to focus the DR on the separation of specific Objects of Interest (OoI), simply by neglecting all the others. In PCA for instance, instead of using the variance of the scene in each spectral channel, we show that i…
Fast Estimation of the Median Covariation Matrix with Application to Online Robust Principal Components Analysis
2017
International audience; The geometric median covariation matrix is a robust multivariate indicator of dispersion which can be extended without any difficulty to functional data. We define estimators, based on recursive algorithms, that can be simply updated at each new observation and are able to deal rapidly with large samples of high dimensional data without being obliged to store all the data in memory. Asymptotic convergence properties of the recursive algorithms are studied under weak conditions. The computation of the principal components can also be performed online and this approach can be useful for online outlier detection. A simulation study clearly shows that this robust indicat…
Large-sample properties of unsupervised estimation of the linear discriminant using projection pursuit
2021
We study the estimation of the linear discriminant with projection pursuit, a method that is unsupervised in the sense that it does not use the class labels in the estimation. Our viewpoint is asymptotic and, as our main contribution, we derive central limit theorems for estimators based on three different projection indices, skewness, kurtosis, and their convex combination. The results show that in each case the limiting covariance matrix is proportional to that of linear discriminant analysis (LDA), a supervised estimator of the discriminant. An extensive comparative study between the asymptotic variances reveals that projection pursuit gets arbitrarily close in efficiency to LDA when the…
Process Modeling and Planning for Robotic Cold Spray Based Additive Manufacturing
2020
Cold spray (CS) is a solid-state coating deposition technology that has recently been applied as an additive manufacturing (AM) process to fabricate individual components. This potential AM process is attracting more and more attention because of its advantages: high-forming efficiency, low temperature, and no phase changing of materials. These advantages make CS able to form large-volume objects to become an efficient and effective AM process. Nowadays, new advances in cold spray additive manufacturing (CSAM) call for new process implementation to improve the manufacturing accuracy and flexibility. Therefore, the purpose of this study is to enhance CS-based AM through the modeling and plan…
Study of low-pressure suspension plasma spray nanostructured coating : structural characteristics and application in solid oxide fuel cell
2021
Suspension plasma spraying (SPS) has attracted more and more attention in terms of the preparation of nanostructured / sub-microstructured ceramic coatings. However, conventional SPS techniques are conducted under atmospheric pressure, which inevitably causes some disadvantages. Recently, a novel suspension spraying technology – low-pressure suspension plasma spraying (LPSPS) – was proposed, in which the sus-pension spraying process is conducted under low environmental pressure. Benefit from the significant impact of low pressure on the coating deposition, LPSPS is expected to improve the disadvantage of SPS as well as to obtain distinct coating structures not achievable in conventional SPS…
Registration of moving surfaces by means of one-shot laser projection
2005
The acquisition of three-dimensional models of a given surface is a very interesting subject in computer vision. Most of techniques are based on the use of laser range finders coupled to a mechanical system that scans the surface. These techniques lacks of accuracy in the presence of vibrations or non-controlled surface motion because of the misalignments between the acquired images. In this paper, we propose a new one-shot pattern which benefits from the use of registration techniques to recover a whole surface in the presence of non-controlled motion.
Determination of the object surface function by structured light: application to the study of spinal deformities.
1999
The projection of structured light is a technique frequently used to determine the surface shape of an object. In this paper, a new procedure is described that efficiently resolves the correspondence between the knots of the projected grid and those obtained on the object when the projection is made. The method is based on the use of three images of the projected grid. In two of them the grid is projected over a flat surface placed, respectively, before and behind the object; both images are used for calibration. In the third image the grid is projected over the object. It is not reliant on accurate determination of the camera and projector pair relative to the grid and object. Once the met…
Contour/Outline/Silhouette
2020
The contour is the locus at which the parts of opaque solid objects appear to form an edge because it corresponds for the viewer to the projection of the rim, namely the curve that divides the surfaces into visible and invisible parts. The rim between the visible front and the invisible rear side is projected onto the contour that is the envelope of all the curves of equal depth. Although the rim and the contour run into depth, they are distinct concepts that regard the object-centred and the viewer-centred description. The outline is the boundary of the surface delimited by the contour, which fills a spatial region. Rubin (1921) discovered the property that allows the contour and the outli…