Institution

# École normale supérieure de Cachan

Education•Cachan, Île-de-France, France•

About: École normale supérieure de Cachan is a(n) education organization based out in Cachan, Île-de-France, France. It is known for research contribution in the topic(s): Decidability & Finite element method. The organization has 2717 authors who have published 5585 publication(s) receiving 175925 citation(s).

##### Papers published on a yearly basis

##### Papers

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TL;DR: A new measure, the method noise, is proposed, to evaluate and compare the performance of digital image denoising methods, and a new algorithm, the nonlocal means (NL-means), based on a nonlocal averaging of all pixels in the image is proposed.

Abstract: We propose a new measure, the method noise, to evaluate and compare the performance of digital image denoising methods. We first compute and analyze this method noise for a wide class of denoising algorithms, namely the local smoothing filters. Second, we propose a new algorithm, the nonlocal means (NL-means), based on a nonlocal averaging of all pixels in the image. Finally, we present some experiments comparing the NL-means algorithm and the local smoothing filters.

5,832 citations

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TL;DR: In this article, a two-dimensional array of optical resonators with spatially varying phase response and subwavelength separation can imprint phase discontinuities on propagating light as it traverses the interface between two media.

Abstract: Conventional optical components rely on gradual phase shifts accumulated during light propagation to shape light beams. New degrees of freedom are attained by introducing abrupt phase changes over the scale of the wavelength. A two-dimensional array of optical resonators with spatially varying phase response and subwavelength separation can imprint such phase discontinuities on propagating light as it traverses the interface between two media. Anomalous reflection and refraction phenomena are observed in this regime in optically thin arrays of metallic antennas on silicon with a linear phase variation along the interface, which are in excellent agreement with generalized laws derived from Fermat’s principle. Phase discontinuities provide great flexibility in the design of light beams, as illustrated by the generation of optical vortices through use of planar designer metallic interfaces.

5,384 citations

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TL;DR: The main classes of fluorescent molecular sensors for cation recognition are presented: they differ by the nature of the cation-controlled photoinduced processes: photoinduced electron transfer, photoinduced charge transfer, excimer formation or disappearance as discussed by the authors.

Abstract: The main classes of fluorescent molecular sensors for cation recognition are presented: they differ by the nature of the cation-controlled photoinduced processes: photoinduced electron transfer, photoinduced charge transfer, excimer formation or disappearance. In each class, distinction is made according to the structure of the complexing moiety: chelators, podands, coronands (crown ethers), cryptands, calixarenes. The most representative examples are presented in each subclass with special attention given to selectivity.

2,013 citations

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TL;DR: The Euler-Lagrange equations characterizing the minimizing vector fields vt, t∈[0, 1] assuming sufficient smoothness of the norm to guarantee existence of solutions in the space of diffeomorphisms are derived.

Abstract: This paper examine the Euler-Lagrange equations for the solution of the large deformation diffeomorphic metric mapping problem studied in Dupuis et al. (1998) and Trouve (1995) in which two images I 0, I 1 are given and connected via the diffeomorphic change of coordinates I 0???1=I 1 where ?=?1 is the end point at t= 1 of curve ? t , t?[0, 1] satisfying .? t =v t (? t ), t? [0,1] with ?0=id. The variational problem takes the form
$$\mathop {\arg {\text{m}}in}\limits_{\upsilon :\dot \phi _t = \upsilon _t \left( {\dot \phi } \right)} \left( {\int_0^1 {\left\| {\upsilon _t } \right\|} ^2 {\text{d}}t + \left\| {I_0 \circ \phi _1^{ - 1} - I_1 } \right\|_{L^2 }^2 } \right),$$
where ?v t? V is an appropriate Sobolev norm on the velocity field v t(·), and the second term enforces matching of the images with ?·?L 2 representing the squared-error norm.
In this paper we derive the Euler-Lagrange equations characterizing the minimizing vector fields v t, t?[0, 1] assuming sufficient smoothness of the norm to guarantee existence of solutions in the space of diffeomorphisms. We describe the implementation of the Euler equations using semi-lagrangian method of computing particle flows and show the solutions for various examples. As well, we compute the metric distance on several anatomical configurations as measured by ?0 1?v t? V dt on the geodesic shortest paths.

1,434 citations

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TL;DR: The proposed affine-SIFT (ASIFT), simulates all image views obtainable by varying the two camera axis orientation parameters, namely, the latitude and the longitude angles, left over by the SIFT method, and will be mathematically proved to be fully affine invariant.

Abstract: If a physical object has a smooth or piecewise smooth boundary, its images obtained by cameras in varying positions undergo smooth apparent deformations. These deformations are locally well approximated by affine transforms of the image plane. In consequence the solid object recognition problem has often been led back to the computation of affine invariant image local features. Such invariant features could be obtained by normalization methods, but no fully affine normalization method exists for the time being. Even scale invariance is dealt with rigorously only by the scale-invariant feature transform (SIFT) method. By simulating zooms out and normalizing translation and rotation, SIFT is invariant to four out of the six parameters of an affine transform. The method proposed in this paper, affine-SIFT (ASIFT), simulates all image views obtainable by varying the two camera axis orientation parameters, namely, the latitude and the longitude angles, left over by the SIFT method. Then it covers the other four parameters by using the SIFT method itself. The resulting method will be mathematically proved to be fully affine invariant. Against any prognosis, simulating all views depending on the two camera orientation parameters is feasible with no dramatic computational load. A two-resolution scheme further reduces the ASIFT complexity to about twice that of SIFT. A new notion, the transition tilt, measuring the amount of distortion from one view to another, is introduced. While an absolute tilt from a frontal to a slanted view exceeding 6 is rare, much higher transition tilts are common when two slanted views of an object are compared (see Figure hightransitiontiltsillustration). The attainable transition tilt is measured for each affine image comparison method. The new method permits one to reliably identify features that have undergone transition tilts of large magnitude, up to 36 and higher. This fact is substantiated by many experiments which show that ASIFT significantly outperforms the state-of-the-art methods SIFT, maximally stable extremal region (MSER), Harris-affine, and Hessian-affine.

1,364 citations

##### Authors

Showing all 2717 results

Name | H-index | Papers | Citations |
---|---|---|---|

Shi Xue Dou | 122 | 2028 | 74031 |

Olivier Hermine | 111 | 1026 | 43779 |

John R. Reynolds | 105 | 607 | 50027 |

Shaul Mukamel | 95 | 1030 | 40478 |

Tomás Torres | 88 | 625 | 28223 |

Ifor D. W. Samuel | 74 | 605 | 23151 |

Serge Abiteboul | 73 | 278 | 24576 |

Stéphane Roux | 68 | 627 | 19123 |

Zeger Debyser | 67 | 404 | 16531 |

Louis Nadjo | 64 | 264 | 12596 |

Praveen K. Thallapally | 64 | 190 | 12110 |

Andrew Travers | 63 | 193 | 13537 |

Shoji Takeuchi | 63 | 692 | 14704 |

Bineta Keita | 63 | 274 | 12053 |

Yves Mély | 62 | 368 | 13478 |