Perret B.,University Paris Est Creteil |
Collet C.,CNRS Computer Science and Engineering Laboratory
Computer Vision and Image Understanding | Year: 2015
This article presents a new approach for constructing connected operators for image processing and analysis. It relies on a hierarchical Markovian unsupervised algorithm in order to classify the nodes of the traditional Max-Tree. This approach enables to naturally handle multivariate attributes in a robust non-local way. The technique is demonstrated on several image analysis tasks: filtering, segmentation, and source detection, on astronomical and biomedical images. The obtained results show that the method is competitive despite its general formulation. This article provides also a new insight in the field of hierarchical Markovian image processing showing that morphological trees can advantageously replace traditional quadtrees. © 2014 Elsevier Inc. All rights reserved.
Studholme C.,University of Washington |
Rousseau F.,CNRS Computer Science and Engineering Laboratory
International Journal of Developmental Neuroscience | Year: 2014
Recent advances in medical imaging are beginning to allow us to quantify brain tissue maturation in the growing human brain prior to normal term age, and are beginning to shed new light on early human brain growth. These advances compliment the work already done in cellular level imaging in animal and post mortem studies of brain development. The opportunities for collaborative research that bridges the gap between macroscopic and microscopic windows on the developing brain are significant. The aim of this paper is to provide a review of the current research into MR imaging of the living fetal brain with the aim of motivating improved interfaces between the two fields. The review begins with a description of faster MRI techniques that are capable of freezing motion of the fetal head during the acquisition of a slice, and how these have been combined with advanced post-processing algorithms to build 3D images from motion scattered slices. Such rich data has motivated the development of techniques to automatically label developing tissue zones within MRI data allowing their quantification in 3D and 4D within the normally growing fetal brain. These methods have provided the basis for later work that has created the first maps of tissue growth rate and cortical folding in normally developing brains in-utero. These measurements provide valuable findings that compliment those derived from post-mortem anatomy, and additionally allow for the possibility of larger population studies of the influence of maternal environmental and genes on early brain development. © 2013 Published by Elsevier Ltd.
Mavromatidis L.E.,CNRS Computer Science and Engineering Laboratory
Energy and Buildings | Year: 2015
The present review paper focuses on the exploration and qualitative evaluation of hybrid optimization methods applied to architectural design, computational morphogenesis and energy consumption problems. After introducing the computational morphogenesis notion and the novel institutional framework of nZEB labeling, we define here computational morphogenesis as a design procedure where the environmental qualities of the envelope and especially thermal storage and load shifting have the potential to guide an automation process of shape creation in the building scale. For this reason we focus on reviewing the well-cited literature on scale that introduced novel hybrid optimization tools especially developed for thermal load, energy consumption optimization and/or computational morphogenesis optimization issues. Different approaches and methods are reported in this review paper, while at the end of the paper an exhaustive list of conclusions and potential perspectives of these approaches is explicitly presented. Inexorably, we seek to review here hybrid optimization tools that are (or could be) applied on computational morphogenesis problems with the aim to optimize, facilitate and encourage a creative architectural design in relation to innovative envelope conception to promote interdisciplinary research coupling the fields of architectural design and building physics. © 2015 Elsevier B.V.
Gunzburger Y.,CNRS Georesources lab |
Magnenet V.,CNRS Computer Science and Engineering Laboratory
Tectonophysics | Year: 2014
We investigate the source of non-purely gravitational horizontal stresses in the Paris basin, a nowadays tectonically quiet intracratonic basin, in its eastern border of which outstandingly dense stress measurements are available. Based on a synthesis of published data, the stress state in the basin is first shown to be very close to the one that may be extrapolated for the underlying basement, in terms of principal stress orientations and horizontal to vertical stress ratios. This is in favour of a mechanical coupling between the basement and its sedimentary cover, which may seem contradictory to the presence of several weak rock layers in the basin fill, e.g. an argillite layer that was shown to bear low deviatoric stresses, and salt layers that are implicated in a major décollement elsewhere. To unravel this apparent contradiction, a 3D-numerical modelling is performed, following a rigorous inverse problem approach, to determine the long-term elastic properties of both the basement and the basin rocks. The objective is to find the set of elastic constants that provides the best fit between the calculated stress state in the basin and the in situ data, by assuming that the stress state in the basement is known. This methodology provides a realistic set of mechanical parameters, in agreement with previous studies, which leads to the conclusion that the horizontal stresses in the basin constitute its mechanical response to the stresses that developed in the underlying basement during and since the last tectonic event (Alpine phase). The fact that horizontal stresses could be transmitted across the weak horizons, contrary to what may be expected at first glance, is explained both by the geometry of the basin and the fact that, over the long term, the stiffnesses of the various sedimentary rocks are only slightly different from each other. © 2014 Elsevier B.V.
Charpentier I.,CNRS Computer Science and Engineering Laboratory
Computer Physics Communications | Year: 2016
Considerable research efforts have been directed at implementing the Faddeeva function w(z) and its derivatives with respect to z, but these did not consider the key computing issue of a possible dependence of z on some variable t. The general case is to differentiate the compound function w(z(t))=w(ring operator)z(t) with respect to t by applying the chain rule for a first order derivative, or Faà di Bruno's formula for higher-order ones. Higher-order automatic differentiation (HOAD) is an efficient and accurate technique for derivative calculation along scientific computing codes. Although codes are available for w(z), a special symbolic HOAD is required to compute accurate higher-order derivatives for w(ring operator)z(t) in an efficient manner. A thorough evaluation is carried out considering a nontrivial case study in optics to support this assertion. Program summary: Program title: HOAD_MathFun. Catalogue identifier: AFAG_v1_0. Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AFAG_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland. Licensing provisions: yes. No. of lines in distributed program, including test data, etc.: 4737. No. of bytes in distributed program, including test data, etc.: 103450. Distribution format: tar.gz. Programming language: Fortran 90. Computer: Non-specific. Operating system: Non-specific. RAM: 1 megabyte. Classification: 4.12. External routines: Algorithm 680 , Mathematical functions (included). Nature of problem: General optimized higher-order automatic differentiation of mathematical functions. Complex refractive index as a case study. Solution method: Higher-order differentiation for the general second order ordinary equation defining the mathematical functions. Optimized operator overloading recurrence formula. Unusual features: Automatic differentiation, Quadratic complexity. Running time: 1 second. © 2016 Elsevier B.V.
Mavromatidis L.E.,CNRS Computer Science and Engineering Laboratory
Energy and Buildings | Year: 2016
The coupled natural convection-radiation heat transfer across cavities is an extremely important research issue commonly encountered in many innovative building envelope applications. Extensive both experimental and numerical studies were conducted to analyse the natural convection flow coupled with radiation heat transfer across vertical and inclined rectangular cavities, proposing accurate empirical or regression correlations according to the particularities of the studied cavity problem. Nevertheless, there is a lack of correlations accurate and adapted enough to model coupled natural convection-radiation across cavities in the vicinity of low emissivity surfaces. The present work aims to cover this subject, through an exhaustive numerical analysis validated and evaluated enough with the use of experimental data. A numerical model is firstly updated to simulate infrared radiation and convective heat transfer across a sophisticated innovative building envelope prototype, while 8 different approximations have been implemented in the model in order to evaluate a variety of available correlations on the subject. Formerly the numerical approach presented here used available experimental data for the same prototype. The air's temperature experimental data served as input to the model boundaries in order to exactly impose the same initial conditions for obtaining the results. Furthermore, experimental data regarding the temperature on the sample's interfaces were used for validating the proposed theoretical model. Satisfactory enough agreements are observed between the theoretically simulated and experimentally measured temperatures and the model is afterwards evaluated to determine the most accurate approximation. Finally, the numerical study presented in this paper concluded in the proposition of 2 new updated correlations to model natural convection across vertical cavities in the vicinity of low emissivity surfaces with the perspective to further support their implementation into Computational Fluid Dynamic (CFD) codes. © 2016 Elsevier B.V. All rights reserved.
Mavromatidis L.,CNRS Computer Science and Engineering Laboratory
Energy Procedia | Year: 2015
This paper consists a first numerical approach to evaluate the main geometrical and non-geometrical characteristics of glazed areas and evaluate their influence on the daylight conditions and the visual comfort in the adjoining spaces. Since visual comfort is the main factor of well-being and also influences the occupant to produce measurable, long term improvements in his professional performance providing higher quality services, we deeded to focus our case study on an office room prototype (3m × 3m × 5.40m) where openings exist only in the one side. Hence, the present work is a case study where a numerical approach limited on daylight calculation is presented. As literature reveals, the transparency and the roughness of the glazed area as well as the length and the height are important parameters in the daylighting design of office buildings. So, the present paper presents a singular case study where a simplified methodology on the basis of a classic composite DOE method is employed, to predict the daylight factor for different simulation scenarios applied to a given 3D geometry. The entire numerical analysis is developed through computer simulation using DIATux 4.5 copy as a tool. Then a parametric study has been conducted, where the influence of each investigated parameter that concerns the main geometrical and non-geometncal glazed area's characteristics (length, height, transparency and roughness of the glazing area) is investigated and expressed in the form of adjoining coefficient values, while the mean daylight factor in the working plane is evaluated in detail. As a conclusion, the main aim of this paper is to define and evaluate the influence of each investigated parameter linking selected geometrical and non-geometrical characteristics through statistical modeling via a polynomial function, in order to provide essential information for daylight effectiveness assessment at early design stages to maximize occupant's visual comfort in office buildings according to the international standards. © 2015 The Authors.
Dresp-Langley B.,CNRS Computer Science and Engineering Laboratory
Computational and Mathematical Methods in Medicine | Year: 2013
Generic properties of curvature representations formed on the basis of vision and touch were examined as a function of mathematical properties of curved objects. Virtual representations of the curves were shown on a computer screen for visual scaling by sighted observers (experiment 1). Their physical counterparts were placed in the two hands of blindfolded and congenitally blind observers for tactile scaling. The psychophysical data show that curvature representations in congenitally blind individuals, who never had any visual experience, and in sighted observers, who rely on vision most of the time, are statistically linked to the same mathematical properties of the curves. The perceived magnitude of object curvature, sensed through either vision or touch, is related by a mathematical power law, with similar exponents for the two sensory modalities, to the aspect ratio of the curves, a scale invariant geometric property. This finding supports biologically motivated models of sensory integration suggesting a universal power law for the adaptive brain control and balance of motor responses to environmental stimuli from any sensory modality. © 2013 Birgitta Dresp-Langley.
Bodein Y.,Tata Technologies |
Rose B.,CNRS Computer Science and Engineering Laboratory |
Caillaud E.,CNRS Computer Science and Engineering Laboratory
Computers in Industry | Year: 2014
Today parametric associative CAD systems must help companies to create more efficient virtual development processes. While dealing with complex parts (e.g. The number of surfaces of the solid) no CAD modeling methodology is existing. Based on the analysis of industrial designers' practices as well as student practices on CAD, we identified key factors that lead to better performance. Our objective in this article is to propose a practical method for complex parts modeling in parametric CAD system. An illustration of the performances and the results obtained by this method are presented comparing the traditional method with the proposed one while using an academic case and then an industrial case. © 2013 Elsevier B.V.
Dresp-Langley B.,CNRS Computer Science and Engineering Laboratory
Computational Intelligence and Neuroscience | Year: 2015
Planar geometry was exploited for the computation of symmetric visual curves in the image plane, with consistent variations in local parameters such as sagitta, chordlength, and the curves' height-to-width ratio, an indicator of the visual area covered by the curve, also called aspect ratio. Image representations of single curves (no local image context) were presented to human observers to measure their visual sensation of curvature magnitude elicited by a given curve. Nonlinear regression analysis was performed on both the individual and the average data using two types of model: (1) a power function where y (sensation) tends towards infinity as a function of x (stimulus input), most frequently used to model sensory scaling data for sensory continua, and (2) an "exponential rise to maximum" function, which converges towards an asymptotically stable level of y as a function of x. Both models provide satisfactory fits to subjective curvature magnitude as a function of the height-to-width ratio of single curves. The findings are consistent with an in-built sensitivity of the human visual system to local curve geometry, a potentially essential ground condition for the perception of concave and convex objects in the real world. © 2015 Birgitta Dresp-Langley.