3,125 research outputs found
Using ATL to define advanced and flexible constraint model transformations
Transforming constraint models is an important task in re- cent constraint
programming systems. User-understandable models are defined during the modeling
phase but rewriting or tuning them is manda- tory to get solving-efficient
models. We propose a new architecture al- lowing to define bridges between any
(modeling or solver) languages and to implement model optimizations. This
architecture follows a model- driven approach where the constraint modeling
process is seen as a set of model transformations. Among others, an interesting
feature is the def- inition of transformations as concept-oriented rules, i.e.
based on types of model elements where the types are organized into a hierarchy
called a metamodel
Rewriting Constraint Models with Metamodels
An important challenge in constraint programming is to rewrite constraint
models into executable programs calculat- ing the solutions. This phase of
constraint processing may require translations between constraint programming
lan- guages, transformations of constraint representations, model
optimizations, and tuning of solving strategies. In this paper, we introduce a
pivot metamodel describing the common fea- tures of constraint models including
different kinds of con- straints, statements like conditionals and loops, and
other first-class elements like object classes and predicates. This metamodel
is general enough to cope with the constructions of many languages, from
object-oriented modeling languages to logic languages, but it is independent
from them. The rewriting operations manipulate metamodel instances apart from
languages. As a consequence, the rewriting operations apply whatever languages
are selected and they are able to manage model semantic information. A bridge
is created between the metamodel space and languages using parsing techniques.
Tools from the software engineering world can be useful to implement this
framework
Distributed archive and single access system for accelerometric event data : a NERIES initiative
We developed a common access facility to homogeneously formatted
accelerometric event data and to the corresponding sheet of ground motion
parameters. This paper is focused on the description of the technical
development of the accelerometric data server and the link with the
accelerometric data explorer. The server is the third node of the 3-tier
architecture of the distributed archive system for accelerometric data. The
server is the link between the data users and the accelero- metric data portal.
The server follows three main steps: (1) Reading and analysis of the end-user
request; (2) Processing and converting data; and (3) Archiving and updating the
accelerometric data explorer. This paper presents the description of the data
server and the data explorer for accessing data
A Positive/Unlabeled Approach for the Segmentation of Medical Sequences using Point-Wise Supervision
The ability to quickly annotate medical imaging data plays a critical role in training deep learning frameworks for segmentation. Doing so for image volumes or video sequences is even more pressing as annotating these is particularly burdensome. To alleviate this problem, this work proposes a new method to efficiently segment medical imaging volumes or videos using point-wise annotations only. This allows annotations to be collected extremely quickly and remains applicable to numerous segmentation tasks. Our approach trains a deep learning model using an appropriate Positive/Unlabeled objective function using sparse point-wise annotations. While most methods of this kind assume that the proportion of positive samples in the data is known a-priori, we introduce a novel self-supervised method to estimate this prior efficiently by combining a Bayesian estimation framework and new stopping criteria. Our method iteratively estimates appropriate class priors and yields high segmentation quality for a variety of object types and imaging modalities. In addition, by leveraging a spatio-temporal tracking framework, we regularize our predictions by leveraging the complete data volume. We show experimentally that our approach outperforms state-of-the-art methods tailored to the same problem
Rewriting Constraint Models with Metamodels
International audienceAn important challenge in constraint programming is to rewrite constraint models into executable programs calculat- ing the solutions. This phase of constraint processing may require translations between constraint programming lan- guages, transformations of constraint representations, model optimizations, and tuning of solving strategies. In this paper, we introduce a pivot metamodel describing the common fea- tures of constraint models including different kinds of con- straints, statements like conditionals and loops, and other first-class elements like object classes and predicates. This metamodel is general enough to cope with the constructions of many languages, from object-oriented modeling languages to logic languages, but it is independent from them. The rewriting operations manipulate metamodel instances apart from languages. As a consequence, the rewriting operations apply whatever languages are selected and they are able to manage model semantic information. A bridge is created between the metamodel space and languages using parsing techniques. Tools from the software engineering world can be useful to implement this framework
Solving an Air Conditioning System Problem in an Embodiment Design Context Using Constraint Satisfaction Techniques
International audienceIn this paper, the embodiment design of an air condition- ing system (ACS) in an aircraft is investigated using interval constraint satisfaction techniques. The detailed ACS model is quite complex to solve, since it contains many coupled variables and many constraints corresponding to complex physics phenomena. Some new heuristics and notions based on embodiment design knowledge, are briefly introduced to undertake some embodiment design concepts and to obtain a more relevant and more efficient solving process than classical algorithms. The benefits of using constraint programming in embodiment design are discussed and some difficulties for designers using CP tools are shortly detailed
Iterative multi-path tracking for video and volume segmentation with sparse point supervision
Recent machine learning strategies for segmentation tasks have shown great
ability when trained on large pixel-wise annotated image datasets. It remains a
major challenge however to aggregate such datasets, as the time and monetary
cost associated with collecting extensive annotations is extremely high. This
is particularly the case for generating precise pixel-wise annotations in video
and volumetric image data. To this end, this work presents a novel framework to
produce pixel-wise segmentations using minimal supervision. Our method relies
on 2D point supervision, whereby a single 2D location within an object of
interest is provided on each image of the data. Our method then estimates the
object appearance in a semi-supervised fashion by learning
object-image-specific features and by using these in a semi-supervised learning
framework. Our object model is then used in a graph-based optimization problem
that takes into account all provided locations and the image data in order to
infer the complete pixel-wise segmentation. In practice, we solve this
optimally as a tracking problem using a K-shortest path approach. Both the
object model and segmentation are then refined iteratively to further improve
the final segmentation. We show that by collecting 2D locations using a gaze
tracker, our approach can provide state-of-the-art segmentations on a range of
objects and image modalities (video and 3D volumes), and that these can then be
used to train supervised machine learning classifiers
Concern-Focused Evaluation for Ambiguous and Conflicting Policies: An Approach From the Environmental Field
International audienceEnvironment and sustainable development show how policies are becoming ever more complex and ambiguous. This trend calls for new evaluation approaches. They need to be more clearly focused on specific, explicit concerns. They must be driven by a strategic concept of use to overcome the vulnerability to manipulation of many integrative, essentially procedural, approaches to policy making and evaluation. This article presents a conceptual framework for such evaluations and a four-step approach: defining the focal concern; developing criteria and synthesizing observations on the extent to which the focal concern is met; identifying and assessing all policies contributing to this outcome; and complementing this with the evaluation of policies specifically aimed at meeting the focal concern. Examples are taken essentially from wetland-related policies in France and Senegal. The article discusses how this approach tackles some crucial issues in evaluation research and practice and advocates closer connections between evaluation and critical research on policies
A Two-Tier Estimation of Distribution Algorithm for Composite Laminate Optimization
http://www.emse.fr/~leriche/mao_paper_2004.pdfInternational audienceThe paper proposes a new evolutionary algorithm for composite laminate optimization, named Double-Distribution Optimization Algorithm (DDOA). DDOA belongs to the family of estimation of distributions algorithms (EDA) that build a statistical model of promising regions of the design space based on sets of good points, and use it to guide the search. A generic framework for introducing statistical variable dependencies by making use of the physics of the problem is presented. The algorithm uses two distributions simultaneously: the marginal distributions of the design variables, complemented by the distribution of auxiliary variables. The combination of the two generates complex distributions at a low computational cost. The paper demonstrates the efficiency of DDOA for laminate strength maximization problem where the design variables are the fiber angles and the auxiliary variables are the lamination parameters. The results show that its reliability in finding the optima is greater than that of a simple EDA, the univariate marginal distribution algorithm. The paper specifically investigates how the compromise exploitation/exploration can be adjusted. It demonstrates that DDOA maintains a high level of exploration without sacrificing exploitation
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