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11.
Jorge M Santos Joaquim Marques de Sa Luis A Alexandre 《IEEE transactions on pattern analysis and machine intelligence》2008,30(1):62-75
Hierarchical clustering is a stepwise clustering method usually based on proximity measures between objects or sets of objects from a given data set. The most common proximity measures are distance measures. The derived proximity matrices can be used to build graphs, which provide the basic structure for some clustering methods. We present here a new proximity matrix based on an entropic measure and also a clustering algorithm (LEGClust) that builds layers of subgraphs based on this matrix, and uses them and a hierarchical agglomerative clustering technique to form the clusters. Our approach capitalizes on both a graph structure and a hierarchical construction. Moreover, by using entropy as a proximity measure we are able, with no assumption about the cluster shapes, to capture the local structure of the data, forcing the clustering method to reflect this structure. We present several experiments on artificial and real data sets that provide evidence on the superior performance of this new algorithm when compared with competing ones. 相似文献
12.
A distortion measure to validate and generate curved high‐order meshes on CAD surfaces with independence of parameterization 下载免费PDF全文
A. Gargallo‐Peiró X. Roca J. Peraire J. Sarrate 《International journal for numerical methods in engineering》2016,106(13):1100-1130
A framework to validate and generate curved nodal high‐order meshes on Computer‐Aided Design (CAD) surfaces is presented. The proposed framework is of major interest to generate meshes suitable for thin‐shell and 3D finite element analysis with unstructured high‐order methods. First, we define a distortion (quality) measure for high‐order meshes on parameterized surfaces that we prove to be independent of the surface parameterization. Second, we derive a smoothing and untangling procedure based on the minimization of a regularization of the proposed distortion measure. The minimization is performed in terms of the parametric coordinates of the nodes to enforce that the nodes slide on the surfaces. Moreover, the proposed algorithm repairs invalid curved meshes (untangling), deals with arbitrary polynomial degrees (high‐order), and handles with low‐quality CAD parameterizations (independence of parameterization). Third, we use the optimization procedure to generate curved nodal high‐order surface meshes by means of an a posteriori approach. Given a linear mesh, we increase the polynomial degree of the elements, curve them to match the geometry, and optimize the location of the nodes to ensure mesh validity. Finally, we present several examples to demonstrate the features of the optimization procedure, and to illustrate the surface mesh generation process. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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Marta Alberti Joaquim Ciurana Ciro A. Rodríguez Tugrul Özel 《Journal of Intelligent Manufacturing》2011,22(2):263-277
Economic globalization, together with heightened market competition and increasingly short product life cycles are motivating
companies to use advanced manufacturing technologies. Use of high speed machining is increasingly widespread; however, as
the technology is relatively new, it lacks a deep-rooted knowledge base which would facilitate implementation. One of the
most frequent problems facing companies wishing to adopt this technology is selecting the most appropriate machine tool for
the product in question and own enterprise characteristics. This paper presents a decision support system for high speed milling
machine tool selection based on machine characteristics and performance tests. Profile machining tests are designed and conducted
in participating machining centers. The decision support system is based on product dimension accuracy, process parameters
such as feed rate and interpolation scheme used by CNC and machine characteristics such as machine accuracy and cost. Experimental
data for process error and cycle operation time are obtained from profile machining tests with different geometrical feature
zones that are often used in manufacturing of discrete parts or die/moulds. All those input parameters have direct impact
on productivity and manufacturing cost. Artificial neural network models are utilized for decision support system with reasonable
prediction capability. 相似文献
16.
Bruno R. de Araújo Tiago Guerreiro Manuel J. Fonseca Joaquim A. Jorge João M. Pereira Monica Bordegoni Francesco Ferrise Mario Covarrubias Michele Antolini 《Journal of Real-Time Image Processing》2010,5(2):73-90
Currently, the design of aesthetic products is a process that requires a set of activities where digital models and physical
mockups play a key role. Typically, these are modified (and built) several times before reaching the desired design, increasing
the development time and, consequently, the final product cost. In this paper, we present an innovative design environment
for computer-aided design (CAD) surface analysis. Our system relies on a direct visuo-haptic display system, which enables
users to visualize models using a stereoscopic view, and allows the evaluation of sectional curves using touch. Profile curves
are rendered using an haptic device that deforms a plastic strip, thanks to a set of actuators, to reproduce the curvature
of the shape co-located with the virtual model. By touching the strip, users are able to evaluate shape characteristics, such
as curvature or discontinuities (rendered using sound), and to assess the surface quality. We believe that future computer-aided
systems (CAS)/CAD systems based on our approach will contribute in improving the design process at industrial level. Moreover,
these will allow companies to reduce the product development time by reducing the number of physical mockups necessary for
the product design evaluation and by increasing the quality of the final product, allowing a wider exploration and comparative
evaluation of alternatives in the given time. 相似文献
17.
Localization is a fundamental operation for the navigation of mobile robots. The standard localization algorithms fuse external measurements of the environment with the odometric evolution of the robot pose to obtain its optimal estimation. In this work, we present a different approach to determine the pose using angular measurements discontinuously obtained in time. The presented method is based on an Extended Kalman Filter (EKF) with a state-vector composed of the external angular measurements. This algorithm keeps track of the angles between actual measurements from robot odometric information. This continuous angular estimation allows the consistent use of the triangulation methods to determine the robot pose at any time during its motion. The article reports experimental results that show the localization accuracy obtained by means of the presented approach. These results are compared to the ones obtained applying the EKF algorithm with the standard pose state-vector. For the experiments, an omnidirectional robotic platform with omnidirectional wheels is used. 相似文献
18.
Ian R. Chittick Joaquim R. R. A. Martins 《Structural and Multidisciplinary Optimization》2008,36(1):59-70
A new subspace optimization method for performing aero-structural design is introduced. The method relies on a semi-analytic
adjoint approach to the sensitivity analysis that includes post-optimality sensitivity information from the structural optimization
subproblem. The resulting coupled post-optimality sensitivity approach is used to guide a gradient-based optimization algorithm.
The new approach simplifies the system-level problem, thereby reducing the number of calls to a potentially costly aerodynamics
solver. The aero-structural optimization of an aircraft wing is performed using linear aerodynamic and structural analyses,
and a performance comparison is made between the new approach and the conventional multidisciplinary feasible method. The
new asymmetric suboptimization method is found to be the more efficient approach when it adequately reduces the number of
system evaluations or when there is a large enough discrepancy between disciplinary solution times. 相似文献
19.
We propose how to model enterprise facilities (like factories, warehouses, etc.) in a multi-product production/distribution network, capacity management at those facilities, and scheduling agents which act as enterprise managers, taking decisions that affect the available capacity. A coordination mechanism through which scheduling agents can locally perceive hard global temporal constraints is also proposed. 相似文献
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