Search results for "complexity"
showing 10 items of 1094 documents
Spatial risks and complex systems: methodological perspectives
2007
Research on risk and industrial catastrophes question the complexity theories. Besides the concepts of complexity which lead us to reconsider concepts of risk, hazard and vulnerability, we propose to think about more practical aspects, for example the modelling of human behaviour in crisis situations. The link between concepts as critical self-organization, emergence, bifurcation, and the methods in the Distributed Artificial Intelligence (DAI) used to model them is however difficult. In this paper, we present ongoing analysis on the key concepts of risk science, such as hazards and catastrophes. We propose to enrich them with complex systems theories. First, we present methodological persp…
The application of AI techniques in the optimal design of multi-pass cold drawing processes
2001
Abstract In the paper the problem of optimal pass schedule design in multi-pass wire drawing process is investigated. An automatic design procedure based on an effective artificial intelligence (AI) technique, namely simulated annealing (SA), is proposed. The developed algorithm is aimed to achieve a satisfactory balance of the drawing stresses on the material along the reduction sequence, maintaining in the meantime the drawing stress at each pass below a safety value. In this way both the optimal number of passes and the optimal drawing sequence are determined. The effectiveness of the design procedure is tested through the comparison of the sequences suggested by the algorithm with a set…
Crowded comparison operators for constraints handling in NSGA-II for optimal design of the compensation system in electrical distribution networks
2006
This paper proposes an improvement of an efficient multiobjective optimization algorithm, Non-dominated Sorting Genetic Algorithm II, NSGA-II, that has been here applied to solve the problem of optimal capacitors placement in distribution systems. The studied improvement involves the Crowded Comparison Operator and modifies it in order to handle several constraints. The problem of optimal location and sizing of capacitor banks for losses reduction and voltage profile flattening in medium voltage (MV) automated distribution systems is a difficult combinatorial constrained optimization problem which is deeply studied in literature. In this paper, the efficiency of the proposed Crowded Compari…
Comparison between Entropy and Resilience as Indirect Measures of Reliability in the Framework of Water Distribution Network Design
2014
Abstract The aim of this paper is to investigate which between the entropy and resilience indices represents a better indirect measure of reliability in the framework of water distribution network design. The methodology adopted consisted of (a) multi-objective optimizations performed in order to minimize costs and maximize reliability, expressed by means of one of the indirect indices at time; (b) retrospective performance assessment of the solutions of Pareto fronts obtained. Two case studies of different topological complexity were considered. Results showed that indices based on energetic concepts (resilience and modified resilience) represent a better compact estimate of reliability th…
An abstract inf-sup problem inspired by limit analysis in perfect plasticity and related applications
2020
This work is concerned with an abstract inf-sup problem generated by a bilinear Lagrangian and convex constraints. We study the conditions that guarantee no gap between the inf-sup and related sup-inf problems. The key assumption introduced in the paper generalizes the well-known Babuska-Brezzi condition. It is based on an inf-sup condition defined for convex cones in function spaces. We also apply a regularization method convenient for solving the inf-sup problem and derive a computable majorant of the critical (inf-sup) value, which can be used in a posteriori error analysis of numerical results. Results obtained for the abstract problem are applied to continuum mechanics. In particular, …
On Optimizing Locally Linear Nearest Neighbour Reconstructions Using Prototype Reduction Schemes
2010
This paper concerns the use of Prototype Reduction Schemes (PRS) to optimize the computations involved in typical k-Nearest Neighbor (k-NN) rules. These rules have been successfully used for decades in statistical Pattern Recognition (PR) applications, and have numerous applications because of their known error bounds. For a given data point of unknown identity, the k-NN possesses the phenomenon that it combines the information about the samples from a priori target classes (values) of selected neighbors to, for example, predict the target class of the tested sample. Recently, an implementation of the k-NN, named as the Locally Linear Reconstruction (LLR) [11], has been proposed. The salien…
Multi-party metering: An architecture for privacy-preserving profiling schemes
2013
Several privacy concerns about the massive deploy- ment of smart meters have been arisen recently. Namely, it has been shown that the fine-grained temporal traces generated by these meters can be correlated with different users behaviors. A new architecture, called multi-party metering, for enabling privacy-preserving analysis of high-frequency metering data without requiring additional complexity at the smart meter side is here proposed. The idea is to allow multiple entities to get a share of the high-frequency metering data rather than the real data, where this share does not reveal any information about the real data. By aggregating the shares provided by different users and publishing …
Greedy and K-Greedy algoritmhs for multidimensional data association
2011
[EN] The multidimensional assignment (MDA) problem is a combinatorial optimization problem arising in many applications, for instance multitarget tracking (MTT). The objective of an MDA problem of dimension $d\in\Bbb{N}$ is to match groups of $d$ objects in such a way that each measurement is associated with at most one track and each track is associated with at most one measurement from each list, optimizing a certain objective function. It is well known that the MDA problem is NP-hard for $d\geq3$. In this paper five new polynomial time heuristics to solve the MDA problem arising in MTT are presented. They are all based on the semi-greedy approach introduced in earlier research. Experimen…
Generalized person-by-person optimization in team problems with binary decisions
2008
In this paper, we extend the notion of person by person optimization to binary decision spaces. The novelty of our approach is the adaptation to a dynamic team context of notions borrowed from the pseudo-boolean optimization field as completely local-global or unimodal functions and sub- modularity. We also generalize the concept of pbp optimization to the case where the decision makers (DMs) make decisions sequentially in groups of m, we call it mbm optimization. The main contribution are certain sufficient conditions, verifiable in polynomial time, under which a pbp or an mbm optimization algorithm leads to the team-optimum. We also show that there exists a subclass of sub-modular team pr…
Determination of charge carrier mobility of hole transporting polytriarylamine-based diodes
2010
Hole transport properties of three different side chain poly(triarylamines) have been determined by means of the analysis of steady-state current-voltage characteristics using co-planar diode structures. The interpretation is based on space-charge limited models with field-dependent mobility. Mobilities between ~ 10- 8 and 10- 6 cm2 V- 1 s- 1 are obtained. The highest mobility is achieved for poly(tetraphenylbenzidine) devices and the lowest for poly(triphenylamine) devices. Electron-rich methoxy substituents increase the mobility of poly(triphenylamine)s. A comparison of the mobility values with those obtained using organic field-effect transistors is also given. © 2009 Elsevier B.V. All r…