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451.
Michael O'Neill Conor Ryan Maarten Keijzer Mike Cattolico 《Genetic Programming and Evolvable Machines》2003,4(1):67-93
We present an investigation into crossover in Grammatical Evolution that begins by examining a biologically-inspired homologous crossover operator that is compared to standard one and two-point operators. Results demonstrate that this homologous operator is no better than the simpler one-point operator traditionally adopted.An analysis of the effectiveness of one-point crossover is then conducted by determining the effects of this operator, by adopting a headless chicken-type crossover that swaps randomly generated fragments in place of the evolved strings. Experiments show detrimental effects with the utility of the headless chicken operator.Finally, the mechanism of crossover in GE is analysed and termed ripple crossover, due to its defining characteristics. An experiment is described where ripple crossover is applied to tree-based genetic programming, and the results show that ripple crossover is more effective in exploring the search space of possible programs than sub-tree crossover by examining the rate of premature convergence during the run. Ripple crossover produces populations whose fitness increases gradually over time, slower than, but to an eventual higher level than that of sub-tree crossover. 相似文献
452.
A response surface based optimisation algorithm for the calculation of fuzzy envelope FRFs of models with uncertain properties 总被引:1,自引:0,他引:1
Maarten De Munck David Moens Wim Desmet Dirk Vandepitte 《Computers & Structures》2008,86(10):1080-1092
This paper describes a response surface based optimisation technique for the calculation of envelope frequency response functions (FRFs) of imprecisely defined structures using the interval and fuzzy finite element method.The authors developed a hybrid - global optimisation and interval arithmetic - procedure for interval and fuzzy envelope FRF calculation. This hybrid approach reduces the computational cost of the analysis compared to a full global optimisation approach and reduces the conservatism on the envelope FRF compared to a full interval arithmetic approach.Still, the optimisation step is the computationally most expensive part of the algorithm. To handle industrially sized applications, a very efficient optimisation procedure is imperative. The response surface based procedure described in this paper decreases the computational cost of a fuzzy envelope FRF calculation with a factor 50 or more compared to the commonly used two-level full factorial design of experiments, while giving a comparable accuracy. 相似文献
453.
Jiyin He Wouter Weerkamp Martha Larson Maarten de Rijke 《International Journal on Document Analysis and Recognition》2009,12(3):185-203
When searching for blogs on a specific topic, information seekers prefer blogs that place a central focus on that topic over
blogs whose mention of the topic is diffuse or incidental. In order to present users with better blog feed search results,
we developed a measure of topical consistency that is able to capture whether or not a blog is topically focused. The measure,
called the coherence score, is inspired by the genetics literature and captures the tightness of the clustering structure of a data set relative to
a background collection. In a set of experiments on synthetic data, the coherence score is shown to provide a faithful reflection
of topic clustering structure. The properties that make the coherence score more appropriate than lexical cohesion, a common
measure of topical structure, are discussed. Retrieval experiments show that integrating the coherence score as a prior in
a language modeling-based approach to blog feed search improves retrieval effectiveness. The coherence score must, however,
be used judiciously in order to avoid boosting the ranking of irrelevant but topically focused blogs. To this end, we experiment
with a series of weighting schemes that adjust the contribution of the coherence score according to the relevance of a blog
to the user query. An appropriate weighting scheme is able to improve retrieval performance. Finally, we show that the coherence
score can be reliably estimated with a sample exceeding 20 posts in size. Consistent with this finding, experiments show that
the best retrieval performance is achieved if coherence scores are used when a blog contains more than 20 posts. 相似文献
454.
Several ergonomic studies have estimated computer work duration using registration software. In these studies, an arbitrary pause definition (Pd; the minimal time between two computer events to constitute a pause) is chosen and the resulting duration of computer work is estimated. In order to uncover the relationship between the used pause definition and the computer work duration (PWT), we used registration software to record usage patterns of 571 computer users across almost 60,000 working days. For a large range of Pds (1-120 s), we found a shallow, log-linear relationship between PWT and Pds. For keyboard and mouse use, a second-order function fitted the data best. We found that these relationships were dependent on the amount of computer work and subject characteristics. Comparison of exposure duration from studies using different pause definitions should take this into account, since it could lead to misclassification. Software manufacturers and ergonomists assessing computer work duration could use the found relationships for software design and study comparison. 相似文献
455.
David Rijlaarsdam Tom Oomen Pieter Nuij Johan Schoukens Maarten Steinbuch 《Automatica》2012,48(9):2381-2384
The notion of frequency response functions has been generalized to nonlinear systems in several ways. However, a relation between different approaches has not yet been established. In this paper, frequency domain representations for nonlinear systems are uniquely connected for a class of nonlinear systems. Specifically, by means of novel analytical results, the generalized frequency response function (GFRF) and the higher order sinusoidal input describing function (HOSIDF) for polynomial Wiener–Hammerstein systems are explicitly related, assuming the linear dynamics are known. Necessary and sufficient conditions for this relation to exist and results on the uniqueness and equivalence of the HOSIDF and GFRF are provided. Finally, this yields an efficient computational procedure for computing the GFRF from the HOSIDF and vice versa. 相似文献
456.
Thijs van Keulen Dominique van Mullem Bram de Jager Maarten Steinbuch 《Control Engineering Practice》2012,20(5):547-558
Hybrid electric vehicles require an algorithm that controls the power split between the internal combustion engine and electric machine(s), and the opening and closing of the clutch. Optimal control theory is applied to derive a methodology for a real-time optimal-control-based power split algorithm. The presented strategy is adaptive for vehicle mass and road elevation, and is implemented on a standard Electronic Control Unit of a parallel hybrid electric truck. The implemented strategy is experimentally validated on a chassis dynamo meter. The fuel consumption is measured on 12 different trajectories and compared with a heuristic and a non-hybrid strategy. The optimal control strategy has a fuel consumption lower (up to 3%) than the heuristic strategy on all trajectories that are evaluated, except one. Compared to the non-hybrid strategy the fuel consumption reduction ranged from 7% to 16%. 相似文献
457.
Nicky G. Agelopoulos Marcel Dicke Maarten A. Posthumus 《Journal of chemical ecology》1995,21(11):1789-1811
The role of volatile infochemicals emitted by feces of larvae in the host-searching behavior of the parasitoidCotesia rubecula was evaluated during single- and dual-choice tests inside a wind tunnel. The following treatments were tested: feces produced by second and fourth instars ofPieris rapae (preferred host), second instars ofP. brassicae (inferior host), second instars ofP. napi (nonhost), and wet feces of second instars ofP. rapae. During a single-choice situation females ofC. rubecula oriented to all types of feces tested. When a preference was to be made,C. rubecula preferred feces of second instars ofP. rapae over that of fourth, feces ofP. rapae over that ofP. brassicae, feces ofP. napi over that ofP. brassicae, and wet over normal host feces. No preference was exhibited between feces of second instars ofP. napi and that of second instars ofP. rapae. The relative importance of infochemicals from host feces versus plant damage caused by host larvae to the searching behavior ofC. rubecula was also evaluated. Plant damage was more important to the searching females than host feces when feces were present in specific concentrations in relation to damage. The volatiles released by normal and wet feces of second instars ofP. rapae, wet feces of fourth instars ofP. rapae, and normal and wet feces ofP. brassicae were collected and identified. Overall, 85 chemical compounds were recorded belonging to the following chemical groups: alcohols, ketones, aldehydes, esters, isothiocyanates, sulfides, nitriles, furanoids, terpenoids and pyridines. The blend of chemicals emitted by feces of different instars ofP. rapae and different species ofPieris exhibited an instar and species specificity in both quantity and quality. Wetting of normal feces increased the amount of volatile chemicals released, and it was also responsible for the appearance of new compounds. The role of feces of larvae in the host-seeking behavior ofC. rubecula is discussed. 相似文献
458.
459.
Letizia Mattiacci Marcel Dicke Maarten A. Posthumus 《Journal of chemical ecology》1994,20(9):2229-2247
Induction of plant defense in response to herbivory includes the emission of synomones that attract the natural enemies of herbivores. We investigated whether mechanical damage to Brussels sprouts leaves (Brassica oleracea var.gemmifera) is sufficient to obtain attraction of the parasitoidCotesia glomerata or whether feeding byPieris brassicae caterpillars elicits the release of synomones not produced by mechanically damaged leaves. The response of the parasitoidCotesia glomerata to different types of simulated herbivory was observed. Flight-chamber dual-choice tests showed that mechanically damaged cabbage leaves were less attractive than herbivore-damaged leaves and mechanically damaged leaves treated with larval regurgitant. Chemical analysis of the headspace of undamaged, artificially damaged, caterpillar-infested, and caterpillar regurgitant-treated leaves showed that the plant responds to damage with an increased release of volatiles. Greenleaf volatiles and several terpenoids are the major components of cabbage leaf headspace. Terpenoids are emitted in analogous amounts in all treatments, including undamaged leaves. On the other hand, if the plant is infested by caterpillars or if caterpillar regurgitant is applied to damaged leaves, the emission of green-leaf volatiles is highly enhanced. Our data are in contrast with the induction of more specific synomones in other plant species, such as Lima bean and corn. 相似文献
460.
Manoj Nag Soeren Steudel Ajay Bhoolokam Adrian Chasin Maarten Rockele Kris Myny Joris Maas Thomas Fritz Jutta Trube Guido Groeseneken Paul Heremans 《Journal of the Society for Information Display》2014,22(1):23-28
In this work, we report on high‐performance bottom‐gate top‐contact (BGTC) amorphous‐Indium‐Gallium‐Zinc‐Oxide (a‐IGZO) thin‐film transistor (TFT) with SiO2 as an etch‐stop‐layer (ESL) deposited by medium frequency physical vapor deposition (mf‐PVD). The TFTs show field‐effect mobility (μFE) of 16.0 cm2/(V.s), sub‐threshold slope (SS?1) of 0.23 V/decade and off‐currents (IOFF) < 1.0 pA. The TFTs with mf‐PVD SiO2 ESL deposited at room temperature were compared with TFTs made with the conventional plasma‐enhanced chemical vapor deposition (PECVD) SiO2 ESL deposited at 300 °C and at 200 °C. The TFTs with different ESLs showed a comparable performance regarding μFE, SS?1, and IOFF, however, significant differences were measured in gate bias‐stress stability when stressed under a gate field of +/?1 MV/cm for duration of 104 s. The TFTs with mf‐PVD SiO2 ESL showed lower threshold‐voltage (VTH) shifts compared with TFTs with 300 °C PECVD SiO2 ESL and TFTs with 200 °C PECVD SiO2 ESL. We associate the improved bias‐stress stability of the mf‐PVD SiO2 ESL TFTs to the low hydrogen content of the mf‐PVD SiO2 layer, which has been verified by Rutherford‐Back‐Scattering‐Elastic‐Recoil‐Detection technique. 相似文献