Developed Algorithms (developed + algorithms)

Distribution by Scientific Domains


Selected Abstracts


On the analysis of non-linear allometries

ECOLOGICAL ENTOMOLOGY, Issue 1 2009
ROBERT J. KNELL
Abstract 1.,Non-linear allometries are those where a log,log scatterplot of trait size against body size deviates from simple linearity. These are found in many insects, including the horns of beetles, the forceps of earwigs, and the heads of certain castes of ant. 2.,Non-linear allometries are often associated with polyphenism that is itself related to behaviour: for example, the alternative mating tactics displayed by many species of beetle are widely associated with dimorphisms in horn size. 3.,This paper critically reviews the current techniques used to analyse these datasets. 4.,Recommendations include the use of scatterplots and assessment of the goodness of fit of simple linear models as an initial screen for non-linear allometry. The use of recently developed algorithms for ,segmented' regression to analyse continuous allometric relationships, and a pragmatic approach to the analysis of discontinuous relationships that recognises that there is no simple way to distinguish between morphs in some cases, and that all of the proposed methods for doing so have some drawbacks. 5.,Worked examples of the analysis of two sets of data from animals that have been the subject of controversy regarding the nature of their allometric relationships are given: further worked examples are provided as online Supporting Information. [source]


Hybrid domain decomposition algorithms for compressible and almost incompressible elasticity

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 2 2010
Clark R. Dohrmann
Abstract Overlapping Schwarz methods are considered for mixed finite element approximations of linear elasticity, with discontinuous pressure spaces, as well as for compressible elasticity approximated by standard conforming finite elements. The coarse components of the preconditioners are based on spaces, with a number of degrees of freedom per subdomain which are uniformly bounded, which are similar to those previously developed for scalar elliptic problems and domain decomposition methods of iterative substructuring type, i.e. methods based on nonoverlapping decompositions of the domain. The local components of the new preconditioners are based on solvers on a set of overlapping subdomains. In the current study, the dimension of the coarse spaces is smaller than in recently developed algorithms; in the compressible case all independent face degrees of freedom have been eliminated while in the almost incompressible case five out of six are not needed. In many cases, this will result in a reduction of the dimension of the coarse space by about one half compared with that of the algorithm previously considered. In addition, in spite of using overlapping subdomains to define the local components of the preconditioner, values of the residual and the approximate solution need only to be retained on the interface between the subdomains in the iteration of the new hybrid Schwarz algorithm. The use of discontinuous pressures makes it possible to work exclusively with symmetric, positive-definite problems and the standard preconditioned conjugate gradient method. Bounds are established for the condition number of the preconditioned operators. The bound for the almost incompressible case grows in proportion to the square of the logarithm of the number of degrees of freedom of individual subdomains and the third power of the relative overlap between the overlapping subdomains, and it is independent of the Poisson ratio as well as jumps in the Lamé parameters across the interface between the subdomains. Numerical results illustrate the findings. Copyright © 2009 John Wiley & Sons, Ltd. [source]


Sliding mesh algorithm for CFD analysis of helicopter rotor,fuselage aerodynamics

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 5 2008
R. Steijl
Abstract The study of rotor,fuselage interactional aerodynamics is central to the design and performance analysis of helicopters. However, regardless of its significance, rotor,fuselage aerodynamics has so far been addressed by very few authors. This is mainly due to the difficulties associated with both experimental and computational techniques when such complex configurations, rich in flow physics, are considered. In view of the above, the objective of this study is to develop computational tools suitable for rotor,fuselage engineering analysis based on computational fluid dynamics (CFD). To account for the relative motion between the fuselage and the rotor blades, the concept of sliding meshes is introduced. A sliding surface forms a boundary between a CFD mesh around the fuselage and a rotor-fixed CFD mesh which rotates to account for the movement of the rotor. The sliding surface allows communication between meshes. Meshes adjacent to the sliding surface do not necessarily have matching nodes or even the same number of cell faces. This poses a problem of interpolation, which should not introduce numerical artefacts in the solution and should have minimal effects on the overall solution quality. As an additional objective, the employed sliding mesh algorithms should have small CPU overhead. The sliding mesh methods developed for this work are demonstrated for both simple and complex cases with emphasis placed on the presentation of the inner workings of the developed algorithms. Copyright © 2008 John Wiley & Sons, Ltd. [source]


Neural Signal Manager: a collection of classical and innovative tools for multi-channel spike train analysis

INTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 11 2009
Antonio Novellino
Abstract Recent developments in the neuroengineering field and the widespread use of the micro electrode arrays (MEAs) for electrophysiological investigations made available new approaches for studying the dynamics of dissociated neuronal networks as well as acute/organotypic slices maintained ex vivo. Importantly, the extraction of relevant parameters from these neural populations is likely to involve long-term measurements, lasting from a few hours to entire days. The processing of huge amounts of electrophysiological data, in terms of computational time and automation of the procedures, is actually one of the major bottlenecks for both in vivo and in vitro recordings. In this paper we present a collection of algorithms implemented within a new software package, named the Neural Signal Manager (NSM), aimed at analyzing a huge quantity of data recorded by means of MEAs in a fast and efficient way. The NSM offers different approaches for both spike and burst analysis, and integrates state-of-the-art statistical algorithms, such as the inter-spike interval histogram or the post stimulus time histogram, with some recent ones, such as the burst detection and its related statistics. In order to show the potentialities of the software, the application of the developed algorithms to a set of spontaneous activity recordings from dissociated cultures at different ages is presented in the Results section. Copyright © 2008 John Wiley & Sons, Ltd. [source]


Iterative correlation-based controller tuning

INTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 8 2004
A. Karimi
Abstract This paper gives an overview on the theoretical results of recently developed algorithms for iterative controller tuning based on the correlation approach. The basic idea is to decorrelate the output error between the achieved and designed closed-loop systems by iteratively tuning the controller parameters. Two different approaches are investigated. In the first one, a correlation equation involving a vector of instrumental variables is solved using the stochastic approximation method. It is shown that, with an appropriate choice of instrumental variables and a finite number of data at each iteration, the algorithm converges to the solution of the correlation equation. The convergence conditions are derived and the accuracy of the estimates are studied. The second approach is based on the minimization of a correlation criterion. The frequency analysis of the criterion shows that the two norm of the error between the desired and achieved closed-loop transfer functions is minimized independent of the noise characteristics. This analysis leads to the definition of a generalized correlation criterion which allows the mixed sensitivity problem to be handled in two norm. Copyright © 2004 John Wiley & Sons, Ltd. [source]


A sociodental approach to assessing dental needs of children: concept and models

INTERNATIONAL JOURNAL OF PAEDIATRIC DENTISTRY, Issue 2 2006
S. GHERUNPONG
Summary. Objectives., Traditional normative methods of assessing dental needs do not correspond to current concepts of ,health' and ,need'. Although there is dental research on quality of life, evidence-based practice, and oral behaviours, those concepts are rarely applied to dental needs estimation. Dental needs are usually calculated mainly from clinical data and are likely to be inaccurate. A structured comprehensive method for assessing dental needs is required. The objectives of this study are to develop and test a new sociodental system of needs assessment for overall dental needs of primary schoolchildren. Furthermore, normative and sociodental estimates of need are compared. Design., The study developed a theoretical framework and pathway algorithms of sociodental needs assessment and applied them to assessing overall dental needs. Normative dental needs were assessed using standard normative criteria. The child oral impacts on daily performances (Child-OIDP) was used to assess oral impacts, and a self-administered questionnaire was used to obtain information on demographic variables and oral behaviours. Data were analysed according to the developed algorithms. Setting., A cross-sectional survey in Suphanburi Province, Thailand. Participants., All 1126 children aged 11,12 years in a town. Main results., The sociodental approach was acceptable and not costly. In all, 54·4% had normative need under the dental needs model for life-threatening and progressive conditions, but only 16·6% had high propensity-related need; the remaining 37·8% would require dental health education or oral health promotion (DHE/OHP) or both and appropriately adjusted clinical interventions. Under the basic model of dental needs, 45·1% had normative need. Two-thirds of them (30·9%) had impact-related need and the remaining 14·2% did not have oral impacts and therefore should only receive dental health education. Only one-third of those with impact-related need had high propensity and were suitable for evidence-based conventional treatments; the remaining two-thirds should receive DHE/OHP and alternative clinical interventions. Conclusions., A sociodental system of dental needs assessment was developed and tested on school children. It decreased the estimates of conventionally assessed dental treatment needs and introduced a broader approach to care. [source]


Coverage path planning algorithms for agricultural field machines

JOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 8 2009
Timo Oksanen
In this article, a coverage path planning problem is discussed in the case of agricultural fields and agricultural machines. Methods and algorithms to solve this problem are developed. These algorithms are applicable to both robots and human-driven machines. The necessary condition is to cover the whole field, and the goal is to find as efficient a route as possible. As yet, there is no universal algorithm or method capable of solving the problem in all cases. Two new approaches to solve the coverage path planning problem in the case of agricultural fields and agricultural machines are presented for consideration. Both of them are greedy algorithms. In the first algorithm the view is from on top of the field, and the goal is to split a single field plot into subfields that are simple to drive or operate. This algorithm utilizes a trapezoidal decomposition algorithm, and a search is developed of the best driving direction and selection of subfields. This article also presents other practical aspects that are taken into account, such as underdrainage and laying headlands. The second algorithm is also an incremental algorithm, but the path is planned on the basis of the machine's current state and the search is on the next swath instead of the next subfield. There are advantages and disadvantages with both algorithms, neither of them solving the problem of coverage path planning problem optimally. Nevertheless, the developed algorithms are remarkable steps toward finding a way to solve the coverage path planning problem with nonomnidirectional vehicles and taking into consideration agricultural aspects. © 2009 Wiley Periodicals, Inc. [source]