Search results for "selection"
showing 10 items of 1940 documents
Transplantation assessment of degraded Posidonia oceanica habitats: site selection and long-term monitoring
2014
A model developed for Zostera marina was adapted and used to select suitable areas for Posidonia oceanica transplantation in the Gulf of Palermo, where recent rehabilitation programmes have reduced human pressure. This model consists of three steps: (1) habitat selection, by calculation of the Preliminary Transplant Suitability Index (PTSI); (2) field assessments and test-transplanting, to evaluate the site suitability and to estimate the effects of tearing on transplant units (about 50%); (3) identification of suitable restoration sites, by calculation of the Transplant Suitability Index (TSI). A new parameter was added to the literature model: the number of grids detached, which is linked…
Nest building in a Mediterranean wrasse (Symphodus ocellatus): are the algae used randomly chosen or actively selected?
2014
To increase their reproductive success, fish species have evolved various strategies, including both simple processes and more complex mechanisms that involve parental care by nest-building. In Symphodus ocellatus, a species that lives in rocky infralittoral zones of the Mediterranean Sea, during the reproductive period, the male builds a nest within a hole or crevice using fragments of algae and/or sand particles. Data on the nesting activity of wrasses are rare, and previous descriptions regarding the algal composition of nests have provided conflicting results. In this regard, it is unclear whether territorial males actively select algal species for nest construction or algal choice is r…
Hiding behaviour ofOxynoe olivacea(Mollusca: Opisthobranchia: Sacoglossa) in the invasive seaweedCaulerpa taxifolia
2013
The occurrence of the invasive seaweed Caulerpa taxifolia in the Straits of Messina (Italy) provides an excellent opportunity to examine the spatial and temporal patterns of abundance of the endemic Mediterranean sacoglossan Oxynoe olivacea. Densities of this species were recorded in March, June and October 2000 on three different habitats: the underside of boulders (UNB), the upper side of boulders (UPB), and the surface of concrete blocks (CB). Results showed that in March, O. olivacea was consistently more abundant on UNB whereas in June it was present exclusively on CB. The density of O. olivacea was similar in the three habitats in October. The hiding behaviour of O. olivacea and its s…
Exploring relationships between pixel size and accuracy for debris flow susceptibility models: a test in the Giampilieri catchment (Sicily, Italy).
2014
Debris flows are among the most hazardous phenomena in nature, which typically take the form of multiple-occurrence regional landslide events triggered by intense driving inputs such as storms or earthquakes. The main tasks of this study were to verify whether cell-based susceptibility models is capable of predicting debris flow initiations in the Giampilieri catchment (southern Italy) and to explore the relationships between the pixel size of the adopted mapping units in terms of predictive performances of the derived models. The Giampilieri catchment is a small area (10km 2 ) hit by a storm on the 1 st October 2009 which resulted in the triggering of more than one thousand landslides and …
Algorithmic paradigms for stability-based cluster validity and model selection statistical methods, with applications to microarray data analysis
2012
AbstractThe advent of high throughput technologies, in particular microarrays, for biological research has revived interest in clustering, resulting in a plethora of new clustering algorithms. However, model selection, i.e., the identification of the correct number of clusters in a dataset, has received relatively little attention. Indeed, although central for statistics, its difficulty is also well known. Fortunately, a few novel techniques for model selection, representing a sharp departure from previous ones in statistics, have been proposed and gained prominence for microarray data analysis. Among those, the stability-based methods are the most robust and best performing in terms of pre…
A new feature selection strategy for K-mers sequence representation
2014
DNA sequence decomposition into k-mers (substrings of length k) and their frequency counting, defines a mapping of a sequence into a numerical space by a numerical feature vector of fixed length. This simple process allows to compute sequence comparison in an alignment free way, using common similarities and distance functions on the numerical codomain of the mapping. The most common used decomposition uses all the substrings of length k making the codomain of exponential dimension. This obviously can affect the time complexity of the similarity computation, and in general of the machine learning algorithm used for the purpose of sequence classification. Moreover, the presence of possible n…
Structured methodology for selection of maintenance key performance indicators: Application to an oil refinery plant
2017
The novel contribution of the work is the proposal of a structured multi-step methodology that may support the Decision Maker (DM) in the measurement of maintenance performance by means of Maintenance Key Performance Indicators (MKPIs). To this aim, a multi-level hierarchical framework able to synthesize the most meaningful aspects affecting the maintenance results is designed. Then, MKPIs are selected from the literature, assigned to the hierarchical framework and ranked by an Analytic Hierarchy Process-based approach with incomplete comparison matrices. A mathematical model is finally formulated to select the optimal set of MKPIs. The methodology is implemented in an oil refinery plant an…
Fast adaptive frame preprocessing for 3D reconstruction
2015
Abstract: This paper presents a new online preprocessing strategy to detect and discard ongoing bad frames in video sequences. These include frames where an accurate localization between corresponding points is difficult, such as for blurred frames, or which do not provide relevant information with respect to the previous frames in terms of texture, image contrast and non-flat areas. Unlike keyframe selectors and deblurring methods, the proposed approach is a fast preprocessing working on a simple gradient statistic, that does not require to compute complex time-consuming image processing, such as the computation of image feature keypoints, previous poses and 3D structure, or to know a prio…
A MAS metamodel-driven approach to process fragments selection
2009
The construction of ad-hoc design processes is more and more required today. In this paper we present our approach for the construction of a new design process following the Situational Method Engineering paradigm. We mainly focus on the selection and assembly activities on the base of what we consider a key element in agent design processes: the MAS metamodel. The paper presents an algorithm establishing a priority order in the realization (instantiation) of MAS metamodel elements by the fragments that will compose the new process.
Simulation and anticipation as tools for coordinating with the future
2013
A key goal in designing an artificial intelligence capable of performing complex tasks is a mechanism that allows it to efficiently choose appropriate and relevant actions in a variety of situations and contexts. Nowhere is this more obvious than in the case of building a general intelligence, where the contextual choice and application of actions must be done in the presence of large numbers of alternatives, both subtly and obviously distinct from each other. We present a framework for action selection based on the concurrent activity of multiple forward and inverse models. A key characteristic of the proposed system is the use of simulation to choose an action: the system continuously sim…