Search results for "cluster analysis."
showing 10 items of 805 documents
Normalised compression distance and evolutionary distance of genomic sequences: comparison of clustering results
2009
Genomic sequences are usually compared using evolutionary distance, a procedure that implies the alignment of the sequences. Alignment of long sequences is a time consuming procedure and the obtained dissimilarity results is not a metric. Recently, the normalised compression distance was introduced as a method to calculate the distance between two generic digital objects and it seems a suitable way to compare genomic strings. In this paper, the clustering and the non-linear mapping obtained using the evolutionary distance and the compression distance are compared, in order to understand if the two distances sets are similar.
Fuzzy Smoothed Composition of Local Mapping Transformations for Non-rigid Image Registration
2009
This paper presents a novel method for medical image regis- tration. The global transformation is obtained by composing affine trans- formations, which are recovered locally from given landmarks. Transfor- mations of adjacent regions are smoothed to avoid blocking artifacts, so that a unique continuous and differentiable global function is obtained. Such composition is operated using a technique derived from fuzzy C- means clustering. The method was successfully tested on several datasets; results, both qualitative and quantitative, are shown. Comparisons with other methods are reported. Final considerations on the efficiency of the technique are explained.
The Switch to Online Learning during the COVID-19 Pandemic: The Interplay between Personality and Mental Health on University Students
2023
The switching from traditional to online learning during the COVID-19 pandemic was challenging for students, determining an increase in physical and mental health problems. The current paper applied a two-step cluster analysis in a large sample of n = 1028 university students (Mage = 21.10 years, SD = 2.45 years; range: 18–30 years; 78.4% females). Participants responded to an online survey exploring neuroticism, trait/state anxiety, general self-efficacy, academic motivation, fear of COVID-19, the impact of the COVID-19 pandemic on physical and mental health, and the help requests. Results showed two significant clusters of students having a Maladaptive Academic Profile (n = 456; 44.4%) or…
The relation between emotional support, self-concept, and social functioning among school-aged children
2013
The study examined the relations between perceived emotional support from parents and peers, self-concept and social functioning among a sample of school-aged children. The study had three main purposes. Firstly, the study was aimed at evaluating the association between emotional support perceived from parents and peers, and self concept. Secondly, the study was aimed at inquiring the existence of different children’s profiles on the basis of the level of perceived emotional support from parents and peers, and their self-concept. Finally, the study was aimed at exploring any difference that could have emerged in their social functioning. The participants were 270 children (F = 137, M = 133)…
Soft Topographic Map for Clustering and Classification of Bacteria
2007
In this work a new method for clustering and building a topographic representation of a bacteria taxonomy is presented. The method is based on the analysis of stable parts of the genome, the so-called “housekeeping genes”. The proposed method generates topographic maps of the bacteria taxonomy, where relations among different type strains can be visually inspected and verified. Two well known DNA alignement algorithms are applied to the genomic sequences. Topographic maps are optimized to represent the similarity among the sequences according to their evolutionary distances. The experimental analysis is carried out on 147 type strains of the Gammaprotebacteria class by means of the 16S rRNA…
The routes of Southern Italy university students: an explorative analysis
2022
The neoclassical migration approach postulates that different conditions in labour markets among territories are the driving forces behind migration. On the other hand, exponents of the new economics of migration argue that the decision to move is not made at the individual level. Considering migration as the result of a decision taken within a social network helps to explain the so-called chain migration. In this paper, we pay attention to the migratory chain of university students. This work introduces a statistical technique to “classify” migratory chains of students living in Sicily, Sardinia or Apulia, and enrolled in some centre-north regions from 2008 to 2017.
Implementing Immersive Clustering with VR Juggler
2005
Continuous, rapid improvements in commodity hardware have allowed users of immersive visualization to employ high-quality graphics hardware, high-speed processors, and significant amounts of memory for much lower costs than would be possible with high-end, shared memory computers traditionally used for such purposes. Mimicking the features of a single shared memory computer requires that the commodity computers act in concert—namely, as a tightly synchronized cluster. In this paper, we describe the clustering infrastructure of VR Juggler that enables the use of distributed and clustered computers for the display of immersive virtual environments. We discuss each of the potential ways to syn…
COMPARISON OF TWO SIMPLIFICATION METHODS FOR SHORELINE EXTRACTION FROM DIGITAL ORTHOPHOTO IMAGES
2018
Abstract. The coastal ecosystems are very sensitive to external influences. Coastal resources such as sand dunes, coral reefs and mangroves has vital importance to prevent coastal erosion. Human based effects also threats the coastal areas. Therefore, the change of coastal areas should be monitored. Up-to-date, accurate shoreline information is indispensable for coastal managers and decision makers. Remote sensing and image processing techniques give a big opportunity to obtain reliable shoreline information. In the presented study, NIR bands of seven 1:5000 scaled digital orthophoto images of Riga Bay-Latvia have been used. The Object-oriented Simple Linear Clustering method has been utili…
An enhanced random walk algorithm for delineation of head and neck cancers in PET studies
2017
An algorithm for delineating complex head and neck cancers in positron emission tomography (PET) images is presented in this article. An enhanced random walk (RW) algorithm with automatic seed detection is proposed and used to make the segmentation process feasible in the event of inhomogeneous lesions with bifurcations. In addition, an adaptive probability threshold and a k-means based clustering technique have been integrated in the proposed enhanced RW algorithm. The new threshold is capable of following the intensity changes between adjacent slices along the whole cancer volume, leading to an operator-independent algorithm. Validation experiments were first conducted on phantom studies:…
Trademarks recognition based on local regions similarities
2010
This paper deals with content based image retrieval. We propose a logo recognition algorithm based on local regions, where the trademark (or logo) image is segmented by the clustering of points of interest obtained by Harris corners detector. The minimum rectangle surrounding each cluster is detected forming the regions of interest. Global features such as Hu moments and histograms of each local region are combined to find similar logos in the database. Similarity is measured based on the integrated minimum average distance of the individual components. The results obtained demonstrate tolerance to logos distortions such as rotation, occlusion and noise.