2,979 publications from this institution
Fuzzy clustering has emerged as one of the fundamental conceptual and algorithmic frameworks supporting the development of information granules. Generic fuzzy clustering such as fuzzy C-means (FCM) has been utilized in a broad range of applications. However, the constructs resulting from fuzzy clustering, namely a partition matrix and prototypes, are numeric and as such are not capable of fully capturing the essence of the overall data. In this study, we propose an alternative augmented way of building information granules by generating hypercube-like information granules. A collection of hypercubes is referred to as a family of ε-information granules. This family is constructed around numeric prototypes generated through a modified version of the FCM algorithm whose running time is linear with respect to the number of clusters. By admitting a certain level of information granularity (ε), a collection of hypercubes is formed around the prototypes. The quality of information granules realized in this way is assessed by involving them in the granulation-degranulation process as well as determining a value of the coverage criterion. The level of information granularity and the number of the granular prototypes in the family of ε-information granules form an important design asset directly impacting the obtained coverage level of the data. The computational facet of the approach is stressed. It has been demonstrated that the granular enhancements of the description of data come with a very limited computing overhead. Experimental studies involve synthetic data as well as data coming from the UCI Machine Learning repository. The granular reconstruction capabilities delivered by the family of ε-information granules are discussed.
Anomaly detection in spatial time series (spatiotemporal data) is a challenging problem with numerous potential applications. A comprehensive anomaly detection approach not only should be able to detect and identify the emerging anomalies but has to characterize the essence of these anomalies by visualizing the structures revealed within data in a way that is understandable to the end-user as well. In this paper, we consider fuzzy c-means (FCM) as a conceptual and algorithmic setting to deal with the problem of anomaly detection. Using a sliding window, the time series are divided into a number of subsequences, and the available spatiotemporal structure within each time window is discovered using the FCM method. In the sequel, an anomaly score is assigned to each cluster, and using a fuzzy relation formed between revealed structures, a propagation of anomalies occurring in consecutive time intervals is visualized. To illustrate the proposed method, several datasets (synthetic data, a simulated disease outbreak scenario, and Alberta temperature data) have been investigated.
The semantic vision of the Web involves the processing of data by automated tools as well as by people, where the association of meaning with content, facilitates the search, the interoperability and the composition of several services. The Semantic Web forms a new scenario, where advanced methods and techniques are developed for the description, the retrieval and filtering of Web-based content. In the light of existing challenges and open issues concerning the actual cyberspace, this study proposes an approach for binding the "semantic" facet with the usual textual one, that together constitutes a typical web page, or specifically, a semantic web document. Through the use of unsupervised learning, we offer a new alternative of organizing web documents which emphasizes a direct separation between the syntactic and semantic facets of the web information. In this study, we discuss a collaborative proximity-based fuzzy clustering and show how this type of clustering is used to discover a structure of web information by a prudent reliance on the structures in the spaces of semantics and data. The method focuses on the reconciliation between the two separated facets of web information and a combination of results leading to a comprehensive data organization. The information arranged in this manner can provide an integral description of web resources, becoming in this manner an essential technique for the next generation of Web search engines.
A fast solving method of the solution for max continuous t-norm composite fuzzy relational equation of the type G(i, j)=(R/sup T//spl square/A/sub i/)/sup T//spl square/B/sub j/, i=1, 2, ..., I, j=1, 2, ..., J, where A/sub i//spl isin/F(X)X={x/sub 1/, x/sub 2/, ..., x/sub M/}, Bj/spl isin/F(Y) Y={y/sub 1/, y/sub 2/, ..., y/sub N/}, R/spl isin/F(X/spl times/Y), and /spl square/: max continuous t-norm composition, is proposed. It decreases the computation time IJMN(L+T+P) to JM(I+N)(L+P), where L, T, and P denote the computation time of min, t-norm, and relative pseudocomplement operations, respectively, by simplifying the conventional reconstruction equation based on the properties of t-norm and relative pseudocomplement. The method is applied to a lossy image compression and reconstruction problem, where it is confirmed that the computation time of the reconstructed image is decreased to 1/335.6 the compression rate being 0.0351, and it achieves almost equivalent performance for the conventional lossy image compression methods based on discrete cosine transform and vector quantization.
We present a new programmable neighborhood mechanism for hardware implemented Kohonen self-organizing maps (SOMs) with three different map topologies realized on a single chip. The proposed circuit comes as a fully parallel and asynchronous architecture. The mechanism is very fast. In a medium sized map with several hundreds neurons implemented in the complementary metal-oxide semiconductor 0.18 μm technology, all neurons start adapting the weights after no more than 11 ns. The adaptation is then carried out in parallel. This is an evident advantage in comparison with the commonly used software-realized SOMs. The circuit is robust against the process, supply voltage and environment temperature variations. Due to a simple structure, it features low energy consumption of a few pJ per neuron per a single learning pattern. In this paper, we discuss different aspects of hardware realization, such as a suitable selection of the map topology and the initial neighborhood range, as the optimization of these parameters is essential when looking from the circuit complexity point of view. For the optimal values of these parameters, the chip area and the power dissipation can be reduced even by 60% and 80%, respectively, without affecting the quality of learning.
