Metal-poor globular clusters (MPGCs) are a unique probe of the early universe, in particular the reionization era. A popular hypothesis is that the observed truncation of MPGC formation is due to reionization. Under this hypothesis, constraining the formation epoch of MPGCs provides a complementary constraint on the epoch of reionization. Moreover, as the earliest reionizing sources first forme...

A general correction term in the radius of gyration ~caling law is discussed. The work incorporates the finite size effect considered by Ball and Jullien (J. Ph_»s. Left. Fiance 45 (1984) L1031j and is a potentially useful extension of their analysis to polydisperse systems. Numerical simulations verify these re~ults for one particular model, and demonstrate the remarkable

Stability in cluster analysis is strongly dependent on the data set, especially on how well separated and how homogeneous the clusters are. In the same clustering, some clusters may be very stable and others may be extremely unstable. The Jaccard coefficient, a similarity measure between sets, is used as a clusterwise measure of cluster stability, which is assessed by the bootstrap distribution...

In this paper, we introduce a notion of unistructural cluster algebras, for which the set of cluster variables uniquely determines the clusters. We prove that cluster algebras of Dynkin type and cluster algebras of rank 2 are unistructural, then prove that if A is unistructural or of Euclidean type, then f : A → A is a cluster automorphism if and only if f is an automorphism of the ambient fiel...

Radio continuum emission at 1.4 GHz was used to identify active galaxies in a sample of 20 nearby Abell clusters. The radio emission indicates either an active galactic nucleus or current star formation, and optical spectroscopy was used to evaluate which of these dominates for each of the radio-selected galaxies. In an analysis which parallels the blue fractions of Butcher-Oemler studies, we c...

It is proved that any cluster-tilted algebra defined in the cluster category C(H) has the same representation type as the initial hereditary algebra H . For any valued quiver (Γ,Ω), an injection from the subset PI(Ω) of the cluster category C(Ω) consisting of indecomposable preprojective objects, preinjective objects and the first shifts of indecomposable projective modules to the set of cluste...

In this paper an application of the cluster analysis technique in educational planning is demonstrated by means of a developed computer software with some characteristics of an expert system. The main idea is based on the knowledge-based systems which have been applied in group technology. The software is applied to weekly schedules of the courses and professors of the Industrial Engineering De...

Clusters are geographically close groups of related companies or institutions related to a certain area which are inherently more efficient than the other companies due to advantages such as being located in one place, networks, external knowledge, variability of human capital, etc. Today, development through clusters plays a pivotal role in the economic and industrial policies of developed...

Today, small and medium enterprises are considered as one of the main components of economic development for various reasons. To name a few, job creation, resource efficiency, the ability to enhance local technology, the ability to meet new needs, quick decision-making, and training successful managers will all lead to the growth and economic development of countries. Despite these benefits, sm...

an efficient cluster head selection algorithm in wireless sensor networks is proposed in this paper. the implementation of the proposed algorithm can improve energy which allows the structured representation of a network topology. according to the residual energy, number of the neighbors, and the centrality of each node, the algorithm uses fuzzy inference systems to select cluster head. the alg...