Efficient bulk-loading on dynamic metric access methods

This paper presents a new technique and two algorithms to bulk-load data into multi-way dynamic metric access methods, based on the covering radius of representative elements employed to organize data in hierarchical data structures. The proposed algorithms are sample-based, and they always build a valid and height-balanced tree. We compare the proposed algorithm with existing ones, showing the behavior to bulk-load data into the Slim-tree metric access method. After having identified the worst case of our first algorithm, we describe adequate counteractions in an elegant way creating the second algorithm. Experiments performed to evaluate their performance show that our bulk-loading methods build trees faster than the sequential insertion method regarding construction time, and that it also significantly improves search performance. (C) 2009 Elsevier B.V. All rights reserved.

Study of bulk matter properties through strange quark hadrons with the STAR experiment

Relativistic heavy ion collisions are the ideal experimental tool to explore the QCD phase diagram. Several results show that a very hot medium with a high energy density and partonic degrees of freedom is formed in these collisions, creating a new state of matter. Measurements of strange hadrons can bring important information about the bulk properties of such matter. The elliptic flow of strange hadrons such as phi, K(S)(0), Lambda, Xi and Omega shows that collectivity is developed at partonic level and at intermediate p(T) the quark coalescence is the dominant mechanism of hadronization. The nuclear modification factor is an another indicator of the presence of a very dense medium. The comparison between measurements of Au+Au and d+Au collisions, where only cold nuclear matter effects are expected, can shed more light on the bulk properties. In these proceedings, recent results from the STAR experiment on bulk matter properties are presented.