A simple deterministic self-organized critical system

We introduce a new continuous cellular automaton that presents self-organized criticality. It is one-dimensional, totally deterministic, without any kind of embedded randomness, not even in the initial conditions. This system is in the same universality class as the Oslo rice pile system, boundary driven interface depinning and the train model for earthquakes. Although the system is chaotic, in the thermodynamic limit chaos occurs only in a microscopic level.Comment: System slightly modified. New results on Liapunov exponents. Submitted for publication (8 pages

Avaliação da qualidade tecnológica do feijão armazenado em Silobolsa.

O objetivo principal deste trabalho foi verificar a qualidade culinária e o aspecto visual do feijão armazenado em SILOBOLSA por um período de quatro meses e compará-lo com os grãos armazenados em ambiente natural. Adicionalmente, o produto foi avaliado como semente.bitstream/CNPAF/25025/1/comt_116.pd

Breakdown of self-organized criticality

We introduce two sandpile models which show the same behavior of real sandpiles, that is, an almost self-organized critical behavior for small systems and the dominance of large avalanches as the system size increases. The systems become fully self-organized critical, with the critical exponents of the Bak, Tang and Wiesenfeld model, as the system parameters are changed, showing that these systems can make a bridge between the well known theoretical and numerical results and what is observed in real experiments. We find that a simple mechanism determines the boundary where self-organized can or cannot exist, which is the presence of local chaos.Comment: 3 pages, 4 figure

On the Complexity of Query Result Diversification

Query result diversification is a bi-criteria optimization problem for ranking query results. Given a database D, a query Q and a positive integer k, it is to find a set of k tuples from Q(D) such that the tuples are as relevant as possible to the query, and at the same time, as diverse as possible to each other. Subsets of Q(D) are ranked by an objective function defined in terms of relevance and diversity. Query result diversification has found a variety of applications in databases, information retrieval and operations research. This paper studies the complexity of result diversification for relational queries. We identify three problems in connection with query result diversification, to determine whether there exists a set of k tuples that is ranked above a bound with respect to relevance and diversity, to assess the rank of a given k-element set, and to count how many k-element sets are ranked above a given bound. We study these problems for a variety of query languages and for three objective functions. We establish the upper and lower bounds of these problems, all matching, for both combined complexity and data complexity. We also investigate several special settings of these problems, identifying tractable cases. 1

A agricultura brasileira: desempenho, desafios e perspectivas.

Primeira parte: Desempenho produtivo e estrutura. Cap. 1 - Produtividade total dos fatores e transformações da agricultura brasileira: análise dos dados dos censos agropecuários; Cap. 2 - Evolução recente da estrutura fundiária e propriedade rural no Brasil. Segunda parte: Mudança tecnológica e especificidades setoriais. Cap. 3 Trajetória tecnológica e aprendizado no setor agropecuário; Cap. 4 - Inovação tecnológica na agricultura, o papel da biotecnologia agrícola e a emergência de mercados regulados; Cap. 5 - Mudanças e reiteração da heterogeneidade do mercado de trabalho agrícola. terceira parte: Segmentações sociais e disputas sociopolíticas. Cap. 6 - Os desafios das agriculturas brasileiras; Cap. 7 - A agricultura familiar no Brasil: entre a política e as transformações da vida econômica. Quarta parte: Qual o futuro da agricultura? Cap. 8 - A expansão produtividade em regiões rurais - há um dilema entre crescimento econômico, coesão social e conservação ambiental?; Cap. 9 - Política agrícola no Brasil: subsídios e investimentos; Cap. 10 - A dificuldade de mudar: o caso da política agrícola no Brasil; Cap. 11: Ganhar tempo é possível?bitstream/item/47917/1/A-agricultura-brasileira-livro-IPEA.pd

OPE for Super Loops

We extend the Operator Product Expansion for Null Polygon Wilson loops to the Mason-Skinner-Caron-Huot super loop, dual to non MHV gluon amplitudes. We explain how the known tree level amplitudes can be promoted into an infinite amount of data at any loop order in the OPE picture. As an application, we re-derive all one loop NMHV six gluon amplitudes by promoting their tree level expressions. We also present some new all loops predictions for these amplitudes.Comment: 16 pages + appendices; 5 figure

Onset of dissipation in ballistic atomic wires

Electronic transport at finite voltages in free-standing gold atomic chains of up to 7 atoms in length is studied at low temperatures using a scanning tunneling microscope (STM). The conductance vs voltage curves show that transport in these single-mode ballistic atomic wires is non-dissipative up to a finite voltage threshold of the order of several mV. The onset of dissipation and resistance within the wire corresponds to the excitation of the atomic vibrations by the electrons traversing the wire and is very sensitive to strain.Comment: Revtex4, 4 pages, 3 fig

Correlation property of length sequences based on global structure of complete genome

This paper considers three kinds of length sequences of the complete genome. Detrended fluctuation analysis, spectral analysis, and the mean distance spanned within time $L$ are used to discuss the correlation property of these sequences. The values of the exponents from these methods of these three kinds of length sequences of bacteria indicate that the long-range correlations exist in most of these sequences. The correlation have a rich variety of behaviours including the presence of anti-correlations. Further more, using the exponent $\gamma$, it is found that these correlations are all linear ($\gamma=1.0\pm 0.03$). It is also found that these sequences exhibit $1/f$ noise in some interval of frequency ($f>1$). The length of this interval of frequency depends on the length of the sequence. The shape of the periodogram in $f>1$ exhibits some periodicity. The period seems to depend on the length and the complexity of the length sequence.Comment: RevTex, 9 pages with 5 figures and 3 tables. Phys. Rev. E Jan. 1,2001 (to appear

Konishi operator at intermediate coupling

TBA equations for two-particle states from the sl(2) sector proposed by Arutyunov, Suzuki and the author are solved numerically for the Konishi operator descendent up to 't Hooft's coupling lambda ~ 2046. The data obtained is used to analyze the properties of Y-functions and address the issue of the existence of the critical values of the coupling. In addition we find a new integral representation for the BES dressing phase which substantially reduces the computational time.Comment: lots of figures, v2: improved numerics, c1=2, c2=0, c4 does not vanis