Fluidization of Group B particles with a rotating distributor

A novel rotating distributor fluidized bed is presented. The distributor is a rotating perforated plate, with 1% open-area ratio. This work evaluates the performance of this new design, considering pressure drop, Δp, and quality of fluidization. Bed fluidization was easily achieved with the proposed device, improving the solid mixing and the quality of fluidization. In order to examine the effect of the rotational speed of the distributor plate on the hydrodynamic behavior of the bed, minimum fluidization velocity, Umf, and pressure fluctuations were analyzed. Experiments were conducted in the bubbling free regime in a 0.19 m i.d. fluidized bed, operating with Group B particles according to Geldart's classification. The pressure drop across the bed and the standard deviation of pressure fluctuations, σp, were used to find the minimum fluidization velocity, Umf. A decrease in Umf is observed when the rotational speed increases and a rise in the measured pressure drop was also found. Frequency analysis of pressure fluctuations shows that fluidization can be controlled by the adjustable rotational speed, at several excess gas velocities. Measurements with several initial static bed heights were taken, in order to analyze the influence of the initial bed mass inventory, over the effect of the distributor rotation on the bed hydrodynamics.Publicad

Linear cryptanalysis of pseudorandom functions

Relatório de projeto de pesquisa.In this paper, we study linear relations propagating across block ciphers from the key input to the ciphertext (for a fixed plaintext block). This is a usual setting of a one-way function, used for instance in modes of operation such as KFB (key feedback). We instantiate the block cipher with the full 16-round DES and $s^2$-DES, 10-round LOKI91 and 24-round Khufu, for which linear relations with high bias are well known. Other interesting targets include the full 8.5-round IDEA and PES ciphers for which high bias linear relations exist under the assumption of weak keys. Consequences of these findings impact the security of modes of operation such as KFB and of pseudorandom number/bit generators. These analyses were possible due to the linear structure and the poor diffusion of the key schedule algorithms. These findings shall motivate carefull (re)design of current and future key schedule algorithms

An unpublished interview with Paulo Freire: radical pedagogy & social transformation

Pulling together the inedited works by Paulo Freire in the XXI century shows us how his works are up-to-date with current issues in the field. Most of his works have been disseminated all over the World, as those of the greatest educator of all times; however, his simplicity and outspoken voice is unique and cannot be reproduce in a simple manner. This is possibly why many writers use his citations, instead of paraphrasing his writings. Therefore, this paper represents another attempt to focus on his own voice and perspective on some of the questions raised by students three decades ago, that had never reach a broad audience but are nevertheless still in the minds of many students who are today interested in his work. The paper presents a short unpublished interview with Freire in 1988, when he talks about theoretical affiliation, critiques and the objectives of his works. In a conversation format the interview is a re-encounter between Paulo Freire and his former student Carmen de Mattos

FOLKSONOMIA: UMA ANÁLISE DE SUA OPERACIONALIDADE E SUA POSSÍVEL APLICABILIDADE NA CIÊNCIA DA INFORMAÇÃO

O artigo apresenta uma análise da operacionalidade das Folksonomias e a possibilidade de\ud aplicação dessa ferramenta nos sistemas de organização da informação da área de Ciência\ud da Informação. Para tanto foi realizada uma análise de coerência de tags e dos recursos\ud disponíveis para etiquetagem em dois websites, a Last.fm e o CiteULike. Por meio dessa\ud análise constatou-se que em ambos os websites ocorreram incoerências e discrepâncias\ud nas tags utilizadas. Todavia, o sistema da Last.fm demonstrou-se mais funcional que o do\ud CiteULike obtendo um desempenho melhor. Por fim, sugere-se a junção das Folksonomias\ud às Ontologias, que permitiriam a criação de sistemas automatizados de organização de\ud conteúdos informacionais alimentados pelos próprios usuáriosThe article presents an analysis of the operability of Folksonomies and the possibility of\ud applying this tool in the systems of information organization in the area of Information\ud Science.It begins with an analysis of consistency of tags and tagging of resources available\ud on two websites: Last.fm and CiteULike. This analysis identify that in both sites where found\ud inconsistencies and discrepancies in the used tags. Moreover, the system demonstrated the\ud Last.fm was more functional than CiteULike, getting a better performance. Finally, we\ud suggest the fusion of Folksonomies to Ontologies, which allow the creation of automated\ud systems to organize informational content supplied by the user

Weak measurement og the composite Goo-Haenchen shift in the critical region

By using a weak measurement technique, we investigated the interplay between the angular and lateral Goos-Haenchen shift of a focused He-Ne laser beam for incidence near the critical angle. We verified that this interplay dramatically affects the composite Goos-Haenchen shift of the propagated beam. The experimental results confirm theoretical predictions that recently appeared in the literature.Comment: 10 pages, 3 figure

Programming languages in economics: a comparison among Fortran77, C++, and Java

The main objective of this paper was to compare the computer programming languages Fortran77, C++, and Java under four aspects: runtime efficiency, readability, ease of learning, and reliability. For this comparison, we revised the specialized literature on programming languages and used pieces of codes of these three programming languages. The purpose of this comparison was to provide some objective information for economists interested in learning one or more of these languages.Programming language, Runtime efficiency, Readability, Reliability, Teaching/Communication/Extension/Profession,

The determinants of demand in football matches during the 2007 Brazilian Championship

In view of the structural changes experienced by Brazilian football as a whole, which is becoming better regulated and more transparently managed, it is necessary to examine the factors that now determine the attendance at football matches. This paper aims to examine the demand for tickets in the 2007 Brazilian Championship games, the main competition in that sport in the country, based on the methodology created by Souza and Angelo (2004), which conducted a study for the championship of 2002. The present study, using the Ordinary Least Squares method, showed that in 2007 the demand for football was price-inelastic, but no inference can be made with respect to income. Moreover, in general, the determinants were found to be steady.microeconomics, economics of sports, theory of demand, attendance