Effects of sulfonation process on thermal behavior and microstructure of sulfonated polysulfone membranes as a material for Proton Exchange Membrane (PEM)

This paper reports the effect of sulfonation processon thermal behavior and microstrucutre of sulfonated polysulfone membrane. Various degree of sulfonation reactin has been conducted and the sulfonated membranes were characterized by thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), x-ray diffraction (XRD) and scanning electron microscopy (SEM). Modifications of the origin polysulfone polymer resulted in an increment value of glass transition temperature (Tg) due to the introduction of sulfonic acid group to the polymer backbone. However, due to some hindrance such as trace amount of organic solvent left during solvent evaporation and high hydrophilicity of the produced sulfonated membranes resulted in decreasing values of Tg. The polymer membrane showed lower degradation temperature as a function of degree of sulfonation. From XRD analysis, it was found that the membrane shows slight crystalline behavior after the sulfonation reaction. Detail discussions and observation of the alteration in microstructure of the sulfonated membrane were supported by SEM micrograph

Scaling in Tournaments

We study a stochastic process that mimics single-game elimination tournaments. In our model, the outcome of each match is stochastic: the weaker player wins with upset probability q<=1/2, and the stronger player wins with probability 1-q. The loser is eliminated. Extremal statistics of the initial distribution of player strengths governs the tournament outcome. For a uniform initial distribution of strengths, the rank of the winner, x_*, decays algebraically with the number of players, N, as x_* ~ N^(-beta). Different decay exponents are found analytically for sequential dynamics, beta_seq=1-2q, and parallel dynamics, beta_par=1+[ln (1-q)]/[ln 2]. The distribution of player strengths becomes self-similar in the long time limit with an algebraic tail. Our theory successfully describes statistics of the US college basketball national championship tournament.Comment: 5 pages, 1 figure, empirical study adde

On The Structure of Competitive Societies

We model the dynamics of social structure by a simple interacting particle system. The social standing of an individual agent is represented by an integer-valued fitness that changes via two offsetting processes. When two agents interact one advances: the fitter with probability p and the less fit with probability 1-p. The fitness of an agent may also decline with rate r. From a scaling analysis of the underlying master equations for the fitness distribution of the population, we find four distinct social structures as a function of the governing parameters p and r. These include: (i) a static lower-class society where all agents have finite fitness; (ii) an upwardly-mobile middle-class society; (iii) a hierarchical society where a finite fraction of the population belongs to a middle class and a complementary fraction to the lower class; (iv) an egalitarian society where all agents are upwardly mobile and have nearly the same fitness. We determine the basic features of the fitness distributions in these four phases.Comment: 8 pages, 7 figure

Randomness in Competitions

We study the effects of randomness on competitions based on an elementary random process in which there is a finite probability that a weaker team upsets a stronger team. We apply this model to sports leagues and sports tournaments, and compare the theoretical results with empirical data. Our model shows that single-elimination tournaments are efficient but unfair: the number of games is proportional to the number of teams N, but the probability that the weakest team wins decays only algebraically with N. In contrast, leagues, where every team plays every other team, are fair but inefficient: the top $\sqrt{N}$ of teams remain in contention for the championship, while the probability that the weakest team becomes champion is exponentially small. We also propose a gradual elimination schedule that consists of a preliminary round and a championship round. Initially, teams play a small number of preliminary games, and subsequently, a few teams qualify for the championship round. This algorithm is fair and efficient: the best team wins with a high probability and the number of games scales as $N^{9/5}$, whereas traditional leagues require N^3 games to fairly determine a champion.Comment: 10 pages, 8 figures, reviews arXiv:physics/0512144, arXiv:physics/0608007, arXiv:cond-mat/0607694, arXiv:physics/061221

Dynamics of Multi-Player Games

We analyze the dynamics of competitions with a large number of players. In our model, n players compete against each other and the winner is decided based on the standings: in each competition, the mth ranked player wins. We solve for the long time limit of the distribution of the number of wins for all n and m and find three different scenarios. When the best player wins, the standings are most competitive as there is one-tier with a clear differentiation between strong and weak players. When an intermediate player wins, the standings are two-tier with equally-strong players in the top tier and clearly-separated players in the lower tier. When the worst player wins, the standings are least competitive as there is one tier in which all of the players are equal. This behavior is understood via scaling analysis of the nonlinear evolution equations.Comment: 8 pages, 8 figure

Self-Similarity in Random Collision Processes

Kinetics of collision processes with linear mixing rules are investigated analytically. The velocity distribution becomes self-similar in the long time limit and the similarity functions have algebraic or stretched exponential tails. The characteristic exponents are roots of transcendental equations and vary continuously with the mixing parameters. In the presence of conservation laws, the velocity distributions become universal.Comment: 4 pages, 4 figure

Análise da quantidade de azoto em excesso em solos agrícolas na zona vulnerável n.º 1

O conceito de Zona Vulnerável com vista a proteger as águas contra a poluição difusa causada por nitratos de origem agrícola, foi definido na Directiva 91/676/CEE, publicada no Jornal Oficial das Comunidades de 31 de Dezembro de 1997, a qual foi transposta para a ordem jurídica interna pelo Dec-Lei 235/97 de 3 de Setembro. Os objectivos deste diploma são: a redução da poluição das águas contra a poluição causada por nitratos de origem agrícola, bem como impedir a propagação desta poluição (artº 2). Com o presente trabalho pretende-se elaborar um modelo que permita quantificar a produção de chorume bovino que é um dos principais factores influentes na concentração de nitratos na Zona Vulnerável nº 1 Esposende – Vila do Conde

Entropic Tightening of Vibrated Chains

We investigate experimentally the distribution of configurations of a ring with an elementary topological constraint, a ``figure-8'' twist. Using vibrated granular chains, which permit controlled preparation and direct observation of such a constraint, we show that configurations where one of the loops is tight and the second is large are strongly preferred. This agrees with recent predictions for equilibrium properties of topologically-constrained polymers. However, the dynamics of the tightening process weakly violate detailed balance, a signature of the nonequilibrium nature of this system.Comment: 4 pages, 4 figure