High rate filtration using buoyant medium : experiments and mathematical models

In this study, the high rate filtration system using buoyant medium of polypropylene or polystyrene was introduced with the study on its performance evaluation via: (i) specific surface coverage, (ii) ultimate specific deposit, (iii) blocking effect and (iv) particle detachment. The filter system was arranged in the downflow mode with an in-line flocculation. Experimental results obtained were analyzed using filtration models. This study showed that: (i) the specific surface coverage increased with the increase in the velocity; (ii) the ultimate specific deposit changed slightly at different filtration velocities and different flocculants; (iii) the blocking effect was significant in the transient stage removal of flocs; and (iv) the detachment model parameter was found to decrease with the increase in the adhesive force, Fad that acts on the flocs (above-micron size).

A model to estimate the US term structure of interest rates

The US term structure of interest rates plays a central role in fixed-income analysis. For example, estimating accurately the US term structure is a crucial step for those interested in analyzing Brazilian Brady bonds such as IDUs, DCBs, FLIRBs, EIs, etc. In this work we present a statistical model to estimate the US term structure of interest rates. We address in this report all major issues which drove us in the process of implementing the model developed, concentrating on important practical issues such as computational efficiency, robustness of the final implementation, the statistical properties of the final model, etc. Numerical examples are provided in order to illustrate the use of the model on a daily basis.

Does location matter to explain loan interest rates? evidence from Brazilian highly concentrad local markets

O setor bancário brasileiro é altamente concentrado. Embora concentração não signifique necessariamente que o mercado se comporta de forma não competitiva, o grau de competição é freqüentemente questionado no país. Utilizando uma base de dados extensiva e única do mercado de crédito brasileiro, este trabalho procura avaliar muitos dos fatores que contribuem para a variação nas taxas de juros cobradas pelos bancos nos diferentes mercados locais em duas categorias de empréstimos. A concentração não é significante ou mesmo associada a taxas de juros mais baixas, em parte devido ao papel dos bancos públicos. O prêmio de default é positivo e significante, e há alguma evidência de imperfeição de mercado. Neste trabalho, analisamos também o comportamento de precificação dos bancos em diferentes regiões do país, e encontramos que a localização é importante para explicar as taxas de juros dos empréstimos.

Stochastic growth and monetary policy: the impacts on the term structure of interest rates

This paper builds a simple, empirically-verifiable rational expectations model for term structure of nominal interest rates analysis. It solves an stochastic growth model with investment costs and sticky inflation, susceptible to the intervention of the monetary authority following a policy rule. The model predicts several patterns of the term structure which are in accordance to observed empirical facts: (i) pro-cyclical pattern of the level of nominal interest rates; (ii) countercyclical pattern of the term spread; (iii) pro-cyclical pattern of the curvature of the yield curve; (iv) lower predictability of the slope of the middle of the term structure; and (v) negative correlation of changes in real rates and expected inflation at short horizons.

US real interest rates and default risk in emerging economies

This paper empirically investigates the impact of changes in US real interest rates on sovereign default risk in emerging economies using the method of identification through heteroskedasticity. Policy-induced increases in US interest rates starkly raise default risk in emerging market economies. However, the overall correlation between US real interest rates and the risk of default is negative, demonstrating that the effects of other variables dominate the anterior relationship

Business cycles in emerging economies : the role of interest rates

This paper documents the empirical relation between the interest rates that emerging economies face in international capital markets and their business cycles. It shows that the patterns observed in the data can be interpreted as the equilibrium of a dynamic general equilibrium model of a small open economy, in which (i) firms have to pay for a fraction of the input bill before production takes place, and (ii) preferences generate a labor supply that is independent of the interest rate. In our sample, interest rates are strongly countercyclical, strongly positively correlated with net exports, and they lead the cycle. Output is very volatile and consumption is more volatile than output. The sample includes data for Argentina during 1983-2000 and for four other large emerging economies, Brazil, Mexico, Korea, and Philippines, during 1994-2000. The model is calibrated to Argentina’s economy for the period 1983-1999. When the model is fed with actual US interest rates and the actual default spreads of Argentine sovereign interest rates, interest rates alone can explain forty percent of output fluctuations. When simulated technology shocks are added to the model, it can account for the main empirical regularities of Argentina’s economy during the period. A 1% increase in country risk causes a contemporaneous fall in output of 0.5 ’subsequent recovery. An increase in US rates causes output to fall by the same on impact and by almost 2% two years after the shock. The asymetry in the effect of shocks to US rates and country risk is due to the fact that US interest rates are more persistent than country risk and that there is a significant spillover effect from US interest rates to country risk.

Comparing equilibrium real interest rates : different approaches to measure Brazilian rates

Despite the difficulties involved in the precise determination of equilibrium real interest rates, it seems clear that nominal interest rates has been higher in Brazil than in similar emerging economies. This paper aims to shed light on the possible reasons for this feature of the Brazilian economy. We extend Miranda and Muinhos (2003) one-country study to a sample of 20 countries, using many methods to compare measures of the real interest: (i) extracting equilibrium interest rates from IS curves; (ii) extracting steady state interest rates from marginal product of capital; (iii) capturing relevant variables and the fixed effects having real interest rates as dependent variable in a panel for emerging countries; and (iv) extracting inflation expectation from the spread between fixed rate and inflation-indexed treasure notes.

Mathematical models of generalized diffusion

We discuss in this paper equations describing processes involving non-linear and higher-order diffusion. We focus on a particular case (u(t) = 2 lambda (2)(uu(x))(x) + lambda (2)u(xxxx)), which is put into analogy with the KdV equation. A balance of nonlinearity and higher-order diffusion enables the existence of self-similar solutions, describing diffusive shocks. These shocks are continuous solutions with a discontinuous higher-order derivative at the shock front. We argue that they play a role analogous to the soliton solutions in the dispersive case. We also discuss several physical instances where such equations are relevant.

Mathematical models for Isoptera (Insecta) mound growth

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Test systems and mathematical models for transmission network expansion planning

The data of four networks that can be used in carrying out comparative studies with methods for transmission network expansion planning are given. These networks are of various types and different levels of complexity. The main mathematical formulations used in transmission expansion studies-transportation models, hybrid models, DC power flow models, and disjunctive models are also summarised and compared. The main algorithm families are reviewed-both analytical, combinatorial and heuristic approaches. Optimal solutions are not yet known for some of the four networks when more accurate models (e.g. The DC model) are used to represent the power flow equations-the state of the art with regard to this is also summarised. This should serve as a challenge to authors searching for new, more efficient methods.

United States interest rates, Latin American debt and financial contagion

Includes bibliography

Use of mathematical models in the study of bodily growth in GIFT strain Nile tilapia

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

MATHEMATICAL MODELS AND POLYHEDRAL STUDIES FOR INTEGRAL SHEET METAL DESIGN

We deal with the optimization of the production of branched sheet metal products. New forming techniques for sheet metal give rise to a wide variety of possible profiles and possible ways of production. In particular, we show how the problem of producing a given profile geometry can be modeled as a discrete optimization problem. We provide a theoretical analysis of the model in order to improve its solution time. In this context we give the complete convex hull description of some substructures of the underlying polyhedron. Moreover, we introduce a new class of facet-defining inequalities that represent connectivity constraints for the profile and show how these inequalities can be separated in polynomial time. Finally, we present numerical results for various test instances, both real-world and academic examples.