The Effect of Reagents on Ultrafine Iron Ore Vacuum Filtration

Continuous vacuum filters normally carry out the final removal of water from iron ore products. The objective of this investigation is to check the possibility of enhancing the industrial performance of a horizontal belt filter by adding one flocculant and two surfactants to the filtration feed slurry. The mineral sample came from the Iron Quadrangle (State of Minas Gerais, Brazil). X-ray diffraction showed a predominance of hematite and small amounts of quartz and goethite. The filtration tests were performed at laboratory scale using a modified Büchner funnel apparatus, which was connected to a scale/computer system. The results indicated: a) the best filtration condition was achieved near the zero charge condition; b) cake moisture, cake porosity, cake formation time and the specific cake resistance were pronouncedly influenced by the flocculant addition; and c) surfactants tested were not able to significantly reduce the cake moisture.     

Development of a predictive model for polymer/solvent diffusion coefficient calculations

A new calculation procedure for free‐volume parameters is considered in this work by using viscosity prediction methods and the Levenberg‐Marquardt calculation scheme. All parameters used in the Vrentas–Duda free‐volume theory can be estimated from pure component properties. The prediction results are compared with experimental data for some polymer/solvent systems. The diffusion coefficient calculated by Vrentas–Duda theory can be used in the modeling of membrane separation processes. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Link quality estimation in wireless multi-hop networks using Kernel based methods

A new approach for link modelling in wireless multi-hop networks is described for portable devices, based on Kernel Regression Statistics. A non-parametric estimation of errors in the wireless medium provides an efficient and accurate model of link errors between any two nodes. This estimation results from the analysis of the inter-arrival time between any periodically sent packets. The obtained results prove that it is possible to infer on link quality without having unrealistic assumptions or additional overhead, by using Kernel Methods. Moreover, similar performances were achieved for different scenarios, without requiring model recalculations. The presented results show that the proposed link quality estimation can be used in order to improve wireless connectivity and ubiquity in future networks.     

Structure and catalytic activity of highly ordered AlMCM-48 materials with different Si/Al ratios on the degradation of high-density polyethylene

Journal of Porous Materials - Catalysts of AlMCM-48 with different Si/Al molar rations were synthesized by modified hydrothermal method with respect to previous works. As a consequence, the...     

Determination of catalytic active sites in (Ce, Ca)-supported Y zeolite by Fourier transform IR spectroscopy

Catalytic active sites in an aluminosilicate matrix Y zeolite were generated by exchange with calcium and cerium chloride solutions, followed by calcination. Acid properties of the (Ce, Ca)^ex-NaY zeolite were studied by semi quantitative (Fourier transform) IR spectroscopy of the pyridine adsorption. The molecular probe interacts with Brönsted active sites (BASs) and bonds coordinatively to Lewis active sites (LASs). The main observed frequencies were 1459 cm⁻¹ (BAS) and 1443 cm⁻¹ (LAS). It has been found that the BAS:LAS optical density ratio was ca. 1.4. The observed protonic active sites may be due to cerium cation-hydroxyl supported on the Y zeolite matrix under specific ion exchange and thermal conditions.     

Edge Fracture Prediction Using Uncoupled Ductile Fracture Models for DP780 Sheet

This paper is a contribution to the prediction of edge fracture behavior using uncoupled ductile fracture models. A fully integrated simulation framework for the edge fracture prediction is proposed with the shear-induced pre-damage considered. User-defined material subroutines are coded with uncoupled ductile fracture models (Lou-Huh, Oh, Brozzo) incorporated, which are calibrated using the fracture strains of various loading paths. A series of 3D numerical simulations are performed and compared with the results of hole-expansion tests. The effects of pre-damage field and fracture models are analyzed and discussed.

     

A hybrid evolutionary approach for solving constrained optimization problems over finite domains

A novel approach for the integration of evolution programs and constraint-solving techniques over finite domains is presented. This integration provides a problem-independent optimization strategy for large-scale constrained optimization problems over finite domains. In this approach, genetic operators are based on an arc-consistency algorithm, and chromosomes are arc-consistent portions of the search space of the problem. The paper describes the main issues arising in this integration: chromosome representation and evaluation, selection and replacement strategies, and the design of genetic operators. We also present a parallel execution model for a distributed memory architecture of the previous integration. We have adopted a global parallelization approach that preserves the properties, behavior, and fundamentals of the sequential algorithm. Linear speedup is achieved since genetic operators are coarse grained as they perform a search in a discrete space carrying out arc consistency. The implementation has been tested on a GRAY T3E multiprocessor using a complex constrained optimization problem.     

A New Distribution System Reconfiguration Approach Using Optimum Power Flow and Sensitivity Analysis for Loss Reduction

This paper presents a new approach for distribution system reconfiguration (DSR) based on optimum power flow (OPF) in which the branch statuses (open/close) are represented by continuous functions. In the proposed approach, all branches are initially considered closed, and from the OPF results, a heuristic technique is used to determine the next loop to be broken by opening one switch. Then the list of switches that are candidates to be opened is updated, and the above process is repeated until all loops are broken, making the distribution system radial. This paper includes results and comparisons on test systems utilized in three classical papers published in the technical literature, as well as in a previous paper by the authors. Results obtained on a real large-scale distribution system are also presented     

NAROAS: a neural network-based advanced operator support system for the assessment of systems reliability

We have developed and implemented a computerized reliability monitoring system for nuclear power plant applications, based on a neural network. The developed computer program is a new tool related to operator decision support systems, in case of component failures, for the determination of test and maintenance policies during normal operation or to follow an incident sequence in a nuclear power plant. The NAROAS (Neural Network Advanced Reliability Advisory System) computer system has been developed as a modularized integrated system in a C++ Builder environment, using a Hopfield neural network instead of fault trees, to follow and control the different system configurations, for interventions as quickly as possible at the plant. The observed results are comparable and similar to those of other computer system results. As shown, the application of this neural network contributes to the state of the art of risk monitoring systems by turning it easier to perform online reliability calculations in the context of probabilistic safety assessments of nuclear power plants.