Assisted History Matching Using Streamline Simulation

The quantity and quality of the information obtained from modern reservoir characterization techniques is still not sufficient to perfectly represent the reservoir. Therefore, reservoir models must be calibrated in order to provide a more reliable production forecast. This process is called production history matching. History matching is one of the most time-consuming tasks of a reservoir study due to the complexity of the process, multiple acceptable solutions, and demand for specialist knowledge. Many times this task is still based on a trial and error procedure, which is normally very inefficient because it involves a large number of cycles. This paper shows that it is possible to integrate the experience of the professionals involved in the process with some automatic techniques to accelerate the process and to obtain better solutions. This process is called Assisted History Matching. The use of streamline simulation as a complementary technique is applied to allow a better understanding of fluid flow behavior on the reservoir, mapping heterogeneities location, and then choosing adequate geological parameters, such as permeability and porosity, according to the identified flow patterns. Reservoir parameters are modified along blocks mapped by the streamlines. Automatic procedures are then applied along with parallel computing to find the best combination of the selected parameters. The methodology was applied to a complex real field where satisfactory results were obtained.     

Digital modular control of high frequency DC–DC converters

This paper presents a solution for controlling integrated DC–DC converters with high switching frequency (>20 MHz). The increase of the switching frequency is a trend biased by output filter volume restrictions and integration demand. The control of DC–DC converters operating at high frequency presents an opportunity to speed up the converter response time but also a challenge specially for the control solution, quiescent current and to limit the sensitivity to process and operating conditions for the mixed signal circuits involved. The solution presented in this work relies on separating the duty-cycle into three parts: a load-free value that depends only on the input and output voltages, a transient fast correction contribution, and an accurate compensation for the IR drop that depends on the load current. The load-free portion of the duty-cycle has a compensation of PVT variations and the fast transient part of the duty-cycle uses a non-linear sliding mode control solution. All the analog blocks required for the implementation of the proposed solution are detailed.     

Electrochemical and spectroelectrochemical characterization of meso-tetra-alkyl porphyrins

A series of three meso-tetra-alkyl porphyrins (H₂TAPs) were synthesised and their electrochemical properties were studied in dichloromethane containing either tetra-butyl ammonium perclorate (TBAP) or tetra-butyl ammonium hexafluorophosphate TBA(PF₆) as supporting electrolyte (SE) by cyclic voltammetry and in situ UV/vis spectroelectrochemistry. Values of E_1/2 for the recorded four redox processes of these porphyrins and of the meso-tetra-phenyl porphyrin (H₂TPP) on glassy carbon and platinum were measured and compared. The redox data collected on the first oxidation and the first reduction processes predict that the value of Δ(LUMO − HOMO) for the H₂TAPs is lower than for meso-tetra-phenyl porphyrin and, therefore, that the first Q band of the electronic spectra of the H₂TAPs is red shifted relatively to the same band in the spectrum of H₂TPP; this shift was indeed found. The second oxidation process of the H₂TAPs is influenced by the supporting electrolyte used and the dication then formed is consumed by an irreversible chemical reaction. The species produced in this reaction is irreversibly reduced at a considerably lower potential. The electrochemical and spectroelectrochemical data collected are consistent with the occurrence of structural distortion in the macrocycle rings of the H₂TAPs.     

Dispersion characteristics of asymmetric coupled anisotropic dielectric waveguides using FDFD

The formulation is developed in the frequency domain and the finite difference method is used for the numerical solution of the scalar wave equation, written in terms of the transverse components of the magnetic field. As a result a conventional eigenvalue problem is obtained without the presence of spurious modes due to the implicit inclusion of the divergence of the magnetic field equal to zero. The formulation is developed to include biaxial anisotropic dielectrics with an index profile varying arbitrarily in the cross section of the waveguide under analysis. This formulation is then applied to the analysis of the influence on the dispersion characteristics of the dimensions of asymmetric coupled rectangular uniaxial anisotropic dielectric waveguides. As expected, the reduction of the height or the width of one of the rectangular dielectric waveguides causes the dispersion curves to move towards higher frequencies.     

Preparation and characterization of LaNbO4 from amorphous precursors

Amorphous precursors of LaNbO₄ have been prepared by coprecipitation and mechanical alloying. Powder characteristics before and after calcination were studied by thermogravimetric analysis, differential thermal analysis, Fourier transform-infrared spectroscopy and X-ray diffraction, and the crystallographic changes during thermal treatment were documented by high-temperature X-ray diffraction. The tetragonal structure was stabilized at room temperature for the mechanically alloyed product; cells dimensions were determined from the X-ray diffraction patterns and volume change between monoclinic and tetragonal phase was evaluated and is discussed.     

Refactoring by Transformation

In this paper we present how refactoring of object-oriented programs can be accomplished by using refinement. Our approach is based on algebraic laws of an object-oriented language for refinement similar to Java. We follow a strategy involving data and algorithmic refinement of classes.     

Modelling of polymerization reactions

Summary The paper reports the development of a mathematical model which has been applied to the polymerization of styrene initiated by iodine in ethylene dichloride solution. Our previous work on the system concluded for a pseudocationic mechanism based on the admission of non-ionic propagating species.The computer analysis performed using the mathematical model allowed us to derive theoretical conversion-and conductivity-time curves which perfectly reproduce the experimental shapes under different conditions. The agreement between the theoretical and experimental results demonstrates that the reaction mechanism previously formulated and the mathematical treatment proposed are correct.List of Symbols M monomer (styrene) - MI unsaturated side product - MI₂ styrene diiodide - M_n dead polymer chains - P _n growing polymer chains - k1, k2, k3, k4 initiation rate constants - k5 propagation rate constant - k6 chain breaking rate constant - K equilibrium constant - C conversion - a, b, c, d, e conductivity coefficients - specific conductivity - t time     

A study on the recovery of xylitol by batch adsorption and crystallization from fermented sugarcane bagasse hydrolysate

Xylitol was recovered from fermented sugarcane bagasse hemicellulosic hydrolysate by adsorption and crystallization procedures. Silica gel adsorption was employed to purify the broth containing xylitol. In this step, different mixtures of the solvents ethyl acetate, ethanol and acetone were used as eluent, and different proportions of fermented broth volume incorporated per gram of silica gel (V_b/M_sg, varying from 1.0 to 2.0 cm³ g^?1) were used to pack the column employed as stationary phase bed. The xylitol purification efficiency varied for each mixture of solvent, and for each V_b/M_sg ratio used. The purified broth was submitted to different crystallization procedures (cooling, concentration and supplementation with commercial xylitol) aiming to recover xylitol crystals. The best result (60% crystallization yield and 33% total recovery of xylitol from fermented broth) was obtained when the column was packed with a V_b/M_sg ratio of 2 cm³ g^?1, and the broth was purified with a mixture of ethyl acetate and ethanol, concentrated 6.5‐fold, and supplemented with commercial xylitol to force the precipitation. Copyright © 2006 Society of Chemical Industry     

Molecular genetic diagnosis of autosomal dominant polycystic kidney disease in a newborn with bilateral cystic kidneys detected prenatally and multiple skeletal malformations

We report a case of leiomyosarcoma of the pancreas. A spindle cell pattern at light microscopy, immunocytochemical reactivity with desmin, alpha-1-antitrypsin, vimentin and actin and ultrastructural features of smooth muscle differentiation help to establish the diagnosis.     

Effect of active packaging incorporated with triclosan on bacteria adhesion

ABSTRACT: Antimicrobial polyethylene and cellulose based films incorporated with triclosan were studied. The antimicrobial efficacy, the hydrophobicity, microscopic and the mechanical characteristics of the films, as well free energy of adhesion between bacteria and antimicrobial films were evaluated. It was observed that both polyethylene and cellulose based films incorporated with the antimicrobial were homogeneous. Furthermore, the addition of triclosan did not affect mechanical characteristics of the films (P > 0.05). However, triclosan incorporated into polyethylene films reduced its hydrophobicity while antimicrobial cellulose based films became more hydrophobic. The adhesion was thermodynamically favorable between tested bacteria and polyethylene films. On the other hand, the adhesion to triclosan cellulose based film was thermodynamically unfavorable to Staphylococcus aureus and Escherichia coli and favorable to Listeria innocua and Pseudomonas aeruginosa. Polyethylene and cellulose based films showed inhibitory effect against S. aureus and E. coli, being the inhibition halo higher for polyethylene films. This study improves the knowledge about antimicrobial films.