Subband decomposition strategies for object‐based image coding

In order to attain perfect reconstruction, subband decomposition of arbitrarily shaped objects requires special strategies to deal with the decimation problem. One of the two strategies described in this paper (scheme 1) inserts pixels with amplitudes equal to the mean values of the neighboring ones belonging to the object. The requirement of transmitting (coding) these pixels reduces the coding gain and is avoided by the second strategy (scheme 2) examined in this paper. This strategy determines specific values of the pixels added to the object in such a way that they result in predefined amplitudes after decimation. For this reason, this method outperforms scheme 1. PSNR versus bit rate are presented for two objects. © 2003 Wiley Periodicals, Inc. Int J Imaging Syst Technol 13, 179–187, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.10054     

Novel oxide-dispersion-strengthened copper alloys from rapidly solidified precursors: Part 1. Microstructural development

ZrO₂, Y₂O₃, and rare earth oxides with related structures are attractive candidates for dispersion strengthening of copper alloys but pose significant processing challenges owing to the low solubility of the oxide-forming elements in Cu. It is shown that the problems may be circumvented by a synthesis approach coupling rapid solidification and internal oxidation, followed by standard powder metallurgy consolidation. Cu-Zr and Cu-Y alloys were melt spun into ribbons ∼-50-to 150-Μm thick and internally oxidized at 1023 to 1223 K to yield ∼1 vol pct of ZrO₂ or Y₂O₃ particles ranging in size from 5 nm up to ∼3150 nm. The coarser oxides result from direct oxidation of the intermetallic segregate, whereas the finer ones are generated by a dissolution-reprecipitation process. The relative proportions of fine and coarse oxides and the homogeneity of the distribution are related to segregation scale in the melt-spun ribbon and the relative permeabilities of oxygen and the oxidizable element in the alloy, which depend on the internal oxidation temperature. The oxide dispersoids were mostly cubic zirconia or cubic yttria and exhibited predominantly cube-on-cube orientation relationships with the matrix. Analysis of particle shapes revealed that the dominant interfaces are of the type {001}_OX ∥ {001}_Cu and {1ˉ11}_OX ∥ {1ˉ11}_Cu and could be explained by image charge interaction concepts. Extrusion produced an elongated grain structure but no significant changes in the oxide distribution. MICHAEL S. NAGORKA, formerly Graduate Research Assistant, High Performance Composites Center, Materials Department, College of Engineering, University of California at Santa Barbara     

Production of β‐galactosidase from recombinant Saccharomyces cerevisiae grown on lactose

Improved productivity and costs reduction in fermentation processes may be attained by using flocculating cell cultures. The production of extracellular heterologous β‐galactosidase by recombinant flocculating Saccharomyces cerevisiae cells, expressing the lacA gene (coding for β‐galactosidase) of Aspergillus niger under the ADHI promotor and terminator in a bioreactor was studied. The effects of lactose concentration and yeast extract concentration on β‐galactosidase production in a semi‐synthetic medium were analysed. The extracellular β‐galactosidase activity increased linearly with increasing initial lactose concentrations (5–150 g dm^?3). β‐Galactosidase production also increased with increased yeast extract concentration. During the entire fermentation, no accumulation of the hydrolysed sugars, glucose and galactose, was observed. The catabolic repression of the recombinant strain when cultured in a medium containing equal amounts of glucose and galactose was confirmed. In complete anaerobiosis, the fermentation of lactose resulted in a very slow fermentation pattern with lower levels of β‐galactosidase activity. The bioreactor operation together with optimisation of culture conditions (lactose and yeast extract concentration) led to a 21‐fold increase in the extracellular β‐galactosidase activity produced when compared with preliminary Erlenmeyer fermentations. Copyright © 2004 Society of Chemical Industry     

Dissolving pulp from TCF bleached Acetosolv beech pulp

Beech wood samples subjected to pulping in HCl‐catalysed acetic acid media (Acetosolv process) under selected conditions were bleached using several Totally Chlorine Free (TCF) sequences including peracetic acid (Paa), alkaline (E), oxygen (O), chelating (Q) and peroxide (P) treatments. PaaEQPP sequences starting from acetic acid media led to pulps with poor brightness, which was improved when the same sequence was carried out starting from aqueous media. An EOQPP sequence led to a pulp with acceptable properties, which were improved by a optimised EOQPaaP sequence, in which a fully bleached pulp was obtained at a SCAN viscosity of 604 cm³ g^?1. EOQPaaP‐bleached pulp was explored for carboxymethyl cellulose (CMC) manufacture employing heterogeneous conditions in isopropanol media, and a CMC with a degree of substitution of 1.16 was obtained. Copyright © 2004 Society of Chemical Industry     

Dynamic Contextual Adaptation

When developing systems based on COTS, components need to be adapted in most of the occasions to work under certain conditions which were not initially predicted by their developers. Thus, it is very important to provide systems with the skill to dynamically alter their behaviour while running, depending on the changing conditions of the environment. In this work we describe a context-dependent, dynamic mapping between the interfaces of the components being adapted, overcoming some of the limitations of the static mappings presented in previous works. This is achieved by means of contextual environments, which define flexible adaptation policies. We also present a case study, illustrating the proposal, and discuss the improvements these mappings represent in comparison with previous works, as well as some open issues.     

Ph<Subscript>2</Subscript>Zn-metallocene-MAO initiator systems in the homo- and copolymerization of styrene/<Emphasis Type="Italic">p</Emphasis>-alkylstyrene

Summary The homo- and copolymerization of styrene (S) with p-methylstyrene (p-MeS) and p-tert-butylstyrene (p-Bu^tS) has been tested using initiator systems of the Ph₂Zn-metallocene-MAO type. The metallocenes used were CpTiCl₃, IndTiCI₃, (n-BuCp)₂TiCl₂, Ind₂ZrCl₂ and Et(Ind)₂ZrCl₂. The Ph₂Zn-metallocene-MAO systems homopolymerize styrene, p-methylstyrene and p-tert-butylstyrene, producing syndiotactic polymers in the case of the titanocenes and amorphous polymers in the case of the zirconocenes. The S/p-MeS and S/p-Bu^tS copolymers obtained with the Ph₂Zn-titanocene-MAO systems are enriched in the comonomer with respect to the initial feed.     

Hydrodynamic considerations on optimal design of a three‐phase airlift bioreactor with high solids loading

The hydrodynamic study of a three‐phase airlift (TPAL) bioreactor with an enlarged gas–liquid dual separator was carried out. Different lengths and diameters of the draft tube were tested to show how the design of the separator zone affects the hydrodynamic performance of the TPAL reactor. Ca‐alginate beads with entrapped yeast biomass at different loadings (0, 7, 14 and 21% v/v) were used in order to mimic the solid phase of conventional high cell density systems, such as those with cells immobilized on carriers or flocculating cells. Important information on multiphase flow and distribution of gas and solid phases in the internal‐loop airlift reactor (ALR) with high solids loading was obtained, which can be used for suggesting optimal hydrodynamic conditions in a TPAL bioreactor with high solids loading. It is finally suggested that the ALR with a dual separator and a downcomer to riser cross‐sectional area ratio (A_D/A_R) ranging from 1.2 to 2.0 can be successfully applied to batch/continuous high cell density systems, where the uniform distribution of solid phase, its efficient separation of particles from the liquid phase, and an improved residence time of air bubbles inside the reactor are desirable. Copyright © 2003 Society of Chemical Industry     

Monodisperse and Corrosion-Resistant Metallic Nanoparticles Embedded into Sepiolite Particles for Optical and Magnetic Applications

The preparation of large quantities of heterogeneous materials containing non-agglomerated and monodispersed nanoparticles is becoming one of the bottlenecks that hinders the development of commercial devices. Here we describe a method to prepare monodispersed metallic (Cu, Ag, Au, Ni, Co, and Fe) nanoparticles in a silicate matrix (sepiolite) by means of a reduction process of metallic cations associated with a dehydration process of the matrix. This process is characterized by the huge amount of monodispersed metallic nanoparticles that it produces. Additionally, these nanoparticles have been revealed to be remarkably stable against oxidation because the transformed sepiolite matrix becomes a diffusion barrier for oxygen. Furthermore, the nanoparticles present suitable properties to be used for optical and magnetic applications.     

Embedding Branch and Bound within Evolutionary Algorithms

A framework for hybridizing evolutionary algorithms with the branch-and-bound algorithm (B&B) is presented in this paper. This framework is based on using B&B as an operator embedded in the evolutionary algorithm. The resulting hybrid operator will intelligently explore the dynastic potential (possible children) of the solutions being recombined, providing the best combination of formae (generalized schemata) that can be constructed without introducing implicit mutation. As a basis for studying this operator, the general functioning of transmitting recombination is considered. Two important concepts are introduced, compatibility sets, and granularity of the representation. These concepts are studied in the context of different kinds of representation: orthogonal, non-orthogonal separable, and non-separable.The results of an extensive experimental evaluation are reported. It is shown that this model can be useful when problem knowledge is available in the form of an optimistic evaluation function. Scalability issues are also considered. A control mechanism is proposed to alleviate the increasing computational cost of the algorithm for highly multidimensional problems.