Reduced basis method for managed pressure drilling based on a model with local nonlinearities

To circumvent restrictions of conventional drilling methods, such as slow control actions and inability to drill depleted reservoirs, a drilling method called managed pressure drilling (MPD) has been developed. In MPD, single-phase flow processes can be modeled as a feedback interconnection of a high-order linear system and a low-order nonlinear system. These nonlinearities appear locally both inside and at the boundaries of the computational domain. To obtain a fast simulation platform for real-time purposes (eg, online model-based controller implementation), model order reduction is required for MPD. However, the local nonlinearities render applying model order reduction techniques challenging. In this study, a new approach is proposed to deal with such nonlinearities within the reduced basis (RB) context and it is successfully tested on a model for MPD. Contrary to the classical RB technique, the proposed approach not only does not generate nonphysical spikes at the locations of these local nonlinearities but also yields high speedup factors. The obtained reduced-order model can be used for efficient online simulation and controller design for drilling systems with MPD.     

Esophageal stenosis in epidermolysis bullosa hereditaria]

Benign esophageal strictures in the upper esophagus may be caused by systemic diseases. A rare reason for esophageal strictures are the mechanobullous disorders marked by blister formation following relatively minor trauma, e.g. epidermolysis bullosa. In this report we present a 63-year-old patient who had suffered from epidermolysis bullosa simplex since birth. The epicutaneous symptoms were no longer present but an esophageal stricture had developed. The stricture was treated by X-ray-controlled balloon dilation twice, with a functionally good result. We suggest managing a recurrence recidiv of stricture with balloon dilation to minimize trauma and prevent further lesions.     

Scaling XML query processing: distribution, localization and pruning

Distributing data collections by fragmenting them is an effective way of improving the scalability of a database system. While the distribution of relational data is well understood, the unique characteristics of the XML data and query model present challenges that require different distribution techniques. In this paper, we show how XML data can be fragmented horizontally and vertically. Based on this, we propose solutions to two of the problems encountered in distributed query processing and optimization on XML data, namely localization and pruning. Localization takes a fragmentation-unaware query plan and converts it to a distributed query plan that can be executed at the sites that hold XML data fragments in a distributed system. We then show how the resulting distributed query plan can be pruned so that only those sites are accessed that can contribute to the query result. We demonstrate that our techniques can be integrated into a real-life XML database system and that they significantly improve the performance of distributed query execution.     

Impacts of structural characteristics on activated sludge floc stability

Activated sludge samples from seven full-scale plants were investigated in order to determine the relationship between floc structure and floc stability. Floc stability was determined by shear sensitivity and floc strength. Floc structure was considered in terms of two size scales, the micro- and macrostructure. The microstructure refers to the organization of the floc components, such as the individual microorganisms. The macrostructure refers to the overall floc. The floc macrostructure was characterized by filament index, sludge volume index, size, and fractal dimension. It had a significant impact on floc stability. Large and open flocs with low fractal dimensions containing large number of filaments were more shear sensitive and had lower floc strength compared to small and dense flocs. Fluorescent in situ hybridization analysis indicated that the organization of the bacterial cells might also have an effect on the floc stability.     

Exploring the Influence of Personality on Depressive Symptoms and Self-Esteem Across a Significant Life Transition.

This study investigates the influence of personality on adjustment to a particular life transition, community relocation. Participants were 285 women (average age=69.5) who were interviewed once before they moved, and then multiple times after the move. Within the context of this multiwave design, personality traits were used to predict changes in depressive symptoms (DS) and self-esteem (SE) across the move. Neuroticism and Openness to Experience predicted increases in DS over time, whereas Extraversion and Openness predicted increases in SE. Stressful reactions to the move and sense of mastery about the move partially mediated these effects. The study documents the dynamic influence of personality on positive and negative aspects of adjustment and investigates differing routes through which such effects occur. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dealing with Uncertainties in Fresh Water Supply: Experiences in the Netherlands

Developing fresh water supply strategies for the long term needs to take into account the fact that the future is deeply uncertain. Not only the extent of climate change and the extent and nature of its impacts are unknown, also socio-economic conditions may change in unpredictable ways, as well as social preferences. Often, it is not possible to find solid ground for estimating probabilities for the relevant range of imaginable possible future developments. Yet, some of these may have profound impacts and consequences for society which could be reduced by timely proactive adaptation. In response to these and similar challenges, various approaches, methods and techniques have been proposed and are being developed to specifically address long-term strategy development under so-called deep uncertainty. This paper, first, offers a brief overview of developments in the field of planning under (deep) uncertainty. Next, we illustrate application of three different approaches to fresh water provision planning under uncertainty in case studies in the Netherlands: a resilience approach, oriented to (re) designing fresh water systems in such a way that they will be less vulnerable, resp. will be able to recover easily from future disturbances; a robustness approach, oriented to quantitative assessment of system performance for various system configurations (adaptation options) under a range of external disturbances, and an exploratory modeling approach, developed to explore policy effectiveness and system operation under a very wide set of assumptions about future conditions.     

Preparation of core‐shell latexes for paper coatings

Novel core‐shell latices with a partially crosslinked hydrophilic polymer core and a hard hydrophobic shell of polystyrene were prepared to improve optical properties of coated paper such as gloss and brightness. These core‐shell latices were prepared by sequential addition of a monomer mixture of styrene, n‐butylacrylate and methacrylic acid. Different crosslinkers were used to form the polymer core and in the second stage styrene to form the hard shell component. In addition, attempts were made to further improve optical properties by introducing a new polymerizable optical brightener, i.e., 1‐[(4‐vinylphenoxy)methyl]‐4‐(2‐phenylethylenyl)benzene during polymerization either into the core or into the shell. The prepared core‐shell latex particles were used as specialty plastic pigments for paper coating together with kaolin as the primary pigment. The runability of paper coating formulation by either using a laboratory scale Helicoater or pilot scale JET‐coating machine was very good. The produced coated papers were printed on both sides employing a heat set web offset (HSWO) printer to study the quality of image reproduction in terms of print gloss, print mottle, print through, etc. The core‐shell latices improved the overall print quality. Furthermore, the results demonstrated that by optimizing polymer composition one can significantly enhance the optical properties and surface smoothness of coated paper. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Direct precision manufacturing of three-dimensional components using organically modified ceramics

The authors report on direct precision manufacturing (DPM) of three-dimensional parts using the stereo lithography technique. Organically modified ceramics (Ormocer) are photo polymerised in a layer based production fashion with a custom designed micro stereo lithography (MSL) apparatus. In order to achieve spatial process resolutions as high as 10 μm, both the Ormocer and apparatus are adapted in terms of high resolution manufacturing. Using micro computer tomography, form tolerances smaller than 50 μm are achieved. Through the highest degree of flexibility in three-dimensional manufacturing, new fields of applications in the MEMS sector are conceivable, as exemplary micro mechanical or micro fluidic systems.     

Investigations on imperfection sensitivity and deduction of improved knock-down factors for unstiffened CFRP cylindrical shells

In the field of aerospace engineering but also in the fields of civil and mechanical engineering the industry demands for significantly reduced costs for development and operating. Reduction of structural weight at safe design is one avenue to achieve this objective. In many cases it results in thin-walled structures, which are prone to buckling if subjected to compression or shear. The presented paper is based on a recent European Space Agency (ESA) study, conducted at DLR Braunschweig, on Probabilistic Aspects of Buckling Knock-Down Factors and contributes to this goal by striving for an improved buckling knock-down factor (the ratio of buckling loads of imperfect and perfect structures) for unstiffened CFRP cylindrical shells. Buckling tests and buckling simulations were performed to investigate the imperfection sensitivity and to validate the applied simulation methodologies. Test results as well as deterministic and probabilistic buckling simulation results are presented and compared. Finally, improved knock-down factors are deduced and discussed.     

Lorrin Andrews Riggs (1912-2008).

Lorrin Andrews Riggs was a leading scholar in the field of visual psychophysics and physiology. His research brought new understanding to the functioning of the visual system, and his numerous students have continued to make notable contributions to visual science. Although he received an extraordinary number of professional honors during his lifetime, he remained a humble scientist and congenial colleague and friend. Lorrin Riggs died on April 10, 2008, in Hanover. He was 95. (PsycINFO Database Record (c) 2010 APA, all rights reserved)