Robust Iterative Solution of a Class of Time-Dependent Optimal Control Problems

The fast iterative solution of optimal control problems, and in particular PDE-constrained optimization problems, has become an active area of research in applied mathematics and numerical analysis. In this paper, we consider the solution of a class of time-dependent PDE-constrained optimization problems, specifically the distributed control of the heat equation. We develop a strategy to approximate the (1,1)-block and Schur complement of the saddle point system that results from solving this problem, and therefore derive a block diagonal preconditioner to be used within the MINRES algorithm. We present numerical results to demonstrate that this approach yields a robust solver with respect to step-size and regularization parameter

A mesocosm experiment investigating the effects of substratum quality and wave exposure on the survival of fish eggs

In a mesocosm experiment, the attachment of bream (Abramis brama) eggs to spawning substrata with and without periphytic biofilm coverage and their subsequent survival with and without low-intensity wave exposure were investigated. Egg attachment was reduced by 73% on spawning substrata with a natural periphytic biofilm, compared to clean substrata. Overall, this initial difference in egg numbers persisted until hatching. The difference in egg numbers was even increased in the wave treatment, while it was reduced in the no-wave control treatment. Exposure to a low-intensity wave regime affected egg development between the two biofilm treatments differently. Waves enhanced egg survival on substrata without a biofilm but reduced the survival of eggs on substrata with biofilm coverage. In the treatment combining biofilm-covered substrata and waves, no attached eggs survived until hatching. In all treatments, more than 75% of the eggs became detached from the spawning substrata during the egg incubation period, an

RP Process Selection for Rapid Tooling in Sand Casting

The significant cycle-time improvements and geometrical capabilities of solid freeform fabrication systems have led to applications in sand casting industry for design verification and tooling. The time and cost effective deployment of rapid tooling processes using rapid prototyping technology has thus becoming an emerging area to be studied. To make full use of the advantages of rapid prototyping processes, the factors influencing the tooling approach must be identified and understood. This understanding is then used to develop a decision-making structure for RP process selection for rapid tooling in sand casting. In this manuscript we review our work in evaluating and building a framework for tooling process selection for sand castingMechanical Engineerin

The Effect of Anthraquinone in the Kraft Pulping Process

Due to current attitudes arid regulations concerning the odorous emission of mercaptans from the Kraft pulping process, new technology must be developed to enable the process to be run at lower sulfide levels. The use of cyclic-keto compounds, as pulping catalyst, could be a major step in the reduction of sulfide levels in Kraft pulping, while acting to increase the pulping yield through a mechanism that stabilizes the carbohydrates during the process and catalyzes delignification. The objective of this research project is to evaluate the performance of one cyclic keto compound that has recently received the attention of many researchers of anthraquinone

Thermal degradation of citrus pectin in low-moisture environment - Influence of acidic and alkaline pre-treatment

Pectin powder is degraded during storage and transport by demethoxylation and depolymerisation. The degradation mechanisms and especially the influence of pre-treatments on the degradation reactions are not completely understood. In this study, commercial citrus pectin was modified by either acidic or alkaline demethoxylation. The modified pectins, as well as the commercial pectin, were thermally degraded during four weeks of storage at 60 °C and 80% relative humidity. Demethoxylation and depolymerisation as well as colour alterations were examined during degradation, and the course of the reactions was monitored. It was found that the type of pre-treatment during modification determined the material properties and, thus, the water uptake of the modified pectin powders. The resulting water availability in the samples was crucial to the extent of demethoxylation and to the type and intensity of depolymerisation since some of these reactions competed for the water in the climate chamber. The pre-treatment also determined the content of neutral sugars and sodium ions of the modified pectins. High contents of these components limited the extent of degradation in different ways. A previously assumed third depolymerisation mechanism of pectins, beside backbone hydrolysis and β-elimination, was confirmed.DFG, 268547215, Strukturabhängige Abbaureaktionen von Pektinen und deren Auswirkungen auf nicht-enzymatische Bräunung und technologische Funktionalitä

Lake Monona Causeway - Madison, Wisconsin, USA

In 1965 and 1966, a 3,500’ long, hydraulically-placed, highway embankment was constructed over the very soft lakebed deposits of Lake Monona. The compressible deposits, which ranged in thickness from 40’ to 80’, included marl, organic silt and silty clay. An incipient shear failure occurred near the end of the 1965 construction season, necessitating embankment design and construction modifications. Pertinent slope stability and settlement data are summarized, as are time dependent changes in in-situ subsoil parameters. Measured settlements, which currently range from 3’ to more than 12’, agree well with basic consolidation theory and engineering predictions formulated at project inception. General observations with respect to design, construction and overall performance of the causeway embankment are also provided

Ground state properties of heavy alkali halides

We extend previous work on alkali halides by calculations for the heavy-atom species RbF, RbCl, LiBr, NaBr, KBr, RbBr, LiI, NaI, KI, and RbI. Relativistic effects are included by means of energy-consistent pseudopotentials, correlations are treated at the coupled-cluster level. A striking deficiency of the Hartree-Fock approach are lattice constants deviating by up to 7.5 % from experimental values which is reduced to a maximum error of 2.4 % by taking into account electron correlation. Besides, we provide ab-initio data for in-crystal polarizabilities and van der Waals coefficients.Comment: accepted by Phys. Rev.

Empirical evidence for the Birch and Swinnerton-Dyer conjectures for modular jacobians of genus 2 curves

This paper provides empirical evidence for the Birch and Swinnerton-Dyer conjectures for modular Jacobians of genus 2 curves. The second of these conjectures relates six quantities associated to a Jacobian over the rational numbers. One of these six quantities is the size of the Shafarevich-Tate group. Unable to compute that, we computed the five other quantities and solved for the last one. In all 32 cases, the result is very close to an integer that is a power of 2. In addition, this power of 2 agrees with the size of the 2-torsion of the Shafarevich-Tate group, which we could compute

Retinoid regulation of heparin-binding EGF-like growth factor gene expression in human keratinocytes and skin *

Retinoic acid (RA) has profound effects on epidermal homeostasis; however, the molecular mechanisms by which retinoids regulate keratinocyte cell proliferation and differentiation are not well understood. Here we report that mRNA expression of heparin-binding EGF-like growth factor (HB-EGF), a member of the EGF family of growth factors, is induced by RA in human keratinocytes and skin, and is overexpressed in the context of epidermal hyperplasia in vivo. Treatment of normal adult human keratinocytes with micromolar concentrations of RA significantly induced the expression of HB-EGF. The response was efficiently blocked by specific inhibitors of ErbB tyrosine kinase activity, MAP kinase kinase (MEK), or p38 stress-activated protein kinase. RA also enhanced the induction of HB-EGF mRNA in human skin organ culture, an ex vivo model system displaying many similarities to wound healing in vivo. HB- EGF transcripts were markedly increased in human skin by topical treat- ment with RA under conditions known to provoke epidermal hyperplasia. HB-EGF transcripts were also markedly overexpressed in the hyperplas- tic epidermis of psoriatic lesions, relative to normal skin. These results support the hypothesis that the effects of RA on epidermal hyperplasia are mediated at least in part by HB-EGF, and suggest that signal transduction mechanisms other than or in addition to nuclear RA receptors contribute to this effect.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72809/1/j.1600-0625.1998.tb00339.x.pd