Rule-based supervisory control of a two-link flexible manipulator

In this paper, we propose a two level hierarchical control strategy to achieve accurate end-point position of a planar two-link flexible manipulator. The upper level consists of a feedforward rule-based supervisory controller that incorporates fuzzy logic, whereas the lower level consists of conventional controllers that combine shaft position-endpoint acceleration feedback for disturbance rejection properties and shaping of the (joint) actuator inputs to minimize the energy transferred to the flexible modes during commanded movements. The effectiveness of this hierarchical control strategy is verified by experimental results for various movements of the links, in various configurations. In particular, we illustrate how the hierarchical intelligent control strategy performs better than conventional control techniques for endpoint position control in the presence of flexure effects.     

Die großtechnische Oxosynthese mit immobilisiertem Katalysator

Industrial Oxo Synthesis with Immobilised Catalyst. The use of water-soluble catalysts represents a significant advance in homogeneous catalysis; “immobilisation” of the catalyst in a second immiscible liquid phase has the effect of “heterogenisation” and allows the advantages of heterogeneous processing (long lifetimes, straightforward technology) to the combined with those of the homogeneous mode (gentle reaction conditions, high activity and selectivity). In particular, the decisive advantage of homogeneous catalysts, viz. the wide range of variation of their steric and electronic properties which can be adapted to the specific reaction at hand, can be exploited for tailoring highly effective catalysts. Moreover, the mode of action of these homogeneous catalysts remains understandable as a model and under the reaction conditions chosen – in complete contrast to the case of many heterogeneous catalytic systems. The first successful industrial application of water-soluble catalysts was in the oxo process of Ruhrchemie/Rhǒne Poulenc. The following article reports on ten years' experience with this process and the HRh(CO)[P(msulphophenyl-Na)₃]₃ catalyst.     

Simulation des dichteabhängigen Stofftransportes im Grundwasser und Verifizierung am Beispiel der Saltpool-Experimente

Kurzfassung Die Saltpool-Experimente von OSWALD (1998) und OSWALD & KINZELBACH (2004), im Jahre 1998 an der ETH Zürich ausgeführt, sind exzellente Benchmark-Tests für numerische Simulationsprogramme der dichtevariablen Strömung. Zahlreiche Autoren haben Ergebnisse dazu veröffentlicht. Die kritischen Probleme hierbei sind sowohl die zu dicke Übergangszone von hoher Konzentration an der Sohle der Versuchsbox zum Süßwasser am Top der Box in der Injektionsphase und in der Ruhephase als auch die extrem langen Rechenzeiten.Die Untersuchungen von HÄFNER & BOY (2003a) wurden fortgeführt mit dem erweiterten Code MODCALIF-MST (MODular Flow and CALIbration with Front Limitation algorithm—Multi Species and Temperature). Insbesondere werden Methoden zur Rechenzeitbeschleunigung diskutiert und verifiziert. Durch Nutzung eines algebraischen Multigrid- Gleichungslösers konnte die Rechenzeit um den Faktor 4 verringert werden. Zur Prüfung der Leistungsfähigkeit von MODCALIF-MST wurden die Saltpool Experimente, case 1 und case 2, nachsimuliert und Gitterkonvergenzstudien sowie eine Modellkalibrierung durchgeführt.

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Simulation of density-dependent solute transport in groundwater and verification with saltpool experiments

Abstract The Saltpool experiments by OSWALD (1998) and OSWALD & KINZELBACH (2004), carried out in 1998 at the ETH Zurich, are an excellent benchmark test for numerical simulation programmes of the variable-density flow. Numerous authors published results on this subject. Here, critical problems are the thick transition zones from high concentration at the bottom to fresh water at the top of the box in the injection phase and the rest phase (phases 1–2) as well as the extremely long computing time.We have continued the investigations by HÄFNER & BOY (2003a) with the extended code MODCALIF-MST (MODular Flow and CALIbration with Front Limitation algorithm—Multi Species and Temperature) in double porosity porous media. Especially, the methods for code acceleration are discussed and verified. By incorporating the algebraic multigrid package as linear equation solver, computing times could be reduced by a factor of about 4. Simulations, a grid convergence study and a model calibration were carried out for the experiments case 1 and case 2 with MODCALIF.

     

Crystallinity in secondary cellulose esters

Cellulose esters which have a high degree of esterification are readily crystallizable by simple heat treatments. Such esters include cellulose triacetate, cellulose tripropionate, and mixed cellulose triesters. X-ray diffraction analysis shows distinct crystal patterns for these crystalline cellulose esters, and differential thermal analysis shows strong melting peaks. X-ray diffraction analysis of secondary cellulose esters, that is, esters having a substantially lower degree of esterification, shows very diffuse patterns which are only slightly indicative of crystalline structure. Differential thermal analysis, on the other hand, shows strong endothermic peaks which appear to indicate melting of crystalline material. Once melted, secondary cellulose esters cannot be recrystallized easily by simple heat treatments, but it has been found that treatment with certain solvents will induce crystallization. For instance, precipitation of secondary cellulose acetate from acetic acid gave a material which showed two melting peaks by differential thermal analysis, and precipitation from acetone gave a material which showed a single melting peak. A secondary mixed ester, cellulose acetate butyrate, precipitated from acetone had three melting peaks. The coincidence of two of the peak temperatures of this ester with those of the separate triesters of acetic and butyric acids indicated a block rather than a random substitution into the cellulose chain.     

Formation of phase structure and crystallization behavior in blends containing polystyrene–polyethylene block copolymers

The microphase separation structure in the molten state and the structure formation in crystallization from such ordered melt were investigated for the blends of polystyrene–polyethylene block copolymers (SE) with polystyrene homopolymer (PS) and polyethylene homopolymer (PE) and for the blends consisting of two kinds of SE with different copolymer compositions from each other, using synchrotron small-angle X-ray scattering techniques (SAXS). The copolymer compositions of SE block copolymers employed were 0.34, 0.58 and 0.73 wt. fraction of PE, and their melt morphologies were cylindrical, lamellar and lamellar, respectively. Macrophase separation or the morphology change in the melt occurred depending on the molecular weight and the blend composition, as reported so far. In crystallization from such macrophase-separated and microphase-separated melts, the melt morphology was completely kept for all the blends. Crystallization behavior was also investigated for the blends. The crystallization within the spherical and cylindrical domains surrounded by glassy PS was not observed for SE/PS blends. In the crystallization from the macrophase-separated melt, two exothermal peaks were observed in the DSC measurements, while a single peak was observed for other blends. For the blends with PS, the degree of crystallinity was depressed and the apparent activation energy of crystallization was high, compared to those for the corresponding neat SE. For SE/PE and SE/SE blends, those were changed depending on the blend composition.     

Efficiency of mineral admixtures in mortars: Quantification of the physical and chemical effects of fine admixtures in relation with compressive strength

This work is the fourth part of an overall project the aim of which was the development of general mix design rules for concrete containing different kinds of mineral admixtures. The two first parts presented the separation and quantification, by means of an empirical model based on semi-adiabatic calorimetry measurements, of the different physical effects responsible for changes in cement hydration (short terms) when chemically inert quartz powders were used in mortars. Part three dealt with an intensive experimental program, presenting and commenting more than 2000 compressive strength measurements. This program concerned 1 day to 6 months old mortars containing up to 75% of inert and pozzolanic admixtures. All these compressive strength results are analyzed in this fourth part and the influence of three effects, namely dilution, heterogeneous nucleation and the pozzolanic effect, are discriminated and quantitatively evaluated. An efficiency concept is proposed in order to take into account the effect of mineral admixture in mortars from both the physical and chemical points of view. It uses an efficiency function ξ(p) that has notable properties: it is independent of time, independent of fineness and independent of the type of mineral admixture.     

Air impingement and intermittent drying: Application to apple and to mango

An original drying process combining air impingement and intermittent drying was studied on apple slices and mango cubes. The influence of four operating parameters (air velocity, drying/tempering periods, upper height, and air temperature) on the drying time and on the drying rate was evaluated. Continuous and intermittent drying were compared. The intermittency α = 1/7 (τ_on = 10 seconds and τ_off = 60 seconds) gave the best results. A time savings of 54% for apple and 67% for mango was reached. In continuous drying, a time savings of 4620 seconds was observed by increasing the air velocity from 6 to 40 m s^?1 for apple. Air temperatures of 328 K for apple and of 328 K or 338 K for mango were determined as optimum to prevent case‐hardening. Experimental results were fitted with the analytical solution of Fick's second law and the modified Page equation (average values R² = 0.985 and 0.961, for apple and mango, respectively). For both products, the apparent moisture diffusivity D_app, the drying constant k, the drying coefficient n, and the activation energy E_a, were identified. Activation energies calculated from the analytical solution were 30.3 and 36.8 kJ mol^?1 and were 25.4 and 30.0 kJ mol^?1 using the modified Page equation for apple and mango, respectively. Mango has an increased temperature sensitivity and thus will need less energy for drying than apple.     

Thermal spray vitrification process for the removal of lead-based paint from steel structures: An applications note

Lead-based paints and primers have long been used to protect steel structures from corrosion, but are now recognized as environmental hazards. During lead-based paint removal via abrasive blasting, federal, state and local environmental requirements mandate the use of containment structures to prevent contamination of air, soil, or water. The thermal spray vitrification (TSV) process was developed and optimized in laboratory experiments to remove hazardous lead-based paint. TSV consists of thermal spraying a molten glass onto the painted surface. As the glass strikes the substrate, it reacts with the paint, and organic components are pyrolyzed, while lead ions are trapped on the glass surface. Quenching stresses in the glass cause it to crack and spall off the substrate. The resulting glass fragments are collected, and further remelted to completely immobilize lead (Pb) ions in the glassy iron (Fe) silicate matrix. The glass waste is thus rendered non-hazardous, as determined by the Toxicity Characteristic Leaching Procedure (TCLP). The TSV process was field tested on a fire hydrant, using minimal personal protective equipment and without using a containment structure. The lead-containing paint was removed, without producing hazardous waste, leaving de-painted surfaces suitable for repainting.     

Towards a smooth design process for static communicative node‐link diagrams

Node‐link infographics are visually very rich and can communicate messages effectively, but can be very difficult to create, often involving a painstaking and artisanal process. In this paper we present an investigation of node‐link visualizations for communication and how to better support their creation. We begin by breaking down these images into their basic elements and analyzing how they are created. We then present a set of techniques aimed at improving the creation workflow by bringing more flexibility and power to users, letting them manipulate all aspects of a node‐link diagram (layout, visual attributes, etc.) while taking into account the context in which it will appear. These techniques were implemented in a proof‐of‐concept prototype called GraphCoiffure, which was designed as an intermediary step between graph drawing/editing software and image authoring applications. We describe how GraphCoiffure improves the workflow and illustrate its benefits through practical examples.