Polyketones containing indane structure elements

Summary Polyketones with indane structure elements were prepared by Friedel-Crafts polycondensation in three different reaction media. Only oligomers or insoluble material could be obtained, probably due to a side reaction of the indane ring, which leads to crosslinking at high conversion. The oligomers are soluble in common organic solvents such as THF and CHCl₃. Melting points, glass transition temperatures, and thermal stability of the oligomers were determined.     

Breitung beim Warmwalzen auf geneigter Bahn

Zur Erweiterung der Grundlagen des Warmwalzens wurde das Walzen auf geneigter Bahn experimentell und theoretisch analysiert. Den Schwerpunkt der Arbeit stellt eine Untersuchung des Breitungsverhaltens dar. Basierend auf den Versuchsdaten wird eine Breitungsformel angegeben, die für Walzbahnneigungswinkel bis 60° anwendbar ist und als Sonderfall auch das Flachwalzen beinhaltet. Ausgehend vom Satz der ?Oberen Schranke“ wurde ein Rechenmodell entwickelt, das die Berechnung der Breitung für beliebige Walzbahnneigungswinkel kleiner als 60° ermöglicht. Während die Anwendung der Breitungsformel aufgrund ihrer einfachen Handhabung eher für den praktischen Einsatz im Walzbetrieb sinnvoll erscheint, ist die mit wesentlich größerem Rechenaufwand verbundene Modellrechnung in rechnergestützten Systemen zur Stichplanoptimierung einsetzbar oder als Ansatz für die Entwicklung weiterer mathematischer Modelle zu werten.     

Block Copolymers by Using Combined Controlled Radical and Radical Promoted Cationic Polymerization Methods

Summary A novel synthetic procedure for the preparation of block copolymers based on the combination of diphenylethene (DPE) mediated controlled radical polymerization and radical promoted cationic polymerization is described. In the first step, the controlled polymerization of styrene (St) and methyl methacrylate (MMA) in presence of DPE yields polymers with various structures of diphenylethyl units in the main chain. Upon heating these prepolymers undergo scission to give polymeric radicals. Oxidation of these radicals by onium salts such as diphenyliodonium heaxfluorophosphate (Ph₂I⁺PF₆ ⁻) and N-ethoxy-2-methylpyridinium hexafluorophosphate (EMP⁺PF₆ ⁻) yields reactive cations capable of initiating cationic polymerization of cyclohexene oxide (CHO). Block copolymer structure was confirmed by IR and NMR spectral measurements and GPC analysis. Received: 13 December 2002/Revised version: 25 March 2003/ Accepted: 11 March 2003 Correspondence to Yusuf Yagci     

Cationic polymerization of selected α- and β-substituted vinyl ethers

Summary The cationic polymerization of various α- and β-substituted vinyl ethers, initiated by 1-iodo-1-(2-methylpropyloxy)ethane 1 and tetrabuty lammonium perchlorate (TBAP) was investigated. The polymerization of 2,3-dihydrofuran (DHF, 3a) in CH₂Cl₂ at -40°C proceeds via opening of the ethylenic double bond and yields polymers with narrow molar mass distributions and high glass transitions. The number average of molar mass increased linearly with conversion. Under these conditions, a controlled polymerization of two propenyl ethers (1-ethoxypropene 2a and 2-methoxypropene 2b) and two other cyclic unsaturated ethers (3,4-dihydro-2H-pyran 3b and 5-methyl-2,3-dihydrofuran 3c) could not be achieved. Either transfer reactions or the decomposition of 1 prevented the formation of high molar mass polymers of these vinyl ethers.     

A framework for controlling model-based diagnosis systems with multiple actions

In recent years reasoning about structure and function of physical systems for the purpose of diagnosis has seen a dramatic increase in activities. New exciting results concerning modelling issues, diagnostic inference patterns and inferential power have emerged. A state of the art diagnosis agent now has a considerable toolset at hand. A main obstacle for building large diagnosis systems, however, remains. How can we controlwhen to usewhich inference pattern or representation? We argue that the actions available to a diagnosis agent can be understood in terms of change ofworking hypotheses. The control problem then becomes a belief revision problem: when to adopt or drop beliefs. Our approach proceeds in two steps. First, we adopt the principle of informational economy from Gärdenfors, Knowledge in Flux (MIT Press, 1988) as kind of a law of inertia for diagnostic processes, that helps us identify candidates for revised belief states. In a second step we employ specificdiagnostic knowledge to actually choose the next belief state. We demonstrate the use of our concepts on an example in the domain of ballast tank systems as e.g. used in offshore plants.     

A path planning and path‐following control framework for a general 2‐trailer with a car‐like tractor

Maneuvering a general 2‐trailer with a car‐like tractor in backward motion is a task that requires a significant skill to master and is unarguably one of the most complicated tasks a truck driver has to perform. This paper presents a path planning and path‐following control solution that can be used to automatically plan and execute difficult parking and obstacle avoidance maneuvers by combining backward and forward motion. A lattice‐based path planning framework is developed in order to generate kinematically feasible and collision‐free paths and a path‐following controller is designed to stabilize the lateral and angular path‐following error states during path execution. To estimate the vehicle state needed for control, a nonlinear observer is developed, which only utilizes information from sensors that are mounted on the car‐like tractor, making the system independent of additional trailer sensors. The proposed path‐planning and path‐following control framework is implemented on a full‐scale test vehicle and results from simulations and real‐world experiments are presented.     

Pectin degrading glycoside hydrolases of family 28: sequence-structural features, specificities and evolution

Family 28 belongs to the largest families of glycoside hydrolases.It covers several enzyme specificities of bacterial, fungal,plant and insect origins. This study deals with all availableamino acid sequences of family 28 members. First, it focuseson the detailed analysis of 115 sequences of polygalacturonasesyielding their evolutionary tree. The large data set allowedmodification of some of the existing family 28 sequence characteristicsand to draw the sequence features specific for bacterial andfungal exopolygalacturonases discriminating them from the endopolygalacturonases.The evolutionary tree reflects both the taxonomy and specificityso that bacterial, fungal and plant enzymes form their own clusters,the endo- and exo-mode of action being respected, too. The onlyinsect (animal) representative is most related to fungal endopolygalacturonases.The present study brings further: (i) the analysis of availablerhamnogalacturonase sequences; (ii) the elucidation of relatednessbetween the recently added member, the endo-xylogalacturonanhydrolase and the rest of the family; and (iii) revealing thesequence features characteristic of the individual enzyme specificitiesand the evolutionary relationships within the entire family28. The disulfides common for the individual enzyme groups werealso proposed. With regard to functionally important residuesof polygalacturonases, xylogalacturonan hydrolase possessesall of them, while the rhamnogalacturonases, known to lack thehistidine residue (His223; Aspergillus niger polygalacturonaseII numbering), have a further tyrosine (Tyr291) replaced bya conserved tryptophan. Evolutionarily, the xylogalacturonanhydrolase is most related to fungal exopolygalacturonases andthe rhamnogalacturonases form their own cluster on the adjacentbranch.     

Numerical Solution of Infinite-Horizon Optimal-Control Problems

The paper presents an algorithm that solvestwo-point boundary-value problems that arise in economic control models incontinuous time with an infinite time horizon and several state variables.The algorithm can determine optimal trajectories that converge to anisolated equilibrium point. It therefore provides a numerical solution toa large class of problems for which no solvers were yet available.