A regularised estimator for long-range dependent processes

There is significant interest in long-range dependent processes since they occur in a wide range of phenomena across different areas of study. Based on the available models capable of describing long-range dependence, various parameter estimation methods have been developed. In this paper we revisit the maximum likelihood estimator and its computationally efficient approximations: Whittle’s Estimator and the Circulant Embedding Estimator. In particular, this paper proves the asymptotic properties of the Circulant Embedding estimator and establishes the asymptotic equivalence between the three estimators. Furthermore, it is shown that the three methods are ill-conditioned and thus highly sensitive to the presence of measurement errors. Finally, we introduce a regularisation method that improves the performance of the maximum likelihood methods when the datasets have been largely contaminated with errors.     

A new approach for kinetic modeling and optimization of rubber molding

Although extensive research has been carried out on the understanding of the complex vulcanization process, the influence of reversion through exposure time and temperature on the vulcanization degree remains unclear. Therefore, the main aim of this study was a novel optimization approach that can help the industrial practitioners to select the optimal operating parameters, exposure time, and molding temperature, to achieve desired vulcanization degree of selected product. Spheres of four different diameters (2.5, 5, 10, and 20 cm) were selected as test geometry for simulation and optimization of rubber molding. Obtained vulcanization rheometer data for commercially available rubber blend (NR/SBR) were fitted by a new modeling approach, dividing vulcanization curve into two fitting sets: curing and reversion. The heat transfer equations for chosen geometry were coupled with proposed kinetic model. A new temperature-dependent kinetic parameter x, as the maximal reversion degree, was introduced, enabling determination of the lowest operating molding temperature (T_min = 132.36 °C), preventing high reversion and overheating of the rubber product. The final optimization goal was assessment of the optimal temperature and vulcanization time dependence on the rubber products dimensions. Proposed models have precise prediction with R² values greater than 0.8328 and MAPE less than 2.3099%.     

Synthesis and characterization of photopolymers with azo units. Interfacial polyaddition,photolysis, photodegradation

The synthesis of an aryl alkyl azo diisocyanate and a model azo urea is described. From the azo diisocyanate new azo polyureas were created by interfacial polyaddition. Molecular weights M_n in the range of 6000 to 9000 were determined by gel permeation chromatography (GPC). Photolysis and thermolysis of both, model compounds and polymers, were studied by UV-spectroscopy and differential scanning calorimetry (DSC), respectively, and the results were compared with those of similar azo amides. Photochemical polymer degradation was followed by GPC.     

Studies on new non-shrinking,thermally stable,araldite-type photopolymers with pendent arylacryloyl groups III. Photopolymers with pendent cinnamic acid ester and furan acrylic ester groups and their reactions with low molar mass modifiers

Commercially available Araldite?-type polymers have been modified with cinnamic and furan acrylic acid chlorides. The polymers were photochemically crosslinked via a [2 + 2] cycloaddition. The resulting polymers show glass transition temperatures up to 130°C and dielectrical constants of ?_r = 3.0. Therefore, these polymers can be applied as permanent resists in multi-layered wiring structures. Numerous well-defined multifunctional modifiers have been synthesized. The effect of those modifiers on the polymerization and properties of the araldite-type polymers has been studied in some detail.     

Gegenzbiete der Lebensmittelwissenschaft

Ohne Zusammenfassung     

Copolymers from 1-phenyl-2-(3-vinylphenylthio)-diazen and styrene and grafting with acrylonitrile

Summary A new azo monomer (2) was synthesized and copolymerized with styrene. The resulting azo copolymer could be used as an initiator for the acrylonitrile polymerisation yielding grafted copolymers. Quantitative treatment of the grafting experiments leads to the conclusion that the intermediate thiyl radicals show less reactivity towards monomers than phenyl radicals.     

Messung der Druckverteilung beim Hohlzug von Rohren und beim Ziehen von Rundstäben

Messung mit durchgehenden Druckstiften und Messung der Durchwölbung membranartiger Meßstellen in der Ziehholwand. Ziehversuche an Rohren ohne Innenwerkzeug im gesamten Bereich des Wanddicken-Durchmesser-Verhältnisses unter Einschluß des Stabes als Gremfall. Einfluß der Umformbedingungen auf den Druckverlauf. Berechnung des Reibungsbeiwertes aus den gemessenen Drücken und Ziehkräften. Vergleich des Druckverlaufs beim Ziehen und Einstoßen.