Hydrogen pressure-dependence in the ring-opening reactions of substituted cyclopropanes over Rh/SiO2 catalyst

The hydrogen coverage and the structures of the reactants influence the selectivity and mechanism of the ring-opening reactions of ethyl-(ECP),cis-1,2-dimethyl-(cDMCP),trans1,2-dimethyl-(tDMCP), 1,1-dimethyl-(1, 1DMCP) and 1, 1, 2, 2-tetramethylcyclopropane (TMCP) over Rh/SiO₂ catalyst; a new phenomenon was observed for the transformations of ECP,tDMCP and 1, 1DMCP, viz. the turnover frequency vs. H₂ pressure functions pass through a minimum.     

Investigating the influence of QoS on personal evaluation behaviour in a mobile context

The efficiency of personal video suggestions generated by recommender systems is highly dependent on the quality of the obtained user feedback. This feedback has to reflect the personal interest in the content of the viewed video, to obtain accurate results. However, user feedback might undesirably be influenced by additional aspects such as the loading speed or the quality of the video. To date, this issue has received very little research attention. Therefore, this study investigates the direct influence of audio-visual quality parameters on explicit user feedback for the first time to our knowledge via a mobile, Living Lab experiment. This paper proposes a feedback model which takes the Quality of Service (QoS) parameters of the mobile network into account. This model can be used as an additional feedback filter for video recommendation systems that could help to eliminate the influences of QoS on explicit user feedback.     

Foundations for Streaming Model Transformations by Complex Event Processing

Streaming model transformations represent a novel class of transformations to manipulate models whose elements are continuously produced or modified in high volume and with rapid rate of change. Executing streaming transformations requires efficient techniques to recognize activated transformation rules over a live model and a potentially infinite stream of events. In this paper, we propose foundations of streaming model transformations by innovatively integrating incremental model query, complex event processing (CEP) and reactive (event-driven) transformation techniques. Complex event processing allows to identify relevant patterns and sequences of events over an event stream. Our approach enables event streams to include model change events which are automatically and continuously populated by incremental model queries. Furthermore, a reactive rule engine carries out transformations on identified complex event patterns. We provide an integrated domain-specific language with precise semantics for capturing complex event patterns and streaming transformations together with an execution engine, all of which is now part of the Viatra reactive transformation framework. We demonstrate the feasibility of our approach with two case studies: one in an advanced model engineering workflow; and one in the context of on-the-fly gesture recognition.     

Novel polyurethane elastomer continuous carbon fiber composites: Preparation and characterization

Preparation and characterization of novel polyurethane (PUR)–carbon fiber (CF) composites are reported. The reinforcement of PUR elastomers was achieved using unidirectional continuous CFs with different coatings (uncoated and epoxy and polyester resin coatings) by applying molding for the preparation of PUR‐CF composites. Considerable reinforcement of PUR was attained even at relatively low CF content, e.g., maximum stress and Young's modulus of PUR‐CF composite at CF content 3% (m/m) were found to be 3–5 and 4–10 times higher than those of the PUR‐matrix, respectively. In addition, a linear relationship between the Young's modulus and the CF content was found as well as linear variation of maximum stress with the CF content was also observed. The adhesion of CF to the PUR‐matrix was strong in each case as concluded from the strain–stress and the scanning electron microscopy (SEM) investigations. However, the extent of reinforcement of PUR at a given CF content was found to depend greatly on the coatings of CF, and increased in the following order: epoxy resin < polyester resin < uncoated. The effect of the coating of CF on the reinforcement of PUR is also discussed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 287–292, 2007     

Reactions of methylcyclopentane on Rh–Pt catalyst prepared by underpotential deposition of Rh on Pt/SiO2

Rh was deposited on to a well-characterized 3.1% Pt/SiO₂ (InCat-1) parent catalyst by underpotential deposition method to obtain a model Rh–Pt bimetallic catalyst. TEM and EDS was used to determine its mean particle size and bulk composition: the particles of ca. 3 nm contained ca. 60% Pt and 40% Rh. The Rh–Pt catalyst was tested in methylcyclopentane (MCP) reaction between 513 K and 603 K and 60–480 Torr H₂ pressure (with 10 Torr MCP). The parent Pt/SiO₂ as well as a 5% Rh/SiO₂ catalyst were also studied for comparison. Four subsequent treatments with O₂ and H₂ up to T = 673 K were applied on the bimetallic catalyst before the catalytic runs. The overall activity showed positive hydrogen order on all samples, bimetallic Rh–Pt resulting in the lowest TOF values. Ring opening and hydrogenolysis products, as well as unsaturated hydrocarbons were formed from MCP. The selectivity of ring opening products and fragments over Rh–Pt catalyst was between the values observed on Pt and Rh, while the selectivity towards benzene formation was highest on the bimetallic sample, especially at higher temperatures. “Selective” ring opening occurred on all samples, resulting mostly in 2 and 3-methylpentane and less hexane. Different pretreatments with H₂ and O₂ affected slightly the dispersion values and the catalytic behavior of Rh–Pt sample. The selectivities of the Rh–Pt catalyst being between the values observed for Pt/SiO₂ and Rh/SiO₂ indicates that the sample studied represented a real bimetallic catalyst, resembling both components and exhibiting at the same time, new properties in addition to those, characteristic of Pt or Rh. Dedicated to Konrad Hayek.     

Cyclodimerisation and Cyclotrimerisation During the Ring-Opening Reactions of Ethylene Sulfide (Thiirane) over Acidic Molecular Sieves and Alumina

Liquid phase benzylation (by benzyl chloride) and acylation (by benzoyl chloride) of benzene and toluene over a Ga–Mg hydrotalcite (which is a basic anionic clay) with or without HCl gas pretreatment and also over the hydrotalcite used earlier in the toluene benzylation (at 110°C) have been investigated. The fresh, used and HCl-gas-pretreated hydrotalcite catalysts were characterized for their surface area, basicity, crystalline structure and phases and also for their surface composition. The fresh hydrotalcite showed no catalytic activity for both the benzylation and benzoylation reactions for a long period. However, after a long induction period (2.7 h), the catalyst showed a very high activity in the toluene benzylation (at 110°C). Whereas, the catalyst after its use in the toluene benzylation or after its HCl gas pretreatment showed very high activity for both the reactions with a much shorter induction period. The hydrotalcite-derived catalyst consists essentially highly dispersed gallium and magnesium chlorides on MgO. The presence of moisture in the reaction mixture has beneficial effects on the acylation reactions over the used catalyst.     

Query-driven soft traceability links for models

Model repositories play a central role in the model driven development of complex software-intensive systems by offering means to persist and manipulate models obtained from heterogeneous languages and tools. Complex models can be assembled by interconnecting model fragments by hard links, i.e., regular references, where the target end points to external resources using storage-specific identifiers. This approach, in certain application scenarios, may prove to be a too rigid and error prone way of interlinking models. As a flexible alternative, we propose to combine derived features with advanced incremental model queries as means for soft interlinking of model elements residing in different model resources. These soft links can be calculated on-demand with graceful handling for temporarily unresolved references. In the background, the links are maintained efficiently and flexibly by using incremental model query evaluation. The approach is applicable to modeling environments or even property graphs for representing query results as first-class relations, which also allows the chaining of soft links that is useful for modular applications. The approach is evaluated using the Eclipse Modeling Framework (EMF) and EMF-IncQuery in two complex industrial case studies. The first case study is motivated by a knowledge management project from the financial domain, involving a complex interlinked structure of concept and business process models. The second case study is set in the avionics domain with strict traceability requirements enforced by certification standards (DO-178b). It consists of multiple domain models describing the allocation scenario of software functions to hardware components.     

LP-based velocity profile generation for robotic manipulators

In this paper we examine the minimum-time velocity profile generation problem which belongs to the second stage of the decoupled robot motion planning. The time-optimal profile generation problem can be translated to a convex optimal control task through a nonlinear change of variables. When the constraints of the problem have special structure, the time-optimal solution can be obtained by linear programming (LP). In this special case, the velocity of the robot along the path is maximised, instead of time minimising. The benefit of the LP solution is the lower computational time. Validation of the LP algorithm is also presented based on simulation results.     

Cross-layer optimized wireless multicast for layered media

This paper discusses the maximization of user-perceived quality of layered media in wireless networks. We present a system model and an optimization framework for such networks assuming: (i) the data rates are nested, (ii) the media is multicast, (iii) layered and (iv) the media layer information is available in lower network layers based on cross-layer information. In order to show the general applicability of the proposal, different maximization targets and algorithmic solutions are presented.     

Wirkung des Zentrifugalkraftfeldes auf den Wärmezustand der Gase,Erklärung der Ranque-Erscheinung

Zusammenfassung In Zentrifugalkraftfeldern, in denen man Beschleunigungen vom 10⁷ fachen der Fallbeschleunigung erreicht, k?nnen Temperaturgradienten bis über 10 grd/mm auftreten. Auf diesem Effekt beruhen die bei dem Ranque-Rohr auftretenden Temperatur?nderungen. Aus der entwickelten Theorie geht hervor, da? die erreichbare Temperaturdifferenz unter den eingeführten Voraussetzungen nicht von den Abmessungen der Rohre und vom Druck des einstr?menden Gases, sondern nur vom Adiabatenexponenten, vom Verh?ltnis der Drücke vor und hinter dem Wirbelrohr sowie von der absoluten Temperatur des Gases beim Eintritt in das Rohr abh?ngt. Ein Vergleich mit Versuchsergebnissen best?tigt die Richtigkeit der Theorie. Aus einer Betrachtung der Vorg?nge im Ranque-Rohr mit Hilfe des Entropie-Enthalpie-Diagramms nach den Verfahren der klassischen Thermodynamik ergeben sich Folgerungen über die erreichbaren Wirkungsgrade.