Improving constrained clustering with active query selection

In this article, we address the problem of automatic constraint selection to improve the performance of constraint-based clustering algorithms. To this aim we propose a novel active learning algorithm that relies on a k-nearest neighbors graph and a new constraint utility function to generate queries to the human expert. This mechanism is paired with propagation and refinement processes that limit the number of constraint candidates and introduce a minimal diversity in the proposed constraints. Existing constraint selection heuristics are based on a random selection or on a min–max criterion and thus are either inefficient or more adapted to spherical clusters. Contrary to these approaches, our method is designed to be beneficial for all constraint-based clustering algorithms. Comparative experiments conducted on real datasets and with two distinct representative constraint-based clustering algorithms show that our approach significantly improves clustering quality while minimizing the number of human expert solicitations.     

Hydrothermal Syntheses and Catalytic Properties of Dispersed Molybdenum Sulfides

Reactions of ammonium thiomolybdate under mild hydrothermal conditions were studied, and the range of conditions leading to the dispersed MoS₂ product has been determined. The morphology and the catalytic properties of the hydrothermal MoS₂ preparations have been compared with those of reference MoS₂ produced from the thermal decomposition of thiosalts. It has been shown that the length of the slabs and their stacking number of the crystallites of hydrothermal MoS₂ preparations differ considerably from those in the reference sulfides. The morphological differences strongly influence the hydrogenation to hydrodesulfurization activity ratio in these systems.     

Hyperbranched polyol/carbon nanofiber composites

Carbon nanofiber (CNF) and carbon nanotube (CNT) composites have enhanced mechanical and electrical properties that make these composites desirable for antistatic and electronic dissipation technology. These applications require a homogenous dispersion of CNFs within a polymer matrix. To improve the compatibility/dispersability of CNFs within a polymer matrix, a hyperbranched polyol CNF composite was synthesized by the chemical modification of oxidized CNFs with glycidol and boron trifluoride diethyl etherate. The resulting polyol CNFs were characterized by TGA, FTIR, TEM/SEM and XPS. The hydroxyl groups were reacted with heptafluorobutyryl chloride to determine the amount of oxidized groups in the sample. The resulting composite was characterized by FTIR and elemental analysis. The amount of hydroxyl groups increased by 550% for the polyol CNFs as compared to the oxidized CNFs and an improvement in dispersion ability was observed.     

Toward a business model reference for interoperability services

The importance of interoperability for businesses is undoubted. After an evolution from electronic data interchange to interoperability in electronic business and enterprise interoperability both the scientific and the practitioners’ community are today discussing the notion of interoperability service utilities. Furthermore, researchers are studying decentralized and distributed interoperability approaches such as peer-to-peer networks, for example. However, a comprehensive investigation of business models for such decentralized approaches to interoperability is still missing. Drawing from recent literature on business modeling on the one hand and interoperability research on the other hand this paper designs a business model reference for interoperability services. The business model reference assumes interoperability information as an economic good and is applied in two case studies and evaluated from multiple perspectives. The paper contributes to the scientific body of knowledge as it proposes a novel design artifact which lays the foundation for a number of future research opportunities.     

Using part–whole relations for automatic deduction of compound-internal relations in GermaNet

This paper provides a deduction-based approach for automatically classifying compound-internal relations in GermaNet, the German version of the Princeton WordNet for English. More specifically, meronymic relations between simplex and compound nouns provide the necessary input to the deduction patterns that involve different types of compound-internal relations. The scope of these deductions extends to all four meronymic relations modeled in version 6.0 of GermaNet: component, member, substance, and portion. This deduction-based approach provides an effective method for automatically enriching the set of semantic relations included in GermaNet.     

The Heard-Of model: computing in distributed systems with benign faults

Problems in fault-tolerant distributed computing have been studied in a variety of models. These models are structured around two central ideas: (1) degree of synchrony and failure model are two independent parameters that determine a particular type of system, (2) the notion of faulty component is helpful and even necessary for the analysis of distributed computations when faults occur. In this work, we question these two basic principles of fault-tolerant distributed computing, and show that it is both possible and worthy to renounce them in the context of benign faults: we present a computational model based only on the notion of transmission faults. In this model, computations evolve in rounds, and messages missed in a round are lost. Only information transmission is represented: for each round r and each process p, our model provides the set of processes that p “hears of” at round r (heard-of set), namely the processes from which p receives some message at round r. The features of a specific system are thus captured as a whole, just by a predicate over the collection of heard-of sets. We show that our model handles benign failures, be they static or dynamic, permanent or transient, in a unified framework. We demonstrate how this approach leads to shorter and simpler proofs of important results (non-solvability, lower bounds). In particular, we prove that the Consensus problem cannot be generally solved without an implicit and permanent consensus on heard-of sets. We also examine Consensus algorithms in our model. In light of this specific agreement problem, we show how our approach allows us to devise new interesting solutions. A. Schiper’s research funded by the Swiss National Science Foundation under grant number 200021-111701 and Hasler Foundation under grant number 2070.     

The influence of crystallographic orientation on the wetting of silicon on quartz single crystals

Dynamic hexagonal spreading patterns of small silicon droplets on the basal plane (001) of quartz were observed by video microscopy. A detailed analysis of the hexagonal triple line demonstrates that the patterns show slight chiral distortions that can be attributed to the screw axis of the substrate crystal. This article reveals the detailed influence of crystal symmetry on the anisotropy of reactive wetting. In this context, a first discussion about the interplay of wetting and etching of a crystal is provided.     

Investigation on a Deep Drawing and In‐Process Electromagnetic Calibration

Extending forming limits is one of the most important aims of research work in production engineering. One possibility to improve material formability is the application of high strain rates, which can be realized e.g. by means of electromagnetic forming (EMF). A further extension of the forming limits can be achieved by a beneficial combination of EMF and quasistatic forming operations, which allow exploiting the complementary advantages of the different technologies involved. This approach will be described on the basis of a deep drawing and inprocess electromagnetic sheet metal forming calibration in this paper. Thereby, the design as well as the subsequent analysis of the components as well as the combined process plays a distinctive role. Furthermore, the stages of development regarding the integrated tool coil will be presented and the resulting examples discussed. Finally, the setup of the integrated process as well as the feasibility will be shown on an exemplary semi‐industrial workpiece.