Mapping Hierarchical Structures with Synchrony for Binding: Preliminary Investigations

Synchrony of firing has recently become a popular technique for dynamic binding in neural networks, and has been applied to numerous problem domains. However, hierarchical structures are difficult to represent using synchrony for binding. This paper presents our progress toward a framework for representing hierarchies in a neural network using synchrony for dynamic binding. We illustrate the approach with a model of analogical mapping. The model (IMM2) uses synchrony to bind case roles to objects within propositions. Hierarchies are established by allowing units representing propositions to play a dual role, acting both as the argument of one proposition and as a pointer to another

Frequency-dependent material properties of copper and aluminum alloys

In this paper, the dynamic behavior of copper and aluminum alloys as used in electric drive units is investigated. Isothermal frequency sweeps are performed from 0.1 up to 50 Hz at temperatures of up to 400 °C. An evaluation of the test results at a constant frequency of 1 Hz shows a decrease in the storage modulus and an increase in the material damping. Considering all frequencies, a supplementary frequency dependency related to the material composition is detected. The lower the volume fraction of the alloying elements, the higher the impact of temperature and frequency on the material properties. The variations of the material parameters allow applying the time temperature superposition principle to estimate the dynamic behavior beyond the limited tested frequency range and temperatures by fitting the Williams–Landel–Ferry equation. Additional thermal aging of CU-ETP specimens does not affect the storage modulus, but diminishes the material damping. The findings show that each material has to be tested with regard to its respective application, material composition and manufacturing process. Furthermore, they demonstrate the relevance of considering the frequency-dependent material properties of low-alloyed copper and aluminum, especially in case of temperatures above 100 °C

Piezoresistive effect in SiOC ceramics for integrated pressure sensors

Piezoresistivity was found in silicon oxycarbide (SiOC) ceramics synthesized using a polymer-to-ceramic transformation process. A commercial polysiloxane, namely poly(methylsilsesquioxane), was used as the starting material. The SiOC ceramic synthesized at 1400 degrees C exhibits high piezoresistivity, leading to strain sensitivities (k factors) of similar to 145, while lower pyrolysis temperatures (1000 degrees-1300 degrees C) do not show a piezoresistive effect. Structural characterization by X-ray diffraction in combination with micro-Raman spectroscopy revealed that with increasing pyrolysis temperature, the content of free carbon in the X-ray amorphous SiOC matrix increases without changes in the overall composition. Percolation effects related to the carbon-based phase segregated from the SiOC matrix are responsible for the piezoresistivity analyzed in the SiOC ceramic