New results for the degree/diameter problem

The results of computer searches for large graphs with given (small) degree and diameter are presented. The new graphs are Cayley graphs of semidirect products of cyclic groups and related groups. One fundamental use of our ``dense graphs'' is in the design of efficient communication network topologies.Comment: 15 page

Development of an integrated solar-fossil powered steam generation system for industrial applications

Das Poster gibt eine kurze Einführung in das Projekt SolSteam, in dem die Integration solaren Prozessdampfes in einen konventionellen Dampferzeuger untersucht wird

A One Line Derivation of DCC: Application of a Vector Random Coefficient Moving Average Process

One of the most widely-used multivariate conditional volatility models is the dynamic conditional correlation (or DCC) specification. However, the underlying stochastic process to derive DCC has not yet been established, which has made problematic the derivation of asymptotic properties of the Quasi-Maximum Likelihood Estimators. The paper shows that the DCC model can be obtained from a vector random coefficient moving average process, and derives the stationarity and invertibility conditions. The derivation of DCC from a vector random coefficient moving average process raises three important issues: (i) demonstrates that DCC is, in fact, a dynamic conditional covariance model of the returns shocks rather than a dynamic conditional correlation model; (ii) provides the motivation, which is presently missing, for standardization of the conditional covariance model to obtain the conditional correlation model; and (iii) shows that the appropriate ARCH or GARCH model for DCC is based on the standardized shocks rather than the returns shocks. The derivation of the regularity conditions should subsequently lead to a solid statistical foundation for the estimates of the DCC parameters

Self-Assembly of Monatomic Complex Crystals and Quasicrystals with a Double-Well Interaction Potential

For the study of crystal formation and dynamics we introduce a simple two-dimensional monatomic model system with a parametrized interaction potential. We find in molecular dynamics simulations that a surprising variety of crystals, a decagonal and a dodecagonal quasicrystal are self-assembled. In the case of the quasicrystals the particles reorder by phason flips at elevated temperatures. During annealing the entropically stabilized decagonal quasicrystal undergoes a reversible phase transition at 65% of the melting temperature into an approximant, which is monitored by the rotation of the de Bruijn surface in hyperspace.Comment: 4 pages, 6 figures. Physical Review Letters, in Press (April 2007

Sparse Coding with a Somato-Dendritic Rule

© 2020 Elsevier Ltd. All rights reserved. This manuscript is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International Licence http://creativecommons.org/licenses/by-nc-nd/4.0/.Cortical neurons are silent most of the time. This sparse activity is energy efficient, and the resulting neural code has favourable properties for associative learning. Most neural models of sparse coding use some form of homeostasis to ensure that each neuron fires infrequently. But homeostatic plasticity acting on a fast timescale may not be biologically plausible, and could lead to catastrophic forgetting in embodied agents that learn continuously. We set out to explore whether inhibitory plasticity could play that role instead, regulating both the population sparseness and the average firing rates. We put the idea to the test in a hybrid network where rate-based dendritic compartments integrate the feedforward input, while spiking somas compete through recurrent inhibition. A somato-dendritic learning rule allows somatic inhibition to modulate nonlinear Hebbian learning in the dendrites. Trained on MNIST digits and natural images, the network discovers independent components that form a sparse encoding of the input and support linear decoding. These findings con-firm that intrinsic plasticity is not strictly required for regulating sparseness: inhibitory plasticity can have the same effect, although that mechanism comes with its own stability-plasticity dilemma. Going beyond point neuron models, the network illustrates how a learning rule can make use of dendrites and compartmentalised inputs; it also suggests a functional interpretation for clustered somatic inhibition in cortical neurons.Peer reviewe

The future of trans-Atlantic collaboration in modelling and simulation of Cyber-Physical Systems - A strategic research agenda for collaboration

Smart systems, in which sophisticated software/hardware is embedded in physical systems, are part of everyday life. From simple products with embedded decision-making software, to massive systems in which hundreds of systems, each with hundreds or thousands of embedded processors, interoperate the use of Cyber-Physical Systems (CPS) will continue to expand. There has been substantial investment in CPS research in Europe and the United States. Through a series of workshops and other events, the TAMS4CPS project has established that there is mutual benefit in the European Union and US collaborating on CPS research. An agenda for collaborative research into modelling and simulation for CPS is thus set forth in the publication at hand. The agenda includes models for many different purposes, including fundamental concepts, design models (e.g. architectures), predictive techniques, real-time control, human-CPS interaction, and CPS governance. Within this framework, seven important themes have been identified where mutual benefits can be realised by EU-US cooperation. To actively advance research and innovation in these fields, a number of collaboration mechanisms is presented and concrete actions to encourage, enhance and implement trans-Atlantic collaboration in modelling and simulation of CPS are recommended

The decentering component of mindfulness reduces reactions to mental imagery

Four experiments examined whether reactions to mental imagery can be reduced by the mindfulness component of decentering, that is, the insight that experiences are impermanent mental states. In Experiments 1a, 1b, and 1c, participants vividly imagined an unpleasant autobiographical event or a rewarding food. When instructed to adopt a decentering perspective in comparison to an immersed perspective during imagery, participants experienced less negative affect and fewer cravings to eat. In Experiment 2, participants were exposed to an attractive or a neutral food, and we assessed salivation and eating-related imagery. Although imagery did not differ between groups, the attractive food elicited less salivation in decentering relative to control participants. We suggest that decentering can make one’s imagery of consuming a food and of reliving of negative experiences less compelling, and thus reduce affective responses to both unpleasant and rewarding imagery, even if the imagery itself is kept active in mind

Cooperative Collision Avoidance at Intersections: Algorithms and Experiments

In this paper, we leverage vehicle-to-vehicle (V2V) communication technology to implement computationally efficient decentralized algorithms for two-vehicle cooperative collision avoidance at intersections. Our algorithms employ formal control theoretic methods to guarantee a collision-free (safe) system, whereas overrides are only applied when necessary to prevent a crash. Model uncertainty and communication delays are explicitly accounted for by the model and by the state estimation algorithm. The main contribution of this work is to provide an experimental validation of our method on two instrumented vehicles engaged in an intersection collision avoidance scenario in a test track

Einfache Umwandlung des Azulen-Systems in das Pentalen-System

Cycloadditionsreaktionen des Azulens 1 mit elektronenarmen sowie mit elektronenreichen Alkinen bieten einen einfachen Zugang zu Derivaten des Heptalens 2[¹] und Cyclopentacyclononens 3[²]. Jüngst konnten wir auch die Transformation von 1 in das Pentalen-System 4 verwirklichen