Neural networks as surrogate models for nonlinear, transient aerodynamics within an aeroelastic coupling-scheme in the time domain

In this paper the creation of a nonlinear, transient surrogate model is described that can be used within an aeroelastic coupling-scheme in the transonic range. The method is based on the theory of artifical neural networks as well as the autoregressive moving average method (ARMA). It can be shown that the method is able to approximate the nonlinear aeroelastic behaviour of the NLR7301 airfoil. Also limit cycle oscillations can be approximated with acceptable accuracy

Hierarchical Strategy of Model Partitioning for VLSI-Design Using an Improved Mixture of Experts Approach

The partitioning of complex processor models on the gate and register-transfer level for parallel functional simulation based on the clock-cycle algorithm is considered. We introduce a hierarchical partitioning scheme combining various partitioning algorithms in the frame of a competing strategy. Melting together different partitioning results within one level using superpositions we crossover to a mixture of experts one. This approach is improved applying genetic algorithms. In addition we present two new partitioning algorithms both of them taking cones as fundamental units for building partitions

Optimal design of nanoplasmonic materials using genetic algorithms as a multi-parameter optimization tool

An optimal control approach based on multiple parameter genetic algorithms is applied to the design of plasmonic nanoconstructs with pre-determined optical properties and functionalities. We first develop nanoscale metallic lenses that focus an incident plane wave onto a pre-specified, spatially confined spot. Our results illustrate the role of symmetry breaking and unravel the principles that favor dimeric constructs for optimal light localization. Next we design a periodic array of silver particles to modify the polarization of an incident, linearly-polarized plane wave in a desired fashion while localizing the light in space. The results provide insight into the structural features that determine the birefringence properties of metal nanoparticles and their arrays. Of the variety of potential applications that may be envisioned, we note the design of nanoscale light sources with controllable coherence and polarization properties that could serve for coherent control of molecular or electronic dynamics in the nanoscale.Comment: 13 pages, 6 figures. submitted to J. Chem. Phy

Searching for the Rail Bonus

The inherent superiority of rail-based public transport options over bus-based alternatives, all other things being equal, has been stipulated in the literature and in the public policy discussion for some time. The exact strength of any such rail bonus is important to a public transport operator which has to consider the replacement of rail-based services by bus services. The public transport operator of the city of Dresden (DVB), while generally upgrading its services, has to consider this option, in particular where the continuing tram operation would require a costly rehabilitation of the tracks. The measurement of any such systematic preference for rail-based modes is difficult, as is requires either a before-and-after study of such a switch, controlled for the other relevant service attributes, e.g. frequency, speed, reliability, price, route, etc., or a study of a network, in which rail- and road-based modes offer comparable types of services, with bus services inparticular not restricted to feeder services to rail/tram lines. Both are rare for obvious reasons. A recent service change of the DVB offered the opportunity to look at the issue in detail. A series of surveys were undertaken for this purpose before and after: A one-day travel diary (including a household questionnaire)  A survey of the image of the services A between-mode stated preference exercise focusing on the choice between public transport and private motorised transport where public transport was provided by either bus or tram (7 choice situations) A within-mode stated preference exercise looking at the trade-offs between public transport modes, in particular levels of comfort, travel times and transfers (7 choice situations). The paper reports detailed results from this study addressing the differences in preferences between the waves (effects of familiarity with an alternative) from both separate and joint stated preference and stated preference/revealed preference models. The modelling so far indicates a consistent, but weak preference for the rail option through a higher value-of-time for rail usage, higher valuation of new rail vehicles in comparison to new busses, although they are partially balanced by a higher transfer penalty. &nbsp

M-theory on Calabi-Yau Five-Folds

We study the compactification of M-theory on Calabi-Yau five-folds and the resulting N=2 super-mechanics theories. By explicit reduction from 11 dimensions, including both bosonic and fermionic terms, we calculate the one-dimensional effective action and show that it can be derived from an N=2 super-space action. We find that the Kahler and complex structure moduli of the five-fold reside in 2a and 2b super-multiplets, respectively. Further 2b super-multiplets arise from zero-modes of the M-theory three-form and lead to cross-couplings between 2a and 2b multiplets. Fermionic zero modes which arise from the (1,3) sector of the 11-dimensional gravitino do not have bosonic super-partners and have to be described by purely fermionic super-multiplets in one dimension. We also study the inclusion of flux and show that the scalar potential from (2,2) flux is consistent with one-dimensional N=2 supersymmetry and can be described in terms of a superpotential. This superpotential can also be obtained from a Gukov-type formula which we present. Supersymmetric vacua, obtained by solving the F-term equations, always have vanishing vacuum energy due to the form of this scalar potential. We show that such supersymmetric solutions exist for particular examples. Two substantial appendices develop the topology and geometry of Calabi-Yau five-folds and the structure of one-dimensional N=2 supersymmetry and supergravity to the level of generality required for our purposes

Hierarchical Model Partitioning for Parallel VLSI-Simulation Using Evolutionary Algorithms improved bei superpositions of partitions

Parallelization of VLSI-simulation exploiting model-inherent parallelism is a promising way to accelerate verification processes for whole processor designs. Thereby partitioning of hardware models influences the effciency of following parallel simulations essentially. Based on a formal model of Parallel Cycle Simulation we introduce partition valuation combining communication and load balancing aspects. We choose a 2-level hierarchical partitioning scheme providing a framework for a mixture of experts strategy. Considering a complete model of a PowerPC 604 processor, we demonstrate that Evolutionary Algorithms can be applied successfully to our model partitioning problem on the second hierarchy level, supposing a reduced problem complexity after fast pre-partitioning on the first level. For the first time, we apply superpositions during execution of Evolutionary Algorithms, resulting in a faster decreasing fitness function and an acceleration of population handling

RF-MEMS switch actuation pulse optimization using Taguchi's method

Copyright @ 2011 Springer-VerlagReliability and longevity comprise two of the most important concerns when designing micro-electro-mechanical-systems (MEMS) switches. Forcing the switch to perform close to its operating limits underlies a trade-off between response bandwidth and fatigue life due to the impact force of the cantilever touching its corresponding contact point. This paper presents for first time an actuation pulse optimization technique based on Taguchi’s optimization method to optimize the shape of the actuation pulse of an ohmic RF-MEMS switch in order to achieve better control and switching conditions. Simulation results show significant reduction in impact velocity (which results in less than 5 times impact force than nominal step pulse conditions) and settling time maintaining good switching speed for the pull down phase and almost elimination of the high bouncing phenomena during the release phase of the switch

Get It in Writing: Formal Contracts Mitigate Social Dilemmas in Multi-Agent RL

Multi-agent reinforcement learning (MARL) is a powerful tool for training automated systems acting independently in a common environment. However, it can lead to sub-optimal behavior when individual incentives and group incentives diverge. Humans are remarkably capable at solving these social dilemmas. It is an open problem in MARL to replicate such cooperative behaviors in selfish agents. In this work, we draw upon the idea of formal contracting from economics to overcome diverging incentives between agents in MARL. We propose an augmentation to a Markov game where agents voluntarily agree to binding state-dependent transfers of reward, under pre-specified conditions. Our contributions are theoretical and empirical. First, we show that this augmentation makes all subgame-perfect equilibria of all fully observed Markov games exhibit socially optimal behavior, given a sufficiently rich space of contracts. Next, we complement our game-theoretic analysis by showing that state-of-the-art RL algorithms learn socially optimal policies given our augmentation. Our experiments include classic static dilemmas like Stag Hunt, Prisoner's Dilemma and a public goods game, as well as dynamic interactions that simulate traffic, pollution management and common pool resource management.Comment: 12 pages, 8 figures, AAMAS 202

Fail Forward! Perspectives on Failure in the Writing Classroom

In this inaugural Teacher-to-Teacher column, three classroom teachers discuss how they approach failure to normalize it and help students work toward problem solving rather than answer getting in their own classrooms. Missy Springsteen-Haupt explains how sharing her own authentic writing failures helps students see the natural emotional connection to their writing as normal and also to prove to them, as Shirley Rose notes, that \u27all writers always have more to learn about writing\u27 (59). Framing student writing in terms of growth mindsets, Stacy Stosich discusses a practical strategy for allowing for ugly drafts and redefining success and failure. Finally, Nora K. Rivera delineates a system of peer review and weekly sentence work designed to allow for experimentation without penalty; her methods not only pushed students to carefully evaluate their own and others’ work, but also resulted in a reduced grading load and student success in district testing

Nichtlineare Viskoelastizität von gummiartigen Werkstoffen: Experimentelle Untersuchung, Modellierung und Identifikation

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