Qualms regarding the optimality of cumulative path length control in CSA/CMA-evolution strategies

Cumulative step-size adaptation (CSA) based on path length control is regarded as a robust alternative to the standard mutative self-adaptation technique in evolution strategies (ES), guaranteeing an almost optimal control of the mutation operator. This paper shows that the underlying basic assumption in CSA--the perpendicularity of expected consecutive steps--does not necessarily guarantee optimal progress performance for (mu/mu(I), lambda) intermediate recombinative ES.     

Optimum tracking with evolution strategies

Evolutionary algorithms are frequently applied to dynamic optimization problems in which the objective varies with time. It is desirable to gain an improved understanding of the influence of different genetic operators and of the parameters of a strategy on its tracking performance. An approach that has proven useful in the past is to mathematically analyze the strategy's behavior in simple, idealized environments. The present paper investigates the performance of a multiparent evolution strategy that employs cumulative step length adaptation for an optimization task in which the target moves linearly with uniform speed. Scaling laws that quite accurately describe the behavior of the strategy and that greatly contribute to its understanding are derived. It is shown that in contrast to previously obtained results for a randomly moving target, cumulative step length adaptation fails to achieve optimal step lengths if the target moves in a linear fashion. Implications for the choice of population size parameters are discussed.     

Evolution strategies with cumulative step length adaptation on the noisy parabolic ridge

This paper presents an analysis of the performance of the (μ/μ,λ)-ES with isotropically distributed mutations and cumulative step length adaptation on the noisy parabolic ridge. Several forms of dependency of the noise strength on the distance from the ridge axis are considered. Closed form expressions are derived that describe the mutation strength and the progress rate of the strategy in high-dimensional search spaces. It is seen that as for the sphere model, larger levels of noise present lead to cumulative step length adaptation generating increasingly inadequate mutation strengths, and that the problem can be ameliorated to some degree by working with larger populations.     

Time-Resolved Structural Kinetics of an Organic Mixed Ionic–Electronic Conductor

The structure and packing of organic mixed ionic–electronic conductors have an especially significant effect on transport properties. In operating devices, this structure is not fixed but is responsive to changes in electrochemical potential, ion intercalation, and solvent swelling. Toward this end, the steady-state and transient structure of the model organic mixed conductor, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), is characterized using multimodal time-resolved operando techniques. Steady-state operando X-ray scattering reveals a doping-induced lamellar expansion of 1.6 Å followed by 0.4 Å relaxation at high doping levels. Time-resolved operando X-ray scattering reveals asymmetric rates of lamellar structural change during doping and dedoping that do not directly depend on potential or charging transients. Time-resolved spectroscopy establishes a link between structural transients and the complex kinetics of electronic charge carrier subpopulations, in particular the polaron–bipolaron equilibrium. These findings provide insight into the factors limiting the response time of organic mixed-conductor-based devices, and present the first real-time observation of the structural changes during doping and dedoping of a conjugated polymer system via X-ray scattering.     

An integrated approach for validating micro mechanical systems based on simulation and test

Miniaturization of macroscopic mechanical systems enables the opening of new areas of application for micro technological systems. Because of technological restrictions, especially when applying miniaturized conventional manufacturing techniques, shape and material deviations cannot be scaled down in the same dimension like micro parts. Thus, the long-term objective is to ensure the functioning by appropriate design measures. In doing so, determination of the transfer behavior by modeling and simulation is required. This work presents two ways for ensuring the required properties of micro gears and describes how the results do correlate. The experimental way uses the radial composite inspection as it is used in the macroscopic world. The simulative way deploys a rolling simulation by utilization of finite element analysis. The virtual prototypes are originated on measured real test gears. When comparing experiment and simulation of the rolling behavior, in some short and long wave areas deviations can be recognized. These can be ascribed to the reduction from three to two dimensions when modeling. Other deviations might be based on inaccuracies when mounting into the test rig. In other areas quite good correlations of test and simulation could be ascertained.     

On the simulation of molded micro components and systems

Regarding micro components and systems, experimental work for characterizing materials’ properties as well as components’ and systems’ behaviors have to be supplemented by numerical analyses. These analyses should cover component and system issues. On a component level, macroscopic approaches are extended by methods allowing consideration of the influence of components’ grain structures including possible defects. On a system level, the high tolerances accepted for the individual components due to production inaccuracy and their effects on the expected load distribution capability of the system are taken into account. This paper presents approaches for simulation of micro components and systems using the finite element method and multi body simulation. Methods to overcome the abovementioned issues will be shown, as well as the effects of grain structure on the stress distribution in the individual components.     

Influence of the geometry on the pressure distribution of granular heaps

We investigate the effect of the geometry of granular heaps on the pressure distribution. For given pressure distributions under cones we compute the pressure distribution under wedges using linear superposition. For cones with a pressure minimum, the pressure minimum for the corresponding wedge vanishes. Comparisons with experimental data gives good qualitative aggreement, but the total pressure is overestimated.