Approximation Error and Error Accumulation for the Landen Transform

In this note we derive explicit a priori error bounds for the approximation error and error accumulation of the descending Landen transform. Our results apply to incomplete elliptic integral of the first kind and give the framework to calculate error bounds in the representation of Jacobi's Zeta- and Theta-function.     

Comparison of littoral and deep water sampling methods for assessing macroinvertebrate assemblages along the longitudinal profile of a very large river (the Danube River,Europe)

We comparatively examined the role of littoral and deep water sampling methods in assessing macroinvertebrate assemblages and in characterizing longitudinal changes in assemblage structure along >2,500‐km–long course of the Danube River, Europe. The effectiveness of detecting taxa corresponded well with an inshore–offshore gradient in sampling (i.e., distance from shore). Nevertheless, each method (i.e., littoral multihabitat sampling, kick and sweep sampling, and deep water dredging) contributed to some degree to overall taxa richness and species composition. Sampling in different depth zones characterized different assemblages, and consequently, inshore–offshore position was at least as important determinant of assemblage structure as longitudinal position of sampling sites in the river. Although we found significant congruency in the spatial variability of assemblages among the sampling methods, the relationships were only moderate. Our study on the large Danube River confirms studies from smaller rivers in other geographic regions that littoral monitoring provides higher taxa richness and more responsive changes to longitudinal gradients than deep water samples. Nevertheless, it also shows that sampling in different depth zones provides supplementary information on assemblage structure. Understanding changes in macroinvertebrate assemblages related to differences in sampling method is crucial to improve the bioassessment and environmental management of large rivers.     

Monte Carlo planning for active object classification

Classifying objects in complex unknown environments is a challenging problem in robotics and is fundamental in many applications. Modern sensors and sophisticated perception algorithms extract rich 3D textured information, but are limited to the data that are collected from a given location or path. We are interested in closing the loop around perception and planning, in particular to plan paths for better perceptual data, and focus on the problem of planning scanning sequences to improve object classification from range data. We formulate a novel time-constrained active classification problem and propose solution algorithms that employ a variation of Monte Carlo tree search to plan non-myopically. Our algorithms use a particle filter combined with Gaussian process regression to estimate joint distributions of object class and pose. This estimator is used in planning to generate a probabilistic belief about the state of objects in a scene, and also to generate beliefs for predicted sensor observations from future viewpoints. These predictions consider occlusions arising from predicted object positions and shapes. We evaluate our algorithms in simulation, in comparison to passive and greedy strategies. We also describe similar experiments where the algorithms are implemented online, using a mobile ground robot in a farm environment. Results indicate that our non-myopic approach outperforms both passive and myopic strategies, and clearly show the benefit of active perception for outdoor object classification.     

Investigation of earth-alkaline (EA = Mg,Ca, Sr) containing methylammonium tin iodide perovskite systems

Methylammonium tin iodide systems containing earth-alkaline ions (CH₃NH₃Sn_1?x (EA) _x I₃, EA = Ca²⁺, Sr²⁺, Mg²⁺, 0 ≤ x ≤ 0.30) were investigated. The X-ray diffraction patterns detected the formation of tetragonal nearly cubic CH₃NH₃SnI₃ (space group P4mm), SnI₂, and not identified phases. The morphological analysis confirmed the presence of secondary phases with formation of irregularly shaped crystallites. The Sn3d and I3d photoemission spectra revealed the typical position and separation of spin–orbit components for Sn²⁺ in halides. Static thermogravimetric measurements (T = 85 °C) showed a barely measurable weight loss for EA = Mg, a dramatic decrease of the weight loss rate for EA = Ca, and recorded weight losses till t ≈ 1.5 h only for EA = Sr, respectively. The optical spectra displayed absorption edges which increased at increasing the (EA)-content with maximum values for x = 0.050 (λ _on-set = 1754 nm, EA = Mg; λ _on-set = 1692 nm, EA = Ca; and λ _on-set = 1338 nm, EA = Sr, respectively). The Tauc plots revealed a direct semiconducting behavior with band energy gaps depending on the nature and amount of the (EA)-ions. The photoluminescence (PL) spectra showed, for EA = Mg, an increase of the PL-band intensity at increasing the Mg content with a maximum at x = 1.0 and, for EA = Ca, an increase of band intensity at increasing the Ca-content and for EA = Sr, a band intensity maximum at x = 0.025. This was explained by the similar ionic radius between Sn²⁺ and Sr²⁺ ions which can be easily exchanged in the SnI₆ ^2? octahedra.     

Tunable Volatility of Ge2Sb2Te5 in Integrated Photonics

The operation of a single class of optical materials in both a volatile and nonvolatile manner is becoming increasingly important in many applications. This is particularly true in the newly emerging field of photonic neuromorphic computing, where it is desirable to have both volatile (short‐term transient) and nonvolatile (long‐term static) memory operation, for instance, to mimic the behavior of biological neurons and synapses. The search for such materials thus far have focused on phase change materials where typically two different types are required for the two different operational regimes. In this paper, a tunable volatile/nonvolatile response is demonstrated in a photonic phase‐change memory cell based on the commonly employed nonvolatile material Ge₂Sb₂Te₅ (GST). A time‐dependent, multiphysics simulation framework is developed to corroborate the experimental results, allowing us to spatially resolve the recrystallization dynamics within the memory cell. It is then demonstrated that this unique approach to photonic memory enables both data storage with tunable volatility and detection of coincident events between two pulse trains on an integrated chip. Finally, improved efficiency and all‐optical routing with controlled volatility are demonstrated in a ring resonator. These crucial results show that volatility is intrinsically tunable in normally nonvolatile GST which can be used in both regimes interchangeably.     

Flow amplitude or up-ramping rate? Quantifying single and combined effects on macroinvertebrate drift during hydropeaking simulations,considering sensitive traits

The hydrological regime of many alpine rivers is heavily altered due hydroelectric power generation. Hydropeaking operation produces frequent and irregular discharge fluctuations. Depending on the operational changes of flow amplitude and/or up-ramping rate as well as on river morphology, hydropeaking can lead to quick and strong variations in hydraulic stress affecting stream invertebrates and causing increased drift. In the present flume experimental study, we analyzed trait-specific drift reactions to single and combined effects of increased flow amplitude and up-ramping rate. We analyzed taxa according to their hydraulic habitat preference and flow exposure, as these traits seem to be indicative toward hydropeaking. The results show that the sudden increase in discharge and related flow velocity led to increased macroinvertebrate drift proportions in hydropeaking treatments, which differed significantly to parallel control runs (mean drift proportion in all hydropeaking setups: 13% compared to 5% in controls). Increasing flow amplitudes led to an increase in drift for most taxa and traits. This was particularly significant for taxa associated with lentic areas. The effect of the up-ramping rate on macroinvertebrate drift was nonsignificant but showed strong interactive effects with the flow amplitude, especially for taxa dwelling on the substrate surface. Our results therefore indicate that discharge-related parameters, such as flow velocity, primarily affect macroinvertebrate drift and the importance of the up-ramping rate increases, if certain discharge-related thresholds are exceeded. Vice versa, a reduction of the up-ramping rate at hydropeaking events with high flow amplitudes may reduce the effect on macroinvertebrate drift. Flow-exposed (surface) and flow-sensitive (lentic) taxa showed distinct drift reactions following hydropeaking treatments, which were significantly higher compared to effects on taxa associated to lotic and interstital habitats. Therefore, we conclude that both traits (hydraulic and vertical habitat preference) have proven as promising for analyzing hydropeaking effects. The trait classifications should be extended to a higher number of taxa and to different life stages as these may show different drift patterns.     

Unification in datastructure multisets

In a recent paper A. Herold and J. Siekmann generalize pure AC unification to terms containing additional function symbols. Generalized AC unification thus attains practical relevance for a broad range of applications. Pure AC unification is used as a basic mechanism and it is this key role that has motivated our research. We have improved upon earlier approaches by basing (pure) AC unification on a firm theoretical basis and presenting algorithms which fully exploit the properties of the underlying mathematical structure. In particular, the high degree of parallelism for AC unification will become apparent. Our algorithms have been designed for parallel hardware but still yield significant improvements over earlier algorithms when used in the sequential mode.     

SOME OBSERVATIONS ON THE AGING OF ENAMELS1

The tendency toward more rapid production of enameled ware has reduced to minimum the time allowed in most plants for aging of enamels. Aging of the enamel slip allows the clay to become thoroughly slaked, adsorb the larger enamel particles, and thus prepare it for its cohesion to the metal base. Aging or soaking of the clay before use is an excellent substitute for part of the time consumed in aging the enamel slip. Observations of results obtained in commercial application of enamels has lead to the following conclusions: (1) Enamels should be aged before use in order to gain the full benefit of the adsorption properties of the clay and enamel colloids. (2) If the proper time of aging of enamels cannot be allowed, at least the clay should be brought to fine state of subdivision by aging or soaking in water. (3) If aging is not allowed in some form, the enamel usually is not as easily applied with the ordinary handling encountered in average production. (4) If aging of the clay is allowed there is quicker turn over of the stock enamel in the mill room.     

A New Method for the Study of Adhesion: Application of Inelastic Electron Tunneling Spectroscopy

Inelastic electron tunneling spectroscopy provides an incredibly sensitive and versatile method of detecting and identifying molecular species adsorbed on the surface of a metal oxide. IETS spectra have been measured on the components of the commercial adhesive, Hercules 3501. This epoxy system consists of two molecular components; diamino diphenyl sulfone (DPS) and tetraglycidycl 4,4' diamino diphenyl methane (DPM). IETS spectra of the individual components and of the epoxy mixture adsorbed on aluminum oxide have been obtained and the vibrational modes and frequencies assigned by comparison with computer calculations and existing infrared optical spectra.

IETS is a useful tool for the study of molecular adhesion to an oxide. It is one of the most important methods available for determining the interface physics and chemistry of adhesive bondlines. Its usefulness is greatly enhanced by the fact that in situ studies can be made.

Spectra have been obtained on the components and mixture of the high performance, two component epoxy Hercules 3501. The vibrational modes were identified by comparison with infrared and Raman data, and with computer calculations using force constant information. Evidence for an aging effect was found in the DPS component.

It is suggested that initial studies using IETS should be applied to adhesives of simple molecular structure before proceeding to more complex systems.