Analyzing Granger causality in climate data with time series classification methods

Attribution studies in climate science aim for scientifically ascertaining the influence of climatic variations on natural or anthropogenic factors. Many of those studies adopt the concept of Granger causality to infer statistical cause-effect relationships, while utilizing traditional autoregressive models. In this article, we investigate the potential of state-of-the-art time series classification techniques to enhance causal inference in climate science. We conduct a comparative experimental study of different types of algorithms on a large test suite that comprises a unique collection of datasets from the area of climate-vegetation dynamics. The results indicate that specialized time series classification methods are able to improve existing inference procedures. Substantial differences are observed among the methods that were tested

Experimental Investigations and Numerical Modelling of Lateral Variations of Hydraulics and Sediment Transport in Braided Rivers

Measurement and prediction of cross section averaged bedload transport rates in braided rivers have been long standing problem. Moreover, because bedload transport is non-linear, width averaged calculations of sediment transport will underestimate the true bedload flux where there is marked spatial and temporal variability in hydraulic parameters. However, at present very little is known about this effect or the actual lateral distribution of bedload. This thesis presents results from a series of micro-scale laboratory experiments designed to quantify the role of lateral variation of sediment transport as controls on braided river evolution. The experimental approach follows the “similarity of processes” concept and is therefore not scaled to a real world prototype. In all the five runs, the water discharge was held constant and the sediment feed rate was varied to simulate consecutive aggradation and degradation scenarios. The qualitative observations of the experiments were supplemented with sediment transport data at the flume outlet and quantitative analysis of high resolution laser profiler attached to the experimental apparatus which measured bed elevations of the experimental channels as they evolved. This allowed the construction of a time series of data on the sediment storage and channel morphology and the changing lateral hydraulic variability on the channel. Aggradation was associated with channel multiplication and an increase in braiding intensity. During degradation, channel pattern was transformed to single thread. Simple averaging of sediment transport computations over the width of the channel is found to underestimate the sediment transport rate. A clear relationship appears to exist between braiding intensity and the width of shear stress distribution shape parameter. Maxima in braiding intensity and minima in shape parameter values occur around the flume outlet. In contrast, minima in braiding intensity and maxima in shape parameter values occur at the flume entrance. The experimental data generated provides a unique opportunity to observe in detail the spatial and temporal changes in the width of shear stress shape parameter that occurred on the channels as they evolved. The digital elevation models collected from the experiments were also used to run a two-dimensional hydraulic model that helped to understand the controls of shear stress on the experimental channels. A relationship was established that relates the width of shear stress distribution shape parameter and channel morphological parameters (channel width to depth ratio and braiding intensity) and the relationship was also compared with observations of the Megech gravel bed braided river in the Northern Ethiopia. Overall, the investigation has demonstrated the potential for micro scale physical models to investigate aggradation and degradation scenarios and provide rich data concerning the lateral variability of sediment transport in braided channels. These data demonstrate the idea that increasing braiding intensity is a morphological response to high sediment load from upstream. Channel aggradation increases sediment transport by promoting lateral flow variability. This in turn feeds back to further aggradation depending on the response of the channel. This process will continue up to a point where there is no substantial variation in channel width to depth ratio. Beyond this point, there will be a reduction in sediment transport rates as a result of reduction in mean shear stress. This will in turn feed back to promote further aggradation

Technology for large space systems: A bibliography with indexes (supplement 14)

This bibliography lists 645 reports, articles and other documents introduced into the NASA scientific and technical information system between July 1, 1985 and December 31, 1985. Its purpose is to provide helpful information to the researcher, manager, and designer in technology development and mission design according to system, interactive analysis and design, structural and thermal analysis and design, structural concepts and control systems, electronics, advanced materials, assembly concepts, propulsion, and solar power satellite systems

Space station systems: A bibliography with indexes (supplement 2)

This bibliography lists 904 reports, articles and other documents introduced into the NASA scientific and technical information system between July 1, 1985 and December 31, 1985. Its purpose is to provide helpful information to the researcher, manager, and designer in technology development and mission design according to system, interactive analysis and design, structural and thermal analysis and design, structural concepts and control systems, electronics, advanced materials, assembly concepts, propulsion, and solar power satellite systems. The coverage includes documents that define major systems and subsystems, servicing and support requirements, procedures and operations, and missions for the current and future space station

Crystal Plasticity (Volume II)

With the second volume, we continue our mission to providing theoretical and experimental research that contribute new insights and practical findings in the field of crystal plasticity-related topics. Once again, a completely new set of 26 original works (including 22 research articles, 3 communications, and 1 review) has been collected. As in the case of the first volume, here, a full spectrum of topics belonging to the field of crystal plasticity is represented, including both numerical simulations and experimental works. By taking into account the investigated materials, the papers can be assigned to the following thematic groups: Steels and iron-based alloys; Non-ferrous alloys with fcc- (Ni- and Cu-based), or hcp crystal structure (Mg- and Ti-based). Other examples include Zirconium, Bi-Sn alloy, or polycarbonate resins; Multicomponent and high-entropy alloys; General theoretical studies on crystal plasticity. Specifically, the reprint should be interesting for students of material science and engineering, Ph.D. candidates, and researchers dealing with various theoretical and practical aspects of plastic deformation in crystalline materials