Tailored least-squares solvers implementation for high-performance gravity field research

Least-squares (LS) problems occur in almost every scientific and engineering discipline. Basically, they are generated by providing more observations than unknown parameters to be resolved. Appropriate LS solvers depend on both quality and computational issues. With regard to the latter, this paper focuses on the tailored parallel implementation of two LS solvers: the iterative LSQR method (substitutional for any Krylov-space method) and the “brute-force” inversion approach. Both implementations demonstrate very good scaling results in a parallel processing environment. Even so, the present investigations show that, from the computational and hardware point of view, iterative solvers outperform the “brute-force” approach. LSQR not only provides superior speed-up values; but, in addition, source code portability and hardware requirements are much more convenient for the iterative solver. These conclusions are drawn in the context of state-of-the-art terrestrial geopotential recovery with regard to the forthcoming Gravity field and steady-state Ocean Circulation Explorer (GOCE) satellite mission.     

Considerations about the relationship between animal and machine ethics

Ethics researches morality in respect to humans and animals. Usually, it implies human morality; therefore, the focus is on human–human relationships (generally in ethics) and human–animal relationships (in animal ethics). Ethics can also deal with the morality of machines such as unmanned aerial vehicles, robots and agents or of self-driving cars and computers in automated trading, in other words more or less autonomous systems and programs. Machine ethics almost exclusively concentrates on machine–human relationships rather than on machine–animal relationships. Before this background, this article contributes some basic considerations about the relationship between animal and machine ethics.     

Large area forest stem volume mapping in the boreal zone using synergy of ERS-1/2 tandem coherence and MODIS vegetation continuous fields

ERS-1/2 tandem coherence was reported to have high potential for the mapping of boreal forest stem volume (e.g. Santoro et al., 2002, 2007a; Wagner et al., 2003; Askne & Santoro, 2005). Large-scale application of the data for forest stem volume mapping, however, is hindered by the variability of coherence with meteorological and environmental acquisition conditions. The traditional way of stem volume retrieval is based on the training of models, relating coherence to stem volume, with the aid of forest inventory data which is generally available for a few small test sites but not for large areas. In this paper a new approach is presented that allows model training using the MODIS Vegetation Continuous Fields canopy cover product (Hansen et al., 2003) without further need for ground data. A comparison of the new approach with the traditional regression-based and ground-data dependent model training is presented in this paper for a multi-seasonal ERS-1/2 tandem dataset covering several well known Central Siberian forest sites. As a test scenario for large-area application, the approach was applied to a multi-seasonal ERS-1/2 tandem dataset of 223 ERS-1 and ERS-2 image pairs covering Northeast China (~ 1.5 million km²) to map four stem volume classes (0-20, 20-50, 50-80, and > 80 m³/ha).     

Technological determinism in educational technology research: some alternative ways of thinking about the relationship between learning and technology

This paper argues that research on the educational uses of technology frequently overemphasizes the influence of technology. Research in the field is considered a form of critical perspective, and assumptions about technology are questioned. Technological determinism is introduced, and different positions on this concept are identified. These are used to discuss the ways in which work within the field might be described as technologically deterministic. Four theoretical perspectives (activity theory, communities of practice, actor–network theory, and the social construction of technology) are then briefly characterized, demonstrating that alternative positions are viable, and positioning each in relation to the earlier discussion of technological determinism. The paper concludes by arguing that research, building on such alternative conceptions of technology, is important in developing our understanding of the relationship between technology and learning, as well as identifying potential methodological implications.     

Supporting ordering and consistency in a distributed Event Heap for Ubiquitous Computing

The Stanford Event Heap has been shown to provide appropriate support for constructing interactive workspace applications. Given this success it is natural to consider the Event Heap as a platform to support other classes of Ubiquitous Computing applications. In this paper we argue that the distributed, spontaneous nature of these applications places additional demands on the Event Heap that require extensions to both the engineering and API. Suitable extensions are described and their use to support a typical Ubicomp application is discussed.

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