55 research outputs found
Wind power prediction risk indices based on numerical weather prediction ensembles
No full textInternational audienceThe large-scale integration of wind generation imposes several difficulties in the management of power systems. Wind power forecasting up to a few days ahead contributes to a secure and economic power system operation. Prediction models of today are mainly focused on spot or probabilistic predictions of wind power. However, in many applications, endusers require additional tools for the on-line estimation of the uncertainty of the predictions. One solution to this is prediction risk indices, computed on wind power forecast ensembles derived from numerical weather prediction ensembles. This paper investigates the usefulness of such risk indices as a complement to usual wind power forecasts for informing on the expected level of uncertainty and the risk for large forecast errors. Results show that risk indices are useful to extract information from power ensembles and can give valuable information about the expected prediction uncertainty
Competition and substitution between public transport modes
Get PDFThe management and understanding of modal split between public transport (PT) modes is of interest for numerous reasons. It may, for example, be desirable to stimulate passengers to switch from crowded buses and over to higher capacity rail. This requires a good understanding of drivers of transit modal substitution.
The evidence put forward in this paper is based on more than 150 empirically estimated cross elasticities between PT modes from over 20 sources collected from Australia, Europe and USA. These sources include scientifically published evidence as well as grey literature.
This evidence is coded into a database from which our paper presents and analyses the available cross-PT-modal demand relations. We focus on evidence for how fares, travel time and service intervals on PT ‘mode A’ affect the demand for PT ‘mode B’.
Despite generally low levels of substitution between PT modes, passengers are particularly sensitive to in-vehicle, access/egress and waiting time in choosing PT mode and less so for fare variations. In general, rail demand is less sensitive to changes in bus than bus demand is to changes in rail. We also find that peak-hour demand more markedly switches between PT modes than off-peak demand does
Consistent patterns of common species across tropical tree communities
Get PDFTrees structure the Earth’s most biodiverse ecosystem, tropical forests. The vast number of tree species presents a formidable challenge to understanding these forests, including their response to environmental change, as very little is known about most tropical tree species. A focus on the common species may circumvent this challenge. Here we investigate abundance patterns of common tree species using inventory data on 1,003,805 trees with trunk diameters of at least 10 cm across 1,568 locations1,2,3,4,5,6 in closed-canopy, structurally intact old-growth tropical forests in Africa, Amazonia and Southeast Asia. We estimate that 2.2%, 2.2% and 2.3% of species comprise 50% of the tropical trees in these regions, respectively. Extrapolating across all closed-canopy tropical forests, we estimate that just 1,053 species comprise half of Earth’s 800 billion tropical trees with trunk diameters of at least 10 cm. Despite differing biogeographic, climatic and anthropogenic histories7, we find notably consistent patterns of common species and species abundance distributions across the continents. This suggests that fundamental mechanisms of tree community assembly may apply to all tropical forests. Resampling analyses show that the most common species are likely to belong to a manageable list of known species, enabling targeted efforts to understand their ecology. Although they do not detract from the importance of rare species, our results open new opportunities to understand the world’s most diverse forests, including modelling their response to environmental change, by focusing on the common species that constitute the majority of their trees.Publisher PDFPeer reviewe
Wissenschaftliche Ergebnisse einer Forschungsreise nach Ostindien, ausgef\ufchrt im Auftrage der Kgl. Preu f. Akademie der Wissenschaften zu Berlin von H. v. Buttel-Reepen. III. Termiten aus Sumatra, Java, Malacca und Ceylon gesammelt von Herrn Prof. Dr. v. Buttel-Reepen in den Jahren 1911—1912
No full textVolume: 36Start Page: 229End Page: 29
Quality Assurance in Agile Teams : How is customer value balanced against increased risk of unstable software?
No full textAgile software development aims to minimize risk by using a short and iterative process, a test-centric development approach by continuous integration, and test automation. Scrum aims to maximize collaboration and collective responsibility for quality by using a team approach. Regardless of this, the risk of project failure due to budget and time overruns is still a severe problem in software development projects. Despite the power that testing offers to mitigate these risks, testing remains a challenge to implement in agile teams regarding a test first or a test early context. This qualitative case study of two agile teams with differing approaches to agile methodology aims to provide some clarity on what driving forces contribute to an agile teams’ possibilities or what impediments contribute to an agile teams’ challenges pertaining to “why do we test software”
Quality Assurance in Agile Teams : How is customer value balanced against increased risk of unstable software?
No full textAgile software development aims to minimize risk by using a short and iterative process, a test-centric development approach by continuous integration, and test automation. Scrum aims to maximize collaboration and collective responsibility for quality by using a team approach. Regardless of this, the risk of project failure due to budget and time overruns is still a severe problem in software development projects. Despite the power that testing offers to mitigate these risks, testing remains a challenge to implement in agile teams regarding a test first or a test early context. This qualitative case study of two agile teams with differing approaches to agile methodology aims to provide some clarity on what driving forces contribute to an agile teams’ possibilities or what impediments contribute to an agile teams’ challenges pertaining to “why do we test software”
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