230 research outputs found
Spectrometric study of condensed phase species of thorium and palladium-based modifiers in a complex matrix for electrothermal atomic absorption spectrometry
No full textThe chemical and morphological transformations of condensed phase species of a thorium-based modifier were studied over the temperature range 200–2500 °C, without and with the presence of aluminium and silicon as matrix components, and in some instances, arsenic as an analyte element. A similar study was also conducted with palladium as the modifier, for comparison. Results were derived using scanning electron microscopy (SEM), energy dispersive (ED) X-ray spectrometry, Raman microanalysis and attenuated total reflectance (ATR) Fourier transform-infrared (FT-IR) spectrometry. Comparable results were found using pyrolytic and non-pyrolytic graphite platforms, with processes occurring at slightly higher temperatures on the pyrolytic graphite platform. With thorium as the modifier, metal oxides were the predominant species on the platform surface at relatively low temperatures (<1500 °C), whereas metal phases became prevalent at high temperatures, when thorium and aluminium tended to behave independently from one other. Some spatial variations in the composition of the salt residues on different regions of the platform were observed (from the region closest to the slot in the tube, to the region furthest from the slot). Nonetheless, thorium metal remained on the graphite platform to higher temperatures than did aluminium metal. In the presence of arsenic, the existence of mixtures of thorium and arsenic oxides, just before the appearance temperature of gas phase arsenic atoms, was confirmed by SEM studies, ED X-ray spectra and Raman microanalysis. This suggests that any modifying effect of thorium on arsenic occurs while the modifier is in the oxide phase rather than in the metal phase. The presence of silicon added as silica, did not influence significantly the thermochemical behaviour of mixtures of thorium and aluminium. However, coexistence of silicon and arsenic oxides at the appearance temperature of the atomic absorption signal of arsenic was obtained, confirming that silicon can act as an internal modifier for arsenic. In the presence of palladium, aluminium exhibited greater interaction with the modifier; consequently, aluminium metal was retained on the platform surface to higher temperatures than thorium, which could explain how interference effects of aluminium on e.g. arsenic are avoided or reduced. Similarly, there was evidence for interaction of palladium and arsenic in the reduced state. However, when aluminium and silicon were present, the transformation of the palladium oxide to the metallic state was affected, which could diminish the modifying benefits of palladium for arsenic in the presence of aluminium
Regime complex and energy cooperation in Southeast Asia
No full textDue to the importance of energy to economic growth, ASEAN member states (AMS) have devoted to energy development and regional energy cooperation in recent decades but received limited progress. This thesis is interested in investigating this phenomenon. Upon reflecting on the ASEAN way of cooperation and the trajectory of energy cooperation development, it argues that a patchwork of energy regimes exists and even governs the regional energy cooperation alongside with the ASEAN-led institution. By borrowing the existing wisdom of regime complex, this thesis develops a dynamic holistic framework for complex regime analysis and employs it to examine the current energy cooperation in Southeast Asia (SEA). The author finds that an energy regime complex does exist for SEA energy cooperation as a consequence of fulfilling the multiple interests of AMS. While the regime complex exerts both positive and adverse impact on cooperation, the latter could be overcome by adjusting the regime complex structure so as to facilitate the regional energy cooperation.Master of Science (International Political Economy
Guidelines on how to quantify extremes in models using EVT (Milestone MS4)
No full textBlue-Action project
Milestone: MS4
Work package in charge: WP1 Improving seasonal long range forecast skill of risks for hazardous
weather and climate events
Actual achievement date of this milestone: Project‐month 18
Partner organisation in charge of the milestone and lead author:
The University of Reading (UREAD): Tamas Bodai
Other contributing authors:
Danish Meteorological Institute (DMI): Torben Schmith, Shuting Yang
Milestone Type: Report
Dissemination level: Public
Means of verification of attainment of the milestone: Analysis routines uploaded to data
Achieved: Yes
Abstract: The objective of this part of the project is to establish the statistical framework of predicting extremes
by a seasonal forecast system. This report summarises some preliminary results. Nonstationary extreme
value statistics of cold temperatures in Kiev has been evaluated, with some index of the NAO as a covariate
responsible for nonstationary conditions. We found that while mean DJF temperatures depend
more on negative values of an NAO index, some extremal features depend more on its positive values.
Furthermore, the lowest temperatures occur for intermediate values of the NAO index.The Blue-Action project has received funding from the European Union's Horizon 2020 Research and Innovation Programme under Grant Agreement No 727852 www.blue-action.e
Computational Methods for Transition States and Pathways in Rare Events
No full textBased on the calculation of transition states and the identification of transition paths, this book aims to provide a comprehensive guide to understanding and simulating rare events.
The author introduces both fundamental concepts of transition states and pathways and advanced computational techniques, focusing on Gentlest Ascent Dynamics (GAD) and its variants. In particular, she explores enhanced numerical methods such as the convex splitting method and the Scalar Auxiliary Variable (SAV) approach within the Iterative Minimization Formulation (IMF). In addition, the book applies these methods to real-world problems, highlighting the string method and the geometric Minimum Action Method (gMAM) for computing transition paths.
The book is written for researchers and practitioners in fields such as applied mathematics, physics, chemistry, and computational science who are interested in the underlying mechanisms of rare events and their transition processes.
Chapters 3 and 4 of this book are each freely available as a downloadable Open Access PDF at http://www.taylorfrancis.com under a Creative Commons Attribution-Non Commercial-No Derivatives (CC-BY-NC-ND) 4.0 license
Chapter 3 Variants of Gentlest Ascent Dynamics for Transition States
No full textBased on the calculation of transition states and the identification of transition paths, this book aims to provide a comprehensive guide to understanding and simulating rare events. The author introduces both fundamental concepts of transition states and pathways and advanced computational techniques, focusing on Gentlest Ascent Dynamics (GAD) and its variants. In particular, she explores enhanced numerical methods such as the convex splitting method and the Scalar Auxiliary Variable (SAV) approach within the Iterative Minimization Formulation (IMF). In addition, the book applies these methods to real-world problems, highlighting the string method and the geometric Minimum Action Method (gMAM) for computing transition paths. The book is written for researchers and practitioners in fields such as applied mathematics, physics, chemistry, and computational science who are interested in the underlying mechanisms of rare events and their transition processes. Chapters 3 and 4 of this book are each freely available as a downloadable Open Access PDF at http://www.taylorfrancis.com under a Creative Commons Attribution-Non Commercial-No Derivatives (CC-BY-NC-ND) 4.0 license
Chapter 4 Enhanced Numerical Schemes in IMF for Transition States
No full textBased on the calculation of transition states and the identification of transition paths, this book aims to provide a comprehensive guide to understanding and simulating rare events. The author introduces both fundamental concepts of transition states and pathways and advanced computational techniques, focusing on Gentlest Ascent Dynamics (GAD) and its variants. In particular, she explores enhanced numerical methods such as the convex splitting method and the Scalar Auxiliary Variable (SAV) approach within the Iterative Minimization Formulation (IMF). In addition, the book applies these methods to real-world problems, highlighting the string method and the geometric Minimum Action Method (gMAM) for computing transition paths. The book is written for researchers and practitioners in fields such as applied mathematics, physics, chemistry, and computational science who are interested in the underlying mechanisms of rare events and their transition processes. Chapters 3 and 4 of this book are each freely available as a downloadable Open Access PDF at http://www.taylorfrancis.com under a Creative Commons Attribution-Non Commercial-No Derivatives (CC-BY-NC-ND) 4.0 license
Enhancing clustering blog documents by utilizing author/reader comments
No full textBlogs are a new form of internet phenomenon and a vast ever-increasing information resource. Mining blog files for information is a very new research direction in data mining. Blog files are different from standard web files and may need specialized mining strategies. We propose to include the title, body, and comments of the blog pages in clustering datasets from blog documents. In particular, we argue that the author/reader comments of the blog pages may have more discriminating effect in clustering blog documents. We constructed a word-page matrix by downloading blog pages from a well-known website and experimented a k-means clustering algorithm with different weights assigned to the title, body, and comment parts. Our experimental results show that assigning a larger weight value to the blog comments helps the k-means algorithm produce better clustering solutions. The experimental results confirm our hypothesis that the author/reader comments of the blog files are very useful in discriminating blog files
Computational Methods for Transition States and Pathways in Rare Events
No full textBased on the calculation of transition states and the identification of transition paths, this book aims to provide a comprehensive guide to understanding and simulating rare events.
The author introduces both fundamental concepts of transition states and pathways and advanced computational techniques, focusing on Gentlest Ascent Dynamics (GAD) and its variants. In particular, she explores enhanced numerical methods such as the convex splitting method and the Scalar Auxiliary Variable (SAV) approach within the Iterative Minimization Formulation (IMF). In addition, the book applies these methods to real-world problems, highlighting the string method and the geometric Minimum Action Method (gMAM) for computing transition paths.
The book is written for researchers and practitioners in fields such as applied mathematics, physics, chemistry, and computational science who are interested in the underlying mechanisms of rare events and their transition processes.
Chapters 3 and 4 of this book are each freely available as a downloadable Open Access PDF at http://www.taylorfrancis.com under a Creative Commons Attribution-Non Commercial-No Derivatives (CC-BY-NC-ND) 4.0 license
Diminished choice effect on anticipating improbable rewards
No full text
Previous research found that the neural substrates underlying perceived control highly overlap those of reward system, especially during reward anticipation stage. The current event-related potential study examined whether the experience of choice by which individuals exercise control is modulated by reward probability during reward anticipation stage as indexed by the stimulus-preceding negativity (SPN). Thirty participants performed a cued gambling task during which choices could be made either by themselves (a choice condition) or by a computer (a no-choice condition) with three levels of reward probability (low, medium, and high) while their EEG was recording. As expected, the participants perceived higher control during the choice compared to no-choice condition. Correspondingly, the SPN was enhanced in the choice condition than the no-choice condition. Critically, the SPN choice effect was present when reward probability was high and medium, but was diminished when reward probability was low. These findings suggest that the perceived control as exercised by choice is associated with reward anticipation, which may be sensitive to the fundamental properties of reward.</p
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