16,328 research outputs found
AFM study of the oxide film formed on dual phase Fe3Al-Fe3AlC intermetallies
No full textThe topography of the oxide film formed during initial stage of oxidation at 800 degreesC on the Fe3Al and Fe3AlC phases in an Fe- 16Al-0.5C alloy was analyzed using atomic force microscopy. The oxide film formed on the carbide phase was found to be thicker than that on the matrix, and the difference in thickness between two layers was around 0.5 mum. This was related to the presence of low Al content in the Fe3AlC phase compared with that in the Fe3Al phase. Due to different rate of oxidation in Fe3Al and Fe3AlC phases, the Fe- 16Al-0.5C alloy does not follow the parabolic rate behaviour. (C) 2004 Elsevier Ltd. All rights reserved.The author VSR thanks Prof. V.S. Raja of corrosion
science and engineering program, Indian Institute of
Technology, Bombay and Dr R.G. Baligidad of Defense
Metallurgical Research Laboratory, Hyderabad, India for
providing the material
Normal forms for pseudo-Riemannian 2-dimensional metrics whose geodesic flows admit integrals quadratic in momenta
No full textWe discuss pseudo-Riemannian metrics on 2-dimensional manifolds such that the geodesic flow admits a nontrivial integral quadratic in velocities. We construct local normal forms of such metrics. We show that these metrics have certain useful properties similar to those of Riemannian Liouville metrics, namely: they admit geodesically equivalent metrics; one can use them to construct a large family of natural systems admitting integrals quadratic in momenta; the integrability of such systems can be generalized to the quantum setting; these natural systems are integrable by quadratures. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved
A solution of a problem of Sophus Lie: Normal forms of two-dimensional metrics admitting two projective vector fields
No full textWe give a complete list of normal forms for the two-dimensional metrics that admit a transitive Lie pseudogroup of geodesic-preserving transformations and we show that these normal forms are mutually non-isometric. This solves a problem posed by Sophus Lie. © 2007 Springer-Verlag
Open access self-archiving: An author study
No full textThis, our second author international, cross-disciplinary study on open access had 1296 respondents. Its focus was on self-archiving. Almost half (49%) of the respondent population have self-archived at least one article during the last three years. Use of institutional repositories for this purpose has doubled and usage has increased by almost 60% for subject-based repositories. Self-archiving activity is greatest amongst those who publish the largest number of papers. There is still a substantial proportion of authors unaware of the possibility of providing open access to their work by self-archiving. Of the authors who have not yet self-archived any articles, 71% remain unaware of the option. With 49% of the author population having self-archived in some way, this means that 36% of the total author population (71% of the remaining 51%), has not yet been appraised of this way of providing open access. Authors have frequently expressed reluctance to self-archive because of the perceived time required and possible technical difficulties in carrying out this activity, yet findings here show that only 20% of authors found some degree of difficulty with the first act of depositing an article in a repository, and that this dropped to 9% for subsequent deposits. Another author worry is about infringing agreed copyright agreements with publishers, yet only 10% of authors currently know of the SHERPA/RoMEO list of publisher permissions policies with respect to self-archiving, where clear guidance as to what a publisher permits is provided. Where it is not known if permission is required, however, authors are not seeking it and are self-archiving without it. Communicating their results to peers remains the primary reason for scholars publishing their work; in other words,
researchers publish to have an impact on their field. The vast majority of authors (81%) would willingly comply with a mandate from their employer or research funder to deposit copies of their articles in an institutional or subject-based repository. A further 13% would comply reluctantly; 5% would not comply with such a mandate
Average per-author h-index vs Average REF Impact Score.
No full textAverage per-author h-index vs Average REF Impact Score.</p
Opinion Dynamics in Social Networks with Hostile Camps: Consensus vs. Polarization
No full textMost of the distributed protocols for multi-agent consensus assume that the agents are mutually cooperative and “trustful”, and so the couplings among the agents bring the values of their states closer. Opinion dynamics in social groups, however, require beyond these conventional models due to ubiquitous competition and distrust between some pairs of agents, which are usually characterized by repulsive couplings and may lead to clustering of the opinions. A simple yet insightful model of opinion dynamics with both attractive and repulsive couplings was proposed recently by C. Altafini, who examined first-order consensus algorithms over static signed graphs. This protocol establishes modulus consensus, where the opinions become the same in modulus but may differ in signs. In this paper, we extend the modulus consensus model to the case where the network topology is an arbitrary time-varying signed graph and prove reaching modulus consensus under mild sufficient conditions of uniform connectivity of the graph. For cut-balanced graphs, not only sufficient, but also necessary conditions for modulus consensus are given
Proportion of junior vs. senior authors positioned first in the author byline of POA publications.
No full textProportion of junior vs. senior authors positioned first in the author byline of POA publications.</p
Compressible vs. incompressible pore water in fully-saturated poroelastic soil
No full textThis thesis aims to contribute to the understanding of how waves interact with soil. It is crucial for various applications in Civil Engineering to analyze the behaviour of soil and to understand the physics behind it. This master thesis contributes to this understanding via studying the impact of the boundary conditions on the model results with the aim of being able to model interaction between waves and soil.We assume a media that is poroelastic and fully-saturated, unless stated otherwise. We also assume that the porous media consists of incompressible soil particles and pore water particles that may either be compressible or incompressible. The main goals of this thesis are (1) to describe the response of porous media to transient hydraulic loads using numerical methods like the Finite-Element Method, and (2) to apply it to a one-dimensional case whereby a sandbed is subjected to waves. Currently, it is common to predict the changes in pore water pressures in porous media subjected to transient hydraulic loads using Biot’s model, which often assumes compressible pore water, assumes zero effective stresses on the surface of the seabed, and assumes that the wave load is completely carried by the pore water pressure only. Recently, a new model is proposed by Van Damme and Den Ouden-Van der Horst suggesting that transient hydraulic loads acting on a porous medium affect both the pore water pressures and effective stresses in soils. Note that this makes sure that the momentum balance equations are satisfied throughout the computational domain and its boundaries. The boundary conditions in this case do not satisfy Terzaghi’s effective stress principle, whereas the standard has been to impose Terzaghi’s effective stress principle when solving Biot’s equations. Terzaghi’s principle states that the sum of the effective stresses and pore water pressures must equal the hydraulic loads, whereas Biot’s model is in line with this principle.The model of Biot and the new model of Van Damme and Den Ouden-Van der Horst describe the physics differently which can have a large impact on the results. For example, the assumption of compressibility can significantly impact the distribution of the effective stress in the soil and thus the results.Biot’s model is more sensitive for changing the compressibility parameter than the new model. Both models give similar solutions to the water pressure. However, they give different solutions to the other variables like the volumetric strain and displacements which appear in both models. Furthermore, the new model in one dimension is in line with the momentum balance equations and satisfies the volume balance equation. On the other hand, the standard is to solve Biot’s model by imposing Terzaghi’s principle at the boundary. For the new model we found promising results for the water pressure, when validating with the data of two experiments. At the end, which model predict the best solutions for volumetricstrain, water pressure and displacements depends on what kind of problem the model is used for and the corresponding physics. The used code can be found at https://github.com/fpmklein/Compressiblevs.-incompressible-pore-water-in-fully-saturated-poroelastic-soil.https://github.com/fpmklein/Compressible-vs.-incompressible-pore-water-in-fully-saturated-poroelastic-soil The used code for this master thesis.Applied Mathematic
EasyCompress: Automated Compression for Deep Learning Models
No full textOver the past years the size of deep learning models has been growing consistently. This growth has led to significant improvements in performance, but at the expense of increased computational resource demands. Compression techniques can be used to improve the efficiency of deep learning models by shrinking their size and computational needs, whilepreserving performance.This thesis presents EasyCompress, an automated and user-friendly tool to compress deep learning models. The tool improves on existing compression research by focusing on generalizability and practical usability, in three ways. Firstly, it aligns with specific compression objectives and performance requirements, ensuring the compression accomplishes its intended goal effectively. Secondly, it employs flexible compression techniques, so that it is applicable to a diverse set of models without requiring deep model knowledge. Finally, it automates the compression process, eliminating difficult and time-consuming implementationefforts.EasyCompress intelligently selects, tailors, and combines various compression techniques to minimize model size, latency, or number of computations while preserving performance. It employs structured pruning to reduce the number of parameters and computations, uses knowledge distillation techniques to ensure better accuracy recovery, and uses quantization to achieve additional compression.The tool’s effectiveness is evaluated across diverse model architectures and configurations. Experimental results on a range of models and datasets demonstrate its ability to reduce the model size at least 5-fold, inference time by at least 1.5-fold, and the number of computations by at least 3-fold. Most compression rates are even higher, reaching up to 10, 20, and even 100-fold reductions.The tool is available online at https://thesis.abelvansteenweghen.com.https://thesis.abelvansteenweghen.com Deployed version of the web app. https://github.com/abel-vs/thesis GitHub repository containing the thesis code. https://github.com/abel-vs/thesis-app GitHub repository containing the web app code.Computer Science | Software Technolog
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