Institution
Chalmers University of Technology
Education•Gothenburg, Sweden•
About: Chalmers University of Technology is a education organization based out in Gothenburg, Sweden. It is known for research contribution in the topics: Catalysis & Finite element method. The organization has 17191 authors who have published 53951 publications receiving 1520592 citations. The organization is also known as: Chalmers Tekniska Högskola & Chalmers.
Papers published on a yearly basis
Papers
More filters
••
TL;DR: In this article, high-angular-resolution observations indicate at what distances from the stars dust condensation occurs, and they give information on the chemical composition and sizes of dust grains in the close vicinity of cool giants.
Abstract: As low- and intermediate-mass stars reach the asymptotic giant branch (AGB), they have developed into intriguing and complex objects that are major players in the cosmic gas/dust cycle. At this stage, their appearance and evolution are strongly affected by a range of dynamical processes. Large-scale convective flows bring newly-formed chemical elements to the stellar surface and, together with pulsations, they trigger shock waves in the extended stellar atmosphere. There, massive outflows of gas and dust have their origin, which enrich the interstellar medium and, eventually, lead to a transformation of the cool luminous giants into white dwarfs. Dust grains forming in the upper atmospheric layers play a critical role in the wind acceleration process, by scattering and absorbing stellar photons and transferring their outward-directed momentum to the surrounding gas through collisions. Recent progress in high-angular-resolution instrumentation, from the visual to the radio regime, is leading to valuable new insights into the complex dynamical atmospheres of AGB stars and their wind-forming regions. Observations are revealing asymmetries and inhomogeneities in the photospheric and dust-forming layers which vary on time-scales of months, as well as more long-lived large-scale structures in the circumstellar envelopes. High-angular-resolution observations indicate at what distances from the stars dust condensation occurs, and they give information on the chemical composition and sizes of dust grains in the close vicinity of cool giants. These are essential constraints for building realistic models of wind acceleration and developing a predictive theory of mass loss for AGB stars, which is a crucial ingredient of stellar and galactic chemical evolution models. At present, it is still not fully possible to model all these phenomena from first principles, and to predict the mass-loss rate based on fundamental stellar parameters only. However, much progress has been made in recent years, which is described in this review. We complement this by discussing how observations of emission from circumstellar molecules and dust can be used to estimate the characteristics of the mass loss along the AGB, and in different environments. We also briefly touch upon the issue of binarity.
344 citations
••
TL;DR: In this article, the authors explored the occurrence of network effects in the construction industry and concluded that these characteristics are having a hampering effect on both efficiency and innovation in the industry today.
343 citations
••
TL;DR: A new class of algorithms which is based on rational functions of the matrix is described, and there are also new algorithms which correspond to rational functions with several poles.
343 citations
••
Leiden University1, Cardiff University2, European Space Research and Technology Centre3, Kapteyn Astronomical Institute4, Max Planck Society5, California Institute of Technology6, United States Naval Research Laboratory7, University of Maryland, College Park8, University College London9, Harvard University10, University of Alcalá11, University of Lethbridge12, Chalmers University of Technology13, University of Crete14, National Radio Astronomy Observatory15, University of Virginia16, Chinese Academy of Sciences17, University of Copenhagen18, Spanish National Research Council19, University of Hawaii20, Cornell University21
TL;DR: In this article, a full high-resolution SPIRE FTS spectrum of the nearby ultraluminous infrared galaxy Mrk 231 is presented, including 25 lines, including CO J = 5-4 through J = 13-12, 7 rotational lines of H2O, 3 of OH+ and one line each of H 2O+, CH+, and HF.
Abstract: We present a full high resolution SPIRE FTS spectrum of the nearby ultraluminous infrared galaxy Mrk 231. In total 25 lines are detected, including CO J = 5-4 through J = 13-12, 7 rotational lines of H2O, 3 of OH+ and one line each of H2O+, CH+, and HF. We find that the excitation of the CO rotational levels up to J = 8 can be accounted for by UV radiation from star formation. However, the approximately flat luminosity distribution of the CO lines over the rotational ladder above J = 8 requires the presence of a separate source of excitation for the highest CO lines. We explore X-ray heating by the accreting supermassive black hole in Mrk 231 as a source of excitation for these lines, and find that it can reproduce the observed luminosities. We also consider a model with dense gas in a strong UV radiation field to produce the highest CO lines, but find that this model strongly overpredicts the hot dust mass in Mrk 231. Our favoured model consists of a star forming disk of radius 560 pc, containing clumps of dense gas exposed to strong UV radiation, dominating the emission of CO lines up to J = 8. X-rays from the accreting supermassive black hole in Mrk 231 dominate the excitation and chemistry of the inner disk out to a radius of 160 pc, consistent with the X-ray power of the AGN in Mrk 231. The extraordinary luminosity of the OH+ and H2O+ lines reveals the signature of X-ray driven excitation and chemistry in this region.
343 citations
••
03 Jul 2000TL;DR: A probability-sensitive confidentiality specification-a form of probabilistic noninterference-for a small multi-threaded programming language with dynamic thread creation and shows how the security condition satisfies compositionality properties which facilitate straightforward proofs of correctness for, e.g., security type systems.
Abstract: We present a probability-sensitive confidentiality specification-a form of probabilistic noninterference-for a small multi-threaded programming language with dynamic thread creation. Probabilistic covert channels arise from a scheduler which is probabilistic. Since scheduling policy is typically outside the language specification for multi-threaded languages, we describe how to generalise the security condition in order to define how to generalise the security condition in order to define robust security with respect to a wide class of schedulers, not excluding the possibility of deterministic (e.g., round-robin) schedulers and program-controlled thread priorities. The formulation is based on an adaptation of Larsen and Skou's (1991) notion of probabilistic bisimulation. We show how the security condition satisfies compositionality properties which facilitate straightforward proofs of correctness for, e.g., security type systems. We illustrate this by defining a security type system which improves on previous multi-threaded systems, and by proving it correct with respect to our stronger scheduler-independent security condition.
342 citations
Authors
Showing all 17401 results
Name | H-index | Papers | Citations |
---|---|---|---|
Jens Nielsen | 149 | 1752 | 104005 |
Frede Blaabjerg | 147 | 2161 | 112017 |
Galen D. Stucky | 144 | 958 | 101796 |
Naomi J. Halas | 140 | 435 | 82040 |
Peter Nordlander | 130 | 482 | 67703 |
Yuri S. Kivshar | 126 | 1845 | 79415 |
Henrik Zetterberg | 125 | 1736 | 72452 |
Christoph J. Brabec | 120 | 896 | 68188 |
Mathias Uhlén | 117 | 861 | 68387 |
Anders Ekbom | 116 | 613 | 51430 |
Flemming Besenbacher | 114 | 728 | 51827 |
Olle Inganäs | 113 | 627 | 50562 |
Philip Hugenholtz | 109 | 452 | 75841 |
Licheng Sun | 106 | 747 | 49992 |
Ralf P. Richter | 105 | 661 | 45214 |