| 1. |
- Johansson, Sven, 1981, et al.
(author)
-
A computational study of special grain boundaries in WC–Co cemented carbides
- 2015
-
In: Computational Materials Science. - : Elsevier BV. - 0927-0256. ; 98, s. 345-353
-
Journal article (peer-reviewed)abstract
- In this work, we model Sigma = 2 and Sigma = 1 {10 (1) over bar0}parallel to{10 (1) over bar0} WC/WC boundaries in WC-Co using density functional theory (DFT). In particular, the misfit structure of the Sigma = 2 twist boundary is modeled explicitly with a previously developed Peierls-Nabarro model for misfit dislocations. The grain boundary energy of the twist boundary is found to be 0.7 J/m(2), which is small in comparison with energies of general WC/WC boundaries. The misfit structure can be described as a square network of screw dislocations with Burgers vectors 1/6 . Our calculations show that Co will not segregate to the Sigma = 2 twist boundary, which contrasts with predictions for other WC/WC boundaries that typically give half a monolayer of segregated Co.
|
|
| 2. |
- Petisme, Martin, 1981, et al.
(author)
-
A computational study of interfaces in WC-Co cemented carbides
- 2015
-
In: Modelling and Simulation in Materials Science and Engineering. - : IOP Publishing. - 1361-651X .- 0965-0393. ; 23:4, s. 045001-
-
Journal article (peer-reviewed)abstract
- Interfaces in WC-Co cemented carbides have been investigated using the density functional theory (DFT). Six different model WC/WC grain boundaries are considered, together with the corresponding WC surfaces and WC/Co phase boundaries. The contribution to the grain boundary energies arising from misfit is estimated using an analytical bond order potential (ABOP) and the effect of magnetism is investigated using spinpolarized and non-spinpolarized calculations. A systematic study of adsorption of Co to WC surfaces, Co segregation to WC/WC grain boundaries and Co substitution at WC/Co phase boundaries has been carried out. Adsorption of Co to most WC surfaces is predicted, and result in a monolayer coverage of Co and sometimes a mixed Co/W or Co/W monolayer. The WC surfaces will become prewetted with Co as soon as the atoms become mobile at finite temperatures. Co substitutional segregation is predicted to all model WC/WC grain boundaries in 0.5 monolayer proportion. The segregation of Co to grain boundaries stabilizes the continuous skeleton network of hard WC grains in cemented carbides. Using the obtained interfacial energies, the wetting and the driving force for cobalt grain boundary infiltration are discussed. A dependence on the wetting efficiency on the carbon chemical potential is predicted, which could be an explanation for the better wetting observed experimentally under W-rich conditions.
|
|
| 3. |
- Johansson, Sven, 1981, et al.
(author)
-
First-principles derived complexion diagrams for phase boundaries in doped cemented carbides
- 2016
-
In: Current Opinion in Solid State and Materials Science. - : Elsevier BV. - 1359-0286. ; 20:5, s. 299-307
-
Research review (peer-reviewed)abstract
- This article reviews a method for calculating an equilibrium interfacial phase diagram depicting regions of stability for different interface structures as function of temperature and chemical potentials. Density functional theory (DFT) is used for interfacial energies, Monte Carlo simulations together with cluster expansions based on DFT results for obtaining configurational free energies, and CALPHAD-type modeling for describing the thermodynamic properties of the adjoining bulk phases. An explicit case, vanadium doped cemented carbides, is chosen to illustrate the progress in the research field and the interfacial diagram, a complexion diagram, for the phase boundary WC(0001)/Co is constructed as function of temperature and chemical potentials.
|
|
| 4. |
- Sattler, Florian, et al.
(author)
-
Lifting inter-app data-flow analysis to large app sets
- 2018
-
In: Automated Software Engineering : An International Journal. - : Springer Science and Business Media LLC. - 0928-8910. ; 25:2, s. 315-346
-
Journal article (peer-reviewed)abstract
- LLC Mobile apps process increasing amounts of private data, giving rise to privacy concerns. Such concerns do not arise only from single apps, which might—accidentally or intentionally—leak private information to untrusted parties, but also from multiple apps communicating with each other. Certain combinations of apps can create critical data flows not detectable by analyzing single apps individually. While sophisticated tools exist to analyze data flows inside and across apps, none of these scale to large numbers of apps, given the combinatorial explosion of possible (inter-app) data flows. We present a scalable approach to analyze data flows across Android apps. At the heart of our approach is a graph-based data structure that represents inter-app flows efficiently. Following ideas from product-line analysis, the data structure exploits redundancies among flows and thereby tames the combinatorial explosion. Instead of focusing on specific installations of app sets on mobile devices, we lift traditional data-flow analysis approaches to analyze and represent data flows of all possible combinations of apps. We developed the tool Sifta and applied it to several existing app benchmarks and real-world app sets, demonstrating its scalability and accuracy.
|
|
