2,094 research outputs found
Workshop report. Linear-Scaling Ab Initio Calculations: Applications and Future Directions
No full textThe study of properties and of processes in materials, frequently hinges upon understanding phenomena which originate at the atomic level. In such cases the accurate description of the interactions between large numbers of atoms is critical and in turn requires the accurate description of the electrons which play a crucial role in the bonding of atoms into molecules, surfaces and solids. This can only be achieved by solving the equations of quantum mechanics. These
equations are too complicated to solve exactly; however their solutions can be approximated by computational techniques. The most accurate ? but also most computationally demanding ? are the “ab initio” techniques which do not use any empirical adjustable parameters. Amongst them, the Density Functional Theory (DFT) formulation of quantum mechanics stands out as an excellent compromise between accuracy and computational efficiency. However, the applicability of ab initio techniques is severely limited by poor scaling: the computational effort needed to perform an ab initio calculation increases with (at least) the third power of the number of atoms, N. This cubic-scaling bottleneck limits the number of atoms we can study to a few hundred at most, even on parallel supercomputers. To overcome this length-scale limitation, a number of researchers worldwide have been pioneering the development of a novel class of ab initio methods with linear-scaling or “Order N” (O(N)) computational cost which nevertheless retain the same high level of accuracy as the conventional approaches. While physically motivated, such methods have proved particularly hard to develop as they introduce highly non-trivial localisation constraints. Nevertheless, many major obstacles have been overcome and a number of O(N)
methods (SIESTA, CONQUEST, ONETEP, etc.) for ground state DFT calculations on systems with a gap (e.g. molecules, semiconductors and insulators) are now available and have reached a state of maturity that allows them to be used to study ”real” materials. The particular focus of this workshop is therefore to look forward to what can be achieved in the next few years. Our aim is twofold: (1) As O(N) methods are currently extending the applicability of DFT calculations
to problems involving biomolecules and nanostructures they are leading to completely new levels of understanding of these systems. This CECAM meeting will give us the opportunity to make an appraisal of such large-scale simulations and their potential to connect more directly to experiments. (2) We also want to examine the options for extending linear-scaling to problems that cannot be treated by ground-state DFT but require other, more complex approaches. These include methods for treating metallic systems, excited states and wavefunction-based theories for including electronic correlation. Finding ways to transform these methods to linear-scaling
cost, and hence extent their applicability to the nano-scale, is the next big challenge that the community of developers of large-scale electronic structure methods is beginning to face. We
hope that this workshop will stimulate these major new O(N) methodological developments by bringing together the leading groups in the development of O(N) DFT methods with the leading
groups in the development of metal and excited-state or wavefunction-based methods. Strong emphasis during the workshop will be given to discussion in order to promote the exchange
of ideas between different communities (Physics, Chemistry, Materials Science, Biochemistry) which are all interested in large-scale applications with ab initio accuracy but are approaching
them from different perspectives
Response model of superconductive, pulsed eddy-current probes for detection of deep-lying flaws
No full textMaintenance of aging aircraft requires methods of nondestructive evaluation sensitive enough to detect small cracks and corrosion embedded in multi-layered structures of airframes. Combining pulsed eddy-current technology with the unrivalled magnetic-field sensitivity of superconductive probes can meet this need. It is shown experimentally and theoretically that this combination has an outstanding capability for detecting deep-lying flaws. Results from validation of the theoretical model are presented here. Experimental data and model predictions are in close agreement.This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Bowler, N., J. R. Bowler, and W. Podney. "Response model of superconductive, pulsed eddy-current probes for detection of deep-lying flaws." In AIP Conference Proceedings, vol. 557, no. 1, pp. 941-948. American Institute of Physics, 2001, and may be found at DOI: 10.1063/1.1373857. Copyright 2001 American Institute of Physics. Posted with permission
Eddy current measurements on case hardened steel
No full textThe case-hardening process modifies the near-surface permeability and conductivity of steel, as can be observed through changes in eddy current probe signals measured over a range of frequency. In this work, experiments have been performed using normal absolute probe coils on flat steel specimens and coils encircling case-hardened steel rods. By fitting model results to the experimental data, estimates of electrical material properties are found. The approach also allows an assessment of the sensitivity of the measurements to the case depth.This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing.
This article appeared in Sun, H., J. R. Bowler, N. Bowler, and M. J. Johnson. "Eddy current measurements on case hardened steel." In AIP Conference Proceedings, vol. 615, no. 1, pp. 1561-1568. American Institute of Physics, 2002, and may be found at
DOI: 10.1063/1.1472979.
Copyright 2002 American Institute of Physics.
Posted with permission
Silex énigmatiques de Grande-Bretagne
No full textBowler-Kelley Alice. Silex énigmatiques de Grande-Bretagne. In: Bulletin de la Société préhistorique de France, tome 32, n°10, 1935. pp. 499-506
Multilevel societies in new world primates? Flexibility may characterize the organization of Peruvian red uakaris (Cacajao calvus ucayalii)
No full textResearchers have described multilevel societies with one-male, multifemale units (OMUs) forming within a larger group in several catarrhine species, but not in platyrhines. OMUs in multilevel societies are associated with extremely large group sizes, often with >100 individuals, and the only platyrhine genus that forms groups of this size is Cacajao. We review available evidence for multilevel organization and the formation of OMUs in groups of Cacajao, and test predictions for the frequency distribution patterns of male–male and male–female interindividual distances within groups of red-faced uakaris (Cacajao calvus ucayalii), comparing year-round data with those collected at the peak of the breeding season, when group cohesion may be more pronounced. Groups of Cacajao fission and fuse, forming subgroup sizes at frequencies consistent with an OMU organization. In Cacajao calvus ucayalii and Cacajao calvus calvus, bachelor groups are also observed, a characteristic of several catarrhine species that form OMUs. However, researchers have observed both multimale–multifemale groups and groups with a single male and multiple females in Cacajao calvus. The frequency distributions of interindividual distances for male–male and male–female dyads are consistent with an OMU-based organization, but alternative interpretations of these data are possible. The distribution of interindividual distances collected during the peak breeding season differed from those collected year-round, indicating seasonal changes in the spatial organization of Cacajao calvus ucayalii. We suggest a high degree of flexibility may characterize the social organization of Cacajao calvus ucayalii, which may form OMUs under certain conditions. Further studies with identifiable individuals, thus far not possible in Cacajao, are required to confirm the social organization.Peer reviewe
Un micro-burin double provenant du Cap Blanc (Mauritanie)
No full textBowler-Kelley Alice. Un micro-burin double provenant du Cap Blanc (Mauritanie). In: Bulletin de la Société préhistorique de France, tome 32, n°11, 1935. pp. 585-586
Linda L. Bowler et Robert D. McClure. — Political Ambition. Who Decides to Run for Congress
No full textBody-Gendrot Sophie. Linda L. Bowler et Robert D. McClure. — Political Ambition. Who Decides to Run for Congress. In: Revue Française d'Etudes Américaines, N°45, juillet 1990. Classiques américains : anciens et nouveaux. pp. 201-202
Bowler I.R., Bryant C.R., Nellis M.D. (Ed.). - Contemporary Rural Systems in Transition.
No full textDelorme Hélène. Bowler I.R., Bryant C.R., Nellis M.D. (Ed.). - Contemporary Rural Systems in Transition.. In: Économie rurale. N°222, 1994. 48 heures - 48 thèses d'Économie et de Sociologie Rurales. pp. 52-53
Linda L. Bowler et Robert D. McClure. — Political Ambition. Who Decides to Run for Congress
No full textBody-Gendrot Sophie. Linda L. Bowler et Robert D. McClure. — Political Ambition. Who Decides to Run for Congress. In: Revue Française d'Etudes Américaines, N°45, juillet 1990. Classiques américains : anciens et nouveaux. pp. 201-202
Annotated translation: Jade Bowler, The Only Study Guide You'll Ever Need. Bonnier Books, 2021, chapter 5 and part of chapter 6
No full textThis bachelor thesis consists of two parts, namely a translation of Chapter 5 It's time for timetables and a part of Chapter 6 Productivity Hacks from The Only Study Guide You'll Ever Need (2021) by British author and YouTuber Jade Bowler, and a commentary of the translation, which includes an analysis of the original text and a subsequent description of translation problems, methods and shifts. Keywords: Jade Bowler, YouTube, study guide, productivity hacks, time-management, pre- translation text analysis, translation procedures, translation shift
- …
