| 1. |
- Jiang, Shi, et al.
(författare)
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Preparation, characteristics and crystal structures of novel N-heterocyclic carbene substituted furan- and pyridine-containing azadithiolate Fe-S complexes
- 2007
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Ingår i: Polyhedron. - : Elsevier BV. - 0277-5387 .- 1873-3719. ; 26:7, s. 1499-1504
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Tidskriftsartikel (refereegranskat)abstract
- Two novel N-heterocyclic carbene disubstituted furan- and pyridine-containing azadithiolate Fe-only hydrogenase models (2 and 4) have been synthesized, and characterized by IR and H-1 NMR spectra and X-ray single crystal diffraction. Cyclic voltammetry (CV) experiments indicate that they show more negative reductive potentials at -2.53 V and -2.49 V, respectively versus the ferrocene/ferrocenium couple (Fc/Fc(+)) and are easier to capture proton attributing to the strong electron-donating ligand NHC. After the protonation under F3CCO2H the reductive potentials of 2 and 4 have 1.02 V and 0.77 V shifts, indicating the formation of Fe-H-Fe bond. The results also are confirmed by the data changes in IR spectra and the negative H signals are detected by 1H NMR spectra at -27 ppm and -55 ppm.
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| 2. |
- Masud, Abu Naser, et al.
(författare)
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On the Computation of Interprocedural Weak Control Closure
- 2022
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Ingår i: CC 2022 - Proceedings of the 31st ACM SIGPLAN International Conference on Compiler Construction. - New York, NY, USA : Association for Computing Machinery, Inc. - 9781450391832 ; , s. 65-76
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Konferensbidrag (refereegranskat)abstract
- Many program analysis techniques depend on capturing the control dependencies of the program. Most existing control dependence algorithms either compute intraprocedural control dependencies only, or they compute control dependence relations that are not precise in general including nonterminating systems. Weak control closure (WCC) subsumes all known nontermination insensitive control dependence relations, including those that are appropriate for nonterminating systems. In this paper, we provide the first formal development of an algorithm to compute the WCC for interprocedural programs capturing the weak form of interprocedural control dependencies. The method is widely applicable due to the generality of WCC. Theorems on the theoretical results of soundness, precision, and the worst-case complexity of our method are also included. We have compared our algorithm with a WCC computation algorithm based on a state-of-The-Art interprocedural control dependence computation algorithm. The latter algorithm loses soundness, and we improve the precision by 15.21% on all our experimental benchmarks. This empirical evidence suggests that our algorithm is more effective for any client application of WCC requiring interprocedural program analysis.
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| 3. |
- Thomas, N., et al.
(författare)
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The geomorphology of (21) Lutetia : Results from the OSIRIS imaging system onboard ESA's Rosetta spacecraft
- 2012
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Ingår i: Planetary and Space Science. - : Elsevier. - 0032-0633 .- 1873-5088. ; 66:1, s. 96-124
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Tidskriftsartikel (refereegranskat)abstract
- The surface of (21) Lutetia is highly complex with significant interactions between ancient and more recent structures. This work attempts to summarize the surface geomorphology observed using the high resolution images from OSIRIS, the imaging system onboard the European Space Agency's Rosetta spacecraft. A wide range of surface morphologies are seen including heavily cratered terrain, extensive sets of lineaments, young impact craters, and a ridge, the height of which is more than 1/5th of the mean radius of the body. Very young and very old terrains (as inferred from crater densities) are seen in close proximity. The longest continuous lineament is over 80 km long. The lineaments show regional-dependent organization and structure. Several categories of lineament can be described. Lineaments radial to impact craters as seen on other asteroidal bodies are mostly absent. Although the lineaments may be of seismic origin (and possibly the result of several impact-induced events), impacts producing recent large craters place constraints on seismic phenomena. In particular, stronger attenuation of shocks than seen on other asteroidal bodies seems to be required. Inhomogeneous energy transport, possibly matching observed inhomogeneous ejecta deposition may offer explanations for some of the observed phenomena. Some impact craters show unusual forms, which are probably the result of impact into a surface with relief comparable to the resultant crater diameter and/or oblique impact. There is evidence that re-surfacing through landslides has occurred at several places on the object. (C) 2011 Elsevier Ltd. All rights reserved.
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| 4. |
- Sott, Richard, 1974, et al.
(författare)
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Kinetic and NMR spectroscopic studies of chiral mixed sodium/lithium amides used for the deprotonation of cyclohexene oxide.
- 2005
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Ingår i: Chemistry (Weinheim an der Bergstrasse, Germany). - : Wiley. - 0947-6539. ; 11:16, s. 4785-92
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Tidskriftsartikel (refereegranskat)abstract
- The mixed-metal complex formed from n-butylsodium, n-butyllithium, and a chiral amino ether has been studied by NMR spectroscopy. Three different mixed-metal amides were used as chiral bases for the deprotonation of cyclohexene oxide. The selectivity and initial rate of reaction were compared for sodium-amido ethers, lithium-amido ethers, and mixtures of sodium and lithiumamido ethers in diethyl ether and tetrahydrofuran, respectively. The mixed sodium/lithium amides are more reactive than the single sodium and lithium amides, whereas the stereoselectivities are higher when lithium amides are used. The alkali-metal/gamma-amido ethers exhibit both higher initial reaction rates and stereoselectivities than their beta-amido ether analogues. NMR spectroscopic studies of mixtures of n-butylsodium (nBuNa), n-butyllithium (nBuLi), and the gamma-amino ethers in diethyl ether show the exclusive formation of dimeric mixed-metal amides. In diethyl ether, the lithium atom of the mixed-metal amide is internally coordinated and the sodium atom is exposed to solvent; however, in tetrahydrofuran, both metals are internally coordinated.
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| 5. |
- Dackland, Krister, et al.
(författare)
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Blocked Algorithms and Software for Reduction of a Regular Matrix Pair to Generalized Schur Form
- 1999
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Ingår i: ACM Transactions on Mathematical Software. ; 25:4, s. 425-454
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Tidskriftsartikel (refereegranskat)abstract
- A two-stage blocked algorithm for reduction of a regular matrix pair (A, B) to upper Hessenberg-triangular form is presented. In stage 1 (A, B) is reduced to block upper Hessenberg-triangular form using mainly level 3 (matrix-matrix) operations that permit data reuse in the higher levels of a memory hierarchy. In the second stage all but one of the r subdiagonals of the block Hessenberg A-part are set to zero using Givens rotations. The algorithm proceeds in a sequence of supersweeps, each reducing m columns. The updates with respect to row and column rotations are organized to reference consecutive columns of A and B. To further improve the data locality, all rotations produced in a supersweep are stored to enable a left-looking reference pattern, i.e., all updates are delayed until they are required for the continuation of the supersweep. Moreover, we present a blocked variant of the single diagonal double-shift QZ method for computing the generalized Schur form of(A, B) in upper Hessenberg-triangular form. The blocking for improved data locality is done similarly, now by restructuring the reference pattern of the updates associated with the bulge chasing in the QZ iteration. Timing results show that our new blocked variants outperform the current LAPACK routines, including drivers for the generalized eigenvalue problem, by a factor 2-5 for sufficiently large problems.
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| 6. |
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| 7. |
- Conte, Gianpaolo, 1974-
(författare)
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Vision-Based Localization and Guidance for Unmanned Aerial Vehicles
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The thesis has been developed as part of the requirements for a PhD degree at the Artificial Intelligence and Integrated Computer System division (AIICS) in the Department of Computer and Information Sciences at Linköping University.The work focuses on issues related to Unmanned Aerial Vehicle (UAV) navigation, in particular in the areas of guidance and vision-based autonomous flight in situations of short and long term GPS outage.The thesis is divided into two parts. The first part presents a helicopter simulator and a path following control mode developed and implemented on an experimental helicopter platform. The second part presents an approach to the problem of vision-based state estimation for autonomous aerial platforms which makes use of geo-referenced images for localization purposes. The problem of vision-based landing is also addressed with emphasis on fusion between inertial sensors and video camera using an artificial landing pad as reference pattern. In the last chapter, a solution to a vision-based ground object geo-location problem using a fixed-wing micro aerial vehicle platform is presented.The helicopter guidance and vision-based navigation methods developed in the thesis have been implemented and tested in real flight-tests using a Yamaha Rmax helicopter. Extensive experimental flight-test results are presented.
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| 8. |
- Gurt, Carl Johan
(författare)
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Den visionssökande ritualen uusimichhos den amerikanska ursprungsbefolkningen nuu-chah-nulth
- 2021
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Ingår i: Chaos. - Köpenhamn : Forlaget Chaos. - 0108-4453 .- 1901-9106. ; 76:2, s. 79-110
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Tidskriftsartikel (refereegranskat)abstract
- Among the American indigenous people Nuu-chah-nulth of Vancouver Island, uusimich, the vision quest ritual is practised. Nuu-chah-nulth history, social and cultural conditions as well as missionization history is presented in the article to set the broader context of the ritual. Uusimich is discussed in relation to other collective Nuu-chah-nulth rituals and its individual character is emphasized. The ritual is examined through historical and ethnographic sources and the ritual’s present form is also highlighted, based on interviews with informants and previous research. Emphasis is placed on how to situate this ritual among the contemporary Nuu-chah-nulth and how the informants perceive rituals as religious practices but also as important to their identity as a group.
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