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排序方式: 共有140条查询结果,搜索用时 927 毫秒
61.
Ruy Fabila-Monroy David Flores-Peñaloza Clemens Huemer Ferran Hurtado Jorge Urrutia David R. Wood 《Graphs and Combinatorics》2012,28(3):365-380
For a graph G and integer k ≥ 1, we define the token graph F k (G) to be the graph with vertex set all k-subsets of V(G), where two vertices are adjacent in F k (G) whenever their symmetric difference is a pair of adjacent vertices in G. Thus vertices of F k (G) correspond to configurations of k indistinguishable tokens placed at distinct vertices of G, where two configurations are adjacent whenever one configuration can be reached from the other by moving one token along an edge from its current position to an unoccupied vertex. This paper introduces token graphs and studies some of their properties including: connectivity, diameter, cliques, chromatic number, Hamiltonian paths, and Cartesian products of token graphs. 相似文献
62.
Prosenjit Bose Erik D. Demaine Ferran Hurtado John Iacono Stefan Langerman Pat Morin 《Discrete and Computational Geometry》2007,37(3):325-339
Let P be a simple polygon with m vertices, k of which are reflex, and which contains r red points and b blue
points in its interior. Let n = m + r + b. A ham-sandwich geodesic is a shortest path in P between two points on the boundary
of P that simultaneously bisects the red points and the blue points. We present an O(n log k)-time algorithm for finding a
ham-sandwich geodesic. We also show that this algorithm is optimal in the algebraic computation tree model when parameterizing
the running time with respect to n and k. 相似文献
63.
Inside Cover: Enantiopure Narrow Bite‐Angle POP Ligands: Synthesis and Catalytic Performance in Asymmetric Hydroformylations and Hydrogenations (Chem. Eur. J. 47/2014) 下载免费PDF全文
64.
Enantiopure Narrow Bite‐Angle POP Ligands: Synthesis and Catalytic Performance in Asymmetric Hydroformylations and Hydrogenations 下载免费PDF全文
Dr. Héctor Fernández‐Pérez Dr. Jordi Benet‐Buchholz Prof. Dr. Anton Vidal‐Ferran 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(47):15375-15384
Herein is reported the preparation of a set of narrow bite‐angle P–OP ligands the backbone of which contains a stereogenic carbon atom. The synthesis was based on a Corey–Bakshi–Shibata (CBS)‐catalyzed asymmetric reduction of phosphomides. The structure of the resulting 1,1‐P–OP ligands, which was selectively tuned through adequate combination of the configuration of the stereogenic carbon atom, its substituent, and the phosphite fragment, proved crucial for providing a rigid environment around the metal center, as evidenced by X‐ray crystallography. These new ligands enabled very good catalytic properties in the Rh‐mediated enantioselective hydrogenation and hydroformylation of challenging and model substrates (up to 99 % ee). Whereas for asymmetric hydrogenation the optimal P–OP ligand depended on the substrate, for hydroformylation, a single ligand was the highest‐performing one for almost all studied substrates: it contains an R‐configured stereogenic carbon atom between the two phosphorus ligating groups, and an S‐configured 3,3′‐diphenyl‐substituted biaryl unit. 相似文献
65.
A variety of methyl esters are converted into the corresponding propyl esters upon treatment with l-propanol and chlorotrimethylsilane. Among them acyclic aliphatic esters have the best conversion rate. 相似文献
66.
Josep Altet José Luis González Dídac Gomez Xavier Perpiñà Wilfrid Claeys Stephane Grauby Cedric Dufis Miquel Vellvehi Diego Mateo Ferran Reverter Stefan Dilhaire Xavier Jordà 《Microelectronics Journal》2014
This paper reports on the design solutions and the different measurements we have done in order to characterize the thermal coupling and the performance of differential temperature sensors embedded in an integrated circuit implemented in a 65 nm CMOS technology. The on-chip temperature increases have been generated using diode-connected MOS transistors behaving as heat sources. Temperature measurements performed with the embedded sensor are corroborated with an infra-red camera and a laser interferometer used as thermometer. A 2 GHz linear power amplifier (PA) is as well embedded in the same silicon die. In this paper we show that temperature measurements performed with the embedded temperature sensor can be used to monitor the PA DC behavior and RF activity. 相似文献
67.
Toward Bioelectronic Nanomaterials: Photoconductivity in Protein–Porphyrin Hybrids Wrapped around SWCNT 下载免费PDF全文
Javier López‐Andarias Sara H. Mejías Tsuneaki Sakurai Wakana Matsuda Shu Seki Ferran Feixas Sílvia Osuna Carmen Atienza Nazario Martín Aitziber L. Cortajarena 《Advanced functional materials》2018,28(24)
The development of sophisticated ordered functional materials is one of the important challenges in current science. One of the keys to enhance the properties of these materials is the control of the organization and morphology at different scales. This work presents a novel bioinspired methodology to achieve highly ordered donor/acceptor bio‐nanohybrids using a designed repeat protein as scaffold, endowed with photoactive and electron donating porphyrin (P) units, to efficiently wrap around electron accepting single wall carbon nanotubes (SWCNT). A systematic experimental and theoretical study to evaluate the effect of the length of the protein reveals that longer proteins wrap around the SWCNT in a more efficient manner due to the stronger supramolecular interaction existing between the inner concave surface of the protein (namely Trp and His residues) and the convex surface of the (7,6)‐SWCNT. Interestingly, spectroscopy and X‐ray diffraction data further confirm that the so‐called protein‐P–SWCNT donor–acceptor bio‐nanohybrids retain the original protein structure. Finally, the new bio‐nanohybrids show a remarkable enhancement on the photoconductivity values by flash‐photolysis microwave conductivity (FP‐TRMC technique) demonstrating that the major charge carriers of electrons are injected into the SWCNTs and move along the 1D‐structures. 相似文献
68.
Binary partition trees for object detection 总被引:3,自引:0,他引:3
Veronica Vilaplana Ferran Marques Philippe Salembier 《IEEE transactions on image processing》2008,17(11):2201-2216
This paper discusses the use of Binary Partition Trees (BPTs) for object detection. BPTs are hierarchical region-based representations of images. They define a reduced set of regions that covers the image support and that spans various levels of resolution. They are attractive for object detection as they tremendously reduce the search space. In this paper, several issues related to the use of BPT for object detection are studied. Concerning the tree construction, we analyze the compromise between computational complexity reduction and accuracy. This will lead us to define two parts in the BPT: one providing accuracy and one representing the search space for the object detection task. Then we analyze and objectively compare various similarity measures for the tree construction. We conclude that different similarity criteria should be used for the part providing accuracy in the BPT and for the part defining the search space and specific criteria are proposed for each case. Then we discuss the object detection strategy based on BPT. The notion of node extension is proposed and discussed. Finally, several object detection examples illustrating the generality of the approach and its efficiency are reported. 相似文献
69.
Alfredo García Ferran Hurtado Clemens Huemer Javier Tejel Pavel Valtr 《Computational Geometry》2009,42(9):913-922
Let S be a set of n4 points in general position in the plane, and let h<n be the number of extreme points of S. We show how to construct a 3-connected plane graph with vertex set S, having max{3n/2,n+h−1} edges, and we prove that there is no 3-connected plane graph on top of S with a smaller number of edges. In particular, this implies that S admits a 3-connected cubic plane graph if and only if n4 is even and hn/2+1. The same bounds also hold when 3-edge-connectivity is considered. We also give a partial characterization of the point sets in the plane that can be the vertex set of a cubic plane graph. 相似文献
70.
Given a pair of matrices (A, B) we study the Lipschitz stability of its controlled invariant subspaces. A sufficient condition is derived from the geometry
of the set formed by the quadruples (A, B, F, S) where S is an (A, B)-invariant subspace and F a corresponding feedback. 相似文献