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81.
82.
Lorente N Pascual JI 《Philosophical transactions. Series A, Mathematical, physical, and engineering sciences》2004,362(1819):1227-1238
Inelastic tunnelling electrons are a proper excitation source to induce chemical transformations on a single adsorbate. When their energy is tuned to that of molecular vibrational states, the modification may follow complex internal vibrational pathways. Here, we analyse our recent results on the selective excitation of ammonium stretching or bending modes to control the outcome of a simple bond-cleavage reaction. With the help of model calculations, we provide a detailed molecular-scale picture of the competing internal pathways leading to molecular movement. A mode-selective strategy, based on local excitations of specific reaction coordinates, has an important drawback when applied to adsorbate systems due to the problem of fast energy randomization. The success of such a mode-selective strategy is determined here by the ability of the scanning tunnelling microscope to study reactivity in the limit of very low yield and very low power irradiation, in a regime where vibrational heating of the adsorbate/surface system becomes negligible. 相似文献
83.
J. Santamaría O. Cordón S. Damas I. Aleman M. Botella 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2007,11(9):819-828
Different tasks in forensic anthropology require the use of three-dimensional models of forensic objects (skulls, bones, corpses,
etc) captured by 3D range scanners. Since a whole object cannot be completely scanned with a single image, multiple scans
from different views are needed to supply the information to construct the 3D model. Range image registration methods study
the accurate integration of the different views acquired by range scanners, with pair-wise approaches progressively processing
every adjacent pair of scanned views until reconstructing the whole 3D model of the object. Our proposal is based on the adaptation
of our previous work (Cordon et al, IEEE Conference on Evolutionary Computation, pp 2738–2744, 2005 in Pattern Recognit Lett
27(11); 1191-1200, 2006) in order to apply the scatter search evolutionary algorithm to pair-wise image registration in forensic
anthropology applications. To measure the performance of this adaptation, we design an experimental setup considering some
of the most recent and accurate evolutionary techniques for the problem, as well as one skull from our Physical Anthropology
Lab. Two additional volumes, commonly used in other pair-wise range IR contributions, have also been considered to complement
the comparison of results among the proposals.
This work was supported by the Ministerio de Ciencia y Tecnología of Spain under project TIC2003-00877 (including FEDER fundings). 相似文献
84.
Equilibrium models which attempt for the influence of pH on the solubility of metals can improve the dynamic leaching models developed to describe the long-term behavior of waste-derived forms. In addition, such models can be used to predict the concentration of metals in equilibrium leaching tests at a given pH. The aim of this work is to model the equilibrium concentration of Zn from untreated and stabilized/solidified (S/S) electric arc furnace dust (EAFD) using experimental data obtained from a pH-dependence leaching test (acid neutralization capacity, ANC). EAFD is a hazardous waste generated in electric arc furnace steel factories; it contains significant amounts of heavy metals such as Zn, Pb, Cr or Cd. EAFD from a local factory was characterized by X-ray fluorescence (XRF), acid digestion and X-ray diffraction (XRD). Zn and Fe were the main components while the XRD analysis revealed that zincite, zinc ferrite and hematite were the main crystalline phases. Different cement/EAFD formulations ranging from 7 to 20% dry weight of cement were prepared and subjected to the ANC leaching test. An amphoteric behavior of Zn was found from the pH dependence test. To model this behavior, the geochemical model Visual MINTEQ (VMINTEQ) was used. In addition to the geochemical model, an empirical model based on the dissolution of Zn in the acidic zone and the re-dissolution of zinc compounds in the alkaline zone was considered showing a similar prediction than that obtained with VMINTEQ. This empirical model seems to be more appropriate when the metal speciation is unknown, or when if known, the theoretical solid phases included in the database of VMINTEQ do not allow to describe the experimental data. 相似文献
85.
Jesus Perez Jesus Ibanez Luis Vielva David J. Perez-Blanco Ignacio Santamaria 《Wireless Communications, IEEE Transactions on》2007,6(2):452-457
In this letter we derive a simple and tight closed-form approximation for the ergodic capacity of orthogonal space-time block coding in arbitrary fading channels. The expression is an analytical function of the power covariance matrix of the channel. In the case of uncorrelated channels the expression only depends on the variances of the channel power gains. These channel statistics can be easily obtained from both analytical and physical fading channel models. Simulations results show the accuracy of the proposed expression 相似文献
86.
F. García‐Santamaría M. Xu V. Lousse S. Fan P. V. Braun J. A. Lewis 《Advanced materials (Deerfield Beach, Fla.)》2007,19(12)
Germanium inverse woodpile 3D photonic crystals with a large (25%) photonic band gap in the infrared (background image) were fabricated through a multistep replication procedure. A polymer scaffold was first created by direct‐write assembly, followed by the conformal growth of oxide and semiconductor layers, and removal of the polymer and oxide (foreground), as reported on p. 1567 by Paul Braun, Jennifer Lewis, and co‐workers. 相似文献
87.
D. Santamaría A. Viguria M. Bejar K. Kondak A. Ollero 《Journal of Intelligent and Robotic Systems》2013,69(1-4):171-180
The consideration of safety issues in the operation of helicopters involves the capability to perform emergency descending maneuvers through the autorotation principle when the engine is no longer supplying power. When comparing manned and unmanned helicopters, the lower rotor inertia of UAV configurations makes this functionality even more challenging for the pilot since more accurate timing and speed control of the flare phase are required. This paper presents a complete set of guidelines to design a controller for the autonomous autorotation landing of an UAV. This analysis is based on experimental data that corresponds to autorotation landings of a small-size helicopter carried out by a skillful pilot. 相似文献
88.
Ignacio Fernández Manuel Mazo José L. Lázaro Daniel Pizarro Enrique Santiso Pedro Martín Cristina Losada 《Autonomous Robots》2007,23(4):305-324
This paper presents a new proposal for positioning and guiding mobile robots in indoor environments. The proposal is based
on the information provided by static cameras located in the movement environment. This proposal falls within the scope of
what are known as intelligent environments; in this case, the environment is provided with cameras that, once calibrated,
allow the position of the robots to be obtained. Based on this information, control orders for the robots can be generated
using a radio frequency link. In order to facilitate identification of the robots, even under extremely adverse ambient lighting
conditions, a beacon consisting of four circular elements constructed from infrared diodes is mounted on board the robots.
In order to identify the beacon, an edge detection process is carried out. This is followed by a process that, based on the
algebraic distance, obtains the estimated ellipses associated with each element of the beacon. Once the beacon has been identified,
the coordinates of the centroids for the elements that make up the beacon are obtained on the various image planes. Based
on these coordinates, an algorithm is proposed that takes into account the standard deviation of the error produced in the
various cameras in ascertaining the coordinates of the beacon’s elements. An odometric system is also used in guidance that,
in conjunction with a Kalman Filter, allows the position of the robot to be estimated during the time intervals required to
process the visual information provided by the cameras.
相似文献
Cristina LosadaEmail: |
89.
Ramón J. Durán Ignacio de Miguel Noemí Merayo Patricia Fernández Juan Carlos Aguado Rubén M. Lorenzo Evaristo J. Abril 《Photonic Network Communications》2009,17(1):21-33
A new method to design logical topologies based on genetic algorithms is presented. Not only does the algorithm determine
which nodes should be connected by means of lightpaths with the aim of minimizing congestion, but it also solves the routing
and wavelength assignment problem. In this way, the algorithm guarantees that the logical topology obtained can be embedded
in the optical network subject to the available set of resources. The algorithm is effective in terms of both congestion and
fairness. For instance, when compared with other work, the congestion is significantly reduced (from 20% to 75% depending
on the matrix of traffic considered), and the fairness, when evaluated in terms of the Jain index, is generally higher than
0.94. Moreover, the algorithm brings advantages when employed in dynamic scenarios where the logical topology is frequently
reconfigured, as it is fast and, in contrast to other algorithms previously proposed, the calculation process can be stopped
at any time (if required) in order to give the best virtual topology found up to the moment.
相似文献
Ramón J. DuránEmail: |
90.
Ramón J. Durán Ignacio de Miguel Noemí Merayo Patricia Fernández Rubén M. Lorenzo Evaristo J. Abril 《Photonic Network Communications》2009,18(3):334-344
A new multipurpose genetic algorithm, based on Pareto optimality, is proposed to design logical topologies for wavelength-routed
optical networks with the aim of minimizing both the congestion and the end-to-end delay. Simulation results show its efficiency
when compared with other previously proposed algorithms, achieving in most cases optimal or near-optimal solutions, and in
less time than other methods. Moreover, since the algorithm relies on Pareto optimality, not only does it obtain a single
logical topology but a set of them, so that the network designer can easily select the most appropriate one according to the
current network requirements. 相似文献