Browsing
     by title


0-9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

or enter first few letters:   
OK
Full Text
Peer Reviewed
See detailTwo- and three-body interatomic dispersion energy contributions to binding in molecules and solids
Anatole Von Lilienfeld, O.; Tkatchenko, Alexandre UL

in Journal of Chemical Physics (2010), 132(23),

We present numerical estimates of the leading two- and three-body dispersion energy terms in van der Waals interactions for a broad variety of molecules and solids. The calculations are based on London ... [more ▼]

We present numerical estimates of the leading two- and three-body dispersion energy terms in van der Waals interactions for a broad variety of molecules and solids. The calculations are based on London and Axilrod-Teller-Muto expressions where the required interatomic dispersion energy coefficients, C6 and C9, are computed "on the fly" from the electron density. Inter- and intramolecular energy contributions are obtained using the Tang-Toennies (TT) damping function for short interatomic distances. The TT range parameters are equally extracted on the fly from the electron density using their linear relationship to van der Waals radii. This relationship is empiricially determined for all the combinations of He-Xe rare gas dimers, as well as for the He and Ar trimers. The investigated systems include the S22 database of noncovalent interactions, Ar, benzene and ice crystals, bilayer graphene, C60 dimer, a peptide (Ala10), an intercalated drug-DNA model [ellipticine- d (CG) 2], 42 DNA base pairs, a protein (DHFR, 2616 atoms), double stranded DNA (1905 atoms), and 12 molecular crystal polymorphs from crystal structure prediction blind test studies. The two- and three-body interatomic dispersion energies are found to contribute significantly to binding and cohesive energies, for bilayer graphene the latter reaches 50% of experimentally derived binding energy. These results suggest that interatomic three-body dispersion potentials should be accounted for in atomistic simulations when modeling bulky molecules or condensed phase systems. © 2010 American Institute of Physics. [less ▲]

Detailed reference viewed: 198 (1 UL)
Full Text
Peer Reviewed
See detailTwo- and three-dimensional isogeometric cohesive elements for composite delamination analysis
Nguyen, Vinh-Phu; Kerfriden, Pierre; Bordas, Stéphane UL

in Composites. Part B, Engineering (2014), 60

We propose an automatic numerical method requiring minimal user intervention to simulate delamination in composite structures. We develop isogeometric cohesive elements for two- and three-dimensional ... [more ▼]

We propose an automatic numerical method requiring minimal user intervention to simulate delamination in composite structures. We develop isogeometric cohesive elements for two- and three-dimensional delamination by exploiting the knot insertion algorithm directly from CAD data to generate cohesive elements along delamination. A complete computational framework is presented including pre-processing, processing and post-processing. They are explained in detail and implemented in MIGFEM - an open source Matlab Isogemetric Analysis code developed by the authors. The composite laminates are modeled using both NURBS solid and rotation-free shell elements. Several two and three dimensional examples ranging from standard delamination tests (the mixed mode bending test) to the L-shaped specimen with a fillet, three dimensional (3D) double cantilever beam and a 3D singly curved thick-walled laminate are provided. The method proposed provides a bi-directional system in which one can go forward from CAD to analysis and backwards from analysis to CAD. This is believed to facilitate the design of composite structures. © 2013 Elsevier Ltd. All rights reserved. [less ▲]

Detailed reference viewed: 264 (5 UL)
Full Text
Peer Reviewed
See detailTwo-dimensional fractional linear prediction
Skovranek, Tomas; Despotovic, Vladimir UL; Peric, Zoran

in Computers and Electrical Engineering (2019), 77

Linear prediction (LP) has been applied with great success in coding of one-dimensional, time-varying signals, such as speech or biomedical signals. In case of two-dimensional signal representation (e.g ... [more ▼]

Linear prediction (LP) has been applied with great success in coding of one-dimensional, time-varying signals, such as speech or biomedical signals. In case of two-dimensional signal representation (e.g. images) the model can be extended by applying one-dimensional LP along two space directions (2D LP). Fractional linear prediction (FLP) is a generalisation of standard LP using the derivatives of non-integer (arbitrary real) order. While FLP was successfully applied to one-dimensional signals, there are no reported implementations in multidimensional space. In this paper two variants of two-dimensional FLP (2D FLP) are proposed and optimal predictor coefficients are derived. The experiments using various grayscale images confirm that the proposed 2D FLP models are able to achieve comparable performance in comparison to 2D LP using the same support region of the predictor, but with one predictor coefficient less, enabling potential compression. [less ▲]

Detailed reference viewed: 69 (9 UL)
Full Text
Peer Reviewed
See detailA two-dimensional Isogeometric Boundary Element Method for elastostatic analysis
Simpson, R. N.; Bordas, Stéphane UL; Trevelyan, J. et al

in Computer Methods in Applied Mechanics and Engineering (2012), 209-212

The concept of isogeometric analysis, where functions that are used to describe geometry in CAD software are used to approximate the unknown fields in numerical simulations, has received great attention ... [more ▼]

The concept of isogeometric analysis, where functions that are used to describe geometry in CAD software are used to approximate the unknown fields in numerical simulations, has received great attention in recent years. The method has the potential to have profound impact on engineering design, since the task of meshing, which in some cases can add significant overhead, has been circumvented. Much of the research effort has been focused on finite element implementations of the isogeometric concept, but at present, little has been seen on the application to the Boundary Element Method. The current paper proposes an Isogeometric Boundary Element Method (BEM), which we term IGABEM, applied to two-dimensional elastostatic problems using Non-Uniform Rational B-Splines (NURBS). We find it is a natural fit with the isogeometric concept since both the NURBS approximation and BEM deal with quantities entirely on the boundary. The method is verified against analytical solutions where it is seen that superior accuracies are achieved over a conventional quadratic isoparametric BEM implementation. © 2011 Elsevier B.V. [less ▲]

Detailed reference viewed: 249 (8 UL)
Full Text
See detailA two-dimensional isogeometric boundary element method for linear elastic fracture
Peng, Xuan; Atroshchenko, Elena; Kulasegaram, Sivakumar et al

Report (2014)

Detailed reference viewed: 141 (5 UL)
Full Text
Peer Reviewed
See detailA Two-Dimensional Isogeometric Boundary Element Method For Linear Elastic Fracture
Peng, Xuan; AtroShchenko, Elena; Simpson, Robert et al

Scientific Conference (2014, January)

Detailed reference viewed: 408 (11 UL)
Full Text
See detailA two-dimensional isogeometric boundary element method for linear elastic fracture: a path towards damage tolerance analysis without meshing
Peng, Xuan; Atroshchenko, Elena; Kulasegaram, Sivakumar et al

Report (n.d.)

Detailed reference viewed: 133 (7 UL)
Full Text
Peer Reviewed
See detailTwo-intermediate model to characterize the structure of fast-folding proteins
Roterman, I.; Konieczny, L.; Jurkowski, Wiktor UL et al

in Journal of Theoretical Biology (2011), 283(1), 60-70

This paper introduces a new model that enables researchers to conduct protein folding simulations. A two-step in silico process is used in the course of structural analysis of a set of fast-folding ... [more ▼]

This paper introduces a new model that enables researchers to conduct protein folding simulations. A two-step in silico process is used in the course of structural analysis of a set of fast-folding proteins. The model assumes an early stage (ES) that depends solely on the backbone conformation, as described by its geometrical properties--specifically, by the V-angle between two sequential peptide bond planes (which determines the radius of curvature, also called R-radius, according to a second-degree polynomial form). The agreement between the structure under consideration and the assumed model is measured in terms of the magnitude of dispersion of both parameters with respect to idealized values. The second step, called late-stage folding (LS), is based on the "fuzzy oil drop" model, which involves an external hydrophobic force field described by a three-dimensional Gauss function. The degree of conformance between the structure under consideration and its idealized model is expressed quantitatively by means of the Kullback-Leibler entropy, which is a measure of disparity between the observed and expected hydrophobicity distributions. A set of proteins, representative of the fast-folding group [less ▲]

Detailed reference viewed: 110 (0 UL)
Full Text
Peer Reviewed
See detailA Two-Level Approach to Characterizing Human Activities from Wearable Sensor Data
Faye, Sébastien UL; Louveton, Nicolas UL; Gheorghe, Gabriela UL et al

in Journal of Wireless Mobile Networks, Ubiquitous Computing, and Dependable Applications (2016), 7(3),

The rapid emergence of new technologies in recent decades has opened up a world of opportunities for a better understanding of human mobility and behavior. It is now possible to recognize human movements ... [more ▼]

The rapid emergence of new technologies in recent decades has opened up a world of opportunities for a better understanding of human mobility and behavior. It is now possible to recognize human movements, physical activity and the environments in which they take place. And this can be done with high precision, thanks to miniature sensors integrated into our everyday devices. In this paper, we explore different methodologies for recognizing and characterizing physical activities performed by people wearing new smart devices. Whether it’s smartglasses, smartwatches or smartphones, we show that each of these specialized wearables has a role to play in interpreting and monitoring moments in a user's life. In particular, we propose an approach that splits the concept of physical activity into two sub-categories that we call micro- and macro-activities. Micro- and macro-activities are supposed to have functional relationship with each other and should therefore help to better understand activities on a larger scale. Then, for each of these levels, we show different methods of collecting, interpreting and evaluating data from different sensor sources. Based on a sensing system we have developed using smart devices, we build two data sets before analyzing how to recognize such activities. Finally, we show different interactions and combinations between these scales and demonstrate that they have the potential to lead to new classes of applications, involving authentication or user profiling. [less ▲]

Detailed reference viewed: 209 (14 UL)
Full Text
Peer Reviewed
See detailTwo-level system coupled to phonons: Full analytical solution
Chenu, Aurélia UL; Shiau, S.-Y.; Combescot, Monique

in Physical Review. B (2019), 99

We propose an analytical procedure to fully solve a two-level system coupled to phonons. Instead of using the common formulation in terms of linear and quadratic system-phonon couplings, we introduce ... [more ▼]

We propose an analytical procedure to fully solve a two-level system coupled to phonons. Instead of using the common formulation in terms of linear and quadratic system-phonon couplings, we introduce different phonons depending on the system electronic level. We use this approach to recover known results for the linear-coupling limit in a simple way. More importantly, we derive results for the quadratic coupling induced by a phonon frequency change, a problem considered up to now as not analytically solvable. [less ▲]

Detailed reference viewed: 28 (0 UL)
Peer Reviewed
See detailTwo-mode methods of cluster analysis: Compare and contrast
Krolak-Schwerdt, Sabine UL

in Schader, M.; Gaul, W.; Vichi, M. (Eds.) Studies in classification, data analysis, and knowledge organization (2003)

In this paper methods to cluster analyze two-mode data are discussed which assume that both objects and attributes contribute to the uncovering of meaningful patterns of clusters. Two-mode methods are ... [more ▼]

In this paper methods to cluster analyze two-mode data are discussed which assume that both objects and attributes contribute to the uncovering of meaningful patterns of clusters. Two-mode methods are reviewed and criteria are proposed which aim at a comparison and evaluation of the reviewed methods. The selected criteria show that most two-mode approaches su®er from drawbacks con- cerning interpretation of the data, convergence of algorithms, uniqueness of solu- tions or applicability to larger data sets. They imply some suggestions for future directions in the development of two{ and three{mode cluster analysis. [less ▲]

Detailed reference viewed: 54 (1 UL)
Full Text
Peer Reviewed
See detailTwo-phase concurrent sensing and transmission scheme for full duplex cognitive radio
Sharma, Shree Krishna UL; Bogale, T.E.; Le, L.B. et al

in IEEE 84th Vehicular Technology Conference (2016)

Detailed reference viewed: 167 (4 UL)
Full Text
Peer Reviewed
See detailA two-phase heuristic for the scheduling of independent tasks on computational grids
Pinel, Frédéric UL; Pecero, Johnatan UL; Bouvry, Pascal UL et al

in High Performance Computing and Simulation (HPCS), 2011 International Conference on (2011)

Detailed reference viewed: 135 (3 UL)
Full Text
See detailTwo-Stage Process - a More Flexible Power Production of Biogas
Sobon-Muehlenbrock, Elena UL; Benito Martin, Patricia Cristina UL; Greger, Manfred UL et al

in Revue Technique Luxembourgeoise (2018), 3

Detailed reference viewed: 86 (18 UL)
Full Text
Peer Reviewed
See detailTwo-stage RGB-based Action Detection using Augmented 3D Poses
Papadopoulos, Konstantinos UL; Ghorbel, Enjie UL; Baptista, Renato UL et al

in 18th International Conference on Computer Analysis of Images and Patterns SALERNO, 3-5 SEPTEMBER, 2019 (2019)

In this paper, a novel approach for action detection from RGB sequences is proposed. This concept takes advantage of the recent development of CNNs to estimate 3D human poses from a monocular camera. To ... [more ▼]

In this paper, a novel approach for action detection from RGB sequences is proposed. This concept takes advantage of the recent development of CNNs to estimate 3D human poses from a monocular camera. To show the validity of our method, we propose a 3D skeleton-based two-stage action detection approach. For localizing actions in unsegmented sequences, Relative Joint Position (RJP) and Histogram Of Displacements (HOD) are used as inputs to a k-nearest neighbor binary classifier in order to define action segments. Afterwards, to recognize the localized action proposals, a compact Long Short-Term Memory (LSTM) network with a de-noising expansion unit is employed. Compared to previous RGB-based methods, our approach offers robustness to radial motion, view-invariance and low computational complexity. Results on the Online Action Detection dataset show that our method outperforms earlier RGB-based approaches. [less ▲]

Detailed reference viewed: 193 (11 UL)
Full Text
Peer Reviewed
See detailTwo-stage spectrum sensing for cognitive radios
Maleki, Sina UL; Pandharipande, Ashish; Leus, Geert

in 2010 IEEE International Conference on Acoustics Speech and Signal Processing (ICASSP) (2010, March)

We consider a two-stage sensing scheme for cognitive radios where coarse sensing based on energy detection is performed in the first stage and, if required, fine sensing based on cyclostationary detection ... [more ▼]

We consider a two-stage sensing scheme for cognitive radios where coarse sensing based on energy detection is performed in the first stage and, if required, fine sensing based on cyclostationary detection in the second stage. We design the detection threshold parameters in the two sensing stages so as to maximize the probability of detection, given constraints on the probability of false alarm. We compare this scheme with ones where only energy detection or cyclostationary detection is performed. The performance comparison is made based on the probability of detection, probability of false alarm and mean detection time. [less ▲]

Detailed reference viewed: 173 (3 UL)
Full Text
Peer Reviewed
See detailTwo-state switchable plasmonic tweezers for dynamic manipulation of nano-objects
Messina, Gabriele; Zambrana-Puyalto, Xavier; Maccaferri, Nicolò UL et al

in Nanoscale (2020), 12

In this work, we present a plasmonic platform capable of trapping nano-objects in two different spatial configurations. The switch between the two trapping states, localized on the tip and on the outer ... [more ▼]

In this work, we present a plasmonic platform capable of trapping nano-objects in two different spatial configurations. The switch between the two trapping states, localized on the tip and on the outer wall of a vertical gold nanochannel, can be activated by varying the focusing position of the excitation laser along the main axis of the nanotube. We show that the switching of the trapping site is induced by changes in the distribution of the electromagnetic field and of the trapping force. The “inner” and “outer” trapping states are characterized by a static and a dynamic behavior respectively, and their stiffness is measured by analyzing the positions of the trapped specimens as a function of time. In addition, we demonstrate that the stiffness of the static state is high enough to trap particles with diameter as small as 40 nm. These results show a simple, controllable way to generate a switchable two-state trapping regime, which could be used as a model for the study of dynamic trapping or as a mechanism for the development of nanofluidic devices. [less ▲]

Detailed reference viewed: 106 (6 UL)
Full Text
Peer Reviewed
See detailA TWO-STEP APPROACH FOR THE CORRECTION OF THE SEED MATRIX IN THE DYNAMIC DEMAND ESTIMATION
Cantelmo, Guido UL; Viti, Francesco UL; Tampère, Chris M.J. et al

in Transportation Research Record: Journal of the Transportation Research Board (2014), 2466

In this work deterministic and stochastic optimization methods are tested for solving the Dynamic Demand Estimation problem. All the adopted methods demonstrate the difficulty in reproducing the correct ... [more ▼]

In this work deterministic and stochastic optimization methods are tested for solving the Dynamic Demand Estimation problem. All the adopted methods demonstrate the difficulty in reproducing the correct traffic regime, especially if the seed matrix is not sufficiently close to the real one. Therefore, in this paper a new and intuitive procedure to specify an opportune starting seed matrix is proposed: it is a two-step procedure based on the concept of dividing the problem into small-size problems, focusing on specific OD pairs in different steps. Specifically, the first step focuses on the optimization of a subset of OD variables (the ones who generate the higher flows or the ones who generate the bottlenecks on the network). In the second step the optimization works on all the OD pairs, using as starting matrix the matrix derived from the first step. In this way is possible to use a more performance optimization method for every step, improving the performance of the method and the quality of the result with respect to the classical “one-step” approach. The procedure has been tested on the real network of Antwerp, Belgium, demonstrating its efficacy in combination with different optimization methods. [less ▲]

Detailed reference viewed: 228 (25 UL)
Full Text
See detailA two-step approach to structure the ESPON 2013 DB by themes and sub-themes
Madeira, Nuno; Caruso, Geoffrey UL

Report (2011)

Detailed reference viewed: 71 (0 UL)