Search results for " Optics"

Surrogate Modelling for Oxygen Uptake Prediction Using LSTM Neural Network

2023

Oxygen uptake (V˙O2) is an important metric in any exercise test including walking and running. It can be measured using portable spirometers or metabolic analyzers. Those devices are, however, not suitable for constant use by consumers due to their costs, difficulty of operation and their intervening in the physical integrity of their users. Therefore, it is important to develop approaches for the indirect estimation of V˙O2-based measurements of motion parameters, heart rate data and application-specific measurements from consumer-grade sensors. Typically, these approaches are based on linear regression models or neural networks. This study investigates how motion data contribute to V˙O2 …

Copper-hydride nanoclusters with enhanced stability by N-heterocyclic carbenes

2021

AbstractCopper-hydrides have been intensively studied for a long time due to their utilization in a variety of technologically important chemical transformations. Nevertheless, poor stability of the species severely hinders its isolation, storage and operation, which is worse for nano-sized ones. We report here an unprecedented strategy to access to ultrastable copper-hydride nanoclusters (NCs), namely, using bidentate N-heterocyclic carbenes as stabilizing ligands in addition to thiolates. In this work, a simple synthetic protocol was developed to synthesize the first large copper-hydride nanoclusters (NCs) stabilized by N-heterocyclic carbenes (NHCs). The NC, with the formula of Cu31(RS)2…

CO(2)-water supercritical mixtures: Test of a potential model against neutron diffraction data

2007

Abstract A neutron diffraction experiment on supercritical mixtures of water and CO 2 at two concentrations is presented. Data are analyzed within the EPSR framework and the water–water and water–CO 2 radial distribution functions are compared with those calculated by a Molecular Dynamics simulation performed by using the TIPS2 and EPM-M potential models for water and CO 2 respectively. It is found that the Molecular Dynamics simulation reproduces the overall shape of the site–site radial distribution functions, although missing a few subtle changes brought along when the CO 2 concentration is increased.

Engineered surface waves in hyperbolic metamaterials

2013

We analyzed surface-wave propagation that takes place at the boundary between a semi-infinite dielectric and a multilayered metamaterial, the latter with indefinite permittivity and cut normally to the layers. Known hyperbolization of the dispersion curve is discussed within distinct spectral regimes, including the role of the surrounding material. Hybridization of surface waves enable tighter confinement near the interface in comparison with pure-TM surface-plasmon polaritons. We demonstrate that the effective-medium approach deviates severely in practical implementations. By using the finite-element method, we predict the existence of long-range oblique surface waves. This research was fu…

Variable fractional Fourier processor: a simple implementation: erratum

1997

Spin-lattice relaxation of deuterated methyl groups: Implications of the pauli principle

1999

The high-field spin-lattice relaxation of deuterated methyl groups undergoing rotational tunneling is investigated theoretically. It is found that for systems showing a tunneling frequency comparable to accessible Larmor frequencies the relaxation to equilibrium of the Zeeman energy does not follow a simple exponential time dependence even in powdered samples due to a finite coupling to the relaxation of the tunneling system. This finding contrasts to the high-temperature behavior of reorienting methyl groups which undergo simple exponential relaxation. The nonexponentiality has its origin in the statistical coupling of the three deuteron spins due to the Pauli principle.

Symmetry breaking in ligand-protected gold clusters probed by nonlinear optics

2016

The first hyperpolarizabilities of [Au25(SR)18](-1/0) and Au38(SR)24 clusters were determined by Hyper-Rayleigh Scattering. A strong dependence on the molecular symmetry was observed, and we explore two strategies to destroy the center of inversion in [Au25(SR)18](-1/0), protection by chiral ligands and alloying of the cluster with silver. This may open new avenues to applications of Au : SR clusters in second-order nonlinear optics.

Force Distribution Analysis of Mechanochemically Reactive Dimethylcyclobutene

2013

Internal molecular forces can guide chemical reactions, yet are not straightforwardly accessible within a quantum mechanical description of the reacting molecules. Here, we present a force-matching force distribution analysis (FM-FDA) to analyze internal forces in molecules. We simulated the ring opening of trans-3,4-dimethylcyclobutene (tDCB) with on-the-fly semiempirical molecular dynamics. The self-consistent density functional tight binding (SCC-DFTB) method accurately described the force-dependent ring-opening kinetics of tDCB, showing quantitative agreement with both experimental and computational data at higher levels. Mechanical force was applied in two different ways, namely, exter…

Curvelet-based method for orientation estimation of particles from optical images

2014

A method based on the curvelet transform is introduced to estimate the orientation distribution from two-dimensional images of small anisotropic particles. Orientation of fibers in paper is considered as a particular application of the method. Theoretical aspects of the suitability of this method are discussed and its efficiency is demonstrated with simulated and real images of fibrous systems. Comparison is made with two traditionally used methods of orientation analysis, and the new curvelet-based method is shown to perform better than these tradi- tional methods. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of th…

Coupling high-resolution satellite imagery with ALS-based canopy height model and digital elevation model in object-based boreal forest habitat type …

2014

We developed a classification workflow for boreal forest habitat type mapping. In object-based image analysis framework, Fractal Net Evolution Approach segmentation was combined with random forest classification. High-resolution WorldView-2 imagery was coupled with ALS based canopy height model and digital terrain model. We calculated several features (e.g. spectral, textural and topographic) per image object from the used datasets. We tested different feature set alternatives; a classification accuracy of 78.0 % was obtained when all features were used. The highest classification accuracy (79.1 %) was obtained when the amount of features was reduced from the initial 328 to the 100 most imp…