Computing the minimum distance between a point and a NURBS curve

International audienceA new method is presented for computing the minimum distance between a point and a NURBS curve. It utilizes a circular clipping technique to eliminate the curve parts outside a circle with the test point as its center point. The radius of the elimination circle becomes smaller and smaller during the subdivision process. A simple condition for terminating the subdivision process is provided, which leads to very few subdivision steps in the new method. Examples are shown to illustrate the efficiency and robustness of the new method

Computing the minimum distance between a point and a clamped B-spline surface

International audienceThe computation of the minimum distance between a point and a surface is important for the applications such as CAD/CAM, NC verification, robotics and computer graphics. This paper presents a spherical clipping method to compute the minimum distance between a point and a clamped B-spline surface. The surface patches outside the clipping sphere which do not contain the nearest point are eliminated. Another exclusion criterion whether the nearest point is on the boundary curves of the surface is employed, which is proved to be superior to previous comparable criteria. Examples are also shown to illustrate efficiency and correctness of the new method

Computing the minimum distance between two Bézier curves

International audienceA sweeping sphere clipping method is presented for computing the minimum distance between two Bézier curves. The sweeping sphere is constructed by rolling a sphere with its center point along a curve. The initial radius of the sweeping sphere can be set as the minimum distance between an end point and the other curve. The nearest point on a curve must be contained in the sweeping sphere along the other curve, and all of the parts outside the sweeping sphere can be eliminated. A simple sufficient condition when the nearest point is one of the two end points of a curve is provided, which turns the curve/curve case into a point/curve case and leads to higher efficiency. Examples are shown to illustrate efficiency and robustness of the new method

Modes of Antiviral Action of Chemical Portions and Constituents from Woad Root Extract against Influenza Virus A FM1

Woad root has been used for the prevention of influenza for hundreds of years in many Asian countries. In this study, the antiviral modes of clemastanin B (CB), epigoitrin, phenylpropanoid portion (PEP), and the mixture of phenylpropanoids, alkaloids, and organic acid portions (PEP + ALK + OA) from wood root extract against influenza virus A FM1 were investigated. The results revealed that CB, epigoitrin, PEP, and PEP + ALK + OA exert their anti-influenza activity via inhibiting the virus multiplication, prophylaxis, and blocking the virus attachment. The primary mode of action of PEP and PEP + ALK + OA is the inhibition of virus replication. The inhibitory effect on virus attachment and multiplication is the main modes for epigoitrin. All the compounds or chemical portions from woad root extract tested in this study do not have direct virucidal activity. Our results provided the comprehensive analysis of the antiviral mechanism of wood root extract

Anisotropy of Antiferromagnetic Domains in a Spin-orbit Mott Insulator

The temperature-dependent behavior of magnetic domains plays an essential role in the magnetic properties of materials, leading to widespread applications. However, experimental methods to access the three-dimensional (3D) magnetic domain structures are very limited, especially for antiferromagnets. Over the past decades, the spin-orbit Mott insulator iridate $Sr_2IrO_4$ has attracted particular attention because of its interesting magnetic structure and analogy to superconducting cuprates. Here, we apply resonant x-ray magnetic Bragg coherent diffraction imaging to track the real-space 3D evolution of antiferromagnetic ordering inside a $Sr_2IrO_4$ single crystal as a function of temperature, finding that the antiferromagnetic domain shows anisotropic changes. The anisotropy of the domain shape reveals the underlying anisotropy of the antiferromagnetic coupling strength within $Sr_2IrO_4$. These results demonstrate the high potential significance of 3D domain imaging in magnetism research

Robust variable structure observer design for non-linear large-scale systems with non-linear interconnections

In this paper, a variable structure observer is designed for a class of non-linear large-scale interconnected systems in the presence of uncertainties and non-linear interconnections. The modern geometric approach is used to explore system structure and a transformation is employed to facilitate the observer design. Based on the Lyapunov direct method, a set of conditions are developed such that the proposed variable structure systems can be used to estimate the states of the original interconnected systems asymptotically. The internal dynamical structure of the isolated nominal subsystems as well as the structure of the uncertainties are employed to reduce the conservatism. The bounds on the uncertainties are non-linear and are employed in the observer design to reject the effect of the uncertainties. A numerical example is presented to illustrate the approach and the simulation results showthat the proposed approach is effective

Joint associations between weekday and weekend physical activity or sedentary time and childhood obesity

OBJECTIVE: To evaluate the single and joint associations of objectively measured moderate-to-vigorous physical activity (MVPA) and sedentary time on week and weekend days with obesity in children from 12 countries across all inhabited continents.METHODS: A multinational, 12-country cross-sectional study of 5779 children aged 9-11 years was conducted. Time spent in MVPA and sedentary behaviors was assessed by waist-worn accelerometry. Logistic regression was used to examine the independent and joint associations of MVPA and sedentary time on weekdays and weekend with the odds of obesity.RESULTS: After adjustment for all confounding factors, the odds ratios (ORs) of childhood obesity were the highest among children with a low level of MVPA on both weekdays and weekend (OR 4.67), high among children with a high level of MVPA on weekdays and a low level of MVPA on weekend (OR 1.99) and high among children with a low level of MVPA on weekdays and a high levels of MVPA on weekend (OR 2.20), compared to those with a high level of MVPA on both weekdays and weekend. Similarly, the ORs of childhood obesity were significantly higher among children with a high level of sedentary time on both weekdays and weekend (OR 1.87) compared with those with low levels of sedentary time on both weekdays and weekend.CONCLUSIONS: Lower levels of MVPA or higher levels of sedentary time on either weekdays or weekend were associated with increased odds of obesity in 9-11 year old children in 12 countries.</p

Insights into the mechanism of nitrobenzene reduction to aniline over Pt catalyst and the significance of the adsorption of phenyl group on kinetics

This paper was accepted for publication in the journal Chemical Engineering Journal and the definitive published version is available at http://dx.doi.org/10.1016/j.cej.2016.02.066Aniline (C6H5NH2) plays a significant role in both industry and daily life, and can be synthesized via catalytic hydrogenation of nitrobenzene (C6H5NO2) over transition metals; however fundamental investigations on reaction mechanisms in the heterogeneous catalysis are still lacking. In this work, the nitrobenzene reduction reaction over the Pt(111) model catalyst was studied using density functional theory (DFT) with the inclusion of van der Waals interaction, for fundamentally understanding the mechanisms at atomic and molecular levels. It was found that the double H-induced dissociation of N-O bond was the preferential path for the activation of nitro group, having a much lower reaction barrier than that of the direct dissociation and single H-induced dissociation paths. The overall mechanisms have been identified as: C6H5NO2* → C6H5NOOH* → C6H5N(OH)2* → C6H5NOH* → C6H5NHOH* → C6H5NH* → C6H5NH2*. The overall barrier of the nitro group reduction was calculated to be 0.75 eV, which is much lower than that of the benzene reduction (1.08 eV). Our DFT data elucidates clearly the reason why the major product of nitrobenzene reduction reaction was aniline. Furthermore, the adsorption/desorption of phenyl group was found to have significant impacts on kinetic barriers. Generally, in the hydrogenation process (N-H or O-H bond association), the phenyl group preferred to adsorb on the surface; but in the dissociation process (N-O bond dissociation) it preferred to desorb transiently at the transition state and to adsorb again when the dissociation was completed. This study also provides a solid theoretical insight into the selective catalysis of the large aromatic compounds