34,639 research outputs found
Ownership structure and efficiency: An incentive mechanism approach
Corporate Performance;Corporate Ownership
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Relativistic Ab initio Study On PtF and HePtF
The electronic structures and spectroscopic constants of the first three low-lying electronic states (Omega = 1/2, 3/2, and 5/2) of the linear HePtF complex were investigated by highly accurate relativistic ab initio methods, in which the spin-orbit coupling was taken into account, and compared with the results of PtF. It shows that the complex is significantly different from the typical van der Waals systems because of short He-Pt bond distances (1.80 similar to 1.87 angstrom), large He-Pt stretching frequencies (500 similar to 600 cm(-1)), considerable binding energies (1400 similar to 2500 cm(-1) with corrections), and a small electron transfer from helium (about 0.06). However, the topological analysis of the electron density distribution indicates that there is strong van der Waals interaction in the He-Pt bond instead of weak covalent one.Welch Foundation F-100Chemistr
Monopoles without magnetic charges: Finite energy monopole-antimonopole configurations in CP1 model and restricted QCD
We propose a new type of regular monopole-like field configuration in quantum
chromodynamics (QCD) and CP^1 model. The monopole configuration can be treated
as a monopole-antimonopole pair without localized magnetic charges. An exact
numeric solution for a simple monopole-antimonopole solution has been obtained
in CP^1 model with an appropriate potential term. We suppose that similar
monopole solutions may exist in effective theories of QCD and in the
electroweak standard model.Comment: 8 pages, 8 figures, 1 table, final version accepted by Phys. Lett.
Subject-specific finite element modelling of the human hand complex : muscle-driven simulations and experimental validation
This paper aims to develop and validate a subject-specific framework for modelling the human hand. This was achieved by combining medical image-based finite element modelling, individualized muscle force and kinematic measurements. Firstly, a subject-specific human hand finite element (FE) model was developed. The geometries of the phalanges, carpal bones, wrist bones, ligaments, tendons, subcutaneous tissue and skin were all included. The material properties were derived from in-vivo and in-vitro experiment results available in the literature. The boundary and loading conditions were defined based on the kinematic data and muscle forces of a specific subject captured from the in-vivo grasping tests. The predicted contact pressure and contact area were in good agreement with the in-vivo test results of the same subject, with the relative errors for the contact pressures all being below 20%. Finally, sensitivity analysis was performed to investigate the effects of important modelling parameters on the predictions. The results showed that contact pressure and area were sensitive to the material properties and muscle forces. This FE human hand model can be used to make a detailed and quantitative evaluation into biomechanical and neurophysiological aspects of human hand contact during daily perception and manipulation. The findings can be applied to the design of the bionic hands or neuro-prosthetics in the future
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Neuromodulated attention and goal-driven perception in uncertain domains.
In uncertain domains, the goals are often unknown and need to be predicted by the organism or system. In this paper, contrastive Excitation Backprop (c-EB) was used in two goal-driven perception tasks - one with pairs of noisy MNIST digits and the other with a robot in an action-based attention scenario. The first task included attending to even, odd, low, and high digits, whereas the second task included action goals, such as "eat", "work-on-computer", "read", and "say-hi" that led to attention to objects associated with those actions. The system needed to increase attention to target items and decrease attention to distractor items and background noise. Because the valid goal was unknown, an online learning model based on the cholinergic and noradrenergic neuromodulatory systems was used to predict a noisy goal (expected uncertainty) and re-adapt when the goal changed (unexpected uncertainty). This neurobiologically plausible model demonstrates how neuromodulatory systems can predict goals in uncertain domains and how attentional mechanisms can enhance the perception for that goal
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