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

A Free Boundary Characterisation of the Root Barrier for Markov Processes

We study the existence, optimality, and construction of non-randomised stopping times that solve the Skorokhod embedding problem (SEP) for Markov processes which satisfy a duality assumption. These stopping times are hitting times of space-time subsets, so-called Root barriers. Our main result is, besides the existence and optimality, a potential-theoretic characterisation of this Root barrier as a free boundary. If the generator of the Markov process is sufficiently regular, this reduces to an obstacle PDE that has the Root barrier as free boundary and thereby generalises previous results from one-dimensional diffusions to Markov processes. However, our characterisation always applies and allows, at least in principle, to compute the Root barrier by dynamic programming, even when the well-posedness of the informally associated obstacle PDE is not clear. Finally, we demonstrate the flexibility of our method by replacing time by an additive functional in Root's construction. Already for multi-dimensional Brownian motion this leads to new class of constructive solutions of (SEP).Comment: 31 pages, 14 figure

KNbO3 single crystal growth by the radio frequency heating Czochralski method

A radio frequency heating Czochralski technique to obtain single crystal KNbO3 is first presented. The technological parameters of KNbO3 crystal growth by the Czochralski technique and its pulling conditions were studied in detail. The experiments on second harmonic generation using 1.06 micrometer Nd:YAG laser in KNbO3 have been conducted. The second harmonic efficiency for upconversion of KNbO3 is found to be as high as that of NaBa2Nb5O15. An automatic scanning measurement for the optical homogeneity of KNbO crystal is also described. KNbO3 is revealed to be a potentially useful nonlinear material for optical device applications

Bosonic resonating valence bond wave function for doped Mott insulators

We propose a new class of ground states for doped Mott insulators in the electron second-quantization representation. They are obtained from a bosonic resonating valence bond (RVB) theory of the t-J model. At half filling, the ground state describes spin correlations of the S=1/2 Heisenberg model very accurately. Its spin degrees of freedom are characterized by RVB pairing of spins, the size of which decreases continuously as holes are doped into the system. Charge degrees of freedom emerge upon doping and are described by twisted holes in the RVB background. We show that the twisted holes exhibit an off diagonal long range order (ODLRO) in the pseudogap ground state, which has a finite pairing amplitude, but is short of phase coherence. Unpaired spins in such a pseudogap ground state behave as free vortices, preventing superconducting phase coherence. The existence of nodal quasiparticles is also ensured by such a hidden ODLRO in the ground state, which is non-Fermi-liquid-like in the absence of superconducting phase coherence. Two distinct types of spin excitations can also be constructed. The superconducting instability of the pseudogap ground state is discussed and a d-wave superconducting ground state is obtained. This class of pseudogap and superconducting ground states unifies antiferromagnetism, pseudogap, superconductivity, and Mott physics into a new state of matter.Comment: 28 pages, 5 figures, final version to appear in Phys. Rev.

Fast extraction of somatosensory evoked potential using RLS adaptive filter algorithms

This paper evaluates the efficacy of the recursive least squares (RLS) in adaptive noise canceller (RLS-ANC) for fast extraction of somatosensory evoked potentials (SEPs). The RLSANC method was verified by simulation of electroencephalography (EEG) and Gaussian noise contaminated SEP signals at different signal-to-noise ratios (SNRs). RLS was found to converge faster than the least mean squares (LMS) algorithm in ANC, i.e. SEP extraction by RLS-ANC required fewer trials than LMS-ANC. Experimental results showed that RLS-ANC with less than 50 trials could provide similar performance in SEP extraction to those extracted by the conventional ensemble averaging with 500 trials even at SNR of - 20dB. ©2009 IEEE.published_or_final_versionThe 2nd International Congress on Image and Signal Processing (CISP 2009), Tianjin, China, 17-19 October 2009. In Proceedings of the 2nd CISP, 2009, p. 1-

Analysis of traffic noise distribution and influence factors in Chinese urban residential blocks.

To improve the acoustic environment of residential blocks, noise mapping is employed in this study to analyze traffic noise distribution and the influence factors of four types of residential blocks in China. The study shows that high-rise small blocks have the highest average noise level (Lavg) for ground and building facades, followed by small low-rise blocks while modern residential blocks yield the lowest value. An analysis of the standard deviation (STD) of spatial statistical noise level (Ln) shows that the STD of the ground and building façade of two types of small blocks is higher than that of other blocks. The analysis of influence factors indicates that the lot area of residential block has significant negative correlation with ground and building facade average noise level (Lavg), and street coverage ratio (SCR) has significant positive correlation with ground and building facade average noise level (Lavg). In low-rise and high-rise small blocks, ground space index (GSI) has significant negative correlation with ground and building facade average noise level (Lavg); street interface density (SID) has significant positive correlation with the STDs of ground and building facade noise. Floor space index (FSI) shows significant positive correlation with the STDs of ground and building facade noise in low-rise small block