121 research outputs found
Krasovskii's Passivity
In this paper we introduce a new notion of passivity which we call
Krasovskii's passivity and provide a sufficient condition for a system to be
Krasovskii's passive. Based on this condition, we investigate classes of
port-Hamiltonian and gradient systems which are Krasovskii's passive. Moreover,
we provide a new interconnection based control technique based on Krasovskii's
passivity. Our proposed control technique can be used even in the case when it
is not clear how to construct the standard passivity based controller, which is
demonstrated by examples of a Boost converter and a parallel RLC circuit
Differentiation and Passivity for Control of Brayton-Moser Systems
This paper deals with a class of Resistive-Inductive-Capacitive (RLC)
circuits and switched RLC (s-RLC) circuits modeled in Brayton Moser framework.
For this class of systems, new passivity properties using a Krasovskii's type
Lyapunov function as storage function are presented. Consequently, the
supply-rate is a function of the system states, inputs and their first
time-derivatives. Moreover, after showing the integrability property of the
port-variables, two simple control methodologies called output shaping and
input shaping are proposed for regulating the voltage in RLC and s-RLC
circuits. Global asymptotic convergence to the desired operating point is
theoretically proved for both proposed control methodologies. Moreover,
robustness with respect to load uncertainty is ensured by the input shaping
methodology. The applicability of the proposed methodologies is illustrated by
designing voltage controllers for DC-DC converters and DC networks
AUTOLOGOUS OSTEOCHONDRAL GRAFTING FOR OSTEOCHONDRITIS DESSICANS A CASE REPORT
Osteochondral defects are common injuries among the young population. Athletes are more prone to these injuries given the amount the stress and strain they put on their lower limbs. The viscoelastic nature of cartilage, which allows load bearing, is disrupted. Early recognition and treatment is needed to prevent Early Osteoarthritis. We are presenting one such case, where a 25 year old male patient with Grade 4 OCD was treated with Autologous osteochondral graft taken from the Non weight bearing part of the femur
AUTOLOGOUS OSTEOCHONDRAL GRAFTING FOR OSTEOCHONDRITIS DESSICANS A CASE REPORT
Osteochondral defects are common injuries among the young population. Athletes are more prone to these injuries given the amount the stress and strain they put on their lower limbs. The viscoelastic nature of cartilage, which allows load bearing, is disrupted. Early recognition and treatment is needed to prevent Early Osteoarthritis. We are presenting one such case, where a 25 year old male patient with Grade 4 OCD was treated with Autologous osteochondral graft taken from the Non weight bearing part of the femur
Variability of Manual Segmentation of the Prostate in Axial T2-weighted MRI: A Multi-Reader Study
Purpose
To evaluate the interreader variability in prostate and seminal vesicle (SV) segmentation on T2w MRI.
Methods
Six readers segmented the peripheral zone (PZ), transitional zone (TZ) and SV slice-wise on axial T2w prostate MRI examinations of n = 80 patients.
Twenty different similarity scores, including dice score (DS), Hausdorff distance (HD) and volumetric similarity coefficient (VS), were computed with the VISCERAL EvaluateSegmentation software for all structures combined and separately for the whole gland (WG = PZ + TZ), TZ and SV. Differences between base, midgland and apex were evaluated with DS slice-wise.
Descriptive statistics for similarity scores were computed. Wilcoxon testing to evaluate differences of DS, HD and VS was performed.
Results
Overall segmentation variability was good with a mean DS of 0.859 (±SD = 0.0542), HD of 36.6 (±34.9 voxels) and VS of 0.926 (±0.065). The WG showed a DS, HD and VS of 0.738 (±0.144), 36.2 (±35.6 vx) and 0.853 (±0.143), respectively. The TZ showed generally lower variability with a DS of 0.738 (±0.144), HD of 24.8 (±16 vx) and VS of 0.908 (±0.126). The lowest variability was found for the SV with DS of 0.884 (±0.0407), HD of 17 (±10.9 vx) and VS of 0.936 (±0.0509). We found a markedly lower DS of the segmentations in the apex (0.85 ± 0.12) compared to the base (0.87 ± 0.10, p < 0.01) and the midgland (0.89 ± 0.10, p < 0.001).
Conclusions
We report baseline values for interreader variability of prostate and SV segmentation on T2w MRI. Variability was highest in the apex, lower in the base, and lowest in the midgland
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