49 research outputs found

    Treatment of hemimasticatory spasm secondary to parry-romberg syndrome via partial resection of the trigeminal nerve motor branch under intraoperative neurophysiological monitoring: A case report and literature review

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    Parry-Romberg syndrome (PRS) combined with hemimasticatory spasm (HMS) is a rare craniofacial disorder characterized by unilateral facial tissue atrophy with paroxysmal involuntary contractions of the jaw-closing muscles. Although a majority believe that this is a result of demyelination changes from the effect of the facial involvement of PRS on the trigeminal nerve motor branches, the mechanism of PRS is presently unclear. Moreover, the therapeutic effects of existing drugs that target PRS have not been satisfactory. For intolerable spasms of the masticatory muscles, botulinum toxin injection may temporarily relieve the symptoms of spasms. We report a case of HMS secondary to PRS that was treated via a partial resection of the trigeminal nerve motor branch under intraoperative neurophysiological monitoring

    The level effect and volatility effect of uncertainty shocks in China

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    Previous studies have assumed that the volatility of exogenous shocks is constant, which can only measure the level effects of uncertain shocks. This article introduces the time-varying volatility model into a Dynamic Stochastic General Equilibrium (D.S.G.E.) model and uses the third-order perturbation method to identify and decompose the level and volatility effects of uncertainty shocks. Based on the results of empirical research in China, the effect of volatility shocks is different from that of level shocks: the effect of level shocks is direct and positive, and its impact is larger, while the effect of volatility shocks is indirect and negative, and its impact is smaller. This article also finds that the impact of uncertainty shocks will lead to economic stagnation, inflation, and the stagflation effect

    Analysis of electrical drive speed control limitations of a power take-off system for wave energy converters

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    The active control of wave energy converters with oil-hydraulic power take-off systems presents important demands on the electrical drives attached to their pumps, in particular on the required drive accelerations and rotational speeds. This work analyzes these demands on the drives and designs reliable control approaches for such drives by simulating a wave-to-wire model in a hardware in-the-loop simulation test rig. The model is based on a point absorber wave energy converter, being the wave, hydrodynamic and oil-hydraulic part simulated in a computer that sends and receives signals from the real embedded components, such as the drive generator, controller and back-to-back converter. Three different control strategies are developed and tested in this test rig and the results revealed that despite the drive limitations to acceleration levels, well above 1 × 104 rpm/s, these do not significantly affect the power take-off efficiency, because the required acceleration peaks rarely achieve these values. Moreover this drive is much more economical than an oil-hydraulic and equivalent one that is able to operate at those peaks of acceleration.This work was performed within the Strategic Research Plan of the Center for Marine Technology and Ocean Engineering, which is financed by Portuguese Foundation for Science and Technology (Fundacao para a Ciencia e Tecnologia-FCT) and the project "Generic hydraulic power take-off system for wave energy converters" funded by the Portuguese Foundation for Science and Technology (FCT) under contract PTDC/EMS-SIS-1145/2014. The testing has received support from MARINET, a European Community - Research Infrastructure Action under the FP7 "Capacities" Specific Programme, grant agreement nr. 262552. The research leading to these results is also part of the OceaNET project, which has received funding from the European Union's Seventh Framework Programme for research, technological development and demonstration under grant agreement nr. 607656

    The Mental Health of Healthcare Staff Working During the COVID-19 Crisis: Their Working Hours as a Boundary Condition

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    Purpose: Healthcare staff operate at the forefront of the fight against COVID-19 and hence face enormous physical and mental pressures. We aim to investigate healthcare staff’s mental health issues and the associated predictors during the COVID-19 pandemic. Specifically, this paper aims to identify some unique predictors of healthcare staff’s mental health issues in Iran, the second country after China to experience a major COVID-19 crisis. Methods: An online survey of 280 healthcare staff in all 31 provinces of Iran assessed staff’s mental distress (K6), depression, and anxiety (PHQ-4) during April 5–20, 2020 during the COVID-19 crisis. Results: Nearly a third of healthcare staff surpassed the cut-off for distress, depression, and anxiety symptoms. Females or more educated healthcare staff were more likely to experience distress. Those who were unsure whether they had COVID-19 were more likely to experience distress and depression symptoms. The number of COVID-19 cases among a healthcare worker’s colleagues or friends positively predicted the worker’s anxiety symptoms. Amongst healthcare staff, doctors were less likely than radiology technologists to experience distress and anxiety symptoms. Technicians and obstetrics staff experienced fewer anxiety symptoms. The age and the weekly working days of healthcare staff interacted such that age is a significant predictor of mental health issues among younger but not older healthcare staff. Conclusion: The identification of the predictors of mental health issues can guide healthcare organizations to screen healthcare workers who are more likely to be mentally vulnerable in the ongoing COVID-19 pandemi

    Uncertainty analysis of the hydrodynamic coefficients estimation of a nonlinear manoeuvring model based on planar motion mechanism tests

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    Uncertainty analysis of the identified hydrodynamic coefficients of a nonlinear manoeuvring model is presented in this paper. The classical parameter estimation method, Least Square, is briefly introduced, and the uncertainty of the hydrodynamic coefficients due to the noise in the measured data is analysed using singular value decomposition. Then, two methods, truncated singular values decomposition and Tikhonov regularization, are introduced to diminish the uncertainty. A nonlinear manoeuvring mathematical model of a marine surface ship is derived using Lagrange's method. The dimensionless hydrodynamic coefficients are obtained using the Least Squares method, truncated singular values decomposition and Tikhonov regularization with Planar Motion Mechanism test data. The validation process is carried out to test the performance and accuracy of the resulting nonlinear manoeuvring models. The result shows that identification of the uncertain parameters using the truncated singular values decomposition and Tikhonov regularization resulted in good estimating the parameters and significantly diminish the uncertainty.acceptedVersio

    Unbalance Suppression for AMB Rotor System Using APF-SRF Algorithm

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    With the great capability in levitating rotors, active magnetic bearings (AMB) have been increasingly applied in high-speed rotating machinery applications. Typically, for the practical application of AMB rotor systems, synchronous unbalance vibration has long been a critical issue. Thus, exploring a facile yet effective approach to address this issue has attracted tremendous interest from both industrial and academic perspectives. Herein, in this work, we propose a novel strategy to suppress the unbalance vibration through a compensation control algorithm method. The compensation control algorithm which is established based on the combination of first-order all-pass filter (APF) and synchronous rotating frame (SRF) algorithm demonstrates to be efficient in greatly reducing the unbalance vibration and resulting in excellent system stability according to both simulation and experimental results. This work not only confirms the applicability of APF-SRF algorithm for the AMB rotor systems but also opens up a new paradigm to modulate and minimize the unbalance vibration of AMB rotor systems

    Parameters Estimation of Nonlinear Manoeuvring Model for Marine Surface Ship Based on PMM Tests

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    A nonlinear manoeuvring mathematical model of marine surface ship model is briefly introduced. In order to obtain the hydrodynamic coefficients, system identification is used to estimate the parameters using Planar Motion Mechanism (PMM) test data. Usually, the obtained parameters using measured data have a large uncertainty due to the ill-conditioned processes of identification. An optimal Truncated Singular Value Decomposition (TSVD) method is exploited to reduce the uncertainty of the estimated parameters. The optimal number of retaining singular values is calculated by using the L-curve, which is a log-log plot of the norm of a regularized solution versus the norm of the corresponding residual norm. It is a graphical tool for displaying the trade-off between the estimated parameters norm and the corresponding residual error norm. The validation process is performed by comparison of the prediction values with the experimental data in the time domain
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