In this paper, adaptive dynamic surface control (DSC) is developed for a class of pure-feedback nonlinear systems with unknown dead zone and perturbed uncertainties using neural networks. The ...explosion of complexity in traditional backstepping design is avoided by utilizing dynamic surface control and introducing integral-type Lyapunov function. It is proved that the proposed design method is able to guarantee semi-global uniform ultimate boundedness of all signals in the closed-loop system, with arbitrary small tracking error by appropriately choosing design constants. Simulation results demonstrate the effectiveness of the proposed approach.
In this paper, adaptive neural control is proposed for a class of uncertain multi-input multi-output (MIMO) nonlinear state time-varying delay systems in a triangular control structure with unknown ...nonlinear dead-zones and gain signs. The design is based on the principle of sliding mode control and the use of Nussbaum-type functions in solving the problem of the completely unknown control directions. The unknown time-varying delays are compensated for using appropriate Lyapunov–Krasovskii functionals in the design. The approach removes the assumption of linear functions outside the deadband as an added contribution. By utilizing the integral Lyapunov function and introducing an adaptive compensation term for the upper bound of the residual and optimal approximation error as well as the dead-zone disturbance, the closed-loop control system is proved to be semi-globally uniformly ultimately bounded. Simulation results demonstrate the effectiveness of the approach.
The Atmosphere Radiation Measurements Program's Ancillary Facility (AAF/SMART‐COMMIT) was deployed to Zhangye (39.082°N, 100.276°E), which is located in a semidesert area of northwest China, during ...the period of late April to mid June in 2008. We selected 11 cases to retrieve dust aerosol optical depth (AOD), Angstrom exponent, size distribution, single‐scattering albedo (SSA) and asymmetry parameter (ASY) from multifilter rotating shadowband radiometer (MFRSR) measurements. These cases are dominated by large particles with Angstrom exponent values ranging from 0.34 to 0.93. The values of AOD at 0.67 μm range from 0.07 to 0.25. The mean SSA value increases with wavelength from 0.76 ± 0.02 at 0.415 μm to 0.86 ± 0.01 at 0.870 μm, while the mean ASY value decreases from 0.74 ± 0.04 to 0.70 ± 0.02. Before estimating dust aerosol direct radiative forcing, a radiative closure experiment was performed to verify that the retrieved aerosol optical properties and other input parameters to the radiative transfer model appropriately represent atmospheric conditions. The daytime‐averaged differences between model simulations and ground observations are −8.5, −2.9, and −2.1 W m−2 for the total, diffuse, and direct normal fluxes, respectively. The mean difference in the instantaneous reflected solar fluxes at the top of atmosphere (TOA) between the model and CERES observations is 8.0 W m−2. The solar aerosol direct radiative forcing (ARF), averaged over a 24 h period, at the surface is −22.4 ± 8.9 W m−2, while the TOA ARF is small and has an average value of only 0.52 ± 1.69 W m−2. The daily averaged surface aerosol radiative forcing efficiency at 0.5 μm is −95.1 ± 10.3 W m−2τ−1. Our results illustrate that the primary role of dust aerosol is to alter the distribution of solar radiation within the climate system rather than to reflect solar energy to space. We assess the satellite aerosol optical depth products from Mutiangle Imaging Spectroradiometer (MISR) and Moderate Resolution Imaging Spectroradiometer (MODIS) observations by comparing them with our ground‐based retrievals. Reasonable agreements with the ground‐based observations are found for the MISR product and MODIS Deep Blue product.
Purpose
Arterial inflammation and vascular calcification are regarded as early prognostic markers of cardiovascular disease (CVD). In this study we investigated the relationship between CVD risk and ...arterial inflammation (
18
F-FDG PET/CT imaging), vascular calcification metabolism (Na
18
F PET/CT imaging), and vascular calcium burden (CT imaging) of the thoracic aorta in a population at low CVD risk.
Methods
Study participants underwent blood pressure measurements, blood analyses, and
18
F-FDG and Na
18
F PET/CT imaging. In addition, the 10-year risk for development of CVD, based on the Framingham risk score (FRS), was estimated. CVD risk was compared across quartiles of thoracic aorta
18
F-FDG uptake, Na
18
F uptake, and calcium burden on CT.
Results
A total of 139 subjects (52 % men, mean age 49 years, age range 21 – 75 years, median FRS 6 %) were evaluated. CVD risk was, on average, 3.7 times higher among subjects with thoracic aorta Na
18
F uptake in the highest quartile compared with those in the lowest quartile of the distribution (15.5 % vs. 4.2 %;
P
< 0.001). CVD risk was on average, 3.7 times higher among subjects with a thoracic aorta calcium burden on CT in the highest quartile compared with those in the lowest two quartiles of the distribution (18.0 % vs. 4.9 %;
P
< 0.001). CVD risk was similar in subjects in all quartiles of thoracic aorta
18
F-FDG uptake.
Conclusion
Our findings indicate that an unfavourable CVD risk profile is associated with marked increases in vascular calcification metabolism and vascular calcium burden of the thoracic aorta, but not with arterial inflammation.
We employ an exact solution of the simplest model for pump-probe time-resolved photoemission spectroscopy in charge-density-wave systems to show how, in nonequilibrium, the gap in the density of ...states disappears while the charge density remains modulated, and then the gap reforms after the pulse has passed. This nonequilibrium scenario qualitatively describes the common short-time experimental features in TaS(2) and TbTe(3), indicating a quasiuniversality for nonequilibrium "melting" with qualitative features that can be easily understood within a simple picture.
Abstract Objective The purpose of this study was to compare the effects of 3 different exercise approaches on neck muscle endurance (NME), kinesiophobia, exercise compliance, and patient satisfaction ...in patients with chronic whiplash. Methods This prospective randomized clinical trial included 216 individuals with chronic whiplash. Participants were randomized to 1 of 3 exercise interventions: neck-specific exercise (NSE), NSE combined with a behavioral approach (NSEB), or prescribed physical activity (PPA). Measures of ventral and dorsal NME (endurance time in seconds), perceived pain after NME testing, kinesiophobia, exercise compliance, and patient satisfaction were recorded at baseline and at the 3- and 6-month follow-ups. Results Compared with individuals in the prescribed physical activity group, participants in the NSE and NSEB groups exhibited greater gains in dorsal NME ( P = .003), greater reductions in pain after NME testing ( P = .03), and more satisfaction with treatment ( P < .001). Kinesiophobia and exercise compliance did not significantly differ between groups ( P > .07). Conclusion Among patients with chronic whiplash, a neck-specific exercise intervention (with or without a behavioral approach) appears to improve NME. Participants were more satisfied with intervention including neck-specific exercises than with the prescription of general exercise.
We sought to develop and validate a quantitative risk‐prediction model for predicting the risk of posttransplant in‐hospital mortality in pediatric heart transplantation (HT). Children <18 years of ...age who underwent primary HT in the United States during 1999–2008 (n = 2707) were identified using Organ Procurement and Transplant Network data. A risk‐prediction model was developed using two‐thirds of the cohort (random sample), internally validated in the remaining one‐third, and independently validated in a cohort of 338 children transplanted during 2009–2010. The best predictive model had four categorical variables: hemodynamic support (ECMO, ventilator support, VAD support vs. medical therapy), cardiac diagnosis (repaired congenital heart disease CHD, unrepaired CHD vs. cardiomyopathy), renal dysfunction (severe, mild‐moderate vs. normal) and total bilirubin (≥ 2.0, 0.6 to <2.0 vs. <0.6 mg/dL). The C‐statistic (0.78) and the Hosmer–Lemeshow goodness‐of‐fit (p = 0.89) in the model‐development cohort were replicated in the internal validation and independent validation cohorts (C‐statistic 0.75, 0.81 and the Hosmer–Lemeshow goodness‐of‐fit p = 0.49, 0.53, respectively) suggesting acceptable prediction for posttransplant in‐hospital mortality. We conclude that this risk‐prediction model using four factors at the time of transplant has good prediction characteristics for posttransplant in‐hospital mortality in children and may be useful to guide decision‐making around patient listing for transplant and timing of mechanical support.
This article describes a model to predict the risk of in‐hospital mortality in children undergoing heart transplant in the US, which the authors validated both internally in their development cohort and externally in a prospective cohort.
Cardiovascular disease (CVD) morbidity and mortality is highly prevalent in patients with rheumatoid arthritis (RA) with debilitating effects for the individual as well as significant healthcare ...impact. Current evidence demonstrates that engaging in aerobic and resistance exercise (i.e. structured physical activity) can significantly improve patient-reported and clinical index-assessed outcomes in RA. In addition to this, engagement in exercise programmes improves, in a dose-dependent manner, the risk of developing CVD as well as CVD symptoms and outcomes. The present narrative review uses evidence from systematic reviews and meta-analyses as well as controlled trials, to synthesize the current state-of-the-art on the potential effects of aerobic and resistance exercise on CVD risk factors as well as on cardiac and vascular function and structure in people with RA. Where there is a lack of evidence in RA to explain potential mechanisms, relevant studies from the general population are also discussed and linked to RA.
Flow units, which accommodate deformations and initiate transformation from glass to supercooled liquid state, have been proved to significantly influence the properties of metallic glasses (MGs). We ...study the time dependent activation of the flow units in MGs, and find that the size and the fraction of the flow units increase with the applied time, which lead to the time dependences of the mechanical behaviors, flow phenomenon and relaxations of MGs. A diagram for the flow in glass based on the concept of flow unit, activation time, and imposed energy (stress or temperature) is constructed to understand the deformations and flow mechanisms of MGs.
Display omitted
•The time dependent activation of the flow units in metallic glasses.•The time dependences of the mechanical behaviors, flow phenomenon and relaxations of metallic glasses.•A diagram for the flow in metallic glass.
Fast power converters are desired in microprocessors, audio, and servomotor power supplies. Fixed-topology dc-dc converters have a minimum time in which to respond to line, load, and control change. ...This response depends on converter control, topology, and circuit parameters. Minimum-time control (MTC) considers these three items when it predicts postdisturbance steady-state points and directs capacitor voltage and inductor current in the shortest time. In this paper a nonlinear model-predictive control steers energy using geometrical curved control surfaces derived from piecewise linear (PWL) and bilinear models. The MTC differs from previous work on the topic in that it considers lossy components (a cause for nontriangular ripple) and is an open-form solution (as originally proposed by LaSalle in 1959). The different approach revealed a quantitative link between the needed control surface memory and state/parameter resolution. Results are generalized for two-state dc-dc converters and all parameter/control disturbances. An unconventional digital method was devised to accommodate the open-form solutions. It involved a priori control surface calculations, A/D scaling, surface quantizing, and image compression. The final control executed no real-time arithmetic operations. MTC performance was compared with other pulsewidth modulation controls and time-optimal control in simulations, and tests were performed in hardware using synchronous buck and boost converters.
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