Neurologic findings are being increasingly recognized in coronavirus disease 2019. We present a patient with a unique involvement of the corpus callosum that we relate to the cytokine storm seen in ...patients with Severe Acute Respiratory Syndrome coronavirus 2 infection. As the infection is increasingly seen around the world, recognition of these unique patterns may facilitate early identification of the progression of this disease and potentially facilitate appropriate management.
One of the important issues in networked control systems is the appropriate handling of the nonlinearities arising from uncertain time-varying delays. In this paper, using the Cayley–Hamilton ...theorem, we develop a novel method for creating discrete-time models of linear systems with time-varying input delays based on polytopic inclusions. The proposed method is compared with existing approaches in terms of conservativeness, scalability and suitability for controller synthesis.
This note addresses the output feedback stabilization problem of a chain of integrators using multiple delays. We shall prove that either n distinct delays or a proportional+delay compensator with ...n-1 distinct delays are sufficient to stabilize a chain including n integrators. We present two different approaches. Both are constructive and rely on frequency-domain techniques: on a derivative feedback approximation idea, and a pole placement idea, respectively. An illustrative example (triple integrator) is presented.
On the shape of the d¯−u¯ asymmetry Accardi, A.; Keppel, C.E.; Li, S. ...
Physics letters. B,
02/2020, Letnik:
801, Številka:
C
Journal Article
Recenzirano
Odprti dostop
Using data from a recent reanalysis of neutron structure functions extracted from inclusive proton and deuteron deep-inelastic scattering (DIS), we re-examine the constraints on the shape of the ...d¯−u¯ asymmetry in the proton at large parton momentum fractions x. A global analysis of the proton–neutron structure function difference from BCDMS, NMC, SLAC and Jefferson Lab DIS measurements, and of Fermilab Drell-Yan lepton-pair production cross sections, suggests that existing data can be well described with d¯>u¯ for all values of x currently accessible. We compare the shape of the fitted d¯−u¯ distributions with expectations from nonperturbative models based on chiral symmetry breaking, which can be tested by upcoming Drell-Yan data from the SeaQuest experiment at larger values of x.
This paper focuses on the design of P-δ controllers for single-input-single-output linear time-invariant systems. The basis of this work is a geometric approach allowing to partitioning the parameter ...space in regions with constant number of unstable roots. This methodology defines the hyper-planes separating the aforementioned regions and characterises the way in which the number of unstable roots changes when crossing such a hyper-plane. The main contribution of the paper is that it provides an explicit tool to find P-δ gains ensuring the stability of the closed-loop system. In addition, the proposed methodology allows to design a non-fragile controller with a desired exponential decay rate σ. Several numerical examples illustrate the results and a haptic experimental set-up shows the effectiveness of P-δ controllers.
In drilling operations, the interaction of the drillstring with the borehole leads to vibrations affecting the performance and increasing the drilling cost. The development of controllers to get a ...faster and efficient drilling operation is based on a mathematical modeling allowing a proper system characterization and the identification of the vibration sources to avoid them or mitigate their influence. This paper presents an overview of the modeling of axial and torsional self-excited drilling vibrations.
This note presents some sufficient conditions for a linear system with (point or distributed) delay in the state to be passive. Passivity based (memoryless) stabilization of linear delay systems is ...also addressed. The proposed approach is based on a Lyapunov-Krasovskii functional construction. Numerical examples are also included.
We study the stability of a linear system with a point-wise, time-varying delay. We assume that the delay varies around a nominal value in a deterministic way and investigate the influence of this ...variation on stability. More precisely we are interested in characterizing situations where the time-varying delay system is stable, whereas the system with constant delay is unstable. Our approach consists of relating the stability properties of a system with a fast varying point-wise delay with these of a time-invariant system with a distributed delay. Then we can use frequency domain methods to analyze the problem and to derive stability criteria. The results are first illustrated with two theoretical examples. Then, we study a model of a variable speed rotating cutting tool. Based on the developed theory, we thereby provide both a theoretical explanation and a quantitative analysis tool for the beneficial effect of a variation of the machine speed on enhancing stability properties, which was reported in the literature.
Background
Seasonal influenza outbreaks are associated with increased mortality and hospitalisation rates. Herein we tried to identify predictors of mortality in hospitalised patients with influenza ...virus infection.
Materials/methods
In this exploratory retrospective observational single-centre-study we included all influenza-positive patients older than 18 years who were hospitalised and treated at the flu-isolation-ward during the influenza season 2017/18. Diagnosis was based on point-of-care-test with the Alere™ i. First we performed
χ
2
tests and Mann–Whitney
U
tests to identify predictors of mortality. Significant variables were used in a stepwise-forward-logistic-regression-model to predict in-hospital and 90-day mortality.
Results
Of the 396 patients who tested positive for influenza 96 (24.2%) had influenza A and 300 (75.8%) influenza B. Twenty-two (5.6%) died in hospital and the 90-day mortality rate was 9.4%. In the stepwise logistic regression older age (OR 1.1 per year 95% CI 1.03–1.17), history of atrial fibrillation (OR 5.91 95% CI 1.91–18.34), dementia (OR 3.98 95% CI 1.24–12.78), leucocyte count (OR 1.11 per G/L 95% CI 1.03–1.20), pneumonia (OR 4.39 95% CI 1.44–13.39) and acute heart failure (OR 23.15 95% CI 4.33–123.76) increased the risk of in-hospital mortality. The risk for 90-day mortality was increased by older age (OR 1.04 per year 95% CI 1.01–1.07), history of atrial fibrillation (OR 3.1, 95% CI 1.36–7.05), history of congestive heart failure (OR 4.7 95% CI 1.94–11.48), pneumonia (OR 3.2 95% CI 1.45–6.91) and decreased by statin use (OR 0.28 95% CI 0.10–0.78).
Conclusions
Older age, history of atrial fibrillation and pneumonia are associated with increased risk of influenza-associated in-hospital and 90-day mortality. Statin use may decrease 90-day mortality.
In this paper, we propose a method of iterative proportional-integral-derivative parameter tuning for mechanical systems that possibly possess hidden mechanical resonances, using a parameter chart ...which visualises the closed-loop characteristics in a 2D parameter space. We employ a hypothetical assumption that the considered mechanical systems have their upper limit of the derivative feedback gain, from which the feasible region in the parameter chart becomes fairly reduced and thus the gain selection can be extremely simplified. Then, a two-directional parameter search is carried out within the feasible region in order to find the best set of parameters. Experimental results show the validity of the assumption used and the proposed parameter tuning method.
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