A game theory approach to mixed H2/H∞ control for a class of stochastic time-varying systems with randomly occurring nonlinearities

Copyright @ 2011 Elsevier B.V. This is the author’s version of a work that was accepted for publication in Systems and Control Letters. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published and may be accessed at the link below.This paper is concerned with the mixed H2/H∞ control problem for a class of stochastic time-varying systems with nonlinearities. The nonlinearities are described by statistical means and could cover several kinds of well-studied nonlinearities as special cases. The occurrence of the addressed nonlinearities is governed by two sequences of Bernoulli distributed white sequences with known probabilities. Such nonlinearities are named as randomly occurring nonlinearities (RONs) as they appear in a probabilistic way. The purpose of the problem under investigation is to design a controller such that the closed-loop system achieves the expected H2 performance requirements with a guaranteed H∞ disturbance attenuation level. A sufficient condition is given for the existence of the desired controller by means of solvability of certain coupled matrix equations. By resorting to the game theory approach, an algorithm is developed to obtain the controller gain at each sampling instant. A numerical example is presented to show the effectiveness and applicability of the proposed method

Robust H∞ control of time-varying systems with stochastic non-linearities: the finite-horizon case

The official published version can be obtained from the link below.This paper is concerned with the robust H∞ control problem for the class of uncertain non-linear discrete time-varying stochastic systems with a covariance constraint. All the system parameters are time-varying and the uncertainties enter into the state matrix. The non-linearities under consideration are described by statistical means and they cover several classes of well-studied non-linearities. The purpose of the addressed problem is to design a dynamic output-feedback controller such that, the H∞ disturbance rejection attenuation level is achieved in the finite-horizon case while the state covariance is not more than an individual upper bound at each time point. An algorithm is developed to deal with the addressed problem by means of recursive linear matrix inequalities (RLMIs). It is shown that the robust H∞ control problem is solvable if the series of RLMIs is feasible. An illustrative simulation example is given to show the applicability and effectiveness of the proposed algorithm.This work was supported in part by the Engineering and Physical Sciences Research Council (EPSRC) of the UK under grant GR/S27658/01, the Royal Society of the UK, and the Alexander von Humboldt Foundation of Germany

Robust H-infinity sliding mode control for nonlinear stochastic systems with multiple data packet losses

This is the post-print version of this Article. The official published version can be accessed from the link below - Copyright @ 2012 John Wiley & SonsIn this paper, an ∞ sliding mode control (SMC) problem is studied for a class of discrete-time nonlinear stochastic systems with multiple data packet losses. The phenomenon of data packet losses, which is assumed to occur in a random way, is taken into consideration in the process of data transmission through both the state-feedback loop and the measurement output. The probability for the data packet loss for each individual state variable is governed by a corresponding individual random variable satisfying a certain probabilistic distribution over the interval [0 1]. The discrete-time system considered is also subject to norm-bounded parameter uncertainties and external nonlinear disturbances, which enter the system state equation in both matched and unmatched ways. A novel stochastic discrete-time switching function is proposed to facilitate the sliding mode controller design. Sufficient conditions are derived by means of the linear matrix inequality (LMI) approach. It is shown that the system dynamics in the specified sliding surface is exponentially stable in the mean square with a prescribed ∞ noise attenuation level if an LMI with an equality constraint is feasible. A discrete-time SMC controller is designed capable of guaranteeing the discrete-time sliding mode reaching condition of the specified sliding surface with probability 1. Finally, a simulation example is given to show the effectiveness of the proposed method.This work was supported in part by the Engineering and Physical Sciences Research Council (EPSRC) of the U.K. under Grant GR/S27658/01, the Royal Society of the U.K., the National Natural Science Foundation of China under Grant 61028008 and the Alexander von Humboldt Foundation of German

A study on the anticancer activity of ethanol extract of Aristolochia mollissima hance on osteosarcoma HOS cells

This paper mainly studied the extraction process of traditional Chinese medicine Aristolochia mollissima Hance (Aristolochiaceae) and the inhibitory effect of its extracts on osteosarcoma HOS cells. The extraction process included the ultrasonic extraction method, heat reflux method and decoction method to obtain three different extracts. MTT assay was used to test the effect of the extracts on proliferation of HOS cells, to compare the degree of inhibitory activity of three extracts, and to calculate cell survival rates. The results showed that among the three extracts obtained by the ultrasonic extraction method, heat reflux method and decoction method, the one obtained by ultrasonic extraction has the largest yield, but the extractobtained by heat reflux method has the strongest anticancer activity. Nevertheless, the three extracts all have a good inhibitory activity on theproliferation of osteosarcoma HOS cells.Key words: Aristolochia mollissima Hance; HOS cells; MTT; Anticance

A New Method to Calculate Electromagnetic Impedance Matching Degree in One-Layer Microwave Absorbers

A delta-function method was proposed to quantitatively evaluate the electromagnetic impedance matching degree. Measured electromagnetic parameters of {\alpha}-Fe/Fe3B/Y2O3 nanocomposites are applied to calculate the matching degree by the method. Compared with reflection loss and quarter-wave principle theory, the method accurately reveals the intrinsic mechanism of microwave transmission and reflection properties. A possible honeycomb structure with promising high-performance microwave absorption according to the method is also proposed.Comment: 13 pages, 3 figure

Remediation of diesel contaminated sediments by worms (Perinereis sp.) bioturbation

21-28Impacts of bioturbation by worms on remediation of diesel contaminated sediments were studied in a laboratory experiment. The total petroleum hydrocarbons (TPH) were represented by the oil or diesel particles which were detected in seawater as well as in the upper, middle and lower layer of sediments at every three days of experiment. The whole experiment was lasted for 21 days and the TPH in the worms was measured by fluorescence analysis and the components of residual oil in the sediments were detected by gas chromatography-mass spectrometry (GC-MS) at the end of the experiment. The results showed that the TPH were declined to 18.37±0.62 and 20.85±1.74 mg/kg in the surface and sub-surface sediments, respectively, which were the worms’ frequently active areas. TPH was found to increase slightly in deeper sediments as well as in the water column because of bioturbation by worms. The feeding behavior of worms led to the accumulation of TPH in the worm’s body and was reached from 0.998±0.171 to 23.764±3.878 mg/kg. Many components of the diesel such as alkanes, Polycyclic Aromatic Hydrocarbons (PAHs) etc. were removed through bioturbation by worms. In conclusion, the petroleum hydrocarbons in the area where the worms are located will decrease over time

Cardiac magnetic resonance analysis of left atrium function in patients with pre-apical hypertrophic cardiomyopathy

Background: Patients presenting with unexplained T wave inversion on electrocardiogram combined with thickened left ventricular apex but less than 15 mm had been proposed as a preclinical scope of apical hypertrophy cardiomyopathy (pre-ApHCM). However, analysis of left atrial (LA) function in these patients has not been studied. This study aims to evaluate the LA function in pre-ApHCM patients and compare it with patients with ApHCM using cardiac magnetic resonance (CMR) imaging. Methods: In this retrospective case-control study, a total of 3,593 CMR reports from Beijing Anzhen Hospital, Capital Medical University, China were reviewed. Finally, 31 pre-ApHCM patients were identified and 40 ApHCM and 31 normal controls were included for comparison. LA volumetric and strain were analyzed by CMR. Two-tailed one-way ANOVA was used to analyze the difference of three groups. Pearson correlation test was used for correlation analysis. Results: All of the volumetric parameters in pre-ApHCM group were higher than those in control group. LA reservoir (LA total EF, εs) and conduit function (LA passive EF, εe) parameters, were significantly different among the three groups, which were the lowest in the ApHCM group, intermediate in the pre-ApHCM group, and the highest in the control group ((all P<0.001). Compared with the control group, the LA booster pump function, both the booster EF and booster pump strain (εa) in ApHCM were impaired (P=0.003 and P=0.002 respectively). Meanwhile, only the εa was impaired (P=0.016) while LA booster EF was not (P=0.064) in the pre-ApHCM group, neither εa nor the booster EF show difference between the ApHCM and pre-ApHCM (P=0.272 and P=0.518 respectively). Conclusions: LA function features in pre-ApHCM patients were similar to ApHCM but different from the normal controls. In pre-ApHCM and ApHCM patients, LA reservoir and conduit function impaired earlier before left atrium enlarged and decreased progressively as apex thickens. These findings may help to understand the LA functional change from pre-ApHCM to ApHCM, and to detect subclinical changes in patients with pre-ApHCM before overt hypertrophy or clinical symptoms develop

Proof of Gravity and Yang-Mills Amplitude Relations

Using BCFW on-shell recursion techniques, we prove a sequence of explicit n-point Kawai-Lewellen-Tye relations between gravity and Yang-Mills amplitudes at tree level.Comment: 17 pages, no figures, JHE

Remediation of diesel contaminated sediments by worms (Perinereis sp.) bioturbation

Impacts of bioturbation by worms on remediation of diesel contaminated sediments were studied in a laboratory experiment. The total petroleum hydrocarbons (TPH) were represented by the oil or diesel particles which were detected in seawater as well as in the upper, middle and lower layer of sediments at every three days of experiment. The whole experiment was lasted for 21 days and the TPH in the worms was measured by fluorescence analysis and the components of residual oil in the sediments were detected by gas chromatography-mass spectrometry (GC-MS) at the end of the experiment. The results showed that the TPH were declined to 18.37±0.62 and 20.85±1.74 mg/kg in the surface and sub-surface sediments, respectively, which were the worms’ frequently active areas. TPH was found to increase slightly in deeper sediments as well as in the water column because of bioturbation by worms. The feeding behavior of worms led to the accumulation of TPH in the worm’s body and was reached from 0.998±0.171 to 23.764±3.878 mg/kg. Many components of the diesel such as alkanes, Polycyclic Aromatic Hydrocarbons (PAHs) etc. were removed through bioturbation by worms. In conclusion, the petroleum hydrocarbons in the area where the worms are located will decrease over time

STREAMER WAVES DRIVEN BY CORONAL MASS EJECTIONS

Between July 5th and July 7th 2004, two intriguing fast coronal mass ejection(CME)-streamer interaction events were recorded by the Large Angle and Spectrometric Coronagraph (LASCO). At the beginning of the events, the streamer was pushed aside from their equilibrium position upon the impact of the rapidly outgoing and expanding ejecta; then, the streamer structure, mainly the bright streamer belt, exhibited elegant large scale sinusoidal wavelike motions. The motions were apparently driven by the restoring magnetic forces resulting from the CME impingement, suggestive of magnetohydrodynamic kink mode propagating outwards along the plasma sheet of the streamer. The mode is supported collectively by the streamer-plasma sheet structure and is therefore named "streamer wave" in the present study. With the white light coronagraph data, we show that the streamer wave has a period of about 1 hour, a wavelength varying from 2 to 4 solar radii, an amplitude of about a few tens of solar radii, and a propagating phase speed in the range 300 to 500 km s$^{-1}$. We also find that there is a tendancy for the phase speed to decline with increasing heliocentric distance. These observations provide good examples of large scale wave phenomena carried by coronal structures, and have significance in developing seismological techniques for diagnosing plasma and magnetic parameters in the outer corona.Comment: 8 pages, 7 figures, accepted for publication in Ap