Mixed sensitivity H_∞ control for LTI systems with varying time delays

Designing a robust controller for a system with timevarying delays poses a major challenge. In this paper, we propose a method based on mixed sensitivity H∞ for the control of linear time invariant（LTI） systems with varying time delays. The time delay is assumed bounded and the upper bound is known. In the technique we propose, the delay affecting the plant to be controlled is treated as an unmodeled uncertainty（in form of multiplicative uncertainty）. That uncertainty is approximated and then an H∞based controller, for the plant represented by the multiplicative uncertainty and the nominal model, is calculated. The obtained H∞controller is used to control the LTI systems with varying time delays. Simulation examples are given to illustrate the effectiveness of the proposed method.

A unified approach of PID controller design for unstable processes with time delay

This paper addresses a unified approach of the PID controller design for low as well as high order unstable processes with time delay.The design method is based on the direct synthesis(DS)approach to achieve the enhanced load disturbance rejection.To improve the servo response,a two-degree of freedom control scheme has been considered.A suitable guideline has been provided to select the desired reference model in the DS scheme.The direct synthesis controller has been approximated to the PID controller using the frequency response matching method.A consistently better performance has been obtained in comparison with the recently reported methods.

An Analytical Delay Model

Delay considerttion has been a major issue in design and test of high performance digital circuits . The assumption of input signal change occurring only when all internal nodes are stable restricts the increase of clock frequency. It is no longer true for wave pipelining circuits. However, previous logical delay models are based on the assumption. In addition, the stable time of a robust delay test generally depends on the longest sensitizable path delay. Thus , a new delay model is desirable. This paper explores the necessity first. Then, Boolean process to analytically describe the logical and timing behavior of a digital circuit is reviewed . The concept of sensitization is redefined precisely in this paper. Based on the new concept of sensitization, an analytical delay model is introduced . As a result , many untestable delay faults under the logical delay model can be tested if the output waveforms can be sampled at more time points. The longest sensitiaable path length is computed for circuit design and delay test .

Gender difference in network relationship between inter-temporal decisions and prefrontal activation levels in internet gaming disorder

Background:Impulsivity and decision-making are key factors in addiction.However,little is known about how gender and time sensitivity affect impulsivity in internet gaming disorder(IGD).Objective:To investigate the gender difference of impulsive decision-making and relevant brain responses in IGD.Methods:We conducted a functional magnetic resonance imaging(fMRI)study with 123 participants,including 59 IGD individuals(26 females)and 64 matched recreational game users(RGUs,23 females).Participants performed a delay-discounting task during fMRI scanning.We examined gender-by-group effects on behavioral and neural measures to explore the preference for immediate over delayed rewards and the associated brain activity.We also investigated the network correlations between addiction severity and behavioral and neural measures,and analyzed the mediating role of brain activity in the link between delay discounting parameters and IGD severity.Results:We found significant gender-by-group interactions.The imaging results revealed gender-by-group interactions in the dor-solateral prefrontal cortex,medial frontal gyrus,and inferior frontal gyrus(IFG).Post hoc analysis indicated that,for females,RGUs showed higher activity than IGD individuals in these brain regions,while for males IGD individuals exhibited higher activity than RGUs.The activation in the left IFG mediated the relation between Internet Addiction Test score and discount rate in females.In males,the activation in the right dlPFC mediated the relation between IAT score and time sensitivity.Discussion:Our findings imply that male IGD participants demonstrate impaired intertemporal decisions associated with neural dysfunction.Influencing factors for impulsive decision-making in IGD diverge between males(time sensitivity)and females(discount rate).These findings augment our comprehension of the neural underpinnings of gender differences in IGD and bear significant implications for devising effective intervention strategies for treating people with IGD.

Auto-ignition of biomass synthesis gas in shock tube at elevated temperature and pressure

Ignition delay times of multi-component biomass synthesis gas （bio-syngas） diluted in argon were measured in a shock tube at elevated pressure （5, 10and 15 bar, 1 bar = 105 Pa）, wide temperature ranges （1,100-1,700 K） and various equivalence ratios （0.5, 1.0, 2.0）. Additionally, the effects of the variations of main constituents （H2：CO = 0.125-8） on ignition delays were investigated. The experimental results indicated that the ignition delay decreases as the pressure increases above certain temperature （around 1,200 K） and vice versa. The ignition delays were also found to rise as CO concentration increases, which is in good agreement with the literature. In addition, the ignition delays of bio-syngas were found increasing as the equivalence ratio rises. This behavior was primarily discussed in present work. Experimental results were also compared with numerical predictions of multiple chemical kinetic mechanisms and Li＇s mechanism was found having the best accuracy. The logarithmic ignition delays were found nonlinearly decrease with the H2 concentration under various conditions, and the effects of temperature, equivalence ratio and H2 concentration on the ignition delays are all remarkable. However, the effect of pressure is rela- tively smaller under current conditions. Sensitivity analysis and reaction pathway analysis of methane showed that R1 （H ＋O2= O -9 OH） is the most sensitive reaction promot- ing ignition and R13 （H ＋O2 （＋M） = HO2 （＋M））, R53（CH3＋H （＋M）= CH4 （＋M））, R54 （CH4＋H= CH3 ＋ H2） as well as R56 （CH4 ＋ OH = CH3 ＋ H2O） are key reactions prohibiting ignition under current experimental conditions. Among them, R53 （CH3 ＋ H （＋M） = CH4 （＋M））, R54 （CH4 ＋ H = CH3 ＋ H2） have the largest posi- tive sensitivities and the high contribution rate in rich mixture. The rate of production （ROP） of OH of R1 showed that OH ROP of R1 decreases sharply as the mixture turns rich. Therefore, the ignition delays become longer as the equiva- lence ratio increases.