Adaptive Fixed-Time Control of Nonlinear MASs With Actuator Faults

The adaptive fixed-time consensus problem for a class of nonlinear multi-agent systems(MASs)with actuator faults is considered in this paper.To approximate the unknown nonlinear functions in MASs,radial basis function neural networks are used.In addition,the first order sliding mode differentiator is utilized to solve the“explosion of complexity”problem,and a filter error compensation method is proposed to ensure the convergence of filter error in fixed time.With the help of the Nussbaum function,the actuator failure compensation mechanism is constructed.By designing the adaptive fixed-time controller,all signals in MASs are bounded,and the consensus errors between the leader and all followers converge to a small area of origin.Finally,the effectiveness of the proposed control method is verified by simulation examples.

Recent Advances in Bronchopulmonary Dysplasia Protection and Therapy

For preterm infants, bronchopulmonary dysplasia (BPD) is usually caused by abnormal lung development due to various factors during prenatal and postnatal process. One of the reasons for death and bad prognosis of preterm infants is to have BPD. Up to now, there are no unified strategies or drugs to treat BPD. In clinical, many intervention treatments have been applied to achieve BPD therapy, mainly including preterm protection, protective ventilation strategies, and delivery of corticosteroids, pulmonary vasodilators, and antioxidants. This review summarizes the current advances in BPD protection and treatment, and notes that gut microbiota and mesenchymal stem cells (MSCs) can be the promising strategy for protecting and treating BPD in the future.

Heterostructured bimetallic phosphide nanowire arrays with latticetorsion interfaces for efficient overall water splitting

Designing cost-effective and high-efficiency electrocatalysts is critical to the water splitting performance during hydrogen generation.Herein,we have developed Fe_(2)P-Co_(2)P heterostructure nanowire arrays with excellent lattice torsions and grain boundaries for highly efficient water splitting.According to the microstructural investigations and theoretical calculations,the lattice torsion interface not only contributes to the exposure of more active sites but also effectively tunes the adsorption energy of hydrogen/oxygen intermediates via the accumulation of charge redistribution.As a result,the Fe_(2)P-Co_(2)P heterostructure nanowire array exhibits exceptional bifunctional catalytic activity with overpotentials of 65 and 198 mV at 10 mA cm^(-2) for hydrogen and oxygen evolution reactions,respectively.Moreover,the Fe_(2)P-Co_(2)P/NF-assembled electrolyzer can deliver 10 mA cm^(-2) at an ultralow voltage of1.51 V while resulting in a high solar-to-hydrogen conversion efficiency of 19.8%in the solar-driven water electrolysis cell.

Event-based performance guaranteed tracking control for constrained nonlinear system via adaptive dynamic programming method

An optimal tracking control problem for a class of nonlinear systems with guaranteed performance and asymmetric input constraints is discussed in this paper.The control policy is implemented by adaptive dynamic programming(ADP)algorithm under two event-based triggering mechanisms.It is often challenging to design an optimal control law due to the system deviation caused by asymmetric input constraints.First,a prescribed performance control technique is employed to guarantee the tracking errors within predetermined boundaries.Subsequently,considering the asymmetric input constraints,a discounted non-quadratic cost function is introduced.Moreover,in order to reduce controller updates,an event-triggered control law is developed for ADP algorithm.After that,to further simplify the complexity of controller design,this work is extended to a self-triggered case for relaxing the need for continuous signal monitoring by hardware devices.By employing the Lyapunov method,the uniform ultimate boundedness of all signals is proved to be guaranteed.Finally,a simulation example on a mass–spring–damper system subject to asymmetric input constraints is provided to validate the effectiveness of the proposed control scheme.

火焰原子吸收光谱测定葡萄糖酸锌口服液中锌含量

“火焰原子吸收光谱”是本科生仪器分析实验教学中的重要实验之一。原子吸收光谱用于实际样品中某一特定元素的定量测定,具有测定准确度高、精密度高和选择性好等优点。葡萄糖酸锌口服液是生活中常见的口服补锌类非处方药,通过本科生自主实验,建立火焰原子吸收实验方法,测定葡萄糖酸锌口服液中锌含量,方法简便、易于操作。通过该自主实验,培养学生利用课堂所学理论知识解决实际问题的能力,实现“学以致用,用以促学”的育人目标。

An Overview of Finite/Fixed-Time Control and Its Application in Engineering Systems

The finite/fixed-time stabilization and tracking control is currently a hot field in various systems since the faster convergence can be obtained. By contrast to the asymptotic stability,the finite-time stability possesses the better control performance and disturbance rejection property. Different from the finite-time stability, the fixed-time stability has a faster convergence speed and the upper bound of the settling time can be estimated. Moreover, the convergent time does not rely on the initial information.This work aims at presenting an overview of the finite/fixed-time stabilization and tracking control and its applications in engineering systems. Firstly, several fundamental definitions on the finite/fixed-time stability are recalled. Then, the research results on the finite/fixed-time stabilization and tracking control are reviewed in detail and categorized via diverse input signal structures and engineering applications. Finally, some challenging problems needed to be solved are presented.

Rabdosia serra alleviates dextran sulfate sodium salt-induced colitis in mice through anti-inflammation,regulating Th17/Treg balance,maintaining intestinal barrier integrity,and modulating gut microbiota

Rabdosia serra(R.serra),an important component of Chinese herbal tea,has traditionally been used to treat hepatitis,jaundice,cholecystitis,and colitis.However,the chemical composition of R.serra and its effect against colitis remain unclear.In this study,the chemical composition of the water extract of R.serra was analyzed using ultra performance liquid chromatography coupled with a hybrid linear ion trap quadrupole-orbitrap mass spectrometer(UPLC-LTQ-Orbitrap-MS).A total of 46 compounds,comprising ent-kaurane diterpenoids,flavonoids,phenolic acids,and steroids,were identified in the water extract of R.serra,and the extract could significantly alleviate dextran sulfate sodium salt-induced colitis by improving colon length,upregulating anti-inflammatory factors,downregulating proinflammatory factors,and restoring the balance of T helper 17/T regulatory cells.R.serra also preserved intestinal barrier function by increasing the level of tight junction proteins(zonula occludens 1 and occludin)in mouse colonic tissue.In addition,R.serra modulated the gut microbiota composition by increasing bacterial richness and diversity,increasing the abundance of beneficial bacteria(Muribaculaceae,Bacteroides,Lactobacillus,and Prevotellaceae_UCG-001),and decreasing the abundance of pathogenic bacteria(Turicibacter,Eubacterium_fissicatena_group,and Eubacterium_xylanophilum_group).Gut microbiota depletion by antibiotics further confirmed that R.serra alleviated colitis in a microbiota-dependent manner.Overall,our findings provide chemical and biological evidence for the potential application of R.serra in the management of colitis.

Human-in-the-Loop Consensus Control for Nonlinear Multi-Agent Systems With Actuator Faults

This paper considers the human-in-the-loop leader-following consensus control problem of multi-agent systems(MASs)with unknown matched nonlinear functions and actuator faults.It is assumed that a human operator controls the MASs via sending the command signal to a non-autonomous leader which generates the desired trajectory.Moreover,the leader’s input is nonzero and not available to all followers.By using neural networks and fault estimators to approximate unknown nonlinear dynamics and identify the actuator faults,respectively,the neighborhood observer-based neural fault-tolerant controller with dynamic coupling gains is designed.It is proved that the state of each follower can synchronize with the leader’s state under a directed graph and all signals in the closed-loop system are guaranteed to be cooperatively uniformly ultimately bounded.Finally,simulation results are presented for verifying the effectiveness of the proposed control method.

FeCo alloy catalysts promoting polysulfide conversion for advanced lithium-sulfur batteries

Lithium sulfur batteries(LSBs)draw extensive interest because of the ultra-high capacity and low material cost.However,the sluggish lithium polysulfides(LIPSs)conversion processes are detrimental to cycle stability and rate capability,inhibiting the commercial application of LSBs.Here we present the well-designed Fe Co alloy catalysts anchored on porous carbon(FeCo-C)as sulfur host to improve the electrochemical performance by accelerating the conversion reactions.The FeCo alloy demonstrates high catalytic effect and strong adsorption capability of LIPSs,in which potential polarization can be greatly decreased and"shuttle effects"can be largely avoided.As a result,the obtained S/Fe Co-C composites show an initial specific capacity of 791.9 m Ah g^-1 at a large current density of 2 C and maintain 502.5 mAh g^-1 even after 500 cycles.Moreover,720 m Ah g^-1(corresponding to 70%retention)can be achieved after 100 cycles at 0.2 C with a high sulfur content of 80 wt%,enabling high sulfur utilization.This work not only provides a new insight to investigate the conversion kinetics of Li PSs,but also opens up a new avenue for advanced lithium sulfur batteries.

Role of blowing snow in snow processes in Qilian Mountainous region

Blowing snow is an important part of snow hydrologic processes in mountainous region, however the related researches were rare for the Qilian mountainous region where blowing snow is frequent. Using the observation dataset in 2008 snow season in Binggou wa- tershed in Qilian mountainous region, we systematically studied the energy and mass processes of blowing snow by field observation and model simulation. The results include the analysis of snow observation, the occurrence probability of blowing snow, blowing snow transport and blowing snow sublimation. It was found that blowing snow was obvious in high altitude region （4,146 m）, the snow redislribution phenomena was remarkable. In Yakou station in the study region, blowing snow was easily occurred in midwinter and early spring when no snowmelt, the blowing snow transport was dominated in this period; when snowmelt beginning, the occur- rence probability of blowing snow decreased heavily because of the increasing air temperature, melt, and refrozen phenomena. The blowing snow sublimation accounted for 41.5% of total snow sublimation at Yakou station in 2008 snow season.

Using the match-and-locate method to characterize foreshocks of the July 2019 M_(W)6.4 Ridgecrest,California earthquake

The July 2019 M_(W)6.4 Ridgecrest,California earthquake and its distinct foreshocks were well recorded by local and regional stations,providing a great opportunity to characterize its foreshocks and investigate the nucleation mechanisms of the mainshock.In this study,we utilized the match-and-locate(M&L)method to build a high-precision foreshock catalog for this M_(W)6.4 earthquake.Compared with the sequential location methods(matched-filter+cross-correlation-based hypoDD),our new catalog contains more events with higher location accuracy.The M_(W)6.4 mainshock was preceded by 40 foreshocks within~2 h(on July 4,2019 from 15:35:29 to 17:32:52,UTC).Their spatiotemporal distribution revealed a complex seismogenic structure consisting of multiple fault strands,which were connected as a throughgoing fault by later foreshocks and eventually accommodated the 2019 M_(W)6.4 mainshock.To better understand the nucleation mechanism,we determined the rupture dimension of the largest M_(L)4.0 foreshock by calculating its initial rupture and centroid points using the M&L method.By estimating Coulomb stress change we suggested that the majority of foreshocks following the M_(L)4.0 event and M_(W)6.4 mainshock occurred within regions of increasing Coulomb stress,indicating that they were triggered by stress transfer.The nucleation process before the M_(L)4.0 event remains unclear due to the insufficient sampling rate of waveforms and small magnitude of events.Thus,our study demonstrates that the M&L method has superior detection and location ability,showing potential for studies that require high-precision location(e.g.,earthquake nucleation).

Can environmental regulations achieve both profitability and profit quality?A natural experiment based on the China Cleaner Production Standards

Numerous studies evaluated the effects of end-of-pipe control environmental regulations(EER).However,few scholars discussed the effects of process management environmental regulations(PER),such as the China Cleaner Production Standards(CCPS)implemented by the country's Ministry of Ecology and Environment.Using data on China's manufacturing enterprises,this paper adopts the CCPS policies as quasi-natural experiments and uses differences-in-differences(DID)methods to analyze their effects on enterprise profitability and profit quality,respectively.The results show that:first,the CCPS significantly improve both profitability and profit quality;that is,the implementation of the environmental regulation policy plays a significant role in improving enterprise profit rates and cash flows.Second,for the profitability mediator effects,the short-term Porter effect of CCPS is not significant but shows the opposite during the lag period and significantly reduces the management cost and wage levels,comprehensively promoting enterprise profitability.Third,for the profit quality meditator effects,environmental regulations improve the enterprises'cash flow by reducing management costs and increasing government subsidies;however,its effect on bank credit subsidies is not significant.Fourth,for the moderator effects,the environmental regulations'effect on enterprises profitability and profit quality depends on the strategic interaction among local governments,the scale and ownership of the enterprise,and regional differences.That is,the strategic interaction weakens the effect of environmental regulations on enterprise performance.Environmental regulations have a stronger influence on profitability and profit quality for large-scale,state-owned,and coastal enterprises.

Camera,LiDAR,and IMU Based Multi-Sensor Fusion SLAM:A Survey

In recent years,Simultaneous Localization And Mapping(SLAM)technology has prevailed in a wide range of applications,such as autonomous driving,intelligent robots,Augmented Reality(AR),and Virtual Reality(VR).Multi-sensor fusion using the most popular three types of sensors(e.g.,visual sensor,LiDAR sensor,and IMU)is becoming ubiquitous in SLAM,in part because of the complementary sensing capabilities and the inevitable shortages(e.g.,low precision and long-term drift)of the stand-alone sensor in challenging environments.In this article,we survey thoroughly the research efforts taken in this field and strive to provide a concise but complete review of the related work.Firstly,a brief introduction of the state estimator formation in SLAM is presented.Secondly,the state-of-the-art algorithms of different multi-sensor fusion algorithms are given.Then we analyze the deficiencies associated with the reviewed approaches and formulate some future research considerations.This paper can be considered as a brief guide to newcomers and a comprehensive reference for experienced researchers and engineers to explore new interesting orientations.

Adaptive Attitude Control for Multi-MUAV Systems With Output Dead-Zone and Actuator Fault

Many mechanical parts of multi-rotor unmanned aerial vehicle(MUAV)can easily produce non-smooth phenomenon and the external disturbance that affects the stability of MUAV.For multi-MUAV attitude systems that experience output dead-zone,external disturbance and actuator fault,a leader-following consensus anti-disturbance and fault-tolerant control(FTC)scheme is proposed in this paper.In the design process,the effect of unknown nonlinearity in multi-MUAV systems is addressed using neural networks(NNs).In order to balance out the effects of external disturbance and actuator fault,a disturbance observer is designed to compensate for the aforementioned negative impacts.The Nussbaum function is used to address the problem of output dead-zone.The designed fault-tolerant controller guarantees that the output signals of all followers and leader are synchronized by the backstepping technique.Finally,the effectiveness of the control scheme is verified by simulation experiments.

Finite Frequency Fuzzy H∞Control for Uncertain Active Suspension Systems With Sensor Failure

This paper investigates the problem of finite frequency fuzzy H_∞ control for uncertain active vehicle suspension systems, in which sensor failure is taken into account. TakagiSugeno(T-S) fuzzy model is established for considered suspension systems. In order to describe the sensor fault effectively, a corresponding model is introduced. A vital performance index,H_∞ performance, is utilized to measure the drive comfort. In the framework of Kalman-Yakubovich-Popov theory, the H_∞ norm from external perturbation to controlled output is optimized effectively in the frequency domain of 4 Hz-8 Hz to enhance ride comfort level. Meanwhile, three suspension constrained requirements, i.e., ride comfort level, manipulation stability,suspension deflection are also guaranteed. Furthermore, sufficient conditions are developed to design a fuzzy controller to guarantee the desired performance of active suspension systems. Finally, the proposed control scheme is applied to a quarter-vehicle active suspension, and simulation results are given to illustrate the effectiveness of the proposed approach.

Love wave tomography in Italy from seismic ambient noise

We estimate Love wave empirical Green＇s functions from cross-correlations of ambient seismic noise to study the crust and uppermost mantle structure in Italy. Transverse-component ambient noise data from October 2005 through March 2007 recorded at 114 seismic stations from the Istituto Nazionale di Geofisica e Vulcanologia （INGV） national broadband network, the Mediterranean Very Broadband Seismographic Network （MedNet） and the Austrian Central Institute for Meteorology and Geodynamics （ZAMG） yield more than 2 000 Love wave group velocity measurements using the multiple-filter analysis technique. In the short period band （5-20 s）, the cross-correlations show clearly one-sided asymmetric feature due to non-tmiform noise distribution and high local activities, and in the long period band （〉20 s） this feature becomes weak owing to more diffusive noise distribution. Based on these measurements, Love wave group velocity dispersion maps in the 8-34 s period band are constructed, then the SH wave velocity structures from the Love wave dispersions are inverted. The final results obtained from Love wave data are overall in good agreement with those from Rayleigh waves. Both Love and Rayleigh wave inversions all reveal that the Po plain basin is resolved with low velocity at shallow depth, and the Tyrrhenian sea is characterized with higher velocity below 8 km due to its thin oceanic crust.

Vertical aerosol data assimilation technology and application based on satellite and ground lidar:A review and outlook

Observations and numerical models are mainly used to investigate the spatiotemporal distribution and vertical structure characteristics of aerosols to understand aerosol pollution and its effects.However,the limitations of observations and the uncertainties of numerical models bias aerosol calculations and predictions.Data assimilation combines observations and numerical models to improve the accuracy of the initial,analytical fields of models and promote the development of atmospheric aerosol pollution research.Numerous studies have been conducted to integrate multi-source data,such as aerosol optical depth and aerosol extinction coefficient profile,into various chemical transport models using various data assimilation algorithms and have achieved good assimilation results.The definition of data assimilation and the main algorithms will be briefly presented,and the progress of aerosol assimilation according to two types of aerosol data,namely,aerosol optical depth and extinction coefficient,will be presented.The application of vertical aerosol data assimilation,as well as the future trends and challenges of aerosol data assimilation,will be further analysed.

Dynamic event-triggered-based human-in-the-loop formation control for stochastic nonlinear MASs

The dynamic event-triggered(DET)formation control problem of a class of stochastic nonlinear multi-agent systems(MASs)with full state constraints is investigated in this article.Supposing that the human operator sends commands to the leader as control input signals,all followers keep formation through network topology communication.Under the command-filter-based backstepping technique,the radial basis function neural networks(RBF NNs)and the barrier Lyapunov function(BLF)are utilized to resolve the problems of unknown nonlinear terms and full state constraints,respectively.Furthermore,a DET control mechanism is proposed to reduce the occupation of communication bandwidth.The presented distributed formation control strategy guarantees that all signals of the MASs are semi-globally uniformly ultimately bounded(SGUUB)in probability.Finally,the feasibility of the theoretical research result is demonstrated by a simulation example.

Functional Recovery with Electro-Acupuncture Stimulation in an Mecp2-Knockout Rat Model of Rett Syndrome

Rett syndrome is a progressive neurodevelopmental disorder that lacks effective treatments.Although deep-brain stimulation can alleviate some symptoms in Rett model mice,this interventional manipula-tion requires deliberate surgical operations.Here,we report that electro-acupuncture stimulation(EAS)can ameliorate symptoms of an Mecp2-knockout rat model of Rett syndrome from the remote acupoints Baihui(GV 20),Yongquan(KI 1),and Shenmen(HT 7).We find that EAS not only prolongs the survival time of Rett rats,but also improves their behavior ability,including locomotion,motor coordination,and social interaction.Neural activation was observed in the substantia nigra of the midbrain,corpus striatum,and cerebral cortex of wild-type and Rett model rats,as reflected by the increased expression of the c-Fos protein.Hence,EAS provides a potential promising therapeutic tool for treating neurodevel-opmental diseases.

A BOUNDARY SCHWARZ LEMMA FOR PLURIHARMONIC MAPPINGS FROM THE UNIT POLYDISK TO THE UNIT BALL

In this article, we present a Schwarz lemma at the boundary for pluriharmonic mappings from the unit polydisk to the unit ball, which generalizes classical Schwarz lemma for bounded harmonic functions to higher dimensions. It is proved that if the pluriharmonic mapping f ∈ P（Dn, BN） is C1＋α at z0 ∈ ErDn with f（0） = 0 and f（z0） = ω0∈BN for any n,N ≥ 1, then there exist a nonnegative vector λf =（λ1,0,…,λr,0,…,0）T∈R2 nsatisfying λi≥1/（22 n-1） for 1 ≤ i ≤ r such that where z’0 and w’0 are real versions of z0 and w0, respectively.