Adaptive Sliding Mode Control for Re-entry Attitude of Near Space Hypersonic Vehicle Based on Backstepping Design

Combining sliding mode control method with radial basis function neural network(RBFNN), this paper proposes a robust adaptive control scheme based on backstepping design for re-entry attitude tracking control of near space hypersonic vehicle(NSHV) in the presence of parameter variations and external disturbances. In the attitude angle loop, a robust adaptive virtual control law is designed by using the adaptive method to estimate the unknown upper bound of the compound uncertainties. In the angular velocity loop, an adaptive sliding mode control law is designed to suppress the effect of parameter variations and external disturbances. The main benefit of the sliding mode control is robustness to parameter variations and external disturbances. To further improve the control performance, RBFNNs are introduced to approximate the compound uncertainties in the attitude angle loop and angular velocity loop, respectively. Based on Lyapunov stability theory, the tracking errors are shown to be asymptotically stable. Simulation results show that the proposed control system attains a satisfied control performance and is robust against parameter variations and external disturbances.

Disruption of the bHLH transcription factor Abnormal Tapetum 1 causes male sterility in watermelon

Although male sterility has been identified as a useful trait for hybrid vigor utilization and hybrid seed production,its underlying molecular mechanisms in Cucurbitaceae species are still largely unclear.Here,a spontaneous male-sterile watermelon mutant,Se18,was reported to have abnormal tapetum development,which resulted in completely aborted pollen grains.Map-based cloning demonstrated that the causal gene Citrullus lanatus Abnormal Tapetum 1(ClATM1)encodes a basic helix-loop-helix(bHLH)transcription factor with a 10-bp deletion and produces a truncated protein without the bHLH interaction and functional(BIF)domain in Se18 plants.qRT–PCR and RNA in situ hybridization showed that ClATM1 is specifically expressed in the tapetum layer and in microsporocytes during stages 6–8a of anther development.The genetic function of ClATM1 in regulating anther development was verified by CRISPR/Cas9-mediated mutagenesis.Moreover,ClATM1 was significantly downregulated in the Se18 mutant,displaying a clear dose effect at the transcriptional level.Subsequent dual-luciferase reporter,β-glucuronidase(GUS)activity,and yeast one-hybrid assays indicated that ClATM1 could activate its own transcriptional expression through promoter binding.Collectively,ClATM1 is the first male sterility gene cloned from watermelon,and its self-regulatory activity provides new insights into the molecular mechanism underlying anther development in plants.

Expert consensus on the prevention and treatment of substance use and addictive behaviour-related disorders during the COVID-19 pandemic

In early 2020,the COVID-19 outbreak complicated the diagnosis,treatm ent and rehabilitation of patients with substance use disorders and increased the risks of substance abuse and addictive behaviours,such as online gaming disorders,in the general public.Substance use disorder is a chronic recurrent brain disease characterised by strong cravings,high recurrence rates,and a high proportion of comorbidity of mental and physical disorders.1 Therefore,regular long-term therapeutic interventions are critical to preventing dm g relapses while maintaining withdrawal.

Adaptive Nonsingular Terminal Sliding Mode Control Design for Near Space Hypersonic Vehicles

This paper presents an adaptive nonsingular terminal sliding mode approach for the attitude control of near space hypersonic vehicles(NSHV) in the presence of parameter uncertainties and external disturbances. Firstly, a novel nonsingular terminal sliding surface is developed and its finitetime convergence is analyzed. Then, an adaptive nonsingular terminal sliding mode control law is proposed, which is chattering free. In the proposed approach, all parameter uncertainties and external disturbances are lumped into one term, which is estimated by an adaptive uncertainty estimation for eliminating the boundary requirement needed in the conventional control design. Subsequently, stability of the closed-loop system is proven based on Lyapunov theory. Finally, the proposed approach is applied to the attitude control design for NSHV. Simulation results show that the proposed approach attains a satisfactory performance in the presence of parameter uncertainties and external disturbances.

Assessment of carbon sink potential and methane reduction scenarios of marine macroalgae(Gracilaria)cultivation

Marine macroalgae cultivation is an important part of the effort to address climate change through carbon sinks.Gracilaria,especially Gracilaria lemaneiformis and Gracilaria lichenoides are the major macroalgae cultivated in China.This study proposes a method to assess the net carbon sink of marine macroalgae(Gracilaria)cultivation.First,the net carbon sink of Gracilaria cultivation in China is calculated based on the yield of annual cultivated Gracilaria recorded in China Fishery Statistical Yearbook from 2011 to 2020.Next,we predict the net carbon sink trend of Gracilaria cultivation from 2021 to 2030 using the autoregressive integrated moving average model(ARIMA).Finally,the potential carbon sink increase and methane reduction related to Gracilaria cultivation in China is explored through a scenario analysis.We find that the net carbon sink of Gracilaria cultivation in China was about 32.1-92.4 kilotons per year from 2011 to 2020,and shows a great annual growth trend.Moreover,the predicted net carbon sink of Gracilaria cultivation would increase to 77.8-191.4 kilotons per year from 2021 to2030,thereby could contribute considerably in the achievement of China's carbon peak goal.Under a scenario of producing ruminant green feed with additional Gracilaria cultivation,each ton of macroalgae is predicted to reduce carbon emission(i.e.,methane)by 0.33-0.68 tons.Thus,marine macroalgae cultivation might form a synergistic chain of"carbon sink increase-water purification-economy-methane reduction".This study proposes a synergistic new model that operates through marine macroalgae cultivation,economic aquaculture,and green feed production.

Nano-copper ions assembled cellulose-based composite with antibacterial activity for biodegradable personal protective mask

The current SARS-CoV-2 pandemic has resulted in the widespread use of personal protective equipment,particularly face masks.However,the use of commercial disposable face masks puts great pressure on the environment.In this study,nano-copper ions assembled cotton fabric used in face masks to impart antibacterial activity has been discussed.To produce the nanocomposite,the cotton fabric was modified by sodium chloroacetate after its mercerization,and assembled with bactericidal nano-copper ions(about 10.61 mg·g^(–1))through electrostatic adsorption.It demonstrated excellent antibacterial activity against Staphylococcus aureus and Escherichia coli because the gaps between fibers in the cotton fabric allow the nano-copper ions to be fully released.Moreover,the antibacterial efficiency was maintained even after 50 washing cycles.Furthermore,the face mask constructed with this novel nanocomposite upper layer exhibited a high particle filtration efficiency(96.08%±0.91%)without compromising the air permeability(28.9 min·L^(–1)).This green,economical,facile,and scalable process of depositing nano-copper ions onto modified cotton fibric has great potential to reduce disease transmission,resource consumption,and environmental impact of waste,while also expanding the range of protective fabrics.

Second-order terminal sliding mode control for hypersonic vehicle in cruising flight with sliding mode disturbance observer

This paper focuses on the design of nonlinear robust controller and disturbance observer for the longitudinal dynamics of a hypersonic vehicle （HSV） in the presence of parameter uncertainties and external disturbances. First, by combining terminal sliding mode control （TSMC） and second-order sliding mode control （SOSMC） approach, the second- order terminal sliding control （2TSMC） is proposed for the velocity and altitude tracking control of the HSV. The 2TSMC possesses the merits of both TSMC and SOSMC, which can provide fast convergence, continuous control law and high- tracking precision. Then, in order to increase the robustness of the control system and improve the control performance, the sliding mode disturbance observer （SMDO） is presented. The closed-loop stability is analyzed using the Lyapunov technique. Finally, simulation results illustrate the effectiveness of the proposed method, as well as the improved overall performance over the conventional sliding mode control （SMC）.

Investigation Into Vibration Characteristic in Vibrothermography

Vibration characteristic plays an important role in vibrothermography, which directly affects the heating during the test. In this work, involving all the contacts in the vibrothermography, the "double-mass-thiree-spring" model is established to explore the vibration characteristic. The obtained results show that ultrasonic gun vibrates at fundamental frequency (FF), while the specimen vibrates at multi-frequencies including FF, 2FF, 3FF, and 4FF, which is validated through experimental investigation results. Additionally, the model proposed in this work reveals a high order harmonics in the vibrothermography test and makes the specimen conduct the steady vibration, which indicates that the model is closer to the practical equipment and can ensure the heating efficiency induced by vibration of specimen to improve the detection capability.

On-line RNN compensated second order nonsingular terminal sliding mode control for hypersonic vehicle

Purpose–The purpose of this paper is to design a robust control scheme to achieve robust tracking of velocity and altitude commands for a general hypersonic vehicle(HSV)in the presence of parameter variations and external disturbances.Design/methodology/approach–The robust control scheme is composed of nonsingular terminal sliding mode control(NTSMC),super twisting control algorithm(STC)and recurrent neural network(RNN).First,by combing a novel NTSMC and STC algorithm,a second order NTSMC approach for HSV is proposed to provide fast,continuous and high precision tracking control.Second to relax the requirements for the bounds of the lumped uncertainties in control design,a RNN disturbance observer is presented to increase the robustness of the control system.The weights of RNN are updated by adaptive laws based on Lyapunov theorem,thus the closed-loop stability can be guaranteed.Findings–Simulation results demonstrate that the proposed method is effective,leading to promising performance.Originality/value–The main contributions of this work are:first,both parameter variations and external disturbances are considered in control design for the longitudinal dynamic model of HSV;and second,the proposed controller can remove chattering and achieve more favorable tracking performances than conventional sliding mode control.

Optimal portfolio design of energy storage devices with financial and physical right market

With the continuous development of the spot market,in the multi-stage power market environment with the day-ahead market and right market,the study associated with the portfolio of energy storage devices requires that attention should be paid to transmission congestion and power congestion.To maximize the profit of energy storage and avoid the imbalance of power supply and consumption and the risk of node price fluctuation caused by transmission congestion,this paper presents a portfolio strategy of energy storage devices with financial/physical contracts.First,the concepts of financial/physical transmission rights and financial/physical storage rights are proposed.Then,the portfolio models of financial contract and physical contract are established with the conditional value-at-risk to measure the risks.Finally,the portfolio models are verified through the test data of the Pennsylvania-New Jersey-Maryland(PJM)electric power spot market,and the comparison between the risk aversion of portfolios based on financial/physical contract with the portfolio of the market without rights.The simulation results show that the portfolio models proposed in this paper can effectively avoid the risk of market price fluctuations.

Integrative analysis of transcriptomic and metabolomic profiles reveals new insights into the molecular foundation of fruit quality formation in Citrullus lanatus(Thunb.)Matsum.&Nakai

In this study,an integrated transcriptome and metabolome analysis was used to explore the molecular foundation of fruit quality in two parent lines of Citrullus lanatus with distinct flesh characteristics,including ‘14-1’(sweet,red,and soft)andW600'(bitter,light yellow,and firm),as well as the corresponding F,population(bitter,light yellow,and firm).Numerous differentially expressed genes(DEGs)were identified in the fruit samples:3766 DEGs for ‘14-1’vs.W600,2767 for ‘14-1’vs.F_(1),and 1178 for F_(1) vs.‘W600’at the transition stage;and 4221 for ‘14-1’vs.W6002447 for ‘14-1’vs.F,and 446 for F,vs.‘W600’at the maturity stage.Weighted gene co-expression network analysis(WGCNA)revealed that a gene module including 1111 DEGs was closely associated with flesh taste and color,and another gene module including 1575 DEGs contributed significantly to flesh texture.The metabolomic results showed that there were 447 differential metabolites(DMs)for ‘14-1’vs.‘W600’fruits,394 for ‘14-1’vs.F,and 298 for F,vs.‘W600’at the maturity stage.Combining WGNCA and metabolomic results,several DEGs and DMs were further identified as hub players in fruitqualityformation:6DEGs with 4DMs for flesh sweetness;6DEGs with 13DMs forbitterness;9DEGs with 10 DMs for flesh color;and 9 DEGs with 4 DMs for flesh texture.Altogether,these observations not only expand our knowledge of the molecular basis of fruit quality in watermelon,but also provide potential targets for future watermelon improvement.