This paper investigates adaptive fuzzy neural network (NN) control using impedance learning for a constrained robot, subject to unknown system dynamics, the effect of state constraints, and the ...uncertain compliant environment with which the robot comes into contact. A fuzzy NN learning algorithm is developed to identify the uncertain plant model. The prominent feature of the fuzzy NN is that there is no need to get the prior knowledge about the uncertainty and a sufficient amount of observed data. Also, impedance learning is introduced to tackle the interaction between the robot and its environment, so that the robot follows a desired destination generated by impedance learning. A barrier Lyapunov function is used to address the effect of state constraints. With the proposed control, the stability of the closed-loop system is achieved via Lyapunov's stability theory, and the tracking performance is guaranteed under the condition of state constraints and uncertainty. Some simulation studies are carried out to illustrate the effectiveness of the proposed scheme.
Metal–organic frameworks (MOFs) can be fine‐tuned to boost sorbent‐sorbate interactions in order to improve gas sorption and separation performance, but the design of MOFs with ideal structural ...features for gas separation applications remains a challenge. Herein it is reported that unsaturated alkali metal sites can be immobilized in MOFs through a tetrazole based motif and that gas affinity can thereby be boosted. In the prototypal MOF of this type‐NKU‐521 (NKU denotes Nankai University), K+ cations are effectively embedded in a trinuclear Co2+‐tetrazole coordination motif. The embedded K+ sites are exposed to the pores of NKU‐521 through water removal, and the isosteric heat (Qst) for CO2 is boosted to 41 kJ mol‐1. The nature of the binding site is validated by molecular simulations and structural characterization. The K+ cations in effect serve as gas traps and boost the CO2‐framework affinity, as measured by the Qst, by 24%. In addition, the impact of unsaturated alkali metal sites upon the separation of hydrocarbons is evaluated for the first time in MOFs using ideal adsorbed solution theory (IAST) calculations and column breakthrough experiments. The results reveal that the presence of exposed K+ sites benefits gas sorption and hydrocarbon separation performances of this MOF.
K+ cations in effect serve as CO2 traps and enhance the CO2 selective sorption in an embedded K+ MOF.
A simple and practical method for the synthesis of alkenyl dithiocyanates and alkenyl diselenocyanates has been developed via stereoselective difunctionalization of alkynes with NaSCN or KSeCN at ...room temperature. Through this methodology, a series of alkenyl dithiocyanates and alkenyl diselenocyanates could be efficiently and conveniently obtained in moderate to good yields under mild and metal-free conditions by the simple use of oxone and PhI(OAc)2 as the oxidants.
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We study a relation between asymptotic spectra of the quantum mechanics problem with a four components elliptic function potential, the Darboux-Treibich-Verdier (DTV) potential, and the ...Omega background deformed N=2 supersymmetric SU(2) QCD models with four massive flavors in the Nekrasov-Shatashvili limit. The weak coupling spectral solution of the DTV potential is related to the instanton partition function of supersymmetric QCD with surface operator. There are two strong coupling spectral solutions of the DTV potential, they are related to the strong coupling expansions of gauge theory prepotential at the magnetic and dyonic points in the moduli space. A set of duality transformations relate the two strong coupling expansions for spectral solution, and for gauge theory prepotential.
We still know very little about how the human immune system responds to SARS-CoV-2. Here we construct a SARS-CoV-2 proteome microarray containing 18 out of the 28 predicted proteins and apply it to ...the characterization of the IgG and IgM antibodies responses in the sera from 29 convalescent patients. We find that all these patients had IgG and IgM antibodies that specifically bind SARS-CoV-2 proteins, particularly the N protein and S1 protein. Besides these proteins, significant antibody responses to ORF9b and NSP5 are also identified. We show that the S1 specific IgG signal positively correlates with age and the level of lactate dehydrogenase (LDH) and negatively correlates with lymphocyte percentage. Overall, this study presents a systemic view of the SARS-CoV-2 specific IgG and IgM responses and provides insights to aid the development of effective diagnostic, therapeutic and vaccination strategies.
In this brief, the control problem for flexible wings of a robotic aircraft is addressed by using boundary control schemes. Inspired by birds and bats, the wing with flexibility and articulation is ...modeled as a distributed parameter system described by hybrid partial differential equations and ordinary differential equations. Boundary control for both wing twist and bending is proposed on the original coupled dynamics, and bounded stability is proved by introducing a proper Lyapunov function. The effectiveness of the proposed control is verified by simulations.
The pandemic of coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has become a global crisis. Replication of SARS-CoV-2 requires the viral ...RNA-dependent RNA polymerase (RdRp) enzyme, a target of the antiviral drug remdesivir. Here we report the cryo-electron microscopy structure of the SARS-CoV-2 RdRp, both in the apo form at 2.8-angstrom resolution and in complex with a 50-base template-primer RNA and remdesivir at 2.5-angstrom resolution. The complex structure reveals that the partial double-stranded RNA template is inserted into the central channel of the RdRp, where remdesivir is covalently incorporated into the primer strand at the first replicated base pair, and terminates chain elongation. Our structures provide insights into the mechanism of viral RNA replication and a rational template for drug design to combat the viral infection.
The first highly diastereo‐ and enantioselective multicomponent reaction of diazooxindoles, nitrosoarenes, and nitroalkenes using a newly developed hydrogen‐bond catalyst has been successfully ...developed for the efficient construction of a series of spirooxindole derivatives with excellent functional‐group tolerance. Spirooxindoles are formed in excellent yields and stereoselectivities, and the method represents an unprecedented approach for trapping the active intermediate with a nitroalkene to form biologically important compounds having three contiguous stereogenic centers with excellent asymmetric induction.
Multiple players: The first highly stereoselective multicomponent reaction of diazooxindoles, nitrosoarenes, and nitroalkenes with a newly developed hydrogen‐bond catalyst has been successfully developed. The spirooxindole products are isolated in excellent yields and stereoselectivities, and contain three contiguous stereogenic centers. R′′′=aryl or alkyl.
In this paper, we present the vibration control design for a Euler-Bernoulli beam with the boundary output constraint. To prevent the constraint violation, a novel barrier Lyapunov function is ...employed for the control design and stability analysis. This paper represents an important step in extending the barrier Lyapunov function theory to distributed parameter systems. Model-based barrier control is proposed to suppress the vibration of a flexible Euler-Bernoulli beam under the boundary output constraint. Then, adaptive control is designed to handle the system parametric uncertainties. The vibration suppression is well achieved without violation of the constraint. Numerical simulations are provided to illustrate the performance of the control system.
A simple and practical method for the synthesis of 2-aminobenzothiazoles through visible-light-initiated malic acid-promoted cascade coupling/cyclization of aromatic amines and KSCN with ambient air ...as an oxidant in eco-friendly bis(methoxypropy) ether at ambient temperature was developed.
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By using ambient air as the oxidant and malic acid as the promoter, a practical method for the preparation of 2-aminobenzothiazoles through visible-light-initiated cascade reaction of aromatic amines and KSCN in eco-friendly bis(methoxypropy)ether under metal-, hazardous additive-, photocatalyst-free conditions was established.
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