Model-free controller design for positioning tables

In this paper, a new control scheme for a nonlinear motorized positioning table is presented. The proposed controller directly feeds the signal back from the linear encoder in the mounting plate instead of from the rotatory encoder, as in conventional control approaches. As a result, a completely closed-loop is achieved which yields high positioning accuracy. The reason for the nonlinear positioning table can be completely closed in the control loop without making it unstable is that the proposed controller identifies the system dynamics on-line and cancels out the nonlinearities and uncertainties in real time. Hence, the closed-loop system behaves as a first-order dominated system plus a small residual. By adding a robust part into the controller to deal with the small residual, asymptotic stability and better performance can be achieved. The details of the controller design, stability and performance analysis of the closed-loop system are presented in the paper. Experimental results are included to demonstrate the effectiveness of the proposed controller

Microstructure evolution during oxidation of quinary Ti3(AlSiSn)C2 at high temperatures and induced probable performance

Quinary Ti3Al0.6Si0.2Sn0.2C2 and Ti3Al0.5Si0.4Sn0.1C2 solid solution bulks were synthesized via hot-pressing process. High temperature oxidation behaviors were then investigated over a temperature range of 800–1200 °C. The weight gain per surface area and oxidation layer thickness were measured to study the oxidation kinetics. The as-synthesized compounds with varying solid solution ingredients exhibited comparable oxidation kinetics which fitted a parabolic kinetic better with the oxidation duration of 0–20 h, while it appeared to get more complicated after prolonging the oxidation time. The microstructure evolution and phase compositions of the oxide scales during breakaway oxidation were characterized to illuminate the oxidation mechanism. The oxidation layers exhibited a multi-layer structure resulting from the disparities between the diffusion and migration energies of the multi-elements. Anticipated performance induced by high temperature oxidation was further explored through investigation on the crack self-healing and tribological optimization capacities. It was revealed that cracks could be filled by predominant TiO2 and Al2O3 with a high efficiency at 1000 °C during annealing in air. At 800 °C, Ti3Al0.6Si0.2Sn0.2C2 exhibited self-lubricating properties that was attributed to the formation of smoothing tribo-oxide films, as demonstrated by the increasing oxygen content of the friction surface during sliding

Fabrication, mechanical properties, and tribological behaviors of Ti2AlC and Ti2AlSn0.2C solid solutions

Abstract Highly pure and dense Ti2AlC and Ti2AlSn0.2C bulks were prepared by hot pressing with molar ratios of 1:1.1:0.9 and 1:0.9:0.2:0.85, respectively, at 1450 °C for 30 min with 28 MPa in Ar atmosphere. The phase compositions were investigated by X-ray diffraction (XRD); the surface morphology and topography of the crystal grains were also analyzed by scanning electron microscopy (SEM). The flexural strengths of Ti2AlC and Ti2AlSn0.2C have been measured as 430 and 410 MPa, respectively. Both Vickers hardness decreased slowly as the load increased. The tribological behavior was investigated by dry sliding a low-carbon steel under normal load of 20–80 N and sliding speed of 10–30 m/s. Ti2AlC bulk has a friction coefficient of 0.3–0.45 and a wear rate of (1.64–2.97)×10−6 mm3/(N·m), while Ti2AlSn0.2C bulk has a friction coefficient of 0.25–0.35 and a wear rate of (2.5–4.31)×10−6 mm3/(N·m). The influences of Sn incorporation on the microstructure and properties of Ti2AlC have also been discussed

Wetting kinetics of TixMo1-xC in molten Fe and its influence on bicontinuous TixMo1-xC/Fe composite mechanics: Experimental, DFT and ML studies

The TixMo1-xC precursor was rendered porous through PUF foam replication using a slurry of TiC and Mo powders. Mo was incorporated to increase the strength of pressureless sintering (PS). The precursor served as a reinforcement for bicontinuous TixMo1-xC/Fe composites through pressureless infiltration. The interaction between Fe and TixMo1-xC was studied through experimental and theoretical analyses, establishing interfacial adhesion as a key determinant of wettability. At 1550 °C, the TiC/Fe interface exhibits non-reactive wetting, with a contact angle of 9.5°. Addition of 10 wt% Mo escalates interfacial adhesion to 3.768 J/m2 and reduces the contact angle to 9.3° at 1400 °C. TixMo1-xC's precursor has a continuous structure, while composites exhibit slight continuity as predicated by convolutional neural networks (CNNs). The morphological classifications of TixMo1-xC/Fe composites were posited. Alteration from TiC to Ti0.95Mo0.05C increases Young's modulus and hardness from 449.74 GPa to 28.58 GPa–520.55 GPa and 32.32 GPa, respectively. Without heat treatment, the tensile strength of composites rises from 125 MPa to 208 MPa. Increased strain energy density increases the prominence of dimples

A Wearable Electrochemical Sensor Based on Anti-Fouling and Self-Healing Polypeptide Complex Hydrogels for Sweat Monitoring

Although continuous monitoring of constituents in complex sweat is crucial for noninvasive physiological evaluation, biofouling on the sweat sensor surface and inadequate flexible self-healing materials restrict its applications. Herein, a fully self-healing and strong anti-biofouling polypeptide complex hydrogel (AuNPs/MoS2/Pep hydrogel) with excellent electrochemical performances was created. The anti-fouling electrochemical sweat sensor was fabricated based on the AuNPs/MoS2/Pep hydrogel to address these issues. It was found that the polypeptide hydrogel was designed to form a network structure and carried abundant hydrophilic groups, resulting in a AuNPs/MoS2/Pep hydrogel with superior anti-biofouling properties in sweat for 30 min and even long-term stability in undiluted human sweat. In addition, SEM, TEM, UV, XPS, and infrared spectrogram demonstrated that the binding force of π–π stacking force between MoS2 and naphthalene groups in the designed peptide endowed the polypeptide complex hydrogel with an excellent self-healing property. Furthermore, the polypeptide complex hydrogel preserved wearable device function of continuously monitoring uric acid (UA) and ascorbic acid (AA) in sweat in situ. This novel fabricated sweat sensor with high anti-biofouling ability, excellent self-healing property, and sensitive and selective analytical capability describes a new opportunity for health monitoring in situ

SINAT E3 Ligases Control the Light-Mediated Stability of the Brassinosteroid-Activated Transcription Factor BES1 in Arabidopsis

10.1016/j.devcel.2017.03.014DEVELOPMENTAL CELL41147-

SINAT E3 Ligases Control the Light-Mediated Stability of the Brassinosteroid-Activated Transcription Factor BES1 in Arabidopsis

© 2017 Elsevier Inc. The plant hormones brassinosteroids (BRs) participate in light-mediated regulation of plant growth, although the underlying mechanisms are far from being fully understood. In addition, the function of the core transcription factor in the BR signaling pathway, BRI1-EMS-SUPPRESSOR 1 (BES1), largely depends on its phosphorylation status and its protein stability, but the regulation of BES1 is not well understood. Here, we report that SINA of Arabidopsis thaliana (SINATs) specifically interact with dephosphorylated BES1 and mediate its ubiquitination and degradation. Our genetic data demonstrated that SINATs inhibit BR signaling in a BES1-dependent manner. Interestingly, we found that the protein levels of SINATs were decreased in the dark and increased in the light, which changed BES1 protein levels accordingly. Thus, our study not only uncovered a new mechanism of BES1 degradation but also provides significant insights into how light conditionally regulates plant growth through controlling accumulation of different forms of BES1

GSK3-like kinases positively modulate abscisic acid signaling through phosphorylating subgroup III SnRK2s in Arabidopsis

Arabidopsis glycogen synthase kinase 3 (GSK3)-like kinases have versatile functions in plant development and in responding to abiotic stresses. Although physiological evidence suggested a potential role of GSK3-like kinases in abscisic acid (ABA) signaling, the underlying molecular mechanism was largely unknown. Here we identified members of Snf1-related kinase 2s (SnRK2s), SnRK2.2 and SnRK2.3, that can interact with and be phosphorylated by a GSK3-like kinase, brassinosteroid insensitive 2 (BIN2). bin2-3 bil1 bil2, a loss-of-function mutant of BIN2 and its two closest homologs, BIN2 like 1 (BIL1) and BIN2 like 2 (BIL2), was hyposensitive to ABA in primary root inhibition, ABA-responsive gene expression, and phosphorylating ABA Response Element Binding Factor (ABF) 2 fragment by in-gel kinase assays, whereas bin2-1, a gain-of-function mutation of BIN2, was hypersensitive to ABA, suggesting that these GSK3-like kinases function as positive regulators in ABA signaling. Furthermore, BIN2 phosphorylated SnRK2.3 on T180, and SnRK2.3(T180A) had decreased kinase activity in both autophosphorylation and phosphorylating ABFs. Bikinin, a GSK3 kinase inhibitor, inhibited the SnRK2.3 kinase activity and its T180 phosphorylation in vivo. Our genetic analysis further demonstrated that BIN2 regulates ABA signaling downstream of the PYRABACTIN RESISTANCE1/PYR1-LIKE/REGULATORY COMPONENTS OF ABA RECEPTORS receptors and clade A protein phosphatase 2C but relies on SnRK2.2 and SnRK2.3. These findings provide significant insight into the modulation of ABA signaling by Arabidopsis GSK3-like kinases

GSK3-like kinases positively modulate abscisic acid signaling through phosphorylating subgroup III SnRK2s in Arabidopsis

Arabidopsis glycogen synthase kinase 3 (GSK3)-like kinases have versatile functions in plant development and in responding to abiotic stresses. Although physiological evidence suggested a potential role of GSK3-like kinases in abscisic acid (ABA) signaling, the underlying molecular mechanism was largely unknown. Here we identified members of Snf1-related kinase 2s (SnRK2s), SnRK2.2 and SnRK2.3, that can interact with and be phosphorylated by a GSK3-like kinase, brassinosteroid insensitive 2 (BIN2). bin2-3 bil1 bil2, a loss-offunction mutant of BIN2 and its two closest homologs, BIN2 like 1 (BIL1) and BIN2 like 2 (BIL2), was hyposensitive to ABA in primary root inhibition, ABA-responsive gene expression, and phosphorylating ABA Response Element Binding Factor (ABF) 2 fragment by in-gel kinase assays, whereas bin2-1, a gain-of-function mutation of BIN2, was hypersensitive to ABA, suggesting that these GSK3-like kinases function as positive regulators in ABA signaling. Furthermore, BIN2 phosphorylated SnRK2.3 on T180, and SnRK2.3T180A had decreased kinase activity in both autophosphorylation and phosphorylating ABFs. Bikinin, a GSK3 kinase inhibitor, inhibited the SnRK2.3 kinase activity and its T180 phosphorylation in vivo. Our genetic analysis further demonstrated that BIN2 regulates ABA signaling downstream of the PYRABACTIN RESISTANCE1/PYR1-LIKE/REGULATORY COMPONENTS OF ABA RECEPTORS receptors and clade A protein phosphatase 2C but relies on SnRK2.2 and SnRK2.3. These findings provide significant insight into the modulation of ABA signaling by Arabidopsis GSK3-like kinases