Switching Experiments Research Articles

Multivariable switching control of a compliant piezoelectric microgripper with force/position interaction interferences

This paper presents multivariable switching control of a piezoelectric microgripper regarding its output displacement, gripping force, and manipulated position. Unlike existing microgripper control, it simultaneously regulates force/position variables. Meanwhile, force/position interaction interferences and signal itself overshooting are suppressed. Firstly, a symmetrical microgripper with two independent gripping arms is introduced. Then, a generalized dynamic model is established by considering structural dynamics, electromechanical coupling, and force/position interaction. After that, multivariable switching control is proposed to achieve clamp-carry-release manipulation using dual-input and dual-output (DIDO) perturbation displacement and force/position controllers. Finally, various switching experiments are conducted, demonstrating that force/position interaction interferences are reduced by 83.76 % and 87.51 %, and interference-suppression time is shortened from 0.86 s and 0.70 s to 0.49 s and 0.41 s. Also, overshoots of gripping force and position are eliminated with a smaller settling time. The proposed multivariable switching control exhibits superior regulation performance, guaranteeing manipulation accuracy and stability.

Perihatch surge of thyroid hormone drives cognitive flexibility in newborn chicks

Early experience in infancy affects cognitive development. Birds, like mammals, acquire cognitive flexibility attributed to a well-developed telencephalon. Precocial chicks acquire imprintability just after hatching when thyroid hormone (T 3 ) flows into the brain and primes later learning. Here, we show that the perihatch synthesis of T 3 paralleling thyroid development is crucial for imprinting and endows newborn chicks with cognitive flexibility via a mechanism involving the nidopallium dorsocaudale, the avian “prefrontal cortex.” Imprinted chicks showed higher cognitive flexibility than those unimprinted in switching or reversal task experiments. Notably, we discovered that exogenous T 3 endowed similar flexibility in unimprinted chicks. Cognitive stimulation by a surge of thyroid hormone indicates a vertebrate tactic involving high cognitive ability for adapting to environmental changes.

Modulation of fatty acid profiles and turnover dynamics in jellyfish polyps through copepod diets: Insights into trophic interactions and nutrient flux.

Fatty acids (FAs) are vital biomolecules crucial for determining food quality for higher trophic levels. To investigate FA transfer and turnover time in predators, we conducted a diet switch experiment using jellyfish polyps. These polyps were fed food sources including Artemia sinica nauplii and FA-manipulated copepod Pseudodiaptomus annandalei, maintained on distinct algal diets with varied FA compositions. Our findings reveal that copepods may have a strong potential to synthesize long-chain polyunsaturated FA to maintain biochemical homeostasis when consuming low-quality food. Consequently, the species-specific fatty acid composition within plankton, combined with effects of seasonal environmental fluctuations and climate change, leads to changes in the FA composition of foundational food web components. These alterations create a complex "nutrient black box" effect as they propagate up trophic levels. Our study shows that jellyfish polyps fail to accumulate EPA and DHA but display high levels of ARA compared to their zooplankton and phytoplankton food sources, suggesting a potential association with dietary EPA and DHA through an unidentified pathway. Certain FA components indicate variations in the turnover time when polyps undergo a dietary shift. Understanding the trajectory of FA metabolism across the "phytoplankton-zooplankton" interface, along with its turnover time, provides crucial insights for modeling diet estimation of components within food webs.

Study of intricate extraordinary Hall effect and magnetization switching behavior in graded GdFeCo ferrimagnet

Abstract This study delves into the unique properties of the GdFeCo Hall bar with a vertical composition gradient. Our exploration includes a detailed analysis of the temperature-dependent extraordinary Hall effect (EHE) response and magnetization-switching behavior. The findings reveal a FeCo-rich state at room temperature, characterized by an asymmetric drop at 20 Oe and a magnetic compensation temperature (Tcomp) around 150 K. The presence of triple hysteresis loops at 280 K and 270 K, along with unexpected changes in the EHE resistance difference (ΔRXY) at temperatures distant from Tcomp, hint at complex compositional effects similar to the artificial skyrmion-like Hall effect. The temperature points for zero ΔRXY values at ±30 kOe and ±4 kOe show a difference of 18 K, suggesting a spin-flop effect at compensation. Detailed analysis near Tcomp uncovers multiple loops, indicating coexisting Gd and FeCo sublattices with varied compositions. The magnetization switching experiments demonstrate field-driven switching and a limited role of electrical current in the system. These unique findings enhance our understanding of compositionally controlled ferrimagnets for spintronic applications.

Unravelling the multiple effects of H2O on the NH3-SCR over Mn2Cu1Al1Ox-LDO by transient kinetics and in situ DRIFTS

Understanding detrimental effects of water in the low-temperature NH3-SCR is very important for advancing the design of novel catalytic materials. Herein, the effects of 5 vol% H2O on the performance of NH3-SCR over Mn2Cu1Al1Ox-LDO were investigated through steady-state and transient kinetic analysis of step-gas switching experiments, in-situ DRIFTS and 15NO-SSITKA-DRIFTS operando. Water exhibited a significant negative activity effect at T<180 °C. Slightly positive activity (200–300 °C) and N2-selectvity (120–300 °C) effects were observed due to suppression of NH3 oxidation and NH4NO3 decomposition to N2O. The decline in activity at 140 °C by ∼ 45 % in the presence of water was found to be related to the decrease of the site activity (k) and not of surface coverage (θ) of active species formed in the NH3-SCR reaction paths of N2/N2O formation. An increase in the concentration of inactive NOx-s might also contribute to the inhibitive effect of water.

Picosecond Femtojoule Resistive Switching in Nanoscale VO2 Memristors.

Beyond-Moore computing technologies are expected to provide a sustainable alternative to the von Neumann approach not only due to their down-scaling potential but also via exploiting device-level functional complexity at the lowest possible energy consumption. The dynamics of the Mott transition in correlated electron oxides, such as vanadium dioxide, has been identified as a rich and reliable source of such functional complexity. However, its full potential in high-speed and low-power operation has been largely unexplored. We fabricated nanoscale VO2 devices embedded in a broadband test circuit to study the speed and energy limitations of their resistive switching operation. Our picosecond time-resolution, real-time resistive switching experiments and numerical simulations demonstrate that tunable low-resistance states can be set by the application of 20 ps long, <1.7 V amplitude voltage pulses at 15 ps incubation times and switching energies starting from a few femtojoule. Moreover, we demonstrate that at nanometer-scale device sizes not only the electric field induced insulator-to-metal transition but also the thermal conduction limited metal-to-insulator transition can take place at time scales of 100s of picoseconds. These orders of magnitude breakthroughs can be utilized to design high-speed and low-power dynamical circuits for a plethora of neuromorphic computing applications from pattern recognition to numerical optimization.

CMOS-compatible Hf0.5Zr0.5O2-based ferroelectric memory crosspoints fabricated with damascene process

We report the fabrication of Hf0.5Zr0.5O2 (HZO) based ferroelectric memory crosspoints using a complementary metal-oxide-semiconductor-compatible damascene process. In this work, we compared 12 and 56 µm2 crosspoint devices with the 0.02 mm2 round devices commonly used as a benchmark. For all devices, a 9 nm thick ferroelectric thin film was deposited by plasma-enhanced atomic layer deposition on planarized bottom electrodes. The wake-up appeared to be longer for the crosspoint memories compared to 0.02 mm2 benchmark, while all the devices reached a 2Pr value of ∼50 µC cm−2 after 105 cycles with 3 V/10 µs squared pulses. The crosspoints stand out for their superior endurance, which was increased by an order of magnitude. Nucleation limited switching experiments were performed, revealing a switching time <170 ns for our 12 and 56 µm2 devices, while it remained in the µs range for the larger round devices. The downscaled devices demonstrate notable advantages with a rise in endurance and switching speed.

SP-DG: A programmable packet-level scheduling for queuing delay guarantees in time-critical networks

Time-critical applications, such as remote surgery, virtual reality, and automatic driving, impose stringent requirements for minimizing delay and jitter. The queuing delay at forwarding nodes significantly affects application traffic. To tackle this challenge, Time-Sensitive Networking (TSN) techniques have been proposed to ensure deterministic queuing delay. However, existing deterministic solutions, including the Time-Aware Shaper (TAS) and the Cyclic Queuing and Forwarding (CQF) model, encounter limitations due to their reliance on precise synchronization and dedicated forwarding plane devices. In this paper, we present a novel solution: the Strict Priority queuing model with a queuing Delay Guarantees (SP-DG), specifically designed for programmable forwarding planes. This model introduces an upper bound on the queuing delay for packets at each switch, effectively characterizing their distinct queuing delay requirements. By utilizing exponential smoothing to predict traffic intensity, packets are intelligently scheduled to appropriate queues based on their upper-bound queuing delay requirements. Our Netbench simulation and P4 software switch experiments demonstrate that the proposed SP-DG algorithm, compared to the state-of-the-art SP-based queue scheduling algorithms, achieves superior performance in delay-bounded queue scheduling.

High‐Speed and Low‐Power 2 × 2 Thermo‐Optic Switch Based on Dual Silicon Topological Nanobeam Cavities

AbstractA 2 × 2 thermo‐optic (TO) switch using dual topological photonic crystal nanobeam (PCN) cavities on the silicon‐on‐insulator (SOI) platform is proposed and experimentally demonstrated. A Fano resonance is observed due to the interference between the topological interface state of the 1D topological PCN cavity and the Fabry‐Perot (F‐P) cavity mode formed between the two facets of the finitely long nanobeam waveguide. Thanks to the sharp rising edge of the spectral response of the Fano resonance and the high confinement of light in the topological PCN cavities, a 2 × 2 TO switch is realized with short switching time and low power consumption. The measured switching power is only 1.55 mW, and the rising time and the falling time are 3 and 5.6 µs, respectively in the on‐off switching experiments. To the best of the knowledge, this is the first time that a dual topological PCN structure is utilized to realize a high‐speed and low‐power TO switch, revealing the possibility of designing high‐performance reconfigurable optical devices and networks using topological photonics.

Activating information backflow with the assistance of quantum SWITCH

There are certain dynamics while being non-Markovian, do never exhibit information backflow. We show that if two such dynamical maps are considered in a scenario where the order of application of these two dynamical maps are not definite, the effective channel can manifest information backflow. In particular, we use quantum SWITCH to activate such a channel. In contrast, activation of those channels are not possible even if one uses many copies of such channels in series or in parallel action. We then investigate the dynamics behind the quantum SWITCH experiment and find out that after the action of quantum SWITCH both the CP (Complete Positive)- divisiblity and P (Positive)- divisibility of the channel breaks down, along with the activation of information backflow. Our study elucidate the advantage of quantum SWITCH by investigating its dynamical behaviour.

Learned switch readiness via concurrent activation of task sets: Evidence from task specificity and memory load.

Cognitive flexibility increases when switch demands increase. In task switching experiments, repeated pairing of flexibility-demanding situations with specific contexts leads subjects to become more prepared to adapt to changing task demands in those contexts. One form of such upregulated cognitive flexibility has been demonstrated with a list-wide switch probability (LWSP) effect, where switch costs are smaller in lists with frequent switches than in lists with rare switches. According to a recent proposal, the LWSP effect is supported by a concurrent activation mechanism whereby both task rules are kept available simultaneously in working memory. We conducted four experiments to test two key features in this concurrent activation account of LWSP effects. First, we asked whether the LWSP effects are limited to only the trained tasks, and second, we asked whether concurrent working memory load would reduce the LWSP effects. In Experiment 1, we replicated and extended previous findings that the LWSP manipulation modulates both performance (switch costs) and voluntary switch rates, indicating that context-driven increases in flexibility are generalizable so long as the task-sets remain the same. Results of Experiments 2 and 3 showed that novel tasks do not benefit from the concurrent activation of the two other tasks, suggesting that the LWSP effect is task specific. Experiment 4 showed that holding additional information in working memory reduces the LWSP effect. While these findings support the hypothesis of concurrent activation underlying the increased flexibility in the LWSP effect, caveats remain; additional research is needed to further test this account.

Effects of outcome revaluation on attentional prioritisation of reward-related stimuli.

Stimuli associated with rewards can acquire the ability to capture our attention independently of our goals and intentions. Here, we examined whether attentional prioritisation of reward-related cues is sensitive to changes in the value of the reward itself. To this end, we incorporated an instructed outcome devaluation (Experiment 1a), "super-valuation" (Experiment 1b), or value switch (Experiment 2) into a visual search task, using eye-tracking to examine attentional prioritisation of stimuli signalling high- and low-value rewards. In Experiments 1a and 1b, we found that prioritisation of high- and low-value stimuli was insensitive to devaluation of a previously high-value outcome, and super-valuation of a previously low-value outcome, even when participants were provided with further experience of receiving that outcome. In Experiment 2, following a value-switch manipulation, we found that prioritisation of a high-value stimulus could not be overcome with knowledge of the new values of outcomes alone. Only when provided with further experience of receiving the outcomes did patterns of attentional prioritisation of high- and low-value stimuli switch, in line with the updated values of the outcomes they signalled. To reconcile these findings, we suggest that participants were motivated to engage in effortful updating of attentional control settings when there was a relative difference between reward values at test (Experiment 2) but that previous settings were allowed to persist when both outcomes had the same value at test (Experiments 1a and 1b). These findings provide a novel framework to further understand the role of cognitive control in driving reward-modulated attention and behaviour.

Unusual magnetic behavior in Dy-doped LuFe0.5Cr0·5O3 perovskite ceramics

In this paper, polycrystalline Lu1-xDyxFe0.5Cr0·5O3 (0≤x≤0.15) perovskite ceramics were synthesized via a conventional solid-state-reaction technique. Structural and magnetic properties of the samples were experimentally studied. The cell volume of the lattice expands with the rise in Dy3+ amount. The measuring of magnetic properties shows that the undoped sample exhibits a negative magnetization effect with a compensation temperature of 231.1 K, while the Dy-doped samples display negative magnetization effects between two compensation temperatures. The magnetic switch experiment demonstrates the significant potential for practical applications through stable and repeatable switching of magnetization state by adjusting the external magnetic field between 50 Oe and 300 Oe. Besides, the presence of two compensation temperatures which can be regulated by changing the doping content or external magnetic field provides more possibilities for application. Moreover, based on the comprehensive analysis of the experimental results, it is believed that the negative magnetization effect originates from the competition of magnetic moments in different directions. Meanwhile, the second compensation temperature occurs in low temperature region might be attributed to the additional positive magnetic moment contributed by the paramagnetic Dy3+ ions.

Operando DRIFTS Investigations on Surface Intermediates and Effects of Potassium in CO2 Hydrogenation over a K−Fe/YZrOx Catalyst

AbstractA detailed operando DRIFTS study on the CO2 Fischer‐Tropsch reaction with K‐promoted Fe/YZrOx catalysts was performed to investigate the influence of this modification on the catalytic performance in the formation of lower olefins as well as higher hydrocarbons and to gain insights into mechanistic aspects. Catalytic testing revealed an enhanced formation of olefins and hydrocarbons by adding potassium to the catalysts, while spectroscopic studies revealed various stable adsorbates and intermediates such as monodentate carbonates, bicarbonates, formates, formyl, and methoxy on the surface of the K‐promoted Fe/YZrOx catalysts compared to the unpromoted one. Based on gas‐feed switching experiments and statistical analysis of literature IR data regarding Fe‐containing catalysts, it was found that carbonate species interacting with H2 are transformed to higher hydrocarbons and methane via formate and formyl formation, while bicarbonate species are decomposed accompanied by the formation of CO, which then further reacts to form formate or formyl and finally hydrocarbons.

A Novel Mixture-Devices-Based Submodule for MMC by Using Low on-State Voltage IGCT and High di/dt Ability IGBT

At present, insulated-gate bipolar transistor (IGBT) is widely used as the converter component in the submodule of modular multilevel converter (MMC) for its excellent performance in driving circuit and switching speed, but the further application is restricted by its high conduction loss and cost rate. Integrated gate-commutated thyristor (IGCT) is another converter device used in MMC with low conduction loss and cost. However, the d <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</i> /d <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i> capability of IGCT is limited so that a snubber circuit is required in the submodule for protection, which generates unwanted power loss for MMC. For better performance and reliability, this paper proposes a mixture-devices-based submodule (MS) for MMC based on the cooperation of parallel IGCT and IGBT devices. Double-pulse switching experiments for the MS are conducted to verify its effectiveness, and to get the data for the follow-up switching power loss calculation. The power loss of MMC based on IGBT, IGCT and mixture devices are calculated based on the model established in this paper. Furthermore, the comprehensive comparison for power loss among IGBT-based, IGCT-based and mixture-device-based MMCs are performed, proving the effectiveness of the mixture topology in terms of power loss reduction. Meanwhile, the proposed MS is cost-competitive.

Autonomous gait switching method and experiments of a hexapod walking robot for Mars environment with multiple terrains

Autonomous gait switching method and experiments of a hexapod walking robot for Mars environment with multiple terrains

Reinforcement learning of adaptive control strategies

Humans can up- or downregulate the degree to which they rely on task information for goal-directed behaviour, a process often referred to as cognitive control. Adjustments in cognitive control are traditionally studied in response to experienced or expected task-rule conflict. However, recent theories suggest that people can also learn to adapt control settings through reinforcement. Across three preregistered task switching experiments (n = 415), we selectively rewarded correct performance on trials with either more (incongruent) or less (congruent) task-rule conflict. Results confirmed the hypothesis that people rewarded more on incongruent trials showed smaller task-rule congruency effects, thus optimally adapting their control settings to the reward scheme. Using drift diffusion modelling, we further show that this reinforcement of cognitive control may occur through conflict-dependent within-trial adjustments of response thresholds after conflict detection. Together, our findings suggest that, while people remain more efficient at learning stimulus-response associations through reinforcement, they can similarly learn cognitive control strategies through reinforcement.

Multi‐Level Optical Switching by Amorphization in Single‐ and Multi‐Phase Change Material Structures

AbstractThe optical properties of phase‐change materials (PCMs) can be tuned to multiple levels by controlling the transition between their amorphous and crystalline phases. In multi‐material PCM structures, the number of discrete reflectance levels can be increased according to the number of PCM layers. However, the effect of increasing the number of layers on quenching and reversibility has not been thoroughly studied. In this work, the phase‐change physics and thermal conditions required for reversible switching of single and multi‐material PCM switches are discussed based on thermo‐optical phase‐change models and laser switching experiments. By using nanosecond laser pulses, 16 different reflectance levels in Ge2Sb2Te5 are demonstrated via amorphization. Furthermore, a multi‐material switch based on Ge2Sb2Te5 and GeTe with four discrete reflectance levels is experimentally proven with a reversible multi‐level response. The results and design principles presented herein will impact active photonics applications that rely on dynamic multi‐level operation, such as optical computing, beam steering, and next‐generation display technologies.

Inhibition of farnesylation of Ras-GTPases ameliorates inflammation-induced loss of endothelial barrier integrity and leukocyte transmigration

Abstract Background and Aims The family of small GTPases (Rho- and Ras-GTPases) is known to regulate endothelial cytoskeleton dynamics and hence barrier integrity. The role of Rho GTPases (RhoA and Rac1) in endothelial barrier integrity is well characterized; however, little is known about the role of Ras-GTPases. The activity of small GTPases is regulated by several mechanisms, including post-translational prenylation (farnesylation or geranylgeranylation). The Ras-GTPases are preferentially post-translationally farnesylated by farnesyl transferases (FTs). The aim of the present study was to investigate whether inhibition of farnesylation of Ras-GTPases protects loss of endothelial barrier integrity induced by inflammatory mediators. Methods and Results Treatment of human primary endothelial cells (ECs; HUVEC and lung microvascular ECs) with pharmacological inhibitor of farnesyl transferases (FTIs), LB42708 (LB) and tipifarnib, stabilized basal endothelial barrier function (albumin-flux) and abrogated thrombin-induced hyperpermeability in a concentration- and time-dependent manner reaching maximum at a concentration of 2 mmol/L after 12 h of incubation. These concentrations of the FTIs reduced farnesylation of all the Ras isoforms but not the geranylgeranylation of Rho GTPases. Likewise, LB abrogated the TNFa-induced leucocyte transendothelial migration (Trans-well assay). Interestingly, FTIs treatment caused an enhanced translocation of VE-cadherin to cell-cell junctions (confocal microscopy) without exerting any effect on the actin cytoskeleton or endothelial contractile machinery; mainly regulated by Rho GTPases. The Ca2+-switch experiments demonstrated an inhibition of VE-cadherin internalization. These data were reproduced by lentiviral-mediated stable over-expression of the prenylation-dead mutants of Ras isoforms but not RhoA or Rac1. Conclusion The novel data of the present study demonstrate that FTIs protect endothelial barrier function against inflammatory mediator-induced endothelial hyperpermeability. We propose that FTIs are novel drug candidates for the treatment of edematous conditions (such as lung edema) where endothelial barrier integrity is compromised.

Nitric Oxide is required for Primary Nitrate Response in Arabidopsis. Evidence for S-nitrosation of NLP7.

Nitrogen (N) is an essential nutrient for plant growth and seed production, being nitrate the main source of N in soils. Although several molecular players of plant responses to nitrate signaling were unraveled, it still remains a complex pathway with gaps demanding further investigation. The aim of our study is to analyze the role of Nitric Oxide (NO) in the Primary Nitrate Response (PNR). Using a combination of genetic and pharmacological approaches, we demonstrate that NO is required for the expression of the nitrate-regulated genes NIA1, NIR, NRT1.1, and NRT2.1 in Arabidopsis. The PNR is blocked in the Arabidopsis mutant noa1, defective in NO production. Our results also show that Phytoglobin 1, involved in NO homeostasis, is rapidly induced during PNR in wt but not in mutants nrt1.1 and nlp7, suggesting that NRT1.1-NLP7 cascade modulates Phytoglobin expression. Biotin switch experiments demonstrate that NLP7, the PNR-master regulator, is S-nitrosated. NO appears to be not involved in the decrease of ROS concentration necessary for the PNR to take place, indicating that ROS and NO acts in independent ways. Besides, in the absence of NO, PNR does not occur even when the ROS concentration is low, indicating that the decrease in ROS concentration is a necessary but not sufficient condition for PNR to occur. Conclusion and Innovation: NO, a byproduct of nitrate metabolism and a well characterized signal molecule in plants, is a critical player in the PNR.