This article proposes a multiple self-sensing gripper (MssGripper) driven by the shape memory alloy (SMA) and empowered by machine learning algorithms. The MssGripper can identify objects without ...external sensors. A single SMA wire can drive the gripper for self-sensing accurately. This article confirms the resistance of the SMA can reflect the phase transition and can be used for displacement and force prediction, as well as for object stiffness prediction. Through machine learning, a backpropagation neural network and long-short-term-memory (LSTM) are used to establish multiple self-sensing models for prediction. The robustness experimental results show that the self-sensing models based on LSTM have higher prediction accuracy. The average root-mean-square errors of displacement prediction and force prediction are 0.063 mm and 0.236 N, respectively, and the stiffness prediction error is less than 9.4%. Moreover, the accuracy of the classifier in stiffness identification is 97.2%. The MssGripper can accurately predict the displacement, force, and stiffness and identify objects such as springs, rubber bars and steel bars. The establishment of the models expands the novel idea of gripper sensing, which is beneficial to promoting miniaturization and compactness.
An experimental setup, on which the shape-memory effect is based, is developed to measure the free-response frequency and musical pitches of shape memory alloy (SMA) wires. In this article, the ...voltage, force, and sound signals of SMA wires are determined simultaneously under two kinds of experiments: 1) constant-temperature uniaxial tensile tests and 2) fixed-length thermal cycle tests. Based on constitutive equations and thermodynamic equations, an empirical formula for the driving voltage and the steady-state stress of SMA wires is proposed, and the undetermined coefficients at radii of 0.050 and 0.070 mm are determined by experiments. The musical pitches of SMA wires under a constant voltage are obtained by combining the empirical formula with the string vibration equation. The theoretical results are compared with the actual musical pitches measured by the sound signals, and the theoretical results are highly consistent with the actual musical pitch. Just for an SMA wire with a radius of 0.070 mm, the free-response frequency range reaches 640-1120 Hz, which covers 6 whole musical tones in total. Thus, the SMA wire can be used as a string to play simple music.
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•Detection method and driving strategy of shape memory alloy wires are discussed.•An improved phase transformation equation with the Logistic function is proposed.•SMA wires electric ...resistance and its rate are studied in theory and experiment.•Phase transformation start/end points are detected by electric resistance method.•Optimized driving strategy is proposed to reduce power consumption of SMA wires.
To propose a novel driving strategy for power consumption reduction, this paper studies the electric resistance behaviors of shape memory alloy (SMA) wires, which are heated by the short-time large current. With a concern for the relationship between electric resistance and shape memory effect, an improved phase transformation equation with the Logistic function is proposed. Moreover, based upon electric resistance and its rate, a new detection method for the driving strategy of SMA wires is proposed. The proposed method is compared with the traditional deformation detection method. The results show that the method effectively resists the interference of system noise and captures the start and end points of phase transformation. To assess the deformation response of SMA wires by the proposed method, constant load tests are conducted, which are applied with the periodic excitation signals of triangular wave, sine wave, and square wave, respectively. The experimental results show the square wave is more suitable for driving the SMA wire actuator. The heating and cooling cycle experiment verifies the effectiveness of the proposed method. Compared with the method using pulse width modulation signals, the proposed method reduces power consumption obviously, and does not need external sensors or material parameters. Based on the proposed method, the power consumption can be reduced by the optimized driving strategy, which improves the lightweight and reliability of SMA actuators.
The adjustment of cellular redox homeostasis is essential in when responding to environmental perturbations, and the mechanism by which cells distinguish between normal and oxidized states through ...sensors is also important. In this study, we found that acyl-protein thioesterase 1 (APT1) is a redox sensor. Under normal physiological conditions, APT1 exists as a monomer through S-glutathionylation at C20, C22 and C37, which inhibits its enzymatic activity. Under oxidative conditions, APT1 senses the oxidative signal and is tetramerized, which makes it functional. Tetrameric APT1 depalmitoylates S-acetylated NAC (NACsa), and NACsa relocates to the nucleus, increases the cellular glutathione/oxidized glutathione (GSH/GSSG) ratio through the upregulation of glyoxalase I expression, and resists oxidative stress. When oxidative stress is alleviated, APT1 is found in monomeric form. Here, we describe a mechanism through which APT1 mediates a fine-tuned and balanced intracellular redox system in plant defence responses to biotic and abiotic stresses and provide insights into the design of stress-resistant crops.
Shape memory alloy (SMA) springs have been widely applied in engineering. However, there are few studies on the driving characteristics of the reverse deformation SMA springs which stretch during ...heating and contract during cooling. It is necessary to develop a specialized experimental setup that can measure the driving characteristics of these special SMA springs, including temperature, deformation, and restoring force in a reciprocating continuous way. In this paper, an experimental setup with a water bath has been developed. Based on the setup, the comprehensive relationship between temperature, deformation, and restoring force of the reverse deformation SMA spring can be obtained by only one thermal cycle. The experiment results show that the maximum deformation decreases linearly with the increase of restoring force, and the deformation is negatively correlated with the maximum restoring force. Moreover, the martensite reverse transformation leads to an increase of the spring coefficient. The shear modulus increases with the increase of temperature. It is also concluded that the size of the spring affects the restoring force and deformation. Finally, the driving characteristics are modeled and analyzed theoretically, and the simulation results are consistent with the experimental results. The experimental setup and methods can be useful for designing temperature control valves and switches, without an additional heat source.
Abstract We present a detailed analysis of the unusual absorption- and emission-line spectrum of the quasar SDSS J074850.39+442439.0 (hereafter J0748+4424) at a redshift of z = 2.18. The archival ...SDSS optical spectrum is abundant in narrow absorption lines (NALs) originating from mostly singly ionized iron, nickel, and silicon ions at both ground and excited levels. With the aid of the photoionization simulations, we find that these NALs can be reasonably well reproduced by a homogeneous gas slab with a neutral hydrogen column density of 10 21.6 –10 21.9 cm −2 and a number density of 10 6.0 –10 6.6 cm −3 illuminated by the quasar central engine with an ionization parameter of 10 −2.8 –10 −2.1 . We infer the gas is located at a distance of ∼30–130 pc from the black hole. This circumnuclear gas can reveal itself in emission lines of a width of ∼1000 km s −1 . Such intermediate-width emission lines (IELs) are indeed dominant in the observed Ly α emission, as the Ly α broad emission line (BEL) is mostly eaten up by the expected damped Ly α absorption (DLA). The IELs, though rather weak, are also detected in H α and O iii emission lines. The IEL intensities largely agree with the predicted values by the simplified photoionization models using the parameters derived from the absorption lines and a covering fraction of 10%. The intrinsic DLA in J0748+4424, while itself contains abundant information on the circumnuclear environment, may serve as a “natural coronagraph” at the line of sight, exposing the IELs that are otherwise overwhelmed by the BELs.
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•A new method for energy storage ejection is proposed using superelastic SMA wire.•A novel concept of correlating energy and SMA resistance change rate is proposed.•Ejection energy ...density and energy conversion efficiency are investigated by test.•Theoretical prediction model for ejection energy density of SMA wire is developed.
Superelastic shape memory alloy (SMA) wire is a memorable deformation material with large resilience and high energy density. In this paper, a revolutionary and yet explainable property of the SMA is investigated and confirmed: superelastic SMA energy storage and release can be quantitatively measured using electrical resistance. This finding boosted the SMA with significant advantages and potential in the field of mechanical energy storage and ejection release. A state-of-the-art energy storage ejection device is designed to test the relationship among SMA wires' stress, strain, and electrical resistance. The resistance change rate, ejection energy density and energy conversion efficiency are studied in the SMA wire energy tests. The experimental results confirm that the resistance change rate of the superelastic SMA wire has a stable linear relationship with the strain. The ejection energy density increases with the resistance change rate. A theoretical model of the relationship between the ejection energy density and resistance change rate is established based on the experimental results. In conclusion, the superelastic SMA wire can achieve sophisticated tasks that require ‘programmable’ and predictable energy storage or ejection.
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•A phase transition detection method is proposed for self-sensing and robustness.•Excitation signal is optimized for the thermal cycle pretreatment of SMA wire.•Thermal equilibrium ...points and end points of phase transition are distinguished.•A detection algorithm is developed based upon filtering and outlier processing.•A resistance-displacement regression model is built for displacement estimation.
Shape memory alloy (SMA) wires are widely used as actuators because of their simplicity, high energy ratio, and Joule heat activation. The resistance behavior caused by the phase transition can predict the stress or strain of the SMA wire, which is called self-sensing. At present, there are researches on detecting the start and end points of phase transition based on resistance. However, the anti-interference ability of these researches is poor, and it is difficult to identify the thermal equilibrium points. Therefore, this paper proposes a novel resistance-based phase transition detection method with good robustness and displacement estimation. Firstly, the excitation signal is optimized for the thermal cycle pretreatment of the SMA wire. Secondly, the interferences of the resistance signal are determined, which are noise, small current signals, and step signals. Finally, using filtering and outlier processing, a phase transition region detection algorithm based on the difference of resistance extreme values is proposed. Moreover, a resistance-displacement model is established through linear regression. The experimental results show that the proposed method effectively resists the interference of signals and has good robustness. The mean relative error between the estimated and measured displacements is 4.43%. The resistance-displacement model effectively estimates the displacement of the SMA wire actuator and distinguishes the thermal equilibrium points and the end points of the phase transition. The proposed method can be used potentially for real-time phase transition detection, overheating protection, power consumption reduction, and self-sensing drive of sensorless actuators.
Water scarcity is a worldwide problem, and in order to obtain plenty of production, agricultural irrigation water accounts for a large portion. Many studies have shown that the interaction of root ...microorganisms and soil can promote crop growth. Developing ways to reduce irrigation to maintain soil fertility and ensure crop yield by regulating the root microenvironment is an important research goal. Here, we developed a reasonable irrigation plan for eggplant cultivation in a solar greenhouse. The maximum theoretical amount of water demand during eggplant planting obtained from a previous study was used as the control (CK), and the irrigation in the treatments was reduced by 10, 20 and 30% relative to this amount. The 10% irrigation reduction treatment (T1) significantly improved soil nutrients and increased soil catalase, urease and alkaline phosphatase activities (
p
< 0.05). Further analysis of rhizosphere microorganisms revealed the highest richness and diversity of the microbial community under the T1 treatment, with Bacilli as the most abundant bacteria and Aspergillaceae as the most abundant fungi and lower relative abundances of Chloroflexi and Acidobacteria (
p
< 0.05). Changes in microbial community structure under the influence of different irrigation treatments resulted in improvements in rhizosphere N cycling and nutrient catabolism. The plant–microbe interactions led to significant increases in eggplant plant height, root vigour, root surface area, leaf chlorophyll a, leaf net photosynthetic rate, water use efficiency, transpiration rate, and stomatal conductance under the T1 treatment compared to the CK treatment; soluble sugar, soluble protein and free amino acid contents in eggplant fruit increased by 10.8, 12.3 and 6.7%, respectively; and yield increased by 3.9%. Our research proved that the 10% irrigation reduction treatment (T1) could improve microbial community richness and fruit yield, which would improve irrigation efficiency and cost reduction in agriculture.
