This paper aimed to develop and evaluate an environment-aware locomotion mode recognition system for volitional control of powered artificial legs. A portable terrain recognition (TR) module, ...consisting of an inertia measurement unit and a laser distance meter, was built to identify the type of terrain in front of the wearer while walking. A decision tree was used to classify the terrain types and provide either coarse or refined information about the walking environment. Then, the obtained environmental information was modeled as a priori probability and was integrated with a neuromuscular-mechanical-fusion-based locomotion mode (LM) recognition system. The designed TR module and environmental-aware LM recognition system was evaluated separately on able-bodied subjects and a transfemoral amputee online. The results showed that the TR module provided high quality environmental information: TR accuracy is above 98% and terrain transitions are detected over 500 ms before the time required to switch the prosthesis control mode. This enabled smooth locomotion mode transitions for the wearers. The obtained environmental information further improved the performance of LM recognition system, regardless of whether coarse or refined information was used. In addition, the environment-aware LM recognition system produced reliable online performance when the TR output was relatively noisy, which indicated the potential of this system to operate in unconstructed environment. This paper demonstrated that environmental information should be considered for operating wearable lower limb robotic devices, such as prosthetics and orthotics.
A low‐profile patch antenna with dual‐polarisation and high gain is proposed in this study. It contains a primary radiator, a secondary radiator, and a planar feed network. The primary and secondary ...radiators are square patches placed 5 mm from each other. Two planar feed networks are electrically connected with the primary radiator through the stepped impedance transformer, providing equal amplitude and 180° phase shift signals. These two feed networks are settled in different layers to weaken the coupling effect. The resonance generated by the primary radiator is merged with the one by the secondary radiator, covering the 3.3–3.6 GHz band. Benefiting from the differential feed method, antenna specifications such as port isolation and cross‐polarisation discrimination (XPD) are ideal. Moreover, as the primary radiator is fed by planar microstrip, the overall height can be reduced, and the gain can be enhanced. Finally, a 2 × 2 subarray is investigated. Desirable results show that the proposed antenna is suitable for application in Massive Multiple Input and Multiple Output (MIMO) systems.
A low‐profile patch antenna with dual‐polarisation and high gain is proposed in this paper. Benefiting from the differential feed method, antenna specifications such as port isolation and cross‐polarisation discrimination (XPD) are ideal. Moreover, as the primary radiator is fed by planar microstrip, the overall height can be reduced, and the gain can be enhanced.
Algorithms for locomotion mode recognition (LMR) based on surface electromyography and mechanical sensors have recently been developed and could be used for the neural control of powered prosthetic ...legs. However, the variations in input signals, caused by physical changes at the sensor interface and human physiological changes, may threaten the reliability of these algorithms. This study aimed to investigate the effectiveness of applying adaptive pattern classifiers for LMR. Three adaptive classifiers, i.e., entropy-based adaptation (EBA), LearnIng From Testing data (LIFT), and Transductive Support Vector Machine (TSVM), were compared and offline evaluated using data collected from two able-bodied subjects and one transfemoral amputee. The offline analysis indicated that the adaptive classifier could effectively maintain or restore the performance of the LMR algorithm when gradual signal variations occurred. EBA and LIFT were recommended because of their better performance and higher computational efficiency. Finally, the EBA was implemented for real-time human-in-the-loop prosthesis control. The online evaluation showed that the applied EBA effectively adapted to changes in input signals across sessions and yielded more reliable prosthesis control over time, compared with the LMR without adaptation. The developed novel adaptive strategy may further enhance the reliability of neurally-controlled prosthetic legs.
Monolayer of 2D transition metal dichalcogenides, with a thickness of less than 1 nm, paves a feasible path to the development of ultrathin memristive synapses, to fulfill the requirements for ...constructing large‐scale high density 3D stacking neuromorphic chips. Herein, memristive devices based on monolayer n‐MoS2 on p‐Si substrate with a large self‐rectification ratio, exhibiting photonic potentiation and electric habituation, are successfully fabricated. Versatile synaptic neuromorphic functions, such as potentiation/habituation, short‐term/long‐term plasticity, and paired‐pulse facilitation, are successfully mimicked based on the inherent persistent photoconductivity performance and the volatile resistive switching behavior. These findings demonstrate the potential applications of ultrathin transition metal dichalcogenides for memristive synapses. These memristive synapses with the combination of photonic and electric neuromorphic functions have prospective in the applications of synthetic retinas and optoelectronic interfaces for integrated photonic circuits based on mixed‐mode electro‐optical operation.
Synergetic optical and electrical neuromorphic functions are demonstrated in the memristive synapses based on monolayer MoS2. These ultrathin artificial synapses with the behavior of photonic potentiation and electric habituation have prospective in the applications of synthetic retinas and optoelectronic interfaces for integrated photonic circuits based on the mixed electro‐optical operation.
Over the last two decades, tremendous advances have been made for constructing large-scale quantum computers. In particular, quantum computing platforms based on superconducting qubits have become ...the leading candidate for scalable quantum processor architecture, and the milestone of demonstrating quantum supremacy has been first achieved using 53 superconducting qubits in 2019. In this study, we provide a brief review on the experimental efforts towards the large-scale superconducting quantum computer, including qubit design, quantum control, readout techniques, and the implementations of error correction and quantum algorithms. Besides the state of the art, we finally discuss future perspectives, and which we hope will motivate further research.
The ability to efficiently simulate random quantum circuits using a classical computer is increasingly important for developing noisy intermediate-scale quantum devices. Here, we present a tensor ...network states based algorithm specifically designed to compute amplitudes for random quantum circuits with arbitrary geometry. Singular value decomposition based compression together with a two-sided circuit evolution algorithm are used to further compress the resulting tensor network. To further accelerate the simulation, we also propose a heuristic algorithm to compute the optimal tensor contraction path. We demonstrate that our algorithm is up to 2 orders of magnitudes faster than the Schrödinger-Feynman algorithm for verifying random quantum circuits on the 53-qubit Sycamore processor, with circuit depths below 12. We also simulate larger random quantum circuits with up to 104 qubits, showing that this algorithm is an ideal tool to verify relatively shallow quantum circuits on near-term quantum computers.
Considering that the human brain uses ≈1015 synapses to operate, the development of effective artificial synapses is essential to build brain‐inspired computing systems. In biological synapses, the ...voltage‐gated ion channels are very important for regulating the action‐potential firing. Here, an electrolyte‐gated transistor using WO3 with a unique tunnel structure, which can emulate the ionic modulation process of biological synapses, is proposed. The transistor successfully realizes synaptic functions of both short‐term and long‐term plasticity. Short‐term plasticity is mimicked with the help of electrolyte ion dynamics under low electrical bias, whereas the long‐term plasticity is realized using proton insertion in WO3 under high electrical bias. This is a new working approach to control the transition from short‐term memory to long‐term memory using different gate voltage amplitude for artificial synapses. Other essential synaptic behaviors, such as paired pulse facilitation, the depression and potentiation of synaptic weight, as well as spike‐timing‐dependent plasticity are also implemented in this artificial synapse. These results provide a new recipe for designing synaptic electrolyte‐gated transistors through the electrostatic and electrochemical effects.
An electrolyte‐gated transistor using WO3 with a unique tunnel structure to successfully emulate the synaptic functions of both short‐term and long‐term plasticity is proposed. Short‐term plasticity is mimicked with the help of electrolyte ion dynamics under low gate bias, and the long‐term plasticity is realized via proton insertion in WO3 under high gate bias.
Engineering proteins for thermostability is an exciting and challenging field since it is critical for broadening the industrial use of recombinant proteins. Thermostability of proteins arises from ...the simultaneous effect of several forces such as hydrophobic interactions, disulfide bonds, salt bridges and hydrogen bonds. All of these interactions lead to decreased flexibility of polypeptide chain. Structural studies of mesophilic and thermophilic proteins showed that the latter need more rigid structures to compensate for increased thermal fluctuations. Hence flexibility can be an indicator to pinpoint weak spots for enhancing thermostability of enzymes. A strategy has been proven effective in enhancing proteins' thermostability with two steps: predict flexible sites of proteins firstly and then rigidify these sites. We refer to this approach as rigidify flexible sites (RFS) and give an overview of such a method through summarizing the methods to predict flexibility of a protein, the methods to rigidify residues with high flexibility and successful cases regarding enhancing thermostability of proteins using RFS.
•RFS approach used for enhancing thermostability of enzymes is overviewed.•We summarize the methods to predict flexibility and to rigidify flexible sites.•Cases using RFS are analyzed and its performance is discussed.•We firstly give a schematic representation of RFS.
The electrophotocatalytic SNAr reaction of unactivated aryl fluorides at ambient temperature without strong base is demonstrated.
Unactivated aryl fluorides engage in SNAr reactions at room ...temperature and without a strong base using DDQ as an electrophotocatalyst.
A method to weaken the interference of antennas working in different frequencies is proposed in this paper. It uses a Frequency Selective Surface (FSS) placed between two different antennas. For one ...antenna, the FSS acts as an electromagnetically transparent structure, so the electromagnetic wave will penetrate the FSS and radiates into the free space. For the other one, the FSS acts as an artificial magnetic conductor, reflecting the incoming energy. With this design, two adjacent antennas could keep their individual performance especially radiation patterns normal. It is worth noting that although the FSS has been used in many aspects, such as reducing antenna's radar cross section or reducing the coupling between the identical antennas, its application in the field of 'different antennas decoupling' is the first time. An embodiment is displayed in this paper for verification. Two antennas worked at different bands of 5G are placed very close with an FSS structure inserted. It turns out that the whole antenna has good electrical and radiation properties over the working band. This decoupling strategy can be very useful in 5G Massive MIMO application.
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