Construction of a Fish-like Robot Based on High Performance Graphene/PVDF Bimorph Actuation Materials.

Smart actuators have many potential applications in various areas, so the development of novel actuation materials, with facile fabricating methods and excellent performances, are still urgent needs. In this work, a novel electromechanical bimorph actuator constituted by a graphene layer and a PVDF layer, is fabricated through a simple yet versatile solution approach. The bimorph actuator can deflect toward the graphene side under electrical stimulus, due to the differences in coefficient of thermal expansion between the two layers and the converse piezoelectric effect and electrostrictive property of the PVDF layer. Under low voltage stimulus, the actuator (length: 20 mm, width: 3 mm) can generate large actuation motion with a maximum deflection of about 14.0 mm within 0.262 s and produce high actuation stress (more than 312.7 MPa/g). The bimorph actuator also can display reversible swing behavior with long cycle life under high frequencies. on this basis, a fish-like robot that can swim at the speed of 5.02 mm/s is designed and demonstrated. The designed graphene-PVDF bimorph actuator exhibits the overall novel performance compared with many other electromechanical avtuators, and may contribute to the practical actuation applications of graphene-based materials at a macro scale

Neuro-symbolic Models for Interpretable Time Series Classification using Temporal Logic Description

Most existing Time series classification (TSC) models lack interpretability and are difficult to inspect. Interpretable machine learning models can aid in discovering patterns in data as well as give easy-to-understand insights to domain specialists. In this study, we present Neuro-Symbolic Time Series Classification (NSTSC), a neuro-symbolic model that leverages signal temporal logic (STL) and neural network (NN) to accomplish TSC tasks using multi-view data representation and expresses the model as a human-readable, interpretable formula. In NSTSC, each neuron is linked to a symbolic expression, i.e., an STL (sub)formula. The output of NSTSC is thus interpretable as an STL formula akin to natural language, describing temporal and logical relations hidden in the data. We propose an NSTSC-based classifier that adopts a decision-tree approach to learn formula structures and accomplish a multiclass TSC task. The proposed smooth activation functions for wSTL allow the model to be learned in an end-to-end fashion. We test NSTSC on a real-world wound healing dataset from mice and benchmark datasets from the UCR time-series repository, demonstrating that NSTSC achieves comparable performance with the state-of-the-art models. Furthermore, NSTSC can generate interpretable formulas that match with domain knowledge

Characteristics of Pollen from Transgenic Lines of Apple Carrying the Exogenous CpTI Gene

AbstractIt is fundamental for gene transformation and ecosystem hazard evaluation to study the pollen characteristics of transgenic plants. In this research, the characteristics of pollen from 7- or 8-year-old transgenic apple plants carrying an exogenous CpTI gene were analyzed. The results showed that there was no significant difference in terms of size, morphology, or exine ornamentation between the pollen of the transgenic plants and the non-transgenic control. However, the transgenic plants had more abnormal pollen grains. Of the 13 transgenic lines tested, 12 had a significantly lower amount of pollen and six exhibited a significantly lower germination rate when cultured in vitro. The pollen viability of three transgenic lines was determined, with two showing significantly lower viability than the control. The transgenic Gala apple pollen grains germinated normally via controlled pollination on Fuji apple stigmas. However, the pollen tubes extended relatively slowly during the middle and late development stages, and another 8h were needed to reach the ovules compared with the control. The gibberellic acid concentration in transgenic Gala apple flowers was lower than in the non-transgenic control during all development stages tested. The abscisic acid concentration in the transgenic flowers was lower during the pink stage, and higher during the ball and fully open stages. Microscopic observation of the anther structure showed no difference. The tapetum of the pollen sac wall in transgenic plants decomposed late and affected pollen grain development, which could be one of the reasons for the lower number of pollen grains and poor viability in the transgenic plants

Evaluation of IEEE802.15.4g for Environmental Observations

International audienceIEEE802.15.4g is a low-power wireless standard initially designed for Smart Utility 1 Networks, i.e. for connecting smart meters. IEEE802.15.4g operates at sub-GHz frequencies to offer 2 2-3× longer communication range compared to its 2.4 GHz counterpart. Although the standard 3 offers 3 PHYs (FSK, OFDM and O-QPSK) with numerous configurations, 2-FSK at 50 kbps is the 4 mandatory and most prevalent radio setting used. This article looks at whether IEEE802.15.4g can 5 be used to provide connectivity for outdoor deployments. We conduct range measurements using 6 the totality of the standard (all modulations with all further parametrization) in the 863-870 MHz 7 band, within four scenarios which we believe cover most low-power wireless outdoor applications: 8 line of sight, smart agriculture, urban canyon, and smart metering. We show that there are radio 9 settings that outperform the "2-FSK at 50 kbps" base setting in terms of range, throughput and 10 reliability. Results show that highly reliable communications with data rates up to 800 kbps can 11 be achieved in urban environments at 540 m between nodes, and the longest useful radio link is 12 obtained at 779 m. We discuss how IEEE802.15.4g can be used for outdoor operation, and reduce 13 the number of repeater nodes that need to be placed compared to a 2.4 GHz solution

Constructive Interference in 802.15.4: A Tutorial

International audienceConstructive Interference (CI) can happen when multiple wireless devices send the same frame at the same time. If the time offset between the transmissions is less than 500 ns, a receiver will successfully decode the frame with high probability. CI can be useful for achieving low-latency communication or low-overhead flooding in a multi-hop low-power wireless network. The contribution of this article is threefold. First, we present the current state-of-the-art CI-based protocols. Second, we provide a detailed hands-on tutorial on how to implement CI-based protocols on TelosB motes, with well documented open-source code. Third, we discuss the issues and challenges of CI-based protocols, and list open issues and research directions. This article is targeted at the level of practicing engineers and advanced researchers and can serve both as a primer on CI technology and a reference to its implementation

6TiSCH Minimal Scheduling Function: Performance Evaluation

International audience6TiSCH is a standardization group within the Internet Engineering Task Force (IETF) that works on IPv6-enabled Time-slotted Channel Hopping (TSCH) networks. The 6TiSCH protocol stack, designed by the standardization work at the IETF, has direct applicability to low-power Internet of Things (IoT) use cases, including smart factory, building, infrastructure and home applications. A key component of the 6TiSCH stack is the Minimal Scheduling Function (MSF). MSF implements a traffic adaptation algorithm which allocates link-layer resources, i.e. cells in the TSCH schedule, according to the traffic load. MAX_NUMCELL is an important parameter defined in the MSF draft standard which determines the length of the running window used to measure cell usage. MSF draft standard does not recommend a value of MAX_NUMCELL to use. This paper provides recommendations on how to choose the value of MAX_NUMCELL, validated through simulation. For periodic traffic , setting MAX_NUMCELL to at least 4 times the traffic load is recommended to increase efficiency. For bursty traffic, we show that setting MAX_NUMCELL to a small value achieves a low end-to-end latency but at high communication overhead. In addition, an improved version of MSF is implemented and tested, which shows a 44% reduction in the communication overhead, considering MAX_NUMCELL = 4, while maintaining the same end-to-end latency

Surviving the Hair Dryer: Continuous Calibration of a Crystal-Free Mote-on-Chip

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Key Performance Indicators of the Reference 6TiSCH Implementation in Internet-of-Things Scenarios

International audienceTens of thousands of wireless industrial monitoring deployments exist today, logging more than 18 billion operating hours. These solutions have been around for over a decade and are based on standards such as WirelessHART and ISA100.11a to provide performance guarantees to the applications. The new trend in industry deployments is the convergence of operational and information technologies happening through the Industrial Internet of Things (IIoT) paradigm. The challenge is to bridge the performance of these well-proven industrial standards with the interoperability of IP-based systems. The Internet Engineering Task Force (IETF), the organization behind most of the technical solutions of the Internet, has produced a set of specifications with this requirement in mind. The output of this effort is the 6TiSCH protocol stack based on open standards, such as those that have played a key role in the Internet's ubiquitous adoption. The standardization of 6TiSCH is done. The state-of-the-art research work focus is on important, but niche, optimizations and performance evaluations of the 6TiSCH stack. This paper takes a different approach-it evaluates the performance of the standards-compliant 6TiSCH solution from the end user point of view. It does so on two experimental testbeds, in typical IoT test scenarios based on a well-defined experimentation methodology. We provide a set of Key Performance Indicators (KPIs) useful for the end user to decide whether the 6TiSCH technology is a good fit performance-wise for a particular use case. We demonstrate reliability of a vanilla open-source implementation of 6TiSCH above 99.99%, upstream latency on the order of a second and radio duty cycle well below 1%