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Vibration energy harvesting systems via an X-structure coupled with piezoelectric patches of special arrangements are investigated in this study. Two piezoelectric harvesters are specially installed on the X-shaped structure to explore potential benefits that the X-shaped structure could provide, and each piezoelectric pad has two layers composed of a polyvinyl chloride base patch and a micro-fibre composite patch. The theoretical analysis and experiment results indicate that the energy harvesting performance of the proposed novel arrangements of the piezoelectric harvesters can be enhanced especially in low-frequency range (below 10 Hz), compared with conventional cantilevered piezoelectric harvesters. More and higher energy harvesting peaks can be created and the effective harvesting frequency band can be obviously enlarged by expanding it to low-frequency range with the proposed methods. The X-structure-based generators can enable piezoelectric materials to harvest power from low-frequency vibration sources due to its advantages in designable equivalent nonlinear stiffness, which can be easily tuned by adjusting the key structural parameters. The design and results would provide an innovative solution and insight for smart piezoelectric materials to improve the energy harvesting efficiency in the low-frequency range including small-scale ocean wave power harvesting, human motion power and animal kinetic power harvesting, etc.

Gradient heterostructure is one of fundamental interfaces and provides an effective platform to achieve gradually changed properties in mechanics, optics, and electronics. Among different types of heterostructures, the gradient one may provide multiple resistive states and immobilized conductive filaments, offering great prospect for fabricating memristors with both high neuromorphic computation capability and repeatability. Here, we invent a memristor based on a homologous gradient heterostructure (HGHS), comprising a conductive transition metal dichalcogenide and an insulating homologous metal oxide. Memristor made of Ta–TaSxOy–TaS2 HGHS exhibits continuous potentiation/depression behavior and repeatable forward/backward scanning in the read‐voltage range, which are dominated by multiple resistive states and immobilized conductive filaments in HGHS, respectively. Moreover, the continuous potentiation/depression behavior makes the memristor serve as a synapse, featuring broad‐frequency response (10−1–105 Hz, covering 106 frequency range) and multiple‐mode learning (enhanced, depressed, and random‐level modes) based on its natural and motivated forgetting behaviors. Such HGHS‐based memristor also shows good uniformity for 5 × 7 device arrays. Our work paves a way to achieve high‐performance integrated memristors for future artificial neuromorphic computation. We invent a memristor based on a homologous gradient heterostructure (HGHS), comprising a conductive transition metal dichalcogenide and an insulating homologous metal oxide. Memristor made of Ta–TaSxOy–TaS2 HGHS exhibits continuous potentiation/depression behavior and repeatable forward/backward scanning in the read‐voltage range, which are dominated by multiple resistive states and immobilized conductive filaments in HGHS, respectively.

Speech production gives rise to distinct auditory and somatosensory feedback signals which are dynamically integrated to enable online monitoring and error correction, though it remains unclear how the sensorimotor system supports the integration of these multimodal signals. Capitalizing on the parity of sensorimotor processes supporting perception and production, the current study employed the McGurk paradigm to induce multimodal sensory congruence/incongruence. EEG data from a cohort of 39 typical speakers were decomposed with independent component analysis to identify bilateral mu rhythms; indices of sensorimotor activity. Subsequent time-frequency analyses revealed bilateral patterns of event related desynchronization (ERD) across alpha and beta frequency ranges over the time course of perceptual events. Right mu activity was characterized by reduced ERD during all cases of audiovisual incongruence, while left mu activity was attenuated and protracted in McGurk trials eliciting sensory fusion. Results were interpreted to suggest distinct hemispheric contributions, with right hemisphere mu activity supporting a coarse incongruence detection process and left hemisphere mu activity reflecting a more granular level of analysis including phonological identification and incongruence resolution. Findings are also considered in regard to incongruence detection and resolution processes during production.

Changes in the acoustic signalling of animals occupying urban ecosystems is often associated with the masking effects of noise pollution, but the way in which they respond to noise pollution is not straightforward. An increasing number of studies indicate that responses can be case specific, and some species have been found to respond differently to high levels of natural versus anthropogenic noise, as well as different levels of the latter. While the perception of noise between species may vary with its source, amplitude and temporal features, some species may possess broader environmental tolerance to noise pollution, as they use higher frequency vocalizations that are less masked by low-frequency urban noise. In this study, we explored the song variation of two closely related leaf warblers, the Common Chiffchaff Phylloscopus collybita and the Willow Warbler Phylloscopus trochilus , inhabiting urban green spaces and nonurban forests. The main goal of our study was to evaluate the impact of moderate levels of noise pollution on the songs of species which use higher frequency vocalizations and large frequency bandwidth. Previous studies found that the Common Chiffchaff modified their song in response to intense noise pollution, while no such data is available for the Willow Warbler. However, the majority of urban green spaces, which serve as wildlife hot spots in urban environments are usually polluted with moderate noise levels, which may not mask the acoustic signals of species that communicate with higher frequency. We analysed the spectral and temporal song parameters of both warblers and described the ambient noise present in males’ territories. Additionally, we looked at the social and seasonal aspects of bird song, since there is more than just noise in urban ecosystems which may affect acoustic communication. We found no evidence for noise-related bird song divergence in either species, however, we showed that social factors, time of day and season influence certain Common Chiffchaff and Willow Warbler song characteristics. Lack of noise-related bird song divergence may be due to the relatively low variation in its amplitude or other noise features present within the song frequency range of the studied species. Similar results have previously been shown for a few songbird species inhabiting urban ecosystems. Although in many cases such results remain in the shadow of the positive ones, they all contribute to a better understanding of animal communication in urban ecosystems.

Time domain THz spectroscopy measurements were performed on a series of undoped and Mg-doped congruent lithium niobate crystals with 1.2, 6.1, and 8.4 mol% Mg concentrations and on undoped and Mg-doped stoichiometric lithium niobate crystals with 0.7, 1.5, and 4.2 mol% Mg concentrations with polarization parallel (extraordinary) and perpendicular (ordinary) to the z axis of the crystal at 300 K. The absorption coefficient and refractive index spectra were determined in the THz frequency range from 0.25 to ~2.5 THz. In the case of congruent samples for both polarizations, both the refractive index and the absorption coefficient have minimal values for compositions close to the photorefractive threshold. In the case of stoichiometric samples, similar tendencies close to the photorefractive threshold at lower Mg concentration were observed but only for extraordinary polarization, while for ordinary polarization the measured values, especially for the absorption coefficient, were only weakly dependent on the Mg content.

A compact CPW-fed triple band-notched antenna for ultra-wide bandwidth (UWB) application is presented. By introducing an stepped impedance resonator-defected ground structure (SIR-DGS) and fork-shaped stubs, three sharp notches are achieved at frequencies of 3.5, 5.68 and 7.48 GHz. The proposed antenna working from 2.8 to 11.3 GHz with a voltage standing wave ratio of <2 is demonstrated, except for the selected notched bands. The main advantage of the antenna is that the frequency of the notched band can be tuned easily in a wide frequency range. A good agreement between the measurement and the simulation was achieved. The measurements confirm that the technique introduces negligible antenna radiation pattern distortion, except at the triple-notched frequencies.

To prevent noise pollution, a hexagonal acoustic metamaterial cell combining multiple parallel Helmholtz resonators with optional apertures is proposed. There were 6 trapezoidal chambers and 6 triangular chambers, and each front panel had 6 different apertures, which meant that there were 6 12 = 2176782336 possible permutations. The distribution of sound pressures obtained by acoustic finite element simulation revealed the acoustic absorption mechanism, which provided effective guidance to alter the absorption capacity. For certain scenarios, the acoustic absorption performance was optimized by the joint combination of artificial neural network and acoustic finite element simulation. Through manufacturing and testing the sample, actual average acoustic absorption coefficients were achieved at 0.6733, 0.7296, 0.8785 and 0.7065 for the target frequency ranges 350–950 Hz, 400–1000 Hz, 500–800 Hz and 350–700 Hz, respectively, with total thickness 40 mm. The tunable acoustic absorption property proved that the hexagonal acoustic metamaterial cell was appropriate for noise reduction with variable frequency ranges.

Urban environments are characterised by different microclimates, ecological resources and habitat connectivity compared to nonurban environments. Hence, urban environments may affect phenotypic variation of local populations relative to populations in adjacent nonurban environments through different mechanisms (phenotypic plasticity, natural selection, phenotypic sorting). We analysed the effects of urbanisation on phenotypic traits in adults of the grasshopper Chorthippus brunneus at three spatial scales (0.5, 3, and 5 km). Traits included functional morphology, personality-related behaviours (i.e. boldness and exploration), metabolic rate and song parameters. Our experimental tests pointed to several lines of behavioural divergence between individuals of urban and nonurban populations. Grasshoppers of urban population origin were on average shyer and less explorative, but they were more rapid to reach the edges of an artificial environment deprived of any food or conspecifics compared to individuals of nonurban population origin. Songs of urban grasshoppers were characterised by a narrower frequency range than songs of nonurban grasshoppers. Their constitutive bursts of sound (echemes) were more spaced out than songs of nonurban conspecifics. Interestingly, we found more autotomized grasshoppers (i.e. self-amputated individuals) in the urban environment, and these individuals tended to be bolder, while also having more spaced echemes in comparison to uninjured conspecifics. We also demonstrate that the spatial scale at which urbanisation showed the most pronounced effects varied considerably for behavioural and song traits. The detectability and size effects of urbanisation on traits may vary with the spatial scale at which urbanisation is studied around focal populations or habitat patches. Our study motivates for a documented characterisation of the multiple and complex effects of urbanisation on functional phenotypic trait values at the intraspecific level.Significance statementWe analysed the impact of urbanisation on multiple phenotypic traits of a thermophilous grasshopper species. We integrated information on morphology, physiology, behaviour and song characteristics, and we addressed the relationships of those traits with urbanisation at several spatial scales. Our study points at phenotypic differences between urban and nonurban environments, and we show that such relationships are spatial-scale dependent or sensitive. We provide evidence for spatial-scale dependent effects of urbanisation on boldness and explorative behaviour. Our study contributes to our understanding of how urban areas shape behavioural variation across anthropogenic landscapes. We also observed a high incidence of autotomized grasshoppers in highly urbanised environments. Autotomy refers to the extreme escape tactic where the grasshopper sheds a limb to escape predation.

Bottlenose dolphin communication has been studied extensively. Nevertheless, the combined effect of several variables on whistle structure has yet to be clearly understood. Here, we investigated the influence of underwater noise, boat presence, behaviour, group size and calf presence on the whistles of a small population of common bottlenose dolphins (Tursiops truncatus). Surface behaviour and acoustic data were collected in Sardinia (Italy-Western Mediterranean Sea) between 2015 and 2017. Whistle frequency parameters (minimum, maximum, start, end frequencies and frequency range), duration, number of inflection points and number of harmonics were correlated with the ambient noise levels recorded prior to the whistle display and to behavioural and social factors by means of GAM models. Whistle frequencies varied as a function of the interaction between noise and boat presence, mainly when the noise increased at lower frequencies. Dolphin whistles also varied according to group size, which was further affected by the presence of calves, and behaviours characterised by high levels of arousal such as feeding. The study provides sufficient evidence to support that multiple factors need to be considered when investigating whistle structure as the species is capable of adopting different strategies depending on environmental, social and behavioural context. Finally, this data indicates that communication within a small population of bottlenose dolphins is vulnerable to acoustic pollution, thereby highlighting the need for further investigation into the effects of different noises on whistle structure, as well as the consistency of patterns across different populations.

Abstract The present study combined three-dimensional (3D) motion capture with finite element simulation to reconstruct a real shaking adult syndrome (SAS) case and further explore the injury biomechanics of SAS. The frequency at which an adult male can shake the head of another person, head-shaking amplitude, and displacement curves was captured by the VICON 3D motion capture system. The captured shaking frequency and shaking curve were loaded on the total human model for safety (THUMS) head to simulate the biomechanical response of brain injury when a head was shaken in anterior–posterior, left–right, and left anterior-right posterior directions at frequencies of 4 Hz (Hz), 5 Hz, 6 Hz, and 7 Hz. The biomechanical response of the head on impact in the anterior, posterior, left, left anterior, and right posterior directions at the equivalent velocity of 6 Hz shaking was simulated. The violent shaking frequency of the adult male was 3.2–6.8 Hz; head shaking at these frequencies could result in serious cerebral injuries. SAS-related injuries have obvious directionality, and sagittal shaking can easily cause brain injuries. There was no significant difference between the brain injuries caused by shaking in the simulated frequency range (4–7 Hz). Impact and shaking at an equivalent velocity could cause brain injuries, though SAS more commonly occurred due to the cumulative deformation of brain tissue. Biomechanical studies of SAS should play a positive role in improving the accuracy of forensic identification and reducing this form of abuse and torture in detention or places of imprisonment.