Small Radius Of Curvature Research Articles

Flexible all-inorganic Sm-doped PMN-PT film with ultrahigh piezoelectric coefficient for mechanical energy harvesting, motion sensing, and human-machine interaction

In the era of artificial intelligence and the internet of things, the emergence of flexible MICAtronics, heterostructures made by van der Waals epitaxy on layered mica, has attracted great research interest due to applications in the fields of flexible ferroelectric memory, dielectric capacitors, and others, but less effort has been dedicated to the realization of flexible piezoelectric inorganic films for energy harvesters and sensors. In this work, an all-inorganic transparent Sm-doped Pb(Mg1/3Nb2/3)O3-PbTiO3 (Sm:PMN-PT) film has been successfully grown on Mica substrate via a simple one-step sol-gel process. The flexible film shows an ultrahigh piezoelectric coefficient d33 of 380 pm V−1 owing to the enhanced local structural heterogeneity and the weak substrate clamping effect. Simultaneously, superior flexibility is realized without sacrificing its electrical performance, as reflected by withstanding a small radius of curvature of 2 mm and even 103 mechanical bending cycles. Utilizing this Sm:PMN-PT film, the fabricated device exhibits an excellent energy harvesting performance with output voltage of 6 V, current density of 150 μA cm−2, andultrahigh force sensitivity of 5.86 V N−1. Besides, it also possesses a certain temperature resistance and favorable hydrophobicity. In practical applications, it can not only be employed to monitor body motions, including finger pressing, hand tapping, foot stepping, finger/wrist bending, and hand grasping, but also serves as a tactile sensor to record the touch of a finger to unlock a smartphone. This work demonstrates that the flexible PMN-PT based film on Mica substrate has full application potential in mechanical energy harvesting, motion sensing, and human-machine interaction.

A super-flexible and transparent wood film/silver nanowire electrode for optical and capacitive dual-mode sensing wood-based electronic skin

A Super-flexible and transparent wood film/silver nanowire electrode for optical and capacitive dual-mode sensing wood-based electronic skin. This work opens new directions for directly incorporating natural wood into e-skin sensors and may offer potential applications in wearable electronics, artificial intelligence, soft robots and so on. • A wood-based e-skin with instrument- and naked eye-readable characteristics. • A pyramidal microstructure polydimethlysiloxane film was used as a sensing layer. • A super-flexible transparent wood film was used as the electrodes. • The e-skin can map the spatial distribution of static and dynamic pressures. • The e-skin in luminescence exhibited a maximum sensitivity value at 1.28 kPa −1 . Flexible electronic skin (e-skin) with multimode broad-range pressure sensing and high sensitivity is highly desirable for robotics, artificial intelligence and human–machine interaction applications. Most research on e-skin has focused on improving the sensitivity of sensing layers interfaced with an electronic output device, with only a limited number of studies focused on user interfaces based on a human-readable output. Moreover, naturally degradable materials are receiving increasing attention for e-skin. Herein, inspired by a bioluminescent noctiluca, a wood-based e-skin with instrument- and naked eye-readable characteristics was sandwich assembled using silver nanowires and a super-flexible transparent wood (STW) film as an electrode and a pyramidal microstructure polydimethlysiloxane film as a stimuli-responsive layer. The electrode was prepared by depositing silver nanowires on the surface of the STW film through a Meyer rod coating method. The film demonstrated outstanding performance with high transmittance (91.4%), a small curvature radius (2 mm) and excellent sheet resistance stability even after greater than 1500 bending cycles. The e-skin showed notable changes in electroluminescence from 0 to 150 kPa (where humans feel pain) and the sensitivity remains larger than 0.15 kPa −1 over the broad pressure range. The sensitivity in capacitance exhibited high sensitivity at 1.01 kPa −1 in the low-pressure regime, meanwhile, the luminescence exhibited a maximum value at 1.28 kPa −1 at medium pressure. Furthermore, the e-skin accurately mapped the spatial distribution of static and dynamic pressures through optical sensing. This work not only improves the sustainable development of materials in electrodes but also illustrates the potential of utilizing natural wood in high value-added e-skin.

Synchrotron radiation from a cluster plasma in a circularly polarised laser field

An analytical model is developed for the generation of synchrotron radiation from a laser cluster plasma in the focal waist of an ultra-intense short circularly polarised laser pulse. The rotation of relativistic electrons around the ionised core of the cluster with a radius of rotation smaller than the laser wavelength leads to intense synchrotron radiation in the direction transverse to the laser wave vector. The parameters of the cluster plasma and laser pulse are determined at which, due to the small radius of curvature of the electron trajectory of the cluster shell, the intensity of synchrotron radiation exceeds the intensity of betatron radiation of the electron flux in the longitudinal (along the wave vector) direction.

Evaluation of Blast Simulation Methods for Modeling Blast Wave Interaction With Human Head.

Blast-induced traumatic brain injury (bTBI) research is crucial in asymmetric warfare. The finite element analysis is an attractive option to simulate the blast wave interaction with the head. The popular blast simulation methods are ConWep-based pure Lagrangian, Arbitrary-Lagrangian-Eulerian, and coupling method. This study examines the accuracy and efficiency of ConWep and coupling methods in predicting the biomechanical response of the head. The simplified cylindrical, spherical surrogates and biofidelic human head models are subjected to field-relevant blast loads using these methods. The reflected overpressures at the surface and pressures inside the brain from the head models are qualitatively and quantitatively evaluated against the available experiments. Both methods capture the overall trends of experiments. Our results suggest that the accuracy of the ConWep method is mainly governed by the radius of curvature of the surrogate head. For the relatively smaller radius of curvature, such as cylindrical or spherical head surrogate, ConWep does not accurately capture decay of reflected blast overpressures and brain pressures. For the larger radius of curvature, such as the biofidelic human head, the predictions from ConWep match reasonably well with the experiment. For all the head surrogates considered, the reflected overpressure-time histories predicted by the coupling method match reasonably well with the experiment. Coupling method uniquely captures the shadowing and union of shock waves governed by the geometry-driven flow dynamics around the head. Overall, these findings will assist the bTBI modeling community to judiciously select an objective-driven modeling methodology.

Spiny gold nanoparticles colloids as substrate for sensing of methyl parathion based on surfaced-enhanced Raman scattering

Herein, two kinds of spiny gold nanoparticles (S-AuNPs1, S-AuNPs2) and a triangular AuNPs (T-AuNPs) colloids were synthesized and utilized as surface-enhanced Raman scattering (SERS) substrates for the methyl parathion (MP) detection. High enhancement factors at 104 level were obtained for three substrates, which is resulted from the high density of “hot spot”. Favorable quantitative analysis capability of three AuNPs toward MP was acquired in the concentration range of micromoles to millimoles per liter, with actual detection limits at several micromoles per liter. Reproducibility and feasibility of the sensors were also verified. All these results suggest the promising potential of application for AuNPs with small curvature radius of nanostructures in trace detection.

Длительность пучка убегающих электронов при субнаносекундном фронте импульса напряжения

The conditions for obtaining runaway electron (RE) current pulses with a minimum duration at a subnanosecond breakdown of centimeter gaps filled with air at atmospheric pressure were studied. It is shown that the RE current pulse duration depends on many parameters, such as the cathode form, the magnitude of the interelectrode distance, the diameter of the diaphragm, which is part of the anode, as well as on the size of the receiving part of the collector. It has been established that the use of cathodes with an extended edge having a small radius of curvature, RE current pulses consisting of two peaks of picosecond duration can be recorded.

Duration of runaway electron current pulses when applying voltage pulses with a subnanosecond rise time

The conditions for obtaining runaway electron (RE) current pulses with a minimum duration at a subnanosecond breakdown of centimeter gaps filled with air at atmospheric pressure were studied. It is shown that the RE current pulse duration depends on many parameters, such as the cathode form, the magnitude of the interelectrode distance, the diameter of the diaphragm, which is part of the anode, as well as on the size of the receiving part of the collector. It has been established that the use of cathodes with an extended edge having a small radius of curvature, RE current pulses consisting of two peaks of picosecond duration can be recorded. Keywords: runaway electrons, beam current, picosecond pulse duration, subnanosecond breakdown.

Making the most of limited resources in wet-lab training during COVID-19

Dear Editor, Wet labs and virtual simulators are often used to augment surgical training. Being more economical, wet labs are more popular, especially having gained importance during the Coronavirus-19 pandemic.[12] Here, we are sharing some techniques that have worked for us to maximally use a single goat’s eye. With the goat’s eye remaining taut, steps one can practice without entering the anterior chamber Peritomy, extending from the limbus up to the equator choosing the broader radius of the curvature of the goat’s eye. Scleral scratch incisions—straight, frown, etc. Multiple scratch incisions can be placed successively posterior to one another over the exposed sclera [Fig. 1a]. Sclero-corneal tunnel, which can be practiced at the smaller radius of curvature on both sides. If the tunnel gives way, one may practice scleral suturing [Fig. 1b]. Side-port entry at one of the smaller radii of curvature. More than one side-port entry may be attempted and then sealed by simple interrupted sutures. Figure 1: Single microscope with goat’s eye set-up showing (a) successive scratch incisions placed posterior to a sclero-corneal tunnel (marked with the crescent knife), (b) scleral suturing practiced over a sclero-corneal tunnel, (c) capsulorhexis using a bent 23-gauge needle, (d) sclero-corneal suturing on a ragged incisionSteps upon entering the anterior chamber If the cornea becomes hazy and precludes visualization, the corneal epithelium can be debrided locally. Entry through the sclera-corneal tunnel. Passing instruments through the side-port and main-port—injection of trypan blue dye and forming of the anterior chamber with ocular visco-surgical devices. An anterior capsular opening made with the longer 23- or 24-gauge needle to accommodate for the larger size of the goat’s eyeball[3] [Fig. 1c]. Hydrodissection, an effort at nuclear rotation, and delivery if the conditions remain favorable. Irrigation and aspiration with a Simcoe cannula. Intraocular lens implantation. A ragged incision on the sclera and/or cornea may be made and sutured. With the collapsing globe, this may simulate a traumatic globe rupture [Fig. 1d]. The feel of an enucleated eye is different from live surgeries. An important cause for frustration when practicing in the enucleated eye is that the eye may move during surgery and frequently collapses during practice. The Spring-action Apparatus for Fixation of Eyeball (SAFE) helps in keeping the eye stable within the cylinder and also increasing the intraocular pressure so that the globe does not collapse.[4] This would be a worthwhile addition to the wet labs. The practice of surgical steps need not be restricted to patients or wet lab. Ambidexterity can be encouraged by using a non-dominant hand in some everyday activities. Further, the commonly available household items can provide reasonably good simulation for certain surgical steps as demonstrated by Akkara et al.[5] In the wet lab, residents of different years can coordinate to practice steps most relevant to them, permitting the eye to be used by more than one resident. Though, not a replacement for hands-on surgical training on patients, this provides a reasonable means to practice skills when surgical opportunities are scarce during this pandemic. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.

Dynamic response analysis of isolated curved beam bridge under multi-dimensional non-stationary random excitation considering the torsion component

The coupling effect of bending and torsion caused by plane irregularity of the isolated curved beam bridge makes its seismic response more complex than that of the isolated straight beam bridge. In order to study the influence of multi-dimensional non-stationary random excitation considering torsion component on seismic response of tqiongw@mls.sinanet.com he isolated curved beam bridge. The classical Bouc-Wen model was used to simulate the hysteretic characteristics of the curved beam bridge, and the nonlinear dynamic equation considering the eccentricity of superstructure was established. The pseudo excitation was transformed into harmonic external load by Euler formula, and combining with the precise integration method, the precise integration forms of the special solution under different modulation functions were derived. By using these integral forms to solve the response at each time, the time-varying variance of displacement of the isolated curved beam bridge under multi-dimensional non-stationary random excitation was obtained, and the law of time-varying variance of displacement, including the upper and lower structures of the isolated curved beam bridge, was analyzed with different deck width, curvature radius and yield ratio of bearing. The results show that the multi-dimensional non-stationary random excitation with torsion component has significant influence on the seismic response of the isolated curved beam bridge. Under the rare non-stationary random excitation, the dynamic response of the isolated curved beam bridge presents strong non-stationarity, and the time-lag phenomenon is apparent. For the isolated curved beam bridge with large deck width and small yield ratio of bearing, the influence of non-stationary random excitation on the structure is particularly obvious. The influence of non-stationary random excitation considering torsion component on dynamic response of the isolated curved beam bridge with large deck width, small curvature radius and large yield ratio of bearing is more significant.

Orientation smoothing in multi-axis additive manufacturing

In multi-axis processes, such as material extrusion like Fused Filament Fabrication (FFF), the orientation of the tool relatively to the workspace is usually set by the CAM software to an angle that is locally constant relative to the manufacturing surface. However, in the case of large curvature gradients or small curvature radius of the surface or the path, this method leads to significant variations of the tool orientation. These variation require large compensating movements of the axes to maintain the desired deposition tool orientation along the path. Kinematic constraints such as acceleration or jerk limits can lead to a reduction of the path velocity or noticeable positioning errors along the movement, as well as unwante vibrations, which means poor process conditions and defects in the parts. The paper presents a post path planning algorithm that allows smooth in of the tool orientation to avoid jerky compensation motion of the CNC system by varying the orientation within a defined tolerance. This tolerance depends on the deposition process, and is determined experimentally for a FFF process. The proposed methodology was successfully validated b the manufacturing of two sample parts using a robotic additive manufacturing cell.

A phase-field model for <i>in-situ</i> reaction process of metal-matrix composite materials

The <i>in-situ</i> reaction is an important method of preparing metal matrix composites: it can produce more uniform distribution of the reinforcement particles and more excellent structure of the phase boundary between the particles and the matrix. Therefore, the kinetics of <i>in-situ</i> reaction process deserves to be further studied. However, as the <i>in-situ</i> reaction is a rapid random process under high-temperature condition, it is difficult to observe the reaction process of metal-matrix composite materials experimentally. In this work, we propose a new phase-field model to describe the <i>in-situ</i> reaction process, and investigate the nucleation kinetic processes of <i>in-situ</i> reaction under different physical conditions. We find that the nucleation rate increases with the augment of curvature radius and noise intensity, and the size distribution of the particles is more uniform under the conditions of a small curvature radius and strong noise. With the increase of the undercooling, the nucleation rate first increases and then decreases, which is consistent with the classical nucleation theory.

Acrylate-based nanocomposite zirconium-dispersed polymer dielectric for flexible oxide thin-film transistors with a curvature radius of 2 mm

Novel hybrid dielectric film is synthesized at a low temperature of 150 °C using a solution process. Zirconium acrylate (ZrA) and poly(methyl methacrylate) (PMMA) comprise the inorganic and organic components, respectively. The acrylate-based molecular structure of both ingredients allows the facile formation of hybrid ZrA/PMMA dielectric film with neither additional coupling agent nor ultraviolet photon irradiation. The high quality of the hybrid ZrA/PMMA dielectric film is confirmed by its high dielectric constant of 5.5 and low leakage current density of 1.7 × 10−8 A/cm2 at the electric field of 1 MV/cm. The indium gallium tin oxide (IGTO) transistors with the optimal ZrA/PMMA gate insulator layer are fabricated on the polyimide substrate at the maximum high temperature of 150 °C. They exhibit hysteresis-free high performance with high carrier mobility of 24.3 cm2V−1s−1, gate swing of 0.61 V/decade and ION/OFF ratio of 4 × 106. Owing to the intrinsic deformability of hybrid dielectric film, these transistors maintained electrical performance after 100 cycles of mechanical bending to the extremely small radius of curvature of 2 mm.

Lowering the reflection on curved flexible substrates over a broad wavelength range by the structure with Ag nanoparticles on SiO2 nanocolumns

A broadband antireflective structure with Ag nanoparticles on SiO2 nanocolumns for curved flexible substrates is presented. Experimental results show that the structure can lower effectively the light reflection on curved surfaces over a broad wavelength range. It is found that increasing incident angle leads to the blue-shift of position of the minimum light reflection due to the reduced travel distance of resonated electrons of Ag nanoparticles and the weakened mutual attraction between the resonated electrons in neighbouring Ag nanoparticles. The surfaces with smaller curvature radii have higher light reflection than those with larger curvature radii. The light reflection on a curved surface can be calculated through the weighted summation of the angle-dependent reflections on a flat surface, which agrees well with experimental results.

Protruding bullet heads indicating dark matter pull

ABSTRACT A clump moving through the intracluster medium of a galaxy cluster can drive a bow shock trailed by a bullet-like core. In some cases, such as in the prototypical Bullet cluster, X-rays show a gas bullet with a protruding head and pronounced shoulders. We point out that these features, while difficult to explain without dark matter (DM), naturally arise as the head of the slowed-down gas is gravitationally pulled forward toward its unhindered DM counterpart. X-ray imaging thus provides a unique, robust probe of the offset, collisionless DM, even without gravitational lensing or other auxiliary data. Numerical simulations and a toy model suggest that the effect is common in major mergers, is often associated with a small bullet-head radius of curvature, and may lead to distinct bullet morphologies, consistent with observations.

Temperature distribution and characteristics induced by fire smoke in L-shaped utility tunnels with small curvature radii

A computational fluid dynamics model is established to investigate the behavior of fire smoke spreading in L-shaped utility tunnels with small curvature radii (R). The fire evolution process for tunnels with R = 0–25 m and critical ventilation velocities (V) of 0.5–3.0 m/s is analyzed, and the Richardson number (Ri) is introduced to determine the critical value for the development of fire smoke back-layering. The results show that R and V strongly influence the fire-induced spatiotemporal evolution characteristics in such utility tunnels. Smaller R or higher V are associated with stronger centrifugal forces, which causes the smoke to move downstream of the fire source and increases the instability and risk. The non-dimensional smoke back-layering length shows a linear relationship with ln(Q*/V*3), where Q* is the dimensionless fire source power. Integrated with the V and smoke force in a curved tunnel, the critical Ri value is found to be 6.34 for R = 10 m. This means that smoke back-layering will appear when Ri > 6.34 and disappear when Ri < 6.34. The present work positively provides a tool for the assessment of thermal environment of L-shaped utility tunnel's fire safety in engineering practice.

Flexible polymer network liquid crystals using imprinted spacers bonded by UV-curable reactive mesogen for smart window applications

We propose junction-type, vertically aligned polymer network liquid crystals using plastic substrates for flexible smart windows, in which the spacers are formed with the imprinting method and are bonded to the substrate surface by UV-curable reactive mesogen (RM). We clarified that the optical property can be improved by suppressing the aggregation of RMs around the spacers through thinning of the coating of the RM and the simultaneous improvement of the wettability of the parallel alignment film. We achieved excellent haze properties of 3.0% with voltage off and 92.7% with voltage on, and high curvature performance with a small curvature radius of 9.0 mm.

Modes of runaway electron beams during formation of diffuse discharges in air and nitrogen

Investigations of the generation of runaway electron beams (REs) and the for-mation of diffuse discharges during breakdown of gaps with a cathode, which has a small radius of curvature, have been carried out. In air and nitrogen at elevated pressure, based on the registration and analysis of the characteristics of radiation from discharge, as well as parameters of the RE beam current and dynamic dis-placement current, it is shown that, depending on the conditions (E/N, gas type and its pressure, design and material of the cathode, amplitude and front of the voltage pulse), diffe-&#x0D; rent modes of generation of runaway electron beams are realized. It was found that the ratio of the velocity of the front of the ionization wave (streamer) and the runaway electrons, as well as the design of the cathode and the delay time before the explosion of cathode microinhomogeneities, significantly affect the generation of runaway electrons. The conditions for the realization of various modes are de-termined; oscillograms of the beam current pulses and photographs of the glow of the gap are presented.

Cracking Pattern of Indented Ice Sheet Bending Failures

AbstractIce sheet bending failures have been investigated extensively for ice loads on conical offshore structures and icebreakers in arctic regions. Most previous theoretical studies focus on bending failures of semi-infinite level ice, ice wedges, or finite-sized rectangular ice floes. For indented ice sheet bending failures, analytical ice load models have been developed by assuming a radial-before-circumferential cracking pattern. Recently, real-time simulations of ice-structure interactions are gaining increasing traction due to their great application potential. The analytical or semi-analytical models implemented into the real-time simulator significantly influence the accuracy of real-time simulations. Against this backdrop, the cracking pattern assumption needs to be more critically examined, and the criterion for cracking pattern determinations is in demand for utilizing different models for different cracking patterns in real-time simulations. Motivated by this need, the current paper establishes the cracking pattern determination criterion for indented ice sheet bending failures, based on the theory of plates on elastic foundations and normalized formulae. It is found that large indentation lengths and radii of structure waterline curvature induce a circumferential-before-radial cracking pattern. Conversely, small indentation lengths and radii of structure waterline curvature result in a radial-before-circumferential cracking pattern.

Effects of trench configuration on the film cooling effectiveness of a fan-shaped hole

In this study, the effects of three trench configurations – the height, the distance from the hole exit to the downstream sidewall, and the radius of the curvature of the downstream sidewall – on the film cooling effectiveness of fan-shaped holes were experimentally investigated. The film cooling effectiveness was measured using pressure sensitive paint (PSP), and the experiment was conducted with blowing ratios of 1.0, 1.5, 2.0, and 2.5, and density ratios of 1.0 and 2.0. The results demonstrated that the film cooling effectiveness inside the trench was generally higher for cases with larger trench heights, smaller distances between the hole exit and downstream sidewall, and smaller radii of curvature. The smaller distances between the hole exit and downstream sidewall showed higher film cooling effectiveness outside the trench. The higher density ratio cases resulted in higher overall film cooling effectiveness. In general, the film cooling effectiveness for fan-shaped holes with a trench was higher than that without a trench. However, a lower trench resulted in lower film cooling effectiveness.

Molecular droplets vs bubbles: Effect of curvature on surface tension and Tolman length

Droplets and bubbles are thought to be two sides of the same coin; this work determines how true this is at the molecular scale. Stable cylindrical nanodroplets and nanobubbles are obtained in Molecular Dynamics (MD) simulations with three-phase contact lines pinned by alternate hydrophobic and hydrophilic patterns. The surface tension and Tolman length for both types of curved interfaces are obtained with the Kirkwood–Buff method, based on the difference between normal and tangential pressure components. Both bubble and droplet cases are compared to the flat interface case for reference. Results show that the surface tension decreases linearly while the Tolman length increases linearly with the gas/liquid density ratio. By running a careful parameter study of the flat interface over a range of densities, the effect of the density ratio can be corrected isolating the effects of curvature on the surface tension and Tolman length. It is found that such effects start to be seen when the equimolar curvature radius goes down to 20 reduced Lennard–Jones (LJ) units. They have the same magnitude but act with opposite signs for nanodroplet and nanobubble interfaces. Considering effects of the density ratio and curvature, a fitted Tolman equation was obtained, which predicts the surface tension of a curved interface. Results obtained by the fitted Tolman equation agree well with those obtained by the MD simulations except at very small curvature radius (&amp;lt;10 reduced LJ units) due to the accumulation of the curvature dependence of the Tolman length.