Current soft pneumatic grippers cannot robustly grasp flat materials and flexible objects on curved surfaces without distorting them. Current electroadhesive grippers, on the other hand, are ...difficult to actively deform to complex shapes to pick up free-form surfaces or objects. An easy-to-implement PneuEA gripper is proposed by the integration of an electroadhesive gripper and a two-fingered soft pneumatic gripper. The electroadhesive gripper was fabricated by segmenting a soft conductive silicon sheet into a two-part electrode design and embedding it in a soft dielectric elastomer. The two-fingered soft pneumatic gripper was manufactured using a standard soft lithography approach. This novel integration has combined the benefits of both the electroadhesive and soft pneumatic grippers. As a result, the proposed PneuEA gripper was not only able to pick-and-place flat and flexible materials such as a porous cloth but also delicate objects such as a light bulb. By combining two soft touch sensors with the electroadhesive, an intelligent and shape-adaptive PneuEA material handling system has been developed. This work is expected to widen the applications of both soft gripper and electroadhesion technologies.
Abstract
Fine-grained dust rims (FGRs) surrounding chondrules in carbonaceous chondrites encode important information about early processes in the solar nebula. Here, we investigate the effect of the ...nebular environment on FGR porosity, dust size distribution, and grain alignment, comparing the results for rims comprised of ellipsoidal and spherical grains. We conduct numerical simulations in which FGRs grow by collisions between dust particles and chondrules in both neutral and ionized turbulent gas. The resultant rim morphology is related to the ratio
ϵ
of the electrostatic potential energy at the collision point to the relative kinetic energy between colliding particles. In general, large
ϵ
leads to a large rim porosity, large rim grain size, and low growth rate. Dust rims comprised of ellipsoidal monomers initially grow faster in thickness than rims comprised of spherical monomers, due to their higher porosity. As the rims grow and obtain a greater electrostatic potential, repulsion becomes dominant, and this effect is reversed. Grain size coarsening toward the outer regions of the rims is observed for low- and high-
ϵ
regimes, and is more pronounced in the ellipsoidal case, while for the medium-
ϵ
regime, small monomers tend to be captured in the middle of the rims. In neutral environments, ellipsoidal grains have random orientations within the rim, while in charged environments ellipsoidal grains tend to align with maximum axial alignment for
ϵ
= 0.15. The characterization of these FGR features provides a means to relate laboratory measurements of chondrite samples to the formation environment of the parent bodies.
The microstructure and corrosion behavior of AlCoCrFeNiSi0.1 high-entropy alloy are investigated. The alloy was prepared by vacuum arc melting and subsequent injection casting. Two different phases, ...including one disordered BCC (A2) phase and one ordered BCC (B2) phase, are identified in this alloy. The alloy shows a typical equiaxed dendritic microstructure, both of the dendritic and interdendritic regions have an (Al, Ni)-rich matrix with B2 structure and (Cr, Fe)-rich precipitates with A2 structure. The precipitates present different morphologies in the dendritic and interdendritic regions, whereas the chemical composition and crystal structure are very similar. With regard to the corrosion behavior in deaerated 3.5 wt% NaCl solution, the pits were formed at the dendrites, and the selective dissolution of the dendrites could be mainly ascribed to the lower Cr content and galvanic coupling between the dendrites and the interdendrites. The alloy exhibits an active-passive corrosion behavior in deaerated 0.5 mol/L H2SO4 solution. The preferential dissolution of the A2 phase is more severe than the B2 phase. The correlation between chemical composition, microstructure, and corrosion behavior is well illustrated.
•The AlCoCrFeNiSi0.1 alloy has a disordered BCC phase and an ordered BCC phase.•The AlCoCrFeNiSi0.1 alloy exhibits a typical equiaxed dendritic microstructure.•Selective dissolution of the (Cr, Fe)-rich precipitates occurred in H2SO4 solution.•The relationship between the microstructure and corrosion behavior is elucidated.
In this paper, we develop a time‐dependent MHD model driven by the daily‐updated synoptic magnetograms (MHD‐DUSM) to study the dynamic evolution of the global corona with the help of the 3D ...Solar‐Interplanetary (SIP) adaptive mesh refinement (AMR) space‐time conservation element and solution element (CESE) MHD model (SIP‐AMR‐CESE MHD Model). To accommodate the observations, the tangential component of the electric field at the lower boundary is specified to allow the flux evolution to match the observed changes of magnetic field. Meanwhile, the time‐dependent solar surface boundary conditions derived from the method of characteristics and the mass flux limit are incorporated to couple the observation and the 3D MHD model. The simulated evolution of the global coronal structure during 2007 is compared with solar observations and solar wind measurements from both Ulysses and spacecrafts near the Earth. The MHD‐DUSM model is also validated by comparisons with the standard potential field source surface (PFSS) model, the newly improved Wang‐Sheeley‐Arge (WSA) empirical formula, and the MHD simulation with a monthly synoptic magnetogram (MHD‐MSM). Comparisons show that the MHD‐DUSM results have good overall agreement with coronal and interplanetary structures, including the sizes and distributions of coronal holes, the positions and shapes of the streamer belts, and the transitions of the solar wind speeds and magnetic field polarities. The MHD‐DUSM results also display many features different from those of the PFSS, the WSA, and the MHD‐MSM models.
Key Points
A time‐dependent model is developed for the dynamic evolution of global corona
The model is driven by the daily‐updated magnetic field synoptic data
MHD results have good agreement with coronal and interplanetary observations
The coagulation of dust aggregates plays an important role in the formation of planets and is of key importance to the evolution of protoplanetary disks (PPDs). The characteristics of dust, such as ...the diversity of particle size, porosity, charge, and the manner in which dust couples to turbulent gas, affect the collision outcome and the rate of dust growth. Here we present a numerical model of the evolution of the dust population within a PPD which incorporates all of these effects. The probability that any two particles collide depends on the particle charge, cross-sectional area, and their relative velocity. The actual collision outcome is determined by a detailed collision model that takes into account the aggregate morphology, trajectory, orientation, and electrostatic forces acting between charged grains. Our model is applicable to the epoch of time during which hit-and-stick is the primary collision outcome, the duration of which varies greatly depending on the environment. The data obtained in this research reveal the characteristics of dust populations in different environments at the end of the hit-and-stick growth, which establishes the foundation for the onset of the next growth stage where bouncing, mass transfer, and fragmentation become important. For a given level of turbulence, neutral and weakly charged particles collide more frequently and grow faster than highly charged particles. In general, the epoch of hit-and-stick growth is much shorter in high turbulence than it is in regions with low turbulence or highly charged grains. In addition, highly charged particles grow to a larger size before reaching the bouncing barrier, especially in environments with low turbulence, and exhibit "runaway" growth, in which a few large particles grow quickly by accreting smaller particles while the rest of the population grows very slowly. In general, highly charged aggregates have a more compact structure and are comprised of larger monomers than neutral/weakly charged aggregates. The differences in the particle structure/composition not only affect the threshold velocities for bouncing and fragmentation, but also change the scattering and absorption opacity of dust, influencing the appearance of PPDs.
Nanowire fabrication methods can be classified either as 'top down', involving photo- or electron-beam lithography, or 'bottom up', involving the synthesis of nanowires from molecular precursors. ...Lithographically patterned nanowire electrodeposition (LPNE) combines attributes of photolithography with the versatility of bottom-up electrochemical synthesis. Photolithography defines the position of a sacrificial nickel nanoband electrode, which is recessed into a horizontal trench. This trench acts as a 'nanoform' to define the thickness of an incipient nanowire during its electrodeposition. The electrodeposition duration determines the width of the nanowire. Removal of the photoresist and nickel exposes a polycrystalline nanowire--composed of gold, platinum or palladium--characterized by thickness and width that can be independently controlled down to 18 and 40 nm, respectively. Metal nanowires prepared by LPNE may have applications in chemical sensing and optical signal processing, and as interconnects in nanoelectronic devices.
Fully bioresorbable polymer matrix composites have long been considered as potential orthopaedic implant materials, however their combination of mechanical strength, stiffness, ductility and ...bioresorbability is also attractive for cardiac stent applications. This work investigated reinforcement of polylactide-based polymers with phosphate glasses, addressing key drawbacks of current polymer stents, and examined the often-neglected evolution of structure and mechanical properties during degradation. Incorporation of 15–30 wt% phosphate glass led to modulus increases of up to 80% under simulated body conditions, and 15 wt% glass composites retained comparable ductility to pure polymers, crucial for stent applications where ductility and stiffness are required. Two-stage degradation was observed, dominated by interfacial water absorption and glass dissolution. Polymer embrittlement mechanisms (crystallisation, enthalpy relaxation) were suppressed by glass addition, allowing composites to achieve a more controlled loss of mechanical properties during degradation, which could allow gradual transfer of loading to newly healed tissue. These results provide a valuable new system for understanding the structural and mechanical changes occurring during degradation of fully bioresorbable polymer matrix composites, providing important new data to underpin the design of effective cardiac stent materials.
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A combination of good mechanical properties, excellent corrosion resistance and superior irradiation resistance made high-entropy alloys (HEAs) as promising nuclear materials. In this work, the ...Mo0.5VNbTiCrx (x = 0–2.0) HEAs containing elements with low thermal neutron absorption cross-sections were designed and prepared. The alloys were produced by vacuum arc melting, followed by hot isostatic pressing at 1200 °C and 150 MPa for 2 h and annealing at 1200 °C for 72 h. The crystal structure, microstructure, hardness, and mechanical properties of the annealed alloys were investigated. The corrosion resistance in superheated steam was also preliminarily studied. When 0 ≤ x ≤ 0.75, the alloys consist of one body-centered cubic (BCC) phase. When 1.0 ≤ x ≤ 2.0, the alloys are composed of one BCC phase, one C15 Laves phase, and another face-centered cubic (FCC) phase. The effect of Cr content on the phase formation is discussed. The hardness and yield strength increase substantially with increasing Cr content, which could be attributed to the solid-solution-like strengthening. Moreover, the addition of Cr improves the anti-corrosion properties in superheated steam and the studied alloys exhibit better corrosion resistance than a currently used Zr-4 alloy. The Mo0.5VNbTi and Mo0.5VNbTiCr0.25 alloys exhibit the promising potential to be used as nuclear materials, as they show a good combination of mechanical properties and corrosion resistance.
•The novel Mo0.5VNbTiCrx (x = 0–2.0) high-entropy alloys were designed and prepared.•The primary BCC phase is destabilized by the addition of Cr.•With increasing Cr content, the volume fraction of the Laves phase increases.•The Mo0.5VNbTiCrx alloys exhibit good corrosion resistance in superheated steam.
In this study, it is the first time to overall compare three types of spherical Ti-6Al-4V powders by gas atomization, plasma rotating electrode process and plasma atomization in terms of ...microstructure, porosity, argon gas content and pore spatial structure using scanning electron microscopy, mass spectrometer gas analyzer and synchrotron X-ray computed tomography (CT). It is found that the particle size plays a crucial role in the micro-morphology, porosity and argon gas content of the atomized powders. The experimental results show that the argon content of the gas atomized (GAed), plasma rotating electrode processed (PREPed) and plasma atomized (PAed) powders below 150 μm is 0.77 ± 0.06, 0.16 ± 0.06 and 0.70 ± 0.06 μg/g, while its porosity is 0.20 ± 0.01%, 0.08 ± 0.01% and 0.12 ± 0.01%, respectively. Both argon content and porosity within powders increase with increasing particle size for each type of powders. The results of three-dimensional reconstructed images from CT scanning present that the pore population, size and porosity within powders gradually increase with the increase of particle size. The pore sphericity of the GAed and PAed powders exhibits relatively higher than that of the PREPed powders due to different gas pressures inside of powders.
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•Comparison was conducted on porosity and argon content within powders.•Argon content of the atomized powders below 150 μm is under 0.77 ± 0.06 μg/g.•Porosity of the atomized powders below 150 μm is less than 0.20 ± 0.01%.•Average pore sphericity within the atomized powders is in the range of 0.35–0.65.•Detailed information of individual pores in powders was given and discussed.
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