Active beating modes of two clamped filaments driven by molecular motors

Biological cilia pump the surrounding fluid by asymmetric beating that is driven by dynein motors between sliding microtubule doublets. The complexity of biological cilia raises the question about minimal systems that can re-create similar patterns of motion. One such system consists of a pair of microtubules that are clamped at the proximal end. They interact through dynein motors that cover one of the filaments and pull against the other one. Here, we study theoretically the static shapes and the active dynamics of such a system. Using the theory of elastica, we analyse the shapes of two filaments of different lengths with clamped ends. Starting from equal lengths, we observe a transition similar to Euler buckling leading to a planar shape. When further increasing the length ratio, the system assumes a non-planar shape with spontaneously broken chiral symmetry after a secondary bifurcation and then transitions to planar again. The predicted curves agree with experimentally observed shapes of microtubule pairs. The dynamical system can have a stable fixed point, with either bent or straight filaments, or limit cycle oscillations. The latter match many properties of ciliary motility, demonstrating that a two-filament system can serve as a minimal actively beating model.

Influence of 1.5 wt.% Bi on the Microstructure, Hardness, and Shear Strength of Sn-0.7Cu Solder Joints after Isothermal Annealing

This manuscript reports the isothermal annealing effect on the mechanical and microstructure characteristics of Sn-0.7Cu-1.5Bi solder joints. A detailed microstructure observation was carried out, including measuring the activation energy of the intermetallic compound (IMC) layer of the solder joints. Additionally, the synchrotron µX-ray fluorescence (XRF) method was adopted to precisely explore the elemental distribution in the joints. Results indicated that the Cu6Sn5 and Cu3Sn intermetallic layers thickness at the solder/Cu interface rises with annealing time at a rate of 0.042 µm/h for Sn-0.7Cu and 0.037 µm/h for Sn-0.7Cu-1.5Bi. The IMC growth’s activation energy during annealing is 48.96 kJ mol-1 for Sn-0.7Cu, while adding Bi into Sn-0.7Cu solder increased the activation energy to 55.76 kJ mol−1. The µ-XRF shows a lower Cu concentration level in Sn-0.7Cu-1.5Bi, where the Bi element was well dispersed in the β-Sn area as a result of the solid solution mechanism. The shape of the IMC layer also reconstructs from a scallop shape to a planar shape after the annealing process. The Sn-0.7Cu hardness and shear strength increased significantly with 1.5 wt.% Bi addition in reflowed and after isothermal annealing conditions.

Type Synthesis of Long Symmetric Planar Shape-Morphing Mechanism Arrays

This paper describes a novel type synthesis methodology for creating planar shape-morphing mechanism chains of any length with specified mobility (degree-of-freedom). It is expected that this will be of use in designing complex shape-morphing objects. The methodology is based on using graph theory in conjunction with symmetry theory for borders (Frieze groups). It is shown that the methodology can produce chains of a variety of lengths and mobility, and these chains have symmetric topologies and that symmetric kinematics may be possible for some of the chains, which simplifies their analysis. Techniques for decreasing and increasing the mobility of the chains are discussed. Finally, a gallery of shape morphing chains is given to provide concrete illustrations of the diversity of designs generated using this methodology.

Design and Simulation of Metamaterial based Circularly Polarized Antenna Array

The microstrip patch array antenna is usually designed as a broadside radiator. The radiating area of the patch can be of any planar shape from elliptical to square, but rectangular is preferred over other shapes. When elements of antenna are repeated, it is called as an array of antennas. When the distance between antennas is reduced, mutual coupling effect occurs. This effect occurs when the distance between the antennas is less than 0.5and this affects the gain and efficiency of the antennas. This effect can be reduced by using metamaterials. To reduce the mutual coupling between the antenna elements the metamaterial structure is artificially designed to obtain negative permittivity and permeability using HFSS and the results are verified using MATLAB. These metamaterials are placed between the patch elements of 1×2 circularly polarized array antenna when the distance between the patches is 0.2 for both RT duroid and FR4 epoxy substrate for 5GHz resonant frequency.

Idiosyncratic Functions of Active Touch Strategies in Shape Perception.

Hand movements are essential for tactile perception of objects. However, the specific functions served by active touch strategies, and their dependence on physiological parameters, is unclear and understudied. Focusing on planar shape perception, we tracked at high resolution the hands of eleven participants during shape recognition task. Two dominant hand movements strategies were identified: Contour-following movements, either tangential to the contour or oscillating perpendicular to it, and exploration by scanning movements, crossing between distant parts of the shapes’ contour. Both strategies exhibited non-uniform coverage of the shapes’ contours. Idiosyncratic movement patterns were specific to the sensed object and could be explained in part by spatial and temporal tactile thresholds of the participant. Using simulations, we show how some strategy choices may affect receptors activation. These results suggest that motion strategies of active touch adapt to both the sensed object and to the perceiver’s physiological parameters.

Towards the Automated Coverlay Assembly in FPCB Manufacturing: Concept and Preliminary Tests

In modern electronics, flexible and rigid-flex PCBs are largely used due to their intrinsic versatility and performance, allowing to increase the available volume, or enabling connection between unconstrained components. Rigid-flex PCBs consists of rigid board portions with flexible interconnections and are commonly used in a wide variety of industrial applications. However, the assembly process of these devices still has some bottlenecks. Specifically, they require the application of cover layers (namely, coverlays), to provide insulation and protection of the flexible circuits. Due to the variability in planar shape and dimensions, the coverlay application is still performed manually, requiring troublesome manipulation steps and resulting in undetermined time-cycle and precision.This paper aims at the improvement of the industrial process currently performed, by proposing an approach for the automation of Kapton coverlay manipulation and application. Since these products are commercially provided as a film with a protective layer to be removed, the peeling issue is addressed, representing a challenging step of the automated process; the results of a systematic series of tests, performed in order to validate the peeling strategy, are reported in the paper. The overall assembly strategy relies on the development of a customized multi-hole vacuum gripper, whose concept is presented and contextualized in the proposed assembly process by outlining a suitable workcell architecture.

Active palpation underlying shape perception is shaped by physiological thresholds and experience

ABSTRACTHand movements are essential for tactile perception of objects. However, why different individuals converge on specific movement patterns is not yet clear. Focusing on planar shape perception, we tracked the hands of 11 participants while they practiced shape recognition. Our results show that planar shape perception is mediated by contour-following movements, either tangential to the contour or spatially-oscillating perpendicular to it, and by scanning movements, crossing between distant parts of the shapes’ contour. Both strategies exhibited non-uniform coverage of the shapes’ contours. We found that choice of strategy during the first experimental session was strongly correlated with two idiosyncratic parameters: participants with lower tactile resolution tended to move faster; and faster-adapting participants tended to employ oscillatory movements more often. In addition, practicing on isolated geometric features increased the tendency to use the contour-following strategy. These results provide insights into the processes of strategy selection in tactile perception.SIGNIFICANCE STATMENTHand movements are integral components of tactile perception. Yet, the specific motion strategies used to perceive specific objects and features, and their dependence on physiological features and on experience, are understudied. Focusing on planar shape perception and using high-speed hand tracking we show that human participants employ two basic palpation strategies: Contour-following and scanning. We further show that the strategy chosen by each participant and its kinematics depend strongly on the participant’s physiological thresholds – indicative of spatial resolution and temporal adaptation - and on their perceptual experience.

Continuing Development of Metal-Loss Severity Criteria, Including Width Effects

The emergence in the early 1970s of what about a decade later became the first release of ASME B31G began the development and evolution of criteria to assess the severity of metal-loss defects. Motivated by the desire to reduce the conservatism embedded in B31G, the late 1980s saw the release of Modified B31G, with that same report also introducing RSTRENG, which quantified “riverbottom” effects. The desire to avoid excessive conservatism in their application to higher-strength Grades gave rise to alternative criteria for such applications. PCORRC appeared in 1997, with early versions of DNV RP-F101 and British Gas’ LPC-1 criteria following shortly thereafter. It has since become evident for isolated smooth-bottomed features that in addition to feature length and depth, its width can be a factor, as can its planar shape, and through-thickness profile. This paper builds on insight gained from the prior work, presenting and validating a Level 1 failure criteria for isolated metal-loss features. The defect-free term for this Level 1 criterion relies on the Zhu-Leis criterion for defect-free pipe failure. That criterion is coupled to a recalibrated defect term analogous to PCORRC, whose extension to include the effects of width is considered. The resulting Level 1 criterion is validated in reference to full-scale tests of pipe with metal-loss, which include a mix of real corrosion and flat-bottomed machined features. These tests consider Grades from Gr B to X100, a wide range of diameters and thicknesses, and in many cases the effect of width. Finite element results are used to illustrate the role of width. Benchmarked against almost 80 full-scale tests it is shown that this new approach affects a reduction in conservatism. At the same time, it provides clear benefits in regard to reduced predictive scatter, as well as a reduction in required maintenance, and the scope of features that must be considered in field-digs.