Comprehending Optimality of Finger Flexor Tendon Pulley System using Computational Analysis

It is rare that existing prosthetic/orthotic designs are based on kinetostatics of a biological finger, especially its tendon- pulley system (TPS). Whether a biological TPS is optimal for use as a reference, say for design purposes, and if so in what sense, is also relatively unknown. We expect an optimal TPS to yield high range of flexion while operating with lower tendon tension, bowstringing, and pulley stresses. To gain insight into the TPS designs, we present a parametric study which is then used to determine optimal TPS configurations for the flexor mechanism. A compliant, flexure-based computational model is developed and simulated using the pseudo rigid body method, with various combinations of pulley/tendon attachment point locations, pulley heights, and widths. Results suggest that three distinct types of TPS configurations corresponding to single stiff pulley, or two stiff pulleys, or one stiff and one flexible-inextensible pulley per phalange can be optimal. For a TPS configuration similar to a biological one, the distal pulleys on the proximal and intermediate phalanges need to be like flexible-inextensible string loops that effectively model the behavior of joint and cruciate pulleys. We reckon that a biological flexor TPS may have evolved to maximize flexion range with minimum possible actuation tension, bowstringing and pulley stress. Our findings may be useful in not only developing efficient hand devices, but also in improving TPS reconstruction surgery procedures.

HOMOGENEOUS LOW-CRESTED STRUCTURES FOR BEACH PROTECTION IN CORAL REEF AREAS

In many countries, the health of the marine ecosystems and the sun-sand-sea tourism depend on the coral reefs, which have been retreating around the world during the last decades. Homogeneous Low-Crested Structures (HLCS), made of large rocks or pre-cast concrete units, can be placed to mimic the functions of beach protection and eventually serve as a refuge for species. HLCS is a type of multi-purpose green infrastructure which is functionally similar to conventional low-crested structures but have higher porosity and are more easily dismantled for re-use. Contrary to conventional low-crested structures, the functionality of HLCS protecting beaches depends on the selected placement grid; this paper describes physical and numerical placement tests on horizontal bottom used to characterize the layers coefficients of Cubipod HLCS. The Bullet Physic Engine (BPE) numerical model used in the gaming industry, which is based on the rigid body method, is calibrated using the physical placement tests. The layer coefficients of Cubipod HLCS measured in the physical placement tests were similar to those obtained with the BPE numerical model, which could be used to optimize placement grids of HLCS on specific sea bottom conditions. Finally, the influence of the placement grid of Cubipod HLCS on the structure height, crest freeboard and wave transmission is analyzed.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/5bi-jpuJYcQ

Implementing Primordial Binaries in Simulations of Star Cluster Formation with a Hybrid MHD and Direct N-Body Method

The fraction of stars in binary systems within star clusters is important for their evolution, but what proportion of binaries form by dynamical processes after initial stellar accretion remains unknown. In previous work, we showed that dynamical interactions alone produced too few low-mass binaries compared to observations. We therefore implement an initial population of binaries in the coupled MHD and direct N-body star cluster formation code Torch. We compare simulations with, and without, initial binary populations and follow the dynamical evolution of the binary population in both sets of simulations, finding that both dynamical formation and destruction of binaries take place. Even in the first few million years of star formation, we find that an initial population of binaries is needed at all masses to reproduce observed binary fractions for binaries with mass ratios above the q ≥ 0.1 detection limit. Our simulations also indicate that dynamical interactions in the presence of gas during cluster formation modify the initial distributions towards binaries with smaller primary masses, larger mass ratios, smaller semi-major axes and larger eccentricities. Systems formed dynamically do not have the same properties as the initial systems, and systems formed dynamically in the presence of an initial population of binaries differ from those formed in simulations with single stars only. Dynamical interactions during the earliest stages of star cluster formation are important for determining the properties of binary star systems.

A Novel Two-Stage Constant Force Compliant Microgripper

The manipulating objects of the micron scale are easily damaged, hence the microgrippers, the key components in micro manipulating systems, demand precise force control, plus miniaturized size. Consequently, the constant force microgrippers, generally lack the ability to fit different sizes. To avoid the overload damage, apply multi-size microparts and simplify the control method, a novel two-stage compliant constant force microgripper is proposed in this paper. Based on the negative stiffness effect, this gripper is connected in parallel with a two-stage negative stiffness module and a positive stiffness module. Then, the elliptic integral method and the pseudo-rigid-body method are both employed to derive the kinetostatic and dynamic performances. Finally, the analytical results are validated. It is observed that two-stage constant forces of 1.33 N in 305.6 μm and 1.11 N in 330.8 μm are acquired.