Rigid Stiffness Research Articles

Biomechanical Impacts of Toe Joint With Transfemoral Amputee Using a Powered Knee-Ankle Prosthesis.

Transfemoral amputees are currently forced to utilize energetically passive prostheses that provide little to no propulsive work. Among the several joints and muscles required for healthy walking, the ones most vital for push-off assistance include the knee, ankle, and metatarsophalangeal (MTP) joints. There are only a handful of powered knee-ankle prostheses (also called powered transfemoral prostheses) in literature and few of them comprise a toe-joint. However, no one has researched the impact of toe-joint stiffness on walking with a power transfemoral prosthesis. This study is aimed at filling this gap in knowledge. We conducted a study with an amputee and a powered transfemoral prosthesis consisting of a spring loaded toe-joint. The prosthesis's toe-joint stiffness was varied between three values: 0.83 Nm/deg, 1.25 Nm/deg, and infinite (rigid). This study found that 0.83 Nm/deg stiffness reduced push-off assistance and resulted in compensatory movements that could lead to issues over time. While the joint angles and moments did not considerably vary across 1.25 Nm/deg and rigid stiffness, the latter led to greater power generation on the prosthesis side. However, the 1.25 Nm/deg joint stiffness resulted in the least power production from the intact side. We, thus, concluded that the use of a stiff toe-joint with a powered transfemoral prosthesis can reduce the cost of transport of the intact limb.

AN ESTIMATING METHOD FOR LATERAL BEHAVIOR OF PILED-RAFT FOUNDATION

Some simplified design methods were proposed to predict behavior of lateral loaded piled-raft foundations on homogenous soil. One of them is the cone model method. However, only one average solution of pile behavior can be given by this method. It can’t evaluate the location factors of piles. Therefore, this paper describes a new simplified method to predict behavior of lateral loaded piled raft foundations covering the location factor of piles. At first, ground surface displacement is derived theoretically by Cerutti’s solution, then assuming that the raft foundation has rigid stiffness, these displacements are the same to calculation lateral loading distribution. Second, the ground displacement where pile placed could be estimated under calculated lateral loading. Third, the piles behavior are evaluated based on these lateral ground displacements. In addition, 3-D FEM numerical analysis were performed to compared with these solutions.

Electron beam direct write of chalcogenide glass integrated optics

The authors present experimental results of electron beam driven structuring of GexSe1-x glass films with composition (x ∼ 0.2) that lies very close to the floppy to rigid stiffness transition for the purpose of achieving planar ridge optical waveguides. Chalcogenide thin films were deposited by pulsed laser deposition and spin-coating on thermally oxidized silicon substrates. The height and width of the induced deformations tend to increase with slower beam scan rates, greater number of exposures, larger beam currents, and thicker GexSe1-x films. Deformations greater than three times the original film thickness were obtained. Numerical analysis shows that guided wave optical modes are supported. Fabricated directional coupler, ring resonator, and grating structures are promising advances toward realizing planar lightwave devices by direct writing with an electron beam.

Dynamic analysis of gear-rotor system with viscoelastic supports under residual shaft bow effect

This paper investigates the dynamic behaviors of a gear-rotor system with viscoelastic supports under effects of the gear eccentricity, the transmission error of gear mesh and the residual shaft bow. The investigated dynamic characteristics include system natural frequencies and steady-state response. The finite element method is used to model the system and Lagrangian approach is applied to derive the system equations of motion. The results show that the mass, the stiffness and the loss factor of the viscoelastic support will significantly affect system critical speeds and steady-state response. It needs larger loss factor and more rigid stiffness of the viscoelastic supports to suppress the systematic amplitude of resonance. As the results shown, the magnitude and phase angle of the residual bow have tremendous influence on first critical speed when the geared system mounted on stiff viscoelastic supports. The transmission error of the gear mesh is assumed to be sinusoidal with tooth passing frequency and it will induce multiple low resonant frequencies in the system response. It is observed that the excited critical speed equals to the original critical speed divided by gear tooth number.

Slab waveguides and nanoscale patterning of pulsed laser-deposited Ge0.2Se0.8 chalcogenide films

Planar slab waveguides were fabricated by pulsed laser deposition from GexSe1−x glass compounds with composition (x∼0.2) that lies very close to the floppy to rigid stiffness transition. These high quality active structures, which were deposited on SiO2 cladding layers above silicon substrates, support several transverse-electric (TE) modes, and a loss of 0.24dB∕cm for the TE0 mode was measured at 632.8nm wavelength. The ability to exploit electron beam writing at these special Ge in Se compositions to create nanoscale surface motifs are promising advances to create unique miniature optical processing devices.