Respiratory dynamic resistance

1962 ◽  
Vol 17 (4) ◽  
pp. 609-612 ◽  
Author(s):  
Ernest Croft Long ◽  
Wayland Elroy Hull ◽  
Emile Louis Gebel
Keyword(s):  
Respiratory Cycle ◽  
Dynamic Resistance ◽  
Respiratory Resistance ◽  
Differential Coefficient ◽  
Energy Dissipated ◽  
Nonlinear Resistance

Sinusoidal forcing at frequencies up to 17 cycles/sec was applied to the anesthetized, apneic dog by a body respirator. Forcing pressure and volume displacement were displayed in quadrature on an oscilloscope and planimetric integration of these loops indicated an increase in energy dissipated by total respiratory resistance per liter of air displaced, due to turbulence and changing airway geometry, with increasing frequency. Nonlinear resistance was calculated and the differential coefficient, dP/dV (dynamic resistance), was determined at 10° intervals throughout the respiratory cycle, at each of three frequencies in four dogs. Total respiratory resistance is a “nonohmic” dependent variable and changes progressively throughout the cycle. Submitted on October 20, 1961

Nonlinear-resistance harmonic generators

1967 ◽  
Vol 3 (12) ◽  
pp. 534 ◽  
Author(s):  
F.A. Benson ◽  
F. Winder
Keyword(s):  
Nonlinear Resistance

scholarly journals Design of a 3D-printed hand prosthesis featuring articulated bio-inspired fingers

2020 ◽  
pp. 095441192098088
Author(s):  
Juan Sebastian Cuellar ◽  
Dick Plettenburg ◽  
Amir A Zadpoor ◽  
Paul Breedveld ◽  
Gerwin Smit
Keyword(s):  
3D Printing ◽  
Design Principles ◽  
Prosthetic Hand ◽  
Hand Prosthesis ◽  
Fused Deposition ◽  
Pinch Force ◽  
Actuation System ◽  
3D Printed ◽  
Energy Dissipated ◽  
Dual Material

Various upper-limb prostheses have been designed for 3D printing but only a few of them are based on bio-inspired design principles and many anatomical details are not typically incorporated even though 3D printing offers advantages that facilitate the application of such design principles. We therefore aimed to apply a bio-inspired approach to the design and fabrication of articulated fingers for a new type of 3D printed hand prosthesis that is body-powered and complies with basic user requirements. We first studied the biological structure of human fingers and their movement control mechanisms in order to devise the transmission and actuation system. A number of working principles were established and various simplifications were made to fabricate the hand prosthesis using a fused deposition modelling (FDM) 3D printer with dual material extrusion. We then evaluated the mechanical performance of the prosthetic device by measuring its ability to exert pinch forces and the energy dissipated during each operational cycle. We fabricated our prototypes using three polymeric materials including PLA, TPU, and Nylon. The total weight of the prosthesis was 92 g with a total material cost of 12 US dollars. The energy dissipated during each cycle was 0.380 Nm with a pinch force of ≈16 N corresponding to an input force of 100 N. The hand is actuated by a conventional pulling cable used in BP prostheses. It is connected to a shoulder strap at one end and to the coupling of the whiffle tree mechanism at the other end. The whiffle tree mechanism distributes the force to the four tendons, which bend all fingers simultaneously when pulled. The design described in this manuscript demonstrates several bio-inspired design features and is capable of performing different grasping patterns due to the adaptive grasping provided by the articulated fingers. The pinch force obtained is superior to other fully 3D printed body-powered hand prostheses, but still below that of conventional body powered hand prostheses. We present a 3D printed bio-inspired prosthetic hand that is body-powered and includes all of the following characteristics: adaptive grasping, articulated fingers, and minimized post-printing assembly. Additionally, the low cost and low weight make this prosthetic hand a worthy option mainly in locations where state-of-the-art prosthetic workshops are absent.

scholarly journals The Indentation Rolling Resistance in Belt Conveyors: A Model for the Viscoelastic Friction

Lubricants ◽  
2019 ◽  
Vol 7 (7) ◽  
pp. 58 ◽  
Author(s):  
Nicola Menga ◽  
Francesco Bottiglione ◽  
Giuseppe Carbone
Keyword(s):  
Contact Problem ◽  
Finite Thickness ◽  
Numerical Procedure ◽  
Contact Problems ◽  
Accurate Solution ◽  
Rolling Contact ◽  
Viscoelastic Layer ◽  
Force Coefficient ◽  
Belt Conveyors ◽  
Energy Dissipated

In this paper, we study the steady-state rolling contact of a linear viscoelastic layer of finite thickness and a rigid indenter made of a periodic array of equally spaced rigid cylinders. The viscoelastic contact model is derived by means of Green’s function approach, which allows solving the contact problem with the sliding velocity as a control parameter. The contact problem is solved by means of an accurate numerical procedure developed for general two-dimensional contact geometries. The effect of geometrical quantities (layer thickness, cylinders radii, and cylinders spacing), material properties (viscoelastic moduli, relaxation time) and operative conditions (load, velocity) are all investigated. Physical quantities typical of contact problems (contact areas, deformed profiles, etc.) are calculated and discussed. Special emphasis is dedicated to the viscoelastic friction force coefficient and to the energy dissipated per unit time. The discussion is focused on the role played by the deformation localized at the contact spots and the one in the bulk of the thin layer, due to layer bending. The model is proposed as an accurate solution for engineering applications such as belt conveyors, in which the energy dissipated on the rolling contact of idle rollers can, in some cases, be by far the most important contribution to their energy consumption.

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