Effect of load disturbances during centrally initiated movements

1978 ◽  
Vol 41 (3) ◽  
pp. 542-556 ◽  
Author(s):  
E. Bizzi ◽  
P. Dev ◽  
P. Morasso ◽  
A. Polit
Keyword(s):  
Mechanical Properties ◽  
Mathematical Model ◽  
Visual Discrimination ◽  
Muscle Spindles ◽  
Head Movements ◽  
Afferent Loop ◽  
Reflex Action ◽  
Combined Action ◽  
Head Neck ◽  
Neck Musculature

1. We have investigated the relative contributions of mechanical and reflex mechanisms in generating the forces produced by the neck muscles when loads were unexpectedly applied during centrally programmed head movements in monkeys. These movements, subserved by muscles well endowed with muscle spindles, are part of the coordinated eye-head response to the appearance of a stimulus in the animal's visual field. Our preparation was a chronically vestibulectomized monkey trained to make a visual discrimination. 2. Two procedures were used to evaluate the torque generated by the neck musculature when an unexpected load disturbance was applied: first, by surgically interrupting the afferent loop subserving the reflex action (section of cervical dorsal roots) and second, by building a mathematical model of the head-neck system and carrying out a process of simulation. 3. Our results indicated that the compensatory torque of reflex origin stimulated by the application of an opposing force was less than 10--30% of that required for perfect compensation, and the larger fraction of the observed compensation was due to the mechanical properties (inertial, viscous, and elastic) of the neck musculature. The combined action of reflex and mechanical processes never completely compensated for the disturbance.

The effect of pressure on the compressibility of aluminum alloys

2020 ◽  
pp. 102-107
Keyword(s):  
Mechanical Properties ◽  
Mathematical Model ◽  
Liquid Metal ◽  
Control Systems ◽  
Physical And Mechanical Properties ◽  
Reliable Data ◽  
Output Process ◽  
Automated Control ◽  
Input And Output ◽  
Crystallization Under Pressure

To obtain reliable data on the properties of liquid metal and create automated control systems, the technological process of molding with crystallization under pressure is studied. A mathematical model of the input and output process parameters is developed. It is established that the compressibility of the melt can represent the main controlled parameter influencing on the physical-mechanical properties of the final products. The obtained castings using this technology are not inferior in their physical and mechanical properties to those produced by forging or stamping.

scholarly journals Recyclable Self-Healing Polyurethane Cross-Linked by Alkyl Diselenide with Enhanced Mechanical Properties

Polymers ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 773 ◽  
Author(s):  
Yuqing Qian ◽  
Xiaowei An ◽  
Xiaofei Huang ◽  
Xiangqiang Pan ◽  
Jian Zhu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Room Temperature ◽  
Amide Bond ◽  
Self Healing ◽  
Healing Efficiency ◽  
Polyurethane Networks ◽  
Combined Action ◽  
Cross Linker ◽  
Dynamic Structures ◽  
External Interventions

Dynamic structures containing polymers can behave as thermosets at room temperature while maintaining good mechanical properties, showing good reprocessability, repairability, and recyclability. In this work, alkyl diselenide is effectively used as a dynamic cross-linker for the design of self-healing poly(urea–urethane) elastomers, which show quantitative healing efficiency at room temperature, without the need for any catalysts or external interventions. Due to the combined action of the urea bond and amide bond, the material has better mechanical properties. We also compared the self-healing effect of alkyl diselenide-based polyurethanes and alkyl disulfide-based polyurethanes. The alkyl diselenide has been incorporated into polyurethane networks using a para-substituted amine diphenyl alkyl diselenide. The resulting materials not only exhibit faster self-healing properties than the corresponding disulfide-based materials, but also show the ability to be processed at temperatures as low as 60 °C.

Mathematical Model of the Sintering Process of Iron-Copper Bearings

2007 ◽  
Vol 23 ◽  
pp. 119-122
Author(s):  
Cristina Teișanu ◽  
Stefan Gheorghe ◽  
Ion Ciupitu
Keyword(s):  
Experimental Data ◽  
Mechanical Properties ◽  
Mathematical Model ◽  
Regression Analysis ◽  
Function Optimization ◽  
Chemical Compositions ◽  
Sintering Process ◽  
Molybdenum Disulphide ◽  
Iron Copper ◽  
Antifriction Properties

The most important features of the self-lubricating bearings are the antifriction properties such as friction coefficient and wear resistence and some mechanical properties such as hardness, tensile strength and radial crushing strength. In order to improve these properties new antifriction materials based on iron-copper powders with several additional components (tin, lead and molybdenum disulphide) have been developed by PM techniques. To find the optimal relationship between chemical compositions, antifriction and mechanical properties, in this paper a mathematical model of the sintering process is developed, which highlighted the accordance of the model with data by regression analysis. For the statistical processing of the experimental data the VH5 hardness values of the studied materials were considered. The development of mathematical model includes the enunciation of the model, the establishment of the performance function (optimization) and the establishment of the model equations and verifying. The accordance of the model with experimental data has been highlighted by regression analysis

Sensory Reinnervation of Muscles Following Nerve Section and Suture in Cats

1985 ◽  
Vol 10 (3) ◽  
pp. 340-344
Author(s):  
R. W. BANKS ◽  
D. BARKER ◽  
H. G. BROWN
Keyword(s):  
Common Peroneal Nerve ◽  
Muscle Spindles ◽  
Sensory Impairment ◽  
Normal Muscle ◽  
Axon Terminals ◽  
Reflex Action ◽  
Stretch Receptors ◽  
The Common ◽  
Sensory Reinnervation ◽  
Tendon Organ

The common peroneal nerve was transected and repaired by epineurial suture in nine cats. In a further nine the nerve was transected twice and similarly repaired so as to produce a short autograft. Recovery of stretch receptors in peroneus brevis was monitored histologically and physiologically from six to fifty weeks. In recovery after single neurotomy functionally identifiable muscle-spindle and tendon-organ afferents were reduced to 25% and 45% of normal, respectively; after double neurotomy (autograft) both were reduced to about 10% of normal. Muscle spindles were reinnervated with annulospiral terminals, or wholly abnormal fine axon terminals, or both. Recovery evidently entails not only a reduction in number of stretch afferents, but also the making of some incorrect reconnections that presumably result in abnormal proprioceptive feedback and reflex action. When a graft is used the sensory impairment is compounded.

DYNAMICS OF A2 FINGER PULLEY RUPTURE

2007 ◽  
Vol 07 (01) ◽  
pp. 75-87 ◽  
Author(s):  
MING A. TAN ◽  
FRANZ K. FUSS ◽  
GÜNTHER NIEGL
Keyword(s):  
Mechanical Properties ◽  
Mathematical Model ◽  
Initial Rate ◽  
Constant Force ◽  
Common Occurrence ◽  
Pulley System ◽  
Convergence Test ◽  
A2 Pulley ◽  
The Common ◽  
Rupture Mechanism

A mathematical model of the A2 pulley system will enable us to have a better understanding of the mechanics of the pulley-tendon system and provide us with insights of the pulley rupture mechanism. The A2 pulley was modeled based on parallel pulley fibers attached to a phalanx with a tendon passing them. Mechanical properties of the pulleys such as stiffness, strength and friction were included in the model. A convergence test was done to ensure the accuracy of the test. The model managed to show high loads on flexed finger may lead to pulley ruptures. Further studies on the rupture mechanism showed that pulley ruptures are self-propagating when a constant force is applied and the rate of rupture increases, as fewer intact fibers are present to support the load. The initial rate of propagation is much slower and this accelerates as more fibers are ruptured. This explains the common occurrence of partial pulley ruptures.

scholarly journals Fire and mechanical properties of DGEBA-based epoxy resin cured with a cycloaliphatic hardener: Combined action of silica, melamine and DOPO-derivative

2020 ◽  
Vol 193 ◽  
pp. 108862 ◽  
Author(s):  
Aurelio Bifulco ◽  
Dambarudhar Parida ◽  
Khalifah A. Salmeia ◽  
Rashid Nazir ◽  
Sandro Lehner ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Epoxy Resin ◽  
Combined Action

An On-Line Model to Calculate the Strip Temperature at Run-Out Table of Tisco’s Hot Strip Mill

2003 ◽  
Author(s):  
A. Mukhopadhyay ◽  
S. Sikdar ◽  
S. Sen
Keyword(s):  
Mechanical Properties ◽  
Mathematical Model ◽  
Hot Strip Mill ◽  
Water Cooling ◽  
Coiling Temperature ◽  
Line Model ◽  
Finite Difference Technique ◽  
Hot Strip ◽  
On Line ◽  
Explicit Finite Difference

A Mathematical model has been developed to predict the temperature profile of the strip during water-cooling on the Run-out Table (ROT) of the Hot Strip Mill (HSM). This work describes the development and implementation of the model at Tisco’s HSM. The model has been developed using Explicit Finite Difference technique to predict the coiling temperature (CT). The model has been implemented successfully after having been validated with the actual coiling temperature (CT) for several thousand coils. A number of grades of steel with various thicknesses have been tested with this on-line model and the agreement of actual CT with the predicted ones was found very good. The on-line model is used to calculate the cooling rates at different segments of the strip that are used to obtain microstructure and mechanical properties.

Simulation of frequency dependence of compliance and resistance in healthy man

1975 ◽  
Vol 38 (3) ◽  
pp. 427-435 ◽  
Author(s):  
H. Bobbaers ◽  
J. Clement ◽  
J. Pardaens ◽  
K. P. Woestijne
Keyword(s):  
Mechanical Properties ◽  
Mathematical Model ◽  
Frequency Dependence ◽  
Infinite Number ◽  
Pressure Difference ◽  
Healthy Adult ◽  
Lung Parenchyma ◽  
Pleural Pressure ◽  
Bronchial Wall ◽  
Sinusoidal Input

The frequency dependence of effective compliance, Ceff, and resistance, Reff, are reproduced by means of a two- or four-compartment linear mathematical model with pleural pressure as a sinusoidal input. The model simulates the mechanical properties of lung parenchyma, alveolar gas, bronchial wall, and cheeks, as well as the distribution of gaseous resistances and inertances within the airways. Values, representative for a young healthy adult, are assigned to these various parametersmit appears from this study: 1) that the gas inertance produces a very marked increase of Ceff, noticeable already below 1 cycle/smto obtain a frequency independence of Ceff between 0 and 2 cycles/s, it is necessary to introduce a marked inhomogeneity in the model. 2) Such an inhomogeneity is realized by simulating a pleural pressure difference of 6 cmH2O between the compartments of the bialveolar model. It can be shown that this corresponds to a total pleural pressure difference of about 9 cmH2O in a model consisting of an infinite number of compartments. 3) The influence of the compressibility of alveolar gas and of mechanical properties of the bronchial wall and of the cheeks on Ceff and Reff is small or negligible.

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