Reflex Organization in the Swimmeret System of the Lobster

1969 ◽  
Vol 51 (3) ◽  
pp. 565-573
Author(s):  
W. J. DAVIS
Keyword(s):  
Dynamic Properties ◽  
Motor Command ◽  
Homarus Americanus ◽  
Reflex Response ◽  
Limb Position ◽  
Cycle Basis ◽  
Sinusoidal Movement ◽  
Wide Range ◽  
Motor Neurones ◽  
Maximum Amplification

1. The dynamic properties of the intrasegmental swimmeret reflexes of the lobster Homarus americanus were studied by recording the discharge of the motor neurones while the swimmeret was moved sinusoidally in its natural arc over a wide range of frequencies. 2. The reflex responses of the excitor neurones of both powerstroke (retractor) and returnstroke (protractor) muscles display hysteresis. In both cases the efferent response corresponding to a given limb position is usually greater during imposed retraction than during protraction. 3. The cyclic efferent reflex response follows the sinusoidal movement stimulus at movement frequencies up to and beyond those which occur naturally during swimmeret beating, with no change in the position of maximum reflex activity in the cycle. The reflexes are therefore capable of influencing the motor output on a cycle-by-cycle basis. 4. The strength of the reflex response is maximum between 1 and 3 Hz. of imposed movement, and declines to either side of this range. The dynamic properties of the reflexes are therefore adjusted so that the maximum amplification of the rhythmic central motor command occurs at the natural frequency of swimmeret beating.

Reflex Organization in the Swimmeret System of the Lobster

1969 ◽  
Vol 51 (3) ◽  
pp. 547-563
Author(s):  
W. J. DAVIS
Keyword(s):  
Sensory Feedback ◽  
Motor Command ◽  
Homarus Americanus ◽  
Motor Output ◽  
Motor Patterns ◽  
Motor Neurones ◽  
Output Pattern

1. The intrasegmental feedback reflexes in the swimmeret system of the lobster Homarus americanus were activated while recording the responses from the swimmeret nerves and muscles. 2. Two main sources of sensory feedback were identified; proprioceptors in the coxal region of the swimmeret, and sensory setae on the edges of the two rami of each swimmeret. The reflexes activated by these inputs are described. 3. Reflexive feedback from the powerstroke movement to the powerstroke excita tory motor neurones is positive, further reinforcing the movement. Intrasegmental reflexes capable of independently initiating or terminating the powerstroke activity are absent, however. Therefore the powerstroke movement of each cycle can begin and end only in response to a purely central nervous motor command. It follows that the intrasegmental swimmeret reflexes are incapable of contributing to the periodicity seen in the motor output pattern which underlies swimmeret beating. 4. In addition to strengthening the powerstroke, the intrasegmental reflexes strengthen the linkage between the powerstroke and the returnstroke within each movement cycle. The reflexes may also reinforce the reciprocity between excitor and inhibitor axon activity to the main powerstroke and returnstroke muscles. 5. It is shown, however, that these three features of the motor output pattern are programmed into the CNS independently of the sensory feedback. The intrasegmental reflexes thus act as subservient amplifying devices for cyclic motor patterns which are produced independently by purely central nervous mechanisms.

scholarly journals Simulation Verification of the Contact Parameter Influence on the Forces’ Course of Cereal Grain Impact against a Stiff Surface

2021 ◽  
Vol 11 (2) ◽  
pp. 466
Author(s):  
Włodzimierz Kęska ◽  
Jacek Marcinkiewicz ◽  
Łukasz Gierz ◽  
Żaneta Staszak ◽  
Jarosław Selech ◽  
...  
Keyword(s):  
Dynamic Properties ◽  
Decisive Role ◽  
Force Sensor ◽  
Contact Forces ◽  
Correct Selection ◽  
Contact Parameter ◽  
Cereal Grain ◽  
Wide Range ◽  
The Impact ◽  
Selection Of

The continuous development of computer technology has made it applicable in many scientific fields, including research into a wide range of processes in agricultural machines. It allows the simulation of very complex physical phenomena, including grain motion. A recently discovered discrete element method (DEM) is used for this purpose. It involves direct integration of equations of grain system motion under the action of various forces, the most important of which are contact forces. The method’s accuracy depends mainly on precisely developed mathematical models of contacts. The creation of such models requires empirical validation, an experiment that investigates the course of contact forces at the moment of the impact of the grains. To achieve this, specialised test stations equipped with force and speed sensors were developed. The correct selection of testing equipment and interpretation of results play a decisive role in this type of research. This paper focuses on the evaluation of the force sensor dynamic properties’ influence on the measurement accuracy of the course of the plant grain impact forces against a stiff surface. The issue was examined using the computer simulation method. A proprietary computer software with the main calculation module and data input procedures, which presents results in a graphic form, was used for calculations. From the simulation, graphs of the contact force and force signal from the sensor were obtained. This helped to clearly indicate the essence of the correct selection of parameters used in the tests of sensors, which should be characterised by high resonance frequency.

What Kind of Friction Model Is Needed to Predict Brake Squeal?

2012 ◽  
Author(s):  
Tore Butlin ◽  
Jim Woodhouse
Keyword(s):  
Large Scale ◽  
Dynamic Properties ◽  
Theoretical Work ◽  
Friction Model ◽  
Coupled Systems ◽  
Brake Squeal ◽  
Model Framework ◽  
Wide Range ◽  
Pin On Disc ◽  
Almost All

Predictive models of friction-induced vibration have proved elusive despite decades of research. There are many mechanisms that can cause brake squeal; friction coupled systems can be highly sensitive to small perturbations; and the dynamic properties of friction at the contact zone seem to be poorly understood. This paper describes experimental and theoretical work aimed at identifying the key ingredients of a predictive model. A large-scale experiment was carried out to identify squeal initiations using a pin-on-disc test rig: approximately 30,000 squeal initiations were recorded, covering a very wide range of frequencies. The theoretical model allows for completely general linear systems coupled at a single sliding point by friction: squeal is predicted using a linearised stability analysis. Results will be presented that show that almost all observed squeal events can be predicted within this model framework, but that some subsets require innovative friction modelling: predictions are highly dependent on the particular choice of friction model and its associated parameters.

Modeling and Experimental Characterization of Viscoelastic 3D Printed Spring/Damper Systems

2017 ◽  
Author(s):  
Heather L. Lai ◽  
Cuiyu Kuang ◽  
Jared Nelson
Keyword(s):  
Dynamic Behavior ◽  
Material Properties ◽  
Dynamic Properties ◽  
Viscoelastic Materials ◽  
Vibration Isolators ◽  
Damping Behavior ◽  
Wide Range ◽  
3D Printed ◽  
Printed Materials

The development of flexible, viscoelastic materials for consumer 3D printers has provided the opportunity for a wide range of devices with damping behavior such as tuned vibration isolators to be innovatively developed and inexpensively manufactured. However, there is currently little information available about the dynamic behavior of these 3D printed materials necessary for modeling of dynamic behavior prior to print. In order to fully utilize these promising materials, a deeper understanding of the material properties, and the subsequent dynamic behavior is critical. This study evaluates the use of three different types of models: transient response, frequency response and hysteretic response to predict the dynamic behavior of viscoelastic 3D printed materials based on static and dynamic material properties. Models of viscoelastic materials are presented and verified experimentally using two 3D printable materials and two traditional viscoelastic materials. The experimental response of each of the materials shows agreement with the modeled behavior, and underscores the need for improved characterization of the dynamic properties of viscoelastic 3D printable materials.

Respiratory and Circulatory Responses to Hypoxia in the Lobster Homarus Americanus

1975 ◽  
Vol 62 (3) ◽  
pp. 637-655 ◽  
Author(s):  
B. R. MCMAHON ◽  
J. L. WILKENS
Keyword(s):  
Oxygen Consumption ◽  
Oxygen Uptake ◽  
Homarus Americanus ◽  
Control Mechanisms ◽  
Blood Oxygen ◽  
Experimental Conditions ◽  
Oxygen Levels ◽  
Wide Range ◽  
Oxygen Tensions

Contrary to previous reports, oxygen consumption is maintained over a wide range of external oxygen tensions in the lobster Homarus americanus. In animals acclimated to the experimental conditions this response is mediated by increased branchial pumping, increased effectiveness of oxygen uptake by the gills and an increased contribution by the respiratory pigment to the oxygen delivered to the tissues. Circulatory blood oxygen levels are generally high in lobsters resting in well-aerated water. Mechanisms for detection of hypoxia and possible control mechanisms are discussed.

Contributions of motor-unit recruitment and rate modulation of compensation for muscle yielding

1982 ◽  
Vol 47 (5) ◽  
pp. 797-809 ◽  
Author(s):  
P. J. Cordo ◽  
W. Z. Rymer
Keyword(s):  
Motor Unit ◽  
Stretch Reflex ◽  
Muscle Force ◽  
Motor Units ◽  
Muscle Stiffness ◽  
Motor Unit Recruitment ◽  
Reflex Response ◽  
Rate Modulation ◽  
Stimulus Rate ◽  
Wide Range

1. Subdivided portions of the cut ventral root innervation of the soleus muscle were electrically stimulated in 14 anesthetized cats. The stimulus trains imposed on these nerves simulated the recruitment and rate-modulation patterns of single motor units recorded during stretch-reflex responses in decerebrate preparations. Each activation pattern was evaluated for its ability to prevent muscle yield. 2. Three basic stimulus patterns, recruitment, step increases in stimulus rate, and doublets were imposed during the course of ramp stretches applied over a wide range of velocities. The effect of each stimulus pattern on muscle force was compared to the force output recorded without stretch-related recruitment or rate modulation. 3. Motor-unit recruitment was found to be most effective in preventing yield during muscle stretch. Newly recruited motor units showed no evidence of yielding for some 250 ms following activation, at which time muscle stiffness declined slightly. This time-dependent resistance to yield was observed regardless of whether the onset of the neural stimulus closely preceded or followed stretch onset. 4. Step increases in stimulus rate arising shortly after stretch onset did not prevent the occurrence of yield at most stretch velocities, but did augment muscle stiffness later in the stretch. Doublets in the stimulus train were found to augment muscle stiffness only when they occurred in newly recruited motor units. 5. These results suggest that at low or moderate initial forces, the prevention of yield in lengthening, reflexively intact muscle results primarily from rapid motor-unit recruitment. To a lesser extent, the spring-like character of the stretch-reflex response also derives from step increases in firing rate of motor units active before stretch onset and doublets in units recruited during the course of stretch. Smooth rate increases appear to augment muscle force later in the course of the reflex response.

scholarly journals Modelling Properties of an Alkaline Electrolyser

Energies ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 3073
Author(s):  
Krzysztof Górecki ◽  
Małgorzata Górecka ◽  
Paweł Górecki
Keyword(s):  
Potassium Hydroxide ◽  
Dynamic Properties ◽  
Operating Conditions ◽  
High Productivity ◽  
Electrolysis Process ◽  
Average Value ◽  
Current Voltage ◽  
Wide Range ◽  
Current Voltage Characteristics ◽  
Parameter Values

This paper proposes a model of an electrolyser in the form of a subcircuit dedicated for SPICE. It takes into account both the electric static and dynamic properties of the considered device and is devoted to the optimisation of the parameters of the signal feeding this electrolyser, making it possible to obtain a high productivity and efficiency of the electrolysis process. Parameter values the describing current-voltage characteristics of the electrolyser take into account the influence of the concentration of the potassium hydroxide (KOH) solution. A detailed description of the structure and all the components of this model is included in the paper. The correctness of the elaborated model is verified experimentally in a wide range of changes in the value of the feeding current and concentration of the KOH solution. Some computations illustrating the influence of the amplitude, average value, duty factor, and frequency of feeding current on the productivity and efficiency of the electrolysis process are performed. On the basis of the obtained results of the investigations, some recommendations for the operating conditions of electrolysers are formulated.

Dynamic Properties of a Circuit Breaker with Friction-Based Seismic Dampers

1996 ◽  
Vol 12 (2) ◽  
pp. 297-314 ◽  
Author(s):  
R. Kar ◽  
J. H. Rainer ◽  
A. C. Lefrançois
Keyword(s):  
Design Parameter ◽  
Natural Frequencies ◽  
Dynamic Properties ◽  
Circuit Breaker ◽  
Ground Acceleration ◽  
Discrete Parameter ◽  
Wide Range ◽  
Sf6 Circuit Breaker ◽  
Energy Dissipated

The design parameter of 1.05 g peak seismic ground acceleration for a 300 kV SF6 circuit breaker necessitated the provision of supplemental friction-based dampers. This paper describes the dampers and the dynamic properties of the circuit breaker as obtained from a series of pull-release tests with increasing force amplitudes. These tests permitted a determination of a wide range of damping ratios and natural frequencies as a function of displacements. A comparison is also presented between the measured and the calculated damping ratios and frequencies, using common engineering approximation of the energy dissipated per cycle for damping, and a discrete parameter and linearized stiffness approach for the calculation of natural frequency. Reasonable comparisons were achieved between the measured and calculated values.

Nonlinearity in the Dynamic Properties of Vulcanized Rubber Compounds

1954 ◽  
Vol 27 (1) ◽  
pp. 209-222 ◽  
Author(s):  
W. P. Fletcher ◽  
A. N. Gent
Keyword(s):  
Simple Shear ◽  
Dynamic Modulus ◽  
Dynamic Properties ◽  
Mechanical Vibration ◽  
Frequency Range ◽  
Vulcanized Rubber ◽  
Rubber Compounds ◽  
Chemical Combination ◽  
Wide Range ◽  
Static Shear

Abstract Measurements are described of the dynamic properties of rubber, loaded with various amounts and types of filler, when subjected to mechanical vibration in simple shear at amplitudes from 0 to 3 per cent shear in the frequency range 20 to 120 c.p.s. The decrease of dynamic modulus with increasing amplitude is shown, for a wide range of filler types and concentrations, to be determined by the amount of stiffening produced by the filler. This relationship is not influenced by variations in the vulcanizing ingredients, reasonable variations in state of vulcanization, addition of softener, or imposition of static shear strain. Rubber compounds stiffened by mixture with, or chemical combination of, other polymers exhibit a smaller order of nonlinearity than that described above and also exhibit much lower hysteresis values within the amplitude range 0 to 3 per cent shear.

Autocatalysis: At the Root of Self-Replication

2011 ◽  
Vol 17 (3) ◽  
pp. 219-236 ◽  
Author(s):  
Raphaël Plasson ◽  
Axel Brandenburg ◽  
Ludovic Jullien ◽  
Hugues Bersini
Keyword(s):  
Chemical Reactions ◽  
Chemical Compound ◽  
Dynamic Properties ◽  
General Definition ◽  
Mathematical Form ◽  
Fundamental Level ◽  
Autopoietic Systems ◽  
Wide Range ◽  
Kinetic Pattern ◽  
Self Replication

Autocatalysis is a fundamental concept, used in a wide range of domains. From its most general definition, that is, a process in which a chemical compound is able to catalyze its own formation, several different systems can be described. We detail the different categories of autocatalyses, and compare them on the basis of their mechanistic, kinetic, and dynamic properties. It is shown how autocatalytic patterns can be generated by different systems of chemical reactions. The notion of autocatalysis covers a large variety of mechanistic realizations with very similar behaviors; it is proposed that its key signature is its kinetic pattern expressed in a mathematical form. This notion, while describing dynamic behaviors at the most fundamental level, is at the basis for developing higher-level concepts towards life: autocatalytic sets, and autopoietic systems.

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