scholarly journals The mechanical efficiency of frog’s muscle

1939 ◽  
Vol 127 (849) ◽  
pp. 434-451 ◽  
Keyword(s):  
Mechanical Efficiency ◽  
Constant Speed ◽  
Maximum Work ◽  
The Given

The factors determining the maximum work and the mechanical efficiency of muscle were discussed by Hartree and Hill in 1928. Work was measured with the Levin-Wyman ergometer (Levin and Wyman 1927), the muscle being allowed to shorten at constant speed, adjustable as required, and recording a tension-length curve on a smoked surface. The whole of the work which the muscle can do in a single shortening at the given speed is thus obtained, as in no other method. The mechanical efficiency, therefore, should be the highest possible.

Automatic Generation of Piecewise Constant Speed Motion with Smooth Transition for Multi-Axis Machines

1994 ◽  
Vol 116 (2) ◽  
pp. 581-586 ◽  
Author(s):  
D. C. H. Yang ◽  
Jui-Jen Chou
Keyword(s):  
Automatic Generation ◽  
Constant Speed ◽  
Smooth Transition ◽  
Speed Profile ◽  
Piecewise Constant ◽  
Smooth Motion ◽  
Path Geometry ◽  
Five Axes ◽  
The Given ◽  
Motion Profile

This paper presents a general theory on generating a smooth motion profile for the coordinated motion of five-axes CNC/CMM machines. Motion with constat speed is important and required in many manufacturing processes, such as milling, welding, finishing, and painting. In this paper, a piecewise constant speed profile is constructed by a sequence of Hermite curves to form a composite Hermite curve in parametric domain. Given the continuity of acceleration in our proposed speed profile, it generates relatively better product quality than traditional techniques. We also provide a method for the feasibility study of manufacturing capability in terms of the given machine, the desired path, and the assigned speed. We consider machine dynamics, actuator limitation, path geometry, jerk constraints, and motion kinematics.

scholarly journals Efficiency at optimal work from finite source and sink: A probabilistic perspective

2015 ◽  
Vol 40 (1) ◽  
pp. 1-12 ◽  
Author(s):  
Ramandeep S. Johal
Keyword(s):  
Prior Information ◽  
Present Formulation ◽  
Weighted Mean ◽  
Initial State ◽  
Standard Analysis ◽  
Valid Inference ◽  
Maximum Work ◽  
The Mean ◽  
Expected Values ◽  
The Given

AbstractWe revisit the classic thermodynamic problem of maximum work extraction from arbitrary-sized source of heat and sink, modelled as perfect gases. For a given initial state of the process, we assume ignorance of the final temperatures. We quantify the prior information about the process and assign a prior distribution to the unknown temperature(s). This requires that we also take into account the temperature values which are not regarded in standard analysis. In the present formulation, however, such values appear to be consistent with the given prior information and hence are included here in the inference. We derive estimates of the efficiency at optimal work from the expected values of the final temperatures, and show that these match with the exact expressions in the limit when any one of the systems is very large compared to the other. For other relative sizes of the source and the sink, a weighted mean is defined over the estimates from two valid inference procedures, that generalizes the procedure suggested earlier in [J. Phys. A: Math. Theor. 46 (2013), 365002]. The mean estimate for efficiency obtained in this way agrees with the results of the optimal performance quite accurately.

scholarly journals STUDY OF TORQUE NONUNIFORMITY IN DOUBLE-ACTION HYDRAULIC ROTARY VANE MO-TORS

2020 ◽  
Vol 47 (1) ◽  
pp. 39-47
Author(s):  
V. Yu. Savin ◽  
V. Yu. Ilyichev
Keyword(s):  
Mechanical Efficiency ◽  
Theoretical Expression ◽  
Working Fluid ◽  
Constant Acceleration ◽  
Hydraulic Machine ◽  
Nominal Pressure ◽  
Hydraulic Motors ◽  
Braking Torque ◽  
Maximum Stability ◽  
The Given

Abstract. Aim. Hydraulic rotary vane motors rely on the principle of torque maintained at a nominal pressure. In this case, the most important parameter of the torque is its nonuniformity. The problem of determining nonuniform torque in hydraulic motors having ten and twelve vanes is investigated with the aim of ensuring the maximum stability of this parameter.Method. Braking torque occurs on the vanes of hydraulic rotary vane motors due to the pressure of the working fluid on the stator; the theoretical expression for torque does not take the braking effect of the vanes into account. Therefore, an expression is compiled for the braking torque of the vanes with a type of stator curve that provides constant acceleration of the vane relative to the rotor.Results. Plots of changes in braking torques were constructed for 10- and 12-vane motors. Ratios of the minimum and maximum braking torques equal to 0.33 and 0.5 for motors with ten and twelve vanes, respectively, were obtained.Conclusion. The torque nonuniformity coefficients for hydraulic motors for the given parameters of d =11,6% and d = 8,8% for motors having ten and twelve vanes, respectively, were obtained. The results of the analysis of the obtained parameters indicate a slight increase in the nonuniformity of torque in a ten-vane motor. In this case, a decrease in the number of vanes leads to an increase in the mechanical efficiency of the hydraulic machine.

Automatic Generation of Piecewise Constant Speed Motion for Multi-Axis Machines

1992 ◽  
Author(s):  
D. C. H. Yang ◽  
Jui-Jen Chou
Keyword(s):  
General Theory ◽  
Automatic Generation ◽  
Constant Speed ◽  
Manufacturing Processes ◽  
Speed Profile ◽  
Coordinated Motion ◽  
Piecewise Constant ◽  
Smooth Motion ◽  
Path Geometry ◽  
The Given

Abstract This paper presents a general theory on the generation of smooth motion profiles for the coordinated motion of multi-axis manipulators with orthogonal regional structures. Motion with constant speed is important and required in many manufacturing processes, such as milling, welding, finishing and painting. In this paper, a piecewise constant speed profile is constructed by a sequence of Hermite cuves to form a composite Hermite curve in parametric domain. Due to the continuity of acceleration in the proposed speed profile, it generates relatively better product quality than traditional techniques. Besides, we also provide a method for the feasibility study of manufacture capability in terms of the given manipulator, the desired path, and the assigned speed. This includes the consideration of manipulator dynamics, actuator limitation, path geometry, jerk constraints and motion kinematics. The result is a general one and is applicable to all curves tracked by multi-axis manipulators with orthogonal regional structures.

scholarly journals The factors determining the maximum work and the mechanical efficiency of muscle

1928 ◽  
Vol 103 (724) ◽  
pp. 234-251 ◽  
Keyword(s):  
High Efficiency ◽  
Mechanical Efficiency ◽  
Internal Resistance ◽  
Point Of View ◽  
Short Stimulus ◽  
Human Muscles ◽  
Maximum Work ◽  
Work Done ◽  
Speed Of Shortening

In order, in a prolonged contraction, to obtain the maximum work from a muscle, the load must be so adjusted that at every stage the muscle is just, and only just, able to overcome it; and the speed of shortening must be as low as possible. Levin and Wyrnan (1), in their work on the "viscosity" of muscles, employed an ergometer which, allowing the muscle to shorten at any described speed, measured the maximum work which it was capable of performing at that speed. Their instrument, which records a tension-length curve on a fixed smoked surface, is very accurate and convenient to use, and it is theoretically inconceivable that greater work—at a given constant speed—could be recorded by any other means. The only way to increase the work is to decrease the speed, in order to reduce the energy wasted in overcoming the internal resistance of the muscle. From the point of view of the mechanical efficiency of muscle ( i. e. , ratio of work done to total energy liberated) prolonged contractions are to be avoided, since they require large amounts of energy to be liberated in maintaining them (7). The matter has been discussed by one of us and his colleagues in several places (2), (3), (4), (5), p. 32, (6), pp. 48 and 81. It is clear that for a high efficiency the contraction must be of comparatively short duration: there is indeed, for human muscles, an optimum duration at which the efficiency is greatest. We were led therefore to a consideration of the maximum work obtainable in the response to a short stimulus, and to an experimental determination of the maximum mechanical efficiency of the frog's isolated muscle. The matter is much more complicated than is the simple case of a prolonged contraction, considered by Levin and Wyman, and it has required the examination of the effects of varying several different factors.

scholarly journals Gearbox Mechanical Efficiency Determination by Strain Gauges Direct Application

2021 ◽  
Vol 11 (23) ◽  
pp. 11150
Author(s):  
František Lopot ◽  
Martin Dub ◽  
Jan Flek ◽  
Daniel Hadraba ◽  
Martin Havlíček ◽  
...  
Keyword(s):  
Fem Analysis ◽  
Mechanical Efficiency ◽  
Functional Condition ◽  
Strain Gauges ◽  
Torque Measurement ◽  
Current Configuration ◽  
Unique Method ◽  
The Given ◽  
Efficiency Determination ◽  
Better Than

This article describes a unique method of measuring the efficiency of gearboxes using foil strain gauges, which allows maintaining the current configuration of the gearbox within the overall assembly of the machine and its functional condition. The presented method is applicable to gearboxes located in the original equipment assembly without the need to use a test rig. Using foil strain gauges, the torque at the input and output of the gearbox is detected. Therefore, the accuracy of torque measurement is key. The crucial step is the calibration of the instrumentation to the given application conditions, which, in this case, is ensured by a virtual calibration using a very accurate FEM analysis. The accuracy of the position of strain gauges and virtual calibration of measurements generate inaccuracies affecting the resulting uncertainty of the determined efficiency. The present article shows, on the example of several measurements, that when using 24-bit converters, after processing the obtained data, mechanical stress with a sensitivity better than hundredths of an MPa can be reliably detected even without signal amplification from strain gauges. It follows that the efficiency is determined with an accuracy of better than low units of tenths.

scholarly journals A method for evaluating theoretical and real operation of diesel engines in energy conversion formulation taking into account their operating indices

2011 ◽  
Vol 18 (3) ◽  
pp. 31-36 ◽  
Author(s):  
Jerzy Girtler
Keyword(s):  
Energy Conversion ◽  
Diesel Engines ◽  
Power Plants ◽  
Mechanical Efficiency ◽  
Engine Operation ◽  
Screw Propeller ◽  
Main Engine ◽  
The Given ◽  
Direct Use ◽  
Measuring Unit

A method for evaluating theoretical and real operation of diesel engines in energy conversion formulation taking into account their operating indices The article proposes valuating the operation of an arbitrary diesel engine, based on the sample case of a ship's main engine in which energy conversion processes take place in a given time. The above operation is understood as the energy transfer to the screw propeller in the given time in which the energy conversion into work and/or heat and its further transmission take place. The here proposed method for evaluating the operation of the main engines installed in marine power plants consists in comparing the operation of these engines to a physical quantity the measuring unit of which is the joule-second (joule x second). A new term is introduced which bears the name of the theoretical engine operation and is the standard (ideal) operation which can be compared to the operation of real engines revealing different levels of wear. It was shown that the calculations of the theoretical operation defined in the above way cannot make direct use of commonly known theoretical Diesel and Sabathe cycles. Instead they should use the cycles modified by heat abstraction taking place in accordance with the isobaric, or isothermal process. Other new terms introduced in the article are: the degree of excellence of energy conversion to work, considered as the measure of excellence of engine operation, and the degree of engine operation dissipation, being the measure of its real operation. It is shown that if in time t of engine operation the case takes place that: Li = idem and Le = idem, then the engine operation dissipation is equal to its mechanical efficiency.

How to speed up to be in time: Action-judgment dissociations in children and adults

2004 ◽  
Vol 63 (1) ◽  
pp. 17-29 ◽  
Author(s):  
Friedrich Wilkening ◽  
Claudia Martin
Keyword(s):  
Rating Scale ◽  
Constant Speed ◽  
Linear Condition ◽  
Speed Up ◽  
Nonlinear Condition ◽  
Speed Change ◽  
Catch Up ◽  
Normative Rule ◽  
Judgment Condition ◽  
Time Linear

Children 6 and 10 years of age and adults were asked how fast a toy car had to be to catch up with another car, the latter moving with a constant speed throughout. The speed change was required either after half of the time (linear condition) or half of the distance (nonlinear condition), and responses were given either on a rating scale (judgment condition) or by actually producing the motion (action condition). In the linear condition, the data patterns for both judgments and actions were in accordance with the normative rule at all ages. This was not true for the nonlinear condition, where children’s and adults’ judgment and also children’s action patterns were linear, and only adults’ action patterns were in line with the nonlinearity principle. Discussing the reasons for the misconceptions and for the action-judgment dissociations, a claim is made for a new view on the development of children’s concepts of time and speed.

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