scholarly journals A PZT Array Actuator Using Buckling Strain Amplification and Preload Mechanisms

2011 ◽  
Author(s):  
James Torres ◽  
Devin Neal ◽  
H. Harry Asada
Keyword(s):  
Small Strain ◽  
Mechanical Efficiency ◽  
Mechanical Work ◽  
Work Output ◽  
High Power Density ◽  
Nonlinear Buckling ◽  
Gear Design ◽  
Low Stiffness ◽  
Flexure Joints ◽  
Density Force

Displacement amplification mechanisms have been a topic of research for piezoelectric actuators for decades to overcome their significantly small strain, but still utilize their high power density, force, and efficiency. This paper further analyzes a nonlinear buckling mechanism to improve its efficiency, defined as the ratio of mechanical work output of the buckling actuator to the mechanical work output of the PZT actuator, as well as, employing two methods, preload and loading conditions, that improve its work output per cycle. This is accomplished by running a numerical analysis of the geometry of the flexure joints in the buckling mechanism which found a maximum mechanical efficiency of 48%. The preload is applied using shape memory alloy wire to exploit the low stiffness of the super elastic regime; which in turn allows a larger work output due to a loading condition supplied by a novel gear design. Finally, a prototype was fabricated to provide a baseline of comparison against these concepts.

Myocardial anaerobic metabolism in intact dogs

1963 ◽  
Vol 204 (3) ◽  
pp. 427-432 ◽  
Author(s):  
William A. Neill ◽  
Norman Krasnow ◽  
Herbert J. Levine ◽  
Richard Gorlin
Keyword(s):  
Energy Source ◽  
Oxygen Consumption ◽  
Oxidative Metabolism ◽  
Anaerobic Metabolism ◽  
Muscle Metabolism ◽  
Mechanical Work ◽  
Work Output ◽  
Heart Work ◽  
Anaerobic Energy ◽  
The Difference

Energy liberated from substrates of heart muscle metabolism appears as mechanical work and heat. External mechanical work and heat production of the left ventricle were compared with its oxygen consumption in intact dogs. Under control conditions, within the range of accuracy possible, the sum of work and heat was equal to energy from oxidative metabolism. Intravascular administration of cyanide increased heart work but reduced its rate of aerobic metabolism. During the cyanide effect, work plus heat exceeded the energy available from oxidative metabolism. The difference represents myocardial anaerobic metabolism. Since the energy of mechanical work output alone was greater than the myocardial aerobic energy source, a portion of the anaerobic energy liberated must have been converted to mechanical work.

Energy expenditure while performing gymnastic-like motion in spacelab during spaceflight: case study

2006 ◽  
Vol 31 (5) ◽  
pp. 631-634 ◽  
Author(s):  
Masahiro Kaneko ◽  
Kazuki Miyatsuji ◽  
Satoru Tanabe
Keyword(s):  
Energy Expenditure ◽  
Control Subject ◽  
Center Of Mass ◽  
Mechanical Efficiency ◽  
Video Camera ◽  
The Body ◽  
Mechanical Work ◽  
Whole Body ◽  
Total Power ◽  
External Work

To estimate energy cost of a gymnastic-like exercise performed by an astronaut during spaceflight (cosmic exercise), energy expenditure was determined by measuring mechanical work done around the center of mass (COM) of the body. The cosmic exercise, which consisted of whole-body flexion and extension, was performed during a spaceflight and recorded with a video camera. By analyzing the videotape, the internal mechanical work (Wint) against inertia load of the body segments was calculated. To compare how human muscles work on Earth, a motion similar to the cosmic exercise was performed by a control subject who had a physique similar to that of the astronaut. The total mechanical power of the astronaut was determined to be about 119 W; although the control subject showed a similar total power value, half of the power was external work (Wext) against gravitational load. By assuming a mechanical efficiency of 0.25, the energy expenditure was estimated to be 476 W or 7.7 W/kg, which is equivalent to that expended during fast walking and half of that used during moderate-speed running. Our results suggest that this form of cosmic exercise is appropriate for astronauts in space and can be performed safely, as there are no COM shifts while floating in a spacecraft and no vibratory disturbance.

Mechanical efficiency of breathing

1960 ◽  
Vol 15 (3) ◽  
pp. 359-362 ◽  
Author(s):  
G. Milic-Emili ◽  
J. M. Petit
Keyword(s):  
Oxygen Consumption ◽  
Tidal Volume ◽  
Dead Space ◽  
Energy Cost ◽  
Respiratory Muscles ◽  
Normal Subjects ◽  
Mechanical Efficiency ◽  
Mechanical Work ◽  
Closed Circuit ◽  
Simultaneous Measurements

Simultaneous measurements of mechanical work and energy cost of breathing were performed on four normal subjects with ventilation increased by adding dead space. Mechanical work was obtained from simultaneous records of endoesophageal pressure and tidal volume. The associated energy cost was estimated by measuring oxygen consumption of respiratory muscles by means of a closed-circuit spirometer. In all subjects studied and over the range of ventilations involved (ca. 30–110 l/min.), the mechanical efficiency of breathing was found to be in the order of 0.19–0.25. Submitted on July 6, 1959

Determinants of work produced by skeletal muscle: potential limitations of activation and relaxation

1997 ◽  
Vol 273 (3) ◽  
pp. C1049-C1056 ◽  
Author(s):  
V. J. Caiozzo ◽  
K. M. Baldwin
Keyword(s):  
Skeletal Muscle ◽  
Length Change ◽  
Small Strain ◽  
Mechanical Work ◽  
Slow Skeletal Muscle ◽  
Loop Technique ◽  
Force Velocity ◽  
The Difference ◽  
Kinetics Of ◽  
Work Loop

The objective of this study was to estimate the limitations imposed by the kinetics of activation and relaxation on the ability of slow skeletal muscle to produce mechanical work. These estimates were made by the following methods: 1) using the work loop technique and measuring the actual mechanical work (WA) produced by rat soleus muscles (n = 6) at four different frequencies (0.5, 1, 2, and 4 Hz) and seven different amplitudes of length change (1, 2, 3, 4, 5, 6, and 7 mm); 2) determining the force-velocity relationships of the soleus muscles and using this data to quantify the theoretical mechanical work (WT) that could be produced under the work loop conditions described above; and 3) subtracting WA from WT. The difference between WT and WA was interpreted to represent limitations imposed by activation and relaxation. Under certain conditions (high frequency, small strain), factors controlling the kinetics of activation and relaxation reduced the mechanical work of the soleus muscle by approximately 60%. Hence, activation and relaxation collectively represent important factors limiting the production of mechanical work by slow skeletal muscle.

Effect of resistive loading on inspiratory work output in anesthetized cats

1984 ◽  
Vol 57 (3) ◽  
pp. 839-849 ◽  
Author(s):  
L. Zocchi ◽  
S. C. Luijendijk ◽  
W. A. Zin ◽  
A. Rossi ◽  
J. Milic-Emili
Keyword(s):  
Esophageal Pressure ◽  
Mechanical Work ◽  
Work Output ◽  
Inspiratory Muscles ◽  
Model Predictions ◽  
Resistive Loading ◽  
The Face ◽  
The Stability ◽  
Spontaneously Breathing ◽  
Inspiratory Work

In five spontaneously breathing anesthetized cats, we determined the inspiratory elastic (Wel), resistive (Wres), and total (WI) mechanical work rates (power) during control and first loaded inspirations through graded linear resistances (delta R) by “Campbell diagrams” based on measurement of esophageal pressure. WI did not change with delta R's up to 0.31 cmH2O X ml-1 X s, the concomitant decrease in Wel being balanced by an increase in Wres. The stability of WI in the face of delta R's was due to the vagally mediated prolongation of inspiration and the intrinsic properties of the respiratory system and of the contracting inspiratory muscles. To assess the separate contributions of volume-related and flow-related intrinsic mechanisms to the stability of WI, we made model predictions of the immediate effects of delta R's on inspiratory mechanical work output based on measurements of inspiratory driving pressure waves and passive and active respiratory resistance and elastance on the same five cats. The results suggest that the intrinsic stability of WI in the face of delta R's is provided primarily by the active elastance.

Mechanical work of breathing during muscular exercise

1960 ◽  
Vol 15 (3) ◽  
pp. 354-358 ◽  
Author(s):  
R. Margaria ◽  
G. Milic-Emili ◽  
J. M. Petit ◽  
G. Cavagna
Keyword(s):  
Energy Cost ◽  
Work Of Breathing ◽  
Pulmonary Ventilation ◽  
Respiratory Muscles ◽  
Mechanical Efficiency ◽  
Mechanical Work ◽  
Muscular Exercise ◽  
Additional Energy ◽  
External Work ◽  
Small Magnitude

The mechanical work of breathing was measured during muscular exercise on three normal subjects from simultaneous records of intra-esophageal pressure and tidal volume. At the maximal values of ventilation attained during exercise, the mechanical work of breathing amounts to about 100–120 cal/min. The maximum pulmonary ventilation useful for external work is attained when the energy cost of breathing due to any additional unit of air ventilated (dWre/dV) equals the additional energy provided by the same change in ventilation (dWtot/ dV), i.e. when dWre/dV = dWtot/dV. The maximal values of ventilation obtained experimentally during muscular exercise are in good agreement with that assumption, if the mechanical efficiency of the respiratory muscles is taken as 0.25. This implies that the mechanical efficiency of the respiratory muscles is the same as that of the muscles involved in performing useful external work. The work of breathing is of relatively small magnitude: during exercise the work of a breathing cycle amounts, at maximum, to 8% of the maximum potential work of breathing, calculated from the pressure-volume diagram of the respiratory apparatus, and the energy cost of respiration represents no more than 3% of the total energy consumed by the subject. Submitted on May 21, 1959

scholarly journals Energetic Assessment of the Nonexercise Activities under Free-Living Conditions

2016 ◽  
Vol 2016 ◽  
pp. 1-7
Author(s):  
Shijie Sun ◽  
Qiang Tang ◽  
Haiying Quan ◽  
Qi Lu ◽  
Ming Sun ◽  
...  
Keyword(s):  
Energy Expenditure ◽  
Daily Life ◽  
Mechanical Efficiency ◽  
Living Condition ◽  
Portable Device ◽  
Mechanical Work ◽  
Mechanical Modeling ◽  
Free Living ◽  
Mechanical Models ◽  
Activity Energy

Nonexercise activities (NAs) are common types of physical activity in daily life and critical component in energy expenditure. However, energetic assessment of NA, particularly in free-living subjects, is a technical challenge. In this study, mechanical modeling and portable device were used to evaluate five common types of NA in daily life: sit to stand, lie to sit, bowing while standing, squat, and right leg over left. A human indirect calorimeter was used to measure the activity energy expenditure of NA. Mechanical work and mechanical efficiency of NA were calculated for mechanical modeling. Thirty-two male subjects were recruited for the study (20 subjects for the development of models and 12 subjects for evaluation of models). The average (mean ± SD) mechanical work of 5 NAs was 2.31 ± 0.50, 2.88 ± 0.57, 1.75 ± 0.55, 3.96 ± 1.25, and 1.25 ± 0.51 J/kg·m, respectively. The mean mechanical efficiencies of those activities were 22.0 ± 3.3%, 26.5 ± 5.1%, 19.8 ± 3.7%, 24.0 ± 5.5%, and 26.3 ± 5.5%. The activity energy expenditure estimated by the models was not significantly different from the measurements by the calorimeter (p>0.05) with accuracies of 102.2 ± 20.7%, 103.7 ± 25.8%, 105.6 ± 14.6%, 101.1 ± 28.0%, and 95.8 ± 20.7%, respectively, for those activities. These findings suggest that the mechanical models combined with a portable device can provide an alternative method for the energetic analysis of nonexercise activities under free-living condition.

Comparison of the efficiency of rat papillary muscles during afterloaded isotonic contractions and contractions with sinusoidal length changes

2001 ◽  
Vol 204 (10) ◽  
pp. 1765-1774 ◽  
Author(s):  
L.J. Mellors ◽  
C.L. Gibbs ◽  
C.J. Barclay
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Length Change ◽  
Mechanical Efficiency ◽  
Left Ventricular ◽  
Maximum Efficiency ◽  
Papillary Muscles ◽  
Work Output ◽  
Length Changes ◽  
Isotonic Contractions

The results of previous studies suggest that the maximum mechanical efficiency of rat papillary muscles is lower during a contraction protocol involving sinusoidal length changes than during one involving afterloaded isotonic contractions. The aim of this study was to compare directly the efficiency of isolated rat papillary muscle preparations in isotonic and sinusoidal contraction protocols. Experiments were performed in vitro (27 degrees C) using left ventricular papillary muscles from adult rats. Each preparation performed three contraction protocols: (i) low-frequency afterloaded isotonic contractions (10 twitches at 0.2 Hz), (ii) sinusoidal length change contractions with phasic stimulation (40 twitches at 2 Hz) and (iii) high-frequency afterloaded isotonic contractions (40 twitches at 2 Hz). The first two protocols resembled those used in previous studies and the third combined the characteristics of the first two. The parameters for each protocol were adjusted to those that gave maximum efficiency. For the afterloaded isotonic protocols, the afterload was set to 0.3 of the maximum developed force. The sinusoidal length change protocol incorporated a cycle amplitude of +/−5 % resting length and a stimulus phase of −10 degrees. Measurements of force output, muscle length change and muscle temperature change were used to calculate the work and heat produced during and after each protocol. Net mechanical efficiency was defined as the proportion of the energy (enthalpy) liberated by the muscle that appeared as work. The efficiency in the low-frequency, isotonic contraction protocol was 21.1+/−1.4 % (mean +/− s.e.m., N=6) and that in the sinusoidal protocol was 13.2+/−0.7 %, consistent with previous results. This difference was not due to the higher frequency or greater number of twitches because efficiency in the high-frequency, isotonic protocol was 21.5+/−1.0 %. Although these results apparently confirm that efficiency is protocol-dependent, additional experiments designed to measure work output unambiguously indicated that the method used to calculate work output in isotonic contractions overestimated actual work output. When net work output, which excludes work done by parallel elastic elements, rather than total work output was used to determine efficiency in afterloaded isotonic contractions, efficiency was similar to that for sinusoidal contractions. The maximum net mechanical efficiency of rat papillary muscles performing afterloaded isotonic or sinusoidal length change contractions was between 10 and 15 %.

The energetics of rat papillary muscles undergoing realistic strain patterns

2001 ◽  
Vol 204 (21) ◽  
pp. 3765-3777
Author(s):  
L. J. Mellors ◽  
C. J. Barclay
Keyword(s):  
Muscle Length ◽  
Mechanical Efficiency ◽  
Male Rats ◽  
Papillary Muscles ◽  
Work Output ◽  
Muscle Energetics ◽  
Relaxation Period ◽  
Muscle Dynamics

SUMMARYStudies of cardiac muscle energetics have traditionally used contraction protocols with strain patterns that bear little resemblance to those observed in vivo. This study aimed to develop a realistic strain protocol, based on published in situ measurements of contracting papillary muscles, for use with isolated preparations. The protocol included the three phases observed in intact papillary muscles: an initial isometric phase followed by isovelocity shortening and re-lengthening phases. Realistic papillary muscle dynamics were simulated in vitro (27°C) using preparations isolated from the left ventricle of adult male rats. The standard contraction protocol consisted of 40 twitches at a contraction rate of 2 Hz. Force, changes in muscle length and changes in muscle temperature were measured simultaneously. To quantify the energetic costs of contraction, work output and enthalpy output were determined, from which the maximum net mechanical efficiency could be calculated. The most notable result from these experiments was the constancy of enthalpy output per twitch, or energy cost, despite the various alterations made to the protocol. Changes in mechanical efficiency, therefore, generally reflected changes in work output per twitch. The variable that affected work output per twitch to the greatest extent was the amplitude of shortening, while changes in the duration of the initial isometric phase had little effect. Decreasing the duration of the shortening phase increased work output per twitch without altering enthalpy output per twitch. Increasing the contraction frequency from 2 to 3 Hz resulted in slight decreases in the work output per twitch and in efficiency. Using this realistic strain protocol, the maximum net mechanical efficiency of rat papillary muscles was approximately 15 %. The protocol was modified to incorporate an isometric relaxation period, thus allowing the model to simulate the main mechanical features of ventricular function.

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