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Ebrahim, Rahim, Kamyar Mahbobian i Farshad Tahmasebi Gandomkari. "Effects of Cut-Off Ratio on Performance of an Endoreversible Dual Cycle". Applied Mechanics and Materials 110-116 (październik 2011): 2847–53. http://dx.doi.org/10.4028/www.scientific.net/amm.110-116.2847.
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—This study is aimed at investigating the effects of cut-off ratio on the endoreversible Dual cycle performance with considerations of heat transfer loss and specific heat ratio. By using finite time thermodynamics theory, the relations between the net work output and the compression ratio, between the thermal efficiency and the compression ratio, as well as the optimal relation between net work output and the thermal efficiency of the cycle, are derived. The results shows that if compression ratio is less than certain value, the net work output first decreases and then starts to increase as the cut-off ratio increases. While if compression ratio exceeds certain value, the increase of cut-off ratio make the net work output bigger. The results also shows that the maximum net work output and the optimal thermal efficiency corresponding to maximum net work output first increase and then start to decline as the cut-off ratio increases. The thermal efficiency and the working range of the cycle decrease when the cut-off ratio increased. The results obtained in this work can help us to understand how the cycle performance is influenced by the variation of the cut-off ratio, and they should be considered in practical cycle analysis.
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Costa, Rui, i Brendan MacDonald. "Comparison of the Net Work Output between Stirling and Ericsson Cycles". Energies 11, nr 3 (16.03.2018): 670. http://dx.doi.org/10.3390/en11030670.
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Gutiérrez, Marcos. "La eficiencia térmica de las mezclas de combustibles reciclados de aceites lubricantes y comestibles". INNOVA Research Journal 4, nr 1 (31.01.2019): 34–47. http://dx.doi.org/10.33890/innova.v4.n1.2019.796.
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The energy demand increases with the social, industrial and technological requirements, independent of the sources to supply it. More than half of the total energy consumption is supplied by fossil fuels, which can be replaced by alternative and more environmentally friendly fuels. The present research evaluates thermal efficiency, net output work and energy availability from recycled vegetable-animal and synthetic-mineral substances, in a pure state and blended with neat diesel. The calculation uses mainly the heat value of each fuel and the air properties along each stroke of the diesel cycle. The purpose of the present research consists in the evaluation of the thermal efficiency of alternative fuels in functions of the whole engine cycle and not only Stoichiometric the heat value and quantity of each fuel. It was found that the neat fuel from recycled edible sources provides more net output work and is able to perform longer combustions, while the advantage of higher thermal efficiencies using recycled lubricating oil relies on its use as an additive in a blend with neat diesel. The use of alternative and ecological neat fuels of blends is conditioned by the efforts to produce them and by the resulting thermal efficiency, net output work and remaining energetic availability.
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Staines, Anthony Spiteri. "Ordinary Petri Net Matrices". ITM Web of Conferences 24 (2019): 02007. http://dx.doi.org/10.1051/itmconf/20192402007.
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This work presents some ideas and theory on representing ordinary Petri nets using matrices and builds on previous work in [11],[12]. The three main types of matrices used for Petri net representation are the input, output and incidence matrices. The motivation for this work is that matrices can provide an alternative way to describe Petri nets from the conventional graphical representation. As is indicated several properties can be inferred, observed and derived from the matrices. Some definitions and examples are used.
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Rampun, Andrik, Deborah Jarvis, Paul D. Griffiths, Reyer Zwiggelaar, Bryan W. Scotney i Paul A. Armitage. "Single-Input Multi-Output U-Net for Automated 2D Foetal Brain Segmentation of MR Images". Journal of Imaging 7, nr 10 (1.10.2021): 200. http://dx.doi.org/10.3390/jimaging7100200.
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In this work, we develop the Single-Input Multi-Output U-Net (SIMOU-Net), a hybrid network for foetal brain segmentation inspired by the original U-Net fused with the holistically nested edge detection (HED) network. The SIMOU-Net is similar to the original U-Net but it has a deeper architecture and takes account of the features extracted from each side output. It acts similar to an ensemble neural network, however, instead of averaging the outputs from several independently trained models, which is computationally expensive, our approach combines outputs from a single network to reduce the variance of predications and generalization errors. Experimental results using 200 normal foetal brains consisting of over 11,500 2D images produced Dice and Jaccard coefficients of 94.2 ± 5.9% and 88.7 ± 6.9%, respectively. We further tested the proposed network on 54 abnormal cases (over 3500 images) and achieved Dice and Jaccard coefficients of 91.2 ± 6.8% and 85.7 ± 6.6%, respectively.
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Syme, D. A., i R. K. Josephson. "Influence of muscle length on work from trabecular muscle of frog atrium and ventricle." Journal of Experimental Biology 198, nr 10 (1.10.1995): 2221–27. http://dx.doi.org/10.1242/jeb.198.10.2221.
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The work capacity of segments of atrial and ventricular muscle from the frog Rana pipiens was measured as a function of muscle length using the work loop technique. Both the work done during shortening and the work required to re-lengthen the muscle after shortening increased with muscle length. Net work increased with length up to a maximum, beyond which work declined. The optimum sarcomere length for work output was 2.5-2.6 microns for both atrial and ventricular muscle. Isometric force increased with muscle length to lengths well beyond the optimum for work output. Thus, the decline in work at long lengths is not simply a consequence of a reduction in the capacity of heart muscle to generate force. It is proposed that it is the non-linear increase in work required to re-lengthen muscle with increasing muscle length which limits net work output and leads to a maximum in the relationship between net work and muscle length. Extension of the results from muscle strips to intact hearts suggests that the work required to fill the ventricle exceeds that available from atrial muscle at all but rather short ventricular muscle lengths.
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González, Johan, José Matías Garrido i Héctor Quinteros-Lama. "Analysis of the Maximum Efficiency and the Maximum Net Power as Objective Functions for Organic Rankine Cycles Optimization". Entropy 25, nr 6 (31.05.2023): 882. http://dx.doi.org/10.3390/e25060882.
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Maximum efficiency and maximum net power output are some of the most important goals to reach the optimal conditions of organic Rankine cycles. This work compares two objective functions, the maximum efficiency function, β, and the maximum net power output function, ω. The van der Waals and PC-SAFT equations of state are used to calculate the qualitative and quantitative behavior, respectively. The analysis is performed for a set of eight working fluids, considering hydrocarbons and fourth-generation refrigerants. The results show that the two objective functions and the maximum entropy point are excellent references for describing the optimal organic Rankine cycle conditions. These references enable attaining a zone where the optimal operating conditions of an organic Rankine cycle can be found for any working fluid. This zone corresponds to a temperature range determined by the boiler outlet temperature obtained by the maximum efficiency function, maximum net power output function, and maximum entropy point. This zone is named the optimal temperature range of the boiler in this work.
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Josephson, R. K. "Dissecting muscle power output". Journal of Experimental Biology 202, nr 23 (1.12.1999): 3369–75. http://dx.doi.org/10.1242/jeb.202.23.3369.
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The primary determinants of muscle force throughout a shortening-lengthening cycle, and therefore of the net work done during the cycle, are (1) the shortening or lengthening velocity of the muscle and the force-velocity relationship for the muscle, (2) muscle length and the length-tension relationship for the muscle, and (3) the pattern of stimulation and the time course of muscle activation following stimulation. In addition to these primary factors, there are what are termed secondary determinants of force and work output, which arise from interactions between the primary determinants. The secondary determinants are length-dependent changes in the kinetics of muscle activation, and shortening deactivation, the extent of which depends on the work that has been done during the preceding shortening. The primary and secondary determinants of muscle force and work are illustrated with examples drawn from studies of crustacean muscles.
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JOSEPHSON, ROBERT K., i STOKES R. DARRELL. "Strain, Muscle Length and Work Output in a Crab Muscle". Journal of Experimental Biology 145, nr 1 (1.09.1989): 45–61. http://dx.doi.org/10.1242/jeb.145.1.45.
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The relationships between muscle length, fractional change in length (strain) and work output during cyclic contraction were examined in scaphognathite levator muscle L2B of the green crab Carcinus maenas (L.). The muscle was subjected to sinusoidal strain at 2 Hz and to phasic stimulation in the strain cycle. At an average length and stimulus phase which are optimum for net work output, the work from muscle L2B during shortening rises to a peak or a plateau with increasing strain. The failure of shortening work to increase continuously with strain is due, in part, to the greater shortening velocity associated with greater strain, and to the consequent reduction in muscle force during shortening at higher velocity. The work required to re-lengthen a muscle following contraction is a complex function of strain, with an initial peak followed by a work minimum and then a monotonic rise in work with further increase in strain. The early work minimum is a result of shortening inactivation which reduces muscle force and thus the work which must be done to re-lengthen the muscle. Because shortening work rises to a peak or plateau with increasing strain while lengthening work, for the most part, increases with strain, there is a sharp optimum strain (about 8%) for net work output. Muscle relaxation becomes slower with increasing muscle length. As muscle length is increased, fusion of tension from cycle to cycle becomes more pronounced and shortening inactivation becomes a more important determinant of optimum strain.
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Josephson, R. "Power output from a flight muscle of the bumblebee Bombus terrestris. II. Characterization of the parameters affecting power output". Journal of Experimental Biology 200, nr 8 (1.04.1997): 1227–39. http://dx.doi.org/10.1242/jeb.200.8.1227.
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1. Length-tension relationships and work output were investigated in the intact, dorso-ventral flight muscle of the bumblebee Bombus terrestris. The muscle is an asynchronous muscle. Like other asynchronous flight muscles, it has high resting stiffness and produces relatively low active force in response to tetanic stimulation. 2. The muscle shows shortening deactivation and stretch activation, properties that result in delayed force changes in response to step changes in length, a phase lag between force and length during imposed sinusoidal strain and, under appropriate conditions, positive work output during oscillatory length change. 3. Work loops were used to quantify work output by the muscle during imposed sinusoidal oscillation. The curves relating net work per cycle with muscle length, oscillatory strain and oscillatory frequency were all roughly bell-shaped. The work-length curve was narrow. The optimum strain for net work per cycle was approximately 3 %, which is probably somewhat greater than the strain experienced by the muscle in an intact, flying bumblebee. The optimum frequency for net work output per cycle was 63 Hz (30 °C). The optimum frequency for power output was 73 Hz, which agrees well with the normal wing stroke frequency if allowance is made for the elevated temperature (approximately 40 °C) in the thorax of a flying bumblebee. The optimal strain for work output was not strongly dependent on oscillation frequency. 4. Resilience (that is the work output during shortening/work input during lengthening) for unstimulated muscle and dynamic stiffness (=stress/strain) for both stimulated and unstimulated muscles were determined using the strain (3 %) and oscillation frequency (64 Hz) which maximized work output in stimulated muscles. Unstimulated muscle is a good energy storage device. Its resilience increased with increasing muscle length (and increasing resting force) to reach values of over 90 %. The dynamic stiffness of both stimulated and unstimulated muscles increased with muscle length, but the increase was relatively greater in unstimulated muscle, and at long muscle lengths the stiffness of unstimulated muscle exceeded that of stimulated muscle. Effectively, dynamic stiffness is reduced by stimulation! This is taken as indicating that part of the stiffness in an unstimulated muscle reflects structures, possibly attached cross bridges, whose properties change upon stimulation.
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Layland, J., I. S. Young i J. D. Altringham. "The length dependence of work production in rat papillary muscles in vitro." Journal of Experimental Biology 198, nr 12 (1.12.1995): 2491–99. http://dx.doi.org/10.1242/jeb.198.12.2491.
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The influence of length on work production was investigated for rat papillary muscles using the work loop technique. Active and passive length-force relationships were first determined under isometric conditions and the length for maximum force production (Lmax) was derived. Starting from different lengths within the physiological range, a series of work loops was generated using the stimulation phase shift, strain amplitude and cycle frequency previously found to be optimal for power output at 37 degrees C. The relationship between muscle length and net work was used to determine the length at which work output was maximal (Lopt). In order to examine the dynamic passive properties of the muscles, unstimulated muscles were subjected to the same regime of sinusoidal oscillation as used for the active loops. From the hysteresis loops, lengthening work (work done to extend the passive muscle), passive shortening work (work returned during shortening) and net energy loss (hysteresis) could be measured. The decline in net work production at lengths greater than 95% Lmax could largely be attributed to the rapid and non-linear increase in muscle stiffness and the increase in net energy loss over this range of lengths. The physiological significance of the length-work relationship is considered and the mechanical properties of active and passive papillary muscles are discussed with reference to sarcomere length and cardiac muscle ultrastructure.
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Vassilakos, George, Rob S. James i Valerie M. Cox. "Effect of stimulation frequency on force, net power output, and fatigue in mouse soleus muscle in vitro". Canadian Journal of Physiology and Pharmacology 87, nr 3 (marzec 2009): 203–10. http://dx.doi.org/10.1139/y09-002.
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The effects of electrical stimulation frequency on force, work loop power output, and fatigue of mouse soleus muscle were investigated in vitro at 35 °C. Increasing stimulation frequency did not significantly affect maximal isometric tetanic stress (overall mean ± SD, 205 ± 16.6 kN·m–2 between 70 and 160 Hz) but did significantly increase the rate of force generation. The maximal net power output during work loops significantly increased with stimulation frequency: 18.2 ± 3.7, 22.5 ± 3.3, 26.8 ± 3.7, and 28.6 ± 3.4 W·kg–1 at 70, 100, 130, and 160 Hz, respectively. The stimulation frequency that was used affected the pattern of fatigue observed during work loop studies. At stimulation frequencies of 100 and 130 Hz, there were periods of mean net negative work during the fatigue tests due to a slowing of relaxation rate. In contrast, mean net work remained positive throughout the fatigue test when stimulation frequencies of 70 and 160 Hz were used. The highest cumulative work during the fatigue test was performed at 70 and 160 Hz, followed by 130 Hz, then 100 Hz. Therefore, stimulation frequency affects power output and the pattern of fatigue in mouse soleus muscle.
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James, Rob S., Robbie S. Wilson i Graham N. Askew. "Effects of caffeine on mouse skeletal muscle power output during recovery from fatigue". Journal of Applied Physiology 96, nr 2 (luty 2004): 545–52. http://dx.doi.org/10.1152/japplphysiol.00696.2003.
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The effects of 10 mM (high) and 70 μM (physiologically relevant) caffeine on force, work output, and power output of isolated mouse extensor digitorum longus (EDL) and soleus muscles were investigated in vitro during recovery from fatigue at 35°C. To monitor muscle performance during recovery from fatigue, we regularly subjected the muscle to a series of cyclical work loops. Force, work, and power output during shortening were significantly higher after treatment with 10 mM caffeine, probably as a result of increased Ca2+ release from the sarcoplasmic reticulum. However, the work required to relengthen the muscle also increased in the presence of 10 mM caffeine. This was due to a slowing of relaxation and an increase in muscle stiffness. The combination of increased work output during shortening and increased work input during lengthening had different effects on the two muscles. Net power output of mouse soleus muscle decreased as a result of 10 mM caffeine exposure, whereas net power output of the EDL muscle showed a transient, significant increase. Treatment with 70 μM caffeine had no significant effect on force, work, or power output of EDL or soleus muscles, suggesting that the plasma concentrations found when caffeine is used to enhance performance in human athletes might not directly affect the contractile performance of fatigued skeletal muscle.
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Kumar, P. V. Ram, i R. S. Misra. "Thermodynamic Analysis on Steam Injected Gas Turbine cycle". International Journal of Advance Research and Innovation 5, nr 2 (2017): 213–18. http://dx.doi.org/10.51976/ijari.521735.
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This paper presents thermodynamic methodology for the performance evaluation of steam injected gas turbine(STIG) cycle. The effects of pressure ratio, turbine inlet temperature and specific mass flow rate of steam per kg of air used in the thermodynamic analysis of steam injected gas turbine(STIG) cycle on thermal efficiency of the cycle, specific work output and specific fuel consumption have been investigated. From the results obtained in graphs it is observed that thermal efficiency of steam injected gas turbine(STIG) cycle increases and net work output increases and specific fuel consumption decreases as pressure ratio increases; thermal efficiency of steam injected gas turbine(STIG) cycle and specific work output increases with increase in turbine inlet temperature. Results also show that STIG cycle efficiency is always greater than simple gas turbine cycle for same pressure ratio and turbine inlet temperature and for wide range of parameters STIG cycle is superior to simple gas turbine cycle. In STIG cycle as specific mass flow rate per kg of air increases cycle efficiency and net work output also increases.
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Harrod, J., P. J. Mago, K. Srinivasan i L. M. Chamra. "First and second law analysis of a Stirling engine with imperfect regeneration and dead volume". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 223, nr 11 (21.07.2009): 2595–607. http://dx.doi.org/10.1243/09544062jmes1651.
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This article discusses the thermodynamic performance of an ideal Stirling cycle engine. This investigation uses the first law of thermodynamics to obtain trends of total heat addition, net work output, and thermal efficiency with varying dead volume percentage and regenerator effectiveness. Second law analysis is used to obtain trends for the total entropy generation of the cycle. In addition, the entropy generation of each component contributing to the Stirling cycle processes is considered. In particular, parametric studies of dead volume effects and regenerator effectiveness on Stirling engine performance are investigated. Finally, the thermodynamic availability of the system is assessed to determine theoretical second law efficiencies based on the useful exergy output of the cycle. Results indicate that a Stirling engine has high net work output and thermal efficiency for low dead volume percentages and high regenerator effectiveness. For example, compared to an engine with zero dead volume and perfect regeneration, an engine with 40 per cent dead volume and a regenerator effectiveness of 0.8 is shown to have ∼60 per cent less net work output and a 70 per cent smaller thermal efficiency. Additionally, this engine results in approximately nine times greater overall entropy generation and 55 per cent smaller second law efficiency.
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Ettema, G. J., P. A. Huijing, G. J. van Ingen Schenau i A. de Haan. "Effects of prestretch at the onset of stimulation on mechanical work output of rat medial gastrocnemius muscle-tendon complex". Journal of Experimental Biology 152, nr 1 (1.09.1990): 333–51. http://dx.doi.org/10.1242/jeb.152.1.333.
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Work output of rat gastrocnemius medialis (GM) muscle (N = 5) was measured for stretch-shortening contractions, in which initiation of stretch occurred prior to the onset of activation, and for contractions with an isometric prephase. Duration of the active prephase (prestretch and pre-isometric) varied from 20 to 200 ms. Subsequent shortening (from optimum length + 4 mm to optimum length −2mm) lasted 150 ms. Stretch velocities of 5, 10 and 20 mm s-1 were used, and the shortening velocity was 40 mm s-1. The effects of several combinations of active stretch duration and active stretch amplitude were compared. Using force-compliance characteristics, the work of the contractile element (CE), elastic energy storage and release of the undamped series elastic component (SEC) were distinguished. During shortening, an extra amount of work output was produced, induced by active stretch, of which the largest contribution (70–80%) was due to higher elastic energy release. Enhancement of the storage and utilization of elastic energy during the stretch-shortening cycle, caused by higher transition-point forces (i.e. force at onset of shortening), increased with active stretch amplitude and was associated with a net loss of work, probably due to cross-bridge detachment during active stretch. Net work over the stretch-shortening cycle remained positive for all prestretch contractions, indicating that when a muscle performs this type of contraction, it is able to contribute to work performance on body segments. It is concluded that, in stretch-shortening movements of rat GM muscle, maximal positive work output is incompatible with maximal net work output. Consequences for complex movements in vivo are discussed.
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Rustamova, I. B., i M. M. Babadjanova. "Economic Analysis of Innovation Development Processes in Agriculture of the Republic of Uzbekistan". Vestnik of the Plekhanov Russian University of Economics, nr 2 (13.04.2022): 93–104. http://dx.doi.org/10.21686/2413-2829-2022-2-93-104.
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The article provides econometric analysis of agricultural production efficiency in the Republic of Uzbekistan. As methodology for identifying the impact of land, labour resources and capital on the net output of agriculture Kobba - Douglas production function was used. The results of analyzing parameters of the production function let the authors make a conclusion about the necessity to work out a new concept of innovation development and a new model of efficient running of agriculture and its development on the basis of innovative technologies and agrarian sector diversification. The plotted econometric model is statistically reliable and it can show the state of the net output of Uzbekistan agriculture. Kobba – Douglas production function by the net output of Uzbekistan agriculture and factors affecting it, as well as all its parameters checked by Fisher criterion, Student t-criterion and Darbin – Watson DW-criterion showed that the function by parameters meet all the requirements, which testifies to the possibility to use the model (multiplying model in the form of variables’ product) for the current analysis and future forecast of the net output of the Republic agriculture. On the basis of system econometric analysis the forecast parameters of the net output up to 2025 were identified that were found by raising efficiency of innovative processes in agriculture.
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Layland, J., I. S. Young i J. D. Altringham. "The effect of cycle frequency on the power output of rat papillary muscles in vitro." Journal of Experimental Biology 198, nr 4 (1.04.1995): 1035–43. http://dx.doi.org/10.1242/jeb.198.4.1035.
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Papillary muscles were isolated from the right ventricles of rats and the length for maximum active force generation (Lmax) was determined isometrically. The work loop technique was used to derive the length for maximum work production (Lopt) at the cycle frequency, strain amplitude and stimulation phase shift found to be optimal for power output. Lopt was typically 7% shorter than Lmax and within the physiological length range (87.5% Lmax to Lmax). Net work and power output were measured during sinusoidal strain cycles around Lopt, over the cycle frequency range 1-9 Hz, strain amplitude and phase shift being optimised for work and power at each frequency. Experiments were performed at 37 degrees C. Distinct optima were found in both the work-frequency and the power-frequency relationships. The optimum cycle frequency for net work production was lower than the frequency for maximum power output. The mean maximum power output at 37 degrees C was 8.62 +/- 0.50 W kg-1 (mean +/- S.E.M., N = 9) and was achieved at a cycle frequency of approximately 6 Hz, close to the estimated resting heart rate of 5.8 Hz for the rats used (mean mass 223 +/- 25 g). The cycle frequency, strain amplitude and stimulation phase shift found to be optimal for power output produced an in vitro contraction closely simulating the basal in vivo contraction.
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Askew, G. N., I. S. Young i J. D. Altringham. "Fatigue of mouse soleus muscle, using the work loop technique." Journal of Experimental Biology 200, nr 22 (1.11.1997): 2907–12. http://dx.doi.org/10.1242/jeb.200.22.2907.
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The function of many muscles requires that they perform work. Fatigue of mouse soleus muscle was studied in vitro by subjecting it to repeated work loop cycles. Fatigue resulted in a reduction in force, a slowing of relaxation and in changes in the force-velocity properties of the muscle (indicated by changes in work loop shape). These effects interacted to reduce the positive work and to increase the negative work performed by the muscle, producing a decline in net work. Power output was sustained for longer and more cumulative work was performed with decreasing cycle frequency. However, absolute power output was highest at 5 Hz (the cycle frequency for maximum power output) until power fell below 20% of peak power. As cycle frequency increased, slowing of relaxation had greater effects in reducing the positive work and increasing the negative work performed by the muscle, compared with lower cycle frequencies.
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Curtin, N. A., i R. C. Woledge. "EFFICIENCY OF ENERGY CONVERSION DURING SINUSOIDAL MOVEMENT OF WHITE MUSCLE FIBRES FROM THE DOGFISH SCYLIORHINUS CANICULA". Journal of Experimental Biology 183, nr 1 (1.10.1993): 137–47. http://dx.doi.org/10.1242/jeb.183.1.137.
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Net work output and heat production of white myotomal muscle fibres from the dogfish were measured during complete cycles of sinusoidal movement at 12°C. The peak-to-peak movement was about 9 % of the muscle fibre length; three stimuli at 32 ms intervals were given in each mechanical cycle. The frequency of movement and the timing of the stimulation were varied for each preparation to find the optimal conditions for power output and those optimal for efficiency (the ratio of net work output to total energy output as heat+work). To achieve either maximum power or maximum efficiency, the tetanus must start while the muscle fibres are being stretched, before the beginning of the shortening part of the mechanical cycle. The highest power output, averaged over one cycle, was 0.23+/−0.014 W g-1 dry mass (+/−s.e.m., N=9, 46.9+/−2.8 mW g-1 wet mass) and was produced during movement at 3.5 Hz. The highest efficiency, 0.41+/−0.02 (+/−s.e.m., N=13), occurred during movements at 2.0-2.5 Hz. This value is higher than the efficiency previously measured during isovelocity shortening of these fibres. The implications of the high efficiency for crossbridge models of muscle contraction are discussed.
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Baxi, J., C. J. Barclay i C. L. Gibbs. "Energetics of rat papillary muscle during contractions with sinusoidal length changes". American Journal of Physiology-Heart and Circulatory Physiology 278, nr 5 (1.05.2000): H1545—H1554. http://dx.doi.org/10.1152/ajpheart.2000.278.5.h1545.
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The mechanical efficiency of rat cardiac muscle was determined using a contraction protocol involving cyclical, sinusoidal length changes and phasic stimulation at physiological frequencies (1–4 Hz). Experiments were performed in vitro (27°C) using rat left ventricular papillary muscles. Efficiency was determined from measurements of the net work performed and enthalpy produced by muscles during a series of 40 contractions. Net mechanical efficiency was defined as the percentage of the total, suprabasal enthalpy output that appeared as mechanical work. Maximum efficiency was ∼15% at contraction frequencies between 2 and 2.5 Hz. At lower and higher frequencies, efficiency was ∼10%. Enthalpy output per cycle was independent of cycle frequency at all but the highest frequency used. The basis of the high efficiency between 2 and 2.5 Hz was that work output was also greatest at these frequencies. At these frequencies, the duration of the applied length change was well matched to the kinetics of force generation, and active force generation occurred throughout the shortening period.
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Mellors, L. J., C. L. Gibbs i C. J. Barclay. "Comparison of the efficiency of rat papillary muscles during afterloaded isotonic contractions and contractions with sinusoidal length changes". Journal of Experimental Biology 204, nr 10 (15.05.2001): 1765–74. http://dx.doi.org/10.1242/jeb.204.10.1765.
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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 %.
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Nawaz, Muhammad. "The Impact of Exchange Rate on Output Level: Bounds Testing Approach for Pakistan". Pakistan Development Review 51, nr 4II (1.12.2012): 419–34. http://dx.doi.org/10.30541/v51i4iipp.419-434.
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The stabilisation of growth process has been the aspiration of the nations in modern era. Since the industrial revolution in the world, most of the developing nations have been in the paradigm of chronic current account situation, loss in output, high import bill, less integration of their export sector, and less competitiveness in trade with the world. The process to devalue their currency may be evaluated as optimism for the improvement of their national growth that not only overcome the soaring trade deficit but also may be helpful to compete in international market. In theoretical literature, there has been contradiction among the researchers based on its effects in determining the net output of the economy. Since the work of Cooper (1971) and Krugman and Taylor (1978), the ambiguity arises for the effects of currency depreciation on output and their pioneer work explain the demand side as well as supply side channels through which depreciation may appear as loss in net output. The devaluation induces higher prices of tradable products that appear as loss in real balance of the economy and ultimately result in less output and growth. Some studies [Krugman and Taylor (1978); Edwards (1986) and Lizondo and Montiel (1989)] also support to contractionay output hypothesis with the induction of income redistribution channel that just redistribute income from the wage earners towards profit earners having the excess savings. This process ultimately leads to less aggregate demand as well as output via meager consumption. On the supply side, depreciation of currency result in higher input cost and less output level [Krugman and Taylor (1978); Van Wijnbergen (1986)]. In addition, wage indexation mechanism is also important that reduces the net benefits on producer side and escorts to the contraction in output [Agenor and Montiel (1996)].
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Mellors, L. J., i C. J. Barclay. "The energetics of rat papillary muscles undergoing realistic strain patterns". Journal of Experimental Biology 204, nr 21 (1.11.2001): 3765–77. http://dx.doi.org/10.1242/jeb.204.21.3765.
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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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Jurado, Ulises Tronco, Suan Hui Pu i Neil M. White. "Water-Dielectric Single Electrode Mode Triboelectric Nanogenerators for Ocean Wave Impact Energy Harvesting". Proceedings 2, nr 13 (21.12.2018): 714. http://dx.doi.org/10.3390/proceedings2130714.
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The effect of water wave impacts and breakdown on the output performance of Water-Dielectric Single Electrode Mode Triboelectric Nanogenerators (WDSE-TENG) has been evaluated. When water contacts a TENG consisting of a hydrophobic dielectric layer, the triboelectric effect is generated with a net negative charge on the dielectric material and net positive charge on the water surface. The hydrophobic dielectric materials, which show the highest electrical output performance in contact with water, were FEP, silicone rubber and polyimide. The average output power of each sample for a load resistance of 10 MΩ was found to be in the range 14.69 to 19.12 µW. The results demonstrate that WDSE-TENG devices can work as an alternative energy harvesting mechanism by using water as a triboelectric material.
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Badescu, Viorel. "Optimal piston motion for maximum net output work of Daniel cam engines with low heat rejection". Energy Conversion and Management 101 (wrzesień 2015): 181–202. http://dx.doi.org/10.1016/j.enconman.2015.05.020.
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Barclay, C. J. "Efficiency of fast- and slow-twitch muscles of the mouse performing cyclic contractions." Journal of Experimental Biology 193, nr 1 (1.08.1994): 65–78. http://dx.doi.org/10.1242/jeb.193.1.65.
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The mechanical efficiency of mouse fast- and slow-twitch muscle was determined during contractions involving sinusoidal length changes. Measurements were made of muscle length, force production and initial heat output from bundles of muscle fibres in vitro at 31 degrees C. Power output was calculated as the product of the net work output per sinusoidal length cycle and the cycle frequency. The initial mechanical efficiency was defined as power output/(rate of initial heat production+power output). Both power output and rate of initial heat production were averaged over a full cycle of length change. The amplitude of length changes was +/- 5% of muscle length. Stimulus phase and duration were adjusted to maximise net work output at each cycle frequency used. The maximum initial mechanical efficiency of slow-twitch soleus muscle was 0.52 +/- 0.01 (mean +/- 1 S.E.M. N = 4) and occurred at a cycle frequency of 3 Hz. Efficiency was not significantly different from this at cycle frequencies of 1.5-4 Hz, but was significantly lower at cycle frequencies of 0.5 and 1 Hz. The maximum efficiency of fast-twitch extensor digitorum longus muscle was 0.34 +/- 0.03 (N = 4) and was relatively constant (0.32-0.34) over a broad range of frequencies (4-12 Hz). A comparison of these results with those from previous studies of the mechanical efficiency of mammalian muscles indicates that efficiency depends markedly on contraction protocol.
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Rasheduzzaman, Md, Poria Fajri, Jonathan Kimball i Brad Deken. "Modeling, Analysis, and Control Design of a Single-Stage Boost Inverter". Energies 14, nr 14 (7.07.2021): 4098. http://dx.doi.org/10.3390/en14144098.
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A single-phase, single-stage, differential boost inverter comprises two independently-controlled boost DC-DC converters, with the load connected between their outputs. The net voltage on the load is sinusoidal and has a controllable frequency and magnitude that is larger than that of the DC source. The present work first derives steady-state and small-signal models of the inverter with parasitic elements. The results obtained from the line-to-output transfer function, control-to-output transfer function, open-loop input impedance, and open-loop output impedance models are compared with that of the ones obtained from the experimental testbed. Using the new models, a voltage mode controller is designed in the synchronous reference frame. The regulator design is explored through the use of an example. The results are verified against the small-signal model, then PLECS simulations, and finally a laboratory experiment. The results indicate excellent agreement between the model and experiment during transients in voltage reference, input source voltage, and output load. A sensitivity analysis is performed based on the inverter model considering the parameter variation. Finally, loss and efficiency estimations are provided in this work.
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Liu, Qiang, Ran Chen, Xinliu Yang i Xiao Xiao. "Thermodynamic Analyses of Sub- and Supercritical ORCs Using R1234yf, R236ea and Their Mixtures as Working Fluids for Geothermal Power Generation". Energies 16, nr 15 (28.07.2023): 5676. http://dx.doi.org/10.3390/en16155676.
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Organic Rankine cycles (ORCs) have been widely used to convert medium-low-temperature geothermal energy to electricity. Proper cycle layout is generally determined by considering both the thermo-physical properties of the working fluid and the geothermal brine temperature. This work investigates saturated, superheated and supercritical ORCs using R1234yf/R236ea for brine temperatures of 383.15 K, 403.15 K and 423.15 K. The evaporation and condensation pressures were optimized to maximize the net power outputs. The thermodynamic characteristics of the cycles at the optimal conditions were analyzed. The saturated ORCs produced slightly more net power than superheated cycles for the R1234yf mole fraction less than 0.2 due to lower exergy losses in the evaporator and condenser; however, the limited evaporation pressure by the turning point at the higher R1234yf mole fraction led to excessive exergy losses in the evaporator. Two R1234yf mole fractions maximized the net power and exergy efficiency in a superheated cycle, with the maximum net power output occurring at the R1234yf mole fraction of 0.8 for brine temperatures of 383.15 K and 403.15 K. The exergy losses for evaporation were reduced by 6–12.7% due to the use of an IHE, while those for condensation were reduced up to 42% in a superheated cycle for a brine temperature of 423.15 K, resulting in a 1–17.8% increase in the exergy efficiency. A supercritical cycle with an IHE using R1234yf/R236ea (0.85/0.15) generated the maximum net power output for a brine temperature of 423.15 K, 8.2–17.5% higher than a superheated cycle with an IHE.
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Curtin, N. A., i R. C. Woledge. "EFFICIENCY OF ENERGY CONVERSION DURING SINUSOIDAL MOVEMENT OF RED MUSCLE FIBRES FROM THE DOGFISH SCYLIORHINUS CANICULA". Journal of Experimental Biology 185, nr 1 (1.12.1993): 195–206. http://dx.doi.org/10.1242/jeb.185.1.195.
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Bundles of red myotomal muscle fibres isolated from dogfish were electrically stimulated at 12 sC. Peak twitch force was 54 % of that produced by a brief isometric tetanus. Relaxation was slower than in white fibres, but much faster than would be expected for the tonic fibres found in amphibian muscle. These two results indicate that the red fibres in dogfish are slow, but not tonic, in their behaviour. Net work output and heat production were measured during complete cycles of sinusoidal movement. The following variables were kept constant: peak-to-peak movement, about 7 % of the muscle fibre length; tetanus duration, 33 % of the mechanical cycle time; stimulus frequency, 40 Hz. The frequency of movement and the timing of the stimulation were varied for each preparation to find the conditions optimal for power output and those optimal for efficiency (the ratio of net work output to total energy output as heat+work). To achieve either maximum power or maximum efficiency, the tetanus must start while the muscle fibres are being stretched, before the beginning of the shortening part of the mechanical cycle. The highest power output was produced during movement at 1.02 Hz. The highest efficiency, 0.507+/−0.045 (+/−s.e.m., N=9), was at 0.61-0.95 Hz. The efficiency is higher than that previously measured during sinusoidal movement of white fibres; the difference, 0.095+/− 0.045 (+/−s.e.m. of the difference, d.f. 20), is statistically significant at the 5 % level.
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Wang, Shuai, i Defa Pan. "Effect of Cascaded Phase Change Heat Storage on the Performance of Waste Heat Recovery Systems". Journal of Physics: Conference Series 2473, nr 1 (1.04.2023): 012008. http://dx.doi.org/10.1088/1742-6596/2473/1/012008.
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Abstract The cascades phase change heat storage (CLTES) and trans-critical CO2 Rankine cycle were combined to study the effects of the number of phase change materials in series on heat storage on the performance of waste heat recovery systems in order to overcome the influence of heat source volatility. In terms of net work, 3-CLTES is 12.5% higher than 2-CLTES, but with 30.4% more heat exchange area. Compared with 4-CLTES, the net output work decreased by 2.6%, and the heat transfer area increased by 6.7%.
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Xu, Likang, i Guihua Lin. "Simulation and optimization of liquefied natural gas cold energy power generation system on floating storage and regasification unit". Thermal Science, nr 00 (2020): 205. http://dx.doi.org/10.2298/tsci200404205x.
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In this paper, based on the idea of reducing heat exchanger exergy destruction and increasing turbine work, a new three-stage cascade Rankine system and a new four-stage cascade Rankine system is proposed to improve the cold energy utilization rate during liquefied natural gas(LNG) gasification on liquefied natural gas-floating storage and regasification unit. Then compare them with the original cascade Rankine cycle established under the same conditions. The results show that under the condition of 175 t/h LNG flow, the maximum net output power of the new three-stage cascade Rankine cycle system is 4593.31 kW, the exergy efficiency is 20.644%. The maximum net output power of the new four-stage cascade Rankine cycle system is 5013.93 kW, and the exergy efficiency is 22.509%. Compared with the original cascade Rankine cycle system, the maximum net output power of the new three-stage cascade Rankine cycle system and the new four-stage cascade Rankine cycle system is increased by 9.41% and 11.45%, respectively, and the system exergy efficiency is increased by 9.29% and 11.28%, respectively.
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Brown, David A., i Steven A. Kautz. "Speed-Dependent Reductions of Force Output in People With Poststroke Hemiparesis". Physical Therapy 79, nr 10 (1.10.1999): 919–30. http://dx.doi.org/10.1093/ptj/79.10.919.
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Abstract Background and Purpose. Movement is slow in people with poststroke hemiparesis. Moving at faster speeds is thought by some researchers to exacerbate of abnormal or unwanted muscle activity. The purpose of this study was to quantify the effects of increased speed on motor performance during pedaling exercise in people with poststroke hemiparesis. Subjects. Twelve elderly subjects with no known neurological impairment and 15 subjects with poststroke hemiparesis of greater than 6 months' duration were tested. Methods. Subjects pedaled at 12 randomly ordered workload and cadence combinations (45-, 90-, 135-, and 180-J workloads at 25, 40, and 55 rpm). Pedal reaction forces were used to calculate work done by each lower extremity. Electromyographic activity was recorded from 7 lower-extremity muscles. Results. The main finding was that net mechanical work done by the paretic lower extremity decreased as speed increased in all subjects. The occurrence of inappropriate muscle activity on the paretic side, however, was not exacerbated in that the vastus medialis muscle on the paretic side did not show a consistent further increase in its prolonged activity at higher speeds. The mechanics of faster pedaling resulted in greater net negative mechanical work because, at higher pedaling rates, the prolonged vastus medialis muscle activity is present during a greater portion of the cycle. Conclusion and Discussion. The lessened force output by the paretic limb is mainly the result of the inherent mechanical demands of higher-speed pedaling and not due to exacerbation of impaired neural control.
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Zhao, Yuan, Chenghao Gao, Chengjun Li, Jie Sun, Chunyan Wang, Qiang Liu i Jun Zhao. "Energy and Exergy Analyses of Geothermal Organic Rankine Cycles Considering the Effect of Brine Reinjection Temperature". Energies 15, nr 17 (26.08.2022): 6230. http://dx.doi.org/10.3390/en15176230.
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The organic Rankine cycles (ORCs) have been used to convert low-enthalpy geothermal brine into power. Parameter optimization and working fluid selection are the main approaches to enhance geothermal ORC performance. This work uses environmentally friendly fluids, including R1224yd(Z), R1233zd(E), R1336mzz(Z), R601 and R601a, as the geothermal ORC working fluids. The evaporation temperatures of the selected fluids were optimized to maximize the cycle net power outputs. The thermodynamic characteristics are investigated with the consideration of the influence of the allowed reinjection temperature (ARIT). Among the selected fluids, R1224yd(Z) has the highest optimal evaporation temperature with the maximum turbine power output for a brine inlet temperature (BIT) higher than 120 °C, especially at a lower allowed reinjection temperature. However, the parasitic power consumption by the pumps in an ORC with R1224yd(Z) is also higher than with the other four fluids. The net power output for ORC with R1336mzz(Z) is slightly more than that with R1224yd(Z). Although the optimal evaporation temperature for a RORC is lower than that for an ORC, the higher preheater inlet temperature leads to a higher geothermal heating exergy efficiency and more power output for a BIT less than 120 °C. The RORC with R1336mzz(Z) produces 2.6% more net power than an ORC for a brine inlet temperature of 100 °C. As the ARIT increases from 70 °C to 75 °C, the plant exergy efficiencies of ORCs are decreased by 6–8% for a geothermal brine inlet temperature of 100 °C.
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Chen, Lingen, Chih Wu, Fengrui Sun i Shui Cao. "Heat transfer effects on the net work output and efficiency characteristics for an air-standard Otto cycle". Energy Conversion and Management 39, nr 7 (maj 1998): 643–48. http://dx.doi.org/10.1016/s0196-8904(97)10003-6.
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Lobachev, Ivan M., Svitlana G. Antoshchuk i Mykola A. Hodovychenko. "DISTRIBUTED DEEP LEARNING FRAMEWORK FOR SMART BUILDING TRANSDUCER NETWORK". Applied Aspects of Information Technology 4, nr 2 (30.06.2021): 127–39. http://dx.doi.org/10.15276/aait.02.2021.1.
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This work is devoted to the development of a distributed framework based on deep learning for processing data from various sensors that are generated by transducer networks that are used in the field of smart buildings. The proposed framework allows you to process data that comes from sensors of various types to solve classification and regression problems. The framework architecture consists of several subnets: particular convolutional net that handle input from the same type of sensors, a single convolutional fusion net that processes multiple outputs of particular convolutional nets. Further, the result of a single convolutional fusion net is fed to the input of a recurrent net, which allows extracting meaningful features from time sequences. The result of the recurrent net opera- tion is fed to the output layer, which generates the framework output based on the type of problem being solved. For the experimental evaluation of the developed framework, two tasks were taken: the task of recognizing human actions and the task of identifying a person by movement. The dataset contained data from two sensors (accelerometer and gyroscope), which were collected from 9 users who performed 6 actions. A mobile device was used as the hardware platforms, as well as the Edison Compute Module hardware device. To compare the results of the work, variations of the proposed framework with different architectures were used, as well as third-party approaches based on various methods of machine learning, including support machines of vectors, a random forest, lim- ited Boltzmann machines, and so on. As a result, the proposed framework, on average, surpassed other algorithms by about 8% in three metrics in the task of recognizing human actions and turned out to be about 13% more efficient in the task of identifying a per- son by movement. We also measured the power consumption and operating time of the proposed framework and its analogues. It was found that the proposed framework consumes a moderate amount of energy, and the operating time can be estimated as acceptable.
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Basha, Mehaboob, S. M. Shaahid i Luai Al-Hadhrami. "Impact of inlet fogging and fuels on power and efficiency of gas turbine plants". Thermal Science 17, nr 4 (2013): 1107–17. http://dx.doi.org/10.2298/tsci110708042b.
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A computational study to assess the performance of different gas turbine power plant configurations is presented in this paper. The work includes the effect of humidity, ambient inlet air temperature and types of fuels on gas turbine plant configurations with and without fogger unit. Investigation also covers economic analysis and effect of fuels on emissions. GT frames of various sizes/ratings are being used in gas turbine power plants in Saudi Arabia. 20 MWe GE 5271RA, 40 MWe GE-6561B and 70 MWe GE-6101FA frames are selected for the present study. Fogger units with maximum mass flow rate of 2 kg/s are considered for the present analysis. Reverse Osmosis unit of capacity 4 kg/s supplies required water to the fogger units. GT PRO software has been used for carrying out the analysis including; net plant output and net efficiency, break even electricity price and break even fuel LHV price etc., for a given location of Saudi Arabia. The relative humidity and temperature have been varied from 30 to 45 % and from 80 to 100? F, respectively. Fuels considered in the study are natural gas, diesel and heavy bunker oil. Simulated gas turbine plant output from GT PRO has been validated against an existing gas turbine plant output. It has been observed that the simulated plant output is less than the existing gas turbine plant output by 5%. Results show that variation of humidity does not affect the gas turbine performance appreciably for all types of fuels. For a decrease of inlet air temperature by 10 ?F, net plant output and efficiency have been found to increase by 5 and 2 %, respectively for all fuels, for GT only situation. However, for GT with Fogger scenario, for a decrease of inlet air temperature by 10 ?F, net plant output and efficiency have been found to further increase by 3.2 and 1.2 %, respectively for all fuels. For all GT frames with fogger, the net plant output and efficiency are relatively higher as compared to GT only case for all fuels. More specifically, net plant output and efficiency for natural gas are higher as compare to other fuels for all GT scenarios. For a given 70 MWe frame with and without fogger, break even fuel price and electricity price have been found to vary from 2.2 to 2.5 USD/MMBTU and from 0.020 to 0.0239 USD/kWh respectively. It has been noticed that turbines operating on natural gas emit less carbon relatively as compared to other fuels.
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Onoroh, F., M. Ogbonnaya i U. P. Onochie. "Modeling and simulation of the effect of moisture content and ambient temperature on gas turbine power plant performance in Ughelli, Nigeria". Nigerian Journal of Technology 39, nr 1 (3.04.2020): 182–88. http://dx.doi.org/10.4314/njt.v39i1.20.
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The influence of ambient temperature and moisture content on the performance of Transcorp Power Plant, Ughelli, Delta State, Nigeria was investigated with the aid of a digital psychrometer. The simulation was done using codes developed on MATLAB R2017a and the results show that compressor power consumption increased by 1.65% for 0.7% rise in temperature, and 0.50% for 71.4% rise in moisture content. The specific fuel consumption also increased with increase in temperature where a 1.71% rise in ambient temperature resulted in a 0.15% rise in specific fuel consumption but it decreased by 0.49% for a 41.7% rise in moisture content. A 1.62% rise in temperature led to a 0.13% drop in net power output and a 29.4% rise in moisture content resulted in a 0.48% drop in net power output. Thus gas turbine plant operates optimally in areas with low ambient temperatures and high moisture content.
Keywords: Work ratio, net power, efficiency, moisture content, specific fuel consumption, heat rate.
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Tu, M., i M. Dickinson. "MODULATION OF NEGATIVE WORK OUTPUT FROM A STEERING MUSCLE OF THE BLOWFLY CALLIPHORA VICINA". Journal of Experimental Biology 192, nr 1 (1.07.1994): 207–24. http://dx.doi.org/10.1242/jeb.192.1.207.
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Of the 17 muscles responsible for flight control in flies, only the first basalar muscle (b1) is known to fire an action potential each and every wing beat at a precise phase of the wing-beat period. The phase of action potentials in the b1 is shifted during turns, implicating the b1 in the control of aerodynamic yaw torque. We used the work loop technique to quantify the effects of phase modulation on the mechanical output of the b1 of the blowfly Calliphora vicina. During cyclic length oscillations at 10 and 50 Hz, the magnitude of positive work output by the b1 was similar to that measured previously from other insect muscles. However, when tested at wing-beat frequency (150 Hz), the net work performed in each cycle was negative. The twitch kinetics of the b1 suggest that negative work output reflects intrinsic specializations of the b1 muscle. Our results suggest that, in addition to a possible role as a passive elastic element, the phase-sensitivity of its mechanical properties may endow the b1 with the capacity to modulate wing-beat kinematics during turning maneuvers.
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Bartošová, Nina. "From Biography to a Net of Interpretations: The Plurality of Approaches to Vladimír Karfík’s work". Muzeológia a kultúrne dedičstvo 11, nr 1 (marzec 2023): 37–51. http://dx.doi.org/10.46284/mkd.2023.11.1.3.
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The aim of this study is to justify a partial shift from the biographical approach in the author’s ongoing research into the work of architect Vladimír Karfík’s, especially if that research is directed towards raising present-day appreciation of his output. The inspiration comes from pragmatic aesthetics, as understood by philosopher Richard Shusterman, which considers the possibility of appreciating a work of art and architecture without the premise of one universal truth. The “net of interpretations” metaphor suggests that different interpretative lines can be perceived as equivalent in all their diversity, and there is no single “true” image of the work that lies underneath. The proposition of the study is argued both on a theoretical level and through the analysis of existing publications devoted to Karfík’s work and personality.
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Stevens, E. D., i D. A. Syme. "Effect of stimulus duty cycle and cycle frequency on power output during fatigue in rat diaphragm muscle doing oscillatory work". Canadian Journal of Physiology and Pharmacology 71, nr 12 (1.12.1993): 910–16. http://dx.doi.org/10.1139/y93-138.
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Isolated rat diaphragm muscle was stimulated repetitively to induce fatigue, and the work done during each contraction was measured. Work per cycle was calculated by measuring force as the activated muscle was subjected to sinusoidal length changes (from 97 to 103% of L0, where L0 is rest length). Work was calculated from the loop formed when force was plotted against length. Work done was positive when the muscle was shortening and was negative when it was lengthening; net work was the difference. Work output was varied by changing the stimulus duty cycle (4, 8, or 16% of the total cycle duration) and cycle frequency (1, 2, or 4 Hz). The rate and extent of the decrease in power was influenced much more by changes in cycle frequency than by changes in duty cycle. Duty cycle and cycle frequency combinations that resulted in greater power in the prefatigue trials were associated with a more rapid rate of fatigue. However, net positive power at the end of the 15-min fatigue period was greater under these same conditions (i.e., high duty cycle and high cycle frequency). Fatigue in working diaphragm muscle depends more on cycle frequency than on duty cycle.Key words: skeletal muscle, muscle power, respiratory muscle, muscle lengthening.
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Yang, Xiaowei, Yanjun Liu, Yun Chen i Li Zhang. "Optimization Design of the Organic Rankine Cycle for an Ocean Thermal Energy Conversion System". Energies 15, nr 18 (13.09.2022): 6683. http://dx.doi.org/10.3390/en15186683.
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This study selects five parameters as decision variables for the optimization design of an ocean thermal energy conversion system, including the evaporating temperature, the condensing temperature, the pinch-point temperature difference between the evaporator and condenser, and the working fluid flow rate. The optimization goal is to maximize the net output power per unit area and the exergy efficiency. The final scheme is comprehensively screened out from the Pareto solution set through some evaluation indexes. Finally, this study also analyzes the effects of four decision variables on the optimization objectives and the evaluation indexes. This study finds that evaporating temperature and condensing temperature have similar effects on the two objective functions. However, the pinch-point temperature difference has different effects on them. The back work ratio is obviously affected by the condensing temperature. A small pinch-point temperature difference is beneficial and improves the performance of an ocean thermal energy conversion system. The effects of evaporating temperature and condensing temperature on the investment cost per unit net output power are roughly similar to those on the net output power per unit heat exchange area. However, the effects of the pinch-point temperature difference on the two performance aspects are inconsistent.
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Kezrane, Cheikh, Sadam Houcine Habib, Youcef Abdellah Ayoub Laouid, Yahia Lasbet i Apostolos Pesyridis. "Evaluating the thermal efficiency and net power output of ORC for three wet fluids". Journal of Engineering and Exact Sciences 9, nr 5 (16.06.2023): 15982–01. http://dx.doi.org/10.18540/jcecvl9iss5pp15982-01e.
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Low-grade heat can be successfully recovered from waste energy sources for power production by an organic Rankine cycle (ORC). In this work, reheat ORC has been studied with three different wet organic fluids. The performance of R1270, R152a and Cyclopropane has been modelled in an ORC operated by a source of heat of 413.15K. The reheat ORC model contains economizer, evaporator, superheater, reheater, two turbine, pump and condensers. With variable turbine inlet temperature and reheat pressure, the net power output and thermal efficiency have been estimated. The results show that there exists an optimum temperature at the turbine inlet maximizing . The increase of reheat pressure gives only a marginal growth in the cycle efficiency, but it rises the with about 16.88 %, 16.26 % and 13.23 % for R1270, R152a and cyclopropane respectively.
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Wang, Feng, Jin Hai Wang i Chun Hua Wei. "Design on Interferometric Sensor Demodulation System of OMAP-Based Asymmetrical 3x3 Coupler Output". Advanced Materials Research 468-471 (luty 2012): 911–15. http://dx.doi.org/10.4028/www.scientific.net/amr.468-471.911.
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Based on the asymmetry characteristic of 33 coupler output signal, the improved demodulation arithmetic of 3x3 coupler was studied and deduced. To satisfy the requirement of fiber-optic sensor for real time, high accuracy and net work processing, a design method for embedded signal processing based on dual-core microprocessor OMAP is provided. The results of the experiments show that the system can meet the requirements of processing accuracy and real-time property and it has very high practical value.
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JOHNSON, TIMOTHY P., i IAN A. JOHNSTON. "POWER OUTPUT OF FISH MUSCLE FIBRES PERFORMING OSCILLATORY WORK: EFFECTS OF ACUTE AND SEASONAL TEMPERATURE CHANGE". Journal of Experimental Biology 157, nr 1 (1.05.1991): 409–23. http://dx.doi.org/10.1242/jeb.157.1.409.
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Fast muscle fibres were isolated from the abdominal myotomes of the shorthorned sculpin Myoxocephalus scorpius L. Sinusoidal length changes were imposed about resting muscle length and fibres were stimulated at a selected phase during the strain cycle. The work output per cycle was calculated from the area of the resulting force-position loops. The strain amplitude required for maximum work per cycle had a distinct optimum at ±5 % of resting length, which was independent of temperature. Maximum positive work loops were obtained by retarding the stimulus relative to the start of the length-change cycle by 30° (full cycle=360°). The maximum negative work output was obtained with a 210° stimulus phase shift. At intermediate stimulus phase shifts, work loops became complex with both positive (anticlockwise) and negative (clockwise) components. The number and timing of stimuli were adjusted, at constant strain amplitude (±5% of resting muscle length), to optimize net positive work output over a range of cycle frequencies. The cycle frequency required for maximum power output (work per cycle times cycle frequency) increased from around 5–7 Hz at 4°C to 9–13 Hz at 15°C. The maximum tension generated per cycle at 15°C was around two times higher at all cycle frequencies in summer-relative to winter-acclimatized fish. Fast muscle fibres from summer fish produced consistently higher tensions at 4°C, but the differences were only significant at 15 Hz. Acclimatization also modified the relationship between peak length and peak force at 4°C and 15°C. The maximum power output of muscle fibres showed little seasonal variation at 4°C and was in the range 20–25 W kg−1. In contrast, at 15°C, maximum muscle power output increased from 9 W kg−1 in the winter- to 30 W kg−1 in the summeracclimatized fish
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Jing, Xing Peng. "Reservoir Pressure of Coal-Bed Methane Prediction Research Based on Analysis Method by Neural Net-Work". Advanced Materials Research 756-759 (wrzesień 2013): 4758–62. http://dx.doi.org/10.4028/www.scientific.net/amr.756-759.4758.
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In Order to Achieve Accurate Quantitative Results of Parameters for Reservoir Pressure of Coal-Bed Methane, Neural Network Prediction Analytic Method is Adopted to Predict the Reservoir Pressure of Coal-Bed Methane. the Main Controlling Factors such as Conformation Stress, Buried Depth, in-Situ Stress and Permeability are Investigated. Mathematical Models of Neural Network of Reservoir Pressure of Coal-Bed Methane of Mathematical Analysis and System Architecture are Established; Taking the Qinshui Basin Coal Seam as Example to Forecast and use Reservoir Pressure of Coal-Bed Methane. Projections Show that: the use of Neural Network Prediction of Reservoir Pressure of Coal-Bed Methane is Feasible; Neural Network Method Makes up a Mathematical Point of Linear and Regularity in Order to Solve the Non-Linear Complex Relationship between the Input and Output Parameter Variables.
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Mansbridge, R. J., J. A. Metcalf, J. D. Oldham, J. S. Blake i J. R. Newbold. "The response of net milk protein output to metabolisable protein supply in dairy cows". Proceedings of the British Society of Animal Science 1999 (1999): 19. http://dx.doi.org/10.1017/s1752756200001745.
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The UK Metabolisable Protein (MP) system (AFRC, 1993) assumes that MP intake is converted to milk net protein with an efficiency of 0.68 and that MP for maintenance is 2.30*liveweight0.75. Previous work has indicated that the efficiency of MP use for milk production may be too high or that the amount of MP required for maintenance may be too low (Newbold et al, 1994). This experiment was designed to investigate the relationship between MP supply and net protein output in diets of differing MP to Metabolisable Energy (ME) ratios.Four‘cornerstone’ diets based on grass and maize silage (0.33:0.67 dry matter basis), were formulated to meet ME requirements and either 0.25 above or below MP requirements for either 46 or 24 kg milk/d. A total of 72 multiparous Holstein cows, on average 46 days post calving at the start of the study, were grouped into blocks of 4 cows on the basis of milk energy output in the covariance period. ME and MP requirements for each block of cows were calculated from milk energy and milk protein yield in the covariance period.
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Moon, T. W., J. D. Altringham i I. A. Johnston. "Energetics and power output of isolated fish fast muscle fibres performing oscillatory work". Journal of Experimental Biology 158, nr 1 (1.07.1991): 261–73. http://dx.doi.org/10.1242/jeb.158.1.261.
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Fast myotomal muscle fibres were isolated from the cod (Gadus morhua L.) and the energy cost of contraction was measured under conditions simulating swimming. Fibre bundles were subjected to sinusoidal cycles of shortening and lengthening about their in situ fibre length, and stimulated at selected phases in each cycle. The preparations were poisoned with iodoacetic acid and bubbled with nitrogen to block the synthesis of ATP. After an initial rapid decline over the first 10 cycles, force and net work remained steady in some cases for up to 64 oscillatory length cycles, but more commonly declined slowly after about 30 cycles. The total mechanical work performed increased largely in proportion to the number of work cycles. At the end of each experiment fibres were frozen in isopentane cooled in liquid nitrogen and metabolite concentrations determined by high performance liquid chromatography (HPLC) and enzymatic analysis. Concentrations of adenylates did not differ significantly from control values, although a significant increase in IMP concentrations at 64 cycles accounted for the maintenance of relatively high energy charge values. Creatine (C) concentrations increased and creatine phosphate (CP) concentrations decreased, implying a tight coupling of the ATP/ADP reaction to the CP/C reaction. Muscle economy was calculated as the positive work performed during a work cycle divided by the total chemical energy expended. These values (approx. 7 mJ mumol-1) were found to be independent of the number of work cycles performed, although a trend to increase was observed. Muscle efficiency values, calculated assuming a Gibb's force free energy change for CP splitting in vivo of 55 kJ mol-1, were in the range 12–23%.
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Agnew, B., A. Anderson i T. H. Frost. "Cycle Optimization and Comparison of Ideal Thermal Cycles for Maximum Specific Output". International Journal of Mechanical Engineering Education 22, nr 3 (lipiec 1994): 177–90. http://dx.doi.org/10.1177/030641909402200303.
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The thermal efficiencies of several thermodynamic cycles are evaluated and compared for the condition of maximum specific net work output for a specified cycle temperature ratio. It is shown at this condition that the efficiencies of all of the cycles are very similar and that an objective selection of a cycle for a particular application cannot be made on the basis of thermal efficiency alone. The different cycles are then compared with respect to other important design parameters for the optimized condition and comments are made with regard to power generation and the associated controlling rate processes.
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Harwood, CL, IS Young i JD Altringham. "Influence of cycle frequency, muscle strain and muscle length on work and power production of rainbow trout (Oncorhynchus mykiss) ventricular muscle". Journal of Experimental Biology 201, nr 19 (1.10.1998): 2723–33. http://dx.doi.org/10.1242/jeb.201.19.2723.
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This study investigates the effects of cycle frequency, strain and length on work and power output of isolated rainbow trout (Oncorhynchus mykiss) ventricular preparations using the work loop technique. These effects are discussed in the context of the whole heart using analogies with heart rate, stroke volume and end-diastolic volume. Power output was dependent on cycle frequency, increasing threefold beween 0.3 and 1.1 Hz. The frequency for maximum power output was approximately 1.1 Hz, corresponding to the frequency for maximum power in perfused heart experiments. The length for maximum work production (Lopt) was found to be the same as the length for maximum isometric force production (Lmax). The decline in net work at lengths greater than Lopt/Lmax was attributed to an increase in passive work (the work done on an unstimulated muscle) or to hysteresis and to a large increase in lengthening work. The strain yielding maximum work decreased with increasing frequency. This is discussed in the context of the decline in stroke volume observed at increased heart rates in vivo. Muscle strain in intact hearts paced at 0.3 Hz was +/-11.9 % (23.8 % peak to peak), a value similar to the optimum strain at 0.3 Hz in vitro (+/-12 %).