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Maximum Power (maximum + power)
Terms modified by Maximum Power Selected AbstractsUndulatory fish swimming: from muscles to flowFISH AND FISHERIES, Issue 2 2006Ulrike K. Müller Abstract Undulatory swimming is employed by many fish for routine swimming and extended sprints. In this biomechanical review, we address two questions: (i) how the fish's axial muscles power swimming; and (ii) how the fish's body and fins generate thrust. Fish have adapted the morphology of their axial musculature for high power output and efficiency. All but the superficial muscle fibres are arranged along curved trajectories, and the myomeres form nested cones. Two conflicting performance goals shape the fibre trajectories of the axial muscles. Maximum power output requires that all fibres contract uniformly. In a bending fish, uniform contraction in a single myomere can be ensured by curved fibre trajectories. However, uniform strain is only desirable if all muscle fibres have the same contractile properties. The fish needs several muscle-fibre types that generate maximum power at different contraction speeds to ensure effective muscle power generation across a range of swimming speeds. Consequently, these different muscle-fibre types are better served by non-uniform contractions. High power output at a range of swimming speeds requires that muscle fibres with the same contractile properties contract uniformly. The ensuing helical fibre trajectories require cone-shaped myomeres to reduce wasteful internal deformation of the entire muscle when it contracts. It can be shown that the cone-shaped myomeres of fish can be explained by two design criteria: uniform contraction (uniform strain hypothesis) and minimal internal deformation (mechanical stability hypothesis). So far, only the latter hypothesis has found strong support. The contracting muscle causes the fish body to undulate. These body undulations interact with the surrounding water to generate thrust. The resulting flow behind the swimming fish forms vortex rings, whose arrangement reflects the fish's swimming performance. Anguilliform swimmers shed individual vortex rings during steady swimming. Carangiform swimmers shed a connected chain of vortex rings. The currently available sections through the total flow fields are often not an honest representation of the total momentum in the water , the wake of carangiform swimmers shows a net backward momentum without the fish accelerating , suggesting that our current picture of the generated flow is incomplete. To accelerate, undulatory swimmers decrease the angle of the vortex rings with the mean path of motion, which is consistent with an increased rate of backward momentum transfer. Carangiform swimmers also enlarge their vortex rings to accelerate and to swim at a higher speed, while eel, which are anguilliform swimmers, shed stronger vortex rings. [source] Studies of the micellar effect on photogalvanics: Solar energy conversion and storage,EDTA,safranine O,DSS systemINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 13 2010Prerna Gangotri Abstract The studies of the micellar effect on photogalvanics was done for solar energy conversion and storage in photogalvanic cell containing dioctyl sodium sulphosuccinate as anionic micellar species, EDTA as reductant and safranine O as photosensitizer. The photopotential and photocurrent generated were 800.0,mV and 65.0,µA respectively. The observed conversion efficiency was 0.2532 per cent, the fill factor was 0.38 and the maximum power of the cell was 52.0,µW whereas the power at power point of the photogalvanic cell was 26.34,µW. The rate of initial generation of current was 37.5,µA,min,1. The photogalvanic cell can be used for 80.0,minutes in the dark. The effects of different parameters on the electrical output of the photogalvanic cell were observed and a mechanism has also been proposed for the generation of photocurrent in the photogalvanic cell. Copyright © 2009 John Wiley & Sons, Ltd. [source] Efficient power analysis for an irreversible Carnot heat engineINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 7 2008Tamer Yilmaz Abstract In this paper, the finite-time thermodynamic optimization is carried out based on the efficient power criterion for an irreversible Carnot heat engine. The obtained results are compared with those obtained by using the maximum power (MP) and maximum power density (MPD) criteria. The optimal design parameters have been derived analytically, and the effect of the irreversibilities on the general and optimal performances is investigated. Maximizing the efficient power gives a compromise between power and efficiency. The results showed that the design parameter at the maximum efficient power (MEP) condition leads to more efficient engines than at the MP conditions and that the MEP criterion may have a significant power advantage with respect to the MPD criterion. Copyright © 2007 John Wiley & Sons, Ltd. [source] Fundamentals of exergy analysis, entropy generation minimization, and the generation of flow architectureINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 7 2002Adrian Bejan Abstract This paper outlines the fundamentals of the methods of exergy analysis and entropy generation minimization (or thermodynamic optimization,the minimization of exergy destruction). The paper begins with a review of the concept of irreversibility, entropy generation, or exergy destruction. Examples illustrate the accounting for exergy flows and accumulation in closed systems, open systems, heat transfer processes, and power and refrigeration plants. The proportionality between exergy destruction and entropy generation sends the designer in search of improved thermodynamic performance subject to finite-size constraints and specified environmental conditions. Examples are drawn from energy storage systems for sensible heat and latent heat, solar energy, and the generation of maximum power in a power plant model with finite heat transfer surface inventory. It is shown that the physical structure (geometric configuration, topology) of the system springs out of the process of global thermodynamic optimization subject to global constraints. This principle generates structure not only in engineering but also in physics and biology (constructal theory). Copyright © 2002 John Wiley & Sons, Ltd. [source] Functional Impact of Relative Versus Absolute Sarcopenia in Healthy Older WomenJOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 11 2007Marcos Estrada MD OBJECTIVES: To determine whether adjustment of muscle mass for height2 or for body mass represents a more-relevant predictor of physical performance. DESIGN: Cross-sectional study, using baseline data from a trial comparing upper- and lower-body training. SETTING: Women recruited from the community and gynecological practices in Connecticut. PARTICIPANTS: One hundred eighty-nine healthy older (aged 67.5 ± 4.8), active women receiving estrogen for osteoporosis over 2 years. MEASUREMENTS: Total and appendicular skeletal muscle (ASM) and fat mass (AFM) were determined using dual x-ray absorptiometry. Physical performance, muscle strength, and fitness measures were obtained at baseline. RESULTS: Adjusting ASM for height2 identifies lean women who are sarcopenic according to published standards yet fails to identify overweight and obese women whose ASM adjusted for body mass is low. ASM divided by body mass (ASM/body mass) is a stronger physical performance predictor, explaining 32.5%, 13.5%, 11.6%, 6.3%, and 6.8% of the variance in maximum time on treadmill, 6-minute walk, gait speed, 8-foot walk, and single leg stance, respectively, whereas ASM divided by height in m2 (ASM/height2) explained only 2.9%, 0.2%, 2.0%, 0.04%, and 0.1%. Multivariate modeling demonstrated considerable overlap in aspects of ASM/body mass and AFM/body mass associated with performance, with ASM/body mass dominant. In contrast, ASM/height2 is a much stronger predictor of leg press 1 repetition maximum and maximum power. CONCLUSION: The results suggest that relative sarcopenia with ASM adjusted for body mass is a better mobility predictor, with absolute sarcopenia a better indicator of isolated muscle group function in healthy postmenopausal women receiving estrogen replacement. [source] Functional anatomy and muscle moment arms of the thoracic limb of an elite sprinting athlete: the racing greyhound (Canis familiaris)JOURNAL OF ANATOMY, Issue 4 2008S. B. Williams Abstract We provide quantitative muscle,tendon architecture and geometry data for the racing greyhound thoracic limb. Muscle mass, belly length, fascicle lengths, pennation angles and moment arms were measured, as were tendon masses and lengths. Maximum isometric force and maximum power were estimated for muscles, and maximum stress and strain were estimated for tendons. Results are compared with other fast quadrupedal runners, and to previously published data in mixed-breed dogs. The implications of the functional adaptations of the greyhound thoracic limb for sprinting performance are discussed. The thoracic limb was found to benefit from a similar proportion of locomotor muscle mass to the pelvic limb, suggesting that it may be used to some extent in propulsion, or alternatively that stabilisation is very important in this animal. Extrinsic muscles, especially latissimus dorsi and pectoralis profundus, were predicted to be powerful and important for generating net positive work during accelerations. Proximal biarticular muscles show specialisation toward preventing collapse of the shoulder and elbow joints to enable strut-like limb function, or some form of dynamic control. Distal muscles did not appear specialised for elastic energy storage, a functional difference to pelvic limb muscles, and the equivalents in horse thoracic limbs. The greyhound thoracic limb appears to possess substantial differences from both that of more ,sub-maximal specialist' quadrupeds, and from the greyhound pelvic limb. [source] Clinical Experience with a Single Catheter for Mapping and Ablation of Pulmonary Vein OstiumJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 4 2009PAOLO DE FILIPPO M.D. Introduction: The aim of this single center study is to evaluate the safety and the efficacy of performing pulmonary vein isolation (PVI) using a single high-density mesh ablator (HDMA) catheter. Methods: A total of 17 consecutive patients with paroxysmal (10 patients) or persistent atrial fibrillation (7 patients) and no heart disease were enrolled. A single transseptal puncture was performed and the HDMA was placed at each PV ostium identified with anatomic and electrophysiological mapping. Pulsed radiofrequency (RF) energy was delivered at the targeted temperature of 58°C with maximum power of 80 watts. No other ablation system was utilized. The primary objective of the study was acute isolation of the targeted PV, and the secondary objective was clinical efficacy and safety of PVI with HDMA for atrial fibrillation (AF) prevention. Patients were followed at intervals of 1, 3, 6, and 12 months. Results: PVI was attempted with HDMA in 67/67 PVs. [Correction made after online publication October 27, 2008: PVs changed from 6/67 to 67/67] Acute success rate were: 100% (16/16) for left superior PV, 100% (16/16) for left inferior PV, 100% (17/17) for right superior PV, 100% (1/1) for left common trunk and 47% (8/17) for right inferior PV. Total procedure time was 200 ± 36 minutes (range 130,240 minutes) and total fluoroscopy time was 42 ± 18 minutes (range 23,75 minutes). During a mean follow-up of 11 ± 4 months, 64% of patients remained in sinus rhythm (8/10 paroxysmal AF and 3/7 for persistent AF). No complications occurred either acutely or at follow-up. Conclusions: PV isolation with HDMA is feasible and safe. The midterm efficacy in maintaining sinus rhythm is higher in paroxysmal than in persistent patients. [source] Cooled Needle Catheter Ablation Creates Deeper and Wider Lesions Than Irrigated Tip Catheter AblationJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 5 2005ARAVINDA THIAGALINGAM F.R.A.C.P. Objectives: To design and test a catheter that could create deeper ablation lesions. Background: Endocardial radiofrequency (RF) ablation is unable to reliably create transmural ventricular lesions. We designed an intramural needle ablation catheter with an internally cooled 1.1-mm diameter straight needle that could be advanced up to 14 mm into the myocardium. The prototype catheter was compared with an irrigated tip ablation catheter. Methods: Ablation lesions were created under general anesthesia in 14 male sheep (weight 44 ± 7.3 kg) with fluoroscopic guidance. Each of the catheters was used to create two ablation lesions at randomly allocated positions within the left ventricle. The irrigation rate, target temperature, and maximum power were: 20 mL/min, 85°C, 50 W for the intramural needle catheter and 20 mL/min, 50°C, 50 W for the irrigated tip catheter, respectively. All ablations were performed for 2 minutes. After the last ablation, blue tetrazolium (12.5 mg/kg) was infused intravenously. The heart was removed via a left thoracotomy after monitoring the sheep for one hour. Results: There was no evidence of cardiac tamponade in any sheep. The intramural needle catheter lesions were significantly wider (10.9 ± 2.8 mm vs 10.1 ± 2.4 mm, P = 0.01), deeper (9.6 ± 2.0 mm vs 7.0 ± 1.3 mm, P = 0.01), and more likely to be transmural (38% vs 0%, P = 0.03). Conclusions: Cooled intramural needle ablation creates lesions that are significantly deeper and wider than endocardial RF ablation using an irrigated tip catheter in sheep hearts. This technology may be useful in treating ventricular tachycardia resistant to conventional ablation techniques. [source] Influence of operating conditions on friction and temperature characteristics of a wet clutch engagementLUBRICATION SCIENCE, Issue 2 2000Mikael HolgersonArticle first published online: 9 MAR 200 Abstract To optimise the gear change in automatic transmissions, more knowledge is needed of the engagement behaviour of wet clutches. A factorial design investigation of the engagement of a wet clutch has been carried out. The friction and temperature characteristics have been studied. The experiments were carried out in an apparatus that can vary sliding velocity, drive torque, inertia, force rate, and lubricant flow. The results show how these parameters affect the response data: engagement time, developed energy, temperature rise, maximum torque, maximum power, static friction, dynamic friction, and initial friction. There are interaction effects between some of the input parameters, but they are relatively small. The friction coefficient varies over time but is independent of the input parameters, except for dynamic friction, which decreases with increasing sliding velocity, drive torque, and inertia. The temperature rise was found to be proportional to developed energy and both these were most affected by sliding velocity. The drive torque and force rate have the greatest effect on the engagement time. [source] Compatibility factor for the power output of a thermogeneratorPHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 6 2007W. Seifert Abstract The compatibility approach introduced by Snyder and Ursell enables the description of both thermoelectric generator (TEG) and Peltier cooler (TEC) within the framework of a unified 1D model. Both TEG's efficiency , and TEC's coefficient of performance (C.O.P.) can be formulated in terms of the reduced current density u, which has been introduced as a new, intensive state variable of a thermoelectric system. For , and C.O.P., integral expressions are formed from additive contributions of all length segments of a thermoelectric ele-ment, enabling exact calculation of these quantities even for arbitrarily graded elements. Maximization of these global performance parameters can thus be deduced to local maximization. Here the maximum power from a TEG with fixed length but variable heat supply is considered, which leads to the new concept of power-related compatibility and to the introduction of a new, different compatibility factor. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Long-term stability of dye-sensitised solar cellsPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 6 2001A. Hinsch Accelerated ageing tests on large numbers of nanocrystalline dye-sensitised solar cells (nc-DSC) show that, to first order, separation between the effects of the stresses of visible light soaking, UV illumination and thermal treatment on long-term stability is possible. The corresponding mechanisms are electrochemical, photochemical and purely chemical in nature. It was found that visible light soaking alone is not a dominant stress factor. A dramatic improvement in UV stability has been achieved by using MgI2 as additive to the electrolyte. Thermal stress appears to be one of the most critical factors determining the long-term stability of nc-DSC and is strongly related to the chemical composition of electrolyte solvents and additives. Encouraging stability results have been obtained for cells based on pure nitrile-based solvents: (1) A minor decrease in performance of initially 5.5% solar efficient cells has been found after 2000 h at 60°C without light soaking; (2) After 900 h ageing at 85°C, a decrease of 30% in maximum power has been observed; (3) After 3400 h of combined thermal stress and continuous light soaking (45°C, 1 sun equivalent) good stability with 15% decrease in maximum power can be demonstrated. It should be noted that such good thermal stability has not been reported previously for dye-sensitised solar cells so far. Copyright © 2001 John Wiley & Sons, Ltd. [source] Procedure for determining the uncertainty of photovoltaic module outdoor electrical performance,PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 2 2001K. Whitfield This paper sets forth an uncertainty estimation procedure for the measurement of photovoltaic (PV) electrical performance using natural sunlight and calibrated secondary reference cells. The actual test irradiance should be restricted to values between 800 and 1000,W/m2 in order to assume that maximum power varies linearly with irradiance. Only the uncertainty of maximum power at standard test conditions (STC), i.e., 1000,W/m2 plane-of-array irradiance and 25°C cell temperature, is developed in its entirety. The basic uncertainty analysis principles developed herein, however, can be applied to any electrical variable of interest (e.g., short-circuit current, open-circuit voltage and fill factor). Although the equations presented appear cumbersome, they are easily implemented into a computer spreadsheet. Examples of uncertainty analyses are also presented herein to make the concepts more concrete. Published in 2001 by John Wiley & Sons, Ltd. [source] | |||||||||||||