6,704 research outputs found
Audiomobiles, Sculptures and Conundrums
No full textRoberto Gerhard was a pioneer of electronic music in England creating a number of substantial concert, theatre and radio works from as early as 1954. Gerhard’s electronic music is one of the richest repositories for understanding the development of the composer’s late compositional technique. Apart from the Symphony no.3, ‘Collages’, none of Gerhard’s electronic music is published. This paper will discuss aspects of Gerhard’s electronic music, focusing on Audiomobiles (1958-59) and Sculptures (1963)
Roberto Gerhard’s Sound Compositions: A Historical-Philological Perspective. Archive, Process, Intent and reenactment
No full textThis research advances the current state of knowledge in the field of early tape music both empirically and methodologically. The purpose of this study is to evaluate the impact that the electronic medium exerted in the musical thinking of Roberto Gerhard, one of the most outspoken, prolific and influential composers in the Spanish diaspora whose musical legacy, for the most part unknown, is a major landmark in the early history of electroacoustic music. Gerhard’s personal tape collection, one of the largest historical archives of its kind reported in the literature, is exceptional for both its antiquity (50+-year-old tapes) and its abundance of production materials. Through the digitisation and analysis of the composer’s tape collection this research argues that the empirical study of audio documents sets out a basis for a broader understanding of textual processes. More specifically, the research demonstrates that the reconstruction of works based on magnetic tape sketches is a powerful method to advance the understanding of early tape music. This research also examines Gerhard’s sound compositions in relation to the post-war context in which they were composed. Finally, this research presents performance documentation that proposes an approach to the electroacoustic music repertoire in which creativity is not at odds with rigor and critical discernment demonstrating that archival study can be closely aligned to the concept of re-enactment
AN IMPROVED MORIN EQUATION TO ESTIMATE THE PERFORMANCE OF UNDERSHOT AND BREASTSHOT WATER WHEELS
No full text- Undershot and breastshot water wheels are low head hydropower converters
- A modified Morin equation was developed to estimate their performance
- The new equation estimates the efficiency with average discrepancy on experimental tests of 11%
- The new equation can be used in practical applications for an easy estimation of the power outpu
CFD simulations to optimize the blade design of water wheels
No full textAt low head sites and at low discharges, water wheels can be considered among the most convenient hydropower converters to install. The aim of this work is to improve the performance of an existing breastshot water wheel by changing the blade shape using computational fluid dynamic (CFD) simulations. Three optimal profiles are investigated: the profile of the existing blades, a circular profile and an elliptical profile. The results are validated by performing experimental tests on the wheel with the existing profile. The numerical results show that the efficiency of breastshot wheels is affected by the blade profile. The average increase in efficiency using the new circular profile is about 4 % with respect to the profile of the existing blades
Influenza di due diverse metodiche di prelievo di sangue sui livelli ematici di glucosio nel bovino
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Gravity water wheels as a micro hydropower energy source: A review based on historic data, design methods, efficiencies and modern optimizations
No full textNowadays, due to the need for clean energy and sustainable electricity production, hydropower plays a central role in satisfying the energy demand. Particularly, use of low head micro hydropower plants is spreading worldwide, due to their low payback periods and good environmental sustainability. Gravity water wheels are micro hydropower converters typically used in sites with heads less than 6 m and discharges of a few cubic meters per second. Although water wheels were scientifically investigated as far back as the eighteenth century, they were largely ignored throughout the twentieth century, and only in the last two decades has there been a renewed interest in their use among the scientific community.
In this paper a review on gravity water wheels is presented, distinguishing between undershot, breastshot and overshot water wheels. Water wheels technology is discussed focusing on geometric and hydraulic design; data and engineering equations found in historic books of the nineteenth century are also presented. Water wheels' performance is described examining experimental results, and modern theoretical models for efficiency estimation are presented. Finally, results achieved through experiments and numerical simulations were discussed with the aim of optimizing the performance of gravity water wheels. The results showed that maximum efficiency of overshot and undershot water wheels was around 85%, while that of breastshot water wheels ranged from 75% to 80%, depending on inflow configuration. Maximum efficiency of modern water wheels can be maintained at such high values over a wider range of flow rates and hydraulic conditions with respect to older installations. Hence well designed water wheels can be considered as efficient and cost-effective micro hydropower converters
Output power and power losses estimation for an overshot water wheel
No full textThanks to a new sensibility to renewable energy and to local and smart electricity production, traditional water wheels are regarded again as a clean and accessible way for pico-micro hydro electricity generation, especially in presence of very low heads and small flowrates. In particular, among the different kinds of water wheels, the overshot ones exploit the lowest flowrates with the highest efficiency (efficiency up to 85-90%). Therefore, in order to determine the performance characteristics and to estimate the power losses and the output power for overshot water wheels, theoretical and experimental analyses are here developed. By a numerical optimization process, the power losses and the mechanical output power are theoretically quantified. A critical angular velocity is also identified (about 65% of the runaway speed). When the wheel rotation speed approaches the critical velocity, volumetric losses at the top of the wheel begin to increase linearly with the rotational velocity, while the other power losses start to decrease, due to the lower amount of water available to the whee
CFD simulations to optimize the design of water wheels: study case of an existing breastshot water wheel
No full textIn low head sites and at low discharges, water wheels can be considered among the most convenient hydropower converters to install. The scope of this work is to improve the performance of an existing breastshot water wheel changing the blades shape, using Computational Fluid Dynamic (CFD) simulations. Three optimal profiles are investigated: the profile of the existing blades, a circular profile and an elliptical profile. The results are validated performing experimental tests on the wheel with the existing profile. The numerical results show that the efficiency of breastshot wheels is affected by the blades profile. The average increase in efficiency using the new circular profile is about 4% with respect to the profile of the existing blade
Performance characteristics, power losses and mechanical power estimation for a breastshot water wheel
No full textBreastshot water wheels were in widespread use in the Nineteenth and Early Twentieth century for the production of energy; although they represent an economic, efficient and sustainable technology, only a small amount of research has been paid to water wheels nowadays, in particular to the breastshot ones. In this work a theoretical approach is adopted to estimate the different kinds of power losses occurring inside a breastshot water wheel, in order to predict its mechanical output power. The theoretical results are then validated with experimental results on a physical steel model. The characteristics experimental curves of the wheel are also illustrated, reporting the wheel efficiency and output power versus the flowrate, stream and wheel velocity. The average estimated error between the experimental and the estimated theoretical output power is 9%, which is much lower than that calculated using some past formulations found in literature. The theoretical results show that the big power losses are the dissipation of the stream kinetic energy against the blades and the hydraulic losses in the headrace, after the passage through the sluice gate; therefore, a better design of the inlet and blades geometry may improve the efficiency of the whee
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