132,344 research outputs found
The Spatial Equalizer
No full textComplete reproduction of spatial impression of sound is what human beings have dreamed to have. It is interesting, however, 3-D sound cannot be scientifically well defined. The sensation of 3-D sound can vary with listeners and reproduction environments. To tackle this problem, an interface that can implement the desired 3-D sound in space and time by the listener is proposed. The interface, called 'Spatial Equalizer', controls the sound field using a point or multiple points related with the location of the virtual sound source. The user controls the points and listens to the sound until it is satisfactory
Overview of noise policies in Korea
No full textThe Noise and Vibration Control Act covers the majority of noise related issues in Korea. This paper introduces the environmental noise standards, the industrial noise and vibration emission permissible standard, the construction noise standard, the railroad noise limit, the road traffic noise limit, the aircraft noise limit, and the permissible standard of motor vehicle noise that are described in the act
High Acoustic Pressure Near Resonance in an Oscillating Tube
No full textWhen a piston located at one end of a closed pipe excites an interior medium at a resonance frequency, a shock wave is often generated and propagates periodically back and forth in the pipe. This nonlinear phenomenon has been extensively investigated in many works([1]~[3]) theoretically and experimentally. Recent studies([4], [5]) performed at MacroSonix Corp. have focused attention on inducing high acoustic pressure without shock formation in an oscillating axisymmetric tube. The results revealed that the waveform of acoustic pressure is strongly related to the shape of the tube. However, while acoustic losses were considered by allowing viscous damping, an isentropic process was also assumed at all positions to simplify the governing equation. This contrary proposition may yield undesirable results for a viscous gas because the viscous damping strongly affects the motion of the gas near a resonance frequency. Therefore, it is necessary to study the motion of a fluid for obtaining more meaningful results at a resonance frequency. In this paper, we have studied the fundamentals of nonlinear acoustic phenomena such as shocks and macrosonic waves caused by the oscillation of an entire tube. Firstly, we derived a general governing equation including viscous effects. In contrast to the previous studies, an isentropic process was assumed only at both ends of the tube. A numerical code was developed to solve the nonlinear governing equation by using a finite difference scheme. In order to see the damping effects on the shock formation in the cylindrical and conical tubes, numerical simulations were performed with changing the magnitude of viscosity. In addition, we investigated a pressurizing performance for various conical tubes with the same volume and length. Experiments were accomplished for the cylindrical and conical tubes, too
Effects of Tube Shape on Nonlinear Resonant Oscillations of Interior Gas
No full textAn investigation is conducted to get an outline of designing the tube shape for a sonic compressor with high efficiency. When a closed tube oscillates with its resonant frequency, the interior acoustic properties such as density, velocity, and pressure undergo very large perturbation with nonlinear patterns. In order to analyze the nonlinear acoustic phenomena such as harmonic generation, shock formation, and resonant frequency shift, two-dimensional axisymmetric governing equations are derived and solved numerically. Numerical simulations are performed to investigate the effect of the tube shape that gives us maximum possible pressure. Results show that the resonant frequency and patterns of pressure waves strongly depend on not only the tube shape but also the amplitude of driving acceleration. The degree of nonlinearity of pressure signals is measured by the newly defined nonlinear energy ratio of the signals. The nonlinear energy ratio well describes not only the energy transfer to higher harmonics but also the compression efficiency, so that it can be a good measure for designing tube shape
Hadron production from e⁺e⁻ collisions around the Z⁰ mass
No full textThesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1990.Includes bibliographical references (p. 35-37).by Yuan-Hann Chang.Ph.D
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
Creating a counter-space: Tahrir Square as a platform for linguistic creativity and political dissent
No full textBook synopsis: The Politics of Language and Creativity in a Globalised World, edited by David Hann and Theresa Lillis, explores the many ways in which linguistic creativity is a resource for political activity. It examines the politics surrounding the production, ownership and evaluation of different kinds of creative activity in contemporary society. The book focuses on the explosion of creative ‘production’ across texts, modes, media and technologies in contemporary society and examines how this historic shift from reception to production is raising questions about what gets valued as ‘creative’ and why.
The book uses authentic examples from the spectrum of creative text-making practices - including adverts, social media, hip hop and political speeches – to illustrate the nature, value and significance of creative activity for everyday life. The book includes a range of analytic approaches that are essential for examining contemporary creative practice, drawing from stylistics, social semiotics, multimodality, aesthetics, discourse studies and rhetoric
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