3,351 research outputs found
The radiating part of circular sources
An analysis is developed linking the form of the sound field from a circular
source to the radial structure of the source, without recourse to far-field or
other approximations. It is found that the information radiated into the field
is limited, with the limit fixed by the wavenumber of source multiplied by the
source radius (Helmholtz number). The acoustic field is found in terms of the
elementary fields generated by a set of line sources whose form is given by
Chebyshev polynomials of the second kind, and whose amplitude is found to be
given by weighted integrals of the radial source term. The analysis is
developed for tonal sources, such as rotors, and, for Helmholtz number less
than two, for random disk sources. In this case, the analysis yields the
cross-spectrum between two points in the acoustic field. The analysis is
applied to the problems of tonal radiation, random source radiation as a model
problem for jet noise, and to noise cancellation, as in active control of noise
from rotors. It is found that the approach gives an accurate model for the
radiation problem and explicitly identifies those parts of a source which
radiate.Comment: Submitted to Journal of the Acoustical Society of Americ
DETERMINANTS OF DEMAND FOR BEEF: THE IMPACT OF FAT TRIMMING
Beef products, lower fat, consumer demand, demand elasticities, Demand and Price Analysis,
Adolescent D-amphetamine treatment in a rodent model of attention deficit/hyperactivity disorder: impact on cocaine abuse vulnerability in adulthood
RATIONALE: Stimulant medications for attention-deficit/hyperactivity disorder (ADHD) in adolescents remain controversial with respect to later development of cocaine abuse. Past research demonstrated that adolescent methylphenidate treatment increased several aspects of cocaine self-administration during adulthood using the spontaneously hypertensive rat (SHR) model of ADHD. Presently, we determined effects of the alternate stimulant medication, d-amphetamine, on cocaine self-administration.
OBJECTIVES: We tested the hypothesis that adolescent d-amphetamine would not increase cocaine self-administration in adult SHR, given that d-amphetamine has a different mechanism of action than methylphenidate.
METHODS: A pharmacologically relevant dose of d-amphetamine (0.5 mg/kg) or vehicle was administered throughout adolescence to SHR and two control strains, Wistar-Kyoto (WKY) and Wistar (WIS). Three aspects of cocaine abuse vulnerability were assessed in adulthood after discontinuing adolescent treatments: acquisition rate and dose-related responding under fixed (FR) and progressive (PR) ratio schedules.
RESULTS: Adult SHR acquired cocaine self-administration faster and self-administered more cocaine across multiple doses compared to WKY and WIS under FR and PR schedules, indicating that SHR is a reliable animal model of comorbid ADHD and cocaine abuse. Relative to vehicle, SHR and WIS with adolescent d-amphetamine treatment self-administered less cocaine upon reaching acquisition criteria, and WIS additionally acquired cocaine self-administration more slowly and had downward shifts in FR and PR cocaine dose-response curves. WKY with adolescent d-amphetamine treatment acquired cocaine self-administration more quickly relative to vehicle.
CONCLUSIONS: In contrast to methylphenidate, adolescent d-amphetamine did not augment cocaine self-administration in SHR. Adolescent d-amphetamine treatment actually protected against cocaine abuse vulnerability in adult SHR and WIS.National Institutes of Health grant DA011716 and the Clara Mayo Memorial Fellowship at Boston University. (DA011716 - National Institutes of Health; Clara Mayo Memorial Fellowship at Boston University)https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5026317/Published versio
FACTORS INFLUENCING SOUTHERN DAIRY FARMERS' CHOICE OF MILK HANDLERS
Survey data of 2,538 dairy farmers located in 12 southern states were used to analyze the factors influencing farmers' choice of milk handlers. Results from a qualitative response model indicate that a combination of price and non-price factors contribute to dairy farmers' attitudes toward their milk handlers. Specifically, the decision to change milk handlers was significantly influenced by prices paid and deductions charged. However, non-price factors including field services, friendly personnel, and loyalty to a handler contributed to the longer term affiliation of dairy farmers with their milk handlers.Dairy farmers, Milk handlers, Market channels, Qualitative response, Marketing, Agribusiness,
Inversion of spinning sound fields
A method is presented for the reconstruction of rotating monopole source
distributions using acoustic pressures measured on a sideline parallel to the
source axis. The method requires no \textit{a priori} assumptions about the
source other than that its strength at the frequency of interest vary
sinusoidally in azimuth on the source disc so that the radiated acoustic field
is composed of a single circumferential mode. When multiple azimuthal modes are
present, the acoustic field can be decomposed into azimuthal modes and the
method applied to each mode in sequence.
The method proceeds in two stages, first finding an intermediate line source
derived from the source distribution and then inverting this line source to
find the radial variation of source strength. A far-field form of the radiation
integrals is derived, showing that the far field pressure is a band-limited
Fourier transform of the line source, establishing a limit on the quality of
source reconstruction which can be achieved using far-field measurements. The
method is applied to simulated data representing wind-tunnel testing of a
ducted rotor system (tip Mach number~0.74) and to control of noise from an
automotive cooling fan (tip Mach number~0.14), studies which have appeared in
the literature of source identification.Comment: Revised version of paper submitted to JASA; five more figures;
expanded content with more discussion of error behaviour and relation to
Nearfield Acoustical Holograph
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