Random and systematic measurement errors in acoustic impedance as determined by the transmission line method

The effect of random and systematic errors associated with the measurement of normal incidence acoustic impedance in a zero-mean-flow environment was investigated by the transmission line method. The influence of random measurement errors in the reflection coefficients and pressure minima positions was investigated by computing fractional standard deviations of the normalized impedance. Both the standard techniques of random process theory and a simplified technique were used. Over a wavelength range of 68 to 10 cm random measurement errors in the reflection coefficients and pressure minima positions could be described adequately by normal probability distributions with standard deviations of 0.001 and 0.0098 cm, respectively. An error propagation technique based on the observed concentration of the probability density functions was found to give essentially the same results but with a computation time of about 1 percent of that required for the standard technique. The results suggest that careful experimental design reduces the effect of random measurement errors to insignificant levels for moderate ranges of test specimen impedance component magnitudes. Most of the observed random scatter can be attributed to lack of control by the mounting arrangement over mechanical boundary conditions of the test sample

An experimental study of the effects of water repellant treatment on the acoustic properties of Kevlar

The treatment consisted of immersing samples of Kevlar in a solution of distilled water and Zepel. The samples were then drained, dried in a circulating over, and cured. Flow resistance tests showed approximately one percent decrease in flow resistance of the samples. Also there was a density increase of about three percent. It was found that the treatment caused a change in the texture of the samples. There were significant changes in the acoustic properties of the treated Kevlar over the frequency range 0.5 to 3.5 kHz. In general it was found that the propagation constant and characteristic impedance increased with increasing frequency. The real and imaginary components of the propagation constant for the treated Kevlar exhibited a decrease of 8 to 12 percent relative to that for the untreated Kevlar at the higher frequencies. The magnitude of the reactance component of the characteristic impedance decreased by about 40 percent at the higher frequencies

NONCONSTANT PRICE EXPECTATIONS AND ACREAGE RESPONSE: THE CASE OF COTTON PRODUCTION IN GEORGIA

An adaptive regression model is used to examine the relative importance of cash and government support prices in determining cotton production over time. The results show that the cash price is more important as a source of price information for cotton producers than the government program price. The cash price was shown to have a greater influence on acreage response in every year, including periods thought to be dominated by government commodity programs.Adaptive regression, Cotton acreage response, Price expectations, Crop Production/Industries,

Student Perceptions of Simulation Games and Training Software on Improving Course Learning Objectives and Career Preparedness

Online simulation and training games were used in two undergraduate courses in agribusiness to help improve student understanding and course objectives. Students responded positively to the teaching activities. The activities also extended the out of class learning environment.student outcomes, technology in the classroom, simulation and teaching, Teaching/Communication/Extension/Profession, A20, A22,

Radiation from a Charge Uniformly Accelerated for All Time

A recent paper of Singal [Gen. Rel. Grav. 27 (1995), 953-967] argues that a uniformly accelerated particle does not radiate, in contradiction to the consensus of the research literature over the past 30 years. This note points out some questionable aspects of Singal's argument and shows how similar calculations can lead to the opposite conclusion.Comment: LaTeX, 9 pages, to appear in General Relativity and Gravitatio

Developing cross disciplinary skills through an undergraduate research project

Undergraduate students can benefit from a research experience with a faculty mentor. Students perceived the research project and faculty mentorship as more beneficial than directed coursework. Mentoring is key to enhancing undergraduate research experiences, but the impact on time should be considered. Linkages between coursework and application should also be considered.student mentor, undergraduate research, Teaching/Communication/Extension/Profession, Q1,

A particle swarm model for tracking multiple peaks in a dynamic environment using speciation

A particle swarm optimisation model for tracking multiple peaks in a continuously varying dynamic environment is described. To achieve this, a form of speciation allowing development of parallel subpopulations is used. The model employs a mechanism to encourage simultaneous tracking of multiple peaks by preventing overcrowding at peaks. Possible metrics for evaluating the performance of algorithms in dynamic, multimodal environments are put forward. Results are appraised in terms of the proposed metrics, showing that the technique is capable of tracking multiple peaks and that its performance is enhanced by preventing overcrowding. Directions for further research suggested by these results are put forward

A common graphical form

We present the Common Graphical Form, a low level, abstract machine independent structure which provides a basis for implementing graph reduction on distributed processors. A key feature of the structure is its ability to model disparate abstract machines in a uniform manner; this enables us to experiment with different abstract machines without having to recode major parts of the run-time system for each additional machine. Because we are dealing with a uniform data structure it is possible to build a suite of performance measurement tools to examine interprocessor data-flow and to apply these tools to different abstract machines in order to make relative comparisons between them at run-time. As a bonus to our design brief we exploit the unifying characteristics of the Common Graphical Form by using it as an intermediate language at compile-time

Multi-objective techniques in genetic programming for evolving classifier systems

The application of multi-objective evolutionary computation techniques to the genetic programming of classifiers has the potential to both improve the accuracy and decrease the training time of the classifiers.The performance of two such algorithms are investigated on the even 6-parity problem and the Wisconsin Breast Cancer, Iris and Wine data sets from the UCI repository. The first method explores the addition of an explicit size objective as a parsimony enforcement technique. The second represents a program¿s classification accuracy on each class as a separate objective. Both techniques give a lower error rate with less computational cost than was achieved using a standard GP with the same parameters

Growing older in secure mental health care: the user experience

Background: The proportion of older adults using secure forensic psychiatric services is rising. Research is needed to examine the experience of older service users and evidence how adult services can adapt to meet their needs. Aim: To explore user experiences of being an older adult in secure forensic services. Methods: Thematic analysis of interviews and observations of weekly routines conducted with fifteen service users aged 50 and over residing in a low and medium secure NHS unit in England. Results: User experiences of ageing and age-related needs are reported using five themes: age-related identities; ward environments; participation in activities; management of physical health; and ageing futures. Older adults living with people their own age reported more social integration than those on wards dominated by younger adults. Most wished to self-manage their physical health needs with the support of primary care staff. Older adults were reluctant to identify as “old” or “vulnerable”. Some older adults downplayed their changing care needs. Conclusions: Placement of older people in adult secure services requires awareness of the age balance of the ward. A culture of inclusivity, sensitivity and respect for older persons’ agency is key to collaboratively meeting additional care needs and discharge planning