The accuracy of far-field noise obtained by the mathematical extrapolation of near-field noise data

Results are described of an analytical study of the accuracy and limitations of a technique that permits the mathematical extrapolation of near-field noise data to far-field conditions. The effects of the following variables on predictive accuracy of the far-field pressure were examined: (1) number of near-field microphones; (2) length of source distribution; (3) complexity of near-field and far-field distributions; (4) source-to-microphone distance; and (5) uncertainties in microphone data and imprecision in the location of the near-field microphones. It is shown that the most important parameters describing predictive accuracy are the number of microphones, the ratio of source length to acoustic wavelength, (L/wavelength), and the error in location of near-field microphones. If microphone measurement and location errors are not included, then far-field pressures can be accurately predicted up to L/wavelength values of 15 using approximately 50 microphones. For maximum microphone location errors of + or - 1 cm, only an accuracy of + or - 2-1/2 db can be attained with approximately 40 microphones for the highest L/wavelength of 10

Lifting classes for the fixed point theory of nn-valued maps

The theory of lifting classes and the Reidemeister number of single-valued maps of a finite polyhedron $X$ is extended to $n$-valued maps by replacing liftings to universal covering spaces by liftings with codomain an orbit configuration space, a structure recently introduced by Xicot\'encatl. The liftings of an $n$-valued map $f$ split into self-maps of the universal covering space of $X$ that we call lift-factors. An equivalence relation is defined on the lift-factors of $f$ and the number of equivalence classes is the Reidemeister number of $f$. The fixed point classes of $f$ are the projections of the fixed point sets of the lift-factors and are the same as those of Schirmer. An equivalence relation is defined on the fundamental group of $X$ such that the number of equivalence classes equals the Reidemeister number. We prove that if $X$ is a manifold of dimension at least three, then algebraically the orbit configuration space approach is the same as one utilizing the universal covering space. The Jiang subgroup is extended to $n$-valued maps as a subgroup of the group of covering transformations of the orbit configuration space and used to find conditions under which the Nielsen number of an $n$-valued map equals its Reidemeister number. If an $n$-valued map splits into $n$ single-valued maps, then its $n$-valued Reidemeister number is the sum of their Reidemeister numbers.Comment: near complete rewrite from previous versio

Two-Level Systems in Evaporated Amorphous Silicon

In $e$-beam evaporated amorphous silicon ($a$-Si), the densities of two-level systems (TLS), $n_{0}$ and $\overline{P}$, determined from specific heat $C$ and internal friction $Q^{-1}$ measurements, respectively, have been shown to vary by over three orders of magnitude. Here we show that $n_{0}$ and $\overline{P}$ are proportional to each other with a constant of proportionality that is consistent with the measurement time dependence proposed by Black and Halperin and does not require the introduction of additional anomalous TLS. However, $n_{0}$ and $\overline{P}$ depend strongly on the atomic density of the film ($n_{\rm Si}$) which depends on both film thickness and growth temperature suggesting that the $a$-Si structure is heterogeneous with nanovoids or other lower density regions forming in a dense amorphous network. A review of literature data shows that this atomic density dependence is not unique to $a$-Si. These findings suggest that TLS are not intrinsic to an amorphous network but require a heterogeneous structure to form

A Survey of AACSB Accredited Institutions and the Use of Work Experiences as part of the Business Curricula

This paper describes a survey of all American AACSB-accredited schools of business. The survey gathered information concerning work experiences (internships or cooperative education) required or offered in business curricula. Of the targeted schools, 133 responded. Results are presented regarding internship characteristics (prerequisites, student compensation, and course credit); assessment of students\u27 performance (grading. learning objectives, academic and work components of grade determination); and administrative issues (site visits, release time, and faculty compensation). Of the 133 respondents. 12 require work experience of all majors, 14 require it of some majors, 88 offer but do not require, and J 9 offer no work experience

Minimum entropy production principle from a dynamical fluctuation law

The minimum entropy production principle provides an approximative variational characterization of close-to-equilibrium stationary states, both for macroscopic systems and for stochastic models. Analyzing the fluctuations of the empirical distribution of occupation times for a class of Markov processes, we identify the entropy production as the large deviation rate function, up to leading order when expanding around a detailed balance dynamics. In that way, the minimum entropy production principle is recognized as a consequence of the structure of dynamical fluctuations, and its approximate character gets an explanation. We also discuss the subtlety emerging when applying the principle to systems whose degrees of freedom change sign under kinematical time-reversal.Comment: 17 page

The Effect of Teaching Methods on Examination Performance and Attitudes in an Introductory Financial Accounting Course

This article describes a study in which a group-Socratic teaching method and an interactive lecture style were compared for their effect on students\u27 examination performance in an introductory financial accounting course. The effect of teaching method on students\u27 attitudes toward the accounting profession and the course was also analyzed. An ANOVA design was used to test for differences between experimental and control groups of undergraduate students. The results provide no evidence that either method of instruction results in significantly higher scores on examinations; nor was there any statistically significant difference in attitudes toward the accounting profession or the course

Introducing sustainable development in engineering education: competences, pedagogy and curriculum

Introducing sustainable development (SD) in engineering education has been a key topic in many technological universities [1], accreditation agencies and International and National networks of universities. At the UNESCO chair of Sustainability of the Technical University of Catalonia (UPC) under their PhD program on Sustainability the authors have carried out a research on: 1. Which SD competences may engineers have when graduating? 2. How should SD competences be taught/learned at technological universities? 3. Which curriculum structure is more suitable to facilitate the acquisition of SD competences? To evaluate the competences we compared three leading European universities in introduction of SD. The competences are classified in three categories: knowledge and understanding, skills and abilities and attitudes [2]. To evaluate the pedagogical approach that facilitates the SD learning we analysed 10 case studies of courses on Sustainability from 5 European technological universities. We used conceptual maps [3, 4] as assessment tool. To analyse the curriculum design for SD 50 experts on curriculum design and teaching SD courses were interviewed. The methodology and results of this work are presented and recommendations to introduce SD in technological universities in the three fields: competences, pedagogy and curriculum are suggested.Peer Reviewe