Implementing Rapid Prototyping Using CNC Machining (CNC-RP) Through a CAD/CAM Interface

This paper presents the methodology and implementation of a rapid machining system using a CAD/CAM interface. Rapid Prototyping using CNC Machining (CNC-RP) is a method that has been developed which enables automatic generation of process plans for a machined component. The challenge with CNC-RP is not the technical problems of material removal, but with all of the required setup, fixture and toolpath planning, which has previously required a skilled machinist. Through the use of advanced geometric algorithms, we have implemented an interface with a CAD/CAM system that allows true automatic NC code generation directly from a CAD model with no human interaction; a capability necessary for a practical rapid prototyping system.Mechanical Engineerin

Inverse Bremsstrahlung in Shocked Astrophysical Plasmas

There has recently been interest in the role of inverse bremsstrahlung, the emission of photons by fast suprathermal ions in collisions with ambient electrons possessing relatively low velocities, in tenuous plasmas in various astrophysical contexts. This follows a long hiatus in the application of suprathermal ion bremsstrahlung to astrophysical models since the early 1970s. The potential importance of inverse bremsstrahlung relative to normal bremsstrahlung, i.e. where ions are at rest, hinges upon the underlying velocity distributions of the interacting species. In this paper, we identify the conditions under which the inverse bremsstrahlung emissivity is significant relative to that for normal bremsstrahlung in shocked astrophysical plasmas. We determine that, since both observational and theoretical evidence favors electron temperatures almost comparable to, and certainly not very deficient relative to proton temperatures in shocked plasmas, these environments generally render inverse bremsstrahlung at best a minor contributor to the overall emission. Hence inverse bremsstrahlung can be safely neglected in most models invoking shock acceleration in discrete sources such as supernova remnants. However, on scales > 100pc distant from these sources, Coulomb collisional losses can deplete the cosmic ray electrons, rendering inverse bremsstrahlung, and perhaps bremsstrahlung from knock-on electrons, possibly detectable.Comment: 13 pages, including 2 figures, using apjgalley format; to appear in the January 10, 2000 issue, of the Astrophysical Journa

The Impact of Tobacco Control Program Expenditures on Aggregate Cigarette Sales: 1981-1998

Since the 1998 Master Settlement Agreement between states and the tobacco industry, states have unprecedented resources for programs to reduce tobacco use. Decisions concerning the use of these funds will, in part, be based on the experiences of states with existing programs. We review the experiences of several states that have adopted comprehensive tobacco control programs. We also report estimates from econometric analyses of the impact of tobacco control expenditures on aggregate tobacco use in all states and in selected states with comprehensive programs for the period from 1981 through 1998. Our analyses clearly show that increases in funding for state tobacco control programs reduce tobacco use.

“You Got To Know Us”: A Hopeful Model for Music Education in Urban Schools

Urban schools, and the students and teachers within, are often characterized by a metanarrative of deficit and crisis, causing the complex realities of urban education to remain unclear behind a wall of assumptions and stereotypes. Within music education, urban schools have received limited but increasing attention from researchers. However, voices from practitioners are often missing from this dialogue, and the extant scholarly dialogue has had a very limited effect on music teacher education. In this article, five music educators with a combined thirty years of experience in urban schools examine aspects of their experiences in the light of critical pedagogy in an attempt to disrupt the metanarrative of deficit, crisis, and decline that continues to surround urban music education. By promoting the lived-stories of successful urban music students, teachers, and programs, the authors hope to situate urban music education as a site of renewal, reform, and meaningful learning. This paper emerged from a panel discussion regarding promising practices in secondary general music with urban youth that took place at the New Directions in Music Education conference held at Michigan State University in October of 2011

Engaging the articulators enhances perception of concordant visible speech movements

PURPOSE This study aimed to test whether (and how) somatosensory feedback signals from the vocal tract affect concurrent unimodal visual speech perception. METHOD Participants discriminated pairs of silent visual utterances of vowels under 3 experimental conditions: (a) normal (baseline) and while holding either (b) a bite block or (c) a lip tube in their mouths. To test the specificity of somatosensory-visual interactions during perception, we assessed discrimination of vowel contrasts optically distinguished based on their mandibular (English /ɛ/-/æ/) or labial (English /u/-French /u/) postures. In addition, we assessed perception of each contrast using dynamically articulating videos and static (single-frame) images of each gesture (at vowel midpoint). RESULTS Engaging the jaw selectively facilitated perception of the dynamic gestures optically distinct in terms of jaw height, whereas engaging the lips selectively facilitated perception of the dynamic gestures optically distinct in terms of their degree of lip compression and protrusion. Thus, participants perceived visible speech movements in relation to the configuration and shape of their own vocal tract (and possibly their ability to produce covert vowel production-like movements). In contrast, engaging the articulators had no effect when the speaking faces did not move, suggesting that the somatosensory inputs affected perception of time-varying kinematic information rather than changes in target (movement end point) mouth shapes. CONCLUSIONS These findings suggest that orofacial somatosensory inputs associated with speech production prime premotor and somatosensory brain regions involved in the sensorimotor control of speech, thereby facilitating perception of concordant visible speech movements. SUPPLEMENTAL MATERIAL https://doi.org/10.23641/asha.9911846R01 DC002852 - NIDCD NIH HHSAccepted manuscrip

Automated fixture design for a rapid machining process

Rapid prototyping techniques for CNC machining have been developed in an effort to produce functional prototypes in appropriate materials. One of the major challenges for rapid machining is to develop an automatic fixturing system for securing the part during the machining process. The method proposed in this paper is the use of sacrificial fixturing, similar to the support structures in existing rapid processes like Stereolithography. During the machining process, sacrificial supports emerge incrementally and, at the end of the process, are the only entities connecting the part to the stock material. This paper presents methodologies for the design of sacrificial support structures for a rapid machining process and illustrates them using a complex sample part machined in the laboratory