Acoustic Attenuation in Fans and Ducts by Vaporization of Liquid Droplets

A cloud of small water droplets in saturated air attenuates acoustic disturbances by viscous drag, heat transfer, and vapor exchange with the ambient gas. The viscous and heat transfer phenomena attenuate at frequencies above 104 Hz for I-J.l droplets. The processes associated with phase exchange attenuate at a much lower frequency that may he controlled by choice of the liquid mass fraction. The strength of this attenuation is proportional to the mass of water vapor in the air, a factor controlled by air temperature. For plane waves, the attenuation magnitude e~ceeds 5 db!m ~t a temperature of 25°C with a cloud of 0.7 J.l radius droplets constituting 1 % of the gas mass. ThiS attenuation mcreases to more than 7 dbjm at frequencies above 1000 Hz where viscous and heat transfer mechanisms contribute significantly. The attenuation of higher order duct modes is strongly increased over the above values, similarly to the attenuation by duct lining. When the droplet cloud occupies only a fraction of the duct height close to the walls, the droplet clond may be up to twice as elfective as the uniform cloud, and a significant saving is possible in the water required to saturate the air and furnish the water droplets

Some comments on certain technical aspects on geographic information systems Technical report no. 2

Two-dimensional machine language and spatial statistics for design and development of geographic information system

PC1643+4631A,B: The Lyman-Alpha Forest at the Edge of Coherence

This is the first measurement and detection of coherence in the intergalactic medium (IGM) at substantially high redshift (z~3.8) and on large physical scales (~2.5 h^-1 Mpc). We perform the measurement by presenting new observations from Keck LRIS of the high redshift quasar pair PC 1643+4631A, B and their Ly-alpha absorber coincidences. This experiment extends multiple sightline quasar absorber studies to higher redshift, higher opacity, larger transverse separation, and into a regime where coherence across the IGM becomes weak and difficult to detect. We fit 222 discrete Ly-alpha absorbers to sightline A and 211 to sightline B. Relative to a Monte Carlo pairing test (using symmetric, nearest neighbor matching) the data exhibit a 4sigma excess of pairs at low velocity splitting (<150 km/s), thus detecting coherence on transverse scales of ~2.5 h^-1 Mpc. We use spectra extracted from an SPH simulation to analyze symmetric pair matching, transmission distributions as a function of redshift and compute zero-lag cross-correlations to compare with the quasar pair data. The simulations agree with the data with the same strength (~4sigma) at similarly low velocity splitting above random chance pairings. In cross-correlation tests, the simulations agree when the mean flux (as a function of redshift) is assumed to follow the prescription given by Kirkman et al. (2005). While the detection of flux correlation (measured through coincident absorbers and cross-correlation amplitude) is only marginally significant, the agreement between data and simulations is encouraging for future work in which even better quality data will provide the best insight into the overarching structure of the IGM and its understanding as shown by SPH simulations.Comment: 15 pages, 11 figures; accepted for publication in Astronomical Journa

Turbulence-Augmented Minimization of Combustion Time in Mesoscale Internal Combustion Engines

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76256/1/AIAA-2006-1350-451.pd

Irradiation of amorphous Ta42Si13N45 film with a femtosecond laser pulse

Films of 260nm thickness, with atomic composition Ta42Si13N45, on 4″ silicon wafers, have been irradiated in air with single laser pulses of 200 femtoseconds duration and 800nm wave length. As sputter-deposited, the films are structurally amorphous. A laterally truncated Gaussian beam with a near-uniform fluence of ∼0.6J/cm2 incident normally on such a film ablates 23nm of the film. Cross-sectional transmission electron micrographs show that the surface of the remaining film is smooth and flat on a long-range scale, but contains densely distributed sharp nanoprotrusions that sometimes surpass the height of the original surface. Dark field micrographs of the remaining material show no nanograins. Neither does glancing angle X-ray diffraction with a beam illuminating many diffraction spots. By all evidence, the remaining film remains amorphous after the pulsed femtosecond irradiation. The same single pulse, but with an enhanced and slightly peaked fluence profile, creates a spot with flat peripheral terraces whose lateral extents shrink with depth, as scanning electron and atomic force micrographs revealed. Comparison of the various figures suggests that the sharp nanoprotrusions result from an ejection of material by brittle fraction and spallation, not from ablation by direct beam-solid interaction. Conditions under which spallation should dominate over ablation are discusse

An Ethnographic Study of the Use of Puppetry with a Children's Group

This study utilized an ethnographic methodology to examine and describe the various aspects and processes occurring in a children's group as the members created their own puppets and accompanying puppet plays. Individual and interactive behavior patterns were isolated and analyzed as a means of gaining an in depth understanding of the puppetry process. The puppetry process, in turn, was viewed in terms of information it provided regarding the individual members and the group process. The facilitative and non-facilitative aspects of the procedure were delineated. The adult leader met with a group of six boys, in grades four and five, for 12 one-hour sessions in which they made puppets and then created puppet plays around issues that they had articulated as problems. The group sessions were videotaped and transcribed. The transcriptions were coded in an effort to extensively analyze the puppetry process and the group process, and the ways in which the two processes interacted. An independent observer/rater was utilized in order to provide some validity for the researcher's reported results. The puppet-making task appeared to offer an opportunity for individuals to begin to come together in a common, but individual task. Characteristic styles and individual personality dynamics were evidenced. General response to the task was enthusiastic, with varying degrees of satisfaction expressed regarding their finished products. The play-creating and performing process met with less success than the puppet-making. While the group members appeared to be generally amenable to contributing ideas for the puppet plays, the process met with far more resistance in the cooperative task of putting their ideas into a finished product. The group discussion and interaction that occurred around these tasks provided a vehicle by which to view levels of interpersonal skills and the group's overall stage of development. The puppets the children created appeared to act as metaphors in expressing the group members' views of themselves and in enabling the symbolic representation of some of their central concerns. The plays they created paralleled the process that actually took place in the group. The subject matter and content of the puppets and plays provided information and evidence as to how each member approached and solved problems. The discrepancies in the ways in which the researcher and the independent observer/rater viewed the positive and negative social/emotional interactions of the group members, coupled with the small number of subjects included in this study preclude generalizing to other groups of children at this time. Further studies, with additional groups of children, utilizing parametric statistics are called for before any such generalizations can be made

21-cm synthesis observations of VIRGOHI 21 - a possible dark galaxy in the Virgo Cluster

Many observations indicate that dark matter dominates the extra-galactic Universe, yet no totally dark structure of galactic proportions has ever been convincingly identified. Previously we have suggested that VIRGOHI 21, a 21-cm source we found in the Virgo Cluster using Jodrell Bank, was a possible dark galaxy because of its broad line-width (~200 km/s) unaccompanied by any visible gravitational source to account for it. We have now imaged VIRGOHI 21 in the neutral-hydrogen line and find what could be a dark, edge-on, spinning disk with the mass and diameter of a typical spiral galaxy. Moreover, VIRGOHI 21 has unquestionably been involved in an interaction with NGC 4254, a luminous spiral with an odd one-armed morphology, but lacking the massive interactor normally linked with such a feature. Numerical models of NGC 4254 call for a close interaction ~10^8 years ago with a perturber of ~10^11 solar masses. This we take as additional evidence for the massive nature of VIRGOHI 21 as there does not appear to be any other viable candidate. We have also used the Hubble Space Telescope to search for stars associated with the HI and find none down to an I band surface brightness limit of 31.1 +/- 0.2 mag/sq. arcsec.Comment: 8 pages, accepted to ApJ, uses emulateapj.cls. Mpeg animation (Fig. 2) available at ftp://ftp.naic.edu/pub/publications/minchin/video2.mp

A Theory of Change for One-on-One Peer support for older adolescents and young adults

Peer support has become increasingly available as a formal mental health service. However, high quality research and implementation of peer support has been hampered over the years by the lack of theory that clarifies peer support roles and explains exactly how these roles foster positive outcomes for peer support users. Observers have noted that theory is particularly sparse in regard to peer support for older adolescents and young adults, and they have called for theory that not only clarifies roles and mechanisms of impact, but also identifies how peer support for young people might differ from peer support for older adults This qualitative study brought young people with experience providing and using peer support together in small group discussions focused on understanding the activities and outcomes of peer support. This information was used to develop a theory of change that outlines key activities that constitute a one-on-one peer support role for young people, and describes how and why carrying out these activities should lead to positive outcomes. The theory highlights the characteristics of a successful “peerness-based relationship,” and proposes that the development of this kind of relationship mediates other positive outcomes from peer support. The article concludes with a discussion of how this theory can usefully inform the development and specification of peer support roles, training and supervision, and other organizational supports

An HST/WFPC2 Snapshot Survey of 2MASS-Selected Red QSOs

Using simple infrared color selection, 2MASS has found a large number of red, previously unidentified, radio-quiet QSOs. Although missed by UV/optical surveys, the 2MASS QSOs have K-band luminosities that are comparable to "classical" QSOs. This suggests the possible discovery of a previously predicted large population of dust-obscured radio-quiet QSOs. We present the results of an imaging survey of 29 2MASS QSOs observed with WFPC2 onboard the Hubble Space Telescope. I-band images, which benefit from the relative faintness of the nuclei at optical wavelengths, are used to characterize the host galaxies, measure the nuclear contribution to the total observed I-band emission, and to survey the surrounding environments. The 2MASS QSOs are found to lie in galaxies with a variety of morphologies, luminosities, and dynamical states, not unlike those hosting radio-quiet PG QSOs. Our analysis suggests that the extraordinary red colors of the 2MASS QSOs are caused by extinction of an otherwise typical QSO spectrum due to dust near the nucleus.Comment: 23 pages including 9 figures and 7 tables, accepted for publication in ApJ, higher resolution HST images at: http://shapley.as.arizona.edu/~amarble/papers/twomq