Usefulness of VRML building models in a direction finding context

This paper describes an experiment which aims to examine the effectiveness and efficiency of a Virtual Reality Modelling Language (VRML) building model compared with equivalent architectural plans, for direction finding purposes. The effectiveness and efficiency issues being primarily investigated were number of tasks completed overall and task completion times. The experiment involved a series of tasks where participants had to find a number of locations/objects in a building unknown to them at the outset of the experiment. Statistically significant results are presented for the benefit of the research community, law enforcement officers and fire fighters where it is clear that in this context, the VRML model led to better task completions than the equivalent architectural plans. Regarding the task completion times, no statistical significance was found. Given the current climate of security issues and terrorist threats, it is important that law enforcement officers have at their disposal the best information possible regarding the layout of a building, whilst keeping costs down. This also applies to fire fighters when rescuing victims. This experiment has shown that a VRML model leads to better task completions in direction finding

A double main sequence turn-off in the rich star cluster NGC 1846 in the Large Magellanic Cloud

We report on HST/ACS photometry of the rich intermediate-age star cluster NGC 1846 in the Large Magellanic Cloud, which clearly reveals the presence of a double main sequence turn-off in this object. Despite this, the main sequence, sub-giant branch, and red giant branch are all narrow and well-defined, and the red clump is compact. We examine the spatial distribution of turn-off stars and demonstrate that all belong to NGC 1846 rather than to any field star population. In addition, the spatial distributions of the two sets of turn-off stars may exhibit different central concentrations and some asymmetries. By fitting isochrones, we show that the properties of the colour-magnitude diagram can be explained if there are two stellar populations of equivalent metal abundance in NGC 1846, differing in age by approximately 300 Myr. The absolute ages of the two populations are ~1.9 and ~2.2 Gyr, although there may be a systematic error of up to +/-0.4 Gyr in these values. The metal abundance inferred from isochrone fitting is [M/H] ~ -0.40, consistent with spectroscopic measurements of [Fe/H]. We propose that the observed properties of NGC 1846 can be explained if this object originated via the tidal capture of two star clusters formed separately in a star cluster group in a single giant molecular cloud. This scenario accounts naturally for the age difference and uniform metallicity of the two member populations, as well as the differences in their spatial distributions.Comment: 9 pages, 8 figures, accepted for publication in MNRAS. A version with full resolution figures may be obtained at http://www.roe.ac.uk/~dmy/papers/MN-07-0441-MJ_rv.ps.gz (postscript) or at http://www.roe.ac.uk/~dmy/papers/MN-07-0441-MJ_rv.pdf (PDF

Mackey, Eugene (3)

H/S Co 1321 Engineers G.S. Regimenthttps://dh.howard.edu/prom_corres/1100/thumbnail.jp

Mackey, Eugene

H/S Co 1321 Engineers G.S. Regimenthttps://dh.howard.edu/prom_corres/1098/thumbnail.jp

Mackey, Eugnee

H&S Co. 1321st Engineer GS Regiment Camp Sutton, North Carolinahttps://dh.howard.edu/prom_members/1054/thumbnail.jp

Does A Mobile-Bearing Vs. Fixed-Bearing Total Knee Replacement Affect Post-Operative Knee Pain at One Year?

OBJECTIVE: The objective of this selective EBM review is to determine whether or not a mobile-bearing vs. fixed-bearing total knee replacement affects post-operative knee pain at one year. STUDY DESIGN: Review of three English language primary studies, published between 2008 and 2012. DATA SOURCES: Three randomized controlled trials published after 2008 comparing post-operative knee pain in mobile vs. fixed-bearing total knee replacements using PubMed and Cochrane databases. OUTCOMES MEASURED: Knee pain, reported by patients post-operatively using various professional questionnaires, was the primary outcome measured. Subjects reported pain experienced during specific provoking activities on the EuroQol, Western Ontario & McMaster Universities OA Index, Knee Society Score, visual analog scales, Oxford 12-item Questionnaire, and SF-36. Results were then compared one year postoperatively. The tool used to assess significance of outcomes measured was p-value. RESULTS: One year post-operatively, Lampe et al showed no significant difference in post-operative knee pain in mobile vs. fixed-bearing knee replacements. Breugem et al demonstrated less knee pain when using the mobile-bearing implant. Jolles et al showed significantly less pain in the fixed-bearing knee implants in two of the questionnaires, but no difference in the three other evaluation methods, consequently deeming the study inconclusive. CONCLUSIONS: The results of the RCTs are inconclusive in determining whether or not type of implant affects post-operative knee pain one year after a total knee replacement. Further research may identify one of the implants as more effective in a particular gender or race

Mackey, Eugene (2)

H/S Co 1321 Engineers G.S. Regimenthttps://dh.howard.edu/prom_corres/1099/thumbnail.jp

Concerted [4 + 2] and Stepwise (2 + 2) Cycloadditions of Tetrafluoroethylene with Butadiene: DFT and DLPNO-UCCSD(T) Explorations.

Tetrafluoroethylene and butadiene form the 2 + 2 cycloadduct under kinetic control, but the Diels-Alder cycloadduct is formed under thermodynamic control. Borden and Getty showed that the preference for 2 + 2 cycloaddition is due to the necessity for syn-pyramidalization of the two CF2 groups in the 4 + 2 transition state. We have explored the full potential energy surface for the concerted and stepwise reactions of tetrafluoroethylene and butadiene with density functional theory, DFT (B3LYP and M06-2X), DLPNO-UCCSD(T), and CASSCF-NEVPT2 methods and with the distortion/interaction-activation strain model to explain the energetics of different pathways. The 2 + 2 cycloadduct is formed by an anti-transition state followed by two rotations and a final bond formation transition state. Energetics are compared to the reaction of maleic anhydride and ethylene

Iterated function systems, representations, and Hilbert space

This paper studies a general class of Iterated Function Systems (IFS). No contractivity assumptions are made, other than the existence of some compact attractor. The possibility of escape to infinity is considered. Our present approach is based on Hilbert space, and the theory of representations of the Cuntz algebras O_n, n=2,3,.... While the more traditional approaches to IFS's start with some equilibrium measure, ours doesn't. Rather, we construct a Hilbert space directly from a given IFS; and our construction uses instead families of measures. Starting with a fixed IFS S_n, with n branches, we prove existence of an associated representation of O_n, and we show that the representation is universal in a certain sense. We further prove a theorem about a direct correspondence between a given system S_n, and an associated sub-representation of the universal representation of O_n.Comment: 22 pages, 3 figures containing 7 EPS graphics; LaTeX2e ("elsart" document class); v2 reflects change in Comments onl

Asymmetric supernova remnants generated by Galactic, massive runaway stars

After the death of a runaway massive star, its supernova shock wave interacts with the bow shocks produced by its defunct progenitor, and may lose energy, momentum, and its spherical symmetry before expanding into the local interstellar medium (ISM). We investigate whether the initial mass and space velocity of these progenitors can be associated with asymmetric supernova remnants. We run hydrodynamical models of supernovae exploding in the pre-shaped medium of moving Galactic core-collapse progenitors. We find that bow shocks that accumulate more than about 1.5 Mo generate asymmetric remnants. The shock wave first collides with these bow shocks 160-750 yr after the supernova, and the collision lasts until 830-4900 yr. The shock wave is then located 1.35-5 pc from the center of the explosion, and it expands freely into the ISM, whereas in the opposite direction it is channelled into the region of undisturbed wind material. This applies to an initially 20 Mo progenitor moving with velocity 20 km/s and to our initially 40 Mo progenitor. These remnants generate mixing of ISM gas, stellar wind and supernova ejecta that is particularly important upstream from the center of the explosion. Their lightcurves are dominated by emission from optically-thin cooling and by X-ray emission of the shocked ISM gas. We find that these remnants are likely to be observed in the [OIII] lambda 5007 spectral line emission or in the soft energy-band of X-rays. Finally, we discuss our results in the context of observed Galactic supernova remnants such as 3C391 and the Cygnus Loop.Comment: 21 pages, 16 figure