4,842 research outputs found
Implementing flexible rules of interaction for object manipulation in cluttered virtual environments
Object manipulation in cluttered virtual environments (VEs)
brings additional challenges to the design of interaction
algorithms, when compared with open virtual spaces. As the
complexity of the algorithms increases so does the flexibility with
which users can interact, but this is at the expense of much
greater difficulties in implementation for developers. Three rules
that increase the realism and flexibility of interaction are outlined:
collision response, order of control, and physical compatibility.
The implementation of each is described, highlighting the
substantial increase in algorithm complexity that arises. Data are
reported from an experiment in which participants manipulated a
bulky virtual object through parts of a virtual building (the piano
movers’ problem). These data illustrate the benefits to users that
accrue from implementing flexible rules of interaction
Reflectionless measures and the Mattila-Melnikov-Verdera uniform rectifiability theorem
A new proof is given of the Mattila-Melnikov-Verdera theorem on the uniform
rectifiability of an Ahlfors-David regular measure whose associated Cauchy
transform operator is bounded.Comment: 31 pages, 5 figure
Comparison of outcome measures for patients with chronic obstructive pulmonary disease (COPD) in an outpatient setting
BACKGROUND: To assist clinicians and researchers in choosing outcome measures for patients with chronic obstructive pulmonary disease attending routine outpatient clinics, a comparative assessment was undertaken of four questionnaires designed to reflect the patients' perception of their physical and emotional health in terms of their feasibility, validity, reliability, and responsiveness to health change. METHODS: Two condition specific questionnaires, the St George's Respiratory Questionnaire (SGRQ) and Guyatt's Chronic Respiratory Questionnaire (CRQ), and two generic questionnaires, the Short Form-36 Health Survey (SF-36) and Euroqol (EQ), were compared for their discriminative and evaluative properties. Spirometric tests and a walking test were also performed. One hundred and fifty six adults who were clinically judged to have COPD and who attended an outpatient chest clinic were assessed at recruitment and six and 12 months later. Patients were also asked whether their health had changed since their last assessment. RESULTS: Completion rates and consistency between items for dimensions of the SGRQ were lower than for dimensions of the other questionnaires. The distributions of responses were skewed for certain dimensions in all questionnaires except the CRQ. Validity was supported for all instruments insofar as patients' scores were associated with differences in disease severity. The generic questionnaires better reflected other health problems. All instruments were reliable over time. The condition specific questionnaires were more responsive between baseline and first follow up visit but this difference did not persist. While certain dimensions of the SF-36 were responsive to patient perceived changes, this did not apply to the derived single index of the EQ. The rating scale of the EQ, however, provided a quick and easy indicator of change. CONCLUSIONS: Evidence from this study supports the CRQ and the SF-36 as comprehensive outcome measures for patients with longstanding COPD
On the Thermal Ignition of Wood Waste
Self-heating tests on sawdust in ovens, using baskets of various shapes as sample containers, are reported and times to ignition measured according to a definition of such times different from that conventionally used. Findings are also discussed semiquantitatively in terms of the measured kinetic parameters. The possibility of reactivity loss by prior exposure to air is looked into directly
Inductive Signals: Revolving vertebrates
AbstractAn old idea about the relationship between arthropod and vertebrate body plans has been given new life by studies of the signalling genes controlling dorsal and ventral development in Drosophila and Xenopus
Verification of Java Bytecode using Analysis and Transformation of Logic Programs
State of the art analyzers in the Logic Programming (LP) paradigm are
nowadays mature and sophisticated. They allow inferring a wide variety of
global properties including termination, bounds on resource consumption, etc.
The aim of this work is to automatically transfer the power of such analysis
tools for LP to the analysis and verification of Java bytecode (JVML). In order
to achieve our goal, we rely on well-known techniques for meta-programming and
program specialization. More precisely, we propose to partially evaluate a JVML
interpreter implemented in LP together with (an LP representation of) a JVML
program and then analyze the residual program. Interestingly, at least for the
examples we have studied, our approach produces very simple LP representations
of the original JVML programs. This can be seen as a decompilation from JVML to
high-level LP source. By reasoning about such residual programs, we can
automatically prove in the CiaoPP system some non-trivial properties of JVML
programs such as termination, run-time error freeness and infer bounds on its
resource consumption. We are not aware of any other system which is able to
verify such advanced properties of Java bytecode
2W/nm Peak-power All-Fiber Supercontinuum Source and its Application to the Characterization of Periodically Poled Nonlinear Crystals
We demonstrate a uniform high spectral brightness and peak power density
all-fiber supercontinuum source. The source consists of a nanosecond Ytterbium
fiber laser and an optimal length PCF producing a continuum with a peak power
density of 2 W/nm and less than 5 dB of spectral variation between 590 to 1500
nm. The Watt level per nm peak power density enables the use of such sources
for the characterization of nonlinear materials. Application of the source is
demonstrated with the characterization of several periodically poled crystals.Comment: 8 pages 4 figures v2 includes revisions to the description of the
continuum formatio
Fiber depolymerization
Depolymerization is, by definition, a crucial process in the reversible assembly of various biopolymers. It may also be an important factor in the pathology of sickle cell disease. If sickle hemoglobin fibers fail to depolymerize fully during passage through the lungs then they will reintroduce aggregates into the systemic circulation and eliminate or shorten the protective delay (nucleation) time for the subsequent growth of fibers. We study how depolymerization depends on the rates of end- and side-depolymerization, kend and kside, which are, respectively, the rates at which fiber length is lost at each end and the rate at which new breaks appear per unit fiber length. We present both an analytic mean field theory and supporting simulations showing that the characteristic fiber depolymerization time View the MathML source depends on both rates, but not on the fiber length L, in a large intermediate regime 1 much less-than ksideL2/kend much less-than (L/d)2, with d the fiber diameter. We present new experimental data which confirms that both mechanisms are important and shows how the rate of side depolymerization depends strongly on the concentration of CO, acting as a proxy for oxygen. Our theory remains rather general and could be applied to the depolymerization of an entire class of linear aggregates, not just sickle hemoglobin fibers
The Wide Field Spectrograph (WiFeS)
This paper describes the Wide Field Spectrograph (WiFeS) under construction
at the Research School of Astronomy and Astrophysics (RSAA) of the Australian
National University (ANU) for the ANU 2.3m telescope at the Siding Spring
Observatory. WiFeS is a powerful integral field, double-beam, concentric,
image-slicing spectrograph designed to deliver excellent thoughput, wavelength
stability, spectrophotometric performance and superb image quality along with
wide spectral coverage throughout the 320-950 nm wavelength region. It provides
a 25x38 arcsec. field with 0.5 arcsec. sampling along each of twenty five 38X1
arcsec slitlets. The output format is optimized to match the 4096x4096 pixel
CCD detectors in each of two cameras individually optimized for the blue and
the red ends of the spectrum, respectively. A process of "interleaved
nod-and-shuffle" will be applied to permit quantum noise-limited sky
subtraction. Using VPH gratings, spectral resolutions of 3000 and 7000 are
provided. The full spectral range is covered in a single exposure at R=3000,
and in two exposures in the R=7000 mode. The use of transmissive coated optics,
VPH gratings and optimized mirror coatings ensures a throughput (including
telescope atmosphere and detector) > 30% over a wide spectral range. The
concentric image-slicer design ensures an excellent and uniform image quality
across the full field. To maximize scientific return, the whole instrument is
configured for remote observing, pipeline data reduction, and the accumulation
of calibration image libraries.Comment: Accepted for publication in Astrophysics & Space Science, 16 pages,
14 figure
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