21,131 research outputs found
User's manual for MacPASCO
A user's manual is presented for MacPASCO, which is an interactive, graphic, preprocessor for panel design. MacPASCO creates input for PASCO, an existing computer code for structural analysis and sizing of longitudinally stiffened composite panels. MacPASCO provides a graphical user interface which simplifies the specification of panel geometry and reduces user input errors. The user draws the initial structural geometry and reduces user input errors. The user draws the initial structural geometry on the computer screen, then uses a combination of graphic and text inputs to: refine the structural geometry; specify information required for analysis such as panel load and boundary conditions; and define design variables and constraints for minimum mass optimization. Only the use of MacPASCO is described, since the use of PASCO has been documented elsewhere
Highly stable analog-to-digital converter
Device has been developed for use in pulse-height analyzer of gamma-ray telescope. Unit shows integral linearity of 0.05 percent and differential linearity of less than 2 percent
Fault Localization in Multi-Threaded C Programs using Bounded Model Checking (extended version)
Software debugging is a very time-consuming process, which is even worse for
multi-threaded programs, due to the non-deterministic behavior of
thread-scheduling algorithms. However, the debugging time may be greatly
reduced, if automatic methods are used for localizing faults. In this study, a
new method for fault localization, in multi-threaded C programs, is proposed.
It transforms a multi-threaded program into a corresponding sequential one and
then uses a fault-diagnosis method suitable for this type of program, in order
to localize faults. The code transformation is implemented with rules and
context switch information from counterexamples, which are typically generated
by bounded model checkers. Experimental results show that the proposed method
is effective, in such a way that sequential fault-localization methods can be
extended to multi-threaded programs.Comment: extended version of paper published at SBESC'1
Damage-cluster distributions and size effect on strength in compressive failure
We investigate compressive failure of heterogeneous materials on the basis of
a continuous progressive damage model. The model explicitely accounts for
tensile and shear local damage and reproduces the main features of compressive
failure of brittle materials like rocks or ice. We show that the size
distribution of damage-clusters, as well as the evolution of an order
parameter, the size of the largest damage-cluster, argue for a critical
interpretation of fracture. The compressive failure strength follows a normal
distribution with a very small size effect on the mean strength, in good
agreement with experiments
Evidence for Ubiquitous Collimated Galactic-Scale Outflows along the Star-Forming Sequence at z~0.5
We present an analysis of the MgII 2796, 2803 and FeII 2586, 2600 absorption
line profiles in individual spectra of 105 galaxies at 0.3<z<1.4. The galaxies,
drawn from redshift surveys of the GOODS fields and the Extended Groth Strip,
fully sample the range in star formation rates (SFRs) occupied by the
star-forming sequence with stellar masses log M_*/M_sun > 9.5 at 0.3<z<0.7.
Using the Doppler shifts of the MgII and FeII absorption lines as tracers of
cool gas kinematics, we detect large-scale winds in 66+/-5% of the galaxies.
HST/ACS imaging and our spectral analysis indicate that the outflow detection
rate depends primarily on galaxy orientation: winds are detected in ~89% of
galaxies having inclinations (i) <30 degrees (face-on), while the wind
detection rate is only ~45% in objects having i>50 degrees (edge-on). Combined
with the comparatively weak dependence of the wind detection rate on intrinsic
galaxy properties, this suggests that biconical outflows are ubiquitous in
normal, star-forming galaxies at z~0.5. We find that the wind velocity is
correlated with host galaxy M_* at 3.4-sigma significance, while the equivalent
width of the flow is correlated with host galaxy SFR at 3.5-sigma significance,
suggesting that hosts with higher SFR may launch more material into outflows
and/or generate a larger velocity spread for the absorbing clouds. Assuming
that the gas is launched into dark matter halos with simple, isothermal density
profiles, the wind velocities measured for the bulk of the cool material
(~200-400 km/s) are sufficient to enable escape from the halo potentials only
for the lowest-M_* systems in the sample. However, the outflows typically carry
sufficient energy to reach distances of >50 kpc, and may therefore be a viable
source of cool material for the massive circumgalactic medium observed around
bright galaxies at z~0. [abridged]Comment: Submitted to ApJ. 61 pages, 25 figures, 4 tables, 4 appendices. Uses
emulateapj forma
First fringes with an integrated-optics beam combiner at 10 um - A new step towards instrument miniaturization for mid-infrared interferometry
Observations at mas-resolution scales and high dynamic range hold a central
place in achieving, for instance, the spectroscopic characterization of
exo-Earths or the detailed mapping of their protoplanetary disc birthplace.
Ground or space-based multi-aperture infrared interferometry is a promising
technique to tackle these goals. But significant efforts still need to be
undertaken to achieve a simplification of these instruments if we want to
combine the light from a large number of telescopes. Integrated-optics appears
as an alternative to the current conventional designs, especially if its use
can be extended to a higher number of astronomical bands. This article reports
for the first time the experimental demonstration of the feasibility of an
integrated-optics approach to mid-infrared beam combination for single-mode
stellar interferometry. We have fabricated a 2-telescope beam combiner
prototype integrated on a substrate of chalcogenide glasses, a material
transparent from 1 to 14 um. We have developed laboratory tools to characterize
the modal properties and the interferometric capabilities of our device. We
obtain fringes at 10 um and measure a mean contrast V=0.981 \pm 0.001 with high
repeatability over one week and high stability over 5h. We show experimentally
- as well as on the basis of modeling considerations - that the component has a
single-mode behavior at this wavelength, which is essential to achieve
high-accuracy interferometry. From previous studies, the propagation losses are
estimated to 0.5 dB/cm for such components. We also discuss possible issues
that may impact the interferometric contrast. The IO beam combiner performs
well at 10. We also anticipate the requirement of a better matching between the
numerical apertures of the component and the (de)coupling optics to optimize
the total throughput. The next step foreseen is the achievement of wide-band
interferograms.Comment: Accepted in A&A; 7 pages; 7 figure
Scalable simultaneous multi-qubit readout with 99.99% single-shot fidelity
We describe single-shot readout of a trapped-ion multi-qubit register using
space and time-resolved camera detection. For a single qubit we measure
0.9(3)x10^{-4} readout error in 400us exposure time, limited by the qubit's
decay lifetime. For a four-qubit register (a "qunybble") we measure an
additional error of only 0.1(1)x10^{-4} per qubit, despite the presence of 4%
optical cross-talk between neighbouring qubits. A study of the cross-talk
indicates that the method would scale with negligible loss of fidelity to
~10000 qubits at a density <~1 qubit/um^2, with a readout time ~1us/qubit.Comment: 4 pages, 3 figures; simulations added to fig.3, with some further
text and figure revisions. Main results unchanged
The Impact of Office Automation on the Organization: Some Implications for Research and Practice
Computer technology has recently been applied to
the automation of office tasks and procedures. Much of
the technology is aimed not at improving the efficiency
of current office procedures, but at altering the nature of
office work altogether. The development of automated
office systems raises a number of issues for the organization.
How will this technology be received by organization
members? How will it affect the definition of
traditional office work? What will be its impact on
individuals, work groups, and the structure of the organization?
This paper presents a descriptive model and
propositions concerning the potential impacts of office
automation on the organization and it stresses the need,
when implementing automated office systems, to take a
broad perspective of their potential positive and negative
effects on the organization. The need for further research
examining the potential effects of office automation is
emphasized.Information Systems Working Papers Serie
Reduction in jejunal fluid absorption in vivo through distension and cholinergic stimulation not attributable to enterocyte secretion
Jejunal fluid absorption in vivo was reduced by distension and by hydrostatic pressure and further declined on adding E. coli STa enterotoxin but no net fluid secretion was detected. Luminal atropine reduced pressure mediated reductions in fluid absorption to normal values but intravenous hexamethonium was without effect. A neural component to inhibition of absorption by pressure (though not stretch) may be mediated by axon reflexes within cholinergic neurons.Perfusion of cholinergic compounds also reduced net fluid absorption but did not cause secretion. In order to show that these actions were not secretory processes stimulated by cholinergic compounds that offset normal rates of absorption, these compounds were tested for their ability to cause net secretion in loops that were perfused with solutions in which choline substituted for sodium ion. In addition, these perfusates additionally contained E. coli STa enterotoxin or EIPA (ethyl-isopropyl-amiloride) to minimize absorption.In these circumstances, where it might be expected to do so if it were acting through a secretory rather than an absorptive mechanism, carbachol did not cause net fluid secretion. Cholinergic stimulation and pressure induced distension are thought to reduce net fluid absorption through inducing secretion but are found only to reduce fluid absorption.In conclusion, distension and cholinergic stimulation of the small intestine are two further circumstances in which fluid secretion is assumed to explain their action on fluid movement, as required by the enterocyte secretion model of secretion but, which like STa enterotoxin, instead are only able to reduce fluid absorption. This casts further doubt on the widespread validity of the enterocyte secretion model for fluid appearance in the lumen in diarrhoeal diseases
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