4,489 research outputs found
Estimating Local Compliance in a Beam from Bending Measurements Part I. Computing "Span Function"
Bending modulus of elasticity measurements have been useful and profitable for decades in the sorting of dimension lumber for its structural quality. Bending and tensile strengths of lumber are known to be correlated with modulus of elasticity. Previous research indicates that bending elasticity on short spans, shorter than can be practically measured with precision, may improve correlation with strength. It is expected, therefore, that the optimal estimation method of the present two-part paper will be applied in the machine stress rating (MSR) process for more accurate sorting of dimension lumber into MSR grades.Using weighting functions called "span functions," the estimation method processes a sequence of bending measurements from overlapping spans, such as those obtained from equipment for MSR lumber production. A span function is specific to the support configuration of a particular bending span and defines how much the local elastic properties along a beam contribute to a measurement. Intuitively, the local elasticity values of a beam near span center affect the measurement more than values near span ends. Span function defines this effect as a function of position along the bending span. In Part I, a procedure is developed for computing span function of a general bending span configuration. Span functions are graphed for bending spans of a production-line machine used in MSR lumber production and for other bending span configurations. In Part II, use of span functions in optimal estimation of local elasticity is described
The geology and petrogenesis of the southern closepet granite
The Archaean Closepet Granite is a polyphase body intruding the Peninsular Gneiss Complex and the associated supracrustal rocks. The granite out-crop runs for nearly 500 km with an approximate width of 20 to 25 km and cut across the regional metamorphic structure passing from granulite facies in the South and green schist facies in the north. In the amphibolite-granulite facies transition zone the granite is intimately mixed with migmatites and charnockite. Field observations suggests that anatexis of Peninsular gneisses led to the formation of granite melt, and there is a space relationship between migmatite formation, charnockite development and production and emplacement of granite magma. Based on texture and cross cutting relationships four major granite phases are recognized: (1) Pyroxene bearing dark grey granite; (2) Porphyritec granite; (3) Equigranular grey granite; and (4) Equigranular pink granite. The granite is medium to coarse grained and exhibit hypidiomorphic granular to porphyritic texture. The modal composition varies from granite granodiorite to quartz monzonite. Geochemical variation of the granite suite is consistent with either fractional crystallization or partial melting, but in both the cases biotite plus feldspar must be involved as fractionating or residual phases during melting to account trace element chemistry. The trace element data has been plotted on discriminant diagrams, where majority of samples plot in volcanic arc and within plate, tectonic environments. The granite show distinct REE patterns with variable total REE content. The REE patterns and overall abundances suggests that the granite suite represents a product of partial melting of crustal source in which fractional crystallization operated in a limited number of cases
âYou Sound Like a Good Program Managerâ: An Analysis of Gender in Womenâs Computing Life Histories
Through the eyes of professional women in computing, we can better understand the impact of workplace structures, higher education pathways, and the particular closed nature of the tech industry. This study of womenâs life histories contributes to the work of in-depth qualitative examinations of CS learning contexts and psychological studies investigating phenomena such stereotype threat which contextualize the experience of women in computing environments. Drawing inspiration from Margolis and Fisherâs work drawing the âblueprintsâ of the âboyâs clubhouseâ of computing education [20], as well as McDermott and Webberâs analysis of when math learning occurs [22], we ask when, where, and how is gender being invoked and created, as a way to unpack the places, events, and interactions that shape womenâs participation in the Silicon Valley workforce. This qualitative analysis of 13 life history interviews with professional women in computing shows that gender becomes salient for women in public settings, particularly in early adulthood when women enter male-dominated classrooms, teams, and workplaces that foster âbrogrammingâ culture. CS educators, hiring managers, and recruiters all need to be aware that the effects of gender go beyond just including more women in classrooms and on teams. The learning environment, incentives for participation, and the goal of diversity all need to be better aligned in order to foster an equitable workforce
Rugged switch responds to minute pressure differentials
Pressure responsive switching device exhibits high sensitivity but is extremely rugged and resistant to large amplitude shock and velocity loading. This snap-action, single pole-double throw switch operates over a wide temperature range
A systematic review of associations between environmental exposures and development of asthma in children aged up to 9 years
Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.Peer reviewedPublisher PD
Spectroscopy of Seven Cataclysmic Variables with Periods Above Five Hours
We present spectroscopy of seven cataclysmic variable stars with orbital
periods P(orb) greater than 5 hours, all but one of which are known to be dwarf
novae. Using radial velocity measurements we improve on previous orbital period
determinations, or derive periods for the first time. The stars and their
periods are
TT Crt, 0.2683522(5) d;
EZ Del, 0.2234(5) d;
LL Lyr, 0.249069(4) d;
UY Pup, 0.479269(7) d;
RY Ser, 0.3009(4) d;
CH UMa, 0.3431843(6) d; and
SDSS J081321+452809, 0.2890(4) d.
For each of the systems we detect the spectrum of the secondary star,
estimate its spectral type, and derive a distance based on the surface
brightness and Roche lobe constraints. In five systems we also measure the
radial velocity curve of the secondary star, estimate orbital inclinations, and
where possible estimate distances based on the MV(max) vs.P(orb) relation found
by Warner. In concordance with previous studies, we find that all the secondary
stars have, to varying degrees, cooler spectral types than would be expected if
they were on the main sequence at the measured orbital period.Comment: 25 pages, 2 figures, accepted for Publications of the Astronomical
Society of the Pacifi
Surface Acoustic Wave Driven Microchannel Flow
We demonstrate that the propagation of surface acoustic waves, arising from the excitation of the acoustic field on a piezoelectric crystal (lithium niobate) substrate, along the sidewalls of microchannels (50 ÎŒm or 280 ÎŒm wide and 200 ÎŒm deep) fabricated in the substrate, can give rise to throughflow with velocities of the order 10 mm/s. This streaming flow in the direction along which the surface acoustic wave propagates is a result of the leakage of acoustic radiation from the substrate walls into the fluid. Good agreement is obtained between these preliminary experimental results with those from numerical simulations of the classical acoustic streaming model. In any case, these results show the potential of surface acoustic wave micropumps to be an effective fluid-driving mechanism for microfluidic devices
The masses, radii and luminosities of the components of U Geminorum
We present a phase-resolved spectroscopic study of the secondary star in the
cataclysmic variable U Gem. We use our data to measure the radial velocity
semi-amplitude, systemic velocity and rotational velocity of the secondary
star. Combining this with literature data allows us to determine masses and
radii for both the secondary star and white dwarf which are independent of any
assumptions about their structure. We use these to compare their properties
with those of field stars and find that both components follow field
mass-radius relationships. The secondary star has the mass, radius, luminosity
and photometric temperature of an M2 star, but a spectroscopic temperature of
M4. The latter may well be due to a high metallicity. There is a troubling
inconsistency between the radius of the white dwarf inferred from its
gravitational redshift and inclination and that inferred from its temperature,
flux, and astrometric distance.
We find that there are two fundamental limits to the accuracy of the
parameters we can derive. First the radial velocity curve of the secondary star
deviates from a sinusoid, in part because of its asphericity (which can be
modelled) and in part because the line flux is not evenly distributed over its
surface. Second we cannot be certain which spectral type is the best match for
the lines of the secondary star, and the derived rotational velocity is a
function of the spectral type of the template star used.Comment: 12 pages, 10 figures. Accepted for MNRA
Correlation of the Quasi-Periodic Oscillation Frequencies of White Dwarf, Neutron Star, and Black Hole Binaries
Using data obtained in 1994 June/July with the Extreme Ultraviolet Explorer
deep survey photometer and in 2001 January with the Chandra X-ray Observatory
Low Energy Transmission Grating Spectrograph, we investigate the
extreme-ultraviolet (EUV) and soft X-ray oscillations of the dwarf nova SS Cyg
in outburst. We find quasi-periodic oscillations (QPOs) at nu_0 ~ 0.012 Hz and
nu_1 ~ 0.13 Hz in the EUV flux and at nu_0 ~ 0.0090 Hz, nu_1 ~ 0.11 Hz, and
possibly nu_2 ~ nu_0 + nu_1 ~ 0.12 Hz in the soft X-ray flux. These data,
combined with the optical data of Woudt & Warner for VW Hyi, extend the
Psaltis, Belloni, & van der Klis nu_high-nu_low correlation for neutron star
and black hole low-mass X-ray binaries (LMXBs) nearly two orders of magnitude
in frequency, with nu_low ~ 0.08 nu_high. This correlation identifies the
high-frequency quasi-coherent oscillations (so-called ``dwarf nova
oscillations'') of cataclysmic variables (CVs) with the kilohertz QPOs of
LMXBs, and the low-frequency QPOs of CVs with the horizontal branch
oscillations (or the broad noise component identified as such) of LMXBs.
Assuming that the same mechanisms produce the QPOs in white dwarf, neutron
star, and black hole binaries, we find that the data exclude the relativistic
precession model and the magnetospheric and sonic-point beat-frequency models
(as well as any model requiring the presence or absence of a stellar surface or
magnetic field); more promising are models that interpret QPOs as
manifestations of disk accretion onto any low-magnetic field compact object.Comment: 15 pages including 4 encapsulated postscript figures; LaTeX format,
uses aastex.cls; accepted on 2002 July 23 for publication in The
Astrophysical Journa
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