40,127 research outputs found
An Analysis Of Fatigue Crack Growth Of A Notched Aircraft Component Under Compression-Dominated Spectrum Loading
In engineering structures, fatigue cracks often emanate from geometrical discontinuities such as holes and notches. Experimentally it has been observed that there exists a notch-affected zone, in which the crack growth exhibits a transitional behaviour. Depending on the loading level and the geometry of the notch, the crack growth rate may initially decrease with crack length to reach a minimum. It will then either grow at an accelerated rate, or stop growing. This report details ongoing work in modelling crack growth in the presence of notch plasticity. The local stress-strain distribution ahead of a notch root is determined based on an empirical distribution of the equivalent stress, and the evolution of the notch root stress and strain is calculated using Neuber's rule and an Armstrong-Chaboche type nonlinear kinematic hardening model. The stress intensity factor is then calculated using a Green's function approach. A crack growth analysis program has been developed, implementing the above procedures
The relationship between HIV seroconversion illness, HIV test interval and time to AIDS in a seroconverter cohort.
Seroconversion illness is known to be associated with more rapid HIV disease progression. However, symptoms are often subjective and prone to recall bias. We describe symptoms reported as seroconversion illness and examine the relationship between illness, HIV test interval (time between antibody-negative and anibody-positive test dates) and the effect of both on time to AIDS from seroconversion. We used a Cox model, adjusting for age, sex, exposure group and year of estimated seroconversion. Of 1820 individuals, information on seroconversion illness was available for 1244 of whom 423 (34%) reported symptomatic seroconversion. Persons with a short test interval (< or = 2 months) were significantly more likely to report an illness than people with a longer interval (OR 6.76, 95% CI 4.75-9.62). Time to AIDS was significantly faster (P = 0.01) in those with a short test interval. The HIV test interval is a useful replacement for information on seroconversion illness in studies of HIV disease progression
Extinction Map of Baade's Window
Recently Wo\'zniak \& Stanek (1996) proposed a new method to investigate
interstellar extinction, based on two band photometry, which uses red clump
stars as a means to construct the reddening curve. I apply this method to the
color-magnitude diagrams obtained by the Optical Gravitational Lensing
Experiment (OGLE) to construct an extinction map of region of
Baade's Window, with resolution of . Such a map should be
useful for studies of this frequently observed region of the Galactic bulge.
The map and software useful for its applications are available via {\tt
anonymous ftp}. The total extinction varies from to
within the field of view centered on (18:03:20.9,--30:02:06), i.e. . The
ratio is determined with this new method.Comment: revised version accepted for publication in ApJ Letters, 8 pages,
uuencoded PostScript with 4 figures included; complete paper available
through WWW at http://www.astro.princeton.edu/~library/prep.html; tables and
auxiliary software available at
ftp://www.astro.princeton.edu/stanek/Extinctio
Fast track children's hearing pilot: final report of the evaluation of the pilot
This report presents key findings of the evaluation of the Fast Track children’s hearings pilot in Scotland1. The research was undertaken by staff at the Universities of Glasgow, Stirling and Strathclyde between February 2003 and January 2005
Magnetic and electrical properties of dhcp NpPd3 and U(1-x)Np(x)Pd3
We have made an extensive study of the magnetic and electrical properties of
double-hexagonal closepacked NpPd3 and a range of U(1-x)Np(x)Pd3 compounds with
x=0.01, 0.02, 0.05, and 0.50 using magnetization, magnetic susceptibility,
electrical resistivity, and heat capacity measurements on polycrystalline
samples, performed in the temperature range 2-300 K and in magnetic fields up
to 9 T. Two transitions are observed in NpPd3 at T=10 and 30 K. Dilute Np
samples (x<0.05) exhibit quadrupolar transitions, with the transition
temperatures reduced from those of pure UPd3.Comment: 10 pages, 18 figure
Determination of the Antiferroquadrupolar Order Parameters in UPd3
By combining accurate heat capacity and X-ray resonant scattering results we
have resolved the long standing question regarding the nature of the
quadrupolar ordered phases in UPd_3. The order parameter of the highest
temperature quadrupolar phase has been uniquely determined to be antiphase
Q_{zx} in contrast to the previous conjecture of Q_{x^2-y^2} . The azimuthal
dependence of the X-ray scattering intensity from the quadrupolar superlattice
reflections indicates that the lower temperature phases are described by a
superposition of order parameters. The heat capacity features associated with
each of the phase transitions characterize their order, which imposes
restrictions on the matrix elements of the quadrupolar operators.Comment: 4 pages, 5 figure
Balloon-borne radiometer measurement of Northern Hemisphere mid-latitude stratospheric HNO3 profiles spanning 12 years
Low-resolution atmospheric thermal emission spectra collected by balloon-borne radiometers over the time span of 1990–2002 are used to retrieve vertical profiles of HNO3, CFC-11 and CFC-12 volume mixing ratios between approximately 10 and 35 km altitude. All of the data analyzed have been collected from launches from a Northern Hemisphere mid-latitude site, during late summer, when stratospheric dynamic variability is at a minimum. The retrieval technique incorporates detailed forward modeling of the instrument and the radiative properties of the atmosphere, and obtains a best fit between modeled and measured spectra through a combination of onion-peeling and global optimization steps. The retrieved HNO3 profiles are consistent over the 12-year period, and are consistent with recent measurements by the Atmospheric Chemistry Experiment-Fourier transform spectrometer satellite instrument. This suggests that, to within the errors of the 1990 measurements, there has been no significant change in the HNO3 summer mid-latitude profile
- …