2,336 research outputs found
Computer programs for estimating civil aircraft economics
Computer programs for calculating airline direct operating cost, indirect operating cost, and return on investment were developed to provide a means for determining commercial aircraft life cycle cost and economic performance. A representative wide body subsonic jet aircraft was evaluated to illustrate use of the programs
Aerodynamic characteristics of raked-off circular and elliptical cones at a Mach number of 20 in helium
Longitudinal and lateral directional aerodynamic characteristics of raked-off circular and elliptical cones at Mach 20 in heliu
Oocyte cryopreservation as an adjunct to the assisted reproductive technologies
The document attached has been archived with permission from the editor of the Medical Journal of Australia. An external link to the publisher’s copy is included. See page 2 of PDF for this item.Keith L Harrison, Michelle T Lane, Jeremy C Osborn, Christine A Kirby, Regan Jeffrey, John H Esler and David Mollo
Threshold effects for two pathogens spreading on a network
Diseases spread through host populations over the networks of contacts
between individuals, and a number of results about this process have been
derived in recent years by exploiting connections between epidemic processes
and bond percolation on networks. Here we investigate the case of two pathogens
in a single population, which has been the subject of recent interest among
epidemiologists. We demonstrate that two pathogens competing for the same hosts
can both spread through a population only for intermediate values of the bond
occupation probability that lie above the classic epidemic threshold and below
a second higher value, which we call the coexistence threshold, corresponding
to a distinct topological phase transition in networked systems.Comment: 5 pages, 2 figure
Self-avoiding walks on scale-free networks
Several kinds of walks on complex networks are currently used to analyze
search and navigation in different systems. Many analytical and computational
results are known for random walks on such networks. Self-avoiding walks (SAWs)
are expected to be more suitable than unrestricted random walks to explore
various kinds of real-life networks. Here we study long-range properties of
random SAWs on scale-free networks, characterized by a degree distribution
. In the limit of large networks (system size ), the average number of SAWs starting from a generic site
increases as , with . For finite ,
is reduced due to the presence of loops in the network, which causes the
emergence of attrition of the paths. For kinetic growth walks, the average
maximum length, , increases as a power of the system size: , with an exponent increasing as the parameter is
raised. We discuss the dependence of on the minimum allowed degree in
the network. A similar power-law dependence is found for the mean
self-intersection length of non-reversal random walks. Simulation results
support our approximate analytical calculations.Comment: 9 pages, 7 figure
Effectiveness of a social support intervention on infant feeding practices : randomised controlled trial
Background: To assess whether monthly home visits from trained volunteers could improve infant feeding practices at age 12 months, a randomised controlled trial was carried out in two disadvantaged inner city London boroughs.
Methods: Women attending baby clinics with their infants (312) were randomised to receive monthly home visits from trained volunteers over a 9-month period (intervention group) or standard professional care only (control group). The primary outcome was vitamin C intakes from fruit. Secondary outcomes included selected macro and micro-nutrients, infant feeding habits, supine length and weight. Data were collected at baseline when infants were aged approximately 10 weeks, and subsequently when the child was 12 and 18 months old.
Results: Two-hundred and twelve women (68%) completed the trial. At both follow-up points no significant differences were found between the groups for vitamin C intakes from fruit or other nutrients. At first follow-up, however, infants in the intervention group were significantly less likely to be given goats’ or soya milks, and were more likely to have three solid meals per day. At the second follow-up, intervention group children were significantly less likely to be still using a bottle. At both follow-up points, intervention group children also consumed significantly more specific fruit and vegetables.
Conclusions: Home visits from trained volunteers had no significant effect on nutrient intakes but did promote some other recommended infant feeding practices
Spin Glass Phase Transition on Scale-Free Networks
We study the Ising spin glass model on scale-free networks generated by the
static model using the replica method. Based on the replica-symmetric solution,
we derive the phase diagram consisting of the paramagnetic (P), ferromagnetic
(F), and spin glass (SG) phases as well as the Almeida-Thouless line as
functions of the degree exponent , the mean degree , and the
fraction of ferromagnetic interactions . To reflect the inhomogeneity of
vertices, we modify the magnetization and the spin glass order parameter
with vertex-weights. The transition temperature () between the
P-F (P-SG) phases and the critical behaviors of the order parameters are found
analytically. When , and are infinite, and the
system is in the F phase or the mixed phase for , while it is in the
SG phase at . and decay as power-laws with increasing
temperature with different -dependent exponents. When ,
the and are finite and related to the percolation threshold. The
critical exponents associated with and depend on for () at the P-F (P-SG) boundary.Comment: Phys. Rev. E in pres
TB133: Experimental Stream Application of B.t.i. for Human Nuisance Black Fly Management in a Recreational Area
Biting and swarming black flies are abundant in Maine and can cause serious discomfort to humans, especially in recreational areas where their presence may substantially decrease satisfaction in outdoor activities. In 1985, 1986 and 1987 a series of experimental applications of B.t.i. was made on property owned by the Sugarloaf Mountain Corporation. The 198 5 study determined the persistenc e o f B.t.i. in stream and river water and the concentration necessary to achieve \u3e90% mortality in black fly larvae. It also indicated that B.t.i. had no detectable impact on non-target organisms. In 1986 and 1987 the objective was to determine if controlling the black fly larvae in streams within the Sugarloaf property would result in decreasing adult human nuisance flies to an acceptable level.https://digitalcommons.library.umaine.edu/aes_techbulletin/1069/thumbnail.jp
Effect of jet exit vanes on flow pulsations in an open-jet wind tunnel
An investigation was conducted of various jet exit vane configurations in the open test section of the Langley 4- by 7-Meter Tunnel to determine their effectiveness in reducing flow pulsations. The data consist of the instantaneous velocity fluctuations measured with hot-wire anemometers located at the tunnel centerline, 39.5 ft (12.0) downstream of the jet exit. The data are presented in the form of measured root-mean-square turbulence levels in the test section and a time series analysis for the baseline jet exit configuration (without vanes) and forthe most effective vane configuration, which consisted of triangular vanes alternating into and out of the flow around the jet exit
Irreversible Opinion Spreading on Scale-Free Networks
We study the dynamical and critical behavior of a model for irreversible
opinion spreading on Barab\'asi-Albert (BA) scale-free networks by performing
extensive Monte Carlo simulations. The opinion spreading within an
inhomogeneous society is investigated by means of the magnetic Eden model, a
nonequilibrium kinetic model for the growth of binary mixtures in contact with
a thermal bath. The deposition dynamics, which is studied as a function of the
degree of the occupied sites, shows evidence for the leading role played by
hubs in the growth process. Systems of finite size grow either ordered or
disordered, depending on the temperature. By means of standard finite-size
scaling procedures, the effective order-disorder phase transitions are found to
persist in the thermodynamic limit. This critical behavior, however, is absent
in related equilibrium spin systems such as the Ising model on BA scale-free
networks, which in the thermodynamic limit only displays a ferromagnetic phase.
The dependence of these results on the degree exponent is also discussed for
the case of uncorrelated scale-free networks.Comment: 9 pages, 10 figures; added results and discussion on uncorrelated
scale-free networks; added references. To appear in PR
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