25,535 research outputs found
Cryogenic gear technology for an orbital transfer vehicle engine and tester design
Technology available for gears used in advanced Orbital Transfer Vehicle rocket engines and the design of a cryogenic adapted tester used for evaluating advanced gears are presented. The only high-speed, unlubricated gears currently in cryogenic service are used in the RL10 rocket engine turbomachinery. Advanced rocket engine gear systems experience operational load conditions and rotational speed that are beyond current experience levels. The work under this task consisted of a technology assessment and requirements definition followed by design of a self-contained portable cryogenic adapted gear test rig system
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School-university partnerships: fulfilling the potential. Summary Report: October 2014
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Using shared goal setting to improve access and equity: a mixed methods study of the Good Goals intervention
Background: Access and equity in childrenâs therapy services may be improved by directing cliniciansâ use of resources toward specific goals that are important to patients. A practice-change intervention (titled âGood Goalsâ) was designed to achieve this. This study investigated uptake, adoption, and possible effects of that intervention in childrenâs occupational therapy services.
Methods: Mixed methods case studies (n = 3 services, including 46 therapists and 558 children) were conducted. The intervention was delivered over 25 weeks through face-to-face training, team workbooks, and âtools for changeâ. Data were collected before, during, and after the intervention on a range of factors using interviews, a focus group, case note analysis, routine data, document analysis, and researchersâ observations.
Results: Factors related to uptake and adoptions were: mode of intervention delivery, competing demands on therapistsâ time, and leadership by service manager. Service managers and therapists reported that the intervention: helped therapists establish a shared rationale for clinical decisions; increased clarity in service provision; and improved interactions with families and schools. During the study period, therapistsâ behaviours changed: identifying goals, odds ratio 2.4 (95% CI 1.5 to 3.8); agreeing goals, 3.5 (2.4 to 5.1); evaluating progress, 2.0 (1.1 to 3.5). Childrenâs LoT decreased by two months [95% CI â8 to +4 months] across the services. Cost per therapist trained ranged from ÂŁ1,003 to ÂŁ1,277, depending upon service size and therapistsâ salary bands.
Conclusions: Good Goals is a promising quality improvement intervention that can be delivered and adopted in practice and may have benefits. Further research is required to evaluate its: (i) impact on patient outcomes, effectiveness, cost-effectiveness, and (ii) transferability to other clinical contexts
Mass-radius relation for magnetized strange quark stars
We review the stability of magnetized strange quark matter (MSQM) within the
phenomenological MIT bag model, taking into account the variation of the
relevant input parameters, namely, the strange quark mass, baryon density,
magnetic field and bag parameter. A comparison with magnetized asymmetric quark
matter in -equilibrium as well as with strange quark matter (SQM) is
presented. We obtain that the energy per baryon for MSQM decreases as the
magnetic field increases, and its minimum value at vanishing pressure is lower
than the value found for SQM, which implies that MSQM is more stable than
non-magnetized SQM. The mass-radius relation for magnetized strange quark stars
is also obtained in this framework.Comment: 7 pages, 6 figures. To be published in the Proceedings of 4th
International Workshop on Relativistic Astrophysical and Astronomy IWARA0
Magnetism in Nb(1-y)Fe(2+y) - composition and magnetic field dependence
We present a systematic study of transport and thermodynamic properties of
the Laves phase system NbFe. Our measurements confirm that
Fe-rich samples, as well as those rich in Nb (for ), show
bulk ferromagnetism at low temperature. For stoichiometric NbFe, on the
other hand, magnetization, magnetic susceptibility and magnetoresistance
results point towards spin-density wave (SDW) order, possibly helical, with a
small ordering wavevector \AA. Our results suggest that on
approaching the stoichiometric composition from the iron-rich side,
ferromagnetism changes into long-wavelength SDW order. In this scenario,
changes continuously from 0 to small, finite values at a Lifshitz point in the
phase diagram, which is located near . Further reducing the Fe content
suppresses the SDW transition temperature, which extrapolates to zero at
. Around this Fe content magnetic fluctuations dominate the
temperature dependence of the resistivity and of the heat capacity which
deviate from their conventional Fermi liquid forms, inferring the presence of a
quantum critical point. Because the critical point is located between the SDW
phase associated with stoichiometric NbFe and the ferromagnetic order which
reemerges for very Nb-rich NbFe, the observed temperature dependences could
be attributed both to proximity to SDW order or to ferromagnetism.Comment: 13 pages, 20 figure
Non-local nuclear spin quieting in quantum dot molecules: Optically-induced extended two-electron spin coherence time
We demonstrate the extension of coherence between all four two-electron spin
ground states of an InAs quantum dot molecule (QDM) via non-local suppression
of nuclear spin fluctuations in both constituent quantum dots (QDs), while
optically addressing only the upper QD transitions. Long coherence times are
revealed through dark-state spectroscopy as resulting from nuclear spin locking
mediated by the exchange interaction between the QDs. Lineshape analysis
provides the first measurement of the quieting of the Overhauser field
distribution correlating with reduced nuclear spin fluctuations.Comment: Supplementary materials can be found on the publication page of our
website. http://research.physics.lsa.umich.edu/dst/Publications.htm
A novel method of supplying nutrients permits predictable shoot growth and root: shoot ratios of pre-transplant bedding plants
BACKGROUND AND AIMS: Growth of bedding plants, in small peat plugs, relies on nutrients in the irrigation solution. The object of the study was to find a way of modifying the nutrient supply so that good-quality seedlings can be grown rapidly and yet have the high root : shoot ratios essential for efficient transplanting.
METHODS: A new procedure was devised in which the concentrations of nutrients in the irrigation solution were modified during growth according to changing plant demand, instead of maintaining the same concentrations throughout growth. The new procedure depends on published algorithms for the dependence of growth rate and optimal plant nutrient concentrations on shoot dry weight Ws (g mâ2), and on measuring evapotranspiration rates and shoot dry weights at weekly intervals. Pansy, Viola tricola âUniversal plus yellowâ and petunia, Petunia hybrida âMultiflora light salmon veinâ were grown in four independent experiments with the expected optimum nutrient concentration and fractions of the optimum. Root and shoot weights were measured during growth.
KEY RESULTS: For each level of nutrient supply Ws increased with time (t) in days, according to the equation {Delta}Ws/{Delta}t=K2Ws/(100+Ws) in which the growth rate coefficient (K2) remained approximately constant throughout growth. The value of K2 for the optimum treatment was defined by incoming radiation and temperature. The value of K2 for each sub-optimum treatment relative to that for the optimum treatment was logarithmically related to the sub-optimal nutrient supply. Provided the aerial environment was optimal, Rsb/Ro{approx}Wo/Wsb where R is the root : shoot ratio, W is the shoot dry weight, and sb and o indicate sub-optimum and optimum nutrient supplies, respectively. Sub-optimal nutrient concentrations also depressed shoot growth without appreciably affecting root growth when the aerial environment was non-limiting.
CONCLUSION: The new procedure can predict the effects of nutrient supply, incoming radiation and temperature on the time course of shoot growth and the root : shoot ratio for a range of growing conditions
The (In)Stability of Planetary Systems
We present results of numerical simulations which examine the dynamical
stability of known planetary systems, a star with two or more planets. First we
vary the initial conditions of each system based on observational data. We then
determine regions of phase space which produce stable planetary configurations.
For each system we perform 1000 ~1 million year integrations. We examine
upsilon And, HD83443, GJ876, HD82943, 47UMa, HD168443, and the solar system
(SS). We find that the resonant systems, 2 planets in a first order mean motion
resonance, (HD82943 and GJ876) have very narrow zones of stability. The
interacting systems, not in first order resonance, but able to perturb each
other (upsilon And, 47UMa, and SS) have broad regions of stability. The
separated systems, 2 planets beyond 10:1 resonance, (we only examine HD83443
and HD168443) are fully stable. Furthermore we find that the best fits to the
interacting and resonant systems place them very close to unstable regions. The
boundary in phase space between stability and instability depends strongly on
the eccentricities, and (if applicable) the proximity of the system to perfect
resonance. In addition to million year integrations, we also examined stability
on ~100 million year timescales. For each system we ran ~10 long term
simulations, and find that the Keplerian fits to these systems all contain
configurations which may be regular on this timescale.Comment: 37 pages, 49 figures, 13 tables, submitted to Ap
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