8,603 research outputs found
Integrated support structure
This Major Qualifying Project is part of the Advanced Space Design Program at WPI. The goal is to design a support structure for a NASA GetAway Special experimental canister. The payload integration, weight, volume, and structural integrity of the canister as specified by NASA guidelines were studied. The end result is a complete set of design drawings with interface drawings and data to specify the design and leave a base on which the next group can concentrate
Simulation Based Evaluation of Integrated Adaptive Control and Flight Planning Technologies
The objective of this work is to leverage NASA resources to enable effective evaluation of resilient aircraft technologies through simulation. This includes examining strengths and weaknesses of adaptive controllers, emergency flight planning algorithms, and flight envelope determination algorithms both individually and as an integrated package
Relation between body weight, amount of wool or feathers, and temperature regulation.
Publication authorized July 1, 1938.Includes bibliographical references
Science requirements for a global change technology architecture trade study
Science requirements for a global change technology initiative (GCTI) Architecture Trade Study were established by reviewing and synthesizing results from recent studies. A scientific rationale was adopted and used to identify a comprehensive set of measureables and their priorities. Spatial and temporal requirements for a number of measurement parameters were evaluated based on results from several working group studies. Science requirements were defined using these study results in conjunction with the guidelines for investigating global changes over a time scale of decades to centuries. Requirements are given separately for global studies and regional process studies. For global studies, temporal requirements are for sampling every 1 to 12 hours for atmospheric and radiation parameters and 1 day or more for most earth surface measurements. Therefore, the atmospheric measureables provide the most critical drivers for temporal sampling. Spatial sampling requirements vary from 1 km for land and ocean surface characteristics to 50 km for some atmospheric parameters. Thus, the land and ocean surface parameters have the more significant spatial variations and provide the most challenging spatial sampling requirements
Modelling and results for an array of 32 oscillating water columns
As part of an investigation into the feasibility of
an offshore combined wind/wave energy converting platform,
comprising one or more wind turbines mounted on a floating
structure in which a number of oscillating water columns (OWCs)
are embedded, testing was carried out on a 1:50 scale model of the
wave energy converting component of the platform. The model
comprises two legs joined at one end at an angle of 90 degrees. A
form of soft latching is implemented through the use of high and
low-pressure plenums to which the OWC chambers communicate
via air admittance valves. The model was tested in a number of
configurations, subject to varying amounts of simulated power
take-off damping and over a range of incident regular-wave
periods. Platform motions, OWC chamber and plenum pressure
and water column motions were recorded for each test. This
paper discusses some considerations in the design, construction,
instrumentation and testing of the model. Thermodynamic theory
describing the flow of air throughout the system, based on the
conservation of mass, is developed and related to the motion of
the water columns. Representative results from the model testing
in the time domain are presented. Finally, some conclusions are
drawn from these results
Association is not causation: treatment effects cannot be estimated from observational data in heart failure
Aims:
Treatment ‘effects’ are often inferred from non-randomized and observational studies. These studies have inherent biases and limitations, which may make therapeutic inferences based on their results unreliable. We compared the conflicting findings of these studies to those of prospective randomized controlled trials (RCTs) in relation to pharmacological treatments for heart failure (HF).
Methods and results:
We searched Medline and Embase to identify studies of the association between non-randomized drug therapy and all-cause mortality in patients with HF until 31 December 2017. The treatments of interest were: angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, beta-blockers, mineralocorticoid receptor antagonists (MRAs), statins, and digoxin. We compared the findings of these observational studies with those of relevant RCTs. We identified 92 publications, reporting 94 non-randomized studies, describing 158 estimates of the ‘effect’ of the six treatments of interest on all-cause mortality, i.e. some studies examined more than one treatment and/or HF phenotype. These six treatments had been tested in 25 RCTs. For example, two pivotal RCTs showed that MRAs reduced mortality in patients with HF with reduced ejection fraction. However, only one of 12 non-randomized studies found that MRAs were of benefit, with 10 finding a neutral effect, and one a harmful effect.
Conclusion:
This comprehensive comparison of studies of non-randomized data with the findings of RCTs in HF shows that it is not possible to make reliable therapeutic inferences from observational associations. While trials undoubtedly leave gaps in evidence and enrol selected participants, they clearly remain the best guide to the treatment of patients
Next-to-leading order corrections to Wt production and decay
We present the results of a next-to-leading order calculation of Wt
production, including the decays of both the top quark and the W boson. The
effects of radiation in the decay of the top quark are also included. The
separation of diagrams which appear in the real corrections, into singly- and
doubly-resonant contributions, is performed using a b-jet veto which is
motivated by the use of the bottom quark distribution function. We find that,
for a choice of scale which is suitable for this approach, the QCD corrections
are very mild and only change the cross section by up to 10% at the LHC,
depending on the severity of the b-jet veto. When further cuts are applied,
applicable for a Higgs boson search in the H->WW channel, we find that the
radiative effects greatly decrease the number of background events expected
from this process. In addition, the shapes of relevant distributions can be
significantly changed at next-to-leading order.Comment: 31 pages, 12 figure
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