2,327 research outputs found
Global Sentry: NASA/USRA high altitude reconnaissance aircraft design, volume 2
The Global Sentry is a high altitude reconnaissance aircraft design for the NASA/USRA design project. The Global Sentry uses proven technologies, light-weight composites, and meets the R.F.P. requirements. The mission requirements for the Global Sentry are described. The configuration option is discussed and a description of the final design is given. Preliminary sizing analyses and the mass properties of the design are presented. The aerodynamic features of the Global Sentry are described along with the stability and control characteristics designed into the flight control system. The performance characteristics are discussed as is the propulsion installation and system layout. The Global Sentry structural design is examined, including a wing structural analysis. The cockpit, controls and display layouts are covered. Manufacturing is covered and the life cost estimation. Reliability is discussed. Conclusions about the current Global Sentry design are presented, along with suggested areas for future engineering work
Stochastic Co-design of Storage and Control for Water Distribution Systems
Water distribution systems (WDSs) are typically designed with a conservative
estimate of the ability of a control system to utilize the available
infrastructure. The controller is subsequently designed and tuned based on the
designed water distribution system. This sequential approach may lead to
conservativeness in both design and control steps, impacting both operational
efficiency and economic costs. In this work, we consider simultaneously
designing infrastructure and developing a control strategy, the co-design
problem, to improve the overall system efficiency. However, implementing a
co-design problem for water distribution systems is a challenging task given
the presence of stochastic variables (e.g. water demands and electricity
prices). In this work, we propose a tractable stochastic co-design method to
design the best tank size and optimal control parameters for WDS, where the
expected operating costs are established based on Markov chain theory. We also
give a theoretical result that investigates the average long-run co-design cost
converging to the expected cost with probability 1. Furthermore, the method can
also be applied to an existing WDS to improve operation of the system. We
demonstrate the proposed co-design method on three examples and a real-world
case study in South Australia
Data-driven aerodynamic shape design with distributionally robust optimization approaches
We formulate and solve data-driven aerodynamic shape design problems with
distributionally robust optimization (DRO) approaches. Building on the findings
of the work \cite{gotoh2018robust}, we study the connections between a class of
DRO and the Taguchi method in the context of robust design optimization. Our
preliminary computational experiments on aerodynamic shape optimization in
transonic turbulent flow show promising design results
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A Gata3âMafb transcriptional network directs post-synaptic differentiation in synapses specialized for hearing
Information flow through neural circuits is determined by the nature of the synapses linking the subtypes of neurons. How neurons acquire features distinct to each synapse remains unknown. We show that the transcription factor Mafb drives the formation of auditory ribbon synapses, which are specialized for rapid transmission from hair cells to spiral ganglion neurons (SGNs). Mafb acts in SGNs to drive differentiation of the large postsynaptic density (PSD) characteristic of the ribbon synapse. In Mafb mutant mice, SGNs fail to develop normal PSDs, leading to reduced synapse number and impaired auditory responses. Conversely, increased Mafb accelerates synaptogenesis. Moreover, Mafb is responsible for executing one branch of the SGN differentiation program orchestrated by the Gata3 transcriptional network. Remarkably, restoration of Mafb rescues the synapse defect in Gata3 mutants. Hence, Mafb is a powerful regulator of cell-type specific features of auditory synaptogenesis that offers a new entry point for treating hearing loss. DOI: http://dx.doi.org/10.7554/eLife.01341.00
Use of Pharmacokinetic Modeling to Design Studies for Pathway-Specific Exposure Model Evaluation
Validating an exposure pathway model is difficult because the biomarker, which is often used to evaluate the model prediction, is an integrated measure for exposures from all the exposure routes and pathways. The purpose of this article is to demonstrate a method to use pharmacokinetic (PK) modeling and computer simulation to guide the design of field studies to validate pathway models. The childrenâs dietary intake model is discussed in detail as an example. Three important aspects are identified for a successful design to evaluate the childrenâs dietary intake model: a) longitudinally designed study with significant changes in the exposure for the route/pathway of interest, b) short biologic half-life of the selected chemical, and c) surface loading of the selected chemical at sufficient levels. Using PK modeling to guide a study design allowed a path-specific exposure model to be evaluated using urinary metabolite biomarkers
A Classic Type 2 QSO
In the Chandra Deep Field South 1Msec exposure we have found, at redshift
3.700 +- 0.005, the most distant Type 2 AGN ever detected. It is the source
with the hardest X-ray spectrum with redshift z>3. The optical spectrum has no
detected continuum emission to a 3sigma detection limit of ~3 10^{-19}
ergs/s/cm^2/AA and shows narrow lines of Ly_alpha, CIV, NV, HeII, OVI, [OIII],
and CIII]. Their FWHM line widths have a range of ~700-2300 km/s with an
average of approximately ~1500 km/s. The emitting gas is metal rich (Z ~2.5-3
Z_solar). In the X-ray spectrum of 130 counts in the 0.5-7 keV band there is
evidence for intrinsic absorption with N_H > 10^{24} cm^{-2}. An iron K_alpha
line with rest frame energy and equivalent width of ~6.4 keV and ~1 keV,
respectively, in agreement with the obscuration scenario, is detected at a
2sigma level. If confirmed by our forthcoming XMM observations this would be
the highest redshift detection of FeK_alpha. Depending on the assumed cosmology
and the X-ray transfer model, the 2-10 keV rest frame luminosity corrected for
absorption is ~10^{45 +- 0.5} ergs/s, which makes our source a classic example
of the long sought Type 2 QSOs. From standard population synthesis models,
these sources are expected to account for a relevant fraction of the
black-hole-powered QSO distribution at high redshift.Comment: 24 LaTeX pages including 6 postscript figures. Revised version,
accepted by Ap
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