937 research outputs found
Entrainment characteristics of unsteady subsonic jets
The effectiveness of jet unsteadiness in enhancing flow entrainment was assessed. It was conducted that entrainment depends on the type and amount of jet unsteadiness. Apparently, the mere introduction of jet unsteadiness by small sinusoidal flow angle variations is insufficient to enhance entrainment but, it should be noted that the results were obtained at measuring stations which are all many nozzle widths downstream of the jet nozzle. Thus, no fully conclusive statement can be made at this time about the entrainment close to the nozzle. The high entrainment of the fluidically oscillated jet was caused by the high-frequency content of this square wave type of oscillation but more detailed measurements are clearly needed, in particular for the fluidically oscillated and the pulsed jets. Practical ejector application requires the proper trade-off between entrainment and primary nozzle thrust efficiency
An Axiomatic Approach to Liveness for Differential Equations
This paper presents an approach for deductive liveness verification for
ordinary differential equations (ODEs) with differential dynamic logic.
Numerous subtleties complicate the generalization of well-known discrete
liveness verification techniques, such as loop variants, to the continuous
setting. For example, ODE solutions may blow up in finite time or their
progress towards the goal may converge to zero. Our approach handles these
subtleties by successively refining ODE liveness properties using ODE
invariance properties which have a well-understood deductive proof theory. This
approach is widely applicable: we survey several liveness arguments in the
literature and derive them all as special instances of our axiomatic refinement
approach. We also correct several soundness errors in the surveyed arguments,
which further highlights the subtlety of ODE liveness reasoning and the utility
of our deductive approach. The library of common refinement steps identified
through our approach enables both the sound development and justification of
new ODE liveness proof rules from our axioms.Comment: FM 2019: 23rd International Symposium on Formal Methods, Porto,
Portugal, October 9-11, 201
An Investigation of the Fluid-Structure Interaction in an Oscillating-Wing Micro-Hydropower Generator
in Fluid Structure Interaction II, Eds. Chakrabarti, S.K., Brebbia, C.A., Almorza, D. and Gonzalez-Palma, R., WIT Press, Southampton, UK, 2003, pp. 73-82.Results of a computational and experimental investigation of the fluid-structure phenomena occurring in an oscillating-wing micro-hydropower generator are presented. The generator consists of tandem wings which oscillate in a combined pitch-plunge mode with approximately 90 degree phase angle between the two motions. Two-dimensional inviscid and viscous flow codes are used to predict the oscillatory flow field and the power transferred from the water flow to the oscillating wings. Experimental results of water tunnel tests of this hydropower generator are also described and comparisons between the measured and predicted power output are given
Verifying the Safety of a Flight-Critical System
This paper describes our work on demonstrating verification technologies on a
flight-critical system of realistic functionality, size, and complexity. Our
work targeted a commercial aircraft control system named Transport Class Model
(TCM), and involved several stages: formalizing and disambiguating requirements
in collaboration with do- main experts; processing models for their use by
formal verification tools; applying compositional techniques at the
architectural and component level to scale verification. Performed in the
context of a major NASA milestone, this study of formal verification in
practice is one of the most challenging that our group has performed, and it
took several person months to complete it. This paper describes the methodology
that we followed and the lessons that we learned.Comment: 17 pages, 5 figure
Constructive Hybrid Games
Hybrid games are models which combine discrete, continuous, and adversarial
dynamics. Game logic enables proving (classical) existence of winning
strategies. We introduce constructive differential game logic (CdGL) for hybrid
games, where proofs that a player can win the game correspond to computable
winning strategies. This is the logical foundation for synthesis of correct
control and monitoring code for safety-critical cyber-physical systems. Our
contributions include novel static and dynamic semantics as well as soundness
and consistency.Comment: 60 pages, preprint, under revie
A misplaced lncRNA causes brachydactyly in humans
Translocations are chromosomal rearrangements that are frequently associated with a variety of disease states and developmental disorders. We identified 2 families with brachydactyly type E (BDE) resulting from different translocations affecting chromosome 12p. Both translocations caused downregulation of the parathyroid hormone-like hormone (PTHLH) gene by disrupting the cis-regulatory landscape. Using chromosome conformation capturing, we identified a regulator on chromosome 12q that interacts in cis with PTHLH over a 24.4-megabase distance and in trans with the sex-determining region Y-box 9 (SOX9) gene on chromosome 17q. The element also harbored a long noncoding RNA (lncRNA). Silencing of the lncRNA, PTHLH, or SOX9 revealed a feedback mechanism involving an expression-dependent network in humans. In the BDE patients, the human lncRNA was upregulated by the disrupted chromosomal association. Moreover, the lncRNA occupancy at the PTHLH locus was reduced. Our results document what we believe to be a novel in cis- and in trans-acting DNA and lncRNA regulatory feedback element that is reciprocally regulated by coding genes. Furthermore, our findings provide a systematic and combinatorial view of how enhancers encoding lncRNAs may affect gene expression in normal development
HERWIG 6.4 Release Note
A new release of the Monte Carlo program HERWIG (version 6.4) is now
available. The main new features are: spin correlations between the production
and decay of heavy fermions, i.e. top quarks, tau leptons and SUSY particles;
polarization effects in SUSY production processes in lepton-lepton collisions;
an interface to TAUOLA for tau decays; MSSM Higgs processes in lepton-lepton
collisions
Pluripoietin alpha: a second human hematopoietic colony-stimulating factor produced by the human bladder carcinoma cell line 5637.
Labour Market and Social Policy in Italy: Challenges and Changes. Bertelsmann Policy Brief #2016/02
vEight years after the outbreak of the financial crisis, Italy has still to cope with and
overcome a plethora of economic and social challenges. On top of this, it faces an
unfavourable demographic structure and severe disparities between its northern and
southern regions. Some promising reforms have recently been enacted, specifically
targeting poverty and social exclusion. However, much more remains to be done on
the way towards greater economic stability and widely shared prosperity
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