258 research outputs found
Coupled flight dynamics and CFD - demonstration for helicopters in shipborne environment
The development of high-performance computing and computational fluid dynamics methods have evolved to the point where it is possible to simulate complete helicopter configurations with good accuracy. Computational fluid dynamics methods have also been applied to problems such as rotor/fuselage and main/tail rotor interactions, performance studies in hover and forward flight, rotor design, and so on. The GOAHEAD project is a good example of a coordinated effort to validate computational fluid dynamics for complex helicopter configurations. Nevertheless, current efforts are limited to steady flight and focus mainly on expanding the edges of the flight envelope. The present work tackles the problem of simulating manoeuvring flight in a computational fluid dynamics environment by integrating a moving grid method and the helicopter flight mechanics solver with computational fluid dynamics. After a discussion of previous works carried out on the subject and a description of the methods used, validation of the computational fluid dynamics for ship airwake flow and rotorcraft flight at low advance ratio are presented. Finally, the results obtained for manoeuvring flight cases are presented and discussed
Pancreatic Allograft Thrombosis: Implementation of the CPAT-Grading System in a Retrospective Series of Simultaneous Pancreas-Kidney Transplantation
Pancreatic graft thrombosis (PAT) is a major surgical complication, potentially leading to graft loss. The recently proposed Cambridge Pancreas Allograft Thrombosis (CPAT) grading system provides diagnostic, prognostic and therapeutic recommendations. The aim of the present study was to retrospectively assess computed tomography angiography (CTA) examinations performed routinely in simultaneous pancreas-kidney (SPK) recipients to implement the CPAT grading system and to study its association with the recipients' outcomes. We retrospectively studied 319 SPK transplant recipients, who underwent a routine CTA within the first 7 postoperative days. Analysis of the CTA scans revealed PAT in 215 patients (106 grade 1, 85 grade 2, 24 grade 3), while 104 showed no signs. Demographic data of the patients with and without PAT (thrombosis and non-thrombosis group) were not significantly different, except for the higher number of male donors in the thrombosis group. Pancreatic graft survival was significantly shorter in the thrombosis group. Graft loss due to PAT was significantly associated with grade 2 and 3 thrombosis, while it did not differ for recipients with grade 0 or grade 1 thrombosis. In conclusion, the CPAT grading system was successfully implemented in a large series of SPK transplant recipients and proved applicable in clinical practice
Deep structure of the Ionian Sea and Sicily Dionysus - Cruise No. M111, October 10 - November 1, 2014, Catania (Italy) – Catania (Italy)
Summary
The origin of the Ionian Sea lithosphere and the deep structure of its margins remain a little
investigated part of the Mediterranean Sea. To shed light on the plate tectonic setting in this
central part of southern Europe, R/V METEOR cruise M111 set out to acquire deep penetrating
seismic data in the Ionian Sea. M111 formed the core of an amphibious investigation covering
the Ionian Sea and island of Sicily. A total of 153 OBS/OBH deployments using French and
German instruments were successfully carried out, in addition to 12 land stations installed on
Sicily, which recorded the offshore air gun shots.
The aim of this onshore-offshore study is to quantify the deep geometry and architecture of the
Calabria subduction zone and Ionian Sea lithosphere and to shed light on the nature of the Ionian
Sea crust (oceanic crust vs. thinned continental crust). Investigating the structure of the Ionian
crust and lithospheric mantle will contribute to unravel the unknown ocean-continent transition
and Tethys margin. Analyzing the tectonic activity and active deformation zones is essential for
understanding the subduction processes that underlie the neotectonics of the Calabrian
subduction zone and earthquake hazard of the Calabria/Sicily region, especially in the vicinity of
local decoupling zones
Limits on the production of scalar leptoquarks from Z (0) decays at LEP
A search has been made for pairs and for single production of scalar leptoquarks of the first and second generations using a data sample of 392000 Z0 decays from the DELPHI detector at LEP 1. No signal was found and limits on the leptoquark mass, production cross section and branching ratio were set. A mass limit at 95% confidence level of 45.5 GeV/c2 was obtained for leptoquark pair production. The search for the production of a single leptoquark probed the mass region above this limit and its results exclude first and second generation leptoquarks D0 with masses below 65 GeV/c2 and 73 GeV/c2 respectively, at 95% confidence level, assuming that the D0lq Yukawa coupling alpha(lambda) is equal to the electromagnetic one. An upper limit is also given on the coupling alpha(lambda) as a function of the leptoquark mass m(D0)
Helicopter CFD Coupled with Flight Mechanics - Current Status and Future Perspectives
The development of High Performance Computing and CFD methods have evolved to the
point where it is possible to simulate complete helicopter configurations with good accuracy. CFD
methods have also been applied to problems such as rotor/fuselage and main/tail rotor interactions,
performance studies in hover and forward flight, rotor design, etc. The GOAHEAD project is
a good example of a coordinated effort to validate CFD for complex helicopter configurations.
Nevertheless, current efforts are limited to steady flight and focus mainly on expanding the edges
of the flight envelope. The present work tackles the problem of simulating manoeuvring flight in
a CFD environment by integrating a multi-body grid motion method and the Helicopter Flight
Mechanics (HFM) solver with CFD. After a discussion of previous works carried out on the subject
and a description of the methods used, validation of CFD for ship airwake flow and rotorcraft flight
at low advance ratio are presented. Finally, the results obtained for manoeuvring flight cases are
presented and discussed
Helicopter CFD Coupled with Flight Mechanics - Current Status and Future Perspectives
The development of High Performance Computing and CFD methods have evolved to the
point where it is possible to simulate complete helicopter configurations with good accuracy. CFD
methods have also been applied to problems such as rotor/fuselage and main/tail rotor interactions,
performance studies in hover and forward flight, rotor design, etc. The GOAHEAD project is
a good example of a coordinated effort to validate CFD for complex helicopter configurations.
Nevertheless, current efforts are limited to steady flight and focus mainly on expanding the edges
of the flight envelope. The present work tackles the problem of simulating manoeuvring flight in
a CFD environment by integrating a multi-body grid motion method and the Helicopter Flight
Mechanics (HFM) solver with CFD. After a discussion of previous works carried out on the subject
and a description of the methods used, validation of CFD for ship airwake flow and rotorcraft flight
at low advance ratio are presented. Finally, the results obtained for manoeuvring flight cases are
presented and discussed
The discrete spectrum of perturbed selfadjoint operators under non-signdefinite perturbations with a large coupling constant
Given two selfadjoint operators A and V=V_+-V_-, we study the motion of the eigenvalues of the operator A(t)=A-tV as t increases. Let #alpha#>0 and let #lambda# be a regular point for A. We consider the quantity N(#lambda#, A, W_+, W_-, #alpha#) defined as the difference between the number of the eigenvalues of A(t) that pass point #lambda# from the right to the left and the number of the eigenvalues passing #lambda# from the left to the right as t increases from 0 to #alpha#>0. We study asymptotic characteristics of N(#lambda#, A, W_+, W_-, #alpha#) as #alpha##->##infinity#. Applications to Schroedinger and Dirac operators are given. (orig.)SIGLEAvailable from TIB Hannover: RR 1596(387) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman
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