Search results for "Opel"

Extensible Wind Towers

2014

The diffusion of wind energy generators is restricted by their strong landscape impact. The PERIMA project is about the development of an extensible wind tower able to support a wind machine for several hundred kW at its optimal working height, up to more than 50 m. The wind tower has a telescopic structure, made by several tubes located inside each other with their axis in vertical direction. The lifting force is given by a jack-up system confined inside a shaft, drilled below the ground level. In the retracted tower configuration, at rest, tower tubes are hidden in the foundation of the telescopic structure, located below the ground surface, and the wind machine is the only emerging part …

Understanding Augmented Reality Game Players : Value Co-destruction Process in Pokémon Go

2017

We conceptualize the mobile game Pokémon Go as a service provider aiming to offer customers value propositions over an augmented reality (AR) platform, where players engage in co-creating value, such as fun, social unity and health. However, playing Pokémon Go can also ensue to value co-destruction through critical service interactions involving e.g. increased mobile costs, trespassing, accidents or assaults. Such could ensue to negative value outcomes, such as frustration, humiliation or unsafety. In order to prevent critical service interactions, it is significant to gain an understanding of value codestruction, which currently remains an unclear concept with a call for empirical studies.…

Controllable Solid Propellant Rocket Motor Stability: Deep and Rapid Variable Thrust Operations

2008

When flow and combustion processes couple with the acoustic modes of the combustion chamber, the solid rocket motors experience unsteady gas motion and associated thrust oscillation and motor vibration. The operations of the variable nozzle introduce relevant dynamic changes in the chamber flow and combustion. This article proposes a non-linear approach for the analysis of the effects of severe nozzle manoeuvres on the controllable solid rocket motor stability and provides the evidence that the acoustic wave amplitude evolution is influenced by the nozzle manoeuvre severity, shape and direction. The additional complexity in the problem of the combustion stability analysis introduced by the …

Planar Bragg Grating Sensor for the Detection of CFC-11

2018

We demonstrate the fabrication of a highly sensitive opto-chemical sensor system based on cyclodextrin derivative functionalized planar Bragg gratings for an online in-situ detection and measurement of the environmentally harmful propellant trichlorofluoromethane in real-time.

An analytical model of heat transfer and fluid dynamic performances of an unconventional NTR engine for manned interplanetary missions

2009

Abstract An analytical model of fluid flow and heat transfer of a Nuclear Thermal Rocket (NTR) engine concept is presented. The engine is based on the direct conversion of the kinetic energy of the fission fragments (FFs) into the propellant enthalpy. The FFs can escape from an extremely thin layer of fissionable material: a sufficiently large surface coated with few micrometers of Americium 242m, confined by a neutron moderator–reflector, may become a critical reactor. Three dimensional coupled CFD-Monte Carlo simulations have already been presented in Di Piazza and Mulas (2006) . In this paper, an analytical integral 1-D model of fluid dynamics and heat transfer is built in order to fores…

Propeller Flaps: A Review of Indications, Technique, and Results

2014

In the last years, propeller flaps have become an appealing option for coverage of a large range of defects. Besides having a more reliable vascular pedicle than traditional flap, propeller flaps allow for great freedom in design and for wide mobilization that extend the possibility of reconstructing difficult wounds with local tissues and minimal donor-site morbidity. They also allow one-stage reconstruction of defects that usually require multiple procedures. Harvesting of a propeller flap requires accurate patient selection, preoperative planning, and dissection technique. Complication rate can be kept low, provided that potential problems are prevented, promptly recognized, and adequate…

Conflicting coccolithophore and geochemical evidence for productivity levels in the Eastern Mediterranean sapropel S1

2011

Abstract The cyclic development of anoxic conditions in the eastern Mediterranean deep sea waters is one of the most fascinating research topics in paleoceanographic studies. In combination with bottom water stagnation, enhanced primary production is a common explanation for the deposition of organic-rich layers (sapropels). This is supported by extensive evidence from both geochemical and micropaleontological studies. The correspondence of recent sapropel layers with peaks of the lower photic zone coccolithophore species Florisphaera profunda has been interpreted as a proxy for the development of a deep chlorophyll maximum (DCM), due to the pycnocline/nutricline shallowing into the lower p…

Computational Fluid Dynamics Simulation for Propeller

2017

A Reynolds-Averaged Navier-Stokes (RANS) method has been employed in conjunction with an overlapping moving grid approach to provide accurate resolution of a five-blade propeller flows under both the design and offdesign conditions. It is well known that some off-design propeller flow phenomena are dominated by viscous effects and cannot be accurately predicted by the potential flow methods. To properly account for viscous effects, it is necessary to employ accurate and robust numerical methods which can provide detailed resolution of the propeller boundary layer, turbulent wake, leading edge separation,and unsteady ring vortices induced by propeller operations under off-design conditions. …

Reverse rotation of the right kidney associated with vascular anomaly producing ipsilateral ureteropelvic junction obstruction.

2009

The Postglacial Isotopic Record of Intermediate Water Connects Mediterranean Sapropels and Organic‐Rich Layers

2020

Carbon‐rich layers exist at both sides of the Mediterranean Sea sedimentary record and are called sapropels and organic rich layers (ORLs), respectively, in the eastern and western basins. They have different levels of organic carbon accumulation and seafloor oxygen deprivation. The most recent sapropel and ORL depositions have a different timing, approximately 10.8–6.1 and 14.5–9.0 ka, respectively. Here we investigate oxygen isotopic records of three foraminifera species that occupy different habitats within the Sicily Channel water column since ~12.0 ka, thus in the sill between the eastern and western Mediterranean basins. These data are ice volume corrected, to get information on water…