33 research outputs found
Fabrication of micromechanical structures with a new electrodeless electrochemical etch stop
No full textFabrieksschema voor de bereiding van ureum
No full textDocument(en) uit de collectie Chemische ProcestechnologieDelftChemTechApplied Science
Etching and passivation of silicon in alkaline solution a coupled chemical electrochemical system
No full textFormation flight in civil aviation
No full textA model has been developed to demonstrate the value of a decentralized approach to formation flight routing. In the considered scenario, formation flight is an in-flight option. While centralized approaches are well covered in the literature, anticipating the use of formation flight before take-off, decentralized approaches have received less attention. Several examples do exist, noting that only one completely decentralized method was encountered. A completely decentralized approach is herein defined as one that does not use any kind of pre-flight formation flight planning or routing restrictions. While flying, each aircraft may communicate with others when they breach each other's communication range. During these communications, a formation flight strategy is formulated and the flights have to choose directly if they wish to commit to it. This method of obtaining fuel savings characterizes this work. Its compactness allowed for a broad evaluation of the potential of a decentralized approach within the project time frame. The sub-optimality of this greedy method enhances the value of any positive findings from this research, since it is likely that a global optimum has not yet been found. The decentralized approach that was developed during this project shows promising results when considering the efficiency with which large scenarios can be evaluated. A typical simulation in the performed transatlantic case study, containing 347 flights, took less than 6 minutes on a standard PC. Additionally, the capability of the model to sustain obtained savings when flights are delayed has been shown. The ability of flights to perform multiple consecutive formation flight segments is new to the research area. The latter significantly increases the usage rate of formation flight in the considered scenarios. It is noted that, in any current publication on formation flight implementation, the estimation of overall fuel savings strongly depends on assumptions. As such, the added value of this research is of a more relative nature. Based on the conservative assumption that any formation member other than the formation leader experiences a fuel flow reduction of 10%, the resulting routes and used formations were studied. The maximum obtained overall fuel savings estimation is 4.3% in a case study on 347 transatlantic flights. These savings were found when a combined objective was used, taking into account both fuel consumption and additional flight time. More significantly, formation sizes ranging from 2 to 6 aircraft were commonly used. A formation flight usage rate of 73%, with respect to total flight time, was recorded during the same simulation.Control and OperationsAir Transport OperationsAerospace Engineerin
Analysis of the Sun-Earth Lagrangian environment for the New Worlds Observer (NWO)
No full textExoplanets have been detected for more than 15 years. In the vast majority of instances, this has been accomplished through indirect observation. Such methods include among others the observation of radial velocity, transit photometry, and timing variations. These techniques allow for the vast majority of exoplanet detections up to date. An example for a very successful detection that has been achieved recently is the TRAPPIST-1 system. Indirect methods like these can provide us with estimates of a planet’s size and orbit for Earth-like planets. Yet, when we would like to detect life outside our Solar System, the fact alone that a planet lies in the habitable zone and that it has the right size is not a guarantee, but an indication of possible habitability. In order to have absolute certainty, a direct analysis of the atmosphere is needed. Direct observations would allow for a first-hand spectroscopy of the atmosphere in order to search for bio-signatures. These bio-signatures are markers created through biological processes and are indicative of life. Such elements include oxygen, ozone, nitrous oxide and methane. In order to allow for direct observations of Earth-like exoplanets, the New Worlds Observer (NWO) has been proposed as part of NASA Innovative Advanced Concepts (NIAC). NWO is a space-based observatory that will search for Earth-like planets that are located in the habitable zone in neighboring stellar systems. NWO consists of two spacecraft: a 4 m aperture-diameter diffraction-limited telescope and an occulter, called Starshade, which is 50 m in diameter. These spacecraft are located thousands of kilometers apart. This thesis discusses an analysis of the behavior of a satellite pair to be used for a preliminary observation campaign design for the NWO mission concept. In this concept, the two NWO spacecraft are positioned in Halo orbits about the Sun-Earth L2 point. This study demonstrates a novel method that may be used to redirect NWO’s observation vector from one star to another using dynamical systems theory, taking advantage of the non-linear dynamics around L2. To analyze the sensitivity of this method variations of the given constraints have been explored and analyzed.Aerospace EngineeringSpace Fligh
De rol van de grensvlakenergie bij metaal / niet-metaalverbindingen
No full textApplied SciencesTechnische Materiaalwetenschappe
