SNG: Lurgi of hygas?

Document(en) uit de collectie Chemische Procestechnologie.DelftChemTechApplied Science

Bodembescherming met behulp van boomstammen

Door menselijke ingrepen zoals versmalling en rechttrekken van de rivier, winning van bouwstoffen en de bouw van waterwerken krijgen Nederlandse rivieren steeds minder zand en grind aangevoerd. De stroomsnelheid en daarmee de erosie nemen toe. Er ontstaan grote ontgrondingskuilen, die het risico op het bezwijken van de oever vergroten. Om dit erosieproces tegen te gaan wil Rijkswaterstaat bomen uit de uiterwaarden gaan gebruiken om de bodem mee te beschermen. Echter kunnen de bomen hinder opleveren voor de scheepvaart als ze in de schroef terecht komen. Om veiligheid te garanderen is informatie nodig over de kritieke stroomsnelheid van de boomstammen. De hoofdvraag van dit onderzoek luidt: In hoeverre kunnen boomstammen toegepast worden als bodembescherming om erosie en ontgronding te voorkomen. Verschillende bomenconstructie worden op schaal getest aan de hand van experimenten in de laboratorium goten in Stevinlab III te Delft. Per constructie wordt gekeken naar het bezwijkmechanisme, de kritieke stroomsnelheid en turbulentie. Ook wordt er onderzocht of de kritieke stroomsnelheid van boomstammen beschreven kan worden met formules op basis van Izbash en op basis van Shields. Uiteindelijk wordt het schaalmodel vertaald naar de werkelijkheid. Uit dit onderzoek komt naar voren dat boomstammen kunnen worden toegepast om de bodem mee te beschermen op basis van de kritieke stroomsnelheid en de turbulentie. Het toepassen is echter niet op elke plek in de rivier mogelijk en er zal dus voor elke situatie gekeken moeten worden wat de maximale stroomsnelheid is in de rivier en welke constructie van boomstammen het best gebruikt kan worden. Wat op valt is dat de bomenconstructies bestaande uit één laag de hoogste kritieke stroomsnelheid behalen maar een lage relatieve fluctuatie intensiteit. Voor de constructies met meer lagen is het omgekeerde het geval, de kritieke stroomsnelheid is lager maar de relatieve fluctuatie intensiteit is hoger. Er wordt aangeraden om in een vervolgonderzoek de nauwkeurigheid te vergroten. Dit kan door te werken met een bredere stroomgoot, grotere boomstammen en betere snelheidsmeters. Voor het gebruik van formules om de kritieke stroomsnelheid van boomstammen mee te beschrijven is verder onderzoek nodig. Uit dit onderzoek komt naar voren dat de formules nog niet correct zijn. Er zijn een aantal variabelen verwaarloosd wat deze fout veroorzaakt kan hebben.Civil Engineering and GeosciencesHydraulic Engineerin

Tuning of a central controller for a sewer network using multiple simplified models

Water Resource

The influence of joint rigidity on the buckling behaviour of a diagonal in a truss or offshore structure

Civil Engineering and GeosciencesStructural Engineerin

Determining Resource Needs of Autonomous Agents in Decoupled Plans

At airports, the turnaround process of aircraft is crucial for a timely and efficient handling of air traffic. During this process, a number of services need to be provided during the time the aircraft is at the gate: e.g., de-boarding, cleaning, catering, fuelling, and boarding. These services are provided by different service providers (agents), who have to coordinate their activities in order to respect the turnaround timeslot, the required service times and existing regulations. These temporal dependencies between services can be planned, but if disruptions occur re-planning is complex and often impossible. For this reason, in previous research a methodology and prototype have been devised to simplify the planning process by decoupling the overall plan into local plans for each agent. This paper builds on this research and introduces an important extension to the existing methodology and prototype: a new algorithm is introduced to take into account the minimal number of resources each service provider will need to accomplish its task.Computer ScienceElectrical Engineering, Mathematics and Computer Scienc

Blind driving by means of auditory feedback

Driving is a safety-critical task that predominantly relies on vision. However, visual information from the environment is sometimes degraded or absent. In other cases, visual information is available, but the driver fails to use it due to distraction or impairment. Providing drivers with real-time auditory feedback about the state of the vehicle in relation to the environment may be an appropriate means of support when visual information is compromised. In this study, we explored whether driving can be performed solely by means of artificial auditory feedback. We focused on lane keeping, a task that is vital for safe driving. Three auditory parameter sets were tested: (1) predictor time, where the volume of a continuous tone was a linear function of the predicted lateral error from the lane centre 0 s, 1 s, 2 s, or 3 s into the future; (2) feedback mode (volume feedback vs. beep-frequency feedback) and mapping (linear vs. exponential relationship between predicted error and volume/beep frequency); and (3) corner support, in which in addition to volume feedback, a beep was offered upon entering/leaving a corner, or alternatively when crossing the lane centre while driving in a corner. A dead-zone was used, whereby the volume/beep-frequency feedback was provided only when the vehicle deviated more than 0.5 m from the centre of the lane. An experiment was conducted in which participants (N = 2) steered along a track with sharp 90-degree corners in a simulator with the visual projection shut down. Results showed that without predictor feedback (i.e., 0 s prediction), participants were more likely to depart the road compared to with predictor feedback. Moreover, volume feedback resulted in fewer road departures than beep-frequency feedback. The results of this study may be used in the design of in-vehicle auditory displays. Specifically, we recommend that feedback be based on anticipated error rather than current error.Intelligent Vehicles & Cognitive Robotic

Shooting mechanisms in Nature: A systematic review

BackgroundIn nature, shooting mechanisms are used for a variety of purposes, including prey capture, defense, and reproduction. This review offers insight into the working principles of shooting mechanisms in fungi, plants, and animals in the light of the specific functional demands that these mechanisms fulfill.MethodsWe systematically searched the literature using Scopus and Web of Knowledge to retrieve articles about solid projectiles that either are produced in the body of the organism or belong to the body and undergo a ballistic phase. The shooting mechanisms were categorized based on the energy management prior to and during shooting.ResultsShooting mechanisms were identified with projectile masses ranging from 1·10−9 mg in spores of the fungal phyla Ascomycota and Zygomycota to approximately 10,300 mg for the ballistic tongue of the toad Bufo alvarius. The energy for shooting is generated through osmosis in fungi, plants, and animals or muscle contraction in animals. Osmosis can be induced by water condensation on the system (in fungi), or water absorption in the system (reaching critical pressures up to 15.4 atmospheres; observed in fungi, plants, and animals), or water evaporation from the system (reaching up to −197 atmospheres; observed in plants and fungi). The generated energy is stored as elastic (potential) energy in cell walls in fungi and plants and in elastic structures in animals, with two exceptions: (1) in the momentum catapult of Basidiomycota the energy is stored in a stalk (hilum) by compression of the spore and droplets and (2) in Sphagnum energy is mainly stored in compressed air. Finally, the stored energy is transformed into kinetic energy of the projectile using a catapult mechanism delivering up to 4,137 J/kg in the osmotic shooting mechanism in cnidarians and 1,269 J/kg in the muscle-powered appendage strike of the mantis shrimp Odontodactylus scyllarus. The launch accelerations range from 6.6g in the frog Rana pipiens to 5,413,000g in cnidarians, the launch velocities from 0.1 m/s in the fungal phylum Basidiomycota to 237 m/s in the mulberry Morus alba, and the launch distances from a few thousands of a millimeter in Basidiomycota to 60 m in the rainforest tree Tetraberlinia moreliana. The mass-specific power outputs range from 0.28 W/kg in the water evaporation mechanism in Basidiomycota to 1.97·109 W/kg in cnidarians using water absorption as energy source.Discussion and conclusionsThe magnitude of accelerations involved in shooting is generally scale-dependent with the smaller the systems, discharging the microscale projectiles, generating the highest accelerations. The mass-specific power output is also scale dependent, with smaller mechanisms being able to release the energy for shooting faster than larger mechanisms, whereas the mass-specific work delivered by the shooting mechanism is mostly independent of the scale of the shooting mechanism. Higher mass-specific work-values are observed in osmosis-powered shooting mechanisms (≤ 4,137 J/kg) when compared to muscle-powered mechanisms (≤ 1,269 J/kg). The achieved launch parameters acceleration, velocity, and distance, as well as the associated delivered power output and work, thus depend on the working principle and scale of the shooting mechanism.Medical Instruments & Bio-Inspired Technolog

Sustainability as a procurement criterion for port investments

Ports are known to be one of the most polluting sectors, and therefore provide an opportunity to reduce emission significantly. Until now, the attention has been given to reduction of emissions in transport and shipping. The scope of research must expand to include port infrastructures, which should be made more sustainable. In many industries, sustainable purchasing and procurement is already integrated, but the procurement by port authorities for construction works seems to be lagging behind. The objective of this paper is to promote sustainable procurement, through preparing a tool, method or model that can be easily used by all stakeholders. The research has been divided into four phases: Analysis, Synthesis, Simulation and Evaluation. In the first phase, i.e. Analysis, insight is gained in the processes for (sustainable) procurement of different institutions and stakeholders, e.g. governments, port authorities and contractors. In addition, the legal aspects of procurement are examined. In the next phase, i.e., Synthesis, a procurement model is set up. This requires a selection of procurement criteria based on Life Cycle Analysis, and a selection of weight factors to be assigned to the various criteria. The format and type of model too needs to be determined based on requirements such as flexibility, stability and user-friendliness. During the third step, i.e., Simulation the model is tested using reference contracts from current or existing projects. The impact of different criteria can be examined in this manner and, eventually, the model can be adapted. In the last step, Evaluation and recommendations over the application of the model will be given.Hydraulic EngineeringCivil Engineering and Geoscience